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Adsorption characteristics of water vapor on ferroaluminophosphate for desalination cycle
Abstract
The adsorption characteristics of microporous ferroaluminophosphate adsorbent (FAM-Z01, Mitsubishi Plastics) are evaluated for possible application in adsorption desalination and cooling (AD) cycles. A particular interest is its water vapor uptake behavior at assorted adsorption temperatures and pressures whilst comparing them to the commercial silica gels of AD plants. The surface characteristics are first carried out using N2 gas adsorption followed by the water vapor uptake analysis for temperature ranging from 20 °C to 80 °C. We propose a hybrid isotherm model, composing of the Henry and the Sips isotherms, which can be integrated to satisfactorily fit the experimental data of water adsorption on the FAM-Z01. The hybrid model is selected to fit the unusual isotherm shapes, that is, a low adsorption in the initial section and followed by a rapid vapor uptake leading to a likely micropore volume filling by hydrogen bonding and cooperative interaction in micropores. It is shown that the equilibrium adsorption capacity of FAM-Z01 can be up to 5 folds higher than that of conventional silica gels. Owing to the quantum increase in the adsorbate uptake, the FAM-Z01 has the potential to significantly reduce the footprint of an existing AD plant for the same output capacity.
... Type IV corresponds to materials with a surface more susceptible or accessible to adsorption of a given adsorbate, while Type V describes adsorption processes burdened by certain constraints. Those constraints can be of chemical characteristics, such as lower affinity towards the selected adsorbate (e.g., silica without hydroxyl groups with water), or of physical characteristics in case of a small opening window to the pores of some zeolite materials [22][23][24][25] resulting in higher activation energy. The Type IV isotherm is further divided to Type IV(a) with an adsorption/desorption hysteresis, and Type IV(b) without hysteresis [21]. ...
... This way, the differentiated parts of the adsorption process on a given adsorption pair can be described reasonably and more clearly. A combined model of Henry and Sips isotherms was proposed by Kim et al. [24]. The empirical combination of the original equations of Henry and Sips with a proportionality factor β HS is written in the following way: ...
... From the explanation above, it is evident that simple models would be difficult to apply to mesoporous materials as materials with strong duality (or triality) in their adsorption mechanisms. For the comparison of the new isotherm model, we have chosen the Rutherford model [42], Henry-Sips model [24] and Ng's model [18] with two nominal peaks (n = 2) (Ng-2f) as suggested in their work for the isotherm types IV and V. The selection of the comparison models was done based on the best fit out of the regular models described previously in this work. ...
A new model of adsorption isotherms Type IV and V is proposed as a basis for theoretical calculations and modelling of adsorption systems such as adsorption heat storage and heat pumps. As the current models have decent yet limited applicability, in this work, we present a new combined model with universal use for micro-mesoporous silica/water adsorption systems. Experimental measurement of adsorption isotherm of water onto seven different samples of micro and mesoporous silica and aluminium-silica were used to fit new adsorption models based on a combination of classical theories and a distribution function related to the pore-size distribution of the selected materials. The fitting was conducted through a repeated non-linear regression using Trust Region Reflective algorithm with weighting factors to compensate for the scalability of the adsorption amount at low relative pressure with optimization of the absolute average deviation fitting parameter. The results display a significant improvement for most of the samples and fitting indicators compared to more common models from the literature with average absolute deviation as low as AAD = 0.0025g/g for material with maximum uptake of q = 0.38g/g. The newly suggested model, which is based on a combination of BET theory and adjusted normal distribution function, proved to bring a higher degree of precision and universality for mesoporous silica materials with different levels of hydrophilicity.
... Saha et al. [2] presented a numerical analysis for the performance evaluation of a silica-gel water AD system to estimate the influences of operating conditions on AD system performance. In addition, various adsorbents were developed as adsorption agents in the AD system to enhance the system performance [15][16][17][18][19][20][21][22][23][24][25][26]. The performance evaluation studies of the AD system were conducted with FAM-Z01, which is manufactured based on zeolite material [15][16][17][18]. ...
... In addition, various adsorbents were developed as adsorption agents in the AD system to enhance the system performance [15][16][17][18][19][20][21][22][23][24][25][26]. The performance evaluation studies of the AD system were conducted with FAM-Z01, which is manufactured based on zeolite material [15][16][17][18]. The FAM-Z01 has an S-shape isotherm graph, and the adsorption and desorption rates may exhibit sudden jumps at certain relative pressure values. ...
... Therefore, the AD system with FAM-Z01, which has S-shape isotherm characteristics, can utilize a lower hot-water temperature for the desorption process. Hong et al. [17] and Kim et al. [18] showed the system performance of the AD system with FAM-Z01 and demonstrated the excellent effect of the S-shape isotherm characteristics on the system performance. In addition, a new class of metal organic framework (MOF) adsorbents was developed, which have been projected as next-generation adsorbents due to their advantages such as high surface area, high degree of porosity, and possible fine-tuning of chemical structure [19][20][21][22][23][24][25][26]. ...
In this study, the performance evaluation of an adsorption chiller (AD) system with three different adsorbents—silica-gel, aluminum fumarate, and FAM-Z01—was conducted to investigate the effects of adsorption isotherms and physical properties on the system’s performance. In addition, the performance evaluation of the AD system for a low inlet hot-water temperature of 60 °C was performed to estimate the performance of the system when operated by low quality waste heat or sustainable energy sources. For the simulation work, a two-bed type AD system is considered, and silica-gel, metal organic frameworks (MOFs), and ferro-aluminophosphate (FAPO, FAM-Z01) were employed as adsorbents. The simulation results were well matched with the laboratory-scale experimental results and the maximum coefficient of performance (COP) difference was 7%. The cooling capacity and COP of the AD system were investigated at different operating conditions to discuss the influences of the adsorbents on the system performance. Through this study, the excellence of the adsorbent, which has an S-shaped isotherm graph, was presented. In addition, the influences of the physical properties of the adsorbent were also discussed with reference to the system performance. Among the three different adsorbents employed in the AD system, the FAM-Z01 shows the best performance at inlet hot water temperature of 60 °C, which can be obtained from waste heat or sustainable energy, where the cooling capacity and COP were 5.13 kW and 0.47, respectively.
... 85 The isotherms are usually strongly sigmoidal. [3][4][5][6] AlPO 4 -5 has the AFI type zeolite structure and contains 1-dimensional micropores with a diameter of 0.742 nm. 86 The materials, presented in the following, contain some iron in addition. ...
... 86 The materials, presented in the following, contain some iron in addition. [3][4][5] Fig. 11 shows that the experimental water sorption isotherm follows eqn (24). Another literature source 5,50,75 has the advantage that it contains a XRD spectrum that proves the crystallographic structure. ...
... [3][4][5] Fig. 11 shows that the experimental water sorption isotherm follows eqn (24). Another literature source 5,50,75 has the advantage that it contains a XRD spectrum that proves the crystallographic structure. Also a N 2 adsorption at 77 K is provided in that literature. ...
Based on the biochemical multi-site receptor-ligand theory of Klotz (1946) a sigmoidal proceeding adsorption isotherm is derived. The special case of an arbitrarily large number of equal interaction sites and a separate one yields an equation which corresponds to the -isotherm differently derived by Ward et al. (2007) for surface tension of solid-fluid interfaces. From the mathematical point of view it is analogous to the BET-isotherm for a limited number of adsorption layers (1938). It is shown that the isotherm maps type IV and V isotherms. The isotherm is compared with others including the type IV isotherm of Do and Do (2009). The present isotherm is unified in contrast to existing hybrid models. It is successfully applied to numerous literature data concerning the adsorption of water on microporous carbon.
... However, although adsorption systems have the advantages mentioned above, they are characterised by low thermal efficiency emanating from poor heat and mass transfer, resulting in low process efficiency [4][5][6]. The performance of adsorption systems is strongly linked to the sorption pair's behaviour: adsorption isotherms and kinetics [7]. Considerable research has been undertaken to improve the component-level adsorption cooling and water desalination systems [8]. ...
... Additionally, the primary purpose of this study was to evaluate the system performance of an adsorption chiller working with the novel composite adsorbents developed here. Many empirical isotherm models have been developed to determine the isotherms based on several properties such as the heat of adsorption, temperature-dependent saturation, amount of loading to create a monolayer coverage per unit volume of the packing media (solid saturation loading) and adsorption equilibrium constant [7,48,49]. Examples of such models include Sips, Dubinin-Astakhov, Tóth, Henry, Freundlich, Langmuir, Temkin and Hill-de Boer; each broadly suits a specific isotherm type. In this study, the developed composites showed type II isotherm with water, which can be modelled using the Dubinin-Astakhov (D-A) adsorption isotherms model, as stated by Eq. (2) [50]. ...
... In addition, SAPO-34, named FAM-Z02, is another proven successful example of this strategy. It possesses a high adsorption capacity at a very low P/P o , i.e. <10 % [82,83]. ...
... AlPO 4 -5 (Table 1, Entry 5) is among the most commonly synthesized structures for dehumidification and water adsorption applications [82]. The water adsorption isotherms of AlPO 4 -5 were investigated and categorized as type V and showed three filling steps, as illustrated in Fig. 2, compared to the isotherms of other sorbate species, such as methane and deuterium, which display type I isotherms. ...
Freshwater resources are being heavily depleted and not replenished at the same high rate, thus, atmospheric water vapor harvesting has earned growing interest. Development of high-performing desiccant or adsorbent materials offering high sorption capacity and selectivity as well as regeneration capability in atmospheric conditions is crucial to tackle water scarcity. The required properties to generate potent water sorbents include pore accessibility, high specific surface area and porosity to enable high capture capacity and kinetics, and hydrothermal resilience to resist cyclic sorption and desorption. Further, polarity, hydrogen bonding, adhesion ability of water molecules to adsorbent surface, and hydrophilic functional groups can boost water adsorption. A highly promising class of water vapor adsorbents is the aluminophosphate molecular sieves (AlPOs), which are microporous zeotype materials. In this review, AlPO-based adsorbents are discussed for water sorption applications and a link is established between performance of materials and their chemical and morphological properties. Synthesis-properties-performance relationships are elucidated in light of synthesis techniques and adsorption behavior, and prospects to enhance AlPOs' water vapor sorption performance toward large-scale water harvesting applications are highlighted.
... Utilizing renewable energy in desalination system has high interest from researchers. Adsorption desalination-cooling systems (ADCS) have been becoming a promising alternative to traditional cooling and desalination systems avoiding their common problems such as high energy consumption and global warming [4]. Unlike the traditional units, a sorption system utilizes low-grade heat from renewable sources or industrial wastes to produce freshwater and cooling effect [5][6][7]. ...
... Ferroaluminophosphate/water was presented as an adsorption pair for ADCS by Kim et al. [4]. Characteristics of adsorption were experimentally tested. ...
In the present study, benefits of utilizing acid activated montmorillonite as a proposed new adsorbent material in adsorption desalination-cooling systems-have been experimentally expressed. Montmorillonite is a natural clay mineral which is composed mainly of alumina-silicate. Effect of acid activation on montmorillonite has been illustrated using infra-red spectra analysis. Adsorption characteristics (isotherm and kinetic) of acid activated montmorillonite (with 2 mole of hydrochloric acid/water vapor pair have been expressed. Isotherms results have been fitted with Dubinin-Astakhov and Sun-Chakraborty models. An experimental adsorption desalination-cooling test rig has been erected to explore the adsorption desalination-cooling systems performance with montmorillonite /water pair and axial finned tube adsorption bed design. The experimental results indicates that the daily water production is about 4.4 m 3 /ton of montmorillonite, its specific cooling power is 110 W/kg and the coefficient of performance is 0.41 at a driving temperature less than 100 • C. Solar energy can drive adequately the investigated system. The experiment also illustrates that the ADCS is very significant in removing all forms of salts, as proven by the weighty drop of the total dissolved salt, TDS (measured by TDS analyzer), level from approximately 40,000 ppm in seawater intake to less than 30 ppm.
... Fitted model is not available (i) Hu et al. [18] (ii) Cychosz et al. [19] ( (i) El-Sharkawy et al. [20] (ii) Rahman et al. [21] (iii) Pal et al. [22] (iv) Pal et al. [23,24] (v) Pal et al. [23,24] (vi) Wang et al. [25] (vii) Brancato et al. [26] (viii) Berdenova et al. [27] (ix) Pal et al. [28] (x) Younes et al. [29] (i) PBA/water at 25 °C (ii) Alumina/water at 20 °C (iii) PCB/water at 22 °C Type-II (i) GAB model (ii) BET model (iii) Not fitted (i) Sultan et al. [30] (ii) Naono et al. [31] (iii) Wang et al. [32] (i) ACP/water at 30 °C (ii) Dried fruits/moisture Type-III (i) D-A model (ii) GAB model (i) Sultan et al. [30] (ii) Maroulis et al. [33] (i) Oxidized carbon/water (ii) PVDC/water at 35 [34] (ii) Do et al. [34] (iii) Rakitskaya et al. [35] (i) IRMOF-74-V-hex/argon at 87 K (ii) IRMOF-74-V-hex/nitrogen at 77 K (pore size less than 4 nm) Type-IV(b) The fitted model is not available (i) Cho et al. [36] (ii) Cho et al. [36] (i) ACF/water at 30 °C (ii) Hydrophobic carbon/water (iii) AQSOA-Z01/water and AQSOA-Z02/water (iv) Ferroaluminophosphate/water (v) AQSOA zeolite/ water [30] (ii) Do et al. [34] (iii) Kayal et al. [37] (iv) Kim et al. [38] (v) Teo et al. [39] (vi) Brancato et al. [40] [41] (ii) Yahia et al. [42] * Activated carbon from various biomass sources. ...
... The hybrid model proposed by Kim et al. [38] comprising both the Henry and Sips isotherms includes nine parameters that are physically meaningful. The hybrid model is expressed as, ...
Adsorption heat transformation (AHT) systems can play a major role in protecting our environment by decreasing the usage of fossil fuels and utilizing natural and alternative working fluids. The adsorption isotherm is the most important feature in characterizing an AHT system. There are eight types of International Union of Pure and Applied Chemistry (IUPAC) classified adsorption isotherms for different “adsorbent-adsorbate” pairs with numerous empirical or semi-empirical mathematical models to fit them. Researchers face difficulties in choosing the best isotherm model to describe their experimental findings as there are several models for a single type of adsorption isotherm. This study presents the optimal models for all eight types of isotherms employing several useful statistical approaches such as average error; confidence interval (CI), information criterion (ICs), and proportion tests using bootstrap sampling. Isotherm data of 13 working pairs (which include all eight types of IUPAC isotherms) for AHT applications are extracted from literature and fitted with appropriate models using two error functions. It was found that modified Brunauer–Emmet–Teller (BET) for Type-I(a) and Type-II; Tóth for Type-I(b); GAB for Type-III; Ng et al. model for Type-IV(a) and Type-IV(b); Sun and Chakraborty model for Type-V; and Yahia et al. model for Type-VI are the most appropriate as they ensure less information loss compared to other models. Moreover; the findings are affirmed using selection probability; overall; and pairwise proportion tests. The present findings are important in the rigorous analysis of isotherm data.
... Due to evaporation of seawater at temperatures below 35 °C, scaling and corrosion are rare in the evaporator [7]. Ng and his collaborators [8][9][10][11][12] have made great contributions to the research and development of adsorption desalination. However, adsorbent performance decreases after being used for a period of time and control of the adsorber beds is complex. ...
... Due to evaporation of seawater at temperatures below 35 • C, scaling and corrosion are rare in the evaporator [7]. Ng and his collaborators [8][9][10][11][12] have made great contributions to the research and development of adsorption desalination. However, adsorbent performance decreases after being used for a period of time and control of the adsorber beds is complex. ...
The paper presents an experimental investigation of a steam ejector in a single-effect thermal vapor compression (S-TVC) desalination system driven by a low-temperature (below 100 °C) heat source. To investigate the performance of the steam ejector in the S-TVC desalination system, an experimental steam ejector system was designed and built. The influences of the nozzle exit position (NXP), operating temperatures, and the area ratio of the ejector (AR) on the steam ejector performance were investigated at primary steam temperatures ranging from 40 °C to 70 °C, and at secondary steam temperatures ranging from 10 °C to 25 °C. The experimental results showed that the steam ejector can work well in the S-TVC desalination system driven by a low-temperature heat source below 100 °C. The steam ejector could achieve a higher coefficient of performance (COP) by decreasing the primary steam temperature, increasing the secondary steam temperature, and increasing the AR. The steam ejector could also be operated at a higher critical condensation temperature by increasing the primary steam temperature and secondary steam temperature, and decreasing the AR. This study will allow S-TVC desalination to compete with adsorption desalination (AD).
... Two theoretical models were used to validate the water sorption properties of the MDCs obtained from the water adsorption analyses and further expand their practical application range. The first model used was the Henry-Sips model, expressed as follows: [34] where q is the equilibrium adsorption capacity, q m is maximum adsorption capacity, p is the equilibrium pressure (in kPa), p 0 is the saturation pressure (in kPa), K H is the Henry constant, K s is the Sips constant, and n is the degree of surface nonhomogeneity. The second model is the Do-Do model, expressed by the following equation [35,36]: ...
The characteristics of water vapor adsorption depend on the structure, porosity, and functional groups of the material. Metal–organic framework (MOF)-derived carbon (MDC) is a novel material that exhibits a high specific area and tunable pore sizes by exploiting the stable structure and porosity of pure MOF materials. Herein, two types of aluminum-based MOFs were used as precursors to synthesize hydrophobic microporous C-MDC and micro-mesoporous A-MDC via carbonization and activation depending on the type of ligands in the precursors. C-MDC and A-MDC have different pore characteristics and exhibit distinct water adsorption properties. C-MDC with hydrophobic properties and micropores exhibited negligible water adsorption (108.54 mgg−1) at relatively low pressures (P/P0~0.3) but showed a rapid increase in water adsorption ability (475.7 mgg−1) at relative pressures of about 0.6. A comparison with the isotherm model indicated that the results were consistent with the theories, which include site filling at low relative pressure and pore filling at high relative pressure. In particular, the Do–Do model specialized for type 5 showed excellent agreement.
... This type of technology is used in the industry, where the adsorption process is used in the first phase (evaporation process) to produce cooling energy. In the second phase, fresh water is obtained during desorption and condensation [23][24][25]. ...
The paper presents an innovative concept of the fluidization of an adsorption bed carried out under low-pressure conditions. Additionally, different bed mixes were used to test the effects of the bed composition on fluidization. Fluidization was caused by the pressure difference and the velocity of the flowing water vapor. These features make the research presented in this article significantly different from other studies known in the literature and constitute the main novelty of the paper. Silica gel with a particle diameter of 200–250 µm (Geldart group B) with aluminum and carbon nanotube additives was fluidized under reduced pressure (10–25 mbar). The pressure difference results in the flow of water vapor and, consequently, induces fluidization. The pressure in the evaporator was approx. 10 mbar, while in the reaction chamber it was approx. 25 mbar. The pressure difference of about 10–15 mbar allows for a flow of water vapor between the evaporator and the reaction chamber. During the tests, the pressures, temperatures and mass were measured. The pressure drop in the bed was closely related to the mass change in the fluidized bed.
... High pollution, high cost and high energy consumption limit the further development of electric and thermal driven desalination technologies [6]. Therefore, developing low-energy desalination technologies using clean energy is essential for safeguarding our environment [7]. In addition, the increasing demand for cold energy in human society results in a large amount of high-grade electrical energy loss. ...
The adsorption desalination and cooling system (ADCS), a promising technology for alleviating water scarcity, requires adsorbents with high performance, low cost, and low energy consumption. Enhancing the operating efficiency and minimizing the energy consumption of the system entails improving the adsorption performance and thermal conductivity of adsorbents. In this study, nanoparticles (NP) embedded silica gel (SG) composite adsorbents with CaCl2 were synthesized for use in ADCS. The effects of nano-Fe, nano-Cu and carbon nanotubes (CNT) as SG thermal conductivity enhancers were thoroughly compared through microscopic properties, thermal properties and adsorption properties. The experimental results show that SG/CNT/CaCl2 composite performs the largest specific surface area and pore volume of 180.72 m² g⁻¹ and 0.13 cm³ g⁻¹. Scanning electron microscopy (SEM), accelerated surface area and porosimetry (ASAP) and constant thermal analyzer (TCA) were used to characterize the various performance of the enhanced adsorbents comprehensively. SG/CNT/CaCl2 sample exhibits high thermal conductivity and thermal diffusion coefficient, measuring as high as 0.664 W m⁻¹ K⁻¹ and 0.701 × 10⁻⁶ m² s⁻¹, respectively. Based on dynamic water adsorption performance tests, the SG/CNT/CaCl2 composite had an adsorption capacity of 0.665 g g⁻¹, five times higher than SG. The composite’s adsorption capacity and thermal conductivity did not decline significantly during cycling, indicating a high degree of sustainability. Therefore, these results imply that the nanoparticles-embedded SG/CaCl2 adsorbent with excellent integrated properties has promising prospects in adsorption desalination systems.
Graphical abstract
It was investigated how different embedded nanoparticles affected the thermal and adsorption performance of SG. The results showed that the composite SG/CNT/CaCl2 exhibited the best performance, with the thermal conductivity and adsorption capacity being enhanced to 0.664 W m⁻¹ K⁻¹ and 0.665 g g⁻¹, respectively.
... For example, ferro-aluminophosphate adsorbent (FAM-Z01), partially iron exchanged AlPO-5 material with 2−8 mol % iron content, was evaluated for possible application in adsorption desalination and cooling cycles and gave promising results. 144 As already mentioned, the very steep water uptake of zeolites at low P/P 0 demands a high regeneration (desorption) temperature. On the other hand, the very high hydrophobic nature and hence the evident absence of stepwise adsorption for pure silica gel adsorbents make them less suitable for applications such as adsorption heat pumps and dehumidification. ...
In recent years, the deployment of chemically stable physisorbents in various water sorption-related applications has received significant attention. Depending on their structural features, different types of porous sorbents manifest distinct shapes of water sorption isotherms. The translation of water sorption profiles of adsorbents into appropriate practical applications is yet to be established. This Review gives an overview of the water adsorption studies conducted on different hydrolytically stable porous solids selected from different classes of solid-state materials (organic, inorganic, and hybrid materials). Brief analyses of the water sorption behavior and the relations to materials' intrinsic structural features are made. Based on adsorbents' observed water sorption characteristics, the prospects of their practical/commercial deployment in chosen sectors are also commented. The criteria for using porous adsorbents in specific water-related technologies, which can help guide the design and assembly of suitable water adsorbents, are also reviewed. In addition, the challenges that need to be overcome in developing efficient water vapor adsorbents for a given application are also discussed.
... An experimental work is performed on the N 2 gas adsorption followed by water uptake behavior on FAMZ01 at a temperature ranging from 293 K to 353 K for the potential use in adsorption cum desalination system (ACDS) [177]. Furthermore, a hybrid AIM (combination of Henry and the Sips isotherms) for water adsorption on the FAM-Z01 adsorbent is proposed. ...
Due to the ever-increasing cooling demand, alternative refrigeration is being explored for the last few decades that are less energy-intensive and can utilize ozoenvironmental friendly working fluid. Vapor adsorption refrigeration is one of the most promising alternatives among all heat-driven refrigeration systems. One of the most important requirements in an adsorption-based cooling system is to enhance the adsorption uptake capacity of the adsorbent materials for their impactful, effective, and economical operation. However, there are several working pairs explored during the recent decades but none of them could be suitable as an ideal one, for all the operating conditions. In this article, the various characteristics of different adsorbents including the highly porous activated carbons derived from waste biomass, the composites, and compounds developed, are thoroughly reviewed. Further, the synthesization, the optimal assortment, regeneration, coatings on adsorber, and commercial application of novel adsorbents including the advanced adsorption reactors and the current scenario of industrial adsorption chillers are discussed in detail. Finally, the impact of operating parameters, such as adsorbent-adsorbate mass ratio, desorption pressure, operating temperatures, and adsorption/desorption cycle time on the specific cooling power, coefficient of performance, and the chiller efficiency are summarized.
... The adsorption amount is expressed in isotherms, and the isotherm of FAM-Z01 was applied, which was extracted from Hong et al. [28] was applied. Eq. (10) is a combined isotherm equation of both the Henry and Sips equations for FAM-Z01, proposed by Kim et al. [29]. ...
3-bed adsorption cooling systems have the advantage of maintaining a uniform chilled water temperature. Because the number of parameters in a 3-bed system is very large, using artificial neural networks (ANN) is often suggested as an alternative to conducting experiments in many recent studies. We systematically determined the optimal time allocation for a 3-bed, 2-evaporation adsorption cooling system, using ANN with five variables, i.e., adsorption/desorption time ratio (f ad), high/low evaporator time ratio (f p), cycle time (τ), and the time lag between each adsorption bed (δ 2 , δ 3). Each case was methodically modeled using a process that our research team had previously developed and verified. When the coefficient of performance (COP) and specific cooling power (SCP) estimated by ANN were compared with the actual results, errors were within ±4%. Finally, the best strategy for each performance indicator, i.e., COP, SCP, and standard deviation of chilled-out temperature, was proposed for the 5 operating parameters of f ad , f p , τ, δ 2 , and δ 3. The cycle time was found to have 42.9% relative importance for the COP, and 33.1% relative importance for the SCP, but the most influential factor to the SCP was the high/ low pressure evaporator time ratio with a relative importance of 33.3%.
... The adsorption amount is expressed in isotherms, and the isotherm of FAM-Z01 from Ref. [36] was applied. Eq. (10) is a combined isotherm equation of both the Henry and Sips equations for FAM-Z01, proposed by Ref. [37]. ...
An adsorption chiller is a highly promising cooling technology, but it has not been widespread because there are many uncertainties to solve the complex thermal and mass transfer phenomena. An adsorption chiller is composed of multi-modules and the tube inlet temperature decreases (or increases) during the adsorption process (or desorption process) from module to module in serially connected modules. It has been reported that the optimal fin height depends on the tube inlet temperature, thus using a different fin height for each module should potentially enhance the overall system performance of the adsorption chiller. Till now, there have been few studies which evaluated adsorption chiller performance from a system viewpoint. Most only considered a single fin space. Thus, no study has considered improving total system performance by using different conditions for different modules in series. We conducted a numerical study of 5 modules in series, using different fin heights. The coefficient of performance (COP) and specific cooling power (SCP) of modules with stepwise-linearly decreasing fin height were compared with those of modules with constant fin height. An 8.5% increase in COP and a 9.56% increase in SCP were observed. This enhancement will be much larger if more than five modules are connected to match the cooling capacity. The decrease (or increase) in tube inlet temperature accumulated in the series of modules. The last module, the 5th showed the most significant enhancement in COP and SCP, of 27.9% and 38.4%, respectively.
... The isotherm of FAM-Z01 was described in [23,44], and the thermophysical properties of FAM-Z01 and the Epoxy resin binder are listed in Table 2. ...
Most previous studies on adsorption chillers were conducted using the same adsorption and desorption times. Instead, this study analyzed various adsorption/desorption time allocations, and systematically examined the effect of cycle time allocation on system performance. The results provide physical insights for 3-bed adsorption chillers. The effect of hot water temperature and cycle time on the optimum adsorption/desorption time ratio was also examined. Setting the proper adsorption and desorption times was much more important for smaller cycle times. The highest degradation in COP (coefficient of performance) found was 36 % at 300 s of cycle time, compared with the conventional 1:1 ratio. When the temperature of the heat source is low, the ratio of adsorption/desorption time was not significantly affected, however, for higher performance at high temperature, a longer adsorption time than desorption time was required.
... To evaluate and extend the usage range of the data, the adsorption isotherms from the experiment were fitted into Henry-Sips model (Kim et al., 2014): ...
Adsorption thermal energy storage plays a vital role in supporting the availability of renewable energy. Activated carbons produced from local waste biomass have been attracting considerable attention in adsorption technology due to their unique properties and sustainability. However, their limitation in water vapor uptake hinders the practical application of this material. In this work, acorn nutshells were utilized as a base material to produce activated carbon. Air oxidation was performed as a versatile and low-cost technique to enhance the material’s properties and water adsorption capacity. By applying air oxidation as a post-treatment during material production, the amount of active functional groups and the water adsorption on activated carbon has been successfully enhanced. From the theoretical calculation, it is found that activated carbon–water working pairs shown promising performance to be used for adsorption thermal energy storage applications. The adsorption of water vapor on the post-treated-activated carbon releases the isosteric heat between 2400 kJ/kg to 2500 kJ/kg. Moreover, this study’s working pair can be driven by a temperature of less than 50 °C. From the results, it is confirmed that by controlling the adsorbent’s surface properties, activated carbon–water working pairs can be a promising way to provide alternative material and reduce the energy demand for driving the system.
... Muttakin et al. [3] fitted different isotherm models for different types of IUPAC classified adsorption isotherms. Kim et al. [4] fitted Hybrid model, which was a combination of Henry and Sip's models, for water adsorption onto ferroaluminophosphate. But, still there is a lack of information about the selection of the most suitable model for different types of isotherm also the reason behind selection in terms of statistical point of view. ...
In this study, HYBRID and RMSD error functions are used to calculate the error deviation between the experimental and predicted data for carbon based composite/CO2 and AQSOA-ZO1/water pairs. For fitting, six isotherm models, namely Dubinin-Astakhov (D-A), Modified D-A, Tòth, Langmuir, Freundlich, and Hill model are selected for the Type-I isotherm, whilst Mahle, Modified Langmuir, Sun and Chakraborty, Guggenheim-Anderson-de Boer (GAB), Hybrid model (Henry+Sips) and D-A models are selected for the Type-V isotherm. Based on error values, Tòth model provides less error compared to other models for Type-I, likewise Sun and Chakraborty model for Type-V isotherm. Seven information criterion (IC's) are employed to predict the optimum isotherm model for the studied pairs. Here, 1000 bootstrap samples are taken to measure the accuracy of sample estimation and error is measured for each sample. Hence, the error distribution is found with average error and confidence interval (CI). Using average error, all IC's are calculated. On the basis of IC's, Tòth model provides less information loss compared to other models for Type-I isotherm, similarly Sun and Chakraborty model provides less information loss for Type-V isotherm. This analysis found that using bootstrap HYBRID mean error Sun and Chakraborty model reduces 4% more information loss compare to modified Langmuir model of Type-V isotherm. Introduction In order to standardized experimental data of different adsorbent/refrigerant pairs, it is important to correlate with different isotherm models. Generally, isotherm data are correlated applying various isotherm models where the best fitted model is used to analyse the system performance. For instance, Pal et al. [1] used Tόth and modified D-A models for CO2 adsorption onto composite, Kayal et al. [2] used D-A, modified Langmuir, and Sun & Chakraborty models for water adsorption onto AQSOA zeolite. Muttakin et al. [3] fitted different isotherm models for different types of IUPAC classified adsorption isotherms. Kim et al. [4] fitted Hybrid model, which was a combination of Henry and Sip's models, for water adsorption onto ferroaluminophosphate. But, still there is a lack of information about the selection of the most suitable model for different types of isotherm also the reason behind selection in terms of statistical point of view. In this study, statistical information criteria using bootstrap sample has been used to select the optimized isotherm model for Type-I and Type-V isotherms. Two sets of equilibrium adsorption data, CO2 onto a carbon based consolidated composite [1] and water onto AQSOA zeolite [2], are investigated to find the optimum isotherm model. Two error functions, RMSD and HYBRID, are used to optimize the fitting parameters. Using R-programming, bootstrap samples of N = 1000 are taken and model selection criteria are used for finding optimum isotherm model.
... Regenerated vapors from the desorber are condensed on the surfaces of the condenser and are collected as potable water [24]. It is well known that the performance of the AD cycle depends on the adsorbents [25,26]. A considerable number of studies have been conducted on adsorbents such as silica gel and zeolite [16,17,[27][28][29]. ...
... Zejli et al. reported the simulation results on a solar adsorption desalination device in 2004 [9]. Recently, adsorption desalination has gained reasonable interest (Theoretical development and experimental confirmation of conventional and advanced adsorption desalination cum cooling cycles by Thu et al. [10,11]; Ng et al. on the overview of adsorption desalination as an emerging low-cost desalination method [12]; adsorption characteristics of ferroaluminophosphate for desalination cycle by Kim et al. [13]; single and two-stage adsorption desalination cum cooling cycle by Mitra et al. [14,15]; Wu et al. on the relative performances of various adsorption desalination cycles in terms of specific energy consumption and fresh water productivity [16]; performance comparison of adsorption desalination system utilizing AQSOA-Z02 and silica gel as adsorbents by Youssef et al. [17]) together with possible hybridization for improved performance (Hybridization of adsorption desalination with multi-effect desalination (ADMED) by Thu et al. [18,19]; Shahzad et al. on the emerging hybrid multi-effect distillation and adsorption desalination system [20]; regenerative adsorption distillation system using adsorption and distillation principles by Ng et al. [21]; numerical study on a novel integrated thermal-/ membrane-based solar energy-driven hybrid desalination system by Kim et al. [22]; the theoretical development and the numerical simulation on the multi-effect adsorption desalination (MEAD) system by Thu et al. [23]; theoretical simulation on the hybridization of adsorption desalination and reverse osmosis by Ali et al. [24]). Moreover, the widespread applications of renewable energy sources call for advanced energy storage techniques whilst adsorption related energy storage systems gained significant attention [25][26][27][28]. ...
... As CuSO4 has high DRA about 97 % at 25 o C which makes CuSO 4 remain in its solid state if RH less than 97%[26].According to literature survey, introducing new adsorbent pairs and investigate their adsorption characteristics are very important for modelling and improve the performance of adsorption cooling systems. The dehydration of the CuSO 4 for the first four molecules can be driven by low temperature heat source 60-85 o C. The chemical reaction (CuSO 4 and water vapor) is a reversible process. ...
In this study benefits of employing copper sulfate salt hydrate with water vapor as a new adsorption pair in thermally driven adsorption desalination-cooling systems (ADCSs) have been investigated. Adsorption characteristics (isotherm and kinetic) of copper sulfate/water vapor pair have been presented in this study within temperature range of 25-55°C. Sun-Chakraborty (S-C) and Dubinin-Astakhov (D-A) models have been used for fitting isotherms results, while linear driving force (LDF) model has been used for the kinetics results. Experimental adsorption capacity of water vapor onto copper sulfate is found to be around 0.51 kg/kg at 25 C. Activation energy (Ea) and the pre-exponential coefficient (Dso) are estimated to be 25.053 kJ/mol and 1.89×10 m /s respectively. A
theoretical model for an ADCS has been investigated employing copper sulfate as adsorbent material. The proposed system can produce specific daily water 3 production about 8.2 m per ton of copper sulfate, 227 W/kg of copper sulfate specific cooling power and 0.57 coefficient of performance. The performance of the modeled system indicates that the proposed system can be driven efficiently by renewable energy such as solar energy.
... This isotherm type is observed for water adsorption onto different types of zeolites. This isotherm curve is discernible by initial low uptake attributed to the adsorption onto non-polar or weakly polar pore surface [48] followed by an abrupt rise in adsorption due to the hydrophilic nature of adsorbent allowing micropore filling with condensed water. Subsequently, the uptake rise reduces after a threshold adsorption has been achieved. ...
An adsorption chiller requires thermal energy to regenerate the adsorbent by desorbing the refrigerant vapor. Minimum desorption temperature is the parameter which defines the lowest possible heat source temperature required for driving adsorption chiller. In this study minimum desorption temperature is evaluated for different types of adsorption isotherms classified by International Union of Pure and Applied Chemistry (IUPAC). For each type, adsorption isotherm model is utilized to estimate the minimum desorption temperature and then compared to the mathematical expression reported in literature derived using Dubinin-Astakhov isotherm model. This allows for critical scrutiny of the universal validity of mathematical expression. It is observed that this expression can estimate the minimum desorption temperature with reasonable accuracy for all isotherm models.
... Different studies illustrated the adsorption characteristics includes isotherms and kinetics for different adsorbent materials with water vapor that can be used in AD applications. For example, Kim et al. [4] presented ferroaluminophosphate for adsorption desalination (AD) system as a new adsorbent material. The adsorption characteristics of ferroaluminophosphate/water vapor pair were experimentally studied. ...
... The performance ratio of the MEAD cycle was reported as high as 6.3 and the cycle-averaged specific water production rate was about 1.0 m3/h per ton of silica gel. Kim et al. investigated the potential of ferroaluminophosphate as a novel adsorbent in a temperature range from 20°C to 80°C [24]. A hybrid isotherm consisting of Henr's and Sips' isotherms successfully captured the unique trend of the uptake ratio, i.e., a monotonous increase followed by a sudden jump with respect to the vapor partial pressure. ...
This paper introduces a novel time-scheduling scheme for adsorption desalination (AD). Mathematically, a critical bed pressure of the Toth isotherm is defined as the pressure above which the uptake ratio scarcely changes. Heat balance equations of sorption beds for precooling, adsorption, preheating, and desorption are unified into a single equation. This general governing equation is used to model AD systems, which consists of an arbitrary number of bed pairs with specifically preset initial thermal phases. A theoretical minimum of switching interval is derived as a function of thermal properties of reaction beds and heat exchangers. In the new time scheduling scheme, no bed pairs are in an identical process schedule, because each bed has its initial time lag (ITL) when the operation starts. We found that specific AD performances vary noticeably depending on the ITL values, the num- ber of beds, and more importantly, the number of beds in a time-lag group. There must be an optimal ITL for given operational parameters, which can distinctly increase the water production rate without using extra heat sources. This can dynamically optimize the relative performance of desalination rates and cooling capacities of AD processes.
Water-based adsorption chillers (ADC) driven by low-grade thermal energy are environment-friendly alternatives to the traditional compression ones to realize the net zero carbon target. Aluminophosphates molecular sieve (AlPOs) is an excellent material for water-based adsorption applications. However, AlPOs suffers from relatively high cost attributed to the extensive use of expensive structure direct agents (SDAs). This study employed a dual-template method, using cheap organic amine as a dual-template, to synthesize low-cost and excellent adsorbent AlPOs with SFO topology (AlPO-SFO). AlPO-SFO synthesized with dual templates shows high crystallinity, large micropore volume, excellent water uptake, and low regeneration temperature. AlPO-SFO guided by 4-dimethylaminopyridine (4-DMAPy) and diethanolamine (DEOA) molar composition of 0.4 and 0.1 exhibits large microporous volume (0.30 ml g⁻¹), high water uptake (0.26 g g⁻¹ at P/P0 = 0.25) and low regeneration temperature (65 °C). Importantly, this AlPO-SFO exhibits a high coefficient of performance (COP) of 0.89 for cooling at a low driven temperature of 64 °C. The additive amine providing alkaline medium ensures the practical synthesis of AlPO-SFO when expensive 4-DMAPy decreases, endowing the 42 % reduction of the raw material cost. The results provide a cheaper synthesis route of AlPO-SFO, which is conducive to its large-scale production as a distinguished adsorbent for adsorption chillers.
Heavy metal pollution is an urgent challenge worldwide due to the acceleration of industrialization. While adsorption desalination is regarded as an innovative method for wastewater treatment, the current technologies have been impeded by high costs and intensive energy consumption. In this work, a novel low-temperature evaporation wastewater treatment apparatus based on hydrate adsorption was proposed. The water vapor from wastewater evaporation reacted with CO2 to form hydrate under the pressure of 3.3 MPa, constantly promoting wastewater evaporation due to the consumption of water vapor. The effect of feeding concentration on treatment effect was analyzed in terms of removal efficiency, water yield, and enrichment factor. Remarkably, a maximum removal efficiency of 97.4% can be achieved by treating an artificial solution with a Cu2+ concentration of 500 mg/L. Furthermore, compared with the control group that only depended on evaporation and condensation without forming hydrate, the maximum water yield of purified water in the experimental group increased to 310%. This innovative design concept for a low-temperature wastewater treatment apparatus based on hydrate adsorption presents a promising solution for the green and energy-efficient treatment of heavy metal wastewater.
Adsorption cooling and desalination (ACD) system presents a solution for water, energy, and environmental dilemma. This study expresses an enhancement of adsorption system performance in terms of cooling and desalination effects by improving an activated carbon Maxsorb III (Max) as an adsorbent. Max has been initially treated with HCl. Then, it has been activated by impregnating it in salt hydrates ((NH 4 ) 2 CO 3 ). Characterization methods, including XRD, N 2 and water adsorption isotherm, and water adsorption kinetics have been conducted for raw Max, treated Max, and activated Max with (NH 4 ) 2 CO 3 . The experimental values have been fitted with the Dubinin & Astakhov equilibrium model for isotherm and the model of linear driving force for kinetics. These fitted parameters have been utilized in a previously validated model to estimate adsorption cooling-desalination system performance with and without heat recovery. Max/(NH 4 ) 2 CO 3 achieves a water uptake of 0.53 kg H2O .kg ⁻¹ . Max/(NH 4 ) 2 CO 3 produces 13.2 m ³ .ton ⁻¹ of freshwater per day with a specific cooling power of 373 W.kg ⁻¹ and 0.63 COP. Also, the freshwater reaches 22.5 m ³ .ton ⁻¹ of Max/(NH 4 ) 2 CO 3 per day with condenser-evaporator heat recovery. These results indicate the potential of utilizing the Max material in dual cooling and desalination applications to achieve double what silica gel can offer.
Adsorption desalination is prescribed as a promising and eco-friendly solution for mitigating water scarcity, owing to its utilization of low-grade thermal waste and zero liquid brine discharge. The keystones that regulate the performance of the adsorption desalination system (ADS) include nature of adsorbents, system design, and operating conditions. The present study aims to provide a state of the art review on the keystones of ADS. Metal-organic frameworks (MOFs) hold remarkable adsorption capacity and tunable structure. However, hydrothermal instability, high cost, and complex synthesizing procedures are the potential challenges that need to be addressed. The technological advancements in ADS have been classified into: (i) Conventional Approach, (ii) Heat and Mass Recovery Approaches, (iii) Hybridization Approaches, (iv) and Adsorbent Substituting Approach. The study provides critical insight and compares the performance of each approach based on specific daily water production (SDWP), specific cooling power (SCP), and coefficient of performance (COP). The conventional ADS produce SDWP of 4.7 m3/ton/d, however producing zero and/or minimal SCP while using payable energy of 1.50 kWh/m3. In heat/mass recovery approaches, pressure equalization-valve delay schemes and master–slave configuration provide ∼ 5 % additional water adsorption/desorption on/from silica-gel and reduce ∼ 50 % thermal heating load, respectively. Evaporator-condenser amalgamation emphasizes the evaporator temperature of 30–42 °C leading towards ∼ 69 % higher SDWP with zero SCP. Dual stage, multi evaporators/condensers scheme is found supportive in cogenerating feature of ADS thereby improvising COP to ∼ 0.87. In hybridization approach, ejector integrated ADS produces SDWP of 80 m3/ton and COP of 2.22 using payable energy of 0.92 kWh/m3, however, needs experimental validation. In the adsorbent substituting approach, CPO-27(Ni), Emim-Ac/Syloid 72FP, and composite adsorbent manifest the SDWP to higher levels. The operating conditions are sensitive and need to optimize depending on the configuration of ADS. Possible future research directions may include efficient designing/ sizing of evaporators/ condensers, minimizing the heat and mass transfer resistances in adsorber/desorber reactor, optimize the thickness of the adsorbent layer in heat exchangers, and investigating wide range of adsorbent classes that can be driven with very low regeneration temperature.
This study aims to reduce adsorption desalinated water cost by innovative employing silica gel/CaCl2 composite and novel silica gel/(NH4)2CO3 activated materials. Raw silica gel (SG), which served as the host matrix, was acid-treated and impregnated with CaCl2 and (NH4)2CO3. The prepared samples characteristics (XRD, N2 adsorption, water vapor adsorption) have been investigated and compared to the raw SG. A simulation model has been used to investigate the impact of the study samples on adsorption desalination (AD) system performance with and without heat recovery (HR). The study also includes a cost analysis of the AD water production system (using the tested materials) that uses solar energy or a waste heat source. The SG/CaCl2 achieved the highest water adsorption (0.95 kgH2O/kg) with a SDWP of 23.3 m³/ton per day, SCP 660 W/kg, and COP 0.71. With HR, the system could produce 35 m³/ton of SG/CaCl2 per day SDWP. The study concluded that the tested samples outperform the raw material as the total production cost of AD water using SG/CaCl2 has been reduced to approximately 37% using solar energy and 60% using waste heat as a regenerative heat source.
This paper studies improving the performance of an adsorption system by improving raw bentonite as an adsorbent. Acid treatment has been used for the pretreatment of raw bentonite. Then, a composite and activated adsorbents are prepared by bentonite impregnated in salt hydrates (CaCl2 and (NH4)2CO3). XRD, nitrogen adsorption isotherm, water vapor adsorption isotherm and kinetics are used to characterize raw and modified bentonite. Experimental results of adsorption isotherms and kinetics have been fitted using Dubinin–Astakhov equilibrium model and linear driving force model, respectively. MATLAB software has been used to solve a simulation model of an adsorption desalination system with and without heat recovery (HR). The effect of the modified adsorbents on the adsorption system performance has been investigated. The results illustrated that the surface area and pore volume of Bent/CaCl2 increased by about 200% and 500%, respectively, compared to raw bentonite. The Bent/CaCl2 achieved the highest water uptake (0.82 kgH2O.kg⁻¹). Bent/CaCl2 achieved SDWP of 11.5 m³.ton⁻¹ per day with SCP 326 W.kg⁻¹ and COP 0.52 at 85°C desorption temperature. Also, the SDWP reached 26 m³.ton⁻¹ per day with HR under the same conditions. The SDWP can be increased to 29 m³.ton⁻¹ at 95 oC desorption temperature.
Low-grade thermal-driven water-based sorption chillers and heat pumps are promising strategies to realize the near-zero-carbon target. However, developing excellent-performance water-sorption materials driven by ultralow-temperature thermal energy is still a key issue. In this study, silicoaluminophosphate with SFO topology (SAPO-SFO) synthesized by hydrothermal method is proposed as a more-effective adsorbent for water-based sorption applications. SAPO-SFO exhibits large micropore volume of 0.22 ∼ 0.28 ml g⁻¹, high water uptake of 0.24 ∼ 0.28 g g⁻¹ at P/P0 = 0.2, low regeneration temperature, and excellent hydrothermal stability. Importantly, the water-based sorption applications employing SAPO-SFO with 7 wt% Si achieve extremely high coefficients of performance of 0.86 for cooling and 1.76 for heating at low-driven temperatures of 64 °C and 82 °C, respectively. Furthermore, the mechanism of water adsorption for SAPO-SFO is revealed as that large purely siliceous regions and defects induced by uneven silicon insertion result in low enthalpy of adsorption. These results make SAPO-SFO a potential high-performance and ultralow-temperature thermal driven porous material for water-based sorption applications.
With the rapid advancement of the phosphorus chemical industry, the typical by-products have become a major challenge in maintaining the profitability of phosphorus production under the premise of protecting public health and the environment. Currently, many countries are paying increasing attention to environmental protection and numerous stringent requirements have severely restricted the development of such industries with more serious pollution as the chemical and metallurgical engineering. It is estimated that there are nearly hundreds of millions of tons of solid wastes discharged annually. Among them, the output of phosphogypsum and yellow phosphorus slag is about 80 and 9.6 million tons, which would impose onerous burdens on the environmental protection. With the increasing demand for phosphorus resources, it is crucial to achieving near-zero emissions for phosphorus chemical enterprises and continuous production. In addition, it is required to closely integrate the development and environmental protection. In this paper, a critical review was performed on the current technologies and the prospect of two conventional preparation techniques of phosphoric acid and three types of by-product utilization. Besides, the advantages and disadvantages of the conventional and unconventional production conventional processes were subjected to a comparison with respect to the production and environmental protection. Further, four unconventional wet and thermal production processes were analyzed. Moreover, the utilization prospects of related resource technologies were explored by providing the theoretical support for the realization of cross-process, cross-industry, and cross-field ecologically linked clean processing technology of three main unconventional production technologies available. Furthermore, a feasible basis for the clean processing technology of phosphorus chemical enterprises was discussed. In summary, the objective of this review is to provide guidance for eliminating the bottleneck in the development of the phosphorus chemical industry, and explore the advancement path for its green development.
Desiccant dehumidification systems can be utilized for decoupling moisture removal duty from the conventional mechanical vapor compression systems. Dehumidification using desiccant dehumidifiers is expected to exhibit a better energy efficiency. However, the high energy needed in the regeneration process limits its applicability. To realize the full potential of this technology, it is necessary to develop materials that can be regenerated using heat sources under 70 °C. In this study, activated carbons (ACs) derived from waste biomass were developed as desiccant materials. The ability of activated carbon (AC) to remove the moisture was controlled by carefully preparing the material to achieve the right operation window for optimum moisture sorption processes. The porous and surface characteristics of the newly-prepared AC were analyzed and compared with those of silica gel. The adsorption isotherm measurements were conducted, and the data were fitted with Henry–Sips and Do–Do isotherm models. The current ACs exhibit an excellent water adsorption capacity (up to 0.41 g/g). The efficacy of the ACs for dehumidification applications was assessed using the weather data from several regions of Indonesia, from North Sumatera to Papua. The results revealed that under the studied conditions, the new desiccant material showed a better dehumidification capacity than silica gel. Moreover, the reported AC can be regenerated using temperatures as low as 40 °C, which is readily available from waste heat, including the heat rejection from the condenser of an air-conditioning unit.
Indoor air humidity plays a vital role in determining occupants’ health and industrial product quality. Removing excess humidity by adsorption dehumidification is still facing a challenge in finding a suitable material with high adsorption capacity and low regeneration temperature. In this study, the theoretical dehumidification capacity of prepared acorn nutshell-based activated carbons was calculated and compared with silica gel type RD and RD-2060. The calculation was based on the outdoor air condition in two Asian capital cities: Jakarta and Tokyo. The theoretical study found that prepared activated carbon has better dehumidification performance under Jakarta conditions using regeneration temperatures of less than 60°C. Under Tokyo conditions, activated carbon shows auspicious performance during the summer season. Compared with silica gels, acorn nutshell-based activated carbon has a better dehumidification capacity to process high humidity ambient air with a lower regeneration temperature.
This study provides an in-depth analysis of the sequence of procedures required to evaluate the performance of adsorption desalination (AD) using functional adsorbent material zeolites (i.e., FAM-Z series with AFI and CHA types). The applicability of zeolite as an adsorbent for the AD cycle was also demonstrated by comparing it with the performance of AD using silica gel. The adsorption isotherm of the adsorbent, which is the most important parameter in the performance and design of the AD cycle, is recognized as a crucial parameter that significantly affects the AD performance. The thermophysical properties of the FAM-Z series were analyzed using argon adsorption and desorption isotherms at 87 K, followed by water vapor adsorption isotherms. Modified Do–Do and hybrid Langmuir–Sips isotherm models were proposed and are suitable for the anomalous stepwise isotherms of the FAM-Z series and the mesoporous adsorption characteristics of silica gel. The performance of the AD cycle was assessed in terms of the specific daily water production, specific cooling capacity, coefficient of performance, and performance ratio with respect to chilled and hot water temperatures and cycle times using a mathematical model of the AD cycle validated through a comparison with experimental data. AFI-type zeolites showed the applicability of residential (FAM-Z01) and district cooling (FAM-Z05), which have a low regeneration temperature of 55 ℃ owing to an unusual isotherm (i.e., sigmoid adsorption isotherm). In addition, FAM-Z05 exhibited considerable potential as an adsorbent for AD cycles driven by extremely low-grade heat sources (<55 ℃) found in industrial plants and solar energy.
The study aims to achieve energy savings of air conditioning systems using desiccant dehumidification with low-cost adsorbent. For this purpose, two existing activated carbons were evaluated in terms of water adsorption capacity. The theoretical calculation of effective adsorption from the water adsorption isotherms revealed that the studied activated carbons have promising potential in dehumidification application. In addition to that, the improvement of cooling COP of air conditioners was predicted by simulation of heat pump cycle. The results showed that the COP improved by 50%, which was equivalent to the reduction of electricity input by 30%, with the raise of evaporation temperature from 8.5°C to 18.5°C. The results encouraged the separation of dehumidification load from air conditioners to achieve large energy savings.
In adsorption desalination applications, adsorption isotherms are considered to be a crucial factor, significantly impacting performance. From this perspective, a number of isotherm models have been implemented to describe the adsorption characteristics of an adsorbent. However, conventional isotherm models can produce significant discrepancies in predictions of anomalous adsorption isotherms under specific operating conditions (e.g., in the presence of polar or nonpolar adsorbates). In this study, a hybrid isotherm model consisting of Langmuir and Sips isotherms was proposed. With this model, optimal compatibility is demonstrated with the adsorption isotherms of four different commercial silica gels. First, the thermophysical properties of silica gel were analyzed using nitrogen adsorption and desorption isotherms at 77 K; then, adsorption isotherms of water vapor were evaluated. The results of the hybrid isotherm model were compared with those of the conventional isotherm models (i.e., Toth and Dubinin-Astakhov) at relative pressures ranging from 0 to 0.9 at temperatures ranging from 30 to 70 °C. The hybrid isotherm model demonstrated good agreement with the adsorption data measured for all silica gels. The coefficient of determination for the hybrid isotherm model was found to be higher than 0.99 for all silica gels, unlike the coefficients for the conventional isotherm models. The hybrid isotherm model also exhibited the lowest average relative error and maximum relative error.
A numerical analysis was conducted to examine the effect of a coating technique on adsorption cooling system (ACS) performance compared to a fully-filled grain configuration. The main interest was the effect of coating thickness, binder and cycle time for adsorption cooling applications. Validation of the numerical model was confirmed by comparison with experiment. The coating configuration resulted in a larger interfacial area to open space and also a shorter length of vapor flow path compared to the fully-filled configuration, which enhanced the vapor flow and resulted in higher performance. The optimal coating thickness was found to be 0.2–0.5 mm. A short cycle time was enough for the coating configuration, which improved system performance. For example, at coating thickness t = 0.2 mm, a 34.17% enhancement in specific cooling power (SCP) was achieved with a shorter cycle time of 480 s rather than 840 s, with the penalty of 9.87% decrease in coefficient of performance (COP). The coating technique with reduced cycle time is a good design approach for adsorption cooling systems. The binder had a negative effect on system performance, but the coating technique had clear advantages compared to the fully-filled configuration, and there was no other way of binding the adsorbent particles together. Thus, it is recommended that the binder content be kept as small as it can be.
We synthesized an aluminophosphate (AlPO4)-based adsorbent that shows great cooling performance when used in a water adsorption chiller as an adsorbent. This adsorbent is crystalline microporous (CHA-type structure) material, which is composed of aluminum, phosphine, and oxygen atoms. It shows high water adsorption capacity (0.3 gH2O gads⁻¹) at 308 K under 12 Torr of water vapor pressure (typical adsorption conditions of the adsorption chiller), and almost zero adsorption capacity at 348 K under 42 Torr (typical desorption conditions). This adsorbent shows much larger working capacity between the adsorption and desorption steps than silico-aluminophosphate (SAPO4) adsorbent which has same physico-chemical properties as the AlPO4, except for the absence of silicon species in framework. The commercial water adsorbent, FAM-Z02 is known to have the same structure as this SAPO4. We confirmed that AlPO4 can be easily synthesized in a large scale with a high hydrothermal stability, and easily pelletized to 0.6–1 mm sphere-shaped particles. The present AlPO4 adsorbent was tested in lab-made water adsorption chiller with 5 kW scale, and it shows 523 W kg⁻¹ of specific cooling power (SCP). This experimental value was in good agreement with SCP (513 W kg⁻¹) derived from simulation. The SCP of the AlPO4 adsorbent is 28% larger than that of the SAPO4 adsorbent calculated from simulation.
In this study, a prototype of an adsorption desalination (AD) system was designed and manufactured using commercially available alumina silica gel to evaluate and improve its performance. To develop the AD system, the thermophysical properties of the adsorbent were first investigated based on adsorption isotherms of nitrogen and water vapor on the adsorbent; thereby, its applicability as a candidate adsorbent was verified. The performance of the AD system was then evaluated for different types of brine feeders in the evaporator (i.e., perforated plate and spray nozzles) using tap water as a feed over a wide range of key operating conditions such as hot-, cooling-, and chilled-water temperatures. Moreover, the performance of the AD process was assessed to verify the desalination mechanism and consistent desalting performance of the AD process; the process recovered more freshwater from seawater than conventional desalination technologies. The performance of the AD system was demonstrated to be independent of the brine concentration of the evaporator; moreover, the chemical quality of the freshwater recovered was revealed to be comparable to that of deionized water. Spray-assisted evaporation exhibited high water vapor uptake owing to the effect of pressurization during the adsorption process, and hence, exhibited remarkable performance.
A three-dimensional numerical analysis was conducted to examine the effect on performance of un-balanced heating/cooling water supply and nonuniform pressure distribution in the beds, issues observed in an experiment by our colleague during the development of a 35kW prototype finned-tube type adsorption chiller. Case studies were conducted with reference values of v=1m/s, Pc=4144Pa and Pe=1447Pa, and the differences in Δv=0.25m/s, ΔPc=415Pa and ΔPe=145Pa. A remarkable increase in COP was found for the cases of un-balanced heating water supply and nonuniform pressure distribution when the bed was connected to the evaporator. However, after integration of multi-modules, the effect was smoothed out, which removed the worry about the degradation in the overall COP. The effect of un-balanced cooling water supply and nonuniform pressure distribution when the bed was connected to the condenser was not discernible. In all cases, the change in SCP was negligible.
Aluminophosphate molecular sieves (AlPO-5) were substituted with seven metals (Ca, Co, Mg, Ni, Sr, Cr and Fe). From XRD measurement, all patterns of seven substituted AlPO-5 were identical to that of the AFI structure. Except for Cr substituted AlPO-5, they were mainly in a hexagonal pillar structures based on the SEM images. For Mg, Ni, Sr and Fe substituted AlPO-5, the water adsorption capacity at 30°C and the difference in the amount of adsorbed water between 30°C (adsorption temperature) and 100°C (desorption temperature) increased by the substitution. Although, for Fe substituted AlPO-5, the initial water adsorption rate was slightly decreased by the substitution, the water desorption temperature was equal for the temperature of AlPO-5. This is because Fe substituted AlPO-5 had about 1.8 times water adsorption capacity at 30°C and was able to be regenerated at 100°C, Fe substituted AlPO-5 was the most advantageous adsorbents.
Emission and heat rejection from automobiles are largely responsible for urban environmental issues. Adsorption systems driven by engine waste heat exhibit huge potential to meet the demand for cabin thermal comfort while improving fuel economy. However, the mechanical vapour compression (MVC) systems are still the undisputed champions in automobile air conditioning. This paper provides a critical review on the development and progress of adsorption heat pumps specifically for automobile air conditioning. In doing so, some of the progress and development in land-based adsorption chillers (heat pump), which are not realistically relevant to automobile adsorption systems, are explicitly excluded. Matching the energy density, durability, and reliability of the MVC systems remain major hurdles. The importance of improving the energy density based on the overall system weight or volume, real-world tests under various driving modes and durability aspects are discussed.
Freeze desalination (FD) is an emerging technology to overcome limitations of membrane- and thermal-energy-based desalination processes. Extant studies concerning FD have primarily focused on ice-quality and productivity enhancement. Numerous crystallizer designs operating under various conditions have been investigated to achieve highest possible fresh-water purity. Few post-treatment techniques have also been developed to boost quality and productivity of fresh water. Some obstacles, have been faced in attempts to scale-up the FD process, and possible remedies to these are discussed in this paper. In addition, there exists a possibility towards combining FD with other desalination technologies, thereby developing a hybrid process. The proposed paper discusses extant research trends in FD as a comprehensive review along with discussion of future prospects concerning utility of the FD process.
Problems of energy and fresh water shortage become hard challenges facing survival of the human beings. Egypt especially is facing increasing of water supply challenges due to population growth. In this study, a new proposed solar adsorption desalination-cooling (ADC) system is designed, built, and tested under Egypt's climate conditions. A commercially available silica gel of about 13.5 kg is used. The Adsorption characteristics of the selected silica gel-water pair are evaluated firstly to design the proposed system. In addition, a theoretical dynamic model is developed to predict the system performance. A good agreement is found between the theoretical and experimental results under different Egypt climate conditions. The results show that, the average specific cooling power is 112 W/kg and average specific daily water production is 4 m3 per ton silica gel with a COP of 0.45. Based on the obtained results, ADC system driven by solar energy proven to be an adequate solution to offer proper alternative to the traditional desalination systems and have promising future in Egypt's climate. However, studies about improving the performance of such system and new designs are still needed.
Desiccant cooling systems have advantages in environmentally friendly operation and separate control of sensible and latent cooling loads, which leads to comfortable indoor air quality. In addition, the desiccant cooling system is a heat-driven cycle and therefore has the ability to use low-grade energy. However, the wide spread use of this technology is not yet possible due to its relatively large size and low system performance. The wheel is the most crucial component of the desiccant cooling system. Therefore, mathematical modeling of the desiccant wheel plays an important role in enhancing the overall system performance. Heat and mass transfer are coupled, and multiple parameters are involved in understanding the complicated phenomena in desiccant wheels. Mathematical models are commonly accepted as an effective method for analyzing the performance of rotary wheels and systems. The models can also be used to guide system operation, interpret experimental results and assist in system design and optimization. Several mathematical models have been constructed and employed to analyze, develop and design desiccant wheels. In this work, a brief review on the mathematical modeling of the desiccant wheel is examined, and some typical issues and results of case studies are discussed.
Multi-bed adsorption cycle with the internal heat recovery between the condenser and the evaporator is investigated for desalination application. A numerical model is developed for a 4-bed adsorption cycle implemented with the master-and-slave configuration and the aforementioned internal heat recovery scheme. The present model captures the reversed adsorption/desorption phenomena frequently associated with the unmatched switching periods. Mesoporous silica gel and water vapor emanated from the evaporation of the seawater are employed as the adsorbent and adsorbate pair. The experimental data and investigation for such configurations are reported for the first time at heat source temperatures from 50 °C to 70 °C. The numerical model is validated rigorously and the parametric study is conducted for the performance of the cycle at assorted operation conditions such as hot and cooling water inlet temperatures and the cycle times. The specific daily water production (SDWP) of the present cycle is found to be about 10 m³/day per tonne of silica gel for the heat source temperature at 70 °C. Performance comparison is conducted for various types of adsorption desalination cycles. It is observed that the AD cycle with the current configuration provides superior performance whilst is operational at unprecedentedly low heat source temperature as low as 50 °C.
This paper presents the performance testing of Zeolite adsorption cooling system driven by low grade waste heat source extracted from prime mover’s exhaust, power plant’s exhaust and the solar energy. The adsorbent FAM Z01 is used as an adsorbent in the adsorption chiller facility. Owing to its large equilibrium pore volume, it has the high affinity for the water vapor adsorbate. The key advantages of the Zeolite adsorption cooling system are: (i) it has no moving parts rendering less maintenance, (ii) the energy efficient means of cooling by the adsorption process with a low temperature heat source, (iii) the use of vapor pipes are replaced by self actuating vapor valves rendering smaller footprint area and (iv) it is environmental friendly with low carbon footprint. The experimental investigations were carried out for Zeolite adsorption chiller at different key operating conditions namely (i) heat source temperature, (ii) the cycle time and (iii) the heat recovery time. It is investigated that performance of coefficient (COP) of this system could be as high as 0.48 while the waste heat source temperature is applicable as low as 55 °C.
AlPO4-11 adsorbs water at room temperature, resulting in significant structural changes. These changes have been shown to be readily reversible and have been characterized by X-ray powder diffraction, thermogravimetry, n.m.r., and i.r. spectroscopy. No evidence was found for the presence of chemisorbed water.
Solar refrigeration represents an important application of solar energy due to the excellent matching between the high sunshine and the refrigeration needs. Solar adsorption refrigeration devices are among the significant techniques used to meet the needs for cooling requirements. Several solar refrigeration systems have been proposed and are under development such as sorption systems including liquid/vapor, solid/vapor absorption, adsorption, vapor compression and others. The purpose of this paper is to identify the influence of a cylindrical adsorber on the performances of a solar adsorption refrigerating machine. The adsorber heated by solar energy contains an activated carbon-ammonia pair; it is composed by many cylindrical tubes welded using external fins. A model based on the conservation equations of energy and mass in the adsorber has been developed and well described. Using real solar irradiance data as well as many initial conditions, the model computes for each point and in the considered time interval during the day, the temperature, the adsorbed mass, the pressure inside the adsorber and the solar performance coefficient (COP). The results show that the optimal diameter of the adsorber with fins is greater than the one without fins. Moreover the mass cycled in the case of an adsorber equipped with external fins is more significant than the one without fins, and the maximal temperature reached in the adsorber with fins attains 97 degrees C while in the adsorber without fins reaches 77 degrees C. Thus, the performances of the solar adsorption refrigerating machine with an adsorber equipped with fins are higher than the machine without fins.
Mise au point comportant des definitions generales et la terminologie, la methodologie utilisee, les procedes experimentaux, les interpretations des donnees d'adsorption, les determinations de l'aire superficielle, et les donnees sur la mesoporosite et la microporosite
Differential heats of adsorption have been measured calorimetrically for benzene and n-hexane on AlPO4-5. Adsorption isotherms have been determined for benzene, n-hexane and H2O. The heat of adsorption for benzene on AlPO4-5 was found to be less than the heat of adsorption for n-hexane. Isotherms of all adsorbates investigated exhibited hysteresis loops. The hydrophilicity of AlPO4-5 is explained by capillary condensation and/or coordinately bonded water.
A combination of physical techniques, including FTIR, XRD, gas adsorption and thermal methods, have been used to characterise two modified ALPO-5 phases. The first of these, designated as ZAPO-5, was prepared by the incorporation of zinc at the crystallisation step, whereas the second, Si-ALPO-5, resulted from interaction with SiCl4. The latter phase was found to possess mesopores as well as micropores. The surface acidity of both these solids and of pristine ALPO-5 was investigated. © 1988 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands.
Variable temperature X-ray powder diffraction showed no structure change upon template removal and subsequent rehydration for AlPO4 or SAPO-5 and -34. However, rehydration induces a reversible phase transition for AlPO4 and SAPO-11, and a loss of crystallinity for SAPO-37. As shown by 27Al MAS NMR. there is, in all cases, a change in coordination of certain framework Al upon rehydration. Such a coordination change was observed too for MeAPO-5 and -34 samples (Me = Mg, Co). In addition divalent element extraction may occur during template removal and rehydration. The extent depends on the structure, composition and treatment, as suggested by UV-VIS diffuse reflectance and NMR spectroscopies.
The adsorption equilibrium of hydrocarbons and water on AlPO 4-5 has been investigated using the methods of calorimetry and isostere measurement. AlPO 4-5 behaves in the adsorption of nonpolar molecules like an homogeneous adsorbent. The equilibrium data are well described by equatioreof the cell theory. Monte-Carlo-calculatioreof the thermodynamic functions are performed.
Adsorption refrigeration systems are commercially developed due to the need of replacing the conventional systems which utilise environmentally harmful refrigerants and consume high grade electrical power. This paper presents the key equations necessary for developing a novel empirical lumped analytical simulation model for commercial 450 kW two-bed silica gel/water adsorption chiller incorporating mass and heat recovery schemes. The adsorption chiller governing equations were solved using MATLAB (R) platform integrated with REFPROP (R) to determine the working fluids thermo-physical properties. The simulation model predicted the chiller performance within acceptable tolerance and hence it was used as an evaluation and optimisation tool. The simulation model was used for investigating the effect of changing fin spacing on chiller performance where changing fin spacing from its design value to minimum permissible value increased chiller cooling capacity by 3.0% but decreased the COP by 2.3%. Furthermore, the effect of generation temperature lift on chiller performance and the feasibility of using it as a load control tool will be discussed. Genetic Algorithm optimisation tool was used to determine the optimum cycle time corresponding to maximum cooling capacity, where using the new cycle time increased the chiller cooling capacity by 8.3%.
In this study, a thermally driven adsorption cooling unit using natural zeolite–water as the adsorbent–refrigerant pair has been built and its performance investigated experimentally at various evaporator temperatures. The primary components of the cooling unit are a shell and tube adsorbent bed, an evaporator, a condenser, heating and cooling baths, measurement instruments and supplementary system components. The adsorbent bed is considered to enhance the bed’s heat and mass transfer characteristics; the bed consists of an inner vacuum tube filled with zeolite (zeolite tube) inserted into a larger tubular shell. Under the experimental conditions of 45 °C adsorption, 150 °C desorption, 30 °C condenser and 22.5 °C, 15 °C and 10 °C evaporator temperatures, the COP of the adsorption cooling unit is approximately 0.25 and the maximum average volumetric cooling power density (SCPv) and mass specific cooling power density per kg adsorbent (SCP) of the cooling unit are 5.2 kW/m3 and 7 W/kg, respectively.
Environmental concerns and the rising energy cost necessitate looking for renewable energy driven environmentally benign adsorption cooling systems. Solar powered adsorption chillers with non-concentrating flat plate or evacuated tube collectors face the problem of not getting adequate driving source temperature during some months of the year. Multi-staging of the adsorption cycle is then needed to exploit the low driving source temperature. A simulation study of a solar thermal driven dual-mode, four-bed silica gel–water adsorption chiller is undertaken in this work. The solar thermal collector data of Durgapur (23.48 °N, 87.32 °E), India has been used as the heat source for the dual-mode chiller. For a driving source temperature above 60 °C, the chiller works as a single stage four-bed adsorption chiller; while the chiller functions as a two stage adsorption chiller when the driving source temperature falls below 60 °C. With a cooling water temperature of 30 °C, this two stage chiller has been found to produce cooling effect with a driving source temperature as low as 40 °C. Results indicate that the dual-mode chiller is capable of providing cooling throughout the year under the climatic condition of Durgapur, India.
Climate change is leading to an increasing interest in desalination. The large ‘carbon footprint’ of traditional desalination technologies has spurned interest in several potential alternative technologies. This contribution here is concerned with one of these alternatives: adsorption-based desalination (AD), which uses waste heat or solar energy to generate potable water and, depending on the cycle details, cooling as well. We have previously proposed a number of possible theoretical thermodynamic cycles of AD and analysis thereof (Wu et al., Applied Energy 90: 316–22, 2011). In this paper, the practical implementation of these cycles is outlined and their validity experimentally shown. This work means these models can now be used with confidence to better understanding the performance of AD systems.
Desalination, other than the natural water cycle, is hailed as the panacea to alleviate the problems of fresh water shortage in many water stressed countries. However, the main drawback of conventional desalination methods is that they are energy intensive. In many instances, they consumed electricity, chemicals for pre- and post-treatment of water. For each kWh of energy consumed, there is an unavoidable emission of Carbon Dioxide (CO2) at the power stations as well as the discharge of chemically-laden brine into the environment. Thus, there is a motivation to find new direction or methods of desalination that consumed less chemicals, thermal energy and electricity.This paper describes an emerging and yet low cost method of desalination that employs only low-temperature waste heat, which is available in abundance from either the renewable energy sources or exhaust of industrial processes. With only one heat input, the Adsorption Desalination (AD) cycle produces two useful effects, i.e., high grade potable water and cooling. In this article, a brief literature review, the theoretical framework for adsorption thermodynamics, a lumped-parameter model and the experimental tests for a wide range of operational conditions on the basic and the hybrid AD cycles are discussed. Predictions from the model are validated with measured performances from two pilot plants, i.e., a basic AD and the advanced AD cycles. The energetic efficiency of AD cycles has been compared against the conventional desalination methods. Owing to the unique features of AD cycle, i.e., the simultaneous production of dual useful effects, it is proposed that the life cycle cost (LCC) of AD is evaluated against the LCC of combined machines that are needed to deliver the same quantities of useful effects using a unified unit of $/MWh. In closing, an ideal desalination system with zero emission of CO2 is presented where geo-thermal heat is employed for powering a temperature-cascaded cogeneration plant.
A Tian-Calvet microcalorimeter has been used to determine the heat of interaction of water vapor with a range of oxides at 303 K. New data for SiO2, TiO2, ZnAl2O4 and CaO are reported which, together with already established results for Al2O3, enable an overall view to be given of the hydrophilic behavior of oxides. The change of the differential heat of adsorption with uptake for a given oxide allows the proportions of surface with high and low hydrophilicity, and with hydrophobicity if present, to be assessed. For the highly hydrophilic oxide CaO, the interaction occurs in depth, but this is suppressed when Mn ions are introduced in solid solution in CaO. The change from hydrophilic to hydrophobic behavior in oxides is correlated with the gradation from ionic to covalent bonding.
A number of new desiccant materials have been proposed which have the potential to improve the performance of desiccant wheels being regenerated at low temperature. Desiccant wheels containing two such desiccant materials (zeolite and superadsorbent polymer) were compared with a conventional silica gel desiccant wheel. The superadsorbent polymer desiccant wheel achieved greater dehumidification than the silica gel wheel when dehumidifying high relative humidity air with low temperature (50 °C) regeneration air. The temperature of dehumidified air exiting the polymer wheel was also lower. The zeolite desiccant wheel was generally less effective at dehumidifying air and had a higher pressure drop.
This article presents the performance analysis of a waste heat-driven adsorption cycle. With the implementation of adsorption–desorption phenomena, the cycle simultaneously produces cooling energy and high-grade potable water. A mathematical model is developed using isotherm characteristics of the adsorbent/adsorbate pair (silica gel and water), energy and mass balances for the each component of the cycle. The cycle is analyzed using key performance parameters namely (i) specific cooling power (SCP), (ii) specific daily water production (SDWP), (iii) the coefficient of performance (COP) and (iv) the overall conversion ratio (OCR). The numerical results of the adsorption cycle are validated using experimental data. The parametric analysis using different hot and chilled water temperatures are reported. At 85 °C hot water inlet temperature, the cycle generates 3.6 m3 of potable water and 23 Rton of cooling at the produced chilled water temperature of 10 °C.
The paper focuses on development of new adsorbent material of aluminophosphate (FAM-Z05) which could be subsequently used in utilization of waste beat below 373 K. To evaluate this new material, water vapor adsorption isotherms of FAM-Z05 were measured at several temperatures. Furthermore, an attempt was made to improve the heat exchanger by coating FAM materials onto rin tube type heat exchanger. Then, the dehumidification performance of direct cooling and heating desiccant system was evaluated. It was found that the water vapor adsorption isotherms of FAM-Z05 were characterized by S-shape and the adsorption character of FAM-Z05 was dependent on temperature. Further, the new adsorbent of FAM-Z05 was able to adsorb water vapor in lower regeneration temperature than FAMZ02 and FAMZ01, which was attributed to FAM-Z05 ability to adsorb water vapor in high humidity range. However, when FAM-Z05 is used in low humidity range, the dehumidification performance of FAM-Z05 might be lower than those of FAM-Z01 and FAM-Z02.
AFI-type structure ferroaluminophosphate zeolite (FAPO-5) was examined as an AHP adsorbent. FAPO-5 with iron content of 2-8mol% (Functional Adsorbent Material-Zeolite 01; FAM-Z01) was selected for further testing. The water vapor adsorption isotherm of FAM-Z01 was S-shaped and highly dependent on temperature, and almost no hysteresis was observed with adsorption/desorption at 333 K and 348 K. No changes were observed in the properties of FAM-Z01 after 200,000 cycles of water vapor adsorption-desorption, indicating that FAM-Z01 is suitably durable for practical use. When the AHP was operated under conditions of TL/TM/TH= 283 K/303 K/333 K, the adsorption capacity of FAM-Z01 was 4 times that of silica gel.
The potential to use waste heat to co-generate cooling and fresh water from saline water using adsorption on silica is attracting increasing attention. A variety of different thermodynamic cycles of such an adsorption desalination (AD) system arise as the temperature of the saline water evaporator is varied relative to temperature of the water used to cool the adsorbent as it adsorbs the evaporated water. In this paper, all these possible thermodynamic cycles are enumerated and analysed to determine their relative performances in terms of specific energy consumption and fresh water productivity.
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Thermo-physical properties, surface characteristics and water vapor uptake capacity are key parameters in the selection of adsorbent for an adsorption desalination (AD) cycle. In the AD cycles, silica gel is used as adsorbent due to their high water vapor uptake capacity, reliability, repeatability and inexpensiveness as compared to other adsorbents. Three types of commercially available silica gels (Type-RD 2560,Type-A5BW and Type-A++) are investigated using a surface characteristic analyzer and their thermo-physical properties are evaluated using several analysis methods. The instrument used in this investigation employs the static volumetric method with liquid Nitrogen at 77 K as the filing fluid. The surface area of each adsorbent is studied using Brunauer–Emmett–Teller (BET) method whilst the pore size distribution (PSD) analysis is conducted with the Non-Local Density Functional Theory (NLDFT). It is observed that the Type-A++ silica gel (granular type) possesses the highest surface area of 863.6 m2/g amongst the three parent silica gels studied. It has a two-maxima or bimodal distribution pattern where the pore diameters are distributed mostly between 10 Å and 30 Å. Water vapor uptake capacity of silica gels are studied with water vapor dosage apparatus and the results show that the Type-A++ silica gel exhibits a highest equilibrium uptake at 537 cm3/g. These thermo-physical properties are essential for the design and the numerical simulation of AD cycles.
A modeling approach to predict the performance of a commercial diesel oxidation catalyst (DOC) under actual vehicle operating conditions is presented in this study. Prior to completing this prediction, the performance characteristics of DOCs, as previously published, are examined to validate the currently developed in-house computational code. Steady-state experiments with DOCs mounted on a light-duty four-cylinder 2.0-L turbocharged diesel engine then are performed, using an engine-dynamometer system to calibrate the kinetic parameters such as activation energies and pre-exponential factors of heterogeneous reactions. The reaction rates for CO, HC, and NO oxidations over a fresh Pt/Al2O3 catalyst are determined in conjunction with a transient one-dimensional (1D) heterogeneous plug-flow reactor (PFR) model with diesel exhaust gas temperatures in the range of 150−450 °C and space velocities in the range of (1−5) × 105 h−1. To determine the kinetic parameters that best fit the experimental data, a two-step optimization procedure is introduced. First, the results from the conjugated gradient method (CGM) with individual temperatures for each species are plotted in an Arrhenius plot to generate proper intermediate guesses from initial guesses for all pre-exponential factors and activation energies. Here, the kinetic parameters for CO oxidation are calibrated to provide the best fits to the lowest temperature data with fixed initial activation energy without implementing the first-step tuning procedure, because of complete conversion of CO over the temperature range of 150−450 °C. Kinetic parameters for all species then are obtained simultaneously by searching the best fits to experimental data using the CGM from the intermediate guesses for all species. The prediction accuracy of the model through first step optimization procedure against experimental results is slightly improved by performing a second-step optimization procedure, and the simulation results of optimized kinetic parameters are compared to the experimental data obtained at both 1500 and 2000 rpm.
The adsorption refrigeration tube (ART) has drawn increasing attention because of its advantages of no moving parts, compact structure and use of low grade heat as the heat source. A new design of ART was developed, in which activated carbon–methanol was selected as the working pair for either refrigeration or air-conditioning purposes. Based on the typical configuration of the generator of the ART, a dynamic mathematical model was developed under the non-uniform pressure assumption and the introduction of a transient boundary condition of diffusion equation. Moreover, experiments were conducted for validating the model. The experimental data and numerical results were compared in terms of temperature development inside the carbon bed, with the transient and two popular simplified boundary conditions of vapor density respectively. The comparison shows that the transient boundary condition improves accuracy of the model and more importantly it is capable of reflecting the dynamic shift of dominant driving forces of the adsorption process inside the generator, i.e. shifting to temperature driving gradually from diffusion driving.
This paper presents the performances of an adsorption desalination (AD) system in two-bed and four-bed operational modes. The tested results are calculated in terms of key performance parameters namely, (i) specific daily water production (SDWP), (ii) cycle time, and (iii) performance ratio (PR) for various heat source temperatures, mass flow rates, cycle times along with a fixed heat sink temperature. The optimum input parameters such as driving heat source and cycle time of the AD cycle are also evaluated. It is found from the present experimental data that the maximum potable water production per tonne of adsorbent (silica gel) per day is about 10 m3 whilst the corresponding performance ratio is 0.61, and a longer cycle time is required to achieve maximum water production at lower heat source temperatures. This paper also provides a useful guideline for the operational strategy of the AD cycle.
A description of the pore dimensions has been obtained for a group of carbon blacks by means of the universal t curve as given in Parts I and VI in this series. An important quantity of very narrow pores has been ascertained. The surface area of the wide pores was equal to the geometrical surface.
Adsorption of water vapor on mesoporous materials such as MCM-41, MCM-48, KIT-1, SBA-1, and SBA-15, which have different pore sizes and shapes, was investigated by using a gravimetric system. In addition, adsorption of water vapor on KIT-1 mesoporous material was examined at 293.15 to 353.15 K. A hybrid isotherm model composed of a Henry isotherm and a Sips isotherm was applied to the analysis of water adsorption on mesopores including its surface adsorption and capillary condensation. The proposed isotherm nicely simulated measured adsorption data over the whole range at these experimental conditions. The capillary condensation of water vapor on mesoporous materials was highly dependent on temperature and pore sizes rather than on their pore shapes.
The tetrahedral atom arrangements of silicon, phosphorus, and aluminum in silicoaluminophosphates with sodalite structure have been elucidated. No evidence of Si-O-P linkages is provided. Silicon atoms are found to have silicon and/or aluminum neighbors while phosphorus is surrounded by aluminum only. Two distinct physicochemical environments of aluminum are observed: phosphorus rich and silicon rich.
The 27Al NMR and 31P NMR MAS spectra of four crystalline aluminophosphate molecular sieves, AlPO4-5, AlPO4-11, AlPO4-17, and AlPO4-31 were studied at 4.7 T and compared to some nonmicroporous materials, AlPO4-quartz, metavariscite, and AlPO4-tridymite. The molecular sieve spectra are generally consistent with their known framework structures constructed of alternating AlO4 and PO4 tetrahedra; however, the 27Al NMR chemical shift range was wide and asymmetrical lines and multiple peak maxima were observed. Both as-synthesized and calcined forms were examined and in one case (AlPO4-17) adsorbed water reversibly resulted in a chemical shift into a region previously found from octahedral Al in aluminophosphates and herein from metavariscite. High fields (9.4 T) and {1H-27Al} cross-polarization techniques helped assign the most unusual 27Al NMR chemical shifts to the result of secondary interactions of framework Al with occluded template or H2O within the micropores. Quadrupole effects are so severe in AlPO4-quartz that even at 9.4 T a residual powder pattern persists under MAS conditions. All the 31P NMR MAS results are consistent with tetrahedral phosphorus.
Adsorption cycle is a practical and inexpensive method of desalinating the saline and brackish water to produce potable water for both industrial and residential applications. As compared with the commercial desalination methods, the adsorption technology has the unique advantages such as (i) the utilization of the low-temperature waste heat, (ii) low corrosion and fouling rates on the tube materials due to the low-temperature evaporation of saline water, (iii) and it has almost no major moving parts which renders inherently low maintenance cost. In addition, the adsorption cycle offers two important benefits that are not available to the existing desalination technologies; namely, (i) a two-prong phenomenal barrier to any “bio-contamination” during the water generation process as compared with existing methods and (ii) the reduction in global warming due to the utilization of low-temperature waste heat which otherwise would have been purged to the atmosphere. This paper describes an experimental investigation and the specific water yields from a four-bed adsorption desalination plant is presented with respect to major assorted coolant and feed conditions.
This article presents the transient modelling for a two-bed, activated carbon fiber (ACF)–ethanol adsorption chiller. This innovative adsorption chiller employs pitch based ACF of type A-20 as adsorbent which is a fibrous adsorbent having the advantages of fast adsorption rate, high porosity and ease of handling when compared with granular adsorbents and powdered adsorbents. Ethanol is used as refrigerant as it has no harm to environment, it is a non-toxic substance, moreover, ethanol has comparatively higher vapor pressure even at low temperature. This innovative system utilizes effectively low-temperature waste heat sources of temperature between 60 and 95 °C along with a coolant at 30 °C. We have found that, regardless of the initial mass distribution, the ACF–ethanol adsorption chiller is able to achieve the same cyclic-steady-state within three cycles or 1890 s.
The water sorption isotherm over AlPO4-5, in which a low sorption capacity in the initial region followed by a steep rise in sorption is observed, is different from those obtained for polar molecules, namely acetonitrile, ammonia and methanol. An attempt has been made to explain the water sorption behaviour on the basis of a condensation phenomenon using the structural characteristics of AlPO4-5.
This article presents a transient distributed-parameter model for a two-bed, silica gel–water adsorption chiller. Compared with our previous lumped-parameter model, we found better agreement between our model prediction and experimental data. We discussed the important effect of heat recovery and the effect of extra system piping on the system performance. Time constants of sensors were also considered. We found that the chiller was able to maintain its cooling capacity over a fairly broad range of cycle times and the previous lumped-parameter model tended to under-predict the cooling capacity at long cycle times.
A novel class of crystalline, microporous, aluminophosphate phases has been discovered that represents the first family of framework oxide molecular sieves synthesized without silica. The new family of aluminophosphate materials (AlPOâ-n)³ currently includes about 20, three-dimensional framework structures, of which at least 14 are microporous and 6 are two-dimensional layer-type materials. The aluminophosphate materials have interesting properties for potential use in adsorptive and catalytic applications, due to both their unique surface selectivity characteristics and novel structures.