The effects of acidic properties and structural changes of Y zeolite, produced by steaming, on the zeolite cracking activity, coking tendency and distribution of various products during catalytic conversion of bulky 1,3,5-triisopropylbenzene (TIPB) are reported. NaY zeolite with framework Si/Al ratio of 2.4 was synthesized by a hydrothermal method and ammonium exchanged. The zeolite was dealuminated by a temperature-programmed steaming to form USY1 and USY2 zeolites with framework Si/Al ratio of 8.1 and 12.3 respectively. The catalysts were characterized by XRD, XRF, SEM, AAS, NH3–TPD and N2 adsorption–desorption techniques. The samples were in-situ activated at 748 K and evaluated by TIPB cracking at 623 K. The coke content of the catalyst beds was estimated by TPO using an FT-IR gas cell. The results of activity measurements reveal that the dealuminated zeolites lead to lower cracking activity initially; while, they exhibit higher activity at longer times. In addition, a slight modification of the window diameter of Y zeolite, as revealed by pore size distribution analyses, alters the diffusion limitation of the reactant and products through the pores of the zeolite and significantly affects the adsorbent–adsorbate interactions. TPO experiments show that compared to the precursor zeolite, lower amount of coke is formed on the dealuminated catalysts possessing lower density of acid sites. However, the coke formed on USY samples is heavier than that formed on its precursor Y zeolite. This may be attributed to the larger pores shaped in the dealuminated catalysts which in turn provide suitable places for coke formation and growth.
The U.S. Department of Energy commissioned the National Renewable Energy Laboratory (NREL) to develop a long-term research plan for commercializing lipid fuels and coproducts, thereby displacing petroleum and establishing a new biobased industry. This article summarizes the findings of a more detailed report: Biomass Oil Analysis: Research Needs and Recommendations, NREL/TP-510-34796. This paper provides a summary of the needs and challenges involved in displacing petroleum with lipid fuels. It identifies research agendas that could support a larger lipid fuel industry and provides guidance for researchers and funding organizations. This analysis found that modest production cost reductions and significant increases in lipid production could be achieved, but only if there are government incentives to promote the use of the high cost lipid fuels. Without the incentives, lipid fuel use will remain modest and there will be little need for research to increase supply. Research that reduces production costs is not sufficient to bring the cost of lipids in line with petroleum fuel.
Fixed bed biomass gasification is a promising technology to produce heat and power from a renewable energy source. A twin-fire fixed bed gasifier based CHP plant was realized in the year 2003 in Wr. Neustadt, Austria. Wood chips are used as fuel, which are dried and sieved before being gasified to a low calorific gas of about 5.8 MJ/Nm3dry. Before the clean gas is fed into a gas engine a cyclone and a RME (rapemethylester)/H2O quench system followed by a wet electrostatic precipitator (ESP) is used for gas cleaning. The CHP plant has a fuel power of 2 MWth and an electric output of 550 kWel. As scale up and optimization tool a hot test rig with a capacity of 125 kWth was built. Basic parameters like the type of wood chips, power and air distribution were varied to investigate the effect on gas composition, tar content in the producer gas and carbon content in the ash. Additionally a temperature profile over the height of the 125 kW hot test rig was measured. Furthermore, the results from the hot test rig are discussed and compared with the results from the 2 MWth demonstration plant.
Biodiesel was synthesized from rocket seed oil by base-catalyzed transesterification with methanol. The synthesis of biodiesel was confirmed by FT-IR and NMR (1H and 13C) spectroscopy. Various fuel properties of the synthesized biodiesel were determined using ASTM methods and discussed accordingly. A total of eleven fatty acid methyl esters (FAMEs) were identified in rocket seed oil biodiesel (RSOB) by the retention time and the fragmentation pattern data of GC/MS analysis. The identified FAMEs were, methyl 9-hexadecenoate (C16:1), 14-methyl pentadecanoate (C16:0), methyl 9,12-octadecadienoate (C18:2), methyl 9-octadecenoate (C18:1), methyl octadecanoate (C18:0), methyl 11-eicosenoate (C20:1), methyl eicosanoate (C20:0), methyl 13-docosenoate (C22:1), methyl docosanoate (C22:0), methyl 15-tetracosenoate (24:1) and methyl tetracosanoate (C24:0). The percentage conversion of triglycerides to corresponding methyl esters determined by 1H NMR was 88.49%.
A 2-year demonstration program is carried out by the Danish utility I/S Midtkraft at a 150-MWe PF-boiler unit reconstructed for co-firing straw and coal. As a part of the demonstration program, a comprehensive in situ measurement campaign was conducted during the spring of 1996 in collaboration with the Technical University of Denmark. Six sample positions have been established between the upper part of the furnace and the economizer. The campaign included in situ sampling of deposits on water/air-cooled probes, sampling of fly ash, flue gas and gas phase alkali metal compounds, and aerosols as well as temperature measurements. Material balance closures were carried out at all operating conditions. The experimental data was evaluated together with researchers from the Technical University of Denmark and the results were stored in a data base program developed under the CHEC-research program to predict deposition propensities and high temperature corrosion during co-combustion of straw and coal in PF-boilers. Danish full scale results from co-firing straw and coal, the test facility and test program, and the potential theoretical support from the Technical University of Denmark are presented in this paper.
This paper reports a relatively simple low-temperature non-isothermal oxidative desulphurisation of coal organic sulphur by weakening the CS bond using HgCl2 solution to an inorganic sulphur-free high-sulphur Indian coal. When oxidised from 50°C to 150°C in air under normal atmospheric pressure, there is continuous decrease of organic sulphur content in the samples of the feed and Hg-treated coals. Desulphurisation is more in the Hg-treated coal (4.97–14.53 wt.%) than in the feed coal (3.72–10.93 wt.%). Kinetic study reveals that the oxidative desulphurisation process follows pseudo-first order kinetics and the rate constants have been found to be in the range (3.09–5.06)×10−5 s−1 for feed coal and (4.19–6.80)×10−5 s−1 for Hg-treated coal. The activation energies for the sulphur loss reaction in the oxidative desulphurisation process by using the pseudo-first order kinetic (feed coal: 2.21×102 J mol−1; Hg-treated coal: 1.53×102 J mol−1) have been found to be almost similar to those calculated by applying the Coats and Redfern's equation (feed coal: 2.19×102 J mol−1; Hg-treated coal: 1.53×102 J mol−1). However, the value is higher (feed coal: 3.50×102 J mol−1; Hg-treated coal: 2.70×102 J mol−1) when Horowitz and Metzger's equation is applied. The frequency factors computed by the pseudo-first order kinetics are very low and have been found to be 2.66×10−5 s−1 for feed coal and 3.96×10−5 s−1 for Hg-treated coal, suggesting very low rate of successful collisions for the formation of the activated complex. Evaluation of thermodynamic parameters viz., ΔH, ΔU, ΔS and ΔG, reveals that this oxidative desulphurisation process is non-spontaneous in nature and the degree of non-spontaneity of such a process in the feed coal is more relative to that of the Hg-treated coal.
Wood pellets have become an important renewable energy fuel. Nowadays the main raw materials used for their production are wood wastes from wood industries. However, these wood wastes have other uses in Spain and it is necessary to look for other possible raw materials. In this work, vine shoots and industrial cork residue were studied as raw materials. The results showed that pelletisation of vine shoots presented a high energy demand. This energy requirement was reduced with the addition of industrial cork residue. Moreover, industrial cork residue decreased the ash content of pellets and increased their heating value, although it decreased their physical properties at the same time. Regarding combustion, the addition of industrial cork residue decreased the accumulation of ash in the pellet burner and its sintering tendency. The major conclusion of the work is that the most appropriate blend to improve pelletisation and combustion processes is 30% wt. of vine shoots and 70% wt. of industrial cork residue.
Cofiring of biomass with coal has been conducted using all kinds of combustion technologies which include cyclone boilers, wall-fired and tangentially-fired pulverized coal boilers, fluidized-bed boilers and stoker-fired boilers. Fundamental studies and experiments were also performed on biofuel safety issues, blended biofuel/coal storage and transport and fuel chemistries. The cofiring programs has led to the development of a database concerning biofuel properties which was coupled with computer programs to evaluate certain issues associated with blending.
The current volume presents 19 papers that advance research and technology in C1 chemistry and fuel science technology. This introductory paper contains a brief outline of the material presented in those papers.
The total and size fractionated concentrations of As, Cd, Cr, Cu, Ni, Pb and Zn in bottom ash and two fly ash fractions from a large-sized (246 MW) fluidized bed boiler were compared to Finnish statutory limit values for forest fertilizers, which came into force in March 2007. Fly ashes were sampled from the different fields (i.e. electrodes) of the electrostatic precipitator (ESP) unit treating the stack gases. The bottom ash and the fly ash from the first ESP field are suitable for use a forest fertilizer. Due to the elevated As concentration (40 mg/kg; d.w.), which exceeded its Finnish limit value of 30 mg/kg (d.w.), the fly ash from the second ESP field is not suitable as a forest fertilizer alone. The results of ash sieving indicated that an As concentration of 40 mg/kg (d.w.) for particle size less than 0.125 mm for fly ash 2 from the second ESP electrode field exceeded the As limit value of 30 mg/kg (d.w.). In addition, a Pb concentration of 170 mg/kg (d.w.) for fly ash 1 from the first ESP electrode field for particle size 0.5–2.0 mm exceeded the Pb limit value of 150 mg/kg (d.w.). These two specific fractions are therefore not suitable for used as a forest fertilizer alone.
Experiments with a small-scale cyclone burner used for burner enrichment in a down-fired pulverized-coal 300 MWe utility have been conducted on an air/particle test facility. Particle separating efficiency was obtained with different positions of an adjustable vane. Industrial experiments were performed on a full-scale boiler. The gas temperature distribution along the primary air and coal mixture flow, gas temperature distribution of the furnace, and gas components such as O2, CO, CO2 and NOX in the near-wall region were measured for the first time. The influence of the adjustable vane position on coal combustion in the furnace was determined. With the adjustable vanes at the nozzle, ignition of the primary air and pulverized-coal mixture was delayed and the gas temperature peak was above the burner arch, with high NOX emission. Raising the vanes can bring forward the ignition point but results in the fuel-rich flow being up ahead of time, leading to a rise in carbon content in fly ash and NOX emission.
In June 2005, the U.S. Environmental Protection Agency (EPA) finalized the Clean Air Mercury Rule (CAMR). As part of the rule, all coal-fired power plants were required to do continuous mercury measurements. Although CAMR has now been vacated by the courts, based on discussion with the EPA, it is expected that the mercury measurement requirements as written will be part of any future mercury regulations. This paper focuses on the process for certifying a continuous mercury monitor and conducting a relative accuracy test audit using EPA Method 30B. Based on the experience gained at the Energy & Environmental Research Center, a number of recommendations for conducting a RATA are provided.
In this study, the physical and chemical properties of bottom ash and fly ash originating from the co-combustion of biomass-derived fuels (i.e. wood chips, sawdust, bark, and peat) from a 32 MW fluidized bed boiler at a municipal district heating plant were investigated. Silicate minerals were predominant in the bottom ash and calcium minerals in the fly ash, with most of the inorganic nutrients and heavy metals being enriched in the fly ash. The enrichment factors for heavy metals in the fly ash varied between 0.2 for silicon and 16.3 for lead, and for plant nutrients, between 1.5 for phosphorous and 108 for potassium. However, all heavy metal concentrations in both the bottom ash and fly ash were significantly lower than the current Finnish limit for maximum allowable heavy metal concentrations for forest fertilizers, which came into force in March 2007. According to the particle size distribution, the mass loadings of heavy metals in the fly ash were more than 90% contributed by the smallest particle size fraction lower than 0.074 mm. In the bottom ash, between 83.6 and 91.9% of the mass loadings of heavy metals were contributed by the particle size fraction between 0.5 and 2.0 mm.
In this work, a CFD numerical study of co-firing coal and cynara in a 350 MWe utility boiler is presented. The most influent operational factors related to the biomass feeding conditions such as biomass mean particle size, level of substitution of coal by biomass and feeding location in the furnace, are analyzed, determining their influence in the combustion process. Validation of the simulations is performed using measurements gathered at the plant. Results from the study show interesting conclusions for their implementation in the power plant, suggesting recommendable limits in the maximum biomass substitution level and particle size in order to keep a reasonable boiler efficiency, and pointing out the outstanding influence of the biomass injection location discussing thermal and fluid-dynamic implications and the possibility of introducing retrofitted or specific biomass burners.
The dielectric properties of 4,6-dimethyldibenzothiophene (DMDBT), hexadecane (HD), quinoline (QL), and HD/QL mixtures were investigated at six microwave frequencies (0.4, 0.9, 1.4, 1.9, 2.5 and 3.0 GHz) and temperatures ranging from 297 K to 624 K. While both DMDBT and HD exhibited limited response under these conditions, QL demonstrated high dielectric loss with a penetration depth comparable to that of water. Through the use of the Debye relationship and solvent mixing rules, a model is proposed to predict the dielectric constant and loss factor for HD/QL mixtures. Based on the observed dielectric behaviour of QL, microwave-assisted separation/conversion may be effective during upgrading of light cycle oil (LCO) for similar, difficult-to-remove nitrogen compounds.Research Highlights► Hexadecane, quinoline and 4,6-DMDBT as model compounds in LCO upgrading. ► Temperatures of 297 to 624 K, microwave freq.: 0.4, 0.9, 1.4, 1.9, 2.5 and 3.0 GHz. ► Both Hexadecane and 4,6-DMDBT nearly transparent to microwave radiation. ► Quinoline exhibits high dielectric loss, with a penetration depth comparable to water. ► Debye relationship and solvent mixing rules accurately described mixture properties.
Incineration of municipal solid waste is often associated with high temperature corrosion problems. This paper presents results of full-scale corrosion tests in a 65 MW waste fired combined heat and power plant. A failure case indicated alarmingly high corrosion rate of the superheater tubes. Corrosion tests with five different alloys were carried out within this work in order to determine plant specific corrosion rates on different superheater materials. Additional tests were done to determine the effect on the corrosion rate from adding chlorine containing polyvinyl chloride to the ordinary fuel mix. A corrosion probe with metal temperatures ranging from 320 °C to 460 °C was used to estimate corrosion loss and to collect deposits. The sampling was performed at a flue gas temperature of 470 °C for 10 days. The probe rings were analysed using scanning electron microscope and micrometer measurements to determine the deposit chemistry and corrosion rates. The results showed significant differences in corrosion rates depending on tube material. Chlorine was shown to have a key role in the corrosion process, even at these relatively low temperatures. The results indicated a chlorine induced corrosion mechanism involving volatile iron chloride with a high corrosion rate on the superheater materials typically used. Addition of extra polyvinyl chloride to the fuel mix had an increasing effect on the corrosion.
The fundamental natures of the interaction between thiophene and ionic liquids of 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]+[PF6]−) and 1-n-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]+[BF4]−) were investigated using ab initio calculations and correlated with previous experimental results. The optimized structures show that the anions of the ionic liquids are situated outside the ring plane of the thiophene, with the fluorine atoms interacting with the hydrogen atoms of the thiophene, and the cation of the ionic liquids approaches the thiophene with its positively charged atoms approaching the negatively charged atoms of TS. It is concluded that thiophene molecules interact with the ionic liquids mainly via Coulombian attraction. Further analysis explained the results obtained from an absorption experiment that the molar ratios of the absorbed thiophene to the ionic liquids were approximately 3.5/1 and 2.4/1 for [BMIM]+[PF6]− and [BMIM]+[BF4]−, respectively. The strong electron donation of the phosphorus atom to the fluorine atoms in the PF6− cluster is believed to be the major factor resulting in the higher molar ratio of thiophene/[BMIM]+[PF6]−. The other factor is the difference of the compactness between the cation and the anion in the two ionic liquids.
This paper presents the results of a study carried out on a small-scale 10 kW fixed-bed combustor fired by blended pellet fuels burning on a thin depth fuel-bed. The use of the thin fuel-bed may contribute to major advances in the introduction of low-cost, fully automated small-scale combustors by eliminating de-ashing mechanisms, and improving operating conditions. The pellets were made by pressing the mixture of finely ground lignite or its by-product (xylite) with wood chips. The xylite (woody lignite) and the wood chips are wastes produced during the production of lignite fuel and timber, respectively. Therefore, using these materials to produce the high quality pellet fuel contributes to environmental conservation. Water and calcium hydroxide suspensions were used as pelletising agents playing the role of binders. The major objective was to study the improvement of the quality of the blended pellet fuels in regard to their combustion and emission behaviours when burned on the thin fuel-bed. The ignition and combustion behaviour of the pellets were compared to those of conventional lignite briquettes. The study proved that the pellets on the thin fuel-bed ignited faster and had steady burnout. The emissions of NOx, SO2, CO and hydrocarbon compounds were comparatively lower than those from burning of lignite briquettes in a domestic combustor. The addition of calcium hydroxide suspensions played not only the role of binding together the raw material blends, but also provided favourable Ca/S molar ratio optimum for considerable reduction of the SO2 emissions. The need to reduce further the specific emissions of SO2 leads to exceeding the proportional value of Ca/S molar ratio, which lowers the calorific value of the pellets. Thermogravimetric studies helped in establishing the comparative pyrolysis behaviours of the lignite and wood chips.
Modeling mercury speciation is an important requirement for estimating harmful emissions from coal-fired power plants and developing strategies to reduce them. First-principle models based on chemical, kinetic, and thermodynamic aspects exist, but these are complex and difficult to develop. The use of modern data-based machine learning techniques has been recently introduced, including neural networks. Here we propose an alternative approach using abductive networks based on the group method of data handling (GMDH) algorithm, with the advantages of simplified and more automated model synthesis, automatic selection of significant inputs, and more transparent input–output model relationships. Models were developed for predicting three types of mercury speciation (elemental, oxidized, and particulate) using a small dataset containing six inputs parameters on the composition of the coal used and boiler operating conditions. Prediction performance compares favourably with neural network models developed using the same dataset, with correlation coefficients as high as 0.97 for training data. Network committees (ensembles) are proposed as a means of improving prediction accuracy, and suggestions are made for future work to further improve performance.
Dry catalytic hydrogenation, using an impregnated molybdenum catalyst, has been used to explore the processes of coal liquefaction and their relation to coal structure. It was found that for high activity the molybdenum must be present as MoS2 and that the conditions used for impregnation can strongly influence catalyst dispersion and activity. At temperatures of 400°C and lower, a subbituminous coal was more readily converted to liquid products and gases, than a coal of bituminous rank. The low-rank coal products were comparatively richer in hydrogen, possessed higher oil to asphaltene ratios and were more aliphatic than the bituminous coal liquids.It is considered that the higher reactivity of the low-rank coal is attributable to the initial reactions being conducted under conditions which promote hydrogenation while minimizing condensation and cracking reactions.Examination of reacted coals by reflected fluorescent light microscopy showed a close correlation between the yield of extractable liquids and the maximum intensity of vitrinite fluorescence. The fluorescence appears to be directly related to the liberation of relatively low molecular weight species within the coal structure. Coal pretreatment by low-temperature dry hydrogenation, prior to higher temperature liquefaction in the presence of solvent, improved the overall conversion and product selectivity of both bituminous and subbituminous coals. It is suggested that subtle control of the initial conversion reactions can lead to more efficient liquefaction of coals of different rank.
Landfill gas (LFG) was upgraded to pure methane using the adsorption and absorption processes. Different toxic compounds like aromatics and chlorinated compounds were removed using granular activated carbon. The activated carbon adsorbed toxic trace components in the following order: carbon tetrachloride > toluene > chloroform > xylene > ethylbenzene > benzene > trichloroethylene ≈ tetrachloroethylene. After removing all trace components, the gas was fed to absorption apparatus for the removal of carbon dioxide (CO2). Two alkanolamines, monoethanol amine (MEA) and diethanol amine (DEA) were used for the removal of CO2 from LFG. The maximum CO2 loading is obtained for 30 wt.% MEA which is around 2.9 mol L− 1 of absorbent solution whereas for same concentration of DEA it is around 1.66 mol L − 1 of solution. 30 wt% MEA displayed a higher absorption rate of around 6.64 × 10− 5 mol L− 1 min− 1. DEA displayed a higher desorption rate and a better cyclic capacity as compared to MEA. Methane obtained from this process can be further used in the natural gas network for city.
Carbon dioxide transfer capacities of aqueous ammonia solution and monoethanolamine (MEA) solution were compared. The ammonia process for CO2 capture was simulated using a semibatch reactor, where the flow of gas is continuous. The CO2 carrying capacity in g CO2 per g of NH3 solution (8 wt.%) circulated is 0.07 as compared with 0.036 g CO2 per g MEA solution (20 wt.%). The energy requirement for liquid mass circulation of ammonia solution is approximately 50% of MEA solution for equal weight of CO2 carried. In another comparison, the thermal energy required to regenerate CO2 from the rich solution is substantially less as compared to the MEA process. A 3-cycle absorption–regeneration test was conducted in the semibatch reactor to simulate an approach-to-steady state in a flow system. pH values of the absorbent solution was found to oscillate between 9.6 (CO2-lean) and 8.8 (CO2-rich) under the test conditions. Thermodynamics study shows that ammonium bicarbonate required the least thermal energy among the ammonium compounds for CO2 regeneration.
The steam gasification of solid biomass by means of the absorption enhanced reforming process (AER process) yields a high quality product gas with increased hydrogen content. The product gas can be used for a wide range of applications which covers the conventional combined heat and power production as well as the operation of fuel cells, the conversion into liquid fuels or the generation of synthetic natural gas and hydrogen. On the basis of a dual fluidized bed system, steam gasification of biomass is coupled with in situ CO2 absorption to enhance the formation of hydrogen. The reactive bed material (limestone) used in the dual fluidized bed system realizes the continuous CO2 removal by cyclic carbonation of CaO and calcination of CaCO3. Biomass gasification with in situ CO2 absorption has been substantially proven in pilot plant scale of 100 kW fuel input. The present paper outlines the basic principles of steam gasification combined with the AER process the investigations in reactive bed materials, and concentrates further on the first time application of the AER process on industrial scale. The first time application has been carried out within an experimental campaign at a combined heat and power plant of 8 MW fuel input. The results are outlined with regard to the process conditions and achieved product gas composition. Furthermore, the results are compared with standard steam gasification of biomass as well as with application of absorption enhanced reforming process at pilot plant scale.
Naphtha is a volatile petroleum fraction containing C4–C15 hydrocarbon compounds used as feedstock for petrochemical processes which are seriously affected by trace metals. Simple methods for copper, iron, lead and silicon determination in naphtha using graphite furnace atomic absorption spectrometry (GFAAS) have been developed. Two different approaches are presented: direct injection of the sample and oil-in-water microemulsion formation using a mixture of the sample, propan-1-ol and nitric acid aqueous solution. The calibration curves showed linear response for each concentration range with correlation coefficients ranging from 0.9728 to 0.9998. Precision figures of 1.7–20%, reported as the relative standard deviation, were calculated from at least twenty consecutive measurements of solutions containing the metal in a concentration level below 100 μg L−1. The characteristic masses varied from 8.5 to 44 pg and the limit of detection, defined as the metal concentration that gives a response equivalent to three times the standard deviation of the blank (n = 10), was found to be within the range 0.01–26 μg L−1. A critical analysis is presented by the authors emphasizing the advantages and limitations of both approaches. The proposed procedures have been used for copper, iron, lead and silicon determination in naphtha feeds processed in Braskem S.A. (Camacari, Bahia, Brazil).
A two-step process capable of removing NOx and SO2 simultaneously was proposed, which was made up of an ozonizing chamber and an absorber containing a reducing agent solution. Nitrogen oxides (NO plus NO2) in most practical exhaust gases consist chiefly of NO. The injection of ozone into the exhaust gas gives rise to a rapid oxidation of NO to NO2. Compared to NO, NO2 has relatively high solubility in water, and it can readily be reduced to N2 when the NO2-rich exhaust gas is brought into contact with the reducing agent solution. Sodium sulfide (Na2S) used as the reducing agent in this study can also remove SO2, effectively. As the exhaust gas passed through the ozonizing chamber and the absorber sequentially, NOx removal efficiency of about 95% and SO2 removal efficiency of 100% were obtained. The formation of H2S from sodium sulfide could be suppressed by using a basic reagent, together with the reducing agent. The rate of depletion of the reducing agent during the treatment of the exhaust gas was much faster than expected by reaction stoichiometry, obviously due to the oxygen in the exhaust gas. The amount of sodium sulfide required was found to be about four times the amount of NOx and SO2 removed.