Article

Production of Fischer-Tropsch Liquid Fuels from High Temperature Solid Oxide Co-Electrolysis Units

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... However, high voltage increases the power requirements and so the efficiency declines. Thus, the operating temperature of SOECs has to be a balance between the operation at the thermal-neutral voltage in which the energy for isothermal operation is supplied by heat generated from ohmic losses, and the operation below the thermal-neutral voltage that decreases the outlet temperature and, thus increases methanation reaction and decreases the amount of CO produced via RWGS [266]. Hence, if syngas is produced for methane synthesis, the operation at low temperatures and high pressures is advantageous, even though the methanation reaction is exothermic and effective heat removal is required [267]. ...
... Hence, if syngas is produced for methane synthesis, the operation at low temperatures and high pressures is advantageous, even though the methanation reaction is exothermic and effective heat removal is required [267]. which the energy for isothermal operation is supplied by heat generated from ohmic losses, and the operation below the thermal-neutral voltage that decreases the outlet temperature and, thus increases methanation reaction and decreases the amount of CO produced via RWGS [266]. Hence, if syngas is produced for methane synthesis, the operation at low temperatures and high pressures is advantageous, even though the methanation reaction is exothermic and effective heat removal is required [267]. ...
... Molar composition on a dry basis of outlet gaseous compounds with a cathode inlet temperature of 800 °C (a) as a function of operating pressure; (b) as a function of outlet temperature at a pressure of 160 kPa. Reprinted with permission from[266]. ...
Article
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Innovative renewable routes are potentially able to sustain the transition to a decarbonized energy economy. Green synthetic fuels, including hydrogen and natural gas, are considered viable alternatives to fossil fuels. Indeed, they play a fundamental role in those sectors that are difficult to electrify (e.g., road mobility or high-heat industrial processes), are capable of mitigating problems related to flexibility and instantaneous balance of the electric grid, are suitable for large-size and long-term storage and can be transported through the gas network. This article is an overview of the overall supply chain, including production, transport, storage and end uses. Available fuel conversion technologies use renewable energy for the catalytic conversion of non-fossil feedstocks into hydrogen and syngas. We will show how relevant technologies involve thermochemical, electrochemical and photochemical processes. The syngas quality can be improved by catalytic CO and CO2 methanation reactions for the generation of synthetic natural gas. Finally, the produced gaseous fuels could follow several pathways for transport and lead to different final uses. Therefore, storage alternatives and gas interchangeability requirements for the safe injection of green fuels in the natural gas network and fuel cells are outlined. Nevertheless, the effects of gas quality on combustion emissions and safety are considered.
... According to de Klerk [36], this value is in the range of typical industrial low-temperature Fischer-Tropsch syntheses. The total conversion of carbon monoxide was set at 80%, reflecting the work of Becker, et al. [59], Trippe [35], and Schemme [54]. ...
... The required electrolysis power for the base case was determined to be approximately 643.4 MW for the co-electrolysis and 33.8 MW for the water electrolysis processes. According to Brynolf et al. [59], the maximum output by an SOEC to be expected by 2030 is 50 MW. Accordingly, a total of 14 SOEC units are required for the power-to-fuel process. ...
... However, a depreciation period t and an interest rate i must first be specified in order to determine the annuity. According to Brynolf et al. [59], lifetimes of between 10 and 20 years are to be expected for SOEC systems and maximum lifetimes of less than 90,000 operating hours for SOEC stacks. According to Schmidt et al. [78], for SOEC stacks, maximum operating times of over 100,000 h or, according to one of the experts questioned, of just 30,000 h, can be expected. ...
Article
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As a part of the worldwide efforts to substantially reduce CO2 emissions, power-to-fuel technologies offer a promising path to make the transport sector CO2-free, complementing the electrification of vehicles. This study focused on the coupling of Fischer–Tropsch synthesis for the production of synthetic diesel and kerosene with a high-temperature electrolysis unit. For this purpose, a process model was set up consisting of several modules including a high-temperature co-electrolyzer and a steam electrolyzer, both of which were based on solid oxide electrolysis cell technology, Fischer–Tropsch synthesis, a hydrocracker, and a carrier steam distillation. The integration of the fuel synthesis reduced the electrical energy demand of the co-electrolysis process by more than 20%. The results from the process simulations indicated a power-to-fuel efficiency that varied between 46% and 67%, with a decisive share of the energy consumption of the co-electrolysis process within the energy balance. Moreover, the utilization of excess heat can substantially to completely cover the energy demand for CO2 separation. The economic analysis suggests production costs of 1.85 €/lDE for the base case and the potential to cut the costs to 0.94 €/lDE in the best case scenario. These results underline the huge potential of the developed power-to-fuel technology.
... Integration of adjacent units is another way to improve energy efficiency. The research [23] presents an example of the integration of the HTCE unit and the Fischer-Tropsch process. In another research, the authors of [24] created a simplified thermodynamic model of an integrated HTCE unit and a Fischer-Tropsch process. ...
... Since the UniSim software cannot simulate the adsorption column and the chelated iron solution used in the LO-CAT process, it has been assumed that the feedstock is free of sulfur and sulfur derivatives. This assumption is supported by the fact that after its purification, the feedstock contains no more than 1 ppm of sulfur and its derivatives [23]. Therefore, it can be argued that the assumption made will not affect the physicochemical properties of technological streams. ...
... The PFD of syngas production by high-temperature co-electrolysis of CO 2 and H 2 O, proposed in Ref. [23] and the simulation PFD is shown in Fig. 5. ...
Article
This paper deals with the emission reduction in synthesis-gas production by better integration and increasing the energy efficiency of a high-temperature co-electrolysis unit combined with the Fischer-Tropsch process. The investigated process utilises the by-product of Fischer-Tropsch, as an energy source and carbon dioxide as a feedstock for synthesis gas production. The proposed approach is based on adjusting process streams temperatures with the further synthesis of a new heat exchangers network and optimisation of the utility system. The potential of secondary energy resources was determined using plus/minus principles and simulation of a high-temperature co-electrolysis unit. The proposed technique maximises the economic and environmental benefits of inter-unit integration. Two scenarios were considered for sharing the high-temperature co-electrolysis and the Fischer-Tropsch process. In the first scenario, by-products from the Fischer-Tropsch process were used as fuel for a high-temperature co-electrolysis. Optimisation of secondary energy sources and the synthesis of a new heat exchanger network reduce fuel consumption by 47% and electricity by 11%. An additional environmental benefit is reflected in emission reduction by 25,145 tCO2/y. The second scenario uses fossil fuel as a primary energy source. The new exchanger network for the high-temperature co-electrolysis was built for different energy sources. The use of natural gas resulted in total annual costs of the heat exchanger network to 1,388,034 USD/y, which is 1%, 14%, 116% less than for coal, fuel oil and LPG, respectively. The use of natural gas as a fuel has the lowest carbon footprint of 7288 tCO2/y. On the other hand, coal as an energy source has commensurable economic indicators that produce 2 times more CO2, which can be used as a feedstock for a high-temperature co-electrolysis. This work shows how in-depth preliminary analysis can optimise the use of primary and secondary energy resources during inter-plant integration.
... High power consumption and high temperatures of process streams affect the cost of syngas as well as lead to increased CO2 emissions. Integration of the high-temperature co-electrolysis unit and the Fischer-Tropsch process allows reducing the import of electricity due to the use of by-products of the Fischer-Tropsch process for heat and power cogeneration (Becker et al., 2012). The synthesis of a recovery network may maximise the energy benefits and reduce the total cost of the processing. ...
... The object of the research is the unit of high-temperature co-electrolysis of CO2 and H2O, which is described in (Becker et al., 2012). The feedstock for this unit is CO2 from a coal gasification unit. ...
... The stream table (Table 1) is compiled using the data presented in (Becker et al., 2012) and data obtained from the developed simulation model. There are 4 streams with the adjustable target temperature, which may increase the unit's energy efficiency remain the same quality of the final product. ...
... 3 To enable large shares of renewables, thus requires smoothing or shifting the net grid load. Several approaches to address the so-called 'duck curve' are being pursued including development of large-scale electrical energy storage, 4 concentrating solar power plants with thermal energy storage, 5 Power-to-Gas platforms, [6][7][8] and dynamic dispatch of gas turbine plants. 9 Regardless of the method, devices that are capable of rapid transient operation and can serve as flexible, dispatchable power generation sources could act as de facto energy storage (or minimally reduce grid storage capacity requirements), increasing the penetration of renewables through load-following operation and grid flexibility, thereby increasing their market value proposition. ...
... To predict performance of commercialscale cell-level operation, the electrochemical submodel is calibrated against button cell data and coupled with the cell conservation equations (Eqs. [5][6][7][8][9][10][11][12][13][14][15][16]. In order to solve the model, a cell geometry must be imposed which is given in Table II anode, 20 µm BZY20 electrolyte, and 40 µm doped BZY cathode. ...
Article
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Protonic ceramic fuel cells (PCFC) have emerged as a promising candidate for distributed power generation. The reduced temperature cells (∼500°C) have the potential to enable faster start-up times, longer life, and lower cost materials compared to oxygen-ion conducting fuel cells. However, the modeling of PCFCs is confounded by several challenges, including estimating open circuit conditions for mixed charged conductors. Here we present the development of a PCFC computational framework for a predictive cell-level, interface charge transfer model capturing mixed conduction, as well as transients. Our approach employs a 1-D heterogeneous channel-level modeling strategy that resolves fuel depletion and flow configuration effects along the length of the channel and is coupled to a semi-empirical electrochemical model. The model is formulated in such a way that allows for easy integration of modeling parameters extracted from button cell experiments and performance scale-up to cell-level predictions. Humidified methane-fueled simulations display power densities above 0.125 W-cm−2 at 500°C, 0.15 A cm−2, and 80% fuel utilization cell conditions. Dynamic simulations indicate that the lower power density PCFCs (relative to solid oxide fuel cells) result in relatively slow thermal transients that could potentially dampen harmful effects of current-based fuel control during load-following operation.
... The ratio of H2 and CO2 is given by the mean carbon chain length of the diesel or kerosene fraction. The second pathway is based on co-electrolysis, which uses CO2 in combination with water vapor to produce syngas [22]. In addition to the FT synthesis routes, conventional diesel and kerosene supply by crude oil refinement can be used by the energy system model. ...
... All technology parameters used in the energy system simulation are based on [6,21,22] and own assumptions. The H2, CO2 and N2 supply as feedstock for synthesis routes are discussed in 2.2.5. ...
Conference Paper
The integration of the heat sector alongside the electricity sector in energy system analysis is nowadays widely practiced. However, in order to achieve the planned CO2 emission targets, the mobility and transport sector as well as the chemical sector must be considered. Besides a fully electrification or at least decarbonization of the passenger transport, the cargo sector is expected to stay fuel dependent. In the same way, chemical production will continue to be carbon-based in the long term. Therefore, a full decarbonization of the energy and material system is unlikely. However, a complete defossilization is achievable and has to be a long-term goal. One possibility is a purely power-based supply of chemicals und fuels (Power-to-X), which to a certain point would be technically feasible based on simplified estimates for the German energy system. Nevertheless, depending on different possible developments of the mobility, power, heat and chemical demands, a surplus of installed capacities of wind and solar power, as well as storage systems are needed. This paper uses opti-mization to evaluate different future demand scenarios for Germany, to determine the possibilities of defossil-izing the German energy system. This study shows, that to reach CO2-emission targets, extensive changes in demand behavior and large renewable capacities are needed. In contrary, scenarios which follow the current trend, are not able to fulfill the emission targets. The best case scenario, with a 50 % reduction in mobility demand and a fuel switch to electricity and H2 based transportation systems enable net zero CO2-balances in the electricity and transportation sector. Only the chemical sector stays, to some extent, dependent on nat-ural gas.
... 40 Fischer-Tropsch systems produce a wax (hydrocarbon mixture) that can be upgraded into different fuels. Within the scope of this study, it is assumed that for every unit of ptx diesel, nearly one half unit of ptx gasoline is produced (Becker et al. (2012)). See Appendix 5.6 for more information. ...
... 51 Fischer-Tropsch synthesis is a more complex process in which carbon monoxide and hydrogen build carbon chains via a series of exothermic reactions followed by an endothermic hydrocracking isometrisation distillation to separate the crude product into usable fuels (e.g., ptx gasoline, ptx diesel). A simplified production ratio of ptx gasoline to ptx diesel of 9.8 : 20.1 is applied in the model (Becker et al. (2012)). CO 2 is used to create the carbon monoxide via reverse CO shift ). ...
Thesis
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This dissertation analyzes several aspects of the economics of decarbonizing the electricity and transport sectors. All chapters focus on systems with high shares of variable renewable energies, characterized by time-varying and interdependent temporal and spatial distributions of electricity supply and electricity demand. Chapters 2 and 3 focus on the implications of variable renewable energies on security of supply and how reliability targets can efficiently be reached considering the firm capacity provision of variable renewable energies and interconnectors. Chapter 2 develops, based upon probabilistic reliability metrics, an optimization model to determine the efficient amount and location of firm generation capacity to achieve reliability targets in multi-regional electricity systems. Chapter 3 develops an iteration framework, which allows to combine the previously presented optimization model with a large-scale investment and dispatch model for electricity markets. The framework allows to account for balancing effects in electricity generation and firm capacity provision due to the spatial distribution of generation capacities and interconnectors. Chapter 4 investigates the impact of strong climate change on electricity systems. For Europe, most important are effects on variable renewable energy resources, hydro power availability, cooling water availability for thermal power plants and electricity consumption. Two investment planning strategies are compared in their ability to cope with climate change effects, which are then disentangled in terms of their marginal contribution to the potential welfare loss. Chapter 5 assesses, how the electricity and road transport sector can optimally be decarbonized, accounting for synergies in supply and demand when coupling the two sectors via electrification and power-to-x processes. Thereby, an integrated multi-sectoral partial-equilibrium investment model for the electricity and road transport sectors is developed.
... Becker et al. determined a system efficiency of 51% for a plant including the subsequent processing of the Fischer-Tropsch syncrude to gasoline and diesel [37]. Cinti et al. included the recirculation of tail gas to the SOEC (operating in co-electrolysis mode) unit's inlet in combination with a Fischer-Tropsch reactor, and obtained a PtL efficiency of 57% [35]. ...
Article
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Power-to-Liquid (PtL) plants can viably implement carbon capture and utilization technologies in Europe. In addition, local CO2 sources can be valorized to substitute oil and gas imports. This work’s aim was to determine the PtL efficiency obtained by combining a solid oxide electrolyzer (SOEC) and Fischer–Tropsch synthesis. In addition, a recommended plant configuration to produce synthetic fuel and wax at pilot scale is established. The presented process configurations with and without a tail gas reformer were modeled and analyzed using IPSEpro as simulation software. A maximum mass flow rate of naphtha, middle distillate and wax of 57.8 kg/h can be realized by using a SOEC unit operated in co-electrolysis mode, with a rated power of 1 MWel.. A maximum PtL efficiency of 50.8% was found for the process configuration without a tail gas reformer. Implementing a tail gas reformer resulted in a maximum PtL efficiency of 62.7%. Hence, the reforming of tail gas is highly beneficial for the PtL plant’s productivity and efficiency. Nevertheless, a process configuration based on the recirculation of tail gas without a reformer is recommended as a feasible solution to manage the transition from laboratory scale to industrial applications.
... The production of liquid fuels from renewable electricity has been previously studied e.g. by [8][9][10][11][12][13][14][15], who investigated different process designs for example different strategies for using the tail gas, different hydrogen and carbon monoxide production routes and different FT reactors. [13,15] have studied similar PtL process configurations as described in this work. ...
Article
Fischer-Tropsch based fuels from renewable electricity and carbon dioxide provide one possibility to defossilise the transport sector, especially where long distances and high loads require fuels with high energy density. In this work, a stationary Power-to-Liquid (PtL) process model is set up in Aspen Plus®. The process involves CO2 absorption, water electrolysis, CO2 activation by reverse water-gas shift reaction (rWGS), an oxyfuel burner, Fischer-Tropsch synthesis, product separation and hydrocracking. The influence of the rWGS operating conditions (pressure and temperature) on the overall process performance in terms of PtL-efficiency and hydrogen/carbon efficiency is investigated. The operating conditions are varied between 550 and 950 °C and 1–25 bar. The temperature and pressure dependent methane formation in the rWGS is found to have major influence on the efficiencies. For the base case, a maximum Power-to-Liquid efficiency of ηPtL = 38.7 % is obtained at 5 bar and 825 °C, while a maximum hydrogen efficiency of ηH = 28 % results at 1 bar and 725 °C. The carbon efficiency is found to be constant (ηC = 88 %). Sensitivity studies show that the optimum operating conditions are not affected significantly by variation of the investigated process variables.
... Solid Oxide Electrolyzers (SOEC) have been studied especially in experimental research focused, searching resistant materials according to high temperature and oxidation-reduction environments [10]- [12]. However experimental investigations of these electrochemical devices, which requires materials with special characteristics, are extremely expensive. ...
Conference Paper
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High temperature electrolysis process coupled to a very high temperature reactor (HTTR) is one of the most promising methods for hydrogen production using a nuclear reactor as the primary heat source. However there are not references in the scientific publications of a test facility that allow to evaluate the efficiency of the process and other physical parameters that has to be taken into consideration for its accurate application in the hydrogen economy as a massive production method. For this lack of experimental facilities, mathematical models are one of the most used tools to study this process and theirs flowsheets, in which the electrolyzer is the most important component because of its complexity and importance in the process. A computational fluid dynamic (CFD) model for the evaluation and optimization of the electrolyzer of a high temperature electrolysis hydrogen production process flowsheet was developed using Ansys FLUENT®. Electrolyzer’s operational and design parameters will be optimized in order to obtain the maximum hydrogen production and the higher efficiency in the module. This optimized model of the electrolyzer will be incorporated to a chemical process simulation (CPS) code to study the overall high temperature flowsheet coupled to a high temperature accelerator driven system (ADS) that offers advantages in the transmutation of the spent fuel.
... (1)e (3). The syngas can be converted into other fuels with a further approach such as Fischer-Tropch processes [1,4]. rSOFC is appropriated to balance the conflicts between energy supply and demand in both traditional and new energy systems, with advantages of compact, high power density and simple design [5,6]. ...
Article
A two-dimensional mathematical model is developed for a single-cell based on the planar configuration and validated by relevant experimental data, with an aim to describe the coupling phenomena of the multiphysics transport processes and the meso-scale elementary reactions. It is revealed that desorption and adsorption reactions in the electrode mostly take place near the electrolyte and the channel, respectively; the distribution of the surface species depends on the gas diffusion in the porous electrode affected by the thickness and microstructure of the electrode. The electrochemical reactions are centralized in about 100 μm thick electrode from the electrolyte. Nis and COs are the major surface species in both fuel cell (FC) and electrolysis cell (EC) modes. Os is higher in the FC mode, particularly near the electrolyte due to the desorption and charge transfer reactions; The microscopic structure properties, including average porosity, tortuosity and particle size, are also influential on the elementary reactions due to the gas diffusion through the tortuous pathways and the active sites on the catalyst surfaces. It is also found that the performance predicted in the global models is often overestimated, because the limitations of the local elementary reactions are not considered in the global model.
... According to the FT synthesis analysis derived in Becker et al. (2012), the synthesis gas conversion to FT-liquids stated in (30) consumes approximately 50 kJ /mol −CH 2 − of electric energy (compression of synthesis gas to 40 bar) and 30 kJ /mol −CH 2 − (distillation, upgrading processes). ...
Article
Full-text available
Synthetic fuels produced with renewable surplus electricity depict an interesting solution for the decarbonization of mobility and transportation applications which are not suited for electrification. With the objective to compare various synthetic fuels, an analysis of all the energy conversion steps is conducted from the electricity source, i.e., wind-, solar-, or hydro-power, to the final application, i.e., a vehicle driving a certain number of miles. The investigated fuels are hydrogen, methane, methanol, dimethyl ether and Diesel. While their production process is analyzed based on literature, the usage of these fuels is analyzed based on chassis dynanometer measurement data of various EURO-6b passenger vehicles. Conventional and hybrid power-trains as well as various carbon dioxide sources are investigated in two scenarios. The first reference scenario considers market-ready technology only, while the second future scenario considers technology which is currently being developed in industry and assumed to be market-ready in near future. With the results derived in this study and with consideration of boundary conditions, i.e., availability of infrastructure, storage technology of gaseous fuels, energy density requirements, etc., the most energy efficient of the corresponding suitable synthetic fuels can be chosen.
... While direct oxidation and reduction of CO and CO 2 , respectively have been shown to occur in ReSOCs [47], previous modeling work on co-electrolysis of steam and CO 2 [48,49] has shown that because the bulk channel gas is in chemical equilibrium, the relative electrochemical reduction of steam and carbon dioxide does not affect the Fig. 2. Schematic of the ReSOC system in power-to-gas mode. E.P. Reznicek and R.J. Braun Applied Energy 259 (2020) 114118 overall conversion and local energetics. ...
Article
Electrical energy storage (EES) is necessary to enable greater penetration of renewables and as a grid-balancing solution, but current EES technologies suffer from capacity or geological limitations and high cost. Reversible solid oxide cells (ReSOCs) are an electrochemical energy conversion technology that can produce both electricity from fuel (gas-to-power) and fuel from electricity (power-to-gas), depending on resource availability and de-mand. Leveraging in situ C-O-H chemistry and operating at intermediate temperature (600 C) and elevated pressure (10–20 bar) enables these cells to be mildly exothermic, eliminating the need for external heat input or high over-potential (low-efficiency) operation during electrolysis mode. This operating strategy also results in higher methane production during electrolysis, facilitating easier integration with natural gas pipeline infra- structure over steam/hydrogen electrolytic processes. This study proposes a ReSOC system integrated with both natural gas pipeline and carbon capture and storage (CCS) infrastructure to render a flexible, grid energy management resource. In gas-to-power mode, the system takes natural gas from a pipeline to produce electricity. Un-utilized fuel is combusted with oxygen and expanded through a turbine to produce more power. The water in the exhaust is condensed, and the remaining carbon dioxide is compressed for tanker or pipeline transportation to a carbon sequestration site. In power-to-gas mode, carbon dioxide and water are co-electrolyzed in the stack to produce methane and hydrogen, which can be injected directly into a natural gas pipeline or further refined into a purer stream of methane. We explore system design concepts, performance, and cost of a 50 MWe ReSOC system. Results indicate that synthetic natural gas (92.0% methane) can be produced at $22.7/MMBTU with a lower heating value efficiency of 81%. Alternatively, a system that net meters produced syngas and operates in power producing mode 50% of the time can generate electricity at a levelized cost of 10.5 /kWh with an efficiency of 69% (LHV), while producing exhaust that is 95.5% carbon dioxide at 40 bar. If the system operates disproportionally in gas-to-power mode the LCOE drops to near 6¢/kWh. The economic outlook for mature ReSOC systems presented herein are found to be competitive with current energy storage technologies and natural gas peaker plants.
... By combining the electrolysis and gasification with a fuel synthesis reactor, it becomes possible to synthesize SNG [19] or liquid fuels such as DME [20], FT (Fischer-Tropsch) [21] and methanol [22]. Additional hydrogen helps to achieve the required stoichiometry for the maximum production of methanol/SNG from the available biomass [23]. ...
Article
Chemical energy storage in the form of hydrogen is playing an important role in the synthesis of alternative energy carriers such as Synthetic Natural Gas (SNG), Methanol and Dimethyl ether (DME) supplementing with a carbon source. The only renewable carbon source is biomass, which is a limited resource. However, the addition of hydrogen could potentially extend the existing biomass resources. This paper describes the modelling of a novel combined Solid Oxide Electrolysis Cell (SOEC) and oxygen blown biomass gasification system using Aspen Plus. One of the advantages of using such a combined system is the use of oxygen for gasification and reforming. The comparison of reforming technologies showed that an autothermal reformer (ATR) could be an advantage since oxygen is already available from the electrolysis stack and the ATR produced syngas has higher CO/CO2 ratio, which increases the methanol synthesis’s reaction rate. ATR requires much less energy ∼13 MW for almost complete methane conversion compared to ∼35 MW for Steam Reforming (SR). The advantage of using inter cooled compression upstream or downstream for such a combined process has been explained. A methanol thermal conversion efficiency of 72.08 % can be achieved for gasification and SOEC combined system compared to 55.7% for only gasifier system.
... Alternatively, CO 2 and steam can be fed into a high temperature (solid oxide) electrolyser to produce hydrogen and carbon monoxide, as demonstrated by Sunfire at a plant in Germany [61]. Electricity requirements for the complete Fischer-Tropsch process (including for hydrogen production from electrolysis and other process requirements) are around 1.6-2.1 MWh Elec per MWh LHV of hydrocarbons produced [61,62]. CO 2 utilisation is 0.43-0.56 ...
Article
There is increasing interest in carbon capture, utilisation and storage (CCUS) and hydrogen-based technologies for decarbonising energy systems and providing flexibility. However, the overall value of these technologies is vigorously debated. Value chain optimisation can determine how carbon dioxide and hydrogen technologies will fit into existing value chains in the energy and chemicals sectors and how effectively they can assist in meeting climate change targets. This is the first study to model and optimise the integrated value chains for carbon dioxide and hydrogen, providing a whole-system assessment of the role of CCUS and hydrogen technologies within the energy system. The results show that there are opportunities for CCUS to decarbonise existing power generation capacity but long-term decarbonisation and flexibility can be achieved at lower cost through renewables and hydrogen storage. Methanol produced from carbon capture and utilisation (CCU) becomes profitable at a price range of £72–102/MWh, compared to a current market price of about £52/MWh. However, this remains well below existing prices for transport fuels, so there is an opportunity to displace existing fuel demands with CCU products. Nonetheless, the scope for decarbonisation from these CCU pathways is small. For investment in carbon capture and storage to become attractive, additional drivers such as decarbonisation of industry and negative emissions policies are required. The model and the insights presented in this paper will be valuable to policymakers and investors for assessing the potential value of the technologies considered and the policies required to incentivise their uptake.
... The total current flowing and power were estimated by Eqs. (10) and (11), respectively (Becker et al., 2012). ...
Article
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Global climate change is one of the major concerns of today's world. Indeed, the carbon capture and sequestration (CCS) has a great potential to abate global climate changes but the economic infeasibility of this process has motivated the researchers to develop methods for direct utilization of captured carbon dioxide (CO2) to value-added end products. For instance, the methanol production by hydrogenation of CO2 is extensively investigated for over two decades but the high operating cost of this process, especially for hydrogen production, has discouraged its commercial implementation. In this work, a high temperature solid oxide electrolyzer (SOE) as a source of hydrogen production (12.16 ton/hr) from steam is integrated with the CO2 hydrogenation process to reduce the cost of methanol production. Integration of SOE with methanol production process resulted into 22.3% reduction in the cost of hydrogen as compared to the alkaline water electrolyzer. Consequently, the cost of 63.5 ton/hr methanol production was reduced, from 1063 $/ton to 701.5 $/ton, by employing SOE and optimizing the process flowsheet (by considering seven different configurations of the flowsheet, along with heat and process integrations). It is anticipated that a further reduction in the cost of methanol production by aforementioned process is possible by the advancement of hydrogen production technology, especially the high performance materials development and commercialization of electrolyzers.
... process industries. By combining CO 2 with electrolytic H 2 or alternatively co-electrolysis of H 2 O and CO 2 , syngas can be generated for the production of various synthetic fuels, such as Synthetic Natural Gas (SNG) [16,17], Fischer-Tropsch (FT) fuels [18,19], Dimethyl Ether (DME) [20] or Methanol (MeOH) [12]. ...
Article
Synthetic fuels produced from carbonaceous sources and renewable electricity can play an important role in phasing out fossil fuels. By integrating electricity in fuel production, an indirect electrification of long-distance sea, air and road transport becomes feasible. This paper presents the modeling analysis of a flexible system for the conversion of biomass and electricity to methanol. The system integrates an efficient TwoStage biomass gasifier and solid oxide cells (SOC). The SOC can operate in both electrolysis mode and fuel cell mode. In this way, the system can store electricity in the form of methanol in electrolysis mode or have co-production of electricity in fuel cell mode. Additional operational modes are also presented, making it feasible to operate the system no matter the electricity price. The heat for the endothermic gasification reactions is provided either through electric heating or partial oxidation directly in the char fluid bed gasifier. Five operating modes have been modeled and analyzed, showing a promising input–output efficiency ranging between 71% with maximum electricity consumption, and 37% when producing only electricity (LHVdry). The presented system outperforms most of the more conventional state-of-the-art systems using biomass gasification as route to produce methanol. Most importantly, its flexibility enables continuous operation no matter the electricity price.
... Moreover, this type of high temperature electrolysers can also be used to produce synthetic fuels by reducing CO 2 and steam simultaneously. This co-electrolysis reaction consists in a combined reduction of H 2 O and CO 2 into H 2 and CO, respectively, forming the so-called syngas that can be converted afterwards into CH 4 (by methanation through the Sabatier reaction [2]) or a liquid fuel (via Fischer-Tropsch synthesis [3]). Furthermore, these power-to-gas or power-toliquid routes represent a highly efficient strategy to couple the two major energy infrastructures of the current system, i. e. the gas and the electricity networks [4e6]. ...
Article
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Symmetrical solid oxide cells (s-SOC) present several advantages compared to typical configuration, as a reduction of sintering steps or a better thermomechanical compatibility between the electrodes and the electrolyte. Different mixed ionic-electronic conductors (MIEC) have been reported as suitable candidates for symmetrical configuration, allowing operations under steam electrolysis (SOEC) or co-electrolysis (co-SOEC) without the use of reducing safe gas (typically employed in SoA nickel based cells). In the present study, Sr2Fe1.5Mo0.5O6−δ (SFM) electrodes are deposited on both sides of YbScSZ tapes previously coated with a Ce1-xGdxO1.9 (GDC) barrier layer grown by PLD. Electrode sintering temperature is optimized and fixed at 1200 °C by means of electrochemical impedance spectroscopy (EIS) measurements in symmetrical atmosphere. The cell is then characterized at 900 °C in SOEC and co-SOEC modes without the use of any safe gas obtaining high current densities of 1.4 and 1.1 A cm⁻² at 1.3 V respectively. Short-term reversibility is finally proven by switching the gas atmosphere between the cathode and anode sides while keeping the electrolysis conditions. Similar performances are obtained in both configurations.
... Due to the presence of all the components required for the rWGS and CH 4 -forming reactions, these also occur within an HTCE unit, potentially reducing product yield. HTCE for the production of syngas has been studied in the contexts of CH 4 production by SMR [21], methanol production [22] and the Fischer-Tropsch process [23]. The main focus for the HTCE in this study however is syngas for use as reducing gas in steel production. ...
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This study investigates the integration of water electrolysis technologies in fossil-free steelmaking via the direct reduction of iron ore followed by processing in an electric arc furnace (EAF). Hydrogen (H2) production via low or high temperature electrolysis (LTE and HTE) is considered for the production of carbon-free direct reduced iron (DRI). The introduction of carbon into the DRI reduces the electricity demand of the EAF. Such carburization can be achieved by introducing carbon monoxide (CO) into the direct reduction process. Therefore, the production of mixtures of H2 and CO using either a combination of LTE coupled with a reverse water-gas shift reactor (rWGS-LTE) or high-temperature co-electrolysis (HTCE) was also investigated. The results show that HTE has the potential to reduce the specific electricity consumption (SEC) of liquid steel (LS) production by 21% compared to the LTE case. Nevertheless, due to the high investment cost of HTE units, both routes reach similar LS production costs of approximately 400 €/tonne LS. However, if future investment cost targets for HTE units are reached, a production cost of 301 €/tonne LS is attainable under the conditions given in this study. For the production of DRI containing carbon, a higher SEC is calculated for the LTE-rWGS system compared to HTCE (4.80 vs. 3.07 MWh/tonne LS). Although the use of HTCE or LTE-rWGS leads to similar LS production costs, future cost reduction of HTCE could result in a 10% reduction in LS production cost (418 vs. 375 €/tonne LS). We show that the use of HTE, either for the production of pure H2 or H2 and CO mixtures, may be advantageous compared to the use of LTE in H2-based steelmaking, although results are sensitive to electrolyzer investment costs, efficiencies, and electricity prices.
... They assumed the plant will operate 30 years before all equipment are fully depreciated. Another study is the FT fuel synthesis using solid oxide electrolytic cells (SOEC) unit byBecker et al., 2012. They investigated the SOEC with varied operating pressures of 1.6 and 5 bar, where only the latter is included inTable 4.11. ...
Thesis
Greenhouse gas emissions, especially the carbon dioxide out of fossil fuel combustion, has a significant annual inclination. Methanol economy, as proposed by Prof. George Olah, offers a sustainable solution for such a condition. Captured carbon dioxide and electrolytic hydrogen can react to form methanol, where methanol acts as the main hub for the carbon neutral cycle. There are two options for synthesizing methanol, the one-step direct CO2 hydrogenation process, and the two-step CAMERE process via Reverse Water-Gas Shift (RWGS) reaction. This study analyzes the two processes techno-economically, in order to find the best alternative for producing the sustainable methanol. The first step was modeling and simulation of both processes in AspenPlus® environment. Techno-economic assessment was thereafter conducted using the German Aerospace Center (DLR) in-house tool, TEPET. Net production costs of CAMERE were 2.02 €/kg or €2.84 per liter of gasoline equivalent. The one-step process resulted in less than 1 ct€ cheaper net production costs than CAMERE. Operational expenditures from electricity were the main part (around 65%) of the total production costs for both processes. Direct CO2 hydrogenation had higher Power-to-Liquid efficiency of 39.1%. However, CAMERE showed better technical performance in terms of methanol selectivity and net used CO2, where the system carbon conversion reaches 93.5% and 87.6% of total captured CO2 converted to methanol. Furthermore, CAMERE resulted in a higher Hydrogen-to-Liquid efficiency of 81.4%. In conclusion, CAMERE process is the design recommendation for the sustainable methanol synthesis plant.
... In other gasification approaches, lower H 2 /CO are expected and feeding additional hydrogen to the biosyngas would be necessary [7,8]. Besides, utilizing CO 2 from industrial processes, biogenic sources or directly from air to produce synthetic fuels by PtL routes has gained much attention in recent years [9]. As the input of FTS is syngas, CO 2 can be converted in a preliminary unit by reverse water gas shift reactors or using solid oxide electrolysis cells [10]. ...
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The role of lanthanides as promoters on cobalt-based catalysts for Fischer-Tropsch synthesis was evaluated under relevant biomass-derived syngas mixtures. Cerium, lanthanum and a combination of them were impregnated on an industrial cobalt-based micro-catalyst. Lanthanide incorporation did not affect significantly the morphology of the catalyst, although it reduced the available surface cobalt. Catalytic tests revealed that both the presence of carbon dioxide in the feed and lanthanides in the catalyst led to similar outcomes; higher selectivity to long-chain hydrocarbons, at the expense of reactivity. Reaction experiments were well aligned with in-situ DRIFTS measurements, which evidenced the modification of the initial reaction mechanism, CO2 conversion and the presence of lower CO-cobalt coverages. This work reports two relevant findings for FTS development. Firstly, the presence of carbon dioxide is beneficial for long-chain hydrocarbon production. Secondly, the incorporation of lanthanides increases the production of gasoline, kerosene and diesel fractions.
... This is less of an issue for OME x fuels due to their limited range of products and even less of an issue for DME production as a single component fuel, which requires a simple distillation. According to (Becker et al., 2012) and (Hänggi et al., 2019) it takes 80 kJ/mol of electrical energy to transform 1 mol of CO into the desired diesel product. Although only 85% of the initial FT products can be formulated into the desired diesel product (Oscar et al., 2009), the other 15% can be burnt as a heat source for processes such as distillation or the water gas shift reaction. ...
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The utilization of captured CO2 for fuel, chemicals and materials is currently a focus of significant research effort as a method that can simultaneously mitigate greenhouse gas effect while reduce fossil fuel depletion. In this work, CO2 source is provided by a desirable three-stage Fe-based chemical looping combustion power system that can achieve zero-energy-penalty CO2 capture while simultaneously obtain pure H2 source. The aim of this study is to present this designed process for the first time with demonstrating it as an energy-efficient and environmental-friendly CO2-to-liquid fuel pathway. Within this context, the liquid fuels energy output and carbon emissions are compared with different CO2 utilization ratios to the thermodynamic assessment, intending to disclose the insufficiency location within system. With conceivable improvements in an optimum condition, the fuel energy saving ratio and CO2 emission ratio of this process are projected to be 12.19% and 98.46%, respectively in relative to separate production system. The maximal exergy destruction, though projected to be located in chemical looping hydrogen generation unit (as represented by 37.56% of total exergy destruction), still has opportunities to reduce in some extent by elevating oxygen carries high-temperature resistance along with future research needs. Finally the sensitivity analysis is also projected to assess the strong influencing parameters that affect the system performance.
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Kinetics and mechanisms of Fischer–Tropsch synthesis were investigated over a %10Fe/%10Co/%80γ-Al2O3 nano catalyst prepared by the impregnation method in a fixed bed micro-reactor. The ranges of operating conditions varied as T = 573.15–643.15 K, P = 1–7 bar, H2/CO feed ratio =1–2, and GHSV=3000 h⁻¹. The kinetic expressions for CH4, olefins, paraffins formation, and water gas shift reaction (WGSR) were developed based on the occupied sites in three steps. According to this theory, eighteen rate expressions for WGSR, CO consumption, and products formation were tested, and finally, the ethylene production and water step gave the best fitted kinetic model. The Levenberg–Marquardt algorithm was used to estimate the activation energy (66.01 kJ/mol) and the kinetic parameters. It was found that the proposed model could perfectly predict the effects of water and ethylene. These models can be applied to determine the optimum conditions and products in the reactor. Characterization of catalysts was carried out using different techniques, including BET and SEM.
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Renewable electricity has been developed very fast to reduce both the reliance on fossil energy and CO2 emission, and its utilization for the sustainable production of chemical products is of increasingly interest. In this work, opportunities for renewable electricity utilization in coal to liquid fuels process are studied through thermodynamic and techo-economic analysis. Three CPtL (coal and renewable power to liquid fuels) processes are investigated, namely Case GSP+E, Case Shell+E and Case Texaco+E. Exergy losses of the subsystems are quantitatively analyzed, and measures to reduce exergy losses are proposed. By integration with renewable electricity, carbon efficiency could be improved by 69.09-99.44%, and life cycle CO2 emission could be reduced by 37.81-44.85%; however, the production cost is raised by 54.18-94.07% due to the high cost of electricity and electrolyzer. Sensitivity analysis shows that electricity price has the most significant impact on the production cost. At present market conditions, CPtL is incompetent with coal to liquid fuels (CtL) process yet from the viewpoint of economics, but it might become viable in the future by decreasing electricity price (0.07 to 0.01 $/kWh), electrolyzer cost (1150 to 640 $/kW) and electricity consumption of electrolysis (4.70 to 4.05 kWh/Nm³ H2).
Chapter
Solid oxide electrolyser cells (SOECs) are high-temperature electrochemical energy conversion devices. They are capable of electrolysing water and carbon dioxide for hydrogen and carbon monoxide production. In this chapter, mathematical models are developed for SOEC for generation of hydrogen and carbon monoxide syngas, which can be further processed to produce various fuels or chemicals. The fuel-assisted SOECs are also modeled to reduce the consumption of electricity. The results demonstrate that the SOEC is a promising technology for efficient fuel generation using excess renewable power.
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Achieving the global and European climate targets requires a green transformation of the transport sector. Electrification may become a viable option in light road transportation, but the use of liquid fuels with high energy density will likely prevail in aviation, shipping and heavy-duty mobility. For these applications, electrofuels, produced from electricity and CO2, may be a promising option, especially in countries with high wind and solar energy potentials. In the present case study, the prospects of electrofuels in Denmark are investigated. At first, an in-depth analysis of the available raw material and energy resources was conducted. The design of a first Power-to-Liquid (PtL) plant was then developed and implemented in Aspen Plus® for a selected site in Denmark. The plant is subsequently analyzed in a techno-economic and ecological assessment. The results indicate that the unexploited Danish wind power potential is theoretically sufficient to entirely cover the expected future demand for alternative fuels through electrofuel production. Greenhouse gas reductions of 95% compared to fossil fuels can be achieved if electricity from renewable power sources is used. However, fuel production costs are significantly higher than crude oil market prices, resulting in very high GHG abatement costs compared to other carbon mitigation technologies.
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Fixed bed gasifiers are widely used for the production of clean alternative fuels, chemicals and electricity. Of the commercialized fixed bed gasifiers, BGL and Lurgi gasifiers are the most typical. In this paper, modeling, simulation and comparison of the coal to liquid fuels (CTL) process with BGL/Lurgi gasifier are conducted. For a typical CTL process with feeding rate of 852.74 t coal (dry)/h, Case BGL can produce Fischer-Tropsch (FT) liquids of 212.61 t/h, while Case Lurgi can produce 168.48 t/h. Case BGL demonstrates higher energy efficiency (44.91%) than Case Lurgi (41.21%) due to the higher syngas yield of BGL gasifier. The corresponding exergy efficiencies are 44.65% for Case BGL and 40.27% for Case Lurgi, respectively. The exergy losses of the subsystems are quantitatively analyzed and the measures to reduce exergy losses are proposed. The techno-economic and CO2 emission analysis are investigated. Finally, the performances of fixed bed and entrained flow gasifiers for CTL process are compared. It is found that gasification has an important influence on the thermodynamic efficiency, economics, and CO2 emission, and this research is useful for gasifier selection in the CTL process.
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In this study, a high‐temperature steam generator (HTSG) of cyclone cylindrical type has been developed for energy harvesting applications. Solid refuse fuel (SRF) is considered the thermal energy source. The operating conditions are steam temperature of 773 K, steam pressure of 0.3 to 0.6 MPa, and mass flow rate of 10 to 35 kg/h. The pressure drop of steam in the HTSG is analyzed through numerical methods, which can control the outlet pressure of steam for hydrogen stack application based on the experimental results. The maximum heat transfer efficiency of the HTSG system is 66% at 0.3 MP and 35 kg/h, which can generate 306 tons per year of high‐temperature steam. Moreover, the produced steam can be converted to 15.3 tons of hydrogen. The HTSG system can harvest 767 MWh of energy per year, and it is expected to significantly reduce energy consumption while minimizing the environmental impact. HTSG is developed for hydrogen production projects, which uses SRF as fuel. In order to derive a model suitable for hydrogen production conditions, the pressure drop and heat transfer performance are experimentally evaluated. The thermal efficiency of the HTSG system, which changes during steam generation, will be an indicator of industrial design. The high‐temperature steam generated by using SRF as a fuel is used for hydrogen production and is eco‐friendly, and CO2 emissions are reduced compared to other fossil fuels.
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High temperature co-electrolysis of H2O/CO2 allows for clean production of syngas using renewable energy, and the novel fuel-assisted electrolysis can effectively reduce consumption of electricity. Here, we report on symmetric cells YSZ-LSCrF | YSZ | YSZ-LSCrF, impregnated with Ni-SDC catalysts, for CH4-assisted co-electrolysis of H2O/CO2. The required voltages to achieve an electrolysis current density of −400 mA·cm⁻² at 850 °C are 1.0 V for the conventional co-electrolysis and 0.3 V for the CH4-assisted co-electrolysis, indicative of a 70% reduction in the electricity consumption. For an inlet of H2O/CO2 (50/50 vol), syngas with a H2:CO ratio of ≈2 can be always produced from the cathode under different current densities. In contrast, the anode effluent strongly depends upon the electrolysis current density and the operating temperature, with syngas favorably produced under moderate current densities at higher temperatures. It is demonstrated that syngas with a H2:CO ratio of ≈2 can be produced from the anode at a formation rate of 6.5·mL min⁻¹·cm⁻² when operated at 850 °C with an electrolysis current density of −450 mA·cm⁻².
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High temperature co-electrolysis can be a promising technology for the transformation of energy systems as it enables sector coupling and carbon dioxide utilization. In this article, we analyze the optimal layout and operation of distributed electrolysis sites powered exclusively by local renewable energy sources and a local battery storage device for current techno-economic parameters. For this purpose an energy system model with a spatial resolution of 277 regions within Europe is set up, which facilitates the analysis of intermittent renewable electricity generation, a battery storage device and the innovative high temperature co-electrolysis. We discuss the techno-economic competitiveness and analyze potential leverage points for improvement such as an enhanced flexibility. The lowest costs are found in Lincolnshire with 0.24 €/kWh and the highest costs in Central Slovakia with 0.49 €/kWh differing by more than a factor of two. Remarkably, several locations with vastly different resources and layouts lead to a similar techno-economic performance of the investigated system. We compare the techno-economic performance of high temperature co-electrolysis with steam methane reforming as the conventional synthesis gas production route.
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To improve the catalytic activity of La(Sr)FeO3 based perovskites (LSF) for CO2 reduction in solid oxide electrolysis cell (SOEC), CO2 adsorption and reduction reaction mechanism were investigated on 12 surface models describing the effects of surface oxygen vacancies and Ni/Mn doping (25% and 50% surface cation doping ratios). In particular, a phase diagram was established to find the most stable LSF structure under SOEC operating conditions. These were carried out using Density Functional Theory (DFT) + U calculations. A microkinetic model was then developed to simulate polarization curves and compared with the experimental data of pure LSF. Ni-Mn double doping with 2 surface oxygen vacancies of LSF was identified as the most effective electrocatalysts. This is attributed to fine tuning O affinity by Ni, Mn and Fe in B-site (catalytic active site), as indicated by the Bader charge analysis. Experimental studies for this material have yet to be reported in the literature.
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Meeting the Sustainable Development Goals and carbon neutrality targets requires transitioning to cleaner products, which poses significant challenges to the future chemical industry. Identifying alternative pathways to cover the growing demand for chemicals and fuels in a more sustainable manner calls for tight collaborative programs between experimental and computational groups as well as new tools to support these joint endeavours. In this broad context, we here review the role of Process Systems Engineering tools (PSE) in assessing and optimising alternative chemical production patterns based on renewable resources, including renewable carbon and energy. The focus is on the use of process modelling and optimisation combined with life cycle assessment methodologies and network analysis to underpin experiments and generate insight into how the chemical industry could optimally deliver chemicals and fuels with a lower environmental footprint. We identify the main gaps in the literature and provide directions for future work, highlighting the role of PSE concepts and tools in guiding the future transition and complementing experimental studies more effectively.
Article
Despite regulation efforts, CO2 emissions from European road transport have continued to rise. Increased use of electricity offers a promising decarbonization option, both to fuel electric vehicles and run power-to-x systems producing synthetic fuels. To understand the economic implications of increased coupling of the road transport and electricity sectors, an integrated multi-sectoral partial-equilibrium investment and dispatch model is developed for the European electricity and road transport sectors, linked by an energy transformation module to endogenously account for, e.g., increasing electricity consumption and flexibility provision from electric vehicles and power-to-x systems. The model is applied to analyze the effects of sector-specific CO2 reduction targets on the vehicle, electricity and power-to-x technology mix as well as trade flows of power-to-x fuels in European countries from 2020 to 2050. The results show that, by 2050, the fuel shares of electricity and power-to-x fuels in the European road transport sector reach 37% and 27%, respectively, creating an additional electricity demand of 1200 TWh in Europe. To assess the added value of the integrated modeling approach, an additional analysis is performed in which all endogenous ties between sectors are removed. The results show that by decoupling the two sectors, the total system costs may be significantly overestimated and the production costs of power-to-x fuels may be inaccurately approximated, which may affect the merit order of decarbonization options.
Article
Power-to-Liquid (PtL) processes are considered as a key technology for a fossil-free raw material and energy system. With multiple technical analyses being available and technical feasibility being proven by first pilot plants, pathways towards commercial market entry are of increasing interest. In this work multiple economic aspects of Power-to-Liquid plants are being investigated. First and foremost, the seamless integration of an economic analysis in the process modeling workflow will be demonstrated. This allows for an extensive investigation of the influence of operating conditions of the considered solid oxide electrolyzer (SOEL) on process economics and a subsequent optimization not only from an engineering standpoint but considering economics as well. Furthermore, the modular nature of the model allows for a comparison of SOEL to the more mature technology of low-temperature electrolysis with a focus on possible heat integration and by-product utilization. The potential of SOEL technology for high energetic efficiency and subsequently low production cost is highlighted. The conducted forecast to 2050 shows that SOEL-based Power-to-Liquid processes offer lower production cost of NPC = 0.203 €2020/kWhch compared to production cost of NPC = 0.262 €2020/kWhch for the PEMEL-based process. Furthermore, based on the results of the economic assessment possible governmental support mechanisms are studied, showing that projected values for governmental incentives are expected to decrease CO2 mitigation cost from κCO2 = 791 €2020/tCO2 to κCO2 = 419 €2020/tCO2 for the 2050 scenario. Thus, existing measures and currently discussed measures are not sufficient to ensure economic viability. Consequently, more extensive schemes such as mandatory quotas for sustainable PtL products need to be implemented in order to facilitate the market entry.
Article
Power-to-methanol processes with co-electrolysis in solid-oxide electrolyzer provides a promising approach to deal with two problems: large-scale renewable electricity storage and carbon capture and utilization. In this paper, a large-scale power-to-methanol system with solid-oxide electrolyzer co-electrolysis technology is studied. System-level heat integration and techno-economic assessment are conducted through a multi-objective optimization platform. The results indicate that there is a slight trade-off between the overall energy efficiency and methanol production cost. The system can achieve a high energy efficiency (72%) and carbon conversion efficiency (93.6%), with the annual CO2 utilization reaching 146.7 kton. However, its economic cost is high. SOE stack price, stack lifetime, and electricity price are crucial to the economic competitiveness of the system. By reducing the cost of SOE stack, extending its lifetime and reducing electricity price, the payback time can be shortened to 3–5 years. A stable supply of renewable electricity is a prerequisite for project investment. When the annual available hours of renewable electricity drop from 7200 to 3600, the payback time of the project increased to 21 years. Methanol synthesis with SOE co-electrolysis has outstanding heat integration performance. The system can recover heat in a Rankine cycle to enhance the overall energy efficiency.
Thesis
Due to the limited reserves of economically-recoverable fossil fuels and concerns about carbon dioxide emissions from their combustion, many countries have initiated a push to adopt more renewable energy sources in their grid. The fluctuating nature of renewable energy highlights the need for development of varied energy storage alternatives. Among the alternatives, chemical energy storage, in the form of liquid fuels, has gained attention among researchers and industry in the last decade. Various pathways for producing liquid fuels for different applications are subjects of active research. Most of the past and current research has mostly focused on techno-economic feasibility studies, assuming a steadystate operation. However, the fluctuating nature of renewable electricity necessitates a feasibility study of a process in dynamic operation. In this thesis, a case is made for dynamic operation of a Powerto-Liquid process, and an attempt is undertaken to examine commercial viability of intermittent operation compared to steady-state operation. For the dynamic simulation, the electricity profile is retrieved for a wind park of 10 MW rated capacity at Magdeburg, Germany. The maximum electricity output of the wind energy profile, 9.14 MW, is used as an input for steady-state simulation. The evaluation of steadystate Power-to-Liquid process resulted in net production costs of 3.92 €/l for a plant capacity of 206.9 kgproduct/hr. The C5+ selectivity for the Fischer-Tropsch synthesis was observed to be 79%, while that of CH4 was observed to be 12.84%. The dynamic simulation, based on wind electricity input, produced a total product yield of 198.39 tons over the year, compared to 1709 tons of steady-state simulation. Thus, the dynamic Power-to-Liquid process was observed to produce 11.6% product to that of steadystate operation. This reduction in capacity is reflected in the increased net production costs for fuel produced by dynamic operation, as the net production costs reached 17.65 €/l. This was contradictory to the hypothesis, that using the cheap renewable electricity directly could present an opportunity for cost reduction of Power-to-Liquid processes, compared to using the steadybut-expensive electricity from the grid.
Chapter
Synthetic fuels (synfuels) and chemicals (synchems) are produced by synthesis from chemical building blocks rather than by conventional petroleum refining. Synthesis gas or syngas (carbon monoxide and hydrogen) is a common intermediate building block in the production of synfuels and synchems. Syngas can be produced by many processes, including biomass or fossil fuel gasification and by co-electrolysis. In co-electrolysis, CO2 is reacted with water to produce syngas. Conversion of CO2, which would have otherwise been released to the atmosphere, to synfuels using nuclear energy could potentially add value to existing light water reactor (LWR) facilities, while producing transportation fuels that are compatible with conventional petroleum fuels. Valorization of CO2 is complementary to carbon capture and utilization (CCU) and an alternative to carbon capture and sequestration (CCS). This article presents an overview of routes for producing synfuels from CO2 and the conceptual process design, modeling and economic analysis of an example route for hydrocarbon fuel production using LWR heat and power.
Article
In order to fulfil the Paris Climate Protection Agreement, ambitious targets were set in the German Climate Protection Plan 2050. The direct use of renewable energies and sector coupling are two of these central measures to forward the defossilisation of the economy (BMUB 2016). Promising approaches to increase the share of renewable energies in the heating, transport and industrial sectors are offered by power-to‑x technologies. Within these technologies, renewable based electricity can be stored for a later energetic use or can be used in technical processes to produce value-added products or to provide services. This exploits the sector coupling potential of electricity and at the same time opens up for the above-mentioned sector’s defossilisation options.Due to the diversity of processes and the great utilization potential, power-to‑x technologies are currently the focus of a larger debate. An analysis of the terminology “power-to-x” in research publications shows that there is no consensus on the definition of power-to‑x and the associated technologies: Partially the term is used quite narrowly and for only a few technological concepts, sometimes it is used very broadly and for a large variety of concepts. This article gives an overview about the present spectrum in the use of the term “power-to-x”, identifies similarities and differentiations and derives a systematic of the power-to‑x approach. Based on this, a definition proposal is formulated with which power-to‑x technologies can be unambiguously identified and meaningfully classified into categories. This should contribute to a uniform understanding of power-to‑x, on the basis of which the discussion about available technologies and their development possibilities for applications can be conducted.
Article
The study presents a holistic methodology for the discrimination of the contribution of H2O and CO2 electrolysis reactions, as well as of the RWGS, on the production rate of CO during the solid oxide H2O/CO2 co-electrolysis process. The investigation took place on an electrolyte supported cell with Ni/GDC as the fuel electrode, at 800−900 oC, by applying various PΗ2Ο/PCO2 feed ratios, in the range of 0 ≤ PΗ2Ο/PCO2 ≤ 1, and two PΗ2 values (2 and 21 kPa). Critical combination of physicochemical and electrochemical characterization with electrocatalytic measurements and quantitative analysis of products highlighted a competitive adsorption and electro-reduction between H2O and CO2 on Ni/GDC. Moreover, it is confirmed that the H2O/CO2 co-electrolysis process is determined by: (i) PH2O/PCO2 ratio and (ii) PH2. Specifically, at PΗ2Ο/PCO2 = 1 and high PΗ2 = 21 kPa the adsorption of H2O is favored, compared to CO2, and the electrochemical process is 100% selective towards the electrolysis of H2O. The CO production is catalytically controlled by the RWGS reaction. The electrochemical reduction of CO2 occurs at PΗ2Ο/PCO2= 0.3, in combination with H2O electrolysis and the RWGS, whereas its contribution is enhanced by decreasing the PΗ2Ο and PΗ2.
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This paper presents results of recent experiments on simultaneous high-temperature electrolysis (coelectrolysis) of steam and carbon dioxide using solid-oxide electrolysis cells. Coelectrolysis is complicated by the fact that the reverse shift reaction occurs concurrently with the electrolytic reduction reactions. All reactions must be properly accounted for when evaluating results. Electrochemical performance of the button cells and stacks were evaluated over a range of temperatures, compositions, and flow rates. The apparatus used for these tests is heavily instrumented, with precision mass-flow controllers, on-line dewpoint and CO2 sensors, and numerous pressure and temperature measurement stations. It also includes a gas chromatograph for analyzing outlet gas compositions. Comparisons of measured compositions to predictions obtained from a chemical equilibrium coelectrolysis model are presented, along with corresponding polarization curves. Results indicate excellent agreement between predicted and measured outlet compositions. Cell area-specific resistance values were found to be similar for steam electrolysis and coelectrolysis. Coelectrolysis significantly increases the yield of syngas over the reverse water gas shift reaction equilibrium composition. The process appears to be a promising technique for large-scale syngas production.
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This analysis developed detailed process flow diagrams and an Aspen Plus{reg_sign} model, evaluated energy flows including a pinch analysis, obtained process equipment and operating costs, and performed an economic evaluation of two process designs based on the syngas clean up and conditioning work being performed at NREL. One design, the current design, attempts to define today's state of the technology. The other design, the goal design, is a target design that attempts to show the effect of meeting specific research goals.
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This book presents the basic aspects of current petroleum refining technology and economics in a systematic manner. The physical and chemical properties of petroleum and petroleum products are described, along with major modern refining processes. Data for determination of product yields, investment, and operating costs are presented for all major refining processes. Similar data also are given for supporting processes, such as hydrogen generation and elemental sulfur recovery. Ecological problems of petroleum refining operations are described in general terms. Reaction chemistry is described in basic terms with reference to desirable thermodynamic conditions. Capital cost data have been updated to 1973 and are presented on a consistent basis with respect to location, utilities, offsites, and other items. A simplified procedure for developing reasonably accurate investment and operating cost data is given. The yield data for reaction processes have been extended to allow complete material balances to be made from physical properties. Insofar as possible, data for catalytic reactions represent average yields from competing proprietary catalysts and processes. The yield data combined with the cost data will serve the practicing engineer and refinery management as a convenient tool for developing preliminary economic feasibility studies. Examples of such calculations are given as an aid to students.
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The goal of this paper is to find methodologies for removing a selection of impurities (H2O, O2, Ar, N2, SOx and NOx) from CO2 present in the flue gas of two oxy-combustion power plants fired with either natural gas (467 MW) or pulverized fuel (596 MW). The resulting purified stream, containing mainly CO2, is assumed to be stored in an aquifer or utilized for enhanced oil recovery (EOR) purposes. Focus has been given to power cycle efficiency i.e.: work and heat requirements for the purification process, CO2 purity and recovery factor (kg of CO2 that is sent to storage per kg of CO2 in the flue gas). Two different methodologies (here called Case I and Case II) for flue gas purification have been developed, both based on phase separation using simple flash units (Case I) or a distillation column (Case II). In both cases purified flue gas is liquefied and its pressure brought to 110 atm prior to storage.
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An experimental study is under way to assess the performance of solid-oxide cells operating in the steam electrolysis mode for hydrogen production over a temperature range of 800 to 900°C. Results presented in this paper were obtained from a ten-cell planar electrolysis stack, with an active area of 64 cm2 per cell. The electrolysis cells are electrolyte-supported, with scandia-stabilized zirconia electrolytes (∼140 μm thick), nickel-cermet steam/hydrogen electrodes, and manganite air-side electrodes. The metallic interconnect plates are fabricated from ferritic stainless steel. The experiments were performed over a range of steam inlet mole fractions (0.1–0.6), gas flow rates (1000–4000 sccm), and current densities (0 to 0.38 A/cm2 ). Steam consumption rates associated with electrolysis were measured directly using inlet and outlet dewpoint instrumentation. Cell operating potentials and cell current were varied using a programmable power supply. Hydrogen production rates up to 100 Normal liters per hour were demonstrated. Values of area-specific resistance and stack internal temperatures are presented as a function of current density. Stack performance is shown to be dependent on inlet steam flow rate.
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Electrochemical cells employing yttria-stabilized zirconia solid electrolyte were evaluated in the electrolysis of steam at 800–1050°C. Performance levels of 1.23 V at 300 mA cm−2 were obtained with current efficiencies approaching 100%. A limiting current was approached when hydrogen content in the steam exceeded approximately 90% (650 mA cm−2; 1000°C). Voltage-current behavior prior to diffusion control folllows a Tafeltype slope of approximately 250 mV per decade. Polarization in this region has a temperature dependence corresponding to approximately d ln 1/d(1/T) = 30,000/R which permits prediction of cell performance above the 1050°C maximum testing temperature.
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The internal reforming of methane in a solid oxide fuel cell (SOFC) is investigated and modeled for flow conditions relevant to operation. To this end, measurements are performed on anode-supported cells (ASC), thereby varying gas composition (yCO=4–15%, yH2=5−17%, yCO2=6−18%, yH2O=2−30%, yCH4=0.1−20%) and temperature (600–850°C). In this way, operating conditions for both stationary applications (methane-rich pre-reformate) as well as for auxiliary power unit (APU) applications (diesel-POX reformate) are represented. The reforming reaction is monitored in five different positions alongside the anodic gas channel by means of gas chromatography. It is shown that methane is converted in the flow field for methane-rich gas compositions, whereas under operation with diesel reformate the direction of the reaction is reversed for temperatures below 675°C, i.e. (exothermic) methanation occurs along the anode. Using a reaction model, a rate equation for reforming could be derived which is also valid in the case of methanation. By introducing this equation into the reaction model the methane conversion along a catalytically active Ni-YSZ cermet SOFC anode can be simulated for the operating conditions specified above.
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To identify research areas in geosciences, such as behavior of multiphase fluid-solid systems on a variety of scales, chemical migration processes in geologic media, characterization of geologic systems, and modeling and simulation of geologic systems, needed for improved energy systems.
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Although it is not yet technologically mature, the high-temperature steam/CO2 co-electrolysis process offers potentially a feasible and environmentally benign way to convert carbon-free or low-carbon electrical energy into chemical energy stored in syngas with a desired H2 to CO ratio for further processing. An attractive application is to convert the as-produced syngas further into synthetic liquid fuels through the Fischer–Tropsch (F-T) process. The synfuel can be used as alternative fuels in the transportation sector while keeping the existing infrastructure and motor engine technology unchanged. The combination of the high-temperature steam/CO2 co-electrolysis process and the F-T process thus offers an efficient way to store electricity in transportation fuels. The implementation of such a quasi carbon-neutral process depends on its economic competitiveness. In the present paper, an economic assessment of this process is performed through process modelling and sensitivity analysis. As an energy-intensive process, the availability of cost-effective electricity is crucial for its economic competitiveness. Preferred electricity sources are probably nuclear power and surplus wind power, with which synthetic fuels could be produced at a cost comparable to BTL (Biomass to Liquid) process. The present process is biomass-independent, and can also be located in regions where solar energy is abundant.
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An experimental study was performed with an aged Co/Pt/Al2O3 catalyst in a laboratory slurry reactor to develop a macrokinetic expression for the Fischer−Tropsch (FT) synthesis. A semiempirical model was found to be the preferred two-parameter rate equation of the reaction. However, it was shown that this model is virtually indistinguishable from a mechanistically derived three-parameter rate model that assumes the following kinetically relevant steps in the cobalt-FT synthesis: CO dissociation occurs without hydrogen interaction and is not a rate-limiting step; the first hydrogen addition to surface carbon and the second hydrogen addition to surface oxygen are the rate-determining steps.
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This study examines the initial performance and durability of a solid oxide cell applied for co-electrolysis of CO2 and H2O. Such a cell, when powered by renewable/nuclear energy, could be used to recycle CO2 into sustainable hydrocarbon fuels. Polarization curves and electrochemical impedance spectroscopy were employed to characterize the initial performance and to break down the cell resistance into the resistance for the specific processes occurring during operation. Transformation of the impedance data to the distribution of relaxation times (DRT) and comparison of measurements taken under systematically varied test conditions enabled clear visual identification of five electrode processes that contribute to the cell resistance. The processes could be assigned to each electrode and to gas concentration effects by examining their dependence on gas composition changes and temperature.This study also introduces the use of the DRT to study cell degradation without relying on a model. The durability was tested at consecutively higher current densities (and corresponding overpotentials). By analyzing the impedance spectra before and after each segment, it was found that at low current density operation (− 0.25 A/cm2 segment) degradation at the Ni/YSZ electrode was dominant, whereas at higher current densities (− 0.5 A/cm2 and − 1.0 A/cm2), the Ni/YSZ electrode continued to degrade but the serial resistance and degradation at the LSM/YSZ electrode began to also play a major role in the total loss in cell performance. This suggests different degradation mechanisms for high and low current density operation.
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The influence of the catalyst type (Fe and Co) on CO and H2 conversions, CO2 selectivity, and the composition in Fischer-Tropsch synthesis slurry bubble column reactors was simulated for representative commercial-scale units (7 m i.d. and 30 m height). A nonisothermal, core-annulus multicompartment multicomponent two-bubble class model was used to account for a relatively detailed hydrodynamics. It was coupled to comprehensive Fischer-Tropsch synthesis and water−gas-shift reactions, in addition to descriptions of thermodynamics and thermal effects, variable gas flow rate due to chemical/physical contraction, and gas and slurry backmixing and (re)circulation. Two mechanistic kinetic models with consideration of olefin readsorption were employed to describe the paraffin and olefin formation with cobalt- and iron-based catalysts, in addition to relatively large activities for CO2 and oxygenate formation, mainly alcohols, for the latter catalyst. The influence of the temperature and superficial gas velocity on CO and H2 conversions was more evident for a cobalt-based catalyst. For both catalysts, the space-dependent superficial gas velocity directly affected the gas-phase mean residence time, influencing in the return reactor temperature and conversions. Reliable estimation of the gas velocity due to chemical contraction was critical for conversions exceeding 50%. For both catalysts, the nonisothermal simulations reveal that, because heat removal is well managed from the heat-exchange area, the reactor operation can be considered as nearly isothermal.
Article
The rate of synthesis gas consumption over a cobalt Fischer-Tropsch catalyst was measured in a well-mixed, continuous-flow, slurry reactor at 220-240-degrees-C, 0.5-1.5 MPa, H-2/CO feed ratios of 1.5-3.5, and conversions of 6-68% of hydrogen and 11-73% of carbon monoxide. The inhibiting effect of carbon monoxide was determined quantitatively and a Langmuir-Hinshelwood-type equation of the following form was found to best represent the results: R(H)2+CO = Ap P(H2)-CO/(1 + bP(CO))2. The apparent activation energy was 93-95 kJ/mol. Data from previous studies on cobalt-based Fischer-Tropsch catalysts are also well correlated with this rate expression.
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Large-scale gasification-based systems for producing Fischer-Tropsch (F-T) fuels (diesel and gasoline blendstocks), dimethyl ether (DME), or hydrogen from switchgrass – with electricity as a coproduct in each case are assessed using a self-consistent design, simulation, and cost analysis framework. We provide an overview of alternative process designs for coproducing these fuels and power assuming commercially mature technology performance and discuss the commercial status of key component technologies. Overall efficiencies (lower-heating-value basis) of producing fuels plus electricity in these designs ranges from 57% for F-T fuels, 55–61% for DME, and 58–64% for hydrogen. Detailed capital cost estimates for each design are developed, on the basis of which prospective commercial economics of future large-scale facilities that coproduce fuels and power are evaluated. © 2009 Society of Chemical Industry and John Wiley & Sons, Ltd
Article
The Fischer–Tropsch (FT) synthesis is used to produce chemicals, gasoline and diesel fuel. The FT products are predominantly linear, hence the quality of the diesel fuel is very high, having cetane numbers of up to 75. Since purified synthesis gas is used in the FT process all the products are S- and N-free. In this review the production of syngas and the various options used in the FT process (reactors and catalyst types, and high and low temperature operation) are discussed. The best FT option for producing high quality diesel is using cobalt-based catalyst in slurry phase reactor, gearing the process for high wax production and then selectively hydrocracking the wax to diesel fuel. The overall diesel pool has a high cetane number, the aromatic S and N contents are zero and the exhaust emissions are significantly lower than for standard diesel fuels.© 2001 Society of Chemical Industry
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The generation of hydrogen through electrolysis possesses several advantages such as high efficiency, low pollution and decentralized fueling methods. In this paper, we show through modeling and simulation that the efficiency of hydrogen production can be further increased by operating the solid oxide electrolysis cell (SOEC) at the optimum combination of operating conditions. Specifically, the analysis of a recuperative SOEC that utilizes the thermal energy from the exhaust gases has revealed that operating the electrolysis cell above the thermoneutral voltage increased the efficiency of hydrogen production. We also found that the exit temperature of the gas streams depended on the operating voltage and steam utilization simultaneously. The effects of various operating parameters such as voltage, steam utilization, area specific resistance (ASR), the size of the heat exchangers, and the number of cells were analyzed in the system.
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Hydrogen production via steam electrolysis may involve less electrical energy consumption than conventional low temperature water electrolysis, reflecting the improved thermodynamics and kinetics at elevated temperatures. The present paper reports on the development of a one-dimensional dynamic model of a cathode-supported planar intermediate temperature solid oxide electrolysis cell (SOEC) stack. The model, which consists of an electrochemical model, a mass balance, and four energy balances, is here employed to study the steady state behaviour of an SOEC stack at different current densities and temperatures. The simulations found that activation overpotentials provide the largest contributions to irreversible losses while concentration overpotentials remained negligible throughout the stack. For an average current density of 7000 A m−2 and an inlet steam temperature of 1023 K, the predicted electrical energy consumption of the stack is around 3 kW h per normal m3 of hydrogen, significantly smaller than those of low temperature stacks commercially available today. However, the dependence of the stack temperature distribution on the average current density calls for strict temperature control, especially during dynamic operation.
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When catalysts developed for crude oil hydroprocessing are used for syncrude, there are syncrude-specific peculiarities to consider. These relate to differences in the nature and abundance of heteroatoms, olefins, metal species, waxes and aqueous products. Some important aspects are (a) heat release during naphtha and distillate hydroprocessing is very high, but wax hydrocracking is almost isothermal; (b) syncrude is sulphur-free and the use of sulphided base-metal hydroprocessing catalysts require the addition of sulphur-containing compounds to the syncrude; (c) oxygenates strongly adsorb on some catalytic surfaces to affect catalytic behaviour; (d) carbonyl–carboxylic acid interconversion and water produced by hydrodeoxygenation (HDO) may result in catalyst degradation by acid and hydrothermal attack; (e) carboxylic acids in syncrude result in equipment corrosion and catalyst leaching; (f) metal carboxylates are the main metal-containing species in syncrude and are not removed by hydrodemetallation (HDM) catalysis, but by thermal decomposition.
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To improve the sustainability of transportation, a major goal is the replacement of conventional petroleum-based fuels with more sustainable fuels that can be used in the existing infrastructure (fuel distribution and vehicles). While fossil-derived synthetic fuels (e.g. coal derived liquid fuels) and biofuels have received the most attention, similar hydrocarbons can be produced without using fossil fuels or biomass. Using renewable and/or nuclear energy, carbon dioxide and water can be recycled into liquid hydrocarbon fuels in non-biological processes which remove oxygen from CO2 and H2O (the reverse of fuel combustion). Capture of CO2 from the atmosphere would enable a closed-loop carbon-neutral fuel cycle. This article critically reviews the many possible technological pathways for recycling CO2 into fuels using renewable or nuclear energy, considering three stages--CO2 capture, H2O and CO2 dissociation, and fuel synthesis. Dissociation methods include thermolysis, thermochemical cycles, electrolysis, and photoelectrolysis of CO2 and/or H2O. High temperature co-electrolysis of H2O and CO2 makes very efficient use of electricity and heat (near-100% electricity-to-syngas efficiency), provides high reaction rates, and directly produces syngas (CO/H2 mixture) for use in conventional catalytic fuel synthesis reactors. Capturing CO2 from the atmosphere using a solid sorbent, electrolyzing H2O and CO2 in solid oxide electrolysis cells to yield syngas, and converting the syngas to gasoline or diesel by Fischer-Tropsch synthesis is identified as one of the most promising, feasible routes. An analysis of the energy balance and economics of this CO2 recycling process is presented. We estimate that the full system can feasibly operate at 70% electricity-to-liquid fuel efficiency (higher heating value basis) and the price of electricity needed to produce synthetic gasoline at U.S.D$ 2/gal ($ 0.53/L) is 2-3 U.S. cents/kWh. For $ 3/gal ($ 0.78/L) gasoline, electricity at 4-5 cents/kWh is needed. In some regions that have inexpensive renewable electricity, such as Iceland, fuel production may already be economical. The dominant costs of the process are the electricity cost and the capital cost of the electrolyzer, and this capital cost is significantly increased when operating intermittently (on renewable power sources such as solar and wind). The potential of this CO2 recycling process is assessed, in terms of what technological progress is needed to achieve large-scale, economically competitive production of sustainable fuels by this method.
Article
This paper reviews the technical feasibility and economics of biomass integrated gasification–Fischer Tropsch (BIG-FT) processes in general, identifies most promising system configurations and identifies key R&D issues essential for the commercialisation of BIG-FT technology.The FT synthesis produces hydrocarbons of different length from a gas mixture of H2 and CO. The large hydrocarbons can be hydrocracked to form mainly diesel of excellent quality. The fraction of short hydrocarbons is used in a combined cycle with the remainder of the syngas. Overall LHV energy efficiencies,1 calculated with the flowsheet modelling tool Aspenplus, are 33–40% for atmospheric gasification systems and 42–50% for pressurised gasification systems. Investment costs of such systems () are MUS$ 280–450,2 depending on the system configuration. In the short term, production costs of FT-liquids will be about US$ 16/GJ. In the longer term, with large-scale production, higher CO conversion and higher C5+ selectivity in the FT process, production costs of FT-liquids could drop to US$ 9/GJ. These perspectives for this route and use of biomass-derived FT-fuels in the transport sector are promising. Research and development should be aimed at the development of large-scale (pressurised) biomass gasification-based systems and special attention must be given to the gas cleaning section.
Article
The characteristics of a slurry phase reactor are contrasted with those of a conventional tubular fixed bed reactor (TFBR) for the conversion of synthesis gas to long chain hydrocarbons. Hydrodynamic information needed for the design of a commercial scale slurry phase Fischer–Tropsch (FT) reactor were obtained from experiments carried out on a 1 m internal diameter pilot plant reactor. The kinetics, selectivities and deactivation mechanisms of Fe and supported Co FT catalysts are compared for both slurry phase and fixed bed operation. The combined advantages of the slurry phase reactor and a very active Co catalyst create the opportunity to convert remote natural gas to high quality middle distillates in a cost effective manner.
Article
Fischer–Tropsch (FT) diesel derived from biomass via gasification is an attractive clean and carbon neutral transportation fuel, directly usable in the present transport sector. System components necessary for FT diesel production from biomass are analysed and combined to a limited set of promising conversion concepts. The main variations are in gasification pressure, the oxygen or air medium, and in optimisation towards liquid fuels only, or towards the product mix of liquid fuels and electricity. The technical and economic performance is analysed. For this purpose, a dynamic model was built in Aspen Plus®, allowing for direct evaluation of the influence of each parameter or device, on investment costs, FT and electricity efficiency and resulting FT diesel costs. FT diesel produced by conventional systems on the short term and at moderate scale would probably cost 16 €/GJ. In the longer term (large scale, technological learning, and selective catalyst), this could decrease to 9 €/GJ. Biomass integrated gasification FT plants can only become economically viable when crude oil price levels rise substantially, or when the environmental benefits of green FT diesel are valued. Green FT diesel also seems 40–50% more expensive than biomass derived methanol or hydrogen, but has clear advantages with respect to applicability to the existing infrastructure and car technology.
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Hydrogen delivery is a critical contributor to the cost, energy use and emissions associated with hydrogen pathways involving central plant production. The choice of the lowest-cost delivery mode (compressed gas trucks, cryogenic liquid trucks or gas pipelines) will depend upon specific geographic and market characteristics (e.g. city population and radius, population density, size and number of refueling stations and market penetration of fuel cell vehicles). We developed models to characterize delivery distances and to estimate costs, emissions and energy use from various parts of the delivery chain (e.g. compression or liquefaction, delivery and refueling stations). Results show that compressed gas truck delivery is ideal for small stations and very low demand, liquid delivery is ideal for long distance delivery and moderate demand and pipeline delivery is ideal for dense areas with large hydrogen demand.
Article
Recent developments in the Fischer-Tropsch process are reviewed and discussed. Particular attention is given to the commercial slurry-bed reactor which was commissioned by Sasol in May 1993.
Article
It is possible to improve the performance of electrolysis processes by operating at a high temperature. This leads to a reduction in electricity consumption but requires a part of the energy necessary for the dissociation of water to be in the form of thermal energy.Iceland produces low cost electricity and very low cost geothermal heat. However, the temperature of geothermal heat is considerably lower than the temperature required at the electrolyser's inlet, making heat exchangers necessary to recuperate part of the heat contained in the gases at the electrolyser's outlet.A techno-economic optimisation model devoted to a high-temperature electrolysis (HTE) process which includes electrolysers as well as a high temperature heat exchanger network was created. Concerning the heat exchangers, the unit costs used in the model are based on industrial data. For the electrolyser cells, the unit cost scaling law and the physical sub-model we used were formulated using analogies with solid oxide fuel cells.The method was implemented in a software tool, which performs the optimisation using genetic algorithms.The first application of the method is done by taking into account the prices of electricity and geothermal heat in the Icelandic context. It appears that even with a geothermal temperature as low as , the HTE could compete with alkaline electrolysis.
Article
CO2 emission increase inducing global Warming occurs mostly with the growth of the economic activity. Global CO recycling can prevent global warming and supply abundant renewable energy. Global CO2 recycling consists of three district. The electricity is generated by solar cells on deserts. At coasts close to the deserts, the electricity is used for hydrogen production by seawater electrolysis and hydrogen is used for methane production by the reaction with CO2. Methane (CH4) is liquefied and transported to energy consuming districts where after CH4 is used as a fuel CO2 is recovered, liquefied anti transported to the coasts close to the deserts, Ii;ey materials necessary for the global CO2 recycling are the anode and cathode for seawater electrolysis and the catalyst for CO2 conversion All uf them have been tailored by us. amorphous and nanocrystalline nickel alloys are active cathodes for hydrogen production in seawater electrolysis. Anodically deposited nanocrystalline Mn-Mo and Mn-W oxides are the unique substance which can evolve oxygen with 100% efficiency without evolving chlorine in seawater electrolysis. Amorphous Ni-Zr alloys ale excellent precursors of catalysts for conversion of CO2 into CH4 by the reaction with hydrogen at 1 atm. A prototype CO2 recycling plant to supply clean energy preventing global warming has been built on the roof of our Institute (IMR) in 1996 using these key materials and has been operating successfully, (C) 2001 Elsevier Science B.V. All lights reserved.