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Thermochemical water-splitting cycle, bench-scale investigations, and process engineering. Final report, February 1977-December 31, 1981

Description: The sulfur-iodine water-splitting cycle is characterized by the following three reactions: 2H/sub 2/O + SO/sub 2/ + I/sub 2/ ..-->.. H/sub 2/SO/sub 4/ + 2HI; H/sub 2/SO/sub 4/ ..-->.. H/sub 2/O + SO/sub 2/ + 1/2 O/sub 2/; and 2HI ..-->.. H/sub 2/ + I/sub 2/. This cycle was developed at General Atomic after several critical features in the above reactions were discovered. These involved phase separations, catalytic reactions, etc. Estimates of the energy efficiency of this economically reasonable advanced state-of-the-art processing unit produced sufficiently high values (to approx.47%) to warrant cycle development effort. The DOE contract was largely directed toward the engineering development of this cycle, including a small demonstration unit (CLCD), a bench-scale unit, engineering design, and costing. The work has resulted in a design that is projected to produce H/sub 2/ at prices not yet generally competitive with fossil-fuel-produced H/sub 2/ but are projected to be favorably competitive with respect to H/sub 2/ from fossil fuels in the future.
Date: May 1, 1982
Creator: Norman, J.H.; Besenbruch, G.E.; Brown, L.C.; O'Keefe, D.R. & Allen, C.L.
Partner: UNT Libraries Government Documents Department

Equilibrium effects in high-pressure hydrogen production from thermochemical water-splitting cycles

Description: When hydrogen comes into widespread use as a supplemental fuel, a chemical feedstock, and a primary, future energy carrier, it must be available at pressures of the order of 50 atmospheres. Existing studies of hydrogen transmission indicate that pipeline pressures of 50 to 100 atmospheres will yield an energy carrier system with better cost-effectiveness than underground transmission of electricity. Because high capacity hydrogen compressors have a low compression ratio, high supply pressures are required. This requirement will affect product separations steps and process heat load-line matching. The hydrogen production steps of a large number of projected water-splitting cycles were classified according to whether the sum of the mole numbers of gaseous products is larger or smaller than the sum of the mole numbers of gaseous reactants. When product mole numbers are larger, the hydrogen production step occurs at relatively high temperatures (about 600/sup 0/C or higher). When reactant mole numbers are larger, the required temperature is generally low (about 300/sup 0/C or lower). There were few exceptions, though some water-splitting cycles based on organic chemical reactions fit into a temperature range between these two categories. A group of generalized relationships are presented for hydrogen production steps such that ..delta..G, the Gibb's free energy change for the reaction, is zero. For equilibria favored by, and not favored by pressure, a series of relationships between the hydrogen mole fraction and product pressure can be defined. The trade-offs between product stream composition and input heat temperature can be assessed. The degree to which feed stream impurities can be tolerated, given fixed operating variables, can also be determined.
Date: January 1, 1978
Creator: Schreiber, J. D.; Dafler, J. R. & Foh, S. E.
Partner: UNT Libraries Government Documents Department

HYDRGN - a computerized technique for the analysis of thermochemical water-splitting cycles

Description: The HYDRGN computer program was designed to analyze closed thermochemical cycles for the production of hydrogen from water. This report includes the basic theory, assumptions, and methods of calculation used in this analysis along with a description of the program and its use. The source program and necessary data bank are available from the University of Kentucky. These may be obtained by sending a magnetic tape (minimum length 1200 ft) and a written request specifying the type of computer and recording characteristics of the tape. A small fee is charged for the recording and handling of the tape.
Date: June 1, 1977
Creator: Carty, R. H.; Conger, W. L.; Funk, J. E. & Barker, R.
Partner: UNT Libraries Government Documents Department

Cadmium-cadmium carbonate cycle for the thermochemical production of hydrogen

Description: A means of thermally decomposing water using cadmium, cadmium oxide and cadmium carbonate is described. Experimental emphasis is placed on the hydrogen producing step which consists of reacting cadmium with water and carbon dioxide to produce cadmium carbonate and hydrogen. The cycle is completed by decomposing the carbonate, first to the oxide, and then to the metal. Laboratory studies show that hydrogen is evolved slowly in relatively high yields (57 to 65%), but, when produced in the presence of ammonium chloride, both the yield and rate are increased (72% in 0.5 hr). The figure of merit of the cycle is 78% with a probability of some decrease resultant from the ammonium chloride reaction.
Date: January 1, 1980
Creator: Mason, C.F.V. & Bowman, M.G.
Partner: UNT Libraries Government Documents Department

Possible thermochemical cycle based on methanol. [Tetramethylphosphine]

Description: The production of hydrogen from methanol is of particular interest since the two reactions: CH/sub 4/ + H/sub 2/O + CO + 3H/sub 2/ and CO + 2H/sub 2/ = CH/sub 3/OH are individually well known industrial processes. Thus, if a method can be found to obtain the overall reaction: CH/sub 3/OH = CH/sub 4/ + 1/2 O/sub 2/ then, in total, a cyclic water splitting process is complete for which much of the industrial development is already known. A possible method is through the use of trimethylphosphine. This reacts with methanol to form a salt, tetramethyl phosphonium hydroxide: CH/sub 3/OH + (CH/sub 3/)/sub 3/P = (CH/sub 3/)/sub 4/POH. Tetramethylphosphonium hydroxide gives methane and trimethylphosphine oxide very readily: (CH/sub 3/)/sub 4/POH = CH/sub 4/ + (CH/sub 3/)/sub 3/PO. When anhydrous takes place readily at room temperature, but in the presence of water, the rate is retarded. In summary, the overall reaction can be written as: CH/sub 3/OH + (CH/sub 3/)/sub 3/P = CH/sub 4/ + (CH/sub 3/)/sub 3/PO. Thus, provided a way of removing oxygen from trimethylphosphine oxide can be found, (CH/sub 3/)/sub 3/PO = (CH/sub 3/)/sub 3/P + 1/2 O/sub 2/ is a simple method of converting methanol to methane and oxygen.
Date: January 1, 1982
Creator: Mason, C.F.V.
Partner: UNT Libraries Government Documents Department

Hydrogen production by the GA sulfur-iodine process: a progress report

Description: A summary of the progress of the overall total development effort of the General Atomic (GA) sulfur-iodine thermochemical water-splitting cycle over the last two years is reported. The major accomplishments have been the following: (1) Significant improvements in the chemistry of the process. (2) Development, review, and revision of an engineering flowsheet, resulting in a thermal process efficiency of 47%. (3) Screening, identification, and testing of potential materials-of-construction for the corrosive process fluids. (4) Small-scale demonstration of the cycle in a closed loop under recycle conditions. (5) Installation of bench-scale equipment and demonstration of parts of the process in this system. (6) Development of a conceptual, preliminary flowsheet for the GA sulfur-iodine cycle driven by solar energy. The results of the work carried out during the last two years have demonstrated that thermochemical water splitting by the sulfur-iodine cycle is a feasible process and have provided confidence that thermal efficiencies in the range of 50% are achievable.
Date: March 1, 1980
Creator: Besenbruch, G.E.; McCorkle, K.H.; Norman, J.H.; O'Keefe, D.R.; Schuster, J.R. & Yoshimoto, M.
Partner: UNT Libraries Government Documents Department

Progress report on the development of the General Atomic thermochemical water-splitting process

Description: The major accomplishments of the DOE funded part of the GA thermochemical water-splitting program are reported. They include: completion of installation of all bench-scale equipment; operation and preliminary data acquisition for bench-scale subunits I and II; design, installation and operation of a system for iodine removal from the low phase; review and modification of Section III of the engineering flowsheet resulting in an increase in process efficiency and decrease in capital cost; and completion of the Funk panel reivew. The results of the experimental work have demonstrated that flowsheet conditions can be achieved in all cases tested. Continued work on the flowsheet has increased our confidence in the economic viability of the sulfur-iodine process.
Date: August 1, 1980
Creator: Besenbruch, G.E.; Allen, C.L.; Brown, L.C.; McCorkle, K.; Rode, J.S.; Norman, J.H. et al.
Partner: UNT Libraries Government Documents Department

Use of oxides in thermochemical water-splitting cycles for solar heat sources. Recent results on the copper oxide cycle

Description: Additional results on the low temperature reactions for reforming CuO from Cu/sub 2/O are presented. These results pertain to the following reaction in the copper oxide cycle: I/sub 2/ + Cu/sub 2/O + Mg(OH)/sub 2/ = 2CuO + MgI/sub 2/(aq) + H/sub 2/O at 448/sup 0/K, ..delta..G/sup 0/ = -78.5. 4 references, 4 figures.
Date: January 1, 1984
Creator: Jones, W.M. & Bowman, M.G.
Partner: UNT Libraries Government Documents Department

Synfuel (hydrogen) production from fusion power

Description: A potential use of fusion energy for the production of synthetic fuel (hydrogen) is described. The hybrid-thermochemical bismuth-sulfate cycle is used as a vehicle to assess the technological and economic merits of this potential nonelectric application of fusion power.
Date: January 1, 1979
Creator: Krakowski, R.A.; Cox, K.E.; Pendergrass, J.H. & Booth, L.A.
Partner: UNT Libraries Government Documents Department

Two bismuth sulfate-sulfuric acid hybrid thermochemical hydrogen cycles. Some experimental work related to the cycles and their possible improvement. Outline of a proposed antimonyl sulfate cycle in which sulfur dioxide and oxygen are separately evolved

Description: Thermochemical hydrogen production topics discussed include: equilibrium pressures in the decomposition of Bi/sub 2/(SO/sub 4/)/sub 3/ and ..cap alpha..-and ..beta..-Bi/sub 2/O(SO/sub 4/)/sub 2/; survey experiments on the thermal decomposition of Bi/sub 2/(SO/sub 4/)/sub 3/; hydrates sorption of H/sub 2/SO/sub 4/ solutions by the solids; and possible simplification of the SO/sub 3/-SO/sub 2/-O/sub 2/ separation problem with a sulfuric acid-antimonyl sulfate hybrid cycle.
Date: January 1, 1982
Creator: Jones, W.M.
Partner: UNT Libraries Government Documents Department

Utilization of solar thermal sources for thermochemical hydrogen production

Description: The utilization of high temperature solar heat for the production of electricity and/or fuels is a popular concept. However, since solar concentrator systems are expensive and solar radiation intermittent, practical utilization requires processes that exhibit high conversion efficiencies and also incorporate energy storage. The production of hydrogen fulfills the requirement for energy storage and can fulfill the requirement for efficient heat utilization if thermochemical cycles are developed where the temperature and heat requirements of the process match the heat delivery characteristics of the solar receiver system. Cycles based on solid sulfate decomposition reactions may lead to efficient utilization of solar heat at practical temperatures. Higher temperature cycles involving oxide decomposition may also become feasible.
Date: January 1, 1980
Creator: Bowman, M.G.
Partner: UNT Libraries Government Documents Department

LASL thermochemical hydrogen program status on October 31, 1977. [Cycles using sulfuric acid as an intermdiate]

Description: The LASL Hydrogen Program is continuing its investigation of practical schemes to decompose water thermochemically for hydrogen production. Efforts were and are being devoted to process improvements in cycles that use sulfuric acid as an intermediate. Sulfuric acid-hydrogen bromide cycles are being studied as a means of overcoming the heat penalty in drying acid solutions. An alternate approach involves the use of insoluble bismuth sulfate that is precipitated from acid solution. Preliminary energy balances indicate a significant increase in cycle efficiency for both these options.
Date: January 1, 1977
Creator: Cox, K.E. & Bowman, M.G.
Partner: UNT Libraries Government Documents Department

LASL thermochemical hydrogen status on September 30, 1979

Description: The work described in this report was accomplished during the period October 1, 1978 to September 30, 1979. Most of the effort was applied to a study of the Los Alamos Scientific Laboratory (LASL) hybrid bismuth sulfate cycle. The work included a conceptual design of the cycle and experimental work to verify the design conditions. Key findings were: a 50.8% efficiency was obtained when an improved cycle design was coupled to a fusion energy source at 1500 K; experimental results showed an endothermic heat requirement of +172 kJ/mol for the decomposition of Bi/sub 2/O/sub 3/.2SO/sub 3/ to Bi/sub 2/O/sub 3/.SO/sub 3/, and SO/sub 3/; reaction times for bismuth sulfate decomposition were determined as a function of temperature. At 1240 K, < 1.5 min were required for the first two stages of decomposition from Bi/sub 2/O/sub 3/.3SO/sub 3/ to Bi/sub 2/O/sub 3/; tests made to determine the feasibility of decomposing Bi/sub 2/O/sub 3/.2SO/sub 3/ in a 1 inch diameter rotary kiln showed that Bi/sub 2/O/sub 3/.2SO/sub 3/ could be decomposed continuously. In related work, support was given to the DOE Thermochemical Cycle Evaluation Panel (Funk). The Second Annual International Energy Agency (IEA) Workshop on Thermochemical Hydrogen Production from Water met on September 24 to 27, 1979 at Los Alamos.
Date: January 1, 1979
Creator: Cox, K.E.
Partner: UNT Libraries Government Documents Department

LASL bismuth sulfate thermochemical hydrogen cycle

Description: The LASL bismuth sulfate cycle is one of a generic class of solid sulfate cycles in which a metal sulfate is substituted for sulfuric acid in a hybrid (partly electrochemical) cycle. This technique avoids the serious materials and heat penalty problems associated with the handling of concentrated acid solutions, and if the electrolyzer is operated at acid concentrations below 50% it may, in principle, lead to a lower cell voltage with subsequent energy savings. Experiment verification of all steps in the cycle has been obtained, particularly for the decomposition of normal bismuth sulfate and lower bismuth oxysulfates. For the substance, Bi/sub 2/O/sub 3/ 2SO/sub 3/, an endothermic requirement of 172 kJ/mol was obtained, which is considerably less than that for other metal sulfate systems. A rotary kiln was used for continuous experiments and our results show decomposition of this compound to Bi/sub 2/O/sub 3/ SO/sub 3/ in under 8 minutes residence time at 1023 K. Preliminary analysis of the cycle's energy balance shows an overall thermal efficiency of greater than 50% when the maximum cycle reaction temperature is 1500 K. The cycle has potential for hydrogen production when coupled with an energy source such as solar or fusion energy.
Date: January 1, 1980
Creator: Cox, K.E.; Jones, W.M. & Peterson, C.L.
Partner: UNT Libraries Government Documents Department

LASL thermochemical hydrogen program status on September 30, 1980

Description: The work described here was accomplished during the period October 1, 1979-September 30, 1980. Highlights of the experimental program were: a solids decomposition facility was constructed and used to study the handling of bismuth oxysulfates and the kinetics of their decomposition; and the results of our kiln experiments showed that a substantial amount of bismuth oxysulfate decomposition occurs with residence times under 2 min. at temperatures between 973 and 1143/sup 0/K. The LASL bismuth sulfate sub-cycle thus appears a candidate for hydrogen production utilizing a solar heat source. In the evaluation phase of our work, the technoeconomics of the hybrid sulfur cycle were determined and compared with several published results as well as compared to the technoeconomics for water electrolysis processes for hydrogen production. We aided the efforts of the Department of Energy (DOE) Thermochemical Cycle Evaluation Panel in reviewing the Lawrence Livermore Laboratory (LLL) zinc selenide cycle as well as the General Atomic (GA) sulfur-iodine cycle.
Date: January 1, 1980
Creator: Cox, K.E.; Peterson, C.L.; Jones, W.M. & Bowman, M.G.
Partner: UNT Libraries Government Documents Department

Irreversibility analysis of hydrogen separation schemes in thermochemical cycles. [Condensation, physical absorption, diffusion, physical adsorption, thermal adsorption, and electrochemical separation]

Description: Six processes have been evaluated as regards irreversibility generation for hydrogen separation from binary gas mixtures. The results are presented as a series of plots of separation efficiency against the mol fraction hydrogen in the feed gas. Three processes, condensation, physical absorption and electrochemical separation indicate increasing efficiency with hydrogen content. The other processes, physical and thermal adsorption, and diffusion show maxima in efficiency at a hydrogen content of 50 mol percent. Choice of separation process will also depend on such parameters as condition of feed, impurity content and capital investment. For thermochemical cycles, schemes based on low temperature heat availability are preferable to those requiring a work input.
Date: January 1, 1978
Creator: Cox, K.E.
Partner: UNT Libraries Government Documents Department

Use of oxides in thermochemical water-splitting cycles for solar heat sources. Copper oxides

Description: Several oxides can be decomposed to oxygen and a lower oxide at temperatures that might be feasible with a solar heat source. Heat might be directly transmitted to the solid through an air window, rather than quartz, with release of oxygen to the atmosphere. The cycle utilizing CuO, I/sub 2/, and Mg (OH)/sub 2/ is similar to the previous Co/sub 3/O/sub 4/ - CoO cycle. We are concentrating on the reformation of CuO. At 448 K the rate is favorable; for example, the yield rises about linearly with time to 92% at 1.17 h and more slowly thereafter. The only difficulty is the formation of CuI as a metastable intermediate. The oxidation of CuI is thermodynamically very favorable, but its rate limits completion. Excess Mg(OH)/sub 2/ appears to increase the rate but not to the point where IO/sub 3//sup -/ oxidation of CuI competes with oxidation of Cu/sub 2/O. Nevertheless, the batch runs suggest that about 98% of the maximum possible MgI/sub 2/ could be formed. Cuprous iodide complexes formed in the concentrated MgI/sub 2/ may give the necessary improvement by providing a solution path for their oxidation by iodate. Work of others pertaining to the cycle is briefly discussed.
Date: January 1, 1984
Creator: Jones, W.M. & Bowman, M.G.
Partner: UNT Libraries Government Documents Department

Configuring the thermochemical hydrogen sulfuric acid process step for the Tandem Mirror Reactor

Description: This paper identifies the sulfuric acid step as the critical part of the thermochemical cycle in dictating the thermal demands and temperature requirements of the heat source. The General Atomic Sulfur-Iodine Cycle is coupled to a Tandem Mirror. The sulfuric acid decomposition process step is focused on specifically since this step can use the high efficiency electrical power of the direct converter together with the other thermal-produced electricity to Joule-heat a non-catalytic SO/sub 3/ decomposer to approximately 1250/sup 0/K. This approach uses concepts originally suggested by Dick Werner and Oscar Krikorian. The blanket temperature can be lowered to about 900/sup 0/K, greatly alleviating materials problems, the level of technology required, safety problems, and costs. A moderate degree of heat has been integrated to keep the cycle efficiency around 48%, but the number of heat exchangers has been limited in order to keep hydrogen production costs within reasonable bounds.
Date: May 1, 1981
Creator: Galloway, T.R.
Partner: UNT Libraries Government Documents Department

Catalytic-cartridge SO/sub 3/ decomposer

Description: A catalytic cartridge internally heated is utilized as a SO/sub 3/ decomposer for thermochemical hydrogen production. The cartridge has two embodiments, a cross-flow cartridge and an axial flow cartridge. In the cross-flow cartridge, SO/sub 3/ gas is flowed through a chamber and incident normally to a catalyst coated tube extending through the chamber, the catalyst coated tube being internally heated. In the axial-flow cartridge, SO/sub 3/ gas is flowed through the annular space between concentric inner and outer cylindrical walls, the inner cylindrical wall being coated by a catalyst and being internally heated. The modular cartridge decomposer provides high thermal efficiency, high conversion efficiency, and increased safety.
Date: May 22, 1981
Creator: Galloway, T.R.
Partner: UNT Libraries Government Documents Department

Solids decomposition kinetics for LASL bismuth sulfate cycle

Description: The LASL Bismuth Sulfate Cycle includes a solid-decomposition step as an alternative to the high-temperature evaporation and decomposition of concentrated sulfuric acid, with its attendant drying and materials problems. A solids decomposition facility was constructed and used to study the handling of solid sulfates and the kinetics of their decomposition. The decomposition of Bi/sub 2/O(SO/sub 4/)/sub 2/ has been measured as a function of temperature and transit time through a laboratory-scale rotary kiln, constructed from quartz. Temperatures from 973 to 1143/sup 0/K were investigated. The transit time was controlled by varying the slope of the kiln, its rotational speed, and the rate of feed of a bismuth oxysulfate prepared in the prescribed manner. The preparation and characterization of this solid, which has reasonable feeding properties and minimal solution retention, are described. Significant amounts of decomposition were measured in short reaction times at the temperatures investigated.
Date: January 1, 1980
Creator: Peterson, C.L. & Bowman, M.G.
Partner: UNT Libraries Government Documents Department

Interfacing primary heat sources and cycles for thermochemical hydrogen production

Description: Advantages cited for hydrogen production from water by coupling thermochemical cycles with primary heat include the possibility of high efficiencies. These can be realized only if the cycle approximates the criteria required to match the characteristics of the heat source. Different types of cycles may be necessary for fission reactors, for fusion reactors or for solar furnaces. Very high temperature processes based on decomposition of gaseous H/sub 2/O or CO/sub 2/ appear impractical even for projected solar technology. Cycles based on CdO decomposition are potentially quite efficient and require isothermal heat at temperatures that may be available from solar furnaces of fusion reactors. Sulfuric acid and solid sulfate cycles are potentially useful at temperatures available from each heat source. Solid sulfate cycles offer advantages for isothermal heat sources. All cycles under development include concentration and drying steps. Novel methods for improving such operations would be beneficial.
Date: January 1, 1980
Creator: Bowman, M.G.
Partner: UNT Libraries Government Documents Department

Improved efficiency in thermochemical hydrogen cycles through decreasing the use of solvent water. Consideration of the sulfur dioxide: iodine cycle

Description: This paper considers the relationship between evaporation and efficiency and examines experimentally an adaptation of the sulfur dioxide-iodine cycle where little water needs to be evaporated or condensed.
Date: January 1, 1982
Creator: Mason, C.F.V. & Bowman, M.G.
Partner: UNT Libraries Government Documents Department