Thermochemical IS Process Research Articles

Module design of silica membrane reactor for hydrogen production via thermochemical IS process

The potential of the silica membrane reactors for use in the decomposition of hydrogen iodide (HI) was investigated by simulation with the aim of producing CO2-free hydrogen via the thermochemical water-splitting iodine-sulfur process. Simulation model validation was done using the data derived from an experimental membrane reactor. The simulated results showed good agreement with the experimental findings. The important process parameters determining the performance of the membrane reactor used for HI decomposition, namely, reaction temperature, total pressures on both the feed side and the permeate side, and HI feed flow rate were investigated theoritically by means of a simulation. It was found that the conversion of HI decomposition can be improved by up to four times (80%) or greater than the equilibrium conversion (20%) at 400 °C by employing a membrane reactor equipped with a tubular silica membrane. The features to design the membrane reactor module for HI decomposition of the thermochemical iodine-sulfur process were discussed under a wide range of operation conditions by evaluating the relationship between HI conversion and number of membrane tubes.

熱化学水素製造ISプロセス用水素選択透過膜の開発

熱化学水素製造ISプロセス用水素選択透過膜の開発

312 熱化学法ISプロセスにおける直接接触硫酸濃縮試験(OS3-(4)オーガナイズドセッション《環境とエネルギー》)

312 熱化学法ISプロセスにおける直接接触硫酸濃縮試験(OS3-(4)オーガナイズドセッション《環境とエネルギー》)

Development of Hydrogen Production Technology by Thermochemical Water Splitting IS Process Pilot Test Plan

Japan Atomic Energy Agency (JAEA) has been conducting a study on a thermochemical IS process for hydrogen production. A pilot test of IS process is under planning that covers four R&D subjects: (1) construction of a pilot test plant made of industrial materials and completion of a hydrogen production test using electrically-heated helium gas as the process heat supplier, (2) development of an analytical code system, (3) component tests to assist the hydrogen production test and also to improve the process performance for the commercial plant, (4) a design study of HTTR-IS system. Development of innovative chemical reactors is in progress, which are equipped with a ceramic heat exchanger. In the design of the IS plant, it is important to establish the system for “design by analysis”. Therefore, we have developed a multiphase flow analysis code that can analyze systems in which chemical reactions occur.

Development of Hydrogen Production Technology by Thermochemical Water Splitting IS Process Pilot Test Plan

Japan Atomic Energy Agency (JAEA) has been conducting a study on a thermochemical IS process for hydrogen production. A pilot test of IS process is under planning that covers four R&D subjects: (1) construction of a pilot test plant made of industrial materials and completion of a hydrogen production test using electrically-heated helium gas as the process heat supplier, (2) development of an analytical code system, (3) component tests to assist the hydrogen production test and also to improve the process performance for the commercial plant, (4) a design study of HTTR-IS system. Development of innovative chemical reactors is in progress, which are equipped with a ceramic heat exchanger. In the design of the IS plant, it is important to establish the system for “design by analysis”. Therefore, we have developed a multiphase flow analysis code that can analyze systems in which chemical reactions occur.

ICONE15-10177 DEVELOPMENT OF HYDRAULIC ANALYSIS CODE FOR OPTIMIZING THERMO-CHEMICAL IS PROCESS REACTORS

The Japan Atomic Energy Agency has been conducting study on thermochemical IS process for water splitting hydrogen production. Based on the test results and know-how obtained through the bench-scale test, a pilot test plant, which has a hydrogen production performance of 30 Nm^3/h, is being designed conceptually as the next step of the IS process development. In design of the IS pilot plant, it is important to make chemical reactors compact with high performance from the viewpoint of plant cost reduction. A new hydraulic analytical code has been developed for optimizing mixing performance of multi-phase flow involving chemical reactions especially in the Bunsen reactor. Complex flow pattern with gas-liquid chemical interaction involving flow instability will be characterized in the Bunsen reactor. Preliminary analytical results obtained with above mentioned code, especially flow patterns induced by swirling flow agreed well with that measured by water experiments, which showed vortex breakdown pattern in a simplified Bunsen reactor.

Dehydration through pervaporation from HIx solution (HI-H2O-I2 mixture) using a cation exchange membrane for thermochemical water-splitting iodine-sulfur process

Pervaporation (PV) of water from HIx solution (HI-H2O-I2 mixture) using Nafion-117 was evaluated aiming at the application to dehydrate the azeotropic composition in HI decomposition reaction of thermochemical IS process. PV experiment was carried out by using HI solutions of 40–65 wt% and an I2/HI molar ratio of 0–3 in the feed at the room temperature. The permeation flux decreased with increasing HI weight fraction in the feed. The permeation flux is dependent on the I2 concentration in the feed having an I2/HI molar ratio. A long time PV experiment was carried out using I2/HI molar ratio of 1 (in HI solution of 55.9%) in the feed at room temperature. It is expected that the permeation component in the permeate zone using the PV process was mainly H2O, and H2O permeation was constant with increasing operation time.

Research and development on nuclear hydrogen production using HTGR at JAERI

JAERI has been conducting R&D on HTGR and on hydrogen production using HTGR. The reactor technology has been developed using HTTR installed at Oarai site of JAERI. HTTR reached its full power operation of 30MW in 2001 and demonstrated reactor outlet helium temperature of 950°C in April 2004. As for the hydrogen production technology, the thermo-chemical IS process is under study. The process control method for continuous hydrogen production has been examined using a bench-scale apparatus. Also, studies are underway on process improvement and on materials of construction to be used in the corrosive environment. As for the system integration of HTGR and the hydrogen production plant, R&D is underway aiming to develop technologies for safe and economical connection. It covers safety technology against explosion, safety technology against radioactive materials release, control technology to prevent the thermal disturbance from hydrogen production plant to reactor, etc.

512 熱化学水素製造法ISプロセスの研究開発(III) : 三酸化硫黄分解器の開発(関東支部 茨城講演会)

Japan Atomic Energy Research Institute (JAERI) has been conducting R&D on HTGRs and hydrogen production method focusing on thermochemical IS process. In the IS process, sulfur trioxide (SO_3) decomposition reaction works as the oxygen generation reaction where gaseous SO_3 is decomposed into SO_2 and O_2 in the presence of solid catalysts using high temperature heat of about 900℃ supplied by HTGRs. A concept of SO_3 decomposer was developed which features plate-type heat exchanger made of SiC ceramics, in which the heat of reaction is supplied by high temperature helium gas, and a model of the heat-exchanging units was successfully test-fabricated. Also, a test facility was constructed in order to examine the catalyst performance at temperatures of up to 850℃, and pressures of up to 0.75MPa.

Application of an electrochemical membrane reactor to the thermochemical water splitting IS process for hydrogen production

The Bunsen reaction (SO 2 + I 2 + 2H 2O = H 2SO 4 + 2HI) in the thermochemical IS process to produce hydrogen was successfully employed using an electrochemical membrane reactor. H 2SO 4 and HI were concentrated in the anode side and the cathode side of the reactor, respectively. I 2 is the dominant bulk of the recycling chemicals in this process, and I 2 concentration at the outlet of the reactor was reduced ca. 93% by using this technique. The electric energy consumption for the reaction was about 50% smaller by reducing the concentration of I 2 indicating that the IS process can be operate efficiently at low I 2 concentration. The reaction was carried out for 4 h, and the HI concentration was increased by 26%. This amount was the same within 10% as the values calculated from the total loaded electricity. In order to decrease the overpotential at the anode side, small amount of HI was added to the anode side solution. The total voltage was reduced by 0.03 V by the addition of HI.

Stability of a silica membrane prepared by CVD using γ- and α-alumina tube as the support tube in the HI–H 2O gaseous mixture

The stability of a silica membrane prepared by chemical vapor deposition (CVD) in the HI–H 2O gaseous mixture was evaluated aiming at the application for hydrogen iodide decomposition in the thermochemical IS process. Porous α- and γ-alumina tubes having pore sizes of 100 and 10 nm, respectively, were modified by chemical vapor deposition using tetraethoxysilane as the Si source. H 2/N 2 selectivities of the modified membranes which were measured by single-component permeation experiment showed 50.4, 7.5, 63.7, 7.7 and 3.8 at 600 °C for the NS-1, NS-2, NS-3, NS-4 and S-1 membranes, respectively. Stability experiment in the HI–H 2O gaseous mixture was carried out at 450 °C. The prepared membrane using γ-alumina as the support tube was more stable than that using α-alumina as the support tube. The S-1 membrane using α-alumina as the support tube showed the high stability in the HI–H 2O gaseous mixture and had the high H 2/HI selectivity (240–2600 at 300–600 °C) in the H 2–H 2O–HI (molar composition; 0.09:0.78:0.13) gaseous mixture after the stability test.

Hydrogen separation in H 2–H 2O–HI gaseous mixture using the silica membrane prepared by chemical vapor deposition

Hydrogen separation in H 2–H 2O–HI gaseous mixture using the silica membrane prepared by CVD was evaluated aiming at the application for hydrogen iodide decomposition in the thermochemical IS process. Porous alumina tubes having pore size of 100 nm (M1) and 10 nm (M2) were modified by chemical vapor deposition using tetraethoxysilane as the Si source. Single-component permeance to He, H 2, and N 2 was measured at 300–600°C. Hydrogen permeance of the modified membranes at a permeation temperature of 600°C was about 6×10 −9 mol/Pa m 2 s. H 2/N 2 selectivities at 600°C were 5.2 and 160 for M1 and M2 membrane, respectively. Separation experiments of a H 2–H 2O–HI mixture using the modified membranes were carried out at 300–600°C. Hydrogen permeances were almost the same as the single-component permeances, whereas HI permeances were below 1×10 −11 mol/Pa m 2 s. The hydrogen permeances were not changed after one day exposure in a mixture of H 2–H 2O–HI with a molar composition of 0.23:0.65:0.12 at 450°C.

Closed-Cycle Continuous Hydrogen Production Test by Thermochemical IS Process.

実験室規模の装置を用いて, 熱化学水素製造法ISプロセスの閉サイクル連続水素製造試験を行った.酸生成反応, 二液相分離, 酸分解反応等に関する実験結果を考慮して全系物質収支を定めた.水素製造速度1.2dm3 (S.T.P.)/hのもとで24時間の連続運転試験を行った結果, 量論比の水素と酸素を安定に発生させることができた.運転の前後における循環溶液組成はほとんど変化しなかった.

熱化学法ISプロセス装置材料スクリーニング試験

熱化学法ISプロセス装置材料スクリーニング試験