Thermochemical Hydrogen Production Process Research Articles

Solar thermochemical process for hydrogen production via two-step water splitting cycle based on Ce1−xPrxO2−δ redox reaction

Ce1−xPrxO2−δ (x=0, 0.05, 0.1, 0.2 and 0.3), as reactive ceramics synthesized by combustion method for H2 production via two-step water splitting reaction with concentrated solar energy, was investigated in present work. XRD analysis of the samples shows that Pr6O11 underwent a phase transition into Pr2O3and Pr2O3 cannot be oxidized by steam to yield H2 in two-step water splitting reaction. The solid solutions of the samples containing Ce were formed with a single cubic CeO2 fluorite structure after synthesis and even after two-step water splitting reaction. Although Pr cannot be oxidized by steam to generate H2 in two-step water splitting reaction, the promotion effect is present with the introduction of 5mol% and 10mol% Pr into CeO2 on the amounts of O2 and H2, but the volume of H2 evolved is enhanced or not, strongly dependent on the H2-generation temperature. The optimum H2-generation temperature is 1023K.

Biomass Steam Gasification with In-Situ CO2 Capture for Enriched Hydrogen Gas Production: A Reaction Kinetics Modelling Approach

Due to energy and environmental issues, hydrogen has become a more attractive clean fuel. Furthermore, there is high interest in producing hydrogen from biomass with a view to sustainability. The thermochemical process for hydrogen production, i.e. gasification, is the focus of this work. This paper discusses the mathematical modeling of hydrogen production process via biomass steam gasification with calcium oxide as sorbent in a gasifier. A modelling framework consisting of kinetics models for char gasification, methanation, Boudouard, methane reforming, water gas shift and carbonation reactions to represent the gasification and CO2 adsorption in the gasifier, is developed and implemented in MATLAB. The scope of the work includes an investigation of the influence of the temperature, steam/biomass ratio and sorbent/biomass ratio on the amount of hydrogen produced, product gas compositions and carbon conversion. The importance of different reactions involved in the process is also discussed. It is observed that hydrogen production and carbon conversion increase with increasing temperature and steam/biomass ratio. The model predicts a maximum hydrogen mole fraction in the product gas of 0.81 occurring at 950 K, steam/biomass ratio of 3.0 and sorbent/biomass ratio of 1.0. In addition, at sorbent/biomass ratio of 1.52, purity of H2 can be increased to 0.98 mole fraction with all CO2 present in the system adsorbed.

Comparative study of thermochemical processes for hydrogen production from biomass fuels

Different thermochemical configurations (gasification, combustion, electrolysis and syngas separation) are studied for producing hydrogen from biomass fuels. The aim is to provide data for the production unit and the following optimization of the “hydrogen chain” (from energy source selection to hydrogen utilization) in the frame of the Italian project “Filiera Idrogeno”. The project focuses on a regional scale (Tuscany, Italy), renewable energies and automotive hydrogen. Decentred and small production plants are required to solve the logistic problems of biomass supply and meet the limited hydrogen infrastructures. Different options (gasification with air, oxygen or steam/oxygen mixtures, combustion, electrolysis) and conditions (varying the ratios of biomass and gas input) are studied by developing process models with uniform hypothesis to compare the results. Results obtained in this work concern the operating parameters, process efficiencies, material and energetic needs and are fundamental to optimize the entire hydrogen chain.

硫酸流動機器健全性試験装置の運転試験

The Japan Atomic Energy Agency has been conducting R&D on the thermochemical iodine-sulfur process for large-scale hydrogen production using nuclear heat supplied by high-temperature gas-cooled reactors. Since the IS process uses strong acids such as sulfuric acid, it is important to examine the applicability of equipment such as pipes, pumps and instrumentations exposed to corrosive environments, and, therefore, flow tests of concentrated sulfuric acid have been carried out using a test apparatus made of candidate materials of construction at temperatures of up to 300°C for ca.150 h. Glass lining pipes and PTFE gaskets used for high-temperature service were sound during the test term, whereas high-silicon-containing austenitic stainless-steel pipes suffered general corrosion.

Experimental and simulation study on wind affecting particle flow in a solar receiver

The solid particle receiver (SPR) is a direct absorption central receiver that can provide a solar interface with thermal storage for thermo-chemical hydrogen production processes requiring heat input at temperatures up to 1000 °C. In operation, a curtain made up of approximately 697 μm ceramic particles is dropped within the receiver cavity and directly illuminated by concentrated solar energy. Since the SPR has an open aperture, the flow may be disturbed by high ambient winds. Therefore, the objective of this study was to gain insight into the wind effect on the curtain. Experiments were conducted to understand the wind influence on the particle flow and loss. The experimental results showed that winds from certain angles of the attack could cause a critical loss of particles. A MFIX simulation model was developed to validate the experimental results and observation. The simulation has provided us with better understanding on the wind effects.

Complexation in the Cu(II)–LiCl–H 2O system at temperatures to 423 K by UV-Visible spectroscopy

Thermodynamic data for the solubility and formation of copper(I)and copper(II) species are required to model innovative designs of the electrolysis cells used in the thermochemical copper-chloride hydrogen production process. Cumulative formation constants of Cu 2+(aq) complexes with Cl −(aq) were determined by Principal Component Analysis of UV-spectra, obtained over a very wide range of solution compositions and temperature, coupled with an appropriate model for activity coefficients of the solution species. Shortcomings in the existing database and future work to extend these studies to higher temperatures and much higher copper concentrations are discussed.

Simulation of Sulfur-Iodine Thermochemical Hydrogen Production Plant Coupled to High-Temperature Heat Source

The sulfur-iodine (SI) cycle is one of the leading candidates in thermochemical processes for hydrogen production. In this paper a simplified model for the SI cycle is developed with chemical kinetics models of the three main SI reactions: the Bunsen reaction, sulfuric acid decomposition, and hydriodic acid decomposition. Each reaction was modeled with a single control volume reaction chamber. The simplified model uses basic heat and mass balance for each of the main three reactions. For sulfuric acid decomposition and hydriodic acid decomposition, reaction heat, latent heat, and sensible heat were considered. Since the Bunsen reaction is exothermic and its overall energy contribution is small, its heat energy is neglected. However, the input and output streams from the Bunsen reaction are accounted for in balancing the total stream mass flow rates from the SI cycle. The heat transfer between the reactor coolant (in this case helium) and the chemical reaction chamber was modeled with transient energy balance equations. The steady-state and transient behavior of the coupled system is studied with the model, and the results of the study are presented. It was determined from the study that the hydriodic acid decomposition step is the rate-limiting step of the entire SI cycle.

Tin as a Possible Candidate for Solar Thermochemical Redox Process for Hydrogen Production

The feasibility to produce hydrogen in the Sn–H2O/SnO2–C thermochemical water splitting redox process depends mainly on the efficiency of the tin hydrolysis step, which has not been studied adequately so far, while the cassererite carboreduction is implemented by industry for tin production. The present work deals with the hydrolysis of different kinds of tin powders at different experimental conditions at moderate temperature range 180–620°C. In spite of the fact that the rate of hydrogen production is lower compared with other metals, e.g., zinc, at the same reactor temperature, high conversion level was obtained in a controllable reaction. Consequently, tin can be a relevant candidate for solar hydrogen production considering the advantage of significant lower temperatures required for the solar carboreduction of its oxide.

Immobilization of calcium oxide solid reactant on a yttria fabric and thermodynamic analysis of UT-3 thermochemical hydrogen production cycle

UT-3 cycle has been considered as one of the most promising thermochemical processes for hydrogen production. In order to make the cycle practical, however, the solid reactants in the cyclic reactions must have adequate lifespan and better kinetics. In this paper, hydrolysis reaction of calcium bromide, the slowest process in the cycle, was investigated theoretically and experimentally. A new type of calcium oxide reactant was fabricated by dispersing and fixing it on a yttria fabric via a comparatively straightforward and inexpensive immobilization process. The characteristics and cyclic performance of the prepared fabric samples were evaluated and compared with the conventional calcium oxide pellets. It was shown that the calcium oxide immobilized on the yttria fabric had continuous higher reactivity and comparable hydrolysis rate compared with the conventional calcium oxide pellets. A theoretical analysis of the thermodynamic cycle was also conducted. The effect of excess steam on the equilibrium conversion was significant; however, the reaction temperature was limited due to the melting point of calcium bromide. By continuously removing the product gas, the conversion in the hydrolysis reaction which is the slowest reaction in the cycle could be completed theoretically. This hypothesis was found to be true based on the experimental tests.

Analysis of Tritium Behavior in Very High Temperature Gas-Cooled Reactor Coupled with Thermochemical Iodine-Sulfur Process for Hydrogen Production

The tritium concentration in the hydrogen product in Japan's future very high temperature gas-cooled reactor (VHTR) system coupled with a thermochemical water-splitting iodine-sulfur (IS) process (VHTRIS system), named GTHTR300C, was estimated by numerical analysis. The tritium concentration in the hydrogen product significantly depended on undetermined parameters, i.e., the permeabilities of a SO3 decomposer and a H2SO4vaporizer made of SiC. Thus, the estimated tritium concentration in the hydrogen product for the conservative analytical condition ranged from 3.4 × 10−3 Bq/cm3 at STP (38 Bq/g-H2) to 0.18 Bq/cm3 at STP (2,000 Bq/g-H2). By considering the tritium retained by core graphite and the reduction in permeation rate by an oxide film on the heat transfer tube of the IHX and the HI decomposer, the tritium concentration in the hydrogen product decreased to the range from 3.3 × 10−5 Bq/cm3 at STP (0.36 Bq/g-H2) to 5.6 × 10−3 Bq/cm3 at STP (63 Bq/g-H2), which were smaller than those for the conservative analytical condition by factors of about 3.2 × 10−2 and 9.6 × 10−3, respectively. The effectof the helium flow rate in the helium purification system on the tritium concentration in the hydrogen product was also evaluated.

Exergy analysis of hydrogen production by thermochemical water decomposition using the Ispra Mark-10 Cycle

An investigation is reported of the thermodynamic performance of the Ispra Mark-10 thermochemical water decomposition process for hydrogen production. Thermochemical water decomposition has been identified as a potentially important future process for the production of hydrogen, which is currently an important industrial commodity and has significant future potential as a fuel. Exergy analysis is used since energy analysis on its own does not pinpoint true process inefficiencies, and often does not provide rational efficiencies. The analysis indicates that the principle thermodynamic losses occur in the primary water decomposition reactors and are mainly due to internal irreversibilities associated with chemical reaction and heat transfer across large temperature differences, and that the losses associated with effluents (particularly cooling water) are not that significant. Energy and exergy efficiencies are provided and are observed to depend strongly on the main external process inputs, i.e., electricity and process heat, or heat, or the raw resource from which heat and electricity are produced.

Operational strategy of a two-step thermochemical process for solar hydrogen production

Abstract A two-step thermochemical cycle process for solar hydrogen production from water has been developed using ferrite-based redox systems at moderate temperatures. The cycle offers promising properties concerning thermodynamics and efficiency and produces pure hydrogen without need for product separation. The process works by cycling stationary ferrite-coated monoliths through sequential oxidation and reduction steps at 1073 and 1473 K, respectively. By using two such monoliths in parallel, it is possible to quasi-continuously produce hydrogen. A prototype solar reactor and peripherals suitable to proof the process concept were developed and have been successfully tested in DLR's solar furnace in Cologne. Repeated cycling operation is possible with a reproducible amount of hydrogen produced. In most cases, a distinct decay of the amount of the evolved hydrogen is observed from cycle to cycle due to inhomogeneous heating of the monolithic absorber in the very first cycles and due to disappearance of the porosity and the associated loss of surface area in later cycles. Results from experimental campaigns with the prototype reactor and simulations with a corresponding reactor model support the development and verification of a process strategy for the continuous production of hydrogen in a larger scale. The tasks include the enhancement of long-term stability of the redox system, the development of an operational strategy and finally the design and development of a 100 kWth pilot reactor to demonstrate the feasibility of the process on top of a solar tower under real conditions.

Development of a New Thermochemical and Electrolytic Hybrid Hydrogen Production Process for FBR

日本原子力研究開発機構（以下，原子力機構と略記する）では，高速増殖炉の多目的利用研究の一環として，高速増殖炉で発生する熱と電気を利用し，水を水素発生原料として使用するハイブリッド熱化学法と呼ばれる水素製造技術を提案し，研究開発を進めてきた。

Development of Water Electrolysis Cell for Hydrogen Production UtilizingSulfur Dioxide

Water electrolysis utilizing sulfur dioxide is attractive for low-electricity-consumption hydrogen production and has been investigated for the electrolytic and thermochemical hybrid hydrogen production process utilizing the heat generated by a nuclear power plant. In this study, the hydrogen production performance of the water electrolysis cell utilizing sulfur dioxide gas and the sulfur dioxide crossover prevention performance of several polymer electrolytes were investigated experimentally.

Inorganic membranes for hydrogen production and purification: A critical review and perspective

Hydrogen as a high-quality and clean energy carrier has attracted renewed and ever-increasing attention around the world in recent years, mainly due to developments in fuel cells and environmental pressures including climate change issues. In thermochemical processes for hydrogen production from fossil fuels, separation and purification is a critical technology. Where water–gas shift reaction is involved for converting the carbon monoxide to hydrogen, membrane reactors show great promises for shifting the equilibrium. Membranes are also important to the subsequent purification of hydrogen. For hydrogen production and purification, there are generally two classes of membranes both being inorganic: dense phase metal and metal alloys, and porous ceramic membranes. Porous ceramic membranes are normally prepared by sol–gel or hydrothermal methods, and have high stability and durability in high temperature, harsh impurity and hydrothermal environments. In particular, microporous membranes show promises in water gas shift reaction at higher temperatures. In this article, we review the recent advances in both dense phase metal and porous ceramic membranes, and compare their separation properties and performance in membrane reactor systems. The preparation, characterization and permeation of the various membranes will be presented and discussed. We also aim to examine the critical issues in these membranes with respect to the technical and economical advantages and disadvantages. Discussions will also be made on the relevance and importance of membrane technology to the new generation of zero-emission power technologies.

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.

Construction materials development in sulfur–iodine thermochemical water-splitting process for hydrogen production

The sulfur iodine (SI) water splitting cycle for hydrogen production consists of three coupled chemical reactions, which includes the generation and decomposition of HI. The HI x environment is extremely corrosive and the severity increases with temperature. Immersion coupon corrosion screening tests were performed on materials selected from four classes of corrosion resistant materials: refractory metal, reactive metal, superalloys and ceramics. Of the materials tested, only Ta and Nb-based refractory metals and ceramic mullite can tolerate the extreme HI x environment. Severe pitting and dissolution was observed in two different reactive metal zirconium. A nickel based superalloy, C-276, also showed severe dissolution in HI x solution. The materials which showed good corrosion behavior will undergo further long-term immersion testing to assess performance. In addition, C-ring, U-bend and DCB test samples fabricated from qualified materials will be tested under stress corrosion conditions to investigate their crack initiation and growth properties.

An evaluation of reactor cooling and coupled hydrogen production processes using the modular helium reactor

The high-temperature characteristics of the modular helium reactor (MHR) make it a strong candidate for producing hydrogen using either thermochemical or high-temperature electrolysis (HTE) processes. Using heat from the MHR to drive a sulfur-iodine (SI) thermochemical hydrogen production process has been the subject of a U.S. Department of Energy sponsored Nuclear Engineering Research Initiative (NERI) project led by General Atomics, with participation from the Idaho National Laboratory (INL) and Texas A&M University. While the focus of much of the initial work was on the SI thermochemical production of hydrogen, recent activities included development of a preconceptual design for an integral HTE hydrogen production plant driven by the process heat and electricity produced by a 600 MW MHR. This paper describes ATHENA analyses performed to evaluate alternative primary system cooling configurations for the MHR to minimize peak reactor vessel and core temperatures while achieving core helium outlet temperatures in the range of 900–1000 °C that are needed for the efficient production of hydrogen using either the SI or HTE process. The cooling schemes investigated are intended to ensure peak fuel temperatures do not exceed specified limits under normal or transient upset conditions, and that reactor vessel temperatures do not exceed American Society of Mechanical Engineers (ASME) code limits for steady-state or transient conditions using standard light water reactor vessel materials. Preconceptual designs for SI and HTE hydrogen production plants driven by one or more 600 MW MHRs at helium outlet temperatures in the range of 900–1000 °C are described and compared. An initial SAPHIRE model to evaluate the reliability, maintainability, and availability of the SI hydrogen production plant is also described. Finally, a preliminary flowsheet for a conceptual design of an HTE hydrogen production plant coupled to a 600 MW modular helium reactor is presented and discussed.