High-Temperature Co-electrolysis of Steam and Carbon Dioxide for Direct Production of Syngas; Equilibrium Model and Single-Cell Tests

An experimental study has been completed to assess the performance of single solid-oxide electrolysis cells operating over a temperature range of 800 to 850ºC in the coelectrolysis mode, simultaneously electrolyzing steam and carbon dioxide for the direct production of syngas. The experiments were performed over a range of inlet flow rates of steam, carbon dioxide, hydrogen and nitrogen and over a range of current densities (-0.1 to 0.25 A/cm2) using single electrolyte-supported button electrolysis cells. Steam and carbon dioxide consumption rates associated with electrolysis were measured directly using inlet and outlet dewpoint instrumentation and a gas chromatograph, respectively. Cell operating potentials and cell current were varied using a programmable power supply. Measured values of open-cell potential and outlet gas composition are compared to predictions obtained from a chemical equilibrium coelectrolysis model. Model predictions of outlet gas composition based on an effective equilibrium temperature are shown to agree well with measurements. Cell area-specific resistance values were similar for steam electrolysis and coelectrolysis

Carbon Neutral Production Of Syngas Via High Temperature Electrolytic Reduction Of Steam And CO2

This paper presents the most recent results of experiments conducted at the Idaho National Laboratory (INL) studying coelectrolysis of steam and carbon dioxide in solid-oxide electrolysis stacks. Two 10-cell planar stacks were tested under various gas compositions, operating voltages, and operating temperatures. The tests were heavily instrumented, and outlet gas compositions were monitored with a gas chromatograph. Measured outlet compositions, open cell potentials, and coelectrolysis thermal neutral voltages compared reasonably well with a coelectrolysis computer model developed at the INL. Stack ASRs did not change significantly when switching from electrolysis to coelectrolysis operation

Recent Progress At The Idaho National Laboratory In High Temperature Electrolysis For Hydrogen And Syngas Production

This paper presents the most recent results of experiments conducted at the Idaho National Laboratory (INL) studying electrolysis of steam and coelectrolysis of steam / carbon dioxide in solid-oxide electrolysis stacks. Single button cell tests as well as multi-cell stack testing have been conducted. Multi-cell stack testing used 10 x 10 cm cells (8 x 8 cm active area) supplied by Ceramatec, Inc (Salt Lake City, Utah, USA) and ranged from 10 cell short stacks to 240 cell modules. Tests were conducted either in a bench-scale test apparatus or in a newly developed 5 kW Integrated Laboratory Scale (ILS) test facility. Gas composition, operating voltage, and operating temperature were varied during testing. The tests were heavily instrumented, and outlet gas compositions were monitored with a gas chromatograph. The ILS facility is currently being expanded to 15 kW testing capacity (H2 production rate based upon lower heating value)

Thermal and Electrochemical Performance of a High-Temperature Steam Electrolysis Stack

A research program is under way at the Idaho National Laboratory (INL) to simultaneously address the research and scale-up issues associated with the implementation of solid-oxide electrolysis cell technology for hydrogen production from steam. We are conducting a progression of electrolysis stack testing activities, at increasing scales, along with a continuation of supporting research activities in the areas of materials development, single-cell testing, detailed computational fluid dynamics (CFD) and systems modeling. This paper will present recent experimental results obtained from testing of planar solid-oxide stacks operating in the electrolysis mode. The hydrogen-production and electrochemical performance of these stacks will be presented, over a range of operating conditions. In addition, internal stack temperature measurements will be presented, with comparisons to computational fluid dynamic predictions

Design of an Integrated Laboratory Scale Test for Hydrogen Production via High Temperature Electrolysis

The Idaho National Laboratory (INL) is researching the feasibility of high-temperature steam electrolysis for high-efficiency carbon-free hydrogen production using nuclear energy. Typical temperatures for high-temperature electrolysis (HTE) are between 800º-900ºC, consistent with anticipated coolant outlet temperatures of advanced high-temperature nuclear reactors. An Integrated Laboratory Scale (ILS) test is underway to study issues such as thermal management, multiple-stack electrical configuration, pre-heating of process gases, and heat recuperation that will be crucial in any large-scale implementation of HTE. The current ILS design includes three electrolysis modules in a single hot zone. Of special design significance is preheating of the inlet streams by superheaters to 830°C before entering the hot zone. The ILS system is assembled on a 10’ x 16’ skid that includes electronics, power supplies, air compressor, pumps, superheaters, , hot zone, condensers, and dew-point sensor vessels. The ILS support system consists of three independent, parallel supplies of electrical power, sweep gas streams, and feedstock gas mixtures of hydrogen and steam to the electrolysis modules. Each electrolysis module has its own support and instrumentation system, allowing for independent testing under different operating conditions. The hot zone is an insulated enclosure utilizing electrical heating panels to maintain operating conditions. The target hydrogen production rate for the ILS is 5000 Nl/hr

Results Of Recent High Temperature Co-Electrolysis Studies At The Idaho National Laboratory

For the past several years, the Idaho National Laboratory and Ceramatec, Inc. have been studying the feasibility of high temperature solid oxide electrolysis for large-scale, nuclear-powered hydrogen production. Parallel to this effort, the INL and Ceramatec have been researching high temperature solid oxide co-electrolysis of steam/CO2 mixtures to produce syngas, the raw material for synthetic fuels production. When powered by nuclear energy, high temperature co-electrolysis offers a carbon-neutral means of syngas production while consuming CO2. The INL has been conducting experiments to characterize the electrochemical performance of co-electrolysis, as well as validate INL-developed computer models. An inline methanation reactor has also been tested to study direct methane production from co-electrolysis products. Testing to date indicate that high temperature steam electrolysis cells perform equally well under co-electrolysis conditions. Process model predictions compare well with measurements for outlet product compositions. The process appears to be a promising technique for large-scale syngas production

The Development of Models for Carbon Dioxide Reduction Technologies for Spacecraft Air Revitalization

Through the respiration process, humans consume oxygen (O2) while producing carbon dioxide (CO2) and water (H2O) as byproducts. For long term space exploration, CO2 concentration in the atmosphere must be managed to prevent hypercapnia. Moreover, CO2 can be used as a source of oxygen through chemical reduction serving to minimize the amount of oxygen required at launch. Reduction can be achieved through a number of techniques. NASA is currently exploring the Sabatier reaction, the Bosch reaction, and co- electrolysis of CO2 and H2O for this process. Proof-of-concept experiments and prototype units for all three processes have proven capable of returning useful commodities for space exploration. All three techniques have demonstrated the capacity to reduce CO2 in the laboratory, yet there is interest in understanding how all three techniques would perform at a system level within a spacecraft. Consequently, there is an impetus to develop predictive models for these processes that can be readily rescaled and integrated into larger system models. Such analysis tools provide the ability to evaluate each technique on a comparable basis with respect to processing rates. This manuscript describes the current models for the carbon dioxide reduction processes under parallel developmental efforts. Comparison to experimental data is provided were available for verification purposes

Three Dimensional CFD Model of a Planar Solid Oxide Electrolysis Cell for Co-Electrolysis of Steam and Carbon-Dioxide

A three-dimensional computational fluid dynamics (CFD) model has been created to model high temperature co-electrolysis of steam and carbon dioxide in a planar solid oxide electrolyzer (SOE). A research program is under way at the Idaho National Laboratory (INL) to simultaneously address the research and scale-up issues associated with the implementation of planar solid-oxide electrolysis cell technology for syn-gas production from CO2 and steam. Various runs have been performed under different run conditions to help assess the performance of the SOE. An experimental study is also being performed at the INL to assess the SOE. Model results provide detailed profiles of temperature, Nernst potential, operating potential, anode-side gas composition, cathode-side gas composition, current density and syn-gas production over a range of stack operating conditions. Typical results of current density versus cell potential, cell current versus H2 and CO production, temperature, and voltage potential are all presented within this paper. Plots of mole fraction of CO2, CO, H2, H2O, O2, are presented. Currently there is strong interest in the large-scale production of syn-gas from CO2 and steam to be reformed into a usable transportation fuel. This process takes the carbon-neutral approach where the amount of CO2 in the atmosphere does not increase. Consequently, there is a high level of interest in production of syn-gas from CO2 and steam electrolysis. Worldwide, the demand for light hydrocarbon fuels like gasoline and diesel oil is increasing. To satisfy this demand, oil companies have begun to utilize oil deposits of lower hydrogen. In the mean time, with the price of oil currently over $70 / barrel, synthetically-derived hydrocarbon fuels (synfuels) have become economical. Synfuels are typically produced from syngas – hydrogen (H2) and carbon monoxide (CO) -- using the Fischer-Tropsch process, discovered by Germany before World War II. South Africa has used synfuels to power a significant number of their buses, trucks, and taxicabs. The Idaho National Laboratory (INL), in conjunction with Ceramatec Inc. (Salt Lake City, USA) has been researching for several years the use of solid-oxide fuel cell technology to electrolyze steam for large-scale nuclear-powered hydrogen production. Now, an experimental research project is underway at the INL to investigate the feasibility of producing syngas by simultaneously electrolyzing at high-temperature steam and carbon dioxide (CO2) using solid oxide fuel cell technology. High-temperature nuclear reactors have the potential for substantially increasing the efficiency of syn-gas production from CO2 and water, with no consumption of fossil fuels, and no production of greenhouse gases. Thermal CO2-splitting and water splitting for syn-gas production can be accomplished via high-temperature electrolysis or thermochemical processes, using high-temperature nuclear process heat. In order to achieve competitive efficiencies, both processes require high-temperature operation (~850°C). High-temperature electrolytic CO2 and water splitting supported by nuclear process heat and electricity has the potential to produce syn-gas with an overall system efficiency near those of the thermochemical processes. Specifically, a high-temperature advanced nuclear reactor coupled with a high-efficiency high-temperature electrolyzer could achieve a competitive thermal-to-syn-gas conversion efficiency of 45 t