This document summarizes the work performed by SAS to study the utilization of heat as hightemperature steam and CO2 from a fossil fuel power plant. The study also focused on the use ofelectricity from the grid to produce syngas using high-temperature co-electrolysis (HTCE)technology. This technology uses solid oxide electrolysis cells (SOECs) operating at hightemperatures. The study included a literature review of the latest developments in HTCE, selectionof a baseline power plant and development of a process model of the integrated fossil plant andHTCE system. Model validation was performed along with a parametric study. A brief economicanalysis was also conducted which is included in this report.
The literature review showed that there was considerable interest both in the U.S. and around theworld in HTCE. In particular, much work has been done at the Idaho National Laboratory (INL).The total energy required in the splitting reactions to produce syngas from water and carbon dioxideincludes thermal and electrical energy. By using high temperature steam, the amount of electricalenergy needed for HTCE is reduced. Studies at INL showed that models based on the basic theoryof electrolysis could effectively predict the performance of the HTCE process. The baseline powerplant selected for this study was the Deseret’s Bonanza plant in northeastern Utah. A process modelwas developed in the MATLAB coding environment with the code compiled into an executableformat that can be distributed to any 64-bit or 32 bit Windows operating system computer. In thisway licensing fees for Third Party Process codes (e.g., ASPEN or UniSim) would not be needed.The executable code interfaces with MS Excel for easy user interface of both pre-processing (userinputs) and post-processing (data presentation and review). The model was validated against datafrom the INL studies, showing good agreement.
A brief parametric study indicated a potential savings of nearly 25% in electricity demand byoperating at 800 °C verses 600 °C. Plant economics were implemented into the model as a postprocessedportion of the MS Excel sheet. It showed an estimated hydrogen enriched syngas(referred to as tailored syngas) cost of $0.05/lbm or $100/ton (assuming oxygen valued at $0.06/lbm)and $0.16/lbm or $320/ton (assuming oxygen not valued). It is noted that the syngas produced inthis process is specially designed as a feed to a Fisher-Tropsch based synfuel refinery to producegasoline, diesel, jet fuel and chemicals.
Keywords:High Temperature Steam Electrolysis, Carbon Dioxide, Greenhouse Gases, Coal, Syngas, Synfuels