Technology Manager (Acting)
Advanced Combustion Systems
National Energy Technology Laboratory
3610 Collins Ferry Road
P.O. Box 880
Morgantown, WV 26507-0880
Federal Project Manager
National Energy Technology Laboratory
626 Cochrans Mill Road
P.O. Box 10940
Pittsburgh, PA 15236-0940
Washington University in St. Louis
One Brooking Drive
St. Louis, MO 63130-4862
DOE Share: $4,277,184.00
Performer Share: $1,106,617.00
Total Award Value: $5,383,801.00
Performer website: Washington University in St. Louis - http://research.wustl.edu/Offices_Committees/OTM/techsearch/TechPages/Pages/WUSTL013736.aspx
Program Background and Project Benefits
Advanced combustion power generation from fossil fuels involves combustion in a high-oxygen (O2) concentration environment rather than air. This type of system eliminates introduction of most, if not all, of the nitrogen (N2) found in air into the combustion process, generating flue gas composed of CO2, water (H2O), trace contaminants from the fuel, and other gas constituents that infiltrated the combustion system. The high concentration of CO2 (≈60 percent) and absence of nitrogen in the flue gas simplify separation of CO2 from the flue gas for storage or beneficial use. Thus, oxygen-fired combustion is an alternative approach to post-combustion capture for Carbon Capture and Storage (CCS) for coal-fired systems. However, the appeal of oxygen-fired combustion is tempered by a number of challenges, namely capital cost, energy consumption, and operational challenges associated with supplying O2 to the combustion system, air infiltration into the combustion system that dilutes the flue gas with N2, and excess O2 contained in the concentrated CO2 stream. These factors mean oxygen-fired combustion systems are not cost-effective at their current level of development. Advanced combustion system performance can be improved either by lowering the cost of oxygen supplied to the system or by increasing the overall system efficiency. The Advanced Combustion Systems Program targets both of these possible improvements through sponsored cost-shared research into two key technologies: (1) Oxy-combustion, and (2) Chemical Looping Combustion (CLC).
Oxy-combustion power production involves three major components: oxygen production (air separation unit [ASU]), the oxy-combustion boiler (fuel conversion [combustion] unit), and CO2 purification and compression. These components along with different design options are shown below. Based on the different combinations of these components, oxy-combustion can have several process configurations. These different configurations will have different energetic and economic performance.
Today's oxy-combustion system configuration would use a cryogenic process for O2 separation, atmospheric-pressure combustion for fuel conversion in a conventional supercritical pulverized-coal boiler; substantial flue gas recycle; conventional pollution control technologies for SOx, NOx, mercury, and particulates; and mechanical compression for CO2 pressurization. However, costs associated with currently available oxy-combustion technologies are too high. The Advanced Combustion Systems R&D Program is developing advanced technologies to reduce the costs and energy requirements associated with current systems. R&D efforts are focused on development of pressurized oxy-combustion power generation systems, as well as membrane-based oxygen separation technologies.
Washington University in St. Louis is working to improve oxy-combustion technology by developing a staged, high-pressure combustor system. Pressurized oxy-combustion reduces the mass and volume of flue gas, increases heat transfer rates, and makes latent heat recoverable, all of which improves efficiency. Furthermore, pressurization reduces equipment size, potentially reducing capital costs, and prevents air in-leakage, which increases CO2 purity. Fuel-staged combustion is used to manage peak combustion temperatures using excess oxygen as the diluent, allowing the use of conventional boiler materials and eliminating flue gas recycle, which both reduce capital cost. These factors have the ability to drive down the cost of electricity and the cost of CO2 capture relative to conventional coal-fired power plants with post-combustion CCS. Successful development of a laboratory-scale pressurized oxy-combustor, subsequent testing to validate the feasibility of Washington University in St. Louis’ approach, and projected cost and performance analysis of a full-scale system will support design, development, and testing of a small pilot-scale prototype.
Project Scope and Technology Readiness Level
The Phase II research team comprises Washington University in St. Louis and EPRI, with assistance from Praxair and Ameren. The primary tasks include design and construction of a laboratory-scale pressurized combustor and experiments to measure heat flux, temperatures, concentrations of gases and ash, and ash deposition rates. The recipient team will analyze the data to better understand the staged, high-pressure oxy-combustion (SPOC) process and validate the computational fluid dynamics (CFD) models that were relied upon in Phase I. The team will rerun the simulations based on the results of the analysis to ensure optimal boiler design. Corrosion studies will also be conducted to evaluate the corrosion characteristics of common and advanced boiler tube materials when they are subjected to the environments anticipated in the SPOC process as determined by the experiments. The recipient will improve the process modeling—including in the key area of the direct contact cooler—and update the Phase I techno-economic models to reflect the new information.
The Technology Readiness Level (TRL) assessment identifies the current state of readiness of the key technologies being developed under the DOE’s Clean Coal Research Program. This project has not yet been assessed.
The TRL assessment process and its results including definition and description of the levels may be found in the "2012 Technology Readiness Assessment-Analysis of Active Research Portfolio".
The project was selected for continuation into Phase II. Washington University in St. Louis has identified the major equipment needed and completed the collection of performance specs, a schematic design of the pressurized radiant boilers (assisted by CFD modeling), the plant site plan, an ASPEN process simulation model, and economic analysis. Experimental efforts were also undertaken to better understand the combustion of coal in nearly pure oxygen. Combustion tests were conducted utilizing oxygen-enriched air (up to 40 percent volume O2). Combustion tests at atmospheric pressure were performed in the 1-MWth test furnace at Washington University. The team will continue to collect the experimental data needed for CFD model validation during the final quarter. A provisional patent encompassing the SPOC process and boiler design was filed.