Conversion of Coal Wastes and Municipal Solids Mixtures by Pyrolytic Torrefaction and Entrained Flow Gasification

For the foreseeable future, the Nation’s energy demand will continue to come largely from indigenous fossil energy resources and hydrocarbon fuels. Specifically waste coal plus other opportunity fuels need to be utilized as a feedstock to eliminate a waste stream and optimized to maximize energy yield and cleanly minimize pollutant emissions. Modular equipment is needed for installation in coal preparation locations, military installations, and research park facilities. Thermal decomposition of coal, biomass, and mixed solid waste (MSW) have been shown to reduce a waste stream while providing liquid and gaseous fuel products with low pollutant emissions. However, thermal decomposition processes have several challenges associated with preprocessing biomass and MSW, feeding and conveying material into the reactor, and post processing of syngas to remove undesirable products while upgrading to increase yield of high value products. Entrained flow gasifiers produce very little methane and a wide range of H2/CO ratios (0.5–2.0) but are limited in their ability to effectively feed large biomass particles into the reactor. A solution to the feeding problems associated with entrained flow gasifiers is to use a low‐temperature pyrolysis reactor for torrefaction of the biomass mixture, creating a feedstock similar to coal and capable of grinding down, mixing with the coal feed, and feeding into the entrained flow gasifier In Phase II, Mainstream will design a pilot‐scale torrefaction reactor using our prior experience with thermal conversion reactors and collaboration with Earth Care Products, Inc. The pilot‐scale torrefier will be integrated with EERC’s pilot scale EFG to demonstrate a continuous pilot‐scale PT‐EFG conversion system with full characterization of yield and emissions. Mainstream will demonstrate a high‐value syngas with a H2:CO ratio of 2:1 and show that the vitrified slag passes the EPA TCLP test for leaching. Mainstream and EERC will scale up the pilot‐scale system and develop a complete design package of a 200 kW demonstrator‐scale PT‐EFG. A refined commercialization plan and TEA and will be developed to show the cost benefits of the commercial‐scale PT‐ EFG and the benefits associated with mass production of modular units. In Phase III, Mainstream would fabricate and demonstrate a demonstrator‐scale PT‐EFG in the field. Commercial Applications and Other Benefits: The proposed evaluation of thermochemical conversion pathways for waste coal, biomass, and mixed wastes process will address methods for improving energy yields and minimizing pollutant emissions. Increasing total energy output from power plants by utilizing biomass and mixed wastes ultimately lowers energy costs, harmful environmental impacts of emissions, and has significant impacts on the energy security and sustainability of the U.S. economy. This proposal outlines a plan to experimentally investigate three possible reaction pathways for the conversion of coal wastes and coal plus opportunity fuel mixtures that can be implemented in existing coal‐fired power plants. Ultimately, a process model for coal waste plus municipal solids (CWPMS) processing will be developed for a range of power plants to demonstrate a reduction in capital, operational, and maintenance costs for co‐firing biomass and mixed waste with coal.