Pilot-Scale Testing of the Hydrophobic-Hydrophilic Separation (HHS) Process to Produce Value-Added Products from Waste Coals
Sponsor : US Department of Energy
Dates : June 1, 2020 – December 31, 2022
Summary : Mined coal is cleaned of its impurities such as mineral matter and sulfur before utilization. In general, the cost of cleaning increases with decreasing particle size. At present, the industry is discarding coal fines below approximately 44 µm due to the high costs associated with the recovery and dewatering. The amount of the fine coal discarded to impoundments in the United States is estimated to be approximately 6 billion tons. Minerals Refining Company and Virginia Tech have jointly developed a new separation process known as hydrophobic-hydrophilic separation (HHS) that will be tested at pilot scale to collect appropriate scale-up and cost information toward commercial deployment. The basic principles involved in the newly patented process are distinctly different and more efficient than the flotation process, which was patented in 1905 but still is regarded as the best available separation technology for cleaning fine coal. Furthermore, the HHS process is capable of producing dry products without thermal drying, regardless of particle size. The new process has been tested successfully at laboratory, proof-of-concept, and pilot scales on different types of fine coal samples taken from operating coal cleaning plants. The results show that the process can produce high-quality products with high efficiencies. In general, the ash contents of the products decrease with decreasing particle size due to improved liberation of inorganic mineral matter from organic coal matrix, which opens the possibility of producing ultraclean coal with less than 1% ash and with very low moisture. The high-quality coal produced in this manner may create new markets for coal such as activated carbon, carbon black, carbon foams, carbon electrodes, graphene, oil additives, etc. If successful, these new markets will help maintain and create high-paying jobs in the Appalachian coal field. The work proposed herewith include pilot-scale tests to produce low-ash, low-moisture coals that can burn more cleanly and hence generate less CO2 emissions. The tests will be conducted on a bituminous and anthracite coal wastes that have been discarded due to the lack of appropriate separation and dewatering technologies. The pilot-scale tests will also be conducted on a micronized coal sample to produce an ultraclean coal that can create new markets for U.S. coals.