Development of the chemical and electrochemical coal cleaning (CECC) process. Final report

Abstract

The Chemical and Electrochemical Coal Cleaning (CECC) process developed at Virginia Polytechnic Institute and State University was studied further in this project. This process offers a new method of physically cleaning both low- and high-rank coals without requiring fine grinding. The CECC process is based on liberating mineral matter from coal by osmotic pressure. The majority of the work was conducted on Middle Wyodak, Pittsburgh No. 8 and Elkhorn No. 3 coals. The coal samples were characterized for a variety of physical and chemical properties. Parametric studies were then conducted to identify the important operating parameters and to establish the optimum conditions. In addition, fundamental mechanisms of the process were studied, including mineral matter liberation, kinetics of mineral matter and pyrite dissolution, ferric ion regeneration schemes and alternative methods of separating the cleaned coal from the liberated mineral matter. The information gathered from the parametric and fundamental studies was used in the design, construction and testing of a bench-scale continuous CECC unit. Using this unit, the ash content of a Middle Wyodak coal was reduced from 6.96 to 1.61% at a 2 lbs/hr throughput. With an Elkhorn No. 3 sample, the ash content was reduced from 9.43 to 1.8%, whilemore » the sulfur content was reduced from 1.57 to 0.9%. The mass balance and liberation studies showed that liberation played a more dominant role than the chemical dissolution in removing mineral matter and inorganic sulfur from the different bituminous coals tested. However, the opposite was found to be the case for the Wyodak coal since this coal contained a significant amount of acid-soluble minerals.« less