Development of the chemical and electrochemical coal cleaning process

Studies concerning the use of flotation as an alternative method of separating liberated mineral matter from chemical/electrochemical coal cleaning (CECC) treated coal were continued using Elkhorn No. 3 coal. The results obtained using different methods of recovering the clean product after CECC treatment showed trends similar to those observed previously with Pittsburgh No. 8 coal. The use of flotation after CECC treatment of the Elkhorn No. 3 coal was found to be more efficient than wet-screening. Construction of the continuous bench-scale unit was completed in this quarter. The unit was modified to process 2 lbs/hr instead of the original design of 1 lb/hr so as to ensure efficient operation of the vacuum filter unit. Start-up of the continuous unit was successfully conducted and shakedown testings were started. Initial results show that the continuous unit was able to reduce the ash content of a recently acquired Wyodak coal sample to as low as 1.16%. 2 tabs

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

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%, while 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