Large Scale Solvent Recovery in Direct Coal Liquefaction Processing

The utilization of coal for purposes other than power generation is of renewed interest, as indicated by a significant increase in federal funding in the area of late. The UK Center for Applied Energy Research (CAER) has a strong history in direct coal liquefaction (DCL). The DCL process involves the digestion of coal in a ‘solvent’, followed by a filtration step to remove the insoluble. However, due to its high viscosity the coal digest must be diluted with tetrahydrofuran (THF) prior to filtering. In order to filter the material a 1:1 ratio of coal liquid to THF is required. Optimization of the process economics further require the THF to be recovered for reuse. Currently, this THF recovery step is the rate-limiting step in the overall DCL process. We are scaling these processes up to the pilot scale. In a single coal digestion, we can produce 2 L of a THF-diluted coal liquid. However, for THF recovery we are limited to a 500 mL rotovap, which requires 5+ individual runs on the rotovap for a single coal liquid. The acquisition of the proposed piece of equipment, a 20 L rotovap system, would allow for a significantly streamlined process. Further, in the next year, we are set to begin DCL runs at the 30 L scale. This piece of equipment will prove vital for our research efforts.