DIRECT LIQUEFACTION PROOF OF CONCEPT

The eighth bench scale test of POC program, Run PB-08, was successfully completed from August 8 to August 26, 1997. A total of five operating conditions were tested aiming at evaluating the reactivity of different pyrolysis oils in liquefaction of a Wyoming sub-bituminous coal (Black Thunder coal). For the first time, water soluble promoters were incorporated into the iron-based GelCat to improve the dispersion of the promoter metals in the feed blend. The concentration of the active metals, Mo and Fe, was 100 and 1000 ppm of moisture-free coal, respectively. Black Thunder coal used in this run was the same batch as tested in HTIs Run POC-02. Similar to Runs PB-01 through 7, this run employed two back mixed slurry reactors, an interstage gas/slurry separator and a direct-coupled hydrotreater. In addition to the hot vapor from the second stage separator, the first stage separator overhead liquid was also fed to the hydrotreater, which was packed with Criterion C-411 hydrotreating catalyst. Pyrolysis oil was produced off-line from a pyrolysis unit acquired from University of Wyoming. Solids rejection was achieved by purging out pressure filter solid. The recycle solvents consisted of O-6 separator bottoms and pressure filter liquid (PFL). The Run PB-08 proceeded very smoothly without any interruptions. Coal conversion consistently above 90W% was achieved. High resid conversion and distillate yield have been obtained from co-processing of coal and 343°C+ (650°F+) pyrolysis oil. Light gas (C₁-C₃ ) yield was minimized and hydrogen consumption was reduced due to the introduction of pyrolysis oil, compared with conventional coal-derived solvent. Catalytic activity was improved by incorporating a promoter metal into the iron-based GelCat. It seemed that lowering the first stage temperature to 435°C might increase the hydrogenation function of the promoter metal. In comparison with previous coal-waste coprocessing run (PB-06), significant improvements in the process performance were achieved due to catalyst modification and integration of pyrolysis technique into liquefaction