The behaviour of bituminous coals under coprocessing conditions

Three high-volatile bituminous coals -Illinois No. 6, a hvbC from the U.S., Prince Mine, a hvbB and Lingan mine, a hvbA from Eastern Canada - were tested for CANMET coprocessing with Cold Lake vacuum bottoms, using a bench-scale continuous-flow stirred tank reactor unit. The tests were carried out at 425-455°C, pressures in the range of 10.4-17.3 MPa, 0.6-2 kg/h/L space velocities and coal concentrations of 18-30 wt % maf in slurry feed. It was shown that the response of performance parameters to operating conditions depends strongly on coal rank. The formation of anisotropic solids, as determined by petrographic analysis, was more noticeable for bituminous coals than for the subbituminous coal and increased with coal rank. For bituminous coals, the extent of coke formation was related to their swelling and thermoplastic characteristics. Increasing the operating pressure resulted in a significant increase in the measured coal conversion for high-rank coals whereas the effect was marginal for the subbituminous coal. Conversely, increasing the operating temperature resulted in higher coal conversion for the subbituminous coal, whereas the regressive reactions offset the effect for bituminous coals. Under identical operating conditions, although the low-rank coal resulted in higher overall distillate yield, the bituminous coals produced higher yields of the naphtha fraction. Comparison of the yields of residue components shows that bituminous coals produce lower yields of residual oils and much higher yields of asphaltenes and preasphaltenes than low-rank coals.