A slovent de-ashing under high temperature and high pressure is adopted in the twostage brown coal liquefaction process to remove ash from the heavy product (coal liquid bottom, CLB) because of its high efficiency.
Extract yield and residue properties are very important to develop the solvent deashing process because they affect strongly the CLB recovery and residue handling. Therefore, the effects of temperature and properties of the deashing solvent on the extract yield and residue properties were studied using toluene, cyclohexane and mixture of these as deashing solvents.
About a half of preasphaltenes (BI-PS) in the CLBs used was extracted with toluene at 100-250°C. The residue consisted of fine perticles and was handled as a slurry. On the other hand, almost of the preasphaltenes was insoluble in cyclohexane at 250°C although extract yield increased with an increase in temperature. The residue obtained from cyclohexane extraction at above 170°C was sticky, and filtration of the residue was impossible because by plugging up the filter.
From these results, it is found that toluene is a suitable solvent for the solvent deashing.
