In the Brown Coal Liquefaction (BCL) process, a two-stage coal liquefaction process, the solvent de-ashing technique is adopted to remove ash and heavy preasphaltenes from the heavy organic fraction, CLB (Coal Liquid Bottom), of the primary hydrogenation products.
In this report, the effects of properties of extraction solvents and production conditions of CLB on the properties of extracts and residues were examined using various solvents and CLBs. In the case of nonpolar solvents, extracts yields of CLB increased in the order of cyclohexane <toluene <tetralin with the increase of BI-PS concentration in the extracts. On the other hand, in the case of oxygen-containing polar solvents such as methanol and acetone, BI-PS concentrations in the extracts were relatively high in spite of low extract yields. Extract yields of CLBs produced under different temperature were predicted by the solvent extraction analysis for nonpolar solvents while not for oxygen-containing polar solvents. These results suggest that polar components of CLB play an important role in the extraction behavior of CLB, resulting in the difference of properties of extracts and residues, which affects their reactivity and the deactivation of catalysts in the secondary hydrogenation and also the handling of residues in the de-ashing process.
