Ash removal of lignite with chemical treatment and its effect on the extraction of montan wax from lignite

Abstract：Parts of ashes in lignite can be removed by chemical treatment, which could increase the contact surfaces between organics and solvents, and influence extraction rate and the com- position of extracts. The effects of acid and alkali pretreatments on the demineralization of lig- nite were investigated by pretreatment in HC1 and NaOH solution, respectively. The influen- cing mechanism of chemical demineralization on the extraction and composition of extracts with several kinds of solvents were studied. The results show that the ash removal ratio decreased first and then increased with the increasing of particle size for 0.2--10 mm coal under acid pre- treatment. The ash removal ratio changed between 13.24% and 21.95%, and the minimum while particle size of 1--3 mm. The ash removal ratio decreased with the increasing of particle size under alkali pretreatment, which changed between ~6.12% and 72.02%. The higher ex- traction ratio was obtained over lignite with acid pretreatment or extracted with stronger polar solvents, meanwhile the content of small chain hydrocarbons in extracts also increased. The lower extraction ratio was obtained over lignite with alkali pretreatment or extracted with stronger polar solvents, and the compounds except non straight-chained hydrocarbons lost fromthe extracts.