Study On Modification Of Lignite

Chinese lignite resources are abundant.But it has not been effectively utilized,because of its own disadvantages,and brought serious problems of pollution.The super-clean coal,prepared with thermal solvent extraction,is an effective way to realize coal cleaning utilization.In this thesis,the thermal solvent extraction of lignite was studied by self-developed technology.The thermal extraction conditions of lignite for prepared super clean coal was studied.The initial pressure,residence time and other factors were investigated on the properties of coal thermal extraction.The result showed that the best conditions were as follows: coal particle size was 80 mesh,the ratio of solvent volume and coal mass was 10:1,the thermal extraction temperature 380 ℃,residence time 5 min,the initial pressure 0 MPa,the tiring paddle speed 400 r/min,the super clean coal thermal extraction rate was 47.6%.Pretreatment of lignite can effectively change the structure of lignite,and improve the thermal extraction rate.Using acid,alkali,organic solvents and other solvent to pretreat the lignite.The results showed that KOH has the best effect.Using KOH as pretreatment solvent,invesgated the influence of pretreatment conditions on thermal extraction.As results showed,the best pretreatment conditons were as follow: 1 mol/L KOH,the ratio of solvent and coal mass is 10:1,reflux condensation 2h,the liginte extraction rate was66.5%.The super clean coal prepared from lignite was studied to investigate its feasibility as a coking coal blending.It was found that super clean coal’s caking index was 94.7.Gelatineous layer of the mix coal which coordinate super clean coal and lignite was tested.It showed that the samples were in a state of complete fusion.That makes it possible for super clean coal that produced by ligntie through thermal extraction to blending coking.