Pretreatment And Properties Of Lignite By Mild Condition And Their Effect On Slurry Ability

The amount of lignite deposits is estimated to be comparable to that of high rank coal. However,lignite is not widely utilized not only because of its low calorific value but also because of its difficulty in transportation and storage attributed to its high water content and spontaneous ignition.Utilization and exploitation of CWS(Coal Water Slurry)as fuel and gasification material is a kind of clean coal technology conforming to the situation in china.But the slurryability of lignite is poor.In this paper,Huolinhe and Xiaolongtan lignite have been pretreated by pyrolysis in a muffle under nitrogen protection to improve the slurrization performance of said coal sort.Besides,The CWS has been produced from the upgraded coal.The slurryability,viscosity,stability,have been studied.It mainly concludes these contents as follows:Huolinhe and Xiaolongtan lignite was pretreated at low temperature.Physical and chemical properties have been investigated in detail using thermo gravimetric,nitrogen adsorption and oxygen-functional group analysis.The results show that the pretreated samples have higher carbon content,lower oxygen content and volatile matter,and the calorific value obviously increased,indicating that upgraded coals are closer to the higher rank coals than their parent coals.The optimum reaction conditions of Huolinhe lignite was:350℃,20min; The optimum reaction conditions of Xiaolongtan lignite was:300℃,20min.Besides,the oxygen-functional group content of two treated coals obviously decreased,especially carboxyl,at 350℃,the removal rate of two treated coals were respectively 77.64%and 71.87%.The pretreatment can remove oxygen-functional group.CWS has been produced from the upgraded coal.The milling grinding method,intensity and time.and quantity of addition agent have been studied.Comparing with the original coal samples,the slurrization performance of pretreated coal samples has been greatly enhanced. Besides.partial-size graded distribution are put forward to improve the slurring characteristics of CWS.The Huolinhe coal sample pretreated at 350℃during 1h,under condition of their concentration to be enhanced by 11.2%;The Xiaolongtan coal sample pretreated at 450℃during 1.5h.under condition of their concentration to be enhanced by 12.6%.Through multiple experiments,we have got the optimum mixture ratio of particle size of Huolinhe 350℃w(250μm～150μm):w(150μm～75μm):w(75μm～38μm):w(＜38μm)=10:10:20:60.