Pyrolysis Of A Kind Of Ningxia Coal And Simulation On Char Gasification

A kind of Ningxia long flame coal is used as the raw material for pyrolysis. Fixed-bed pyrolysis experiment is carried out at atmosphetic pressure to investigate the influence of pyrolysis temperature on the tar yield. Referring to the results of fixed-bed experiment, pyrolysis experiment is done by using the solid hot carrier pyrolysis technique developed by Dalian University of Technology (DG coal pyrolysis process) to study the optimum temperature of pyrolysis and the products are analyzed. Meanwhile, coal tar made by DG coal pyrolysis process is studied by GC-MS analysis. At last, char prepared at optimum temperature is chosed as material for simulation of gasification and the influencing factors of char gasification process are analyzed by sensitivity study runs.The results of fixed-bed experiment show that:In the selected pyrolysis temperature range (460～560℃), tar yield increases firstly and then decreases while char yield decreases with the increase of pyrolysis temperature. When the temperature is at520℃, the tar yield reaches the maximun value (7.09wt%,d).DG coal pyrolysis process demonstrates that:With the increase of pyrolysis temperature, tar yield performs the same regularity as the fixed-bed experiment. The tar yield achieves the maximun value (4.64wt%,ar). Char yield reduces from64.59wt%to56.15wt%and the yield of gas generated in pyrolysis process increases from6.74wt%to12.71wt%. Consideration from tar yield,520℃is the optimum temperature and this is consistent with the result of fixed-bed experiment. By analysis of520℃coal tar, it can be known that amount of distillate below310℃is as high as68wt%and the content of ash in coal tar is0.1wt%. These illustrate that the coal tar prepared by DG coal pyrolysis process is light oil and it is the good raw material for deep treating to make chemicals.Coal tar prepared by DG coal pyrolysis process is treated with pickling and alkaline cleaning and was seperated into three fractions:acidic fractions, alkaline fractions and neutral oil. And the neutral oil was divided into three different groups including aliphatic group, aromatic group and polar group by column chromatographic seperation. Gas charomatography-mass spectrometry (GC-MS) was used to analyze the fractions obtained from coal tar. Column chromatographic seperation demonstrates that the content of aliphatic group decreases (from17.29wt%to9.24wt%)with the increase of pyrolysis temperatures. However, the aromatic group and polar group show an inverse trend. The content of aromatic group increases significantly (from14wt%to23.09wt%) with the increase of pyrolysis temperatures. And the content of polar group increases from13.89wt%to26.46wt%. Meanwhile, GC-MS analysis of acidic fractions obtained by acid washing shows considerable phenol and extensive series of derivatives of phenol and naphthol. The alkaline fractions mainly contain substituted pyridine, Benzenamine derivatives and quinoline derivatives. Saturated hydrocarbons and olefinic compounds are main compounds in aliphatic series washed down by cyclohexane. And the analyse of aromatic series washed down by toluene indicates considerable benzene derivatives, substituted Indan, naphthalene derivatives and PAHs. Additionally, polar group washed down by the blend solution of toluene and ethanol (1:1) is primarily composed by ketone components.The models of gasification established in this study can well reflect the gaisification process. Oxygen-to-char mass ratio and mass percentage of char in char water slurry are the main factors which affect the Texaco gasification process. And oxygen-to-char mass ratio and stream-to-char mass ratio are the main factors which affect the Shell gasification process.