Study On Pyrolysis Characteristics Of Low Volatile Coal

Coal occupies the largest proportion of energy consumption in our country.The pollutants generated during coal utilization have a great impact on the environment.It is urgent and significant to study and promote the clean and efficient utilization of coal technologies.At present,the research on coal pyrolysis at home and abroad pay more attention to lignite and bituminous coal with higher volatile content.The coal with low volatile content is abundant in our country;however,due to the difficulty in igniting and other reasons,the application range is relatively narrow.In order to explore how much volatility of coal suitable for coal pyrolysis grading use,the pyrolysis characteristics and pyrolysis products of low volatile coal were studied to provide reference data for the possibility of polygeneration.In this paper,lower volatile content coal samples from Qianjiaying mine,Mingxin mine and Niushan mine were selected for pyrolysis experiments of tube furnace respectively.The particle size of coal sample was 75?m,75?150?m and 150?300?m respectively.Pyrolysis was carried out under the conditions of 600,800,1000 and 1200 ? under N2 atmosphere.The effects of coal particle size,pyrolysis temperature and physicochemical properties of raw coal on the generate law of char,tar,gas and product characteristics were analyzed.The change of final pyrolysis temperature has an important effect on the rate of weight loss of char.The higher the volatile content of coal,the higher the rate of weight loss of char is.The difference of coal particle size has no clearly effect on the rate of weight loss of char.Under the same conditions,the larger the particle size of the sample(or the higher the pyrolysis temperature),the higher the ignition temperature,the burnout temperature and the maximum burning rate temperature,while the comprehensive combustion index is lower,the char is more difficult to burn.When the volatile content of raw coal is low,char is less flammable after pyrolysis reaction and less suitable for combustion applications.The higher the volatile content of coal and pyrolysis temperature,the higher the proportion of even carbon atoms in the pyrolysis oil,and the more obvious the phenomenon of odd-even oscillation.The higher the volatile content of raw coal and pyrolysis temperature,the easier to form a larger number of carbon atoms tar molecules,the higher PAHs ratio.The pyrolysis gas pyrolysis rate reaches the maximum at the beginning when pyrolysis at 600 ?.With the progress of pyrolysis reaction,the pyrolysis gas precipitation rate gradually decreases and the precipitation rate curve tends to be gentle.When pyrolyzed at 800 ?,coal tar produced by pyrolysis between 50?100s is pyrolyzed at high temperature to generate gas.With the further increase of pyrolysis temperature,more pyrolyzed tar was pyrolyzed in the furnace to generate a large amount of gas at 1000 and 1200 ?.The main pyrolysis gas compositions of H2,CH4,CO,CO2,C2H4,C2H6 and C2H2 were measured.With the increase of pyrolysis temperature,the content of H2 and CO increased while the content of CH4 and CO2 decreased.When the pyrolysis temperature was lower,more C2H6 was produced.With the increase of pyrolysis temperature,pyrolysis gas began to produce C2H2.The change of C2H4 in pyrolysis gas with temperature was not obvious.In the range of 600-1200?,with the pyrolysis temperature increasing,the yield of semi-coke and tar decreased,and the yield of pyrolysis gas increased.At lower temperatures,the higher the volatility of raw coal,the higher the yield of tar.With the increase of coal particle size,the yield of pyrolysis gas did not change obviously and the tar content decreased.