Study On Pyrolysis Process Of Four Different Rank Of Coals

Pyrolysis reaction of coal is the initial stage of coal gasification, liquefaction and combustion. It is very helpful to study on coal pyrolysis process for understanding coal structure and efficient use of coal. This paper selected Shengli( SL),Alagtogoo(AT),Shenhua(SH),Tawantolgoi(TT)as the object to study. The weight loss properties and gas emission characteristics were investigated during temperature-programmed process by thermal gravimetric analysis and fixed-bed instrument.The chars which were pyrolysed at the different temperature(550-850 ℃) were analysized qualitatively and quantitatively by FTIR.The results showed that ΔT and ΔWmax decreased with the increase of coal rank coal. Characteristics composite index of pyrolysis-P values was in the order of AT≈SL>SH>TT. Low rank coal had strong reactivity in pyrolysis,but it manifested in different ways. SL had a wide temperature reaction zone, weight loss rate remained stable. AT had a narrow temperature zone, weight loss rate changed dramaticly. The reaction order n = 2 was more accurate than n = 1 and n = 1.5.The apparent activation energy decreased first then increased for all samples with the increase of temprature. DTG fitting results indicated that the bond with high bond energy occupy the larger propotion in high rank coal.The temperature zone was relatively concentrated for CH4 and H2 those were generated from coal pyrolysis.And CO and CO2 had relatively wide temperature zone as well as complex generating rate curve.The order of CO2+CO was showed as follow: SL>AT > SH?TT. It indicated that the number of oxygen-containing functional groups decreased deeply with the coal rank increasing. Amount of CH4 and H2 which belonged to TT coal were much larger than the other ones. The calorific value of syngas increased firstly then decreased. The generating of CO2, CO, CH4 and H2 are all made from several different elementary reactions. Same type of elementary reactions had same activation energy values.R1 and R2 which were the two kinds of FTIR parameters of raws increased with the increase of coal rank. That was, with increase of coal rank the proportion of aromatic structures increased significantly. D value also increased with the increase of coal rank and proportion of aromaticity.It indicated that higher rank coal had a greater proportion of condensed aromatic rings. The value of C sharply decreased with the increase of coal rank. The significant reduction of C = O structure resulted in coal maturity. After pyrolysis, the values of R2 and D significantly increased for all kinds of samples. After pyrolysis the values of R2 and D in SH and TT samples increased more rapidly than in SL and AT. That meant higher rank of coals had greater aromaticity degree and condensation for aromaticthan lower rank of coals. C values of SL,SH and TT rapidly reduced to zero after pyolysis. C of AT sample gradually decreased with temperature increasing.Pyrolysis made smaples mature.It helps to enhance the quality of coal.