Research Of Reactivities Of Coal During Pyrolysis And Gasification

Coal is the main energy source and resource in China. Gasification as a process technology, has received considerable attention from many researches because it is not only an important basic technology in coal conversions, but also a committed step and an effective method for a clean conversion of coal. Gasification of coal including two stage, first is pyrolysis, the second is gasification, pyrolysis is the initial stage of coal gasification process and has important influence on subsequent courses, so before research the gasification of coal, the coal's pyrolysis was first studied.Sulfur is a harmful element in the coal, which is an obstacle for it utilization, so a better understanding of sulfur transformation during pyrolysis and gasification is essential for effective utilization of the coal, and consequently for environmental protection, so research the sulfur transfer during pyrolysis and gasification is necessary.'Research reactivates of coal during pyrolysis and gasification' is selected as the title in this paper. In this paper we use non-isothermal thermogravimetric to study pyrolysis kinetic of coal; using fixed bed reactor and GC to study the gaseous products during the pyrolysis of coal; we also using the fixed bed reactor and fluid bed reactor to study the reactivity of the coal char during CO₂ gasification and steam gasification; the sulfur distributed during pyrolysis and gasification was also studied in this experiment.The main conclusions during pyrolysis experiment are the following:(1) The pyrolysis reactivity decreases with the coal rank increasing; different coal had different pyrolysis kinetic parameters due to the different of coal's reactivity. The activation energy of raw coal is between 8.93-72.23kJ/mol in the main pyrolysis section.(2) Because the difference of the chemical bonds and functional groups, following the change of temperature, the gaseous products distributions diversity, the yield of CO and CO₂ are related to oxygen contain of coal, and the yield of hydrogenous gaseous products are related to H/O of coal.(3) During the pyrolysis, sulfur transforms into gas as H₂S and a small amount COS, their quantity is directly relate to sulfur contain of coal. The mineral matters have a large effect on the formation of H₂S and COS. The alkaline-earth mineral in the mineral matters of raw coal has an important role for the fixation of sulfur during pyrolysis.The main conclusions during gasification experiment are the following:(1) During the gasification process, YT coal char have higher reactivity than LS and HJ coal char at the same condition. Between 900℃and 1100℃, with the temperature increasing, the reactivity of coal char enhanced. Compared steam gasification with CO₂ gasification, the coal char has higher reactivity in steam gasification.(2) During the CO₂ gasification, there is more COS and less H₂S produced, during the steam gasification, only H₂S was produced. Compared with CO₂ gasification, more sulfur was transferred into gas during steam gasification.(3) Based relationships of coal conversion with reaction time, the reaction rate constants (k) under different temperatures in CO₂ gasification were determined. The reaction activation energy Ea and the pre-exponential factor A of the experimental of coal chars were predicted respectively from Arrhenius equation, the reactivity of the coal was determined by the order of k.