Experimental Studies On Reaction Kinetics Of In-situ Char Gasification By Steam In A Micro Fluidlized Bed

Char gasifcation is a core technology for converting coal environmentlally and efficiently. Optimizing coal gasification must have a study on the reaction process. There exists visible difference between the process of pyrolyzation and gasification, so it is a necessity to study separately. At present, most of researchers make coke in tube furnaceor equipment made by themselves, then analyze the reaction characterization of coke in a thermogravimetric analyzer. While using this method, the coke after pyrolyzation have a heat-treating process of cooling before warming up. This ex-situ process must have a influence on the structure and properties of coke, and affect the subsequent analysis. The analysis process is low efficiency.This research focus on the gasification reaction kinetics of in-situ coke-steam using micro fluidized bed reaction analyzer-multistage reaction analyzer(mfbra-mra) pyrolyzation and gasification are both conducted in the experiment facility. When the reactor reach the design temperature, a pulse airflow carried with materials enter the reactor.after pyrolyzation, reaction analyzer switch to steam atmosphere immediately. The coke using for gasification without any process, so that ensure the in-situ coke.This paper study influence of different temperatures(1000℃、950℃、900℃、850℃、800℃) and steam concentration(15%、25%、35%、45%, Ar is balance) to the gasification of shenhua bitumite and zhundong subbituminous which pyrolysis in the 1000℃. The result showed that gasification reaction rate significantly speed up with the increasing temperature. With the increasing of steam concentration, gasification reaction rate also increase, when the steam concentration reached 25%, the influence on reaction is very weak with increasing steam concentration. Under the condition of same gasification temperature and steam concentration, at the same time, the convert ratio of zhundong coal char is apparently higher than shenhua coal char.using iso-conversional method to calculate reaction activation energy, that is 151.32 k J mol-1,156.61 k Jmol-1,146.35 k J mol-1,152.64 k J mol-1,shenhua in-situ coal char is 182.98 k J mol-1,176.40 k J mol-1,176.47 k J mol-1,184.80 k J mol-1. shrinking core model and random pore model are used to calculate the activation energy and pre-exponential factor.the calculating result is almost no difference and very close to the result got from iso-conversional method.The reactivity of in-situ coke and ex-situ coke were contrasted, both kinds of coal react with steam, with 25% concentration, under 1000℃and different gasification temperature. Compared to in-situ coke, after pyrolyzation, it undergoes a process of cooling, constant temperature, warming up. The experiment result showed that the gasification time of in-situ coke is shorter than ex-situ coke, and a short time reaching same conversion rate. The reaction rate of in-situ coke is quicker than ex-situ coke reaching same conversion rate. This study also compare the kinetic parameter of in-situ coke and ex-situ coke, the activation energy and pre-exponential factor also have some distinct difference.By in situ way analysis char gasification,the analysis process is reliable,convenient and economic efficiency,so change analysis means has a unique advantage.