Study On Chlorine Release Rules And Dechlorination During Gasification Of Coal And Coal-WP Copyrolysis Coke

Chlorine is one kind of harmful elements in coal, which can cause environmental pollution and technical problems such as equipment corrosion. IGCC (Integrated gasification combined cycle) and MCFC (Molten carbonate fuel cell) have high requirement to the chlorine content in coal gas. The process of coal and waste plastics co-pyrolysis is hot for treating waste plastics and save main coke coal. However, during co-pyrolysis the problem caused by chlorine shouldn't be ignored because PVC plastics are abundant in chlorine. This paper provided a systematic research into chlorine migration and transformation during coal/coke gasification and performed elementary experiments on dechlorination.At first, the paper introduced coal/coke fixed-bed gasification experimental system—double reactor system. This experimental system contains advanced gas distribution system, five-stage programmed control temperature rise system and online gas analyzer, which can well meet the requirement of this research. The chlorine content is analyzed and determined using IC method and quantitative measurement by standard curve method of chlorine in coal and the determining results are of good exactitude and accuracy.Gasification experiments are carried out to the two coal samples and fourcokes of different WP proportion. The influence of gasification temperature,gasification time, flow rate of gasification agent to chlorine release, coal kinds(coal gasification) and WP proportion are studied. And the emission curves of chlorine are obtained. Moreover, by studying the relationship between chlorine release and gasification time, the relation function model is established initially. Finally, dechlorination characteristics of CaCO₃, CaO, MgO are discussed.The results show that the influences of temperature and vapor flow rate are different to chlorine in coke from that in coal: the chorine release ratios in coal are similar in different temperature range while it differs to chlorine in coke; From 800℃to 900℃, release ratio of chlorine in coke is highest and more than 50% of chlorine is released during this period. FTIR results of copyrolysis coke and coal show that there is organic chlorine in coal, but coke contains no organic chlorine. Both chlorine release ratio and release velocity in coke are higher than that in coal. Furthermore, different kinds of coal have different chlorine release characteristics: more volatiles the coal contains, the higher chlorine release ratio it has. The proportion of WP also has effect on chlorine release, that is, cokes of higher WP proportion release more chlorine, but has lower release ratio. Besides, the dechlorination experiments show that CaO is the most efficient agent and the best adding rate of dechlorination agent Ca/S =2.