载气对两段式干煤粉加压气化炉气化特性的影响

doi:10.16085/j.issn.1000-6613.2017.01.018

摘要/Abstract

摘要： 相比于N₂，CO₂作为气化炉煤粉载气会降低合成气中N₂的含量而有利于后续CO₂捕集，但O₂在CO₂中较小的扩散系数会影响焦炭的反应特性，进而影响气化炉运行结果。为此，考虑到气化炉中较高的CO含量及其对煤气化反应的抑制作用，将Langmuir-Hinshelwood动力学模型与缩核模型相结合，提出一个改进的焦炭反应模型，并对两段式干煤粉气化炉内的流场、温度场和组分浓度场进行了模拟分析，结果与实炉实测数据一致。在此基础上，模拟分析了气化炉在不同煤粉载气（N₂、CO₂）、两种二段给煤量下的气化特性。结果表明，煤粉载气由N₂改为CO₂后，由于O₂在CO₂中较低的扩散速率，一段气化室喷嘴区域气体温度和碳转化率降低，该区域CO₂增多对焦炭-CO₂反应的促进作用对提高碳转化率的影响较小；在一段气化室喷嘴区域之上，O₂浓度较低导致O₂扩散性影响减弱，同时CO₂增多促进焦炭-CO₂反应进而提高碳转化率。研究结果还证实，煤粉载气由N₂改为CO₂会促进CO的生成，抑制H₂的生成。

关键词: 气化, 模拟, 煤燃烧, 载气, 两段式气化炉

Abstract: Replacing the N₂ in carrier gas with CO₂ would lower N₂ level in the product gas which is good for CO₂ capture. However,the lower O₂ diffusivity in CO₂ would affect char reactivity,thus gasifier operation performance. To clarify the effect of carrier gas on gasification performance of a two-stage entrained-flow coal gasifier,a modified char reaction model is proposed by combining the shrinking core model with the Langmuir-Hinshelwood kinetic rate expression which considers the inhibitive effect of CO on char gasification reaction. The predictions of the flow,temperature,species distributions are provided and the results consiste with the operating data. In addition,at two coal feed rates of the 2nd stage(3817kg/h,11104kg/h),the effect of carrier gas(N₂,CO₂) on the gasifier operating performance is evaluated by comparing with the distributions of carbon conversion efficiency (CCE),gas temperature and species mole fractions in the gasifier. The results indicate that in the injection region of the 1st stage,the substitution of CO₂ for N₂ results in decreases in the gas temperature and CCE due to the lower O₂ diffusivity in CO₂. And the enhanced char-CO₂ reaction caused by the increased CO₂ has only a minor effect on CCE. Above the injection region of the 1st stage,the O₂ diffusion effect is weaken due to lower O₂ concentration,and the enhanced char-CO₂ reaction increases CCE. Meanwhile,the results also confirmed that replacing the N₂ in carrier gas with CO₂ results in an increase in CO formation and a decrease in H₂ formation.

Key words: gasification, simulation, coal combustion, carrier gas, two-stage entrained-flow gasifier

中图分类号:

TQ54

樊强, 刘银河, 李广宇, 车得福. 载气对两段式干煤粉加压气化炉气化特性的影响[J]. 化工进展, 2017, 36(01): 136-145.

FAN Qiang, LIU Yinhe, LI Guangyu, CHE Defu. Effect of carrier gas on gasification performance of two-stage entrained-flow coal gasifier[J]. Chemical Industry and Engineering Progree, 2017, 36(01): 136-145.

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