西湾煤焦在加压条件下的气化反应特性研究

Study on pressurized gasification reaction characteristics of Xiwan coal char

为阐明加压、多种气化剂共存条件下西湾煤焦的气化反应规律,考察了不同热解制焦与气化条件对煤焦气化过程中碳转化率与气体组分的影响,以指导接近工业化热解-气化一体化反应器的设计与优化,研究了不同热解温度(600℃~900℃)、升温速率(10℃/min~40℃/min)、停留时间(10 min~40 min)及气化温度(900℃~1100℃)、气化压力(常压到4.0 MPa)、气氛(100%(体积分数,下同)CO_(2),50%CO_(2)+50%H2O,100%H2O等)对西湾煤焦加压气化反应特性的影响。结果表明:在升温速率为20℃/min、气化温度为1000℃、反应气氛为100%CO_(2)条件下,加压可以降低煤焦中挥发分的析出与扩散速率,煤焦中自由基分子相互作用发生缩聚、交联等反应能够降低气化反应速率;增大气化剂体积分数可增加气化剂与煤焦表面碳分子的碰撞概率,从而提高气化反应活性,使西湾煤焦的碳转化率由常压下的95.15%减小至4.0 MPa下的78.22%;较高水蒸气分压可抑制煤焦石墨化进程与提升气化反应速率,使加压条件下水蒸气气氛下煤焦气化活性高于二氧化碳气氛下煤焦气化活性。100%H_(2)O气氛下煤焦的碳转化率最大,达到95.12%,较100%CO_(2)气氛下煤焦的碳转化率增加约13.5%。

In order to clarify the gasification reaction characteristics of Xiwan coal char under the conditions of pressure and co-existence of multiple gasification agents,the influences of different pyrolysis preparations and gasification conditions on the carbon conversion and product quality during the pressurized gasification process were investigated,and the aim was to guide the design and optimization of near-industrial pyrolysis-gasification integrated reactors.The effects of various parameters such as pyrolysis temperatures(600℃-900℃),heating rates(10℃/min-40℃/min),residence times(10 min-40 min),gasification temperatures(900℃-1100℃),gasification pressures(atmosphere pressure to 4.0 MPa)and reaction atmospheres(100%(volume fraction,same below)carbon dioxide,50%carbon dioxide+50%vapor,100%vapor,etc.)on the pressurized gasification characteristics of Xiwan coal char were examined.The results show that under the condition of a heating rate of 20℃/min,a gasification temperature of 1000℃and a reaction atmosphere of 100%CO2,pressurization can slow down the precipitation rate and diffusion rate of volatile.The gasification reaction rate is also decreased by condensation and cross-linking reaction of free radical molecules in pressurized atmosphere.Moreover,increasing the volume fraction of gasifying agent enhances the collision probability with carbon molecules on the surface of coal char,thereby improving the gasification reaction activity.As a result,the car-bon conversion of Xiwan coal char reduces from 95.15%at atmospheric pressure to 78.22%at 4.0 MPa.The coal char gasification activity of vapor atmosphere is higher than that of carbon di-oxide atmosphere under pressurized conditions due to the inhibition of graphitization process and enhancement of gasification reaction rate by higher water vapor partical pressure.Specifically,the carbon conversion of Xiwan coal char under a 100%vapor atmosphere reaches a maximum of 95.12%,representing an increase of about 13.5%compared to a 100%carbon dioxide atmos-phere.