固定床提质过程褐煤的热碎裂/粉化特性及其负效应分析

Characteristics of lignite fragmentation/pulverization and its negative effects during upgrading in fixed-bed

定量研究了固定床热提质过程多因素对褐煤碎裂/粉化的影响规律及权重。研究结果表明:温度由120℃升至900℃,产物中25~13 mm保持粒级比率由88.42%降至16.92%;碎裂粒群(13~1 mm)比率由9.81%增至75.17%且13~6 mm粒级增幅最高(39.58%);低于1 mm的粉化粒群比率由1.77%增至7.91%(-0.075 mm粒级变化最显著)。保温时间的延长和入料粒度的增大同样加剧了褐煤的碎裂及粉化程度。灰色关联分析表明,提质温度对碎裂和粉化的影响权重均最大,而入料粒度对碎裂的影响程度高于保温时间,但其弱于时间对粉化程度的影响。结合对褐煤孔隙结构、表观形貌及煤质(水分/挥发分)的测试表征,得到了褐煤热碎的复合产生原因。并基于此明确了褐煤碎裂/粉化对固定床热提质过程的综合负效应(吸附自由基并促进其二次反应;提升焦油灰分;油尘易混致堵;形成尘积)。

The present study investigated size distribution and degree of grading in fixed-bed reactor. The results show that with the temperature fragmentation/pulverization during lignite up- increasing from 120℃ to 900 ℃ ,the fraction of retention particles（25-13 mm） is decreased from 88.42% to 16.92%, the fragmentation particles group（13- 1 ram） are increased from 9.81% to 75.17% ,the group of particles are formed by pulverization（less than 1 ram） are increased from 1.77% to 7.91% （the fractions of particles at -0. 075 mm changed signifieantly） and 13-6 mm grain size go to the highest as 39.58%. The degree of fragmentation and pulverization are increased with holding time and feed size as well. Gray relational analysis shows that greatest impaet faetor for fragmentation and pulverization is upgra- ding temperature. The effect of feed size on fragmentation is higher than that of holding time, but weaker on pulveriza- tion. The fragmentation mechanism during lignite upgrading are revealed by analysis of pore structure, apparent mor- phology and coal quality（moisture/volatile）. Based on experimental behavior, the negative effect will occur during lig- nite upgrading process, as adsorbing free radicals to promote secondary reaction, enhancing ash content of tar, blockingwith oil-dust mixture and dust forming.