水熱及微波處理對(duì)我國(guó)典型褐煤氣化特性的影響

王智化 葛立超 徐超群

摘 要：選取了我國(guó)主要褐煤產(chǎn)區(qū)不同煤階的三種典型褐煤分別用水熱、微波處理對(duì)其進(jìn)行了脫水改性并研究了改性前后褐煤CO2氣化特性的變化。結(jié)果表明，經(jīng)過(guò)水熱處理后，褐煤中的水分大幅度下降，最高降幅達(dá)87.31%，固定碳和熱值上升，氧含量下降，煤階參數(shù)（O/C原子比）下降，褐煤煤階上升。水熱處理過(guò)程中煤質(zhì)結(jié)構(gòu)的復(fù)雜重整導(dǎo)致煤焦孔徑向微孔方向發(fā)展，先降低后增加，而比表面積和孔容呈現(xiàn)先上升后下降的趨勢(shì)。煤質(zhì)結(jié)構(gòu)深度變化和煤階的上升使得改性后褐煤的氣化特性曲線向高溫區(qū)移動(dòng)，碳轉(zhuǎn)化率達(dá)到50%時(shí)的氣化溫度上升。動(dòng)力學(xué)計(jì)算結(jié)果表明經(jīng)過(guò)水熱改性后氣化反應(yīng)活化能上升，反應(yīng)級(jí)數(shù)發(fā)生變化。較高的水熱處理終溫和相對(duì)較低的原煤煤階都使得水熱脫水改性的效果更為顯著。在對(duì)脫水改性前后褐煤煤質(zhì)組成分析的基礎(chǔ)上使用低溫氮吸附法和熱重著重分析了改性前后褐煤孔隙結(jié)構(gòu)和CO2氣化特性上的差異。結(jié)果表明，微波能夠在較短的時(shí)間內(nèi)大幅度降低褐煤中的水分，最高降幅達(dá)到87.93%，處理后褐煤中的水分含量都已在10%內(nèi)，固定碳含量和熱值上升。褐煤微波改性后孔隙結(jié)構(gòu)向微孔方向發(fā)展，比表面積和孔容上升，平均孔徑下降。CO2氣化結(jié)果表明褐煤經(jīng)過(guò)微波處理后氣化速率上升，達(dá)到50%碳轉(zhuǎn)化率時(shí)的特征溫度降低，改性后褐煤的氣化活性變好。動(dòng)力學(xué)計(jì)算結(jié)果表明改性后褐煤氣化活化能下降，反應(yīng)級(jí)數(shù)發(fā)生變化。較高的微波處理終溫使得微波脫水改性的效果更加明顯，褐煤組成、結(jié)構(gòu)和氣化特性的變化也更大。煤階相對(duì)較低含水量較高的褐煤脫水效果更顯著，而煤階相對(duì)較高含水量較少的褐煤改性造成結(jié)構(gòu)和氣化特性的變化更明顯。

關(guān)鍵詞：褐煤 脫水改性 水熱 煤氣化 煤階 微波 變質(zhì)程度

Influence of the Hydrothermal Dewatering and microwave irradiation treatment on the Gasification Characteristics of Typical Chinese Lignite

Wang Zhihua Ge Lichao Xu Chaoqun

（Zhejiang University）

Abstract：The influences of hydrothermal dewatering （HTD） and microwave irradiation performed at different temperatures on the gasification characteristics of typical lignites with different metamorphic grades in China were investigated in this paper. Results show that the upgrading process significantly decreases the inherent moisture at a maximum degree of 87.31% and oxygen content， and increases calorific value and fixed carbon content， According to the oxygen/carbon ratio parameter， the coal rank increases. The complex changes occurred on coal structure during the HTD process lead to pore size of coal char develop to the microporous region， and the surface area and volume increase at first but then decrease. Due to the development of coal structure and the increment of coal rank， the gasification process of upgraded coal is delayed towards high temperature region， the temperatures when carbon conversion rate reaches 50% increase. From the results of kinetic calculation， activation energy increases after treatment， and the reaction order of mechanistic model is changed. Besides， all the changes caused by HTD are more obvious when the upgraded temperature increased from 250 °C to 300 °C and when the rank of raw brown coal was lower. The upgrading process significantly decreased the inherent moisture content at a maximum degree of 87.31 % in a short time， and increased the calorific value and fixed carbon content. The moisture contents of all upgraded coals were less than 10 wt%. After upgrading， pore distribution extended to the micropore region， the surface area and volume increased， and the average pore size decreased. Based on thermo-gravimetric analysis， the temperature when carbon conversion rate reaches 50% decreased， and the gasification rate increased， indicating the increase of gasification activity. From the results of kinetic calculation，activation energy decreased after treatment， and the reaction order of mechanistic model changed. All the changes caused by MI were more obvious when the upgraded temperature increased from 130 °C to 160 °C. Besides， when the raw lignite had a lower coal rank with higher moisture content， the dewatering process was more evident.

Key Words：Lignite； Upgrading； Hydrothermal dewatering； Gasification； Coal rank； Microwave； Metamorphic grade

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