煤焦制备条件对其气化反应性的影响

INFLUENCE OF CHARRING CONDITIONS OF COAL CHARS ON THEIR GASIFICATION REACTIVITY BY AIR

改变制焦条件（温度、升温速率、保温时间）制备了八个煤焦样品。７８℃下ＣＯ２物理吸附和２００℃下Ｏ２化学吸附分别测定了它们的总比表面积和活性表面积。用ＸＲＤ测定了它们的碳微晶尺寸。ＴＧ法测定了煤焦与空气在４５０、５００、５５０℃下的等温气化反应活性，并用Ａｒｈｅｎｉｕｓ方程和半衰期法分别求得了每个样品的反应活化能Ｅ和指前因子Ａ。结果表明：制焦温度越高，升温速率越慢，保温时间越长，煤焦的反应活性越低；煤焦的总比表面积、活性表面积和碳微晶尺寸与其气化反应性之间有较好的关联。还发现Ｅ和Ａ之间存在着动力学补偿效应：ｌｎＡ＝０．１４０２Ｅ７．５８１９。

Gasification rates of coal chars were determined thermogravimetrically in air at temperatures in the range 450￣550℃ The effect of charring conditions, such as temperature, heating rate and soaking time, on reactivity was determined Both reactivity and the activation energy for the gasification of coal chars were found to be strongly influenced by their charring conditions The reactivities of eight coal chars decreased with increasing charring temperature, while the activation energy for their gasification increased Slow charring condition (heating rate: 5℃·min 1 ) led to the production of coal char having lower reactivity and higher activation energy than that of coal char obtained from rapid charring condition (heating rate: 30℃·min 1 ) at the same temperature of gasification With increasing soaking time at the same charring temperature, the reactivity of resulting coal chars was reduced The total surface area (TSA), active surface area (ASA) of coal chars were measured using CO 2 physisorption at 78℃ and O 2 chemisorption at 200℃, respectively The results showed that there was a good correlation between the reactivities and TSA, ASA or carbon microcrystallite size of coal chars, and the simultaneous increase in activation energy (E) and preexponential factor (A) demonstrated the compensation effect: lnA=0 1402E7 5819 (correlation coefficient r=0 99)