炼焦煤热解收缩特性对焦炭成块性能影响

Influence of lumping properties of coking coal by pyrolysis shrinkage

在国家“双碳”目标及富氢高炉开发利用背景下,对焦炭在高炉中的性能提出了更高要求。除常规的热态性能指标外,焦炭的块度受到更多关注。炼焦煤的热解收缩性能是决定焦炭成块性能至关重要的因素。对不同变质程度炼焦煤进行2 kg焦炉炼焦试验,分析炼焦煤细度对其焦炭成块性能的影响规律。采用改进的奥亚膨胀仪对8种不同变质程度炼焦煤在300~900℃内的热解收缩性能进行深入研究,探讨了煤热解收缩系数与其收缩动力学特性对焦炭成块性能的影响,并建立热解收缩系数及热解活化能与焦炭平均块度的数学关系,试图通过炼焦煤热解收缩特性对焦炭平均块度进行预测。结果表明,焦炭的平均块度随炼焦煤变质程度的升高呈增大趋势。YK气煤的平均块度较低,仅为38.9 mm。SAJ焦煤和BBG瘦煤的平均块度较高,分别为50.5、48.5 mm。8种炼焦煤中除BBG瘦煤外,当入炉煤细度为75%时,形成焦炭的平均块度最大。BBG瘦煤在细度为85%时,焦炭平均块度最优。在热解过程中,不同变质程度炼焦煤第1收缩峰的收缩系数及收缩所需活化能差别明显。其中低变质程度YK气煤和SYS1/3焦煤热解收缩系数高于8.33×10^(-4)℃^(-1),热解活化能均低于77 kJ/mol;高变质程度煤LH焦煤、SAJ焦煤和BBG瘦煤热解收缩系数低于4.55×10^(-4)℃^(-1),但热解所需活化能均高于106.1 kJ/mol,说明变质程度高的炼焦煤,热解时需要更高的能量才能完成收缩过程。在相同的炼焦工艺下,炼焦煤第1收缩峰的热解收缩系数越大,所得焦炭的平均块度越小,且热解收缩系数与焦炭平均块度有很好线性关系,相关系数为0.90。同时,热解收缩活化能也与焦炭平均块度有较好关联。因此,能够通过热解收缩系数和收缩活化能对不同变质程度炼焦煤生成焦炭平均块度进行有效预测。

The performance of coke in blast furnace has higher requirement under the carbon emission peak&carbon neutrality goal and hydrogen-rich blast furnace development in China.Except for the thermal performance,the lump size of coke gets more attention.The pyrolysis shrinkage of coking coal is an important factor to determine the lumping performance of coke.The coking tests of coal with different deterioration were carried out with 2 kg coke oven,the effect of fineness of coal on coke lumping property was analyzed.An improved Audibert-Arnu dilatometer was used to study the shrinkage performance of eight kinds of coking coals with different degrees of metamorphism during the pyrolysis pro-cess at 300℃to 900℃.The influence of the shrinkage coefficient of coal pyrolysis and its shrinkage dynamic character-istics on the caking performance of coke was discussed,and the mathematical relationship between the shrinkage coeffi-cient of pyrolysis and the activation energy of pyrolysis of the average caking size of coke was established.It attempts to predict the average lumpiness of coking coal by its pyrolysis shrinkage characteristics.The results show that the average lumpiness of coke is increased with the increase of coking coal metamorphism.The average lumpiness of YK gas coal is only 38.9 mm,while the SAJ coking coal and BBG lean coal are 50.5 mm and 48.5 mm respectively.Among the eight kinds of coking coals,except for BBG lean coal,the average lumpiness of coke formed is the largest when the fineness of coal into furnace is 75%.The average lumpiness of coke is the best when BBG lean coal is 85%in fineness.On the pyro-lysis process,the shrinkage coefficient and activation energy of the first shrinkage peak of coking coal with different meta-morphic degrees are obviously different.The pyrolysis shrinkage coefficient of low-metamorphic YK gas coal and SYS1/3 coking coal is higher than 8.33×10^(-4)℃^(-1),and the pyrolysis activation energy is lower than 77 kJ/mol.The pyrolysis shrinkage coefficient of LH coking coal,SAJ coking coal and BBG lean coal is lower than 4.55×10^(-4)℃^(-1),but the activa-tion energy required for pyrolysis is all higher than 106.1 kJ/mol.It indicates that the coking coal with high metamorph-ism requires higher energy to complete the shrinkage process during pyrolysis.The larger the shrinkage coefficient of cok-ing coal,the smaller the average lumpiness of coke,and the pyrolysis shrinkage coefficient has a good linear relationship with the average lumpiness of coke,the correlation coefficient is 0.90.At the same time,the activation energy of pyrolysis shrinkage is also closely related with the average lumpiness of coke.Therefore,pyrolysis shrinkage coefficient and shrink-age activation energy can be used to effectively predict the average lumpiness of coke generated from coking coal with dif-ferent metamorphic degrees.