焦炭气孔的非均匀劣化特征及其评价方法研究

Research on the characteristics of non-uniform deterioration of coke porosity and its evaluation method

作为多孔固体,焦炭从表面到内部呈现出典型的非均匀劣化特征,对高炉内焦炭层的空隙度有十分重要的影响。文中从多孔焦炭溶损过程的传质反应基本原理出发,分析了焦炭气孔非均匀演化的特征,并在前期研究基础上进一步完善了焦炭基质反应速率k v和气孔扩散系数D_(eff)的测定分析方法,给出更加准确易测的参数√k_(v)/D_(eff)来表征焦炭气孔的非均匀劣化特性,为完善焦炭质量评价体系提供帮助。结果表明:焦炭内部存在从纳米级到毫米级大小差异极大的气孔,有很强的非均匀性,不同孔径的气孔遵守不同的扩散规律和方程,应分别考虑计算,进而综合评估焦炭的孔扩散特性。随着失碳反应的进展,焦炭中的孔隙逐渐膨胀或合并为中孔和大孔,气孔扩散系数逐渐增大,劣化的瞬时非均匀性减小。焦炭√k_(v)/D_(eff)越小,劣化后的粒度均匀性更好,对高炉透气透液性越有利。

As a porous solid,coke exhibits typical non-uniform deterioration characteristics from the surface to the inside,which has a very important influence on the porosity of the coke layer in the blast furnace.Based on the basic principle of mass transfer reaction in the dissolution process of porous coke,the paper analyzes the characteristics of the heterogeneous evolution of coke pores,and further improves the determination and analysis methods of coke matrix reaction rate k v and pore diffusion coefficient D_(eff) on the basis of previous research,and gives a more accurate and easy-to-measure parameter,i.e.,√k_(v)/D_(eff) to characterize the non-uniform deterioration characteristics of coke pores,which provides help for improving the coke quality evaluation system.The results show that there is a strong heterogeneity in the pores with great size differences from nanoscale to millimeter scale,and the pores with different pore sizes obey different diffusion laws and equations,so the pore diffusion characteristics of coke should be considered separately and comprehensively evaluated.With the progress of the carbon loss reaction,the pores in the coke gradually expand or merge into mesopores and macropores,the stomatal diffusion coefficient gradually increases,and the instantaneous inhomogeneity of deterioration decreases.The smaller the coke √k_(v)/D_(eff) value,the better the particle size uniformity after deterioration,which is beneficial to the air and liquid permeability of the blast furnace.