Research And Application Of Coal Coking Mechanism Based On Coal Petrology And Rheological Properties

Due to the diversification of coal formation periods and modes of coking in China,as well as the complex and special geological conditions of coal formation,the quality of coking coal in different regions and the macroscopic and microscopic reactions during coal blending and coking differ greatly.Therefore,in-depth study of the evolution of petrographic composition and plastic mass during coking of coal is of great significance for clarifying the coking mechanism,stabilizing coke quality,and reducing costs and increasing efficiency.This paper takes typical coking coal in Shanxi region as the research object,and studies the basic coal quality characteristics,adhesiveness characteristics,and coking characteristics of coking coal.We studied the changes in the chemical structure of coal,optical microstructure,and pore characteristics during the thermal conversion process.A new indicator for characterizing the comprehensive properties of plastic mass in the plastic range of coking coal has been proposed based on the Gieseler fluidity.Based on coal rock analysis,an experimental method was established to evaluate the degree of softening and melting of active components and their fusion with inert components.A new method for evaluating coking coal based on coal petrology and rheological properties was established,and a new mechanism for coking coal formation was explored.Finally,the industrial application of the new evaluation method was studied.（1）By analyzing the caking characteristics,coal petrographic characteristics,and rheological properties of 19 typical coking coal types in Shanxi Province,the basic coal quality characteristics of coking coal and the differences between coal types with different metamorphic degrees were revealed.It was found that there are significant differences in the thermal and mechanical strength of the coke obtained from coking coal with the same degree of metamorphism.There are significant differences in vitrinite reflectance,microstructure,and structure of coking coal with the same degree of metamorphism.There is no significant correspondence between the rheological parameters of coking coal and the basic coal quality characteristics,as well as the thermal and mechanical strength of coke.（2）The chemical structures that affect the adhesion of plastic materials include the length or degree of branching of fatty chains,the number of hydrogen bonds and other bridging bonds,and the degree of aromatic ring condensation.The determining factor is the degree of condensation.In the process of high-temperature carbonization,the bridge bonds in coal is completely broken,and the aliphatic CH₂ is basically broken and removed,and the aliphatic hydrocarbon structure in coke is basically disappeared.During the rheological process,the optical properties of the semi-coke structures formed are different.Isotropic,inlaid,sheet-like,and fibrous structures are related to the reflectance ranges of vitrinite 0.95-1.35 and 1.35-1.40,while fibrous and fragmented structures are related to the ranges of 1.40-1.90 and>1.90.（3）Conventional evaluation indicators such as ash content,volatile matter,caking index,and plastic layer index are all used to study the composition,chemical properties,and process properties of coal from a chemical perspective.The existing Gieseler flowability parameter cannot accurately and comprehensively characterize the rheological properties of a plastic body throughout the entire plastic range.The existing coal petrology index cannot directly evaluate whether the macerals of coking coal have activity and the degree of reaction during the thermal conversion process.Based on the Gieseler flowability,an indicator called Lg F is proposed to characterize the average fluidity of plastic materials,as well as the fluidity index S_{Lg F}used to characterize the number of plastic materials,which can comprehensively characterize the comprehensive properties of plastic materials.Based on coal petrology analysis,an experimental method has been established to evaluate the degree of softening and melting of active components and their fusion with inert components.By quantitatively analyzing the vitrinite,inertinite,and"intermediate melt"in solid pyrolysis products,the interaction between microscopic and inert components in the coking process and their impact on coke quality can be revealed.A new method for evaluating coking coal based on coal petrology and rheological properties has been established,and the new coking mechanism of coking coal has been explored.（4）Applied research on new evaluation methods for coking coal was conducted using industrial top mounted coke ovens and stamped coke ovens,respectively.The experiment shows that during top charging coke oven coking,while maintaining the quality of coke,the blending amount of coking coal and fat coal is reduced by 4%,and the blending cost is reduced.During the coking process of stamping coke oven,while keeping the thermal strength of the coke basically unchanged,the particle size of the coke is increased from 43.2 mm to 45.0 mm,and the average metallurgical coke rate is increased from 88.6%to over 90.0%.The applicability of the new method and coking mechanism has been verified through application research on top mounted and stamped coke ovens.