Study On Preparation Of Coking Coal By Co-heat Treatment Of Fugu Coal And Binder

China has abundant reserves of low metamorphic pulverized coal,which is characterized by low ash,low sulfur and high calorific value,However,due to the characteristics of high oxygen content,high volatile matter and cohesiveness,it can only be used as power coal.At the same time,the development of low metamorphic bituminous coal often produces a large amount of pulverized coal,which will cause serious environmental pollution and waste of resources.Therefore,the upgrading,transformation and comprehensive utilization of low rank coal has become the focus of energy research.Now,domestic and foreign scholars mainly adopt four methods:hydrothermal treatment,hydrogenation modification,low temperature heating treatment and cold/hot pressing to improve the quality of low rank coal,and the last two are commonly used At present,there is no process combining the viscosity increasing of low rank coal with the quality improvement of briquette coal.In this paper,Fugu coal and medium coal tar pitch are used as raw materials to cold-press to prepare briquette,which is subjected to low temperature heat treatment to achieve the purpose of increasing viscosity,low rank coal upgrading and pulverized coal briquetting were successfully combined and the optimization of process conditions and the exploration of the mechanism of cohesiveness.Finally,in order to verify whether the briquette modified by heat treatment can coke alone,it was carbonized at high temperature,and the optimal process conditions were explored based on the preparation of high mechanical strength briquette.At the same time,the influence of carbonization temperature on pyrolysis products was studied.（1）Low temperature heat treatment of briquette by horizontal furnace,we studied the effects of heat treatment temperature,heat treatment time,asphalt addition ratio and forming pressure on adhesion index and volatile matter.Taking the preparation of briquette with the highest caking index as the standard,the optimum process parameters were determined as heat treatment temperature 360℃,heat treatment time 25 min,asphalt addition 40 wt%,heating rate 10℃/min and forming pressure 30 MPa.The caking index of briquette under the optimum process parameters is 53.33 and the volatile content is 37.9%.According to the national standard,the briquette has been raised to the level of No.44 gas coal.It was successfully upgraded to coking coal grade.（2）There are three reasons for the improvement of adhesion under low temperature heat treatment:（1）Medium temperature coal tar pitch softens and melts at low temperature,which promotes the formation of soluble matter,enhances the fluidity of Fugu coal.（2）The oxygen-containing functional groups such as carboxyl and hydroxyl groups of low rank coal fall off during low-temperature heat treatment,which reduces the oxygen content and improves the cohesiveness of briquette.（3）During the heat treatment,the aliphatic chain breaks and the degree of branched chain increases,which is the most important factor affecting the cohesiveness of briquette.（3）The high temperature carbonization experiment of briquette is carried out by using the vertical infrared heating furnace,we studied he effects of final carbonization temperature,carbonization time and heating rate on the mechanical strength and yield of formed coke.Taking the preparation of formed coke with high mechanical strength as the standard,the high temperature carbonization experiment of briquette was carried out,and the optimum process parameters were determined as follows:carbonization temperature 800℃,carbonization time 90 min,carbonization atmosphere N₂ and heating rate 50℃/min.The mechanical strength of formed coke is the highest under this process condition:the compressive strength of formed coke reached 8.10 MPa and the drop strength reached99.54%.（4）In the process of carbonization,briquette produces a large amount of H₂and CH₄,a small amount of CO and CO₂;the carbonization heating process makes the aliphatic chain in briquette break rapidly,the condensation degree of aromatic ring structure of briquette coke is deepening,and the oxygen-containing groups are almost completely removed,moreover,the aliphatic chain of briquette and the fracture of oxygen-containing tubular energy group are carried out at the same time,and there is a critical temperature of 800℃;with the increase of final carbonization temperature,the microcrystalline structure of formed coke tends to be orderly,which is gradually close to the microstructure of graphite、the quality gradually approaches that of blast furnace coke、the shrinkage degree of blast furnace coke and briquette is gradually deepened;the softening and melting of asphalt makes the surface of carbonized formed coke show a small amount of pore agglomeration,the specific surface area and pore volume of formed coke are small,and the pore structure is irregular.