Optimization Of Combustion For Pulverized Coal Injection In Blast Furnace Based On Coal Petrology

The application and development of pulverized coal injection(PCI)technology is a major revolution in modern blast furnace ironmaking process.At present,the main problem of PCI in blast furnace is that the combustion of pulverized coal in the tuyere raceway is inadequate,resulting in relatively low coke replacement and more unburned coal powder,thus making the permeability of blast furnace worse and limiting the improvement of coal injection ratio.Using the relatively mature theory of coal petrology applied for coking coal blending in coking industry for reference,applying of coal petrology for blast furnace injection coal blending is mainly by adopting coal petrology analysis technology,thermal analysis and high-temperature furnace experimental,to establish the relationship between maceral group composition and combustion characteristic,thus further establish coal blending theory for blast furnace injection coal,in order to provide the theory basis for improving combustion rate of coal injection in blast furnace,so as to improve the blast furnace coal injection ratio,lowering iron-making cost.Firstly,the petrology analysis technology is used to analyze the petrology components of single coal and mixed coal,the calorific value and the ash melting characteristic temperatures of each coal sample are measured,the influence of petrology components on the calorific value of coal samples as well as the influence of coal ash components on the ash fusibility are analyzed.The results show that the average maximum reflectance and the content of vitrinite group of Shenhua coal are lower than that of Yongcheng coal,while the content of inertinite group is higher,and the content of exinite group and mineral are very low and not much different.With the increasing of the ratio of Shenhua coal,the average maximum reflectance and the content of vitrinite group of mixed coal samples decreased,while the content of inert group increased.The calorific value of each coal sample increased with the increasing of vitrinite group and decreasing of inert group.The higher the content of Si O₂and Al₂O₃in coal ash,the higher the characteristic temperatures of ash fusion,while the higher the content of Ca O,the lower the characteristic temperatures of ash fusion.Secondly,the combustion characteristics of separate and collaborative combustion processes of Shenhua coal and Yongcheng coal are studied by thermal analysis method,the relationship between petrology parameters of each coal sample and its combustion characteristic parameters as well as combustion performance is investigated,and the kinetic parameters of combustion process are solved.The results show that Shenhua coal burns more easily than Yongcheng coal,the ignition temperature and burnout temperature are lower,the temperature range in combustion process is narrower,the maximum weight loss rate and the maximum heat release rate are higher.For mixed coals,the ignition temperature T₀and burnout temperature T_bis separately between single coals and T₀,T_bof mixed coal with 70%Shenhua coal is lower,while the combustion temperature range are wider than single coals and that of mixed coal with70%Shenhua coal is narrower.Activation energy E of mixed coals in combustion process are lower than that of single coal in combustion process,and decreased with the increasing of ratio of Shenhua coal.The influence of petrology parameters on combustion characteristic parameters and combustion performance is as follows:the smaller the reflectivity of vitrinite group,the lower the content of vitrinite group or the higher the content of inert group,the lower the ignition temperature and burnout temperature,and the greater the combustion performance index.Finally,the combustion performance of Shenhua coal and Yongcheng coal in separate combustion and collaborative combustion process was studied by using the method of high temperature combustion in drop-tube furnace,and the influence of petrology characteristics on the combustion rate of each coal sample was investigated.The results show that the combustion rate of Shenhua coal is obviously higher than that of Yongcheng coal.For two kinds of single coal and their mixed coal with different ratio,the combustion rate is mainly affected by the average maximum reflectance of vitrinite group,while the content of each petrology component has little influence on the combustion rate of coal sample.The carbon structure of coal sample has obvious influence on its combustion performance:the lower the crystalline degree of the carbon structure is,or the smaller the stacking height is,the higher the combustion rate of coal sample is.