Study On Coal Combustion-supporting Additives For Blast Furnace

With the internationalization of steel market, iron and steel enterprises are facing heavy pressure, technological innovation become the only way to improve their own competitiveness. Pulverized coal injection in blast furnace is a reliable technology choice for iron and steel enterprises facing the problems of coke prices, cost pressures and sustainable development.Anthracite,lean coal and other high metamorphic coals are the preferred raw materials for pulverized coal injection because of high content carbon,high calorific capacity,low price and pulverizing safety et al.and play an dominant role in the total amount of pulverized coal injection materials. However, poor gasification activity,high ignition temperature and higher burnout temperature limit its large number of applications in the blast furnace. Therefore, it is one of hot topics that new technology and process modification are studied to improve poor characteristics of coals to strengthen the amount of pulverized coal injection.In the thesis,experimental study is conducted in fixed-bed condition to simulate blast furnace conditions, the results of study display that: (1)optimal additive amount of NaCl,Na₂CO₃ and NaNO₃ are 0.5%,1.0%,0.5% of the received coal, hydrolysis enhance catalytic action of NaClO₃ as adding amount increased; (2) during the same combustion time, the outflow speed extent of volatile emission affect by additives determine catalytic combustion effects,volatile catalytic effect order is: NaClO₃>Na₂CO₃> NaCl>NaNO₃;(3)long-time catalysis is determined by decompositions and existing pyrolysis forms of additives in the combustion process,persisitence catalytic effect order is NaClO₃>NaCl> NaNO₃>Na₂CO₃。Combining with laboratory research results and the experimental basis, the additives of DCS1,DCS2,DCS3 are developed for low volatile coals. Thermogravimetric method is used to dynamics analysis and combustion characteristic index analysis and discusses the catalytic combustion mechanism.The results show that: ignition time T₁,half peak widthΔT_1/2 and burn-out temperature T_h are drop by 33℃,41℃,64℃,5℃,30℃,45℃and 24℃,27℃,24℃,respectively. Kinetic parameter E are reduced by 15.90%,3.45%,21.26%,Combustion characteristic index P are increased by 19.40%,7.46%,11.94%. catalytic combustion mechanism study show that different additives have different behavior and products during pyrolysis process at different temperatures, which affect coal combustion rate.DCS1 is the additive of industrial test conducted in XiangGang 4# blast furnace.test results show that with the mass ratio of 0.453% , coke rate is reduced by 6.84kg/t (iron),cost of ton of iron drops by 12.3RMB and realizing the expected proposes of cost-saving,improving pulverized coal injection rate and replacing coke for coal et al.