Numerical Simulation Of Flow And Combustion In The Grid-Type Burner

The hot blast stove is one of the most important equipment in the Blast Furnace Iron-making industry, and the quantity and temperature of the hot blast that it provide for Blast Furnace will significantly influence on the production quantity, quality of iron-making and the energy consumption. The whole performances of grid-type ceramic burner is possessed of many advantages over other types of ceramic burner, such as the short combustion flame, high theory combustion temperature, better combustion stability and the completeness of gas combustion. However, the grid-type ceramic burner has not been used widely because of the lack of comprehensive understanding to the principal combustion characteristics, hereby lack of systematical designing experience.In the paper, the physical and mathematical model for the gas flow, species mixing and combustion in the grid-type burner of one tested Blast Furnace was proposed, and the corresponding numerical solution was performed. In the flow and combustion numerical simulation, the turbulence flow was treated with the RNG k ?εmodel, the combustion was taken into account with the PDF model. Total six cases under different experimental operation conditions were numerically investigated for'cold status'and'hot status', respectively. The computed results revealed the flow structure and the process of species mixing and combustion, on the basis of which the static data of the pressure drop characteristics of air and coal gas channels, the species fraction distribution and the combustion efficiency were obtained.The computed results under'cold status'showed that: the uniform pressure drop coefficient in air and coal-gas channel were 13.09 and 13.22, respectively, which were both fallen into the constant coefficient zone. The velocity uniformity computed was 0.751, the concentration uniformity of fuel was 0.851 and the concentration uniformity of oxygen was 0.738. All of the uniformity was slightly decreased with the increase of the flow rate of air and coal-gas. The main reason resulted in the ununiformity of cold blast was analyzed according to the flow structure of grid-type burner, and the improvement methods was proposed, i.g., changing the structure and size of the burner.The computed results under'hot status'showed that: the pre-combustion gases were accomplished mainly within 400mm height from the bottom of the burner. The residual mixture gases of the air and coal-gas were totally reacted in the height from 1500mm to 2000mm. The larger the air and coal-gas's flow rate was, the higher the flame height reached. The combustion efficiency for all cases was within the range of 89.5%~91.37%, the lower flow rate, the higher pre-heat temperature and combustion efficiency.The numerical simulation for the corresponding full-scale burner was also performed. The computed results showed similar features with that of experiment model. The computed velocity uniformity for the full-scale model was 0.713, the concentration uniformity of the fuel 0.871 and the concentration uniformity of the oxygen 0.733. The combustion flame height was about 5m, the average temperature on the exit plane of the burner was 1250℃and the combustion efficiency is 88.99%.