Optimization Study Of Temperature Uniformity In A Novel And Energy-saving Sanitary Roller Kiln

This project studies a new type of sanitary ware roller kiln with a length of48meters, emphasizing on optimizing the temperature uniformity inside the kiln when sintering sanitary wares. Through numerical simulation, quantitative contributions of structural parameters including the burner inclination angle, the burner spacing,an operational parameter, the air-fuel ratio on the temperature uniformity are determined and optimal working conditions are obtained. Detailed research and major conclusions are summarized below.(1) Principle structural and technical characteristics of the burning zone of the sanitary ware roller kiln are discussed and thermal balance calculations of the roller kiln system is analyzed. It is found that the roller kiln is superior to the tunnel kiln with combustion heat of fuel accounting for99.6percent of the total heat gain and the thermal efficiency of the sanitary ware roller kiln increasing to54.2percent. Heat loss from surface and by gas accounts for66.78percent of the total heat loss. Key measures for improving the utilization rate of heat energy includes decreasing air-fuel ratios to reduce surplus air supply while still maintaining full combustion, improving the structure of roller kilns to reduce heat loss, making use of waste heat, etc.(2) A numerical model is built by simplifying the prototype of the sanitary ware roller kiln with reasonable assumptions. The model couples the Realizable k-turbulence model, the PDF combustion reaction model, the DO radiation model to study the fluid flow and heat transfer of the roller kiln. The analytical domain is analyzed and discretized and steady state numerical simulation of the roller kiln is achieved.(3)Temperature and velocity fields are analyzed through numerical simulation of the roller kiln under normal working conditions. Results demonstrate that the maximum jet velocity of flames at burners’exit is41m/s and a small fluid recirculation appears between exit streams of two pairs of neighboring nozzles, which enhance fluid mixing of each jet and improve heat transfer. Temperature uniformity is better at the space below the kiln than that above. Average temperature differences of sanitary ware A is11K with maximum surface temperature at1465K and minimum surface temperature at1435K. The difference between the maximum and minimum surface temperature is30K. Average temperature difference of sanitary ware B is9K with maximum surface temperature at1466K and minimum surface temperature at1439K. The difference between the maximum and minimum surface temperature is27K.(4) To optimize the coefficient of variation for temperatures, single factor analysis of the burner inclination angle, the burner spacing, and the air-fuel ratio is performed. Optimal working zones are determined based on the dependence of the coefficient of variation for temperatures on each individual factors. The optimal combination of working parameters are setting the burner inclination angle at10degree, the burner spacing at470mm and the air-fuel ratio at12obtained from orthogonal test methods. Quantitative contributions of factors influencing the temperature uniformity are determined with the burner inclination angle, the burner spacing, and the air-fuel ratio accounting for50percent,28percent and22percent respectively. The optimized conditions improves temperature uniformity by25percent compared to the original working conditions.22figures,16tables,63references.