The Numerical Simulation Optimization And The Development Of The Series Design Software System Of The Direct-fired Flue Gas Reheater

As the main heating equipment in SCR denitration technology of sintering flue gas,the temperature uniformity of outlet flue gas of direct-fired flue gas reheater will greatly affect the uniformity of sintering flue gas temperature field in the main flue,and then affect the work efficiency of SCR denitration catalyst.Therefore,the research of mixed air structure is of great significance.In this paper,the original mixed structure of direct-fired flue gas reheater is simulated numerically.According to the results,the temperature distribution of flue gas in the flue is very uneven.The temperature above the horizontal section of the flue is950℃,and the temperature below is 280℃.The maximum temperature difference of mixed flue gas outlet is 209.8 ℃,and the standard deviation of dimensionless temperature is 0.1236.In order to improve the uniformity of outlet temperature of mixed flue gas,six different combinations of mixed structures are proposed.According to the results of numerical simulation,the mixing effect is the best under the combination of double pipe + swirl blade + spiral baffle plate,and the local high temperature problem existing in the original mixing structure is effectively avoided.Then,the influences of different tilt angles of swirl blades(15°,30°,45°,60° and 75°)and gap widths of spiral baffle plates(30 mm,50 mm,70 mm,90 mm and 110 mm)on the temperature uniformity of flue gas outlet were studied respectively.According to the results,with the increase of swirl blade tilt angle,the standard deviation of flue gas dimensionless temperature at the flue outlet decreases first and then increases,and the pressure drop at the mixing side increases gradually.With the increase of gap width of the spiral baffle plate,the standard deviation of flue gas dimensionless temperature at the flue outlet decreases quickly before increases slowly,and the pressure drop at the mixing side decreases gradually.When the tilt angle of swirl blade is 45° and the gap width of spiral baffle plate is 50 mm,the mixing effect is the best,the maximum temperature difference at flue gas outlet decreases from 209.8 ℃ to 135.0 ℃,the standard deviation of dimensionless temperature decreases from 0.1236 to 0.1149,but the pressure drop on the mixing side increases from 76.0 Pa to 119.1 Pa.In addition,based on the improved mixed structure,this paper also uses Visual Basic 6.0 to develop auxiliary software for the design of direct-fired flue gas reheater.This software can not only quickly complete the thermal calculation,size calculation and cost calculation of direct-fired flue gas heater,but also call Auto CAD for automatic drawing.It can realize the heat load from 3 million kcal/h ～32 million kcal/h direct fired flue gas heater series design.