Study On Mechanism Of Heat Transfer In The Grate Cooler

Based on reasonable hypotheses, a mathematical model of heat transfer between gas stream and clinker in a grate cooler with an output of 1000t/d is established. A computer program for this model is worked out in FORTRAN. The measurement data collected from a real 1000t/d grate cooler serves for validating the soundness of the model and program. Using this program, several factors which may have influence on the operation of grate cooler are investigated. They are air velocity under grate in QRC zone, air velocity under grate in C zone, driving velocity of grate bed, clinker size and packingstate of clinkers.By analyzing the results of calculation, a series of conclusion are achieved: The air velocities in QRC zone and in C zone are important factors affecting on clinker cooling. The temperature of discharged clinker decreases exponentially with air velocity and equations are given in this regard. The driving velocity of grate bed and the clinker size have some effect on clinker cooling. The temperature of clinker leaving the cooler exit increases linearly with the driving velocity of grate bed and the clinker size and the equations are showed. The packing state of clinkers has a little effect on clinker cooling. Such effect could be neglected for the fluctuation range of all temperatures is not more than +20K.An optimized operating scheme for the grate cooler with a cooling capacity of 1000t/d is given as follows: the proper air velocity under grate in QRC zone should be 1.0~1.5m/s; the one in C zone should be 0.5~0.75m/s; the driving velocity of grate bed should be 0.007-0.010m/s; and clinker size should be less than 0.025m.