A TEMPERATURE PRE-RECTIFIER WITH CONTINUOUS HEAT STORAGE AND RELEASE FOR WASTE HEAT RECOVERY FROM PERIODIC FLUE GAS

Abstract

Flue gas from periodic furnaces with large temperature fluctuation is difficult to be recovered by regular heat exchangers. To recover that unstable waste heat, a temperature pre-rectifier (TPR) with honeycombed structure is developed to smooth down the temperature fluctuation by continuous heat storing and heat releasing. A three-dimensional model of TPR is constructed to analyze the heat transfer process. Temperature rectification rate η is defined to quantify the smoothing-down effect of TPR on temperature fluctuation. The relative size <i>s</i>* as the ratio of hole size to inner wall thickness (i.e., <i>s</i>* = <i>s/δ</i>), can be used to measure the capacity of heat release compared to that of heat storage. The quantity η reaches the highest value when the relative size <i>s</i>* is 1.0, and is increased with dimensionless length <i>l</i>*. When <i>s</i>* = 1.0, η firstly rises and then drops with the increment of <i>s</i>. The peak value of η can be achieved by an optimized hole size <i>s</i><sub>opt</sub>. The <i>s</i><sub>opt</sub> value increases exponentially with the inlet temperature fluctuation intensity. The TPR with segmented structure can enhance n with relatively short length. The three-segment structure with a proportion of 0.18:0.33:0.49 makes η > 0.947, which is recommended for application. Industrial experiments showed that the temperature fluctuation of flue gas can be rectified from 568-1709 K to 1089-1174 K (η = 0.926) by TPR, which verified that the TPR is an effective method for waste heat recovery from periodic flue gas.