Numerical simulation and optimization of heat-insulation material and structure for CFB boiler

Abstract

Performance of different thermal insulator structures for CFB boilers was studied in this work. Taking a 220-t/h CFB boiler as the research object, physical models of the furnace wall, cyclone separator wall and tail flue wall were established. The outer wall temperature for different design schemes was calculated, and the adiabatic properties of some materials were verified experimentally. It is found that the thermal-insulation property for the monolayer material is, in increasing order, PSC, ASFF, and RWIF. The adiabatic effect of the furnace wall multi-layer insulation material depends on the weighted-average thermal conductivity. If RWIF is used as heat-insulation material of furnace wall, the thickness could be less than 110 mm. If PSC or combined material is selected, their thickness should exceed 130 mm. The isotherm for the cylinder and cone of the cyclone separator is a cluster of concentric circles with a uniform distribution. A lower thermal conductivity yields a denser isotherm. For a three-layer material insulation structure, the second layer plays a decisive role in the thermal-insulation property. For tail flue, the insulation effect of the outermost insulation material is most obvious. The temperature field is evenly distributed, and the distribution tightness is related to the thermal conductivity of the material used. A combination of RFB, AIT, and ORB could be selected if the flue-wall thickness needs to be reduced. An optimal heat-insulation point exists for each material, at which the insulation efficiency reaches an extreme value. Various insulation materials could be combined based on the insulation efficiency.