Numerical Study and Parameter Optimization for Suppressing Ash Deposition in Flue Gas Heat Exchanger

An ash deposition suppression technique in flue gas heat exchanger was proposed, and the numerical study on the heat transfer performance and ash deposition behavior of a flue gas heat exchanger with a 6-row tube arrangement was conducted. Then, the orthogonal tests were adopted to analyze the influence of the geometric parameters on the heat exchanger performance. The primary and secondary influencing sequences of the three factors were obtained, and then the optimal combination of the geometric parameters was determined for the suppression of ash deposition. The results showed that the factors influencing the ash deposition rate are arranged in a descending order as follows: the diameter of the added cylinders, the spacing between added cylinder and heat exchange tube, and the setting angle of added cylinder. However, the setting angle is the most significant factor for heat transfer performance. Considering the ash deposition rate and heat transfer performance, the optimal combination was determined as the diameter of 6 mm, spacing of 4 mm and setting angle of 40°. Taking the ash deposition rate as the optimization objective under optimal conditions, the ash deposition rate was decreased by 55.1% compared with the heat exchanger without added cylinders, which can realize efficient recovery and utilization of waste heat from industrial flue gas.