PERFORMANCE ENHANCEMENT FOR ROTARY AIR PREHEATER OF A THERMAL POWER PLANT

Abstract

The corrosion phenomenon is considered the main problems for air preheater in thermal power plant. The boiler flue gas contamination leads to decrease the air preheater performance and increases the maintenance cost, which causes the degradation of the cold end heating elements and thus leads to decrease the heat recovery rate. In this study, an experimental investigation was done for the transient thermal behavior and the pressure drop of the standard regenerative air preheater (Pmatrix) model, evaluating the performance factor, then modifying the air preheater (P+CG) model by changing the plates at the cold end last basket to the coarse gravel media. Since the gravel media have low thermal conductivity and predicted to give a high pressure drop, a new technique was done for the modified air preheater to compensate the low heat transfer rates and reduce the pressure drop in the gravel media by inserting bypass tubes at ratios (i and s), Which, the (i) model represents the inner aperture of tubes for the hot baskets facing to the inner aperture of tubes for the cold basket. While (s) model the insertion the tubes of the hot baskets as a staggered distribution with the tubes for the cold basket. The experimental investigation was carried out for the Reynolds number based on the test duct hydraulic diameter at a range of 24500<Re < 98000 for each charge and discharge periods. The experimental results are presented in terms of the average heat transfer rate and the pumping power for matrix models. The experimental measured results corroborated that the bypass tubes have a significant impact on improving the heat transfer rate and the pressure drop reduction of the modified air preheater matrix. The results showed that the best performance factor was achieved in the air preheater (P+CG+Ts) model which found to be in the range of 0.7-0.31 at high and low Reynolds. However, this improvement increased the pumping power by 13% than the (Pmatrix) model.

Keywords

• air preheater
• modified
• gravel media
• the bypass tube