Common problems with air preheaters
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(1) The problem of poor sealing of the direct exhaust flue of the reaction furnace has not been resolved. According to sampling analysis, the oxygen volume fraction in the radiation chambers of each heating furnace is around 1.2%–1.5%, whereas CEMS data from the chimneys show that the oxygen volume fraction in the flue gas is as high as 4%. This indicates that some air has entered the flue gas system through the convection chambers, resulting in a flue gas volume that is greater than that generated by the actual fuel gas. This leads to an imbalance in heat exchange in the air preheater and an increase in the exhaust gas temperature. (2) There is an internal leak in the cold air bypass of the air preheater. Since the size of the cold air bypass control valve is 1267mm×922mm, which is the same as the cross-sectional area of the main air duct at the preheater inlet, the start point of the bypass is located near the preheater inlet. The data shows that the air after passing through the air preheater is heated from a normal temperature to 250°C; the calculated exhaust temperature should be around 100°C, but in reality it is 115°C. This indicates that there is air leakage through the bypass valve, as some air does not pass through the air preheater for heating, which results in an increase in the exhaust temperature. (3) The heat exchange capacity of the high-temperature section modules in the air preheater is insufficient. The operation data show that the temperature of the modules in the high-temperature section decreased from 269.89°C to 202.85°C, resulting in a temperature difference of 67.04°C; the temperature of the modules in the low-temperature section dropped from 202.85°C to 115.18°C, with a temperature difference of 87.67°C. The heat exchange area of the modules in the high-temperature section is approximately twice that of those in the low-temperature section, indicating that the heat exchange area in the high-temperature section is clearly insufficient. This may be due to internal leaks or blockages in the flue gas and air passages, which affect heat exchange in that section and ultimately influence the exhaust gas temperature.
(1) Problem of inadequate flue closure: It may be due to poor sealing of the flue or the presence of air leaks, which allow some air to enter the flue gas system. This increases the amount of flue gas, affects the heat exchange efficiency of the air preheater, and results in an increase in the exhaust gas temperature. The solution is to check the sealing of the flue, repair any air leaks, and ensure that the flue is tightly closed. (2) Leakage issue in the cold air bypass: It may be due to a poor seal of the valve in the cold air bypass, causing some air to be discharged directly without being heated by the preheater, which raises the exhaust gas temperature. The solution is to repair or replace the bypass valve to ensure it seals properly and prevents air leakage. (3) Insufficient heat transfer capability of the high-temperature section module: This may be due to an inadequate heat transfer area in the high-temperature section, or issues such as blockages and obstructions, which result in poor heat transfer performance and hinder the reduction of flue gas temperature. The solution is to check whether the heat exchange area in the high-temperature section is sufficient, remove any obstructions to ensure unobstructed flow, and thereby improve the heat exchange efficiency. .