Reasons for high flue gas temperature in boilers

There is an excess of air; to maintain the temperature at the outlet of the heating furnace, more fuel is added, which results in an excessively high temperature at the flue gas outlet. Secondly, during heat exchange in the convection section, a low volume of fluid flowing through the coiled tube can also lead to an excessively high temperature of the exhaust flue gas. Additionally, there are issues with the calculations related to the waste heat recovery system

1. Boilers generally have 10 combustion stages, with the best combustion efficiency in stages 3 to 5, and it is relatively good in stages 8 to 10. 2. The combustion in boilers is greatly affected by the quality of the fuel. For a certain period of time, the fuel may be of good quality and the equipment in good condition; but once the fuel is changed, its calorific value changes and the air-fuel ratio becomes unbalanced, which directly leads to a decrease in combustion efficiency. The heat transfer efficiency is also affected by the wind, which blows away the heat, resulting in high exhaust temperatures in the boiler. 3. Summarize possible causes: fluctuations in oil quality, excessive dust inside the equipment, and improper adjustments. Countermeasures: Bring the boiler’s exhaust temperature under the control of a monitoring system (DCS); it should generally be kept below the medium temperature plus 150°C, otherwise efficiency will be low, leading to waste!

1. The boiler’s coils may be slightly clogged; cleaning them should resolve the issue. 2. The ratio of primary air (and in some cases, secondary air) to gas isn’t adjusted properly, or the cam controlling the opening degree of the air valves isn’t set correctly. 3. The gas pressure regulator is operating outside its specified range, and therefore cannot regulate the gas pressure effectively. 4. The gas contains oil

Generally speaking, the reasons for high flue gas temperatures include: 1. Operational factors: significant deviation from normal load operation, issues with the type of coal used (including calorific value, volatiles, and fineness, as well as deviations from design specifications), ash accumulation on the outer walls or scaling on the inner walls of the heat-exchanging surfaces at the rear part of the system………… 2. Design-related factors: usually insufficient arrangement of heat-exchanging surfaces at the rear part, or an excessively low designed flow rate of the flue gas……………… In fact, there are many possible reasons; it’s more appropriate to analyze each specific case individually! Hehe

First, take a look at the economizer. If it’s not present, it’s normal for the flue gas temperature to be around 50 degrees higher than the designed value. If an economizer is available, it depends on the type of boiler: under normal load, for conventional coal-fired boilers with an economizer, a flue gas temperature of around 200 degrees is considered normal. Gas and oil-fired boilers generally have higher thermal efficiency, so their flue gas temperature should be around 170 degrees. In the absence of an economizer, the temperature can be 50 to 100 degrees higher, which is still considered normal. If the flue gas temperature exceeds 300 degrees, it’s abnormal; first, check whether there are any issues with the flue gas flow, then determine the boiler load, and subsequently check the air intake and exhaust volume. For more specific details, please share the exact problem so that we can discuss it together.