What is the maximum allowable exhaust temperature for a boiler?

What is the maximum temperature that can be reached? I said, do you still want to know the boiler’s thermal efficiency? Your way of thinking is a serious waste of energy! The exhaust temperature should be as low as possible.

There is no upper limit for the flue gas temperature; this merely indicates that waste heat is not being utilized effectively, but it certainly shouldn’t be too low! It is generally not lower than 120°C; otherwise, dew point corrosion is likely to occur

I agree with the brother upstairs; especially when the sulfur content in the fuel is high, the exhaust temperature cannot be too low

In this era of tight energy supplies, it’s quite inappropriate of you to ask what the highest exhaust temperature can be.

If the sulfur content in the fuel is high, the flue gas temperature must not reach 180 degrees; otherwise, the economizer will quickly suffer from dew point corrosion and start leaking, which affects long-term operation. Based on experience, the optimal flue gas temperature is between 180 and 200 degrees.

In the case of a direct exhaust chimney, the upper limit of the exhaust temperature must take into account the design capacity of the chimney. When a heat pipe-based waste heat recovery system is used, the temperature of the flue gas entering the heat pipes is generally around 380 degrees. The exhaust temperature is determined by the dew point temperature of the flue gas; to reduce or prevent corrosion, it is necessary to ensure that the temperature of the metal surfaces exposed to low temperatures remains above the dew point temperature of the flue gas. During the design process, various operating conditions also need to be considered, such as those under low load conditions. Therefore, the exhaust temperature should be about 20-30 degrees higher than the dew point temperature to avoid corrosion. Friendly reminder: If a steel chimney is used, be aware that excessively low temperatures can cause corrosion to the chimney

No, your approach is too far removed from comprehensive utilization; consider making use of it instead

The level of flue gas temperature: To save energy, heat should be recovered as much as possible to reduce the flue gas temperature; however, there is a limit to how low it can go, and it generally needs to be kept above the dew point to prevent corrosion. If the smoke exhaust temperature is too high due to issues with the equipment, such as a low heat transfer coefficient resulting from scaling on the furnace tubes, then in order to ensure the proper operation of the device, it is necessary to increase the temperature of the furnace chamber. As a result, the smoke exhaust temperature rises as well. When the smoke exhaust temperature is too high, attention must also be paid to the material of components such as the furnace tubes; excessive temperatures can cause decarburization of these tubes, leading to their rupture.

When the flue gas temperature rises to 250 degrees, it is generally not dangerous; it simply indicates that the efficiency of your waste heat boiler has decreased, possibly due to ash accumulation. It is necessary to carry out soot blowing operations in order to reduce the flue gas temperature. Generally, the exhaust temperature should be as low as possible, but it shouldn’t be too low! Here, the temperature is generally not lower than 150°C; otherwise, sulfur dioxide in the flue gases can easily cause dew point corrosion

The flue gas temperature of the waste heat boiler used for catalytic cracking in our facility is around 190–200 degrees, with a chimney height of 80 meters.

The design for our factory is 123 degrees, but in reality it is 153 degrees. It’s not the case that the lower the value, the better; too low a value can cause corrosion of the flue ducts!!

The upper limit is primarily determined by the design of the equipment (mainly the chimney) as well as energy conservation and consumption reduction. The lower limit is mainly considered in terms of dew point corrosion.

High exhaust temperatures result in resource waste, while too low temperatures can lead to dew point corrosion

It can’t be too low, as there’s a risk of dew point corrosion； It can’t be too high, as there’s a risk of waste, as well as risks related to accidents in the preheating and recovery system. If interlocks are used, there are also concerns regarding the functioning of those interlocks. So it is generally kept around 200°C. Everyone, please add more. Thank you!

Above 130 degrees is more appropriate!