110. What is the maximum allowable temperature at the inlet of the flue gas system? What to do if it overheats?

1) A temperature of over 700℃ is not allowed. 2) When the inlet temperature exceeds 690°C, reduce the inlet temperature by adjusting the reaction parameters; when the inlet temperature exceeds 700°C, close the butterfly valve to throttle the flow ； If the temperature suddenly becomes extremely high and continues to rise, urgently shut down the smoke extractor ； When the temperature suddenly rises to an extremely high level and then returns to normal, check for any abnormalities (the main operator checks the shaft vibration, while the assistant operator goes to the flue gas fan to listen for any abnormal noises during its operation).

Previously, it was said that the temperature should not exceed 680°C; now, there are systems that can control temperatures at 700°C, and others that can handle 720°C. Some even claim that temperatures below 800°C are no problem. It’s still the Lanzhou manufacturer’s version that should be taken as the standard!

Communication with friends on the 3rd floor: 1. The allowable temperature at the inlet of the flue gas extractor is not determined by a single fixed value; the principle is that the combined stresses generated during the rotation of the extractor’s rotor due to factors such as speed, gas conditions, and temperature should not exceed the stress limits allowed by the structure. Temperature is one of these influencing factors, which shows that there is no single fixed value for the inlet temperature. 2. The values of 680 or 700°C mentioned in operational contexts are based on the fact that domestic or some imported catalytic flue gas extractors use similar materials and operate under similar conditions. Certain constraints keep the rotor speed within a certain range, and sufficient safety margins are provided to ensure the extractor can function properly under normal operating conditions; this has led to the establishment of these default values. 3. I would like to provide another set of data here: the continuous temperature at the inlet of the flue gas extractor is 720°C, with a maximum temperature of up to 800°C. These figures are based on reliable sources; however, more explanation is needed to clarify their scope of application. Nevertheless, we still use 700°C as a guideline for operators, but we know the limit, and we won’t make a fuss or blame excessive temperature rise over occasional increases.

Communicating with friends on the 2nd floor: 1. It can be observed that this forum features many experts discussing various topics through Q&A sessions, which is very beneficial for the dissemination and exchange of technical knowledge. 2. Since I am not familiar with the rules and target audience of this Q&A format, I usually just read the content without participating rashly, in order to avoid misunderstandings that might violate the rules. 3. Regarding the point mentioned in the reply on the second floor regarding this topic – \"When the temperature spikes suddenly and then returns to normal, it is necessary to check for any abnormalities (the main operator checks the shaft vibration, while the assistant operator goes to the smoke extractor to listen for any abnormal noises during its operation)\” – this is quite insightful. Here are some topics for discussion: 3.1. If thermal expansion caused by excessive temperatures is taken into account, it generally leads to changes in the structural dimensions at high temperatures, or a decrease in the tightening force of the shafts, and these effects can be observed externally. The reply mentioned checking after the temperature returns to normal; we were not aware of this approach. Could you please provide examples of the possible abnormalities that might occur? 3.2. The consequences of high temperatures are, apart from instantaneous failure due to exceeding strength limits, primarily cumulative damage to the material; this is why the inlet temperature of the smoke extractor, as discussed earlier, is not a simple numerical value. At high temperatures, the grain growth rate of metal materials increases, but it does not reach a level that causes failure through rapid growth in a short period of time; rather, it is a continuous cumulative process. To determine the remaining service life of the high-temperature components of the smoke extractor rotor, it is necessary to measure the grain size during the shutdown period, and to conduct a safety assessment by taking into account the over-temperature values and duration observed during operation. 4. Returning to the second point: I am not familiar with the rules or target audience of this Q&A format; if advice is intended only for specific individuals, then what has been said above may be outside the scope.

The range of inlet temperature for the flue gas extractor should be the range specified by the manufacturer of the extractor; generally, this corresponds to the safe operating temperature for the material used. It depends on what material is employed – for example, with GH864 alloy, the manufacturer requires a temperature of 670°C, although data indicates that no problems occur below 760°C.

In China, it generally does not exceed 680°C; in foreign countries, the design temperature for smoke extractors usually does not exceed 730°C. This depends on the material used for the smoke extractor

Generally, the temperature in our coking furnace chamber should not exceed 800 degrees. In other words, the inlet temperature of the exhaust fan, as mentioned by the original poster, should not be higher than 800 degrees. But in actual operation, the exhaust fan’s temperature doesn’t usually reach such a high level. I’ll go check what the readings on the instruments show

In our catalytic unit, the temperature of the flue gas exchanger does not exceed 690 degrees. However, in actual production, the temperature always rises above this level. To maintain the processing capacity, we modified the system by introducing purified air into the flue at the inlet of the flue gas exchanger as a cooling medium; this reduced the temperature, but it is not clear whether this has any adverse effects on the flue gas exchanger.