How to deal with overtemperature of high-pressure steam coil
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During the startup and shutdown of the Kellogg process large-scale ammonia synthesis plant, the high-pressure steam coil in the convection section of the furnace is prone to overtemperature. Our plant is equipped with a high interlock shutdown protection device for this temperature. I would like to ask all experts to discuss how to deal with this situation correctly when it occurs. This post was last edited by Huang Xinhui on 2009-2-23 12:54 ]
During the process of starting and stopping, it is judged that the high-pressure steam in the convection section of the furnace is prone to over-temperature. Increase the steam output of the auxiliary boiler and reduce the drum pressure to ensure that the high-pressure steam does not over-temperature.
Preparation plan to prevent overheating and high-pressure steam over-temperature. The high-pressure steam coil in the convection section of the first-stage furnace and the high-pressure steam coil in the convection section of the pre-conversion heating furnace are divided into the following two situations:: First, while driving ； The second is due to system fluctuations during the operation of the device and during shutdown. And the following measures should be taken to deal with it. Phenomenon: The high-pressure steam tray in the convection section of the furnace is over-temperature: deal with: (1) During the operation of the device, due to system fluctuations and shutdown, over-temperature caused by insufficient system steam production can be reported to dispatch, appropriately reduce the system load, reduce steam consumption, appropriately increase the PCV-13, increase the high-pressure steam flow, and appropriately open the air duct to control the high-pressure steam temperature at 440-460℃ ； For over-temperature caused by large amounts of external high-pressure steam, part or all of the external high-pressure steam should be withdrawn. ； Increase the 101-BU load and open the air cylinder appropriately to control the high-pressure steam temperature to 440-460℃ ； The fuel gas volume of the first-stage furnace or auxiliary boiler should correspond to the system load. If it is found to be too high, complete combustion cannot occur in the furnace, and secondary combustion occurs in the convection section, the fuel gas volume of the first-stage furnace or auxiliary boiler should be reduced so that the oxygen content of ACV-6 and 8 is within the control index, and the high-pressure steam temperature is controlled at 440-460°C. (2) If the synthesis tower is closed, the synthesis central control should be notified immediately to shut down SP-7, reduce the system load by 95%, reduce the temperature of the furnace to 785°C, increase the temperature of 103-D appropriately, and turn on the air duct on site. (3) If 101-J surges and the synthesis tower is closed at the same time, turn off SP-7, turn off SP-100, reduce FR-34 to 10000M3/h, reduce the load to 80%, fully open the air duct on site, and the central control should pay attention to controlling the oxygen content of the first furnace to not be less than 3%. (4) When dealing with over-temperature, do not turn the HS-1421 interlock switch to bypass without authorization.
In fact, this problem is not difficult, because when an emergency occurs, the general control is in various positions. They are responsible for the internal operation of the steam system and directly reduce the fuel gas volume of the superheater. It also depends on the situation. If there is a problem with a large user of high-pressure steam, the superheater burner must be extinguished on site, and there must be an accurate number of how much must be extinguished. From the internal operation to the operation engineer, when an accident occurs, I do not allow overheating and exceed the temperature.
The key is to immediately reduce the load on the system and reduce the fire. Open the cold air holes in the convection section.