What are some good measures to stop the cold reflux during the startup of a catalytic cracking fractionator?
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The current processing capacity of the distillation tower is at the upper limit of its design value. The amount of material in the top circulation has now reached its maximum, so it cannot be increased any further. However, since the temperature at the top of the tower is high, it is necessary to activate the cold reflux at the tower top in order to regulate this temperature and control the quality of the gasoline product. Is there any good way to stop this cold reflux while still ensuring that the quality of the product at the tower top remains satisfactory?
1 From a reaction perspective, appropriately controlling the reaction depth to reduce the load on the upper fractionation stage can enable the proper production of heavy diesel. 2 If there is still room for adjustment in the circulating water flow, increase it and coordinate with the circulating water system to lower the temperature of the incoming water. If a heat integration device is used, the heat-consuming system can draw more heat. 3. Devices with mechanisms for absorbing oil from both rich and poor streams can appropriately increase the flow rate and thus extract more heat. 4 Reducing the steam consumption in the reaction and distillation systems, as well as increasing the oil-gas partial pressure in the distillation column, helps to lower the dry point at the top of the column, thereby improving temperature control. 4 Increasing the heat absorption in Unit 1 indirectly reduces the load on the upper part of the tower.
At present, the processing load of our unit is relatively low; in order to control the dry point of gasoline, the top temperature is kept very low. To ensure that the top temperature of the tower remains above 100 degrees, we are also using cold reflux at the moment
The heat extraction in the distillation tower is not properly distributed; therefore, more heat should be extracted from the oil slurry at the bottom of the tower. Additionally, heat extraction should also be increased from stages 1 and 2
In my understanding, a distillation tower is used to handle vapor-liquid equilibrium. A high temperature at the top of the tower indicates that the gas load there is greater than the liquid load. Generally, the top temperature is controlled through top circulation, with cold reflux used as a supplement. To stop using cold reflux, while ensuring production safety, one option is to adjust the temperature of the material returning to the tower via top circulation; another approach is to increase the load in the middle and lower sections of the tower in order to reduce the load at the top. Additionally, light diesel can be added to the distillation tower to lower the overall thermal load, but it is important to monitor the liquid level in the tower and increase the amount of liquid removed from it promptly – this will result in increased energy consumption. The reaction can consider appropriately reducing the reaction depth.