On the control of hydrocracking fractionation towers
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In a hydrocracking fractionation tower, why is the diesel extraction temperature 60–65 degrees Celsius higher than the temperature of the diesel mid-stream reflux? Why is it still necessary to maintain a temperature of 60-65 degrees Celsius? Similarly, why is the temperature of the jet fuel extracted higher by 60-65 degrees Celsius than the temperature of the jet fuel returning from the middle stage of the process? Why? To achieve thermal balance, excess heat is removed from the tower, but why 60-65 degrees Celsius?
This should be related to the heat exchange process and product quality.
The control at this temperature should be based on the process requirements. Firstly, the reason why the diesel extraction temperature is 60-65 degrees Celsius higher than the mid-stage reflux temperature is that it is determined by calculating the reflux rate along with the processing capacity of the distillation tower and the temperature control requirements at the tower bottom. The temperature after mid-stage reflux must be such that it allows for effective heat exchange with the hot medium upon entry into the tower, thereby enabling the separation of light and heavy components, while also ensuring that the negative temperature within the tower remains within a reasonable range so as to maintain an appropriate level of light components in the tower bottom product. This data range should be based on the results of years of theory and practice! Only by maintaining the temperature within this range can the best results be achieved, ensuring both the rational use of energy and the highest possible quality of the product.