Hydrocracking shutdown
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During shutdown, the distillation section is kept in a short cycle at 220 degrees. Why is it 220 degrees? What is the significance of this?
The significance of a short distillation cycle is to reduce the startup time. When resuming operations after a shutdown, in order to completely remove the light components generated in the reaction section through distillation in the hydrogen sulfide removal tower, if the temperature at the bottom of the distillation column is below 220 degrees Celsius, the light components (hydrogen, hydrogen sulfide, C1, C2, and liquefied gas components) will mix with the heavier components at the bottom of the column, which is very dangerous! ! !
Some refineries use a short cycle at 250°C, which involves the transfer of heated oil for distillation; this is also the heat-shocking temperature during startup. Also, at the start of operation, in order to reduce the startup time, by waiting for the reaction pre-vulcanization to finish and then feeding fresh material in, it is possible to streamline the process.