Processing of the top-loop system
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During shutdown, does the top circulation system first undergo water washing and then steam purging? Is water washing carried out after the pump is emptied? When washing, oil needs to be pushed into the distillation tower, which inevitably causes water to enter the distillation tower as well. Won’t that have little impact on the pressure of the entire distillation column and the temperature inside it during the purging period?
That won’t happen; this process is completed once everything at the bottom and within the tower has been completely removed, after which the next stage begins. Since the feed has just been stopped, the top circulation continues to be used to control the temperature at the top of the tower, thereby ensuring the quality of the product. After everything at the bottom and in the middle of the tower is completed, open the valve for fresh water supplied by the top circulation pump to start pumping water for washing out the tower. Once the washing is complete, drain all the remaining water and then begin purging with steam. It is essential to turn off both the air cooling and water cooling systems at this stage; otherwise, the purging process will not be possible.
When washing, it is necessary to push the oil into the fractionation tower so that it can be thoroughly cleaned. There’s no problem with water entering the fractionation tower; the oil on the trays also needs to be washed with water. The oil collection tank is also full of oil, and it needs to be flushed with water as well.
Can water topping be done before the steam tower? How can one determine that all the oil in the entire top circulation system has been pushed into the fractionating tower? If water enters a distillation tower, it should have an impact on the vaporizing tower (there will be a lot of water in the oil collection tank)
All pumps are emptied several times to ensure that as much water as possible is removed. Depending on the conditions indicated by the liquid level gauge at the bottom of the tower, the pump at the bottom of the tower is also emptied several times before steam is used for purging and cooking.