Diesel hydrocracking fractionator
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After the diesel hydrocracking distillation tower has been transported by water or road, and its temperature is raised to around 130 degrees, the bottom pump stops pumping fluid – what should be done?
It has happened twice before; now there is no liquid water at the bottom of the tower to use for cutting, so it can only be slowly vaporized and sent to the reflux tank to cool down before cutting； When the situation is not too serious, keep the bottom-of-tower circulation pump running at its minimum flow rate, and use a rubber hose at the pump inlet to cool the water ； In severe cases, the pump must be stopped to reduce temperature, and water must be removed from the bottom of the tower.
We have encountered this problem recently: as the moisture evaporates at the top of the tower, the pump at the bottom of the tower fails to deliver fluid from time to time. Evaporation proceeded slowly, and it took two shifts to remove all the moisture; during that time, fresh oil was continuously fed into the tower to replace it.
The 2 pumps at the bottom of the tower operate in alternation, with the standby pump continuously draining water
It’s probably a common issue that occurs during the first start-up: dirt such as rust on the containers or pipe walls may peel off as the temperature rises, thereby blocking the pump’s inlet filter; or the remaining water after transportation may cause vacuum conditions when the temperature increases. In any case, it’s necessary to allow gradual evaporation so that the situation can improve over time.
Diesel pumps generally start to discharge water at 90 degrees Celsius. You started discharging water a bit too late; moreover, this process should be carried out once per hour. It is necessary to discharge water from the standby pumps as well as those used for transporting diesel, including the lowest points of various towers, heat exchangers, and pipelines, in order to prevent water from accumulating in these low-lying areas. At the same time, if there are fluctuations in liquid level or pressure/temperature during heating, pause the heating process or reduce the heating rate. Also, check again the steam and water pipelines connected to the tower equipment and ensure they are shut off. If things go as described above, there will be basically no water at 130°C.
So, in such a situation, how can it be saved?