Dry point of crude gasoline
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During this special period, the plant needs to reduce costs and improve efficiency by producing less gasoline. Previously, the plant relied on the temperature from the top circulation to control the temperature of the distillation column, but the results were not satisfactory; the final boiling point, as indicated by the analysis data, remained unstable, and the liquid drawn off through the top circulation sometimes contained water. Recently, the use of cold reflux proved to be effective – it allowed the top temperature to be controlled while also increasing the amount of liquid drawn off through the top circulation. The dry point of the crude gasoline met the required standards. I would like to ask: why is there such a big difference between these two methods, both of which are used for temperature control?
After the cold reflux is put into use, the vapor pressure of the oil and gas at the top of the distillation tower increases.
The top circulation is primarily used to remove excess heat from the top of the tower, and by controlling the temperature of the vapor drawn from the top, the dry point of the crude gasoline can be regulated. Although the use of cold reflux increases energy consumption, it controls the vapor pressure at the top of the fractionation tower in order to regulate the dry point of crude gasoline. Without affecting the composition of the target product of the reaction, the amount of steam injected during the reaction can also be adjusted appropriately to modify the dry point of the crude gasoline.
It can be understood that cold reflux entering the fractionator results in low temperature, high pressure drop, and high vapor pressure?
Misunderstanding. The crude gasoline returns to the distillation tower, where it eventually emerges as a vapor from the top of the tower. As a result, the oil and gas composition in the material coming from the tower top increases, which in turn leads to a decrease in the water vapor pressure. At the same top temperature, the dry point of the crude gasoline decreases ； To ensure that the quality of crude gasoline remains unaffected, it is necessary to appropriately raise the top temperature.
Under normal circumstances, a top loop is sufficient to control the tower top temperature and the quality of the crude gasoline product. What is the load on your plant?
For a while, the load on my device was low; to keep the top temperature above 100 degrees, I activated cold reflux for a period of time
The unit load is not high; the top circulation heat exchange is affected by the dual dehydration process in the gas separation unit, resulting in large fluctuations in the amount of circulating oil returning to the tower. The fluid extracted from the top circulation at 130 degrees is prone to containing water, so cooling reflux is applied later on
Under normal conditions, top temperature control using top circulation is sufficient, but when the control threshold for the dry point of gasoline is too low, cold reflux needs to be used to assist in achieving the desired result. This should be a problem faced by many devices recently.