【Gas Fractionation】The propane and propylene separation efficiency in the gas fractionation unit is poor; how to solve this?
Thread Content
This post was last edited by Xiao Gong 1985 on 2016-4-10 at 14:34. Our company requires that the quality of propane and propylene be maintained at levels of 99.2% and 99.5–99.55%, respectively; however, recently… Propane is always below 99%, and the measures being taken now are. T103A increases the bottom temperature of the tower and slightly reduces the reflux of T103B, but the effect is still not satisfactory; it also affects the quality of propylene. The processing capacity of the plant has not been overloaded – seeking advice from experts
Test and analyze the raw materials; the levels of propane and propylene have decreased； Analyze the tray to determine whether it has been washed away or reversed.
The tower trays need to be modified due to poor separation efficiency
1. Does the tower top pressure change? 2. Has the temperature of the circulating water changed, and has there been a significant change in the temperature of the return liquid phase? 3. What is the change in pressure difference between the two towers? Don’t assume blindly that it’s the tray that’s the problem. A problem with the tray is a serious issue, and no conclusions should be drawn lightly. If shutdown is required for repairs to the tray, it’s not something that can be done in just a day or two.
In short, within the allowable limits, increasing the bottom temperature, raising the reflux ratio, and improving separation accuracy; if the operation cycle is long, it is possible that the separation efficiency of the tray plates decreases.
I think there’s an issue with your method of adjustment. Raising the temperature is intended to vaporize more propylene, but reducing the reflux rate is problematic. Increasing the temperature while simultaneously reducing the reflux rate leads to a decrease in the reflux ratio, and a lower reflux ratio results in a decrease in the number of theoretical plates in the tower. As a consequence, the quality of the product at both the top and bottom of the tower suffers. I believe the correct approach is to increase the bottom temperature, while also appropriately raising the reflux rate, increasing the reflux ratio, and boosting the theoretical number of plates in the tower – all in order to improve the quality of both the top and bottom products!
Of course, there is another factor: whether the distribution of propane and propylene in your feed has changed. Specifically, you need to provide the test data
Generally, there should be no problem, as the specifications for both the top and bottom of the tower have been determined. The raw material data can be sent to the manufacturer of the existing internal components, so that they can determine whether those components meet the requirements or what modifications are needed. If switching to another manufacturer would result in too high costs
Agree with the opinion from the sixth floor. Let’s conduct a test first to see if it’s possible to improve the product purity.