Seeking help with operational issues in the solvent regeneration tower
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Our company has a solvent regeneration unit with a design processing capacity of 29 t/h, which is primarily used to treat liquid hydrocarbons, dry gas desulfurization processes, and the rich solvents from units involved in gasoline hydrogenation; its processing capacity is around 15 t/h. The pressure at the top of the tower is 0.07 MPa, while it is 0.08 MPa at the bottom. The temperature at the top of the tower is around 110°C. Recently, our company started up catalytic reforming and diesel hydrogenation units, and the rich solvents from these units are also sent to the regeneration tower, raising the overall processing capacity to around 20 t/h. However, there are frequent fluctuations in the pressure within the solvent regeneration tower; it seems that acidic gases are escaping intermittently, with the pressure relief control valve sometimes opening wider and sometimes narrower, which leads to fluctuations in the temperature after cooling as well as the temperature at the top of the tower. To this day, the cause of these fluctuations has not been identified. @ylb913 @ylb913 If anyone among you knows the reason, please offer some guidance
This is usually caused by fluctuations in the amount of amine-rich liquid from the upstream process.
We have a raw material tank, and the feeding is controlled by a control valve, so the feed is quite steady
This is our DCS page. Due to the pressure fluctuations caused by PRC3306, the opening degree of the PV-3306B control valve is changing significantly, which results in fluctuations in the top temperature and the temperature after cooling. @ylb913
It seems to flow in pulses, and the temperature at the top of the tower also fluctuates. What causes this?
Feeding, discharging, and pressure relief are all manually controlled; you can check our DCS display
This post was last edited by ylb913 on 2016-11-9 at 20:32. I think I know the reason now: the pipeline that carries the acidic gas to the sulfur treatment unit has a liquid seal (there may be multiple U-tubes). When temperatures were high earlier, there was little or no condensate, so it didn’t cause any problems. Recently, as temperatures dropped, more condensate formed, creating a liquid seal. With this seal in place, pressure builds up first, causing the flow rate of acidic gas to decrease; then the seal is broken, and the flow rate of acidic gas increases, and this cycle repeats itself... Which is what results in intermittent flows of gas. The solution is to put steam tracing in the acidic gas pipeline in use and verify the effectiveness of the tracing (drainage).
We have kept the heat tracing in use, and the heat tracing wires are hot. I also checked the pressure relief pipes, and they are hot as well. I’m from Shandong; the temperatures there have been above zero recently. Is the weather’s impact that significant?
This should refer to the curves showing the control process and effects of the relevant control valves, rather than the DCS flow diagram.
Our regeneration tower is equipped with 28 trays, and the pressure difference between the top and bottom is currently only 0.01 MPa. Is this pressure difference normal?