Solvent regeneration conditions and lean liquid quality adjustment
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Our solvent regeneration is currently facing the following issues: 1. The quality of the depleted liquid remains substandard, with hydrogen sulfide levels staying at 2–4 g/l； 2. The glass plate level gauge in the on-site liquid collection tank at the extraction port of the reboiler in our regeneration tower never shows any liquid level; it is difficult to increase the temperature at the bottom of the tower, and steam cannot be supplied to the reboiler. Later, we installed two DN150 connections at the extraction port of the lean liquid from the regeneration tower, connecting them to the inlet pipelines of the two reboilers (the designed inlet diameter for the reboilers is DN250). As a result, although the temperature at the bottom of the tower can be increased by increasing the steam supply due to the higher circulation rate, the temperature of the acidic gas does not decrease. The temperature in the reflux tank can even reach around 90 degrees. Meanwhile, the quality of the lean liquid remains unsatisfactory. Additionally, the gas return line of our reboiler vibrates severely, which in turn causes vibrations in the pipeline used to transport the condensate from the regeneration condensate tank. Dear experts, what are the reasons for these two issues at the moment, and how should they be adjusted?
The last edit to this post was made by sdwfsgyykai on 2018-7-17 08:02. The first issue seems to be an obstruction in the inlet pipeline of the reboiler； The second issue seems to be that the trays have flipped over or too many floating valves have fallen off, resulting in no heat transfer between the gas and liquid phases. With such high environmental standards these days, if it’s not possible to transfer the dry gas and liquefied gas to other units for desulfurization, there is no other choice but to shut down the operation for maintenance. ——I have never encountered such a problem personally, and I wouldn’t dare to draw any conclusions regarding possible issues with the device; my suggestions may not be correct.
1. Is the processing load too high? 2. There might be a leak in the reboiler, in my opinion.
Where were the samples taken? Our underground waste amine liquid storage tanks feed into the lean liquid storage tanks; especially when replenishing the lean liquid tanks, the level of S in the dry gas increases； Another option is to consider amine solution regeneration to see the effects ；
I analyze that there might be debris in the regenerator (such as iron oxide, coke powder, etc.) blocking the inlet to the reboiler; as a result, only a small amount of liquid phase enters the reboiler, and no gas-liquid exchange takes place； Also, steam cannot get in; make sure the pressure in the condensate tank is not too high – it should not be higher than the steam pressure (sometimes there is non-condensable gas in the condensate tank). The vent on top of the condensate tank can be opened to release pressure. We have encountered this issue in our installations before.
We just had maintenance done, yet this kind of situation occurred right after we started working. There has been no liquid level at the semi-poor liquid extraction port of the regeneration tower, whereas there was a liquid level during the previous operating cycle.
You can try cutting open the lowest part of the reboiler inlet line to see if it’s blocked by some kind of black powder residue. We check this every time we conduct a major maintenance task, and in most cases more than half of the lines are blocked.
It’s similar to our situation; initially, it is suspected that the bottom tray has flipped over or that too many floating valves have fallen off, resulting in no heat exchange between the gas and liquid phases. As a result, the temperature at the inlet of the semi-lean liquid in the reboiler cannot be raised to 106°C. There is no increase in temperature inside the tower; the temperature in the middle part of the tower is 105°C, and the temperature at the top of the tower also cannot be increased to a higher level； When the temperature in the middle of the tower exceeds 110°C, the liquid phase cannot flow downward, and the pressure difference inside the tower increases.
We once encountered a blockage in the inlet pipeline of the reboiler at the bottom of the regeneration tower; we resolved this by introducing steam through the vent line to clear the blockage, after which production returned to normal