Heat regeneration tower in low-temperature methanol washing

First, it should be clear that what the original poster is referring to is Linde’s low-temperature methanol washing process (Dalian University of Technology is not very familiar with this; it could also be their own technology), which differs from the LuChi low-temperature methanol washing process. Furthermore, calling them “left” and “right” isn’t very accurate; what seems left when looking from the front becomes right when looking from behind, haha. It should be the ‘methanol side of the extraction cycle’ or the ‘reboiler side’ – that makes more sense! This requires consideration in conjunction with the pipelines at the bottom of the tower. The function of the baffle is to separate the methanol at the bottom; the water content of these two streams of methanol is different, and this is how Linde controls the water content of methanol in the low-temperature methanol washing cycle. From the side where methanol is extracted in the extraction cycle, a branch of the methanol flows together with the methanol from the reboiler side into the reboiler of the regeneration tower, where the methanol is vaporized to increase its purity. The reboiler can be considered as a theoretical plate to reduce the water content in the circulating methanol; of course, the Linde design allows for flexible control of the parameters related to the circulating methanol by adjusting the flow rate of the branches. This post was last edited by Tianya Langji on 2009-1-3 21:14]

My opinion differs from that of the person above. If it’s only the water content that varies, then why is part of the \"methanol with high water content\" you mentioned pumped through a filter and then into the methanol circulation tank for reuse? Isn’t that contradictory? Perhaps you should consider using the cleanliness of the solution as a criterion for making such distinctions. This is what I can see from their process, and I’m also thinking about the advantages and disadvantages of such a design.

I’ve been learning knowledge in this field, and now I come here to show off. Methanol boils on the reboiler side, generating methanol vapor that strips the methanol from the upper tray, thus functioning as one theoretical tray. After being stripped, the methanol on the upper tray sees an improvement in its quality; it then flows down through the downcomer to the recovery side. On the recovery side, part of this methanol goes to the reboiler side after passing through a pump, where it is heated, resulting in an increase in water content (organic decomposition may also occur simultaneously). This methanol is then sent to a methanol/water separation tower for separation. The advantage of this design is that it enables the production of both high-quality methanol and methanol with a high water content; it functions like a distillation tower, with the product outlet corresponding to the top of the tower and the reboiler side corresponding to the bottom of the tower, resulting in better performance compared to ordinary reboilers.

In the regeneration tower, does the hydrogen sulfide content in methanol need to be considered?

I think it makes sense that the water content varies, as well as the degree of dirtiness on both sides of the material! The analysis upstairs is even more incisive!

In low-temperature methanol washing, there is a baffle below the thermal regeneration tower – what is its function? Why is the downcomer on the left and not on the right? We asked Lind’s designers about this issue, and they said that they designed it in this way mainly to account for the tendency of mechanical impurities such as iron sulfide to accumulate at the bottom of the C2404; such a design allows for the removal of these mechanical impurities through a circulation-based bypass filtration system.

Upstairs, I’d like to ask: since all the poor-quality methanol goes through the filter, why is it necessary to add a baffle as well? Why does some of it pass through while the other part doesn’t?

Regarding that question from upstairs, I hope 7# can explain it to everyone.

Please think carefully: if you can accomplish something for one yuan, why would you spend ten yuan to do it? I think it’s mainly to save on equipment investment and operating costs. Sidewashing is used in many chemical processing units, such as in circulating water treatment and the sludge and water discharge from the SHELL gasification 1400 unit.

Where is iron sulfide mainly produced? Is it generated on the reboiler side?