Objections regarding the start-up of methanol distillation

After all the parameters of the pre-tower meet the requirements using this method, the feed pump of the pressure tower is started to establish a liquid level in the pressure tower

Open the other towers once the pre-tower is almost ready! Such products are of high quality!

First, ensure the pre-tower meets the requirements before starting the pressure tower, so that the product is more likely to meet the standards.

We first start the feed pump of the pressure tower; if steam is introduced to one of the towers first, the pump is prone to cavitation if not controlled properly. Secondly, for the product tower, it usually takes three hours to meet the standards. We usually first set the liquid level for the first three towers; for one of the towers, the steam is generally allowed to flow only through a small bypass, at a rate of around 2000. After that, increase the amount in the pressure tower and add steam

In my opinion, there is no dispute regarding the start-up of distillation processes as mentioned above. Here are my personal views: if starting up after a short shutdown, both the tower and the reflux tank have liquid levels, so steam can be introduced simultaneously, but at a slow rate. This allows all sections of the tower to reach full reflux first; once the desired conditions are achieved, feeding can begin. This is equivalent to increasing the load, and wouldn’t that make the process faster? The reason for starting with one tower first is to prevent any light components from reaching the second tower. If that were to happen, introducing steam into the second tower would cause its pressure to rise rapidly. However, there’s no need to worry; once the steam supply is stopped, the pressure will drop on its own. You can introduce steam gradually in order to remove those light components. First, start with one tower, and also adjust the water addition amount; as everyone knows, the water addition amount is an important parameter in distillation as well. Adjusting one tower first has many advantages. Moreover, starting distillation with one tower doesn’t take much time; generally, adjusting one tower first is quick and requires no effort at all. Next is the startup of Tower 2 and Tower 3. I believe there is no fixed pattern for starting distillation processes; it can be done in whatever order is convenient. Sometimes these steps can be carried out simultaneously. If the liquid levels are appropriate after stopping the process, in order to save time, the reboilers of Tower 1 and Tower 2 can be activated at the same time. As long as there is liquid in the reflux tank, the reflux pump can also be started; if that’s not possible, let the pump run on its own with the reflux valve opened. In this case, as long as the temperature of the towers rises or the liquid level in the reflux tank increases, simply open the reflux valve to make adjustments – there’s no fixed procedure. If you are experienced in operating such processes, do you really need to follow the steps outlined in the operation manual? Don’t get it wrong about what I’m saying here! It’s not that the procedure isn’t to be followed; it’s just that some of the steps in the procedure can be carried out simultaneously. Once you become proficient, as long as you drive safely and it also saves time, that’s the goal. Don’t be too rigid. The above are purely my personal opinions; I hope everyone can share their valuable suggestions, and I am willing to learn from them with an open mind. Yes

When starting up the distillation process in our plant, we first establish the liquid levels in the three towers. The process for doing this, in the case of restarting after a long period of shutdown during which none of the towers had any liquid level, is as follows: 1. First, start the feed pump for the pre-tower; once the liquid level in this tower reaches 50% or more, proceed to the next step. 2. Start the feed pump for the pressure tower to establish a liquid level there. 3. Open the valve connecting to the atmospheric tower; by opening the feed valve for the pressure tower, a liquid level can be established in that tower as well. Once the level reaches 50% or more, close the valve leading to the atmospheric tower. 4. At this point, open the large 3KG steam valve for the pre-tower gradually, and at the same time open the large 19KG steam valve for the reboiler in the pressure tower, in order to establish liquid levels in the reflux tanks of both towers. Once the liquid levels reach 50% or more (to prevent the reflux pump from running dry due to too low a liquid level), start the reflux pump to establish reflux.

First, establish the liquid level; start the pressure tower pump once the liquid level reaches 50%

Reply to 7# Ye Yu Han: Did the feed pump stop operating at any point during that process? Should the valve be set to a very low opening degree?

In vacuum distillation, should the vacuum be established first or the liquid level?

It’s fine to start with the pre-tower first. Poor pretreatment in the tower affects product quality