Discussion on the startup plan for multi-column continuous distillation
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This post was last edited by Wille on 2010-6-3 at 17:06. My double-column continuous distillation system consists of two columns; during operation, a certain amount of material is added to the reactor of Column 1, with full reflux applied. Once the conditions in the column become similar to those under normal operating conditions, full reflux is stopped, and feed is added gradually in small amounts, while the reflux ratio is adjusted, with the product being collected from the top of the column. At the same time, the material in the reactor of Tower 1 is transferred to the reactor of Tower 2 until a certain amount is reached. At this point, Tower 1 also stops feeding, and together with Tower 2 it enters full reflux mode (Note: At this time Tower 1 is in equilibrium; this is simply to take into account that if continuous distillation were to continue, the product from the bottom of Tower 1 could not be fed into Tower 2, as Tower 2 is operating in full reflux mode). To save money, we did not add an additional material tank between Tower 1 and Tower 2; as a result, the bottom product from Tower 1 has nowhere to go). Stop full reflux once the conditions in the tower become similar to those under normal operation. Start feeding slowly in small amounts until the feed rate required by the process is reached, and gradually adjust the reflux ratio to the value specified by the process. When the top of the tower temperature approaches the specified value, the product is found to be Qualified (through sampling analysis), and production of the product from the tower top begins. Could an experienced friend help me check whether my driving approach is feasible? If you have a better solution, please share it; I would be very grateful.
While driving the machine, feed into Tower 1 to establish a liquid level and carry out thermal cycling, controlling pressure and temperature to ensure stable distillation at the tower top. Maintain the feed to Tower 1 and feed to Tower 2; stop once the liquid level is established, and a thermal cycle is established in Tower 2. The tower bottom and tower top of Tower 2 maintain reflux and feed back to the preceding unit. After stabilization, gradually increase the feed rate
From the perspective of system stability, buffer tanks should be included in between; however, from a cost standpoint, this is not advantageous for operation
Is it necessary to use a buffer tube? It should be sufficient to design a return line from the reactor liquid of Tower 2 to Tower 1. This allows for the control of the liquid level in Tower 2, while also returning the components from Tower 1 to Tower 2.
In the case of extractive distillation, it is possible to fill both columns with oil and solvent simultaneously. Raise the temperature simultaneously.
In our plant, the operation mode involves 4 towers in cascade. When discussing how to start up the system, two options were considered: first start up Tower 1, wait for full reflux to be established, and then proceed with full reflux in Towers 1 and 2, one after another. . . . . Another scenario is to first achieve full reflux and stability in towers 1, 2, 3, 4, and 5 before connecting them together. In the end, the first option is still the preferred choice; it depends on the specific conditions of your own operation
#cz.liuyan Thank you, could you share the operating procedures?
Reply to 8# Wille: This process is still related to your specific operating conditions; it can’t be generalized. 1. First, you need to check your utility systems to ensure that water and electricity are functioning properly; you can start by operating your circulating water system and vacuum system. 2. Check whether your process pipelines and valve switches are in proper condition. 3. The machine can only be started after completing the checks in steps 2 above. . As for driving the process, feed is supplied to Tower 1 with full reflux; once stability is achieved, feed is sent to Tower 2. It’s actually quite simple in theory, but the actual operation is quite complicated; each case needs to be analyzed on its own.
For the sequential operation of several columns, it is necessary that the feed supplied to the subsequent columns by the preceding column meets the required standards and is within its processing capacity. Therefore, I agree that full reflux in Column 1 should be ensured before feeding it to Column 2, and this process should be repeated sequentially, so as to guarantee that the products from each column meet the specified standards!
Hehe, the three-column distillation process here is exactly the same as the method used by the original poster for driving, but the operating procedures state that all three columns should be operated simultaneously.