Need help with distillation, urgently! ! ! ! ! !

It’s purely a theoretical question; I’m just taking a spot to see the answer. . . The definition and principles of distillation; it is recommended that the original poster review this. Furthermore, you should add your requirements for the product as well as the testing methods. It seems like this is a process similar to distillation in a flask. The original poster didn’t specify the number of tray levels, so it’s likely that they have conducted simulations for this tower. If simulations were done, then the temperature at the bottom of the tower should be possible to determine through those simulations. Once the designed reactor temperature is reached, the methanol content in the tower reactor liquid is tested; if it meets the specifications, the product can be discharged ； Furthermore, it’s unclear how the original poster intends to achieve balance in this tower. Moreover, the main purpose of this tower is to ensure that the methanol distilled from the top of the tower meets the required standards; so why does the original poster ask when the material at the bottom of the tower will be discharged? Is it possible that the material at the bottom of the tower remains there if there is an imbalance? . . In production, it’s certainly not the case that materials are released only after they meet the quality standards.

You just need to control the temperature of the distillation column to the desired distillation temperature. This isn’t a matter of control per se; rather, you should calculate the temperature at which the components reach separation equilibrium, and once that temperature is achieved, the product can be collected. Of course, when there is a discrepancy between the calculated value and the actual temperature, the temperature should be adjusted accordingly to meet the separation requirements； Distillation can also be pressure-controlled, but I assume you are in a laboratory; it’s not clear whether pressure control is feasible there – that is, controlling the pressure at the top of the tower so that material begins to be discharged when the pressure reaches a certain calculated value. TO Floor 2: This is how pressure is maintained in industrial processes. In the case of pressure-driven distillation, the temperature increase is achieved through heating at the bottom of the tower; as the temperature rises, the pressure at the top of the tower gradually increases, and pressure is maintained until the appropriate level is reached, after which the product is discharged. Last edited by terry921 on 2008-1-28 15:18.]

I’m new to this area, so there’s still a lot I don’t understand. Before the experiment, I did indeed conduct a simulation first; the experiment involved continuous distillation. By balance, I mean that under balanced conditions, I feed at a flow rate of 10 ml per minute; the product at the top of the tower is methanol with a purity of 98%, at a flow rate of 6 ml/min, while the stream coming out of the bottom of the tower is a mixture containing water and trace amounts of n-propanol along with methanol, at a flow rate of 4 ml/min. For this to happen, the composition of the liquid in the bottom of the tower must be the same as that of the stream exiting from there. The test column bottom tank is a 4L vessel; before the test, nearly 4L of the reactant solution is added to this tank. It is necessary to adjust the composition of the liquid in the tank to an equilibrium state, as the material coming out of the tank serves as the feed stream for the next column – otherwise, it will have a significant impact on the separation process.

“During the actual experiment, I first need to add a certain amount of feed liquid to the reactor bottom. Since the methanol content in this feed liquid is relatively high, it is necessary to stabilize the conditions at the reactor bottom (so that the composition of the material exiting the reactor bottom corresponds to the equilibrium condition) before material can be discharged from either the top or the bottom of the reactor. ” It means that the discharge should occur simultaneously, right? There isn’t much emphasis on the composition at the bottom of the tower. In a pressurized tower, when the feed composition and temperature remain constant, the composition at the bottom of the tower changes under different pressures. Therefore, I believe there is a direct relationship between overall pressure and the composition at the bottom of the tower. When the separation requirements aren’t met, it’s not necessary to discharge material; whether to discharge or not isn’t a technical issue but rather a matter of operation (you can discharge material, but what comes out doesn’t meet the separation requirements, as intermediate tanks are used in production). Of course, during this process of increasing temperature and pressure, it’s necessary to control the feed

It is possible to determine whether the requirements are met by considering temperature, pressure, and a small amount of output. Because in theory, once the temperature and pressure are determined, the components are also determined. But it's not allowed if there is flooding.

I haven’t worked with the column process in the laboratory, but in production, you wouldn’t operate it in that way. Material is fed into the empty tower; once a liquid level is detected at the bottom of the tower, the bottom reboiler and the top condenser are put into use. Balance is gradually established during the feeding process, and the feeding rate should not be too high at first to prevent sudden accumulation of liquid in the tower bottom. It has been mentioned in previous production discussions that there is a feed-back line, and its purpose is to send back any unsuitable material to the feed tank. In the early stages of operation, the tower operates in an internal circulation mode; once a liquid level is established in the tower bottom, the liquid should be sent out (at this point, the methanol content is certainly not up to standard). Once the temperature in the tower bottom reaches the appropriate level, the inflow and outflow rates should be balanced, at which point the liquid level in the tower bottom should be relatively stable. The liquid sent out can then be returned to the feed or processed separately. Once the temperature of the reactor is at the desired level, the pressure also gradually reaches the required value. At this point, there is essentially full reflux at the top of the tower. When the temperature at the top of the tower reaches the design value, it is possible to consider sending the product out for use (at this stage the product is generally of satisfactory quality, as both pressure and temperature are close to the design values, and its composition should remain constant; however, testing is still necessary). Then, gradually increase the feed rate (which must initially be lower than the designed value), raise the reactor temperature, increase the flow of circulating water, and reduce the reflux rate (but it is necessary to maintain the top temperature constant). This process involves adjusting the operation of the tower to reach the design values. Once all parameters are at the design values and the operation is stable, and sampling tests show satisfactory results, it indicates that the tower is operating properly. . . During the start-up process, either the top or the bottom of the tower must be used to remove the defective products first; it’s not possible for both outlets to produce qualified products at the same time. The load on the tower is also increased gradually, and it cannot reach its full level from the very beginning. I’m not sure if what I say will be helpful to you; these are just my own opinions. If they’re incorrect, please point them out so we can learn from each other.

I hear that the benefits discussed by everyone are rather meager! ! !

The explanation is very detailed, and there’s a lot of practical experience – it seems like this person is an expert in this field. I suddenly thought of a question: are start-up lines provided at the tower top, the tower bottom, and the side lines? Where is the end of the driving line connected to? Could you be more specific, please? Thank you! :handshake