How can feeding be carried out during the start-up of 3-column continuous distillation to obtain qualified product as quickly as possible?
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The feed solution consists of four main components, all of which are liquid organic substances. Their boiling points, from lowest to highest, are: a light component, b product, c by-product, and d heavy component. The process flow involves continuous distillation in 3 columns: the light component a is obtained from the top of column 1, product b is obtained from the top of column 2, by-product c is obtained from the top of column 3, and the heavy component d is obtained from the bottom of column 3. The method as I understand it is: 1) Heat the feed to Tower 1 until the reactor temperature, top temperature, and reflux rate reach the specified values; then establish full reflux and stop feeding. 2) Discharge is permitted only after the component analysis of the top and bottom streams of Tower 1 shows satisfactory results; simultaneously, material is discharged to Tower 2 and feeding is resumed. 3) The operation of 2 towers is the same as that of 1 tower. Or should feeding be continued to the subsequent 2nd and 3rd towers without waiting for the top and bottom of Tower 1 to meet the requirements?
Your reasoning is correct; the product can only be discharged once the bottom and top of the tower meet the required standards. There is another method I often use: set the liquid level in Tower 1 at 30% and then start heating, while reducing the feed rate. When light components emerge at the top of the tower, adjust the feed rate based on the increase or decrease in the liquid level at the bottom of the tower, while simultaneously operating in full reflux mode.
Feeding can be done simultaneously, but keep in mind that it’s easy to separate the light components from the heavy ones; just increase the temperature and that’s all； But don’t put the heavy ones inside the light ones, as it will be difficult to carry them away, and it will take a long time for the products to meet the standards. You can feed several towers simultaneously to raise the temperature, then cycle through towers 1/2/3 (with 3 returning to 1) while raising the temperature; cutting off the total feed will also cut off the feed to tower 1. Once the temperature has risen sufficiently (so that there is no a in the reactor of Tower 1), feed material into Tower 1 gradually, while stopping the recirculation operation in Towers 2 and 3; increase the temperature to bring the conditions in the reactors to the required level. Meanwhile, transfer the material from the reactor of Tower 1 to Tower 2, and once the conditions in Tower 2’s reactor are satisfactory, transfer it to Tower 3. . . When the top product is substandard, it is placed in the substandard tank – this is the fastest way.
Obviously the first type of spreading; otherwise how can it be considered qualified?
This is the fastest way to do it: set failure thresholds for both the top and bottom of the 123 towers, allowing the material to return to the large tank. During operation, as long as the conditions at the bottom of the tower are satisfactory, the process can proceed directly; the conditions at the bottom of the tower are generally influenced only by temperature and pressure, making it easier for them to meet the requirements. In this way, a circulation system can be established quickly for the bottoms of the three towers. For the tops of the towers, reflux control is used to establish single-tower circulation; once the conditions are satisfactory, the process moves to the final product stage, while if the conditions are not satisfactory, the material is sent back to the large tank via the failure pathway or full reflux is applied
There is an intermediate tank between 12 and 23; when the system is stable, reducing the feed rate lowers the liquid level in this intermediate tank. When the system is unstable, the feed rate is reduced or full reflux is used, so that the changes in the liquid level of the intermediate tank can provide a buffer period.