I earnestly ask those experts in distillation operations to help – I’ve been troubled by this for a long time! Kneel in gratitude

The following is for reference only: it depends on the extent to which your components become lighter; if they are too light, process adjustments will not be effective. Lightening the load increases the burden on the stripping section; it is appropriate to increase the heat input to the bottom of the tower and to reduce the reflux rate accordingly. Some towers are designed with two or three feed inlets; if available, these can be adjusted to allow feeding from a higher position.

Increase the heating capacity at the bottom of the tower to raise the bottom temperature and the temperature of the sensitive plate, thereby preventing issues resulting from an excess of light components at the tower bottom; there are no major problems at the tower top, as long as the top temperature does not exceed the normal acceptable levels. If that doesn’t work, follow the suggestion above to raise the feeding layer. The specific temperature increase depends on the purity of the sample and the extent of changes in the feed components; this is a matter of operational experience.

It can be considered in terms of a distillation section and a stripping section. Since the conditions you’ve specified are constant feed rate and constant tower pressure, with only the composition becoming lighter, increasing the heat supply at the bottom of the tower is sufficient; there’s no need to raise the bottom temperature. It’s enough to keep the temperature of the sensitive plate within the specified range, as the tower pressure remaining constant prevents the light components from escaping. There are more light components in the distillation section, so the ratio of light to heavy components on each tray is higher than the ratio with normal feeding. Therefore, the product at the top of the tower can easily meet the standards when the reflux remains unchanged. Because you need to keep the tower pressure constant, you require more cooling energy.

Thank you all for your answers; I’ve learned a lot

As the light components increase, the temperature distribution throughout the tower decreases. Operating under the original conditions will cause the light components to move downward, resulting in the product at the bottom of the tower containing an unacceptable amount of light components; this is why it is necessary to increase the reboiling. At this point, the draw rates at the top and bottom of the tower should be adjusted appropriately, especially those at the top, so that the light components do not accumulate inside the tower. Otherwise, no amount of reboiling will help. The adjustment is mainly in the reboiler. As for changing the feed inlet, it is hardly feasible in actual production, unless the feed inlet is designed to allow for a disturbance-free switch.

Based on the production operations of the units in your facility, as the properties of the raw materials become lighter, production is carried out at lower temperatures and with reduced volumes. The outlet temperature of the heating furnace is adjusted, as well as the temperature at the outlet where the side stream is taken off, in order to prevent an increase in the pressure at the top of the tower and to raise the temperature there. Adjust the production by adjusting the extraction amount from each side line.

The most direct approach is to increase the steam volume at the bottom of the tower, raise the sensitivity temperature to prevent light components from entering that area. Raising the temperature and pressure in the tower will lead to an increase in the amount of product taken from the top of the tower; this increases cooling requirements, which in turn requires a reduction in flow rates, while more product needs to be sent out from the top of the tower. As for changing the location of the feed inlet, this is rare; the feed inlet is only moved if the increase in the light component amount becomes uncontrollable