Distillation column problems

Is the top temperature high? How’s the pressure?

1. The composition of the raw materials has changed; it is necessary to adjust the operating parameters promptly. 2. The temperature at the bottom of the tower is high, causing the light components to be extracted too deeply. 3. The reflux rate is low, resulting in a high temperature at the top of the tower. 4. There is an imbalance between the gas and liquid phases inside the tower. 5. The analytical results are incorrect; more samples should be analyzed! It is recommended to rule them out one by one!

If, after ruling out errors in the analytical tests, there is an excess of heavy components at the tower top, it is possible to increase the reflux rate; by observing the changes in the temperatures at the tower top and on the sensitive plate, it can be determined whether the amount of heavy components at the tower top has decreased. Reasons for the high proportion of heavy components in the product at the top of the tower: 1. An increase in the amount of heavy components in the feed material; 2. Insufficient gas-liquid contact in the distillation tower, unstable operation, and changes in process parameters such as the reflux ratio and the heat load on the reboiler

The temperature at the bottom of the tower is high, and the light components are extracted too deeply. Could you please explain this? I’m not quite understanding it

If products are produced at the bottom of the tower rather than being recycled back, a high temperature at the tower bottom means that the components with lower temperatures will be drawn out to greater depths, resulting in heavier fractions at the bottom of the tower. By \"light components\" I mean those components that are lighter compared to those found further down the tower; hence, these light components are drawn out to greater depths

First, we need to figure out whether there was any problem with this tower in separating these components originally If there were no problems originally, then the issue of whether the tower itself possesses the necessary separation capacity (including the number of trays or the packing height) can be ruled out; what remains are the operational factors. In terms of operation, if the overhead Reconstituted components level is too high, it will definitely be reflected in an elevated top temperature. There are two reasons: one is an insufficient reflux ratio, in which case the reflux ratio should be increased ； Another reason is that the temperature of the reactor is too high, which leads to a loss of balance in the tower. It is necessary to lower the temperature of the reactor; first maintain full reflux operation, and then proceed with distillation once the top temperature drops to an appropriate level.

{:3_65:} One reason is changes in process parameters, and the other is equipment failures. Process parameter issues usually include insufficient reflux, excessively high bottom temperature, a decrease in the amount of light components in the feed, or too high feed temperature. As for equipment problems, these often involve clogged or damaged distributors, as well as leakage from the tray layers or collapse or blockage of the packing. Blockages don’t occur very frequently; if they do happen, the pressure drop will be significant. The most common issue is inaccurate readings from the instruments, so it’s best to compare them with previous process parameters.

1. Whether the unit is balanced: Check the vacuum level; check the temperature of the sensitive plate; examine the heat exchange efficiency of the condenser; check the supply volume and inlet temperature of the cooling water. 2. Equipment: Verify that the packing in the distillation tower is in proper condition, including any caking in the overheating section, as well as issues related to channeling or wall flow in the distillation section. 3. Another factor to consider is the relationship between vacuum and temperature.