Factors influencing the distillation operation of the rectification column

1. The influence of feed heat on distillation operations

The different thermal conditions of the feed make the flow rate of the rising steam and the falling liquid in the rectification section and the distillation section in the distillation column very different

2. The impact of changes in feed composition on distillation operations

1. If the concentration of recombinant components in the feed increases, the load of the distillation section of the distillation column increases. For the column with the fixed number of plates in the distillation section, the recombinant part will be brought to the top of the column, so that the quality of the top product is unqualified.

2. If the concentration of light components in the feed increases, the load of the distillation section increases. For the column with the fixed number of plates in the distillation section, the light components of the distillation section will not be evaporated, and the loss of the light components in the kettle liquid will increase.

3. At the same time, the change of feed composition will also cause changes in the material balance and process conditions of the whole column of the distillation tower. When the components become lighter, the top fraction increases, and the discharge of the kettle decreases. At the same time, the temperature of the whole tower decreases and the tower pressure increases. The components become heavier, and the opposite is true.

When the feed composition changes, the following measures can be taken:

(1) When the composition of the material port is improved, the feed port is changed downward; When the composition becomes lighter, the inlet is changed upward.

(2) Change the reflux ratio When the composition becomes heavier, increase the reflux ratio; When the composition becomes lighter, the reflux ratio is reduced.

(3) Adjust the refrigerant and heat dose According to the change of composition, adjust the refrigerant and heat dose of the tower kettle of the tower top condenser accordingly to maintain the quality of the top and bottom of the tower unchanged.

Three: the influence of feed volume on distillation operation

The relationship between the feed volume and the production volume: The size of the tower feed volume and the size of the top of the tower have a corresponding relationship, that is, the feed amount increases, and the production volume should increase.

* For the tower with internal reflux, when the feed volume remains the same, if the production volume at the top of the tower increases, the reflux ratio will inevitably decrease, resulting in a decrease in the amount of reflux liquid on each plate, poor gas-liquid contact, and a decrease in mass transfer efficiency; At the same time, the operating pressure will also decrease, and the gas-liquid phase composition on each plate will change. As a result, the recombinant content was brought to the top of the tower, and the quality of the product at the top of the tower was not up to standard.

*In the operation of forced reflux, if the feed amount remains unchanged and the production volume at the top of the tower suddenly increases, it is easy to cause the reflux tank to be evacuated. As soon as the reflux fluid is interrupted, the top temperature increases, which also affects the quality of the top product.

If the feed amount increases, but the production amount at the top of the tower remains unchanged, the consequence is that the reflux ratio increases, the material in the tower increases, the rising steam velocity increases, and the pressure difference between the top of the tower and the tower kettle increases, which will cause liquid flooding in serious cases.

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