The issue of increasing the load on the distillation tower

During the process of reducing the load on the distillation tower, the adjustments to the relevant parameters are as follows: 1. Top pressure Generally speaking, as long as the composition of the material fed into the tower remains unchanged, the top pressure should remain constant; this can be controlled using the vapor control valve at the outlet of the top vapor condenser. However, in actual production, when the production load is reduced from 100% to 70%, it is possible that the opening degree of the gas-phase control valve becomes very small, resulting in an inability to maintain the pressure; in such cases, the pressure can only be controlled at its minimum level. 2. Temperature of the sensitive tray: When the production load is reduced from 100% to 70%, the load on each tray also decreases accordingly, and the composition of the material flowing through each tray changes as well (the proportion of heavier components in the liquid phase decreases). At this point, the temperature of the sensitive tray usually needs to be lowered slightly. If the heat load on the reboiler is increased appropriately or the amount of steam supplied is increased (such as when steam is added directly to the tower), the temperature of the sensitive plate can be maintained, but this will result in higher consumption. 3. Bottom temperature Under normal circumstances, as long as the composition of the material fed into the tower remains unchanged, the bottom temperature should also remain constant. For the same reason as in point 2, after the load is reduced, the composition of the material flowing to the bottom of the tower also changes accordingly (the concentration of heavier components in the liquid phase decreases), and at this time the temperature at the bottom of the tower usually needs to decrease slightly. 4. Recycle stream: When the production load decreases, the amount of recycle stream also needs to be reduced, with adjustments being made based on the principle of ensuring the concentration of the gas phase components in the vapor exiting at the top of the tower.

The pressure at the top of the tower must decrease, with the extent of this decrease determined by the phase equilibrium existing at the top of the tower. The temperature of the sensitive plate should also decrease, as this plate is associated with a higher proportion of light components in the mixture. Consequently, the temperature at the bottom of the tower decreases as well. The reflux ratio needs to increase in order to ensure that the purity of the light components at the top of the tower meets the required standards !

To reduce the production load, pressure, temperature, and reflux rate must be decreased accordingly to maintain equilibrium in the operation of the distillation tower.

1. Top pressure: It is related to the top temperature and composition; if the separation requirements and the top temperature remain unchanged, then the top pressure does not change much. 2. Sensing plate temperature: Under conditions where separation requires periodic adjustments, and when the situation remains stable, the concentration distribution throughout the tower remains essentially unchanged; as a result, the temperature of the sensing plate also does not change significantly. 3. Bottom temperature: It is related to the pressure and composition at the bottom of the tower. If the separation requirements remain unchanged, the liquid holdup in the tower decreases slightly due to reduced load, and the bottom pressure drops; therefore, its temperature can be appropriately reduced. 4. Recycle stream: When the production load decreases, if the separation requirements remain unchanged, the reflux ratio stays roughly the same; as a result, the amount of material recycled decreases. However, for a distillation column, there is a minimum liquid load; if the amount of reflux is less than this value, it will not work.

The production load is reduced from 100% to 70%; if the composition of the raw materials and the temperature remain unchanged, as well as the composition of the materials at the top and bottom of the tower, then the temperatures at these locations change only as a result of pressure changes. For trays with higher elasticity, the pressure decreases, and as a result, the temperatures at the top and bottom of the tower also decrease. In actual operation, the temperature of the sensitive plate changes little, and may decrease slightly. The backflow rate should also be reduced accordingly. However, for trays with limited operational flexibility, it is often necessary to sacrifice the reflux rate in order to achieve normal production (i.e., to ensure that the products at the top and bottom of the tower meet the required standards).