Effect of the upper return column of the catalytic fractionation tower on the tower bottom temperature

The outlet of the oil slurry pump is divided into three channels: Return up, return down, throw out. If any one path is moved, the other two paths will be affected. For example: As the upper return increases, the temperature at the bottom of the tower rises.

They should all go down. The lower return tower of the fractionating tower is used to adjust the temperature, and the upper return tower is used to adjust the liquid level. Also, can the amount of return to the tower be kept unchanged and the amount of return to the tower increase?

1. The upper return tower is generally used to lower the temperature of oil and gas. . . If other conditions remain unchanged and the amount of liquid returned to the tower is increased, the amount of liquid falling to the bottom of the tower will increase in a short period of time, but the temperature will be high, so the initial temperature at the bottom of the tower will rise. . . The amount of return to the tower must be adjusted at a constant value combined with the liquid level at the bottom of the tower to keep the liquid level and temperature at the bottom of the tower constant. . . 2. If the liquid level remains unchanged while adjusting the external swing, the temperature must be rising. . . To reduce the temperature at the bottom of the tower, we must ensure that the oil and gas temperature at the upper return tower pressure is below 395°C, and then control it at around 365°C through the lower return tower, and dump it when the liquid level rises to ensure the stability of the parameters at the bottom of the fractionation tower. . . Ha ha. . . :lol

　　It is not advisable to adjust the total circulation volume to adjust the tower bottom temperature while ensuring that the return volume remains unchanged, and it is easy to cause changes in the heat taken by the entire fractionation system. 　　Generally, under the condition that the total circulation volume remains unchanged, the upper and lower return volumes are reasonably distributed to ensure the washing effect of oil and gas, and the tower bottom temperature is controlled by adjusting the lower return volume.

What is cooled in the return tower is oil and gas. . . Therefore, if the amount is large, more liquid will reach the bottom of the tower. If you do not adjust the amount of liquid returned to the tower at this time, the liquid level at the bottom of the tower will rise. . . That temperature will definitely rise. . . Either increase the external throw to keep the oil slurry level constant, or increase the return tower temperature to suppress the tower bottom temperature, and then increase the external throw. . . . The temperature at the bottom of the tower will gradually decrease only after the oil and gas temperature in the entire upper return area drops and stabilizes. The whole process will first rise and then fall. . . Support the 4th floor's point of view. . . :lol

1. When the amount of return to the tower is increased, the temperature at the bottom of the fractionation tower will definitely rise. Increasing the amount of upper return to the tower will definitely affect the amount of lower return to the tower. Even if the amount of lower return to the tower does not decrease, because the total heat is constant, after increasing the amount of upper return to the tower, the heat "washed" by the upper return to the tower will increase, and the bottom temperature of the fractionation tower will definitely increase. 2. The external rejection volume is large and the temperature at the bottom of the tower decreases. ； The amount of external rejection is small and the temperature at the bottom of the tower is high. Because the external rejection is a separate external rejection oil slurry pump, it is also extracted from the bottom of the fractionation tower and sent out after cooling. When the delivery volume is large, more heat is taken away from the bottom of the tower and the temperature decreases.

As long as the circulation volume at the bottom of the tower increases, the temperature at the bottom of the tower will definitely drop. So the two situations mentioned by the poster have the same result - the temperature at the bottom of the tower drops.

The temperature may rise when you first start adjusting, but then it will drop over time.

Through actual operation, it can be concluded that when the upper return tower is opened larger, due to the short heat exchange time between the oil slurry and the raw material, the temperature of the return tower will rise, and the bottom temperature of the fractionation tower will also rise at the same time.； In addition, due to the increase in the flow rate back to the upper tower, according to the principle of material balance, the flow rate back to the lower tower will inevitably decrease, even if the control valve position is not adjusted. An important function of the lower return tower is to adjust the temperature at the bottom of the fractionation tower. Reducing the flow rate will also cause the temperature at the bottom of the fractionation tower to rise.

1. While keeping the amount of lower return to the tower unchanged, increasing the amount of upper return to the tower will cause the liquid level at the bottom of the fractionation tower to rise. Since the temperature thermocouple at the bottom of the fractionation tower is below the liquid level at the bottom of the fractionation tower, the thickness of the liquid layer between the thermocouple and the oil and gas will increase and the temperature will decrease. 2. Control the liquid level at the bottom of the tower through external rejection, so as to increase the amount of upper return to the tower while maintaining the same amount of lower return to the tower, which will increase the amount of heat taken by the oil slurry and reduce the temperature at the bottom of the tower. To sum up: The temperature has dropped! In addition, I personally think that there is no need to pay attention to changes at a certain moment after increasing the circulation volume. It is best to wait until the gas-liquid balance is re-established before observing. Hope this helps.