Can’t the liquid level at the bottom of the deethanizer rise?
Thread Content
From the top outlet of the depropanizer, it enters the deethanizer! A circulating water cooler is installed at the top of the tower; the gas at the tower top is ethane non-condensable gas. When the pressure at the top of the tower is high, the non-condensable gas valve is opened to direct it to the fuel gas line! The bottom of the tower contains C3 and C4, which are sent to the propylene distillation tower. Currently, the liquid level at the bottom of the tower is high, exceeding 90%; the liquid level in the reflux tank is low, and the reflux pump has been turned off. Feeding is normal, and the bottom discharge of the tower is normal! The pressure at the top of the tower is 2.5 MP; under normal conditions, it does not exceed 2.4 MP. Measures have been taken: the reflux pump was turned off, the heat source at the bottom of the tower was reduced, and the pressure at the top of the tower was lowered first. Once the pressure at the top of the tower had decreased, vaporization was carried out gradually to build up a liquid level in the reflux tank! Start the reflux pump only after the liquid level in the reflux tank meets the requirements. Result: The top pressure increased, the liquid level in the reflux tank decreased, the liquid level at the bottom of the tower increased, so the reflux pump was turned off again!
Keep the tower pressure under control and stabilize the reboiler operation.
There may be other factors at the site that you haven’t taken into account, such as changes in the composition of the feed material, or whether the pressure control system is functioning properly, etc
The deethanizer itself operates in full reflux to remove the small amount of C2 components carried in the C3/C4 stream. First, conduct on-site inspections to confirm whether the liquid level in the return tank is accurate Have there been any changes to the process? Second, increase the feed temperature to the tower and the top temperature of the tower; raise the top temperature to above 60°C, and maintaining this pressure will suffice.
It’s possible that the gas isn’t condensing inside; the uncondensed gas at the top is preventing the removal of the material from the top of the tower. Try emptying it batch by batch
Just raise the temperature after cooling the water.
You didn’t describe the changes in the liquid level in the tower bottom. Is the liquid level in the tower bottom empty? 15 t/h enters and 18 t/h exits; if the liquid level in the tower bottom is normal, it means that the non-condensable gas at the top of the tower isn’t being removed. If non-condensable gases are not removed, the condenser cannot cool down – C3. Hope this helps you.
The reboiler at the bottom of the tower must be properly controlled, as it is responsible for supplying energy to the entire tower; without it, neither the pressure nor the reflux in the tower can be maintained. Additionally, the water cooler at the top of the tower should reduce the amount of cooling water used in order to keep the tower’s pressure stable.
The temperature at the bottom of your tower must be low; it seems that a vicious cycle has formed inside the tower.
I agree with the opinion from the 5th floor. In cases such as the first operation after maintenance, it is usually because the nitrogen used to purge the system has not been completely expelled; it’s likely that the non-condensable gases have not been fully removed. This can be verified by considering the actual situation
Take a sample from the cylinder and analyze the feed to the tower or the total feed, to determine how much C2 component is present and how much non-condensable gas there is.