When starting the machine after a long shutdown, if the self-liquid-sealing valve is not closed, what changes will occur in the system during the discharge of material from the synthesis tower? (CO2 stripping method)
Thread Content
When starting the machine after a long shutdown, if the self-liquid-sealing valve is not closed, what changes will occur in the system during the discharge of material from the synthesis tower? How to tell?
The steam consumption of the stripping tower will definitely increase; since methylammonium is not fed into the tower, it is decomposed there after being converted into urea, and the load on the circulation system also increases significantly.
:victory: Agree with this view! In a high-pressure system, it’s as if there is no synthesis tower; as a result, the conversion rate and the concentration of urea produced drop significantly. A large amount of ammonium methoxide ends up in the gas tower, leading to a sharp increase in gas consumption. The temperature of the liquid output keeps rising, and large amounts of ammonia and CO2 are sent to distillation, evaporation, hydrolysis, and other units, which can no longer function. Eventually, this leads to severe overpressure conditions, resulting in environmental disasters – an unimaginable situation! This post was last edited by ymtuegj12 on 2009-2-9 19:17.]
When starting the machine after a long shutdown, if the self-liquid sealing valve is not closed, no liquid seal will be formed in the discharge pipe of the synthesis tower; this is when CO2 backflow is most likely to occur. The specific phenomenon is: the pressure in the high-pressure chamber rises rapidly ； The high-pressure condenser has no reactive load ； The temperature on the liquid outlet pipe of the urine tower (near the temperature of the stripping tower) should increase, to a level slightly higher than the temperature of CO2 ； The stripping tower does not have liquid level readings, etc. The main phenomenon is a rapid increase in pressure, which is extremely dangerous! ! !
If the liquid seal valve is not closed, it will only cause some of the liquid to take a short circuit, resulting in an increased load on the stripping tower and a rise in system pressure
If the self-sealing valve is not closed after a long shutdown when the plant is restarted, then no liquid seal is established, which can easily lead to backflow of carbon dioxide. As a result, the gas generation rate in the low-pressure drum decreases, the pressure in the high-pressure system rises rapidly, the steam consumption in the stripping tower increases, and the temperature of the overflow pipe rises!
On this point, there is no doubt: it is completely impossible to produce it. We have encountered similar situations before; back then, the self-liquid-sealing valve was not fully closed, and the main discharge valve was also not closed. As a result, the circulation system could not function and remained in a venting mode, while it was also impossible to establish a vacuum in the evaporation system! ! ! This post was last edited by qiwu9981 on 2009-2-13 10:36.]
As for the question raised below, I personally believe that such a situation will not occur. At least in our factory, we use self-liquid seals instead of external liquid seals. The outlet control valve of the synthesis tower suffers from severe internal leakage, and external liquid seals are not suitable for fulfilling the requirements of sealing the flow; therefore, self-liquid seals are used. These self-liquid seals are usually closed only just before the liquid exits the synthesis tower. Yet, during the period from when materials are fed into the tower to when the liquid is discharged (which is also over two hours), there has never been any issue with the seal breaking. At least based on our actual production experience, the process from starting up the equipment and feeding materials in to discharging the liquid from the synthesis tower is safe, and there is no risk of the seal breaking. If that were to happen, it would be impossible to operate our equipment at all. Hehe! ! !
Primarily, it can lead to safety accidents involving high pressure acting on low pressure, as well as CO2 backflow that blocks equipment pipelines!
If the long-stop self-liquid seal valve is not closed, the liquid level in the synthesis tower will drop, the temperatures of the tower walls as well as the top and bottom of the tower will decrease, the downcomer valve will close to a lesser extent than normal, and the amount of steam used in the stripping tower will increase. Low pressure, overpressure. In severe cases, evaporation is also affected, causing the nozzles to become diluted.