How can the desorption and hydrolysis system be controlled in production to ensure that wastewater is discharged in compliance with standards? (CO2 stripping method)

I think the following aspects should be given primary attention: 1. It is necessary to strictly control all the parameters of the desorption system; in particular, the temperature of the liquid coming out of the upper part of the desorption tower must meet the specified range (138–142°C), so as to ensure a low ammonia content in that liquid and thus lay a foundation for effective hydrolysis. 2. The hydrolysis liquid level should be kept as high as possible to increase the residence time and thereby improve the hydrolysis efficiency. 3. Sufficient hydrolysis steam must be supplied, and the hydrolysis temperature should reach the specified level; the higher, the better. 4. The liquid outlet temperature at the lower part of the desorption tower must meet the specified criteria. At the same time, its liquid level must be kept stable to prevent air from entering and causing the wastewater levels to exceed the allowed limits. 5. The outlet gas temperature at the upper part of the desorption tower should be controlled appropriately (that is, the amount of reflux liquid must be regulated properly) to avoid excessive temperatures, which could increase the load on the hydrolysis-desorption system and steam consumption, and may even lead to wastewater exceeding regulatory limits.

Control the top and bottom temperatures of the desorption tower, as well as the top and bottom temperatures of the hydrolysis tower. Control the liquid level in each tower, but prevent flooding. It can also be observed that the conductivity of the process wastewater is less than 10 PPm, ensuring that the hydrolysis wastewater meets the required standards.

Additional note: Control the liquid-to-gas ratio in the hydrolysis tower and desorption tower, and ensure that the steam input corresponds to the load

Strictly controlling all process parameters will definitely ensure no problems

The load for desorption should not be too high; first, it is necessary to control the conversion rate of the high-pressure zone in order to minimize the ammonia concentration as much as possible； The liquid-to-gas ratio in the desorption tower should be maintained at around 1:4 to prevent flooding ； The temperature at the top of the desorption tower is maintained between 100°C and 110°C, while the temperature at the bottom is roughly equal to the temperature of the steam condensate corresponding to the desorption pressure ； The desorption pressure should not be too high ； The hydrolysis tower must have sufficient residence time, with a temperature of over 210°C.

A urea content of 0 in the ammonia tank seems unlikely, right? Evaporation systems more or less always have some liquid in the gas phase; how is it possible to achieve a gas phase free of liquid? This post was last edited by Fan Zhou Wu Hu on 2009-3-11 12:28.]

What the people upstairs mentioned as “compliant emissions” – does it refer to emissions, or will the purified water coming out of the desorption tower be used?

Regardless of the urea production process, the associated desorption and hydrolysis units remain the same, and the hydrolysis system is easy to control. It’s mainly temperature and pressure; as long as they are within the specified limits, there are no issues with meeting the emission standards.

It is necessary to pay attention to the components and concentration of the ammonium carbonate solution used for hydrolysis; if these values are too high and exceed the specified limits, dilution should be carried out. Attention must also be given to the amount of material fed for hydrolysis, so that the hydrolysis system operates at its optimal load. Finally, it is important to control the process parameters to ensure that they meet the required standards

The amount of steam should correspond to the desorption load. Mass ratio of 4:1. Ensure the temperature of T2807 remains above 140 degrees. The hydrolysis of T2812 occurs at temperatures above 200 degrees. The desorption top temperature should be between 100-120 degrees to avoid flooding. A pressure of 0.25–0.35 MPa is sufficient.