Urea hydrolysis

Adding too much steam can cause overpressure or liquid presence in the hydrolysis tower, as well as excessive temperature. It is sufficient to keep the temperature, pressure, and liquid level of the hydrolysis tower within the specified ranges.

Urea hydrolysis depends on the type of hydrolyzer used; in the case of a horizontal hydrolyzer, there is only one theoretical stage for separation, and temperature and pressure can only be adjusted using steam to ensure efficient hydrolysis. In the case of a vertical hydrolysis tower, the trays serve a distillation function, and it constitutes reactive distillation; the efficiency of these trays is a crucial factor. While ensuring proper temperature and pressure conditions, it is important to use trays with high efficiency.

The main factors affecting the efficiency of urea hydrolysis are: first, the hydrolysis temperature. High temperatures are favorable for hydrolysis ； Conversely, it is not conducive to hydrolysis. Second, the length of time that the ammonium carbonate solution or ammonia water stays in the hydrolysis tower. A long time is favorable for hydrolysis ； Conversely, it is not conducive to hydrolysis. Third, the level of ammonia and urea in the ammonium carbonate solution or ammonia water. A low content of ammonia or urea facilitates hydrolysis ； Conversely, it is not conducive to hydrolysis. Although the hydrolysis temperature plays an important role in the efficiency of urea hydrolysis, and adding steam helps to raise this temperature, it is clear from the above that relying solely on steam is not sufficient.

Urea hydrolysis tower internals. Can regular packing be used? Is a sieve tray better, or is packing better?

Which teacher can provide information on the desorption and hydrolysis of urea at Ningbo Far East?

The advanced hydrolysis technology for desorbing waste liquids has been developed; Snaim’s desorption-hydrolysis process utilizes low-pressure desorption and high-pressure hydrolyzers； The desorption-hydrolysis technology used by Stamicarbon Company involves low-pressure desorption and medium-pressure hydrolysis towers ； The other processes are basically improvements or optimizations of the above two processes. The advantage of these two processes is that the desorption-hydrolysis system is highly independent; it is possible to adjust the composition of the dilute methylammonium solution in the low-pressure system in response to changes in the amount of waste liquid and its composition, thereby ensuring the correct water-to-carbon ratio in the synthesis system ； Its disadvantage is that the condensation heat of the gas exiting the desorption tower is not recovered, and circulating cooling water is consumed. The newly developed process combines desorption and hydrolysis in a single column, utilizing medium-pressure desorption hydrolysis, which is a form of reactive distillation. Hydrolysis of urea takes place simultaneously with the desorption of ammonia and carbon dioxide. The internals of the desorption hydrolysis column need to be optimized; under conditions of 190°C at the bottom of the column, there must be enough number of trays and adequate tray efficiency to ensure that both ammonia and urea levels remain below 5 ppm ； A fractionator is installed at the top of the tower to adjust the gas composition exiting the desorption and hydrolysis tower; this gas is then fed into the low-pressure decomposition tower, and after its condensation heat is recovered, it is returned to the low-pressure recovery system.

Fillers are generally used in hydrolysis towers~As far as I know, both of SNAM’s large fertilizer plants use fillers

7# TUOHZHE: The hydrolysis technology we use at present is of this type; the process is basically the same, but the urea concentration in the waste liquid is too low – it’s around 5PPM, whereas it should be around 20PPM. Ammonia can also reach approximately 20 M3 per hour, with a bottom temperature of 186 degrees and a top temperature of 170 degrees

Is a packing used in the hydrolysis tower on the 8th floor? It should be a desorption tower. Floor 9 uses that company’s hydrolysis technology. How many trays are there in the hydrolysis tower? Could you provide more details?

The basic requirements for the desorption process are as follows: First, the liquid discharged from the bottom of the tower after desorption (referred to as the desorption fluid) should be free of NH3, in order to reduce NH3 consumption. Second, the water content in the gas discharged from the top of the tower (referred to as desorbed gas) should be minimized, in order to reduce the amount of water returning to the system. This helps maintain the water balance in the urea synthesis process and increases the conversion rate of urea. To meet the first requirement, the liquid at the bottom of the tower should contain essentially no NH3. If the operating pressure is 3 kg/cm2 (absolute), then the temperature here should be equal to the boiling point of water at that pressure, which is 133.00°C; as a result, the desorbed liquid contains very little NH3, thereby achieving the purpose of desorption. Therefore, once the operating pressure of the desorption tower is determined, the corresponding bottom temperature of the desorption tower can be found, which is the saturated steam temperature at that pressure. The temperature of the desorption tower is primarily maintained by the amount of steam added at the bottom of the tower. If the operating pressure remains constant, no matter how much steam is added, it will only increase the vapor volume of the solution; the temperature at the bottom of the tower can only reach its saturated vapor temperature, and it cannot rise any further. To meet the second requirement, the water content in the desorbed gas should be minimized as much as possible. This is determined by the temperature at the top of the tower; the higher the temperature, the greater the equilibrium partial pressure of saturated water vapor in the desorbed gas, and thus the higher its water content. The top temperature of the tower is influenced by three factors: first, the amount of steam added at the bottom of the tower ； Second is the amount of steam added at the bottom of the tower ； Second is the temperature of the ammonia water added at the top of the tower ； Third is the concentration of ammonia solution.