What should be noted during the desorption process

Temperature, pressure, water-to-gas ratio, and effluent parameters of the desorption tower. 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 of 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, which facilitates the water balance in urea synthesis and improves 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. The desorbed liquid thus contains very little NH3, 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. This post was last edited by Slip in with the wind on 2009-2-3 20:08.]

Issues to note in the desorption process for urea production: 1. It is necessary to ensure that the temperature at the bottom of the desorption tower exceeds 145°C, in order to minimize the ammonia nitrogen content in the desorption wastewater. 2. The desorption pressure should be controlled between 0.35 and 0.40 MPa. The higher the desorption pressure, the less favorable it is for desorption ； The lower the desorption pressure, the more favorable it is for desorption. 3. The outlet gas temperature of the desorption tower should be maintained between 110~120°C by controlling the amount of reflux liquid. If the temperature of the gas exiting the desorption tower is too high and the water content is high, it is not conducive to the system’s water balance ； Conversely, it is beneficial for the system's water balance.