Application of Ultrafiltration Technology in Urea Process

The application of ultrafiltration technology in the urea process. A sub-heater plays an important role in the decomposition of urea, and its operating conditions directly affect the system's production capacity. When the decomposition load decreases by 1%, the secondary decomposition load increases by 10%. At the same time, the decomposition is also the main user of high-pressure steam in the urea plant, accounting for about 70%. Due to the fouling of the one-point heater, the factory generally uses a chemical cleaning method to clean the scale during annual maintenance. For the three-stage inlet, the cylinders and valves of the compressor can also be protected, and the continuous operation cycle of the compressor can be greatly improved.

The material in the heater tube is ammonium carbamate, urea, ammonia, carbon dioxide and water, and the shell process is 1.0 MPa saturated steam. From the viewpoint of saving steam, the condensate on the shell side is self-adjusted through the level tank in order to use the latent heat of condensation of the steam to heat a decomposing liquid. Some plants add a leveling tank with poor results, because one point is not enough temperature, it is necessary to open a large regulating valve, and the steam is increased and then the condensation is not reduced in one point. It does not form a liquid level, resulting in high steam consumption. . From the analysis of the tube-scale fouling of one-point heater, the main components are carbon, ammonium salt, etc. The chemical cleaning is mainly the cleaning process. According to the materials and processes, CO compressor 14 is oil-lubricated. The change of oil-free lubrication is not ideal. Between the sections, cooling is performed. The CO at the five-section outlet temperature of about 95e is sent directly to the urea synthesis tower. The lubricating oil carried into the urea synthesis tower is continuously sent to the sub-heater after exiting the tower. At the same time, a decomposed anti-corrosion air is constantly carrying oil to the sub-heater.