Device for stabilizing two-stage evaporation pressure of urea production device
By introducing the mixture of working steam and atomized desalinated water into the urea production device, saturated wet steam is formed, which solves the problem of melted urea droplet crystallization during the urea production process, and the stability of the second stage evaporation pressure and the stability of the urea product quality are achieved.
Patent Information
- Application Number
- CN202422360971.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-27
- Publication Date
- 2025-07-29
- Estimated Expiration
- 2034-09-27
AI Technical Summary
During the urea production process, molten urea droplets crystallize on the steam injector dielectric pipe and the inner wall of the outlet pipe, resulting in unstable evaporation pressure in the second section, affecting the quality of urea products.
By introducing a mixture of working steam and atomized desalted water into the steam injector, saturated wet steam is formed, the concentration of molten urea droplets is reduced, crystallization is prevented, and condensed in the condenser is stabilized, the second stage evaporation pressure is stabilized.
It effectively avoids the crystal accumulation of molten urea droplets on the tube wall, maintains the stability of the second stage evaporation pressure, and ensures the stability of the quality of urea products.
Smart Images
Figure CN223158850U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of urea production, and particularly relates to a device for stabilizing the second-stage evaporation pressure of a urea production device. Background Art
[0002] In modern urea production processes, the evaporation system generally adopts two-stage evaporation to increase the urea solution concentration to about 99.7% and then send it to granulation. The pressure of the first-stage evaporation is about 30 kPa, the pressure of the second-stage evaporation is 3 kPa, and the evaporation temperature is about 138 °C. The secondary steam evaporated in the second stage is mainly water vapor, containing a very small amount of NH3 and CO2; due to the low evaporation pressure and high gas-phase flow rate, a small amount of molten urea droplets will be entrained at the same time. At this evaporation pressure, the secondary steam cannot be directly condensed and needs to pass through a steam ejector. Using 500 kPa low-pressure steam as the working steam, the pressure of the secondary steam is increased to more than 10 kPa and then enters the condenser, where the mixed steam is condensed into dilute ammonia water by circulating cooling water. The suction ratio of the working steam is 3 - 4, and the temperature of the mixed steam after pressure increase is about 135 °C, in a superheated state. The saturation temperature under the working condition is about 50 °C, while the crystallization temperature of the molten urea droplets entrained in the secondary steam is about 132 °C. Therefore, the urea droplets are extremely easy to crystallize and accumulate on the inner wall of the diffuser pipe and the outlet pipeline of the ejector, resulting in a reduction in the flow cross-section and an increase in the flow resistance, thereby increasing the second-stage evaporation pressure and affecting the moisture content of the urea product. Frequent flushing treatment has to be carried out; during the flushing process, the working condition of the ejector, as well as the second-stage evaporation pressure and temperature, will also fluctuate, which has an adverse impact on the quality control of the urea product. Summary of the Invention
[0003] The utility model provides a device for stabilizing the second-stage evaporation pressure of a urea production device, which solves the problem of crystallization of molten urea droplets on the inner wall of the diffuser pipe and the outlet pipeline of the steam ejector in the above process, maintains the stability of the second-stage evaporation pressure, and avoids fluctuations in the quality indicators of urea products.
[0004] The specific solution is as follows:
[0005] A device for stabilizing the second-stage evaporation pressure of a urea production device includes a steam ejector, which includes an inlet section, a mixing section, and an outlet section; a working steam nozzle is arranged at the tail of the inlet section of the steam ejector to connect to the working steam pipeline, and a side pipeline is connected to the second-stage evaporation device of the urea production device. An atomizing nozzle device is arranged in the mixing section and is connected to the desalinated water pipeline, and the outlet section is connected to the condenser.
[0006] The atomizing nozzle device faces the inlet section of the steam ejector to strengthen the gas-liquid contact.
[0007] Flow meters and regulating valves are arranged on both the working steam pipeline and the desalinated water pipeline.
[0008] A pressure gauge and a thermometer are arranged in the front section of the condenser.
[0009] The outlet section of the steam ejector slopes downward to facilitate the discharge of water carried by the wet steam.
[0010] In the utility model, the working steam pipeline feeds 500 kPa saturated working steam into the inlet section of the steam ejector through the working steam nozzle. At the same time, it inhales the secondary steam at about 3 kPa and 138 °C generated by the second-stage evaporation device of the urea production plant, and forms a mixed gas that enters the mixing section of the steam ejector. The mass flow ratio of the working steam to the secondary steam is 3 - 4:1. The atomizing nozzle device connected to the desalinated water pipeline injects atomized desalinated water below 50 °C in the reverse direction. The mass flow ratio of the desalinated water to the working steam is 10 - 20%. Thus, the mixed gas is cooled to make it enter the saturated state and is converted into saturated wet steam. The small amount of molten urea droplets entrained by the secondary steam have their concentration decreased after absorbing the atomized desalinated water and are not prone to crystallization. The saturated wet steam can generate condensed water when cooling on the inner wall of the steam ejector pipe, and can also dissolve and dilute the crystallization of the urea droplets. Then, it is carried by the steam from the outlet section of the ejector into the condenser, thereby avoiding the accumulation of molten urea droplet crystallization and the resulting process fluctuations, and stabilizing the pressure of the secondary steam.
[0011] The utility model provides a device for stabilizing the pressure of the second-stage evaporation in a urea production plant, which solves the problem of crystallization of molten urea droplets on the inner walls of the diffuser pipe and the outlet pipeline of the steam ejector in the above process, maintains the stability of the second-stage evaporation pressure, and avoids fluctuations in the quality indexes of urea products. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 . Schematic diagram of the device of the utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0013] As Figure 1 shown, a device for stabilizing the pressure of the second-stage evaporation in a urea production plant includes a steam ejector 1, and the steam ejector 1 includes an inlet section 1-1, a mixing section 1-2, and an outlet section 1-3. A working steam nozzle 11 is provided at the tail of the inlet section 1-1 of the steam ejector 1 and is connected to the working steam pipeline 2. The side pipeline is connected to the second-stage evaporation device 3 of the urea production plant. An atomizing nozzle device 4 is arranged in the mixing section 1-2 and is connected to the desalinated water pipeline 5. The outlet section 1-3 is connected to the condenser 6.
[0014] The spraying direction of the atomizing nozzle device 4 faces the inlet section 1-1 of the steam ejector 1 to strengthen the gas-liquid contact.
[0015] Flow meters 10 and regulating valves 7 are provided on both the working steam pipeline 2 and the desalinated water pipeline 5.
[0016] A pressure gauge 8 and a thermometer 9 are provided on the pipeline in the front section of the condenser 6.
[0017] The outlet section 1-3 of the steam ejector 1 slopes downward to facilitate the discharge of water carried by the wet steam.
[0018] In the utility model, the working steam pipeline 2 feeds 500 kPa saturated working steam into the inlet section 1-1 of the steam ejector 1 through the working steam nozzle 11. At the same time, secondary steam at about 3 kPa and 138 °C generated by the second-stage evaporation device 3 of the urea production plant is inhaled to form a mixed gas that enters the mixing section 1-2 of the steam ejector 1. The mass flow ratio of the working steam to the secondary steam is 3-4:1. The atomizing nozzle device 4 connected to the desalinated water pipeline 5 injects atomized desalinated water below 50 °C in the reverse direction. The mass flow ratio of the desalinated water to the working steam is 10-20%, thereby cooling the mixed gas to make it enter the saturated state and be converted into saturated wet steam. The small amount of molten urea droplets entrained by the secondary steam have their concentration decreased after absorbing the atomized desalinated water and are not easy to crystallize. The saturated wet steam can generate condensed water when cooling on the wall of the steam ejector 1, and can also dissolve and dilute the crystallization of the urea droplets, and then be carried by the steam from the outlet section 1-3 of the steam ejector 1 into the condenser 6, thus avoiding the accumulation of molten urea droplet crystallization and the resulting operating condition fluctuations, and stabilizing the pressure of the secondary steam.
[0019] The above are only some preferred embodiments of the utility model, and do not impose any form of limitation on the utility model. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the utility model without departing from the content of the technical solution of the utility model still fall within the scope of the technical solution of the utility model.
Claims
1. A device for stabilizing the second-stage evaporation pressure of a urea production plant, characterized in that, It includes a steam ejector, which consists of an inlet section, a mixing section, and an outlet section. At the tail of the inlet section of the steam ejector, a working steam nozzle is provided to connect to the working steam pipeline, and a side pipeline is connected to the second-stage evaporation device of the urea production plant. An atomizing nozzle device is arranged in the mixing section and connected to the desalinated water pipeline, and the outlet section is connected to a condenser.
2. The device for stabilizing the secondary evaporation pressure of the urea production unit according to claim 1, wherein, The atomizing nozzle device faces the inlet section of the steam ejector.
3. The device for stabilizing the second-stage evaporation pressure of the urea production unit according to claim 1, wherein Flow meters and regulating valves are provided in both the working steam pipeline and the desalinated water pipeline.
4. The device for stabilizing the second-stage evaporation pressure of the urea production device according to claim 1, characterized in that, A pressure gauge and a thermometer are provided in the front section of the condenser.
5. The device for stabilizing the second-stage evaporation pressure of the urea production plant according to claim 1, characterized in that, The outlet section of the steam ejector slopes downward.