Urea production system
By separating the gas and liquid phases in the urea production system and optimizing heat energy utilization using medium- and high-pressure decomposition units and medium-pressure decomposition units, the problem of insufficient oxygen utilization in the urea synthesis tower output was solved, achieving stable operation of the high-pressure stripping tower and efficient heat energy utilization, thus reducing equipment costs and ammonia loss.
Patent Information
- Application Number
- CN202423220447.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-25
- Publication Date
- 2025-12-05
- Estimated Expiration
- 2034-12-25
AI Technical Summary
In the ammonia stripping urea process, the urea synthesis tower output is a gas-liquid two-phase mixture, which fails to fully utilize oxygen, resulting in difficulties in passivation and corrosion prevention of the high-pressure stripping tower, high equipment investment and ammonia loss, and the condensation heat energy of ammonium carbamate is not fully utilized.
The gaseous and liquid phases of the urea synthesis tower are respectively introduced into different parts of the high-pressure stripping tower. The gaseous phase is used to provide oxygen for passivation and corrosion prevention. The heat energy utilization is optimized through the medium-high pressure decomposition unit and the medium pressure decomposition unit, the use of inert gas is reduced, and the medium-high pressure decomposition unit and the medium pressure decomposition unit are coupled with the urea evaporation section.
It has achieved stable operation of the high-pressure stripping tower, reduced equipment investment and ammonia loss, improved thermal energy utilization efficiency, reduced steam consumption, and reduced operational difficulty.
Smart Images
Figure CN223628110U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to urea production field, concretely is a urea production system. BACKGROUND
[0002] At present, in the ammonia stripping urea process flow adopted in the domestic, the discharge of urea synthesis tower is all gas-liquid two-phase mixture, the aforementioned gas-liquid two-phase mixture is transported together from the upper portion of urea synthesis tower to the upper portion of high-pressure stripping tower, and the oxygen in the two-phase mixture is directly discharged to the rear section at the top, which cannot be fully utilized in the high-pressure stripping tower; further, in order to realize passivation and corrosion prevention of the high-pressure stripping tower, some enterprises adopt the mode of opening high-pressure air pipeline in the stripping tower, which is not only difficult to control due to high pressure, but also needs to separate inert gas in the subsequent process, which not only causes high equipment investment cost, but also causes ammonia loss, thereby increasing the equipment investment and production cost of urea. SUMMARY
[0003] In order to make up for the above shortcomings, the utility model provides a urea production system to solve the technical problems existing in the prior art.
[0004] The technical scheme adopted by the utility model to solve its technical problems is:
[0005] A urea production system, the system comprises a urea synthesis tower, the gas phase outlet of the urea synthesis tower is connected with the lower portion of a stripping tower, the gas-liquid mixture liquid phase outlet of the urea synthesis tower is connected with the upper portion of the stripping tower, the liquid phase outlet of the stripping tower is connected with a middle-high pressure decomposition unit capable of exchanging heat with a one-stage evaporated urea melt through a pressure reducing valve, and the middle-high pressure decomposition unit is connected with a middle pressure decomposition unit and a middle-high pressure methylamine recovery unit respectively.
[0006] The urea synthesis tower top gas-liquid two-phase flow is changed into gas phase and liquid phase which are separated and enter different parts of the high-pressure stripping tower, the liquid phase is sent to the high-pressure stripping tower top in accordance with the original flow, and the gas phase is sent to the high-pressure stripping tower bottom, oxygen can be provided for passivation of the high-pressure stripping tower, additional air is not needed to be provided from a special compressor, full use of oxygen in the system is realized, passivation air sent into the high-pressure stripping tower is reduced, less inert gas enters the system, ammonia in the medium-pressure process exhaust gas can be completely recovered, passivation corrosion of the stripping tower is realized without introducing external gas, and investment cost and ammonia loss are reduced; further, the high-pressure decomposition unit is additionally arranged, urea solution from the high-pressure stripping tower is flashed to higher pressure, more heat is generated in high-pressure methylamine full condensation, a basis is laid for heat exchange of the one-stage evaporated urea melt, and steam consumption in the subsequent urea solution heating process is saved.
[0007] Preferably, the gas phase outlet of the stripping tower is connected with the methylamine condenser of the urea synthesis section.
[0008] Preferably, the high-pressure decomposition unit comprises a high-pressure decomposition separator which is connected with the liquid phase outlet of the stripping tower, a gas phase outlet of the high-pressure decomposition separator is connected with a first heat exchange channel of the one-stage evaporation heater, and a first heat exchange channel outlet of the one-stage evaporation heater is connected with the high-pressure methylamine recovery unit.
[0009] Preferably, the high-pressure methylamine recovery unit comprises a high-pressure methylamine receiver which is connected with the first heat exchange channel outlet of the one-stage evaporation heater, and a liquid phase outlet of the high-pressure methylamine receiver is connected with the methylamine condenser of the urea synthesis section through a first methylamine pump.
[0010] Preferably, a liquid phase outlet of the high-pressure decomposition separator is connected with a medium-pressure decomposition separator in the medium-pressure decomposition unit, a gas phase of the medium-pressure decomposition separator is connected with a first heat exchange channel of the pre-evaporator, and a first heat exchange channel outlet of the pre-evaporator is connected with the medium-pressure absorption unit.
[0011] Preferably, the medium-pressure absorption unit comprises a medium-pressure absorption tower which is connected with the first heat exchange channel outlet of the pre-evaporator, and a liquid phase outlet of the medium-pressure absorption tower is connected with the high-pressure methylamine receiver of the high-pressure recovery section through a second methylamine pump.
[0012] Preferably, a liquid phase outlet of the medium-pressure decomposition separator is connected with the low-pressure decomposition section.
[0013] Preferably, the urea evaporation section is further arranged, a second heat exchange channel of the pre-evaporator in the urea evaporation section is connected with a second heat exchange channel of the one-stage evaporation heater through a urea pipeline, an outlet of the second heat exchange channel of the one-stage evaporation heater is connected with a two-stage evaporation section through a one-stage evaporation separator, and a urea pump is arranged on the urea pipeline.
[0014] The urea production system made according to the above scheme is a transformation of the existing urea system, and the transformation is based on the fact that the oxygen in the gas-liquid mixture in the urea synthesis tower can passivate and anticorrosion of the stripping tower without introducing high-pressure air from outside; compared with the traditional method of introducing high-pressure air, the above structure can not only greatly reduce the operation difficulty and will not introduce impurities to cause ammonia gas separation loss, but also can make the stripping tower run stably, especially the temperature fluctuation range is small, which lays a foundation for setting a medium-high pressure decomposition unit in the subsequent process; by setting the medium-high pressure decomposition unit, full utilization of heat energy can be realized, and the consumption of steam in the subsequent heating process of the urea solution is saved; further, the medium pressure decomposition unit is also provided in the utility model, and the medium pressure decomposition unit and the medium-high pressure decomposition unit cooperate with each other, not only realizing stable operation of the whole process, but also being coupled with the pre-evaporation section and the first evaporation section of the urea evaporation section, and the full utilization of heat energy and the characteristics of reducing steam consumption are achieved. BRIEF DESCRIPTION OF DRAWINGS
[0015] In order to more clearly illustrate the technical scheme in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or the prior art description, and obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained on the premise of not creating laboriously.
[0016] Figure 1 It is a structural schematic view of the present application.
[0017] In the figure: 1, urea synthesis tower; 2, stripping tower; 3, pressure reducing valve; 4, methylamine condenser; 5, medium-high pressure decomposition separator; 6, first evaporation heater; 7, medium-high pressure methylamine receiver; 8, first methylamine pump; 9, medium pressure decomposition separator; 10, pre-evaporator; 11, medium pressure absorption tower; 12, second methylamine pump; 13, low pressure decomposition section; 14, urea pipeline; 15, urine pump; 16, first evaporation separator; 17, second evaporation section. DETAILED DESCRIPTION
[0018] The technical scheme in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application, and obviously, the described embodiments are only some embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creating laboriously belong to the scope of protection of the present application.
[0019] The following will be combined with the drawings Figure 1Further detailed description of the present application, the utility model relates to a urea production system, the system includes urea synthesis tower 1, the gas phase outlet of urea synthesis tower 1 is connected with the lower part of stripping tower 2, the gas-liquid mixture outlet of urea synthesis tower 1 is connected with the upper part of stripping tower 2, the liquid phase outlet of stripping tower 2 is connected with the medium-high pressure decomposition unit capable of heat exchange to one section evaporated urea melt liquid through pressure reducing valve 3, and the medium-high pressure decomposition unit is connected with medium pressure decomposition unit and medium-high pressure methylamine recovery unit respectively. The utility model makes the reform of the existing urea system, which is improved by sending the gas phase in the urea synthesis tower 1 into the lower part of the stripping tower 2 instead of sending the gas-liquid two-phase in the urea synthesis tower 1 into the upper part of the stripping tower 2, and the material mainly in liquid phase is sent into the upper part of the stripping tower 2 (it should be noted that the gas-liquid mixture outlet of the urea synthesis tower 1 in the utility model refers to the gas-liquid mixture outlet in the original equipment, and after the reform, a small amount of gas phase will still enter the upper part of the stripping tower 2 under the entrainment of the liquid phase, but most of the gas phase is discharged from the gas phase outlet of the urea synthesis tower 1) ; by the above reform, the oxygen in the material can be used to realize the passivation corrosion of the inside of the stripping tower 2, which does not introduce external high-pressure air, not only facilitates the operation and avoids subsequent ammonia loss, but also makes the operation of the inside of the stripping tower 2 stable, especially the stable pressure and temperature in the stripping tower 2 lay a foundation for setting the medium-high pressure decomposition unit.
[0020] Further, the gas phase outlet of the stripping tower 2 is connected with the methylamine condenser 4 of the urea synthesis section.
[0021] Further, the medium-high pressure decomposition unit includes a medium-high pressure decomposition separator 5 connected with the liquid phase outlet of the stripping tower 2, the gas phase outlet of the medium-high pressure decomposition separator 5 is connected with the first heat exchange channel of the one section evaporation heater 6, and the first heat exchange channel outlet of the one section evaporation heater 6 is connected with the medium-high pressure methylamine recovery unit. Flashing is carried out through the high-pressure decomposition separator 5, and the flashed gas phase is applied to the one section evaporation heater 6 to heat and concentrate the urea solution in the second heat exchange channel of the one section evaporation heater 6, so as to fully utilize the heat of methylamine.
[0022] Further, the medium-high pressure methylamine recovery unit includes a medium-high pressure methylamine receiver 7 connected with the first heat exchange channel outlet of the one section evaporation heater 6, and the liquid phase outlet of the medium-high pressure methylamine receiver 7 is connected with the methylamine condenser 4 of the urea synthesis section through the first methylamine pump 8. Through the above setting, the methylamine can be condensed into liquid phase after absorption, which is used as raw material in subsequent production.
[0023] Further, the liquid phase outlet of the middle-high pressure decomposition separator 5 is connected with the middle pressure decomposition separator 9 in the middle pressure decomposition unit, the gas phase of the middle pressure decomposition separator 9 is connected with the first heat exchange channel of the pre-evaporator 10, and the first heat exchange channel outlet of the pre-evaporator 10 is connected with the middle pressure absorption unit. By performing flash evaporation in the middle pressure decomposition separator 9, the flash evaporated gas phase is applied to the pre-evaporator 10, and the urea solution in the second heat exchange of the pre-evaporator 10 is preheated, so that the heat of the methylamine is fully utilized.
[0024] Further, the middle pressure absorption unit comprises a middle pressure absorption tower 11 connected with the first heat exchange channel outlet of the pre-evaporator 10, and the liquid phase outlet of the middle pressure absorption tower 11 is connected with the second methylamine pump 12 and the middle-high pressure methylamine receiver 7 of the middle-high pressure recovery section. Through the above arrangement, the methylamine can be condensed into a liquid phase after absorption, and used as a raw material in subsequent production.
[0025] Further, the liquid phase outlet of the middle pressure decomposition separator 9 is connected with the low pressure decomposition section 13.
[0026] The utility model also includes a urea evaporation section, the second heat exchange channel of the pre-evaporator 10 in the urea evaporation section is connected with the second heat exchange channel of the first evaporation heater 6 through the urea pipeline 14, the outlet of the second heat exchange channel of the first evaporation heater 6 is connected with the second evaporation section 17 through the first evaporation separator 16, and the urea pipeline 14 is provided with the urine pump 15. The middle-high pressure decomposition unit and the middle pressure decomposition unit in the utility model can be coupled with the urea evaporation section, so that the heat energy utilization rate is improved and the steam consumption is reduced.
[0027] The working principle of the utility model is: the urea synthesis tower 1 produces gas phase and liquid phase in the synthesis process of urea, the gas phase enters the lower part of the stripping tower 2 through the gas phase outlet at the top of the urea synthesis tower 1, the liquid phase (can entrain part of the gas phase) enters the upper part of the stripping tower 2 through the gas-liquid mixture outlet of the urea synthesis tower 1, the gas phase is sent to the bottom of the urea synthesis tower 1 and goes up at the same time and provides oxygen for the passivation of the stripping tower 2, thereby realizing full utilization of oxygen in the system, reducing the passivation air sent into the high-pressure stripping tower, so that less inert gas enters the system, which helps to completely recover ammonia from the medium-pressure process exhaust gas; further, the gas phase in the stripping tower 2 enters the methylamine condenser 4 of the urea synthesis section through the gas phase outlet; the liquid phase in the stripping tower 2 enters the medium-high pressure decomposition separator 5 for flash evaporation on the basis of pressure reduction of the pressure reducing valve 3, is heated to 153-155 DEG C by steam after flash evaporation to 3.0-8.0 MPa, the methylamine gas phase after flash evaporation enters the first heat exchange channel of the first evaporation heater 6, exchanges heat with the urea solution in the second heat exchange channel of the first evaporation heater 6, the gas-liquid two-phase mixture after heat exchange enters the medium-high pressure methylamine receiver 7 for separation, the collected methylamine solution is sent into the methylamine condenser 4 of the urea synthesis section by the first methylamine pump 8; the liquid phase after flash evaporation in the medium-high pressure decomposition separator 5 enters the medium-pressure decomposition separator 9 for flash evaporation, the methylamine gas phase after flash evaporation enters the first heat exchange channel of the pre-evaporator 10, exchanges heat with the urea solution in the second heat exchange channel of the pre-evaporator 10, the gas-liquid two-phase mixture after heat exchange enters the medium-pressure absorption tower 11, the collected methylamine solution is separated in the medium-high pressure methylamine receiver 7, the collected methylamine solution is sent into the methylamine condenser 4 of the urea synthesis section by the first methylamine pump 8; the urea solution in the second heat exchange channel of the pre-evaporator 10 is preheated in the above process, is pressurized by the urea pump 15 in the urea pipeline 14 and is sent into the second heat exchange channel of the first evaporation heater 6, the liquid phase after heating in the first evaporation separator 16 enters the second evaporation section 17; the utility model has the advantages of realizing stable operation of the system, reducing operation difficulty, reducing ammonia loss and realizing full utilization of heat energy.
[0028] The basic principle, main features and advantages of the utility model are shown and described above. Those skilled in the art should understand that the utility model is not limited by the above examples, the above examples and descriptions in the specification are only to illustrate the principle of the utility model, various changes and improvements of the utility model can be made without departing from the spirit and scope of the utility model, and these changes and improvements all fall within the scope of the utility model claimed.
Claims
1. A urea production system, the system comprising a urea synthesis tower (1), characterized in that: The gas phase outlet of the urea synthesis tower (1) is connected with the lower part of the stripping tower (2), the gas-liquid mixture outlet of the urea synthesis tower (1) is connected with the upper part of the stripping tower (2), the liquid phase outlet of the stripping tower (2) is connected with a medium-high pressure decomposition unit capable of exchanging heat with the urea melt in the first evaporation through a pressure reducing valve (3), and the medium-high pressure decomposition unit is connected with a medium pressure decomposition unit and a medium-high pressure methylamine recovery unit respectively.
2. A urea production system according to claim 1, characterized in that: The gas phase outlet of the stripping tower (2) is connected with a methylamine condenser (4) in the urea synthesis section.
3. A urea production system according to claim 1, characterized in that: The medium-high pressure decomposition unit comprises a medium-high pressure decomposition separator (5) connected with the liquid phase outlet of the stripping tower (2), the gas phase outlet of the medium-high pressure decomposition separator (5) is connected with the first heat exchange channel of the first evaporation heater (6), and the outlet of the first heat exchange channel of the first evaporation heater (6) is connected with the medium-high pressure methylamine recovery unit.
4. A urea production system according to claim 3, characterized in that: The medium-high pressure methylamine recovery unit comprises a medium-high pressure methylamine receiver (7) connected with the outlet of the first heat exchange channel of the first evaporation heater (6), and the liquid phase outlet of the medium-high pressure methylamine receiver (7) is connected with the methylamine condenser (4) in the urea synthesis section through a first methylamine pump (8).
5. A urea production system according to claim 3, characterized in that: The liquid phase outlet of the medium-high pressure decomposition separator (5) is connected with a medium pressure decomposition separator (9) in the medium pressure decomposition unit, the gas phase of the medium pressure decomposition separator (9) is connected with the first heat exchange channel of a pre-evaporator (10), and the outlet of the first heat exchange channel of the pre-evaporator (10) is connected with a medium pressure absorption unit.
6. A urea production system according to claim 5, characterized in that: The medium pressure absorption unit comprises a medium pressure absorption tower (11) connected with the outlet of the first heat exchange channel of the pre-evaporator (10), and the liquid phase outlet of the medium pressure absorption tower (11) is connected with the medium-high pressure methylamine receiver (7) in the medium-high pressure recovery section through a second methylamine pump (12).
7. A urea production system according to claim 5, characterized in that: The liquid phase outlet of the medium pressure decomposition separator (9) is connected with a low pressure decomposition section (13).
8. A urea production system according to claim 5, characterized in that: A urea evaporation section is further included, the second heat exchange channel of the pre-evaporator (10) in the urea evaporation section is connected with the second heat exchange channel of the first evaporation heater (6) through a urea pipeline (14), the outlet of the second heat exchange channel of the first evaporation heater (6) is connected with a second evaporation section (17) through a first evaporation separator (16), and a urea pump (15) is arranged on the urea pipeline (14).