High-efficiency differential pressure thermal cycle urea production device

Abstract

The utility model relates to urea production technical field, is a kind of high-efficiency differential pressure heat cycle urea production device, this high-efficiency differential pressure heat cycle urea production device includes compressor, synthetic tower, secondary high-pressure decomposer, front reaction unit, middle-pressure pretreatment unit, first material conveying pipeline is communicated between synthetic tower export and secondary high-pressure decomposer bottom import, second material conveying pipeline is communicated between secondary high-pressure decomposer export and middle-pressure pretreatment unit import, third material conveying pipeline is communicated between secondary high-pressure decomposer export and front reaction unit import, and front reaction unit first export, second export are fixedly communicated with middle-pressure pretreatment unit, synthetic tower bottom respectively, the urea mixed solution of the utility model is decomposed in advance in synthetic tower export, reduce the steam use amount of urea middle-low pressure decomposer system and the amount of use of middle-low pressure absorption system circulating water, gas-phase mixture and CO2 etc. are decomposed in advance in secondary high-pressure decomposer, reduce the load of compressor.

Description

Technical Field

[0001] This utility model relates to the field of urea production technology and is a high-efficiency differential pressure thermal cycle urea production device. Background Technology

[0002] The coal gasification process for producing urea uses coal as raw material. The production process involves producing syngas through coal gasification. The main components of the shift gas from the syngas are hydrogen and carbon dioxide. It cannot be directly used for ammonia synthesis and must undergo strict purification treatment, such as a low-temperature methanol washing process, to remove hydrogen sulfide, carbonyl sulfide, and some CO2 from the shift gas, yielding hydrogen and carbon dioxide. The hydrogen is used for ammonia synthesis, while the carbon dioxide can be used as a raw material for urea or directly sent to the urea low-pressure decomposition tower.

[0003] The aqueous solution full-cycle urea production process is a highly efficient urea production technology. Unreacted ammonia and carbon dioxide from the urea synthesis reaction are returned to the reactor in aqueous solution form through a series of pressurized circulation devices, thus improving raw material utilization. The main raw materials are ammonia and carbon dioxide, which enter the synthesis tower under high pressure via pipelines. Ammonia is typically produced by the reaction of hydrogen and nitrogen under high pressure and high temperature via a catalyst, while carbon dioxide is extracted directly from the air or recovered from industrial waste gas. In the aqueous solution full-cycle method, ammonia and carbon dioxide react under high pressure and high temperature in a high-pressure reactor to produce ammonium carbamate solution. The generated ammonium carbamate solution and unreacted ammonium carbamate / ammonia are then subjected to medium-pressure and low-pressure decomposition to obtain urea solution and decomposition gases (NH3, CO2, H2O). The decomposition gases are absorbed by water through medium-pressure and low-pressure absorption to form ammonium carbamate solution for reuse. The urea solution then undergoes a series of evaporations and cooling processes, causing urea to crystallize. The separated urea crystals are washed and dried to obtain the finished urea product.

[0004] Chinese patent document CN117326986A discloses an improved method for producing urea by carbon dioxide stripping, comprising the following steps: (1) Reaction: At a temperature of 175°C to 185°C and a pressure of 13.2 MPa to 14.8 MPa, liquid ammonia and carbon dioxide are mixed and reacted in a high-pressure condenser under water condensation to generate ammonium carbamate, which is then partially dehydrated in a synthesis tower to generate urea; (2) Stripping: The reaction mixture obtained in step (1) is sequentially fed into a high-pressure condenser. In the stripping tower and the medium-pressure stripping tower, carbon dioxide is introduced under heating for stripping, and ammonium carbamate is further dehydrated to produce urea. The operating temperature in the high-pressure stripping tower is 160℃ to 178℃, and the operating pressure is 13.2MPa to 14.8MPa; the operating temperature in the medium-pressure stripping tower is 130℃ to 165℃, and the operating pressure is 1.0MPa to 1.9MPa; the mass flow rate ratio of carbon dioxide introduced into the high-pressure stripping tower to that into the medium-pressure stripping tower is 0.3 to 0.6. The production method using this invention can reduce steam consumption, electricity consumption, and liquid ammonia transportation energy consumption in the production process. However, in the aqueous solution full-cycle urea synthesis process, there is a large amount of unreacted material at the urea synthesis tower outlet, requiring segmented decomposition and recovery. The overall process results in high consumption of steam, circulating water, and electricity.

[0005] Therefore, it is essential to research and invent a high-efficiency differential pressure thermal cycle urea production device. Summary of the Invention

[0006] This invention provides a high-efficiency differential pressure thermal cycle urea production device, which overcomes the shortcomings of the prior art. It can effectively solve the problems of high material and power consumption caused by the large amount of unreacted material at the outlet of the urea synthesis tower and the decomposition and recovery of unreacted material.

[0007] The technical solution of this utility model is achieved through the following measures: A high-efficiency differential pressure thermal cycle urea production device includes a compressor, a synthesis tower, a sub-high pressure decomposer, a pre-reaction unit, and a medium-pressure pretreatment unit. A first carbon dioxide conveying pipeline is fixedly connected between the upper outlet of the compressor and the first inlet at the bottom of the synthesis tower. A first material conveying pipeline is fixedly connected between the top outlet of the synthesis tower and the bottom inlet of the sub-high pressure decomposer. A second material conveying pipeline is fixedly connected between the upper outlet of the sub-high pressure decomposer and the upper inlet of the medium-pressure pretreatment unit. A third material conveying pipeline is fixedly connected between the top outlet of the sub-high pressure decomposer and the inlet of the pre-reaction unit. A fourth material conveying pipeline is fixedly connected between the first outlet of the pre-reaction unit and the upper inlet of the medium-pressure pretreatment unit. A fifth material conveying pipeline is fixedly connected between the second outlet of the pre-reaction unit and the second inlet at the bottom of the synthesis tower. A liquid ammonia conveying pipeline is fixedly connected to the third inlet at the bottom of the synthesis tower.

[0008] The following are further optimizations and / or improvements to the above-mentioned utility model technical solution: The inlet of the aforementioned secondary high-pressure decomposer is fixedly connected to a first steam pipeline, the outlet of the secondary high-pressure decomposer is fixedly connected to a first steam condensate pipeline, and the tail gas pipeline of the melamine unit is fixedly connected to the first material conveying pipeline.

[0009] The aforementioned medium-pressure pretreatment unit includes a medium-pressure pre-separator and a medium-pressure preheater. A second material conveying pipeline is fixedly connected between the upper inlet of the medium-pressure pre-separator and the upper outlet of the secondary high-pressure decomposer. A sixth material conveying pipeline is fixedly connected between the bottom outlet of the medium-pressure pre-separator and the bottom inlet of the medium-pressure preheater. A first gas phase pipeline is fixedly connected to the top outlet of the medium-pressure pre-separator. A condensate pipeline is fixedly connected to the lower outlet of the medium-pressure preheater. A seventh material conveying pipeline is fixedly connected to the bottom outlet of the medium-pressure preheater. A second gas phase pipeline is fixedly connected to the top outlet of the medium-pressure preheater.

[0010] The aforementioned pre-reaction unit includes a mixer, a sub-high-pressure condenser, and a sub-high-pressure buffer tank. A third material conveying pipeline is fixedly connected between the bottom inlet of the mixer and the top outlet of the sub-high-pressure decomposer. An eighth material conveying pipeline is fixedly connected between the right outlet of the mixer and the left inlet of the sub-high-pressure condenser. A fourth material conveying pipeline is fixedly connected between the upper outlet of the sub-high-pressure condenser and the upper inlet of the medium-pressure preheater. A ninth material conveying pipeline is fixedly connected between the left outlet of the sub-high-pressure condenser and the right inlet of the sub-high-pressure buffer tank. A fifth material conveying pipeline is fixedly connected between the bottom outlet of the sub-high-pressure buffer tank and the second inlet at the bottom of the synthesis tower. A tenth material conveying pipeline is fixedly connected to the fourth material conveying pipeline.

[0011] The left inlet of the aforementioned mixer is fixedly connected to the tail liquid pipeline of the melamine unit, the tail liquid pipeline of the melamine unit is fixedly connected to the medium-pressure ammonium methyl ester liquid pipeline, the top outlet of the secondary high-pressure buffer tank is fixedly connected to the third gas phase pipeline, and the bottom inlet of the secondary high-pressure condenser is fixedly connected to the boiler feedwater pipeline.

[0012] The compressor described above is a multi-stage compressor. The four outlets of the compressor are fixedly connected to the inlet of the first carbon dioxide conveying pipeline. The compressor inlet is fixedly connected to a factory air pipeline. The factory air pipeline is fixedly connected to a second carbon dioxide pipeline. The three outlets of the compressor are fixedly connected to a third carbon dioxide pipeline.

[0013] A sub-high pressure ammonium carbamate pump is fixedly installed on the fifth material conveying pipeline. A first pressure gauge and a first pressure regulating valve are fixedly installed in sequence according to the medium flow direction on the first material conveying pipeline. A second pressure gauge, a second pressure regulating valve, and a first thermometer are fixedly installed in sequence according to the medium flow direction on the second material conveying pipeline. A temperature regulating valve is fixedly installed on the first steam pipeline. A third pressure gauge is fixedly installed on the sub-high pressure buffer tank. A third pressure regulating valve is fixedly installed on the third gas phase pipeline. A first liquid level gauge is fixedly installed on the sub-high pressure condenser. A first liquid level regulating valve is fixedly installed on the boiler feedwater pipeline.

[0014] The above also includes a PLC controller, a sub-high pressure ammonium carbamate pump, a first pressure gauge, a first pressure regulating valve, a second pressure gauge, a second pressure regulating valve, a first temperature gauge, a temperature regulating valve, a third pressure gauge, a third pressure regulating valve, a first level gauge, and a first level regulating valve, all of which are electrically connected to the PLC controller. Interlocks are respectively provided between the first pressure gauge and the first pressure regulating valve, between the second pressure gauge and the second pressure regulating valve, between the first temperature gauge and the temperature regulating valve, between the third pressure gauge and the third pressure regulating valve, and between the first level gauge and the first level regulating valve.

[0015] This utility model has a reasonable and compact structure and is easy to use. It decomposes the urea mixed solution from the synthesis tower in advance, reducing the amount of steam used in the medium and low pressure urea decomposition system and the amount of circulating water used in the medium and low pressure absorption system. It also allows the first gas phase mixture to react with the tail liquid from the melamine unit, the medium-pressure ammonium methyl ester solution and CO2 in advance, reducing the load on the compressor. Attached Figure Description

[0016] Appendix Figure 1 This is a schematic diagram of the process flow of this utility model.

[0017] The codes in the attached diagram are as follows: 1 for compressor, 2 for synthesis tower, 3 for sub-high pressure decomposer, 4 for first carbon dioxide conveying pipeline, 5 for first material conveying pipeline, 6 for second material conveying pipeline, 7 for third material conveying pipeline, 8 for fourth material conveying pipeline, 9 for fifth material conveying pipeline, 10 for liquid ammonia conveying pipeline, 11 for first steam pipeline, 12 for first steam condensate pipeline, 13 for melamine unit tail gas pipeline, 14 for medium pressure pre-separator, 15 for medium pressure preheater, 16 for sixth material conveying pipeline, 17 for first gas phase pipeline, 18 for condensate pipeline, 19 for seventh material conveying pipeline, 20 for second gas phase pipeline, 21 for mixer, and 22 for sub-high pressure condenser. 23 is a secondary high-pressure buffer tank; 24 is the eighth material conveying pipeline; 25 is the ninth material conveying pipeline; 26 is the tenth material conveying pipeline; 27 is the melamine unit tail liquid pipeline; 28 is the medium-pressure ammonium methyl ester liquid pipeline; 29 is the third gas phase pipeline; 30 is the boiler feedwater pipeline; 31 is the plant air pipeline; 32 is the second carbon dioxide pipeline; 33 is the third carbon dioxide pipeline; 34 is the secondary high-pressure ammonium methyl ester pump; 35 is the first pressure gauge; 36 is the first pressure regulating valve; 37 is the second pressure gauge; 38 is the second pressure regulating valve; 39 is the thermometer; 40 is the temperature regulating valve; 41 is the third pressure gauge; 42 is the third pressure regulating valve; 43 is the first level gauge; 44 is the first level regulating valve. Detailed Implementation

[0018] This utility model is not limited to the following embodiments, and the specific implementation method can be determined according to the technical solution of this utility model and the actual situation.

[0019] Unless otherwise specified, all equipment and devices used in this invention are existing, publicly known, and commonly used equipment and devices in the field.

[0020] In this utility model, for ease of description, the description of the relative positions of the components is based on the appendix to the specification. Figure 1 The layout is described using a diagrammatic method, such as the positional relationships of front, back, top, bottom, left, and right, which are based on the instructions attached. Figure 1 The orientation of the layout is determined by the direction of the map.

[0021] The present invention will be further described below with reference to the embodiments and accompanying drawings: Example 1: As shown in the attached document Figure 1As shown, the high-efficiency differential pressure thermal cycle urea production device includes a compressor 1, a synthesis tower 2, a sub-high pressure decomposer 3, a pre-reaction unit, and a medium-pressure pretreatment unit. A first carbon dioxide conveying pipeline 4 is fixedly connected between the upper outlet of the compressor 1 and the first inlet at the bottom of the synthesis tower 2. A first material conveying pipeline 5 is fixedly connected between the top outlet of the synthesis tower 2 and the bottom inlet of the sub-high pressure decomposer 3. A second material conveying pipeline 6 is fixedly connected between the upper outlet of the sub-high pressure decomposer 3 and the upper inlet of the medium-pressure pretreatment unit. A third material conveying pipeline 7 is fixedly connected between the top outlet of the sub-high pressure decomposer 3 and the inlet of the pre-reaction unit. A fourth material conveying pipeline 8 is fixedly connected between the first outlet of the pre-reaction unit and the upper inlet of the medium-pressure pretreatment unit. A fifth material conveying pipeline 9 is fixedly connected between the second outlet of the pre-reaction unit and the second inlet at the bottom of the synthesis tower 2. A liquid ammonia conveying pipeline 10 is fixedly connected to the third inlet at the bottom of the synthesis tower 2.

[0022] In this invention, carbon dioxide is pressurized by compressor 1, and liquid ammonia is pressurized and heated to obtain carbon dioxide raw material gas and raw ammonia, respectively. The carbon dioxide raw material gas and raw ammonia are then fed into synthesis tower 2 via the first carbon dioxide delivery pipeline 4 and the liquid ammonia delivery pipeline 10, respectively, and reacted with ammonium carbamate solution from the pre-reaction unit in a specific ratio to obtain a urea mixed solution (containing ammonium carbamate solution). The urea mixed solution undergoes a decomposition reaction in a sub-high-pressure decomposer 3 to obtain a first gas phase mixture (mainly composed of NH3, H2O, and CO2) and a first liquid phase mixture (mainly composed of ammonium carbamate, urea, ammonia, and water). The mixture undergoes an exothermic reaction in the pre-reaction unit to generate a sub-high pressure ammonium carbamate solution, while simultaneously producing 0.27 MPaG of byproduct steam. The first liquid phase mixture is separated by flash evaporation in the medium-pressure pretreatment unit to obtain a second gas phase mixture and a second liquid phase mixture. The second liquid phase mixture undergoes a decomposition reaction under heating conditions to obtain a third gas phase mixture and a third liquid phase mixture. Both the second and third gas phase mixtures are used as heat sources for the subsequent urea evaporation system. The sub-high pressure ammonium carbamate solution is separated into gas and liquid to obtain ammonium carbamate liquid, which is used as a raw material for urea synthesis and enters the synthesis tower 2 via the fifth material conveying pipeline 9 to participate in the reaction.

[0023] As needed, the heating of liquid ammonia is completed by two-stage heating operation. The heat source for the first stage heating is the low-pressure absorbent liquid of the urea absorption system, and the heat source for the second stage heating is the steam condensate. The resulting raw ammonia temperature is 115℃ to 120℃ and the pressure is 23MPaG.

[0024] As required, the low-pressure absorbent used for liquid ammonia heating is a gas-liquid mixture with a gas phase temperature of 113.5℃ and main components of NH3, H2O, and CO2, and a liquid phase temperature of 40℃ and main components of water, liquid ammonia, urea, and ammonium methyl ester. The high-quality steam condensate obtained after heat exchange in the sub-high-pressure decomposer 3 and other heat exchange equipment is then flash-evaporated to obtain a low-pressure steam condensate (pressure 0.25 MPaG, temperature 138℃), which serves as the heat source for the second-stage heating of the liquid ammonia. The equipment used for pressurizing the liquid ammonia is a high-pressure liquid ammonia pump.

[0025] The above-mentioned high-efficiency differential pressure thermal cycle urea production unit can be further optimized and / or improved according to actual needs: Example 2: Its difference from Example 1 is as follows: (See attached) Figure 1 As shown, the inlet of the secondary high-pressure decomposer 3 is fixedly connected to the first steam pipeline 11, the outlet of the secondary high-pressure decomposer 3 is fixedly connected to the first steam condensate pipeline 12, and the tail gas pipeline of the melamine unit is fixedly connected to the first material conveying pipeline 5.

[0026] As needed, the tail gas components from the upstream melamine unit mainly include NH3 and CO2. The urea mixed solution and the tail gas from the melamine unit enter from the bottom of the secondary high-pressure decomposer 3. After indirect heat exchange with 1.3 MPaG steam from the first steam pipeline 11, the ammonium carbamate in the urea mixed solution decomposes into urea and water. The decomposed liquid phase enters the medium-pressure pretreatment unit through the second material conveying pipeline 6 for further medium-pressure decomposition. The decomposed gas phase enters the pre-reaction unit through the third material conveying pipeline 7.

[0027] Pre-decomposition of the urea mixed solution in the secondary high-pressure decomposer 3 can reduce the amount of material entering the subsequent medium-pressure decomposition system, thereby reducing the steam consumption of the medium and low-pressure decomposition systems. At the same time, the amount of gas phase that needs to be recovered flowing into the medium and low-pressure recovery system is reduced, which can also significantly reduce the circulating water consumption of the medium and low-pressure absorption system.

[0028] Example 3: Its difference from Examples 1 to 2 is as follows: (See attached) Figure 1 As shown, the medium-pressure pretreatment unit includes a medium-pressure pre-separator 14 and a medium-pressure preheater 15. A second material conveying pipeline 6 is fixedly connected between the upper inlet of the medium-pressure pre-separator 14 and the upper outlet of the secondary high-pressure decomposer 3. A sixth material conveying pipeline 16 is fixedly connected between the bottom outlet of the medium-pressure pre-separator 14 and the bottom inlet of the medium-pressure preheater 15. A first gas phase pipeline 17 is fixedly connected to the top outlet of the medium-pressure pre-separator 14. A condensate pipeline 18 is fixedly connected to the lower outlet of the medium-pressure preheater 15. A seventh material conveying pipeline 19 is fixedly connected to the bottom outlet of the medium-pressure preheater 15. A second gas phase pipeline 20 is fixedly connected to the top outlet of the medium-pressure preheater 15.

[0029] As needed, the liquid phase obtained from the decomposition of the secondary high-pressure decomposer 3 is transported to the medium-pressure pre-separator 14 via the second material conveying pipeline 6. In the medium-pressure pre-separator 14, flash separation is carried out. The separated liquid phase enters the medium-pressure preheater 15 via the sixth material conveying pipeline 16. After being heated to 134°C, it enters the subsequent medium-pressure decomposition system via the seventh material conveying pipeline 19 for further decomposition.

[0030] The gas phase after decomposition by the medium-pressure pre-separator 14 and the gas phase after heating by the medium-pressure preheater 15 enter the subsequent urea evaporation system for heat recovery through the first gas phase pipeline 17 and the second gas phase pipeline 20, respectively.

[0031] Example 4: Its difference from Examples 1 to 3 is as follows: (See attached) Figure 1 As shown, the pre-reaction unit includes a mixer 21, a sub-high pressure condenser 22, and a sub-high pressure buffer tank 23. A third material conveying pipeline 7 is fixedly connected between the bottom inlet of the mixer 21 and the top outlet of the sub-high pressure decomposer 3. An eighth material conveying pipeline 24 is fixedly connected between the right outlet of the mixer 21 and the left inlet of the sub-high pressure condenser 22. A fourth material conveying pipeline 8 is fixedly connected between the upper outlet of the sub-high pressure condenser 22 and the upper inlet of the medium pressure preheater 15. A ninth material conveying pipeline 25 is fixedly connected between the left outlet of the sub-high pressure condenser 22 and the right inlet of the sub-high pressure buffer tank 23. A fifth material conveying pipeline 9 is fixedly connected between the bottom outlet of the sub-high pressure buffer tank 23 and the second inlet at the bottom of the synthesis tower 2. A tenth material conveying pipeline 26 is fixedly connected to the fourth material conveying pipeline 8.

[0032] If necessary, the mixer 21 can be a gas-liquid mixer with nozzles to ensure uniform mixing and atomization of the medium.

[0033] Example 5: It differs from Examples 1 to 4 in that, as shown in the appendix... Figure 1 As shown, the left inlet of the mixer 21 is fixedly connected to the tail liquid pipeline 27 of the melamine unit, the tail liquid pipeline 27 of the melamine unit is fixedly connected to the medium-pressure ammonium methyl ester liquid pipeline 28, the top outlet of the secondary high-pressure buffer tank 23 is fixedly connected to the third gas phase pipeline 29, and the bottom inlet of the secondary high-pressure condenser 22 is fixedly connected to the boiler feedwater pipeline 30.

[0034] As needed, the gas phase (mainly composed of NH3, H2O, and CO2) obtained from the decomposition of the sub-high pressure decomposer 3 is mixed with the medium-pressure ammonium methyl ester solution (containing ammonium methyl ester solution with a mass concentration of approximately 50%, as well as H2O and NH3) from the urea medium-pressure absorption system and the tail liquid from the melamine unit (mainly composed of CO2, liquid ammonia, and H2O) in mixer 21, and then enters the sub-high pressure condenser 22, where an exothermic reaction occurs, generating a sub-high pressure ammonium methyl ester solution mixture (where the mass concentration of ammonium methyl ester is close to 60%). Simultaneously, heat is released to generate a large amount of low-pressure by-product steam (0.27 MPaG). The by-product steam passes through the... The fourth material conveying pipeline 8 delivers the material to the medium-pressure preheater 15 to provide it with a heat source. The by-product steam can also be conveyed to the urea evaporation system through the tenth material conveying pipeline 26 as an evaporation heat source. The sub-high pressure ammonium methyl ester liquid mixture is cooled by boiler feedwater. After the temperature drops to 150°C, it flows by gravity through the ninth material conveying pipeline 25 to the sub-high pressure ammonium methyl ester buffer tank 23 under its own pressure (8.0 MPaG) for gas-liquid separation. The separated liquid ammonium methyl ester liquid is sent to the urea synthesis tower 2 through the fifth material conveying pipeline 9 to participate in the reaction. The resulting gas phase enters the subsequent urea medium-pressure absorption system through the third gas phase pipeline 29.

[0035] Example 6: Its difference from Examples 1 to 5 is as follows: (See attached) Figure 1 As shown, compressor 1 is a multi-stage compressor. The four outlets of compressor 1 are fixedly connected to the inlet of the first carbon dioxide conveying pipeline 4. The inlet of compressor 1 is fixedly connected to the factory air pipeline 31. The factory air pipeline 31 is fixedly connected to the second carbon dioxide pipeline 32. The three outlets of compressor 1 are fixedly connected to the third material conveying pipeline 7, and the third carbon dioxide pipeline 33 is fixedly connected to the third material conveying pipeline 7.

[0036] As needed, a multi-stage compressor is a mechanical device that gradually increases gas pressure through multi-stage compression. The device achieves this gradual increase in gas pressure through multi-stage compression. 0.8 MPaG plant air from the production unit's pipeline network mixes with carbon dioxide from the methanol washing unit and enters the first inlet of compressor 1. After compression, the carbon dioxide temperature at the fourth outlet of compressor 1 reaches 110℃, and the pressure reaches 23 MPaG.

[0037] When the melamine co-production unit is not operating, the CO2 gas from the third outlet of compressor 1 is sent to mixer 21 via the third carbon dioxide pipeline 33. There, it mixes with the medium-pressure ammonium methylate solution and the first gas phase mixture from the sub-high-pressure decomposer 3, and then reacts. This operation reduces the power consumption of compressor 1 and the amount of byproduct steam. The amount of CO2 sent to mixer 21 is adjusted according to the temperature of urea synthesis tower 2. The operating temperature at the top of synthesis tower 2 is generally controlled at 193℃, and the operating temperature at the bottom of synthesis tower 2 is controlled at 188℃. When the temperature of synthesis tower 2 rises, the amount of CO2 sent to sub-high-pressure mixer 21 is increased, and the amount of CO2 sent to urea synthesis tower 2 is decreased; conversely, the amount of CO2 sent to sub-high-pressure mixer 21 is decreased, and the amount of CO2 sent to urea synthesis tower 2 is increased.

[0038] Example 7: Its difference from Examples 1 to 6 is as follows: (See attached) Figure 1 As shown, a secondary high-pressure ammonium carbamate pump 34 is fixedly installed on the fifth material conveying pipeline 9; a first pressure gauge 35 and a first pressure regulating valve 36 are fixedly installed on the first material conveying pipeline 5 in sequence according to the medium flow direction; a second pressure gauge 37, a second pressure regulating valve 38, and a first thermometer 39 are fixedly installed on the second material conveying pipeline 6 in sequence according to the medium flow direction; a temperature regulating valve 40 is fixedly installed on the first steam pipeline 11; a third pressure gauge 41 is fixedly installed on the secondary high-pressure buffer tank 23; a third pressure regulating valve 42 is fixedly installed on the third gas phase pipeline 29; a first level gauge 43 is fixedly installed on the secondary high-pressure condenser 22; and a first level regulating valve 44 is fixedly installed on the boiler feedwater pipeline 30.

[0039] Example 8: It differs from Examples 1 to 7 in that: as shown in the appendix Figure 1 As shown, it also includes a PLC controller, a sub-high pressure ammonium carbamate pump 34, a first pressure gauge 35, a first pressure regulating valve 36, a second pressure gauge 37, a second pressure regulating valve 38, a first temperature gauge 39, a temperature regulating valve 40, a third pressure gauge 41, a third pressure regulating valve 42, a first level gauge 43, and a first level regulating valve 44, all of which are electrically connected to the PLC controller. Interlocks are respectively set between the first pressure gauge 35 and the first pressure regulating valve 36, between the second pressure gauge 37 and the second pressure regulating valve 38, between the first temperature gauge 39 and the temperature regulating valve 40, between the third pressure gauge 41 and the third pressure regulating valve 42, and between the first level gauge 43 and the first level regulating valve 44.

[0040] As needed, during normal production, the pressure of synthesis tower 2 is controlled between 21.2 MPaG and 22.0 MPaG. This is achieved by adjusting the opening of the first pressure regulating valve 36 to control the pressure of the first pressure gauge 35, thereby reducing the pressure of the second material conveying pipeline at the top of synthesis tower 2 to 8.0 MPaG. The liquid phase pressure of the secondary high-pressure decomposer 3 is adjusted to 1.8 MPaG by adjusting the opening of the second pressure regulating valve 38. The temperature of the secondary high-pressure decomposer 3 is controlled between 176℃ and 180℃ by adjusting the opening of the temperature regulating valve 40. The pressure of the secondary high-pressure buffer tank 23 is adjusted between 7.95 MPaG and 8.10 MPaG by adjusting the opening of the third pressure regulating valve 42. The liquid level of the secondary high-pressure condenser 22 is adjusted between 40% and 65% by adjusting the opening of the first liquid level regulating valve 44.

[0041] Depending on the needs, the pipelines and equipment of this high-efficiency differential pressure thermal cycle urea production unit can also be equipped with conventional valves, thermometers, and pressure gauges known and commonly used in the field. The PLC controller can be a Siemens S7-1500, which is equipped with a Yokogawa CS3000 DCS control system.

[0042] The above technical features constitute various embodiments of this utility model, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

[0043] The usage process of this utility model is as follows: First, carbon dioxide is pressurized by compressor 1, and liquid ammonia is pressurized and heated. These are then transported via the first carbon dioxide transport pipeline 4 and the liquid ammonia transport pipeline 10, respectively, and reacted with ammonium carbamate solution from the pre-reaction unit into synthesis tower 2 to obtain a urea mixed solution. Next, the urea mixed solution undergoes a decomposition reaction in the sub-high pressure decomposer 3 to obtain a first gaseous mixture and a first liquid mixture. Finally, the first gaseous mixture enters mixer 21 via the third material transport pipeline 7, where it mixes with medium-pressure ammonium carbamate solution from the urea medium-pressure absorption system and the tail liquid from the melamine unit. The mixture then enters the sub-high pressure condenser 22, where an exothermic reaction occurs, generating a sub-high pressure ammonium carbamate solution mixture, while simultaneously releasing heat and producing a large amount of low-pressure... The by-product steam and the mixture of sub-high pressure ammonium carbamate solution, after being cooled by boiler feedwater, flow by gravity through the ninth material conveying pipeline 25 to the sub-high pressure ammonium carbamate buffer tank 23. The liquid ammonium carbamate solution obtained after gas-liquid separation is sent to the urea synthesis tower 2 through the fifth material conveying pipeline 9 to participate in the reaction. The resulting gas phase enters the subsequent urea medium-pressure absorption system through the third gas phase pipeline 29. The first liquid phase mixture enters the medium-pressure pre-separator 14 through the second material conveying pipeline 6, where it undergoes flash separation. The separated liquid phase enters the medium-pressure preheater 15 through the sixth material conveying pipeline 16. After being heated by the by-product steam conveyed by the fourth material conveying pipeline 8, it is sent to the subsequent medium-pressure decomposition system through the seventh material conveying pipeline 19 for further decomposition.

Claims

1. A high-efficiency differential pressure thermal cycle urea production device, characterized in that... The system includes a compressor, a synthesis tower, a sub-high-pressure decomposer, a pre-reaction unit, and a medium-pressure pretreatment unit. A first carbon dioxide conveying pipeline is fixedly connected between the upper outlet of the compressor and the first inlet at the bottom of the synthesis tower. A first material conveying pipeline is fixedly connected between the top outlet of the synthesis tower and the bottom inlet of the sub-high-pressure decomposer. A second material conveying pipeline is fixedly connected between the upper outlet of the sub-high-pressure decomposer and the upper inlet of the medium-pressure pretreatment unit. A third material conveying pipeline is fixedly connected between the top outlet of the sub-high-pressure decomposer and the inlet of the pre-reaction unit. A fourth material conveying pipeline is fixedly connected between the first outlet of the pre-reaction unit and the upper inlet of the medium-pressure pretreatment unit. A fifth material conveying pipeline is fixedly connected between the second outlet of the pre-reaction unit and the second inlet at the bottom of the synthesis tower. A liquid ammonia conveying pipeline is fixedly connected to the third inlet at the bottom of the synthesis tower.

2. The high-efficiency differential pressure thermal cycle urea production device according to claim 1, characterized in that... The middle inlet of the secondary high-pressure decomposer is fixedly connected to the first steam pipeline, the lower outlet of the secondary high-pressure decomposer is fixedly connected to the first steam condensate pipeline, and the tail gas pipeline of the melamine unit is fixedly connected to the first material conveying pipeline.

3. The high-efficiency differential pressure thermal cycle urea production device according to claim 1 or 2, characterized in that... The medium-pressure pretreatment unit includes a medium-pressure pre-separator and a medium-pressure preheater. A second material conveying pipeline is fixedly connected between the upper inlet of the medium-pressure pre-separator and the upper outlet of the secondary high-pressure decomposer. A sixth material conveying pipeline is fixedly connected between the bottom outlet of the medium-pressure pre-separator and the bottom inlet of the medium-pressure preheater. A first gas phase pipeline is fixedly connected to the top outlet of the medium-pressure pre-separator. A condensate pipeline is fixedly connected to the lower outlet of the medium-pressure preheater. A seventh material conveying pipeline is fixedly connected to the bottom outlet of the medium-pressure preheater. A second gas phase pipeline is fixedly connected to the top outlet of the medium-pressure preheater.

4. The high-efficiency differential pressure thermal cycle urea production device according to claim 3, characterized in that... The pre-reaction unit includes a mixer, a sub-high-pressure condenser, and a sub-high-pressure buffer tank. A third material conveying pipeline is fixedly connected between the bottom inlet of the mixer and the top outlet of the sub-high-pressure decomposer. An eighth material conveying pipeline is fixedly connected between the right outlet of the mixer and the left inlet of the sub-high-pressure condenser. A fourth material conveying pipeline is fixedly connected between the upper outlet of the sub-high-pressure condenser and the upper inlet of the medium-pressure preheater. A ninth material conveying pipeline is fixedly connected between the left outlet of the sub-high-pressure condenser and the right inlet of the sub-high-pressure buffer tank. A fifth material conveying pipeline is fixedly connected between the bottom outlet of the sub-high-pressure buffer tank and the second inlet at the bottom of the synthesis tower. A tenth material conveying pipeline is fixedly connected to the fourth material conveying pipeline.

5. The high-efficiency differential pressure thermal cycle urea production device according to claim 4, characterized in that... The left inlet of the mixer is fixedly connected to the tail liquid pipeline of the melamine unit, the tail liquid pipeline of the melamine unit is fixedly connected to the medium-pressure ammonium methyl ester liquid pipeline, the top outlet of the secondary high-pressure buffer tank is fixedly connected to the third gas phase pipeline, and the bottom inlet of the secondary high-pressure condenser is fixedly connected to the boiler feedwater pipeline.

6. The high-efficiency differential pressure thermal cycle urea production apparatus according to claim 1, 2, 4, or 5, characterized in that... The compressor is a multi-stage compressor. The four outlets of the compressor are fixedly connected to the inlet of the first carbon dioxide conveying pipeline. The compressor inlet is fixedly connected to the factory air pipeline. The factory air pipeline is fixedly connected to the second carbon dioxide pipeline. The three outlets of the compressor are fixedly connected to the third material conveying pipeline, and the third carbon dioxide pipeline is fixedly connected to the third material conveying pipeline.

7. The high-efficiency differential pressure thermal cycle urea production device according to claim 3, characterized in that... The compressor is a multi-stage compressor. The four outlets of the compressor are fixedly connected to the inlet of the first carbon dioxide conveying pipeline. The compressor inlet is fixedly connected to the factory air pipeline. The factory air pipeline is fixedly connected to the second carbon dioxide pipeline. The three outlets of the compressor are fixedly connected to the third material conveying pipeline, and the third carbon dioxide pipeline is fixedly connected to the third material conveying pipeline.

8. The high-efficiency differential pressure thermal cycle urea production device according to claim 6, characterized in that... A sub-high pressure ammonium carbamate pump is fixedly installed on the fifth material conveying pipeline. A first pressure gauge and a first pressure regulating valve are fixedly installed in sequence according to the medium flow direction on the first material conveying pipeline. A second pressure gauge, a second pressure regulating valve, and a first thermometer are fixedly installed in sequence according to the medium flow direction on the second material conveying pipeline. A temperature regulating valve is fixedly installed on the first steam pipeline. A third pressure gauge is fixedly installed on the sub-high pressure buffer tank. A third pressure regulating valve is fixedly installed on the third gas phase pipeline. A first liquid level gauge is fixedly installed on the sub-high pressure condenser. A first liquid level regulating valve is fixedly installed on the boiler feedwater pipeline.

9. The high-efficiency differential pressure thermal cycle urea production device according to claim 7, characterized in that... A sub-high pressure ammonium carbamate pump is fixedly installed on the fifth material conveying pipeline. A first pressure gauge and a first pressure regulating valve are fixedly installed in sequence according to the medium flow direction on the first material conveying pipeline. A second pressure gauge, a second pressure regulating valve, and a first thermometer are fixedly installed in sequence according to the medium flow direction on the second material conveying pipeline. A temperature regulating valve is fixedly installed on the first steam pipeline. A third pressure gauge is fixedly installed on the sub-high pressure buffer tank. A third pressure regulating valve is fixedly installed on the third gas phase pipeline. A first liquid level gauge is fixedly installed on the sub-high pressure condenser. A first liquid level regulating valve is fixedly installed on the boiler feedwater pipeline.

10. The high-efficiency differential pressure thermal cycle urea production apparatus according to claim 8 or 9, characterized in that... It also includes a PLC controller, a sub-high pressure ammonium carbamate pump, a first pressure gauge, a first pressure regulating valve, a second pressure gauge, a second pressure regulating valve, a first temperature gauge, a temperature regulating valve, a third pressure gauge, a third pressure regulating valve, a first level gauge, and a first level regulating valve, all of which are electrically connected to the PLC controller. Interlocks are respectively set between the first pressure gauge and the first pressure regulating valve, between the second pressure gauge and the second pressure regulating valve, between the first temperature gauge and the temperature regulating valve, between the third pressure gauge and the third pressure regulating valve, and between the first level gauge and the first level regulating valve.

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