Energy-saving urea production system

Abstract

The present application relates to the technical field of urea preparation, and discloses an energy-saving urea production system, a carbon dioxide stripping tower and a high-pressure ammonia ejector are connected with a first high-pressure methylamine condenser, a second high-pressure methylamine condenser is connected between the first high-pressure methylamine condenser and a urea synthesis tower, the second high-pressure methylamine condenser can be connected with a carbon dioxide compressor, and the urea synthesis tower is connected with the upper portion of the carbon dioxide stripping tower to input urea mixture into the carbon dioxide stripping tower. The energy-saving urea production system improves the recovery rate and utilization rate of the synthesis reaction heat through the addition of the second high-pressure methylamine condenser.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of urea production, in particular to an energy-saving urea production system. BACKGROUND

[0002] The raw materials for urea production mainly include coal or natural gas, air and water vapor. Coal and natural gas can be converted into synthetic ammonia and carbon dioxide after a series of treatments, which are the key raw materials for urea production. The synthesis reaction of urea is a balanced chemical reaction, which is generally considered to be completed in two steps: excess liquid ammonia reacts with carbon dioxide to form ammonium carbamate; heating ammonium carbamate to urea.

[0003] The Chinese patent document with the authorization announcement number CN107001247B discloses a urea production device, which includes a reactor, a stripper, a condenser and a scrubber. The reactor, the stripper, the condenser and the scrubber are connected in series, and the condenser and the reactor are separately connected. Ammonia is supplied to the condenser and carbon dioxide is supplied to the stripper. The carbon dioxide after stripping enters the condenser, and reacts with ammonia to form ammonium carbamate, which is referred to as methyl ammonium. The synthesis reaction is an exothermic reaction, and the condenser absorbs the heat released to realize heat recovery and reuse. Then the methyl ammonium mixture enters the reactor to generate urea and water. Then the urea-containing aqueous solution is concentrated in the stripper to realize the recycling of the materials.

[0004] However, the above-mentioned urea production device only sets a single condenser to utilize the heat of the synthesis reaction, which is easy to cause the low recovery rate and utilization rate of the heat of the synthesis reaction. SUMMARY

[0005] The present application provides an energy-saving urea production system, which aims to solve the problem of low recovery rate and utilization rate of the heat of the synthesis reaction in the related art.

[0006] The energy-saving urea production system of the present application comprises a carbon dioxide stripping tower, a first high-pressure methyl ammonium condenser, a high-pressure ammonia ejector and a urea synthesis tower, characterized in that the carbon dioxide stripping tower and the high-pressure ammonia ejector are respectively connected with the first high-pressure methyl ammonium condenser, a second high-pressure methyl ammonium condenser is connected between the first high-pressure methyl ammonium condenser and the urea synthesis tower, the second high-pressure methyl ammonium condenser can be externally connected with a carbon dioxide compressor, and the urea synthesis tower is connected with the upper part of the carbon dioxide stripping tower to input urea mixture into the carbon dioxide stripping tower.

[0007] Preferably, the energy-saving urea production system further comprises a high-pressure scrubber having a gas inlet and a gas outlet, the gas inlet being connected to the top of the urea synthesis tower; the high-pressure scrubber is connected with a high-pressure methylamine pump, and the high-pressure scrubber further has a methylamine liquid outlet connected to the high-pressure ammonia ejector.

[0008] Preferably, the second high-pressure methylamine condenser comprises a shell and condensing pipes, the shell is sequentially divided into a water inlet cavity, a condensing cavity and a water outlet cavity in the left-right direction, the cavity wall of the condensing cavity is provided with a reactant inlet and a reactant outlet which are opposite in the up-down direction and staggered in the left-right direction, the reactant inlet is connected with the first high-pressure methylamine condenser, and the reactant outlet is connected with the urea synthesis tower; a plurality of condensing pipes are arranged in the condensing cavity and communicate with the water inlet cavity and the water outlet cavity at two ends respectively.

[0009] Preferably, the shell has a first partition plate for separating the water inlet cavity and the condensing cavity and a second partition plate for separating the condensing cavity and the water outlet cavity, the first partition plate and the second partition plate are both rotationally assembled on the shell, and the two ends of the condensing pipes are fixedly connected with the first partition plate and the second partition plate respectively; the shell is provided with a driving device for driving at least one of the first partition plate and the second partition plate to rotate.

[0010] Preferably, the condensing pipe is provided with a scraping member capable of sliding in the axial direction of the condensing pipe, the scraping member is used for scraping off the scale in the condensing pipe in the sliding process, and a transmission assembly is connected between the scraping member and the shell so that the scraping member can slide when revolving.

[0011] Preferably, the scraping member comprises a scraping ring, an outer circular surface of the scraping ring is attached to the inner wall of the condensing pipe, and a plurality of water holes are arranged on the scraping ring.

[0012] Preferably, the transmission assembly comprises a threaded guide and a gear mechanism, the threaded guide is coaxially rotationally arranged in the condensing pipe, and a central hole of the scraping ring is threadedly sleeved on the threaded guide; the gear mechanism connects the threaded guide and the shell, and the gear mechanism is used for driving the threaded guide to rotate when the threaded guide revolves.

[0013] Preferably, the transmission assembly further comprises a guide rod, the guide rod is arranged in the condensing pipe and extends in the axial direction of the condensing pipe, and the scraping ring is slidingly connected with the guide rod.

[0014] Preferably, the water outlet cavity is provided with a mounting plate fixedly connected with the second partition plate, one end of the threaded guide is rotationally mounted on the mounting plate, and one end of the guide rod is fixedly mounted on the mounting plate.

[0015] Preferably, the gear mechanism comprises a transmission gear ring and a transmission gear, a plurality of the condenser pipes form a plurality of distribution circles from inside to outside, the transmission gear rings are arranged from inside to outside, the transmission gear rings and the distribution circles correspond to each other, and the transmission gear rings are fixed on the shell; the transmission gear is arranged at the other end of the threaded guide and is engaged with the adjacent transmission gear ring.

[0016] By adopting the technical scheme, the present application has the following beneficial effects:

[0017] 1. The present application realizes further synthesis of intermediate product methylamine, and further formation and collection of reaction heat, thus increasing the amount of subsequent urea and improving the recovery rate and utilization rate of reaction heat.

[0018] 2. The present application realizes rotation of the condenser pipes, so that the condenser pipes can stir the gas-liquid mixture, accelerate the contact and collision between gas molecules and liquid molecules in the gas-liquid mixture, promote the mass transfer process of carbon dioxide and ammonia, make them more fully participate in the reaction, and then improve the generation rate of methylamine and the purity of methylamine. In addition, the rotating condenser pipes can alternately exchange heat with the gas-liquid mixture, rapidly disperse the reaction heat to the whole reaction system, avoid local overheating, and thus maintain the uniformity of the reaction temperature.

[0019] 3. The present application realizes automatic scraping of the scale on the inner wall of the condenser pipe by sliding of the scraping ring, and guarantees the heat exchange effect of the condenser pipe. Since the outer cylindrical surface of the scraping ring is attached to the inner wall of the condenser pipe, the scraping ring supports the condenser pipe, thus reducing the deformation and collapse of the heat exchange pipe and realizing proper protection of the heat exchange pipe. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a device schematic diagram of the energy-saving urea production system of the present application.

[0021] Figure 2 is a sectional view schematic diagram of the second high-pressure methylamine condenser of the present application.

[0022] Figure 3 is an enlarged view schematic diagram of the part A in the present application. Figure 2

[0023] Figure 4 is a three-dimensional view schematic diagram of the first to second baffle parts of the present application.

[0024] Figure 5 is an exploded view schematic diagram of the condenser pipe to threaded guide part of the present application.

[0025] Figure 6 ​Fig. 1 is a structural schematic diagram of a gear mechanism part of the present application.

[0026] Reference numerals:

[0027] 100, carbon dioxide stripping column;

[0028] 200, first high-pressure methylamine condenser;

[0029] 300, high-pressure ammonia ejector;

[0030] 400, urea synthesis column; 401, overflow pipe;

[0031] 500, high-pressure scrubber; 501, gas inlet; 502, gas outlet; 503, methylamine liquid outlet;

[0032] 600, carbon dioxide compressor;

[0033] 700, second high-pressure methylamine condenser;

[0034] 1, housing; 11, water inlet cavity; 111, water inlet; 112, water outlet; 12, condensation cavity; 121, reactant inlet; 122, reactant outlet; 13, water outlet cavity; 131, mounting plate; 14, first partition; 15, second partition; 2, condensation pipe; 31, driving motor; 32, driving gear; 33, driving gear ring; 4, scraping ring; 41, water passage hole; 51, threaded guide; 52, guide rod; 53, transmission gear ring; 54, transmission gear. DETAILED DESCRIPTION

[0035] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings. The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application.

[0036] The present application will be described below in detail with reference to the drawings. Figures 1 to 6 An energy-saving urea production system of the present application is described below.

[0037] As shown in Figure 1 Fig. 1, the energy-saving urea production system of the present application includes a carbon dioxide stripping column 100, a first high-pressure methylamine condenser 200, a high-pressure ammonia ejector 300, a urea synthesis column 400, and a high-pressure scrubber 500.

[0038] The top of the carbon dioxide stripping tower 100 and the top of the high-pressure ammonia ejector 300 are respectively connected to the top of the first high-pressure methylamine condenser 200. The bottom of the carbon dioxide stripping tower 100 is externally connected to a carbon dioxide compressor 600, which is used to introduce carbon dioxide gas into the carbon dioxide stripping tower 100, and the carbon dioxide gas enters the first high-pressure methylamine condenser 200 through the top of the carbon dioxide stripping tower 100; the high-pressure ammonia ejector 300 is used to input liquid ammonia into the first high-pressure methylamine condenser 200, and the ammonia and carbon dioxide react in the first high-pressure methylamine condenser 200 to generate ammonium carbamate and release heat, thereby realizing the first step of ammonium carbamate, i.e., the preparation of methylamine. The synthesis reaction heat is absorbed by the condensing medium in the first high-pressure methylamine condenser 200 as a heating heat source for the medium-pressure decomposition system.

[0039] The first high-pressure methylamine condenser 200 and the urea synthesis tower 400 are connected to the second high-pressure methylamine condenser 700, which can be externally connected to the carbon dioxide compressor 600. The gas-liquid mixture after reaction in the first high-pressure methylamine condenser 200 enters the second high-pressure methylamine condenser 700, and the carbon dioxide compressor 600 introduces carbon dioxide gas into the second high-pressure methylamine condenser 700, so that the remaining ammonia and carbon dioxide gas in the gas-liquid mixture further react to continue generating methylamine, and the synthesis reaction heat is absorbed by the condensing medium in the second high-pressure methylamine condenser 700 as a heating heat source for the low-pressure decomposition system. It should be noted that the carbon dioxide gas introduced by the carbon dioxide compressor 600 into the carbon dioxide stripping tower 100 and the second high-pressure methylamine condenser 700 can be proportionally split, for example, 85% of the carbon dioxide gas enters the carbon dioxide stripping tower 100, and 15% of the carbon dioxide gas enters the second high-pressure methylamine condenser 700, which can ensure the sufficiency of the reaction in the first high-pressure methylamine condenser 200 and the second high-pressure methylamine condenser 700.

[0040] After that, the gas-liquid mixture (temperature about 183°C) in the second high-pressure methylamine condenser 700 enters the urea synthesis tower 400, and the heating causes the methylamine to decompose into urea and water.

[0041] An overflow pipe 401 is inserted inside the urea synthesis tower 400, and the bottom of the overflow pipe 401 is connected to the upper part of the carbon dioxide stripping tower 100. After the reaction, the gas-liquid mixture in the urea synthesis tower 400 contains unreacted reactants, reaction products, and other reaction products. The liquid components, such as urea, water, and ammonium methyl ester, enter the upper part of the carbon dioxide stripping tower 100 through the overflow pipe 401, where they undergo heat and mass transfer with the rising carbon dioxide gas. Under the action of carbon dioxide gas stripping and external steam heating and decomposition, the unreacted substances decompose, promoting the continued formation of urea. The urea synthesis liquid (composed of urea, water, and ammonium methyl ester) exiting the carbon dioxide stripping tower 100 is depressurized and enters a medium-pressure decomposition system or a low-pressure decomposition system for further decomposition. This achieves both further decomposition of ammonium methyl ester and full utilization of the heat of synthesis reaction in the first high-pressure ammonium methyl ester condenser 200 and the second high-pressure ammonium methyl ester condenser 700. The post-treatment of the urea synthesis liquid is a well-known technology in the field and will not be described in detail here.

[0042] As can be seen from the above, by adding the second high-pressure ammonium carbamate condenser 700, the intermediate product ammonium carbamate is further synthesized, and the heat of synthesis reaction is further formed and collected. This not only increases the amount of urea produced later, but also improves the recovery rate and utilization rate of the heat of synthesis reaction.

[0043] The high-pressure scrubber 500 has a gas inlet 501 and a gas outlet 502. The gas inlet 501 is connected to the top of the urea synthesis tower 400. The high-pressure scrubber 500 is connected to a high-pressure ammonium carbamate pump and also has an ammonium carbamate liquid outlet 503, which is connected to a high-pressure ammonia injector 300.

[0044] After the reaction, the gaseous components in the urea synthesis tower 400, such as ammonia, carbon dioxide, hydrogen, and nitrogen (at a temperature of approximately 170°C), enter the high-pressure scrubber 500 from the top of the urea synthesis tower 400 through the gas inlet 501. There, they come into contact with and are scrubbed by the ammonium carbamate liquid from the high-pressure ammonium carbamate pump, thereby removing ammonia and carbon dioxide from the gas phase. The remaining gaseous components are then discharged through the gas outlet 502 for further processing, while the ammonium carbamate liquid flows through the ammonium carbamate liquid outlet 503 into the high-pressure ammonia injector 300. Together with the liquid ammonia ejected from the high-pressure ammonia injector 300, it enters the first high-pressure ammonium carbamate condenser 200 and participates in subsequent reactions, thus improving the utilization rate of the ammonium carbamate liquid, residual ammonia, and carbon dioxide.

[0045] Understandably, the above-mentioned devices are connected by pipes, which facilitates the flow of various chemical materials.

[0046] Continue to refer to Figures 1 to 3The second high-pressure methylamine condenser 700 comprises a shell 1 and a condensing pipe 2. The shell 1 is sequentially divided into a water inlet cavity 11, a condensing cavity 12 and a water outlet cavity 13 in the left-right direction. The cavity wall of the condensing cavity 12 is provided with a reactant inlet 121 and a reactant outlet 122 which are opposite in the up-down direction and staggered in the left-right direction. The reactant inlet 121 is connected with the first high-pressure methylamine condenser 200, and the reactant outlet 122 is connected with the urea synthesis tower 400. A plurality of condensing pipes 2 are uniformly arranged in the condensing cavity 12. The condensing pipes 2 extend in the left-right direction and are respectively communicated with the water inlet cavity 11 and the water outlet cavity 13 at both ends. The shell 1 is respectively provided with a water inlet 111 and a water outlet 112 at both ends. The water inlet 111 is communicated with the water inlet cavity 11, and the water outlet 112 is communicated with the water outlet cavity 13.

[0047] In the embodiment, the condensing medium of the second high-pressure methylamine condenser 700 is cooling water. The cooling water enters the water inlet cavity 11 through the water inlet 111, is then distributed into the plurality of condensing pipes 2, and is finally converged through the water outlet cavity 13 and discharged through the water outlet 112. At the same time, the gas-liquid mixture of the first high-pressure methylamine condenser 200 enters the condensing cavity 12 through the reactant inlet 121 and is discharged through the reactant outlet 122. When the cooling water flows in the condensing pipe 2, it can exchange heat with the gas-liquid mixture through the partition wall, thereby realizing the condensation of the gas-liquid mixture during the reaction, recovering the synthesis reaction heat, and facilitating the reuse of the synthesis reaction heat.

[0048] With reference to the above description, Figures 2 to 4 The shell 1 is provided with a first partition plate 14 for separating the water inlet cavity 11 and the condensing cavity 12 and a second partition plate 15 for separating the condensing cavity 12 and the water outlet cavity 13. The first partition plate 14 and the second partition plate 15 are both rotationally assembled on the shell 1. The two ends of the condensing pipe 2 are fixedly connected with the first partition plate 14 and the second partition plate 15, respectively. The first partition plate 14 and the second partition plate 15 support the condensing pipe 2. The shell 1 is provided with a driving device for driving the first partition plate 14 to rotate.

[0049] When the first partition plate 14 rotates, the second partition plate 15 is driven to rotate by the condensing pipe 2. In this way, the condensing pipe 2 rotates around the condensing cavity 12. When the gas-liquid mixture enters the condensing cavity 12, it will first deposit on the bottom of the condensing cavity 12 due to the gravity. The rotating condensing pipe 2 can stir the gas-liquid mixture, thereby accelerating the contact and collision between the gas molecules and the liquid molecules in the gas-liquid mixture, promoting the mass transfer process of carbon dioxide and ammonia, and making them more fully participate in the reaction. Through stirring, the collision frequency between the reactant molecules increases, which helps to accelerate the reaction kinetics process and improve the generation rate of methylamine. Stirring can promote the full reaction between the reactants, thereby improving the purity of methylamine. In addition, the rotating condensing pipe 2 can alternately exchange heat with the gas-liquid mixture, so that the synthesis reaction heat is rapidly dispersed to the whole reaction system, avoiding the occurrence of local overheating phenomenon, thereby maintaining the uniformity of the reaction temperature.

[0050] The driving device comprises a driving motor 31, a driving gear 32 and a driving gear ring 33, the driving gear ring 33 is coaxially fixed on the first partition plate 14, the driving gear 32 is engaged with the driving gear ring 33, and the driving motor 31 is installed on the shell 1 and connected with the driving gear 32 to drive the driving gear 32 to rotate.

[0051] When the driving gear 32 rotates, the driving gear ring 33 is driven to rotate under the engagement, and the first partition plate 14 is driven to rotate by the driving gear ring 33, so that the revolution of the condenser pipe 2 is realized.

[0052] After the second high-pressure methylamine condenser 700 is used for a long time, scale will continuously accumulate on the inner wall of the condenser pipe 2, thereby affecting the heat exchange effect.

[0053] Therefore, with reference to Figures 2 to 5 , the condenser pipe 2 is provided with a scraping member capable of sliding along the axial direction thereof, the scraping member comprises a scraping ring 4, the outer circular surface of the scraping ring 4 is in contact with the inner wall of the condenser pipe 2, a plurality of water passing holes 41 are uniformly distributed on the scraping ring 4 in the circumferential direction, the water passing holes 41 are used to pass the cooling water, and the cooling water is prevented from being blocked in the condenser pipe 2. When the scraping ring 4 slides, the scale on the inner wall of the condenser pipe 2 can be scraped off by the scraping ring 4, and the scraped scale is carried out by the water flow in the condenser pipe 2, thereby realizing the cleaning of the scale, so that the heat exchange effect of the condenser pipe 2 is ensured. In addition, since the outer circular surface of the scraping ring 4 is in contact with the inner wall of the condenser pipe 2, the scraping ring 4 has a supporting effect on the condenser pipe 2. Due to the temperature difference of substances inside and outside the pipe, thermal stress will be generated in the condenser pipe 2 during long-term use. Long-term thermal stress may cause deformation of the heat exchange pipe, thereby causing collapse and other phenomena. The supporting effect of the scraping ring 4 on the condenser pipe 2 reduces the deformation and collapse of the heat exchange pipe, thereby achieving appropriate protection of the heat exchange pipe.

[0054] The scraping member is connected with the shell 1 through a transmission assembly, and the transmission assembly comprises a threaded guide 51, a guide rod 52 and a gear mechanism.

[0055] The threaded guide 51 is coaxially arranged in the condenser pipe 2 and forms an annular gap between the threaded guide 51 and the condenser pipe 2. Therefore, the threaded guide 51 occupies the axial position of the condenser pipe 2, so that the cooling water can only flow in the annular gap, and the cooling water is closer to the pipe wall of the condenser pipe 2, thereby improving the heat exchange effect of the cooling water and improving the utilization rate of the cooling water. The center hole of the scraping ring 4 is threadedly sleeved on the threaded guide 51, so that the scraping ring 4 and the threaded guide 51 are threadedly connected. The guide rod 52 is arranged in the condenser pipe 2 and extends in the axial direction of the condenser pipe 2. Understandably, the guide rod 52 is located beside the threaded guide 51. One of the water passing holes 41 of the scraping ring 4 constitutes a sliding hole, and the sliding hole is slidably sleeved on the guide rod 52, so that the scraping ring 4 and the guide rod 52 are slidably connected.

[0056] The water outlet cavity 13 is provided with a mounting plate 131, and the mounting plate 131 is fixedly connected with the second partition plate 15 through a connecting column. One end of the threaded guide 51 is rotatably mounted on the mounting plate 131, and one end of the guide rod 52 is fixedly mounted on the mounting plate 131. The mounting plate 131 is used to provide a mounting position for the threaded guide 51 and the guide rod 52.

[0057] When the threaded guide 51 rotates, the scraping ring 4 can rotate synchronously with the threaded guide 51 or can slide along the axial direction of the threaded guide 51 due to the threaded connection. However, under the guidance of the guide rod 52, the scraping ring 4 can only slide along the axial direction of the threaded guide 51, so that the scraping ring 4 slides in the condensing pipe 2, and the scale on the pipe wall is scraped off.

[0058] Continuing to refer to Figures 4 to 6 , the gear mechanism connects the threaded guide 51 and the shell 1, and the gear mechanism includes a transmission gear ring 53 and a transmission gear 54. A plurality of condensing pipes 2 form a plurality of distribution circles from inside to outside, and the transmission gear ring 53 is arranged from inside to outside. The plurality of transmission gear rings 53 correspond to the plurality of distribution circles, the diameters of the transmission gear ring 53 and the corresponding distribution circle are substantially the same, and the transmission gear ring 53 is fixedly arranged on the shell 1. The transmission gear 54 is arranged at the other end of the threaded guide 51 and is engaged with the adjacent transmission gear ring 53.

[0059] When the condensing pipe 2 revolves, the threaded guide 51 is driven to revolve by the second partition plate 15 and the mounting plate 131, the transmission gear 54 is driven to revolve by the threaded guide 51, the transmission gear 54 rotates under the meshing action of the transmission gear ring 53 and the transmission gear 54, thereby driving the threaded guide 51 to rotate, and the threaded guide 51 can realize the sliding of the scraping ring 4 when rotating, thereby realizing the removal of the scale. In this way, the removal of the scale and the revolving stirring action of the condensing pipe 2 are linked, the use of power equipment is reduced, and the cost is saved.

[0060] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0061] Furthermore, the terms "first", "second", etc. are used only for descriptive purposes and do not connote or imply relative importance or a quantity of the indicated technical features. Thus, a feature defined with "first", "second", etc. can include at least one of the features implicitly or explicitly. In the description of the present application, the meaning of "a plurality" is at least two, for example, two, three, etc., unless otherwise specifically defined.

[0062] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and that changes, modifications, substitutions and variations can be made by those skilled in the art without departing from the scope of the present application.

Claims

1. An energy-saving urea production system comprising a carbon dioxide stripping column, a first high-pressure methylamine condenser, a high-pressure ammonia ejector, and a urea synthesis column, characterized by, The carbon dioxide stripping tower and the high-pressure ammonia ejector are connected with the first high-pressure methylamine condenser respectively, a second high-pressure methylamine condenser is connected between the first high-pressure methylamine condenser and the urea synthesis tower, the second high-pressure methylamine condenser can be connected with a carbon dioxide compressor, and the urea synthesis tower is connected with the upper portion of the carbon dioxide stripping tower to input urea mixture into the carbon dioxide stripping tower; The second high-pressure methylamine condenser comprises a shell and a condensing pipe, the shell is sequentially divided into a water inlet cavity, a condensing cavity and a water outlet cavity in the left-right direction, the cavity wall of the condensing cavity is provided with a reactant inlet and a reactant outlet which are opposite in the up-down direction and staggered in the left-right direction, the reactant inlet is connected with the first high-pressure methylamine condenser, and the reactant outlet is connected with the urea synthesis tower; A plurality of condensing pipes are arranged in the condensing cavity and are in communication with the water inlet cavity and the water outlet cavity at two ends respectively; The shell is provided with a first partition plate for separating the water inlet cavity and the condensing cavity and a second partition plate for separating the condensing cavity and the water outlet cavity, the first partition plate and the second partition plate are rotationally assembled on the shell, and the two ends of the condensing pipe are fixedly connected with the first partition plate and the second partition plate respectively; the shell is provided with a driving device for driving at least one of the first partition plate and the second partition plate to rotate; The condensing pipe is provided with a scraping piece which can slide in the axial direction of the condensing pipe, the scraping piece is used for scraping off scale in the condensing pipe in the sliding process, and a transmission assembly is connected between the scraping piece and the shell so that the scraping piece can slide when revolving; The scraping piece comprises a scraping ring, an outer circular surface of the scraping ring is attached to the inner wall of the condensing pipe, and a plurality of water through holes are arranged on the scraping ring; The transmission assembly comprises a threaded guide and a gear mechanism, the threaded guide is coaxially rotationally arranged in the condensing pipe, and a central hole of the scraping ring is threadedly sleeved on the threaded guide; the gear mechanism connects the threaded guide and the shell, and is used for driving the threaded guide to rotate when the threaded guide revolves.

2. The energy-saving urea production system according to claim 1, characterized in that, The energy-saving urea production system further comprises a high-pressure scrubber, the high-pressure scrubber is provided with a gas inlet and a gas outlet, the gas inlet is connected with the top of the urea synthesis tower, the high-pressure scrubber is connected with a high-pressure methylamine pump, and the high-pressure scrubber is further provided with a methylamine liquid outlet, the methylamine liquid outlet is connected with the high-pressure ammonia ejector.

3. The energy-saving urea production system according to claim 1, characterized in that, The transmission assembly further comprises a guide rod, the guide rod is arranged in the condensing pipe and extends in the axial direction of the condensing pipe, and the scraping ring is slidably connected with the guide rod.

4. The energy-saving urea production system according to claim 3, characterized in that, The water outlet cavity is provided with a mounting plate, the mounting plate is fixedly connected with the second partition plate, one end of the threaded guide is rotationally mounted on the mounting plate, and one end of the guide rod is fixedly mounted on the mounting plate.

5. The energy-saving urea production system according to claim 4, characterized in that, The gear mechanism comprises a driving gear ring and a driving gear, a plurality of the condensing pipes form a plurality of distribution circles from inside to outside, the driving gear rings are arranged from inside to outside, the plurality of the driving gear rings and the plurality of the distribution circles correspond to each other, and the driving gear rings are fixed on the shell; the driving gear is arranged at the other end of the threaded guide and is engaged with the adjacent driving gear ring.

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