Urea synthesis device, urea synthesis method, and method for improving existing urea synthesis device

Abstract

Provided is a urea synthesis device with which it is possible to facilitate maintenance of the device, facilitate design and fabrication of the device, and / or promote urea reaction. The present invention is a urea synthesis device for generating urea by reacting ammonia and carbon dioxide, the urea synthesis device comprising a first urea synthesis pipe (R1), a second urea synthesis pipe (R2), a condenser (C), a stripping tower (S), and a unit (E) for supplying a first urea synthesis liquid. The condenser (C) is a separate device from the first urea synthesis tube (R1) and the second urea synthesis tube (R2), and is configured so that a process fluid flows through the tube (Ct) and is cooled by a cooling medium flowing through the housing (Cs) side to condense the mixed gas in the absorption medium to obtain a condensed liquid, and the condenser (C) is configured so as to be separated from the first urea synthesis tube (R1) and the second urea synthesis tube (R2). The first urea synthesis pipe (R1) is a device for obtaining a first urea synthesis liquid from the condensate obtained in the condenser (C), and the second urea synthesis pipe (R2) is a device for obtaining a second urea synthesis liquid from the first urea synthesis liquid.

Description

TECHNICAL FIELD

[0001] The present application relates to a urea synthesis device capable of achieving ease of maintenance of the device, ease of design and manufacture of the device, and / or promotion of urea synthesis. BACKGROUND

[0002] In a urea synthesis process, carbon dioxide and ammonia are generally reacted at high temperature and high pressure to obtain a urea synthesis liquid. In the urea synthesis liquid, not only urea generated by the synthesis reaction, but also unreacted ammonia, unreacted carbon dioxide, and ammonium carbamate as an intermediate are contained. Then, by removing the unreacted components and the intermediate from the urea synthesis liquid, a urea product is obtained.

[0003] The unreacted components and the intermediate removed from the urea synthesis liquid are generally recovered as raw materials for urea synthesis. For example, a mixed gas (a gas containing unreacted ammonia and unreacted carbon dioxide) separated from the urea synthesis liquid in a stripping column is condensed in a condenser in an absorption medium, and the obtained condensed liquid is recovered as a raw material for urea synthesis. As the absorption medium, for example, ammonium carbamate liquid recovered from the urea synthesis liquid in a subsequent process (recovered carbamate liquid) can be used.

[0004] Among them, since ammonium carbamate shows strong corrosiveness to metals, the portion of the condenser to which the absorption medium (recovered carbamate liquid) is contacted needs to be composed of a metal having high corrosion resistance. Also, a full penetration welding (for example, inner bore welding) without a gap is required for the welding portion of the portion to which the absorption medium is contacted to prevent crevice corrosion. In addition, a periodic inspection for confirming the presence or absence of occurrence of a defect such as corrosion is also required.

[0005] On the other hand, as a representative example of a condenser for condensing a mixed gas in an absorption medium, a fixed tube sheet type condenser, a U-tube type condenser, and the like having a shell-and-tube configuration are known. The fixed tube sheet type condenser is a condenser in which tube sheets supporting both ends of the tubes are fixed to both sides of the shell. In its configuration, it is relatively easy to perform inspection and cleaning of the inner surface of the tubes, but it is difficult to perform inspection and cleaning of the shell side. Therefore, in the fixed tube sheet type condenser, it is necessary to circulate a process fluid containing an absorption medium (recovered carbamate liquid) showing strong corrosiveness in the tubes. On the other hand, the U-tube type condenser is a condenser using U-shaped tubes and fixing a tube sheet supporting the U-shaped tubes to one side. In its configuration, it is relatively easy to perform inspection and cleaning of the inner surface of the tubes, and it is relatively easy to perform inspection and cleaning of the outer side of the tube bundle (tube group), but it is relatively difficult to perform inspection and cleaning of the inner side of the tube bundle.

[0006] Further, in the condenser, not only condensation but also a urea synthesis reaction occurs. Moreover, in the U-tube type condenser, in a case where the process fluid flows through the shell side, the reaction volume (volume per unit time of the process fluid staying in the condenser) is larger than in a case where the process fluid flows through the tube side. Therefore, in the case where the process fluid flows through the shell side in the U-tube type condenser (hereinafter referred to as a U-tube submerged type), it is superior to the fixed tube sheet type condenser in terms of promotion of the urea synthesis reaction in the condenser.

[0007] However, in the case where the process fluid flows through the shell side in the U-tube submerged type condenser, in its configuration, in order to prevent crevice corrosion, the welding of the tube to the tube sheet needs to be full penetration welding (for example, hole welding). In the case where such special welding is employed, the efficiency of the equipment production decreases, and the welding work cost also becomes high. Moreover, in order to perform the inspection and cleaning of the shell side, a relatively large space for maintenance is needed between the tube bundle and the inner surface of the shell. This point, in particular, becomes an obstacle to the downsizing of the plant. This is a problem of the U-tube submerged type condenser.

[0008] In International Publication No. 2006 / 118071, a urea synthesis device in which a synthesis tube is integrated with a condenser is described. The condenser is a U-tube submerged type condenser, and the process fluid flows through the shell side. On the other hand, the cooling medium flows through the tube, and it cools the process fluid on the shell side, and under this cooling, the mixed gas is condensed in the absorption medium to obtain a condensed liquid. Then, in this device, since the heavier condenser is integrally provided at a lower position than the synthesis tube, it is superior to the case where the condenser is integrally provided at a higher position than the synthesis tube in terms of ease of installation and fixation of the equipment.

[0009] However, the U-tube submerged type condenser has the above-described several problems. Moreover, in the device in which the synthesis tube is integrated with the U-tube submerged type condenser described in International Publication No. 2006 / 118071, in terms of the downsizing of the plant, not only the condenser but also the synthesis tube integrated with the condenser is difficult to reduce in size. Or, if the synthesis tube is made to conform to the required volume, the length is shorter than the diameter determined in accordance with the requirement on the maintenance space of the condenser, and an optimal design cannot be obtained. That is, in the device of International Publication No. 2006 / 118071, there is room for improvement in the above-described aspects.

[0010] In Japanese Patent Application Publication No. 2006-102590, a reaction apparatus is described that has a first plate-shaped member made of a highly corrosion-resistant metal and a second plate-shaped member made of a lowly corrosion-resistant metal, and a heat transfer pipe (tube) is welded to the first plate-shaped member by inner hole welding, and the second plate-shaped member is configured to be detachable. In this reaction apparatus, since the second plate-shaped member is detachable, it is excellent in terms of ease of welding of the portion where the heat transfer pipe is attached to the first plate-shaped member, and ease of inspection of the equipment. However, the second plate-shaped member is very heavy, and in order to detach the second plate-shaped member, a large crane or a structure for hoisting is required, and a large space for detachment is also required.

[0011] In International Publication No. 01 / 72700, a device having two reactor sections (synthesis tubes) is described. In particular, Figure 3 In International Publication No. 01 / 72700, a device having two reactor sections (synthesis tubes) is described. In particular, Figure 4 In International Publication No. 01 / 72700, a device having two reactor sections (synthesis tubes) is described. In particular,

[0012] This Figure 4 The horizontal pool condenser described in International Publication No. 01 / 72700 is a U-shaped tube submerged type condenser, and thus has several problems described above. Also, since the circulation of the synthesis liquid (circulation of the liquid, gas, or gas-liquid mixture sequentially to the condenser, the upper synthesis tube, the lower synthesis tube, the stripping column, and the condenser) is performed using the pressure and gravity (height difference) of each device, the circulation flow is affected by the pressure of each device, and it is difficult to control the circulation flow rate. Also, the arrangement of the height relationship of each device is restricted, and the height of the plant is high.

[0013] On the other hand, Figure 3 The condenser described in International Publication No. 01 / 72700 is not specifically described, but from the description of the drawing, it can be inferred that it is a fixed tube sheet type condenser. Also, in International Publication No. 01 / 72700, it is described that there are cases where the water for cooling in the heat exchanger (condenser) is circulated on the shell side. However, since Figure 3 The condenser described in International Publication No. 01 / 72700 is integrated with the upper synthesis tube and the lower synthesis tube, and thus in order to perform inspection of the welding of the tubes and the tube sheet of the condenser, the worker needs to enter the inside from the cylindrical portion of the upper or lower portion of the condenser, and this work is difficult. Also, since the shell diameter of the condenser needs to be determined in accordance with the synthesis tube, it is difficult to perform optimal design of the shell diameter of the condenser. Also, since the synthesis tube is connected to the upper and lower portions of the condenser, the height of the device is very high. SUMMARY

[0014] The present application has an object to solve the problems of the above-described conventional devices, and to provide a urea synthesis device capable of achieving ease of maintenance of the device, ease of design and manufacture of the device, and / or promotion of the urea reaction.

[0015] As a result of intensive studies conducted by the inventors in order to achieve the above object, it was found that it is very effective to provide a device in which a condenser is separate from a reaction tube and a process fluid is circulated within the tube, and further to provide at least two reaction tubes, thereby completing the present application.

[0016] That is, the present application is a urea synthesis device for reacting ammonia and carbon dioxide to produce urea,

[0017] having a first urea synthesis tube R1, a second urea synthesis tube R2, a condenser C, a stripping column S, and a unit E for supplying a first urea synthesis solution,

[0018] The condenser C is a device having a tube Ct inside, circulating a process fluid containing an absorption medium and a mixed gas separated in the stripping column S within the tube Ct, and cooling the process fluid with a cooling medium circulated on the side of a housing Cs, thereby condensing the mixed gas in the absorption medium to obtain a condensed solution, and the condenser C is a device separate from the first urea synthesis tube R1 and the second urea synthesis tube R2,

[0019] The first urea synthesis tube R1 is a device for reacting at least a part of the components in the condensed solution obtained in the condenser C to obtain a first urea synthesis solution containing urea, unreacted ammonia, unreacted carbon dioxide, and water,

[0020] The unit E for supplying a first urea synthesis solution is a unit for supplying the first urea synthesis solution obtained in the first urea synthesis tube R1 to the second urea synthesis tube R2,

[0021] The second urea synthesis tube R2 is a device for reacting at least a part of the components in the first urea synthesis solution obtained in the first urea synthesis tube R1, at least a part of the raw material ammonia, and at least a part of the raw material carbon dioxide to obtain a second urea synthesis solution containing urea, unreacted ammonia, unreacted carbon dioxide, and water,

[0022] The stripping column S is a device for separating the second urea synthesis solution obtained in the second urea synthesis tube R2 using at least a part of the raw material carbon dioxide to separate the above-described mixed gas containing unreacted ammonia and unreacted carbon dioxide from the second urea synthesis solution.

[0023] Further, the present application is a urea synthesis method for obtaining a urea synthesis solution using the above-described urea synthesis device of the present application.

[0024] Further, the present application is a method for improving an existing urea synthesis device,

[0025] The existing urea synthesis device has a urea synthesis pipe,

[0026] To the existing urea synthesis device, at least a first urea synthesis pipe R1 and a unit E for supplying a first urea synthesis solution are added,

[0027] In the case where the existing urea synthesis device does not have one or both of a condenser C and a stripping column S, the condenser C and / or the stripping column S which are not present are added,

[0028] The condenser C is a device which has a pipe Ct inside, makes a process fluid containing an absorption medium and a mixed gas separated in the stripping column S flow through the pipe Ct, cools the process fluid using a cooling medium flowing through the shell (Cs) side, thereby condensing the mixed gas in the absorption medium to obtain a condensed liquid, and is a device separate from the first urea synthesis pipe R1 and the second urea synthesis pipe R2,

[0029] The first urea synthesis pipe R1 is a device which makes at least a part of the components in the condensed liquid obtained in the condenser C react to obtain a first urea synthesis solution containing urea, unreacted ammonia, unreacted carbon dioxide, and water,

[0030] The unit E for supplying a first urea synthesis solution is a unit which supplies the first urea synthesis solution obtained in the first urea synthesis pipe R1 to the second urea synthesis pipe R2,

[0031] The second urea synthesis pipe R2 is at least a part of the urea synthesis pipe possessed by the existing urea synthesis device, and is a device which makes at least a part of the components in the first urea synthesis solution obtained in the first urea synthesis pipe R1, at least a part of the raw material ammonia, and at least a part of the raw material carbon dioxide react to obtain a second urea synthesis solution containing urea, unreacted ammonia, unreacted carbon dioxide, and water,

[0032] The stripping column S is a device which separates the second urea synthesis solution using at least a part of the raw material carbon dioxide to separate the above-mentioned mixed gas containing unreacted ammonia and unreacted carbon dioxide from the second urea synthesis solution.

[0033] In the urea synthesis device of the present application, since the process fluid flows through the pipe Ct of the condenser C and the cooling medium flows through the shell Cs side, special welding (for example, hole welding) is not required, and maintenance for inspection and cleaning can be easily performed.

[0034] Further, in the urea synthesizing apparatus of the present application, since the condenser C is a separate apparatus from the first urea synthesizing pipe Rl and the second urea synthesizing pipe R2, compared with the apparatus integrated with the above-mentioned components, the inspection inside the condenser C is easy, and the optimal design of the shell diameter of the condenser C is easy, and the height of the synthesizing pipe can be lowered.

[0035] Further, in the urea synthesizing apparatus of the present application, the reaction volume of the condenser C is relatively small, but since there are two urea synthesizing pipes Rl and R2, by optimizing the reaction conditions of each synthesizing section, the uncondensed gas can be suppressed and the urea reaction can be promoted. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a process flow chart showing the first embodiment of the apparatus of the present application.

[0037] Figure 2 is a process flow chart showing the second embodiment of the apparatus of the present application.

[0038] Figure 3 is a process flow chart showing the third embodiment of the apparatus of the present application.

[0039] Figure 4 is a process flow chart showing the fourth embodiment of the apparatus of the present application. DETAILED DESCRIPTION

[0040] The urea synthesizing apparatus of the present application is an apparatus for reacting ammonia and carbon dioxide to produce urea, which has a first urea synthesizing pipe Rl, a second urea synthesizing pipe R2, a condenser C, a stripping column S, and a unit E for supplying a first urea synthesizing solution. Hereinafter, each of them will be explained.

[0041] <Condenser C>

[0042] The condenser C is configured to have a pipe Ct inside, to flow a process fluid containing an absorption medium and a mixed gas separated in the stripping column S inside the pipe Ct, and to cool the process fluid by a cooling medium flowing outside the shell Cs, thereby condensing the mixed gas in the absorption medium to obtain a condensed liquid. Therefore, no special welding (e.g., hole welding) is required, and the space for maintenance for inspection and cleaning can be reduced. Also, in the case of flowing the process fluid having corrosiveness and high temperature and high pressure outside the shell Cs, both the pipe Ct and the shell Cs need to be formed of a corrosion-resistant material, but in the present application in which the process fluid flows inside the pipe Ct, the member using the corrosion-resistant material can be only the pipe. The corrosion-resistant material is, for example, high-chromium austenitic steel, duplex alloy, titanium, or 316L austenitic steel, etc. Flowing the process fluid having corrosiveness and high temperature and high pressure inside the pipe Ct can reduce the design constraints of the shell Cs, and the shell Cs can be formed of a low-cost and highly reliable material, such as carbon steel, low-alloy steel, etc.

[0043] The temperature for condensation of the condenser C is preferably 160 to 200°C, and the pressure is preferably 13 to 25 MPa.

[0044] The condenser C is a separate device from the first urea synthesis pipe Rl and the second urea synthesis pipe R2. Therefore, the inspection inside the condenser C is easy, and the optimal design of the shell diameter of the condenser C is easy.

[0045] As the condenser C, from the aspect of not requiring special welding and being easy to perform inspection and cleaning, it is preferable to use a fixed tube sheet type condenser. Also, the pipe Ct is preferably a straight pipe. However, the present application is not limited thereto. For example, a condenser in which the rear head is in a U-tube type can also be used as the condenser C. It can also be configured to have a U-shaped pipe Ct and to support the pipe Ct by a tube sheet that fixes one side of the U shape.

[0046] <First urea synthesis pipe Rl>

[0047] The first urea synthesis pipe Rl is a device that reacts at least a part of the components in the condensed liquid obtained in the condenser C to obtain a first urea synthesis liquid containing urea, unreacted ammonia, unreacted carbon dioxide, and water. The first urea synthesis pipe Rl supplements the function of urea synthesis of the condenser C, optimizes the reaction conditions of the first urea synthesis pipe Rl and the second urea synthesis pipe R2 described below, thereby being able to suppress uncondensed gas and promote urea reaction.

[0048] The preferred reaction conditions of the first urea synthesis pipe Rl are different from those of the second urea synthesis pipe R2 described below. Specifically, the temperature of urea synthesis in the first urea synthesis pipe Rl is preferably 160 to 2000C, and the pressure is preferably 13 to 25 MPa. Also, N / C is preferably 2.5 to 4.0.

[0049] The configuration of the synthesis pipe used as the first urea synthesis pipe Rl is not particularly limited. A synthesis pipe of a publicly known configuration used in urea synthesis can be used.

[0050] < Unit E for supplying the first urea synthesis solution >

[0051] The unit E for supplying the first urea synthesis solution is a unit for supplying the first urea synthesis solution obtained in the first urea synthesis pipe Rl to the second urea synthesis pipe R2.

[0052] The unit E for supplying the first urea synthesis solution preferably has an ejector. Also, the ejector is preferably driven using raw material ammonia as a driving source. In this case, the unit E for supplying the first urea synthesis solution also functions as a circulation unit, and it is easy to control the circulation flow rate of the process fluid flowing sequentially in the devices (condenser, first synthesis pipe, second synthesis pipe, stripping column) constituting the synthesis apparatus (process), and it is also possible to place the first urea synthesis pipe Rl and / or the second urea synthesis pipe R2 on the ground. However, the present application is not limited thereto. For example, a pump can also be used as the unit E for supplying the first urea synthesis solution.

[0053] < Second urea synthesis pipe R2 >

[0054] The second urea synthesis pipe R2 is an apparatus for reacting at least a part of the components of the first urea synthesis solution obtained in the first urea synthesis pipe Rl, at least a part of the raw material ammonia, and at least a part of the raw material carbon dioxide to obtain a second urea synthesis solution containing urea, unreacted ammonia, unreacted carbon dioxide, and water.

[0055] The preferred temperature and pressure of the second urea synthesis pipe R2 are different from those of the first urea synthesis pipe Rl described above. Specifically, the temperature of urea synthesis in the second urea synthesis pipe R2 is preferably 170 to 2100C, and the pressure is preferably 13 to 25 MPa. Also, N / C is preferably 3 to 4.5.

[0056] The configuration of the synthesis pipe used as the second urea synthesis pipe R2 is not particularly limited. A synthesis pipe of a publicly known configuration used in urea synthesis can be used.

[0057] Further, the first urea synthesis pipe Rl and the second urea synthesis pipe R2 can be separate devices or can be integrated devices having a structure in which the pipes are separated in one container. Also, the devices can be vertical devices or horizontal devices.

[0058] <Stripping column S>

[0059] The stripping column S is a device in which at least a part of the raw material carbon dioxide is used to separate the second urea synthesis solution obtained in the second urea synthesis pipe R2, thereby separating the above-mentioned mixed gas containing unreacted ammonia and unreacted carbon dioxide from the second urea synthesis solution.

[0060] The temperature and pressure of the stripping column S are not particularly limited. The temperature and pressure of a commonly used separation device used in urea synthesis can be used. Also, the configuration of the stripping column S is not particularly limited. A commonly used stripping column used in urea synthesis can be used.

[0061] <Method for synthesizing urea>

[0062] The method for synthesizing urea of the present application is a method for obtaining a urea synthesis solution using the urea synthesis device of the present application described above. According to the method for synthesizing urea, the above-mentioned easiness of maintenance of the device, the easiness of design and production of the device, and / or the promotion of the urea reaction can be achieved.

[0063] <Method for improving an existing urea synthesis device>

[0064] The existing urea production device can be improved by additionally providing at least the first urea synthesis pipe Rl and the unit E for supplying the first urea synthesis solution, and can become the urea synthesis device of the present application. According to the improvement method, the above-mentioned easiness of maintenance of the device, the easiness of design and production of the device, and / or the promotion of the urea reaction can be achieved.

[0065] Also, in the improvement method, at least a part of the urea synthesis pipe possessed by the existing urea synthesis device functions as the second urea synthesis pipe R2 in the present application. In the case where the existing urea synthesis device has only one urea synthesis pipe, the second urea synthesis pipe R2 in the improvement method is the urea synthesis pipe possessed by the existing urea synthesis device. On the other hand, in the case where the existing urea synthesis device has two or more urea synthesis pipes, for example, in the case where the inside of a pipe-shaped device is divided and functions as two or more urea synthesis pipes, or the like, a part or all of the two or more urea synthesis pipes can be used as the second urea synthesis pipe R2.

[0066] Moreover, in the case where the existing urea synthesis device does not have one or both of the condenser C and the stripping column S, the condenser C and / or the stripping column S can be added. For example, in the case where the existing urea synthesis device is a solution circulation type (non-separation type) urea synthesis device, the condenser C and the stripping column S are further added. Moreover, for example, in the case where the existing urea synthesis device is an ammonia stripping type urea synthesis device, the stripping column (stripping column not supplied with carbon dioxide) is removed, and instead, the stripping column S in the present application is added.

[0067] Hereinafter, an embodiment of the device of the present application will be described using the drawings.

[0068] Figure 1 is a process flow diagram showing the first embodiment of the device of the present application. In the first embodiment, the first urea synthesis pipe Rl and the second urea synthesis pipe R2 are devices that are separate from each other. The first embodiment is advantageous in terms of being able to flexibly design the arrangement and the equipment size, since the urea synthesis pipes are separate. Further, it is also applicable to a modification using an existing urea synthesis pipe.

[0069] Figure 1 In the condenser C, the absorption medium is supplied to the upper side of the condenser C via the line 11, and the mixed gas separated in the stripping column S is supplied to the upper side of the condenser C via the line 12. The condenser C has a pipe Ct inside, and the process fluid (absorption medium and mixed gas) flows through the pipe Ct. A disperser is provided in the passage of the condenser C, and the absorption medium and the mixed gas are configured to flow through each pipe Ct uniformly. On the other hand, the cooling medium is accumulated in the steam drum D, and the cooling medium is supplied to the shell Cs side of the condenser C via the line 13, and is recovered via the line 14, so as to circulate in the path. The process fluid flowing through the pipe Ct is cooled by the cooling medium. Then, the mixed gas is condensed in the absorption medium due to the cooling, so that a condensed liquid is obtained.

[0070] Figure 1 In the condenser C, the absorption medium is supplied to the upper side of the condenser C via the line 11, and the mixed gas separated in the stripping column S is supplied to the upper side of the condenser C via the line 12. The condenser C has a pipe Ct inside, and the process fluid (absorption medium and mixed gas) flows through the pipe Ct. A disperser is provided in the passage of the condenser C, and the absorption medium and the mixed gas are configured to flow through each pipe Ct uniformly. On the other hand, the cooling medium is accumulated in the steam drum D, and the cooling medium is supplied to the shell Cs side of the condenser C via the line 13, and is recovered via the line 14, so as to circulate in the path. The process fluid flowing through the pipe Ct is cooled by the cooling medium. Then, the mixed gas is condensed in the absorption medium due to the cooling, so that a condensed liquid is obtained.

[0071] exist Figure 1 In the second urea synthesis pipe R2, at least a portion of the components in the first urea synthesis liquid, at least a portion of the raw material ammonia added to the first urea synthesis liquid as the driving source of the injector, and at least a portion of the raw material carbon dioxide supplied via pipeline 20 are reacted to obtain the second urea synthesis liquid.

[0072] Figure 1 In the process, the second urea synthesis liquid obtained in the second urea synthesis pipe R2 is supplied to the stripping tower S via pipeline 21. Then, at least a portion of the raw material carbon dioxide supplied via pipeline 22 is used to separate the second urea synthesis liquid, thereby separating a mixed gas containing unreacted ammonia and unreacted carbon dioxide. Heating during this separation is performed by steam supplied and discharged through pipelines 23 and 24. The separated mixed gas is supplied to the condenser C via pipeline 12 as described above. On the other hand, the urea synthesis liquid after the mixed gas separation is supplied to the subsequent process equipment (e.g., a refining unit) via pipeline 25.

[0073] Figure 2 This is a process flow diagram illustrating a second embodiment of the apparatus of the present invention. In this second embodiment, the first urea synthesis pipe R1 and the second urea synthesis pipe R2 are integrated into a single device with a structure separated within a container, and the device is a vertical device with the first urea synthesis pipe R1 located on the lower side and the second urea synthesis pipe R2 located on the upper side. Compared with other embodiments, this second embodiment is advantageous in terms of reducing pressure-resistant components, reducing equipment weight, and reducing the area required for configuration.

[0074] Figure 2 The various devices in the system, except for the conversion of the first urea synthesis pipe R1 and the second urea synthesis pipe R2 into an integrated device, are related to... Figure 1 The devices shown are identical. Furthermore, the pipelines are also identical. Figure 1 The pipelines shown are identical.

[0075] Figure 3 This is a process flow diagram illustrating a third embodiment of the device of the present invention. In this third embodiment, the first urea synthesis pipe R1 and the second urea synthesis pipe R2 are integrated into a device with a structure separated within a container, and the device is a vertical device with the first urea synthesis pipe R1 on the upper side and the second urea synthesis pipe R2 on the lower side.

[0076] Figure 3 The various devices, besides reversing the vertical positions of the first urea synthesis pipe R1 and the second urea synthesis pipe R2 and supplying gas and absorption medium from the stripping tower to the lower part of the condenser pipe Ct, causing it to flow upwards within pipe Ct, are in harmony with... Figure 2 The devices shown are identical. For each pipeline, except for...Figure 2 The line 11 that supplies the absorption medium to the upper side of the condenser C is changed to a line that supplies to the lower side, the line 12 that supplies the mixed gas to the upper side of the condenser C is changed to a line that supplies to the lower side, and the line 15 that discharges the condensed liquid from the lower side of the condenser C is changed to a line that discharges from the upper side, in addition to the lines shown in Figure 2 The above lines are changed in order to adapt to the change in the positions of the first urea synthesis pipe Rl and the second urea synthesis pipe R2. In this third embodiment, the passage portion of the condenser and the pipe Ct are filled with liquid and gas, so the time (reaction time) that the liquid stays in the condenser increases, which is advantageous in terms of promoting the urea synthesis from the components from the absorption.

[0077] Figure 4 is a process flow diagram showing the fourth embodiment of the apparatus of the present application. In this fourth embodiment, the first urea synthesis pipe Rl and the second urea synthesis pipe R2 are an apparatus that is integrated in a structure that is separated within one vessel, and is a horizontal apparatus in which the first urea synthesis pipe Rl and the second urea synthesis pipe R2 are connected in series. This fourth embodiment is advantageous in terms of being able to reduce the height of the plant, compared to the other embodiments.

[0078] Figure 4 The apparatuses in Figure 2 are the same as the apparatuses shown in Figure 2 The lines are also the same as the lines shown in

[0079] Industrial applicability

[0080] The urea synthesis apparatus of the present application is able to realize ease of maintenance of the apparatus, ease of design and manufacture of the apparatus, and / or promotion of the urea reaction, so is very suitable for use in a urea manufacturing plant. Also, it is also useful for improving an existing urea synthesis apparatus.

[0081] Explanation of symbols

[0082] Rl - first urea synthesis pipe, R2 - second urea synthesis pipe, C - condenser, Ct - pipe, Cs - casing, S - stripping column, E - unit that supplies the first urea synthesis liquid, D - steam drum, 11 to 25 - line.

Claims

1. An apparatus for producing urea by reacting ammonia and carbon dioxide, the urea synthesis apparatus comprising: a first urea synthesis pipe (Rl) ; a second urea synthesis pipe (R2) ; a condenser (C) ; a stripping column (S) ; and a unit (E) for supplying a first urea synthesis solution, wherein the condenser (C) is an apparatus having a pipe (Ct) inside which a process fluid containing an absorption medium and a mixed gas separated in the stripping column (S) is circulated, and cooling the process fluid with a cooling medium circulated on the outside of a shell (Cs) to condense the mixed gas in the absorption medium to obtain a condensed liquid, and the condenser (C) is a separate apparatus from the first urea synthesis pipe (Rl) and the second urea synthesis pipe (R2), the first urea synthesis pipe (Rl) is an apparatus for reacting at least a part of the components in the condensed liquid obtained in the condenser (C) to obtain a first urea synthesis solution containing urea, unreacted ammonia, unreacted carbon dioxide, and water, the unit (E) for supplying the first urea synthesis solution is a unit for supplying the first urea synthesis solution obtained in the first urea synthesis pipe (Rl) to the second urea synthesis pipe (R2), the second urea synthesis pipe (R2) is an apparatus for reacting at least a part of the components in the first urea synthesis solution obtained in the first urea synthesis pipe (Rl), at least a part of raw ammonia, and at least a part of raw carbon dioxide to obtain a second urea synthesis solution containing urea, unreacted ammonia, unreacted carbon dioxide, and water, and the stripping column (S) is an apparatus for separating the second urea synthesis solution obtained in the second urea synthesis pipe (R2) using at least a part of the raw carbon dioxide to separate the above-mentioned mixed gas containing unreacted ammonia and unreacted carbon dioxide from the second urea synthesis solution.

2. The apparatus according to claim 1, wherein the unit (E) for supplying the first urea synthesis solution has an ejector driven by raw ammonia as a driving source.

3. The apparatus according to claim 1, wherein the first urea synthesis pipe (Rl) and the second urea synthesis pipe (R2) are separate apparatuses.

4. The apparatus according to claim 1, wherein the first urea synthesis pipe (Rl) and the second urea synthesis pipe (R2) are integrated apparatuses in a structure separated in one vessel.

5. The apparatus according to claim 1, wherein the above-mentioned mixed gas and the absorption medium from the stripping column (S) are supplied from below the condenser (C) and made to flow upward.

6. A urea synthesis method, comprising: using the urea synthesis apparatus according to claim 1 to obtain a urea synthesis solution.

7. A modification method of an existing urea synthesis apparatus, the existing urea synthesis apparatus comprising: a urea synthesis pipe, wherein the existing urea synthesis apparatus is modified by additionally providing at least a first urea synthesis pipe (Rl) and a unit (E) for supplying a first urea synthesis solution. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In the case where the existing urea synthesis device does not have one or both of the condenser (C) and the stripping column (S), the condenser (C) and / or the stripping column (S) not having is added, The condenser (C) is a device that has a pipe (Ct) inside, makes a process fluid containing an absorption medium and a mixed gas separated in the stripping column (S) flow through the pipe (Ct), cools the process fluid using a cooling medium flowing on the outside of the shell (Cs), thereby condensing the mixed gas in the absorption medium to obtain a condensed liquid, and is a device separate from the first urea synthesis pipe (R1) and the second urea synthesis pipe (R2), The first urea synthesis pipe (R1) is a device that reacts at least a part of the components in the condensed liquid obtained in the condenser (C) to obtain a first urea synthesis liquid containing urea, unreacted ammonia, unreacted carbon dioxide, and water, The unit (E) for supplying the first urea synthesis liquid is a unit that supplies the first urea synthesis liquid obtained in the first urea synthesis pipe (R1) to the second urea synthesis pipe (R2), The second urea synthesis pipe (R2) is at least a part of the urea synthesis pipe possessed by the existing urea synthesis device, is a device that reacts at least a part of the components in the first urea synthesis liquid obtained in the first urea synthesis pipe (R1), at least a part of the raw material ammonia, and at least a part of the raw material carbon dioxide to obtain a second urea synthesis liquid containing urea, unreacted ammonia, unreacted carbon dioxide, and water, The stripping column (S) is a device that separates the second urea synthesis liquid obtained in the second urea synthesis pipe (R2) using at least a part of the raw material carbon dioxide to separate the above-mentioned mixed gas containing unreacted ammonia and unreacted carbon dioxide from the second urea synthesis liquid.

8. The improved method according to claim 7, characterized in that The second urea synthesis pipe (R2) is a urea synthesis pipe possessed by the existing urea synthesis device.

9. The improved method according to claim 7, characterized in that The above-mentioned mixed gas and the absorption medium from the stripping column (S) are supplied from below the condenser (C) and made to flow upward.

Images