A process and apparatus for stripping urea with co2

Abstract

A process and apparatus for CO2 stripping of urea, wherein urea is formed by reaction of ammonia with carbon dioxide in a vertical reactor (1); a first urea-containing stream (12) is withdrawn from an intermediate height of the reactor by means of a first downcomer (103) and is fed to a high-pressure stripping column (2); a second urea-containing stream (15) is withdrawn from an upper height of the reactor by means of a second downcomer (104) and is fed to an eductor (4) for reintroduction into the reactor together with fresh ammonia.

Description

Technical Field

[0001] This invention relates to the field of synthesizing urea from ammonia and carbon dioxide using a carbon dioxide stripping method. Background Technology

[0002] Industrially, urea is produced by reacting ammonia with carbon dioxide. For an overview of urea production methods, see the "Ulman Encyclopedia of Industrial Chemistry," section "Urea."

[0003] Urea is formed in a high-pressure, high-temperature (typically around 150 bar and 200°C) urea synthesis reactor. In the reactor, ammonia and carbon dioxide form ammonium carbamate, which is then dehydrated to form urea and water. The reactor effluent is an aqueous solution containing urea and unreacted ammonium carbamate; this solution is typically treated to recover unconverted reactants, except in very old-fashioned "one-pass" systems.

[0004] In the stripping method (the dominant method today), the reactor effluent is fed to a high-pressure stripping tower, where the solution is heated to decompose ammonium carbamate into gaseous ammonia and carbon dioxide. The gaseous stream containing ammonia and carbon dioxide is then discharged from the stripping tower and sent to a high-pressure condenser. In the condenser, the gaseous stream is condensed using a circulating solution from the recovery section, and the resulting circulating stream (typically a two-phase stream) is reintroduced into the reactor. The CO2 stripping method uses gaseous CO2 introduced into the stripping tower as a stripping aid and removes dissolved free ammonia from the urea solution.

[0005] The urea-containing solution from the stripping tower is sent to one or more lower-pressure recovery units, such as a low-pressure recovery unit or a medium-pressure unit followed by a low-pressure unit. Recovery methods typically involve thermally decomposing the remaining ammonium carbamate in the solution, separating gaseous ammonia and CO2, and condensing it to form a circulating solution containing ammonium carbamate, which is then pumped back to the high-pressure synthesis unit.

[0006] The reactor, high-pressure stripping tower, and high-pressure condenser are part of a so-called high-pressure synthesis loop. The reactor, stripping tower, and condenser operate at essentially the same pressure, for example, about 140-150 bar. The loop may include additional equipment such as a high-pressure scrubber. In contrast, the intermediate-pressure recovery section typically operates at about 15-18 bar, while the low-pressure recovery section typically operates at 2-5 bar. Pressure values ​​are given in bar gauge pressure (barg).

[0007] The urea solution produced by the recovery unit mainly contains urea and water. The concentration at the outlet of the recovery unit is typically around 65-70%. In most cases, this solution needs to be concentrated to obtain a high-concentration urea melt, which is accomplished through one or more evaporation steps.

[0008] Over the years, various attempts have been made to improve the CO2 stripping method for urea and eliminate some of its drawbacks. For example, a disadvantage of the traditional CO2 stripping method is that the circulation within the loop relies on natural gravity, which requires the equipment to be installed at various heights of 60 m or more above the ground, increasing installation and piping costs. Another challenge is optimizing the complex conversion process within the reactor of the gas / liquid two-phase system.

[0009] WO-A-2009 / 141346 discloses an air stripping method for urea synthesis with two reaction zones. Summary of the Invention

[0010] This invention aims to improve the CO2 stripping method for urea. It also aims to avoid installing the equipment in the loop at a considerable height and to optimize the processing within the urea reactor.

[0011] The purpose of this invention is achieved by the urea method and urea apparatus according to the claims.

[0012] In this invention, two urea-containing solution streams are drawn from different heights within the reactor, hence referred to as the upper solution and the lower solution. The lower solution is sent to a stripping tower for further processing according to the CO2 stripping principle. The upper solution, along with a fresh ammonia stream, is reintroduced into the lower part of the reactor via an ejector. The introduction point of the mixture of upper urea solution and ammonia is located below the lower solution outlet point. Furthermore, circulating solution from the high-pressure condenser is introduced into the reactor at an intermediate height between the upper and lower solution outlet points.

[0013] Because the circulation within the synthesis loop is driven by an ejector, this invention eliminates the need to install the equipment at a significantly elevated height above ground level. Furthermore, this invention is based on the understanding that it is advantageous to draw the reactor effluent (urea solution sent to the stripping tower) from an intermediate height rather than from the top of the reactor. As explained below, by drawing the reaction effluent from an intermediate height, the remaining upper portion of the reactor is used for further condensation of the gaseous reactants from the high-pressure condenser effluent. Specifically, the solution is drawn from below the solution draw-out point to the ejector.

[0014] This invention stems from an improved understanding of reaction and mass transfer within a reactor. In a vertical urea reactor, an overall upward flow occurs. In most conventional urea reactors, the effluent is drawn from the top. In this invention, the reaction effluent (sent to a stripping tower) is drawn from an intermediate height, while the remainder of the reaction mixture (primarily in a gaseous state) continues to rise until gas-liquid equilibrium is reached at the top of the reactor (top liquid level, above which is the gas phase).

[0015] In this invention, the lower and upper sections of the urea reactor perform different tasks. In the upper section, further condensation of gaseous ammonia and carbon dioxide is achieved, initiating urea formation; in the lower section, urea formation continues, yielding a urea-containing reaction effluent, which is sent to a high-pressure stripping tower for further processing. This invention deviates from the most common method of leading out the reaction effluent through a single downcomer located at the top of the reactor. Another significant feature is that the lower section of the urea reactor receives heat from the portion of the fresh CO2 feed that enters the reactor directly, while the upper section is heated by the condensation of the two-phase mixture from the high-pressure condenser. In essence, the condensation that begins in the high-pressure condenser is completed in the upper section of the reactor, provided that the term "completed" refers to reaching a target condensation level compatible with the operating conditions in the reactor, rather than necessarily complete condensation.

[0016] Description of the invention Urea is formed by reacting ammonia and carbon dioxide in a vertical reactor. A first urea-containing stream is drawn from the reactor at a first point via a first downcomer connected to a high-pressure stripping tower. A second urea-containing stream is drawn from the reactor at a second point via a second downcomer connected to the reactor inlet via an ejector. In the ejector, the second urea-containing stream is mixed with fresh ammonia, and the resulting mixture is reintroduced into the reactor through the inlet.

[0017] The second point is located above the first point, causing the second stream to exit the reactor at a higher height than the first stream. The first point corresponds to the inlet of the first downcomer, and the second point corresponds to the inlet of the second downcomer.

[0018] The inlet of the reactor connected to the ejector is located below the first point, preferably at or near the bottom of the reactor.

[0019] Based on the CO2 stripping principle, gaseous CO2 is fed into a stripping tower. In this invention, a portion of the fresh CO2 feed is introduced into the reactor and a portion is introduced into the stripping tower.

[0020] The urea-containing solution from the stripping tower is sent to a urea recovery unit, which operates at a pressure lower than the synthesis pressure, such as a low-pressure recovery unit or a medium-pressure recovery unit followed by a low-pressure recovery unit.

[0021] The gaseous stream containing ammonia and CO2 drawn from the stripping tower is sent to a high-pressure condenser, where it is condensed in the presence of an ammonium carbamate solution obtained in the recovery section to obtain a circulating stream; the circulating stream is then reintroduced into the reactor at an intermediate height between the first and second points.

[0022] Urea reactors typically include multiple perforated plates. These plates enhance mass transfer between the gas and liquid phases and prevent backmixing in the liquid phase, which can affect the kinetics of urea formation.

[0023] In this invention, the upper and lower parts of the urea reactor can be identified, wherein: The second point for drawing out the second urea-containing stream and sending it to the injector, and the inlet for the ammonium carbamate solution from the condenser are located at the top; The first point for drawing out the first urea-containing stream and sending it to the stripping tower, as well as the inlet for fresh ammonia mixed with the second urea-containing stream and the inlet for part of the CO2 feed, are located at the bottom.

[0024] The upper and lower parts of the reactor can have the same or similar dimensions. In a preferred embodiment, the lower part occupies 50% to 70% of the internal volume of the reactor, more preferably 55% to 65%, with the remainder being the upper part.

[0025] A partition plate defines the boundary between the upper and lower parts of the reactor. The partition plate can be one of the perforated plates described above, or a specially designed separation plate. In embodiments, the separation plate is configured to allow vapor to flow upwards from the lower part to the upper part, and to prevent gas and / or liquid from flowing downwards from the upper part to the lower part. In some embodiments, the separation plate forms a liquid seal to prevent downward flow.

[0026] In a preferred embodiment, the separation plate is designed as a plate chimney with axial openings and a cover plate on top.

[0027] In another embodiment, the separator plate is substantially impermeable to both gas and liquid, making the upper and lower sections separate. In the latter case, the reaction mixture is transferred between the sections of the reactor only through pipelines connecting the downcomer and the ejector.

[0028] In the presence of a separator plate, the upper and lower sections of the urea reactor are physically separated. In some embodiments, the liquid phase may dominate in the lower section, while the gas phase may dominate in the upper section.

[0029] The first location may correspond to the inlet of the first downcomer, and the second location may correspond to the inlet of the second downcomer.

[0030] The first site is preferably located at the middle height of the urea reactor. For example, the height of the first site is in the range of 50% to 70% of the height of the vertical reactor. The second site is located at or near the top of the reactor. Preferably, the height of the second site is 80% or more of the height of the vertical reactor.

[0031] The inlet of the circulating stream from the condenser is preferably located near or adjacent to the top of the partition plate. Preferably, the inlet of the circulating stream is located between the partition plate and a perforated plate immediately above the partition plate.

[0032] The CO2 fed into the stripping tower preferably accounts for 60% to 90% of the total CO2 feed. The remaining 10% to 40% is fed directly into the urea reactor. The amount of CO2 entering the reactor is adjusted to provide a suitable heat input to the lower part of the reactor (from the condensation of gaseous CO2 and the formation of ammonium carbamate). The CO2 fed into the urea reactor is introduced into the lower part of the reactor, preferably at or near the bottom of the reactor.

[0033] The pressure in the urea reactor is preferably 120 to 160 barg, and more preferably 135 to 150 barg. The high-pressure stripping tower and the high-pressure condenser operate within the same range. The reactor, stripping tower, and condenser can operate at the same nominal pressure, or with a slight pressure difference between them.

[0034] Preferably, the ammonia stream is added to the gaseous stream taken from the stripping tower and sent to the high-pressure condenser. This added stream preferably accounts for 30% to 70% of the total ammonia input, with the remainder fed into the reactor through the aforementioned ejector.

[0035] The high-pressure stripping tower is preferably a shell-and-tube type device heated by steam, in which urea solution flows downward inside the tubes; gaseous CO2 (stripping aid) is introduced into the tubes from the bottom; and the tube bundle is heated by hot steam introduced from the shell side of the device.

[0036] In a high-pressure condenser, the gaseous stream exiting the stripping tower (stripping tower vapor) is primarily composed of ammonia and carbon dioxide, which condenses to form ammonium carbamate. In addition to the stripping tower vapor (which may be mixed with fresh ammonia), the condenser also receives an ammonium carbamate solution from the recovery section. A kettle-type condenser is preferred.

[0037] The process steam stream (containing ammonia, CO2, water, and inert gases) is typically drawn from the top of the urea reactor. In the embodiment of interest, the steam stream is partially condensed, and the heat from the condensation is used to evaporate and remove water from the urea solution obtained from the recovery section, thereby concentrating the solution. The condensation of the process steam is carried out at a pressure below the synthesis pressure, preferably between 10 and 40 barg. Thus, a significant amount of reactants in the process steam is recovered as a condensate solution, while water is removed from the urea solution, yielding a concentrated solution of molten urea for further use, such as by granulation or fluidized bed granulation. Preferably, the condensation of the process steam is carried out in a shell-and-tube unit, with the process steam on the shell side and the urea solution on the tube side.

[0038] Another aspect of the present invention is the CO2 stripping urea apparatus as described in claim 1. In this urea apparatus: The reactor is connected to a stripping tower via a discharge pipeline, which is arranged to transport a urea-containing solution from the reactor to the stripping tower. The discharge pipeline is connected to a first downcomer arranged in the reactor, the inlet of which is located at a first height in the reactor. The reactor is connected to the ejector via a circulation line, which is connected to a second downcomer, the inlet of which is located at a second point in the reactor. The injector is also connected to a fresh ammonia input line, and the injector's outlet line is connected to the reactor inlet. The inlet of the second downcomer is located above the inlet of the first downcomer, so that the stream sent to the ejector is drawn out at a higher height than the stream sent to the stripping tower. The reactor inlet, which is connected to the ejector outlet, is located below the inlet of the first downcomer. The fresh CO2 feed line is arranged to introduce part of the CO2 into the reactor and part into the stripping tower. The urea solution discharge pipeline from the stripping tower is connected to the urea recovery unit; The gas pipeline is arranged to deliver the gaseous stream from the stripping tower to the condenser, the ammonium carbamate solution pipeline is arranged to deliver the ammonium carbamate solution from the recovery unit to the condenser, and the ammonium carbamate circulation pipeline connects the condenser to the reactor inlet, thereby reintroducing the circulating stream obtained in the condenser into the reactor. The reactor inlet, which is connected to the condenser, is located at an intermediate height between the inlet of the first downcomer and the inlet of the second downcomer.

[0039] Preferred features of the urea apparatus are described in the dependent claims.

[0040] Preferably, the reactor is installed on the ground. Attached Figure Description

[0041] Figure 1 This is a simplified schematic diagram of the urea method and apparatus in an embodiment of the present invention.

[0042] Figure 2 It shows Figure 1 A variant of .

[0043] Figure 3 It shows Figure 2 Details.

[0044] Figure 1 A urea plant is shown, comprising a urea reactor 1 (or urea converter), a high-pressure stripping tower 2, a high-pressure ammonium carbamate condenser 3, an ejector 4, a recovery unit 5, and a condenser / evaporator 6. The above equipment constitutes a high-pressure synthesis loop.

[0045] Reactor 1 is a vertical device and includes multiple internal perforated plates 10. The reactor also includes a first downcomer 103 (downcomer) with an inlet 110 and a second downcomer 104 (upper downcomer) with an inlet 120. The inlet 110 of the first downcomer 103 is located at approximately half the height of the reactor; the inlet 120 of the second downcomer 104 is located approximately at the top of the reactor.

[0046] The urea solution collected by the first downcomer 103 is transferred to the stripping tower 2 via pipeline 12 and valve 13. Valve 13 controls the amount of urea solution sent from the reactor to the stripping tower. Pipeline 14 represents the hot steam supplied to the shell side of the stripping tower 2.

[0047] The urea solution collected by the second downcomer 104 is sent to the ejector 4 via line 15. The ejector 4 also receives fresh ammonia (line 16) and outputs a stream 17, which is reintroduced to the bottom of the reactor 1.

[0048] It should be noted that the term "urea solution" as used herein refers to a mixture that can be collected from the reactor. This mixture contains urea, water, unconverted ammonium carbamate, carbon dioxide, and ammonia.

[0049] Two sections can be identified in reactor 1: the lower section 101 and the upper section 102. The urea solution sent to the stripping tower 2 is taken from the lower section 101, while the solution circulating inside the reactor through the ejector 4 is taken from the upper section 102.

[0050] Carbon dioxide feed 18 is partially delivered to reactor 1 via pipeline 19 and partially delivered to stripper 2 via pipeline 20. In stripper 2, ammonium carbamate contained in the reactor effluent is thermally decomposed by heat provided by hot steam 14. Carbon dioxide 20 acts as a stripping medium, aiding in the removal of gaseous reactants from the solution. A gaseous stream (stripper vapor), primarily composed of ammonia and carbon dioxide, is discharged from the top of the stripper.

[0051] The urea solution from stripping tower 2 is sent to urea recovery unit 5 via pipeline 21 and pressure reducing valve 22. Stripping tower vapor, along with fresh ammonia 24 and circulating ammonium carbamate solution 25 from recovery unit 5, is sent to condenser 3 via pipeline 23. The resulting condensate stream 26 is reintroduced into reactor 1. The inlet point of stream 26 is located above inlet 110 of downcomer 103 and below inlet 120 of upcomer 104.

[0052] The condensation that occurs in the high-pressure condenser 3 is partial condensation. This means that stream 26 still contains a certain amount of condensable vapor, which is condensed in reactor 1 to provide heat to the upper part 102 of the reactor. The degree of condensation in condenser 3 can be adjusted according to the heat input required by reactor 1 (especially the upper part 102).

[0053] In the recovery section 5, a urea solution 27 is obtained, which mainly contains urea and water. This solution 27 is then sent to a condenser / evaporator 6 for concentration. The condenser / evaporator 6 also receives a stream of process steam discharged from the top of the reactor 1 via line 28 and valve 29. Notably, valve 29 controls the pressure in the reactor 1 and the synthesis loop.

[0054] In the condenser / evaporator 6, the heat from the condensation of the process steam in line 28 is used to evaporate and remove water from solution 27, yielding urea melt 30. In the illustrated embodiment, the condenser / evaporator 6 is a shell-and-tube device, with the urea solution 27 in the tubes and the condensate vapor on the shell side. The condensate (still containing some ammonia and carbon dioxide entrained from the reactor exhaust vapor) is returned to the recovery unit 5 via line 31 to recover the reactants.

[0055] like Figure 1 As shown, the lower part 101 includes an inlet 110 of a downcomer 103 and an inlet connected to the ejector 4 via a pipeline 17. The upper part 102 includes an inlet 120 of an upper downcomer 104 and a reactor inlet connected to the condenser 3 via a pipeline 26. In this example, the plate 10a immediately above the inlet 110 can be considered as a partition plate defining the boundary between the parts 101 and 102.

[0056] The inlet of reactor 1, which receives the condensate circulation stream 26 from the condenser, is located near the partition plate 10a, that is, between the partition plate 10a and the perforated plate 10b immediately above the partition plate 10a.

[0057] In operation, reactor 1 is essentially a two-phase system containing a two-phase mixture moving from the bottom to the top of the reactor. A portion of the mixture destined for the stripping tower is drawn off from the bottom of the reactor via downcomer 103. The remaining portion continues to flow upwards into section 102; at the top of the reactor, gas / liquid equilibrium is reached, and the liquid and gas phases separate; the liquid phase is removed from the top of the reactor and reintroduced to the bottom via ejector 4; the gas phase, containing the main unconverted reactants and inert gases, is discharged through line 28 (the reactor's exhaust line).

[0058] Figure 2 A variation is disclosed in which the partition between the lower portion 101 and the upper portion 102 is specifically designed as a separation plate 105, which differs from the perforated plate 10. Preferably, the separation plate 105 is designed as a plate chimney to facilitate upward gas flow and improve the separation between the liquid phase (below) and the gas phase (above). In this embodiment, the inlet of the stream 26 is preferably located between the separation plate 105 and the perforated plate immediately above the plate 105.

[0059] Figure 2The recovery unit 5 and the condenser / evaporator 6 are not shown, although these devices may also be present in this embodiment, similar to... Figure 1 .

[0060] Figure 3 A preferred embodiment of the separator 105 is shown. The separator 105 includes an axial channel 130, over which a plate 131 covers. The channel 130 is surrounded by a non-porous annulus 133. Liquids or two-phase mixtures can flow radially upwards through a path 132 around the plate 131; however, downward flow of gas is substantially blocked by the liquid.

Claims

1. A CO2 stripping method for synthesizing urea from ammonia and carbon dioxide, comprising: Urea is formed by the reaction of ammonia and carbon dioxide in a vertical reactor (1); A first urea-containing stream (12) is drawn out from the reactor at a first point by means of a first downcomer (103). The first downcomer (103) is connected to a high-pressure stripping tower (2). In the high-pressure stripping tower (2), the first stream is stripped in the presence of gaseous CO2 as a stripping aid. A second urea-containing stream (15) is drawn from the reactor at a second point via a second downcomer (104), the second downcomer (104) being connected to the inlet of the reactor via an injector (4), in which the second stream is mixed with fresh ammonia, and the resulting mixture (17) is reintroduced into the reactor; The second site is located above the first site, such that the second stream is drawn out of the reactor at a higher height than the first stream. The inlet of the reactor—that is, the place where the second urea-containing stream and fresh ammonia are introduced into the reactor—is located below the first site; Fresh CO2 feed (18) is partially introduced into the reactor and partially into the stripping tower; The urea-containing solution (21) discharged from the stripping tower is sent to the urea recovery unit (5). The gaseous stream (23) containing ammonia and CO2 drawn from the stripping tower is sent to the high-pressure condenser (3). In the high-pressure condenser (3), the gaseous stream is condensed in the presence of the ammonium carbamate solution obtained in the recovery section to obtain a circulating stream. The circulating stream (26) is reintroduced into the reactor at an intermediate height between the first site and the second site.

2. The method according to claim 1, wherein, The urea reactor comprises an upper part (102) and a lower part (101), wherein: The inlet for drawing out the second urea-containing stream and sending it to the second site of the injector, and the inlet for the ammonium carbamate solution from the condenser, are located at the upper part; The inlet for drawing out the first urea-containing stream and sending it to the first point of the stripping tower, and the inlet for mixing fresh ammonia with the second urea-containing stream, are located in the lower part.

3. The method according to claim 2, wherein, The portion of the urea reactor is separated by a partition plate (105) configured to allow gas to flow upward from the lower portion to the upper portion and to prevent gas and / or liquid from flowing downward from the upper portion to the lower portion.

4. The method according to any one of the preceding claims, wherein, Ammonia is added to the gas stream drawn from the stripping tower and sent to the condenser.

5. The method according to claim 4, wherein, The ammonia added to the gas stream from the stripping tower accounts for 30% to 70% of the total ammonia feed, with the remainder being sent to the ejector.

6. The method according to any one of the preceding claims, wherein, The carbon dioxide fed directly to the stripping tower accounts for 60% to 90% of the total carbon dioxide feed, with the remainder being fed directly to the reactor.

7. The method according to any one of the preceding claims, wherein, The reactor, the stripping tower, and the condenser operate within a pressure range of 120 to 160 bar (gauge pressure).

8. The method according to any one of the preceding claims further comprises: A stream of process steam containing ammonia, CO2, water, and inert gas is drawn from the top of the reactor; At a pressure lower than the urea synthesis pressure, preferably at a pressure of 10 to 40 barg, the vapor stream is partially condensed; the heat of condensation is used to evaporate and remove water from the urea solution obtained in the recovery section, thereby concentrating the solution.

9. A CO2 stripping urea apparatus for implementing the method of any one of the preceding claims, comprising a high-pressure urea synthesis circuit, the high-pressure urea synthesis circuit comprising a vertical urea reactor (1), a stripping tower (2), a condenser (3), an ejector (4), and further comprising at least one low-pressure urea recovery unit (5), wherein: The reactor (1) is connected to the stripping tower (2) via a discharge pipeline (12), the discharge pipeline being arranged to transport a urea-containing solution from the reactor to the stripping tower, the discharge pipeline being connected to a first downcomer (103), the inlet (110) of the first downcomer being located at a first height in the reactor; The reactor (1) is connected to the ejector (4) via a circulation pipeline (15), which is connected to a second downcomer (104), and the inlet (120) of the second downcomer is located at a second point in the reactor. The injector (4) is also connected to the fresh ammonia input line (16), and the outlet line (17) of the injector (4) is connected to the inlet of the reactor. The inlet (120) of the second downcomer (104) is located above the inlet (110) of the first downcomer (103), such that the stream (15) sent to the ejector (4) is drawn out at a higher height than the stream (12) sent to the gas lift tower (2). The inlet of the reactor, which is connected to the outlet (17) of the ejector, is located below the inlet (110) of the first downcomer; A fresh CO2 feed line (18) is arranged to partially introduce CO2 into the reactor and partially into the stripping tower; The pipeline (21) connects the stripping tower (2) to the urea recovery unit to transport the urea-containing solution discharged from the stripping tower to the urea recovery unit; A gas line (23) is arranged to deliver a gaseous stream from the stripping tower (2) to the condenser (3), an ammonium carbamate solution line (25) is arranged to deliver an ammonium carbamate solution from the recovery unit (5) to the condenser (3), and an ammonium carbamate circulation line (26) connects the condenser to the inlet of the reactor, such that the circulating stream obtained in the condenser is reintroduced into the reactor; The inlet of the reactor connected to the condenser is located at an intermediate height between the inlet (110) of the first downcomer and the inlet (120) of the second downcomer.

10. The apparatus according to claim 9, wherein, The urea reactor is vertically divided into an upper and a lower section, which are separated by a partition plate, wherein: The inlet of the second downcomer and the inlet connected to the condenser are located in the upper part; The inlet of the first downcomer and the inlet connected to the injector are located in the lower part.

11. The apparatus according to claim 10, wherein, The partition plate is a separation plate (105) configured to allow steam to flow upward from the lower part to the upper part and to prevent gas and / or liquid from flowing downward from the upper part to the lower part. The separation plate is preferably configured as a plate chimney structure.

12. The apparatus according to any one of claims 10 to 11, wherein, The height of the inlet of the first downcomer is 40% to 70% of the height of the vertical reactor, and / or the height of the inlet of the second downcomer is 80% or more of the height of the vertical reactor.

13. The apparatus according to any one of claims 10 to 12, further comprising a line arranged to add ammonia to the gas stream drawn from the stripping tower and delivered to the condenser.

14. The apparatus according to any one of claims 10 to 13, wherein, The inlet of the reactor, which is connected to the condenser and is used to introduce a stream of circulating condensate, is located between the partition plate and the perforated plate of the reactor immediately above the partition plate.

15. The apparatus according to any one of claims 10 to 14, further comprising: A pipeline is arranged to draw a stream of process steam containing ammonia, CO2, water and inert gas from the top of the reactor; A condenser / evaporator having a first side connected to the pipeline for process steam and a second side connected to the pipeline for conveying the urea solution obtained from the recovery section, the first side and the second side having an indirect heat exchange relationship, such that in the condenser / evaporator, the process steam stream is partially condensed and the urea solution is evaporated to remove water and concentrate the solution.

Images