EA040529B1 - HIGH PRESSURE CARBAMATE CAPACITOR - Google Patents

Description

The technical field to which the invention belongs

The invention relates to a high pressure carbamate condenser. The condenser contains a shell-and-tube heat exchanger, which contains a tube bundle installed in the shell. The high pressure carbamate condenser can in particular be used to condense carbamate in stripping type urea plants. In some embodiments, carbamate-containing corrosive solutions are present during operation on both the shell side and the tube side, particularly both within at least some of the tubes of the tube bundle and in the space between the tubes.

State of the art

A commonly used type of carbamate condenser is the pool condenser described in A lower cost design for urea, Nitrogen no. 222, July-August 1996, p. 2931. Such a pool condenser contains a tube sheet. Tube sheets, more generally, are a typical part of high-pressure carbamate condensers of the shell-and-tube heat exchanger type. The tube sheet, as a rule, is a flat metal plate separating the annular space in the condenser from the collector. The tube sheet also seals one end of the usually cylindrical casing. The tube sheet is provided with a plurality of bored holes. The pipes are inserted through bored holes or connected to a tube sheet aligned with the holes so that fluid can flow between the manifold and the pipes. A tube bundle often has a very large number of tubes, such as over 100 tubes or even over 1000 tubes. The manifold is used to distribute fluid from an inlet to a plurality of pipes, or to withdraw fluid from a plurality of pipes and supply to an outlet.

In known carbamate condensers, the tube sheet must essentially be capable of withstanding high pressure. In addition, corrosion prevention is difficult because the carbamate is highly corrosive, especially at high high pressure carbamate condensing temperatures. In order to achieve high mechanical strength and high corrosion resistance, prior art tube sheets are often made of carbon steel coated with a layer of highly corrosion resistant steel, such as duplex stainless steel alloys, on the side(s) exposed to the corrosive environment. This increases the cost of construction, for example, due to the difficulty of welding the tubes to the tube sheet.

A known tubesheet for a carbamate boiler-type condenser in a urea plant is shown in EP 0464307 and US 4082797.

The design of the tube sheet is inherently complex and expensive. The present invention essentially addresses the disadvantages of prior art high pressure tubesheet carbamate condensers, such as high construction costs associated with the tubesheet.

Disclosure of invention

Accordingly, the present invention relates in a first aspect to a high-pressure carbamate condenser comprising a shell-and-tube heat exchanger, which is a vessel containing a casing and at least one tube bundle containing pipes having ends, the casing enclosing the space of the vessel, and part of the space of the vessel, located between the pipes and the casing, forms annular space, while the heat exchanger additionally contains a redistribution chamber located in the specified space of the vessel, while the specified redistribution chamber contains a wall for separating the first fluid in the annulus from the second fluid inside the redistribution chamber, and at the same time a plurality of said pipes are connected to one redistribution chamber so that said second fluid can flow between said pipes and said redistribution chamber, wherein the condenser further comprises a branch pipe extending from the second fluid opening in said casing through said vessel space to said redistribution chamber so that the second fluid can flow between the end of the pipe and said second fluid opening in said casing through said redistribution chamber and said nozzle.

The invention also relates to a urea production plant comprising a high pressure urea synthesis section which comprises a reactor, a stripper and a high pressure carbamate condenser, the high pressure carbamate condenser being configured as described above, and optionally the reactor and the high pressure carbamate condenser. pressures are combined in one vessel which has a liquid outlet connected to a stripper.

The invention also relates to a method for producing urea, in which urea is formed in a reactor to obtain a urea synthesis solution, wherein at least a part of said urea synthesis solution is stripped in a stripper to obtain a stripped carbamide solution, and the gas from the stripper is condensed in a high pressure carbamate condenser , the process being carried out in the plant described above and/or the high pressure carbamate condenser

- 1 040529 is made as described above.

In a more general sense, the invention also relates to a shell and tube heat exchanger containing such a vessel and containing such a shell, tube bundle, redistribution chamber and nozzle. The shell and tube heat exchanger is, for example, configured to condense compounds other than carbamate and/or operate at pressures below 100 bar and/or perform heat exchange processes other than condensation. The heat exchanger can be used in the production of urea and in other plants and methods.

Brief description of the drawings

In FIG. 1 shows a comparative tubesheet carbamate condenser not in accordance with the invention;

in fig. 2 shows an example of a high pressure carbamate condenser according to the invention;

in fig. 3 is a schematic representation of an example of a urea plant according to the invention.

Implementation of the invention

In the present application, for process streams (ie not steam lines), high pressure (HP) is greater than 100 bar, eg 120 to 300 bar, typically 150 to 200 bar. The medium pressure (MP) is, for example, 10 to 70 bar (including an intermediate pressure of 30 to 70 bar), in particular 15 to 25 bar, and the low pressure (LP) is, for example, 0 to 10 bar, in in particular 1 to 8 bar or 2 to 5 bar. As used herein, the term carbamate refers to ammonium carbamate.

Unlike the falling film condenser, the high pressure carbamate condenser is preferably a flooded condenser. When operating a flooded condenser, the condensation is carried out in space with liquid as the continuous phase and with the gas to be condensed dispersed in the liquid. Thus, there is a liquid level in the condensation space. For example, during operation, the pipes are covered with condensed liquid (on the inside or outside of the pipes) and preferably the pipes are immersed in the condensed liquid. A flooded condenser containing a shell-and-tube heat exchanger is made with the possibility of condensation inside the pipes or in the annulus. In a suitable case, the condensation is carried out in the annular space. The annular space is an empty space to which the outer surface of the pipes faces. The annular space of the casing is limited by the casing. Shell side condensation is one embodiment of a relatively simple design in which the condensate has a sufficient residence time in the condenser. In this case, the advantage is that part of the urea must already be formed in the condenser. In the case of condensation in pipes, it is also possible to increase the residence time of the condensate by using more and/or larger diameter pipes.

The condenser is, for example, a high-pressure carbamate condenser made in the form of a flooded condenser with condensation performed in the annular space, for example, based on the design of a pool condenser, but modified to provide one or more of these redistribution chambers and nozzles. An example of a pool condenser design is shown in Nitrogen No. 222, July-August 1996, pp. 29-31. Preferably, a cooling fluid is provided in the pipes. In the present invention, the cooling fluid is, for example, a process stream such as a solution containing urea and carbamate, the solution is heated while passing through the pipes, and optionally water (process condensate) is additionally used as the cooling fluid.

The high pressure carbamate condenser has, for example, a vertical configuration with pipes (straight pipe run) vertical to gravity when installed in a urea plant. Essentially, the vertical carbamate condenser is configured to condense in the annular space or in pipes, preferably in the annulus. The condenser has, for example, a U-shaped or straight tube bundle, preferably a U-shaped tube bundle. For example, a vertical carbamate condenser, which is the type of condenser described in US 6,518,457, and/or a condenser having a tube bundle with tube ends at the bottom, can be modified with redistribution chambers and nozzles in accordance with the present invention. In addition, a vertical tube-bundle condenser with tube ends at the top can be provided with redistribution chambers and nozzles according to the invention, which are placed at the top of the condenser, for example.

The high pressure carbamate condenser preferably has a horizontal configuration with pipes (straight pipe run) horizontal to gravity when installed in a urea plant. For example, a high pressure carbamate condenser with a horizontal orientation can be configured to condense in pipes and

- 2 040529 for receiving the cooling fluid into the annulus. For example, a kettle-type carbamate condenser, such as that described in EP 0464307 or US 4899813, can be modified with a redistribution chamber and nozzle as described herein.

In one embodiment, the capacitor is in the form of a horizontal flooded capacitor. This advantageously reduces the installation height. In a preferred embodiment, the condenser is in the form of a horizontal flooded condenser, during operation of which condensation takes place on the shell side (ie in the shell side). This provides the additional advantage that the volume of the condenser can easily be configured to increase the residence time of the condensate. This can also be used to create a pool reactor. Condensation on the shell side also results in the high-pressure medium being on the shell side, which simplifies the manufacturing process of the condenser and, in particular, allows for a simpler design of the redistribution chamber.

Thus, in a preferred embodiment, the vessel comprises a gas inlet to the annulus for the gas to be condensed. The gas inlet contains an opening in the casing. The gas inlet allows operation with condensation in the shell annulus and cooling fluid(s) in the pipes. The vessel further includes an outlet for fluid from the annulus, such as a fluid stream containing carbamate. The outlet contains an opening in the casing. The vessel preferably includes a gas distribution device connected to the gas inlet. The gas distribution device preferably comprises a plurality of channels for supplying gas from the gas inlet to the annulus. The gas distribution device can be used to distribute the gas to be condensed over the entire surface and inside the annular space, in particular into a liquid, during operation. The gas distribution device is preferably located below the liquid level during operation. For example, a gas distribution device comprises a bubbling device with one or more pipes extending along the entire length of the vessel, said pipe being equipped with outlets extending across the width of the vessel on both sides of said pipes, the outlets having multiple gas openings (for example, more than 50 holes per outlet) on the top side of the outlets. The gas to be condensed is, for example, a mixture containing CO2 and NH ₃ from a high pressure stripper. Further, the vessel preferably includes an annular liquid inlet for introducing into the annulus a liquid stream containing the ammonia and/or carbamate recycle stream. In an exemplary embodiment, a carbamate recycle stream from, for example, a medium pressure section of a urea plant is introduced into the annulus through a shell opening at the top of the shell. This can improve mixing because the carbamate recycle fluid has a higher density than the annular condensing mixture. The carbamate recycle opening in the housing is preferably located in the lengthwise direction at a distance of less than 1 m from the redistribution chamber. This ensures good mixing of the fluids in the annulus near the redistribution chamber.

The carbamate condenser is arranged, for example, horizontally or vertically. In the case of a horizontal carbamate condenser with a gas distribution device, the gas distribution device extends horizontally and parallel to the pipes (straight pipe sections) so as to introduce the gas to be condensed into the annular space through different outlet openings of the gas distribution device, which are spaced from each other in the horizontal direction. In this embodiment, the lengthwise direction is also horizontal. The pipes are preferably U-shaped.

The condenser preferably includes a liquid distributor for distributing liquid into the annular space through a plurality of holes. These holes are preferably spaced apart in the direction of the length of the capacitor. The liquid distributor is, for example, connected to the ammonia supply element, for example, in fluid communication with the ammonia supply compressor. Typically, a liquid distributor (eg, an ammonia distributor) is connected to an opening in the casing and in operation, for example, is immersed in the liquid present in the annulus.

The tube bundle essentially comprises a plurality of tubes, the tubes comprising or consisting of straight sections of tubes. As a rule, straight sections of pipes are arranged in parallel and spaced apart from each other. In accordance with this application, when condensation is performed in the casing, the pipes of one tube bundle contain the same cooling fluid. Accordingly, the redistribution chamber is preferably connected to the pipes of one tube bundle. In a further embodiment, two or more cooling fluids (with separate feed elements) are used in the tubes and the condenser comprises a plurality of tube bundles. The tube bundles may be combined into a combined tube bundle. The straight sections of all tubes in the combined tube bundle are preferably parallel to each other.

In order to provide sufficient heat exchange surface, the high pressure carbamate condenser has one or more tube bundles, for example with at least 300 tubes in the bundles in total, typically 1000 to 4000, for example 1500 to 3000 tubes in total, for example at least 100 tubes per tube bundle. For example, pipes have a constant internal diameter along their entire length. Preferably, each redistribution chamber is connected only to the inlet ends or only to the outlet ends of one tube bundle.

In some embodiments, the tube bundle comprises straight tubes with tube ends on opposite sides of the tube bundle in the lengthwise direction. Redistribution chambers may be provided at each end of the tube bundle. In principle, it is also possible to use a tube sheet at one end and a redistribution chamber at the opposite end. The tube bundle may be placed at any position along the length of the vessel, such as at the end or in the center of the vessel. The straight pipe section has, for example, a length of 20-90% of the length of the vessel, for example preferably at least 30%, at least 40%, at least 50% or at least 60% and/or, for example, up to 90%, up to 80% or up to 70% of the length of the vessel. In some embodiments, the straight pipe sections are 60 to 90% of the length of the vessel, and preferably the condensate obtained by condensation in the condenser is fed to the pressure reactor. In some embodiments, the straight pipe sections are between 20% and 60% of the length of the vessel, and preferably the condensate obtained by condensation in the condenser is fed to the high pressure stripper. For example, condensate is fed directly to the stripper, so that the high pressure stripper receives condensate having the same composition as the liquid at the condenser outlet. In a urea plant according to such an embodiment, the reactor and condenser are combined in one vessel.

In some embodiments, redistribution chamber(s) are provided at both ends of the tubes (preferably a straight tube bundle), with the redistribution chamber(s) spaced from the vessel by a lengthwise distance of at least 1%, at least 5%, at least 10% or at least 20% of the length of the vessel, at one or both ends of the tube bundle. The greater distance between the redistribution chamber and the vessel at one or both ends of the tube bundle provides a relatively larger annular space for condensation and can help increase the residence time of the condensate in the annulus. This may provide for the formation of urea and, for example, operation as a pool reactor. The condensed carbamate is typically fed into the urea reactor and, in some embodiments, is directly sent to the stripper during operation. Especially in the case of longer pipes (based on a straight pipe run), for example, over 5 m, over 10 m, over 20 m or over 30 m, straight pipes can be easier to manufacture than U-shaped pipes.

In further embodiments, the tube bundle is a bundle of U-shaped tubes, each tube having a bend and two elbows, the elbows being straight pipe sections. The carbamate condenser optionally includes a reactor section between the bend of the U-shaped tube bundle and the casing (opposite the tube bends), for example, but not exclusively, in the case of a pool reactor. An example of a pool reactor is described in US 5,767,313. The straight pipe sections of the U-shaped tube bundle are located in the direction along the length of the casing. In some embodiments, the housing comprises a substantially cylindrical middle portion having a diameter and length, with cap portions at both ends. In the case of a U-shaped tube bundle, for example, a substantially hemispherical cover (optionally with a manhole) is attached to the end of the middle part that is adjacent to the bend of the tube bundle, as well as to the other end of the middle part. In the prior art, for example as described in US 5767313, at the end remote from the bend of the U-shaped tube bundle, a tube sheet is provided for connecting the ends of the tubes to the supply and drain lines through the header.

The invention as a whole is based on a reasonable understanding of the possibility of placing the redistribution chamber inside the casing and connecting the pipes of the tube bundle to the redistribution chamber, and providing a nozzle connecting the redistribution chamber to the supply or drain line through the opening in the casing. The branch pipe is located inside the casing and makes it possible to locate the redistribution chamber at a distance from the casing. During operation, the nozzle is on one side in contact with the cooling fluid and on the other side with the gas to be condensed and/or condensate formed in the condenser. The same applies to the wall of the redistribution chamber. In embodiments with shell-side condensation (outside the tubes), the shell is a piece of equipment that contains and is in contact with the high-pressure condensing medium from the inside. From the outside, the casing is usually exposed to the environment.

In a typical embodiment, each tube of the tube bundle has two tube ends, and for each tube, one end of the tube is connected to an inlet redistribution chamber (for distributing fluid to a plurality of tubes) and the other end of the tube to an outlet redistribution chamber (for collection of fluid from a plurality of pipes).

In a preferred embodiment, the vessel contains two tube bundles, for example, for two different cooling fluids, each tube bundle with an inlet redistribution chamber and an outlet redistribution chamber, so that the vessel contains four redistribution chambers.

The redistribution chamber contains a wall. The wall includes a section of the wall with bored holes. During operation, the fluid flows between the redistribution chamber and the pipes connected to it through the bore holes. However, in contrast to a conventional tube sheet, this section of the wall, and more particularly the entire redistribution chamber, is located at a distance from the casing. Thus, as a rule, none of the parts of the redistribution chamber is in direct contact with the casing (inner surface of the casing).

The redistribution chamber is connected to the ends of the pipes. In particular, the wall section with bored holes is connected to the ends of the pipes, for example, by means of gapless joints.

Accordingly, at least some of the ends of the pipes are placed within the space enclosed in the casing (vessel space) and are connected (for fluid flow) to the opening in the casing through the redistribution chamber and the nozzle passing between the redistribution chamber and the casing. The redistribution chamber is spaced from the opening in the casing, for example, at least 5 cm, at least 10 cm, or at least 40 cm. The redistribution chamber is also distant, preferably entirely, from the casing, preferably at least 5 cm, by at least 10 cm or at least 40 cm. These distances are preferably provided with a void space which can be filled with a cooling fluid or a condensing medium during operation. Support elements may be present between the redistribution chamber and the casing, as well as the branch pipes.

Advantageously, in a preferred embodiment with the cooling fluid(s) in the pipes, the high pressure is outside the redistribution chamber, not inside it.

Advantageously, the walls of the redistribution chamber can be thinner than known tube sheets due to the smaller dimensions of the redistribution chamber compared to the tube sheet. In particular, the redistribution chamber has a smaller surface area in a cross section perpendicular to the length of the vessel compared to the shell and the tube sheet sealing the shell. This leads to a significant reduction in the forces (stresses), the impact of which must withstand the design of the walls of the redistribution chamber.

In a preferred embodiment, the redistribution chamber bored element (or plate) (or common to the redistribution chamber stack) has, for example, only a relatively small flange around the tube bundles, such as less than 40 cm, less than 20 cm, or less than 10 cm, around each tube bundle. on each side of the outer tubes of each tube bundle.

The redistribution chamber may, for example, be provided with an internal load-bearing structure, such as a divider. The walls of the redistribution chamber may be fabricated or comprised of a single sheet of corrosion resistant material such as duplex stainless steel. For the preferred embodiment, pipes are easier to weld to a redistribution chamber with a single sheet wall, especially because there is no risk of exposure to carbon steel.

In addition, the walls of the redistribution chambers advantageously also contribute to the heat exchange surface, since during operation they can be in contact with the cooling fluid on the one hand and on the other hand with the condensing medium.

The invention also relates to a urea production plant comprising a high pressure urea synthesis section which comprises a high pressure carbamate condenser as described above, a reactor and a stripper. Each of the reactor, condenser and stripper is operated under high pressure. The stripper has a gas line to the condenser, the condenser has a liquid flow line to the reactor, and the reactor has a liquid flow line to the stripper for at least a portion of the urea solution. The reactor and condenser are optionally combined in a single vessel, which is, for example, horizontal and from which the condensate is fed directly to the stripper. Such a single vessel, for example, contains a capacitor part and a reactor part. Also in the case of a condenser and reactor provided as separate vessels (generally with a vertical reactor vessel), optionally some urea is already formed in the condenser. For example, the installation contains a gas pipeline from the stripper to the annulus and a liquid flow line from the stripper to the tube bundle of the carbamate condenser, or, for example, the installation contains a gas pipeline from the stripper to the tube bundle and a liquid flow line from the stripper to the annulus of the carbamate condenser, while said flow line to the tube bundle passes through the nozzle and the redistribution chamber as described above.

During operation, the urea synthesis stream from the reactor, containing urea, water, CO2 and NH3 (partially as carbamate), is at least partially fed to the stripper. The carbamate dissociates into CO2 and NH ₃ in the stripper and some of the unreacted components are removed from the solution as a gas. In the stripper, decomposition of the carbamate is stimulated by heating and counter-current contact with a boil-off gas to promote dissociation. The stripper uses heat and, for example, high pressure CO ₂ supply as stripping agent, so-called thermal stripping is also possible. Heating in the stripper is typically indirect heat exchange with steam, typically with steam on the jacket side and the urea synthesis stream in the tubes of the shell and tube heat exchanger used as the stripper. The stripped urea solution, still containing some carbamate and NH3, is typically expanded to a lower pressure and fed to a regeneration section that removes more carbamate from the urea solution; the regeneration section includes, for example, an LP regeneration section with an LP regeneration section arranged downstream in series, or only an LP regeneration section. The mixed gas stream from the stripper, containing NH ₃ and CO ₂ , is fed into the high pressure condenser, either into the tubes or into the annulus.

In a preferred embodiment, the mixed gas flow is fed into the annulus through an opening in the shell. The pipes are supplied with one or more cooling fluids through a nozzle and a redistribution chamber as described above (with separate nozzles and redistribution chambers for different cooling fluids). Liquid condensate is formed and in this preferred embodiment is present in the annular space, with gas optionally present in the upper part of the annulus. The condensed liquid is in contact with the pipes, so that the condensate is usually supercooled.

In this preferred embodiment, a gas distribution device, such as a bubbling device, is used to distribute the gas to be condensed in the annular space, in particular for distribution in the direction along the length of the condenser. The bubbling device is, for example, a pipe having an inlet connected to the inlet of the casing, optionally with branches, and the pipe has a plurality of gas outlets, the outlets being spaced from each other in the direction along the length. The outlets run along the width of the vessel and have holes for gas. The preferred carbamate condenser contains such a bubbling device. For horizontal condensers, the gas distributor and the straight pipe sections run parallel in the lengthwise direction; preferably at least part of the gas distribution device is located under the straight sections. This advantageously provides improved distribution of the heat of condensation in the shell.

In some embodiments, ammonia is also introduced into the annular space, for example, using a liquid distributor, especially if a CO2 stripper is used.

In some embodiments, the heat of condensation is at least partially removed by the formation of water vapor (evaporation of water) in at least some of the pipes, in the case of condensation in the annular space, and in the annulus, in the case of condensation in the pipes, while water steam, for example, is generated from process condensate.

Parts of a carbamate condenser that are in contact with the process fluid, especially at higher temperatures (for example, the process fluid condensing under high pressure in the condenser) are usually made of corrosion resistant materials, in particular urea grade steel such as austenitic-ferritic duplex stainless steel. steel (duplex steel). For example, on the inside of the casing, there is usually a hardfacing (i.e. welded layer) or an internal lining made of carbamide grade steel or other corrosion resistant metal, such as duplex austenitic-ferritic stainless steel, AISI 316L steel, or steel grade INOX 25/22/2 Cr/Ni/Mo. Such an inner lining is typical of a high pressure carbamate condenser shell. On the outside, the casing is, for example, a carbon steel casing and has a thickness of, for example, at least 30 mm or at least 40 mm.

In some embodiments, the carbamate HP capacitor comprises two tube bundles. They can be used to implement a process in which two different cooling fluids are used, for example, a first tube bundle to produce water vapor from water and a second tube bundle in which an aqueous solution containing urea and carbamate is heated to cause decomposition of the carbamate.

Such a capacitor, for example, can be used in the apparatus and method described in US 2015/0119603.

In one embodiment, a dual tube bundle HP condenser is used in a urea production process in which water vapor (also referred to as condensate) is produced in the first tube bundle. In the second tube bundle, the solution containing the carbamate (and usually also the urea) is heated with the heat of condensation obtained from the high pressure process fluid.

- 6 040529 on the shell side, so that at least part of the carbamate in solution in the second tube bundle dissociates to form NH3 and CO2. This solution is, for example, obtained as stripped urea solution from the HP stripper or as part of the urea synthesis solution from the reactor that is not stripped in the HP stripper. For example, the urea solution, which is part of the liquid from the reactor (optionally from the combination vessel containing the condenser and reactor), and/or the urea solution, which is at least part of the liquid from the stripper, is fed into the second tube bundle, in particular through the inlet a redistribution chamber and an inlet to the second tube bundle, optionally with intermediate steps such as expansion and gas/liquid separation (flash). For example, all or part of the urea solution exiting the stripper is expanded, optionally flashed and optionally further expanded and fed at medium pressure (eg 10-35 bar) into the second tube bundle.

In some embodiments, the second tube bundle receives a solution containing carbamate, for example, in methods for producing urea, including feeding the urea solution into the second tube bundle directly or indirectly from the reactor (or reactor part), for example from a reactor, a stripper, or from a regeneration section, preferably through the inlet pipe and the inlet redistribution chamber. In such embodiments, thermal decomposition of the carbamate (into CO ₂ and NH ₃ gas) may occur in the second tube bundle.

The high pressure condenser can, for example, be used in a stripping type urea production process in which part of the urea solution from the reactor is sent to the high pressure stripper and another part of the solution is fed bypassing the stripper and sent to a medium pressure stage using carbamate decomposition. by heating the solution under medium pressure. The invention also relates to such a method. An example of such a process using another type of high pressure condenser is described in US 2004/0116743. In operation of the high pressure carbamate condenser of the present invention, and in the preferred process of the invention, the medium pressure treatment step is carried out, for example, by feeding the urea solution through the (second) tube bundle of the high pressure carbamate condenser in indirect heat exchange contact with the condensing gases in the condenser, which are taken from stripper. In a further embodiment, the carbamate condenser is used to generate steam (e.g., in a tube bundle), the steam being used to supply heat to the medium pressure decomposition step of the stripper-derived urea solution or the unstripped urea solution from the reactor.

For traditional carbamate HP condensers, the problem with carbamate-containing liquid(s) present during operation in at least some of the tubes as well as in the annulus is the risk of corrosion and the way the tube is attached to the tubesheet, e.g. grid as described in US 2015/0119603. The present invention provides the important advantage that the redistribution chamber, in particular the bored wall section which is exposed on both sides to the corrosive carbamate-containing solution, can in an embodiment be made of (and consist of) a single sheet of stainless steel such as single sheet duplex stainless steel. This applies in particular to the situation where condensation occurs on the shell side. Multi-layered chamber walls are also possible, especially if all layers are made of a corrosion-resistant material. In some embodiments, the thickness of the wall section with bored holes for pipes is 0.5-2 times the thickness of any other section of the wall of the redistribution chamber, and the wall section with bored holes is a flat plate. For example, if the other portions of the redistribution chamber have walls 12 cm thick, the pipe bore wall portion is 0.5-4 cm thick. In some embodiments, the pipe bore wall portion is 0.9-1.1 times thick. exceeds the thickness of other sections of the wall of the redistribution chamber. An advantage of the invention is that the wall section with bored holes for tubes does not have to be a very thick plate, such as in the case of a tube sheet.

In an exemplary embodiment, the condenser comprises two U-shaped tube bundles arranged in a vertical direction in an ABBA configuration, where A is a straight section of the first tube bundle and B is a straight section of the second tube bundle, or where A is a straight section of the second tube bundle. bundle (used in-service, for example, to decompose carbamate), and B is a straight section of the first tube bundle (used in-service, for example, to generate steam), and preferably with a vertical stack of four redistribution chambers connected to two tube bundles. In such an embodiment, the bends of the U-shaped tube bundle may be arranged in a concentric manner (particularly in cross section in the length-height plane). In an alternative embodiment, the design may be an AABB configuration that provides, for example, two sets of concentric bends in each tube bundle.

- 7 040529 position and two sets located one above the other.

In a preferred embodiment of the urea plant according to the invention, the high pressure carbamate condenser comprises a tube bundle which is connected to the feed line via a redistribution chamber and a pipe. The feed line is used to supply the urea solution, which also contains carbamate, to the tubes of the tube bundle. The feed line is connected to the stripper to receive the stripped urea solution from the stripper and/or connected to the reactor to receive part of the urea solution from the reactor. In a preferred embodiment, the feed line comprises an expansion device and preferably a gas/liquid separator for separating the gas from the expanded urea solution. Preferably, the supply line is configured to supply at least a portion of the expanded urea solution to the nozzle.

In a preferred embodiment, the tube bundle (receiving the urea solution also containing carbamate) is connected to the gas/liquid separator via an outlet redistribution chamber and a duct. The gas/liquid separator is preferably in liquid communication with the regeneration section and in gas communication with the second condenser. Ammonia and CO2 from the thermal decomposition of carbamate in the tubes are at least partially condensed in a second condenser. Preferably the second condenser is operated at medium pressure. Preferably the condensation is carried out in heat exchange contact with the evaporation section of the urea plant so that the heat of condensation is used to evaporate the water from the urea solution. Preferably, the second carbamate recycle stream condenser is in fluid communication with the high pressure carbamate condenser, and more preferably with the annulus.

Additionally, the HP condenser may include a second tube bundle connected to a process condensate (ie water) feed line and connected to a steam outlet line.

In a preferred embodiment, the condenser comprises one or more pairs of pipes, each pair including an inlet and an outlet. The condenser preferably comprises one or more pairs of redistribution chambers, each pair including an inlet redistribution chamber for distributing cooling fluid that is supplied from an inlet to a plurality of pipes, and an outlet redistribution chamber for combining heated cooling fluid from a plurality of pipes to an outlet. . For each pair, the redistribution chambers are typically located on the same side of the straight tubes in the case of a U-shaped tube bundle or on opposite sides (in the longitudinal direction) of the tubes in the case of a straight tube bundle.

In a preferred embodiment, the redistribution chamber contains many elements (such as elements - plates) and, therefore, is not completely integral. These elements together form the wall of the redistribution chamber. At least one of the elements is provided with bored holes for the pipe, and the same or another element (for example, another plate) is provided with a hole for the branch pipe. Preferably, at least one other element is openable and closed, for example detachable, thus providing access to the interior of the redistribution chamber. This element is, for example, a cover plate. This element can be used to provide access to the interior of the redistribution chamber, for example, for people and/or devices. Thus, the interior space of the redistribution chamber, i.e. a fluid receiving space accessible for maintenance and inspection of the redistribution chamber from the inside and pipes, in particular for inspection of the internal surfaces of pipes and for plugging pipes. Plugging the pipes may include placing a plug in the pipe at the end of the pipe connected to the redistribution chamber. In a preferred embodiment, the redistribution chamber includes fasteners for attaching the openable element to at least one other element, such as bolts. For example, a box-shaped redistribution chamber having an openable front plate may include a front plate having holes and side plates with slots (eg, a threaded hole) aligned with the holes. These holes and slots can receive a fastener such as a bolt.

The redistributing chamber may additionally contain spacers for separating wall sections (eg plate elements) from each other, for example to provide resistance to compressive forces.

The vessel preferably includes supports for the redistribution chamber, for example located below the redistribution chamber and on the casing. For example, support elements may be provided below (and, for example, at the same location in the lengthwise direction of the vessel) the portion of the wall provided with the counterbores. The support may include a slot for receiving a protrusion of the redistribution chamber for locking the redistribution chamber in place. The redistribution chamber or, for example, the stack of redistribution chambers, for example, is provided with locking means for holding the chambers in place in the housing.

Preferably, the surface area of the cross section of the redistribution chamber (the cross section perpendicular to the axis along the length of the vessel) is less than 90%, or less than 80%, or less than 40% of the surface area of the cross section of the vessel (in particular, the surface area enclosed in the casing in the specified cross section ).

In the case of a (vertical) stack of redistribution chambers, the cross-sectional surface area of the stack in the width-height plane (perpendicular to the central axis along the length of the vessel) is, for example, less than 90%, or less than 80%, or less than 70% of the cross-sectional surface area of the vessel (in in particular, the surface area enclosed by the casing in the indicated cross section).

Preferably, the annular space is a single undivided space in which all parts of the space are in fluid communication with each other; also in such embodiments, the annulus may include baffles to divide the annulus into compartments that are not completely isolated from each other. Preferably the casing is in contact with the annulus, and preferably the entire inner surface of the casing is in contact with the annulus. Preferably, each nozzle extends through the annulus. Preferably, each nozzle contains a length segment in which the entire outer wall of the nozzle faces the annulus. Preferably, the front plate of the redistribution chamber (or each redistribution chamber) in the form of a box (with holes for connection with pipes on the opposite back plate) is on the outside facing the annulus.

In some embodiments, at least one redistribution chamber is at least partially immersed in condensed liquid in operation, preferably each redistribution chamber is at least partially immersed in condensed liquid, and preferably at least one redistribution chamber is completely immersed into a condensed liquid, wherein the condensed liquid is condensed in the annulus.

In a preferred embodiment, the casing comprises a substantially cylindrical middle portion and two cap portions. Each cap portion may comprise a plurality of casing portions. The cap portion is, for example, a substantially hemispherical piece, optionally having a hatch and a plate. The two cap parts close the middle part at opposite ends, in particular at opposite ends in the lengthwise direction. Preferably, the annulus is a single annulus formed by the middle portion and cap portions. Preferably, the annulus is not divided, for example, by dividing walls, but may nevertheless include baffles. Preferably, fluid can flow from the gas distributor into both cap portions.

High pressure carbamate condensers differ from other types of heat exchangers, in particular hot gas coolers, in a number of features that are advantageous for the inventive carbamate condenser. A horizontal carbamate condenser capable of condensing in a shell may, for example, include baffles (or bulkheads) separating the annular space into compartments in the length direction and extending from the bottom of the vessel, but not completely to the top of it, thus leaving gas supply zone in the upper part of the casing; the upper part of the baffles determines the level of the condensate liquid during operation. Some baffles may have openings, for example, at the vertical height of the tube bundle. Typically, the baffle located lowest in the direction of flow has no holes, so that liquid condensate flows through the top of the baffle to the liquid outlet in the casing. Thus, the casing section contains an overflow weir. This makes it possible to control the level of condensate in the condenser, especially for complete submersion of the tube bundle. Moreover, typically the tube bundle, especially the U-tube bundle, has a single pass configuration for each cooling fluid (urea solution and/or process condensate).

A tube-condensing carbamate condenser, for example, of the horizontal boiler type, includes, for example, an ejector at the inlet for the carbamate solution, and, for example, includes a mixing zone for inlet of the gas to be condensed and the carbamate solution. The carbamate condenser has, for example, a passage for the recirculating carbamate solution from the outlet end of the pipe to the inlet for the gas to be condensed.

In the case of a vertical carbamate condenser, which is configured to condense in the annular space, the condenser comprises, for example, a packing part at the top, for example a packing part for cleaning the exhaust gas with a solution supplied through the casing inlet above the packing part, in particular an inlet for carbamate solution, and downpipe located below the nozzle part, but above the U-shaped bend of the tube bundle to the part of the condenser located below the specified bend. Vertical carbamate condenser

- 9 040529 preferably has a liquid inlet in the casing, optionally with a drain pipe, so that during operation the liquid level can be maintained above the U-bend of the tube bundles, with the ends of the pipes located at the bottom of the vessel.

The nozzles preferably comprise or are made of a corrosion resistant steel such as duplex stainless steel. For example, branch pipes are made entirely of such steel. The portions of the walls of the redistribution chambers and any internal structures, such as spacers, that are in contact with the carbamate during operation are preferably made of corrosion resistant steel, such as duplex stainless steel. The pipes and the preferred inner casing lining are preferably made of corrosion resistant steel such as duplex stainless steel.

Suitable duplex stainless steel for these parts of the carbamate capacitor includes, for example, steel available commercially under the trade name Safurex® and having the composition 29Cr-6.5Ni-2Mo-N, which is also referred to as ASME 2295-3 and UNS S32906, or , for example, steel commercially available as DP28W (TM) steel having the composition 27Cr-7.6Ni-1 Mo-2.3W-N, which is also referred to as ASME 2496-1 and UNS S32808. Steel Safurex (R) has, for example, the composition (wt.%): C: max. 0.05 Si: max. 0.8, Mn: 0.3-4.0, Cr: 28-35, Ni: 3-10, Mo: 1.0-4.0, N: 0.2-0.6, Cu: max. 1.0 W: max. 2.0S: max. 0.01 Ce: 0-0.2, the rest is Fe and (inevitable) impurities. Preferably the ferrite content is 30-70% by volume and more preferably 30-55%. More preferably the steel contains (wt%): With max. 0.02 Si max. 0.5, Cr 29-33, Mo 1.0-2.0, N 0.36-0.55, Mn 0.3-1.0, the rest is Fe and impurities. Also acceptable is duplex stainless steel having a composition by weight percentage (wt.%): With max. 0.030; Si max. 0.8; Mn max. 2.0; Cr 29.0-31.0; Ni 5.0-9.0; Mo less than 4.0; W less than 4.0; N 0.25-0.45; Cu max. 2.0; S max. 0.02; R max. 0.03; the rest is Fe and inevitably present impurities; and the content of Mo + W is more than 3.0, but less than 5.0 (wt.%), in addition, preferably with the steel composition described in WO 2017/014632, incorporated herein by reference. In some embodiments, the casing comprises an inner lining made from such steels.

Each nozzle has a first end of the nozzle connected to the wall of the redistribution chamber, and a second end connected to the casing. The first end of the nozzle is aligned with the hole in the wall and the second end of the nozzle is aligned with the hole in the casing so that fluid can flow from the outside of the casing to the redistribution chamber through the nozzle. The nozzle is at least partially located in the vessel. The first end of the pipe is located in the vessel. The branch pipe passes through the space of the vessel. In addition, the outer surface of the branch pipe faces the annulus.

The pipe may consist of one or more pipe parts, such as pipe parts arranged in series and connected to each other.

The first end of the pipe is connected to the redistribution chamber, for example, by welding. The first end of the pipe, for example, is located radially outward from the ends of the pipes connected to this redistribution chamber, i. further removed from the central axis along the length of the vessel in a direction perpendicular to the length. In an illustrative embodiment with a box-shaped redistribution chamber with bottom, top, front, back and two side plates, the end of the pipe is, for example, attached to the side, top or bottom plate, and the ends of the pipes are attached to the back plate, and the front plate is, for example, a cover plate that is openable for maintenance and inspection. In principle, the nozzle can also be connected to the back plate or to the front plate. In an exemplary embodiment with a box-shaped redistribution chamber, a nozzle is attached to the front plate and the side plate is openable.

In a preferred embodiment, a plurality of redistribution chambers are stacked on top of each other to form a stack of preferably box-shaped redistribution chambers and preferably with the stack stacked vertically. Preferably, the plate element is common to stacked redistribution chambers, with preferably the plate element having bored holes. Preferably, the tube bundle comprises U-shaped tubes, each tube having a bend and two elbows. Preferably, the redistribution chamber stack includes an inlet redistribution chamber and an outlet redistribution chamber connected to the same U-shaped tube bundle.

In the case of a (vertical) stack of redistribution chambers, preferably box-shaped, different plates can be common to the redistribution chambers of the stack. This may apply, for example, to the back plate (eg with counterbored holes for connection to the tube bundle) and to the side plate. The horizontal plate may be shared between two adjacent chambers, providing a top plate and a bottom plate, particularly when the chambers receive fluid at the same pressure during operation. In the case of a vertical stack of four or more redistribution chambers, for the upper redistribution chamber, the spigot may be connected to the top plate, for the lower redistribution chamber, the spigot may be connected to the bottom plate, and for the redistribution chambers in the middle, the spigots may be attached to the side plate. plate. In a preferred embodiment, the redistribution chamber is provided with nozzles on two opposite side plates, and these are used during operation, for example, as both inlet and outlet ports. Advantageously, this can promote good distribution of the fluid through the pipes and efficient removal of fluid from the pipes. In particular, due to the fact that in some embodiments, the box-shaped redistribution chamber has a width (from side to side) that exceeds the height of the redistribution chamber, and the same applies to the area of the rear plate, which is provided with holes.

In an exemplary embodiment with a stack of redistribution chambers, all nozzles connected to said stack extend to the top of the housing. In combination, for example, with support structures for the tube bundle in the vessel between the bottom of the shell and the tube bundle, this can accommodate expansion and/or contraction of the equipment. In the case of a stack of redistributing chambers, the chambers may have, for example, a common shared back plate, and for a vertical stack, the side plates may also be shared.

In some illustrative embodiments, the distance in the length direction between the first and second ends of the nozzle is for one or more nozzles (or even for all nozzles) less than 20% or less than 10% of the length of the vessel, or less than 20% or less than 10% of the length of the straight lines. pipe sections.

In a further embodiment, one or more nozzles extend in a length direction, for example, when the nozzles are located essentially parallel (eg, with a deviation of less than 5°) pipes (straight pipe sections). In some illustrative embodiments, the distance in the lengthwise direction between the first and second ends of the nozzle is for one or more, or even for all of the nozzles, more than 10% or more than 20% of the length of the straight pipe sections.

Typically, in a redistribution chamber, the number of pipes connected to this redistribution chamber is at least 10 times the number of nozzles connected to this redistribution chamber, for example, at least 50 times or at least 100 times. Accordingly, the nozzles substantially have a cross-sectional surface area (perpendicular to the flow direction) of the inner flow space of the nozzle that is at least 10 or at least 20 times greater than the same pipe area.

Each branch pipe has at least two pipe ends, and the ends of the pipes belong to the end parts, and not just to the side edge. The nozzle can also have, for example, three nozzle ends in the case of a Y-shaped nozzle. The end of the branch pipe is connected to the redistribution chamber. For example, the end of the nozzle may abut the (flat) side of the redistribution chamber wall by means of a gapless connection. The end of the tube can also be inserted through an opening in the wall of the redistribution chamber, for example when the gap between the wall and part of the tube is sealed with a weld.

Similarly, the end of the pipe (end part) is connected to the casing, for example the end of the nozzle can be adjacent to the casing, for example, through a gapless connection. In case the housing wall includes a carbon steel member and the fluid to be conveyed through the nozzle includes carbamate, the end of the nozzle or the end of the nozzle may be inserted through the opening in the casing. The gap between the inserted part of the pipe and the opening surface of the casing (including any exposed carbon steel) can be closed by welding also from the inside of the casing, since the place for the hole will be available. Optionally, a nozzle part, such as a sleeve (e.g., duplex stainless steel), is first inserted through the hole, the slot is sealed, for example, by welding, and the inserted nozzle part (e.g., sleeve) is connected to another nozzle part, for example, by welding. along the inner edge of the holes. For example, the condenser includes a pipe end inserted through an opening in the casing and having a hermetically sealed gap between the inserted nozzle part and the casing.

In an embodiment in which the redistribution chamber is equipped with a plurality of nozzles, these nozzles are optionally connected to a manifold (or connecting segment) that can be placed inside or outside the vessel. In some embodiments, the nozzle includes a connecting segment (eg, a T-joint) that connects at least three nozzle segments. When such a pipe is used, two ends of the pipe can be, for example, connected to the redistribution chamber and one end of the pipe to the casing. In an exemplary embodiment, the inlet is connected to the bottom plate of the lower redistribution chamber of the vertical redistribution chamber stack by means of two or more pipe segments, each of which is connected to the bottom plate, at least one pipe segment is connected to the casing, and located inside the vessel space, the connecting segment, connecting the specified segments of the branch pipe. Said at least two pipe segments connected to the redistribution chamber can be spaced apart for optimal distribution

- 11 040529 fluids through pipes.

The condenser may be manufactured, for example, by a method including mounting the tube bundle in a casing (having at least one open end), such as on support baffles. The invention also relates to such a manufacturing method. The method may include attaching the redistribution chambers to the ends of the pipes before or after the installation of the tube bundle, for example by welding along the inner edge of the holes. For example, a tube bundle attached to a package of redistribution chambers is installed in the casing. The method may include connecting nozzles to the redistribution chamber after the tube bundle has been installed. The spigots can be inserted through the casing before or after installation. The method may include closing the vessel, for example, by attaching a closure cap (e.g., half head) to a substantially cylindrical middle portion of the vessel having at least one open end, for example, at the end of the middle portion where the redistribution chamber is located.

Illustrative embodiments of the invention are presented and described in conjunction with the drawings, and these drawings do not limit the invention or the claims.

In FIG. 1 shows a comparative high pressure carbamate condenser not in accordance with the invention. The condenser (100) is presented in the form of a shell-and-tube heat exchanger (101) and is made in the form of a horizontal flooded condenser with a U-shaped tube bundle (103) for cooling fluid and has a gas to be condensed in the annulus (105) during operation. A portion of the lower half of the condenser (100) is shown in FIG. 1. The heat exchanger (101) contains a vessel (102), and the vessel contains a casing (1) and a tube bundle (103). The casing is made with the ability to withstand high pressure and encloses the space (104) of the vessel. The vessel (102) also contains a collector (107). The collector (107) is not enclosed in a casing (1) and is located outside the space (104) of the vessel. In the space (104) of the vessel, pipes (2) of the tube bundle (103) are provided. The space between the pipes (2) and the casing (1) is an annulus (105) for receiving the gas to be condensed. Accordingly, the vessel contains a gas inlet (4) into the annulus (105) and an outlet (5) for liquid from the annular space (105), and corresponding openings for the process medium in the casing (1). The vessel additionally contains an inlet (13) for carbamate recirculation, which includes an opening in the casing (1). The vessel additionally contains a gas distribution device (6) connected to the gas inlet (4). The gas distribution device (6) is configured to distribute the gas to be condensed (for example, the gas mixture from the high pressure stripper in the urea plant) in the annular space (105).

The vessel (102) also contains a tube sheet (108). The tube sheet separates the annulus (105) from the header (107) and must therefore withstand large pressure drops. One open end of the substantially cylindrical casing (1) is hermetically sealed by the tube sheet (108). The tube sheet contains bored holes (110) for the cooling fluid. The ends (3) of the tubes (2) are connected to the tube sheet (108) so that fluid can flow between the tubes and the manifold (107). The manifold is provided with an opening (109) which is used as an inlet or outlet so that cooling fluid flows between the opening (109) to a large number of pipes (2), for example more than 100 pipes. The tubesheet (108) is, for example, a substantially circular metal plate and is typically a thick plate of carbon steel (e.g., about 30-60 cm thick carbon steel) lined with corrosion-resistant steel on the side facing the annulus (105 ), such as alloy-clad duplex stainless steel (which includes, for example, a weld deposit).

For the comparative carbamate capacitor shown in FIG. 1 (not in accordance with the invention), the design of the tubesheet (108) is complex and costly in view of the need to withstand high pressure, exposure to at least one side of a highly corrosive process environment, and a very large number of tubes. In addition, any gaps between the tubes and the tube sheet create a high risk of crevice corrosion because they are in contact with the medium containing the carbamate. Slots are present, for example, when pipe bends pass through bored holes whose diameters are, for example, (slightly) larger than the outside diameter of the pipe. Crevice corrosion is particularly severe on metal parts in contact with carbamate. Crevice corrosion can cause difficulty in maintaining a passivating layer on steel with passivating agents (such as oxygen) in the crevices due to limited flow in the crevices. Corrosion also occurs in crevices if carbon steel is attacked in such crevices. Thus, in prior art pool condensers, the tubes are often not inserted into bored holes, but are connected to the tube sheet in a gap-free manner using, for example, welding along the inner edge of the holes. Exposure of a carbon steel part in a tube sheet to process condensate and water vapor in bored holes is not problematic.

In the event that a carbamide solution, which also contains carbamate, is supplied as a cooling fluid to the collector (107), for example, when used in the method described in

- 12 040529

US 2015/0119603, on the side of the tube sheet (108) facing the manifold (107), a corrosion protection layer is also required, and the carbon steel surface of the bores (110) must not be exposed to the cooling fluid. The alternative of a single sheet duplex stainless steel alloy tubesheet is not practicable because there is at least no practical way to produce homogeneous duplex stainless steel plates having a thickness (e.g. 30-60 cm) sufficient to withstand high pressure environments.

US 2015/0086440 describes a manufacturing method in which the sleeves are inserted into bored holes through the tube sheet in such a way that the sleeves pass through the tube sheet. Sleeves are much shorter than pipes. Sleeves may be welded (outside) on both sides of the tubesheet so as to seal off the carbon steel layer of the tubesheet from the fluid in the annular space (105) and from the fluid in the header (107). On one side of the tube sheet, the sleeves are then connected to the elbows of the U-shaped tube bundle by welding along the inner edge of the holes. Thus, after the sleeves are welded to the tube sheet, the ends of the pipes are connected to the sleeves by welding from the inside by inserting the welding electrode into the sleeves from the low pressure side (manifold side) and forming a weld along the inner edge of the holes.

Accordingly, the external welding of the sleeves to the tube sheet is performed before the sleeves are connected to the tube bundle, because otherwise the tube bundle (with a large number of closely spaced tubes) impedes access from one side of the tube sheet. However, the disadvantage is that three welds are required for each pipe, resulting in high construction costs.

If, according to the method described in US 2015/0086440, the sleeve is omitted and the pipes are directly attached to the tube sheet by welding along the inner edge of the holes, the carbon steel plate inside the tube sheet will be exposed in the bored holes to the carbamate present in the urea solution that is used as a cooling fluid inside the pipes. This will cause corrosion. If the pipes are inserted into the bore holes, there will be a gap between the ends of the pipes inserted into the bore holes and the tube sheet, i.e. a gap between the outer surface of the pipe and the inner surface of the hole in the tube sheet, allowing the process fluid to contact with a part of the tube sheet made of carbon steel. In the present invention, the wall of the redistribution chamber (including the wall portion with bored holes, as in a conventional tube sheet) can advantageously be made of single sheet duplex stainless steel, so that a carbamide solution containing carbamate, which is used as a cooling fluid, can be contacted with surface of bored holes without causing a particular risk of corrosion.

One of the options for increasing the residence time of the condensate in the annular space in the condenser shown in Fig. 1 is to increase the diameter of the casing so that the casing has a much larger surface area in cross section than the tube bundle, for example as shown in US 5,767,313. The disadvantage is that the diameter of the tube sheet also increases as the tube sheet is used for sealing from one end of the casing, and as a result, the stress created by the pressure difference also increases.

In FIG. 2A shows an example of a carbamate capacitor (100) in accordance with the invention. In FIG. 2B is an enlarged view. Instead of manifold (107) and tube sheet (108) as shown in FIG. 1, the carbamate condenser (100) comprises a redistribution chamber (7) with a wall (8). The wall (8) is configured to separate the fluid in the redistribution chamber (7) from the fluid in the annulus (105). These two fluids essentially have different compositions during operation. The redistribution chamber (7) is located inside the space (104) of the vessel and is thus enclosed in a casing (1). The casing (1) is configured to hold the fluid in fluid contact with the outer surface of the pipes (2). A plurality of pipes (2a, 2b) are connected to each individual redistribution chamber (7) so that fluid can flow between the pipes (2) and the redistribution chamber (7) through holes (12) (for example, bore holes) in the wall (8) , which are provided on the section (11) of the wall (8).

The ends (3) of the pipes (2) are attached to the wall (8) in such a way that the holes of the ends of the pipes are aligned in accordance with the hole (12) of the wall (8). This is shown schematically in FIG. 2C, with the diameter of the pipes (2a, 2b) being exaggerated compared to the redistribution chamber (7). The ends (3) of the pipes are attached, for example, by welding along the inner edge of the holes. The redistribution chamber (7) is connected to the opening (10) in the casing (1), which is intended for the (cooling) fluid, by means of a pipe (9). The branch pipe (9) is located in the space (104) of the vessel and preferably faces the annular space (105). The branch pipe (9) passes between the opening (10) of the casing (1) and the redistribution chamber (7), more specifically to the opening (14) of the redistribution chamber (7). Thus, the coolant can move between the hole (10) in the casing (1) and the pipes (2) through the redistribution chamber (7) and the pipe (9), while the coolant

- 13 040529 the medium is separated from the process fluid in the annulus (105). During operation, the pipe (9) is in contact with the cooling fluid from the inside and is in contact with the process medium in the annulus (105) from the outside. As shown in FIG. 2A and 2B, the carbamate condenser (100) also includes a manhole (106) and baffles (15).

In FIG. 2D is a schematic cross-sectional view perpendicular to the length of an exemplary embodiment. The carbamate condenser (100) contains a vertical stack of 4 box-shaped redistribution chambers (7), each of which has a branch pipe (9), with a bored portion (11) shown for each redistribution chamber (7). The location of the nozzles (9) in Fig. 2D is schematic, many variations are possible. The pipes (9) essentially extend from the redistribution chambers outward to the opening (1) in the casing (1). Reference numbers that are the same for FIGS. 1 and 2 preferably have the same features in FIG. 2 as described with respect to FIG. 1.

In FIG. 3 shows an example of a urea plant according to the present invention. The plant contains a high-pressure synthesis section containing a carbamide reactor R, a stripper S and a carbamate condenser HP NRSS. The reactor R is in fluid flow communication for the urea synthesis solution USS with the stripper S, which uses CO ₂ feed for stripping in addition to heating by indirect heat exchange with steam. Optionally, reactor R is combined with an HPCC condenser in a single vessel that is in fluid communication with stripper S. The urea synthesis solution USS also contains carbamate, ammonia and water, which must be removed (at least partially) from the final urea product using stripper S and a regeneration section REC comprising a low pressure section and, for example, consisting of a low pressure section without a medium pressure section. An evaporator section EVAP is optionally provided downstream of the REC to remove water to form a urea melt UM, which is optionally solidified in a FINISH section to form a solid urea product SU. The stripper S is in fluid flow communication for the gas mixture SG with the HPCC condenser. The HPCC condenser contains two U-shaped tube bundles T1 and T2. Each tube bundle (T1, T2) contains a plurality of tubes (eg, more than 100 tubes). Each pipe is connected at one end to the inlet redistribution chamber RC1A, RC2A and the other end to the outlet redistribution chamber RC1B, RC2B. The inlet redistribution chamber (RC1A, RC2A) is connected to the inlet pipe D1a, D2a. The outlet redistribution chamber (RC1B, RC2B) is connected to the outlet (D1b, D2b).

Condensation is carried out on the shell side of the HPCC, to which feed NH ₃ is also fed. The stripper S is in fluid flow communication for the stripped urea solution SUSS via an expansion device (eg expansion valve) V1 with a flash vessel F1 for gas/liquid separation. The flash vessel F1 is in fluid flow communication for the medium pressure MPUS urea solution, which still contains the carbamate, with the tube bundle T2. In the T2 tube bundle, the MPUS solution is heated, and as a result, the carbamate in the MPUS decomposes. From the outlet of the tube bundle T2, the MPUS solution is fed into a gas/liquid separator, eg a flash vessel (F2). Gas G1 is sent to the MPC condenser, which is typically operated under medium pressure (MP) and in heat exchange, for example, with an evaporative EVAP section. Fluid US1 from separator F2 is sent, for example, to the low pressure regeneration section (REC) for further removal of carbamate and water and then as urea solution US2 to the evaporation section EVAP. In the regeneration section REC, the urea solution is subjected to decomposition of the carbamate by heating, typically at low pressure, and the removed gases are condensed into a liquid carbamate recycle stream CR2. The MPC condenser can also receive gas G2 from flash vessel F1, non-condensed gases G3 from HPCC and (not shown) off-gas from R. The condensate from MPC is sent by means of a pump (not shown) in the form of liquid carbamate recycle CR1 to the synthesis section, in particular into the HPCC condenser shell space, usually in combination with liquid carbamate recycle (CR2) from the regeneration REC section. The HPCC condenser is in fluid flow communication for condensate C with the reactor. In an alternative or additional embodiment, a portion of the USS may be sent from R to tube bundle T2, eg to F, bypassing stripper S. In tube bundle T1, water (typically condensate) is converted to steam (not shown).

As used herein, the singular forms include the concept of one or more. The term containing implies the presence of elements other than those specified. Various exemplary embodiments have been described above, in part with reference to the accompanying drawings, however, the present invention is not limited to these embodiments. The features of the separately described embodiments can, as such, be combined with one another as will be understood by one of ordinary skill in the art. The steps of the manufacturing process can be implemented with appropriate devices and fluid flow communications for the plant having the features of the invention. The process of the present invention is preferably carried out in a plant as described and using a high pressure carbamate condenser as described with all the preferred device features equally applicable to the process. Reference designations to the drawings in the claims are

Claims (21)

are given by way of illustrative examples only and do not limit the claims. CLAIM 1. High pressure carbamate condenser (100) containing a shell-and-tube heat exchanger (101), which is a vessel (102) containing a casing (1) and at least one tube bundle (103) containing pipes (2) having ends (3 ), moreover, the casing (1) includes the space (104) of the vessel, and moreover, the part of the space (104) of the vessel located between the pipes (2) and the casing (1) forms an annular space (105), while the heat exchanger additionally contains a redistribution a chamber (7) located in said space (104) of the vessel, wherein said redistribution chamber contains a wall (8) for separating the first fluid in the annulus (105) from the second fluid inside the redistribution chamber (7), a plurality of said pipes (2a , 2b) are connected to one redistribution chamber (7) so that said second fluid can flow between said pipes (2a, 2b) and said redistribution chamber (7), and a heat exchanger (101 ) further comprises a branch pipe (9) extending from the hole (10) for the second fluid in the specified casing (1) through the specified space (104) of the vessel to the specified redistribution chamber (7), so that the second fluid can flow between the end (3 ) pipes and the specified hole (10) for the second fluid in the specified casing through the specified redistribution chamber (7) and the specified branch pipe (9). 2. The high pressure carbamate condenser of claim 1, wherein the redistribution chamber comprises a plurality of elements forming a redistribution chamber wall, and wherein at least one of said elements is openable and closed to provide access to the interior of the redistribution chamber. 3. A high pressure carbamate condenser according to claim 1 or 2, wherein a plurality of redistribution chambers are stacked on top of each other to form a stack, and wherein the bored plate element is common to said plurality of redistribution chambers. 4. The high pressure carbamate condenser of claim 3, wherein the tube bundle comprises U-tubes, each tube having a bend and two elbows, and said plurality of redistribution chambers including an inlet redistribution chamber and an outlet redistribution chamber of the same U- shaped tube bundle located in the same package of redistribution chambers. 5. High pressure carbamate condenser according to any one of claims 1 to 4, wherein the nozzle has a first end of the nozzle connected to the wall of the redistribution chamber and a second end connected to the casing. 6. The high pressure carbamate condenser according to claim 5, wherein the first end of the nozzle is aligned with the hole in the wall, and the second end of the nozzle is aligned with the hole in the casing, so that fluid is allowed to flow from the outside of the casing to the redistribution chamber. through the nozzle, and the nozzle, at least partially, is located in the vessel, while the first end of the nozzle is located in the vessel, while the nozzle passes through the space of the vessel, while the outer surface of the nozzle faces the annulus. 7. High pressure carbamate condenser according to claim 5, wherein the first end of the tube is connected to the redistribution chamber, in particular by welding. 8. The high pressure carbamate condenser according to claim 7, wherein the first end of the nozzle is located radially outward from the ends of the pipes connected to the redistribution chamber. 9. Carbamate high pressure condenser according to any one of claims 1 to 8, configured to condense carbamate in the annular space (105), in which the vessel contains a gas inlet (4) into the annulus (105) and an outlet (5) for liquid from the annulus (105), wherein the vessel further comprises a gas distribution device (6) connected to said gas inlet (4) for distributing the gas to be condensed in the annulus. 10. The high pressure carbamate condenser according to claim 9, wherein the condenser comprises at least two of said pipes, including an inlet pipe and an outlet pipe, and contains at least two of said redistribution chambers, including an inlet redistribution chamber for distributing the supply of cooling fluid from the specified an inlet to a plurality of pipes; and an outlet redistribution chamber for combining heated cooling fluid from the plurality of pipes to said outlet. 11. The high-pressure carbamate condenser according to claim 10, wherein the condenser is arranged horizontally during operation, and said pipe contains a straight - 15 040529 washable pipe sections or consists of them, and wherein said gas distribution device and said straight pipe sections are arranged in parallel, and preferably the tube bundle comprises U-shaped pipes, each pipe having a bend and two elbows. 12. High pressure carbamate condenser according to any one of claims 9 to 11, wherein the casing comprises a substantially cylindrical middle part and two cap parts covering said middle part at opposite ends, and wherein said annular space is a single annulus, formed by said middle portion and cap portions so that fluid can flow from said gas distribution device to both of said cap portions. 13. High pressure carbamate condenser according to any one of claims 1 to 12, wherein the tube bundle comprises U-tubes, each tube having a bend and two elbows, wherein the condenser comprises a reactor section between the bend of the U-shaped tube bundle and the casing. 14. A urea production plant comprising a high pressure urea synthesis section which comprises a reactor, a stripper and a high pressure carbamate condenser, the high pressure carbamate condenser being according to any one of claims 1 to 13. 15. The urea plant of claim 14, wherein the reactor and the high pressure carbamate condenser are combined in a single vessel which has a liquid outlet connected to a stripper. 16. Urea production plant according to claim 14 or 15, wherein the high pressure carbamate condenser comprises a tube bundle that is connected through a redistribution chamber and a branch pipe to a supply line for a urea solution also containing carbamate, said supply line being connected to a stripper for receiving stripped carbamide solution from the stripper and/or wherein said feed line is connected to the reactor to receive part of the carbamide solution from the reactor. 17. The urea production plant of claim 16, wherein the feed line comprises an expansion device and a gas/liquid separator for separating gas from the expanded urea solution, and wherein the feed line is configured to supply at least a portion of said expanded urea solution to said nozzle . 18. A urea plant according to claim 16 or 17, wherein said tube bundle is connected via a redistribution chamber and a branch pipe to a gas/liquid separator which is in liquid communication with the regeneration section and in gas flow communication with a second condenser, preferably said the second condenser is operated at medium pressure, and wherein preferably the second condenser is in heat exchange contact with the evaporator section of the urea plant, and preferably said second condenser is preferably in fluid flow for carbamate recycle with the high pressure carbamate condenser. 19. A method for producing carbamide, in which urea is formed in a reactor to obtain a urea synthesis solution, wherein at least a part of said urea synthesis solution is stripped in a stripper to obtain a stripped carbamide solution, and the gas from the stripper is condensed in a high-pressure carbamate condenser, wherein the method carried out in a plant according to any one of claims 14 to 18, and/or wherein the high pressure carbamate condenser is made in accordance with any of claims 1 to 13. 20. The method for producing carbamide according to claim 19, in which at least one of these nozzles on the inside and outside of the nozzle is in contact with a solution containing carbamate, and moreover, the pipes of at least one tube bundle are located on the inside and on the outside sides in contact with a solution containing carbamate. 21. The method for producing urea according to claim 20, in which the gas from the stripper is fed into the annular space of the condenser, and at least a part of the stripped carbamide solution and/or a part of the urea synthesis solution that is not fed to the stripper is expanded, despite the fact that they also contain carbamate, and moreover, at least part of the expanded urea solution, optionally after gas / liquid separation, is fed into the tube bundle of the high pressure carbamate condenser through the nozzle and the redistribution chamber, as indicated in paragraph 1, and heated in the tube bundle by heat exchange with the condensing process medium in the annular space, so that the carbamate in said urea solution decomposes in the tube bundle. -