New high-pressure methylammonium condenser

Abstract

Disclosed in the present invention is a high-pressure methylammonium condenser, comprising: a shell, and a tube bundle and internals, which are located inside the shell, wherein the shell is provided with a methylammonium solution inlet and a CO2 gas inlet at the bottom thereof and is provided with a reaction solution outlet and a gas outlet at the upper part thereof; the heat-exchange tube bundle is of a U-shaped tube structure, and by means of the heat-exchange tube bundle, a heat transfer medium takes away heat generated by the hydrolysis of methylammonium; the internals comprise an efficient tray; and a downcomer is supported by means of the efficient tray. The present invention solves the problems of an existing methylammonium condenser having a small heat transfer coefficient, a large tube-end stress, a large arrangement space and a high difficulty in terms of manufacturing and transport. The high-pressure methylammonium condenser has a small heat exchange area and a small tube-end stress, is convenient to arrange, is easy to manufacture and scale up, and is convenient to transport.

Description

A novel high-pressure ammonium carbamate condenser Technical Field

[0001] This invention belongs to the field of chemical equipment, and specifically relates to a novel high-pressure ammonium carbamate condenser. Background Technology

[0002] The high-pressure coil of a urea plant mainly consists of three stages: synthesis, separation, and heat recovery condensation. It is the core of the entire urea plant. Among them, the high-pressure condenser is the key equipment for completing heat recovery condensation, and its structure varies depending on the urea process.

[0003] Currently, the main urea production processes both domestically and internationally include the Stami-Carbon CO2 stripping process, the Snam ammonia stripping process, the Toyo ACES21 process, and the China Wuhuan high-efficiency synthesis and low-energy urea process. Among these, the CO2 stripping 2000 process is the most competitive in the market. +TM The main technologies used are pool-type condenser technology and China Wuhuan's high-efficiency synthesis and low-energy urea consumption technology.

[0004] The key equipment for heat recovery in the Staminacapon CO2 stripping process is the pool-type condenser, a horizontal U-tube heat exchanger. The process medium flows through the shell side, while the gas-water mixture flows through the tube side. This presents the following problems: 1. Its horizontal layout requires a large floor space, which is inconvenient for installation; 2. Numerous distributors are needed at the bottom of the shell-side tube bundle, resulting in a complex tube bundle support structure and high manufacturing precision requirements; 3. Transportation is limited by height, requiring the equipment's vertical axis to be horizontal, necessitating temporary supports and pre-tightening mechanisms to secure the tube bundle.

[0005] In China's high-efficiency, low-energy urea synthesis process, the key equipment for heat recovery condensation is the high-pressure ammonium carbamate condenser. This equipment is a vertical fixed tube sheet heat exchanger, with the process medium flowing through the tube side and the steam-water mixture flowing through the shell side. It presents the following problems: 1. The process medium flows through the tube side, and low-pressure steam is produced as a byproduct in the shell side. Natural circulation is used, resulting in a low heat transfer coefficient. This requires a large heat exchange area in the fully condensing reactor, leading to a large equipment diameter. As the scale of the plant increases, the equipment diameter also increases, and the materials become excessively thick, posing challenges to the supply and manufacturing of raw materials. 2. In a fixed tube sheet heat exchanger, the thermal expansion difference between the tube and shell sides necessitates the installation of expansion joints. This results in higher stress at the tube ends, increasing the risk of stress corrosion cracking and failure of the heat exchange tubes. 3. The tube bundle includes a long central tube, the length of which often exceeds the manufacturer's supply capacity. Therefore, the central tube has splicing welds, requiring high-precision splicing manufacturing.

[0006] Summary of the Invention

[0007] The purpose of this invention is to solve the above-mentioned technical problems and provide a high-pressure ammonium carbamate condenser with small heat exchange area, low tube head stress, easy layout, easy manufacturing and large-scale production, and convenient transportation.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a novel high-pressure ammonium carbamate condenser, comprising: a shell and a heat exchange tube bundle and internal components inside the shell;

[0009] The shell has an ammonium carbamate liquid inlet and a CO2 gas inlet at the bottom, and a reaction liquid outlet and a gas outlet at the top; the heat exchange tube bundle has a U-shaped tube structure, and the heat transfer medium carries away the heat generated by the hydrolysis of ammonium carbamate through the heat exchange tube bundle;

[0010] The internal components include a high-efficiency tray; the downcomer is supported by the high-efficiency tray;

[0011] Ammonium carbamate solution enters the shell side of the high-pressure ammonium carbamate condenser from the ammonium carbamate solution inlet, and the feed gas enters the shell side of the high-pressure ammonium carbamate condenser from the CO2 gas inlet; the ammonium carbamate solution is baffled in the high-efficiency tray, and the gas is collected in the skirt of the high-efficiency tray and flows upward along the gas phase channel of the tray, reacting between the high-efficiency trays to generate ammonium carbamate. Part of the ammonium carbamate is hydrolyzed to generate urea. Finally, the urea ammonium carbamate solution generated by the reaction flows out from the reaction liquid outlet, and the unreacted gas flows out from the gas outlet.

[0012] Furthermore, the high-efficiency trays are distributed in a baffle pattern within the shell side of the high-pressure ammonium carbamate condenser, with the gap between the high-efficiency trays and the shell serving as liquid phase channels, and gas phase channels provided on the high-efficiency trays.

[0013] Furthermore, the gas phase channel consists of distribution holes with a diameter of 3-4 mm, located in the central and non-supported areas of the baffle support.

[0014] Furthermore, the high-efficiency tray is equipped with a skirt and a short-circuit protection baffle; the skirt is used to collect gas and allow the gas to flow along the gas phase channel; the short-circuit protection baffle is used to prevent short-circuiting of the shell-side fluid flow, so that the fluid flows out directly without passing through the surface of the shell-side heat exchange tubes.

[0015] Furthermore, a tube box is installed at the top of the high-pressure ammonium carbamate condenser, with tube-side inlet and outlet. The heat transfer medium vapor condensate is forced to circulate by a vapor condensate pump, entering from the tube-side inlet and then entering the tube bundle, carrying away the heat generated by the hydrolysis of ammonium carbamate on the shell side. The vapor condensate is heated to generate steam, which flows out from the outlet.

[0016] Furthermore, the pipe box is equipped with a partition plate.

[0017] Furthermore, the internal components also include a downcomer, which is installed inside the high-efficiency tray for circulating unreacted materials. The downcomer is supported by the high-efficiency tray and is a thin-walled, non-pressure-bearing structure with a vortex breaker at the top.

[0018] Furthermore, the internal components also include an ammonium carbamate liquid inlet distributor and a gas inlet distributor; the ammonium carbamate liquid inlet distributor is provided in the ammonium carbamate liquid inlet, and the CO2 gas inlet distributor is provided in the CO2 gas inlet, so that the ammonium carbamate liquid and CO2 are evenly distributed and enter the shell side of the high-pressure ammonium carbamate condenser.

[0019] Furthermore, the ammonium carbamate liquid inlet distributor and the gas inlet distributor are distribution plates with distribution holes or inner tube structures with distribution holes.

[0020] Furthermore, the reactor is a vertical reactor, supported by a skirt, lug, or rigid ring.

[0021] The novel high-pressure ammonium carbamate condenser of this invention has the following advantages:

[0022] (1) Small heat exchange area. The process medium of the new high-pressure ammonium carbamate condenser flows on the shell side, and the shell side is equipped with high-efficiency trays. The liquid phase fluid is baffled between the trays, and the gas phase fluid is collected in the skirt of the high-efficiency tray and flows upward along the distribution holes of the tray, which increases the degree of flow turbulence, improves the heat transfer coefficient and reaction rate, and makes the required heat exchange area small.

[0023] (2) Low tube head stress. The new high-pressure ammonium carbamate condenser tube bundle adopts a U-shaped tube structure, which allows the tube bundle to expand freely, avoiding the thermal stress problem caused by inconsistent thermal expansion on the tube shell side of the traditional high-pressure ammonium carbamate condenser. The equipment does not require expansion joints, reducing the risk of stress corrosion at the tube head.

[0024] (3) Easy to arrange. The new high-pressure ammonium carbamate condenser is a vertical reactor, supported by skirt, lug, or rigid ring supports, which occupies less space than a pool-type condenser and is easier to arrange. The condensation and reaction sections of the new high-pressure ammonium carbamate condenser are both on the shell side, the reactor length is shortened, the required arrangement space is small, and it is easy to arrange.

[0025] (4) Easy to manufacture and scale up. The new high-pressure ammonium carbamate condenser has a simple structure. Compared with pool-type condensers, it does not have a complex distributor and tube bundle support structure. Compared with the thick-walled pressure-bearing central tube structure of traditional high-pressure ammonium carbamate condensers, it is replaced with a thin-walled non-pressure-bearing downcomer structure, which is easy to manufacture. The number of heat exchange tubes required is small, the tube sheet diameter is small, and the calculated tube sheet thickness is small, which makes it easy to scale up the device.

[0026] (5) Convenient transportation. The high-efficiency tray on the shell side of the new high-pressure ammonium carbamate condenser also serves as a support plate for the heat exchange tubes, providing support for the heat exchange tubes. Compared with pool-type condensers, it does not require temporary support and pre-tightening mechanisms during transportation. Compared with traditional high-pressure ammonium carbamate condensers, it is shorter in length, has a smaller turning radius during transportation, and is lighter in weight, making transportation convenient. Attached Figure Description

[0027] Figure 1 is a schematic diagram of a novel high-pressure ammonium carbamate condenser according to the present invention.

[0028] Figure 2 is a schematic diagram of the welding of the heat exchange tube and the inner hole of the tube sheet in a novel high-pressure ammonium carbamate condenser of the present invention.

[0029] Among them, 1-skirt, 2-ammonium carbamate liquid inlet, 3-ammonium carbamate liquid inlet distributor, 4-shell side lower head, 5-manhole, 6-lower cylinder, 7-downcomer, 8-heat exchange tube bundle, 9-high-efficiency tray, 10-shell side upper head, 11-tube sheet, 12-gas outlet, 13-steam condensate inlet, 14-partitioned baffle, 15-tube box, 16-steam outlet, 17-tube sheet weld overlay, 18-reaction liquid outlet, 19-upper single-layer cylinder, 20-layer plate, 21-leak detection hole, 22-inner cylinder, 23-lining, 24-CO2 gas inlet distributor, 25-CO2 gas inlet. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort should fall within the scope of protection of the present application.

[0031] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product or device.

[0032] Referring to Figures 1 and 2, a novel high-pressure ammonium carbamate condenser includes: a shell and heat exchange tube bundles and internal components inside the shell.

[0033] The shell includes a tube box 15, a shell-side upper head 10, an upper single-layer cylinder 19, a shelf 20, an inner cylinder 22, a lining 23, a lower cylinder 6, and a shell-side lower head 4. A leak detection port 21 is also provided on the shell. The shell-side cylinder (including the lower cylinder 6, the upper cylinder 9, and the cylinder between them) can be a single-layer or multi-layer structure. The shelf, inner cylinder, and lining form a multi-layer cylinder structure, which is economical, safe, and reliable. The lining is in direct contact with the medium, and its material has excellent corrosion resistance. The inner cylinder and shelf are designed with sufficient strength to withstand the equipment pressure.

[0034] The shell is vertically arranged and supported by a skirt 1.

[0035] The bottom of the shell-side lower head 4 is provided with an ammonium carbamate liquid inlet 2 and a CO2 gas inlet 25. An ammonium carbamate liquid inlet distributor 3 is provided inside the ammonium carbamate liquid inlet 2, and a CO2 gas inlet distributor 24 is provided inside the CO2 gas inlet 25.

[0036] The shell-side cylindrical body 6 is provided with a reaction liquid outlet 18, and the shell-side upper end cap is provided with a gas outlet 12.

[0037] The tube box 15 is equipped with a steam condensate inlet 13 and a steam outlet 16. The lower cylinder 6 has a single-layer structure and a multi-layer structure, is equipped with a leak detection system, and is provided with a manhole 5.

[0038] The heat exchanger tube bundle 8 has a U-shaped tube structure, and its connection to the tube sheet 11 is achieved through internal welding. The high-efficiency tray 9 is equipped with distribution holes, skirts, and short-circuit protection baffles, and also provides support for the heat exchanger tube bundle 8. The tube box 15 is equipped with a partition plate 14.

[0039] The high-efficiency trays are arranged in a baffle pattern within the shell side of the high-pressure ammonium carbamate condenser. The gap between the high-efficiency trays and the shell serves as a liquid phase channel, while gas phase channels are provided on the high-efficiency trays. The gas phase channels are distribution holes with a diameter of 3-4 mm, located in the central and non-supported areas of the baffle plate support.

[0040] The internal components also include a downcomer, which is installed inside the high-efficiency tray and supported by the high-efficiency tray. It is a thin-walled, non-pressure-bearing structure with a vortex breaker at the top.

[0041] Referring to Figures 1 and 3, the ammonium methyl ester solution from the high-pressure scrubber enters through ammonium methyl ester inlet 2, and after being evenly distributed by ammonium methyl ester inlet distributor 3, it enters the shell side of the high-pressure ammonium methyl ester condenser. Gases (CO2, NH3, H2O) from the stripping tower and urea synthesis tower enter through CO2 gas inlet 25, and after being evenly distributed by CO2 gas inlet distributor 24, they enter the shell side of the high-pressure ammonium methyl ester condenser. The ammonium methyl ester solution is baffled within the high-efficiency trays, and the gas is collected within the skirt of the high-efficiency trays and flows upward along the distribution holes of the trays, reacting between the high-efficiency trays to produce ammonium methyl ester. Part of the ammonium methyl ester hydrolyzes to produce urea. The final urea-ammonium methyl ester solution flows out from the reaction liquid outlet 18 and enters the urea synthesis tower for further reaction. Unreacted gas flows out from the gas outlet 12 and enters the high-pressure scrubber for washing and recovery.

[0042] The condensate from the tube side enters the tube box 15 through the condensate inlet 13, and then flows evenly into the heat exchange tube bundle, carrying away the heat generated by the hydrolysis of ammonium carbamate on the shell side. The condensate is heated to generate steam, which flows out through the steam outlet 16 and enters the low-pressure steam drum.

[0043] Figure 2 shows the connection structure between the tube sheet and the heat exchange tube. The tube sheet 11 is welded with a corrosion-resistant layer 17 and is connected to the heat exchange tube 8 through a welding structure.

[0044] The above is a further detailed description of the present invention and should not be considered as a limitation on the specific implementation of the present invention. For those skilled in the art, simple deductions or substitutions without departing from the concept of the present invention are all within the protection scope of the present invention.

Claims

1. A novel high-pressure ammonium carbamate condenser, characterized in that... include: The shell and the heat exchange tube bundle and internal components inside the shell; The shell has an ammonium carbamate liquid inlet and a CO2 gas inlet at the bottom, and a reaction liquid outlet and a gas outlet at the top; the heat exchange tube bundle has a U-shaped tube structure, and the heat transfer medium carries away the heat generated by the hydrolysis of ammonium carbamate through the heat exchange tube bundle; The internal components include a high-efficiency tray; the downcomer is supported by the high-efficiency tray; Ammonium carbamate solution enters the shell side of the high-pressure ammonium carbamate condenser from the ammonium carbamate solution inlet, and the feed gas enters the shell side of the high-pressure ammonium carbamate condenser from the CO2 gas inlet; the ammonium carbamate solution is baffled in the high-efficiency tray, and the gas is collected in the skirt of the high-efficiency tray and flows upward along the gas phase channel of the tray, reacting between the high-efficiency trays to generate ammonium carbamate. Part of the ammonium carbamate is hydrolyzed to generate urea. Finally, the urea ammonium carbamate solution generated by the reaction flows out from the reaction liquid outlet, and the unreacted gas flows out from the gas outlet.

2. The novel high-pressure ammonium carbamate condenser according to claim 1, characterized in that: The high-efficiency trays are distributed in a baffle pattern within the shell side of the high-pressure ammonium carbamate condenser. The gap between the high-efficiency trays and the shell is a liquid phase channel, and a gas phase channel is provided on the high-efficiency trays.

3. The novel high-pressure ammonium carbamate condenser according to claim 2, characterized in that: The gas phase channel consists of distribution holes with a diameter of 3-4 mm, located in the central and non-support areas of the baffle plate support.

4. The novel high-pressure ammonium carbamate condenser according to claim 2, characterized in that: The high-efficiency tray is equipped with a skirt and a short-circuit protection baffle; the skirt is used to collect gas and allow the gas to flow along the gas phase channel; the short-circuit protection baffle is used to prevent short-circuiting of the shell-side fluid flow, so that the fluid flows out directly without passing through the surface of the shell-side heat exchange tubes.

5. The novel high-pressure ammonium carbamate condenser according to claim 1, characterized in that: The high-pressure ammonium carbamate condenser is equipped with a tube box at the top, with a tube inlet and an outlet on the tube box. The heat transfer medium vapor condensate is forced to circulate by a vapor condensate pump, entering from the tube inlet and then entering the tube bundle, carrying away the heat generated by the hydrolysis of ammonium carbamate on the shell side. The vapor condensate is heated to generate steam, which flows out from the outlet.

6. The novel high-pressure ammonium carbamate condenser according to claim 5, characterized in that: The pipe box is equipped with a partition plate.

7. The novel high-pressure ammonium carbamate condenser according to claim 1, characterized in that: The internal components also include a downcomer, which is installed inside the high-efficiency tray for circulating unreacted materials. The downcomer is supported by the high-efficiency tray and is a thin-walled, non-pressure-bearing structure with a vortex breaker at the top.

8. The novel high-pressure ammonium carbamate condenser according to claim 1, characterized in that: The internal components also include an ammonium carbamate liquid inlet distributor and a gas inlet distributor; the ammonium carbamate liquid inlet distributor is provided in the ammonium carbamate liquid inlet, and the CO2 gas inlet distributor is provided in the CO2 gas inlet, so that the ammonium carbamate liquid and CO2 are evenly distributed and then enter the shell side of the high-pressure ammonium carbamate condenser.

9. The novel high-pressure ammonium carbamate condenser according to claim 8, characterized in that: The ammonium carbamate liquid inlet distributor and the gas inlet distributor are distribution plates with distribution holes or internal extension tube structures with distribution holes.

10. The novel high-pressure ammonium carbamate condenser according to claim 1, characterized in that: The reactor is a vertical reactor, supported by a skirt seat, an ear-type support, or a rigid ring support.

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