Device for producing high-pressure steam by recovering residual heat from trimellitic anhydride rectification

Abstract

The utility model discloses a device of production high pressure steam in the field of chemical production energy -conserving device of trimellitic anhydride rectification residual heat, mainly includes steam generator, circulating pump, primary steam compressor, secondary steam compressor, low pressure water separation storage tank, high pressure water separation storage tank, and the low temperature waste steam residual heat of trimellitic anhydride rectification column top is recovered through steam generator, and low temperature low pressure steam is produced, and then utilizes primary steam compressor and secondary steam compressor to carry out two -stage compression pressure boost and temperature rise to steam, and finally separates and obtains high -quality high pressure steam in high pressure water separation storage tank. The utility model has recovered the low grade residual heat of rectification process effectively, converts waste heat into available high pressure steam, significantly reduces the external energy dependence and operating cost of production process, realizes energy -conserving and consumption reduction.

Description

Technical Field

[0001] This utility model relates to an energy-saving device in chemical production, specifically a device for producing high-pressure steam, which recovers the waste heat from the acetic acid dehydration distillation column during the continuous oxidation of trimesin to produce trimesic anhydride and produces high-pressure steam. Background Technology

[0002] High-pressure steam is widely used in chemical production. Firstly, it serves as a heat source for reboilers in distillation columns, reactor jackets, and material preheaters, heating process materials or vaporizing them to maintain the temperature requirements of reactions and separation processes. Secondly, it drives steam turbines, powering key equipment such as compressors and pumps (e.g., circulating pumps and raw material transfer pumps), providing power for production. Thirdly, it is used for material stirring, pipeline heating (to prevent high-viscosity materials from solidifying), or as a drying medium in drying processes to remove moisture and solvents from materials. Finally, it can serve as an energy recovery medium in waste heat recovery systems, acting as an energy carrier to transfer high-grade heat from one location to another, enabling cross-process energy allocation.

[0003] The current industrial principle for producing high-pressure steam is based on the cascade utilization and energy conversion of waste heat. During the distillation process, the top steam and bottom materials carry a large amount of waste heat, which is transferred to the boiler water through a heat exchanger. After absorbing the waste heat, the boiler water heats up and, under the action of a pressure control device, reaches the saturation temperature at the corresponding pressure, thus vaporizing to produce steam. For heat pump auxiliary systems, the low-grade secondary steam can be pressurized and heated by a compressor to increase its enthalpy value, which can then be used to heat the boiler water or directly as a heat source, improving the waste heat utilization rate and ultimately producing high-pressure steam.

[0004] Currently, industrial equipment for recovering waste heat from distillation to produce high-pressure steam mainly employs multi-effect energy-saving devices and heat pump distillation and evaporation combined devices.

[0005] The utility model disclosed in CN211158645U relates to a multi-effect energy-saving device for a trimellitic anhydride distillation reboiler, comprising a distillation column, a hot water pump, a generator, a condenser, a vacuum pump, a primary purification column, and a primary purification column reboiler. Its advantages are: this multi-effect energy-saving device for a trimellitic anhydride distillation reboiler abandons the heat transfer oil cooling system used in traditional trimellitic anhydride distillation condensers, replacing it with hot water circulation cooling, and uses byproduct steam for the primary purification column to remove low-boiling-point substances. Furthermore, by setting the discharge pressure to control the process temperature range of the primary purification column reboiler, it achieves control over the trimellitic anhydride distillation, while simultaneously reducing energy consumption and production costs.

[0006] The utility model embodiment disclosed in CN212651376U relates to the field of distillation and evaporation technology, and provides a mechanical vapor recompression heat pump distillation system. The mechanical vapor recompression heat pump distillation system provided in this patent embodiment includes: a material preheating subsystem, a distillation subsystem, and an evaporation subsystem. The outlet of the material preheating subsystem is connected to the inlet of the distillation subsystem; the outlet of the distillation subsystem is connected to the inlet of the evaporation subsystem to discharge the vapor generated during the distillation process into the evaporation subsystem for heat exchange, and then condense the vapor into liquid and discharge it to the finished product tank; the outlet of the evaporation subsystem is connected to the inlet of the material preheating subsystem to compress the secondary vapor generated during the evaporation process and use it as the heat source for preheating the material in the material preheating subsystem.

[0007] The invention patent with publication number CN116182133A discloses an apparatus and method for producing high-pressure or ultra-high-pressure steam as a byproduct of a maleic anhydride unit. The apparatus includes an ultra-high-pressure steam drum, a connected molten salt pump, an oxidation reactor, a regulating valve, and a molten salt cooler, as well as a connected switching cooler and a gas cooler. A boiler water buffer device and a boiler water booster pump are installed between the switching cooler and the gas cooler. The unique design of the intermediate boiler water booster and the gas cooler in this invention makes the gas cooler and switching cooler very easy to manufacture. It effectively recovers the heat from the process gas while avoiding dust accumulation and easy cleaning of adhering tar, thus producing more high-pressure or ultra-high-pressure steam. Simultaneously, multiple molten salt coolers are installed on one oxidation reactor, dividing the total reaction heat into multiple parts, reducing the heat exchange load of a single molten salt cooler, and ensuring that the heat exchange area of ​​the molten salt cooler meets the requirements for producing high-pressure or ultra-high-pressure steam, thereby reducing the manufacturing difficulty and risk of the molten salt cooler.

[0008] The shortcomings of existing technologies are that existing distillation waste heat recovery processes and devices for producing high-pressure steam have low heat recovery efficiency, especially for the recovery and reuse rate of low-grade waste heat during evaporation. Utility Model Content

[0009] The purpose of this invention is to provide a device for recovering waste heat from trimellitic anhydride distillation to produce high-pressure steam. The device recovers waste heat from trimellitic anhydride distillation through a steam generator to produce initial steam, which is then compressed in two stages to obtain high-pressure steam. This achieves efficient recovery and reuse of low-grade waste heat during the evaporation process, thereby reducing the demand for external energy.

[0010] The purpose of this utility model is achieved as follows: A device for recovering waste heat from trimellitic anhydride distillation to produce high-pressure steam includes a steam generator. The steam generator has a tube sheet structure, including a horizontally arranged shell. One end of the shell has a tube sheet, and the outer side of the tube sheet has an end cap. The other end of the shell has a tube sheet, and the outer side of the tube sheet has an end cap. Several heat exchange tubes with open ends are horizontally arranged between the tube sheet and the tube sheet. The end cap has a top steam inlet, and the end cap has a top steam outlet. The two ends of the heat exchange tubes are respectively connected to the top steam inlet and the top steam outlet. The heat exchange is carried out inside the shell. Multiple nozzles are installed above the pipe. A gas phase outlet is provided at the top of the steam generator shell. A liquid collection tank is connected to the lower side of the shell. A liquid outlet is provided at the bottom of the liquid collection tank. The liquid outlet is connected to the multiple nozzles via a circulating pump. A gas phase outlet is provided at the top of the shell. The gas phase outlet is connected to the inlet of the first-stage steam compressor. The steam outlet of the first-stage steam compressor is connected to the inlet of the low-pressure steam-water separation tank. The steam outlet of the low-pressure steam-water separation tank is connected to the inlet of the second-stage steam compressor. The steam outlet of the second-stage steam compressor is connected to the inlet of the high-pressure steam-water separation tank. The steam outlet of the high-pressure steam-water separation tank outputs high-pressure steam and connects it to the steam-using equipment.

[0011] During operation, waste steam (100℃, 101 kPa(A)) from the top of the acetic acid dehydration distillation column in the TMA (tumor metahydride) unit enters the steam generator through the top steam inlet. After passing through heat exchange tubes, it exits through the top steam outlet. During this process, water sprayed from the nozzles forms a liquid film on the outer surface of the heat exchange tubes. The steam inside the tubes exchanges heat with the liquid film through the tube wall, causing the liquid film to heat up and evaporate into initial water vapor (90~95℃, 60~90 kPa). The steam is compressed by a first-stage steam compressor, and after being heated and pressurized, it enters a low-pressure steam-water separation tank. After steam-water separation, the low-pressure steam output enters a second-stage steam compressor. After compression by the second-stage steam compressor, high-temperature and high-pressure steam is output and enters a high-pressure steam-water separation tank. The high-pressure steam outlet of the high-pressure steam-water separation tank outputs high-pressure steam that is connected to the steam-using equipment. The water vapor undergoes two stages of compression to form high-temperature and high-pressure water vapor that can be used by the steam-using equipment. The inlet of the first-stage steam compressor is under negative pressure. Since the boiling point of water is lower than the standard boiling point at atmospheric pressure, the low-grade waste heat from the top of the trimellitic anhydride distillation column can be recovered and reused, thus reducing the demand for external energy. The beneficial effects of this invention are: initial steam is produced by recovering waste heat from trimellitic anhydride distillation through a steam generator; high-temperature, high-pressure steam is obtained through two-stage compression; and the low-boiling-point evaporation of water is achieved through the inlet pressure of the first-stage steam compressor, enabling efficient recovery and reuse of the low-grade waste heat from the top of the trimellitic anhydride distillation column. This device achieves energy recovery and reuse, significantly improving the energy efficiency of the evaporation process and reducing energy consumption. Compared to traditional evaporation technology, this device does not require an external steam supply, reducing dependence on steam pipelines and boiler equipment, and lowering operating costs.

[0012] A further improvement is that a primary mixing and cooling device is installed at the steam outlet of the primary steam compressor. The outlet of the circulating pump is connected to the primary mixing and cooling device via a low-pressure spray pump, which is used to spray water from the outlet of the circulating pump into the steam at the steam outlet of the primary steam compressor for cooling. The steam is pressurized and heated by the primary steam compressor. To eliminate overheating during the pressurization process, cooling water is sprayed in by the low-pressure spray pump to cool the steam to 130~150°C before it is supplied to the low-pressure steam-water separator storage tank.

[0013] Similarly, a secondary mixing and cooling device is installed at the steam outlet of the secondary steam compressor. The outlet of the circulating pump is connected to the secondary mixing and cooling device via a high-pressure spray pump, which is used to spray water from the outlet of the circulating pump into the steam at the steam outlet of the secondary steam compressor for cooling. The steam is pressurized and heated by the secondary steam compressor. In the secondary mixing and cooling device, cooling water is sprayed in by the high-pressure spray pump to cool the steam to 160~170°C before it is supplied to the high-pressure steam-water separator storage tank.

[0014] Furthermore, the primary and secondary steam compressors are either centrifugal compressors or Roots compressors. Both types of compressors are existing products in the prior art. Centrifugal compressors apply energy to steam through a high-speed rotating impeller. The steam is drawn in at the center of the impeller, accelerated by centrifugal force, and thrown radially towards the diffuser. In the diffuser section, the steam velocity decreases, and kinetic energy is converted into pressure energy. Roots compressors, on the other hand, are based on rotors driven by a pair of synchronous gears rotating in opposite directions. Through meshing, they draw in low-pressure steam and compress it to a high-pressure state, achieving steam pressure and temperature increase. Both have the advantages of simple structure and reliable operation.

[0015] Furthermore, the lower side of the housing is provided with an upper vent. The upper vent can be used as a channel for draining, cleaning, and leak checking of the housing.

[0016] To further ensure good heat exchange, the multiple nozzles are evenly distributed along the axial direction of the shell, and a spray space is left between the heat exchange tube and the nozzle. The spray space can reduce the amount of liquid droplets entrained in the evaporated water vapor.

[0017] To facilitate steam use, the steam outlet of the low-pressure steam-water separator is connected to the steam-using equipment. When low-temperature, low-pressure steam is required, it can be directly output from the low-pressure steam-water separator for use.

[0018] Furthermore, the inlet branch of the circulating pump is connected to a steam condensation system and other water sources. Attached Figure Description

[0019] Figure 1 This is a flowchart of the process of this utility model.

[0020] Figure 2 This is a schematic diagram of a steam generator.

[0021] In the diagram, 1 is the circulating pump, 2 is the steam generator, 201 is the steam inlet at the top of the tower, 202 is the first end cap, 203 is the first tube sheet, 204 is the vapor outlet, 205 is the heat exchange tube, 206 is the second tube sheet, 207 is the second end cap, 208 is the steam outlet at the top of the tower, 209 is the liquid collection tank, 210 is the liquid outlet, 211 is the upper vent, 212 is the shell, 3 is the first-stage steam compressor, 301 is the first-stage mixing cooler, 4 is the second-stage steam compressor, 401 is the second-stage mixing cooler, 5 is the high-pressure steam-water separator storage tank, 6 is the high-pressure spray pump, 7 is the low-pressure steam-water separator storage tank, 8 is the low-pressure spray pump, and 9 is the spray head. Detailed Implementation

[0022] like Figure 1 , 2 The diagram shows an apparatus for recovering waste heat from trimellitic anhydride distillation to produce high-pressure steam. It includes a steam generator 2, which is a tube sheet structure comprising a horizontally arranged shell 212. One end of the shell 212 has a tube sheet 203, with an end cap 202 on its outer side. The other end of the shell 212 has a tube sheet 206, with an end cap 207 on its outer side. Several heat exchange tubes 205, open at both ends, are horizontally arranged between the tube sheet 203 and the tube sheet 206. The end cap 202 has a top steam inlet 201, and the end cap 207 has a top steam outlet 208. The two ends of the heat exchange tubes 205 are connected to the top steam inlet 201 and the top steam outlet 208, respectively. The shell 212... Multiple nozzles 9 are provided above the internal heat exchange tube 205. A gas phase outlet 204 is provided at the top of the steam generator shell 212. A liquid collection tank 209 is connected to the lower side of the shell 212. A liquid outlet 210 is provided at the bottom of the liquid collection tank 209. The liquid outlet 210 is connected to multiple nozzles 9 via a circulation pump 1. A gas phase outlet 204 is provided at the top of the shell 212. The gas phase outlet 204 is connected to the inlet of the first-stage steam compressor 3. The steam outlet of the first-stage steam compressor 3 is connected to the inlet of the low-pressure steam-water separation tank 7. The steam outlet of the low-pressure steam-water separation tank 7 is connected to the inlet of the second-stage steam compressor 4. The steam outlet of the second-stage steam compressor 4 is connected to the inlet of the high-pressure steam-water separation tank 5. The steam outlet of the high-pressure steam-water separation tank 5 outputs high-pressure steam and connects it to the steam-using equipment.

[0023] A further improvement is that a primary mixing and cooling device 301 is installed at the steam outlet of the primary steam compressor 3. The outlet of the circulating pump 1 is connected to the primary mixing and cooling device 301 via a low-pressure spray pump 8, which is used to spray water from the outlet of the circulating pump 1 into the steam at the steam outlet of the primary steam compressor 3 for cooling. The steam is pressurized and heated by the primary steam compressor 3. To eliminate overheating during the pressurization process, cooling water is sprayed into the steam via the low-pressure spray pump 8 to cool the steam to 130~150℃ before it is supplied to the low-pressure steam-water separator storage tank 7.

[0024] Similarly, a secondary mixing and cooling device 401 is installed at the steam outlet of the secondary steam compressor 4. The outlet of the circulating pump 1 is connected to the secondary mixing and cooling device 401 via a high-pressure spray pump 6, which is used to spray water from the outlet of the circulating pump 1 into the steam at the steam outlet of the secondary steam compressor 4 for cooling. The steam is pressurized and heated by the secondary steam compressor 4. In the secondary mixing and cooling device 401, cooling water is sprayed in by the high-pressure spray pump 6 to cool the steam to 160~170°C before it is supplied to the high-pressure steam-water separator storage tank 5.

[0025] Furthermore, the first-stage steam compressor 3 and the second-stage steam compressor 4 are either centrifugal compressors or Roots compressors. Both types of compressors are existing products in the prior art. The centrifugal compressor applies energy to the steam through a high-speed rotating impeller. The steam is drawn in at the center of the impeller, accelerated by centrifugal force, and thrown radially towards the diffuser. In the diffuser section, the steam velocity slows down, and kinetic energy is converted into pressure energy. The Roots compressor, on the other hand, is based on a pair of synchronous gears driving rotors to rotate in opposite directions. Through meshing, it draws in low-pressure steam and compresses it to a high-pressure state, achieving steam pressure and temperature increase. Both have the advantages of simple structure and reliable operation.

[0026] The housing 212 has an upper vent 211 on its lower side. The upper vent 211 can be used as a channel for venting, cleaning, and leak detection of the housing 212.

[0027] To further ensure good heat exchange, multiple nozzles 9 are evenly distributed along the axial direction of the shell 212, and a spray space is left between the heat exchange tube 205 and the nozzles 9. The spray space can reduce the amount of liquid droplets entrained in the evaporated water vapor.

[0028] To facilitate steam use, the steam outlet of the low-pressure steam-water separator 7 outputs low-pressure steam which is then connected to the steam-using equipment. When low-temperature, low-pressure steam is required, it can be directly output from the low-pressure steam-water separator 7 for use.

[0029] The inlet branch of circulating pump 1 is connected to the steam condensation system and other water sources. The return condensate from the steam condensation system or other water sources replenish the water consumed by the evaporation of steam generator 2.

[0030] During operation, waste steam (100℃, 101kPa(A)) from the top of the acetic acid dehydration distillation column in the TMA unit enters the steam generator through the top steam inlet 201. After passing through heat exchange tubes 205, it exits through the top steam outlet 208. During this process, water sprayed from nozzles 9 forms a liquid film on the outer surface of the heat exchange tubes 205. The steam inside the tubes exchanges heat with the liquid film through the tube wall, causing the liquid film to heat up and evaporate into initial water vapor (90~95℃, 60~90kPa). The steam is compressed by the first-stage steam compressor 3, and after being heated and pressurized, it enters the low-pressure steam-water separation storage tank 7. After steam-water separation, the low-pressure steam output enters the second-stage steam compressor 4. After compression by the second-stage steam compressor 4, high-temperature and high-pressure steam is output and enters the high-pressure steam-water separation storage tank 5. The high-pressure steam output from the steam outlet of the high-pressure steam-water separation storage tank 5 is connected to the steam-using equipment. The water vapor is compressed in two stages to form high-temperature and high-pressure water vapor that can be used by the steam-using equipment. The inlet of the first-stage steam compressor 3 is under negative pressure. Since the boiling point of water is lower than the standard boiling point at atmospheric pressure, the low-grade waste heat from the top of the trimellitic anhydride distillation column can be recovered and reused, thus reducing the demand for external energy. The beneficial effects of this invention are: Initial steam is produced by recovering waste heat from trimellitic anhydride distillation through steam generator 2; high-temperature, high-pressure steam is obtained through two-stage compression; and the low-boiling-point evaporation of water is achieved through the inlet pressure of the first-stage steam compressor 3, allowing for the efficient recovery and reuse of low-grade waste heat from the top of the trimellitic anhydride distillation column. This device enables energy recovery and reuse, significantly improving the energy efficiency of the evaporation process and reducing energy consumption. Compared to traditional evaporation technologies, this device does not require an external steam supply, reducing dependence on steam pipelines and boiler equipment, and lowering operating costs.

[0031] This utility model is not limited to the above embodiments. Based on the technical solutions disclosed in this utility model, those skilled in the art can make some substitutions and modifications to some of the technical features without creative labor, and these substitutions and modifications are all within the protection scope of this utility model.

Claims

1. A device for recovering waste heat from trimellitic anhydride distillation to produce high-pressure steam, comprising a steam generator, characterized in that: The steam generator has a tube sheet structure, including a horizontally arranged shell. One end of the shell has a tube sheet (tube sheet one) with an end cap (end cap one) on its outer side. The other end of the shell has a tube sheet (tube sheet two) with an end cap (end cap two) on its outer side. Several heat exchange tubes with open ends are horizontally arranged between tube sheet one and tube sheet two. The end cap one has a top steam inlet, and the end cap two has a top steam outlet. The two ends of the heat exchange tubes are connected to the top steam inlet and the top steam outlet, respectively. Multiple nozzles are located above the heat exchange tubes inside the shell. A gas phase outlet is located at the top of the steam generator shell. A liquid collection tank is connected to the lower side of the shell, with a liquid outlet at the bottom. The liquid outlet is connected to the multiple nozzles via a circulating pump. A gas phase outlet is located at the top of the shell and is connected to the inlet of a primary steam compressor. The steam outlet of the primary steam compressor is connected to the inlet of a low-pressure steam-water separator. The steam outlet of the low-pressure steam-water separator is connected to the inlet of a secondary steam compressor. The steam outlet of the secondary steam compressor is connected to the inlet of a high-pressure steam-water separator. The steam outlet of the high-pressure steam-water separator outputs high-pressure steam, which is then connected to the steam-using equipment.

2. The apparatus for recovering waste heat from trimellitic anhydride distillation to produce high-pressure steam according to claim 1, characterized in that: A primary mixing and cooling device is installed at the steam outlet of the primary steam compressor. The outlet of the circulating pump is connected to the primary mixing and cooling device via a low-pressure spray pump, which is used to spray water from the outlet of the circulating pump into the steam at the steam outlet of the primary steam compressor for cooling.

3. The apparatus for recovering waste heat from trimellitic anhydride distillation to produce high-pressure steam according to claim 1, characterized in that: The secondary steam compressor is equipped with a secondary mixing and cooling device at its steam outlet. The outlet of the circulating pump is connected to the secondary mixing and cooling device via a high-pressure spray pump, which is used to spray water from the outlet of the circulating pump into the steam at the outlet of the secondary steam compressor for cooling.

4. The apparatus for recovering waste heat from trimellitic anhydride distillation to produce high-pressure steam according to any one of claims 1-3, characterized in that: The primary and secondary steam compressors are centrifugal compressors or Roots compressors.

5. The apparatus for recovering waste heat from trimellitic anhydride distillation to produce high-pressure steam according to any one of claims 1-3, characterized in that: The lower side of the housing is provided with an upper vent.

6. The apparatus for recovering waste heat from trimellitic anhydride distillation to produce high-pressure steam according to any one of claims 1-3, characterized in that: The multiple nozzles are evenly distributed along the axial direction of the shell, and a spraying space is left between the heat exchange tube and the nozzle.

7. The apparatus for recovering waste heat from trimellitic anhydride distillation to produce high-pressure steam according to any one of claims 1-3, characterized in that: The steam outlet of the low-pressure steam-water separator tank outputs low-pressure steam, which is then connected to the steam-using equipment.

8. The apparatus for recovering waste heat from trimellitic anhydride distillation to produce high-pressure steam according to any one of claims 1-3, characterized in that: The inlet branch of the circulating pump is connected to a steam condensation system and other water sources.

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