MTO-grade methanol rectification heat utilization device

Abstract

The utility model provides an MTO-grade methanol rectification heat utilization device which comprises a pre-rectification tower, a pre-tower reboiler is arranged on the lower portion of the pre-rectification tower, and an inlet of the pre-tower reboiler is connected with a heat input device; methanol and the like are adopted as heat exchange media to absorb heat of the heat input device so as to become heating media with higher-level pressure and temperature, waste heat of the heat input device is utilized in a gradient mode, a large amount of heat is recycled, and steam energy consumption of the system is greatly reduced; heat of the heat input device is recycled to heat the pre-tower reboiler, thermal coupling is achieved, a heat exchange network is optimized, and the energy-saving space is enlarged.

Description

Technical Field

[0001] This application relates to the field of methanol distillation technology, specifically to an MTO-grade methanol distillation heat utilization device. Background Technology

[0002] Ethylene and propylene (low-carbon olefins) are important basic chemical raw materials, and their downstream products are widely used in consumer goods, furniture, home appliances, and other industries. my country's petroleum reserves are relatively low, and a coal-based olefin production route has been developed based on its abundant coal resources. Methanol-to-olefins (MTO) technology is an important non-petroleum route for producing light olefins, efficiently converting methanol into petrochemical products such as ethylene and propylene. It serves as a crucial bridge and link between coal chemical, natural gas chemical, and petrochemical industries. In the MTO process, methanol distillation is a key separation operation. In traditional methanol distillation processes, the heat source for the pre-reboiler is usually low-pressure steam, leading to high system energy consumption. For example, in the methanol distillation unit meeting the requirements for producing MTO-grade and AA-grade methanol (application number 202323062318.6), the heat source for the pre-reboiler is low-pressure steam.

[0003] The methanol synthesis reaction tower is one of the key pieces of equipment in the methanol production process. It is located at the front end of the entire production process. In the methanol synthesis reaction tower, carbon monoxide, carbon dioxide and hydrogen undergo a chemical reaction under certain temperature, pressure and catalyst conditions to produce crude methanol. The methanol synthesis reaction tower is an exothermic reaction process. Most of the low-temperature waste heat of the methanol synthesis reaction tower is dissipated into the atmosphere through water cooling, air cooling or evaporative cooling, and is not fully utilized. This application aims to integrate the heat of the synthesis gas generated by the methanol synthesis reaction tower into the distillation system, thereby achieving greater energy saving and carbon reduction benefits.

[0004] The applicant found no relevant inventive ideas through a search; therefore, a new technical solution is provided to solve the above problems. Utility Model Content

[0005] This application provides a heat utilization device for MTO-grade methanol distillation, including a pre-distillation column, wherein a pre-distillation column reboiler is provided at the lower part of the pre-distillation column, and one inlet of the pre-distillation column reboiler is connected to a heat input device.

[0006] As a preferred embodiment, the heat input device is a synthesis reaction tower.

[0007] As a preferred embodiment, the synthesis reaction tower is connected to a heat exchanger, the heat exchanger is connected to a cooling device, the cooling device is connected to the input end of the synthesis gas processing device, and the output end of the synthesis gas processing device is connected to the pre-distillation tower; wherein, the input end of the cooling device is connected to a medium input pipeline, and the output end of the cooling device is connected to the pre-tower reboiler.

[0008] As a preferred embodiment, the cooling device includes a cooler, an input end of which is connected to a medium input pipeline, and an output end of which is connected to a medium gas output pipeline, the medium gas output pipeline being connected to the pre-tower reboiler.

[0009] As a preferred embodiment, a compression pump is installed on the medium gas output pipeline.

[0010] As a preferred embodiment, a feed line is connected to one side of the pre-distillation column, and a feed preheater is connected to the feed line.

[0011] As a preferred embodiment, the medium gas output pipeline is also connected to an inlet of the feed preheater. As another preferred embodiment, the syngas treatment unit includes a condenser connected to a cooler, the condenser being sequentially connected to a high-pressure separator, a crude methanol filter, and a methanol flash evaporator, the methanol flash evaporator being connected to the feed preheater.

[0012] As a preferred embodiment, the methanol flash tank is connected to a crude methanol buffer tank via a pipeline, and the crude methanol buffer tank is connected to a feed preheater via a feed pipeline.

[0013] As a preferred embodiment, the top of the pre-distillation column is provided with a pre-column reflux device.

[0014] As a preferred embodiment, the pre-distillation column reflux device includes a pre-distillation column reflux tank. The top of the pre-distillation column is connected to the pre-distillation column reflux tank via a pre-distillation column top outlet pipeline. A pre-distillation column condenser is installed on the pre-distillation column top outlet pipeline. The bottom of the pre-distillation column reflux tank is connected to the pre-distillation column via a pre-distillation column reflux pipeline. The top of the pre-distillation column reflux tank is connected to a pre-distillation column buffer tank via a reflux tank top pipeline. The bottom of the pre-distillation column buffer tank is connected to the pre-distillation column reflux tank via a buffer tank bottom pipeline. A non-condensable gas outlet pipeline is installed on the top of the pre-distillation column buffer tank. An extraction water pipeline is connected to one side of the pre-distillation column reflux tank.

[0015] As a preferred embodiment, a pre-tower reflux pump is installed on the pre-tower reflux pipeline.

[0016] As a preferred embodiment, the heat exchanger is connected to the syngas discharge pipeline.

[0017] As a preferred embodiment, the crude methanol filter includes a primary crude methanol filter and a secondary crude methanol filter connected in sequence.

[0018] This application utilizes a process that rationally and progressively leverages the heat from the heat input device. Methanol, among other materials, is used as a heat exchange medium to absorb heat from the heat input device, thus becoming a heating medium at a higher pressure and temperature. This progressively utilizes the waste heat from the heat input device, recovering a significant amount of heat and substantially reducing the system's steam energy consumption. Furthermore, the recovered heat from the heat input device is used to heat the pre-distillation tower reboiler, achieving thermal coupling. Approximately 95% methanol is collected from the bottom of the pre-distillation tower. This application employs a thermal coupling process, optimizing the heat exchange network and enhancing energy-saving potential. Compared to traditional methanol distillation, it can reduce steam consumption to 0 t steam / t refined methanol. Attached Figure Description

[0019] Figure 1 This is a schematic block diagram of the structure of this application;

[0020] Figure 2 This is a schematic diagram of the syngas processing device of this application;

[0021] Figure 3 This is a schematic diagram of the structure of this application;

[0022] 1. Pre-distillation column; 2. Pre-column reboiler; 3. Syngas discharge line; 4. Cooler; 5. Condenser; 6. Line; 7. Pre-column reflux tank; 8. Pre-column top outlet line; 9. Pre-column condenser; 10. Pre-column reflux line; 11. Pre-column reflux pump; 12. Top line of reflux tank; 13. Pre-column buffer tank; 14. Bottom line of buffer tank; 15. Non-condensable gas outlet line; 16. Extraction water line; 17. Feed line; 18. Feed preheater; 19. Line 1; 20. Medium gas output line; 21. Medium input line; 22. Heat exchanger; 23. High-pressure separator; 24. Methanol flash tank; 25. Crude methanol primary filter; 26. Crude methanol secondary filter; 27. Crude methanol buffer tank. Detailed Implementation

[0023] The following is in conjunction with the appendix Figure 1 Appendix Figure 2 Appendix Figure 3 The specific embodiments of this utility model will be described in detail below. It should be noted that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of this utility model.

[0024] Example 1:

[0025] like Figures 1 to 3As shown, this application provides a heat utilization device for MTO-grade methanol distillation, including a pre-distillation column 1. A feed line 17 is connected to one side of the pre-distillation column 1, and the feed line 17 is located in the upper middle part of the pre-distillation column 1. A feed preheater 18 is connected to the feed line 17. The bottom of the pre-distillation column 1 is connected to the olefin synthesis section equipment (not shown in the figure) through a pre-column bottom pipeline. The top pressure of the pre-distillation column 1 is 120-180 kPa. A pre-column reboiler 2 is provided at the lower part of the pre-distillation column 1. One inlet of the pre-column reboiler 2 is connected to a heat input device, which heats the pre-column reboiler 2. The heat input device can be a synthesis reaction column, a converter, or other similar equipment. In this embodiment, a synthesis reaction column is used as an example. The synthesis reaction column is connected to a heat exchanger 22, and the heat exchanger 22 is connected to a cooling... The cooling device is connected to the input end of the syngas processing device, and the output end of the syngas processing device is connected to the pre-distillation column 1. The input end of the cooling device is connected to a medium input pipeline 21, through which methanol or other media, such as water or heat transfer oil, are introduced to the cooling device, utilizing the heat from the syngas in the synthesis reaction column to heat the methanol or other media. The output end of the cooling device is connected to the pre-column reboiler 2. More specifically, the cooling device includes a cooler 4, one input end of which is connected to the medium input pipeline 21, and one output end of which is connected to a medium gas output pipeline 20, which is connected to the pre-column reboiler 2. Preferably, a compression pump is installed on the medium gas output pipeline 20 to heat and pressurize the gas phase, providing better heat and simplifying the equipment.

[0026] The medium gas output pipeline 20 is also connected to an inlet of the feed preheater 18; the output end of the syngas treatment device is connected to the feed preheater 18 through the feed pipeline 17, and then enters the pre-distillation column 1 as raw material; the syngas generated by the synthesis reaction column is heated by the heat exchanger 22, the pressure after heat exchange is P = 7.8 MPa, the temperature after heat exchange is T = 125℃-130℃, the material after heat exchange enters the cooler 4, and a medium such as methanol is introduced into one input end of the cooler 4. The heat of the syngas coming out of the synthesis reaction column heats the methanol medium, and the methanol gas generated after heating enters the pre-column reboiler 2 and the feed preheater 18 through the medium gas output pipeline 20, providing the heat required for distillation of the pre-column reboiler 2 and providing heat for the feed preheater 18. The material after being cooled by the cooler 4 continues to enter the syngas treatment device for processing and is then sent to the pre-distillation column 1 as raw material.

[0027] This embodiment utilizes the syngas exiting the synthesis reaction tower for primary heat recovery, supplying heat to the pre-tower reboiler 2 and the feed preheater 18, achieving efficient energy utilization and thermal integration optimization. The syngas treatment device includes a condenser 5 connected to a cooler 4. The condenser 5 is sequentially connected to a high-pressure separator 23, a crude methanol filter, and a methanol flash tank 24. The methanol flash tank 24 is connected to the feed preheater 18. Preferably, a crude methanol buffer tank 27 is provided between the methanol flash tank 24 and the feed preheater 18. The methanol flash tank 24 is connected to the crude methanol buffer tank 27 via a pipeline 6. Specifically, the crude methanol filter includes a primary crude methanol filter 25 and a secondary crude methanol filter 26. The crude methanol buffer tank 27 is connected to the feed preheater 18 via a feed pipeline 17. The specific process of utilizing the heat from the synthesis reaction tower is as follows: the gas exiting from the bottom of the synthesis reaction tower enters the heat exchanger. Heat exchange is performed in tube 22. After heat exchange, the pressure P = 7.8 MPa and the temperature T = 125℃-130℃. Methanol is used as a cold medium to enter the shell side of cooler 4. After heat exchange, all methanol is converted into gas phase. The synthesis gas is further cooled to 83℃ by controlling the methanol feed rate. The gaseous methanol is sent to the pre-reboiler 2 through medium gas output line 20 to provide the heat required for distillation. It is also sent to the feed preheater 18 through medium gas output line 20 to provide heat for feed preheater 18. The synthesis gas cooled by cooler 4 continues to enter condenser 5 to be condensed to about 40℃. After pressure reduction and gas-liquid separation by high pressure separator 23, the resulting liquid phase is filtered by crude methanol primary filter 25 and crude methanol secondary filter 26 and then enters methanol flash tank 24 for flash evaporation. The crude methanol liquid obtained by flash evaporation is used as raw material to enter pre-distillation column 1.

[0028] The top of the pre-distillation column 1 is equipped with a pre-column reflux device; the pre-column reflux device includes a pre-column reflux tank 7, the top of the pre-distillation column 1 is connected to the pre-column reflux tank 7 through a pre-column top outlet pipeline 8, a pre-column condenser 9 is installed on the pre-column top outlet pipeline 8, and the bottom of the pre-column reflux tank 7 is connected to the pre-distillation column 1 through a pre-column reflux pipeline 10 to improve the purity of refined methanol; a pre-column reflux pump 11 is installed on the pre-column reflux pipeline 10; the top of the pre-column reflux tank 7 is connected to the pre-column buffer tank 13 through a reflux tank top pipeline 12, and the bottom of the pre-column buffer tank 13 is connected to the pre-column reflux tank 7 through a buffer tank bottom pipeline 14; a non-condensable gas outlet pipeline 15 is installed on the top of the pre-column buffer tank 13; and an extraction water pipeline 16 is connected to one side of the pre-column reflux tank 7.

[0029] This embodiment utilizes a process that rationally and progressively utilizes the heat from the outlet gas of the synthesis reaction tower. Methanol is used as the heat exchange medium to absorb the heat from the outlet gas, thus becoming a heating medium at a higher pressure and temperature. This progressively utilizes the waste heat from the synthesis reaction tower, recovering a significant amount of heat and substantially reducing the system's steam energy consumption. The heat recovered from the synthesis gas in this application is achieved through thermal coupling via heating the pre-tower reboiler 2 and the feed preheater 18. Approximately 95% methanol is collected from the bottom of the pre-distillation tower 1. This application employs a thermal coupling process, optimizing the heat exchange network and enhancing energy efficiency. Compared to traditional methanol distillation, steam consumption can be reduced to 0 t steam / t refined methanol. This embodiment fully utilizes the heat from the gas exiting the bottom of the synthesis reaction tower, achieving efficient energy utilization and thermal integration optimization.

[0030] Example 2:

[0031] This embodiment provides a specific application:

[0032] At a methanol plant, a new MTO-grade methanol distillation heat utilization unit was installed. The main equipment includes a pre-distillation column 1 with a feed rate of 78,750 kg / h. When the process parameters are optimized to the best, the steam energy consumption of refined methanol is reduced to 0 tons of steam / refined methanol through this thermal coupling process, and the methanol purity can reach 95%.

[0033] Specifically: crude methanol enters the feed preheater 18 for preheating, which preheats the crude methanol to approximately 70°C. The preheated crude methanol then enters the pre-distillation column 1 for distillation. The top pressure of the pre-distillation column 1 is 127 kPag, the top temperature is 68°C, and the bottom temperature is 72°C. The vapor phase collected from the top of the pre-distillation column 1 goes to the pre-column condenser 9. After being cooled by the pre-column condenser 9, it enters the pre-column reflux tank 7. The non-condensable gas produced after extraction in the pre-column reflux tank 7 enters the pre-column buffer tank 13. The vapor phase of the pre-column buffer tank 13 is discharged from its top, and the liquid phase is refluxed back to the pre-column reflux tank. 7. The liquid phase from the pre-distillation column reflux tank 7 is refluxed to the upper middle part of the pre-distillation column 1. Specifically, it is pressurized by the pre-distillation column reflux pump 11 and sent to the upper middle part of the pre-distillation column 1 as reflux feed, thereby improving the purity of refined methanol. The pre-distillation column 1 is provided with the heat required for distillation by the pre-distillation column 1 through indirect heating by the pre-distillation column reboiler 2. The heat source of the pre-distillation column reboiler 2 is methanol gas heated by the synthesis gas of the synthesis reaction column. The feed preheater 18 is provided with the heat required for feed preheater 18 through indirect heating. The heat source of feed preheater 18 is also methanol gas heated by the synthesis gas of the synthesis reaction column.

[0034] In this embodiment, the heat source for both the pre-reboiler 2 and the feed preheater 18 is the primary heat recovery from the synthesis gas at the outlet of the synthesis reaction tower, with an energy consumption of 0 t of low-pressure steam per ton of refined methanol. In this embodiment, the crude methanol feed rate is 78750 kg / h, with a water content of 3.80% and an ethanol content of approximately 0.23%. The operating parameters of the pre-distillation tower 1 are shown in Table 1 below.

[0035] Pre-distillation column Operating pressure / KPa 127 Theoretical number of plates / blocks 38 reflux ratio 170 Condenser load GCAL / h 9.6831 Reboiler load GCAL / h 10.1318

[0036] In this embodiment, steam energy consumption is reduced to 0. For new markets, the investment is small and the operation is highly feasible. Energy-saving measures such as optimizing heat recovery through heat exchange networks are adopted, which greatly reduces steam consumption.

[0037] In summary, by adopting the above technical solutions, the heat recovered from the synthesis gas in the synthesis reaction tower is achieved through thermal coupling via heating of the pre-tower reboiler; the heat recovered from the synthesis gas in the first stage is also achieved through thermal coupling via heating of the feed preheater; the unit consumption of the methanol distillation process can be reduced from 24.1t steam / t refined alcohol to 0t steam / t refined alcohol, so that all the heat required for methanol distillation comes from the heat recovered from the outlet gas of the synthesis reaction tower in the first stage, which greatly reduces the company's operating costs, significantly reduces carbon emissions, and improves the company's competitiveness.

[0038] This application employs a thermal coupling process to optimize the heat exchange network and enhance energy-saving potential; it can transform traditional processes and achieve a significant reduction in energy consumption. Compared with traditional methanol distillation, it can reduce steam consumption to 0t steam / t methanol; and this application can extract methanol with a concentration of approximately 95%.

[0039] The devices and connections not specifically described above are all existing technologies, and will not be described in detail here.

[0040] The preferred embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solution of this application, and these simple modifications all fall within the protection scope of this application.

[0041] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way without contradiction. In order to avoid unnecessary repetition, the various possible combinations in this application will not be described separately.

[0042] Furthermore, various different implementations of this application can be combined in any way, as long as they do not violate the spirit of this application, and such combinations should also be regarded as the content disclosed in this application.

Claims

1. A heat utilization device for MTO-grade methanol distillation, comprising a pre-distillation column (1), characterized in that, The lower part of the pre-distillation column (1) is provided with a pre-column reboiler (2), and one inlet of the pre-column reboiler (2) is connected to a heat input device; the heat input device is a synthesis reaction column or a converter, the synthesis reaction column is connected to a heat exchanger (22), the heat exchanger (22) is connected to a cooling device, the cooling device is connected to the input end of the synthesis gas treatment device, and the output end of the synthesis gas treatment device is connected to the pre-distillation column (1); the cooling device includes a cooler (4), one input end of the cooler (4) is connected to a medium input pipeline (21), one output end of the cooler (4) is connected to a medium gas output pipeline (20), and the medium gas output pipeline (20) is connected to the pre-column reboiler (2); the synthesis gas treatment device includes a condenser (5) connected to the cooler (4), the condenser (5) is connected in sequence to a high-pressure separator (23), a crude methanol filter, and a methanol flash tank (24), and the methanol flash tank (24) is connected to a feed preheater (18).

2. The MTO-grade methanol distillation heat utilization device according to claim 1, characterized in that, The pre-distillation column (1) is connected to a feed line (17) on one side, and a feed preheater (18) is connected to the feed line (17).

3. The MTO-grade methanol distillation heat utilization device according to claim 2, characterized in that, The medium gas output line (20) is also connected to an inlet of the feed preheater (18).

4. The MTO-grade methanol distillation heat utilization device according to claim 1, characterized in that, The methanol flash tank (24) is connected to the crude methanol buffer tank (27) via a pipeline (6), and the crude methanol buffer tank (27) is connected to the feed preheater (18) via a feed pipeline (17).

5. The MTO-grade methanol distillation heat utilization device according to claim 1, characterized in that, The top of the pre-distillation column (1) is equipped with a pre-column reflux device.

6. The MTO-grade methanol distillation heat utilization device according to claim 5, characterized in that, The pre-column reflux device includes a pre-column reflux tank (7). The top of the pre-distillation column (1) is connected to the pre-column reflux tank (7) via a pre-column top outlet pipeline (8). A pre-column condenser (9) is installed on the pre-column top outlet pipeline (8). The bottom of the pre-column reflux tank (7) is connected to the pre-distillation column (1) via a pre-column reflux pipeline (10). The top of the pre-column reflux tank (7) is connected to the pre-column buffer tank (13) via a reflux tank top pipeline (12). The bottom of the pre-column buffer tank (13) is connected to the pre-column reflux tank (7) via a buffer tank bottom pipeline (14). A non-condensable gas outlet pipeline (15) is installed on the top of the pre-column buffer tank (13). An extraction water pipeline (16) is connected to one side of the pre-column reflux tank (7).

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