A cogeneration heating system and method for cascade utilization of waste heat from a methanol distillation unit

Abstract

The invention discloses a cogeneration heating system and method for cascade utilization of waste heat of a methanol distillation unit. The system includes a pressurized distillation tower, an atmospheric distillation tower, a primary heat exchanger, a secondary heat exchanger and a tertiary heat exchanger; a pressurized tower methanol product pipeline is arranged at the top of the pressurized distillation tower, and a pressurized tower kettle bottom liquid pipeline is arranged at the bottom; an atmospheric distillation tower methanol product pipeline is arranged at the top of the atmospheric distillation tower, and an atmospheric tower kettle bottom liquid pipeline is arranged at the bottom; the pressurized tower methanol product pipeline is connected with the atmospheric tower methanol product pipeline after passing through the tertiary heat exchanger, and is connected to the primary heat exchanger together; the pressurized tower kettle bottom liquid pipeline is connected to the inlet of the atmospheric distillation tower; the atmospheric tower kettle bottom liquid pipeline is connected to the secondary heat exchanger. The heat network return water is used as the cold source of the heat exchanger to replace the circulating cooling water conventionally used in the distillation unit, thereby reducing the amount and consumption of circulating cooling water and achieving a certain water-saving effect.

Description

Technical Field

[0001] The invention belongs to the technical field of heat supply from a heat network, and in particular relates to a cogeneration heating system and method for cascade utilization of waste heat from a methanol distillation unit. Background Art

[0002] Coal-to-methanol is a production process based on coal gasification and synthesis gas, and the synthesis gas catalytic synthesis of methanol. The industry is developing towards large-scale and high-efficiency. The development of coal-to-methanol projects is conducive to the full and rational utilization of my country's coal resources. Due to the current excess methanol production capacity in my country, the development trend of methanol production technology is: large-scale production equipment, gradual elimination of high energy and water consumption production capacity, vigorously developing and selecting new water-saving processes, and vigorously developing and selecting appropriate energy-saving technologies.

[0003] In the methanol production process, after the distillation system is started, the bottom liquid produced at the bottom of the atmospheric distillation tower is generally cooled by circulating cooling water and directly discharged after water treatment, while the methanol products at the top of the pressure tower and atmospheric distillation tower are cooled and condensed by circulating cooling water and sent to the methanol storage tank. The heat of the bottom liquid and the methanol product at the top of the tower has not been utilized, resulting in heat waste. Therefore, a method is needed to fully utilize the low-grade heat of the methanol product at the top of the pressure tower and atmospheric distillation tower and the bottom liquid of the atmospheric distillation tower.

[0004] CN 210933964 U discloses a device for utilizing residual heat of distillation wastewater, which introduces the bottom liquid of the atmospheric distillation tower into a heat exchanger for heat exchange with crude methanol, adjusts the feed temperature of the pre-distillation tower in the distillation system, and achieves the purpose of reducing energy consumption to a certain extent.

[0005] Although the existing technology can achieve the purpose of reducing energy consumption to a certain extent, it is not conducive to water saving in the system. At the same time, it is unable to utilize the low-grade heat of the top product gas of the pressurized tower and the atmospheric distillation tower, resulting in heat waste. Summary of the invention

[0006] The object of the present invention is to provide a cogeneration heating system and method for cascade utilization of waste heat from a methanol distillation unit, so as to solve the problem of heat waste in the distillation system in the prior art.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A methanol distillation unit waste heat cascade utilization cogeneration heating system, comprising a pressure distillation tower, an atmospheric distillation tower, a primary heat exchanger, a secondary heat exchanger and a tertiary heat exchanger;

[0009] The top of the pressurized distillation tower is connected to a pressurized tower methanol product pipeline, and the bottom is connected to a pressurized tower kettle bottom liquid pipeline;

[0010] The top of the atmospheric distillation tower is connected to the atmospheric tower methanol product pipeline, and the bottom is connected to the atmospheric tower kettle bottom liquid pipeline;

[0011] The methanol product pipeline of the pressure tower is connected to the methanol product pipeline of the atmospheric pressure tower after passing through the third-stage heat exchanger, and is connected to the first-stage heat exchanger together; the bottom liquid pipeline of the pressure tower is connected to the inlet of the atmospheric distillation tower;

[0012] The atmospheric tower bottom liquid pipeline is connected to the secondary heat exchanger.

[0013] Furthermore, the heat network return pipeline passes through the primary heat exchanger, the secondary heat exchanger and the tertiary heat exchanger in sequence and is connected to the heat supply network pipeline.

[0014] Furthermore, the water in the heat network return pipe enters the first-stage heat exchanger to heat up to 50-80°C, then enters the second-stage heat exchanger to heat up to 85-95°C, and then enters the third-stage heat exchanger to heat up to 100-130°C.

[0015] Furthermore, in the first-stage heat exchanger, the heat source is a mixture of the methanol product distilled from the top of the atmospheric distillation tower and the methanol product distilled from the top of the pressurized distillation tower after heat exchange in the third-stage heat exchanger, and the cold source is water in the heat network return pipe.

[0016] Furthermore, in the secondary heat exchanger, the heat source is the bottom liquid of the atmospheric distillation tower, and the cold source is the return water of the heat network after being heated by heat exchange in the primary heat exchanger.

[0017] Furthermore, in the three-stage heat exchanger, the heat source is the methanol product distilled from the top of the pressurized distillation tower, and the cold source is the heat network return water after heat exchange and temperature increase in the two-stage heat exchanger.

[0018] Furthermore, the methanol product distilled from the top of the pressurized distillation tower enters the tertiary heat exchanger and exchanges heat with the return water from the heat network after heat exchange and temperature rise in the secondary heat exchanger. The temperature of the methanol product after heat exchange is 95-120°C. Then this part of methanol is mixed with the methanol product distilled from the top of the atmospheric distillation tower. The temperature after mixing is 80-100°C. Then it enters the primary heat exchanger and exchanges heat with the return water from the heat network. The temperature of the methanol after heat exchange is 30-60°C.

[0019] Furthermore, the bottom liquid of the atmospheric distillation tower directly enters the secondary heat exchanger to exchange heat with the return water of the heat network after heat exchange and temperature rise in the primary heat exchanger. The bottom liquid temperature after heat exchange is 60-80°C and is sent to the water treatment system for treatment and then discharged.

[0020] Furthermore, the heat exchanger includes but is not limited to a shell and tube heat exchanger, a shell and tube heat exchanger, and a plate heat exchanger.

[0021] Another technical solution provided by the present invention is:

[0022] A method for cogeneration and heating of waste heat cascaded utilization of methanol distillation unit, based on the cogeneration and heating system of waste heat cascaded utilization of methanol distillation unit, comprises the following steps:

[0023] The water in the return water pipeline of the heat network enters the first-stage heat exchanger to heat up to 50-80°C, then enters the second-stage heat exchanger to heat up to 85-95°C, and then enters the third-stage heat exchanger to heat up to 100-130°C;

[0024] The methanol product distilled from the top of the pressure distillation tower enters the third-stage heat exchanger and exchanges heat with the return water of the heat network after heat exchange and temperature rise in the second-stage heat exchanger. The temperature of the methanol product after heat exchange is 95-120°C. Then this part of methanol is mixed with the methanol product distilled from the top of the atmospheric distillation tower. The temperature after mixing is 80-100°C. Then it enters the first-stage heat exchanger and exchanges heat with the return water of the heat network. The temperature of the methanol after heat exchange is 30-60°C.

[0025] The bottom liquid of the atmospheric distillation tower directly enters the secondary heat exchanger to exchange heat with the return water of the heat network after heat exchange and temperature rise in the primary heat exchanger. The bottom liquid temperature after heat exchange is 60-80℃ and is sent to the water treatment system for treatment before discharge.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. The methanol distillation unit waste heat cascade utilization cogeneration heating system provided in the embodiment of the present invention uses the return water from the heat network as the cold source of the heat exchanger, replacing the circulating cooling water conventionally used in the distillation unit, thereby reducing the amount and consumption of circulating cooling water and achieving a certain water-saving effect.

[0028] 2. The methanol distillation unit waste heat cascade utilization cogeneration heating system provided by the embodiment of the present invention fully utilizes the low-grade heat in the methanol product at the top of the distillation tower on the basis of utilizing the heat of the bottom liquid of the atmospheric distillation tower. Through the cascade utilization of energy, hot water with a maximum temperature of 130°C can be supplied.

[0029] 2. The methanol distillation unit waste heat cascade utilization cogeneration heating system provided in the embodiment of the present invention increases the heating income and improves the economic benefits of the methanol plant through the cogeneration of heat by the distillation unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0031] Figure 1 A schematic diagram of the structure of a cogeneration heating system for cascaded utilization of waste heat from a methanol distillation unit provided in an embodiment of the present invention.

[0032] Figure 2Schematic diagram of the method for co-generation of heat by cascaded utilization of waste heat from a methanol distillation unit provided in an embodiment of the present invention.

[0033] Among them: 1 pressure distillation tower; 2 atmospheric distillation tower; 3 primary heat exchanger; 4 secondary heat exchanger; 5 tertiary heat exchanger. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0035] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit exemplary embodiments according to the present invention.

[0036] like Figure 1 As shown, an embodiment of the present invention provides a methanol distillation unit waste heat cascade utilization cogeneration heating system, comprising a pressurized distillation tower 1, an atmospheric distillation tower 2, a primary heat exchanger 3, a secondary heat exchanger 4 and a tertiary heat exchanger 5; a pressurized tower methanol product pipeline is arranged on the top of the pressurized distillation tower 1, and a pressurized tower kettle bottom liquid pipeline is arranged on the bottom; an atmospheric distillation tower methanol product pipeline is arranged on the top of the atmospheric distillation tower 2, and an atmospheric tower kettle bottom liquid pipeline is arranged on the bottom; the pressurized tower methanol product pipeline is connected with the atmospheric tower methanol product pipeline after passing through the tertiary heat exchanger 5, and is connected to the primary heat exchanger 3 together; the pressurized tower kettle bottom liquid pipeline is connected to the inlet of the atmospheric distillation tower 2; the atmospheric tower kettle bottom liquid pipeline is connected to the secondary heat exchanger 4; the heat network return water pipeline passes through the primary heat exchanger 3, the secondary heat exchanger 4 and the tertiary heat exchanger 5 in sequence, and is connected to the heat supply network pipeline.

[0037] In one embodiment of the present invention, in the primary heat exchanger, the heat source is the methanol product distilled from the top of the atmospheric distillation tower 2, and the methanol product distilled from the top of the pressurized distillation tower 1, and the mixture of the heat source outlet methanol product after heat exchange in the tertiary heat exchanger 5, and the cold source is the water in the heat network return water pipeline. In the secondary heat exchanger 4, the heat source is the bottom liquid of the atmospheric distillation tower 2, and the cold source is the heat network return water after heat exchange and temperature increase in the primary heat exchanger 3. In the tertiary heat exchanger 5, the heat source is the methanol product distilled from the top of the pressurized distillation tower 1, and the cold source is the heat network return water after heat exchange and temperature increase in the secondary heat exchanger 4. The water in the heat network return water pipeline enters the primary heat exchanger for heat exchange and temperature increase to 50-80°C, and then enters the secondary heat exchanger for heat exchange and temperature increase to 85-95°C, and then enters the tertiary heat exchanger for heat exchange and temperature increase to 100-130°C. The methanol product distilled from the top of the pressure distillation tower 1 enters the tertiary heat exchanger 5, and exchanges heat with the return water of the heat network after heat exchange and temperature increase in the secondary heat exchanger 4. The temperature of the methanol product after heat exchange is 95-120°C. Then this part of methanol is mixed with the methanol product distilled from the top of the atmospheric distillation tower 2. The temperature after mixing is 80-100°C. Then it enters the primary heat exchanger 3 and exchanges heat with the return water of the heat network. The temperature of the methanol after heat exchange is 30-60°C. The bottom liquid of the atmospheric distillation tower 2 directly enters the secondary heat exchanger 4 and exchanges heat with the return water of the heat network after heat exchange and temperature increase in the primary heat exchanger 3. The temperature of the bottom liquid after heat exchange is 60-80°C. It is sent to the water treatment system for treatment and then discharged.

[0038] In one embodiment of the present invention, since the output of each tower of the methanol plant distillation unit generally does not change, the hot water flow rate supplied can be determined according to the requirements for the heating temperature of the heating network water, and the appropriate form and size of the heat exchanger can be selected accordingly. The heat exchanger includes but is not limited to a shell and tube heat exchanger, a shell and tube heat exchanger, a plate heat exchanger, etc.

[0039] like Figure 2 As shown, another technical solution provided by the present invention is:

[0040] A methanol distillation unit waste heat cascade utilization cogeneration heating method, based on a methanol distillation unit waste heat cascade utilization cogeneration heating system, comprises the following steps:

[0041] The water in the return water pipeline of the heat network enters the first-stage heat exchanger to heat up to 50-80°C, then enters the second-stage heat exchanger to heat up to 85-95°C, and then enters the third-stage heat exchanger to heat up to 100-130°C;

[0042] The methanol product distilled from the top of the pressure distillation tower 1 enters the third-stage heat exchanger 5, and exchanges heat with the heat network return water after heat exchange and temperature increase in the second-stage heat exchanger 4. The temperature of the methanol product after heat exchange is 95-120°C. Then this part of methanol is mixed with the methanol product distilled from the top of the atmospheric distillation tower 2. The temperature after mixing is 80-100°C. Then it enters the first-stage heat exchanger 3 to exchange heat with the heat network return water. The temperature of the methanol after heat exchange is 30-60°C.

[0043] The bottom liquid of the atmospheric distillation tower 2 directly enters the secondary heat exchanger 4 to exchange heat with the return water of the heat network after heat exchange and temperature increase in the primary heat exchanger 3. The bottom liquid temperature after heat exchange is 60-80°C and is sent to the water treatment system for treatment and then discharged.

[0044] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

Claims

1. A method for cogeneration and heating of waste heat from a methanol distillation unit by cascade utilization, based on a cogeneration and heating system for waste heat from a methanol distillation unit, characterized in that: The following steps are involved: The water in the return water pipeline of the heat network enters the first-stage heat exchanger to heat up to 50~80℃, then enters the second-stage heat exchanger to heat up to 85~95℃, and then enters the third-stage heat exchanger to heat up to 100~130℃; The methanol product distilled from the top of the pressure distillation tower (1) enters the third-stage heat exchanger (5) and exchanges heat with the return water from the heat network after the heat exchange in the second-stage heat exchanger (4). The temperature of the methanol product after the heat exchange is 95-120°C. Then, this part of the methanol is mixed with the methanol product distilled from the top of the atmospheric distillation tower (2). The temperature after mixing is 80-100°C. Then, it enters the first-stage heat exchanger (3) and exchanges heat with the return water from the heat network. The temperature of the methanol after the heat exchange is 30-60°C. The bottom liquid of the atmospheric distillation tower (2) directly enters the secondary heat exchanger (4) to exchange heat with the return water of the heat network after heat exchange and temperature increase in the primary heat exchanger (3). The bottom liquid temperature after heat exchange is 60-80°C and is sent to the water treatment system for treatment before discharge. A methanol distillation unit waste heat cascade utilization cogeneration heating system comprises a pressure distillation tower (1), an atmospheric distillation tower (2), a primary heat exchanger (3), a secondary heat exchanger (4) and a tertiary heat exchanger (5); The top of the pressurized distillation tower (1) is connected to a pressurized tower methanol product pipeline, and the bottom is connected to a pressurized tower kettle bottom liquid pipeline; The top of the atmospheric distillation tower (2) is connected to the atmospheric tower methanol product pipeline, and the bottom is connected to the atmospheric tower kettle bottom liquid pipeline; The methanol product pipeline of the pressure tower is connected to the methanol product pipeline of the atmospheric pressure tower after passing through the third-stage heat exchanger (5), and is connected to the first-stage heat exchanger (3); the bottom liquid pipeline of the pressure tower is connected to the inlet of the atmospheric distillation tower (2); The atmospheric tower bottom liquid pipeline is connected to the secondary heat exchanger (4); The heat network return water pipeline passes through the first-stage heat exchanger (3), the second-stage heat exchanger (4) and the third-stage heat exchanger (5) in sequence, and is then connected to the heat supply network pipeline; In the primary heat exchanger, the heat source is a mixture of the methanol product distilled from the top of the atmospheric distillation tower (2) and the methanol product distilled from the top of the pressure distillation tower (1) after heat exchange in the tertiary heat exchanger (5) and the methanol product at the heat source outlet, and the cold source is water in the return water pipeline of the heat network; In the secondary heat exchanger (4), the heat source is the bottom liquid of the atmospheric distillation tower (2), and the cold source is the return water from the heat network after being heated by heat exchange in the primary heat exchanger (3); In the tertiary heat exchanger (5), the heat source is the methanol product distilled from the top of the pressurized distillation tower (1), and the cold source is the return water from the heat network after being heated by heat exchange in the secondary heat exchanger (4).

2. The method for co-generation and heating of methanol distillation unit waste heat cascade utilization according to claim 1, characterized in that: The heat exchanger includes: a shell and tube heat exchanger, a shell and tube heat exchanger, and a plate heat exchanger.

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