Process method for thermally coupling methanol synthesis and rectification

Abstract

The invention discloses a methanol synthesis and rectification thermal coupling process method, and belongs to the technical field of methanol production. After heat exchange, synthesis gas is subjected to gas-liquid separation through a gas-liquid separation tank in sequence, a gas phase enters a pressurizing tower reboiler and an atmospheric tower reboiler in sequence, heat Q1 (a pressurizing tower) and heat Q2 (an atmospheric tower) are released in a grading manner, and the total recovery heat reaches 19000 KW. Wherein the Q1 realizes secondary utilization through an atmospheric tower heat integration reboiler. The liquid phase is sent to a pre-tower through a storage tank, and finally the synthesis gas is cooled to 85 DEG C; according to the method, stepped recovery of waste heat of the synthesis gas is achieved through thermal coupling, external steam of a rectification system is replaced, meanwhile, new pressure of the synthesis gas is increased and reduced by about 26 kpa, the problem of energy waste of a traditional process is solved, and energy consumption and carbon emission are remarkably reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of methanol production, in particular to a process method of heat coupling of methanol synthesis and rectification. BACKGROUND

[0002] In the traditional methanol production process, the methanol synthesis gas after completing the synthesis reaction usually contains a large amount of residual heat. Taking a device with an annual output of 640,000 tons of refined methanol (operating time 7200 hours / year) as an example, the initial parameters of the synthesis gas are pressure 7.1 MPaG and temperature 124℃. After being cooled by the traditional process, the temperature needs to be reduced to 40℃, and a large amount of heat is taken away by the circulating water in this process, causing serious waste of energy. Specifically, the synthesis gas first passes through the heat exchanger E-3301 and exchanges heat with the synthesis gas entering the tower, and then enters the circulating water cooler E-3302, and the temperature is reduced from 124℃ to 40℃ by circulating water. However, these heat is not effectively utilized, not only increasing the load of the circulating water system, but also leading to high energy consumption of the whole device, which does not conform to the current development trend of energy saving and consumption reduction in chemical production.

[0003] In addition, the methanol rectification process (pre-tower-pressurized tower-atmospheric tower) needs to consume a large amount of steam to drive the reboiler, and relies on external steam, which has high operation cost. Therefore, how to efficiently recover the residual heat in the synthesis gas and reasonably apply it to the methanol rectification process has become a key problem to improve the economic and environmental performance of methanol production. SUMMARY

[0004] The purpose of the present application is to provide a process method of heat coupling of methanol synthesis and rectification to solve the problems of low heat recovery rate in the synthesis gas cooling process, the reboiler of the rectification system relying on external steam, and high operation cost, and to realize energy cascade utilization.

[0005] To achieve the above purpose, the present application provides a process method of heat coupling of methanol synthesis and rectification. The synthesis gas after heat exchange by a heat exchanger enters a gas-liquid separation tank for gas-liquid separation, the gas phase enters a pressurized tower reboiler for heat exchange to release heat Q1, and the liquid phase is sent to a pre-tower. After heat exchange, the synthesis gas is separated by a gas-liquid separation tank, the gas phase enters an atmospheric tower reboiler for heat exchange to release heat Q2, and the liquid phase is sent to a pre-tower. Wherein, the heat Q1 is transferred to the atmospheric tower heat integrated reboiler to act on the material in the atmospheric tower, and the heat Q2 acts on the material in the atmospheric tower through the atmospheric tower reboiler, and the sum of the heat Q1 and the heat Q2 is the total heat provided by the synthesis gas.

[0006] Preferably, the initial temperature of the synthesis gas is 124℃, and the final temperature is 85℃.

[0007] Preferably, the total heat Q is 19000KW.

[0008] Preferably, the liquid phase is sent to the pre-column via a liquid phase storage tank.

[0009] Preferably, the process comprises the following steps:

[0010] S1, the synthesis gas is heated by the heat exchanger and then enters the first gas-liquid separation tank for gas-liquid separation, the gas phase enters the pressurized column reboiler for heat exchange to release heat Q1, the temperature is preliminarily reduced, and the liquid phase is sent to the pre-column via the first liquid phase storage tank; the heat Q1 is used to heat the materials in the pressurized column, and the heat is also used to heat the materials in the atmospheric column via the atmospheric column heat integration reboiler;

[0011] S2, the synthesis gas after heat exchange in the pressurized column reboiler is discharged from the pressurized column reboiler and then enters the second gas-liquid separation tank for gas-liquid separation, the gas phase enters the atmospheric column reboiler for heat exchange to release heat Q2 for heating the materials in the atmospheric column, and the temperature is further reduced, and the liquid phase is sent to the pre-column via the first liquid phase storage tank;

[0012] S3, the synthesis gas after heat exchange in the atmospheric column reboiler is discharged and then enters the third gas-liquid separation tank for gas-liquid separation, the gas phase enters the circulating water cooler, and the liquid phase is sent to the pre-column via the second liquid phase storage tank.

[0013] Therefore, the process method for synthesizing and distilling methanol in a heat coupling manner has the following beneficial effects:

[0014] (1) The synthesis gas waste heat is coupled with the pressurized column and the atmospheric column of the distillation system, the heat Q1 is used for the first time in the pressurized column and then transferred to the atmospheric column reboiler for secondary use, the energy utilization efficiency is significantly improved, and the energy consumption and efficiency of the entire methanol production process are reduced.

[0015] (2) The gas-liquid separation tank is added at the key node to realize accurate separation and directional transportation of the gas-liquid materials, and ensure efficient heat exchange and reasonable circulation of the materials.

[0016] (3) The waste heat is efficiently recovered, the consumption of fossil energy such as steam is reduced, the emission of pollutants such as carbon dioxide and sulfur dioxide is reduced, and the environmental protection performance is improved.

[0017] The technical solutions of the present application are described in further detail below by means of the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The figure is a flowchart of the process method for synthesizing and distilling methanol in a heat coupling manner.

[0019] Reference signs:

[0020] 1, first gas-liquid separation tank; 2, pressurized column reboiler; 3, pressurized column; 4, second gas-liquid separation tank; 5, first liquid phase storage tank; 6, atmospheric column reboiler; 7, atmospheric column heat integration reboiler; 8, third gas-liquid separation tank; 9, second liquid phase storage tank; 10, atmospheric column. DETAILED DESCRIPTION

[0021] The technical solutions of the present application are further described below by means of the accompanying drawings and examples. It should be understood that these examples are only used to illustrate the present application and are not used to limit the scope of the present application, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods and are included in the protection scope of the present application. In addition, it should be understood that after reading the content of the present application, those skilled in the art can make various modifications or modifications to the present application, and these equivalent forms also fall within the scope defined by the claims attached to the present application and are within the protection scope of the present application.

[0022] In this paper, the term "embodiment" means that the specific features, structures or characteristics described in conjunction with the embodiment can be included in at least one embodiment of the present application. The term "embodiment" appearing at various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the technical features mentioned in each embodiment can be combined in any way to form a corresponding implementable technical solution.

[0023] Unless otherwise defined, the meaning of the technical terms used herein is the same as that generally understood by those skilled in the art to which the present application belongs; the use of related terms herein is only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0024] Unless otherwise specified, the reagents, instruments, equipment and performance test methods used in the present application are the reagents, instruments, equipment and methods commonly used by those skilled in the art.

[0025] The process modification needs to replace part of the atmospheric column internals, and additionally needs to increase two reboilers and auxiliary equipment such as supporting gas-liquid separation tanks, pipelines, valves and control instruments, and the calculation shows that the new pressure drop of synthesis gas is about 26 kpa.

[0026] EMBODIMENT

[0027] As Figure 1As shown, this embodiment provides a process for thermally coupled methanol synthesis and distillation. After heat exchange in heat exchanger E-3301, the synthesis gas enters the first gas-liquid separation tank 1 for gas-liquid separation. This separation principle is based on the gas-liquid density difference and fluid dynamics, ensuring efficient separation of the gas and liquid phases. The separated gas phase, carrying a high level of heat, enters the pressurized tower reboiler 2 for heat exchange, initially reducing its temperature from 124°C to 109°C, releasing heat Q1. The liquid phase is then steadily transported to the pre-tower via the first liquid phase storage tank 5, providing the pre-tower with material to be processed.

[0028] The gas phase at the separation point exchanges heat with the material in the pressurized tower 3 in the pressurized tower reboiler 2. The released heat Q1, on the one hand, heats the material in the pressurized tower 3, drives the distillation process in the pressurized tower 3, and causes the light components (such as methanol) in the material to evaporate upward, while the heavy components remain at the bottom of the tower; on the other hand, the heat Q1 is transferred to the atmospheric tower 10 through the existing atmospheric tower heat integration reboiler 7, realizing the coupled utilization of heat between the pressurized tower 3 and the atmospheric tower 10, and reducing the demand for external steam by the atmospheric tower 10.

[0029] After heat exchange in the pressure tower reboiler 2, the synthesis gas enters the second gas-liquid separator 4 for further separation. The separated gas phase enters the atmospheric tower reboiler 6, where its temperature is further reduced to 85°C. The released heat Q2 directly heats the materials in the atmospheric tower 10. Under the combined action of heat Q1 and Q2 (19,000 kW), the materials in the atmospheric tower 10 undergo deep distillation, and low-boiling-point components such as methanol are gradually enriched at the top of the tower. The separated liquid phase is then sent back to the pre-tower via the first liquid phase storage tank 5, achieving material recycling.

[0030] After heat exchange in the atmospheric tower reboiler 6, the synthesis gas enters the third gas-liquid separator 8 for the final gas-liquid separation. Having released significant heat, the gas phase enters the circulating water cooler E-3302 for further cooling. The liquid phase is then sent to the pre-column via the second liquid phase storage tank 9. At this point, the methanol vapor accumulated at the top of the atmospheric tower 10 is condensed to produce crude methanol, which is then refined through subsequent refining (such as adsorption and fine distillation) to produce the refined methanol product.

[0031] Therefore, the thermally coupled methanol synthesis and distillation process provided by this invention effectively addresses the energy waste and high cost issues of traditional processes through the cascaded utilization of syngas waste heat and heat integration with the distillation system. This process achieves efficient energy conversion, reduces production energy consumption and operating costs, improves product quality and process stability, and offers significant environmental benefits, providing a new technical path for the greener and more efficient development of methanol production.

[0032] It should be pointed out finally that the above examples are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can still be modified or replaced equivalently, and these modifications or equivalent replacements should not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A process for thermally coupling methanol synthesis and distillation, characterized by: After heat exchange in the heat exchanger, the synthesis gas enters the gas-liquid separation tank for gas-liquid separation, the gas phase enters the pressure tower reboiler for heat exchange to release heat Q1, and the liquid phase is sent to the pre-tower. After the heat exchange, the synthesis gas enters the gas-liquid separation tank for gas-liquid separation, the gas phase enters the atmospheric tower reboiler for heat exchange to release heat Q2, and the liquid phase is sent to the pre-tower; among them, the heat Q1 is transferred to the atmospheric tower heat integration reboiler through the pressure tower to act on the material in the atmospheric tower. At the same time, the heat Q2 acts on the material in the atmospheric tower through the atmospheric tower reboiler. The sum Q of the heat Q1 and the heat Q2 is the total heat provided by the synthesis gas.

2. The process for thermally coupling methanol synthesis and distillation according to claim 1, characterized in that: The initial temperature of the synthesis gas was 124°C and the final temperature was 85°C.

3. The process for thermally coupling methanol synthesis and distillation according to claim 1, characterized in that: The total heat Q is 19000KW.

4. The process for thermally coupling methanol synthesis and distillation according to claim 1, characterized in that: The liquid phase is sent to the pre-tower through the liquid phase storage tank.

5. A process for thermally coupling methanol synthesis and distillation according to any one of claims 1 to 4, characterized in that: The specific steps include: S1, after heat exchange in the heat exchanger, the synthesis gas enters the first gas-liquid separation tank for gas-liquid separation. The gas phase enters the pressure tower reboiler for heat exchange to release heat Q1, and the temperature is initially reduced. At the same time, the liquid phase is sent to the pre-tower through the first liquid phase storage tank; the heat Q1 is used to heat the material in the pressure tower, and at the same time acts on the material in the atmospheric tower through the atmospheric tower heat integration reboiler; S2, the synthesis gas after heat exchange in the pressure tower reboiler is discharged from the pressure tower reboiler and enters the second gas-liquid separation tank for gas-liquid separation. The gas phase enters the atmospheric tower reboiler for heat exchange, and the heat Q2 released is used to heat the material in the atmospheric tower, and the temperature is further reduced. At the same time, the liquid phase is sent to the pre-tower through the first liquid phase storage tank; S3. The synthesis gas after heat exchange in the atmospheric pressure tower reboiler is discharged and enters the third gas-liquid separation tank for gas-liquid separation. The gas phase enters the circulating water cooler, and the liquid phase is sent to the pre-tower through the second liquid phase storage tank.

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