Low-temperature methanol washing gas purification system

Abstract

The utility model provides a low-temperature methanol washing gas purification system, which comprises a shift gas washing tower, a shift gas decarburization tower, a shift gas decarburization tower, a shift gas decarburization tower, a shift gas decarburization tower and a shift gas decarburization tower, and is characterized in that the shift gas decarburization tower is provided with a shift gas inlet, a shift gas decarburization section methanol outlet and a shift gas decarburization section methanol inlet; the unconverted gas washing tower is provided with an unconverted gas desulfurization section and an unconverted gas decarbonization section, and the unconverted gas desulfurization section is provided with an unconverted gas inlet and an unconverted gas desulfurization section methanol outlet; an inlet of the first pump is connected with a methanol outlet of the unconverted gas desulfurization section through a first pipeline; the first branch pipeline is connected with an outlet of the first pump and a methanol inlet of the shift gas desulfurization section; the second branch pipeline is connected with the outlet of the first pump and a pipeline at the downstream of the methanol outlet of the shift gas desulfurization section; and the flow regulating valve is arranged on the first branch pipeline. By optimizing the conveying path of sulfur-containing methanol among different washing towers, the risk that the content of carbon monoxide in the outlet gas of the shift gas washing tower exceeds the standard is reduced.

Description

Technical Field

[0001] This utility model relates to a gas purification system, specifically a low-temperature methanol washing gas purification system, and belongs to the field of gas purification technology. Background Technology

[0002] Low-temperature methanol washing technology is a commonly used gas purification method in chemical production to remove acidic gas components such as hydrogen sulfide (H2S) and carbon dioxide (CO2) from raw material gases, providing qualified raw material gases for subsequent processes. In this process, a washing tower is typically installed, using methanol as an absorbent to contact the raw material gas under low-temperature and high-pressure conditions, achieving selective absorption of acidic gases.

[0003] A typical low-temperature methanol washing unit may include washing towers that wash gases from different sources or with different compositions (such as shifted gas and unshifted gas). For example, both the shifted gas washing tower and the unshifted gas washing tower may contain desulfurization and decarbonization sections. In the unshifted gas washing tower, after the lean methanol absorbent removes acidic gases, the acidic gas content in the feed gas may be low, resulting in the sulfur-containing methanol discharged from the bottom of the desulfurization section not reaching saturation absorption. If this unsaturated methanol directly enters the regeneration system, it will increase regeneration energy consumption.

[0004] In existing technologies, sulfur-containing methanol discharged from the bottom of the desulfurization section of the un-shifted gas scrubber is sometimes pumped to the middle of the desulfurization section of the shifted gas scrubber for further absorption, in order to improve the utilization rate and saturation of methanol. However, in actual operation, due to differences in gas composition and operating conditions between the two towers, such as differences in carbon monoxide partial pressure, directly sending this sulfur-containing methanol into the middle of the desulfurization section of the shifted gas scrubber may cause the dissolved carbon monoxide to be desorbed by gas stripping due to the decrease in partial pressure within the shifted gas scrubber, resulting in excessive carbon monoxide content in the shifted purified gas discharged from the top of the shifted gas scrubber. Utility Model Content

[0005] Based on the above background, the purpose of this utility model is to provide a low-temperature methanol washing gas purification system, which reduces the risk of excessive carbon monoxide content in the outlet gas of the shift gas washing tower by optimizing the transport path of sulfur-containing methanol between different washing towers.

[0006] To achieve the above-mentioned objectives, this utility model provides the following technical solution:

[0007] A low-temperature methanol washing gas purification system, comprising:

[0008] A shift gas scrubbing tower has at least one shift gas desulfurization section and at least one shift gas decarbonization section. The shift gas desulfurization section is provided with a shift gas inlet, a shift gas desulfurization section methanol outlet and a shift gas desulfurization section methanol inlet. The top of the shift gas scrubbing tower is provided with a shift purified gas outlet.

[0009] An unconverted gas scrubbing tower, the unconverted gas scrubbing tower having at least one unconverted gas desulfurization section and at least one unconverted gas decarbonization section, the unconverted gas desulfurization section having an unconverted gas inlet and an unconverted gas desulfurization section methanol outlet;

[0010] The first pump, the inlet of which is connected to the methanol outlet of the unconverted gas desulfurization section via a first pipeline;

[0011] The first branch pipeline connects the outlet of the first pump to the methanol inlet of the shift gas desulfurization section;

[0012] The second branch pipeline connects the outlet of the first pump to the pipeline downstream of the methanol outlet of the shift gas desulfurization section.

[0013] A flow regulating valve is installed on the first branch pipeline.

[0014] By adding a parallel second branch pipeline to the existing pipeline that transports sulfur-containing methanol from the bottom of the unshifted gas scrubber to the desulfurization section of the shifted gas scrubber, a portion of the sulfur-containing methanol is directly merged into the bottom outlet methanol pipeline of the desulfurization section. Simultaneously, a flow regulating valve is installed on the existing methanol inlet (first branch pipeline) leading to the desulfurization section. This structure allows the sulfur-containing methanol pumped out from the first pump to be divided into two streams: one stream, with its flow controlled by the flow regulating valve, enters the methanol inlet of the desulfurization section of the shifted gas scrubber for further washing and absorption to increase its saturation; the other stream merges directly with the methanol discharged from the bottom of the desulfurization section through the second branch pipeline. By adjusting the flow distribution of these two methanol streams, particularly reducing the amount of unsaturated sulfur-containing methanol directly entering the middle of the desulfurization section for washing, the amount of CO desorbed due to changes in CO partial pressure can be reduced, thereby helping to lower the CO content in the purified gas at the top outlet of the shifted gas scrubber.

[0015] Preferably, the first branch pipeline and the second branch pipeline are connected to the outlet of the first pump via a tee fitting.

[0016] Preferably, the methanol inlet of the shift gas desulfurization section is located in the upper middle part of the section. This design allows the methanol to have sufficient countercurrent contact with the rising gas.

[0017] Preferably, the shift gas desulfurization section is located at the bottom of the shift gas scrubbing tower.

[0018] Preferably, the unconverted gas desulfurization section is located at the bottom of the unconverted gas scrubbing tower.

[0019] Preferably, the low-temperature methanol washing gas purification system further includes a second pump, the inlet of which is connected to the methanol outlet of the unconverted gas decarbonization section via a second pipeline, and the outlet of which is connected to the methanol inlet of the convertible gas decarbonization section via a third pipeline.

[0020] Preferably, the methanol outlet of the shift gas desulfurization section is located at the bottom of the shift gas desulfurization section.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] This utility model discloses a low-temperature methanol washing gas purification system. By adding a second branch pipeline containing sulfur-containing methanol, a portion of the unsaturated sulfur-containing methanol is directly introduced into the outlet pipeline of the desulfurization section of the shift gas scrubbing tower. This reduces the amount of methanol that directly contacts the gas inside the desulfurization section of the shift gas scrubbing tower, thereby effectively reducing the phenomenon of excessive CO desorption due to the decrease in CO partial pressure. This helps to ensure that the carbon monoxide content in the purified shift gas at the outlet of the shift gas scrubbing tower meets the standards. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a low-temperature methanol washing gas purification system according to this utility model;

[0025] In the diagram: 1. Shift gas scrubbing tower; 2. Unshift gas scrubbing tower; 3. First pump; 4. Second pump; 5. First branch pipeline; 6. Second branch pipeline; 7. Flow regulating valve; 8. First pipeline; 9. Second pipeline; 10. Third pipeline; 101. Shift gas desulfurization section; 102. Shift gas decarbonization section; 103. Shift gas inlet; 104. Shift gas desulfurization section methanol outlet; 105. Shift gas desulfurization section methanol inlet; 106. Shift gas purified gas outlet; 107. Shift gas decarbonization section methanol inlet; 201. Unshift gas desulfurization section; 202. Unshift gas decarbonization section; 203. Unshift gas inlet; 204. Unshift gas desulfurization section methanol outlet; 205. Unshift gas purified gas outlet; 206. Unshift gas decarbonization section methanol outlet. Detailed Implementation

[0026] The technical solution of this utility model will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of this utility model is not limited to the following embodiments, and any modifications and / or alterations made to this utility model will fall within the protection scope of this utility model.

[0027] In this invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the field. Unless otherwise specified, the methods in the following embodiments are conventional methods in the field. Unless otherwise specified, the components or equipment in the following embodiments are general standard parts or components known to those skilled in the art, and their structures and principles can be learned by those skilled in the art through technical manuals or conventional experimental methods.

[0028] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following detailed description, many specific details are set forth to facilitate explanation and provide a comprehensive understanding of the embodiments of the present invention. However, one or more embodiments may be practiced by those skilled in the art without these specific details.

[0029] An embodiment of this utility model discloses a low-temperature methanol washing gas purification system, including a shift gas scrubbing tower 1, an unshifted gas scrubbing tower 2, a first pump 3, a first branch pipeline 5, a second branch pipeline 6, and a flow regulating valve 7.

[0030] The shift gas scrubbing tower 1 has at least one shift gas desulfurization section 101 and at least one shift gas decarbonization section 102. The shift gas desulfurization section 101 is provided with a shift gas inlet 103, a shift gas desulfurization section methanol outlet 104 and a shift gas desulfurization section methanol inlet 105, and the top of the shift gas scrubbing tower 1 is provided with a shift purified gas outlet 106.

[0031] The shift gas inlet 103 is used to introduce the shift gas to be purified. The methanol outlet 104 of the shift gas desulfurization section is located at the bottom of the shift gas desulfurization section 101 and is used to discharge the methanol that has absorbed sulfides. The methanol inlet 105 of the shift gas desulfurization section is located in the upper part of the shift gas desulfurization section 101 and is used to introduce washing methanol. The purified shift gas outlet 106 is used to send out the purified shift gas.

[0032] The unconverted gas scrubbing tower 2 has at least one unconverted gas desulfurization section 201 and at least one unconverted gas decarbonization section 202. The unconverted gas desulfurization section 201 is provided with an unconverted gas inlet 203 and a methanol outlet 204. The unconverted gas inlet 203 is used to introduce the unconverted gas to be purified. The methanol outlet 204 is located at the bottom of the unconverted gas desulfurization section 201 and is used to discharge methanol that has absorbed sulfides. The unconverted gas scrubbing tower 2 also has an unconverted purified gas outlet 205 at the top.

[0033] The inlet of the first pump 3 is connected to the methanol outlet 204 of the unconverted gas desulfurization section via the first pipeline 8. The first pump 3 is used to pump sulfur-containing methanol discharged from the bottom of the desulfurization section of the tower.

[0034] After exiting the first pump 3, the pipeline splits into a first branch pipeline 5 and a second branch pipeline 6 via a tee connector. A flow regulating valve 7 is installed on the first branch pipeline 5. This first branch pipeline 5, after the flow regulating valve 7, connects to the methanol inlet 105 of the desulfurization section of the shift gas scrubbing tower 1. This methanol is used to scrub the shift gas within the desulfurization section of the shift gas scrubbing tower 1. The second branch pipeline 6 connects directly to the pipeline downstream of the methanol outlet 104 of the shift gas desulfurization section. In other words, this portion of sulfur-containing methanol exiting the first pump 3 does not enter the shift gas scrubbing tower 1 for scrubbing; instead, it directly merges with the sulfur-containing methanol discharged from the bottom of the desulfurization section of the shift gas scrubbing tower 1, and then they are both sent to the subsequent methanol regeneration system.

[0035] In shift gas scrubbing tower 1, the shift gas desulfurization section 101 is the bottom section of the tower, with the methanol outlet 104 located at its bottom and the methanol inlet 105 located in the upper middle part of the shift gas desulfurization section 101. Similarly, the desulfurization section of the unshifted gas scrubbing tower 2 is also the bottom section of the tower.

[0036] The system also includes a second pump 4, the inlet of which is connected to the methanol outlet 206 of the unconverted gas decarbonization section via a second pipeline 9, and the outlet of the second pump 4 is connected to the methanol inlet 107 of the converted gas decarbonization section via a third pipeline 10 for conveying semi-lean methanol, which is added from the top of the tower to the top of the decarbonization section of each scrubbing tower.

[0037] With the above system structure, during operation, the flow rate of sulfur-containing methanol from the bottom of the un-shifted gas scrubber 2, which enters the desulfurization section of the shifted gas scrubber 1 for washing, can be controlled by adjusting the flow regulating valve 7 on the first branch pipe 5 according to actual working conditions. Since this methanol absorbs high-pressure carbon monoxide in the un-shifted gas scrubber 2, if all or a large amount enters the middle of the desulfurization section of the shifted gas scrubber 1, where the carbon monoxide partial pressure is lower, it will lead to carbon monoxide desorption. This invention allows a portion of this sulfur-containing methanol to be bypassed through the second branch pipe 6, preventing it from participating in the internal washing of the desulfurization section of the shifted gas scrubber 1, thereby reducing the amount of CO desorption and helping to control the CO content at the outlet 106 of the shifted purified gas. Simultaneously, the portion of sulfur-containing methanol entering the first branch pipe 5 through the flow regulating valve 7, which may still be unsaturated, can continue to absorb acidic gases in the desulfurization section of the shifted gas scrubber 1, increasing its saturation, which helps reduce energy consumption in the subsequent regeneration section and stabilizes the cooling generated during desorption.

[0038] This article uses specific examples to illustrate the principles and implementation methods of this utility model. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made to this utility model without departing from the principles of this utility model, and these improvements and modifications also fall within the protection scope of the claims of this utility model.

Claims

1. A low temperature methanol wash gas purification system, characterized by: The low-temperature methanol washing gas purification system comprises: a shift gas washing tower (1) having at least one shift gas desulfurization section (101) and at least one shift gas decarburization section (102), the shift gas desulfurization section (101) being provided with a shift gas inlet (103), a shift gas desulfurization section methanol outlet (104) and a shift gas desulfurization section methanol inlet (105), and the shift gas washing tower (1) being provided at the top with a shift gas purification outlet (106); an unshifted gas washing tower (2) having at least one unshifted gas desulfurization section (201) and at least one unshifted gas decarburization section (202), the unshifted gas desulfurization section (201) being provided with an unshifted gas inlet (203) and an unshifted gas desulfurization section methanol outlet (204); a first pump (3) having an inlet connected to the unshifted gas desulfurization section methanol outlet (204) through a first pipeline (8); a first branch pipeline (5) connecting an outlet of the first pump (3) and the shift gas desulfurization section methanol inlet (105); a second branch pipeline (6) connecting the outlet of the first pump (3) and a pipeline downstream of the shift gas desulfurization section methanol outlet (104); a flow regulating valve (7) arranged on the first branch pipeline (5).

2. The rectisol gas purification system of claim 1, wherein: The first branch pipeline (5) and the second branch pipeline (6) are connected to the outlet of the first pump (3) through a tee joint.

3. The low temperature methanol wash gas purification system of claim 1, wherein: The shift gas desulfurization section methanol inlet (105) is located in the middle upper part of the shift gas desulfurization section (101).

4. The rectisol gas purification system of claim 1, wherein: The shift gas desulfurization section (101) is located in the lowermost section of the shift gas washing tower (1).

5. The low temperature methanol wash gas purification system of claim 1, wherein: The unshifted gas desulfurization section (201) is located in the lowermost section of the unshifted gas washing tower (2).

6. The rectisol gas purification system of claim 1, wherein: The low-temperature methanol washing gas purification system further comprises a second pump (4) having an inlet connected to the unshifted gas decarburization section methanol outlet (206) through a second pipeline (9), and an outlet connected to the shift gas decarburization section methanol inlet (107) through a third pipeline (10).

7. The rectisol gas purification system of claim 1, wherein: The shift gas desulfurization section methanol outlet (104) is located at the bottom of the shift gas desulfurization section (101).

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