Aftertreatment process and system for purified tail gas of synthetic ammonia

Abstract

According to the process, tail gas to be treated is washed with soft water to remove methanol, then water and impurities are removed through adsorption, and methanol is recovered from the washed soft water through separation. In the invention, the carbon dioxide gas meets the production requirement of ammonium bicarbonate after being purified; trace methanol in carbon dioxide gas is recycled, resources are saved, the integrated treatment tower is adopted for washing and adsorption, the integration level is higher, the occupied area is smaller, and filler replacement is more facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical waste gas treatment, and in particular relates to a post-treatment process and system for synthetic ammonia purification tail gas. Background Art

[0002] The raw gas purification section of synthetic ammonia will remove a large amount of acidic gases such as CO2 and H2S. The purified gas is sent to the ammonia synthesis reaction, and the waste gas CO2 is exactly what the ammonium bicarbonate unit needs.

[0003] A low-temperature methanol washing device can be used to remove acidic gases such as CO2 and H2S, but the carbon dioxide in the tail gas of the low-temperature methanol washing device contains impurities such as methanol, which has a great impact on the quality of the ammonium bicarbonate product and cannot meet the quality and process requirements of the ammonium bicarbonate product. Summary of the invention

[0004] In view of the above technical problems, this application proposes a post-treatment process and system for purifying tail gas with synthetic ammonia. The specific technical solution is as follows:

[0005] On one hand, the present application provides a post-treatment process for tail gas purification by synthetic ammonia, in which the tail gas to be treated is washed with soft water to remove methanol, and then adsorbed to remove water and impurities, and the soft water from the washing is separated to recover methanol.

[0006] Furthermore, the tail gas to be treated contacts the soft water in a convection manner.

[0007] On the other hand, the present application provides a system for post-processing tail gas purified by synthetic ammonia, the system using the above-mentioned post-processing process for purifying tail gas by synthetic ammonia, the system comprising a washing tower, a compressor, an adsorption tower and a moisture separation tower, soft water is introduced into and sprayed at the top of the washing tower, the tail gas to be treated is introduced into the bottom of the washing tower and discharged from the top, the input end of the compressor is connected to the top of the washing tower, the output end of the compressor is connected to the bottom of the adsorption tower, and the bottom of the washing tower is connected to the moisture separation tower.

[0008] On the other hand, the present application provides a second synthetic ammonia purification tail gas post-treatment system, the system comprising an integrated treatment tower and a moisture separation tower, the integrated treatment tower comprising a tower body and a gas input interface, a waste liquid discharge interface, a washing liquid input interface, and a gas discharge interface arranged on the tower body, and the gas discharge interface, the washing liquid input interface, the gas input interface, and the waste liquid discharge interface are arranged in descending order, and the waste liquid discharge interface is connected to the moisture separation tower;

[0009] The tower body comprises a washing section and an adsorption section, wherein the adsorption section is arranged above the washing section, the washing section and the adsorption section are communicated, the gas input interface is arranged in the washing section, and the gas discharge interface is arranged in the adsorption section.

[0010] Furthermore, a cylindrical shell is provided at the upper part of the tower body, a gap is provided between the cylindrical shell and the inner wall of the tower body, the gap is filled with filler, the cylindrical shell is closed at the top and open at the bottom, a closing plate folded and extended outward is provided at the edge of the bottom opening of the cylindrical shell, the closing plate is sealed and connected to the inner wall of the tower body, and a notch is provided at the connection between the closing plate and the cylindrical shell;

[0011] The tower body below the closing plate is the washing section, and the area enclosed by the closing plate, the tower body and the cylindrical shell is the adsorption section.

[0012] Furthermore, the adsorption section is provided with a packing frame and a packing filled in the packing frame, the packing frame comprises an inner cylinder, an outer cylinder and a connecting plate, the inner cylinder and the outer cylinder are arranged at intervals and connected by the connecting plate, and the connecting plate has a through hole;

[0013] During operation, the filler frame is suspended and fixed in the gap to separate the connecting plate from the closing plate.

[0014] Furthermore, the tower body is also provided with a second gap and a third gap, wherein the second gap is provided at the bottom of the adsorption section, and a first enclosure is provided outside the second gap, and the third gap is provided at the top of the adsorption section, and a second enclosure is provided outside the third gap, and a fourth gap is provided on the outer cylinder of the packing frame;

[0015] When the filler is replaced, the filler frame sinks to make the connecting plate fit with the closing plate, and the fourth gap is exposed through the second gap.

[0016] Furthermore, the inner cylinder is kept in close contact with the cylindrical shell.

[0017] Furthermore, the connecting plate and the closing plate are both conical surfaces.

[0018] Furthermore, a spray plate is arranged in the tower body, the spray plate is spaced apart from the top of the cylindrical shell, a filling body is arranged between the spray plate and the cylindrical shell, and the filling body is a filler or a lightweight closed body.

[0019] The beneficial effects of the present invention are:

[0020] (1) After carbon dioxide gas is purified, it meets the production requirements of ammonium bicarbonate;

[0021] (2) Trace amounts of methanol in carbon dioxide gas are recovered, saving resources;

[0022] (3) An integrated treatment tower is used for washing and adsorption, which has a higher degree of integration, occupies a smaller area, and is more convenient for replacing fillers. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Shown is a schematic diagram of the processing system in Example 1;

[0024] Figure 2 Shown is a schematic diagram of the processing system in Example 2;

[0025] Figure 3 Shown is a schematic diagram of the structure of the integrated treatment tower in Example 2;

[0026] Figure 4 What is shown is the structural schematic diagram of the tower body in Example 2;

[0027] Figure 5 Shown is a schematic diagram of the structure of the packing frame in Example 2;

[0028] Figure 6 The schematic diagram of the state of gas processing by the integrated processing tower in Example 2 is shown;

[0029] Figure 7 Shown is a schematic diagram of the structure of the filler in Example 2. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments.

[0031] Example 1

[0032] Figure 1 What is shown is a schematic diagram of the treatment system of the present application, which includes a washing tower 100, a compressor 200, an adsorption tower 300 and a moisture separation tower 400, wherein the bottom of the washing tower 100 is introduced into the exhaust gas to be treated, and the exhaust gas to be treated mainly contains carbon dioxide, methanol, etc., and soft water is introduced into the top of the washing tower 100 and forms convection with the exhaust gas to be treated through spraying, so that the methanol in the exhaust gas to be treated is washed and removed, and the carbon dioxide is discharged from the top of the washing tower 100; the discharged carbon dioxide is pressurized by the compressor 200 and then passes through the adsorption tower 300 to adsorb water and other impurities and then is sent to the ammonium bicarbonate section to produce ammonium bicarbonate, and the carbon dioxide is introduced from the bottom of the adsorption tower 300 and discharged from the top; the washing water in the washing tower 100 is transported to the moisture separation tower 400 to recover methanol, and the recovered methanol vapor is discharged from the top of the moisture separation tower 400, and the sewage is discharged from the bottom and transported to the terminal sewage treatment section.

[0033] Example 2

[0034] Figure 2Shown is a schematic diagram of another treatment system of the present application, which includes an integrated treatment tower 500 and a moisture separation tower 400, wherein the bottom of the integrated treatment tower 500 is introduced into the exhaust gas to be treated, and the exhaust gas to be treated mainly contains carbon dioxide, methanol, etc., and soft water is introduced into the top of the integrated treatment tower 500 and forms convection with the exhaust gas to be treated through spraying, so as to wash and remove the methanol in the exhaust gas to be treated, and at the same time, the purified carbon dioxide is discharged from the top after dehydration and impurity removal above the integrated treatment tower 500, and the discharged carbon dioxide is sent to the ammonium bicarbonate section to produce ammonium bicarbonate; the washing water in the integrated treatment tower 500 is transported to the moisture separation tower 400 to recover methanol, and the recovered methanol vapor is discharged from the top of the moisture separation tower 400, and the sewage is discharged from the bottom and transported to the terminal sewage treatment section.

[0035] Figure 3 Shown is a schematic diagram of the structure of an integrated processing tower 500, which includes a tower body 510 and a plurality of interfaces arranged on the tower body 510, wherein the interfaces include a gas input interface 511, a waste liquid discharge interface 512, a washing liquid input interface 513, and a gas discharge interface 514.

[0036] The position settings of the above-mentioned interfaces on the tower body 510 should satisfy the requirements that the gas exhaust interface 514, the washing liquid input interface 513, the gas input interface 511 and the waste liquid exhaust interface 512 are arranged in sequence from high to low, so as to achieve the purpose that the tail gas to be treated is transported from the gas input interface 511 to the tower body 510, and after convection is formed with the washing liquid input from the top through the washing liquid input interface 513, the purified gas is discharged from the gas exhaust interface 514, and the washed waste liquid is discharged from the waste liquid exhaust interface 512.

[0037] Figure 4 The structure diagram of the tower body 510 is shown to more clearly illustrate the internal state. Figure 4 The tower body 510 is partially cut away, and the tower body 510 includes a washing section 510a and an adsorption section 510b, wherein the adsorption section 510b is arranged above the washing section 510a, and a cylindrical shell 521 is arranged on the upper part of the tower body 510, and a gap 522 is provided between the cylindrical shell 521 and the inner wall of the tower body 510, and the cylindrical shell 521 is closed at the top and open at the bottom, and a closing plate 523 folded and extended outward is arranged on the edge of the bottom opening of the cylindrical shell 521, and the closing plate 523 is sealed and connected to the inner wall of the tower body 510, thereby forming the aforementioned washing section 510a and adsorption section 510b: the part of the tower body 510 below the closing plate 523 is the washing section 510a, and the area enclosed by the closing plate 523, the tower body 510 and the cylindrical shell 521 is the adsorption section 510b.

[0038] See also Figure 4A spray plate 524 is provided in the tower body 510 . The spray plate 524 is connected to the spray plate 524 after the pipeline of the washing liquid input interface 513 extends into the tower body 510 . Soft water for washing is transported to the spray plate 524 through the washing liquid input interface 513 .

[0039] In addition, a plurality of gaps 525 are provided at the connection between the closing plate 523 and the cylindrical shell 521, and the gaps 522 are filled with fillers required for adsorption. The gaps 525 are provided to allow the gas after soft water washing to enter the adsorption section 510b for further removal of moisture, impurities, etc., that is, the washing section 510a and the adsorption section 510b are connected through the gaps 525.

[0040] An air guide hood 526 is provided on the top of the tower body 510 , and the air guide hood 526 is used to close the tower body 510 and form a gas exhaust interface 514 , so that the gas in the washing section 510a escapes upward and enters the air guide hood 526 and is discharged from the gas exhaust interface 514 .

[0041] For better exhaust, the air guide cover 526 is configured to be an inverted funnel shape, and a bracket 527 is provided on the inner side of the air guide cover 526 and connected to the cylindrical shell 521 to improve the connection strength and stability of the air guide cover 526.

[0042] Figure 5 The figure shows a schematic diagram of the structure of a packing rack 530, which is used to place packing 540. The packing rack 530 includes an inner cylinder 531, an outer cylinder 532 and a connecting plate 533. The inner cylinder 531 and the outer cylinder 532 are arranged at intervals and connected by the connecting plate 533. The connecting plate 533 has a through hole, and the space between the inner cylinder 531 and the outer cylinder is used to place the stacked packing 540.

[0043] Figure 6 The figure shows a schematic diagram of the state of gas treatment by the integrated treatment tower 500. The soft water for washing is input through the washing liquid input interface 513 along the direction of the dotted arrow N, and falls after being sprayed out by the spray plate 524. The gas to be treated is input through the gas input interface 511 along the direction of the solid arrow M, and after convection with the soft water for washing in the washing section 510a, it enters the gap 522 at the notch 1 525, and enters the air guide cover 526 after being dehydrated and impurities are removed through the filler 540 filled in the gap 522, and is finally discharged through the gas discharge interface 514.

[0044] During operation, the filler rack 530 is placed in the gap 522 and fixed in suspension to ensure that the connecting plate 533 and the closing plate 523 are separated, so that the gas entering through the gap 525 can enter the filler rack 530 through the through holes on the connecting plate 533 and contact the filler 540.

[0045] See also Figure 3 and Figure 4A second notch 515 is also provided on the tower body 510. The second notch 515 is provided above the closing plate 523, that is, at the bottom of the adsorption section 510b. A first enclosure 516 is provided outside the second notch 515. The first enclosure 516 is used to close the second notch 515 in the working state. The first enclosure 516 is disassembled and connected by bolts.

[0046] The tower body 510 is also provided with a gap three 517, which is located at the top of the adsorption section 510b. A second enclosure 518 is provided outside the gap three 517. The same enclosure 518 is used to close the gap three 517 in the working state. The enclosure 518 is disassembled and connected by bolts.

[0047] In combination with the above records, when not in operation, enclosure plate 1 516 and enclosure plate 2 518 are removed to expose gap 2 515 and gap 3 517, and at the same time, the filling rack 530 is lowered. A gap 4 534 is provided on the outer tube 532 of the filling rack 530, so that gap 4 534 is exposed through gap 2 515. In this state, the filling 540 at the bottom of the filling rack 530 can be directly pulled out, and new filling 540 can be added to the top of the filling rack 530 through gap 3 517.

[0048] The integrated treatment tower 500 in this embodiment is different from the washing tower 100 and the adsorption tower 300 used separately in Embodiment 1 in that:

[0049] (1) The equipment has a higher degree of integration and occupies a smaller area: The washing tower 100 and the adsorption tower 300 need to be separately set up and equipped with pipes and other structures, which is more complicated and needs to occupy different spaces for layout; while the integrated treatment tower 500 integrates the washing section 510a and the adsorption section 510b in the vertical space, and the gas from the washing section 510a directly enters the adsorption section 510b, which not only avoids the operation of connecting pipes in the middle, making the equipment installation process simpler, but also reduces the number of tanks, greatly reducing the area occupied by the equipment installation;

[0050] (2) It is more conducive to replacing the packing: When the adsorption tower 300 is set up separately, the gas enters from the bottom of the adsorption tower 300 and is discharged from the top. The packing arranged at the bottom of the adsorption tower 300 has more contact with the gas, has a higher adsorption efficiency, and therefore fails faster. Therefore, the height of the packing inside the traditional adsorption tower 300 causes a problem of difference in utilization rate, especially the closer to the bottom, the faster it fails, and the closer to the top, the slower it fails. The traditional adsorption tower 300 is not convenient for layout replacement of packing, especially replacing the packing that fails first at the bottom and retaining the packing that has not failed at the top; while the integrated treatment tower 500 sets the adsorption section 510b above the washing section 510a, and fills the adsorption section 510b with packing 540 through the packing rack 530. Once the packing 540 at the bottom fails or is saturated with adsorption, the packing 540 at the bottom of the packing rack 530 can be extracted through the notch 2 515 to achieve the purpose of partial replacement of the packing 540. Not only is it more convenient to operate, but the packing 540 at the bottom can also be selectively replaced according to the remaining life of the packing 540, thereby improving the utilization efficiency of the packing 540.

[0051] Moreover, in the present application, the state of the filling rack 530 when it is working is different from that when the filling is replaced. More specifically, when it is working, the filling rack 530 is suspended in the gap 522. At this time, there is a space between the connecting plate 533 and the closing plate 523 to allow the gas to enter the filling rack 530 from there between, thereby completing the work of removing water and impurities; when replacing the filling, the filling rack 530 is no longer in a suspended state, but sinks to the bottom of the gap 522. At this time, the connecting plate 533 contacts the closing plate 523, and the closing plate 523 is used to close the through hole on the connecting plate 533. At the same time, the inner cylinder 531 will also close the gap 525, thereby realizing a double closure between the washing section 510a and the adsorption section 510b, thereby achieving an auxiliary shutdown purpose and preventing the escape of unwashed gas.

[0052] In the present application, both the connecting plate 533 and the closing plate 523 are configured as conical surfaces. On the one hand, the conical surface state of the closing plate 523 also forms a funnel structure at the top of the washing section 510a, which plays a role in guiding and gathering the gas, and is more conducive to washing the gas; on the other hand, the connecting plate 533 that cooperates with the closing plate 523 is also configured as a conical surface with the same angle to ensure that the connecting plate 533 and the closing plate 523 are in close contact with each other when replacing the filler to achieve the sealing effect on the through holes on the connecting plate 533, and the conical surface of the connecting plate 533 increases the area of ​​the connecting plate 533, which is conducive to increasing the number and total cross-sectional area of ​​the through holes that can be set on the connecting plate 533, and is further conducive to improving the efficiency of gas adsorption; on the other hand, in order to cooperate with the conical surface setting of the connecting plate 533, the filler 540 filled in the filler frame 530 will also be configured as follows Figure 7The arc shape shown in the figure is formed by splicing a plurality of fillers 540 into a ring as a filler layer, and a plurality of layers of fillers 540 are stacked in an offset manner to form a Figure 5 In the state of the packing 540, since the packing 540 is arc-shaped at one end and has the same conical surface design as the connecting plate 533, it is convenient to extract the packing 540 through the notch 2 515 when replacing the packing 540.

[0053] like Figure 4 and Figure 6 As shown, a gap is provided between the spray plate 524 and the top of the cylindrical shell 521, and a filler 550 can be provided in the gap. The filler 550 can be of the same structure as the filler 540, so that the gas enters the filler 550 for dehydration and impurity removal when escaping upward, and the filler 550 plays an auxiliary adsorption effect; the filler 550 can also be a simple light closed body, and the filler 550 occupies the space above the spray plate 524 to improve the efficiency of the gas entering the adsorption section 510b.

[0054] In some application scenarios, the tower body 510 may be made larger, with a height of up to several meters. Accordingly, an operating platform 561 and a ladder 562 are provided outside the tower body 510 to facilitate operators to stand and operate and climb.

[0055] In addition, a lifting device may be installed on the top of the cylindrical shell 521 and connected to the filling frame 530 , and the lifting device may be used to assist in controlling the rise and fall of the filling frame 530 .

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them.

Claims

1. A post-treatment process for purifying tail gas from synthetic ammonia, characterized in that: The tail gas to be treated is washed with soft water to remove methanol, and then adsorbed to remove water and impurities. The washing soft water is separated to recover methanol.

2. The post-treatment process for purifying tail gas from synthetic ammonia according to claim 1, characterized in that: The tail gas to be treated contacts the soft water in a convection manner.

3. A post-treatment system for purifying tail gas from synthetic ammonia, characterized in that: The system uses the post-treatment process for purifying tail gas with synthetic ammonia as described in claim 1 or 2, and the system includes a washing tower, a compressor, an adsorption tower and a moisture separation tower. Soft water is introduced into the top of the washing tower for spraying, and the tail gas to be treated is introduced into the bottom of the washing tower and discharged from the top. The input end of the compressor is connected to the top of the washing tower, the output end of the compressor is connected to the bottom of the adsorption tower, and the bottom of the washing tower is connected to the moisture separation tower.

4. A post-treatment system for purifying tail gas from synthetic ammonia, characterized in that: The system uses the post-treatment process for purifying tail gas from synthetic ammonia according to claim 1 or 2, and the system includes an integrated treatment tower and a moisture separation tower, the integrated treatment tower includes a tower body and a gas input interface, a waste liquid discharge interface, a washing liquid input interface, and a gas discharge interface arranged on the tower body, and the gas discharge interface, the washing liquid input interface, the gas input interface, and the waste liquid discharge interface are arranged in order from high to low, and the waste liquid discharge interface is connected to the moisture separation tower; The tower body comprises a washing section and an adsorption section, wherein the adsorption section is arranged above the washing section, the washing section and the adsorption section are communicated, the gas input interface is arranged in the washing section, and the gas discharge interface is arranged in the adsorption section.

5. The tail gas post-treatment system for purifying synthetic ammonia according to claim 4, characterized in that: The upper part of the tower body is provided with a cylindrical shell, a gap is provided between the cylindrical shell and the inner wall of the tower body, the gap is filled with filler, the cylindrical shell is closed at the top and open at the bottom, a closing plate folded and extended outward is provided at the edge of the bottom opening of the cylindrical shell, the closing plate is sealed and connected with the inner wall of the tower body, and a notch is provided at the connection between the closing plate and the cylindrical shell; The tower body below the closing plate is the washing section, and the area enclosed by the closing plate, the tower body and the cylindrical shell is the adsorption section.

6. The tail gas post-treatment system for purifying synthetic ammonia according to claim 5, characterized in that: The adsorption section is provided with a packing frame and a packing filled in the packing frame, the packing frame comprises an inner cylinder, an outer cylinder and a connecting plate, the inner cylinder and the outer cylinder are arranged at intervals and connected by the connecting plate, and the connecting plate has a through hole; During operation, the filler frame is suspended and fixed in the gap to separate the connecting plate from the closing plate.

7. The tail gas post-treatment system for purifying synthetic ammonia according to claim 6, characterized in that: The tower body is also provided with a second gap and a third gap, wherein the second gap is provided at the bottom of the adsorption section, and a first enclosure is provided outside the second gap, and the third gap is provided at the top of the adsorption section, and a second enclosure is provided outside the third gap, and a fourth gap is provided on the outer cylinder of the packing frame; When the filler is replaced, the filler frame sinks to make the connecting plate fit with the closing plate, and the fourth gap is exposed through the second gap.

8. The tail gas post-treatment system for purifying synthetic ammonia according to claim 7, characterized in that: The inner cylinder is kept in close contact with the cylindrical shell.

9. The tail gas post-treatment system for purifying synthetic ammonia according to claim 7, characterized in that: The connecting plate and the closing plate are both conical surfaces.

10. The tail gas post-treatment system for purifying synthetic ammonia according to claim 7, characterized in that: A spray plate is arranged in the tower body, the spray plate is spaced apart from the top of the cylindrical shell, a filling body is arranged between the spray plate and the cylindrical shell, and the filling body is a filler or a light closed body.

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