Underground tank gas recovery system

Abstract

The utility model belongs to the technical field of gas recovery, and relates to an underground tank gas recovery system which comprises an underground tank body, a non-condensable gas purge pipe, a non-condensable gas pipe network and a condensate return pipe, the non-condensable gas pipe network is positioned above the ground; the underground tank body and the condensate return pipe are both located under the ground, the underground tank body is communicated with the non-condensable gas pipe network through the non-condensable gas purge pipe, the condensate return pipe is located below the non-condensable gas purge pipe, and the underground tank body is communicated with the non-condensable gas purge pipe through the condensate return pipe. According to the utility model, the gas in the underground tank body is guided into the non-condensable gas pipe network above the ground from the lower part of the ground through the non-condensable gas purge pipe to be recycled, so that the resource waste is avoided, and the device is safe and environment-friendly.

Description

Technical Field

[0001] The utility model belongs to the technical field of gas recovery and relates to an underground tank gas recovery system. Background Art

[0002] The main function of the underground tank is to collect materials generated by various equipment such as pumps, pipelines, and storage tanks during production; currently in the dimethyl oxalate synthesis process (DMO synthesis process), methyl nitrite is generated by the reaction of oxygen, nitrogen oxides and methanol, and methyl nitrite reacts with carbon monoxide to generate dimethyl oxalate; the waste materials generated during the reaction are discharged into the underground tank, but the underground tank is generally set below the ground. In order to allow the materials on the ground to be discharged normally to the underground tank, it is necessary to ensure that the underground tank is operated at normal pressure, and the lower the pressure of the underground tank, the better. The current method of pressure control of the underground tank is to use the valve on the venting pipeline for adjustment and control, specifically by adjusting the opening of the valve to control the pressure in the underground tank at normal pressure, with a maximum of no more than 10KPa. Although the pressure control in the underground tank can be achieved, this method still has the following disadvantages:

[0003] (1) It causes waste of resources and serious environmental pollution. Since the material discharged into the underground tank is a methanol solution with a large amount of nitrogen oxides and methyl nitrite gas dissolved in it, after being discharged into the underground tank, a large amount of nitrogen oxides and methyl nitrite gas are generated in the methanol solution and released. The released gas (also called non-condensable gas) accumulates in the underground tank, which will cause excessive pressure in the underground tank. The general treatment method is to directly discharge these non-condensable gases into the atmosphere through the venting pipeline. Therefore, the non-condensable gases cannot be effectively recovered, resulting in waste of gas resources. At the same time, the direct discharge of these non-condensable gases will cause heavy odor on site, excessive VOC, and yellow smoke will appear when the discharge amount is large, seriously polluting the environment.

[0004] (2) Poor safety: Since these non-condensable gases contain toxic and flammable gases such as nitrogen oxides and methyl nitrite, they are directly discharged on site. A large amount of toxic and flammable gases will escape, which may easily cause the risk of poisoning and suffocation to the operators on site. If special hot work operations are carried out on site, there is also the risk of fire and explosion, which may easily lead to safety accidents and reduce production safety. Utility Model Content

[0005] Aiming at the technical problems of resource waste, serious environmental pollution and poor safety of existing underground tank gas, the utility model provides an underground tank gas recovery system.

[0006] In the utility model, the gas in the underground tank is led from below the ground to the non-condensable gas pipe network above the ground through the non-condensable gas release pipe for recycling, thus avoiding waste of resources and being safe and environmentally friendly.

[0007] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0008] An underground tank gas recovery system comprises an underground tank body, a non-condensable gas relief pipe, a non-condensable gas pipeline network and a condensate return pipe; the non-condensable gas pipeline network is located above the ground; the underground tank body and the condensate return pipe are both located below the ground, the underground tank body is connected to the non-condensable gas pipeline network via the non-condensable gas relief pipe, the condensate return pipe is located below the non-condensable gas relief pipe, and the underground tank body is connected to the non-condensable gas relief pipe via the condensate return pipe.

[0009] It is further defined that the non-condensable gas relief pipe includes a first relief pipe, a second relief pipe and a third relief pipe which are connected in sequence, the first relief pipe is located under the ground and connected to the underground tank body, the third relief pipe is located on the ground and connected to the non-condensable gas pipeline network; the condensate return pipe is located below the first relief pipe, and the first relief pipe is connected to the underground tank body via the condensate return pipe.

[0010] It is further defined that the first relief pipe and the third relief pipe are placed in parallel, and the axial direction of the second relief pipe is perpendicular to the axial direction of the first relief pipe.

[0011] It is further defined that a check valve and a first non-condensable gas relief valve are sequentially arranged on the third relief pipe; and the first non-condensable gas relief valve is arranged close to the non-condensable gas pipeline network.

[0012] A second non-condensable gas relief valve is arranged on the first relief pipe.

[0013] It is further defined that a condensate control valve is provided on the condensate return pipe.

[0014] It is further defined that the underground tank gas recovery system also includes a non-condensable gas compressor and a non-condensable gas treatment tower connected to the non-condensable gas compressor; the non-condensable gas compressor is also connected to the non-condensable gas pipeline network.

[0015] It is further defined that the underground tank gas recovery system also includes a venting pipeline connected to the underground tank body; one end of the venting pipeline is located below the ground, and the other end of the venting pipeline extends upward to the ground.

[0016] It is further defined that a vent valve is provided on the vent pipeline; and the vent valve is located on the ground.

[0017] The beneficial effects of the utility model are:

[0018] 1. In the utility model, the gas in the underground tank in the dimethyl oxalate synthesis process is led from below the ground to the non-condensable gas network above the ground through the non-condensable gas release pipe for effective recycling, thereby avoiding waste of resources and achieving cost reduction and efficiency improvement; effectively eliminating odor on site, improving the working environment of on-site operators, eliminating the emission of toxic and harmful gases on site, and reducing environmental pollution and the occurrence of safety and environmental protection accidents.

[0019] 2. In the utility model, a check valve and a non-condensable gas relief valve are sequentially arranged on the third relief pipe; the check valve can prevent the pressure in the non-condensable gas relief pipe from suddenly increasing, causing the gas to flow back into the underground tank body, causing gas cross-flow in the underground tank body, thereby ensuring the normal operation of the system.

[0020] 3. In the utility model, a condensate return pipe is arranged below the first relief pipe; one end of the condensate return pipe is connected to the first relief pipe, and the other end of the condensate return pipe is connected to the underground tank body; this is because when the gas is discharged upward from the underground tank body, condensate will be generated, and the condensate return pipe is arranged at a low point to facilitate the discharge of the accumulated liquid in the non-condensable gas relief pipe into the underground tank body.

[0021] 4. In the utility model, the gas in the underground tank is recovered to the non-condensable gas pipeline network, enters the non-condensable gas compressor for pressurization, and then enters the non-condensable gas treatment tower, where methanol spray is used to wash the effective components for recycling, and the waste gas after spraying is discharged to the incinerator for treatment, thereby further improving the gas recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of an underground tank gas recovery system provided in Example 1;

[0023] Figure 2 A schematic diagram of an underground tank gas recovery system provided in Example 2;

[0024] in:

[0025] 1-underground tank; 2-vent pipeline; 3-vent valve; 4-non-condensable gas relief pipe; 401-first relief pipe; 402-second relief pipe; 403-third relief pipe; 5-check valve; 6-first non-condensable gas relief valve; 7-non-condensable gas pipeline network; 8-condensate return pipe; 9-condensate control valve; 10-non-condensable gas compressor; 11-non-condensable gas transmission pipe; 12-non-condensable gas treatment tower; 13-second non-condensable gas relief valve; 14-third non-condensable gas relief valve. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0027] Example 1

[0028] See also Figure 1 This embodiment provides an underground tank gas recovery system, including an underground tank body 1, a non-condensable gas release pipe 4 and a non-condensable gas pipeline network 7 connected in sequence; the underground tank body 1 is located under the ground, and the non-condensable gas pipeline network 7 is located above the ground.

[0029] In this embodiment, the underground tank body 1 is used to collect and store waste materials in the dimethyl oxalate synthesis process. The gas (also called non-condensable gas) in the underground tank body 1 is led from bottom to top through the non-condensable gas release pipe 4 to the non-condensable gas pipeline network 7 (the pipeline network outside the boundary of the dimethyl oxalate synthesis process) for reuse, thereby realizing gas recovery, saving resources, and being environmentally friendly and safe.

[0030] In this embodiment, the non-condensable gas relief pipe 4 includes a first relief pipe 401, a second relief pipe 402 and a third relief pipe 403 which are connected in sequence. The first relief pipe 401 is located below the ground and is connected to the underground tank body 1, and the third relief pipe 403 is located above the ground and is connected to the non-condensable gas pipeline network 7.

[0031] Preferably, the first relief pipe 401 and the third relief pipe 403 are placed in parallel, and the axial direction of the second relief pipe 402 is perpendicular to the axial direction of the first relief pipe 401 .

[0032] In this embodiment, a check valve 5 and a first non-condensable gas relief valve 6 are sequentially arranged on the third relief pipe 403; the first non-condensable gas relief valve 6 is arranged close to the non-condensable gas pipe network 7. A second non-condensable gas relief valve 13 is arranged on the first relief pipe 401.

[0033] The function of the check valve 5 is to prevent the pressure in the non-condensable gas pipe network 7 from suddenly increasing, causing the gas to flow back into the underground tank body 1, thereby preventing gas cross-flow in the underground tank body 1 and ensuring the stability of the system.

[0034] Preferably, the check valve 5, the first non-condensable gas relief valve 6 and the second non-condensable gas relief valve 13 are all D80 stainless steel valves. The size of the non-condensable gas relief pipe 4 is DN80.

[0035] The underground tank gas recovery system provided in this embodiment also includes a venting pipeline 2 connected to the underground tank body 1; one end of the venting pipeline 2 is located below the ground, and the other end of the venting pipeline 2 extends upward to the ground. A venting valve 3 is provided on the venting pipeline 2; the venting valve 3 is located on the ground.

[0036] In this embodiment, the vent pipeline 2 is provided to prevent the non-condensable gas compressor 10 from tripping due to a sudden failure. The non-condensable gas is vented and depressurized by opening the vent valve 3, closing the check valve 5, the first non-condensable gas relief valve 6 and the second non-condensable gas relief valve 13, thereby avoiding a sharp increase in the pressure in the underground tank body 1 during a sudden failure and ensuring that the pressure in the underground tank body 1 is below normal pressure. When the sudden failure is resolved, the vent valve 3 is closed, and the check valve 5, the first non-condensable gas relief valve 6 and the second non-condensable gas relief valve 13 are opened to recycle the non-condensable gas.

[0037] During implementation, in order to facilitate the connection and switching between the venting pipeline 2 and the non-condensable gas relief pipe 4 and the underground tank body 1, a vertically upward non-condensable gas main pipe is connected to the underground tank body 1, and the non-condensable gas main pipe is connected to the venting pipeline 2 and the non-condensable gas relief pipe 4 respectively, and the three pipelines form a three-way passage. Specifically, the non-condensable gas main pipe is connected to the first relief pipe 401; preferably, in order to control the discharge of non-condensable gas, a third non-condensable gas relief valve 14 is also provided on the non-condensable gas main pipe.

[0038] See also Figure 1 The underground trough gas recovery system provided in this embodiment also includes a condensate return pipe 8; the condensate return pipe 8 is located below the ground, and the condensate return pipe 8 is located below the non-condensable gas release pipe 4, and the underground trough body 1 is connected to the non-condensable gas release pipe 4 through the condensate return pipe 8.

[0039] Preferably, the condensate return pipe 8 is located below the first relief pipe 401 , one end of the condensate return pipe 8 is connected to the first relief pipe 401 , and the other end of the condensate return pipe 8 is connected to the underground tank body 1 .

[0040] Since the liquid carried by the non-condensable gas will flow downward and accumulate at the vertical connection between the first relief pipe 401 and the second relief pipe 402 during the process of guiding the gas (also called non-condensable gas) in the underground tank body 1 from bottom to top into the non-condensable gas pipe network 7, a condensate return pipe 8 connected to the underground tank body 1 is arranged at a low position below the first relief pipe 401. The pressure of the non-condensable gas relief pipe 4 increases as it moves upward, and the condensate flows downward, thereby automatically returning the condensate accumulated in the non-condensable gas relief pipe 4 to the underground tank body 1.

[0041] Preferably, a condensate control valve 9 is provided on the condensate return pipe 8 to facilitate control of the reflux of the condensate.

[0042] Preferably, the size of the condensate return pipe 8 is DN25, and the condensate control valve 9 is a D25 stainless steel valve.

[0043] Example 2

[0044] See also Figure 2 Based on Example 1 or Example 2, the underground trough gas recovery system provided in this embodiment also includes a non-condensable gas compressor 10 and a non-condensable gas treatment tower 12 connected to the non-condensable gas compressor 10; the non-condensable gas compressor 10 is also connected to the non-condensable gas pipeline network 7.

[0045] Since the non-condensable gas in the underground tank 1 is not slightly negative pressure, the pressure of the non-condensable gas recovered in the non-condensable gas pipe network 7 is still low, and the non-condensable gas contains nitrogen oxide gas and methyl nitrite gas, so the pressure of the non-condensable gas is increased to 30kPa-40kPa by the non-condensable gas compressor 10, and is transported to the non-condensable gas treatment tower 12 through the non-condensable gas delivery pipe 11, and methanol is sprayed at the top of the non-condensable gas treatment tower 12. Methanol spraying is a prior art, and the non-condensable gas is washed by methanol to recover the effective components of nitrogen oxides, methyl nitrite and methanol, and the unwashed gas is discharged to the incinerator for incineration. Further, these effective components can be returned to the DMO synthesis process for recycling. Due to the return of nitrogen oxides, the nitrogen oxide content in the system increases, thereby reducing the system's consumption of nitric acid, saving the use of nitric acid, saving about 0.45 tons of nitric acid per day, and the unit price of each ton of nitric acid is 1,200 yuan / ton; it is estimated that the cost of nitric acid will be saved by about 200,000 yuan per year. Therefore, the underground trough gas recovery system provided in this embodiment can not only solve the disadvantages caused by the on-site discharge of non-condensable gas, but also reduce the consumption of raw nitric acid in the production system and save costs.

[0046] The above description is only an embodiment of the present invention, and does not limit the protection scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An underground trough gas recovery system, characterized in that: The invention comprises an underground tank body (1), a non-condensable gas relief pipe (4), a non-condensable gas pipe network (7) and a condensate return pipe (8); the non-condensable gas pipe network (7) is located above the ground; the underground tank body (1) and the condensate return pipe (8) are both located below the ground, the underground tank body (1) is connected to the non-condensable gas pipe network (7) via the non-condensable gas relief pipe (4), the condensate return pipe (8) is located below the non-condensable gas relief pipe (4), and the underground tank body (1) is connected to the non-condensable gas relief pipe (4) via the condensate return pipe (8).

2. The underground tank gas recovery system according to claim 1, characterized in that: The non-condensable gas relief pipe (4) comprises a first relief pipe (401), a second relief pipe (402) and a third relief pipe (403) which are connected in sequence, wherein the first relief pipe (401) is located below the ground and is connected to the underground tank body (1), and the third relief pipe (403) is located above the ground and is connected to the non-condensable gas pipe network (7); the condensate return pipe (8) is located below the first relief pipe (401), and the first relief pipe (401) is connected to the underground tank body (1) via the condensate return pipe (8).

3. The underground tank gas recovery system according to claim 2, characterized in that: The first relief pipe (401) and the third relief pipe (403) are placed in parallel, and the axial direction of the second relief pipe (402) is perpendicular to the axial direction of the first relief pipe (401).

4. The underground tank gas recovery system according to claim 3, characterized in that: A check valve (5) and a first non-condensable gas relief valve (6) are sequentially arranged on the third relief pipe (403); the first non-condensable gas relief valve (6) is arranged close to the non-condensable gas pipe network (7).

5. The underground tank gas recovery system according to claim 4, characterized in that: The first purge pipe (401) is provided with a second non-condensable gas purge valve (13).

6. The underground tank gas recovery system according to claim 5, characterized in that: The condensate return pipe (8) is provided with a condensate control valve (9).

7. The underground trough gas recovery system according to any one of claims 1 to 6, characterized in that: The underground tank gas recovery system also includes a non-condensable gas compressor (10) and a non-condensable gas treatment tower (12) connected to the non-condensable gas compressor (10); the non-condensable gas compressor (10) is also connected to the non-condensable gas pipeline network (7).

8. The underground tank gas recovery system according to claim 1, characterized in that: The underground tank gas recovery system further comprises a venting pipeline (2) connected to the underground tank body (1); one end of the venting pipeline (2) is located below the ground, and the other end of the venting pipeline (2) extends upward to the ground.

9. The underground tank gas recovery system according to claim 8, characterized in that: A vent valve (3) is provided on the vent pipeline (2); the vent valve (3) is located on the ground.

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