Tail gas treatment device for sodium nitrate production equipment by neutralization method

Abstract

The utility model provides a tail gas treatment device for sodium nitrate production equipment by a neutralization method, which comprises a tail gas air pipe (20), an induced draft fan (2) and an exhaust funnel (6), a primary absorption tower (3) and a secondary absorption tower (4) which are connected in series with a reaction kettle (1) are communicated by the tail gas air pipe (20), an upper air outlet of the secondary absorption tower (4) is connected with the exhaust funnel (6), and the upper side of the exhaust funnel (6) is communicated with the atmosphere. And a sodium bicarbonate solution is sprayed in the first-stage absorption tower (3) and the second-stage absorption tower (4). The induced draft fan (2) is used for generating negative pressure in the reaction kettle (1), tail gas is sucked out, and the tail gas can be prevented from leaking from the sampling opening (11) and the simple manhole (12). The first-stage absorption tower (3) and the second-stage absorption tower (4) are used for spraying sodium bicarbonate to neutralize tail gas generated in the neutralization reaction, the treated tail gas does not contain nitric oxide any more, the treatment process is simple, consumed materials are few, and the cost is low.

Description

Technical Field

[0001] The utility model relates to a tail gas treatment technology, in particular to a tail gas treatment device used for equipment for producing sodium nitrate by a neutralization method. Background Art

[0002] Sodium nitrate is an important basic inorganic chemical raw material, mainly used in the production of glass, enamel, dyes, pigments, explosives, fertilizers, etc. It has a wide range of uses. The neutralization method, that is, the production of sodium nitrate by the neutralization reaction of sodium carbonate (soda ash) and nitric acid, is a simple method for producing sodium nitrate. Thanks to the increase in soda ash production capacity, this method is becoming more and more widely used.

[0003] Soda ash and nitric acid are neutralized in the reactor to generate sodium nitrate, water and carbon dioxide gas, while releasing a large amount of heat. The chemical equation is Na2CO3+HNO3=NaNO3+CO2↑+H2O. During production, due to the high temperature of the neutralization reaction, side reactions such as nitric acid decomposition will also occur, generating nitrogen oxide gas. In the traditional neutralization process, carbon dioxide gas and nitrogen oxides will mix and be discharged from the exhaust pipe as exhaust gas. However, the nitrogen oxides in the exhaust gas of the neutralization method exceed the standard, and direct discharge without treatment will cause environmental pollution. Therefore, the exhaust gas of the neutralization method must be treated.

[0004] The existing exhaust gas treatment method is to set up an absorption tower between the reactor and the exhaust pipe, use an induced draft fan to introduce the exhaust gas into a single-stage absorption tower, use alkaline solutions such as sodium hydroxide as absorbents in the single-stage absorption tower to absorb toxic nitrogen oxides, and then discharge the remaining harmless gases such as carbon dioxide through the exhaust pipe.

[0005] However, since the neutralization tail gas contains a large amount of carbon dioxide that can also react with the alkaline solution, the demand for alkaline solution is huge, the production cost is too high, it is not economical, and it will also cause a waste of resources.

[0006] In addition, since both carbon dioxide and nitrogen oxides are heavier than air, the natural emission of exhaust gas using the chimney effect is not effective. In order to facilitate observation during on-site operations, the manhole on the neutralization reactor is a simple manhole with an open opening. A sampling port is also provided on the top of the reactor. During the production process, exhaust gas can easily overflow from the simple manhole and the sampling port into the factory building, causing nitrogen oxide poisoning to the operators. Utility Model Content

[0007] The first purpose of the utility model is to solve the problem that a large amount of alkaline solution is consumed in the existing strong alkaline solution single-stage adsorption tower for treating the neutralization method tail gas. The second purpose is to solve the problem that since carbon dioxide and nitrogen oxides are heavier than air, the natural exhaust gas discharge effect using the chimney effect is not good, which causes the tail gas to easily leak from the simple manhole and sampling port.

[0008] To achieve the above purpose, the utility model provides a tail gas treatment device for a sodium nitrate production device by a neutralization method. The sodium nitrate production device by a neutralization method comprises a reactor 1, a stirring device 15 is arranged inside, a sodium carbonate solution inlet pipe, a nitric acid inlet pipe, and a sampling port 11 are arranged at the top, and a simple manhole 12 and a sodium nitrate discharge port 17 are arranged at the bottom.

[0009] The tail gas treatment device comprises: a tail gas duct 20 , an induced draft fan 2 , an exhaust pipe 6 , and a tail gas outlet 18 is arranged on the upper side of the reactor 1 .

[0010] The tail gas duct 20 connects the tail gas outlet 18 of the reactor 1 with the lower air inlet of the primary absorption tower 3 , and the induced draft fan 2 is arranged on the tail gas duct 20 .

[0011] The upper air outlet of the primary absorption tower 3 is connected to the lower air inlet of the secondary absorption tower 4, and the upper air outlet of the secondary absorption tower 4 is connected to the exhaust pipe 6. The upper side of the exhaust pipe 6 is connected to the atmosphere. An atomizer 52 is arranged on the upper part of the primary absorption tower 3 and the secondary absorption tower 4, and the atomizer 52 sprays sodium bicarbonate solution downward.

[0012] Therefore, the exhaust gas generated by the neutralization reaction is sucked upward from the reactor 1 by using the induced draft fan 2 to generate negative pressure in the reactor 1 for producing sodium nitrate by the neutralization method, thereby preventing the exhaust gas from leaking from the sampling port 11 and the simple manhole 12. The exhaust gas generated by the neutralization reaction is sprayed with sodium bicarbonate by the primary absorption tower 3 and the secondary absorption tower 4. The exhaust gas after treatment no longer contains nitrogen oxides and can be discharged from the secondary absorption tower 4 into the exhaust pipe 6. The treatment process is simple, less material consumption is required, and the cost is low.

[0013] Preferably, the tail gas treatment device further comprises a recovery tank 7. The lower parts of the primary absorption tower 3 and the secondary absorption tower 4 are respectively provided with drainage pipes, which are connected to the recovery tank 7. The absorption waste liquid formed by spraying in the primary absorption tower 3 and the secondary absorption tower 4 contains substances such as sodium nitrate, sodium nitrite, and sodium carbonate, which are reusable products of the production line and have recycling value, and can be recycled using the recovery tank 7.

[0014] Preferably, the lower part of the recovery tank 7 is connected to the tail gas outlet 18 of the reactor 1 through a recovery pipe 70, and a recovery pump 71 is provided on the recovery pipe 70. The tail gas is discharged into the recovery tank 7 by the discharge pipe and collected, and then pumped to the reactor 1 along the recovery pipe 70 by the recovery pump 71 to participate in the production reaction, which is conducive to improving the yield of sodium nitrate.

[0015] Preferably, there are multiple reactors 1, and the exhaust gas duct 20 includes multiple branch pipes 201 and a main pipe 202. The exhaust gas outlet 18 of each reactor 1 forms an air duct 200 upward to connect the branch pipe 201. The branch pipes 201 are respectively connected to the upstream of the main pipe 202, and the downstream of the main pipe 202 is connected to the lower air inlet of the primary absorption tower 3. The induced draft fan 2 is arranged in the middle of the main pipe 202, and each branch pipe 201 is respectively provided with a shut-off valve.

[0016] In actual production, multiple reactors may not work at the same time, so cut-off butterfly valves are respectively provided on the reactor exhaust pipelines to facilitate the switching of the reactor exhaust.

[0017] Preferably, the diameter of the air duct 200 is smaller than that of the branch air duct 201, and the diameter of the branch air duct 201 is smaller than that of the main duct 202. That is, the closer to the reactor 1, the thinner the tail gas duct 20 is, so as to increase the gas flow rate and ensure the exhaust effect.

[0018] Preferably, the exhaust gas outlet 18 is arranged on the opposite side of the simple manhole 12 .

[0019] Since the specific gravity of nitrogen oxides is greater than that of air, when the induced draft fan 2 is working, if the exhaust gas outlet 18 is too close to the simple manhole 12, it will cause exhaust short circuit and greatly reduce the efficiency of exhaust gas extraction. Therefore, the exhaust gas outlet 18 is arranged on the opposite side away from the simple manhole 12 to avoid this situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural illustration of the equipment for producing sodium nitrate by neutralization method and the tail gas treatment device;

[0021] Figure 2 It is a structural illustration of the equipment used for producing sodium nitrate by neutralization method;

[0022] Figure 3 This is a structural illustration of an exhaust gas treatment device for a sodium nitrate production facility using a neutralization method having six reactors.

[0023] Figure numerals: 1-reactor; 11-sampling port; 12-simple manhole; 13-sodium carbonate tank; 14-nitric acid tank; 15-agitation machine; 16-overflow pipe; 17-discharge pipe; 20-exhaust air duct; 200-air duct; 201-branch pipe; 202-main pipe; 2-induced draft fan; 3-primary absorption tower; 4-secondary absorption tower; 5-configuration tank; 51-delivery pump; 52-atomizer; 6-exhaust pipe; 7-recovery tank; 70-recovery pipeline; 71-recovery pump. DETAILED DESCRIPTION

[0024] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. The following description is a concretization of the claims of the present invention.

[0025] Example 1

[0026] Figure 1 This is a structural diagram of the tail gas treatment device used in the production of sodium nitrate by neutralization method. Figure 2 This is a structural diagram of the equipment used to produce sodium nitrate by neutralization. Figure 1 , 2 The structure of the exhaust gas treatment device and the beneficial effects of using the exhaust gas treatment device are described.

[0027] like Figure 1 As shown, the main equipment for producing sodium nitrate by neutralization method is reactor 1, combined with Figure 2 From the perspective of the reactor 1, a motor-driven stirring device 15 is provided inside the reactor 1, a simple manhole 12 and a discharge port 17 for observing the internal state of the reactor 1 are provided at the lower part, an overflow port 16 for limiting the liquid level in the reactor is provided at the upper part, a sodium carbonate solution inlet pipe (connected to the sodium carbonate tank 13) and a nitric acid inlet pipe (connected to the nitric acid tank 14) are provided at the upper part, and a sampling port 11 for sampling and an exhaust gas outlet 18 for discharging exhaust gas are also provided.

[0028] like Figure 1 As shown, the exhaust gas treatment device includes: an exhaust gas duct 20, an induced draft fan 2, a primary absorption tower 3, a secondary absorption tower 4, an exhaust chimney 6, and a recovery tank 7.

[0029] See Figure 1 On the left side, the tail gas duct 20 connects the tail gas outlet 18 of the reactor 1 to the lower air inlet of the primary absorption tower 3. The tail gas duct 20 is provided with a normally open air valve 210 in the pipe section close to the reactor 1. The induced draft fan 2 is arranged on the tail gas duct 20.

[0030] See also Figure 1 On the right side, the upper air outlet of the primary absorption tower 3 is connected to the lower air inlet of the secondary absorption tower 4, and the upper air outlet of the secondary absorption tower 4 is connected to the exhaust pipe 6, and the upper side of the exhaust pipe 6 is connected to the atmosphere. The exhaust pipe 6 is made according to the "Air Pollutant Emission Standard" and the height is not less than 15m.

[0031] An atomizer 52 is arranged on the upper part of the primary absorption tower 3 and the secondary absorption tower 4. The atomizer 52 is connected to a configuration tank 5 filled with a sodium bicarbonate solution through a line change. The configuration tank 5 is filled with a sodium bicarbonate solution of 10 to 16 g / L. A delivery pump 51 is arranged on the pipeline.

[0032] The delivery pump 51 pumps the sodium bicarbonate solution into the atomizer 52, so that the reactor 1 can spray the sodium bicarbonate solution downward. The primary absorption tower 3 and the secondary absorption tower 4 are also respectively provided with a circulation pump and a circulation pipeline (not shown in the figure), which is a common structure in the industry and will not be repeated here.

[0033] See also Figure 1 At the lower right side, drainage pipes are respectively provided at the lower parts of the primary absorption tower 3 and the secondary absorption tower 4, and the drainage pipes are connected to the recovery tank 7.

[0034] The lower part of the recovery tank 7 is connected to the tail gas outlet 18 of the reactor 1 through a recovery pipe 70 , and a recovery pump 71 is provided on the recovery pipe 70 .

[0035] During production, sodium carbonate solution and nitric acid enter the reactor 1, are stirred and mixed by the stirring device 15, and a neutralization reaction occurs to generate sodium nitrate, while a large amount of carbon dioxide tail gas is generated, and the tail gas contains nitrogen oxides (mainly nitrogen dioxide) as a by-product of the reaction.

[0036] The induced draft fan 2 can generate negative pressure in the reactor 1 to suck the tail gas generated by the neutralization reaction upward from the reactor 1 to prevent the tail gas from leaking from the sampling port 11 and the simple manhole 12 .

[0037] Afterwards, the tail gas enters the bottom of the primary absorption tower 3 through the induced draft fan 2, and the nitrogen oxides in the tail gas are absorbed by the sodium bicarbonate sprayed by the atomizer 5, while the carbon dioxide in the tail gas does not participate in the absorption reaction. Taking nitrogen dioxide as an example, the absorption reaction equation is:

[0038] 2NaHCO3+2NO2=NaNO2+NaNO3+2CO2↑+H2O

[0039] To ensure that the nitrogen oxides in the tail gas can be completely absorbed, the tail gas treated by the primary absorption tower 3 is also passed into the secondary absorption tower 4 for further absorption. The primary absorption tower 3 and the secondary absorption tower 4 have the same structure and also use sodium bicarbonate as the absorption liquid for spraying.

[0040] The tail gas after being treated by the primary absorption tower 3 and the secondary absorption tower 4 no longer contains nitrogen oxides, and can be discharged into the exhaust pipe 6 from the secondary absorption tower 4.

[0041] The absorption waste liquid formed by spraying in the primary absorption tower 3 and the secondary absorption tower 4 contains substances such as sodium nitrate, sodium nitrite, sodium carbonate, etc., which are reusable products of the production line. Therefore, it is discharged into the recovery tank 7 through the discharge pipe for collection, and then pumped to the reactor 1 along the recovery pipeline 70 by the recovery pump 71 to participate in the production reaction, which is beneficial to improve the yield of sodium nitrate.

[0042] It is worth noting that Figure 2 As shown, the tail gas outlet 18 is arranged on the opposite side of the simple manhole 12. Since the specific gravity of nitrogen oxides is greater than that of air, when the induced draft fan 2 is working, if the tail gas outlet 18 is too close to the simple manhole 12, it will cause exhaust short circuit, greatly reducing the exhaust gas extraction efficiency. Therefore, the tail gas outlet 18 is arranged on the opposite side away from the simple manhole 12 to avoid this situation.

[0043] In summary, the utility model uses the induced draft fan 2 to generate negative pressure in the reactor 1 for producing sodium nitrate by the neutralization method, and sucks the tail gas generated by the neutralization reaction upward from the reactor 1, which can prevent the tail gas from leaking from the sampling port 11 and the simple manhole 12. The tail gas generated by the neutralization reaction is sprayed with sodium bicarbonate using the primary absorption tower 3 and the secondary absorption tower 4. The treated tail gas no longer contains nitrogen oxides, and can be discharged from the secondary absorption tower 4 into the exhaust pipe 6. The treatment process is simple, less material consumption, and low cost.

[0044] Modification 1

[0045] The structure of the tail gas treatment device of Modification 1 is basically the same as that of Example 1, and the only difference is that in the equipment for producing sodium nitrate by neutralization method, there are 6 reaction kettles 1 (101-106). Figure 3 This is a structural diagram of the tail gas treatment device for 6 reactors. Figure 2 , 3 The structure of Modification Example 1 will be described.

[0046] like Figure 2 , 3 As shown, the exhaust gas duct 20 includes multiple branch pipes 201 and a main pipe 202. The exhaust gas outlet 18 of each reactor 1 forms an air duct 200 upward to connect the branch pipes 201. The branch pipes 201 are respectively connected to the upstream of the main pipe 202. The downstream of the main pipe 202 is connected to the lower air inlet of the primary absorption tower 3. The induced draft fan 2 is arranged in the middle of the main pipe 202.

[0047] The diameter of the air duct 200 is smaller than that of the branch air duct 201, and the diameter of the branch air duct 201 is smaller than that of the main pipe 202. That is, the closer to the reactor 1, the thinner the tail gas duct 20 is, so as to increase the gas flow rate and ensure the exhaust effect.

[0048] A cut-off valve is provided on each branch pipe 201. In actual production, it is not necessarily necessary for 6 reactors to work at the same time, so a cut-off butterfly valve is provided on each reactor exhaust pipeline to facilitate the switching of the reactor exhaust.

Claims

1. A tail gas treatment device for a sodium nitrate production equipment by a neutralization process, the neutralization process sodium nitrate production equipment comprising a reactor (1), wherein a stirring device (15) is arranged inside the reactor (1), a sodium carbonate solution inlet pipe, a nitric acid inlet pipe, and a sampling port (11) are arranged at the top, and a simple manhole (12) and a sodium nitrate discharge port (17) are arranged at the bottom, characterized in that: The tail gas treatment device comprises: a tail gas duct (20), an induced draft fan (2), and an exhaust pipe (6); a tail gas outlet (18) is arranged on the upper side of the reaction kettle (1). The tail gas duct (20) connects the tail gas outlet (18) of the reactor (1) with the lower air inlet of the primary absorption tower (3), and the induced draft fan (2) is arranged on the tail gas duct (20). The upper gas outlet of the primary absorption tower (3) is connected to the lower gas inlet of the secondary absorption tower (4), and the upper gas outlet of the secondary absorption tower (4) is connected to an exhaust pipe (6), and the upper side of the exhaust pipe (6) is connected to the atmosphere. Atomizers (52) are arranged on the upper parts of the primary absorption tower (3) and the secondary absorption tower (4), and the atomizers (52) spray sodium bicarbonate solution downwards.

2. The exhaust gas treatment device according to claim 1, characterized in that: It also includes a recovery tank (7), The lower parts of the primary absorption tower (3) and the secondary absorption tower (4) are respectively provided with drainage pipes, and the drainage pipes are connected to the recovery tank (7).

3. The exhaust gas treatment device according to claim 2, characterized in that: The lower part of the recovery tank (7) is connected to the tail gas outlet (18) of the reaction kettle (1) through a recovery pipe (70), and a recovery pump (71) is provided on the recovery pipe (70).

4. The exhaust gas treatment device according to any one of claims 1 to 3, characterized in that: There are multiple reaction kettles (1), and the tail gas duct (20) includes multiple branch pipes (201) and a main pipe (202). The tail gas outlet (18) of each reactor (1) forms an air guide pipe (200) upwardly connected to the branch pipe (201), the branch pipes (201) are respectively connected to the upstream of the main pipe (202), and the downstream of the main pipe (202) is connected to the lower air inlet of the primary absorption tower (3), and the induced draft fan (2) is arranged in the middle of the main pipe (202). Each of the branch pipes (201) is provided with a shut-off valve.

5. The tail gas treatment device according to claim 4, characterized in that: The diameter of the air guide pipe (200) is smaller than that of the branch pipe (201), and the diameter of the branch pipe (201) is smaller than that of the main pipe (202).

6. The exhaust gas treatment device according to any one of claims 1 to 3, characterized in that: The exhaust gas outlet (18) is arranged on the opposite side of the simple manhole (12).

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