Device and method for producing refined sulfuric acid with low nitrogen oxide content

Abstract

The invention discloses a low-nitrogen oxide content refined sulfuric acid production device and method, and relates to the technical field of sulfuric acid manufacturing refinement. The device comprises a denitration and degassing tower, a liquid SO2 storage tank is connected with the bottom of the denitration and degassing tower through a vaporizer, the output end of a semi-finished product acid is connected with the upper part of the denitration and degassing tower, the top of the denitration and degassing tower is connected with a negative pressure system, and the bottom of the denitration and degassing tower is connected with a product acid tank. According to the technology, nitric oxide in sulfuric acid is reduced by adopting SO2 flue gas, compared with a chemical agent method, the reaction is more efficient, the SO2 flue gas is easy to obtain and low in cost, and basically no reagent is left in refined acid.

Description

Technical Field

[0001] The invention relates to the technical field of refined sulfuric acid production, and in particular to a method for producing refined sulfuric acid with low nitrogen oxide content. Background Art

[0002] Thermal nitrogen oxides or raw material nitrogen oxides are inevitably produced during the sulfuric acid production process. By using low-nitrogen burners, setting up SCR / SNCR or ozone denitrification devices, the sulfuric acid plant can achieve NO in tail gas. x Low emissions and NO in product acid x Meet the standard requirements of industrial sulfuric acid.

[0003] However, as the sulfuric acid industry develops towards refinement, the demand for refined sulfuric acid (reagent grade, electronic grade, etc.) is increasing. Compared with the quality indicators of industrial sulfuric acid products, there are more indicators that need to be controlled in refined sulfuric acid products, among which nitrogen oxides are a very important indicator. The above technical means alone cannot basically meet the requirements. For example, GB / T625-2007 "Chemical Reagent Sulfuric Acid" requires that the content of analytical pure nitrate (NO3) be ≤0.5ppm, and the US General Services Administration sets the standard for electrolyte grade sulfuric acid to be less than 5ppm NO X .

[0004] Patent CN104768869A discloses a method for reducing the nitrogen oxide content in sulfuric acid by using hydrazine sulfate. The reaction is carried out at 90°C for 1 minute, which can remove 90% of the nitrogen oxides. US3012854A discloses the use of hydrazine sulfate and dihydrazine sulfate to treat sulfuric acid to remove oxidized compounds and make the sulfuric acid pass the Murray test. US5955050 discloses the use of hydrazine, aminosulfonic acid or urea to remove NO from sulfuric acid. X Patent CN116143081 A discloses that an oxidant (peroxide, persulfate, hypochlorite, permanganate or ozone) is added to concentrated sulfuric acid to oxidize nitrogen oxides in the sulfuric acid into nitrate ions, and the nitrate ions are then reduced to nitrogen gas by a reducing agent (urea, aminosulfonic acid, ammonium aminosulfonate, ethylamine or ethylenediamine), thereby removing nitrogen oxides in concentrated sulfuric acid.

[0005] The above methods for removing nitrogen oxides from sulfuric acid all require the consumption of chemical reagents, which are costly and will remain in the sulfuric acid. For example, when hydrazine sulfate is used to remove nitrogen oxides from concentrated sulfuric acid, hydrazine sulfate will remain in the sulfuric acid, and hydrazine sulfate is a toxic chemical substance that will affect the safety of downstream products of sulfuric acid. Summary of the invention

[0006] The present invention aims to provide a method for reducing nitrogen oxides in sulfuric acid during refined sulfuric acid production in view of the above existing technical problems. It has been found that SO2 flue gas can react with nitrosylsulfuric acid in sulfuric acid, and the reaction rate becomes sufficiently fast at at least about 70°C.

[0007] Therefore, the present invention relates to a production method for preparing refined sulfuric acid with reduced nitrogen oxide content, the method comprising: a semi-finished acid with a temperature of at least about 80°C produced by a sulfuric acid main device, the semi-finished acid containing nitrogen oxides (calculated as nitrosylsulfuric acid) far exceeding 5 ppm, SO2 flue gas is mixed with the semi-finished sulfuric acid and reacted, the reaction time is at least about 0.5 minutes, and the reaction temperature is at least about 70°C.

[0008] A device for producing refined sulfuric acid with low nitrogen oxide content comprises a denitration and degassing tower, a liquid SO2 storage tank is connected to the bottom of the denitration and degassing tower through a vaporizer, an output end of semi-finished acid is connected to the upper part of the denitration and degassing tower, the top of the denitration and degassing tower is connected to a negative pressure system, and the bottom is connected to a product acid tank.

[0009] In the above technical solution: the liquid SO2 storage tank is connected to the bottom of the denitrification and degassing tower through a metering pump, a vaporizer and a buffer tank in sequence.

[0010] In the above technical solution: the product acid tank is connected to the product acid cooler through a product acid pump, and the output end of the product acid cooler is refined sulfuric acid.

[0011] Another refined sulfuric acid production device with low nitrogen oxide content, the output end of the semi-finished acid and the output end of the gas SO2 are both connected to the denitrifier, the denitrifier is connected to the upper part of the degassing tower, the top of the degassing tower is connected to the negative pressure system, and the bottom is connected to the product acid tank.

[0012] Furthermore: the product acid tank is connected to the product acid cooler through a product acid pump, and the output end of the product acid cooler is refined sulfuric acid.

[0013] Further: the gas SO2 is connected to the denitrifier through a conveying device.

[0014] In the technical solution of the present invention, the denitration reactor can be a packed tower, an empty tower or a static mixer.

[0015] A method for producing refined sulfuric acid with low nitrogen oxide content using the above-mentioned device, the method is that semi-finished sulfuric acid is sent to a denitration and degassing tower, the SO2 in the liquid SO2 storage tank is sent to a vaporizer through a metering pump to be gasified into SO2 gas and then enters a buffer tank, and then enters the denitration and degassing tower, reacts in the denitration and degassing tower for 45 to 50 seconds, and air is sent to the bottom of the denitration and degassing tower. The air blows off and separates the SO2 dissolved in the semi-finished sulfuric acid, and enters the negative pressure system of the sulfuric acid device together with the N2 generated by the denitration reaction. The refined sulfuric acid with the nitrogen oxides removed flows to the product acid tank by gravity, which is the target product.

[0016] Another method for producing refined sulfuric acid with low nitrogen oxide content using the above-mentioned device is to feed semi-finished sulfuric acid into a denitrifier at 80-90°C, introduce flue gas from the sulfuric acid main device conversion system into the denitrifier, react in the denitrifier for 45-50s, and after the reaction is completed, the gas-liquid mixture enters a degassing tower for gas-liquid separation. Air is also fed into the bottom of the degassing tower, and the air blows off and separates the SO2 dissolved in the semi-finished sulfuric acid, and enters the negative pressure system of the sulfuric acid device together with the N2 generated by the denitrification reaction. The refined sulfuric acid from which the nitrogen oxides have been removed flows by gravity to the product acid tank, which is the target product.

[0017] Beneficial effects:

[0018] Compared with the chemical agent method (compared with patent CN104768869A), the method of using SO2 flue gas to reduce nitrogen oxides in sulfuric acid has the beneficial effects of low reaction temperature, short reaction time, high nitrogen oxide removal rate, etc., and SO2 flue gas is easy to obtain, low cost, and there is basically no reagent residue in the refined acid. The specific beneficial effects are shown in the table below.

[0019] BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the device of the present invention.

[0021] Figure 2 Another schematic diagram of the device of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto:

[0023] Determination of the mass fraction of nitrogen oxides in semi-finished sulfuric acid: The principle of the determination is to oxidize nitrite to nitrate with potassium permanganate. Under specified conditions, nitrate reacts with 2,4-dimethylphenol to form a nitro derivative, which is distilled and absorbed by sodium hydroxide solution, and the absorbance of the yellow solution of sodium nitrophenolate is measured. For details of the determination method, see Section 5.10 Determination of the mass fraction of nitrogen oxides in HG / T2692-2015 "Sulfuric acid for batteries".

[0024] Subtract the absorbance value of the blank test from the absorbance value of the test solution, and obtain the corresponding nitrogen mass from the working curve based on the absorbance value difference. Mass fraction of nitrogen oxides in semi-finished sulfuric acid = mass of nitrogen obtained from the working curve (μg) × 10 6 / Numerical value of the mass of the sample (g)×100%.

[0025] like Figure 1 A refined sulfuric acid production device with low nitrogen oxide content, the device includes a denitration degassing tower 1, a liquid SO2 storage tank 5 is connected to the bottom of the denitration degassing tower 1 through a vaporizer 7, the output end of the semi-finished acid is connected to the upper part of the denitration degassing tower 1, the top of the denitration degassing tower 1 is connected to a negative pressure system, and the bottom is connected to a product acid tank 2. The liquid SO2 storage tank 5 is connected to the bottom of the denitration degassing tower 1 through a metering pump 6, a vaporizer 7 and a buffer tank 8 in sequence. The product acid tank 2 is connected to a product acid cooler 4 through a product acid pump 3, and the output end of the product acid cooler 4 is refined sulfuric acid.

[0026] like Figure 2 A refined sulfuric acid production device with low nitrogen oxide content, the output end of the semi-finished acid and the output end of the gas SO2 are both connected to the denitrifier 10, the denitrifier 10 is connected to the upper part of the degassing tower 11, the top of the degassing tower 11 is connected to the negative pressure system, and the bottom is connected to the product acid tank 2. The product acid tank 2 is connected to the product acid cooler 4 through the product acid pump 3, and the output end of the product acid cooler 4 is refined sulfuric acid. The gas SO2 is connected to the denitrifier 10 through the conveying equipment 9.

[0027] Example 1: Figure 1

[0028] In a 60,000 ton / year refined sulfuric acid plant, the mass fraction of nitrogen oxides in the semi-finished sulfuric acid is determined by the above method to be 200 ppm (equivalent to 400 ppm of nitrosylsulfuric acid content), and the semi-finished sulfuric acid is sent to the denitration and degassing tower 1 at 80°C. The SO2 in the liquid SO2 storage tank 5 is sent to the vaporizer 7 through the metering pump 6 to be gasified into SO2 gas and then enters the buffer tank 8. 1.2Nm 3 / h SO2 gas then enters the denitration degassing tower 1, reacts in the denitration degassing tower for 40s, and air is sent into the bottom of the denitration degassing tower 1. The air blows off and separates the SO2 dissolved in the semi-finished sulfuric acid, and enters the negative pressure system of the sulfuric acid device together with the N2 generated by the denitration reaction. The refined sulfuric acid after the nitrogen oxides are removed flows by gravity to the product acid tank 2, and is sent to the product acid cooler 4 through the product acid pump 3 for cooling and then sent out. The nitrogen reduction rate is 95%.

[0029] Example 2: Figure 2

[0030] In a 100,000 t / a refined sulfuric acid plant, the mass fraction of nitrogen oxides in the semi-finished sulfuric acid was determined by the above method to be 276 ppm (equivalent to 552 ppm of nitrosylsulfuric acid content), which was fed into the denitrifier 10 at 85°C and introduced into the flue gas containing 10.5% SO2 of the sulfuric acid main plant conversion system. 3 / h, and is sent to the denitrifier 10 through the conveying equipment 9, and reacts in the denitrifier for 50s. After the reaction is completed, the gas-liquid mixture enters the degassing tower 11 for gas-liquid separation, and air is sent into the bottom of the degassing tower 11. The air blows off and separates the SO2 dissolved in the semi-finished sulfuric acid, and enters the negative pressure system of the sulfuric acid device together with the N2 generated by the denitrification reaction. The refined sulfuric acid with nitrogen oxides removed flows by gravity to the product acid tank 2, and is sent to the product acid cooler 4 through the product acid pump 3 for cooling and then sent out. The nitrogen reduction rate is 95%.

Claims

1. A refined sulfuric acid production device with low nitrogen oxide content, characterized in that: The device comprises a denitration and degassing tower (1), a liquid SO2 storage tank (5) connected to the bottom of the denitration and degassing tower (1) via a vaporizer (7), an output end of semi-finished acid connected to the upper part of the denitration and degassing tower (1), the top of the denitration and degassing tower (1) connected to a negative pressure system, and the bottom connected to a product acid tank (2).

2. The low nitrogen oxide content refined sulfuric acid production device according to claim 1, characterized in that: The liquid SO2 storage tank (5) is connected to the bottom of the denitration and degassing tower (1) via a metering pump (6), a vaporizer (7) and a buffer tank (8) in sequence.

3. The low nitrogen oxide content refined sulfuric acid production device according to claim 1, characterized in that: The product acid tank (2) is connected to the product acid cooler (4) via a product acid pump (3), and the output end of the product acid cooler (4) is refined sulfuric acid.

4. A refined sulfuric acid production device with low nitrogen oxide content, characterized in that: The output end of the semi-finished acid and the output end of the gas SO2 are both connected to the denitrifier (10), and the denitrifier (10) is connected to the upper part of the degassing tower (11). The top of the degassing tower (11) is connected to the negative pressure system, and the bottom is connected to the product acid tank (2).

5. The low nitrogen oxide content refined sulfuric acid production device according to claim 4, characterized in that: The product acid tank (2) is connected to the product acid cooler (4) via a product acid pump (3), and the output end of the product acid cooler (4) is refined sulfuric acid.

6. The low nitrogen oxide content refined sulfuric acid production device according to claim 4, characterized in that: The SO2 gas is connected to the denitrifier (10) via a conveying device (9).

7. A method for producing refined sulfuric acid with low nitrogen oxide content using the device according to claim 1, characterized in that: The method comprises the following steps: sending semi-finished sulfuric acid into a denitration and degassing tower, sending the SO2 in the liquid SO2 storage tank to a vaporizer through a metering pump, gasifying it into SO2 gas, and then entering a buffer tank, and then entering a denitration and degassing tower, reacting in the denitration and degassing tower for 45 to 50 seconds, and sending air into the bottom of the denitration and degassing tower. The air blows off and separates the SO2 dissolved in the semi-finished sulfuric acid, and the air enters a negative pressure system of the sulfuric acid device together with N2 generated by the denitration reaction. The refined sulfuric acid from which the nitrogen oxides have been removed flows by gravity to the product acid tank, which is the target product.

8. A method for producing refined sulfuric acid with low nitrogen oxide content using the device according to claim 4, characterized in that: The method comprises the following steps: feeding semi-finished sulfuric acid into a denitrifier at 80-90°C, introducing flue gas from a sulfuric acid main device conversion system into the denitrifier, reacting in the denitrifier for 45-50s, and a gas-liquid mixture after the reaction is completed entering a degassing tower for gas-liquid separation. Air is also fed into the bottom of the degassing tower, and the air blows off and separates the SO2 dissolved in the semi-finished sulfuric acid, and the air enters a negative pressure system of the sulfuric acid device together with N2 generated by the denitrification reaction. The refined sulfuric acid from which nitrogen oxides have been removed flows by gravity to a product acid tank, which is the target product.

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