Device and method for efficiently removing nitrate impurities in refined sulfuric acid

Abstract

The invention discloses an efficient removal device and method for nitrate impurities in refined sulfuric acid, and relates to the technical field of refined sulfuric acid denitration. The device comprises an SO2 absorption tower, an SO2 flue gas output pipeline is connected with the bottom of the SO2 absorption tower, the output end of the bottom of the SO2 absorption tower is respectively connected with the upper part of the SO2 absorption tower and a denitration reactor through a circulating acid tank, the output end of the denitration reactor is connected with a finished product acid cooler through a gas-liquid separator, and the output end of the finished product acid cooler is refined sulfuric acid. The application of the invention can completely meet the standard requirements of refined sulfuric acid on nitrate impurities, and provides a new thought and a new method for efficient removal of nitrate impurities in refined sulfuric acid.

Description

Technical Field

[0001] The invention relates to the technical field of refined sulfuric acid denitration, and in particular to a device and method for efficiently removing nitrate impurities in refined sulfuric acid. Background Art

[0002] The raw materials for sulfuric acid production are relatively abundant. The goal of the sulfuric acid production process is to convert sulfur in different raw materials into SO2 and SO3, and finally form sulfuric acid products. Different raw materials include sulfur, pyrite, sulfuric acid gas or waste sulfuric acid, etc. The acid production process is different. However, in the process of raw material processing to produce SO2, pyrite roasting, sulfur incineration, acid gas incineration, waste acid cracking and other processes will produce NO. x , the NO formed x Entering the acid-making system, NO x The presence of NOx will cause scaling or blockage of equipment such as fiber demisters or heat exchangers, directly affecting the operation of sulfuric acid plants; exhaust gas containing NOx is discharged into the atmosphere, which is likely to form acid rain, destroy the ozone layer, and harm the environment; in addition, NO x Finally, it enters the sulfuric acid product and forms nitrates, which affects the quality of the product. For industrial sulfuric acid, according to the GB / T 534-2014 "Industrial Sulfuric Acid" standard, there is no requirement for the nitrate content. Therefore, generally speaking, sulfuric acid products are not deNOxed. x Treatment can meet the quality requirements of industrial acid products. However, according to GB / T 625-2007 "Chemical Reagent Sulfuric Acid", the nitrate (NO3) content in analytical pure sulfuric acid is ≤0.5ppm, and the nitrate (NO3) content in premium pure sulfuric acid is ≤0.2ppm. Production practice shows that if the sulfuric acid products produced by the existing sulfuric acid process do not take denitrification measures, the nitrate concentration in the product will obviously exceed the standard and cannot meet the standard requirements of refined sulfuric acid.

[0003] The existing methods for producing refined sulfuric acid include industrial sulfuric acid distillation, direct absorption of sulfur trioxide gas (purification and preparation of sulfur trioxide) and chemical reagent treatment. The distillation method can be divided into atmospheric distillation and vacuum distillation. The temperature of atmospheric distillation is generally as high as 330°C, and the material requirements of the device are relatively high. Generally, expensive quartz glass is used; the temperature of vacuum distillation is generally 175-190°C, and the pressure is 1.33-2.67 kPa. The device can use cheaper borosilicate glass and fluoropolymer materials. Due to the limitations of equipment and energy, the distillation method is suitable for small-scale production and the energy consumption is too high; the direct absorption of sulfur trioxide gas is to directly absorb clean sulfur trioxide gas with ultrapure water or AR grade sulfuric acid, which is generally suitable for large-scale production, but due to the presence of nicotinic acid evaporation unit, the process flow is long and the energy consumption is high. The chemical reagent treatment method is to add hydrazine sulfate, urea or aminosulfonic acid to the industrial acid with excessive nitrate concentration for mixed reaction to remove nitrogen oxides in concentrated sulfuric acid, but this method has the problems of high reagent cost and chemical reagent residue in sulfuric acid. Summary of the invention

[0004] The present invention aims to provide a low-cost and high-efficiency method for removing nitrate impurities from refined sulfuric acid in order to solve the above-mentioned problems. The product meets the nitrate impurity content requirements of the GB / T 625-2007 "Chemical Reagent Sulfuric Acid" standard.

[0005] A highly efficient device for removing nitrate impurities in refined sulfuric acid comprises a SO2 absorption tower, an output pipeline of SO2 flue gas is connected to the bottom of the SO2 absorption tower, the output end of the bottom of the SO2 absorption tower is respectively connected to the upper part of the SO2 absorption tower and a denitration reactor through a circulating acid tank, the output end of the denitration reactor is connected to a finished acid cooler through a gas-liquid separator, and the output end of the finished acid cooler is refined sulfuric acid.

[0006] In the technical solution of the present invention: the circulating acid tank is connected to the circulating acid cooler through a circulating acid pump, and the output end of the circulating acid cooler is respectively connected to the upper part of the SO2 absorption tower and the denitration reactor.

[0007] In the technical solution of the present invention: the gas-liquid separator is connected to the finished acid cooler through the finished acid pump.

[0008] Another device for efficiently removing nitrate impurities from refined sulfuric acid: the device includes a SO2 absorption tower, a liquid SO2 storage tank connected to the lower part of the SO2 absorption tower through a SO2 gasification device, the top of the SO2 absorption tower is connected to a negative pressure system, the output end of the bottom is connected to the upper part of the SO2 absorption tower and a denitration reactor through a circulating acid tank, the output end of the denitration reactor is connected to a finished acid cooler through a gas-liquid separator, and the output end of the finished acid cooler is refined sulfuric acid.

[0009] In the technical solution of the present invention: the circulating acid tank is connected to the circulating acid cooler through a circulating acid pump, and the output end of the circulating acid cooler is respectively connected to the upper part of the SO2 absorption tower and the denitration reactor.

[0010] In the technical solution of the present invention: the gas-liquid separator is connected to the finished acid cooler through the finished acid pump.

[0011] A method for efficiently removing nitrate impurities from refined sulfuric acid using the above-mentioned device is provided, wherein SO2 flue gas with a concentration of 10-12% from a conversion section is passed into a SO2 absorption tower and is sprayed with 90-95% sulfuric acid for absorption at a spraying temperature of 45-55°C. After absorption, the gas is sent back to the negative pressure system of the sulfuric acid main device, and the circulating acid of the SO2 absorption tower flows into a circulating acid tank, and part of the circulating acid enters the SO2 absorption tower for circulating spraying.

[0012] The remaining circulating acid and semi-finished sulfuric acid enter the denitrification reactor for liquid-liquid denitrification reaction with a reaction time of not less than 20 seconds. They then enter the gas-liquid separator. After being fully separated by the gas-liquid separator, the tail gas containing some SO2, N2, etc. is connected to the negative pressure system of the sulfuric acid main unit. The separated liquid is the target product.

[0013] Another device described above realizes a highly efficient method for removing nitrate impurities from refined sulfuric acid. The liquid SO2 stored in the liquid SO2 storage tank is gasified by the SO2 gasification device 11 and then enters the SO2 buffer tank. The SO2 gas from the buffer tank is passed into the SO2 absorption tower and is sprayed with 90-95% sulfuric acid for absorption at a temperature of 40-60°C. The absorbed gas is sent back to the negative pressure system of the sulfuric acid main device. The circulating acid of the SO2 absorption tower flows into the circulating acid tank. Part of the circulating acid enters the SO2 absorption tower for circulation spraying. The remaining circulating acid enters the denitration reactor for liquid-liquid denitration reaction. The reaction time is not less than 20s. The mixed acid becomes 98% finished refined sulfuric acid and enters the gas-liquid separator. After being fully separated by the gas-liquid separator, the tail gas containing part of SO2, N2, etc. is connected to the negative pressure system of the sulfuric acid main device. The liquid after separation is the target product.

[0014] In the above method: the volume concentration of sulfur dioxide in the gas phase medium in the SO2 absorption tower is not less than 6%; the concentration of the semi-finished concentrated sulfuric acid from the sulfuric acid main device is not less than 95%, and the temperature is not less than 70°C.

[0015] In the above method: the volume concentration of sulfur dioxide in the gas phase medium in the SO2 absorption tower is not less than 6%; the concentration of the semi-finished concentrated sulfuric acid from the sulfuric acid main device is not less than 95%, and the temperature is not less than 70°C.

[0016] In the technical solution of the present invention, the sulfuric acid output of the SO2 absorption tower, the circulating acid tank, the circulating acid pump, the circulating acid cooler and the spray of the SO2 absorption tower are connected in sequence through pipelines to form a circulating acid channel; the SO2-containing sulfuric acid output end of the circulating acid pump, the denitration reactor, the gas-liquid separator and the semi-finished sulfuric acid of the denitration reactor are connected to form a sulfuric acid denitration channel, and the gas phase output end of the gas-liquid separator is connected to the negative pressure system of the sulfuric acid main device; the sulfuric acid output end of the gas-liquid separator, the finished acid pump, the finished acid cooler, and the sulfuric acid output end of the finished acid cooler are connected to the external finished acid tank area through pipelines to form a finished acid system.

[0017] In the technical solution of the present invention, sulfuric acid is used to dissolve and absorb SO2 gas at low temperature in the SO2 absorption tower, so that the dissolution efficiency in the gas-liquid phase mixing process is greatly improved, and the gas-liquid phase mixing is more uniform. In the denitration reactor, sulfuric acid containing SO2 is used as a denitrification agent to react with nitrosylsulfuric acid in the semi-finished sulfuric acid in liquid-liquid phase, the denitration reaction residence time is short, and the denitration efficiency is high.

[0018] In the technical solution of the present invention, the gas-liquid mixed gas phase medium can be SO2 flue gas or pure SO2 gas or a mixed gas of SO2 flue gas and pure SO2 gas, and the sulfur dioxide concentration of the gas phase medium is not less than 6% (vt). The temperature of the gas phase medium is not higher than 70°C. If the gas phase medium is SO2 flue gas, the NOx content in the flue gas must be no higher than 50ppm.

[0019] In the technical solution of the present invention, the absorbent of the SO2 absorption tower is sulfuric acid.

[0020] In the technical solution of the present invention, the finished refined sulfuric acid after sufficient denitration is passed into the gas-liquid separator, and the tail gas containing part of SO2, N2, etc. separated by the gas-liquid separator is sent to the negative pressure system of the sulfuric acid main device, which can be the inlet of the demister of the drying tower of the sulfuric acid device. The pure refined sulfuric acid is pumped into the finished acid cooler through the finished acid pump, and after being cooled to 40°C, it is sent to the finished acid tank area or taken away.

[0021] Efficient removal method of nitrate impurities in refined sulfuric acid: sulfuric acid containing sulfur dioxide is used as a denitrification agent to react with nitrosylsulfuric acid in semi-finished sulfuric acid to achieve the purpose of removing nitrate impurities in sulfuric acid. The reaction formula is:

[0022] 3SO2+2NO(HSO4)+4H2O=5H2SO4+N2

[0023] In view of the fact that SO2 gas phase is mixed with semi-finished sulfuric acid and reacts, there are disadvantages such as longer reaction time required for gas-liquid phase reaction, uneven mixing, and high requirements for the mixed reaction denitrifier. An efficient removal method for nitrate impurities in refined sulfuric acid is proposed, and the steps are as follows:

[0024] a. First, the SO2-containing gas is passed into the SO2 absorber and absorbed by circulating spraying with 0-95% sulfuric acid. After absorption, the gas is sent back to the negative pressure system of the sulfuric acid main device. The circulating acid of the SO2 absorber flows into the circulating acid tank. The circulating acid enters the SO2 absorber for circulating spraying through the circulating acid pump and the circulating acid cooler. A part of the sulfuric acid that fully absorbs SO2 flows out from the outlet of the circulating acid pump and enters the denitrification reactor for liquid-liquid denitrification reaction. The flow rate and concentration balance of the circulating acid are regulated and maintained by sulfuric acid and desalted water from the external pipe gallery.

[0025] b. Then, sulfuric acid containing SO2 is introduced into the denitration reactor and fully mixed with the semi-finished concentrated sulfuric acid from the sulfuric acid main device, and the sulfuric acid containing SO2 and the semi-finished concentrated sulfuric acid undergo a denitration reaction in the liquid-liquid phase, so that the nitrate impurities in the semi-finished concentrated sulfuric acid reach the standard of refined sulfuric acid. In addition, the semi-finished concentrated sulfuric acid and the sulfuric acid dissolved with SO2 are mixed in proportion to reach a concentration of 95% to 98% of the finished refined sulfuric acid.

[0026] c. Finally, the refined sulfuric acid after sufficient denitrification is passed into the gas-liquid separator, and the tail gas containing some SO2, N2, etc. is connected to the negative pressure system of the sulfuric acid main device. The finished refined sulfuric acid is pumped into the finished acid cooler through the finished acid pump, and after being cooled to the appropriate temperature, it is sent to the finished acid tank area or taken away.

[0027] Preferably, in step a, the concentration of the acid flow rate of the circulating acid should be balanced with the concentration of the acid flow rate supplemented by the circulating acid tank.

[0028] Preferably, in step a, the negative pressure system of the sulfuric acid main device to which the process gas after absorption in the SO2 absorption tower is sent back can be a drying tower of the sulfuric acid device.

[0029] Preferably, in step a, the SO2 absorption tower is a packed tower.

[0030] Preferably, in step b, the denitration reaction of sulfuric acid in which SO2 is fully dissolved and semi-finished concentrated sulfuric acid is carried out in a liquid-liquid phase.

[0031] Preferably, in step c, the tail gas containing part of SO2, N2, etc. separated by the gas-liquid separator and fed into the negative pressure system of the sulfuric acid main device can be the inlet of the demister of the drying tower of the sulfuric acid device.

[0032] Preferably, in step c, the temperature of the finished refined sulfuric acid after being cooled in the finished acid cooler is not higher than 40°C.

[0033] Compared with the prior art, the method for efficiently removing nitrate impurities in refined sulfuric acid provided by the present invention has the following advantages:

[0034] The efficient removal method of nitrate impurities in refined sulfuric acid of the present invention has low energy consumption and unlimited scale compared with the distillation method; compared with the direct absorption method of sulfur trioxide gas, the process flow is short and the energy consumption is low; compared with the chemical reagent treatment method, the reagent cost is low and there is no problem of chemical reagent residue. This technology uses sulfuric acid containing SO2 as a denitrification agent to react with nitrosylsulfuric acid in the semi-finished sulfuric acid in a liquid-liquid phase, the residence time of the denitrification reaction is short, and the denitrification efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the device of the present invention.

[0036] Figure 2 Another schematic diagram of the device of the present invention. DETAILED DESCRIPTION

[0037] In order to further illustrate the intended purpose, technical scheme and efficacy of the present invention, the following is a detailed description of the specific implementation, features and performance of a highly efficient method for removing nitrate impurities in refined sulfuric acid proposed by the present invention in combination with the embodiments. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0038] like Figure 1 .An efficient device for removing nitrate impurities in refined sulfuric acid, characterized in that: the device comprises a SO2 absorption tower 1, an output pipe of SO2 flue gas is connected to the bottom of the SO2 absorption tower 1, the output end of the bottom of the SO2 absorption tower is respectively connected to the upper part of the SO2 absorption tower 1 and the denitration reactor 5 through a circulating acid tank 2, the output end of the denitration reactor 5 is connected to a finished acid cooler 8 through a gas-liquid separator 6, and the output end of the finished acid cooler 8 is refined sulfuric acid. The circulating acid tank 2 is connected to the circulating acid cooler 4 through a circulating acid pump 3, and the output end of the circulating acid cooler 4 is respectively connected to the upper part of the SO2 absorption tower 1 and the denitration reactor 5. The gas-liquid separator 6 is connected to the finished acid cooler 8 through a finished acid pump 7.

[0039] like Figure 2.An efficient device for removing nitrate impurities from refined sulfuric acid, characterized in that: the device comprises a SO2 absorption tower 1, a liquid SO2 storage tank 9 is connected to the lower part of the SO2 absorption tower 1 through a SO2 gasification device 11, the top of the SO2 absorption tower 1 is connected to a negative pressure system, the output end of the bottom is connected to the upper part of the SO2 absorption tower 1 and the denitration reactor 5 through a circulating acid tank 2, the output end of the denitration reactor 5 is connected to a finished acid cooler 8 through a gas-liquid separator 6, and the output end of the finished acid cooler 8 is refined sulfuric acid. The circulating acid tank 2 is connected to the circulating acid cooler 4 through a circulating acid pump 3, and the output end of the circulating acid cooler 4 is connected to the upper part of the SO2 absorption tower 1 and the denitration reactor 5 respectively. The gas-liquid separator 6 is connected to the finished acid cooler 8 through a finished acid pump 7.

[0040] Example 1: Figure 1

[0041] In a 30,000 ton / year refined sulfuric acid plant, according to HG / T 2692-2015 "Battery Sulfuric Acid", the NOx mass fraction in the semi-finished sulfuric acid with a concentration of 98.5% is 100ppm (equivalent to 200ppm of NO (HSO4) content). The SO2 flue gas with a temperature of 50°C and a concentration of 10.5% (vt) from the conversion section is ~200Nm 3 / h is passed into the SO2 absorption tower 1 and 93% sulfuric acid is sprayed for absorption. The spraying acid temperature is 50℃. After absorption, the gas is sent back to the negative pressure system of the sulfuric acid main device. The circulating acid of the SO2 absorption tower flows into the circulating acid tank 2. The circulating acid enters the SO2 absorption tower for circulation spraying through the circulating acid pump 3 and the circulating acid cooler 4. The 153kg / h, 93% sulfuric acid fully absorbed with SO2 is discharged from the outlet of the circulating acid pump 3 and the 80℃, 98.5% sulfuric acid from the main device enters the denitration reactor 5 for liquid-liquid denitration reaction. The reaction time is about 35s. The mixed acid becomes 98% finished refined sulfuric acid and enters the gas-liquid separator 6. After being fully separated by the gas-liquid separator 6, the tail gas containing some SO2, N2, etc. is connected to the negative pressure system of the sulfuric acid main device. The pure 98% refined sulfuric acid is pumped into the finished acid cooler 8 through the finished acid pump 7. After cooling to ~40℃, it is sent to the finished acid tank area or directly sold.

[0042] Example 2: Figure 2

[0043] In a 50,000 ton / year refined sulfuric acid plant, the NOx mass fraction in the semi-finished sulfuric acid with a concentration of 98.3% is 200ppm (equivalent to 400ppm of NO (HSO4) content) according to HG / T 2692-2015 "Battery Sulfuric Acid". The liquid SO2 stored in the liquid SO2 storage tank 9 is pumped into the SO2 gasification device 11 through the SO2 metering pump 10, and then enters the SO2 buffer tank 8 after gasification. The 20Nm 3 / h SO2 gas is passed into SO2 absorption tower 1 and absorbed by 95% sulfuric acid circulation spraying, the spraying acid temperature is 50℃, and the gas after absorption is sent back to the negative pressure system of the sulfuric acid main device, the circulating acid of SO2 absorption tower flows into the circulating acid tank 2, and the circulating acid enters the SO2 absorption tower circulation spraying through the circulating acid pump 3 and the circulating acid cooler 4. The 466kg / h, 95% sulfuric acid fully absorbed with SO2 is discharged from the outlet of the circulating acid pump 3 and the 80℃, 98.3% sulfuric acid from the main device enters the denitration reactor 5, and the liquid-liquid denitration reaction is carried out. The reaction time is about 35s, and the mixed acid becomes 98% finished refined sulfuric acid and enters the gas-liquid separator 6. After being fully separated by the gas-liquid separator 6, the tail gas containing part of SO2, N2, etc. is connected to the negative pressure system of the sulfuric acid main device, and the pure 98% refined sulfuric acid is pumped into the finished acid cooler 8 through the finished acid pump 7, and sent to the finished acid tank area or directly sold after being cooled to ~40℃.

Claims

1. An efficient removal device for nitrate impurities in refined sulfuric acid, characterized in that: The device comprises a SO2 absorption tower (1), an output pipeline of SO2 flue gas is connected to the bottom of the SO2 absorption tower (1), the output end of the bottom of the SO2 absorption tower is respectively connected to the upper part of the SO2 absorption tower (1) and a denitration reactor (5) through a circulating acid tank (2), the output end of the denitration reactor (5) is connected to a finished acid cooler (8) through a gas-liquid separator (6), and the output end of the finished acid cooler (8) is refined sulfuric acid.

2. The highly efficient removal device for nitrate impurities in refined sulfuric acid according to claim 1, characterized in that: The circulating acid tank (2) is connected to the circulating acid cooler (4) via a circulating acid pump (3), and the output end of the circulating acid cooler (4) is respectively connected to the upper part of the SO2 absorption tower (1) and the denitration reactor (5).

3. The highly efficient removal device for nitrate impurities in refined sulfuric acid according to claim 1, characterized in that: The gas-liquid separator (6) is connected to the finished acid cooler (8) via the finished acid pump (7).

4. An efficient removal device for nitrate impurities in refined sulfuric acid, characterized in that: The device comprises a SO2 absorption tower (1), a liquid SO2 storage tank (9) connected to the lower part of the SO2 absorption tower (1) through a SO2 gasification device (11), the top of the SO2 absorption tower (1) is connected to a negative pressure system, the output end of the bottom is respectively connected to the upper part of the SO2 absorption tower (1) and a denitration reactor (5) through a circulating acid tank (2), the output end of the denitration reactor (5) is connected to a finished acid cooler (8) through a gas-liquid separator (6), and the output end of the finished acid cooler (8) is refined sulfuric acid.

5. The device for efficiently removing nitrate impurities in refined sulfuric acid according to claim 4, characterized in that: The circulating acid tank (2) is connected to the circulating acid cooler (4) via a circulating acid pump (3), and the output end of the circulating acid cooler (4) is respectively connected to the upper part of the SO2 absorption tower (1) and the denitration reactor (5).

6. The device for efficiently removing nitrate impurities in refined sulfuric acid according to claim 4, characterized in that: The gas-liquid separator (6) is connected to the finished acid cooler (8) via the finished acid pump (7).

7. A method for efficiently removing nitrate impurities from refined sulfuric acid using the device according to claim 1, characterized in that: The method is that SO2 flue gas with a concentration of 10-12% from the conversion section is passed into a SO2 absorption tower and is sprayed with 90-95% sulfuric acid for absorption at a spraying temperature of 45-55°C. After absorption, the gas is sent back to the negative pressure system of the sulfuric acid main device, and the circulating acid of the SO2 absorption tower flows into the circulating acid tank, and part of the circulating acid enters the SO2 absorption tower for circulating spraying. The remaining circulating acid and semi-finished sulfuric acid enter the denitrification reactor for liquid-liquid denitrification reaction with a reaction time of not less than 20 seconds. They then enter the gas-liquid separator. After being fully separated by the gas-liquid separator, the tail gas containing some SO2, N2, etc. is connected to the negative pressure system of the sulfuric acid main unit. The separated liquid is the target product.

8. A method for efficiently removing nitrate impurities from refined sulfuric acid using the device according to claim 4, characterized in that: The liquid SO2 stored in the liquid SO2 storage tank is gasified by the SO2 gasification device 11 and then enters the SO2 buffer tank. The SO2 gas from the buffer tank is passed into the SO2 absorption tower and is sprayed with 90-95% sulfuric acid for absorption at a temperature of 40-60°C. The absorbed gas is sent back to the negative pressure system of the sulfuric acid main device. The circulating acid of the SO2 absorption tower flows into the circulating acid tank. Part of the circulating acid enters the SO2 absorption tower for circulating spraying. The remaining circulating acid enters the denitration reactor for liquid-liquid denitration reaction. The reaction time is not less than 20s. The mixed acid becomes 98% finished refined sulfuric acid and enters the gas-liquid separator. After being fully separated by the gas-liquid separator, the tail gas containing part of SO2, N2, etc. is connected to the negative pressure system of the sulfuric acid main device. The liquid after separation is the target product.

9. The method according to claim 7, characterized in that: The volume concentration of sulfur dioxide in the gas phase medium in the SO2 absorption tower shall not be less than 6%; the concentration of the semi-finished concentrated sulfuric acid from the main sulfuric acid device shall not be less than 95%, and the temperature shall not be less than 70°C.

10. The method according to claim 8, characterized in that: The volume concentration of sulfur dioxide in the gas phase medium in the SO2 absorption tower shall not be less than 6%; the concentration of the semi-finished concentrated sulfuric acid from the main sulfuric acid device shall not be less than 95%, and the temperature shall not be less than 70°C.

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