Denitration device containing nitrate sulfuric acid and flue gas acid making system

Abstract

This application relates to the field of denitrification technology, and discloses a denitrification device for nitrifying sulfuric acid and a flue gas acid production system. The denitrification device includes: a denitrification reactor, which includes: a denitrification reactor body, which is provided with a nitrifying sulfuric acid inlet, a sulfur dioxide inlet, and a waste gas outlet, and the denitrification reactor body defines a reaction space; the reaction space is used to carry out a denitrification reaction on a mixture including nitrifying sulfuric acid and sulfur dioxide to remove nitrosylsulfuric acid from the nitrifying sulfuric acid to obtain first sulfuric acid, wherein the mass concentration of sulfuric acid in the mixture is 93% to 98%; a heater is disposed inside the denitrification reactor body for heating the mixture. Using this denitrification device to treat nitrifying sulfuric acid is low-cost and environmentally friendly.

Description

Technical Field

[0001] This application relates to the field of denitrification technology, specifically to a denitrification device for sulfuric acid containing nitrate and a flue gas acid production system. Background Technology

[0002] Sulfuric acid reagent products have strict requirements regarding the nitrate impurity content. Currently, many domestic sulfuric acid manufacturers' reagent sulfuric acid products easily exceed the nitrate limit due to limitations in equipment and process technology, leading to product substandardness, affecting sales, and causing economic losses. Some methods for treating nitrate impurities in sulfuric acid products are costly, while others, although effective in removing nitrate impurities, generate harmful gases that, when directly emitted, cause new pollution. Therefore, developing a low-cost and environmentally friendly device for treating nitrate impurities in sulfuric acid is currently a significant challenge.

[0003] Application content

[0004] This application aims to at least partially solve one of the technical problems in the related art. To this end, one objective of this application is to provide a nitrate-containing sulfuric acid denitrification device and a flue gas acid production system. Using the nitrate-containing sulfuric acid denitrification device of this application to treat nitrate impurities in sulfuric acid products is low-cost and environmentally friendly. Applying the nitrate-containing sulfuric acid denitrification device of this application to a flue gas acid production system can further improve the quality of the finished acid produced by the flue gas acid production system.

[0005] The first aspect of this application discloses a denitrification device for nitrate-containing sulfuric acid, comprising:

[0006] A denitrification reactor, the denitrification reactor comprising:

[0007] The denitrification reactor body is provided with a nitrate-containing sulfuric acid inlet, a sulfur dioxide inlet and a waste gas outlet, and the denitrification reactor body internally defines a reaction space;

[0008] The reaction space is used to carry out a denitrification reaction of a mixture including nitrated sulfuric acid and sulfur dioxide to remove nitrososulfuric acid from the nitrated sulfuric acid to obtain first sulfuric acid, wherein the mass concentration of sulfuric acid in the mixture is 93% to 98%.

[0009] A heater, located inside the denitrification reactor body, is used to heat the mixture.

[0010] This denitrification device achieves low-cost and environmentally friendly treatment of nitrate impurities in sulfuric acid by subjecting nitrososulfuric acid and sulfur dioxide to an oxidation-reduction reaction in a strongly acidic medium within the denitrification reactor, producing nitrogen gas and sulfuric acid. This improves the quality of sulfuric acid.

[0011] In addition, the nitrate-containing sulfuric acid denitrification device according to the above embodiments of this application may also have the following additional technical features:

[0012] In some embodiments of this application, the denitrification device further includes:

[0013] A denitrification cooler, connected to the denitrification reactor, is used to cool the first sulfuric acid to obtain the second sulfuric acid;

[0014] A sulfur dioxide saturated reactor, connected to the denitrification cooler and the denitrification reactor, is used to dissolve sulfur dioxide in the second sulfuric acid to obtain sulfur dioxide-saturated sulfuric acid. This sulfur dioxide-saturated sulfuric acid is then transported to the denitrification reactor through the sulfur dioxide inlet. This helps to form a closed loop in the denitrification unit containing nitrate-containing sulfuric acid, further improving the system stability and controllability of the device.

[0015] In some embodiments of this application, multiple denitrification reactors are included, which are connected in series or in parallel. This helps to improve denitrification efficiency, ensure the flexibility and reliability of the denitrification device operation, and meet the requirements of continuous and batch reactions.

[0016] In some embodiments of this application, the denitrification reactor satisfies at least one of the following conditions:

[0017] A stirrer, located inside the denitrification reactor body, is used to stir the mixture;

[0018] A thermometer, connected to the denitrification reactor body, is used to monitor the temperature of the denitrification reaction;

[0019] A level gauge, connected to the denitrification reactor body, is used to monitor the operating level of the denitrification reactor. This helps ensure the smooth and accurate progress of the denitrification reaction.

[0020] In some embodiments of this application, the sulfur dioxide saturated reactor satisfies at least one of the following conditions:

[0021] The sulfur dioxide saturated reactor is a packed tower structure;

[0022] The sulfur dioxide saturated reactor is equipped with a demister to remove acid mist that may be generated during the gas-liquid contact process.

[0023] An acid concentration analyzer is installed in the sulfur dioxide saturated reactor to monitor the acid concentration in the reactor. This helps to obtain sulfuric acid saturated with sulfur dioxide.

[0024] In some embodiments of this application, the denitrification device further includes:

[0025] A first delivery pump is disposed between the denitrification reactor and the denitrification cooler for delivering the first sulfuric acid to the denitrification cooler;

[0026] A second transfer pump is installed between the denitrification reactor and the sulfur dioxide saturated reactor to transfer the sulfur dioxide saturated sulfuric acid to the denitrification reactor.

[0027] A dilution water supply unit is connected to the sulfur dioxide saturated reactor and is used to supply dilution water to the sulfur dioxide saturated reactor.

[0028] The quality acid collection unit, connected to the second transfer pump, is used to collect high-quality sulfuric acid that meets nitrate standards. This contributes to the smooth operation of the denitrification unit.

[0029] In some embodiments of this application, the first delivery pump satisfies at least one of the following conditions:

[0030] The first transfer pump includes at least one of a horizontal transfer pump and a vertical submersible transfer pump;

[0031] A level regulating valve is installed at the outlet of the first delivery pump, which is interlocked with the level gauge in the denitrification reactor to control the operating level in the denitrification reactor. This helps to accurately control the denitrification reaction and ensure the smooth operation of the denitrification unit.

[0032] In some embodiments of this application, an acid concentration regulating valve is provided between the dilution water supply unit and the sulfur dioxide saturated reactor to regulate the acid concentration in the sulfur dioxide saturated reactor. This helps to obtain sulfuric acid saturated with sulfur dioxide at the target concentration.

[0033] A second aspect of this application proposes a flue gas acid production system, including the aforementioned nitrate-containing sulfuric acid denitrification device. Therefore, this flue gas acid production system possesses all the features and advantages of the aforementioned nitrate-containing sulfuric acid denitrification device, which will not be elaborated further here.

[0034] In some embodiments of this application, the flue gas acid production system further includes:

[0035] An acid-generating device connected to the denitrification device;

[0036] The acid production device includes:

[0037] A purification component is used to wash the flue gas to obtain the first flue gas;

[0038] A dry suction component, connected to the purification component, is used to remove moisture from the first flue gas to obtain a second flue gas;

[0039] A conversion component, connected to the dry absorption component, is used to convert sulfur dioxide in the second flue gas into sulfur trioxide, thereby obtaining a third flue gas containing sulfur trioxide.

[0040] A connecting pipeline, positioned between the conversion component and the dry absorption component, is used to transport the third flue gas to the dry absorption component for sulfur trioxide absorption, yielding nitrate-containing sulfuric acid. Using this flue gas acid production system helps to obtain high-quality finished acid. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the component connections of a nitrate-containing sulfuric acid denitrification device according to an embodiment of this application.

[0042] Figure 2 This is a schematic diagram of the structure of a nitrate-containing sulfuric acid denitrification device according to an embodiment of this application.

[0043] Figure 3 This is a flowchart of an embodiment of a flue gas acid production system according to this application. Attached image description:

[0045] 1: Denitrification reactor 2: Denitrification cooler 3: Sulfur dioxide saturated reactor 4: First transfer pump 5: Second transfer pump 6: Dilution water supply unit 7: Quality acid collection unit 1-1: Denitrification reactor body 4-1: Liquid level regulating valve 4-2: Liquid level regulating valve 4-3: Dilution water regulating valve 4-4: Reaction regulating valve 4-5: Acid production switch valve A: Nitric acid inlet B: Sulfur dioxide inlet C: Exhaust gas outlet D: Cooling return water pipeline E: Cooling supply water pipeline G: Packing H: Demister T1: Thermometer T2: Thermometer L1: Liquid level gauge L2: Liquid level gauge F1: Flow meter F2: Flow meter C1: Acid concentration analyzer C2: Nitrate analyzer C3: Nitrogen oxide analyzer Detailed Implementation

[0046] The embodiments of this application are described in detail below. The embodiments described below are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0047] This application is based on the applicant's following findings and insights:

[0048] In industrial sulfuric acid products, the content of nitrate impurities must be ≤10 mg / m³. 3The main component of nitrate impurities is NOHSO4. There are three main methods for treating NOHSO4 in sulfuric acid products. The first method is to add a liquid reducing agent to the sulfuric acid product. Commonly used liquid reducing agents can be hydrazine hydrate, hydroxylamine, etc. Taking hydrazine hydrate (N2H4·H2O) as an example, the reaction equation for treating NOHSO4 is: 3N2H4·H2O+4NOHSO4→4H2SO4+5N2+7H2O. On the one hand, the liquid reducing agent used in this method is expensive, which greatly increases the treatment cost. On the other hand, it is necessary to strictly control the amount of liquid reducing agent added, because the reducing agent that does not participate in the reaction will become a new impurity in the sulfuric acid product, further affecting the quality of sulfuric acid. Moreover, these reducing agents are generally carcinogenic. Once they enter the downstream products of sulfuric acid—fertilizers—along with sulfuric acid, they will have a more serious impact. The second method involves adding a small amount of water to the sulfuric acid product for dilution and hydrolysis. During hydrolysis, NOHSO4 decomposes into NO and NO2, which are released in gaseous form. Direct emission of NO and NO2 would cause new pollution, so they need to be absorbed and neutralized with dilute nitric acid solution before being discharged, which significantly increases costs. The third method uses SO2 as a reducing agent, passing a large amount of SO2-containing process gas into the concentrated sulfuric acid product containing nitrates to achieve denitrification. The reaction is as follows: 2NOHSO4 + SO2 + 2H2O → 2NO + 3H2SO4. The NO produced by this method is released in gaseous form, which would cause pollution if directly emitted. Absorption and neutralization with dilute nitric acid solution before discharge would also significantly increase costs. Therefore, all the methods for treating nitrate impurities in sulfuric acid products in the relevant technologies have obvious drawbacks.

[0049] Based on the above research, the inventors discovered that when NOHSO4 in sulfuric acid products is treated with SO2 as a reducing agent, NOHSO4 preferentially reacts with water in the sulfuric acid products, with the reaction equation being: NOHSO4 + 2H2O → 2H2SO4 + 2HNO2. The generated HNO2 is unstable and easily decomposes into NO or NO2 gas. However, if SO2 gas is introduced into the sulfuric acid products while providing a strong acidic reaction medium, the strong acid medium will increase the stability of the reaction intermediate product HNO2, allowing it to exist stably without decomposing into NO or NO2 gas. At the same time, the strong acid medium will also enhance the reducing power of SO2, thereby reducing nitrous acid, an intermediate product of NOHSO4 decomposition, to nitrogen gas. Therefore, using this method to treat nitrates will not generate new pollution and is also low in cost.

[0050] In view of this, in the first aspect of this application, a denitrification device for nitrate-containing sulfuric acid is proposed, referring to... Figure 1The system includes a denitrification reactor 1, which is used for the redox reaction of sulfur dioxide and nitrate-containing sulfuric acid under certain conditions. The reaction equation is: 4H₂O + 2NOHSO₄ + 3SO₂ → 5H₂SO₄ + N₂, and the products are nitrogen gas and sulfuric acid. This removes nitrosylsulfuric acid from the nitrate-containing sulfuric acid to obtain primary sulfuric acid, achieving low-cost and environmentally friendly treatment of nitrate impurities in nitrate-containing sulfuric acid.

[0051] In the embodiments of this application, reference is made to Figure 1 The denitrification device may further include a denitrification cooler 2, connected to the denitrification reactor 1, for cooling the first sulfuric acid to obtain a second sulfuric acid. This reduces the corrosion of equipment and pipelines by the second sulfuric acid under high-temperature conditions, thereby extending equipment lifespan.

[0052] In the embodiments of this application, reference is made to Figure 1 The denitrification device may further include: a sulfur dioxide saturated reactor 3, connected to the denitrification cooler 2 and the denitrification reactor 1, for dissolving sulfur dioxide in the second sulfuric acid to obtain sulfur dioxide saturated sulfuric acid, which is then transported to the denitrification reactor as a reactant. Therefore, this denitrification device forms a closed loop by connecting the denitrification reactor 1, the denitric acid cooler 2, and the sulfur dioxide saturated reactor 3. On the one hand, the first sulfuric acid is cooled in the denitrification reactor to obtain the second sulfuric acid. As the temperature of the sulfuric acid decreases, its solubility increases, allowing the second sulfuric acid to absorb more sulfur dioxide in the sulfur dioxide saturated reactor until it reaches saturation. This provides more reducing agent sulfur dioxide for the denitrification reaction, which helps to further promote the rapid progress of the denitrification reaction. On the other hand, providing sulfur dioxide to the denitrification reaction in the form of sulfur dioxide-saturated sulfuric acid can enhance the reducing power of sulfur dioxide, thereby reducing nitrosulosic acid to nitrogen gas. Furthermore, the denitric acid cooler can remove the heat generated by the exothermic denitrification reaction in the denitrification reactor, preventing excess heat from causing side reactions and ensuring the smooth progress of the denitrification reaction. Thus, the system stability and controllability of the denitrification device can be effectively improved.

[0053] In some embodiments of this application, reference is made to Figure 2 The denitrification device further includes a first transfer pump 4, which is disposed between the denitrification reactor 1 and the denitrification nitric acid cooler 2, for transporting the first sulfuric acid to the denitrification nitric acid cooler. This helps to increase the transmission speed of the first sulfuric acid to the denitrification nitric acid cooler and shorten the transmission time, thereby meeting the requirements of large-scale industrial denitrification treatment of nitrate-containing sulfuric acid.

[0054] In some embodiments of this application, reference is made to Figure 2The denitrification device further includes a second transfer pump 5, which is located between the denitrification reactor 1 and the sulfur dioxide saturated reactor 3, for transporting the sulfur dioxide saturated sulfuric acid to the denitrification reactor. This helps to increase the transfer speed of the sulfur dioxide saturated sulfuric acid to the denitrification reactor, shorten the transfer time, and thus meet the requirements of large-scale industrial denitrification treatment of sulfuric acid containing nitrates.

[0055] In some embodiments of this application, reference is made to Figure 2 The denitrification device further includes a dilution water supply unit 6, connected to the sulfur dioxide saturated reactor 3, for supplying dilution water to the sulfur dioxide saturated reactor. By supplying dilution water to the sulfur dioxide saturated reactor, the mass concentration of sulfuric acid saturated with sulfur dioxide in the reactor is adjusted to meet the requirements of the denitrification reaction. This helps the denitrification reaction proceed smoothly.

[0056] In some embodiments of this application, reference is made to Figure 2 The denitrification device further includes a quality acid collection unit 7, which is connected to the second delivery pump 5, for collecting sulfuric acid saturated with sulfur dioxide that meets the nitrate standard, to obtain a high-quality sulfuric acid product.

[0057] In some embodiments of this application, the denitrification device may include multiple denitrification reactors, which may be connected in series or in parallel. Using multiple denitrification reactors helps improve denitrification efficiency while ensuring the flexibility and reliability of the denitrification device operation.

[0058] In some embodiments of this application, reference is made to Figure 2 The denitrification reactor 1 includes a denitrification reactor body 1-1, which is provided with a nitrate-containing sulfuric acid inlet A, a sulfur dioxide inlet B, and a waste gas outlet C. A flow meter F1 is installed at the nitrate-containing sulfuric acid inlet A to monitor the volumetric flow rate of the nitrate-containing sulfuric acid. The denitrification reactor body defines a reaction space for carrying out a denitrification reaction on a mixture including nitrate-containing sulfuric acid and sulfur dioxide to remove nitrosylsulfuric acid from the nitrate-containing sulfuric acid to obtain first sulfuric acid. The specific reaction equation for the denitrification reaction is as follows:

[0059] 2NOHSO4 + 2H2O → 2H2SO4 + 2HNO2

[0060] 3SO2 + 3H2O → 3H2SO3

[0061] 2HNO2 + 3H2SO3 → 3H2SO4 + N2 + H2O

[0062] The intermediate product HNO2 easily decomposes into NO or NO2 gas, requiring a strong acid medium to prevent its decomposition. Therefore, the mass concentration of the mixture is required to be 93%–98%, specifically 93%, 94%, 95%, 96%, 97%, 98%, etc. The mixture includes sulfuric acid saturated with nitrosulanium and sulfur dioxide. This concentration range improves the stability of the intermediate product HNO2, preventing its decomposition into NO or NO2 gas. It also enhances the reducing power of sulfur dioxide, allowing it to undergo a redox reaction with nitrosulanium to produce nitrogen and sulfuric acid. Thus, this concentration range effectively avoids the problems of high cost and waste of high-quality sulfuric acid due to excessively high sulfuric acid concentration, as well as the problems of easily decomposing HNO2 into NO or NO2 gas and reduced sulfur dioxide reducing power due to excessively low sulfuric acid concentration.

[0063] In some embodiments of this application, the structure of the denitrification reactor body can be any one of the following: trough structure, tubular structure, or kettle structure. This helps to make it applicable to different fields and different processes, and at the same time, the structure of the denitrification reactor body can be flexibly designed according to the site and other factors.

[0064] In some embodiments of this application, a heater is provided inside the denitrification reactor body to heat the mixture. When the heat of the denitrification reaction is insufficient or when the system is restarted, the heater can supplement the heat to meet the heat required for the denitrification reaction and ensure the smooth operation of the denitrification reactor. Specifically, the heater can be electrically heated or steam heated, and the heating coil is made of high-temperature resistant and concentrated acid resistant alloy material or equivalent material.

[0065] In some embodiments of this application, the denitrification reactor body is provided with a stirrer for stirring the mixture, which helps to mix the nitrate-containing sulfuric acid and sulfur dioxide-saturated sulfuric acid evenly, so that the denitrification reaction can proceed more fully.

[0066] In some embodiments of this application, reference is made to Figure 2 The denitrification reactor also includes a thermometer T1, which is connected to the denitrification reactor body 1-1 and is used to monitor the temperature of the denitrification reaction to ensure that the denitrification reaction proceeds smoothly.

[0067] In some embodiments of this application, reference is made to Figure 2 The denitrification reactor also includes a level gauge L1, which is connected to the denitrification reactor body 1-1 and is used to monitor the operating level of the denitrification reactor. This allows for precise control of the denitrification reaction level and promotes efficient and stable reaction.

[0068] In some embodiments of this application, reference is made to Figure 2A nitrogen oxide analyzer C3 is installed at the exhaust gas outlet C of the denitrification reactor body to monitor the nitrogen oxide content in the exhaust gas discharged from the denitrification reactor body, thereby determining whether the denitrification reaction is proceeding normally. Specifically, the nitrogen oxide content in the exhaust gas monitored by the nitrogen oxide analyzer is ≤10mg / Nm³. 3 This indicates that the reaction is proceeding normally.

[0069] In some embodiments of this application, reference is made to Figure 2 The outlet of the first delivery pump 4 is equipped with a liquid level regulating valve 4-1, which is interlocked with the liquid level gauge L1 in the denitrification reactor. This valve is used to control the operating liquid level in the denitrification reactor, which can prevent leakage caused by excessively high denitrification reaction liquid level and insufficient denitrification reaction caused by excessively low liquid level.

[0070] Specifically, the level regulating valve 4-1 is interlocked with the level gauge L1. When the level gauge shows a low level in the denitrification reactor, the level regulating valve can be adjusted to reduce the discharge rate of the first sulfuric acid in the denitrification reactor; when the level gauge shows a high level, the level regulating valve can be adjusted to increase the discharge rate of the first sulfuric acid in the denitrification reactor. This helps to control the smooth progress of the denitrification reaction and further ensures the normal operation of the entire closed loop.

[0071] In some embodiments of this application, the first transfer pump can be either a horizontal transfer pump or a vertical submersible transfer pump. This allows for adaptation to different fields and processes, and also enables flexible design of the denitrification reactor structure based on site conditions.

[0072] In some embodiments of this application, the structure of the denitrification cooler can be any of the following: shell-and-tube type, plate type, or other equipment structure that meets the heat exchange requirements. Therefore, it can be adapted to different fields and different processes, and the structure of the denitrification reactor body can be flexibly designed according to site conditions.

[0073] In some embodiments of this application, the denitrification cooler is made of high-temperature and concentrated acid resistant alloy material to prevent the equipment from being corroded.

[0074] In some embodiments of this application, the denitric acid cooler is provided with a cooling return water pipeline D and a cooling supply water pipeline E, thereby ensuring the smooth operation of the denitric acid cooler. The temperature difference between the water in the cooling return water pipeline and the cooling supply water pipeline is between 8°C and 15°C, specifically 8°C, 9°C, 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, etc. When the temperature difference is within the above range, the temperature of the second sulfuric acid obtained from the denitric acid cooler basically meets the requirements.

[0075] In some embodiments of this application, reference is made to Figure 2A thermometer T2 is installed at the outlet of the denitrification cooler 2 to monitor the temperature of the second sulfuric acid. The temperature of the second sulfuric acid can be controlled by adjusting the temperature difference between the cooling return water and the cooling supply water.

[0076] In some embodiments of this application, the sulfur dioxide saturated reactor 3 is a packed tower structure. The packing material G in the packed tower structure can provide a large specific surface area, which helps to fully contact sulfur dioxide and the second sulfuric acid, thereby promoting the dissolution of sulfur dioxide and obtaining sulfuric acid saturated with sulfur dioxide.

[0077] In some embodiments of this application, the sulfur dioxide saturated reactor is equipped with a demister H to remove acid mist that may be generated during gas-liquid contact, preventing acid mist from entering other equipment and causing corrosion, thereby ensuring the smooth operation of the device. Specifically, the demister can be a wire mesh structure or other Brownian motion type structures.

[0078] In some embodiments of this application, the sulfur dioxide saturated reactor 3 is equipped with an acid concentration analyzer C1 and a dilution water regulating valve 4-3, both of which are interlocked with the dilution water supply unit 6. The mass concentration of sulfur dioxide saturated sulfuric acid in the sulfur dioxide saturated reactor is regulated by the dilution water regulating valve, which helps to ensure that the mass concentration of sulfur dioxide saturated sulfuric acid obtained is between 93% and 98%, thereby ensuring the smooth operation of the denitrification reactor.

[0079] Specifically, the acid concentration analyzer C1 is used to monitor the mass concentration of sulfur dioxide-saturated sulfuric acid in the sulfur dioxide-saturated reactor. Both the dilution water regulating valve 4-3 and the acid concentration analyzer C1 are interlocked with the dilution water supply unit 6. When the acid concentration displayed by the analyzer is low, the dilution water regulating valve can be closed or its flow reduced to decrease the amount of dilution water entering the sulfur dioxide-saturated reactor, thereby increasing the mass concentration of sulfur dioxide-saturated sulfuric acid in the reactor. Conversely, when the acid concentration displayed by the analyzer is high, the dilution water regulating valve can be opened or its flow increased to increase the amount of dilution water entering the reactor, thereby decreasing the mass concentration of sulfur dioxide-saturated sulfuric acid in the reactor. This helps control the mass concentration of sulfur dioxide-saturated sulfuric acid, further ensuring the normal operation of the denitrification reaction.

[0080] In some embodiments of this application, reference is made to Figure 2 A level gauge L2 is installed at the outlet of the sulfur dioxide saturated reactor 3 to monitor the operating level of the sulfur dioxide saturated reactor, thereby accurately controlling the level of the sulfur dioxide saturated reactor and promoting the efficient and stable reaction.

[0081] In some embodiments of this application, reference is made to Figure 2The outlet of the sulfur dioxide saturated reactor 3 is equipped with a liquid level regulating valve 4-2, which is interlocked with the liquid level gauge L2 in the sulfur dioxide saturated reactor. This valve is used to control the operating liquid level in the sulfur dioxide saturated reactor, which can avoid problems such as leakage caused by excessively high liquid level in the sulfur dioxide saturated reactor and insufficient dissolution of sulfur dioxide caused by excessively low liquid level.

[0082] Specifically, the level regulating valve 4-2 is interlocked with the level gauge L2. When the level gauge shows a low level in the sulfur dioxide saturated reactor, the level regulating valve can be adjusted to reduce the discharge rate of sulfur dioxide-saturated sulfuric acid from the reactor. When the level gauge shows a high level, the level regulating valve can be adjusted to increase the discharge rate of sulfur dioxide-saturated sulfuric acid from the reactor. This helps to control the level in the sulfur dioxide saturated reactor to a normal level, further ensuring the smooth progress of the denitrification reaction and thus ensuring the normal operation of the entire closed loop.

[0083] In some embodiments of this application, reference is made to Figure 2 A flow meter F2 and a reaction regulating valve 4-4 are installed between the second transfer pump 5 and the denitrification reactor 1. The flow meter F2 is used to monitor the volume flow rate of sulfur dioxide saturated sulfuric acid transferred from the saturated sulfuric acid transfer pump to the denitrification reactor. The flow meter F2 is interlocked with the flow meter F1. The ratio between the flow meter F1 and the flow meter F2 is controlled by adjusting the reaction regulating valve 4-4, thereby ensuring the smooth progress of the denitrification reaction.

[0084] Specifically, the ratio of flow meter F1 to flow meter F2 is 1:15 to 1:25. When the ratio of flow meter F1 to flow meter F2 is too high, it indicates that too much nitrate-containing sulfuric acid is being input into the denitrification reactor. In this case, the amount of sulfur dioxide-saturated sulfuric acid output from the second delivery pump needs to be increased by adjusting the reaction regulating valve 4-4, thus reducing the ratio of flow meter F1 to flow meter F2 to the aforementioned range. Conversely, when the ratio of flow meter F1 to flow meter F2 is too low, it indicates that too much sulfur dioxide-saturated sulfuric acid is being output from the second delivery pump into the denitrification reactor. In this case, the amount of sulfur dioxide-saturated sulfuric acid output from the second delivery pump needs to be reduced by adjusting the reaction regulating valve 4-4, thus reducing the ratio of flow meter F1 to flow meter F2 to the aforementioned range. This helps ensure the smooth progress of the denitrification reaction.

[0085] In some embodiments of this application, reference is made to Figure 2The nitrate-containing sulfuric acid denitrification device also includes a quality acid collection unit 7, connected to the second delivery pump 5, for collecting high-quality sulfuric acid that meets nitrate standards, thus obtaining a high-quality sulfuric acid product. Specifically, the quality acid collection unit 7 and the second delivery pump 5 are connected to an acid-producing switch valve 4-5 and a nitrate analyzer C2. The nitrate analyzer is used to monitor the nitrate concentration in sulfur dioxide-saturated sulfuric acid. Once the nitrate concentration in the sulfur dioxide-saturated sulfuric acid meets the standard, the acid-producing switch valve can be opened to output the qualified sulfur dioxide-saturated sulfuric acid. Simultaneously, a sulfur dioxide desorption tower needs to be installed at the inlet of the quality acid collection unit 7 to further remove sulfur dioxide from the sulfur dioxide-saturated sulfuric acid, thereby obtaining high-quality sulfuric acid. This high-quality sulfuric acid is then transported to the quality acid collection unit to obtain the high-quality sulfuric acid product. Specifically, the nitrate concentration in the sulfur dioxide-saturated sulfuric acid is ≤10 mg / m³. 3 It can then enter the sulfur dioxide desorption tower for sulfur dioxide removal.

[0086] A second aspect of this application proposes a method for denitrifying nitrate-containing sulfuric acid, comprising the following steps:

[0087] S10: Under conditions of 60℃~90℃, nitrososulfuric acid in nitrate-containing sulfuric acid undergoes a denitrification reaction with water and sulfur dioxide to obtain nitrogen gas and first sulfuric acid. The mass concentration of sulfuric acid in the denitrification reaction system is 93%~98%.

[0088] This step uses sulfuric acid with a mass concentration of 93%–98% as a strong acid medium and provides water as a reactant. Simultaneously, sulfur dioxide is used as a reducing agent to remove nitrososulfuric acid from nitric acid. The reaction equation is: 4H₂O + 2NOHSO₄ + 3SO₂ → 5H₂SO₄ + N₂. Specifically, the concentration of sulfuric acid can be 93%, 94%, 95%, 96%, 97%, 98%, etc. This concentration range can improve the stability of the reaction intermediate HNO₂, preventing it from decomposing into NO or NO₂ gas. On the one hand, it can enhance the reducing power of sulfur dioxide, enabling it to undergo a redox reaction with nitrosulosic acid to produce nitrogen gas and sulfuric acid. The reaction temperature is 60℃~90℃, preferably 70℃~80℃, specifically 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, etc. Within this temperature range, the denitrification reaction proceeds smoothly and efficiently, largely avoiding problems such as high equipment requirements due to excessively high temperatures and incomplete reactions due to excessively low temperatures. The reaction pressure is atmospheric pressure. This denitrification method for removing nitrate impurities from nitrosulosic acid is low-cost, environmentally friendly, and avoids the introduction of new impurities.

[0089] In some embodiments of this application, the denitrification reaction time is 0.5h to 1h, specifically 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, etc. The above reaction time helps the denitrification reaction to proceed fully, and can basically avoid incomplete reaction caused by too short a reaction time, as well as wasted time cost caused by too long a reaction time.

[0090] In some embodiments of this application, the denitrification method for nitrate-containing sulfuric acid further includes:

[0091] S20: Cool the first sulfuric acid to 40℃~60℃ to obtain the second sulfuric acid.

[0092] In this step, the first sulfuric acid is cooled to 40℃~60℃, specifically 40℃, 45℃, 50℃, 55℃, 60℃, etc., to obtain the second sulfuric acid. The temperature of the second sulfuric acid within the above range helps to improve the solubility of sulfur dioxide in the second sulfuric acid. This can basically avoid the problem that the amount of dissolved sulfur dioxide is too small due to the temperature of the second sulfuric acid being too high, which is insufficient to provide the sulfur dioxide required for the denitrification reaction, as well as the problem that the viscosity of the sulfuric acid is too high due to the temperature of the second sulfuric acid being too low, which affects the denitrification reaction and increases energy consumption.

[0093] S30: Sulfur dioxide is dissolved in the second sulfuric acid to obtain sulfuric acid saturated with sulfur dioxide.

[0094] In this step, sulfur dioxide gas is continuously passed into the second sulfuric acid, and the system temperature is maintained at 40℃~60℃, which helps to efficiently complete the sulfur dioxide dissolution process and obtain sulfuric acid saturated with sulfur dioxide.

[0095] S40: A portion of the sulfur dioxide-saturated sulfuric acid is returned to the denitrification reaction to provide the sulfur dioxide, wherein the volume ratio of nitrate-containing sulfuric acid to sulfur dioxide-saturated sulfuric acid in the denitrification reaction is 1:20 to 1:30.

[0096] In this step, sulfuric acid saturated with sulfur dioxide is transported to S10 to provide sulfur dioxide for the denitrification reaction. At the same time, the sulfuric acid saturated with sulfur dioxide can serve as a strong acid medium to ensure the stability of the reaction system. This forms a closed loop, which helps the denitrification reaction proceed stably.

[0097] In some embodiments of this application, the volume ratio of nitrate-containing sulfuric acid to sulfur dioxide-saturated sulfuric acid in the denitration reaction is 1:20 to 1:30. Specifically, it can be 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, etc. This range ensures the smooth progress of the denitration reaction and largely avoids problems such as excessive nitrososulfuric acid and incomplete denitration due to an excessively high volume ratio of nitrate-containing sulfuric acid to sulfur dioxide-saturated sulfuric acid, or excessive space requirements due to an excessively low volume ratio. Therefore, a portion of the sulfur dioxide-saturated sulfuric acid is used to provide sulfur dioxide for the denitration reaction, and the remaining portion, under the condition of meeting the denitration standards, can be collected as a high-quality sulfuric acid product.

[0098] In some embodiments of this application, the denitrification method for nitrifying sulfuric acid is implemented using the aforementioned nitrifying sulfuric acid denitrification device. Therefore, the volume of the denitrification reactor body can be calculated based on the above denitrification method. Specifically, the volume of the denitrification reactor body can be calculated using the following formula: V = Q1 × t / K. Wherein, Q1 is the volumetric flow rate (m³) of sulfur dioxide-saturated sulfuric acid supplied by the sulfur dioxide-saturated reactor to the denitrification reactor. 3 / h); t is the residence time of the denitrification reaction (h); K is the volume coefficient of the denitrification reactor, K = 0.7~0.8, specifically, it can be 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, etc., which helps the denitrification reaction to proceed fully and ensures that the substances in the reaction system are mixed evenly; V is the volume of the denitrification reactor (m³). 3 This method for denitrifying with nitrate-containing sulfuric acid possesses all the features and advantages of the aforementioned nitrate-containing sulfuric acid denitrification device, which will not be repeated here.

[0099] In a third aspect of this application, a flue gas acid production system is provided, including the aforementioned nitrate-containing sulfuric acid denitrification device, as described above. Figure 3 The flue gas sulfuric acid production system also includes an sulfuric acid production device, which comprises a purification component for washing the flue gas to obtain a first flue gas; a dry absorption component connected to the purification component for removing moisture from the first flue gas to obtain a second flue gas; a conversion component connected to the dry absorption component for converting sulfur dioxide in the second flue gas into sulfur trioxide to obtain a third flue gas containing sulfur trioxide; and a connecting pipeline located between the conversion component and the dry absorption component for transporting the third flue gas to the dry absorption component for sulfur trioxide absorption to obtain nitrate-containing sulfuric acid. Thus, the nitrate-containing sulfuric acid obtained from the sulfuric acid production device is transferred to the nitrate-containing sulfuric acid denitrification device of this application for denitrification, ultimately yielding a high-quality sulfuric acid product.

[0100] In some embodiments of this application, the dry absorption device includes a drying tower and an absorption tower. The drying tower is used to remove moisture from the flue gas to obtain the second flue gas. The sulfur dioxide saturated reactor in the nitrate sulfuric acid denitrification device can be connected to the drying tower in the dry absorption device. This helps the sulfur dioxide in the second flue gas coming out of the drying tower to dissolve in the second sulfuric acid in the sulfur dioxide saturated reactor to obtain sulfur dioxide saturated sulfuric acid, thereby further reducing costs.

[0101] Specifically, the second flue gas needs to undergo demisting and dust removal pretreatment to avoid carrying too many impurities, and the volume content of sulfur dioxide in the second flue gas needs to be greater than 6% to ensure dissolution efficiency.

[0102] In some embodiments of this application, the exhaust gas from the denitrification reactor outlet of the denitrification device can be collected with the gas in the sulfur dioxide saturated reactor of the denitrification device and then re-enter the flue gas to produce sulfuric acid. This can further ensure that SO2 can be fully utilized to convert into sulfuric acid without any sulfur loss.

[0103] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual.

[0104] Example 1

[0105] The nitrate-containing sulfuric acid denitrification device of this application is used to treat nitrate-containing sulfuric acid, as follows:

[0106] Provides nitrate-containing sulfuric acid: The nitrate impurity content in the nitrate-containing sulfuric acid is 1200 mg / m³. 3 .

[0107] The high-quality sulfuric acid obtained after denitrification contains 4.5 mg / m³ of nitrate impurities. 3 The nitrogen oxide content in the exhaust gas emitted from the exhaust outlet of the denitrification reactor is 5 mg / Nm³. 3 .

[0108] Conclusion: Using the nitrate-containing sulfuric acid denitrification device of this application to treat nitrate-containing sulfuric acid can effectively improve the quality of sulfuric acid, while the content of nitrogen oxides in the exhaust gas is extremely low.

[0109] Test method:

[0110] Nitrate impurity content: Ultraviolet spectrophotometry / Ion chromatography

[0111] Nitrogen oxide content: spectrophotometry

[0112] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0113] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A denitrification device for nitrate-containing sulfuric acid, characterized in that, include: A denitrification reactor, the denitrification reactor comprising: The denitrification reactor body is provided with a nitrate-containing sulfuric acid inlet, a sulfur dioxide inlet and a waste gas outlet, and the denitrification reactor body internally defines a reaction space; The reaction space is used to carry out a denitrification reaction of a mixture including nitrated sulfuric acid and sulfur dioxide to remove nitrososulfuric acid from the nitrated sulfuric acid to obtain first sulfuric acid, wherein the mass concentration of sulfuric acid in the mixture is 93% to 98%. A heater, located inside the denitrification reactor body, is used to heat the mixture.

2. The denitrification device according to claim 1, characterized in that, Also includes: A denitrification cooler, connected to the denitrification reactor, is used to cool the first sulfuric acid to obtain the second sulfuric acid; The sulfur dioxide saturated reactor is connected to the denitrification cooler and the denitrification reactor. It is used to dissolve sulfur dioxide in the second sulfuric acid to obtain sulfur dioxide saturated sulfuric acid. The sulfur dioxide saturated sulfuric acid is transported to the denitrification reactor through the sulfur dioxide inlet.

3. The denitrification device according to claim 1, characterized in that, It includes multiple denitrification reactors, which are connected in series or in parallel.

4. The denitrification device according to claim 1, characterized in that, The denitrification reactor further includes at least one of the following: A stirrer, located inside the denitrification reactor body, is used to stir the mixture; A thermometer, connected to the denitrification reactor body, is used to monitor the temperature of the denitrification reaction; A level gauge is connected to the denitrification reactor body and is used to monitor the operating level of the denitrification reactor.

5. The denitrification device according to claim 2, characterized in that, The sulfur dioxide saturated reactor satisfies at least one of the following conditions: The sulfur dioxide saturated reactor is a packed tower structure; The sulfur dioxide saturated reactor is equipped with a demister to remove acid mist generated during the contact between sulfur dioxide and sulfuric acid; An acid concentration analyzer is installed in the sulfur dioxide saturated reactor to monitor the acid concentration in the reactor.

6. The denitrification device according to claim 2, characterized in that, Also includes: A first delivery pump is disposed between the denitrification reactor and the denitrification cooler for delivering the first sulfuric acid to the denitrification cooler; A second transfer pump is installed between the denitrification reactor and the sulfur dioxide saturated reactor to transfer the sulfur dioxide saturated sulfuric acid to the denitrification reactor. A dilution water supply unit is connected to the sulfur dioxide saturated reactor and is used to supply dilution water to the sulfur dioxide saturated reactor. The quality acid collection unit is connected to the second delivery pump and is used to collect high-quality sulfuric acid that meets the nitrate standard.

7. The denitrification device according to claim 6, characterized in that, The first delivery pump satisfies at least one of the following conditions: The first transfer pump includes at least one of a horizontal transfer pump and a vertical submersible transfer pump; The first delivery pump outlet is equipped with a liquid level regulating valve, which is interlocked with the liquid level gauge in the denitrification reactor, and is used to control the operating liquid level in the denitrification reactor.

8. The denitrification device according to claim 7, characterized in that, An acid concentration regulating valve is provided between the dilution water supply unit and the sulfur dioxide saturated reactor to regulate the acid concentration in the sulfur dioxide saturated reactor.

9. A flue gas acid production system, characterized in that, The denitrification device includes any one of claims 1 to 8.

10. The flue gas acid production system according to claim 9, characterized in that, The flue gas acid production system also includes: An acid-generating device connected to the denitrification device; The acid production device includes: A purification component is used to wash the flue gas to obtain the first flue gas; A dry suction component, connected to the purification component, is used to remove moisture from the first flue gas to obtain a second flue gas; A conversion component, connected to the dry absorption component, is used to convert sulfur dioxide in the second flue gas into sulfur trioxide, thereby obtaining a third flue gas containing sulfur trioxide. A connecting pipeline is installed between the conversion component and the dry absorption component to transport the third flue gas to the dry absorption component for the absorption of sulfur trioxide, thereby obtaining nitrate-containing sulfuric acid.

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