Nitrate-containing sulfuric acid denitration device, denitration method and flue gas acid making system

Abstract

The invention relates to the technical field of denitration, and discloses a nitrate-containing sulfuric acid denitration device which comprises a denitration reactor, the denitration reactor comprises a denitration reactor body, and the denitration reactor body is provided with a nitrate-containing sulfuric acid inlet, a sulfur dioxide inlet and a waste gas outlet. A reaction space is defined in the denitration reactor body; the reaction space is used for carrying out denitration reaction on a mixture containing nitrate-containing sulfuric acid and sulfur dioxide to remove nitroso sulfuric acid in the nitrate-containing sulfuric acid to obtain first sulfuric acid, and the mass concentration of the sulfuric acid in the mixture is 93-98%; and the heater is arranged in the denitration reactor body and is used for heating the mixture. The denitration device is low in cost and environment-friendly when being used for treating the nitrate-containing sulfuric acid.

Description

Technical Field

[0001] The present application relates to the technical field of denitrification, and specifically, to a nitric acid-containing sulfuric acid denitrification device, a denitrification method, and a flue gas sulfuric acid production system. Background Art

[0002] There are strict requirements for the content of nitrate impurities in sulfuric acid reagent products. At present, for reagent sulfuric acid products produced by quite a number of sulfuric acid manufacturers in China, due to limitations in equipment and process technology conditions, the nitrate index of the products is easily exceeded, resulting in unqualified products, which in turn affects sales and causes economic losses. In related technologies, some methods for treating nitrate impurities in sulfuric acid products have high costs, and some methods can remove nitrate impurities, but at the same time produce harmful gases, and direct emission will cause new pollution. Therefore, developing a device and method for treating nitrate impurities in sulfuric acid with low cost and environmental protection is one of the current challenges.

[0003] Content of the Application

[0004] The present application aims to solve at least one of the technical problems in related technologies to some extent. To this end, an object of the present application is to provide a nitric acid-containing sulfuric acid denitrification device, a denitrification method, and a flue gas sulfuric acid production system. Using the nitric acid-containing sulfuric acid denitrification device and denitrification method in the present application to treat nitrate impurities in sulfuric acid products has low cost and environmental protection. Using the nitric acid-containing sulfuric acid denitrification device of the present application in a flue gas sulfuric acid production system can further improve the quality of the finished acid prepared by the flue gas sulfuric acid production system.

[0005] In a first aspect of the present application, a nitric acid-containing sulfuric acid denitrification device is provided, including:

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

[0007] A denitrification reactor body, on which a nitric acid-containing sulfuric acid inlet, a sulfur dioxide inlet, and an exhaust gas outlet are provided, and a reaction space is defined inside the denitrification reactor body;

[0008] The reaction space is used to carry out a denitrification reaction on a mixture including nitric acid-containing sulfuric acid and sulfur dioxide to remove nitrosylsulfuric acid in the nitric acid-containing sulfuric acid and obtain a first sulfuric acid, wherein the mass concentration of sulfuric acid in the mixture is 93% - 98%;

[0009] A heater, arranged inside the denitrification reactor body, for heating the mixture.

[0010] This denitrification device realizes low-cost and environmental protection treatment of nitrate impurities in nitric acid-containing sulfuric acid and improves the quality of sulfuric acid by carrying out an oxidation-reduction reaction between nitrosylsulfuric acid and sulfur dioxide in a strong acid medium condition in the denitrification reactor, and the products are nitrogen and sulfuric acid.

[0011] In addition, the nitric acid-containing sulfuric acid denitration device according to the above embodiments of the present application may further have the following additional technical features:

[0012] In some embodiments of the present application, the denitration device further includes:

[0013] A nitric acid removal cooler, connected to the denitration reactor, for cooling the first sulfuric acid to obtain a second sulfuric acid;

[0014] A sulfur dioxide saturation reactor, connected to the nitric acid removal cooler and the denitration reactor, for dissolving sulfur dioxide in the second sulfuric acid to obtain sulfuric acid saturated with sulfur dioxide, and the sulfuric acid saturated with sulfur dioxide is transported to the denitration reactor through the sulfur dioxide inlet. Thus, it helps to form a closed loop for the nitric acid-containing sulfuric acid denitration device, further improving the system stability and controllability of the device.

[0015] In some embodiments of the present application, there are multiple denitration reactors, and the multiple denitration reactors are connected in series or in parallel. Thus, it helps to improve the denitration efficiency, ensure the flexibility and reliability of the operation of the denitration device, and at the same time meet the requirements of continuous and batch reactions.

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

[0017] A stirrer, arranged inside the denitration reactor body, for stirring the mixture;

[0018] A thermometer, connected to the denitration reactor body, for monitoring the temperature of the denitration reaction;

[0019] A liquid level gauge, connected to the denitration reactor body, for monitoring the operating liquid level of the denitration reactor. Thus, it helps the denitration reaction to proceed smoothly and accurately.

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

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

[0022] An atomizing eliminator is arranged in the sulfur dioxide saturation reactor for removing the acid mist that may be generated during the gas-liquid contact process;

[0023] An acid concentration analyzer is arranged in the sulfur dioxide saturation reactor for monitoring the concentration of the acid in the sulfur dioxide saturation reactor. Thus, it helps to obtain sulfuric acid saturated with sulfur dioxide.

[0024] In some embodiments of the present application, the denitration device further includes:

[0025] A first transfer pump, disposed between the denitration reactor and the nitric acid cooler, for transferring the first sulfuric acid to the nitric acid cooler;

[0026] A second transfer pump, disposed between the denitration reactor and the sulfur dioxide saturation reactor, for transferring the sulfuric acid saturated with sulfur dioxide to the denitration reactor;

[0027] A dilution water supply unit, connected to the sulfur dioxide saturation reactor, for supplying dilution water to the sulfur dioxide saturation reactor;

[0028] A high-quality acid collection unit, connected to the second transfer pump, for collecting high-quality sulfuric acid with qualified nitrate content. Thereby, it helps the smooth operation of the denitration device.

[0029] In some embodiments of the present application, the first transfer 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 submerged transfer pump;

[0031] A liquid level regulating valve is provided at the outlet of the first transfer pump, which is interlocked with the liquid level gauge in the denitration reactor, for controlling the operating liquid level in the denitration reactor. Thereby, it helps to precisely regulate the denitration reaction and ensure the smooth operation of the denitration device.

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

[0033] In a second aspect of the present application, a denitration method for nitric acid-containing sulfuric acid is proposed, including:

[0034] Under the condition of 60°C to 90°C, subject the nitrosylsulfuric acid in the nitric acid-containing sulfuric acid to a denitration reaction with water and sulfur dioxide to obtain nitrogen and first sulfuric acid, and the concentration of sulfuric acid in the denitration reaction system is 93% to 98%.

[0035] This denitration method uses sulfuric acid in the nitric acid-containing sulfuric acid as a strong acid medium, and uses sulfur dioxide as a reducing agent to remove nitrate impurities in nitric acid. This denitration method is environmentally friendly, has a low cost, and can avoid the introduction of new impurities.

[0036] In some embodiments of the present application, the denitration method for nitric acid-containing sulfuric acid further includes:

[0037] Cool the first sulfuric acid to 40°C to 60°C to obtain second sulfuric acid;

[0038] Dissolve sulfur dioxide in the second sulfuric acid to obtain sulfuric acid saturated with sulfur dioxide;

[0039] Return at least part of the sulfuric acid saturated with sulfur dioxide to the denitrification reaction to provide the sulfur dioxide;

[0040] Wherein, the volume ratio of the nitric acid-containing sulfuric acid to the sulfuric acid saturated with sulfur dioxide in the denitrification reaction is 1:20 to 1:30. Thus, the solubility of sulfur dioxide in sulfuric acid can be further increased, and at the same time, the denitrification method forms a closed loop, which helps the stable progress of the denitrification reaction.

[0041] In the third aspect of the present application, a flue gas sulfuric acid production system is proposed, including the aforementioned nitric acid-containing sulfuric acid denitrification device. Thus, the flue gas sulfuric acid production system has all the features and advantages of the aforementioned nitric acid-containing sulfuric acid denitrification device, which will not be elaborated here.

[0042] In some embodiments of the present application, the flue gas sulfuric acid production system further includes:

[0043] A sulfuric acid production device connected to the denitrification device;

[0044] The sulfuric acid production device includes:

[0045] A purification component for washing the flue gas to obtain a first flue gas;

[0046] A drying and absorption component connected to the purification component for removing moisture from the first flue gas to obtain a second flue gas;

[0047] A conversion component connected to the drying and absorption component for converting sulfur dioxide in the second flue gas into sulfur trioxide to obtain a third flue gas containing sulfur trioxide;

[0048] A connecting pipeline disposed between the conversion component and the drying and absorption component for transporting the third flue gas to the drying and absorption component for absorbing sulfur trioxide to obtain nitric acid-containing sulfuric acid. Using this flue gas sulfuric acid production system to process flue gas helps to obtain a finished acid with higher quality. Description of the Drawings

[0049] Figure 1 It is a schematic diagram of the component connection of a nitric acid-containing sulfuric acid denitrification device according to an embodiment of the present application.

[0050] Figure 2 It is a schematic structural diagram of a nitric acid-containing sulfuric acid denitrification device according to an embodiment of the present application.

[0051] Figure 3 It is a device flow chart of a flue gas sulfuric acid production system according to an embodiment of the present application.

[0052] Description of the Reference Numerals:

[0053] 1: Denitrification reactor 2: Nitric acid cooler 3: Sulfur dioxide saturation reactor 4: First transfer pump

[0054] 5: Second transfer pump 6: Diluted water supply unit 7: Quality acid collection unit 1-1: Denitrification reactor body

[0055] 4-1: Liquid level regulating valve 4-2: Liquid level regulating valve 4-3: Diluted water regulating valve 4-4: Reaction regulating valve

[0056] 4-5: Acid production on-off valve

[0057] A: Nitric acid containing nitrate inlet B: Sulfur dioxide inlet C: Exhaust gas outlet D: Cooling return water pipeline

[0058] E: Cooling water supply pipeline G: Packing H: Demister T1: Thermometer T2: Thermometer

[0059] L1: Liquid level gauge L2: Liquid level gauge F1: Flow meter F2: Flow meter

[0060] C1: Acid concentration analyzer C2: Nitrate analyzer C3: Nitrogen oxide analyzer Detailed implementation manners

[0061] The embodiments of the present application will be described in detail below. The embodiments described below are exemplary and are intended to explain the present application, and should not be construed as a limitation to the present application.

[0062] The present application is completed based on the following discoveries and understandings of the applicant:

[0063] In industrial sulfuric acid products, the content of nitrate impurities is required to be ≤ 10mg / m 3 ,

[0063] , and the main component of the nitrate impurity is NOHSO4. There are mainly three methods for treating NOHSO4 in sulfuric acid products in the related technologies. 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 has a high price, greatly increasing the treatment cost. On the other hand, it is necessary to strictly control the dosage of the added liquid reducing agent because the unreacted reducing agent will become a new impurity in the sulfuric acid product, further affecting the quality of sulfuric acid, and such reducing agents are generally carcinogens. Once they enter the downstream product of sulfuric acid - fertilizer with sulfuric acid, it will have a more serious impact. The second method is to add a small amount of water to the sulfuric acid product for dilution and hydrolysis. During hydrolysis, NOHSO4 will decompose into NO and NO2 and be released in gaseous form. If NO and NO2 are directly discharged, it will cause new pollution. Therefore, it is necessary to wash and absorb them with dilute nitric acid solution and discharge them after neutralization, which also greatly increases the cost. The third method is to use SO2 as a reducing agent. By introducing a large amount of SO2 - containing process gas into the finished concentrated sulfuric acid containing nitrate, the purpose of denitrification is achieved. The reaction formula is as follows: 2NOHSO4 + SO2 + 2H2O → 2NO + 3H2SO4. The NO generated by this method is released in gaseous form. If directly discharged, it will cause pollution. Washing and absorbing it with dilute nitric acid solution and discharging it after neutralization will also greatly increase the cost. Thus, the methods for treating nitrate impurities in sulfuric acid products in the related technologies all have obvious defects.

[0064] Based on the above research, the inventor found that when using SO2 as a reducing agent to treat NOHSO4 in sulfuric acid products, NOHSO4 will react with the water in the sulfuric acid product preferentially. The reaction equation is: 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 product and a strong - acid reaction medium is provided at the same time, the strong - acid medium will improve the stability of the reaction intermediate HNO2, enabling it to exist stably without decomposing into NO or NO2 gas. At the same time, the strong - acid medium will also enhance the reducibility of SO2, thereby enabling the intermediate product nitrous acid decomposed from NOHSO4 to be reduced to nitrogen. Therefore, using this method to treat nitrates will not produce new pollution and has a relatively low cost.

[0065] In view of this, in the first aspect of the present application, a denitrification device for nitric - acid - containing sulfuric acid is proposed. Refer to Figure 1, including: a denitrification reactor 1, which is used for the redox reaction of sulfur dioxide and nitrated sulfuric acid under certain conditions. The reaction equation is: 4H2O + 2NOHSO4 + 3SO2 → 5H2SO4 + N2, and the products are nitrogen and sulfuric acid. Thus, the nitrosylsulfuric acid in the nitrated sulfuric acid is removed to obtain the first sulfuric acid, realizing the low-cost and environmentally friendly treatment of nitrate impurities in the nitrated sulfuric acid.

[0066] In an embodiment of the present application, referring to Figure 1 , the denitrification device may further include: a nitric acid removal cooler 2, connected to the denitrification reactor 1, and used for cooling the first sulfuric acid to obtain the second sulfuric acid. Thus, the corrosion of the second sulfuric acid to equipment and pipelines under high-temperature conditions can be reduced, thereby improving the equipment life.

[0067] In an embodiment of the present application, referring to Figure 1 , the denitrification device may further include: a sulfur dioxide saturation reactor 3, connected to the nitric acid removal cooler 2 and the denitrification reactor 1, and used for dissolving sulfur dioxide in the second sulfuric acid to obtain sulfur dioxide-saturated sulfuric acid, and the sulfur dioxide-saturated sulfuric acid is transported to the denitrification reactor as a reactant. Thus, the denitrification device forms a closed loop by connecting the denitrification reactor 1, the nitric acid removal cooler 2, and the sulfur dioxide saturation reactor 3. On the one hand, the first sulfuric acid is cooled by the denitrification reactor to obtain the second sulfuric acid. The temperature of the sulfuric acid decreases and the solubility increases. Therefore, the second sulfuric acid can absorb more sulfur dioxide in the sulfur dioxide saturation reactor to reach the saturated state, providing 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 in the form of sulfur dioxide-saturated sulfuric acid to the denitrification reaction can enhance the reducibility of sulfur dioxide, so that the nitrosylsulfuric acid can be reduced to nitrogen. On the third hand, the nitric acid removal cooler can remove the heat generated by the denitrification exothermic reaction in the denitrification reactor, avoiding the occurrence of side reactions caused by excessive heat, thereby ensuring the smooth progress of the denitrification reaction. Thus, the system stability and controllability of the denitrification device can be effectively improved.

[0068] In some embodiments of the present application, referring to Figure 2 , the denitrification device further includes: a first transfer pump 4, arranged between the denitrification reactor 1 and the nitric acid removal cooler 2, and used for transporting the first sulfuric acid to the nitric acid removal cooler. Thus, it helps to improve the transmission speed of the first sulfuric acid to the nitric acid removal cooler, shorten the transmission time, and thus meet the industrial large-scale denitrification treatment of nitrated sulfuric acid.

[0069] In some embodiments of the present application, referring to Figure 2, the denitration device further includes: a second transfer pump 5, which is arranged between the denitration reactor 1 and the sulfur dioxide saturation reactor 3 and is used to transfer the sulfuric acid saturated with sulfur dioxide to the denitration reactor. Thus, it helps to improve the transfer speed of the sulfuric acid saturated with sulfur dioxide to the denitration reactor, shorten the transfer time, and further meet the denitration treatment of large-scale nitric acid-containing sulfuric acid in industry.

[0070] In some embodiments of the present application, referring to Figure 2 , the denitration device further includes: a dilution water providing unit 6, which is connected to the sulfur dioxide saturation reactor 3 and is used to provide dilution water for the sulfur dioxide saturation reactor. By providing dilution water to the sulfur dioxide saturation reactor, the mass concentration of the sulfuric acid saturated with sulfur dioxide in the sulfur dioxide saturation reactor is adjusted to meet the requirements of the denitration reaction. Thus, it helps the denitration reaction to proceed smoothly.

[0071] In some embodiments of the present application, referring to Figure 2 , the denitration device further includes: a high-quality acid collecting unit 7, which is connected to the second transfer pump 5 and is used to collect the sulfuric acid saturated with sulfur dioxide with qualified nitrate to obtain a high-quality sulfuric acid product.

[0072] In some embodiments of the present application, the denitration device may include a plurality of the denitration reactors, and the plurality of denitration reactors may be connected in series or in parallel. Arranging a plurality of denitration reactors helps to improve the denitration efficiency and at the same time ensure the flexibility and reliability of the operation of the denitration device.

[0073] In some embodiments of the present application, referring to Figure 2 , the denitration reactor 1 includes: a denitration reactor body 1-1, on which a nitric acid-containing sulfuric acid inlet A, a sulfur dioxide inlet B and an exhaust gas outlet C are provided. A flow meter F1 is provided at the nitric acid-containing sulfuric acid inlet A to monitor the volume flow of the nitric acid-containing sulfuric acid. A reaction space is defined inside the denitration reactor body, and the reaction space is used to carry out a denitration reaction on a mixture including nitric acid-containing sulfuric acid and sulfur dioxide to remove nitrosylsulfuric acid in the nitric acid-containing sulfuric acid and obtain a first sulfuric acid. The specific reaction equation of the denitration reaction is:

[0074] 2NOHSO4 + 2H2O → 2H2SO4 + 2HNO2

[0075] 3SO2 + 3H2O → 3H2SO3

[0076] 2HNO2 + 3H2SO3 → 3H2SO4 + N2 + H2O

[0077] Among them, the intermediate product HNO2 is easily decomposed into NO or NO2 gas, and a strong acid medium needs to be provided to avoid the decomposition of HNO2. Therefore, the mass concentration of the above mixture is required to be 93% - 98%, specifically, it can be 93%, 94%, 95%, 96%, 97%, 98%, etc. Among them, the mixture includes nitrosulfuric acid and sulfuric acid saturated with sulfur dioxide. On the one hand, the above concentration range can improve the stability of the reaction intermediate HNO2 and avoid the decomposition of the reaction intermediate HNO2 into NO or NO2 gas. On the other hand, it can improve the reducibility of sulfur dioxide, which can undergo an oxidation-reduction reaction with nitrosulfuric acid to generate nitrogen and sulfuric acid. Thus, the above concentration range of the mixture can basically avoid the problems of high cost and waste of high-quality sulfuric acid caused by too high a mass concentration of sulfuric acid in the mixture, as well as the problems of easy decomposition of the intermediate product HNO2 into NO or NO2 gas and reduced reducibility of sulfur dioxide caused by too low a mass concentration of sulfuric acid in the mixture, etc.

[0078] In some embodiments of the present application, the structure of the denitration reactor body can be any one of a tank structure, a tubular structure, and a kettle structure. Thus, it is helpful to be applicable to different fields and different process sections, and at the same time, the structure of the denitration reactor body can be flexibly designed according to the site, etc.

[0079] In some embodiments of the present application, a heater is provided inside the denitration reactor body for heating the mixture, and heat can be supplemented when the heat of the denitration reaction is insufficient or when the system is restarted to meet the heat required for the denitration reaction and ensure the smooth progress of the denitration reactor. Specifically, the heater can use electric heating or steam heating, and the heating coil material is selected from high-temperature and concentrated acid-resistant alloy materials or materials with the same performance.

[0080] In some embodiments of the present application, a stirrer is provided inside the denitration reactor body for stirring the mixture, which helps to make the nitrosulfuric acid and sulfuric acid saturated with sulfur dioxide mix evenly and make the denitration reaction proceed more fully.

[0081] In some embodiments of the present application, referring to Figure 2 , the denitration reactor further includes a thermometer T1, which is connected to the denitration reactor body 1-1 and is used to monitor the temperature of the denitration reaction, and can ensure the smooth progress of the denitration reaction.

[0082] In some embodiments of the present application, referring to Figure 2 , the denitration reactor further includes a level gauge L1, which is connected to the denitration reactor body 1-1 and is used to monitor the operating level of the denitration reactor. Thus, the level of the denitration reaction can be accurately controlled to promote the efficient and stable progress of the reaction.

[0083] In some embodiments of the present application, referring to Figure 2, at the exhaust gas outlet C of the denitration reactor body, a nitrogen oxide analyzer C3 is provided to monitor the content of nitrogen oxides in the exhaust gas discharged from the denitration reactor body, so as to judge whether the denitration reaction is proceeding normally. Specifically, the content of nitrogen oxides in the exhaust gas monitored by the nitrogen oxide analyzer ≤ 10mg / Nm 3 , indicating that the reaction is proceeding normally.

[0084] In some embodiments of the present application, referring to Figure 2 , a liquid level regulating valve 4-1 is provided at the outlet of the first transfer pump 4, which is interlocked with the liquid level gauge L1 in the denitration reactor to control the operating liquid level in the denitration reactor, and can avoid problems such as leakage caused by too high a liquid level in the denitration reaction and insufficient denitration reaction caused by too low a liquid level.

[0085] Specifically, the liquid level regulating valve 4-1 is interlocked with the liquid level gauge L1. When the liquid level shown by the liquid level gauge in the denitration reactor is low, the liquid level regulating valve can be adjusted to a smaller value to reduce the discharge rate of the first sulfuric acid in the denitration reactor; when the liquid level shown by the liquid level gauge is high, the liquid level regulating valve can be adjusted to a larger value to accelerate the discharge rate of the first sulfuric acid in the denitration reactor. Thus, it helps to control the smooth progress of the denitration reaction and further ensure the normal operation of the entire closed loop.

[0086] In some embodiments of the present application, the first transfer pump can be any one of a horizontal transfer pump and a vertical submerged transfer pump. Thus, it can be adapted to different fields and different working sections, and at the same time, the structure of the denitration reactor body can be flexibly designed according to the site, etc.

[0087] In some embodiments of the present application, the structure of the denitric acid cooler can be any one of a shell-and-tube type, a plate type, and other equipment structure forms that can meet the heat exchange requirements. Thus, it can be adapted to different fields and different working sections, and at the same time, the structure of the denitration reactor body can be flexibly designed according to the site, etc.

[0088] In some embodiments of the present application, the denitric acid cooler is made of a high-temperature and strong-acid-resistant alloy material to avoid corrosion of the equipment.

[0089] In some embodiments of the present application, the denitric acid cooler is provided with a cooling return water pipeline D and a cooling water supply pipeline E to ensure the smooth operation of the denitric acid cooler. The temperature difference between the water in the cooling return water pipeline and the cooling water supply pipeline is 8°C to 15°C. Specifically, it can be 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.

[0090] In some embodiments of the present application, referring to Figure 2, a thermometer T2 is provided at the outlet of the denitrifying cooler 2 to monitor the temperature of the second sulfuric acid, and the temperature of the second sulfuric acid can be regulated by adjusting the temperature difference between the cooling return water and the cooling feed water.

[0091] In some embodiments of the present application, the sulfur dioxide saturation reactor 3 is a packed tower structure. The packing G in the packed tower structure can provide a large specific surface area, which helps the full contact of sulfur dioxide and the second sulfuric acid, thereby promoting the dissolution of sulfur dioxide to obtain sulfuric acid saturated with sulfur dioxide.

[0092] In some embodiments of the present application, a demister H is provided in the sulfur dioxide saturation reactor to remove the acid mist that may be generated during the gas-liquid contact process, avoiding the acid mist from entering other equipment and causing equipment corrosion, thereby ensuring the smooth operation of the device. Specifically, the demister can be selected from a wire mesh structure and other structures of the Brownian motion type, etc.

[0093] In some embodiments of the present application, an acid concentration analyzer C1 and a dilution water regulating valve 4-3 are provided on the sulfur dioxide saturation reactor 3, both of which are interlocked with the dilution water supply unit 6. The mass concentration of the sulfuric acid saturated with sulfur dioxide in the sulfur dioxide saturation reactor is regulated by the dilution water regulating valve, which helps the mass concentration of the obtained sulfuric acid saturated with sulfur dioxide to be between 93% and 98%, thereby ensuring the smooth operation of the denitrification reactor.

[0094] Specifically, the acid concentration analyzer C1 is used to monitor the mass concentration of the sulfuric acid saturated with sulfur dioxide in the sulfur dioxide saturation reactor. The dilution water regulating valve 4-3 and the acid concentration analyzer C1 are both interlocked with the dilution water supply unit 6. When the acid concentration displayed by the acid concentration analyzer is low, the dilution water regulating valve can be closed or adjusted to reduce the amount of dilution water entering the sulfur dioxide saturation reactor, thereby increasing the mass concentration of the sulfuric acid saturated with sulfur dioxide in the sulfur dioxide saturation reactor; on the contrary, when the acid concentration displayed by the acid concentration analyzer is high, the dilution water regulating valve can be opened or adjusted to increase the amount of dilution water entering the sulfur dioxide saturation reactor, thereby reducing the mass concentration of the sulfuric acid saturated with sulfur dioxide in the sulfur dioxide saturation reactor. Thus, it helps to control the mass concentration of the sulfuric acid saturated with sulfur dioxide and further ensure the normal operation of the denitrification reaction.

[0095] In some embodiments of the present application, referring to Figure 2 , a liquid level gauge L2 is provided at the outlet of the sulfur dioxide saturation reactor 3 to monitor the operating liquid level of the sulfur dioxide saturation reactor. Thus, the liquid level of the sulfur dioxide saturation reactor can be accurately controlled to promote the efficient and stable progress of the reaction.

[0096] In some embodiments of the present application, referring to Figure 2, a liquid level regulating valve 4-2 is provided at the outlet of the sulfur dioxide saturation reactor 3, which is interlocked with the liquid level gauge L2 in the sulfur dioxide saturation reactor and is used to control the operating liquid level in the sulfur dioxide saturation reactor, so as to avoid problems such as leakage caused by too high a liquid level in the sulfur dioxide saturation reactor and insufficient dissolution of sulfur dioxide caused by too low a liquid level.

[0097] Specifically, the liquid level regulating valve 4-2 is interlocked with the liquid level gauge L2. When the liquid level shown by the liquid level gauge in the sulfur dioxide saturation reactor is low, the liquid level regulating valve can be adjusted to a smaller opening to reduce the discharge rate of the sulfuric acid saturated with sulfur dioxide in the sulfur dioxide saturation reactor; when the liquid level shown by the liquid level gauge is high, the liquid level regulating valve can be adjusted to a larger opening to increase the discharge rate of the sulfuric acid saturated with sulfur dioxide in the sulfur dioxide saturation reactor. Thus, it helps to control the liquid level in the sulfur dioxide saturation reactor at a normal level, further ensuring the smooth progress of the denitration reaction and thus ensuring the normal operation of the entire closed loop.

[0098] In some embodiments of the present application, referring to Figure 2 , a flow meter F2 and a reaction regulating valve 4-4 are provided between the second delivery pump 5 and the denitration reactor 1. The flow meter F2 is used to monitor the volume flow rate of the sulfuric acid saturated with sulfur dioxide transported from the saturated sulfuric acid delivery pump to the denitration reactor. The flow meter F2 is interlocked with the flow meter F1, and the ratio between the flow meter F1 and the flow meter F2 is regulated by adjusting the reaction regulating valve 4-4, thereby ensuring the smooth progress of the denitration reaction.

[0099] Specifically, the ratio of the flow meter F1 to the flow meter F2 is 1:15 to 1:25. When the ratio of the flow meter F1 to the flow meter F2 is too large, it indicates that too much nitric acid-containing sulfuric acid is input into the denitration reactor, and the amount of sulfuric acid saturated with sulfur dioxide output by the second delivery pump needs to be increased by adjusting the reaction regulating valve 4-4 to reduce the ratio of the flow meter F1 to the flow meter F2 to the above range; on the contrary, when the ratio of the flow meter F1 to the flow meter F2 is too small, it indicates that too much sulfuric acid saturated with sulfur dioxide is output by the second delivery pump to the denitration reactor, and the amount of sulfuric acid saturated with sulfur dioxide output by the second delivery pump needs to be reduced by adjusting the reaction regulating valve 4-4 to reduce the ratio of the flow meter F1 to the flow meter F2 to the above range. Thus, it helps to ensure the smooth progress of the denitration reaction.

[0100] In some embodiments of the present application, referring to Figure 2, the nitric acid-containing sulfuric acid denitrification device further includes a high-quality acid collection unit 7, which is connected to the second delivery pump 5 and is used to collect high-quality sulfuric acid with qualified nitrate to obtain a high-quality sulfuric acid product. Specifically, an acid production switch valve 4-5 and a nitrate analyzer C2 are connected between the high-quality acid collection unit 7 and the second delivery pump 5. The nitrate analyzer is used to monitor the nitrate concentration in the sulfuric acid saturated with sulfur dioxide. After the nitrate concentration in the sulfuric acid saturated with sulfur dioxide reaches the standard, the qualified sulfuric acid saturated with sulfur dioxide can be output by opening the acid production switch valve. At the same time, a sulfur dioxide desorption tower needs to be equipped at the inlet of the high-quality acid collection unit 7 to further remove sulfur dioxide in the sulfuric acid saturated with sulfur dioxide, thereby obtaining high-quality sulfuric acid. The high-quality sulfuric acid is transported to the high-quality acid collection unit to obtain a high-quality sulfuric acid product. Specifically, the nitrate concentration in the sulfuric acid saturated with sulfur dioxide ≤ 10mg / m 3 can enter the sulfur dioxide desorption tower to remove sulfur dioxide.

[0101] In the second aspect of the present application, a denitrification method for nitric acid-containing sulfuric acid is proposed, including the following steps:

[0102] S10: Under the condition of 60°C to 90°C, make the nitrosyl sulfuric acid in the nitric acid-containing sulfuric acid react with water and sulfur dioxide to carry out denitrification reaction to obtain nitrogen and first sulfuric acid. The mass concentration of sulfuric acid in the denitrification reaction system is 93% to 98%.

[0103] In this step, sulfuric acid with a mass concentration of 93% to 98% is used as a strong acid medium and provides the reactant water. At the same time, sulfur dioxide is used as a reducing agent to remove nitrosyl sulfuric acid in 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. The above concentration range can improve the stability of the reaction intermediate HNO2 and avoid the decomposition of the reaction intermediate HNO2 into NO or NO2 gas. On the other hand, it can improve the reducibility of sulfur dioxide, which can undergo an oxidation-reduction reaction with nitrosyl sulfuric acid to generate nitrogen and sulfuric acid. The reaction temperature is 60°C to 90°C, preferably 70°C to 80°C. Specifically, it can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, etc. Within the above temperature range, it is helpful for the denitrification reaction to proceed smoothly and efficiently, and basically can avoid problems such as high equipment requirements caused by too high temperature and insufficient reaction caused by too low temperature. The reaction pressure is normal pressure. By using this denitrification method to remove nitrate impurities in nitric acid-containing sulfuric acid, the cost is low, environmentally friendly, and new impurities can be avoided from being introduced.

[0104] In some embodiments of the present application, the time of the denitrification reaction is 0.5 h to 1 h. Specifically, it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, etc. The above reaction time helps the denitrification reaction to proceed fully, basically avoiding incomplete reaction caused by too short reaction time and waste of time cost caused by too long reaction time.

[0105] In some embodiments of the present application, the denitrification method of nitric acid-containing sulfuric acid further includes:

[0106] S20: Cooling the first sulfuric acid to 40°C to 60°C to obtain a second sulfuric acid.

[0107] In this step, cooling the first sulfuric acid to 40°C to 60°C, specifically, it can be 40°C, 45°C, 50°C, 55°C, 60°C, etc., to obtain a second sulfuric acid. The temperature of the second sulfuric acid within the above range helps to increase the solubility of sulfur dioxide in the second sulfuric acid, basically avoiding the problem that the amount of dissolved sulfur dioxide is too small due to too high temperature of the second sulfuric acid and insufficient to provide the sulfur dioxide required for the denitrification reaction, as well as problems such as too high viscosity of the sulfuric acid due to too low temperature of the second sulfuric acid, which affects the progress of the denitrification reaction and increases energy consumption.

[0108] S30: Dissolving sulfur dioxide in the second sulfuric acid to obtain sulfuric acid saturated with sulfur dioxide.

[0109] In this step, continuously introducing sulfur dioxide gas into the second sulfuric acid and maintaining the system temperature at 40°C to 60°C helps to efficiently complete the process of dissolving sulfur dioxide and obtain sulfuric acid saturated with sulfur dioxide.

[0110] S40: Returning part of the sulfuric acid saturated with sulfur dioxide to the denitrification reaction to provide the sulfur dioxide. Among them, the volume ratio of the nitric acid-containing sulfuric acid to the sulfuric acid saturated with sulfur dioxide in the denitrification reaction is 1:20 to 1:30.

[0111] In this step, transporting the sulfuric acid saturated with sulfur dioxide to S10 to provide sulfur dioxide in the denitrification reaction. At the same time, the sulfuric acid saturated with sulfur dioxide can act as a strong acid medium to ensure the stability of the reaction system. Thus, a closed loop is formed, which helps the stable progress of the denitrification reaction.

[0112] In some embodiments of the present application, the volume ratio of nitrated sulfuric acid to sulfur dioxide-saturated sulfuric acid in the denitrification 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. The above range can ensure the smooth progress of the denitrification reaction, and basically avoid problems such as excessive nitrosylsulfuric acid in the denitrification reaction due to too high a volume ratio of nitrated sulfuric acid to sulfur dioxide-saturated sulfuric acid, insufficient denitrification, and too large a space required for the denitrification reaction due to too low a volume ratio. Thus, a part of the sulfur dioxide-saturated sulfuric acid is used to provide sulfur dioxide for the denitrification reaction, and the remaining part can be collected as a high-quality sulfuric acid product under the condition of meeting the denitrification standard.

[0113] In some embodiments of the present application, the denitrification method of the nitrated sulfuric acid is implemented by the aforementioned nitrated sulfuric acid denitrification device. Thus, the volume of the denitrification reactor body can be calculated according to the above denitrification method. Specifically, the calculation of the volume of the denitrification reactor body can refer to the following formula: V = Q1 × t / K. Where Q1 is the volume flow rate (m 3 / h) of sulfur dioxide-saturated sulfuric acid provided by the sulfur dioxide saturation reactor for the denitrification reactor; t is the residence time (h) of the denitrification reaction; K is the volume coefficient of the denitrification reactor, K = 0.7 to 0.8. Specifically, it can be 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, etc., which helps the full progress of the denitrification reaction and ensures uniform mixing of substances in the reaction system; V is the volume of the denitrification reactor (m 3 ). This nitrated sulfuric acid denitrification method has all the characteristics and advantages of the aforementioned nitrated sulfuric acid denitrification device and will not be elaborated here.

[0114] In the third aspect of the present application, a flue gas sulfuric acid production system is provided, including the aforementioned nitrated sulfuric acid denitrification device. Referring to Figure 3 , the flue gas sulfuric acid production system further includes a sulfuric acid production device. The sulfuric acid production device includes a purification component for washing the flue gas to obtain a first flue gas; a drying and 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 drying and 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 disposed between the conversion component and the drying and absorption component for transporting the third flue gas to the drying and absorption component for absorption of sulfur trioxide to obtain nitrated sulfuric acid. Thus, the nitrated sulfuric acid obtained in the sulfuric acid production device is transported to the nitrated sulfuric acid denitrification device of the present application for denitrification, and finally a high-quality sulfuric acid product is obtained.

[0115] In some embodiments of the present application, the drying and absorption device includes a drying tower and an absorption tower. The drying tower is used to remove the moisture in the flue gas to obtain the second flue gas. The sulfur dioxide saturation reactor in the nitric acid-containing sulfuric acid denitration device can be connected to the drying tower in the drying and absorption device. Thus, it 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 saturation reactor to obtain sulfuric acid saturated with sulfur dioxide, thereby further reducing costs.

[0116] Specifically, the second flue gas needs to be pretreated by demisting and dust removal to avoid carrying more impurities, and the volume content of sulfur dioxide in the second flue gas needs to be > 6% to ensure the dissolution efficiency.

[0117] In some embodiments of the present application, the waste gas at the outlet of the denitration reactor in the denitration device can be collected with the gas in the sulfur dioxide saturation reactor in the denitration device and then re-enter the flue gas to sulfuric acid system, which can further ensure that SO2 can be fully utilized and converted into sulfuric acid, and there will be no sulfur loss.

[0118] The following describes the present application 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. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications.

[0119] Example 1

[0120] The nitric acid-containing sulfuric acid denitration device of the present application is used to treat nitric acid-containing sulfuric acid as follows:

[0121] Provide nitric acid-containing sulfuric acid: The content of nitrate impurities in the nitric acid-containing sulfuric acid is 1200 mg / m 3 .

[0122] The content of nitrate impurities in the high-quality sulfuric acid obtained after denitration is 4.5 mg / m 3 , and the content of nitrogen oxides in the waste gas discharged from the waste gas outlet on the denitration reactor body is 5 mg / Nm 3 .

[0123] Conclusion: Using the nitric acid-containing sulfuric acid denitration device in the present application to treat nitric acid-containing sulfuric acid can effectively improve the quality of sulfuric acid, and at the same time, the content of nitrogen oxides in the discharged waste gas is extremely low.

[0124] Test method:

[0125] Content of nitrate impurities: Ultraviolet spectrophotometry / Ion chromatography

[0126] Content of nitrogen oxides: Spectrophotometry

[0127] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0128] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill 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 containing nitric acid and sulfuric acid, characterized in that, Comprising: A denitrification reactor, the denitrification reactor comprising: A denitrification reactor body, on which a nitrated sulfuric acid inlet, a sulfur dioxide inlet and an exhaust gas outlet are provided, and a reaction space is defined inside the denitrification reactor body; The reaction space is used to carry out a denitrification reaction on a mixture comprising nitrated sulfuric acid and sulfur dioxide to remove nitrosylsulfuric acid in the nitrated sulfuric acid and obtain a first sulfuric acid, wherein the mass concentration of sulfuric acid in the mixture is 93% - 98%; A heater, arranged inside the denitrification reactor body, for heating the mixture.

2. The denitration device according to claim 1, wherein Further comprising: A denitration cooler, connected to the denitrification reactor, for cooling the first sulfuric acid to obtain a second sulfuric acid; A sulfur dioxide saturation reactor, connected to the denitration cooler and the denitrification reactor, for dissolving sulfur dioxide in the second sulfuric acid to obtain sulfur dioxide-saturated sulfuric acid, and the sulfur dioxide-saturated sulfuric acid is transported to the denitrification reactor through the sulfur dioxide inlet.

3. The denitration device according to claim 1, characterized in that, Comprising a plurality of the denitrification reactors, and the plurality of denitrification reactors are connected in series or in parallel.

4. The denitration device according to claim 1, wherein, The denitrification reactor further comprises at least one of the following: A stirrer, arranged inside the denitrification reactor body, for stirring the mixture; A thermometer, connected to the denitrification reactor body, for monitoring the temperature of the denitrification reaction; A liquid level gauge, connected to the denitrification reactor body, for monitoring the operating liquid level of the denitrification reactor.

5. The denitration device according to claim 2, characterized in that, The sulfur dioxide saturation reactor satisfies at least one of the following conditions: The sulfur dioxide saturation reactor is of a packed tower structure; An atomizing eliminator is arranged in the sulfur dioxide saturation reactor for removing the acid mist generated during the contact of sulfur dioxide and sulfuric acid; An acid concentration analyzer is arranged in the sulfur dioxide saturation reactor for monitoring the concentration of acid in the sulfur dioxide saturation reactor.

6. The denitration device according to claim 2, characterized in that, Further comprising: A first transfer pump, arranged between the denitrification reactor and the denitration cooler, for transporting the first sulfuric acid to the denitration cooler; A second transfer pump, arranged between the denitrification reactor and the sulfur dioxide saturation reactor, for transporting the sulfur dioxide-saturated sulfuric acid to the denitrification reactor; A dilution water supply unit, connected to the sulfur dioxide saturation reactor, for supplying dilution water to the sulfur dioxide saturation reactor; A high-quality acid collection unit, connected to the second transfer pump, for collecting high-quality sulfuric acid with qualified nitrate content.

7. The denitration device according to claim 6, characterized in that, The first transfer pump satisfies at least one of the following conditions: The first transfer pump comprises at least one of a horizontal transfer pump and a vertical submerged transfer pump; A liquid level regulating valve is arranged at the outlet of the first transfer pump, which is interlocked with the liquid level gauge in the denitrification reactor for controlling the operating liquid level in the denitrification reactor.

8. The denitration device according to claim 7, wherein An acid concentration regulating valve is arranged between the dilution water supply unit and the sulfur dioxide saturation reactor for regulating the concentration of acid in the sulfur dioxide saturation reactor.

9. A denitration method using nitric acid and sulfuric acid, characterized in that, Comprising: Under the condition of 60°C to 90°C, the nitrosylsulfuric acid in the nitrosulfuric acid reacts with water and sulfur dioxide to undergo denitrification reaction, obtaining nitrogen and first sulfuric acid, and the concentration of sulfuric acid in the denitrification reaction system is 93% to 98%.

10. The denitration method using nitric acid-containing sulfuric acid according to claim 9, characterized in that, It further includes: Cooling the first sulfuric acid to 40°C to 60°C to obtain second sulfuric acid; Dissolving sulfur dioxide in the second sulfuric acid to obtain sulfuric acid saturated with sulfur dioxide; Returning at least part of the sulfuric acid saturated with sulfur dioxide to the denitrification reaction for providing the sulfur dioxide; Wherein, the volume ratio of the nitrosulfuric acid to the sulfuric acid saturated with sulfur dioxide in the denitrification reaction is 1:20 to 1:

30.

11. A flue gas sulfuric acid production system, characterized in that, It includes the denitrification device according to any one of claims 1 to 8.

12. The sulfuric acid production system from flue gas according to claim 11, characterized in that, The flue gas sulfuric acid production system further includes: A sulfuric acid production device connected to the denitrification device; The sulfuric acid production device includes: A purification component for washing the flue gas to obtain first flue gas; A drying and absorption component connected to the purification component for removing the moisture in the first flue gas to obtain second flue gas; A conversion component connected to the drying and absorption component for converting sulfur dioxide in the second flue gas into sulfur trioxide to obtain third flue gas containing sulfur trioxide; A connecting pipeline arranged between the conversion component and the drying and absorption component for transporting the third flue gas to the drying and absorption component for absorbing sulfur trioxide to obtain nitrosulfuric acid.

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