A treatment agent for removing nitric acid from dilute sulfuric acid and its preparation and use method

Abstract

The present invention discloses a treatment agent for removing nitric acid from dilute sulfuric acid and a preparation and use method thereof, belonging to the technical field of coking wastewater treatment. The treatment agent for removing nitric acid from dilute sulfuric acid is composed of a carrier and a reactive component; the carrier is an activated corn cob, and the carrier accounts for 50% to 70% of the total mass of the treatment agent; the reactive component is prepared by mixing ammonium thiocyanate, ammonium thiosulfate, and urea in a mass ratio of 6 to 8:1 to 2:1 to 2. The nitric acid treatment agent is used to treat the mixed acid, thereby increasing the utilization rate of the dilute acid and the yield of ammonium sulfate. The present invention effectively solves the problem of increased operating costs caused by the waste of impure dilute sulfuric acid in waste liquid acid production, equipment corrosion, foaming, and destruction of ammonium sulfate crystals.

Description

Technical Field

[0001] The present invention relates to a purification process for dilute sulfuric acid acid wastewater containing nitric acid generated during the resource treatment of desulfurization waste liquid in the coking industry, and in particular to a treatment agent for removing nitric acid from dilute sulfuric acid and a preparation and use method thereof, belonging to the technical field of coking wastewater treatment. Background Art

[0002] With increasing environmental pressure, the management and control of various hazardous wastes and production byproducts has become a challenge for the coking industry. The treatment of desulfurization wastewater generated by HPF desulfurization of coke oven gas is a key factor hindering the effective removal of H2S during the gas purification process. The main components of the desulfurization liquid are ammonium thiocyanate, ammonium thiosulfate, ammonium sulfate, desulfurizer, and elemental sulfur. The content of secondary salts and suspended sulfur is the primary factor limiting desulfurization effectiveness. The coking industry generally agrees that the concentration of secondary salts in the desulfurization liquid should be ≤ 250 g / L. Exceeding this range will result in excessive H2S at the desulfurization tower outlet. Because desulfurization wastewater is primarily composed of salts and is highly corrosive, the long-term, large-scale direct discharge of this wastewater can seriously pollute the environment and harm public health. Using desulfurization wastewater as a raw material for acid production fundamentally addresses this issue and allows for the recovery of sulfur resources. During the wet desulfurization process of coke oven gas, large amounts of desulfurization wastewater are discharged, producing low-quality sulfur, sulfur paste, and sulfur sludge. Currently, the sulfur foam produced by wet oxidation desulfurization of coke oven gas in China is mostly recovered using a melting kettle or filtration / filter pressing to recover sulfur sludge / sulfur filter cake. These sulfur recovery processes suffer from severe equipment corrosion, discontinuous production, harsh operating environments for workers, and low sulfur product purity. Desulfurization wastewater contains abundant sulfur resources, both in the by-salts and sulfur. Acid production technology can recover this sulfur resource and produce sulfuric acid and steam. The sulfuric acid can be used as a feedstock for ammonium sulfate production in the ammonium sulfate unit of the gas purification system or for export. The steam can be used to preheat air or reduce pressure during the acid production process and be incorporated into the steam network.

[0003] The desulfurization waste liquid acid production process is a technical route that has been widely adopted in recent years. There are three main desulfurization waste liquid acid production processes currently used in the industry: wet acid production, dry acid production and semi-dry acid production. The main difference between the three is the different treatment of desulfurization waste liquid in the pretreatment section. Apart from that, the three are similar in terms of the process principles and production operations of the incineration system, purification system, conversion system and dry absorption system. Since the catalyst used in the existing conversion system is a dry acid production catalyst, the moisture content of the flue gas before entering the conversion catalyst must be reduced to ≤0.1g / Nm3 by washing, drying and other methods before entering the conversion section. 3Therefore, the water in the desulfurization waste liquid and the salts in it produced during the incineration process in the incinerator are discharged in the form of dilute sulfuric acid during the purification stage. Theoretically, if the incineration process is ideally controlled, the composition of this dilute acid is relatively simple and can be completely digested by the ammonium sulfate section within the enterprise. However, a large amount of ammonium salts in the desulfurization waste liquid will produce NO during the incineration process. x Completely suppressing its production at the source is extremely difficult. Consequently, these nitrogen oxides produce dilute nitric acid within the purification system, resulting in impure dilute sulfuric acid. Once entering the ammonium sulfate unit's saturator, this can cause foaming and disrupt ammonium sulfate crystallization. Effectively handling this dilute sulfuric acid mixed with nitric acid has become a common technical challenge within the industry.

[0004] There are currently no effective measures for the treatment of dilute acid in the coking industry. Some companies neutralize the acid by adding sodium hydroxide and then send it to the company's wastewater treatment system. However, this method is costly and also increases the load on biochemical, recycled water, and subsequent zero-discharge. In terms of waste sulfuric acid denitrification, Li Jianchang et al. (Li Jianchang, Zi Can, Liang Xiaofeng, et al. Simulation and optimization of atmospheric pressure treatment process for waste sulfuric acid containing nitrate [J]. Modern Chemical Industry, 2023, 43(04): 209-212.) established a denitrification-concentration atmospheric pressure treatment process for waste sulfuric acid containing nitrate based on quartz distillation equipment and combined with the physical properties and separation requirements of waste sulfuric acid containing nitrate; however, the quartz tower is not suitable for large-scale application in the strong acid industry. Lin Baoguo (Lin Guobao. Experimental study on the removal of nitrate from reagent sulfuric acid products (I) [J]. Guangzhou Chemical Industry, 2023, 51(12): 93-95+128.) used urea for denitration in the experiment. The reaction time of urea reagent solution with concentrated sulfuric acid sample was controlled within 2-3 minutes, and the sulfuric acid denitration effect was achieved at a reaction temperature of 30-90°C. This experiment mainly focused on the removal of nitrate from concentrated sulfuric acid. Multi-stage nanofiltration membranes were also used for treatment; however, there was no method for denitration of dilute sulfuric acid in the coking industry. Therefore, the treatment of dilute nitric acid contained in dilute sulfuric acid has become a technical problem in the acid production of the coking industry. It is of great significance to study how to remove dilute nitric acid from dilute sulfuric acid. Summary of the Invention

[0005] The present invention aims to provide a method for treating dilute sulfuric acid mixed with nitric acid in the coking industry. Specifically, the method comprises the following steps: first, providing a nitric acid treating agent, treating the mixed acid, thereby increasing the utilization rate of the dilute acid and the yield of ammonium sulfate, thereby solving the problems of equipment corrosion and high operating costs in the prior art process of treating sulfuric acid in dilute sulfuric acid.

[0006] The present invention mainly treats the nitric acid mixed in the dilute sulfuric acid used in the desulfurization waste liquid acid production. The nitric acid treatment agent is composed of a carrier and a reaction component. By utilizing the redox difference between dilute sulfuric acid and dilute nitric acid, the nitric acid treatment agent is added to the mixed acid liquid to produce NO xThe gas is discharged and the dilute nitric acid is removed; the generated pure dilute sulfuric acid enters the ammonium sulfate system; the nitric acid removal rate in the whole process can reach 85%; it effectively solves the problems of waste, equipment corrosion, foaming, damage to ammonium sulfate crystals, etc. caused by the impure dilute sulfuric acid in waste liquid acid production, which leads to increased operating costs.

[0007] The invention provides a treatment agent for removing nitric acid from dilute sulfuric acid. The treatment agent comprises a carrier and a reactive component. The carrier is an activated corn cob, and the carrier accounts for 50% to 70% of the mass of the treatment agent. The reactive component is prepared by mixing ammonium thiocyanate, ammonium thiosulfate, and urea in a mass ratio of 6 to 8:1 to 2:1 to 2.

[0008] The present invention provides a method for preparing the above-mentioned treatment agent for removing nitric acid in dilute sulfuric acid, comprising the following steps:

[0009] (1) Preparation of the carrier: First, sieve the corn cob through 60-80 mesh, then wash it with distilled water until the pH of the target product is neutral; dry it at 100-120 °C for 24 h, then place it in a tube furnace under nitrogen atmosphere, heat it to 800 °C, and keep it at this temperature for 2 h;

[0010] (2) Activation of the carrier: After the corncob was kept at a constant temperature for 2 h in nitrogen in step (1), the atmosphere was changed to a CO2 atmosphere, kept at a constant temperature for 2 h, and then cooled to room temperature in a nitrogen atmosphere;

[0011] (3) Loading of reactive components: ammonium thiocyanate, ammonium thiosulfate and urea were mixed in a mass ratio of 6-8:1-2:1-2, and added into deionized water with a solid-liquid ratio of 1-2 g:50 mL (i.e., 1-2 g of solid reactive component corresponds to 50 mL of water), heated, and stirred at 60°C-90°C for 20-40 min; a carrier was added to the mixed solution with a mass ratio of the carrier to the reactive component of 5-7:3-5, and stirred evenly at 60°C-90°C for 20-40 min. After being fully mixed, the solution was filtered and dried to obtain a nitric acid treatment agent.

[0012] The present invention provides a method for using the above-mentioned treatment agent for removing nitric acid from dilute sulfuric acid, comprising the following steps:

[0013] (1) The dilute sulfuric acid mixed with nitric acid to be treated is passed into the intermediate water tank, which is an existing equipment in the wastewater treatment process;

[0014] (2) Filtering the dilute sulfuric acid mixed with nitric acid;

[0015] (3) The filtered filtrate is passed into a heat exchanger for heat exchange, so that the liquid temperature reaches 60°C~90°C;

[0016] (4) The liquid heated in step (3) is passed into the pre-processor, and the speed is controlled to be 50r / min~200r / min; nitric acid treating agent is added, and the solid-liquid ratio of nitric acid treating agent to mixed acid liquid is 0.5~2g:100mL, and the temperature is controlled to react at 60℃~80℃. After the reaction is carried out for 1~3h, the gas generated in the process is washed. During the washing process, the ferrous catalyst is fed into the top of the washing tower through a pressure pump, and the solution formed by the ferrous catalyst is sprayed from top to bottom for high-efficiency desulfurization and denitrification. The reaction temperature is 30~60℃, and the spray density is 20~40m 3 / (m 2 h), the liquid-to-gas volume ratio of the solution formed by the ferrous catalyst to the gas generated during the reaction is 30-60; the generated liquid enters the next process;

[0017] The ferrous-based catalyst is composed of: 7 parts of a complexing agent, 4 parts of a stabilizer, 9 parts of an active component, 2 parts of a conditioning agent, 2 parts of a preservative, 2 parts of an antioxidant, and 74 parts of a solvent. The catalyst preparation process is as follows: weighing the solvent, the active component, and the complexing agent according to a mass ratio, heating and stirring to dissolve them, the heating temperature being 35° C., the heating time being 3 minutes, and the stirring time being 1 minute; adding the stabilizer, the preservative, and the antioxidant; and adding the conditioning agent to adjust the solution pH to 7. Furthermore, the solvent is deionized water, the active component is a mixture of ferrous sulfate and ferrous nitrate, wherein the mass ratio of ferrous sulfate to ferrous nitrate is 10:9, and the chelating agent is EDTA; the stabilizer is a mixture of xylitol and mannitol, wherein the mass ratio of xylitol to mannitol is 5:4, the preservative is a mixture of ethyl parahydroxybenzoate and propyl parahydroxybenzoate, wherein the mass ratio of ethyl parahydroxybenzoate to propyl parahydroxybenzoate is 7:5, the antioxidant is butylated hydroxyanisole; and the conditioning agent is sodium carbonate.

[0018] (5) The liquid produced in step (4) is passed into an oxidation reactor at a temperature of 120°C to 140°C, a rotation speed of 50 r / min to 200 r / min, and a pressure of 0.2 MPa to 0.5 MPa. Air is introduced at the same time, and the gas-liquid volume ratio of air to the liquid produced in step (4) is 5-20:1. The reaction is carried out for 1 hour to 2 hours. The tail gas generated during the reaction is returned to the incinerator of the acid production system for further treatment. The temperature of the liquid after the reaction is reduced to below 100°C after heat exchange with the mixed acid to be treated in a heat exchanger;

[0019] (6) The cooled liquid is separated into gas and liquid by centrifugation or filtration. After separation, the solid enters the subsequent coal blending process and the liquid enters the ammonium sulfate system.

[0020] Beneficial effects of the present invention:

[0021] By utilizing the redox difference between dilute sulfuric acid and dilute nitric acid, this nitric acid treatment agent is added to the mixed acid liquid to produce NOx The gas is discharged and dilute nitric acid is removed, with a nitric acid removal rate of up to 88%; the generated pure dilute sulfuric acid enters the ammonium sulfate system; the solid coal generated in the whole process is utilized, which effectively solves the problems of waste, equipment corrosion, foaming, damage to ammonium sulfate crystals, etc. caused by the impure dilute sulfuric acid in waste liquid acid production, which leads to increased operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure is a process flow chart of the use of the treatment agent of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further illustrated below by way of examples, but is not limited to the following examples. Example 1

[0024] The treatment object of this embodiment is a simulated mixed acid, the liquid components of which are sulfuric acid with a mass fraction of 10% and nitric acid with a mass fraction of 5%.

[0025] Preparation method of a treatment agent

[0026] ① Preparation of the carrier: First, sieve the corn cob through 80 mesh, then wash it with clean water and distilled water until the pH of the target is neutral, dry it at 105°C for 24 hours, and then heat it to 800°C at a rate of 10°C / min in a tube furnace under a nitrogen atmosphere and keep it at this temperature for 2 hours.

[0027] ② Activation of the carrier: Under the above preparation conditions, the atmosphere was switched to CO2 atmosphere, kept constant temperature for 2 hours, and then cooled to room temperature under nitrogen atmosphere;

[0028] ③ Carrier Impregnation: Mix ammonium thiocyanate, ammonium thiosulfate, and urea in a mass ratio of 8:1:1, add the mixture to deionized water at a solid-liquid ratio of 2g:50mL, heat, and stir at 90°C for 30 minutes. Add the carrier to the mixed solution at a mass ratio of 3:2 between the carrier and the three reactive components. Stir evenly at 90°C for 30 minutes. After thorough mixing, filter and dry the liquid to produce the nitric acid treatment agent.

[0029] Use of dinitric acid treatment agent

[0030] ① Pass the mixed acid to be treated into the intermediate water tank;

[0031] ② Filter the mixed acid solution;

[0032] ③ Pass the filtered liquid into the heat exchanger to exchange heat with the reacted acid solution, so that the liquid temperature reaches 90°C;

[0033] ④ Pass the liquid heated in step ③ into the pre-treatment unit and control the rotation speed to 85r / min. Add nitric acid treatment agent, and the solid-liquid mass ratio of nitric acid treatment agent to mixed acid liquid is 2g:100mL. Control the temperature at 80℃ and carry out the reaction. After 3 hours of reaction, wash the gas generated in the process. The washing process prepares ferrous-based catalyst for washing. The ferrous-based catalyst enters the top of the washing tower through a pressure pump. The ferrous-based catalyst is sprayed from top to bottom for high-efficiency desulfurization and denitrification. The reaction temperature is 60℃ and the spray density is 30m 3 / (m 2 h), the liquid-gas ratio is 50. The produced liquid enters the next process;

[0034] The ferrous-based catalyst is composed of: 7 parts of a complexing agent, 4 parts of a stabilizer, 9 parts of an active component, 2 parts of a conditioning agent, 2 parts of a preservative, 2 parts of an antioxidant, and 74 parts of a solvent. The preparation process of the ferrous-based catalyst is as follows: weighing the solvent, the active component, and the complexing agent according to a mass ratio, heating and stirring to dissolve them, the heating temperature being 35° C., the heating time being 3 minutes, and the stirring time being 1 minute; adding a stabilizer, a preservative, and an antioxidant; and adding a conditioning agent to adjust the pH of the solution to 7.

[0035] The solvent is deionized water, the active component is a mixture of ferrous sulfate and ferrous nitrate, wherein the mass ratio of ferrous sulfate to ferrous nitrate is 10:9, and the chelating agent is EDTA; the stabilizer is a mixture of xylitol and mannitol, wherein the mass ratio of xylitol to mannitol is 5:4, the preservative is a mixture of ethyl parahydroxybenzoate and propyl parahydroxybenzoate, wherein the mass ratio of ethyl parahydroxybenzoate to propyl parahydroxybenzoate is 7:5, the antioxidant is butylated hydroxyanisole; and the conditioning agent is sodium carbonate.

[0036] ⑤ The liquid produced in step ④ is passed into an oxidation reactor at a temperature of 140°C, a rotation speed of 85 r / min, and a pressure of 0.5 MPa, while air is introduced at a gas-to-liquid volume ratio of 15, and the reaction is carried out for 2 hours. The tail gas generated during the reaction is returned to the incinerator of the acid production system for further treatment. The temperature of the reacted liquid is reduced to below 100°C after heat exchange with the mixed acid to be treated in a heat exchanger;

[0037] ⑥ The cooled liquid enters the gas-liquid separation through centrifugation or filtration. After filtration, the carbon powder enters the subsequent coal blending treatment, and the liquid enters the ammonium sulfate system.

[0038] The removal rate of nitric acid in the mixed acid solution of this embodiment is 85%. Example 2

[0039] The treatment object of this embodiment is a simulated mixed acid, and the liquid components are sulfuric acid with a mass fraction of 15% and nitric acid with a mass fraction of 5%.

[0040] Preparation method of a treatment agent

[0041] ① Preparation of the carrier: First, sieve the corn cob through 80 mesh, then wash it with clean water and distilled water until the pH of the target is neutral, dry it at 105°C for 24 hours, and then heat it to 800°C at a rate of 10°C / min in a tube furnace under a nitrogen atmosphere and keep it at this temperature for 2 hours.

[0042] ② Activation of the carrier: Under the above preparation conditions, the atmosphere was switched to CO2 atmosphere, kept constant temperature for 2 hours, and then cooled to room temperature under nitrogen atmosphere;

[0043] ③ Carrier Impregnation: Mix ammonium thiocyanate, ammonium thiosulfate, and urea in a mass ratio of 6:2:2, add the mixture to deionized water at a solid-liquid ratio of 2:50, heat, and stir at 90°C for 30 minutes. Add the carrier to the mixed solution at a total mass ratio of carrier to reaction components of 3:2, stir evenly at 90°C for 40 minutes, thoroughly mix, and filter and dry the liquid to produce the nitric acid treatment agent.

[0044] Use of dinitric acid treatment agent

[0045] ① Pass the mixed acid to be treated into the intermediate water tank;

[0046] ② Filter the mixed acid solution;

[0047] ③ Pass the mixed acid liquid into the heat exchanger to exchange heat with the reacted acid liquid, so that the liquid temperature reaches 90℃;

[0048] ④ Pass the heated mixed acid liquid into the pretreatment device and control the speed to 85r / min. Add nitric acid treatment agent, and the solid-liquid mass ratio of nitric acid treatment agent to mixed acid liquid is 2:100. Control the temperature at 80℃ and react for 3 hours. Wash the gas generated in the process, and wash the ferrous-based catalyst prepared in the washing process (same as Example 1). The catalyst enters the top of the washing tower through a pressure pump, and the ferrous-based catalyst is sprayed from top to bottom for high-efficiency desulfurization and denitrification. The reaction temperature is 60℃ and the spray density is 30m 3 / (m 2 h), the liquid-gas ratio is 50. The produced liquid enters the next process;

[0049] The reaction temperature is 60℃ and the spray density is 30m 3 / (m 2 h), the liquid-gas ratio is 50. The produced liquid enters the next process;

[0050] ⑤ The liquid produced in step ④ is passed into an oxidation reactor at a temperature of 140°C, a rotation speed of 85 r / min, and a pressure of 0.5 MPa, while air is introduced at a gas-to-liquid ratio of 15, and the reaction is carried out for 2 hours. The tail gas generated during the reaction is returned to the incinerator of the acid production system for further treatment. The temperature of the liquid after the reaction is reduced to below 100°C after heat exchange with the mixed acid to be treated in a heat exchanger;

[0051] ⑥ The cooled liquid enters the gas-liquid separation through centrifugation or filtration. After filtration, the carbon powder enters the subsequent coal blending treatment, and the liquid enters the ammonium sulfate system.

[0052] The removal rate of nitric acid in the mixed acid solution of this embodiment is 88%. Example 3

[0053] The treatment object of this embodiment is a simulated mixed acid, and the liquid components are sulfuric acid with a mass fraction of 10% and nitric acid with a mass fraction of 10%.

[0054] Preparation method of a treatment agent

[0055] ① Preparation of the carrier: First, sieve the corn cob through 80 mesh, then wash it with clean water and distilled water until the pH of the target is neutral, dry it at 105°C for 24 hours, and then heat it to 800°C at a rate of 10°C / min in a tube furnace under a nitrogen atmosphere and keep it at this temperature for 2 hours.

[0056] ② Activation of the carrier: Under the above preparation conditions, the atmosphere was switched to CO2 atmosphere, kept constant temperature for 2 hours, and then cooled to room temperature under nitrogen atmosphere;

[0057] ③ Carrier Impregnation: Mix ammonium thiocyanate, ammonium thiosulfate, and urea in a mass ratio of 8:1:1, add the mixture to deionized water at a solid-liquid ratio of 2:50, heat, and stir at 90°C for 30 minutes. Add the carrier to the mixed solution at a total mass ratio of carrier to reaction components of 3:2, stir evenly at 90°C for 30 minutes, thoroughly mix, and filter and dry the liquid to produce the nitric acid treatment agent.

[0058] Use of dinitric acid treatment agent

[0059] ① Pass the mixed acid to be treated into the intermediate water tank;

[0060] ② Filter the mixed acid solution;

[0061] ③ Pass the mixed acid liquid into the heat exchanger to exchange heat with the reacted acid liquid, so that the liquid temperature reaches 90℃;

[0062] ④ Pass the heated mixed acid liquid into the pretreatment device and control the speed to 85r / min. Add nitric acid treatment agent, and the solid-liquid mass ratio of nitric acid treatment agent to mixed acid liquid is 2:100. Control the temperature at 80℃ and react for 3 hours. Wash the gas generated in the process, and wash the ferrous-based catalyst prepared in the washing process (same as Example 1). The catalyst enters the top of the washing tower through a pressure pump, and the ferrous-based catalyst is sprayed from top to bottom for high-efficiency desulfurization and denitrification. The reaction temperature is 60℃ and the spray density is 30m 3 / (m 2 h), the liquid-gas ratio is 50. The produced liquid enters the next process;

[0063] The reaction temperature is 60℃ and the spray density is 30m 3 / (m 2 h), the liquid-gas ratio is 50. The produced liquid enters the next process;

[0064] ⑤ The liquid produced in step ④ is passed into an oxidation reactor at a temperature of 140°C, a rotation speed of 85 r / min, and a pressure of 0.5 MPa, while air is introduced at a gas-to-liquid ratio of 15, and the reaction is carried out for 2 hours. The tail gas generated during the reaction is returned to the incinerator of the acid production system for further treatment. The temperature of the liquid after the reaction is reduced to below 100°C after heat exchange with the mixed acid to be treated in a heat exchanger;

[0065] ⑥ The cooled liquid enters the gas-liquid separation through centrifugation or filtration. After filtration, the carbon powder enters the subsequent coal blending treatment, and the liquid enters the ammonium sulfate system.

[0066] The removal rate of nitric acid in the mixed acid solution of this embodiment is 87%.

Claims

1. A method for preparing a treatment agent for removing nitric acid from dilute sulfuric acid, characterized in that: The treatment agent is composed of a carrier and a reactive component; the carrier is activated corn cob, and the carrier accounts for 50% to 70% of the total mass of the treatment agent; the reactive component is prepared by mixing ammonium thiocyanate, ammonium thiosulfate, and urea in a mass ratio of 6 to 8:1 to 2:1 to 2; The method for preparing the treatment agent for removing nitric acid from dilute sulfuric acid comprises the following steps: (1) Preparation of the carrier: First, sieve the corn cob through 60-80 mesh, then wash it with distilled water until the pH of the target product is neutral; dry it at 100-120 °C for 24 h, then place it in a tube furnace under nitrogen atmosphere, heat it to 800 °C, and keep it at this temperature for 2 h; (2) Activation of the carrier: After the corncob was kept at a constant temperature for 2 h in nitrogen in step (1), the atmosphere was changed to a CO2 atmosphere, kept at a constant temperature for 2 h, and then cooled to room temperature in a nitrogen atmosphere; (3) Loading of reactive components: ammonium thiocyanate, ammonium thiosulfate, and urea are mixed in a mass ratio of 6-8:1-2:1-2, added to deionized water, heated, and stirred at 60°C-90°C for 20-40 min; a carrier is added to the mixed solution in a mass ratio of the carrier to the reactive component of 5-7:3-5, and stirred evenly at 60°C-90°C for 20-40 min. After thorough mixing, the mixture is filtered and dried to obtain a nitric acid treatment agent.

2. The method for preparing a treatment agent for removing nitric acid from dilute sulfuric acid according to claim 1, wherein: In step (3), the solid-liquid ratio of the reactive component to deionized water is 1-2 g:50 mL.

3. A method for using the treatment agent for removing nitric acid from dilute sulfuric acid obtained by the preparation method according to claim 1, characterized in that The following steps are involved: (1) Pass the dilute sulfuric acid solution mixed with nitric acid to be treated into the intermediate water tank; (2) Filtering the dilute sulfuric acid solution mixed with nitric acid; (3) Pass the filtered filtrate into the heat exchanger for heat exchange; (4) The liquid heated in step (3) is passed into the pre-processor, and the speed is controlled to be 50r / min~200r / min; a nitric acid treatment agent is added, and the solid-liquid ratio of the nitric acid treatment agent to the mixed acid liquid is 0.5~2g:100mL, and the temperature is controlled to react at 60℃~80℃. After the reaction is carried out for 1~3h, the gas generated in the process is washed. During the washing process, the ferrous-based catalyst is fed into the top of the washing tower through a pressure pump, and the solution formed by the ferrous-based catalyst is sprayed from top to bottom for efficient desulfurization and denitrification, and the generated liquid enters the next process; (5) The liquid produced in step (4) is introduced into an oxidation reactor, and air is introduced at the same time, and the reaction is carried out for 1 to 2 hours under the condition that the gas-liquid volume ratio of air to the liquid produced in step (4) is 5-20:

1. The tail gas generated during the reaction is returned to the incinerator of the acid production system for further treatment. The temperature of the liquid after the reaction is reduced to below 100°C after heat exchange with the mixed acid to be treated in a heat exchanger; (6) The cooled liquid is separated into gas and liquid by centrifugation or filtration. After separation, the solid enters the subsequent coal blending process and the liquid enters the ammonium sulfate system.

4. The method for using the treatment agent for removing nitric acid from dilute sulfuric acid according to claim 3, wherein: After heat exchange in step (3), the liquid temperature reaches 60°C~90°C.

5. The method for using the treatment agent for removing nitric acid from dilute sulfuric acid according to claim 3, characterized in that: In step (4), during the desulfurization and denitrification process, the reaction temperature is 30-60°C and the spray density is 20-40m 3 / (m 2 h), the volume ratio of the solution formed by the ferrous-based catalyst to the gas generated during the reaction is 30-60.

6. The method for using the treatment agent for removing nitric acid from dilute sulfuric acid according to claim 3, wherein: In step (4), the composition of the ferrous-based catalyst is: 7 parts of a complexing agent, 4 parts of a stabilizer, 9 parts of an active ingredient, 2 parts of a conditioning agent, 2 parts of a preservative, 2 parts of an antioxidant, and 74 parts of a solvent; The catalyst preparation process is as follows: weigh the solvent, active component and complexing agent according to the mass ratio, heat and stir to dissolve, the heating temperature is 35°C, the heating time is 3 minutes, and the stirring time is 1 minute; add stabilizer, preservative and antioxidant; add a blending agent to make the solution pH 7.

7. The method for using the treatment agent for removing nitric acid from dilute sulfuric acid according to claim 6, characterized in that: In step (4), the solvent is deionized water, the active component is a mixture of ferrous sulfate and ferrous nitrate, wherein the mass ratio of ferrous sulfate to ferrous nitrate is 10:9, and the chelating agent is EDTA; the stabilizer is a mixture of xylitol and mannitol, wherein the mass ratio of xylitol to mannitol is 5:4, the preservative is a mixture of ethyl parahydroxybenzoate and propyl parahydroxybenzoate, wherein the mass ratio of ethyl parahydroxybenzoate to propyl parahydroxybenzoate is 7:5, the antioxidant is butylated hydroxyanisole; and the conditioning agent is sodium carbonate.

8. The method for using the treatment agent for removing nitric acid from dilute sulfuric acid according to claim 3, characterized in that: During the oxidation reaction in step (5), the temperature is 120° C. to 140° C., the rotation speed is 50 r / min to 200 r / min, and the pressure is 0.2 MPa to 0.5 MPa.

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