Treatment method of high-ammonia-nitrogen waste sulfuric acid

Abstract

The invention relates to a treatment method of high-ammonia-nitrogen waste sulfuric acid. The treatment method comprises the following steps: (1) carrying out solid-liquid separation to remove insoluble impurities in the high-ammonia-nitrogen waste sulfuric acid so as to obtain high-ammonia-nitrogen waste sulfuric acid filtrate; (2) carrying out diffusion dialysis on the high-ammonia-nitrogen waste sulfuric acid filtrate obtained in the step (1) to respectively obtain ammonia nitrogen enriched residual liquid and sulfuric acid enriched recycled sulfuric acid; (3) adding an oxidizing agent into the diluted recovered sulfuric acid for further reaction to remove ammonia nitrogen in the diluted recovered sulfuric acid; and (4) carrying out post-treatment to obtain a sulfuric acid product. Compared with a traditional treatment method, the method provided by the invention has the advantages that the dosage of chemicals is small, the resource utilization rate is high, the cost is low, the process is simple, mature and efficient, all components in the waste sulfuric acid are effectively utilized, no three wastes are generated in the technological process, and the process is environment-friendly and has relatively high practical value.

Description

Technical Field

[0001] The invention relates to the field of industrial wastewater treatment, and in particular to a method for treating waste sulfuric acid containing high ammonia nitrogen. Background Art

[0002] Waste sulfuric acid is produced during the resin production process, which has the characteristics of high ammonia nitrogen content and sulfuric acid content. Currently, the commonly used methods for treating waste acid include neutralization, chemical oxidation and concentration. Among them, the neutralization method is to use alkaline substances such as sodium hydroxide, calcium hydroxide, potassium hydroxide, etc. to neutralize waste sulfuric acid and convert it into relatively safe and easy-to-dispose salts. During the neutralization process, the reaction rate should be carefully controlled to avoid violent reactions that produce a lot of heat. The chemical oxidation method uses an oxidant to decompose the ammonia nitrogen in the wastewater under appropriate conditions, converting it into nitrogen gas and separating it from the wastewater, thereby purifying the wastewater. For low-concentration ammonia nitrogen-containing wastewater, this method has a good treatment effect and is relatively economical, but for high-concentration wastewater, this method has a high operating cost and more by-products. The concentration regeneration method is to heat the waste sulfuric acid, use a vacuum system to achieve negative pressure evaporation and concentration, remove the water and organic impurities therein, and finally obtain regenerated sulfuric acid. This method can only concentrate sulfuric acid and remove volatile impurities, and cannot separate non-volatile ammonia nitrogen.

[0003] CN 109809447A discloses a method for recovering waste sulfuric acid, which neutralizes waste sulfuric acid with magnesium oxide and produces magnesium sulfate at the same time. The produced magnesium sulfate needs to be further purified, and air cooling and water cooling are required to synchronously control the reaction temperature during the reaction. CN109574351A discloses a method for resource utilization and zero-emission treatment of acid-containing high-ammonia nitrogen and high-salt wastewater, which includes an acid recovery system, a coagulation precipitation system, a stable gas membrane system, and an evaporation crystallization system arranged in sequence, and recovers hydrochloric acid in the waste acid through a diffusion dialysis device, and the recovered hydrochloric acid is reused in the production process.

[0004] The existing technology has the defects of consuming a large amount of reagents or excessive energy consumption when the waste acid concentration is high. Therefore, how to achieve efficient separation and recovery of components in the waste acid has become a problem that needs to be solved urgently. Summary of the invention

[0005] In order to solve the above technical problems, the present invention separates ammonia nitrogen from high-concentration waste sulfuric acid by diffusion dialysis, and further removes residual ammonia nitrogen by oxidation to recover industrial-grade sulfuric acid products. At the same time, ammonia nitrogen can be recycled to produce ammonium sulfate.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for treating waste sulfuric acid containing high ammonia nitrogen, the method comprising the following steps:

[0008] (1) removing insoluble impurities in high-ammonia nitrogen waste sulfuric acid by solid-liquid separation to obtain high-ammonia nitrogen waste sulfuric acid filtrate;

[0009] (2) subjecting the high-ammonia nitrogen waste sulfuric acid filtrate of step (1) to diffusion dialysis to obtain ammonia nitrogen-enriched residual liquid and sulfuric acid-enriched recovered sulfuric acid;

[0010] (3) adding an oxidant to the diluted recovered sulfuric acid to react and remove ammonia nitrogen therein;

[0011] (4) Post-treatment to obtain sulfuric acid product.

[0012] The present invention separates ammonia nitrogen from waste sulfuric acid by diffusion dialysis, thereby solving the problem that the traditional ammonia nitrogen separation method is not suitable for high-concentration acid systems. After completing the preliminary separation of sulfuric acid and ammonia nitrogen, an oxidant is added to the recovered sulfuric acid enriched with sulfuric acid to remove a small amount of residual ammonia nitrogen. The amount of oxidant used is reduced, the side reactions in the oxidation reaction are reduced, and the production efficiency is improved. Compared with the traditional disposal method, the method has a synergistic effect of multiple treatment methods, high resource utilization, low cost, and all components in the waste sulfuric acid are effectively utilized.

[0013] The present invention has no limitation on the solid-liquid separation, and any method known to those skilled in the art for solid-liquid separation may be used, such as filtration, sedimentation or centrifugation.

[0014] As a preferred technical solution of the present invention, the ammonia nitrogen content of the high-ammonia nitrogen waste sulfuric acid is 80g / L to 100g / L, for example, it can be 80g / L, 81g / L, 84g / L, 90g / L or 100g / L, and the sulfuric acid content is ≤50wt%, for example, it can be 1wt%, 10wt%, 15wt%, 20wt%, 40wt% or 50wt%, etc.

[0015] Preferably, the high-ammonia nitrogen waste sulfuric acid comes from a resin production process.

[0016] Preferably, the filter residue from the solid-liquid separation can be returned to the production process for repeated use.

[0017] The technical solution of the present invention is applicable to waste sulfuric acid with high sulfuric acid and ammonia nitrogen contents. The waste sulfuric acid is treated in a coordinated manner through multiple steps and multiple methods. The overall treatment process is mild and does not generate excess waste. All components in the waste liquid are used in production processes and in the production of valuable chemicals, thereby solving the technical problems of difficult separation and incomplete separation of ammonia nitrogen in high-concentration sulfuric acid waste liquid.

[0018] As a preferred technical solution of the present invention, a filter aid is added before the solid-liquid separation in step (1).

[0019] Preferably, the filter aid comprises any one of diatomaceous earth, activated carbon or gypsum, or a combination of at least two of them.

[0020] The amount of the filter aid of the present invention can be adjusted by those skilled in the art according to the filtering conditions, and is not further limited here.

[0021] The invention adds a filter aid into the waste sulfuric acid for stirring, thereby adsorbing tiny suspended particles in the waste sulfuric acid and improving the filtering efficiency.

[0022] As a preferred technical solution of the present invention, the receiving liquid for the diffusion dialysis in step (2) is pure water.

[0023] Preferably, the volume ratio of the pure water to the high-ammonia nitrogen waste sulfuric acid filtrate is 1:1 to 1.3:1, for example, it can be 1:1, 1.1:1, 1.15:1, 1.2:1 or 1.3:1.

[0024] Preferably, the ammonia nitrogen content of the recovered sulfuric acid in step (2) is 3 g / L to 6 g / L, for example, 3 g / L, 3.5 g / L, 4 g / L, 5 g / L or 6 g / L, and the sulfuric acid content is 30 wt% to 40 wt%, for example, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt% or 40 wt%, etc.

[0025] Preferably, the ammonia nitrogen content of the residual liquid in step (2) is 80 g / L to 100 g / L, for example, 80 g / L, 81 g / L, 84 g / L, 90 g / L or 100 g / L, and the sulfuric acid content is 5 wt% to 15 wt%, for example, 5 wt%, 7 wt%, 10 wt%, 12 wt%, 14 wt% or 15 wt%, etc.

[0026] Preferably, the sulfuric acid recovery rate of the recovered sulfuric acid in step (2) is 80-90%, for example, 80%, 82%, 84%, 86% or 90%.

[0027] Preferably, the ammonia nitrogen removal rate of the recovered sulfuric acid in step (2) is 85-90%, for example, it can be 85%, 86%, 87%, 88% or 90%.

[0028] The invention improves the diffusion dialysis efficiency by controlling the ratio of waste sulfuric acid and pure water in the diffusion dialysis process, separates most of the monovalent ammonium ions, significantly reduces the ammonium ions in the recovered sulfuric acid, and significantly reduces the acidity in the residual liquid, and does not introduce too much water, thereby reducing the energy consumption of subsequent reduced pressure evaporation, providing convenient conditions for further preparing sulfuric acid products and recovering ammonia nitrogen in the residual liquid, reducing the amount of auxiliary materials used in subsequent reactions, greatly increasing the reaction speed, and improving the production efficiency.

[0029] As a preferred technical solution of the present invention, the treatment method further comprises step (2) adding ammonium bicarbonate to the residual liquid for neutralization and then evaporating under reduced pressure to obtain ammonium sulfate crystals.

[0030] Preferably, the neutralization pH value is 5 to 7, for example, 5, 5.2, 5.5, 6, 6.5 or 7.

[0031] Preferably, the purity of the ammonium sulfate crystals is greater than 99%, for example, it may be 99%, 99.3%, 99.5%, 99.8% or 99.9%, etc.

[0032] The sulfuric acid content of the residual liquid after diffusion dialysis separation is greatly reduced, the feeding amount of ammonium bicarbonate in the process of preparing ammonium sulfate is reduced, and the secondary pollution of acid steam generated by the intense neutralization reaction and excessively high temperature is avoided.

[0033] As a preferred technical solution of the present invention, the oxidant in step (3) includes chlorine.

[0034] Preferably, the chlorine gas is continuously passed into the diluted recovered sulfuric acid.

[0035] As a preferred technical solution of the present invention, the recovered sulfuric acid in step (3) is diluted to a sulfuric acid content of ≤30wt%, for example, 5wt%, 10wt%, 20wt%, 26wt%, 28wt% or 30wt%.

[0036] The invention reduces the occurrence of side reactions and improves the reaction efficiency of chlorine gas oxidizing ammonia nitrogen by diluting the sulfuric acid content to ≤30wt%.

[0037] Preferably, the reaction temperature in step (3) is 50-60°C, for example, 50°C, 52°C, 54°C, 56°C or 60°C.

[0038] Preferably, the reaction time in step (3) is ≥ 4 h, for example, it can be 4 h, 5 h, 10 h, 20 h or 40 h.

[0039] Preferably, the mass ratio of the available chlorine in the chlorine gas to the nitrogen in the recovered sulfuric acid in step (3) is ≥9:1, for example, it can be 9:1, 10:1, 15:1, 20:1 or 30:1, etc.

[0040] The present invention further improves the oxidation efficiency under acidic conditions by controlling the reaction temperature within the above range, and prevents the hypochlorous acid generated by the dissolution of chlorine from decomposing when the temperature is too high, causing excessive side reactions, reducing the hypochlorous acid involved in the reaction, and insufficient reduction due to too low a temperature, resulting in low ammonia nitrogen removal efficiency. At the same time, the mass ratio of available chlorine to nitrogen in recovered sulfuric acid is controlled to be ≥9:1, and the reaction time is ≥4h to ensure that the ammonia nitrogen can be fully oxidized to nitrogen.

[0041] As a preferred technical solution of the present invention, the tail gas generated in the reaction of step (3) is absorbed by water and then reused to dilute and recover sulfuric acid.

[0042] The present invention absorbs the tail gas generated in step (3) with water to recover excess chlorine, and uses the water to recover the dilution of sulfuric acid. The hypochlorous acid formed by the chlorine dissolving in water can preliminarily oxidize the ammonia nitrogen in the sulfuric acid into nitrogen, thereby avoiding the waste of chlorine and the generation of secondary pollution, and improving the utilization rate of chlorine.

[0043] As a preferred technical solution of the present invention, the post-treatment in step (4) includes evaporation under reduced pressure.

[0044] Preferably, the sulfuric acid content of the sulfuric acid product obtained in step (4) is greater than 70%, for example, it may be 71%, 75%, 80%, 85% or 90%, etc., the chlorine content is less than 50 ppm, for example, it may be 0.1 ppm, 1 ppm, 10 ppm, 20 ppm or 40 ppm, etc., and the ammonia nitrogen content is ≤10 ppm, for example, it may be 0.1 ppm, 1 ppm, 2 ppm, 5 ppm or 10 ppm, etc.

[0045] The sulfuric acid after reduced pressure evaporation can directly meet the product requirements of industrial sulfuric acid, and ammonia nitrogen therein is removed through the synergistic effect of diffusion dialysis and chemical oxidation, and chlorine introduced in the oxidation process is removed in the form of gas in the subsequent reduced pressure evaporation process.

[0046] As a preferred technical solution of the present invention, a method for treating waste sulfuric acid containing high ammonia nitrogen is provided, the method comprising the following steps:

[0047] (1) adding a filter aid to remove insoluble impurities in the high-ammonia nitrogen waste sulfuric acid by solid-liquid separation to obtain a high-ammonia nitrogen waste sulfuric acid filtrate; the filter aid comprises any one of diatomaceous earth, activated carbon or gypsum, or a combination of at least two of them;

[0048] (2) subjecting the high-ammonia nitrogen waste sulfuric acid filtrate of step (1) to diffusion dialysis to obtain ammonia nitrogen-enriched residual liquid and sulfuric acid-enriched recovered sulfuric acid; the receiving liquid of the diffusion dialysis is pure water; the volume ratio of the pure water to the high-ammonia nitrogen waste sulfuric acid filtrate is 1:1 to 1.3:1; the ammonia nitrogen content of the recovered sulfuric acid is 3 g / L to 6 g / L, and the sulfuric acid content is 30 wt% to 40 wt%; the ammonia nitrogen content of the residual liquid is 80 g / L to 100 g / L, and the sulfuric acid content is 5 wt% to 15 wt%;

[0049] (3) Continuously passing chlorine gas into the recovered sulfuric acid diluted to a sulfuric acid content of ≤30wt% to remove ammonia nitrogen therein, and the tail gas generated by the reaction is absorbed by water and then reused in step (2) to dilute the recovered sulfuric acid; the reaction temperature is 50-60°C; the reaction time is ≥4h; the mass ratio of effective chlorine in the chlorine gas to nitrogen in the recovered sulfuric acid is ≥9:1

[0050] (4) evaporating under reduced pressure to obtain a sulfuric acid product having a sulfuric acid content of >70%, a chlorine content of <50 ppm, and an ammonia nitrogen content of ≤10 ppm; adding ammonium bicarbonate to neutralize the residual liquid to a pH value of 5 to 7, and then evaporating to obtain ammonium sulfate crystals having a purity of >99%.

[0051] The present invention solves the technical problems of high dosage of reagents and low resource utilization rate in the recovery and treatment of waste sulfuric acid with high ammonia nitrogen and high acidity through the synergistic effect of multiple separation methods, and provides a mature, efficient and environmentally friendly waste sulfuric acid treatment method that effectively utilizes each component without generating three wastes.

[0052] Compared with the prior art, the present invention has at least the following beneficial effects:

[0053] (1) The present invention is directed to waste sulfuric acid with high ammonia nitrogen and high acidity. By controlling the ratio of influent water to waste sulfuric acid, the majority of monovalent ammonium ions therein are separated by diffusion dialysis, and the ammonium ions in the recovered sulfuric acid are significantly reduced. At the same time, the acidity in the residual liquid is significantly reduced. At this time, the residual liquid is neutralized with ammonium bicarbonate, which reduces the amount of ammonium bicarbonate used for further processing, greatly increases the reaction speed, and improves production efficiency.

[0054] (2) The acidity of the recovered sulfuric acid is reduced, and the amount of the added oxidant and the reaction temperature can be controlled to gently convert the ammonia nitrogen into nitrogen gas and separate it from the system. The obtained sulfuric acid can meet the requirements of industrial sulfuric acid, with a sulfuric acid content of more than 70%, a chlorine content of less than 50 ppm, and an ammonia nitrogen content of ≤10 ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a flow chart of the method for treating high-ammonia nitrogen waste sulfuric acid provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0056] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0057] Example 1

[0058] This embodiment provides a method for treating waste sulfuric acid containing high ammonia nitrogen, such as Figure 1 The method shown comprises the following steps:

[0059] (1) adding 0.1 wt % activated carbon to waste sulfuric acid having a sulfuric acid content of 45 wt % and an ammonia nitrogen content of 100 g / L, stirring for 0.5 h, and then filtering to obtain a high-ammonia nitrogen waste sulfuric acid filtrate;

[0060] (2) subjecting the high-ammonia nitrogen waste sulfuric acid filtrate of step (1) to diffusion dialysis to obtain ammonia nitrogen-enriched residual liquid and sulfuric acid-enriched recovered sulfuric acid; the receiving liquid of the diffusion dialysis is pure water, and the volume ratio of the pure water to the high-ammonia nitrogen waste sulfuric acid filtrate is 1.1:1; the recovered sulfuric acid has an ammonia nitrogen content of 5 g / L and a sulfuric acid content of 35 wt %; the ammonia nitrogen content of the residual liquid is 96 g / L and the sulfuric acid content is 10 wt %;

[0061] (3) continuously passing chlorine gas into recovered sulfuric acid diluted to a sulfuric acid content of 30 wt% to react and remove ammonia nitrogen therein, and the tail gas generated by the reaction is absorbed by water and then reused in step (2) to dilute the recovered sulfuric acid; the reaction temperature is 60° C.; the reaction time is 6 h; the mass ratio of effective chlorine in the chlorine gas to nitrogen in the recovered sulfuric acid is 12:1;

[0062] (4) Recover sulfuric acid and evaporate it under reduced pressure until the sulfuric acid content is greater than 70% and the chlorine content is less than 50 ppm to obtain a sulfuric acid product. The residual liquid is neutralized by adding ammonium bicarbonate to a pH value of 5 and then evaporated under reduced pressure to obtain ammonium sulfate crystals.

[0063] Example 2

[0064] (1) adding 0.1 wt % diatomaceous earth to waste sulfuric acid having a sulfuric acid content of 50 wt % and an ammonia nitrogen content of 98 g / L, stirring for 0.5 h, and then filtering to obtain a high-ammonia nitrogen waste sulfuric acid filtrate;

[0065] (2) subjecting the high-ammonia nitrogen waste sulfuric acid filtrate of step (1) to diffusion dialysis to obtain ammonia nitrogen-enriched residual liquid and sulfuric acid-enriched recovered sulfuric acid; the receiving liquid of the diffusion dialysis is pure water, and the volume ratio of the pure water to the high-ammonia nitrogen waste sulfuric acid filtrate is 1.3:1; the recovered sulfuric acid has an ammonia nitrogen content of 3 g / L and a sulfuric acid content of 32 wt %; the ammonia nitrogen content of the residual liquid is 85 g / L and the sulfuric acid content is 7 wt %;

[0066] (3) continuously passing chlorine gas into recovered sulfuric acid diluted to a sulfuric acid content of 30 wt% to react and remove ammonia nitrogen therein, and the tail gas generated by the reaction is absorbed by water and then reused in step (2) to dilute the recovered sulfuric acid; the reaction temperature is 55° C.; the reaction time is 4 h; the mass ratio of effective chlorine in the chlorine gas to nitrogen in the recovered sulfuric acid is 12:1;

[0067] (4) Recover sulfuric acid and evaporate under reduced pressure until the sulfuric acid content is greater than 70% and the chlorine content is less than 50 ppm to obtain a sulfuric acid product. The residual liquid is neutralized by adding ammonium bicarbonate to a pH value of 6 and then evaporated under reduced pressure to obtain ammonium sulfate crystals.

[0068] Example 3

[0069] This embodiment provides a method for treating waste sulfuric acid containing high ammonia nitrogen, the method comprising the following steps:

[0070] (1) adding 0.1 wt % of gypsum to waste sulfuric acid having a sulfuric acid content of 50 wt % and an ammonia nitrogen content of 98 g / L, stirring for 0.5 h, and then filtering to obtain a high-ammonia nitrogen waste sulfuric acid filtrate;

[0071] (2) subjecting the high-ammonia nitrogen waste sulfuric acid filtrate of step (1) to diffusion dialysis to obtain ammonia nitrogen-enriched residual liquid and sulfuric acid-enriched recovered sulfuric acid; the receiving liquid of the diffusion dialysis is pure water, and the volume ratio of the pure water to the high-ammonia nitrogen waste sulfuric acid filtrate is 1.2:1; the recovered sulfuric acid has an ammonia nitrogen content of 3 g / L and a sulfuric acid content of 32 wt %; the ammonia nitrogen content of the residual liquid is 85 g / L and the sulfuric acid content is 7 wt %;

[0072] (3) continuously passing chlorine gas into recovered sulfuric acid diluted to a sulfuric acid content of 20 wt% to remove ammonia nitrogen therein, and absorbing the tail gas produced by the reaction with water and then returning it to dilute the recovered sulfuric acid in step (2); the reaction temperature is 50° C.; the reaction time is 9 h; the mass ratio of effective chlorine in the chlorine gas to nitrogen in the recovered sulfuric acid is 9:1;

[0073] (4) Recover sulfuric acid and evaporate under reduced pressure until the sulfuric acid content is greater than 70% and the chlorine content is less than 50 ppm to obtain a sulfuric acid product. The residual liquid is neutralized by adding ammonium bicarbonate to a pH value of 7 and then evaporated under reduced pressure to obtain ammonium sulfate crystals.

[0074] Example 4

[0075] This embodiment is the same as embodiment 1 except that the reaction temperature of chlorine oxidation is controlled to be 40°C.

[0076] Example 5

[0077] This embodiment is the same as embodiment 1 except that the reaction temperature of chlorine oxidation is controlled to be 80°C.

[0078] Example 6

[0079] This embodiment is the same as Embodiment 1 except that the recovered sulfuric acid is not diluted before chlorine oxidation.

[0080] Example 7

[0081] This embodiment is the same as Embodiment 1 except that the volume ratio of pure water to filtrate is 2:1.

[0082] Example 8

[0083] This embodiment is the same as Embodiment 1 except that the volume ratio of pure water to filtrate is 0.5:1.

[0084] Comparative Example 1

[0085] This comparative example provides a method for treating waste sulfuric acid containing high ammonia nitrogen, the method comprising the following steps:

[0086] 0.1wt% activated carbon was added to waste sulfuric acid with a sulfuric acid content of 45wt% and an ammonia nitrogen content of 100g / L, stirred for 0.5h and filtered, and the obtained filtrate was oxidized by chlorine gas, with an effective chlorine: nitrogen mass ratio of 12:1, a reaction temperature of 60°C, and a reaction time of 6h. The chlorine content was evaporated under reduced pressure until the chlorine content was less than 50ppm and the sulfuric acid content was greater than 70wt%, and a sulfuric acid product was obtained.

[0087] Comparative Example 2

[0088] This comparative example provides a method for treating waste sulfuric acid containing high ammonia nitrogen, the method comprising the following steps:

[0089] 0.1 wt% activated carbon was added to waste sulfuric acid with a sulfuric acid content of 45 wt% and an ammonia nitrogen content of 100 g / L, stirred for 0.5 h and filtered, and the obtained filtrate was neutralized to pH = 5 by adding ammonium bicarbonate to obtain an ammonium sulfate solution, which was evaporated under reduced pressure to obtain ammonium sulfate crystals. The neutralization reaction in this comparative example released a lot of heat, resulting in the volatilization of acid mist.

[0090] The test results are shown in Table 1.

[0091] Table 1

[0092] Examples and Comparative Examples Ammonia nitrogen content of sulfuric acid product (ppm) Ammonium sulfate purity (%) Example 1 6 99.9 Example 2 8 99.8 Example 3 10 99.9 Example 4 300 99.9 Example 5 2300 99.9 Example 6 20 99.9 Example 7 8 99.9 Example 8 1200 99.9 Comparative Example 1 96000 / Comparative Example 2 / 99.9

[0093] The test results show that:

[0094] (1) It can be seen from Examples 1 to 3 that the present invention separates most of the monovalent ammonium ions in high-ammonia nitrogen waste sulfuric acid by diffusion dialysis, and the ammonium ions in the recovered acid are significantly reduced. At the same time, the acidity in the residual liquid is significantly reduced. At this time, the residual liquid is neutralized with ammonium carbonate, which reduces the amount of raw materials and auxiliary materials, greatly increases the reaction speed, and improves production efficiency. Under acidic conditions, the ammonia nitrogen in sulfuric acid is oxidized by an oxidant, and the ammonia nitrogen is converted into nitrogen and separated from the system by controlling the amount of oxidant added, sulfuric acid content, reaction temperature and reaction time. The ammonia nitrogen content in the obtained sulfuric acid can be ≤10ppm, and the purity of ammonium sulfate is >99%.

[0095] (2) It can be seen from Examples 1 and 4 to 6 that the present invention can achieve better oxidation and removal of ammonia nitrogen by optimizing the reaction temperature and sulfuric acid concentration of chlorine oxidation, and overcome the problem of insufficient removal of ammonia nitrogen caused by excessive side reactions of ammonia nitrogen oxidation under strong acid conditions in the chlorine oxidation reaction. When the reduction temperature in Example 4 is 40°C, the reaction temperature is too low, the residual ammonia nitrogen is not sufficiently removed, and the ammonia nitrogen content in the sulfuric acid product rises to 300ppm. When the reduction temperature in Example 5 is 80°C, the reaction temperature is too high, and side reactions such as hypochlorous acid decomposition are enhanced, and the ammonia nitrogen content in the sulfuric acid product increases sharply to 2300ppm. When the acid solution is recovered in Example 6 without dilution and the chlorine reduction reaction is directly carried out, the strong acidic environment increases the side reactions, and the ammonia nitrogen content in the sulfuric acid product rises to 20ppm.

[0096] (3) It can be seen from Examples 1 and 7 to 8 that the present invention, by optimizing the volume ratio of pure water to filtrate in diffusion dialysis, enables the recovered sulfuric acid and the residual liquid to have ammonia nitrogen and sulfuric acid content suitable for the next step of treatment, while reducing the energy consumption of the subsequent reduced pressure evaporation. When the amount of pure water in the receiving liquid in Example 7 is too much, the ammonia nitrogen content in the sulfuric acid product remains at 8ppm without further reduction, and the energy consumption of the subsequent reduced pressure evaporation increases significantly. When the amount of pure water in the receiving liquid in Example 8 is too little, the ammonia nitrogen content in the sulfuric acid product increases sharply to 1200ppm, which cannot meet the requirements of industrial sulfuric acid.

[0097] (4) It can be seen from Example 1 and Comparative Examples 1-2 that the present invention can fully recover sulfuric acid in high-ammonia nitrogen waste sulfuric acid and produce industrial sulfuric acid with economic value through the synergistic effect of diffusion dialysis, oxidant oxidation and neutralization method, while ammonium radicals and a small amount of sulfuric acid in the residual liquid can be fully utilized to produce ammonium sulfate, without the generation of three wastes. When only the diffusion dialysis step is performed in Example 1, the sulfuric acid content in the recovered sulfuric acid is 35wt%, and the ammonia nitrogen content is 5g / L, and the sulfuric acid content in the residual liquid is 10wt%, and the ammonia nitrogen content is 96g / L. Ammonia nitrogen and sulfuric acid are not fully separated, and the product cannot be directly output as an industrial product. When chlorine oxidation is directly used in Comparative Example 1, due to the high sulfuric acid content of the waste liquid, the optimal reaction pH value of the chlorine oxidation process is 6-7, and a good oxidation effect cannot be exerted when the acidity is too high, resulting in a significant increase in the ammonia nitrogen content. When ammonium bicarbonate is directly used for neutralization reaction in Comparative Example 2, the consumption of ammonium bicarbonate increases significantly due to the excessively high sulfuric acid content, and the economic efficiency is greatly reduced. In addition, due to the intense neutralization reaction, the temperature rises, acid mist is generated, resulting in secondary pollution.

[0098] In summary, the present invention treats high-ammonia nitrogen waste sulfuric acid through the synergistic effect of diffusion dialysis, oxidant oxidation and neutralization. Compared with traditional disposal methods, this method has low reagent usage, high resource utilization, low cost, simple process, mature and efficient, all components in the waste sulfuric acid are effectively utilized, and the process does not produce three wastes, is environmentally friendly, and has high practical value.

[0099] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for treating high-ammonia nitrogen waste sulfuric acid, characterized in that: The processing method comprises the following steps: (1) removing insoluble impurities in high-ammonia nitrogen waste sulfuric acid by solid-liquid separation to obtain high-ammonia nitrogen waste sulfuric acid filtrate; (2) subjecting the high-ammonia nitrogen waste sulfuric acid filtrate of step (1) to diffusion dialysis to obtain ammonia nitrogen-enriched residual liquid and sulfuric acid-enriched recovered sulfuric acid; (3) diluting the recovered sulfuric acid in step (2), and adding an oxidant to react and remove ammonia nitrogen; (4) Post-treatment to obtain sulfuric acid product.

2. The processing method according to claim 1, characterized in that: The high-ammonia nitrogen waste sulfuric acid has an ammonia nitrogen content of 80 g / L to 100 g / L, and a sulfuric acid content of ≤50 wt %.

3. The processing method according to claim 1 or 2, characterized in that: Adding a filter aid before the solid-liquid separation in step (1); Preferably, the filter aid comprises any one of diatomaceous earth, activated carbon or gypsum, or a combination of at least two of them.

4. The processing method according to any one of claims 1 to 3, characterized in that: The receiving solution of the diffusion dialysis in step (2) is pure water; Preferably, the volume ratio of the pure water to the high-ammonia nitrogen waste sulfuric acid filtrate is 1:1 to 1.3:1; Preferably, the ammonia nitrogen content of the recovered sulfuric acid in step (2) is 3 g / L to 6 g / L, and the sulfuric acid content is 30 wt% to 40 wt%; Preferably, the ammonia nitrogen content of the residual liquid in step (2) is 80 g / L to 100 g / L, and the sulfuric acid content is 5 wt% to 15 wt%.

5. The processing method according to any one of claims 1 to 4, characterized in that: The treatment method further comprises the step (2) adding ammonium bicarbonate to the residual liquid for neutralization and then evaporating under reduced pressure to obtain ammonium sulfate crystals; Preferably, the pH value of the neutralization is 5 to 7; Preferably, the purity of the ammonium sulfate crystals is >99%.

6. The processing method according to any one of claims 1 to 5, characterized in that: The oxidant in step (3) comprises chlorine; Preferably, the chlorine gas is continuously passed into the diluted recovered sulfuric acid.

7. The processing method according to any one of claims 1 to 6, characterized in that: The recovered sulfuric acid in step (3) is diluted to a sulfuric acid content of ≤30wt%; Preferably, the reaction temperature in step (3) is 50-60°C; Preferably, the reaction time in step (3) is ≥ 4 h; Preferably, the mass ratio of the available chlorine in the chlorine gas to the nitrogen in the recovered sulfuric acid in step (3) is ≥9:

1.

8. The processing method according to any one of claims 1 to 7, characterized in that: The tail gas generated in the reaction of step (3) is absorbed by water and then reused to dilute and recover sulfuric acid.

9. The processing method according to any one of claims 1 to 8, characterized in that: The post-treatment in step (4) comprises evaporation under reduced pressure; Preferably, the sulfuric acid product obtained in step (4) has a sulfuric acid content of >70%, a chlorine content of <50 ppm, and an ammonia nitrogen content of ≤10 ppm.

10. The processing method according to any one of claims 1 to 9, characterized in that: The processing method comprises the following steps: (1) adding a filter aid to remove insoluble impurities in the high-ammonia nitrogen waste sulfuric acid by solid-liquid separation to obtain a high-ammonia nitrogen waste sulfuric acid filtrate, wherein the filter aid comprises any one of diatomaceous earth, activated carbon or gypsum, or a combination of at least two of them; (2) subjecting the high-ammonia nitrogen waste sulfuric acid filtrate of step (1) to diffusion dialysis to obtain ammonia nitrogen-enriched residual liquid and sulfuric acid-enriched recovered sulfuric acid; the receiving liquid of the diffusion dialysis is pure water, and the volume ratio of the pure water to the high-ammonia nitrogen waste sulfuric acid filtrate is 1:1 to 1.3:1; the ammonia nitrogen content of the recovered sulfuric acid is 3 g / L to 6 g / L, and the sulfuric acid content is 30 wt% to 40 wt%; the ammonia nitrogen content of the residual liquid is 80 g / L to 100 g / L, and the sulfuric acid content is 5 wt% to 15 wt%; (3) continuously passing chlorine gas into recovered sulfuric acid diluted to a sulfuric acid content of ≤30wt% to remove ammonia nitrogen therein, and absorbing the tail gas produced by the reaction with water and then returning it to dilute the recovered sulfuric acid in step (2); the reaction temperature is 50-60° C.; the reaction time is ≥4h; the mass ratio of effective chlorine in the chlorine gas to nitrogen in the recovered sulfuric acid is ≥9:1; (4) evaporating under reduced pressure to obtain a sulfuric acid product having a sulfuric acid content of >70%, a chlorine content of <50 ppm, and an ammonia nitrogen content of ≤10 ppm; adding ammonium bicarbonate to neutralize the residual liquid to a pH value of 5 to 7, and then evaporating under reduced pressure to obtain ammonium sulfate crystals having a purity of >99%.

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