A method and system for recovering and treating waste sulfuric acid generated in the dye industry

Abstract

This invention discloses a method for recycling and treating waste sulfuric acid generated in the dye industry, comprising the following steps: S1, filtration treatment; S2, concentration treatment; S3, decolorization and collection. This invention utilizes a combination of resin adsorption and evaporation processes. The resin adsorption process removes most of the large molecular organic matter, effectively removing organic matter from wastewater and reducing pollutant content during evaporation. Compared to conventional methods such as calcium hydroxide neutralization, resin adsorption reduces wastewater treatment costs and allows for the recovery of sulfuric acid resources from the waste sulfuric acid.

Description

Technical Field

[0001] This invention relates to the field of waste sulfuric acid recovery technology, specifically to a method for recovering and treating waste sulfuric acid generated in the dye industry. Background Technology

[0002] The dye industry uses high-concentration sulfuric acid in its reprocessing, generating waste sulfuric acid with a concentration ranging from 6% to 51%. This waste sulfuric acid has a complex composition, containing certain amounts of heavy metals such as copper ions, as well as hydrochloric acid, bromine, and sulfur. The composition of the waste sulfuric acid varies significantly depending on the product being processed. The conventional treatment method involves neutralizing the waste sulfuric acid with calcium hydroxide. However, this requires large quantities of calcium hydroxide, generating a significant amount of calcium sulfate-containing sludge, which can only be treated as hazardous waste. Wastewater treatment costs are high, and there are also issues such as the inability to recover sulfuric acid resources, high product consumption, and pipe scaling. Waste sulfuric acid needs to be concentrated to a high concentration (above 90%) for resource recovery. Evaporation is a relatively economical and feasible method for concentration; however, due to the numerous impurities in the waste sulfuric acid, direct evaporation results in a mother liquor with a sulfuric acid concentration that does not reach the desired level. Furthermore, the concentration of organic matter makes the mother liquor viscous, hindering effective resource utilization.

[0003] Waste sulfuric acid needs to be concentrated to a high concentration (over 90%) during resource recovery. Evaporation is a relatively economical and feasible method for concentration. However, due to the large amount of impurities in waste sulfuric acid, direct evaporation will result in the mother liquor's sulfuric acid concentration not reaching the expected level. Furthermore, the concentration of organic matter makes the mother liquor viscous, hindering effective resource utilization. Waste sulfuric acid contains a large amount of organic matter, metal ions, inorganic salts, and other impurities. Therefore, most of the organic matter in the wastewater needs to be removed before evaporation and concentration to obtain reusable sulfuric acid that meets the requirements.

[0004] This technical solution employs a resin adsorption + evaporation process specially designed for the characteristics of waste sulfuric acid. First, resin adsorption is used to remove some organic matter from the wastewater. Then, an evaporation process is designed based on the boiling point rise during sulfuric acid concentration and the characteristics of organic matter in the components. Summary of the Invention

[0005] Therefore, the present invention provides a method and system for recycling and treating waste sulfuric acid generated in the dye industry.

[0006] The technical solution of this invention is: a method for recycling and treating waste sulfuric acid generated in the dye industry, comprising the following steps:

[0007] S1. Filtration treatment:

[0008] First, the waste sulfuric acid is pre-filtered to obtain pre-filtered water. Then, the pre-filtered water is filtered a second time using a high-efficiency organic matter removal resin to obtain secondary-filtered water. Finally, the high-efficiency organic matter removal resin is desorbed.

[0009] S2. Concentration Process:

[0010] The filtered water undergoes three preheating processes, three negative pressure evaporations, single-effect negative pressure evaporation concentration, and high-vacuum low-temperature concentration purification in sequence; the temperature range for the three preheating processes is T0.

[0011] S2-1. Based on the initial concentration C of sulfuric acid in the waste sulfuric acid, determine the temperature T1 of the three negative pressure evaporations. Then, adjust the temperature T1 and the time t1 of the three negative pressure evaporations to make the sulfuric acid mass concentration C1 in the initial concentrated liquid obtained by the three negative pressure evaporations ≥ 60%, thus completing the three negative pressure evaporation treatment.

[0012] S2-2. Then, the initial concentrate is concentrated by single-effect preheater and single-effect separator. The temperature T2 and time t2 of the single-effect negative pressure evaporation are adjusted until the sulfuric acid mass concentration C2 in the secondary concentrate is ≥80%, and the treatment is completed.

[0013] S2-3. Subsequently, the secondary concentrate is concentrated and purified under high vacuum and low temperature. The high vacuum and low temperature concentration and purification process is as follows: First, the secondary concentrate is concentrated in a concentration kettle to obtain concentrated sulfuric acid. The high vacuum and low temperature concentration and purification temperature T3 and the high vacuum and low temperature concentration and purification time t3 are adjusted until the mass concentration of concentrated sulfuric acid C3≥90% is obtained.

[0014] S3, Decolorization and Collection:

[0015] Under low vacuum and at a temperature of T4, a 63% nitric acid solution is added to concentrated sulfuric acid for decolorization. After decolorization, the concentrated sulfuric acid is kept warm and distilled for 1 to 1.5 hours, and then cooled to a temperature of 25 to 35°C to obtain a liquid. The liquid is then subjected to solid-liquid separation, and the separated filtrate is collected in a concentrated sulfuric acid collection tank to complete the sulfuric acid recovery process.

[0016] Explanation: The above-mentioned resin adsorption can adsorb and remove large molecular organic matter, while facilitating subsequent evaporation and improving the concentration and purity of the sulfuric acid obtained by evaporation. Through the evaporation process, multiple evaporation processes can be used to remove water and impurities of various boiling points. At the same time, multi-stage treatment can greatly reduce the loss of sulfuric acid.

[0017] Furthermore, the highly efficient organic matter removal resin is an acrylate-based macroporous adsorption resin.

[0018] Note: It has high adsorption capacity and good chemical stability, and can provide a large surface area and pore volume, which is beneficial for adsorbing target substances.

[0019] Furthermore, the high-efficiency organic matter removal resin is a composite resin composed of acrylate-based macroporous adsorption resin, silica powder, 2-aminothiazole, and polystyrene microspheres as raw materials.

[0020] Note: Polystyrene microspheres possess chemical stability and tunable pore size, making them widely used in separation, purification, catalysis, and other fields. They have numerous pores and surface active sites, allowing them to adsorb target substances such as organic matter and metal ions during the adsorption process. 2-Aminothiazole can form complexes with metal ions and adsorb them from the solution to the resin surface through ion exchange. Silica powder has a large specific surface area and microporous structure.

[0021] Furthermore, the preparation method of the composite acrylate-based macroporous adsorption resin is as follows:

[0022] Acrylate-based macroporous adsorption resin, silica powder, 2-aminothiazole, and polystyrene microspheres were prepared according to a mass ratio of 8-9:1-2:5:2-3. The silica powder and 2-aminothiazole were mixed at 130-135℃ and then granulated to obtain powder particles with a particle size of 1-3 mm. The powder particles, acrylate-based macroporous adsorption resin, and polystyrene microspheres were then mixed and added to a twin-screw granulator for shearing and extrusion granulation to obtain a composite acrylate-based macroporous adsorption resin composition.

[0023] Among them, the silicon micro powder is selected with a particle size of 230-350 nm, and the polystyrene microspheres are selected with a particle size of 20-50 μm.

[0024] Note: The above raw materials can be combined with acrylate-based macroporous adsorption resin to achieve complementary effects, thus solving the problems of limited selectivity, difficulty in adsorbing small molecules, and low loading capacity.

[0025] Furthermore, the concentration of sulfuric acid in the waste sulfuric acid ranges from 6% to 51%; the three-stage negative pressure evaporation includes first-effect evaporation, second-effect evaporation, and third-effect evaporation with a temperature difference of 5°C increasing sequentially.

[0026] In step S2, the method for determining the temperature range T1 of the three negative pressure evaporations is as follows: based on the initial concentration C of sulfuric acid in the waste sulfuric acid, when 20% > C ≥ 6%, the value range of T1 is determined to be 89-100℃; when 35% > C ≥ 20%, the value range of T1 is determined to be 105-110℃; when 51% > C ≥ 35%, the value range of T1 is determined to be 120-130℃, and T1 ≥ T0 + 20, T2 ≥ T1 + 10, and 150℃ > T3 ≥ T2 + 10.

[0027] Explanation: By setting the temperature range conditions mentioned above, the corresponding primary temperature range can be determined based on the initial concentration, allowing the system temperature to be gradually heated. This ensures constant treatment of waste sulfuric acid while minimizing energy consumption and achieving energy-saving effects.

[0028] Furthermore, the time range t2 for single-effect negative pressure evaporation is: when 70% > C1 ≥ 60%, t2 = When 80% > C1 ≥ 70% Where k ranges from 0.8 to 1; t1 ranges from 0.5 to 1.5h; and t3 ranges from 0.5 to 1.5h.

[0029] The range of values ​​for T4 is when 95% > C3 ≥ 90%. When 100% > C3 ≥ 95%, T4 = 1.1T3.

[0030] Note: By determining the time range mentioned above, the entire process of the system can be made controllable and adjustable. This ensures that the sulfuric acid concentration can be maximized while minimizing the time required, thereby improving process efficiency. Conversely, directly increasing the temperature would result in the sulfuric acid concentration in the mother liquor not reaching the expected level, thus hindering effective resource utilization.

[0031] Further, in step S1, methanol or liquid alkali is used to desorb the resin that removes organic matter efficiently; in step S3, nitric acid solution is added to concentrated sulfuric acid at a mass ratio of 1:0.0001 to 0.001.

[0032] A treatment system for recycling and treating waste sulfuric acid generated in the dye industry includes an adsorption system, a concentration system, a piping system, and a condensate tank.

[0033] The pipeline system includes a first pipeline, multiple second pipelines and a third pipeline for transporting waste sulfuric acid, a first liquid pipeline and a second liquid pipeline for transporting condensate, and a first steam pipeline, a second steam pipeline, a third steam pipeline and a fourth steam pipeline for transporting steam.

[0034] The adsorption system includes a filter for preliminary filtration and a resin adsorption tower for adsorbing organic matter, the filter and the resin adsorption tower being connected via a first pipe;

[0035] The concentration system includes a primary preheater, a secondary preheater, and a tertiary preheater connected in sequence for three preheating stages, and also includes the following devices connected in sequence through a second pipeline: a primary evaporation unit for single-effect evaporation, a secondary evaporation unit for double-effect evaporation, a tertiary evaporation unit for triple-effect evaporation, a single-effect preheater, a single-effect evaporator, and a single-effect separator for single-effect negative pressure evaporation and concentration, and a concentration kettle, a cooling kettle, a vacuum filter, and a recovery liquid tank for high-vacuum low-temperature concentration and purification.

[0036] Furthermore, the resin adsorption tower, the three-stage preheater, and the first-effect evaporation unit are connected in sequence through a third pipeline. The first-effect evaporation unit, the second-effect evaporation unit, and the third-effect evaporation unit all include an evaporator and a separator. The cooling kettle is equipped with a recovery condenser. The pipeline system is equipped with an electric valve.

[0037] Note: The above system settings enable the filtration, evaporation, and decolorization processes in the waste sulfuric acid treatment method described above.

[0038] Furthermore, the shell side of the evaporator of the first-effect evaporation unit is connected to the third-stage preheater through a first steam pipe, the steam exhaust port of the separator of the first-effect evaporation unit is connected to the shell side of the evaporator of the second-effect evaporation unit through a second steam pipe, and the condensate drain port of the separator of the first-effect evaporation unit is connected to the second-stage preheater through a first liquid pipe.

[0039] The separator steam exhaust port of the double-effect evaporator unit is connected to the shell side of the evaporator of the triple-effect evaporator unit through the third steam pipe, and the separator condensate drain port of the double-effect evaporator unit is connected to the first-stage preheater through the second liquid pipe. The first-stage preheater is connected to the condensate tank.

[0040] The separator steam exhaust port of the triple-effect evaporator unit is connected to the condenser and the condensate tank in sequence through the fourth steam pipe, and the separator condensate drain port of the triple-effect evaporator unit is connected to the condensate tank through the third liquid pipe.

[0041] The shell side of the single-effect evaporator is connected to the single-effect preheater through a fifth steam pipe, the steam exhaust port of the single-effect separator is connected to the liquid tank of the condenser, and the condensate drain port of the single-effect separator is connected to the condensate tank.

[0042] Note: By connecting the above-mentioned evaporator, pipes and separator, the heat generated in the multi-stage evaporation process can be used for multiple preheating processes, thus achieving heat recovery.

[0043] The beneficial effects of this invention are:

[0044] (1) This invention uses a combination of resin adsorption and evaporation to remove most of the large molecular organic matter by resin adsorption in the front stage. The resin adsorption and evaporation process can effectively remove organic matter in wastewater and reduce the pollutant content during the evaporation process. Compared with the calcium hydroxide neutralization treatment in conventional treatment methods, resin adsorption can reduce the cost of wastewater treatment and can recover sulfuric acid resources in waste sulfuric acid.

[0045] (2) This invention, through the design of resin adsorption and evaporation processes, can concentrate waste sulfuric acid into high-concentration sulfuric acid (over 90%). Compared with the method of directly evaporating waste sulfuric acid, this technical solution, by specifically setting multi-stage evaporation temperatures and evaporation times based on the differences in boiling points of impurities in waste sulfuric acid and the complex composition of the waste sulfuric acid solution, and dynamically adjusting them according to the concentration of sulfuric acid after evaporation, can avoid the problem that impurities in waste sulfuric acid cause the sulfuric acid concentration of the mother liquor to not reach the expected level, ensuring efficient concentration in the evaporation process; at the same time, it can effectively solve the problem of viscous mother liquor, realizing the resource utilization of waste sulfuric acid. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0047] The present invention will now be described in more detail with reference to specific embodiments, so as to better demonstrate the advantages of the present invention.

[0048] Example 1:

[0049] A waste sulfuric acid recycling and treatment system for the dye industry includes an adsorption system, a concentration system, and a pipeline system. The pipeline system includes a first pipeline, multiple second pipelines, and a third pipeline for conveying waste sulfuric acid; a first liquid pipeline and a second liquid pipeline for conveying condensate; and a first steam pipeline, a second steam pipeline, a third steam pipeline, and a fourth steam pipeline for conveying steam.

[0050] The adsorption system includes a filter for preliminary filtration and a resin adsorption tower for adsorbing organic matter. The filter and the resin adsorption tower are connected by a first pipe. The filter is a commercially available filter with a pore size of 0.05 μm.

[0051] The concentration system includes a primary preheater, a secondary preheater, and a tertiary preheater connected in sequence for three preheating stages, and also includes the following devices connected in sequence through a second pipeline: a primary evaporation unit for single-effect evaporation, a secondary evaporation unit for double-effect evaporation, a tertiary evaporation unit for triple-effect evaporation, a single-effect preheater, a single-effect evaporator, and a single-effect separator for single-effect negative pressure evaporation and concentration, and a concentration kettle, a cooling kettle, a vacuum filter, and a recovery liquid tank for high-vacuum low-temperature concentration and purification.

[0052] Furthermore, the resin adsorption tower, the three-stage preheater, and the first-effect evaporation unit are connected sequentially through a third pipeline. The first-effect evaporation unit, the second-effect evaporation unit, and the third-effect evaporation unit all include an evaporator and a separator. The cooling kettle is equipped with a recovery condenser. The pipeline system is equipped with an electric valve.

[0053] The shell side of the evaporator of the first-effect evaporator unit is connected to the third-stage preheater through the first steam pipe, the steam exhaust port of the separator of the first-effect evaporator unit is connected to the shell side of the evaporator of the second-effect evaporator unit through the second steam pipe, and the condensate drain port of the separator of the first-effect evaporator unit is connected to the second-stage preheater through the first liquid pipe.

[0054] The separator steam exhaust port of the double-effect evaporator unit is connected to the shell side of the evaporator of the triple-effect evaporator unit through the third steam pipe, and the separator condensate drain port of the double-effect evaporator unit is connected to the shell side of the first-stage preheater through the second liquid pipe. The shell side of the first-stage preheater is connected to the condensate tank.

[0055] The separator steam exhaust port of the triple-effect evaporator unit is connected to the condenser and the condensate tank in sequence through the fourth steam pipe, and the separator condensate drain port of the triple-effect evaporator unit is connected to the condensate tank through the third liquid pipe.

[0056] The shell side of the single-effect evaporator is connected to the single-effect preheater through a fifth steam pipe, the steam exhaust port of the single-effect separator is connected to the condenser, and the condensate drain port of the single-effect separator is connected to the condensate tank.

[0057] All devices in the above system are commercially available.

[0058] Example 2

[0059] A recycling method using the system described in Example 1 includes the following steps:

[0060] S1. Filtration treatment:

[0061] First, the waste sulfuric acid is initially filtered using an adsorption system to obtain pre-filtered water. Then, the pre-filtered water is filtered a second time using a high-efficiency organic matter removal resin to obtain secondary filtered water. Finally, the high-efficiency organic matter removal resin is desorbed. The waste sulfuric acid contains 39% sulfuric acid. In step S1, methanol or liquid alkali is used to desorb the high-efficiency organic matter removal resin. The desorption method adopts existing conventional processes.

[0062] S2. Concentration Process:

[0063] The filtered water is subjected to three preheating processes, three negative pressure evaporations, single-effect negative pressure evaporation concentration, and high-vacuum low-temperature concentration purification in sequence; the temperature of the first preheating is 100℃, the temperature of the second preheating is 103℃, and the temperature of the third preheating is 105℃.

[0064] S2-1. Based on the initial sulfuric acid concentration C = 39% in the waste sulfuric acid, the temperatures for the three negative pressure evaporations are determined as follows: T1 = 120–130℃, T2 = 130–140℃, and T3 = 140–150℃; the time for the three negative pressure evaporations is t1 = 1 hour.

[0065] The specific adjustment process is as follows: evaporation is carried out at temperature T1 at 120℃ for t1 / 2, at T1 at 125℃ for t1 / 4, and at T1 at 130℃ for t1 / 4; the sulfuric acid mass concentration in the initial concentrate is C1 = 65%, completing three negative pressure evaporation treatments;

[0066] S2-2. Then, the initial concentrate is concentrated by single-effect negative pressure evaporation using a single-effect preheater and a single-effect separator. The single-effect negative pressure evaporation time is t2 = 1.16 h. The temperature is adjusted as follows: evaporation at 130℃ for t1 / 2, evaporation at 135℃ for t1 / 4, and evaporation at 140℃ for t1 / 4. The secondary concentrate has a sulfuric acid mass concentration of C2 = 87%, and the treatment is complete.

[0067] S2-3. Subsequently, the secondary concentrate was subjected to high-vacuum low-temperature concentration and purification. The high-vacuum low-temperature concentration and purification process was as follows: First, the secondary concentrate was concentrated in a concentration vessel to obtain concentrated sulfuric acid. The high-vacuum low-temperature concentration and purification time was t3 = 1 hour. The evaporation time was t1 / 2 at 140℃, t1 / 4 at 145℃, and t1 / 4 at 150℃. The mass concentration of the obtained concentrated sulfuric acid was C3 = 93%.

[0068] S3, Decolorization and Collection:

[0069] Under low vacuum and at a temperature of 162.4℃, 63% nitric acid solution was added to concentrated sulfuric acid at a mass ratio of 1:0.005 for decolorization. After decolorization, the concentrated sulfuric acid was kept warm and distilled for 1.2 hours, and then cooled to 30℃ to obtain a liquid. The liquid was then subjected to solid-liquid separation, and the separated filtrate was collected in a concentrated sulfuric acid collection tank to complete the sulfuric acid recovery process. The high-efficiency organic matter removal resin used is an acrylate-based macroporous adsorption resin.

[0070] Example 3

[0071] The difference between this embodiment and Embodiment 1 is that the concentration of sulfuric acid in the waste sulfuric acid is 6%; the value of T1 ranges from 89 to 100°C, with evaporation lasting t1 / 2 at 89°C, t1 / 4 at 95°C, and t1 / 4 at 100°C; t1 = t3 = 1.5 h; t2 = 1.16 h, with the value of T2 ranging from 99 to 110°C, with evaporation lasting t1 / 2 at 99°C and t2 / 4 at 105°C. T1 / 4, T2 evaporates at 110℃ for t1 / 4; T3 ranges from 109 to 120℃; T3 evaporates at 109℃ for t1 / 2, T3 evaporates at 115℃ for t1 / 4, and T3 evaporates at 120℃ for t1 / 4; a 63% nitric acid solution is added to concentrated sulfuric acid at a mass ratio of 1:0.001 for decolorization. After decolorization, the concentrated sulfuric acid is kept warm and distilled for 1 hour, and then cooled to 35℃ to obtain the feed solution.

[0072] Example 4

[0073] The difference between this embodiment and Embodiment 3 is that the concentration of sulfuric acid in the waste sulfuric acid is 22%; the temperature range of T1 is 105–110℃, the temperature range of T2 is 115–120℃, and the temperature range of T3 is 125–130℃; t1 = t3 = 1 h; t2 = 1.16 h; evaporation at temperature T1 at 105℃ lasts for t1 / 2, at T1 at 108℃ lasts for t1 / 4, and at T1 at 110℃ lasts for t1 / 4; evaporation at temperature T2 at 115℃ lasts for t1 / 4. Continuing from t1 / 2, T2 evaporates at 118℃ for t1 / 4, and T2 evaporates at 120℃ for t1 / 4; T3 evaporates at 125℃ for t1 / 2, T3 evaporates at 128℃ for t1 / 4, and T3 evaporates at 130℃ for t1 / 4; a 63% nitric acid solution is added to concentrated sulfuric acid at a mass ratio of 1:0.0001 for decolorization. After decolorization, the concentrated sulfuric acid is kept warm and distilled for 1.5 hours, and then cooled to 25℃ to obtain the feed solution.

[0074] Example 5

[0075] The difference between this embodiment and Embodiment 1 is that C1 is 75%, C2 is 89%, and C3 is 97%. Where k is 1; t2 = 0.9t1, T4 = 1.1T3.

[0076] Example 6

[0077] The difference between this embodiment and Embodiment 5 is that C1 is 75%, C2 is 89%, and C3 is 97%. Where k is 0.8; t2 = 0.7t1, T4 = 1.1T3.

[0078] Example 7

[0079] The difference between this embodiment and Embodiment 2 is that the high-efficiency organic matter removal resin is a composite resin composed of acrylate-based macroporous adsorption resin, silica powder, 2-aminothiazole, and polystyrene microspheres.

[0080] The composite resin is prepared as follows: acrylate-based macroporous adsorption resin, silica powder, 2-aminothiazole, and polystyrene microspheres are prepared in a mass ratio of 8.5:1.5:5:2.5. The silica powder and 2-aminothiazole are mixed at 130°C and then granulated to obtain powder particles with a particle size of 1–3 mm. The powder particles, acrylate-based macroporous adsorption resin, and polystyrene microspheres are then mixed and added to a twin-screw granulator for shearing and extrusion granulation to obtain the composite acrylate-based macroporous adsorption resin composition. The silica powder is selected with a particle size of 230–350 nm, and the polystyrene microspheres are selected with a particle size of 20–50 μm.

[0081] Example 8

[0082] The difference between this embodiment and Embodiment 7 is that the acrylate-based macroporous adsorption resin, silica powder, 2-aminothiazole, and polystyrene microspheres are prepared in a mass ratio of 9:1:5:2.

[0083] Example 9

[0084] The difference between this embodiment and Embodiment 7 is that the acrylate-based macroporous adsorption resin, silica powder, 2-aminothiazole, and polystyrene microspheres are prepared in a mass ratio of 8:2:5:3.

[0085] Experimental Example

[0086] I. Compare the amount of concentrated sulfuric acid recovered under different treatment methods;

[0087] Comparative Example 1: At the same time (24h) and initial concentration of waste sulfuric acid as in Example 2, waste sulfuric acid was recovered by direct evaporation, and the average mass concentration of the concentrated sulfuric acid obtained was 76%.

[0088] The average mass concentration of concentrated sulfuric acid obtained in Example 2 was 93%.

[0089] As can be seen from Comparative Example 1 and Example 2, the sulfuric acid recovery treatment effect in Example 1 is significantly improved;

[0090] II. Energy consumption of comparative adjustment methods;

[0091] Comparative Example 2: The difference from Example 2 is that the set temperature is 120℃, and the total time is 7 hours until the concentrations of C1, C2, and C3 reach the standard; the total energy consumed in 24 hours is approximately E, where E = 55 kg standard coal / t raw liquid;

[0092] The total energy consumed in 24 hours in Example 2 is approximately 0.95E;

[0093] Comparing Example 2 with Comparative Example 2, it can be seen that the adjustment process in Example 2 is more energy-efficient.

[0094] III. Comparison of the effects of the use of adsorption resin on the amount of concentrated sulfuric acid recovered;

[0095] The C3 obtained in Example 7 was 97%, the C3 obtained in Example 8 was 96%, and the C3 obtained in Example 9 was 95%.

[0096] Compared to 93% in Example 2, the composite resin treatment used in Example 7 has a better effect.

Claims

1. A method for recycling and treating waste sulfuric acid generated in the dye industry, characterized in that, Includes the following steps: S1. Filtration treatment: First, the waste sulfuric acid is pre-filtered to obtain pre-filtered water. Then, the pre-filtered water is filtered a second time using a high-efficiency organic matter removal resin to obtain secondary-filtered water. Finally, the high-efficiency organic matter removal resin is desorbed. S2. Concentration Process: The secondary filtered water is subjected to three preheating processes, three negative pressure evaporations, single-effect negative pressure evaporation concentration, and high-vacuum low-temperature concentration purification. The temperature range of the three preheating processes is T0. The concentration range of sulfuric acid in the waste sulfuric acid is 6-51%. The three negative pressure evaporations include first-effect evaporation, second-effect evaporation, and third-effect evaporation with a temperature difference of 5°C increasing sequentially. S2-1. Based on the initial concentration C of sulfuric acid in the waste sulfuric acid, determine the temperature T1 for the three negative pressure evaporations. Then, adjust the temperature T1 and the time t1 of the three negative pressure evaporations to ensure that the sulfuric acid mass concentration C1 in the initial concentrated liquid obtained from the three negative pressure evaporations is ≥60%, thus completing the three negative pressure evaporation treatment. The method for determining the temperature range T1 for the three negative pressure evaporations is as follows: based on the initial concentration C of sulfuric acid in the waste sulfuric acid, when 20% > C ≥ 6%, the value range of T1 is determined to be 89–100℃; when 35% > C ≥ 20%, the value range of T1 is determined to be 105–110℃; when 51% > C ≥ 35%, the value range of T1 is determined to be 120–130℃, and T1 ≥ T0 + 20, T2 ≥ T1 + 10, 150℃ > T3 ≥ T2 + 10. S2-2. Then, the initial concentrate is concentrated by single-effect preheater and single-effect separator. The temperature T2 and time t2 of the single-effect negative pressure evaporation are adjusted until the sulfuric acid mass concentration C2 in the secondary concentrate is ≥80%, and the treatment is completed. S2-3. Subsequently, the secondary concentrate is concentrated and purified under high vacuum and low temperature. The high vacuum and low temperature concentration and purification process is as follows: First, the secondary concentrate is concentrated in a concentration kettle to obtain concentrated sulfuric acid. The high vacuum and low temperature concentration and purification temperature T3 and the high vacuum and low temperature concentration and purification time t3 are adjusted until the mass concentration of concentrated sulfuric acid C3≥90% is obtained. S3, Decolorization and Collection: Under low vacuum and at a temperature of T4, a 63% nitric acid solution is added to concentrated sulfuric acid for decolorization. After decolorization, the concentrated sulfuric acid is kept warm and distilled for 1 to 1.5 hours, and then cooled to a temperature of 25 to 35°C to obtain a liquid. The liquid is then subjected to solid-liquid separation, and the separated filtrate is collected in a concentrated sulfuric acid collection tank to complete the sulfuric acid recovery process.

2. The method for recycling and treating waste sulfuric acid generated in the dye industry as described in claim 1, characterized in that, The high-efficiency organic matter removal resin is an acrylate-based macroporous adsorption resin.

3. The method for recycling and treating waste sulfuric acid generated in the dye industry as described in claim 1, characterized in that, The high-efficiency organic matter removal resin is a composite resin composed of acrylate-based macroporous adsorption resin, silica powder, 2-aminothiazole, and polystyrene microspheres.

4. The method for recycling and treating waste sulfuric acid generated in the dye industry as described in claim 3, characterized in that, The method for preparing the composite resin is as follows: Acrylate-based macroporous adsorption resin, silica powder, 2-aminothiazole, and polystyrene microspheres were prepared according to a mass ratio of 8-9:1-2:5:2-3. The silica powder and 2-aminothiazole were mixed at 130-135℃ and then granulated to obtain powder particles with a particle size of 1-3 mm. The powder particles, acrylate-based macroporous adsorption resin, and polystyrene microspheres were then mixed and added to a twin-screw granulator for shear extrusion granulation to obtain a composite acrylate-based macroporous adsorption resin composition. Among them, the silicon micro powder is selected with a particle size of 230-350 nm, and the polystyrene microspheres are selected with a particle size of 20-50 μm.

5. A method for recycling and treating waste sulfuric acid generated in the dye industry as described in claim 1, characterized in that, In step S1, methanol or liquid alkali is used to desorb the high-efficiency organic matter removal resin; in step S3, nitric acid solution is added to concentrated sulfuric acid at a mass ratio of 1:0.0001 to 0.

001.

6. The method for recycling and treating waste sulfuric acid generated in the dye industry as described in claim 1, characterized in that, The time range t2 for single-effect negative pressure evaporation is: when 70% > C1 ≥ 60%, When 80% > C1 ≥ 70% Where k ranges from 0.8 to 1; t1 ranges from 0.5 to 1.5h; and t3 ranges from 0.5 to 1.5h. The range of values ​​for T4 is when 95% > C3 ≥ 90%. When 100% > C3 ≥ 95%, T4 = 1.1T3.

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