Resource utilization method of waste concentrated sulfuric acid and salt slag

Abstract

The invention belongs to the technical field of industrial waste salt treatment, and particularly relates to a waste concentrated sulfuric acid and salt slag resource utilization method which comprises the following steps: S1, reacting waste concentrated sulfuric acid with concentrated salt slag, and absorbing HCl gas generated by the reaction to prepare hydrochloric acid; s2, acid precipitation; s3, neutralizing the salt solution by using lime slurry, and filtering to remove calcium sulfate precipitate; adding a proper amount of sodium carbonate into the filtrate to remove slightly soluble calcium ions, filtering out precipitates, and then adjusting the pH value of the filtrate back to 4-5 by adopting sulfuric acid; s4, adsorbing organic matters in the filtrate by using activated carbon powder, and filtering to obtain a salt solution to be separated; and S5, separating out potassium sulfate and sodium sulfate in a freezing and heating concentration manner. According to the scheme, the leachate salt residues and the waste concentrated sulfuric acid are subjected to combined treatment, the problem that the simple neutralization treatment efficiency of the concentrated sulfuric acid is too low is solved, the concentrated sulfuric acid is converted into hydrochloric acid capable of being recycled, the waste salt residues are converted into sodium sulfate and potassium sulfate capable of being recycled, resource utilization of waste is achieved, and environmental protection benefits are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial waste salt treatment, and particularly relates to a method for resource utilization of waste concentrated sulfuric acid and salt residue. BACKGROUND

[0002] The hazardous waste landfill leachate is a kind of high-salt wastewater generated in the process of hazardous waste landfill operation. According to the storage capacity of the landfill, the types of waste and the rainwater management, the yield and composition of the leachate are not the same, but most of them are mainly chlorides, the total dissolved solids can reach 160,000 mg / L, mainly calcium chloride, sodium chloride and potassium chloride, and also contain hundreds of ppm of sulfate, nitrate, ammonia nitrogen and trace heavy metals. Due to the large use of lime and cement and other solidification agents, the leachate is alkaline as a whole, with a pH of about 10-11. Leachate management is one of the most important contents in the operation and management of the landfill. In addition to the daily rain and sewage diversion management to control the main source of leachate, the leachate accumulated at the bottom of the library also needs to be treated in time. For the disposal of such high-salt wastewater, combined with the characteristics of the hazardous waste comprehensive disposal center (the incineration line can provide waste heat vapor), the "evaporation + biochemical" method is used to dispose it, and the relatively clean distillate enters the biochemical system for disposal, and the salt residue returns to the landfill in the form of wrapping landfill.

[0003] This disposal method alleviates the accumulation pressure of leachate to a certain extent and realizes the reduction of leachate, but as a makeshift it does not completely solve the problem of salt outlet, only delays the problem, and the salt residue returned to the landfill may enter the leachate again in the form of leakage, causing waste of manpower and material resources in the recycling disposal. On the other hand, as a hazardous waste comprehensive disposal center, the physical and chemical workshop needs to dispose a large amount of waste concentrated sulfuric acid every year, and usually uses the disposal method of neutralizing with slaked lime. Since the dilution and neutralization of concentrated sulfuric acid generates a large amount of heat, and the amount of calcium sulfate precipitate is large, in order to control the reaction temperature and avoid the blockage of the pipeline due to the high solid content of the product, the batch disposal amount needs to be strictly controlled, resulting in extremely low disposal efficiency. At the same time, the plant also needs to purchase a large amount of hydrochloric acid for daily production. From the overall acid-base balance of the plant, in the case of more acid and less base of hazardous waste, the additional purchase of hydrochloric acid will increase the consumption of the whole alkali, causing waste.

[0004] Based on the above background, the present application provides a process route for preparing hydrochloric acid by using waste concentrated sulfuric acid and hazardous waste landfill leachate concentrated salt residue, and recovering potassium sulfate and sodium sulfate, which realizes the resource utilization of salt residue while completing waste disposal. SUMMARY

[0005] The application provides a waste concentrated sulfuric acid and salt residue resource utilization method, and solves the problems in the prior art, such as resource waste and great cumulative pressure caused by recycling treatment of leachate salt residue returned to a landfill site, great mud yield, low treatment efficiency, and much loss of intermediate substances and resource waste caused by waste concentrated sulfuric acid lime neutralization treatment, and imbalance of acid and alkali of a factory caused by additional purchase of hydrochloric acid under the condition of more acid and less alkali in a hazardous waste comprehensive treatment center.

[0006] The application provides the following technical scheme:

[0007] A waste concentrated sulfuric acid and salt residue resource utilization method comprises the following steps:

[0008] S1. Pumping waste concentrated sulfuric acid with a concentration of 65-80% into a reaction kettle, and then adding concentrated salt residue with a theoretical consumption of 80%-90% after starting stirring, and controlling the reaction temperature at 80-120 DEG C, and promoting HCl gas volatilization under negative pressure, and using water or dilute hydrochloric acid to absorb the HCl gas generated in the reaction to prepare hydrochloric acid;

[0009] S2. After the dechlorination reaction is completed, water is added to the reaction kettle to fully dissolve the salt residue, the dissolving temperature is 60-80 DEG C, and then the first filtration is carried out under acidic conditions to filter out organic matter and a small amount of calcium sulfate precipitated from acid;

[0010] S3. The pH of the filtrate in step S2 is adjusted to 7-9 by using lime slurry to neutralize the residual sulfuric acid, the second filtration is carried out to remove the calcium sulfate precipitate, and a certain amount of organic impurities is removed through adsorption of the precipitate, and the calcium sulfate filter residue is used as a solid waste stabilization additive for recycling; then, a proper amount of sodium carbonate is added to the filtrate to remove the slightly soluble calcium ions, the third filtration is carried out, and the filtered calcium carbonate precipitate is all returned to the neutralization link for recycling, and then the pH of the filtrate is adjusted to 4-5 by using sulfuric acid;

[0011] S4. 1-3% of 100-300 mesh activated carbon powder is added to the filtrate after the pH adjustment in step S3, and the mixture is fully stirred for 30-60 minutes to remove color and odor, and to adsorb the organic matter in the filtrate, and the fourth filtration is carried out to obtain a salt solution to be separated;

[0012] S5. The potassium sulfate and sodium sulfate in the salt solution in step S4 are separated by combining freezing and heating concentration to obtain sodium sulfate and potassium sulfate, and the distilled water generated by heating concentration is returned to steps S1 and / or S2.

[0013] The method has the advantages that the waste concentrated salt residue and waste concentrated sulfuric acid are recycled to prepare directly usable hydrochloric acid, sodium and potassium in the salt residue are recycled and utilized as resources, waste is turned into treasure, waste sulfuric acid is converted into hydrochloric acid, and the procurement cost of hydrochloric acid is reduced.

[0014] Further, the first part of hydrochloric acid in step S1 adjusts the pH value and is recycled to the leachate treatment system to adjust the pH value.

[0015] Further, in step S5, the solution is first frozen to precipitate sodium sulfate, and after centrifugal filtration, the filtrate is heated and concentrated to precipitate potassium sulfate. The filtrate after centrifugal separation is returned to the frozen salt solution for recycling crystallization. The recycling crystallization method can continuously crystallize and avoid waste of salt solution. Since the salt solution contains sodium sulfate and potassium sulfate during the crystallization process, complete separation cannot be achieved through crystallization. Therefore, recycling is used for crystallization.

[0016] Further, the four filtrations in steps S2-S4 are all pressure filtrations.

[0017] Further, the filter residue after the third filtration is returned to the landfill site as a solid waste stabilization additive for reuse.

[0018] Further, the second part of hydrochloric acid reacts with lime or fly ash to prepare calcium chloride for physicochemical production, and the third part of hydrochloric acid is used for acid pickling in the incineration workshop. The specific use of the three parts of hydrochloric acid can be adjusted or reserved according to demand.

[0019] Further, the salt residue in step S2 is dissolved by distilled water. The distilled water is produced by subsequent salt solution concentration and crystallization.

[0020] Further, the activated carbon in step S4 is recovered by pyrolysis for reuse, reducing resource waste.

[0021] It should be understood that the above general description and the following detailed description are only exemplary and do not limit the present application.

[0022] In the present application, the leachate salt residue and waste concentrated sulfuric acid are combined and treated, avoiding the problem of low efficiency of simple neutralization of concentrated sulfuric acid, and converting concentrated sulfuric acid into reusable hydrochloric acid, saving the cost of additional purchase, converting waste salt residue into reusable sodium sulfate and potassium sulfate, realizing the resource utilization of waste, and improving the environmental protection benefit.

[0023] The hydrochloric acid is absorbed by water or dilute hydrochloric acid through negative pressure volatilization, effectively ensuring the recovery efficiency of hydrochloric acid, avoiding direct discharge, and preventing hydrochloric acid from being contaminated by other impurities, and ensuring the purity of hydrochloric acid.

[0024] By returning the filtrate after centrifugation to the frozen salt solution, the salt in the solution is repeatedly precipitated, thereby avoiding direct discharge of the tail solution. The distilled water produced during the concentration process can be used to dissolve the salt after the previous dechlorination, or to absorb the volatilized hydrochloric acid, or to wash the filter residue and crystallize the salt, thereby reducing the use cost of water resources in the reaction process.

[0025] By regulating the PH value of the salt solution with sulfuric acid, the adsorption effect of the activated carbon on the organic matter can be improved, and the adsorption efficiency can be increased by at least 60%. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The figure is a schematic diagram of the process route of the present application. DETAILED DESCRIPTION

[0027] The embodiments of the present application will be described below with reference to the accompanying drawings.

[0028] In the description of the embodiments of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection", "installation" should be understood in a broad sense, for example, "connection" can be detachable connection, or can be non-detachable connection; can be direct connection, or can be indirect connection through an intermediate medium. In addition, "communication" can be direct communication, or can be indirect communication through an intermediate medium. Among them, "fixing" means connecting with each other and the relative positional relationship after connection does not change. The orientation terms mentioned in the embodiments of the present application, such as "inner", "outer", "top", "bottom", etc., are only the direction of the drawings, therefore, the orientation terms used are for better, clearer description and understanding of the embodiments of the present application, and are not intended to indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the embodiments of the present application.

[0029] In the embodiments of the present application, the terms "first", "second" are only for description purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features limited by "first", "second" can explicitly or implicitly include one or more of the features.

[0030] In the embodiments of the present application, "and / or" is only a description of the association relationship between the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can mean that there are three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are in an "or" relationship.

[0031] Reference to "one embodiment" or "some embodiments" or "one implementation" or "some implementations" etc. in the present description means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment or implementation of the present application. The appearance of the phrases "in one embodiment" or "in some embodiments" or "in one implementation" or "in some implementations" etc. in various places in the description are not necessarily all referring to the same embodiment, nor are they necessarily referring to some, but not all embodiments, unless otherwise specifically so stated. The terms "including," "comprising," "having" and variations thereof herein are meant to be broad and encompass the terms "consisting of" and "consisting essentially of" unless otherwise noted.

[0032] Embodiment One

[0033] With reference to Figure 1 A method for resource utilization of waste concentrated sulfuric acid and salt residue, comprising the following steps:

[0034] S1. Pumping waste concentrated sulfuric acid with a concentration of 78% into a reaction kettle, and then adding concentrated salt residue with a theoretical consumption of 89% after starting stirring, the concentrated salt residue being salt residue after concentration treatment of leachate, the reaction temperature being controlled at 118°C, negative pressure being used to promote HCl gas volatilization, and water or dilute hydrochloric acid being used to absorb HCl gas generated in the reaction to prepare hydrochloric acid, part of the absorbed hydrochloric acid being adjusted in pH value and then recycled to a leachate treatment system to treat residual sodium sulfate and potassium sulfate in the filter residue; the rest of the hydrochloric acid being reacted with lime or fly ash to prepare calcium chloride for physicochemical production, or used for acid cleaning in a incineration workshop.

[0035] S2. After the dechlorination reaction is completed, distilled water is added to the reaction kettle to fully dissolve the salt residue, the distilled water being distilled water generated in concentration and crystallization of the salt solution in step S5; the dissolving temperature being 60-80°C, and then performing first pressure filtration under acidic conditions to remove organic matter and a small amount of calcium sulfate precipitated by acid precipitation.

[0036] S3. Adjusting the pH of the filtrate in step S2 to 9 using lime slurry to neutralize residual sulfuric acid, removing calcium sulfate precipitate by second pressure filtration, and removing some organic impurities by adsorption of the precipitate, the calcium sulfate filter residue being used as a solid waste stabilization additive for reuse; then adding an appropriate amount of sodium carbonate to the filtrate to remove slightly soluble calcium ions, performing third pressure filtration, returning the calcium carbonate precipitate after pressure filtration to the neutralization link in the previous step for reuse to reduce the loss of alkali; and then adjusting the pH of the filtrate to 5 using sulfuric acid. Preferably, the calcium sulfate filter residue is used as a solid waste stabilization additive, which can effectively provide support for the accumulation of solid waste to avoid safety hazards caused by the over-softening of the accumulated solid waste into mud, and facilitate the filtration of leachate.

[0037] S4. Add 3% of 200 mesh activated carbon powder to the filtrate after the PH value is called back in step S3, fully stir for 58 minutes, deeply decolorize and remove odor, adsorb organic matter in the filtrate, and obtain the salt solution to be separated through the fourth pressure filtration; the filter residue after pressure filtration is recycled through incineration or acid precipitation; in this embodiment, the activated carbon is recycled through pyrolysis, reducing resource waste.

[0038] S5. Separate the potassium sulfate and sodium sulfate in the salt solution in step S4 by combining freezing and heating concentration to obtain sodium sulfate and potassium sulfate; first freeze the solution to precipitate sodium sulfate, centrifuge and filter, then heat and concentrate the filtrate to precipitate potassium sulfate, and return the filtrate after centrifugal separation to the freezing solution for recycling crystallization, and collect the distilled water in the heating and concentration process for recycling.

[0039] The advantage of the scheme is that the waste concentrated salt residue and waste concentrated sulfuric acid are recycled to produce hydrochloric acid that can be directly used, the sodium and potassium in the salt residue are recycled and utilized as resources, waste is turned into treasure, waste sulfuric acid is converted into hydrochloric acid, the use cost of hydrochloric acid is reduced, and the calcium carbonate is recycled, reducing the loss of alkali.

[0040] Example Two

[0041] A waste concentrated sulfuric acid and salt residue resource utilization method, comprising the following steps:

[0042] S1. Pump the waste concentrated sulfuric acid with a concentration of 66% into the reaction kettle, start stirring, and then add the theoretical consumption of 81% of the concentrated salt residue; the concentrated salt residue is the concentrated salt residue of the landfill leachate, the landfill leachate is collected and transported to the leachate treatment system; the reaction temperature of the waste concentrated sulfuric acid and the concentrated salt residue is controlled at 82°C, the negative pressure promotes the volatilization of HCl gas, and water or dilute hydrochloric acid is used to absorb the HCl gas generated in the reaction to prepare hydrochloric acid; part of the absorbed hydrochloric acid is adjusted in PH value and then recycled to the leachate treatment system to treat the residual sodium sulfate and potassium sulfate in the filter residue, so that the residual sulfate salt returns to the reaction to form chloride salt again; the distilled water used for absorbing hydrochloric acid is the distilled water generated in the heating and concentration process of the salt solution in step S5.

[0043] S2. After the dechlorination reaction is completed, distilled water is added to the reaction kettle to fully dissolve the salt residue; the distilled water is the distilled water generated in the heating and concentration process in the subsequent step S5; the dissolution temperature is 63°C, and then the first pressure filtration is carried out under acidic conditions to filter out the organic matter and a small amount of calcium sulfate.

[0044] S3. Adjust the pH of the filtrate in step S2 to 7 using lime slurry to neutralize the residual sulfuric acid, remove the calcium sulfate precipitate by second pressure filtration, and remove some organic impurities by adsorption with the precipitate; then add an appropriate amount of sodium carbonate to the filtrate to remove the slightly soluble calcium ions, perform third pressure filtration, and return the calcium carbonate precipitate after pressure filtration to the neutralization step in the previous step for reuse to reduce alkali consumption; then adjust the pH of the filtrate to 4 using sulfuric acid.

[0045] S4. Add 1.2% of 300-mesh activated carbon powder to the filtrate after adjusting the pH in step S3, stir thoroughly for 35 minutes, and perform deep decolorization and odor removal to adsorb the organic matter in the filtrate; then perform fourth pressure filtration to obtain a salt solution to be separated; and recycle the activated carbon in the filter residue after dilution with acid for reuse.

[0046] S5. Separate the potassium sulfate and sodium sulfate in the salt solution in step S4 by combining freezing and heating concentration to obtain sodium sulfate and potassium sulfate; first freeze the solution to precipitate sodium sulfate, perform centrifugal filtration, heat and concentrate the filtrate to precipitate potassium sulfate, and return the filtrate after centrifugal separation to the frozen solution for recycling crystallization; the recycling crystallization method can continuously perform crystallization and can avoid waste of the salt solution, because the salt solution contains sodium sulfate and potassium sulfate during the crystallization process; in addition, the distilled water during the heating and concentration process is collected and returned to step S1 for absorption of hydrochloric acid and step S2 for dissolution of the salt residue.

[0047] The present application recycles waste concentrated salt residue and waste concentrated sulfuric acid to produce directly usable hydrochloric acid, recycles sodium and potassium in the salt residue for resource utilization, converts waste sulfuric acid into hydrochloric acid to reduce the procurement cost of hydrochloric acid, recycles distilled water to reduce water resource waste, uses calcium sulfate as an aggregate in solid waste to improve the effect of solid waste accumulation and the seepage of leachate in solid waste, recycles calcium carbonate precipitate to reduce alkali consumption.

[0048] Example Three

[0049] A method for recycling waste concentrated sulfuric acid and salt residue, comprising the following steps:

[0050] S1. Pump waste concentrated sulfuric acid with a concentration of 70% into a reaction kettle, add the theoretical consumption of 85% concentrated salt residue after starting stirring, control the reaction temperature at 100℃, promote the volatilization of HCl gas under negative pressure, and use water or dilute hydrochloric acid to absorb the HCl gas generated during the reaction to produce hydrochloric acid; adjust the pH of part of the hydrochloric acid and recycle it to a leachate treatment system to treat residual sodium sulfate and potassium sulfate in the filter residue, return the filter residue to a landfill for stacking, or generate leachate under rainwater scouring, collect the leachate and transport it to the leachate treatment system.

[0051] S2. After the dechlorination reaction is completed, water is added to the reactor to fully dissolve the salt residue at a dissolution temperature of 70°C. Then, the first filter press is performed under acidic conditions to filter out the acid-precipitated organic matter and a small amount of calcium sulfate.

[0052] S3. The pH of the filtrate in step S2 is adjusted to 8 using lime slurry to neutralize the residual sulfuric acid. The calcium sulfate precipitate is removed by a second filter press, and a certain amount of organic impurities are removed by precipitation adsorption. An appropriate amount of sodium carbonate is then added to the filtrate to remove slightly soluble calcium ions. The calcium carbonate precipitate after the filter press is returned to the previous step for reuse in the neutralization step to reduce alkali consumption. The pH of the filtrate is then adjusted to 4.5 using sulfuric acid.

[0053] S4. Add 2% 100-mesh activated carbon powder to the filtrate after adjusting the pH value in step S3 and stir thoroughly for 45 minutes to deeply decolorize and deodorize, and adsorb organic matter in the filtrate. After the fourth filter press, the salt solution to be separated is obtained; the filter residue is incinerated to recover the activated carbon for reuse.

[0054] S5. the potassium sulfate and sodium sulfate in the salt solution of step S4 are separated by freezing and heating and concentrating in a combined manner to obtain sodium sulfate and potassium sulfate; preferably, the solution is first frozen to precipitate sodium sulfate, and the filtrate is heated and concentrated after centrifugation to precipitate potassium sulfate, and the filtrate after centrifugation is returned to the frozen solution for circulation crystallization. Crystallization can be carried out continuously by circulating crystallization, and the waste of salt solution can be avoided at the same time. Because sodium sulfate and potassium sulfate are contained in the salt solution during the crystallization process, it is impossible to completely separate sodium sulfate and potassium sulfate by crystallization, so crystallization is carried out by recycling, which will not cause waste of resources. Distilled water is collected during the heating and concentrating process, and the collected distilled water is used to absorb volatilized hydrochloric acid and dissolved salts. The remaining distilled water can also be used to wash filter residue or crystallization salt to improve the purity of crystallization salt.

[0055] The present invention reuses waste concentrated salt residue and waste concentrated sulfuric acid to produce directly usable hydrochloric acid, and simultaneously recovers sodium and potassium in the salt residue for resource utilization, turning waste into treasure, converting waste sulfuric acid into hydrochloric acid, and reducing the purchase cost of hydrochloric acid.

[0056] Example 4

[0057] Take 200 g of the percolate salt residue and mix with 160 mL of waste concentrated sulfuric acid (concentration about 72%) to heat the reaction. After the HCl is volatilized, take 200 g of the reaction product and dissolve in water and make up to 1 L (sample ①). Take the filtrate and add lime slurry to neutralize the pH to about 10. After filtration, take the filtrate and add a small amount of sodium carbonate. Then take the filtrate and add a small amount of sulfuric acid to adjust the pH to 3. Add 1% activated carbon powder, 200 mesh, and stir for 30 min. Take the filtrate (sample ②) and cool to obtain sodium sulfate (sample ③). The TOC content of the crystallized salt meets the requirements in the regeneration of industrial salt sodium sulfate (T / ZGZS0303-2023) (<8 mg / L). The TOC determination method is the HJ501 combustion oxidation-non-dispersive infrared absorption method described in (T / ZGZS0303-2023).

[0058] Table 1 is the determination results of the TOC of each sample

[0059] Sample Appearance TOC Notes ① Yellowish suspension, rancid smell 275 mg / L ② Colorless and transparent, no smell 50.0 mg / L ③ Salt as white crystals 4.97 mg / L Dissolution test according to standard

[0060] From the above experimental results, it can be seen that after comparing sample ① and sample ②, the total organic carbon (TOC) content in the solution after activated carbon adsorption is 50.0 mg / L, which is significantly lower than 275 mg / L in sample ①. In addition, the total TOC content in the solution is <8 mg / L, which effectively ensures the quality of the extracted sodium sulfate from the waste salt residue.

[0061] Example Five

[0062] ① Take 10 g of dry percolate salt residue and dissolve in about 100 mL of water. Filter and clean the device. Combine the washings and make up to 200 mL. Test the filtrate TOC = 167 mg / L.

[0063] ② Take 100 mL of the filtrate in ① and add 0.5 g of activated carbon. Stir for 30 min. The filtrate TOC = 117 mg / L.

[0064] ③ Take 10 g of dry percolate salt residue and add 10 mL of waste sulfuric acid (concentration about 12 mol / L, TOC = 462 mg / L) to it. Heat on a water bath vapor and stir thoroughly. Then dissolve the semi-solid product in about 100 mL of water. Filter and clean the device. Combine the washings and make up to 200 mL. Test the filtrate TOC = 127 mg / L.

[0065] ④ Take 100 mL of the filtrate in ③ and add 0.5 g of activated carbon, 200 mesh. Stir for 30 min. The filtrate TOC = 69 mg / L.

[0066] The experimental treatment and determination are as follows:

[0067] Treatment one: for directly determining TOC in step ①, and determining TOC again after adsorption by activated carbon after acidification;

[0068] Treatment two: for determining TOC of the solution in step ③;

[0069] Treatment three: for determining TOC of the solution in step ② after adsorption by activated carbon, and determining TOC of the solution in step ④ after acidification;

[0070] The determination mode of TOC is determined by the HJ501 combustion oxidation-non-dispersive infrared absorption method described in (T / ZGZS0303-2023);

[0071] Table two is a TOC determination result table of each treatment

[0072]

[0073] Conclusion:

[0074] ① The overall removal rate of the "acidification + adsorption" process can be increased by about 96% compared with the "direct adsorption", and considering the TOC introduction amount of concentrated sulfuric acid, the actual removal rate can be increased by about 113%.

[0075] ② After acidification treatment, the TOC adsorption amount of the equal mass activated carbon is increased from 10 mg / 0.5 g AC to 11.6 mg / 0.5 g AC, and the adsorption amount is increased by about 16%, and considering the TOC introduction amount of concentrated sulfuric acid, the actual adsorption amount is increased by about 62%.

[0076] The principle of the present application is that by combining the leachate salt slag and waste concentrated sulfuric acid for treatment, the problem of low efficiency of simple neutralization disposal of concentrated sulfuric acid is avoided, and the concentrated sulfuric acid is converted into reusable hydrochloric acid, and the waste salt slag is converted into reusable sodium sulfate and potassium sulfate, realizing the resource utilization of waste, and improving the environmental protection benefit.

[0077] The hydrochloric acid is absorbed by water or dilute hydrochloric acid through negative pressure volatilization, which effectively ensures the recovery efficiency of hydrochloric acid, avoids direct discharge, prevents hydrochloric acid from being contaminated by other impurities, and ensures the purity of hydrochloric acid.

[0078] By returning the filtrate after centrifugation to the frozen salt solution again, the salt in the solution is repeatedly precipitated, thereby avoiding direct discharge of the tail solution; and the distilled water generated in the concentration process can be used to dissolve the salt after the previous dechlorination, or to absorb the volatilized hydrochloric acid, or to wash the filter residue and crystallize the salt, and the water washing and crystallization of the salt need to be carried out under the set conditions and the water consumption is controlled, thereby reducing the use cost of water resources in the reaction process.

[0079] The PH value of the salt solution is adjusted by sulfuric acid, so that the adsorption effect of the activated carbon on the organic matter is improved, and the adsorption efficiency is increased by at least 60%.

[0080] The application provides a resource utilization process for the concentrated salt residue of the leachate of a hazardous waste landfill, reduces recycling accumulation, realizes resource recovery of potassium and sodium elements in the salt residue, turns waste into treasure, and creates benefits, and converts high-concentration sulfuric acid which is difficult to dispose into usable hydrochloric acid, thereby saving production cost.

[0081] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application; in the case of no conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for resource utilization of waste concentrated sulfuric acid and salt residue, characterized in that: The following steps are involved: S1. The reactor is pumped with a concentration of 65 to 80% of waste concentrated sulfuric acid, and after stirring, 80% to 90% of the theoretical consumption of concentrated salt residue is added. The reaction temperature is controlled at 80 to 120 ° C. The negative pressure promotes the volatilization of HCl gas, and the HCl gas produced by the reaction is absorbed by water or dilute hydrochloric acid to produce hydrochloric acid; S2. After the dechlorination reaction is completed, water is added to the reactor to fully dissolve the salt residue at a dissolution temperature of 60 to 80 ° C. After the first filtration under acidic conditions, the acid-precipitated organic matter and a small amount of calcium sulfate are removed by filtration; S3. The filtrate from step S2 is adjusted to a pH of 7 to 9 using lime slurry to neutralize residual sulfuric acid. The calcium sulfate precipitate is removed by a second filtration, and some organic impurities are removed by precipitation adsorption. The calcium sulfate filter residue is reused as a solid waste stabilization additive. An appropriate amount of sodium carbonate is then added to the filtrate to remove slightly soluble calcium ions. The filtered calcium carbonate precipitate is then returned to the neutralization step for reuse, and the filtrate pH is adjusted to 4 to 5 using sulfuric acid. S4. Add 1 to 3% of 100-300 mesh activated carbon powder to the filtrate after adjusting the pH value in step S3 and stir for 30 to 60 minutes to deeply decolorize and deodorize the filtrate and adsorb organic matter. The salt solution to be separated is obtained by filtering for the fourth time; S5. The potassium sulfate and sodium sulfate in the salt solution of step S4 are separated by a combination of freezing and heating concentration to obtain sodium sulfate and potassium sulfate, and the distilled water generated by heating and concentrating is returned to step S1 and / or S2.

2. The method for resource utilization of waste concentrated sulfuric acid and salt residue according to claim 1, wherein: Part of the hydrochloric acid in step S1 is used to adjust the pH value and then circulated to the leachate treatment system to adjust the pH value.

3. The method for resource utilization of waste concentrated sulfuric acid and salt residue according to claim 1, characterized in that: In step S5, the solution is first frozen to precipitate sodium sulfate, and after centrifugal filtration, the filtrate is heated and concentrated to precipitate potassium sulfate. The filtrate after centrifugation is returned to the frozen solution for cyclic crystallization.

4. The method for resource utilization of waste concentrated sulfuric acid and salt residue according to claim 1, characterized in that: The four filtrations in steps S2-S4 are all performed by filter pressing.

5. The method for resource utilization of waste concentrated sulfuric acid and salt residue according to claim 1, characterized in that: The residue after the third filtration is returned to the landfill for reuse as a solid waste stabilization additive.

6. The method for resource utilization of waste concentrated sulfuric acid and salt residue according to claim 1, characterized in that: The second part of hydrochloric acid reacts with lime or fly ash to prepare calcium chloride for physical and chemical production, and the third part of hydrochloric acid is used for pickling and descaling in the incineration workshop.

7. The method for resource utilization of waste concentrated sulfuric acid and salt residue according to claim 1, characterized in that: The salt residue in step S2 is dissolved by distilled water.

8. The method for resource utilization of waste concentrated sulfuric acid and salt residue according to claim 1, characterized in that: The activated carbon in step S4 is recovered and reused by pyrolysis.

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