CN114590942B

CN114590942B - Method for near zero emission and resource utilization of organic hazardous waste gas chilling circulating wastewater

Info

Publication number: CN114590942B
Application number: CN202210254073.8A
Authority: CN
Inventors: 杨彬; 雷乐成; 陈立豪
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2022-03-15
Filing date: 2022-03-15
Publication date: 2023-04-07
Anticipated expiration: 2042-03-15
Also published as: CN114590942A

Abstract

The invention discloses a method for near-zero emission and resource utilization of organic hazardous waste gas chilling circulating wastewater, which fully considers the characteristics of source diversity, composition complexity and the like of elements in the organic hazardous waste, realizes high-efficiency resource utilization of elements such as nitrogen, phosphorus, chlorine, sodium, potassium and the like in the wastewater by maintaining high-content inorganic salt in the circulating wastewater and utilizing various combined treatment technologies, and can recycle the treated wastewater and transport a small amount of concentrated solution and high-concentration residual liquid outwards so as to achieve near-zero emission. The main process technology comprises the steps of firstly, generating struvite from nitrogen, phosphorus and magnesium in the wastewater, further reacting the residual phosphorus with calcium to generate calcium phosphate, further removing residual ammonia nitrogen and organic pollutants by an ozone/hydrogen peroxide combined oxidation method, further separating and purifying inorganic salt by using an electrodialysis technology, finally obtaining byproducts such as sodium chloride and potassium chloride by a fractional evaporation crystallization method, mixing the evaporation distillate and the low-salt wastewater, and directly recycling the mixture, wherein all the wastewater is not discharged.

Description

Method for near zero discharge and resource utilization of organic hazardous waste gas chilling circulating wastewater

Technical Field

The invention relates to a near-zero emission method for recycling organic hazardous waste high-temperature gasification chilling wastewater, realizes resource utilization of nitrogen, phosphorus, potassium and sodium elements in the wastewater, and belongs to the field of resource utilization of the wastewater.

Background

Industrial organic hazardous waste is solid or liquid organic matter and substances in industrial production that have lost their original value of use or that have been discarded or discarded without losing value of use, and that have one or more hazardous characteristics. The method mainly comprises the following steps: rectification residue, industrial production organic waste, biological fermentation residue, organic resin waste, waste mineral oil, industrial sludge, waste catalyst, high-concentration organic waste liquid (water), waste organic solvent, active adsorption material (liquid), washing liquid, waste tire, waste printed circuit board, waste etching liquid and the like. The industrial hazardous organic waste is generally characterized by complex component sources, poor biodegradability, toxicity, harm and the like.

The high temperature technology of gasification and high temperature melting of all industrial organic hazardous wastes is a novel technology for treating organic hazardous wastes. The technology uses industrial organic hazardous waste as a raw material to prepare a charging raw material. The raw materials fed into the furnace have the characteristics of organic wastes, complex components, high salt content and the like. After the industrial organic waste is gasified, the industrial organic waste needs to be chilled and cooled. In the chilling and cooling process, molten inorganic matters contact with chilling wastewater to generate substance transfer, wherein potassium and sodium soluble salts are taken as representatives. A large amount of potassium salt and sodium salt enter the chilling water body to increase the salt content in the water body. In the gasification process, elemental phosphorus and ammonia nitrogen generated in the reaction process react with the chilling wastewater to form phosphoric acid and ammonia nitrogen. Through the cyclic utilization of the chilling wastewater, the concentration of each pollutant is continuously improved, and finally the wastewater with high salt content, high organic matter content, high phosphorus content and high ammonia nitrogen content is formed.

The method for treating the wastewater with high salt content is less and the treatment method is single. The main treatment technology is to treat the salt in the water body by using an evaporation method. The treatment process can generate a large amount of polluted salt and has huge energy consumption. The evaporated polluted salt contains a large amount of pollutants such as organic matters, nitrogen, phosphorus and the like, and the subsequent treatment of the waste salt is difficult. The traditional biological denitrification technology is the most extensive denitrification method for treating wastewater, but the denitrification treatment of the wastewater with high salt content is difficult, and the wastewater with high chloride ion content cannot be treated. The mainstream treatment method is to culture and screen strains, and once the tolerance level of the strains is exceeded, the strains die.

The technology for removing organic matters in water body by Fenton oxidation in the advanced oxidation technology is applied more at present, but the Fenton oxidation technology has the great characteristic that the effect of treating the organic matters is good, but a large amount of iron mud can be generated. The treatment of the iron sludge increases the process treatment cost. The ozone for removing ammonia nitrogen and organic matters in water is one of the existing treatment processes, and the process has a removing effect on the organic matters and ammonia nitrogen in wastewater, but has certain difficulty in treating double-high wastewater containing high ammonia nitrogen and high organic matters. The higher the organic content is, the poorer the effect of ozone on removing ammonia nitrogen is, and the larger the ozone consumption is, so the treatment cost is higher. The methods are common treatment methods for removing pollutants in wastewater, but a single treatment process has advantages and limitations of the single treatment process. The pollutants in the gasification chilling wastewater have the characteristics of complexity, diversity, instability and the like, so that the concentration of inorganic salts is increased and maintained in a certain range by increasing the cycle number of the chilling wastewater, and the elements such as nitrogen, phosphorus, chlorine, sodium, potassium and the like in the wastewater are utilized by utilizing various combined treatment technologies and optimization in a staged and efficient resource utilization manner, so that the cyclic utilization of the wastewater is realized, the technological requirements of the gasification of multi-component organic wastes are met, only a small amount of concentrated solution and high-concentration residual liquid need to be discharged in the whole treatment system, and the near zero emission of the wastewater is realized.

Disclosure of Invention

Aiming at the characteristics of complexity, diversity, instability and the like of the multi-component organic waste gasification chilling wastewater, the invention develops and solves the recycling and resource utilization of the multi-component organic hazardous waste gasification chilling wastewater.

The invention provides a method for near zero emission and resource utilization of organic hazardous waste gas chilling cycle wastewater, which is characterized in that the organic hazardous waste gas chilling cycle wastewater is recycled until the content of inorganic salt is more than 20% and then is treated, wherein the TOC in the wastewater is 1000-5000 mg/L, the ammonia nitrogen is 250-500 mg/L, the total phosphorus is 800-3000 mg/L, the total nitrogen is 400-650 mg/L, the chloride ion is 100000-200000 mg/L, the potassium ion is 50000-100000 mg/L, and the sodium ion is 50000-100000 mg/L. The wastewater which meets the recycling standard after being treated by the combined technology is directly recycled to a chilling chamber, and the main indexes of the water quality require that TOC is less than 100mg/L, ammonia nitrogen is less than 10mg/L, total phosphorus is less than 10mg/L, total nitrogen is less than 50mg/L, chloride ions are less than 1000mg/L, potassium ions are less than 500mg/L, and sodium ions are less than 500mg/L. The treated wastewater meets the recycling standard and then is recycled as gasification chilling circulating wastewater, and the wastewater is not discharged.

The method comprises the following steps:

1) The high-temperature gasification chilling wastewater firstly enters a sedimentation tank to be kept stand for 1-2 hours, after solid-liquid layering and natural cooling, the temperature is reduced to be below 80 ℃, the upper layer wastewater enters a plate-frame filtering device to remove insoluble suspended matters, and the pH value of the filtered clear liquid is adjusted to 8-9; then the mixture enters a reaction sedimentation tank and is added with a proper amount of magnesium chloride hexahydrate for reaction to generate struvite, the pH value is timely adjusted and stabilized between 8 and 9 in the reaction process, the mixture is stirred for 20 to 40 minutes and stays for 30 to 60 minutes, the struvite is obtained after being collected in a sedimentation chamber and can be sold as a compound fertilizer after being cleaned;

2) The supernatant of the reaction settling chamber enters a subsequent calcium chloride dosing coagulation sedimentation tank to further generate calcium phosphate, the adding amount of the calcium chloride is 0.5-4% of the total amount of the treated water body, the stirring reaction is carried out for 10-15 minutes, the stirred solution is settled for 40-60 minutes to generate calcium phosphate sediment, and the calcium phosphate sediment can be compounded and sold as a compound fertilizer after being cleaned;

3) Adding the supernatant of the coagulation sedimentation tank into a sodium carbonate dosing tank, adding sodium carbonate to remove redundant calcium ions, adjusting the pH value of the sodium carbonate dosing tank to 7-8, and maintaining the pH value of a water body;

4) The supernatant fluid of the regulating tank enters an ozone/hydrogen peroxide tubular oxidation reactor at a certain flow velocity to further remove redundant ammonia nitrogen and organic pollutants in the wastewater, and the ozone concentration in the tubular oxidation reactor is kept between 100 and 300g/m ³ The concentration of hydrogen peroxide is controlled to be 1-5 percent, and the reaction time is 30-60 minutes;

5) The wastewater treated by the ozone/hydrogen peroxide tubular oxidation reactor enters an electrodialysis device, the purification and the efficient concentration of inorganic salt are further realized by separating a small amount of organic pollutants from inorganic salt, and the wastewater in an electrodialysis fresh water chamber is recycled as gasification chilling circulating wastewater;

6) Concentrated water obtained after electrodialysis separation and concentration enters an evaporation chamber for evaporation; under the pressure of 1.3-1.7Mpa, the temperature of the waste water is kept between 100 ℃ and 120 ℃, the waste water is evaporated and concentrated to a certain concentration, the concentration point is higher than the concentration point of the precipitated potassium chloride, and the sodium chloride is precipitated by evaporation and crystallization; when the temperature of the evaporated wastewater is reduced to 50-60 ℃, flash evaporation is carried out to separate out potassium chloride crystals; the evaporation distillate is recycled as gasification chilling circulating wastewater, and the residual mother liquor is treated as liquid waste.

As the preferred scheme of the invention, fly ash is removed by plate-and-frame filtration, the filtration cloth is made of high-temperature-resistant nylon, and the mesh number of the filtration cloth is controlled to be 300-400 meshes; the pressure of the plate frame is controlled to be 0.4-0.6Mpa, the temperature of the chilling water is controlled to be below 80 ℃, and the filtered fly ash can be recycled for high-temperature gasification treatment again.

As a preferable scheme of the invention, in the reaction sedimentation tank, the molar ratio of magnesium ions of the added magnesium chloride to ammonia nitrogen in the clear liquid is 0.8-1.5: 1; the speed of the stirrer is controlled at 120-200 r/min, and the pH value in the water body is maintained at 8-9 in the stirring process.

As the preferred scheme of the invention, 5-20ppm PAM is added into the coagulating sedimentation tank to promote sedimentation and sedimentation; adding 10-60 ppm PAM into a calcium chloride dosing coagulation reaction tank to promote precipitation and sedimentation; the settling time of the water body in the settling chamber is reasonably controlled by taking the supernatant as clear and transparent as a standard.

As a preferred scheme of the invention, the mixing mode of the ozone/hydrogen peroxide tubular oxidation reactor is pipeline mixing, the ozone adding mode is directly introducing into a pipeline, the hydrogen peroxide adding mode is to utilize a bypass pipeline to enter wastewater to be treated and utilize a static pipeline mixer to fully mix, the static pipeline mixer is arranged at an ozone adding port and is added with hydrogen peroxideThe flow velocity in the pipeline mixer is controlled to be 1m/s-2m/s between 1m and 2m behind the opening, wherein the sectional area of the pipeline is 0.002m ² ～0.01m ² The length of the reactor pipeline is controlled between 17m and 34m.

As the preferred scheme of the invention, the electrodialysis device adopts a homogeneous membrane or an alloy membrane, the voltage at two sides of the membrane is 100V, and the current between the membranes is 100A; the membrane layer level of the membrane stack is 100 layers, the water yield of the concentration chamber and the dilution chamber is 4L/s, the electrodialysis is treated in an intermittent treatment mode, the single treatment capacity is 200L, the single treatment time is controlled within 30 minutes, and the electrodialysis power is controlled within 10kW-20kW in the treatment process.

As a preferred embodiment of the present invention, the step 6) specifically comprises: electrodialysis is used for separating concentrated water, hydrochloric acid is used for adjusting the pH value to be 4-5, evaporation of small molecular organic acid in a water body is promoted, the adjusted concentrated water enters an evaporation chamber, the pressure is controlled to be 1.3-1.7Mpa, the temperature is controlled to be 100-120 ℃, concentration treatment is carried out on chilling water, and the concentration in the water is controlled to be higher than the concentration point of potassium chloride crystallization; under such conditions, crystallization of sodium chloride is carried out; after sodium chloride crystallization, cooling the mother liquor to 50-60 ℃, and carrying out flash evaporation on the mother liquor; potassium chloride crystals are separated out in the flash evaporation process; the evaporation distillate is recycled as gasification chilling circulating wastewater, and the mother liquor after crystallization is treated as waste liquid.

The invention has the beneficial effects that:

1) Aiming at the chilling wastewater generated in the process of the organic hazardous waste gas chemical treatment, the method carries out targeted treatment. The industrial waste contains a large amount of inorganic salt and a certain content of phosphorus element. In the process of treating wastes by using a gasification process, elemental phosphorus and ammonia gas are generated in the gasification furnace. After chilling and washing, phosphorus in the gasification furnace is dissolved in a water body to form phosphate radicals, ammonia gas is dissolved in the water body to form ammonia nitrogen, and inorganic salt is dissolved in the water body to form high-salt-content wastewater. The chilling wastewater is continuously recycled, and pollutants in a water body are continuously enriched to finally form wastewater with high ammonia nitrogen, high phosphorus, high organic matters and high salt content. The applicant comprehensively considers the characteristics of the waste water generated in the process of chilling organic hazardous waste gas, takes the resource utilization and near-zero emission of the waste water as targets, determines that the chilling waste water is recycled until the content of inorganic salt is more than 20% and then is treated by adopting the method provided by the invention, the method can greatly reduce the water consumption of the chilling process and reduce the amount of the waste water on the premise of normal operation of the chilling process, and the waste water can meet the targets of resource utilization and near-zero emission after being treated by the method provided by the invention. After the chilling wastewater is circulated until the content of inorganic salt is more than 20%, the TOC in the wastewater is 1000-5000 mg/L, the ammonia nitrogen is 250-500 mg/L, the total phosphorus is 800-3000 mg/L, the total nitrogen is 400-650 mg/L, the chloride ion is 100000-200000 mg/L, the potassium ion is 50000-100000 mg/L, and the sodium ion is 50000-100000 mg/L. Therefore, the process combines different process flows aiming at the formation process of the chilling wastewater, and carries out resource utilization on the wastewater. Preparing a struvite compound fertilizer by using phosphorus and ammonia nitrogen in the wastewater; sodium and potassium in water are utilized to produce industrial salt.

2) The process flow has the advantages that process plates are connected in a ring-to-ring manner and organically combined, so that the treatment efficiency of pollutants in the wastewater is improved. The process flow firstly utilizes nitrogen and phosphorus in the wastewater, and the utilized wastewater is oxidized to remove organic matters in the water body. And finally, utilizing potassium salt and sodium salt of the wastewater. Each step is closely linked to the previous step. If the phosphorus in the wastewater is supposed to be removed firstly, and calcium chloride is added into the water body, although the phosphorus in the wastewater can be well removed, ammonia nitrogen in the wastewater cannot be utilized, and the secondary removal of the ammonia nitrogen in the water body by the ozone oxidation process is increased. If the organic matter of the wastewater is supposed to be removed firstly, the wastewater enters the pipeline generator to be oxidized, at the moment, the organic matter and ammonia nitrogen content in the water body are higher, more ozone and hydrogen peroxide are required to be consumed, and the process treatment cost is increased. If the potassium salt and the sodium salt in the wastewater are first separated, the separated potassium salt and sodium salt contain organic matters and other impurities, and thus the potassium salt and the sodium salt cannot be purified.

The method provided by the invention is used as an integral process, can effectively treat the organic hazardous waste gas chilling cycle wastewater, and is mainly characterized by high salt content and high ammonia nitrogen (more than or equal to 300mg NH) ₄ ⁺ -N/L), high phosphorus, etc., available in waste waterThe higher the ammonia nitrogen concentration in the water body is, the more beneficial the process is to the production of the struvite byproducts from ammonia nitrogen and phosphorus.

3) The invention aims at the resource of main elements, improves the efficiency and the yield of each treatment unit by controlling the high concentration of inorganic salt in chilled water, simultaneously couples an electrodialysis treatment process, realizes the purification of inorganic salt such as sodium chloride, potassium chloride and the like and the concentration of waste water, directly recycles most of the waste water to a water recycling system after a combined treatment technology, obtains inorganic salt byproducts by further evaporating and crystallizing only a small amount of waste water, and finally discharges a very small amount of concentrated mother liquor out of the system. The whole treatment process does not need to adopt a biological treatment method, and is a method with simple process, high combination efficiency, high treatment efficiency and low energy consumption for near zero discharge of wastewater and resource utilization.

Drawings

FIG. 1 is a flow chart of resource combined treatment of organic hazardous waste gas chilling cycle wastewater.

FIG. 2 is a graph showing the solubility of sodium chloride, potassium chloride and sodium sulfate as a function of temperature.

Detailed Description

For a better understanding of the present invention, reference is made to the following detailed description of the invention along with the accompanying drawings.

The overall process flow diagram of the present invention can be referred to fig. 1. By maintaining the concentration of inorganic salt in the chilling circulating wastewater and utilizing various combined treatment technologies, the high-efficiency resource utilization of elements such as nitrogen, phosphorus, chlorine, sodium, potassium and the like in the wastewater is realized, meanwhile, the wastewater is recycled, and a small amount of concentrated solution and high-concentration residual liquid are transported outside, thereby achieving near zero emission. The main process technology comprises the steps of firstly generating struvite from nitrogen, phosphorus and magnesium in the wastewater, further reacting the residual phosphorus with calcium to generate calcium phosphate, further removing residual ammonia nitrogen and organic pollutants by an ozone/hydrogen peroxide combined oxidation method, further separating and purifying inorganic salt by using an electrodialysis technology, finally obtaining pure byproducts such as sodium chloride and potassium chloride by a fractional evaporation and freezing crystallization method, and recycling the evaporated distillate and the low-salt wastewater after being treated by a biological method.

The grey water in the gasification and chilling process has the characteristics of high salt content, high ammonia nitrogen content, high phosphorus content and high organic matter content, and the fluctuation conditions of various pollutants in the water body are determined through monitoring and analysis as shown in the following table 1. Various pollutants in the chilling wastewater are higher than those in normal wastewater. Therefore, the chilling wastewater is treated by adopting the combined process, and the wastewater is recycled while the upper limit of treatment is improved.

TABLE 1 chilling wastewater Each contaminant content

The invention organically combines the chemical sedimentation for removing ammonia nitrogen, the advanced oxidation process and the salt separation and purification process. Ammonia nitrogen and phosphorus in the chilling water body are used for producing struvite, the ammonia nitrogen and organic matters in the water body are treated by an ozone oxidation technology, and waste salt in the water body is treated by a salt separation and purification process. The whole process is in a ring-locked manner, so that the chilled wastewater is accurately recycled.

The chilling wastewater is generated in the industrial organic hazardous waste gas chilling process, and the characteristics of pollutants of the chilling wastewater are influenced by the industrial organic hazardous waste treatment process. In the industrial organic hazardous waste treatment process, inorganic salt in the hazardous waste is dissolved in a chilling water body; gaseous elemental phosphorus formed in the gasification furnace is dissolved in water and is converted into phosphate radical; the ammonia gas generated in the gasification process is dissolved in the chilling water body, and the chilling water is continuously recycled. Finally forming the chilling wastewater with high salt content, high ammonia nitrogen content, high organic matter content and high phosphorus content.

In the process of recycling chilling wastewater, a certain amount of water quenching fine slag is contained. The water quenching fine slag is not beneficial to the subsequent treatment of the chilling wastewater, and the filtering operation is required. The chilling wastewater enters a sedimentation tank for sedimentation, the temperature of the water body is reduced to be below 80 ℃, and the chilling wastewater is filtered. The material of the filter cloth is high-temperature resistant nylon filter cloth, and the aperture of the filter cloth is 300-400 meshes. The filter cloth in the aperture range ensures the treatment water quantity and improves the treatment efficiency while removing the particles in the water body.

In the process of recycling the chilling water body, the characteristic pollutants continuously rise. If the content of the pollutants in the water body is lower than the range in the table 1, the wastewater can be continuously recycled after being filtered. If the content of the pollutants in the water body is higher than or equal to that of the pollutants in the table 1, the subsequent treatment is needed.

Phosphorus and ammonia nitrogen in the chilling wastewater are used as byproducts after dangerous waste treatment, and the ammonium magnesium phosphate method can be used for resource utilization. Adjusting the pH value of the filtered wastewater to be 8-9; the water body enters a struvite settling chamber and is added with magnesium chloride hexahydrate for reaction, and the addition amount of the magnesium chloride hexahydrate is Mg ²⁺ ：NH ₃ ⁺ ＝0.8～1.5:1，Mg ²⁺ ：PO ₄ ^2- =1 to 1.2:1, the calculation is carried out. In the process of generating the magnesium ammonium phosphate, the pH value of the water body is ensured to be stabilized at 8-9, the stirring reaction time is 20-30 minutes, and the rotating speed of the stirrer is maintained to be 120-200 r/min. And (3) allowing the stirred wastewater to enter a sedimentation tank for sedimentation, wherein the sedimentation time is controlled to be 40-60 minutes. According to the effect of sedimentation, 5-60ppm PAM is added to promote sedimentation. The struvite at the lower layer of the sedimentation tank can be sold as a product after being washed and purified.

The phosphate content generated in the industrial organic waste treatment process is generally far higher than the ammonia content generated in gasification, so that the wastewater treated by the magnesium ammonium phosphate method still contains a certain amount of phosphate. The partial phosphate radical can be recycled. After the treatment by the magnesium ammonium phosphate method, the water body enters a calcium chloride dosing pool, calcium chloride with the mass concentration of 0.5% -4% is added, the stirring reaction is carried out for 10-15 minutes, the rotating speed of a stirrer is maintained to be 120-200 r/min, the stirred solution is precipitated for 40-60 minutes to generate calcium phosphate precipitate, and 10-60 ppm PAM can be added into the water body to promote the precipitation and precipitation according to the actual precipitation effect. And (4) the supernatant after sedimentation enters the next treatment process.

Through the two treatment flows, phosphate and ammonia nitrogen in the wastewater are fully utilized, and the existing pollutants in the wastewater are mainly inorganic salts and organic matters. The pH value of the water body is adjusted to be 7-8 by using sodium carbonate, redundant calcium ions in the water body can be removed by the step, and scale is prevented from being generated in the subsequent ozone oxidation process to influence the oxidation effect.

The regulated wastewater enters an ozone/hydrogen peroxide pipeline mixer at the flow rate of 10-15L/min. The cross-sectional area of the pipeline reactor is 0.002m ² ～0.01m ² The length of the reactor pipeline is controlled between 17m and 34m. The static pipeline mixer is arranged between the ozone adding port and the 1m-2m behind the hydrogen peroxide adding port, the flow velocity in the pipeline mixer is controlled to be 1m/s-2m/s, and the ozone concentration is kept between 100 g/m and 300g/m ³ The concentration of hydrogen peroxide is controlled to be 1-5%, and the treatment time is kept to be 30-60 min. The hydrogen peroxide and the ozone in the pipeline mixer can fully oxidize organic matters in the wastewater, thereby providing conditions for the subsequent separation of inorganic salts in the wastewater.

The electrodialysis process can realize the concentration of inorganic salt and the separation of organic matters in the wastewater. In the process of ozone oxidation wastewater, part of unoxidized macromolecular organic matters exist, and can be transferred into fresh room wastewater by using an electrodialysis device, and the fresh room wastewater can be recycled. The electrodialysis dense chamber waste water is used for the subsequent step-by-step purification of inorganic salt.

The electrodialysis device adopts a homogeneous membrane or an alloy membrane, the voltage of two sides of the membrane is 100V, and the current between the membranes is 100A. The membrane layer level of the membrane stack is 100 layers, the water yield of the dense chamber and the dilute chamber is 4-5L/s, and the single treatment time is controlled at 30min.

After the chilling wastewater is subjected to a series of treatments, the main components of the water body of the concentration chamber are sodium salt, sylvite and micromolecular organic matters. The solubility curves of sodium chloride, potassium chloride and sodium sulfate have different characteristics along with the change of the temperature. The solubility curves for the three substances are shown in figure 2 below.

The wastewater after ozone oxidation contains a certain amount of micromolecular organic matters such as formic acid, acetic acid and the like, and the pH value in the water body is adjusted to be 4-5 by utilizing hydrogen chloride. The regulated waste water is evaporated in an evaporator, the temperature of the evaporator is controlled to be 100-120 ℃, the pressure is controlled to be 1.3-1.7Mpa, the micromolecule organic matter is evaporated along with the water vapor in the further concentration process of the waste water, and the evaporated distillate is recycled. In the process of concentrating the wastewater, the concentration of inorganic salts in the wastewater needs to be controlled to be lower than the concentration point of potassium chloride crystals. The step realizes the salt separation treatment of the second step of the wastewater, and realizes the crystallization of sodium chloride in the water body. And cooling the mother liquor after the sodium chloride is crystallized to 50-60 ℃, carrying out flash evaporation on the mother liquor, and separating out potassium chloride crystals from the wastewater. The evaporation distillate is recycled as gasification chilling circulating wastewater, and the step realizes the salt separation treatment of the third step of wastewater. And finally, treating the residual mother liquor as waste liquor.

Example of implementation

The invention will be further described with reference to a company's wastewater to be treated.

The indexes of the wastewater with high salt content are shown in the following table 2. The total treatment time of the wastewater in the example is 200t, wherein the dilute chamber is directly recycled for 150t, and is evaporated for 48t, and finally the wastewater is discharged out of the system for 2t.

TABLE 2 wastewater indexes

And (3) allowing the wastewater to be treated to enter a sedimentation tank for sedimentation for 30min. During the settling, the temperature of the wastewater was reduced to 65 ℃. Pumping the wastewater into a plate and frame filter press by using a sewage pump, wherein the size of filter cloth of the plate and frame filter press is 250 meshes. And controlling the pressure in the plate-and-frame filter press, and discharging the slag when the pressure is 1.5 Mpa.

The filtered waste water enters a storage tank for buffer storage, the temperature of the waste water is further reduced, the temperature of the water body is reduced to 50 ℃, and the waste water enters a reaction sedimentation tank for adding medicine for sedimentation.

Controlling the water flow of the reaction sedimentation tank to be 1t/h, adding a sodium hydroxide solution into the reaction sedimentation tank, and adjusting the pH value of the water body to be 9. Adding magnesium chloride into the wastewater, wherein the adding amount is 20kg/h. And stirring the water body by using a stirrer, ensuring the pH value of the water body to be 9 in the process of water body precipitation reaction, and adding a certain amount of PAM according to the precipitation effect. Stirring for 30min by a stirrer at a speed of 100r/min, and then allowing the water body to enter a sedimentation tank for sedimentation. Magnesium ammonium phosphate generated in the water naturally sinks to the bottom layer, and is treated as a raw material of the compound fertilizer after subsequent treatment.

The supernatant fluid enters a calcium chloride dosing pool to generate calcium phosphate precipitate, and the calcium phosphate precipitate naturally settles in a settling chamber. The water flow of the sedimentation tank is 1t/h, and the adding amount of calcium chloride is 5kg/h. And (3) adjusting the pH value of the water body to 8.5 by using sodium carbonate in the settled supernatant, wherein the excessive calcium ions in the water body generate calcium carbonate precipitates, so that the scale formation phenomenon in a pipeline generator in the oxidation process is prevented from influencing the oxidation process of the wastewater.

The adjusted water body enters a pipeline generator for oxidation, and the ozone concentration in the pipeline generator is kept at 260g/m ³ The hydrogen peroxide amount is 2 percent, and the water flow is 10L/min. After 30min treatment, the organic matters in the water body are effectively removed.

Treating the wastewater after ozone oxidation in an electrodialysis device, wherein an electrodialysis membrane stack is a homogeneous membrane, the voltage on two sides of the membrane is 100V, the current between membranes is 100A, the flow of a dilute chamber is 3L/min, the flow of a dense chamber is 3L/min, and the continuous operation time is 30min; the initial volume of the concentration chamber is 50L, and the final volume of the concentration chamber is 190L. The initial conductance of the concentrate was 6.8ms/cm and the end conductance of the concentrate was 125.1ms/cm.

After electrodialysis treatment, inorganic matters in water are effectively removed, and the treated wastewater is recycled. And (3) allowing the wastewater in the concentration chamber to enter an evaporation chamber, evaporating the wastewater at 110 ℃ under 1.5MPa to separate out sodium chloride crystals, controlling the temperature in the crystallization process, reducing the temperature of the water body after evaporating for 30min, ensuring that the temperature of the water body is 55 ℃, and performing flash evaporation treatment on the water body, wherein potassium chloride crystals can be separated out at the moment. After the sodium chloride and potassium chloride crystals are preliminarily collected, the mother liquor is treated as waste liquor.

The data of each pollutant in the process flow is shown in the following table 3, and the electrodialysis treatment effect is shown in the following table 4.

TABLE 3 wastewater contaminant treatment data sheet

	As received	After treatment with magnesium chloride	After ozone treatment
				Toc(mg/L)	2221	1918	61.1
Ammonia nitrogen (mg/L)	264.1	66.43	2.21
				Total nitrogen (mg/L)	350	109.46	60..8
Total phosphorus (mg/L)	2542.6	20.867	20.189

TABLE 4 electrodialysis treatment Effect

The process basically meets the design requirements from the result, and has higher removal efficiency on the removal rate of ammonia nitrogen in the water body. Therefore, the technology can realize the efficient treatment of the high-salt and high-ammonia nitrogen wastewater, and fills the blank of other processes for treating high-salt, high-ammonia nitrogen and high-organic matters.

Example two

The parameters for treating wastewater in this example are shown in Table 5 below. The total amount of the wastewater is 40t, the fresh room is recycled for 35t, the evaporation room is recycled for 4t, and the final discharge is 0.5t.

TABLE 5 wastewater indices

The high phosphorus content of the sewage needs to be treated by adding more calcium chloride. The amount of magnesium chloride added is calculated by utilizing the amount of ammonia nitrogen in the water body, 2.456kg of magnesium chloride hexahydrate is needed by each ton of water, and 12.729kg of calcium chloride is needed by adding calcium chloride into each ton of water.

The plate frame water inlet is 60 ℃, the pH value of the treated grey water is adjusted to be 8.9, the grey water enters a magnesium chloride hexahydrate dosing pool for dosing, and meanwhile, the pH value is ensured to be stable at 8.9 in the reaction process. The wastewater has good sedimentation effect, and the supernatant enters a calcium chloride dosing tank. The reaction was stirred and the settling time was maintained at 40 minutes. And adjusting the pH value of the supernatant of the calcium chloride to 10 by using sodium carbonate, and carrying out reaction precipitation, wherein the precipitation time is controlled to be 45 minutes. The adjusted wastewater enters a pipeline generator at a flow rate of 1t/h, and the concentration of ozone is kept at 200g/m ³ And (6) processing. The addition amount of the hydrogen peroxide is 3 percent. And the treated liquid enters electrodialysis for treatment, the conductivity of the dilute chamber is ensured to be reduced to 15ms/cm for wastewater recycling, and the salt separation treatment is carried out after the conductivity of the concentrated chamber reaches 140 ms/cm.

The treatment data of each substance in the wastewater in the overall process flow are shown in table 6 below.

TABLE 6 wastewater pollutant treatment Effect

	As received	After the struvite treatment process	After ozone treatment	Electrodialytic fresh water
					TOC(mg/L)	896.5	901.2	40.4	38.2
Ammonia nitrogen (mg/L)	161	39.2	0.12	0.03
					Total nitrogen (mg/L)	203	94.3	40.3	1.4
Total phosphorus (mg/L)	3542.36	16.5	15.2	1.2

And the treated wastewater in the concentration chamber enters an evaporation chamber for salt separation treatment. The evaporation device is filled with concentrated water for 5t, the device is pressurized, the pressure in the evaporator is controlled to be 1.2MPa, the water body is continuously evaporated, micromolecular organic matters in the water body are discharged out of the water body along with the evaporation of steam, and the evaporated condensate water is sent into a biochemical pool for treatment. When the water body of the wastewater is changed into 3t, sodium chloride crystals begin to be separated out from the water body, the water temperature is controlled to be 110 ℃, and the water body is evaporated for 30min. And taking out sodium chloride crystals in the water body, and weighing the sodium chloride crystals to obtain 132kg of dry sodium chloride. And (3) carrying out flash evaporation on the subsequent water body, controlling the temperature of the water body to be 50 ℃, separating out potassium chloride crystals in the water body, evaporating for 30min again, taking out potassium chloride crystals in the water body, and weighing dry potassium chloride with the mass of 121kg. Finally, 0.5t of mother liquor can be directly treated as waste liquor.

The amounts of production of each of the materials in the production process of this example are shown in Table 7 below.

TABLE 7 dosage of each substance

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A method for near zero emission and resource utilization of organic hazardous waste gas chilling cycle wastewater is characterized in that the organic hazardous waste gas chilling cycle wastewater is processed after being circulated until the content of inorganic salt is more than 20%, and after the organic hazardous waste gas chilling cycle wastewater is circulated until the content of inorganic salt is more than 20%, the organic hazardous waste gas chilling cycle wastewater has the TOC of 1000 to 5000mg/L, the ammonia nitrogen of 250 to 500mg/L, the total phosphorus of 800 to 3000mg/L, the total nitrogen of 400 to 650mg/L, the chloride ion of 100000 to 200000mg/L, the potassium ion of 50000 to 100000mg/L and the sodium ion of 50000 to 100000 mg/L; the treated wastewater meets the recycling standard and then is recycled as gasification chilling circulating wastewater, and the wastewater is not discharged outside, the method comprises the following steps:

1) The high-temperature gasification chilling wastewater firstly enters a sedimentation tank to be kept stand for 1 to 2 hours, and is cooled to 80 ℃ after solid-liquid delamination and natural cooling ^o After the water content is lower than C, enabling the upper-layer wastewater to enter a plate and frame filter device to remove insoluble suspended matters, and adjusting the pH value of the filtered clear liquid to 8 to 9; then, putting the mixture into a reaction sedimentation tank, adding a proper amount of magnesium chloride hexahydrate, reacting to generate struvite, timely adjusting the pH value in the reaction process, stabilizing the pH value between 8 and 9, stirring and reacting for 20 to 40 minutes, staying for 30 to 60 minutes, collecting the struvite in a sedimentation chamber, and cleaning the struvite to be sold as a compound fertilizer;

2) Enabling the supernatant of the reaction settling chamber to enter a subsequent calcium chloride dosing coagulation reaction tank to further generate calcium phosphate, wherein the adding amount of the calcium chloride is 0.5-4% of the total amount of the treated water body, stirring for reaction for 10-15 minutes, precipitating the stirred solution for 40-60 minutes to generate calcium phosphate precipitate, and after cleaning, compounding the calcium phosphate precipitate to be sold as a compound fertilizer;

3) Allowing supernatant obtained by precipitation in the step 2) to enter an adjusting tank, adding sodium carbonate into the adjusting tank to remove redundant calcium ions, adjusting the pH value of a sodium carbonate adding tank to 7 to 8, and maintaining the pH value of a water body;

4) The supernatant of the regulating reservoir enters an ozone/hydrogen peroxide tubular oxidation reactor at a certain flow rate to further remove redundant ammonia nitrogen and organic pollutants in the wastewater, and the ozone concentration in the tubular oxidation reactor is kept between 100 and 300g/m ³ The concentration of hydrogen peroxide is controlled to be 1-5%, and the reaction time is 30-60 minutes;

the mixing mode of the ozone/hydrogen peroxide tubular oxidation reactor is pipeline mixing, the ozone adding mode is directly introducing a pipeline, the hydrogen peroxide adding mode is to utilize a bypass pipeline to enter wastewater to be treated, a static pipeline mixer is used for fully mixing, the static pipeline mixer is arranged between an ozone adding port and a hydrogen peroxide adding port and is arranged 1m-2m behind the ozone adding port and the hydrogen peroxide adding port, the flow speed in the pipeline mixer is controlled to be 1m/s-2m/s, and the sectional area of the pipeline is 0.002m ² ~0.01m ² The length of the reactor pipeline is controlled to be 17-34 m;

5) The wastewater treated by the ozone/hydrogen peroxide tubular oxidation reactor enters an electrodialysis device, the purification and the efficient concentration of inorganic salt are further realized by separating organic pollutants from inorganic salt, and the wastewater in an electrodialysis fresh water chamber is recycled as gasification chilling circulating wastewater;

the electrodialysis device selects a homogeneous membrane or an alloy membrane, the voltage at two sides of the membrane is 100V, and the current between the membranes is 100A; the membrane layer level of the membrane stack is 100 layers, the water yield of the dense chamber and the dilute chamber is 4L/s, the electrodialysis adopts an intermittent treatment mode to carry out treatment, the single treatment capacity is 200L, the single treatment time is controlled within 30 minutes, and the electrodialysis power is controlled within 10kW-20kW in the treatment process;

6) Adjusting the pH value of the concentrated water subjected to electrodialysis separation to 4-5 by using sodium chloride to promote volatilization of the small molecular organic acid, and allowing the adjusted concentrated water to enter an evaporation chamber for evaporation; under the pressure of 1.3 to 1.7Mpa, keeping the temperature of the wastewater at 100 to 120 ℃, evaporating and concentrating the wastewater to a certain concentration, wherein the concentration point is higher than the concentration point of the precipitated potassium chloride, and then evaporating and crystallizing to precipitate sodium chloride; when the temperature of the evaporated wastewater is reduced to 50-60 ℃, carrying out flash evaporation to separate out potassium chloride crystals; the evaporation distillate is recycled as gasification chilling circulating wastewater, and the residual mother liquor is transported to the outside as waste;

the step 6) is specifically as follows: carrying out electrodialysis separation on the concentrated wastewater in the concentrated water chamber, adjusting the pH value to be 4-5 by using hydrochloric acid, promoting the volatilization of the small molecular organic acid by adjusting the pH value of the water body, allowing the adjusted wastewater to enter an evaporation chamber, controlling the pressure to be 1.3-1.7Mpa and the temperature to be 100-120 ℃, carrying out concentration treatment on the chilled water body, and controlling the concentration in the water body to be higher than the concentration point of potassium chloride crystallization; under such conditions, crystallization of sodium chloride is carried out; after sodium chloride crystallization, the mother liquor is cooled to 50 DEG ^o C~60 ^o C, carrying out flash evaporation on the mother liquor; potassium chloride crystals are separated out in the flash evaporation process; and treating the mother liquor after crystallization as waste liquor.

2. The method of claim 1, wherein fly ash is removed by plate-and-frame filtration, wherein the filtration cloth is made of high temperature resistant nylon, and the mesh number of the filtration cloth is controlled to be 300-400 meshes; the pressure of the plate frame is controlled to be 0.4-0.6Mpa, the temperature of the chilling water is controlled to be below 80 ℃, and the filtered fly ash can be recycled for high-temperature gasification treatment again.

3. The method according to claim 1, wherein in the reaction sedimentation tank, the molar ratio of magnesium ions of the added magnesium chloride to ammonia nitrogen in the clear liquid is 0.8 to 1.5, and the molar ratio of the magnesium ions to phosphorus is 1 to 1.2:1; the speed of the stirrer is controlled within 120 to 200r/min, and the pH value in the water body is maintained within 8 to 9 during stirring.

4. The method according to claim 1, characterized in that 5-20ppm PAM is added to the reaction sedimentation tank to promote sedimentation; adding 10 to 60ppm PAM into a calcium chloride dosing coagulation sedimentation tank to promote sedimentation and sedimentation; the settling time of the water body in the settling chamber is reasonably controlled by taking the supernatant as clear and transparent as a standard.

5. The method according to claim 1, wherein the distillate after the combined process treatment is directly recycled after being mixed with fresh room water, and the water quality meets the following index requirements: TOC is less than 100mg/L, ammonia nitrogen is less than 10mg/L, total phosphorus is less than 10mg/L, total nitrogen is less than 50mg/L, chloride ion is less than 1000mg/L, potassium ion is less than 500mg/L, and sodium ion is less than 500mg/L.