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

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

A method for near-zero discharge and resource utilization of organic hazardous waste gasification chilled circulating wastewater

technical field

The invention relates to a method for recycling nearly zero discharge of organic hazardous waste high-temperature gasification chilled wastewater, and at the same time realizes resource utilization of nitrogen, phosphorus, potassium and sodium elements in wastewater, and belongs to the field of wastewater resource utilization.

Background technique

Industrial organic hazardous waste refers to solid or liquid organic articles and substances that have lost their original use value or have not lost their use value but are discarded or abandoned in industrial production, and have one or more hazardous characteristics. Mainly include: distillation residue, industrial 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 tires, waste printed circuit boards, waste etching liquid, etc. Industrial hazardous organic waste usually has the characteristics of complex composition sources, poor biodegradability, toxicity and hazards.

Gasification and high-temperature melting technology of industrial organic hazardous waste High-temperature technology is a new technology for treating organic hazardous waste. This technology uses industrial organic hazardous waste as a raw material to configure the raw materials for the furnace. The incoming raw material has the characteristics of organic waste, complex composition and high salt content. After the industrial organic waste is gasified, it needs to be chilled to cool down. During the chilling and cooling process, the molten inorganic matter contacts the chilled wastewater, and material transfer occurs, among which potassium and sodium soluble salts are the representatives. A large amount of potassium salt and sodium salt enter the chilled water body, which increases the salt content in the water body. During the gasification process, the reaction process will produce elemental phosphorus and ammonia nitrogen to react with chilled wastewater to form phosphoric acid and ammonia nitrogen. After the recycling of chilled wastewater, the concentration of various pollutants continues to increase, and finally forms wastewater with high salt content, high organic matter, high phosphorus, and high ammonia nitrogen.

There are few and single treatment methods for wastewater with high salt content. The main existing treatment technology is to use evaporation to treat the salt in the water body. This treatment process will produce a large amount of dirty salt, and at the same time consume a lot of energy. The evaporated polluted salt contains a large amount of organic matter, nitrogen, phosphorus and other pollutants, and the follow-up treatment of waste salt is difficult. Traditional biological denitrification technology is the most widely used denitrification method for treating wastewater, but it is difficult to denitrify wastewater with high saline content, and it is even more difficult to treat wastewater with high chloride ion content. The current mainstream treatment method is to cultivate and screen the strains. Once the tolerance of the strains is exceeded, the strains will die.

In the advanced oxidation process, the Fenton oxidation process for removing organic matter in water is widely used today, but the Fenton oxidation process has a major feature, which has a good effect on organic matter treatment, but produces a large amount of iron sludge. The treatment of iron sludge will increase the cost of process treatment. Ozone removal of ammonia nitrogen and organic matter in water is one of the current treatment processes. This process can remove both organic matter and ammonia nitrogen in wastewater, but it has certain difficulties in treating double-high wastewater containing high ammonia nitrogen and high organic matter. The higher the content of organic matter, the worse the removal effect of ozone on ammonia nitrogen, and the greater the amount of ozone depletion required, so the treatment cost is higher. The above methods are common treatment methods for the removal of pollutants in wastewater, but each individual treatment process has its own advantages and limitations. Pollutants in gasification chilled wastewater have the characteristics of complexity, diversity and instability. Therefore, by increasing the number of cycles of chilled wastewater, the concentration of inorganic salts can be increased and maintained within a certain range, and a variety of combined treatment technologies and optimizations can be used. Realize the staged and efficient resource utilization of nitrogen, phosphorus, chlorine, sodium, potassium and other elements in wastewater, so as to realize the recycling of wastewater and meet the process requirements of multi-component organic waste gasification. The entire treatment system only needs a small amount The concentrated liquid and high-concentration residual liquid need to be discharged outside, so as to achieve near zero discharge of waste water.

Contents of the invention

The invention aims at the complexity, diversity and instability of multi-component organic waste gasification quenching wastewater, and develops and solves the recycling and resource utilization of multi-component organic hazardous waste gasification quenching wastewater.

The invention provides a method for near-zero discharge and resource utilization of organic hazardous waste gasification chilled circulating wastewater. The organic hazardous waste gasified chilled circulating wastewater is recycled until the inorganic salt content is greater than 20%. Medium TOC is 1000～5000mg/L, ammonia nitrogen is 250～500mg/L, total phosphorus is 800～3000mg/L, total nitrogen is 400～650mg/L, chloride ion is 100000～200000mg/L, potassium ion is 50000～100000mg /L, sodium ion is 50000～100000mg/L. After the combined technology treatment meets the recycling standard, the waste water is directly reused to the chilling room. The main water quality requirements are TOC less than 100mg/L, ammonia nitrogen less than 10mg/L, total phosphorus less than 10mg/L, total nitrogen 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. After the treated wastewater meets the reuse standard, it will be recycled as gasification quenching circulating wastewater, and the wastewater will not be discharged outside.

The method comprises the steps of:

1) High-temperature gasification chilled wastewater first enters the sedimentation tank and stands still for 1-2 hours. After solid-liquid stratification and natural cooling, after the temperature drops below 80°C, the upper-layer wastewater enters the plate-and-frame filter device to remove insoluble suspended matter. The pH value of the final clear liquid is adjusted to 8-9; then enter the reaction sedimentation tank and add an appropriate amount of magnesium chloride hexahydrate to react to generate struvite, adjust the pH in time during the reaction and stabilize it between 8-9, and stir for 20 ～40 minutes, the residence time is 30～60 minutes, the struvite is obtained after being collected in the sedimentation chamber, and can be sold as compound fertilizer after washing;

2) The supernatant of the reaction precipitation chamber enters the subsequent calcium chloride dosing coagulation sedimentation tank to further generate calcium phosphate, the amount of calcium chloride added is 0.5% to 4% of the total amount of water to be treated, and the reaction is stirred for 10 to 15 minutes. The final solution precipitates for 40 to 60 minutes to form calcium phosphate precipitates, which can be compounded and sold as compound fertilizers after washing;

3) The supernatant of the coagulation sedimentation tank enters the sodium carbonate dosing tank and adds sodium carbonate to remove excess calcium ions, adjusts the pH of the sodium carbonate dosing tank to 7-8, and maintains the pH value of the water body;

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

5) The wastewater treated by the ozone/hydrogen peroxide tubular oxidation reactor enters the electrodialysis device, and through the separation of a small amount of organic pollutants and inorganic salts, the purification and high-efficiency concentration of inorganic salts are further realized, and the wastewater in the electrodialysis freshwater chamber is used as gasification Chilling cycle waste water recycling;

6) The concentrated water separated and concentrated by electrodialysis enters the evaporation chamber for evaporation; under the pressure of 1.3-1.7Mpa, keep the temperature of the wastewater at 100°C-120°C, and evaporate and concentrate the wastewater to a certain concentration, which must be higher than potassium chloride Precipitate the concentration point, at this time, evaporate and crystallize to precipitate sodium chloride; when the evaporated wastewater is cooled to 50°C to 60°C, it will be flash evaporated to precipitate potassium chloride crystals; the evaporated distillate is recycled as gasification chilled circulating wastewater , the remaining mother liquor is treated as liquid waste.

As a preferred solution of the present invention, fly ash is removed by plate and frame filtration, and its filter cloth adopts high temperature resistant nylon material, and the mesh number of filter cloth is controlled at 300 mesh-400 mesh; the plate and frame pressure is controlled at 0.4-0.6Mpa, and the The temperature of the cold water is controlled below 80°C, and the filtered fly ash can be recycled for high-temperature gasification again.

As a preferred version of the present invention, in the reaction sedimentation tank, the mol ratio of the magnesium ions of the added magnesium chloride to ammonia nitrogen in the clear liquid is 0.8～1.5:1, and the mol ratio of magnesium ions to phosphorus is 1～1.2:1; The speed of mixing is controlled at 120-200r/min, and the pH value of the water body should be maintained at 8-9 during the stirring process.

As a preferred scheme of the present invention, 5-20ppm PAM is added to the coagulation sedimentation tank to promote sedimentation; 10-60ppm PAM is added to the calcium chloride dosing coagulation reaction tank to promote sedimentation; The liquid is clear and transparent as the standard and reasonably controlled.

As a preferred solution of the present invention, the mixing method of the ozone/hydrogen peroxide tubular oxidation reactor is pipeline mixing, the ozone dosing method is directly passed into the pipeline, and the hydrogen peroxide dosing method is to use a bypass pipeline to enter the waste water to be treated. The static pipeline mixer is fully mixed, and the static pipeline mixer is installed between the ozone dosing port and the hydrogen peroxide dosing port 1m-2m, and the flow rate in the pipeline mixer is controlled to be 1m/s-2m/s, and the cross-sectional area of the pipeline is 0.002m ² ~0.01m ² , the length of the reactor pipeline is controlled at 17m-34m.

As a preferred solution of the present invention, the electrodialysis device uses a homogeneous membrane or an alloy membrane, the voltage on both sides of the membrane is 100V, and the current between the membranes is 100A; the membrane layer of the membrane stack is 100 layers, and the water output of the concentrated chamber and the dilute chamber is 4L /s, electrodialysis adopts intermittent treatment method, the single treatment volume is 200L, and the single treatment time is controlled at 30 minutes. During the treatment process, the electrodialysis power should be controlled at 10kW-20kW.

As a preferred solution of the present invention, the step 6) is specifically: electrodialysis to separate the concentrated concentrated water, use hydrochloric acid to adjust the pH value to 4-5, promote the evaporation of small molecule organic acids in the water body, and the adjusted concentrated water enters the evaporation chamber , the control pressure is 1.3-1.7Mpa, the temperature is 100°C-120°C, and the chilled water body is concentrated. The concentration in the control water body should be higher than the concentration point of potassium chloride crystallization; under this condition, the chlorination Sodium crystallization; after sodium chloride crystallization, the temperature of the mother liquor is lowered to 50°C-60°C, and the mother liquor is flashed; during the flashing process, potassium chloride crystals are precipitated; the evaporated distillate is recycled as gasification quenching circulating wastewater , the mother liquor after crystallization is treated as waste liquor.

The beneficial effects of the present invention are:

1) Targeted treatment of the chilled wastewater generated during the gasification process of organic hazardous waste. Industrial waste contains a large amount of inorganic salts and a certain amount of phosphorus. During the process of waste treatment by gasification process, elemental phosphorus and ammonia will be produced in the gasification furnace. After chilling and flushing, the phosphorus in the gasifier dissolves in the water to form phosphate, the ammonia gas dissolves in the water to form ammonia nitrogen, and the inorganic salt dissolves in the water to form high-salt wastewater. The chilled wastewater is continuously recycled, and the pollutants in the water body are continuously enriched, eventually forming wastewater with high ammonia nitrogen, high phosphorus, high organic matter, and high salt content. The applicant comprehensively considers the characteristics of the wastewater produced during the gasification and chilling process of organic hazardous waste, and aims at resource utilization and near-zero discharge of wastewater, and determines to circulate the chilled wastewater until the inorganic salt content is greater than 20% before using the method of the present invention. Disposal, the method can greatly reduce the consumption of chilling process water and the amount of waste water under the premise of normal operation of the chilling process, and the waste water treated by the invention can meet the goals of resource utilization and near-zero discharge. After the chilled wastewater is circulated until the inorganic salt content is greater than 20%, the TOC in the wastewater is 1000-5000mg/L, the ammonia nitrogen is 250-500mg/L, the total phosphorus is 800-3000mg/L, the total nitrogen is 400-650mg/L, chlorine The ions are 100,000-200,000 mg/L, the potassium ions are 50,000-100,000 mg/L, and the sodium ions are 50,000-100,000 mg/L. It is a technical problem to be solved by the present invention to recycle such wastewater and achieve near-zero discharge. For this reason, this process aims at the formation process of chilled wastewater, and combines different technological processes to make resourceful utilization of wastewater. Use phosphorus and ammonia nitrogen in wastewater to prepare struvite compound fertilizer; use sodium and potassium in water to produce industrial salt.

2) In this process flow, each process block is connected and organically combined to improve the treatment efficiency of pollutants in wastewater. In this technological process, the nitrogen and phosphorus in the waste water are firstly utilized, and the used waste water is oxidized to remove the organic matter in the water body. Finally, the potassium salt and sodium salt of the wastewater are utilized. Each step is closely connected with the previous step. If it is assumed that the phosphorus in the wastewater is removed first, and calcium chloride is added to the water body, although the phosphorus in the wastewater will be removed well, the ammonia nitrogen in the wastewater cannot be utilized, and the ozone oxidation process will also increase the ammonia nitrogen in the water body. secondary removal. If it is assumed that the organic matter in the wastewater is removed first, and the wastewater enters the pipeline generator for oxidation, then the content of organic matter and ammonia nitrogen in the water body is high, and more ozone and hydrogen peroxide must be consumed, resulting in an increase in process treatment costs. If it is assumed that the potassium salt and sodium salt in the wastewater are separated first, the separated potassium salt and sodium salt will contain organic matter and other impurities, which cannot be purified.

As an overall flow process, the method of the present invention can effectively treat organic hazardous waste gasification chilled circulating wastewater, which is mainly characterized by high salt content, high ammonia nitrogen (≥300mg NH ₄ ⁺ -N/L), high phosphorus, etc., and can use wastewater The ammonia nitrogen and phosphorus in the water body produce struvite by-products, and the higher the concentration of ammonia nitrogen in the water body, the better the process is.

3) The high temperature and gasification system of multi-component organic hazardous waste requires a large amount of chilled water circulation. The present invention aims at recycling the main elements, and improves the efficiency of each treatment unit by controlling the high concentration of inorganic salts in the chilled water and yield, coupled with the electrodialysis treatment process at the same time, the purification of inorganic salts such as sodium chloride and potassium chloride and the concentration of wastewater are realized. Most of the wastewater is directly reused to the water recycling system after the combined treatment technology, and only a small amount Wastewater needs to be further evaporated and crystallized to obtain inorganic salt by-products, and finally a very small amount of concentrated mother liquor is discharged out of the system. The overall treatment process does not require the use of biological treatment methods. It is a method of near-zero discharge of wastewater and resource utilization with simple process, high efficiency combination, high treatment efficiency, and low energy consumption.

Description of drawings

Figure 1 is a flow chart of resource-based joint treatment of organic hazardous waste gasification chilled cycle wastewater.

Fig. 2 is the variation curve of sodium chloride, potassium chloride, sodium sulfate solubility with temperature.

Detailed ways

In order to better understand the present invention, further description will be given below through the accompanying drawings and specific implementation.

The overall process flow chart of the present invention can refer to Fig. 1. By maintaining the concentration of inorganic salts in the chilled circulating wastewater and using a variety of combined treatment technologies, the efficient resource utilization of nitrogen, phosphorus, chlorine, sodium, potassium and other elements in the wastewater has been realized. At the same time, the wastewater can be recycled, and a small amount of concentrated liquid and The high-concentration raffinate is transported outside, so as to achieve near zero discharge. The main process technology includes firstly generating struvite from nitrogen, phosphorus and magnesium in wastewater, and further reacting the remaining phosphorus with calcium to form calcium phosphate, further removing the remaining ammonia nitrogen and organic pollutants through the combined oxidation method of ozone/hydrogen peroxide, and using electrodialysis technology Inorganic salts are further separated and purified, and finally pure by-products such as sodium chloride and potassium chloride are obtained by step-by-step evaporation and freezing crystallization. The evaporated distillate and low-salt wastewater are treated by biological methods and recycled.

The gray water in the gasification chilling process has the characteristics of high salt content, high ammonia nitrogen, high phosphorus, and high organic matter. Through monitoring and analysis, the fluctuations of various pollutants in the water body are determined as shown in Table 1. The pollutants in chilled wastewater were higher than normal wastewater. Therefore, the combined process is used to treat the chilled wastewater, and the wastewater can be utilized as a resource while increasing the upper limit of treatment.

Table 1 Contents of various pollutants in chilled wastewater

The invention is an organic combination of chemical sedimentation to remove ammonia nitrogen, advanced oxidation process and salt separation purification process. Use the ammonia nitrogen and phosphorus in the chilled water body to produce struvite, use the ozone oxidation technology to treat the ammonia nitrogen and organic matter in the water body, and use the salt separation purification process to treat the waste salt in the water body. The overall process is interlocking to realize the precise resource utilization of chilled wastewater.

Chilling wastewater is produced during the gasification chilling process of industrial organic hazardous waste, and the characteristics of its pollutants are affected by the treatment process of industrial organic hazardous waste. During the treatment of industrial organic hazardous waste, the inorganic salts in the hazardous waste are dissolved in the chilled water; the gaseous elemental phosphorus formed in the gasifier is dissolved in the water and transformed into phosphate; the ammonia gas generated during the gasification process is also dissolved in the Chilled water body, chilled water is continuously recycled. Finally, chilled wastewater with high salt content, high ammonia nitrogen, high organic matter, and high phosphorus content is formed.

During the recycling process of chilled wastewater, a certain amount of water-quenched fine slag is contained. The water-quenched fine slag is not conducive to the subsequent treatment of chilled wastewater, and it needs to be filtered. The chilled wastewater enters the sedimentation tank for sedimentation, and the temperature of the water body is lowered to below 80°C, and then it is filtered. The material of the filter cloth is high-temperature-resistant nylon filter cloth, and the pore size of the filter cloth is 300 mesh to 400 mesh. The filter cloth within this pore size range can ensure the water treatment volume and improve the treatment efficiency while removing particulate matter in the water body.

During the recycling process of chilled water, the characteristic pollutants in it continue to rise. If the pollutant content in the water body is lower than the range in Table 1, the wastewater can continue to be recycled after being filtered. If the pollutant content in the water body is higher than or equal to the pollutant content in Table 1, subsequent treatment is required.

Phosphorus and ammonia nitrogen in chilled wastewater are the by-products of hazardous waste treatment, which can be utilized as resources by using the ammonium magnesium phosphate method. After filtering the wastewater, adjust the pH value of the water body to be stable at 8-9; ^the water body enters the struvite settling chamber and adds magnesium _chloride ^hexahydrate for reaction. , Mg ²⁺ :PO ₄ ^2- =1 to 1.2:1 is calculated. During the formation of magnesium ammonium phosphate, the pH value of the water should be kept stable at 8-9, the stirring reaction time should be 20-30 minutes, and the speed of the mixer should be maintained at 120-200r/min. The stirred wastewater enters the settling tank for settling, and the settling time is controlled within 40-60 minutes. According to the effect of sedimentation, add 5-60ppm PAM to promote sedimentation. After the struvite in the lower layer of the sedimentation tank is washed and purified, it can be sold as a product.

The phosphate content produced during the treatment of industrial organic waste is generally much higher than the ammonia content produced by gasification, so the wastewater treated by the ammonium magnesium phosphate method still contains a certain amount of phosphate. This part of the phosphate can be used as a secondary resource. After being treated by the ammonium magnesium phosphate method, the water body enters the calcium chloride dosing pool, and calcium chloride with a mass concentration of 0.5% to 4% is added, and the reaction is stirred for 10 to 15 minutes, and the speed of the mixer is maintained at 120 to 200r/min. The solution precipitates for 40-60 minutes to form calcium phosphate precipitates. According to the actual settlement effect, 10-60ppm PAM can be added to the water body to promote sedimentation. The supernatant after sedimentation enters the next step of processing.

Through the above two treatment processes, the phosphate and ammonia nitrogen in the wastewater are fully utilized, and the existing pollutants in the wastewater are mainly inorganic salts and organic matter. Sodium carbonate is used to adjust the pH value of the water body to 7-8. This step can remove excess calcium ions in the water body and prevent the formation of scale in the subsequent ozone oxidation process that affects the oxidation effect.

The adjusted wastewater enters the ozone/hydrogen peroxide pipeline mixer at a flow rate of 10-15L/min. The pipe cross-sectional area of the pipe reactor is 0.002m ² to 0.01m ² , and the length of the reactor pipe is controlled at 17m-34m. ^The static pipe mixer is installed between the ozone dosing port and the hydrogen peroxide dosing port 1m-2m behind. It is controlled at 1%-5%, and the processing time is kept at 30-60min. The hydrogen peroxide and ozone in the pipeline mixer can fully oxidize the organic matter in the wastewater, thus providing conditions for the subsequent separation of inorganic salts in the wastewater.

The electrodialysis process can realize the concentration of inorganic salts and the separation of organic matter in wastewater. During the ozone oxidation wastewater process, there are some unoxidized macromolecular organic matter, which can be transferred to the desalination wastewater by using the electrodialysis device, and the desalination wastewater can be reused. The electrodialysis concentrated chamber wastewater is used for subsequent step-by-step purification of inorganic salts.

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

After the chilled wastewater has undergone a series of treatments, the main components of the concentrated chamber water are sodium salts, potassium salts and small molecular organic matter. The curves of the solubility of sodium chloride, potassium chloride and sodium sulfate with temperature have different characteristics. The solubility curves of the three substances are shown in Figure 2 below.

The wastewater oxidized by ozone contains a certain amount of small molecule organic matter, such as formic acid, acetic acid, etc., and the pH value of the water body is adjusted to 4-5 by using hydrogen chloride. The adjusted wastewater enters the evaporator for evaporation. The temperature of the evaporator is controlled at 100°C-120°C and the pressure is 1.3-1.7Mpa. During the further concentration of the wastewater, the small molecule organic matter evaporates with the water vapor, and the evaporated distillate returns to the Use to deal with. In the process of wastewater concentration, it is necessary to control the concentration of inorganic salts in the wastewater to be lower than the concentration point of potassium chloride crystals. This step realizes the salt separation treatment of the second step of the waste water, and realizes the crystallization of sodium chloride in the water body. The mother liquor after sodium chloride crystallization is cooled to 50°C to 60°C, and flash evaporated, and potassium chloride crystals are precipitated from the wastewater. The evaporated distillate is recycled as the gasification quenching cycle wastewater, and this step realizes the third step of salt separation treatment of the wastewater. Finally, the remaining mother liquor is disposed of as waste liquid.

Implementation example one

Taking the waste water to be treated of a certain company as an example, the present invention will be further described.

The various indicators of high-salt wastewater are shown in Table 2 below. In this example, 200t of wastewater was treated in total, of which 150t was directly reused in the dilute chamber, 48t was reused by evaporation, and 2t was finally discharged outside the system.

Table 2 Various indicators of wastewater

The wastewater to be treated enters the settling tank for settling, and the settling time is 30 minutes. During the settling process, the temperature of the wastewater was reduced to 65°C. Use the sewage pump to drive the wastewater into the plate and frame filter press, and the filter cloth size of the plate and frame filter press is 250 mesh. Control the internal pressure of the plate and frame filter press, and unload the slag when the pressure is 1.5Mpa.

The filtered wastewater enters the storage tank for buffer storage, and the temperature of the wastewater will be further reduced. The temperature of the water body will drop to 50°C, and then enter the reaction sedimentation tank for dosing and precipitation.

The water flow in the reaction sedimentation tank is controlled at 1t/h, and sodium hydroxide solution is added to the reaction sedimentation tank to adjust the pH of the water to 9. Add magnesium chloride to the wastewater, and the dosage is 20kg/h. Use a mixer to stir the water body. During the precipitation reaction process of the water body, ensure that the pH value of the water body is 9, and add a certain amount of PAM according to the sedimentation effect. After being stirred by the mixer at 100r/min for 30min, the water enters the sedimentation tank for sedimentation. Magnesium ammonium phosphate generated in the water naturally settles to the bottom layer, and after subsequent treatment, it is treated as a compound fertilizer raw material.

The supernatant enters the calcium chloride dosing tank to form a calcium phosphate precipitate, which settles naturally in the settling chamber. The water flow rate of the settlement tank is 1t/h, and the dosage of calcium chloride is 5kg/h. For the supernatant after settlement, use sodium carbonate to adjust the pH value of the water body to 8.5. The excess calcium ions in the water body in this step will form calcium carbonate precipitates to prevent scaling in the pipeline generator during the oxidation process and affect the oxidation process of the wastewater. .

The adjusted water enters the pipeline generator for oxidation. The ozone concentration in the pipeline generator is kept at 260g/m ³ , the hydrogen peroxide volume is 2%, and the water flow rate is 10L/min. After 30 minutes of treatment, the organic matter in the water body can be effectively removed.

The wastewater oxidized by ozone enters the electrodialysis device for treatment. The electrodialysis membrane stack uses a homogeneous membrane. The voltage on both sides of the membrane is 100V, the current between the membranes is 100A, the flow rate of the dilute chamber is 3L/min, and the flow rate of the concentrated chamber is 3L/min. , The continuous operation time is 30min; the initial volume of the concentrated chamber is 50L, and the final volume of the concentrated chamber is 190L. The initial conductance of the concentrated water is 6.8ms/cm, and the end conductance of the concentrated chamber is 125.1ms/cm.

After the electrodialysis treatment, the inorganic substances in the water body are effectively removed from the desalinated wastewater, and the treated wastewater is recycled. The wastewater from the concentration chamber enters the evaporation chamber. After the wastewater is evaporated at 1.5MPa and 110°C, sodium chloride crystals are precipitated. This step controls the temperature during the crystallization process. After evaporating for 30 minutes, the temperature of the water body is lowered to ensure that the temperature of the water body is 55°C. It is flashed, at which point potassium chloride crystals will precipitate out. After the sodium chloride and potassium chloride crystals are preliminarily collected, the mother liquor is treated as waste liquid.

The data of various pollutants in the process flow are shown in Table 3 below, and the electrodialysis treatment effect is shown in Table 4.

Table 3 Wastewater Pollutant Treatment Data Sheet

as it is After magnesium chloride treatment 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

From the results, it can be seen that the process basically meets the design requirements, and has a high removal efficiency for the removal rate of ammonia nitrogen in water. Therefore, this technology can achieve efficient treatment of high-salt and high-ammonia-nitrogen wastewater, filling the gaps in the treatment of high-salt, high-ammonia-nitrogen, and high-organic matter by other processes.

Implementation example two

The various parameters of wastewater treatment in this example are shown in Table 5 below. The total amount of wastewater treated is 40t, 35t is reused in the dilute chamber, 4t is reused in the evaporation chamber, and 0.5t is finally discharged.

Table 5 Various indicators of wastewater

Sewage with high phosphorus content needs to add more calcium chloride for treatment. Using the amount of ammonia nitrogen in the water body to calculate the amount of magnesium chloride to be added, 2.456kg of magnesium chloride hexahydrate is required for each ton of water, and 12.729kg of calcium chloride is required for each ton of water after adding calcium chloride.

The inlet water of the plate and frame is 60°C, and the treated gray water is adjusted to a pH value of 8.9, and enters the magnesium chloride hexahydrate dosing pool for dosing, while ensuring that the pH value is stable at 8.9 during the reaction process. The wastewater has a good settling effect, and the supernatant liquid enters the calcium chloride dosing tank. The stirred reaction was carried out, and the settling time was kept at 40 minutes. The calcium chloride supernatant was adjusted to a pH value of 10 with sodium carbonate for reaction precipitation, and the precipitation time was controlled at 45 minutes. After adjustment, the wastewater enters the pipeline generator at a flow rate of 1t/h, and keeps the ozone concentration at 200g/ ^m3 for treatment. The addition amount of hydrogen peroxide is 3%. After treatment, the liquid enters electrodialysis for treatment to ensure that the conductance of the dilute chamber is reduced to 15ms/cm for wastewater reuse, and the concentration chamber reaches 140ms/cm for salt separation treatment.

The treatment data of each substance in the wastewater in the overall technological process is shown in Table 6 below.

Table 6 Wastewater Pollutant Treatment Effect

as it is After struvite treatment process After ozone treatment Electrodialysis 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

After treatment, the wastewater in the concentration chamber enters the evaporation chamber for salt separation. 5t of concentrated water is flushed into the evaporation device, and the device is pressurized to control the pressure in the evaporator to 1.2MPa. The water body is continuously evaporated, and the small molecular organic matter in the water body is discharged out of the water body with the evaporation of water vapor, and the condensed water after evaporation , sent to the biochemical pool for treatment. When the wastewater water body becomes 3t, sodium chloride crystals begin to precipitate in the water body, control the water temperature at 110°C, and evaporate the water body for 30 minutes. The sodium chloride crystallization in the water body is taken out, and the sodium chloride quality on a dry basis is weighed to be 132kg. The subsequent water body is flash evaporated, and the temperature of the water body is controlled at 50 degrees Celsius. Potassium chloride crystals will be precipitated in the water body, evaporated again for 30 minutes, and the potassium chloride crystals in the water body are taken out. The weight of potassium chloride on a dry basis is 121kg. 0.5t of the final mother liquor can be directly treated as waste liquor.

The output of each substance in the production process of this example is shown in Table 7 below.

Table 7 Dosage of each substance

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the appended claims.

Claims (5)

1. A method for near-zero discharge and resource utilization of organic hazardous waste gasification chilled circulating wastewater, characterized in that the organic hazardous waste gasified chilled circulating wastewater is circulated until the inorganic salt content is greater than 20%, and then it is treated. The organic hazardous waste gasification chilled circulating wastewater is circulated until the inorganic salt content is greater than 20%, its TOC is 1000-5000 mg/L, ammonia nitrogen is 250-500 mg/L, total phosphorus is 800-3000 mg/L, total nitrogen 400-650 mg/L, 100,000-200,000 mg/L chloride ion, 50,000-100,000 mg/L potassium ion, 50,000-100,000 mg/L sodium ion; the treated wastewater meets the reuse standard and is used as gasification The chilled circulating waste water is recycled, and the waste water is not discharged. The method comprises the following steps: 1) The high-temperature gasification chilled wastewater first enters the sedimentation tank and stands still for 1-2 hours. After solid-liquid stratification and natural cooling, after the temperature drops below 80 ^o C, the upper-layer wastewater enters the plate-and-frame filter device to remove insoluble suspended matter. The pH value of the filtered clear liquid is adjusted to 8~9; then enter the reaction sedimentation tank and add an appropriate amount of magnesium chloride hexahydrate to react to form struvite, adjust the pH in time during the reaction and stabilize it between 8~9, and stir the reaction 20-40 minutes, the residence time is 30-60 minutes, the struvite is obtained after being collected in the sedimentation chamber, and can be sold as compound fertilizer after washing; 2) The supernatant of the reaction precipitation chamber enters the subsequent calcium chloride dosing coagulation reaction tank to further generate calcium phosphate. The amount of calcium chloride added is 0.5%~4% of the total amount of water to be treated, and the reaction is stirred for 10~15 minutes. The final solution precipitates for 40 to 60 minutes to form calcium phosphate precipitates, which can be compounded and sold as compound fertilizers after washing; 3) The supernatant obtained in step 2) enters the adjustment tank, and sodium carbonate is added to the adjustment tank to remove excess calcium ions, and the pH of the sodium carbonate dosing tank is adjusted to 7~8 to maintain the pH value of the water body; 4) The supernatant of the regulating tank enters the ozone/hydrogen peroxide tubular oxidation reactor at a certain flow rate to further remove excess ammonia nitrogen and organic pollutants in the wastewater. The ozone concentration in the tubular oxidation reactor is maintained at 100~300g/m ^3. The concentration of hydrogen peroxide is controlled at 1%-5%, and the reaction time is 30-60 minutes; The mixing method of the ozone/hydrogen peroxide tubular oxidation reactor is pipeline mixing, the ozone dosing method is directly into the pipeline, and the hydrogen peroxide dosing method is to use a bypass pipeline to enter the waste water to be treated, and use a static pipeline mixer to fully mix , the static pipeline mixer is installed between the ozone dosing port and the hydrogen peroxide dosing port 1m-2m behind, and the flow velocity in the pipeline mixer is controlled at 1m/s-2m/s, and the cross-sectional area of the pipeline is 0.002m ² ~0.01m ² , the length of the reactor pipeline is controlled at 17m-34m; 5) The wastewater treated by the ozone/hydrogen peroxide tubular oxidation reactor enters the electrodialysis device. Through the separation of organic pollutants and inorganic salts, the purification and high-efficiency concentration of inorganic salts are further realized. The wastewater in the electrodialysis freshwater chamber is used as gasification excitation Cold cycle waste water recycling; The electrodialysis device uses a homogeneous membrane or an alloy membrane. The voltage on both sides of the membrane is 100V, and the current between the membranes is 100A; The treatment method is for treatment, the single treatment volume is 200L, and the single treatment time is controlled within 30 minutes. During the treatment process, the electrodialysis power should be controlled at 10kW-20kW; 6) Use sodium chloride to adjust the pH value of the concentrated water after electrodialysis to 4~5 to promote the volatilization of small molecule organic acids. The adjusted concentrated water enters the evaporation chamber for evaporation; under the pressure of 1.3~1.7 Mpa, the waste water The temperature is 100°C~120°C, and the waste water is evaporated and concentrated to a certain concentration. The concentration point must be higher than the precipitation concentration point of potassium chloride. At this time, sodium chloride is precipitated by evaporation and crystallization; when the evaporated waste water is cooled to 50°C~60°C , carry out flash evaporation, and precipitate potassium chloride crystals; the evaporated distillate is recycled as gasification quenching cycle wastewater, and the remaining mother liquor is transported as waste; The step 6) is specifically: electrodialysis to separate the concentrated concentrated water chamber wastewater, use hydrochloric acid to adjust the pH value to 4~5, and adjust the pH value of the water body to promote the volatilization of small molecule organic acids, and the adjusted wastewater enters the evaporation chamber , the control pressure is 1.3-1.7Mpa, the temperature is 100°C-120°C, and the chilled water body is concentrated. The concentration in the control water body should be higher than the concentration point of potassium chloride crystallization; under this condition, the chlorination Sodium crystallization; after sodium chloride crystallization, the mother liquor is cooled to 50 ^o C ~ 60 ^o C, and the mother liquor is flashed; during the flash evaporation, potassium chloride crystals are precipitated; the mother liquor after crystallization is treated as waste liquid. 2. The method according to claim 1, characterized in that the fly ash is removed by plate and frame filtration, the filter cloth adopts high temperature resistant nylon material, and the mesh number of the filter cloth is controlled at 300 mesh-400 mesh; the plate and frame pressure control At 0.4-0.6Mpa, the temperature of the quenching water is controlled below 80°C, and the filtered fly ash can be recycled for high-temperature gasification treatment again. 3. The method according to claim 1, characterized in that in the reaction sedimentation tank, the mol ratio of the magnesium ions of the added magnesium chloride to ammonia nitrogen in the clear liquid is 0.8 ~ 1.5:1, and the mol ratio of magnesium ions to phosphorus is 1 ~1.2:1; the speed of the mixer is controlled at 120~200 r/min, and the pH value of the water body should be maintained at 8~9 during the stirring process. 4. The method according to claim 1, characterized in that adding 5-20 ppm PAM to the reaction sedimentation tank to promote sedimentation; adding 10 to 60 ppm PAM to the calcium chloride dosing coagulation sedimentation tank to promote sedimentation; The time of settling in the settling chamber should be based on the clear and transparent supernatant, which should be reasonably controlled. 5. The method according to claim 1, characterized in that the distillate treated by the combined process is mixed with fresh room water and then reused directly, and the water quality must meet the following index requirements: TOC less than 100 mg/L, ammonia nitrogen less than 10 mg/L, total phosphorus less than 10 mg/L, total nitrogen less than 50 mg/L, chloride ions less than 1000 mg/L, potassium ions less than 500 mg/L, and sodium ions less than 500 mg/L.

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