Resource Utilization Method of Fly Ash and Waste Salt

Abstract

The present application relates to the field of chemical technology, and specifically provides a technology for resource utilization of fly ash and waste salt. The main steps include "water washing + pretreatment + MBR membrane + nanofiltration + moderate oxidation + electrolytic oxidation + microcrystalline adsorption". The purity of sodium chloride in fly ash is refined to the reuse standard through water washing, pretreatment, MBR membrane and nanofiltration, and then moderate oxidation, electrolytic oxidation and microcrystalline adsorption are used to fully ensure that the effluent TOC meets the salt production standard. This technology recycles the salt and solids in the fly ash and waste salt to avoid entering the environment and causing environmental pollution, thus solving the problem of disposal of fly ash and waste salt.

Description

Technical Field

[0001] The present application relates to the field of chemical technology, and specifically provides a technology for resource utilization of fly ash and waste salt. Background Art

[0002] As the best way to dispose of domestic waste in a "reduced, harmless and resourceful" way, waste incineration power generation has gradually attracted the attention and concern of the society. Fly ash, as a by-product of the waste incineration power generation process, contains high levels of heavy metals, dioxins and other harmful substances. If it is not effectively treated, it will have a huge impact on the natural environment and human health. However, the waste incineration industry generally has the problem of "heavy flue gas and light fly ash", resulting in insufficient fly ash and waste salt disposal technology and capacity, which has become an important bottleneck restricting the development of the waste incineration industry.

[0003] The particle size of fly ash is generally between 10 and 100 μm, and the particle shape is extremely irregular. Fly ash is mainly composed of Ca, Cl, and Na elements, and the soluble salt content is mostly between 10% and 30%, and may be as high as 40%. Soluble chloride is a difficult point in fly ash disposal. Chloride will increase the toxicity and risk of heavy metal leaching, making it difficult to recycle fly ash resources, and will also cause landfill collapse. During the melting / sintering process, the soluble salt of fly ash volatilizes at high temperatures, producing salt spray and other pollution. In the cement kiln co-disposal process, fly ash directly enters the cement kiln, causing cement kiln crusting and blockage, and also causing the produced cement to fail to meet the relevant national standards (GB175-2007).

[0004] Therefore, finding a more reasonable and effective method to deal with fly ash and waste salt is an urgent problem to be solved in waste incineration power plants. If the salt can be recycled and sodium chloride can be recycled, it can not only solve the problem of fly ash and waste salt treatment at the source, but also provide technical support for the further development of incineration power plants.

[0005] In view of this, this application is hereby filed. Summary of the invention

[0006] One of the purposes of the present application is to provide a fly ash waste salt resource utilization technology, so as to provide a fly ash waste salt treatment process.

[0007] In order to achieve the above purpose, this application adopts the following technical solutions:

[0008] A fly ash waste salt resource utilization technology comprises the following steps:

[0009] (1) Washing: First, the fly ash waste salt is placed in the fly ash pool to dissolve and wash, then filtered, and the filter residue is further washed with water. The filtrate is used as the washing water for other stages. After multiple rounds of multi-stage washing and filtration, the washed filter residue is used as the raw material for cement, brick making and construction. The final washing filtrate enters the pretreatment unit;

[0010] (2) Pretreatment unit: The pH of the solution is adjusted to alkaline, and then sodium carbonate solution is added to make the calcium ions generate calcium carbonate precipitates, and then the calcium carbonate precipitates are enriched at the bottom of the sedimentation tank through sedimentation. The calcium carbonate precipitates at the bottom are pumped to the plate and frame filter press for dehydration, and the filtrate is returned to the MBR membrane pool, and the filter cake is transported out for disposal;

[0011] (3) MBR membrane: The pretreatment supernatant and the filtrate from the plate and frame filter press enter the MBR membrane pool, and the submerged MBR membrane is used to achieve solid-liquid separation and ensure the water quality of the nanofiltration inlet;

[0012] (4) Nanofiltration: Through the interception effect of the nanofiltration membrane, the monovalent salt and divalent salt in the solution are separated to improve the purity of sodium chloride;

[0013] Acid adjustment is performed in the intermediate water tank 1, and the water washing filtrate after acid adjustment is used as the influent water for relieving oxidation;

[0014] (5) Mild oxidation: The oxidant H2O2 or O2 is used to oxidize and decompose the influent water, and the effluent enters the intermediate water tank 2;

[0015] (6) Electrolytic oxidation: Electrolytic oxidation is carried out under the action of an external electric field, and the effluent serves as the influent for microcrystal adsorption;

[0016] (7) Microcrystalline adsorption: The huge specific surface area of ​​the microcrystalline adsorption material can adsorb TOC in the water to ensure that the effluent TOC meets the standard. Due to the high purity of the effluent salt, it can directly enter the salt production process section of the factory.

[0017] Furthermore, in step (1), the dissolution is carried out in a batch process, the stirring device is a frame or paddle stirrer, the stirring speed is 60-130 r / min, and the hydraulic retention time of the fly ash pool is 1-3 h;

[0018] Preferably, in step (1), the water washing adopts 2 rounds of water washing or 3 rounds of water washing, each round of water washing includes three-stage water washing and three-stage filtration, the filter residue of the three-stage water washing is used as raw material for cement, brick making and construction, and the filtrate of each stage is used as water for washing in other stages or the next round.

[0019] Furthermore, in step (2), the pretreatment unit includes reaction, precipitation and plate and frame filtration. The hydraulic retention time of the reaction section of the pretreatment unit is 20-40 min, preferably 30 min. Sodium hydroxide solution is first added to adjust the pH to 10-12, preferably 10, and then sodium carbonate solution is added to form calcium carbonate precipitation. The hydraulic retention time of the precipitation section is 30-90 min, preferably 60 min. The bottom precipitate is transported and disposed of after plate and frame filtration, and the supernatant overflows to the MBR membrane pool.

[0020] Furthermore, in step (3), the MBR membrane is an immersed MBR hollow fiber membrane with a designed flux of ≤12.5L / (m2·h), a filtration pressure of -30kPa ~0 kPa, a backwash pressure of 30 ~100 kPa, and a membrane pore size of 0.2μm.

[0021] Furthermore, in step (4), the nanofiltration membrane has a design flux of 15 L / (m2·h), an operating pressure of 0.5-1.0 MPa, and a membrane pore size of more than 1 nm; the nanofiltration produced water enters the intermediate water tank 1, and the concentrated water returns to the pretreatment unit.

[0022] Furthermore, in step (4), the acid adjustment device includes an acid preparation system, a metering system and a control system, and adjusts the pH of the solution in the intermediate water tank 1 to 2-6; preferably, it is a 2%-8% dilute hydrochloric acid solution.

[0023] Furthermore, in step (5), the moderate oxidation conditions are as follows: the oxidant is H2O2 or O2, the H2O2 addition concentration is 0.1%~1%, the reaction temperature is 120°C~220°C, and the reaction pressure is 0.5~3.0MPa.

[0024] Furthermore, in step (6), the electrolytic oxidation device includes a water inlet unit, an electrolytic oxidation unit, a waste gas treatment unit, and a water outlet unit; the electrolytic oxidation unit includes a water inlet pump, an oxidation tank, a direct current, and a slag liquid sedimentation tank; the waste gas treatment unit includes an induced draft fan, a washing tower, an alkali solution storage tank, and a sludge sedimentation tank.

[0025] Furthermore, in step (6), the current density value of the electrolytic oxidation device is 1-10 A / dm2, preferably 1-5 A / dm2, the material is diamond doped with boron or titanium substrate coated with graphene, and the hydraulic retention time of the device is 10-60 min, preferably 10-30 min.

[0026] Furthermore, the electrolytic oxidation device is equipped with a cooling device, and the cooling device adopts a shell and tube heat exchanger or a plate heat exchanger to ensure that the temperature of the liquid in the electrolytic device is lower than 60°C.

[0027] Furthermore, in step (7), the material used for the microcrystalline adsorption is an artificial hydrothermally synthesized aluminosilicate crystal, the flow rate of the liquid is 0.5~1BV / H, and the adsorption temperature is 20~35°C; when the TOC of the NaCl solution after adsorption is below 8mg / L, the resource utilization of NaCl can be achieved.

[0028] Compared with the prior art, the technical effects of this application are:

[0029] The fly ash waste salt resource utilization technology provided in this application first provides a reasonably designed brine washing technology that can refine the purity of sodium chloride in the brine to the reuse standard. Secondly, a relatively comprehensive removal of TOC is achieved through moderate oxidation, electrolytic oxidation and microcrystalline adsorption. The entire process includes both physical and chemical processes; both for difficult-to-degrade organic matter and for easily degradable organic matter, so as to fully ensure that the effluent TOC meets the standards for salt production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The various technical features of the present application and the relationship between them are further explained below with reference to the accompanying drawings. The accompanying drawings are exemplary, and some technical features are not shown in actual proportion. In addition, some drawings may omit technical features that are commonly used in the technical field to which the present application belongs and are not essential for understanding and implementing the present application, or additional technical features that are not essential for understanding and implementing the present application may be shown. In other words, the combination of the various technical features shown in the accompanying drawings is not used to limit the present application. In addition, throughout the present application, the same figure numbers refer to the same content. The specific description of the drawings is as follows:

[0031] Figure 1 The main process flow chart of fly ash and waste salt resource utilization in this application is shown;

[0032] Figure 2 The flow chart of the electrolytic oxidation device in the process of resource utilization of fly ash and waste salt in the present application is shown. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solution of the present application, the technical solution of the present application is further described in detail below in conjunction with specific implementation methods.

[0034] In the prior art, the purity of sodium chloride in fly ash waste salt is low. If it is directly converted into salt, the sodium chloride cannot be recycled and can only be disposed of as hazardous waste. If the sodium chloride is recycled, due to the high salt content of the solution, it is difficult to remove TOC to below 8 mg / L in a high-salt environment with the prior art. This application effectively solves this problem.

[0035] The fly ash waste salt resource utilization technology provided by the present application not only recycles the salt in the fly ash waste salt to avoid entering the environment and causing environmental pollution, but also recycles the fly ash solid, solving the problem of fly ash waste salt disposal. First, a reasonably designed fly ash washing technology is provided, which can refine the purity of sodium chloride in fly ash to the reuse standard. The fly ash waste salt is first placed in a fly ash pool, fully dissolved and washed in the fly ash pool, and then filtered. The filtered residue is further washed with water, and the filtrate is used as washing water for other sections. After multiple rounds of multi-stage washing and filtration, the washed filter residue is used as raw materials for cement, brick making and construction. The final washing filtrate is passed through a pretreatment unit, an MBR membrane and nanofiltration to further purify the sodium chloride and separate the divalent ions therein, so that the purity of the sodium chloride reaches the reuse standard. It also provides a relatively comprehensive technology for removing total organic carbon (TOC). First, through moderate oxidation, under the conditions of high temperature, high pressure and oxidants, the difficult-to-degrade organic matter is decomposed into small molecular organic matter or part of the organic matter is directly oxidized into CO2. Then, under the action of an external electric field, the organic matter in the water is further decomposed or oxidized into CO2 through physical and chemical reactions. Finally, through microcrystal adsorption, it is ensured that the TOC of the effluent meets the salt production standards.

[0036] The fly ash waste salt resource utilization technology provided in this application includes the following steps:

[0037] (1) Washing

[0038] First, the fly ash and waste salt are placed in the fly ash pool, where they are fully dissolved and washed, and then filtered. The filter residue is further washed after filtration, and the filtrate is used as washing water for other sections. After multiple rounds of multi-stage washing and filtration, the washed filter residue is used as raw materials for cement, brick making and construction, and the final washed filtrate enters the pretreatment unit.

[0039] In some embodiments, the water washing adopts 2 rounds of water washing or 3 rounds of water washing, and each round of water washing includes multi-stage water washing and multi-stage filtration. In some embodiments, each round of water washing includes three-stage water washing and three-stage filtration. In some embodiments, the last stage of water washing residue in each round is used as raw materials such as cement, brick making and construction, and each stage filtrate is used as water for washing in other stages or the next round.

[0040] In some embodiments, the fly ash pond is designed as two sets, one for dissolving salt and one for taking in water, which are operated alternately, and the hydraulic retention time of each fly ash pond is 1 to 3 hours, preferably 2 hours. The salt is dissolved in batches, and the stirring device is a frame or paddle stirrer, and the stirring speed is 60 to 130 r / min.

[0041] (2) Preprocessing unit

[0042] The pH of the solution is adjusted to alkaline, and then sodium carbonate solution is added to make the calcium ions generate calcium carbonate precipitates, which are then enriched at the bottom of the sedimentation tank through sedimentation; the calcium carbonate precipitates at the bottom are pumped to a plate and frame filter press for dehydration, the filtrate returns to the MBR membrane pool, and the filter cakes are transported out for disposal.

[0043] In some embodiments, the pretreatment unit is designed as two sets to ensure continuous and stable operation, and the pretreatment unit includes reaction, precipitation and plate and frame filter press. The hydraulic retention time of each reaction section is 20 to 40 minutes, preferably 30 minutes, and the hydraulic retention time of the precipitation section is 30 to 90 minutes, preferably 60 minutes. The precipitation uses inclined plate precipitation, and the bottom precipitation is transported and disposed of after plate and frame filter press, and the supernatant overflows to the MBR membrane pool.

[0044] In some embodiments, the alkali adding device includes three parts: an alkali preparation system, a metering dosing system, and a control system. The pH modulation range of the pretreatment unit reaction section is 10-12, preferably 10; the alkali adjustment is preferably a 5%-15% dilute sodium hydroxide solution. After the alkali adjustment, a sufficient amount of sodium carbonate solution is added, preferably with a concentration of 10%-30%. The reaction section stirring device adopts a frame or paddle stirrer, and the stirring speed is 30-100r / min.

[0045] (3) MBR membrane

[0046] The pretreatment supernatant and the filtrate from the plate and frame filter press enter the MBR membrane pool, and the submerged MBR membrane is used to achieve solid-liquid separation and ensure the water quality of the nanofiltration inlet.

[0047] In some embodiments, the MBR membrane is designed to be ≥2 sets to ensure continuous and stable operation of the system. The MBR membrane is an immersed MBR hollow fiber membrane, with a design flux of ≤12.5L / (m2·h), a single membrane area of ​​12m2, an operating pH of 6.5~7, an operating temperature of 25~35℃, an operating pressure of -30kPa~0 kPa, a backwash pressure of 30~100 kPa, and a membrane pore size of 0.2μm.

[0048] (4) Nanofiltration

[0049] The monovalent salt and the divalent salt in the solution are separated by the interception effect of the nanofiltration membrane to improve the purity of the sodium chloride; the acid is adjusted in the intermediate water tank 1, and the washing filtrate after the acid adjustment is used as the inlet water for moderate oxidation.

[0050] In some embodiments, the nanofiltration membrane is designed to be ≥2 sets to ensure continuous and stable operation of the system. The nanofiltration membrane has a designed flux of 15L / (m2·h), an operating pressure of 0.5~1.0MPa, and a membrane pore size of more than 1nm. The nanofiltration produced water enters the intermediate water tank 1, and the concentrated water returns to the pretreatment unit.

[0051] In some embodiments, the acid adjustment device of the intermediate water tank 1 includes three parts: an acid preparation system, a metering dosing system and a control system. The pH adjustment range is 2 to 6; preferably, it is a 2% to 8% dilute hydrochloric acid solution.

[0052] (5) Alleviate oxidation

[0053] Under certain temperature and pressure conditions, the oxidant is mainly H2O2 or O2, etc., which oxidizes and decomposes pollutants such as TOC and NH3-N in the wastewater, and the effluent enters the intermediate water tank 2.

[0054] In some embodiments, the moderate oxidation conditions are as follows: the oxidant is H2O2 or O2, preferably H2O2, the addition concentration of H2O2 is 0.1%~1%, preferably 0.1%~0.5%, the temperature is 120℃~220℃, and the reaction pressure is 0.5~3.0MPa.

[0055] (6) Electrolytic oxidation

[0056] The water from the middle water tank 2 enters the electrolytic oxidation device, and under the action of the external electric field, the pollutants in the water are efficiently purified through physical and chemical reactions.

[0057] In some embodiments, the current density of the electrolytic oxidation device is generally 1~10 A / dm2, preferably 1~5A / dm2, and the preferred material is diamond doped with boron or titanium substrate coated with graphene, etc., preferably diamond doped with boron, and the hydraulic retention time of the electrolytic oxidation device is 10~60min, preferably 10~30min.

[0058] In some embodiments, the electrolytic oxidation device includes a water inlet unit, an electrolytic oxidation unit, a waste gas treatment unit, and a water outlet unit. The water inlet unit includes a sewage pump, a water inlet tank, an online conductivity meter, etc.; the electrolytic oxidation unit includes a water inlet pump, an oxidation tank, a direct current source, and a slag liquid sedimentation tank; the waste gas treatment unit includes an induced draft fan, a washing tower, an alkali liquid storage tank, and a sludge tank; the water outlet unit includes a water outlet pump, a reflux pump, an online detection device, etc. The electrolytic oxidation device is equipped with a cooling device, which uses a shell and tube heat exchanger or a plate heat exchanger to ensure that the temperature of the liquid in the electrolytic device is lower than 60°C.

[0059] (7) Microcrystal adsorption

[0060] The huge specific surface area of ​​the microcrystalline adsorption material can adsorb TOC in the water to ensure that the effluent TOC meets the standard. Due to the high purity of the effluent salt, it can directly enter the salt-making process section of the factory.

[0061] In some embodiments, the material used for microcrystalline adsorption is artificial hydrothermal synthesis of aluminosilicate crystals, the liquid flow rate is 0.5-1 BV / H, and the adsorption temperature is 20-35° C. When the TOC of the NaCl solution after adsorption is below 8 mg / L, the resource utilization of NaCl can be achieved.

[0062] The embodiments of the present invention will be described in detail below in conjunction with examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer.

[0063] Example 1

[0064] A certain incineration power plant in Zhenhai produces 100,000 tons of fly ash waste salt every year. The fly ash waste salt has a high salt content and contains certain organic matter. The organic matter is highly stable and difficult to degrade at high temperatures. The fly ash waste salt treatment volume and chlorine content are shown in Table 1.

[0065] Table 1 Table of fly ash waste salt treatment capacity and chlorine content in Example 1

[0066]

[0067] As shown in Table 1, the incineration power plant produces an average of 12.5 tons of fly ash waste salt per hour, with soluble matter of 35.55%, chlorine content of 17.23%, and TOC of 104 mg / L. According to the owner's requirements, sodium chloride needs to be recycled, and the final solution sodium chloride concentration is more than 20%, purity is more than 99.5%, and TOC ≤ 8 mg / L. With this process method, the effluent can meet the owner's requirements, and the system is stable. The technical parameters of the main process sections are as follows.

[0068] (1) Washing: Washing is done in batch mode, with one batch every three hours and one round of washing every hour, that is, each batch uses three rounds of washing, and each round of washing has three stages. 50 tons of desalted water is added to each batch. After three rounds of three-stage washing and filtration, 43.56 tons of washing filtrate and 43.94 tons of washing residue are produced. The washing residue is used as raw materials for cement, brick making and construction. The NaCl concentration of the washing filtrate is 21%~22%, and the TOC is 67.45 mg / L.

[0069] (2) Pretreatment unit: Add 1 ton / hour of 5% sodium hydroxide solution to adjust the pH to 10-12, then add 0.38 ton / hour of 20% sodium carbonate solution to convert the calcium ions in the solution into calcium carbonate precipitate, and stir and mix thoroughly. Then, the inclined plate is precipitated for 1 hour, and the bottom precipitate is filtered through plate and frame to form 0.4 ton / hour of filter residue with a moisture content of 80%, which is transported and disposed of. The supernatant in the sedimentation tank and the liquid after the plate and frame filtration enter the MBR membrane pool.

[0070] (3) MBR membrane: Two sets are designed, each with a design flow rate of 32 m3 / h. The design flux of the submerged MBR hollow fiber membrane is 12.5 L / (m2·h), the working pressure is -30 kPa, the backwash pressure is 50 kPa, and the membrane pore size is 0.2 μm.

[0071] (4) Nanofiltration: 4 groups are designed, each with a design flow rate of 16 m3 / h, a nanofiltration membrane design flux of 15 L / (m2·h), an operating pressure of 0.5~1.0 MPa, and a membrane pore size of more than 1 nm. Nanofiltration produced water of 48.55 m3 / h enters the intermediate water tank 1, and concentrated water of 12.14 m3 / h returns to the pretreatment unit. The sodium chloride concentration of nanofiltration produced water is 18.76% and the purity is 98.6%.

[0072] (5) Mild oxidation: Use 5% dilute hydrochloric acid solution to adjust the pH of the brine to about 4, and use 0.3% H2O2 as an oxidant. Under the conditions of 140℃ and 1MPa, TOC in the brine is efficiently removed and degraded. After mild oxidation, TOC is reduced to 19.51 mg / L.

[0073] (6) Electrolytic oxidation: The current density is 5 A / dm2, the material is diamond doped with boron, and the hydraulic retention time is 10 min. The role of electrolytic oxidation is to further remove TOC in the brine. After electrolytic oxidation, TOC is reduced to below 7 mg / L.

[0074] (7) Microcrystalline adsorption: To ensure that the TOC of the effluent meets the standard, the SS of the effluent after microcrystalline adsorption is almost 0, the TOC is still below 6 mg / L, the sodium chloride concentration is 20%~21%, and the purity is above 99.5%. Regardless of TOC, sodium chloride concentration and purity, they all meet the reuse standards.

[0075] Example 2

[0076] A certain incineration power plant in Hangzhou produces 30,000 tons of fly ash waste salt every year. The fly ash waste salt has a high salt content and is mainly composed of Ca, Cl, and Na elements. The soluble salt content is mostly between 10% and 30%. The fly ash waste salt treatment capacity and chlorine content are shown in Table 2.

[0077] Table 2 Table of fly ash waste salt treatment capacity and chlorine content in Example 2

[0078]

[0079] As shown in Table 2, the incineration power plant produces an average of 3.75 tons of fly ash waste salt per hour, with soluble matter of 33.5%, chlorine content of 18%, and TOC of 133 mg / L. According to the owner's requirements, sodium chloride needs to be recycled, and the final solution sodium chloride concentration is more than 20%, purity is more than 99.5%, and TOC ≤ 8 mg / L. With this process method, the effluent can meet the owner's requirements, and the system is stable. The technical parameters of the main process sections are as follows.

[0080] (1) Washing: Washing is done in batch mode, with one batch every three hours and one round of washing every hour, that is, each batch uses three rounds of washing, and each round of washing has three stages. 15 tons of desalted water is added to each batch. After three rounds of three-stage washing and filtration, 12.65 tons of washing filtrate and 13.60 tons of washing residue are produced. The washing residue is used as raw materials for cement, brick making and construction. The NaCl concentration of the washing filtrate is 22%~23%, and the TOC is 101.27 mg / L.

[0081] (2) Pretreatment unit: Add 0.29 tons / hour of 5% sodium hydroxide solution to adjust the pH to 10-12, then add 0.11 tons / hour of 20% sodium carbonate solution to convert the calcium ions in the solution into calcium carbonate precipitate, and stir and mix thoroughly. Then, the inclined plate is precipitated for 1 hour, and the bottom precipitate is filtered through plate and frame to form 0.12 tons / hour of filter residue with a moisture content of 80% for external disposal. The supernatant in the sedimentation tank and the liquid after plate and frame filtration enter the MBR membrane pool.

[0082] (3) MBR membrane: Two sets are designed, each with a design flow rate of 10 m3 / h. The design flux of the submerged MBR hollow fiber membrane is 12.5 L / (m2·h), the working pressure is -30 kPa, the backwash pressure is 50 kPa, and the membrane pore size is 0.2 μm.

[0083] (4) Nanofiltration: Two groups are designed, each with a design flow rate of 10 m3 / h, a nanofiltration membrane design flux of 15 L / (m2·h), an operating pressure of 0.5~1.0 MPa, and a membrane pore size of more than 1 nm. Nanofiltration produced water of 14.14 m3 / h enters the intermediate water tank 1, and concentrated water of 3.54 m3 / h returns to the pretreatment unit. The sodium chloride concentration of nanofiltration produced water is 20.01% and the purity is 98.7%.

[0084] (5) Mild oxidation: Use 5% dilute hydrochloric acid solution to adjust the pH of the brine to about 4, and use 0.3% H2O2 as an oxidant. At 140°C and 1MPa, the TOC in the brine is efficiently removed and degraded. After moderate oxidation, the TOC is reduced to 20.15 mg / L.

[0085] (6) Electrolytic oxidation: The current density is 5 A / dm2, the material is diamond doped with boron, and the hydraulic retention time is 10 min. The role of electrolytic oxidation is to further remove TOC in the brine. After electrolytic oxidation, TOC is reduced to below 8 mg / L.

[0086] (4) Microcrystalline adsorption: To ensure that the TOC of the effluent meets the standard, the SS of the effluent after microcrystalline adsorption is almost 0, the TOC is still below 8 mg / L, the sodium chloride concentration is 22%~23%, and the purity is above 99.5%. Regardless of TOC, sodium chloride concentration and purity, they all meet the reuse standards.

[0087] Unless otherwise defined, all technical and scientific terms used in this application are the same as those generally understood by those skilled in the art to which this application belongs. If there is any inconsistency, the meaning described in the full text of this application or the meaning derived from the content recorded in the full text of this application shall prevail. In addition, the terms used in this description are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

Claims

1. A method for resource utilization of fly ash and waste salt, characterized in that: The following steps are involved: (1) Washing: First, the fly ash waste salt is placed in the fly ash pool to dissolve and wash, then filtered, and the filter residue is further washed with water. The filtrate is used as the washing water for other stages. After multiple rounds of multi-stage washing and filtration, the washed filter residue is used as the raw material for cement, brick making and construction. The final washing filtrate enters the pretreatment unit; (2) Pretreatment unit: The pH of the solution is adjusted to alkaline, and then sodium carbonate solution is added to make the calcium ions generate calcium carbonate precipitates, and then the calcium carbonate precipitates are enriched at the bottom of the sedimentation tank through sedimentation; The calcium carbonate precipitate at the bottom is pumped to the plate and frame filter press for dehydration, the filtrate returns to the MBR membrane pool, and the filter cake is transported out for disposal; (3) MBR membrane: The pretreatment supernatant and the filtrate from the plate and frame filter press enter the MBR membrane pool, and the submerged MBR membrane is used to achieve solid-liquid separation and ensure the water quality of the nanofiltration inlet; (4) Nanofiltration: Through the interception effect of the nanofiltration membrane, the monovalent salt and divalent salt in the solution are separated to improve the purity of sodium chloride; Acid adjustment is performed in the intermediate water tank 1, and the water washing filtrate after acid adjustment is used as the influent water for relieving oxidation; (5) Mild oxidation: The oxidant H2O2 or O2 is used to oxidize and decompose the influent water, and the effluent enters the intermediate water tank 2; (6) Electrolytic oxidation: Electrolytic oxidation is carried out under the action of an external electric field, and the effluent serves as the influent for microcrystal adsorption; (7) Microcrystalline adsorption: The huge specific surface area of ​​the microcrystalline adsorption material can adsorb TOC in the water to ensure that the effluent TOC meets the standard. Due to the high purity of the effluent salt, it can directly enter the salt production process section of the factory.

2. The fly ash waste salt resource utilization method according to claim 1, characterized in that: In step (1), the dissolution is carried out in a batch process, the stirring device is a frame or paddle stirrer, the stirring speed is 60-130 r / min, and the hydraulic retention time of the fly ash pool is 1-3 h; In step (1), the water washing adopts 2 rounds of water washing or 3 rounds of water washing, each round of water washing includes three-stage water washing and three-stage filtration, the filter residue of the three-stage water washing is used as raw material for cement, brick making and construction, and the filtrate of each stage is used as water for washing in other stages or the next round.

3. The fly ash waste salt resource utilization method according to claim 1, characterized in that: In step (2), the pretreatment unit includes reaction, precipitation and plate and frame filtration. The hydraulic retention time of the reaction section is 20-40 min. Sodium hydroxide solution is first added to adjust the pH to 10-12, and then sodium carbonate solution is added to precipitate calcium ions therein into calcium carbonate. The hydraulic retention time of the precipitation section is 30-90 min. Inclined plate precipitation is adopted. The bottom precipitate is transported for disposal after plate and frame filtration, and the supernatant overflows to the MBR membrane pool.

4. The method for resource utilization of fly ash and waste salt according to claim 1, characterized in that: In step (3), the MBR membrane is an immersed MBR hollow fiber membrane with a designed flux of ≤12.5L / (m 2 ·h), the filtration pressure is -30kPa ~0 kPa, the backwash pressure is 30 ~100 kPa, and the membrane pore size is 0.2μm.

5. The fly ash waste salt resource utilization method according to claim 1, characterized in that: In step (4), the nanofiltration membrane is designed to have a flux of 15 L / (m 2 ·h), the operating pressure is 0.5~1.0MPa, the membrane pore size is above 1nm; the nanofiltration water enters the intermediate water tank 1, and the concentrated water returns to the pretreatment unit; In step (4), the acid adjustment device includes an acid preparation system, a metering system and a control system, and the pH of the solution in the intermediate water tank 1 is adjusted to 2-6; a 2%-8% dilute hydrochloric acid solution is used.

6. The method for resource utilization of fly ash and waste salt according to claim 1, characterized in that: In step (5), the moderate oxidation conditions are as follows: the oxidant is H2O2 or O2, the H2O2 addition concentration is 0.1% to 1%, the reaction temperature is 120°C to 220°C, and the reaction pressure is 0.5 to 3.0 MPa.

7. The method for resource utilization of fly ash and waste salt according to claim 1, characterized in that: In step (6), the electrolytic oxidation device includes a water inlet unit, an electrolytic oxidation unit, a waste gas treatment unit, and a water outlet unit; the electrolytic oxidation unit includes a water inlet pump, an oxidation tank, a direct current, and a slag liquid sedimentation tank; the waste gas treatment unit includes an induced draft fan, a washing tower, an alkali solution storage tank, and a slag sedimentation tank.

8. The method for resource utilization of fly ash and waste salt according to claim 1, characterized in that: In step (6), the current density of the electrolytic oxidation device is 1-10 A / dm 2 The material is diamond doped with boron or titanium substrate coated with graphene, and the hydraulic retention time of the device is 10~60min.

9. The method for resource utilization of fly ash and waste salt according to claim 7 or 8, characterized in that: The electrolytic oxidation device is equipped with a cooling device, which adopts a shell-and-tube heat exchanger or a plate heat exchanger to ensure that the temperature of the liquid in the electrolytic device is lower than 60°C.

10. The method for resource utilization of fly ash and waste salt according to claim 1, characterized in that: In step (7), the material used for the microcrystalline adsorption is an artificial hydrothermally synthesized aluminosilicate crystal, the liquid flow rate is 0.5~1BV / H, and the adsorption temperature is 20~35°C; when the TOC of the NaCl solution after adsorption is below 8mg / L, the resource utilization of NaCl can be achieved.

Images