Phosphate flame retardant production wastewater treatment method

Abstract

The invention provides a phosphate flame retardant production wastewater treatment method which comprises the following steps: pretreatment; adjusting the pH value; precipitating and separating; rectification: introducing the precipitated and separated wastewater into a rectification tower, carrying out continuous rectification, and respectively collecting samples from the tower top, the tower tower and the tower kettle; cooling and crystallizing to obtain a mixture of NaCl and TiO2; spraying, washing, filtering and refining to obtain a TiO2 product; evaporating and crystallizing, namely introducing a filtrate obtained by spraying and washing the mixture of NaCl and TiO2 into a rotary evaporator for concentrating and crystallizing to obtain an industrial NaCl product; extracting, namely collecting filtrate obtained by spraying and washing the mixture of NaCl and TiO2, adding a mixed extracting agent for extracting, and recovering to obtain a phosphate product; and returning the residual extract liquor in the last step to be mixed with the wastewater in the fourth step, and introducing the mixture into a rectifying tower for circular treatment. According to the invention, the precipitation effect of suspended solids in wastewater can be improved, pollutants in the wastewater can be effectively separated in an energy-saving manner, and the drainage pollution is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of phosphate ester wastewater treatment, and in particular to a method for treating phosphate ester flame retardant production wastewater. Background Art

[0002] With the rapid development of industrialization, a large amount of difficult-to-degrade organic wastewater is usually produced in the production process of phosphate flame retardants, and phosphorus-containing wastewater is discharged into the environment, causing serious pollution to the water body. It mainly comes from process wastewater (distillation, water washing and other steps), equipment cleaning wastewater and phosphate flame retardant waste spray treatment wastewater. Phosphate flame retardant wastewater contains a large amount of raw materials, by-products and incompletely reacted substances, and is a high-concentration wastewater that is difficult to biochemically treat.

[0003] The COD in the comprehensive wastewater of phosphate combustion aids is as high as 4000mg / L, the total salt is more than 10000mg / L, and the volatile phenol is more than 135mg / L. Therefore, it is a high-concentration wastewater that is difficult to treat. Since the chemical properties of this type of phosphate are stable and difficult to oxidize, it is impossible to directly use biochemical treatment to treat phenol and other components that are difficult to biodegrade or have inhibitory effects on microorganisms.

[0004] At present, the technologies used to degrade and remove organophosphorus flame retardants in water mainly include biodegradation, physical adsorption, advanced oxidation technology, etc. Generally speaking, total phosphorus mainly consists of large molecular weight and difficult-to-treat organophosphate compounds, and total phosphorus includes inorganic phosphorus and organic phosphorus. Inorganic phosphorus can be removed by flocculation and precipitation, and organic phosphorus is usually treated by converting organic phosphorus into inorganic phosphorus and then removing it by flocculation and precipitation.

[0005] In the flocculation and sedimentation process, since the particles of phosphate ester and metal ions are very fine after salt formation, a part of them is dissolved in the water phase. It is necessary to add flocculants to the wastewater to help the formation of particles and precipitate the phosphate ester. However, in the prior art, most of the suspended matter is large in size, and gravity sedimentation requires a certain amount of time. In addition, for a small amount of suspended matter, due to its small size and low density, it can remain in a stable suspended state in the dispersion system for a long time, resulting in poor precipitation effect and failure to achieve the desired precipitation effect.

[0006] In addition, after the organic matter is removed from the existing wastewater, most of the filtrate is subjected to oxidation, precipitation, extraction, biochemical and other recycling treatments. Although this can remove most of the COD, TP and other indicators in the wastewater, new environmental problems such as phosphorus-containing solid waste are generated in the treatment process. Summary of the invention

[0007] In view of this, the present invention aims to propose a method for treating wastewater from the production of phosphate flame retardants, so as to improve the precipitation effect of suspended matter in the wastewater, and to effectively and energy-savingly separate pollutants in the wastewater, thereby reducing drainage pollution.

[0008] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0009] A method for treating wastewater from the production of phosphate flame retardants comprises the following steps:

[0010] Step 1: Pretreatment, passing the wastewater into a grit chamber to remove large solid particles and sediment;

[0011] Step 2: Adjusting the pH value, passing the wastewater treated in step 1 into the regulating tank through the first pump body, adding a regulator into the regulating tank, adjusting the pH value of the wastewater, and filtering;

[0012] Step 3: sedimentation and separation, the wastewater treated in step 2 is passed into the first sedimentation tank through the second pump body, a coagulant is added to the first sedimentation tank, fine suspended matter and difficult-to-degrade colloidal pollutants in the water are aggregated to form alum flowers, and the equipment is stirred to make them fully react to form larger flocs, and the flocs in the wastewater are separated once through the first sedimentation tank; the first sedimentation tank is connected to the second sedimentation tank, and the second sedimentation tank is used to perform secondary separation on the filtered water of the first sedimentation tank;

[0013] Step 4: distillation, passing the wastewater treated in step 3 into a distillation tower for continuous distillation, controlling the distillation temperature of each section in the tower, and collecting samples from the top, middle and bottom of the tower respectively;

[0014] Step 5: Cooling and crystallizing, the high boiling products collected from the bottom of the distillation tower in step 4 are passed into a condenser for cooling and crystallization to obtain a mixture of NaCl and TiO2;

[0015] Step 6: spraying, washing, filtering and refining the mixture of NaCl and TiO2 in step 5 to obtain a TiO2 product;

[0016] Step 7: Evaporation and crystallization: the filtrate in step 5 is passed into a rotary evaporator for concentration and crystallization to obtain an industrial NaCl product;

[0017] Step eight: extraction, collecting the filtrate in step six, adding a mixed extractant for extraction, recovering the phosphate product, returning the remaining extract in this step to mix with the wastewater in step four and passing it into the distillation tower for circulation treatment.

[0018] Furthermore, the first sedimentation tank comprises an inclined plate arranged below the wastewater inlet, the inclined plate is connected to a first grid, the inclined plate divides the first sedimentation tank into a waste tank and a filter tank, and the filter tank is provided with an outlet.

[0019] Furthermore, the second sedimentation tank includes a liquid inlet area, a first static area, a buffer area, and a second static area formed by division;

[0020] The liquid inlet area is provided with a liquid inlet, the second static area is provided with a liquid outlet, and the liquid outlet is communicated with the distillation tower;

[0021] The buffer area is connected to the first static area and the second static area, the buffer area is connected to the liquid inlet area through a first communication path, and the buffer area is connected to the first static area through a second communication path;

[0022] A filter is provided at the inlet of the buffer area, and the second static area is provided between the buffer area and the liquid inlet area. Wastewater flowing out of the liquid inlet area passes through the buffer area and enters the second static area after being filtered by the filter.

[0023] Furthermore, the first communication path and / or the second communication path is provided with a first switch portion;

[0024] The first communication path and / or the second communication path is also provided with a second switch portion.

[0025] Furthermore, the first communicating path and the second communicating path are both provided with a second grid, the first communicating path and the second communicating path are connected to a third communicating path, the third communicating path is connected to the inlet of the buffer area, and the third communicating path is provided with a third grid.

[0026] Furthermore, an intermediate static area is provided between the buffer area and the second static area, and a second connecting port connected to the second static area and a first connecting port connected to the buffer area are provided in the intermediate static area, and the buffer area is connected to an external vacuum device.

[0027] Furthermore, in step three, a coagulant is added into the first sedimentation tank, wherein the coagulant is lime, the CaO mass fraction is ≥80%-90%, the addition amount is 10-20 g / L, and the reaction time is 10-15 min.

[0028] Furthermore, in step three, a flocculant PAM is added into the second sedimentation tank in an amount of 0.5-1.0 mg / L, and the mixture is allowed to stand for 30-35 minutes.

[0029] Furthermore, in step 2, the pH value of the wastewater is adjusted to 12-13.

[0030] Furthermore, a reverse osmosis membrane is provided in the filter part.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The method for treating wastewater produced by phosphate flame retardant of the present invention improves the separation effect of flocculent suspension and wastewater by filtering the wastewater through a grit chamber and a first sedimentation tank, and performing secondary filtration through a second sedimentation tank. The separated wastewater is distilled to obtain low-boiling substances, soft water and high-boiling substances at the top, in the tower and in the bottom of the tower, respectively, and then the high-boiling substances are separated and purified to obtain industrial salt, TiO2 and phosphate products, thereby reducing pollutants discharged from wastewater and meeting emission standards.

[0033] In addition, by setting up a buffer area and a first static area in the second sedimentation tank, the wastewater can be fully static, and the buffering of the buffer area can prevent the water flow movement from affecting the effect of solid-liquid separation, so that the suspended particles in the wastewater flowing into the second static area are greatly reduced, thereby ensuring the sedimentation effect of the sedimentation tank and preventing the suspended matter in the wastewater from entering the distillation tower and affecting the distillation effect of the distillation tower.

[0034] In addition, by providing the first switch part and the second switch part on the first communication path and / or the second communication path, the pressure and flow rate of the wastewater entering the buffer area can be adjusted to improve the static sedimentation effect. In addition, by providing the second grid on the first communication path and the second communication path respectively, and providing the third grid on the third communication path, the floccules are separated layer by layer to improve the separation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0036] Figure 1 This is a flow chart of wastewater treatment from the production of phosphate flame retardants according to an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the connection of the phosphate flame retardant production wastewater treatment equipment according to an embodiment of the present invention;

[0038] Figure 3 It is a schematic diagram of the longitudinal cross-sectional structure of the second sedimentation tank according to an embodiment of the present invention;

[0039] Figure 4 This is an analysis diagram of the influence of the mass fraction of water in PO on the mass fraction of NaCl, the consumption percentage of raw material POCl3, and the increase of the mass fraction of PO during distillation according to an embodiment of the present invention;

[0040] Figure 5 This is the result of treating the wastewater from the production of the phosphate flame retardant described in the embodiment of the present invention.

[0041] Description of reference numerals:

[0042] 1. Grit chamber; 2. First pump body; 3. Regulating tank; 4. Second pump body; 5. First sedimentation tank; 6. Second sedimentation tank; 7. Distillation tower; 8. Condensation tank; 9. Spray tower; 10. Rotary evaporator; 11. Extraction tower; 12. External vacuum device;

[0043] 501, inclined plate; 502, first grille;

[0044] 601, liquid inlet area; 602, first static area; 603, buffer area; 604, second static area; 605, filter part; 606, first switch part; 607, second switch part; 608, second grid; 609, third grid; 610, intermediate static area;

[0045] 6011, liquid inlet;

[0046] 6021. Liquid outlet;

[0047] 6031, first communication port;

[0048] 6041. Second connecting port. DETAILED DESCRIPTION

[0049] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0050] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "inner", "back", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0051] In addition, in the description of the present invention, unless otherwise clearly defined, the terms "installed", "connected", "connected", and "connector" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in combination with specific circumstances.

[0052] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0053] This embodiment relates to a method for treating wastewater from the production of phosphate flame retardants. It should be noted that, since there are many types of phosphate flame retardants, but each type of phosphate flame retardant contains pollutants such as COD and TP, this embodiment is described by taking TCPP phosphate flame retardant production wastewater as an example. Since TCPP phosphate flame retardant wastewater mainly contains TCPP, propylene oxide, sodium chloride, titanium dioxide, etc. The above components are all dissolved in water in a homogeneous state and are difficult to separate. Therefore, this embodiment adopts a process method of pre-treating the wastewater, precipitation separation, distillation, crystallization, and extraction for treatment.

[0054] Based on the above overall introduction, as Figure 1 As shown, the method for treating phosphate flame retardant production wastewater in this embodiment includes the following steps:

[0055] Step 1: Pretreatment, passing the wastewater into a grit chamber 1 to remove large solid particles and sediment;

[0056] Step 2: Adjusting the pH value, passing the wastewater treated in step 1 into the regulating tank 3 through the first pump body 2, adding a regulator into the regulating tank 3, adjusting the pH value of the wastewater, and filtering;

[0057] Step 3: Sedimentation and separation. The wastewater treated in step 2 is passed into the first sedimentation tank 5 through the second pump body 4. A coagulant is added to the first sedimentation tank 5 to make the fine suspended matter and the difficult-to-degrade colloidal pollutants in the water aggregate with each other to form alum flowers, and the equipment is used to stir them to fully react to form larger flocs. The flocs in the wastewater are separated once through the first sedimentation tank 5. The first sedimentation tank 5 is connected to the second sedimentation tank 6, and the second sedimentation tank 6 is used to perform secondary separation on the filtered water of the first sedimentation tank 5.

[0058] Step 4: distillation, the wastewater treated in step 3 is passed into the distillation tower 7 for continuous distillation, the distillation temperature of each section in the tower is controlled, and samples are collected from the top, the middle and the bottom of the tower respectively;

[0059] Step 5: Cooling and crystallizing, the high boiling products collected from the bottom of the distillation tower 7 in step 4 are passed into a condenser 8 for cooling and crystallization to obtain a mixture of NaCl and TiO2;

[0060] Step 6: spraying, washing, filtering and refining the mixture of NaCl and TiO2 in step 5 to obtain a TiO2 product;

[0061] Step 7: Evaporation and crystallization: the filtrate in step 5 is passed into a rotary evaporator 10 for concentration and crystallization to obtain an industrial NaCl product;

[0062] Step eight: extraction, collect the filtrate in step six, add a mixed extractant for extraction, recover the phosphate product, return the remaining extract in this step to mix with the wastewater in step four and pass it into the distillation tower 7 for circulation treatment.

[0063] Based on the above overall introduction, Figure 1 and Figure 2 As shown, the equipment used in the method for treating wastewater from the production of phosphate flame retardants in this embodiment includes, in order, a grit chamber 1, a regulating tank 3, a first sedimentation tank 5, a second sedimentation tank 6, a distillation tower 7, a condensation tank 8, a spray tower 9, an extraction tower 11, etc. It also includes a first pump body 2 and a second pump body 4 for conveying wastewater.

[0064] The method for treating wastewater produced by phosphate flame retardant of this embodiment is to filter the wastewater through the grit chamber 1 and the first sedimentation tank 5, and then perform secondary filtration through the second sedimentation tank 6, so as to improve the separation effect of flocculent suspended matter and wastewater in the wastewater. After the separated wastewater is distilled, low-boiling substances, soft water and high-boiling substances are obtained at the top of the tower, in the tower and in the bottom of the tower respectively, and then the high-boiling substances are separated and purified to obtain industrial salt, TiO2 and phosphate products, thereby reducing the pollutants discharged in the wastewater and meeting the emission standards.

[0065] Combination Figure 1 and Figure 2 As shown, the first sedimentation tank 5 includes an inclined plate 501 disposed below the wastewater inlet, and a first grid 502 is connected to the inclined plate 501. The inclined plate 501 divides the first sedimentation tank 5 into a waste material tank and a filter tank, and the filter tank is provided with an outlet. By providing the inclined plate 501, the contact time between the wastewater and the first grid 502 can be increased, and the flow area between the wastewater and the inclined plate 501 is increased, which is conducive to separating solid particles in the wastewater and avoiding wear on subsequent treatment equipment.

[0066] Preferably, if Figure 3 As shown, the second sedimentation tank 6 includes a liquid inlet area 601, a first static area 602, a buffer area 603, and a second static area 604, which are divided. The liquid inlet area 601 is provided with a liquid inlet 6011, and the second static area 604 is provided with a liquid outlet 6021, and the liquid outlet 6021 is connected to the distillation tower 7. The buffer area 603 is connected to the first static area 602 and the second static area 604, and the buffer area 603 is connected to the liquid inlet area 601 through a first communication path, and the buffer area 603 is connected to the first static area 602 through a second communication path;

[0067] In addition, Figure 3As shown, a filter unit 605 is provided at the inlet of the buffer area 603, and the second static area 604 is provided between the buffer area 603 and the liquid inlet area 601. The wastewater flowing out of the liquid inlet area 601 passes through the buffer area 603 and enters the second static area 604 after being filtered by the filter unit 605.

[0068] Still Figure 3 As shown, the liquid inlet area 601 is separated from the second static area 604 by the first static area 602 and the buffer area, which can effectively avoid the confusion of solid and liquid caused by the liquid inlet process and the radial static sedimentation effect.

[0069] In the first sedimentation tank 5 of this embodiment, the coagulant is CaO powder with high activity, CaO mass fraction ≥ 80%-90%, added in an amount of 10-20g / L, pH value can be adjusted to 10-12, and the reaction time is 10-15min. Then, the flocculant PAM is added to the second sedimentation tank 6, the addition amount is 0.5-1.0mg / L, and it is left to stand for 30-35min.

[0070] With such an arrangement, the coagulant and flocculant are added to two sedimentation tanks separately to avoid the premature addition of PAM, which causes the calcium ions to enter the coagulation reaction without being completely released to react with PO43-. Some CaO is wrapped in large molecular clusters and sinks without playing a role, which not only wastes raw materials but also increases a large amount of sludge. Later, CaO will dissolve back to form Ca(OH)2, which will increase the pH value and interfere with the stability of the pH value of the discharged wastewater.

[0071] It should be pointed out that after the reaction in the first sedimentation tank 5, all phosphates are converted into hydroxyapatite. When PAM is added to the second sedimentation tank 6, organic suspended matter and petroleum in the wastewater can be adsorbed to produce copolymer precipitation, thereby reducing the CODcr in the wastewater. In addition, when the wastewater flows from the first sedimentation tank 5 to the second sedimentation tank 6, the flow rate of the wastewater is reduced from 0.5-0.6 m / s to 0.1-0.2 m / s to prevent the enlarged flocs from breaking. The flocs in the second sedimentation tank 6 continue to collide with the flocculant, and the size of the alum flocs is further increased to 0.6-1.0 mm, reaching the conditions of gravity precipitation and sinking.

[0072] In this embodiment, a buffer area 603 and a first static area 602 are set in the second sedimentation tank 6 to allow the wastewater to be fully static. The buffering of the buffer area 603 prevents the water flow from affecting the solid-liquid separation effect, so that the suspended particles in the wastewater flowing into the second static area 604 are greatly reduced, thereby ensuring the sedimentation effect of the sedimentation tank and preventing the suspended matter in the wastewater from entering the distillation tower 7 and affecting the distillation effect of the distillation tower 7.

[0073] Preferably, if Figure 3As shown, the first communication path and the second communication path are provided with a first switch part 606, and the first communication path and the second communication path are further provided with a second switch part 607. The first switch part 606 of this embodiment adopts a constant flow valve, and the second switch part 607 adopts a pressure valve. By providing the first switch part 606, it can be ensured that the water flow in the first communication path and the second communication path does not impact, and the water flow in the buffer area 603 is stable, providing a guarantee for static sedimentation. By providing the second switch part 607, it can be ensured that the pressure in the circulation process is stable, thereby further ensuring the static effect.

[0074] Further, as Figure 3 As shown, the first communication path and the second communication path are both provided with a second grille 608 , the first communication path and the second communication path are connected to the third communication path, the third communication path is connected to the inlet of the buffer area 603 , and the third communication path is provided with a third grille 609 .

[0075] By setting the second grid 608 on the first communication path and the second communication path respectively, and setting the third grid 609 on the third communication path, the floccules are separated layer by layer. Such a setting can effectively remove tiny suspended matter of 0.5-10.0μm, and the suspended matter content of the filtered water is below 10mg / L, making the effluent clearer, and all kinds of indicators meet the national emission standards.

[0076] In addition, by providing a reverse osmosis membrane in the filter unit 605, organic pollutants and dissolved substances in the water can be effectively filtered, iron, manganese, magnesium, calcium, etc. in the waste liquid can be removed, and hydrochloric acid can be separated from other salts, which is convenient for the extraction of NaCl in step 5 and improves the filtering effect. As a feasible implementation, the filter unit 605 of this embodiment can be set to a detachable connection mode to facilitate the replacement of the reverse osmosis membrane.

[0077] As a specific implementation method, Figure 3 As shown, an intermediate static area 610 is further provided between the buffer area 603 and the second static area 604 of this embodiment. A second connecting port 6041 communicating with the second static area 604 and a first connecting port 6031 communicating with the buffer area 603 are provided in the intermediate static area 610. The buffer area 603 is connected to the external vacuum device 12.

[0078] In this embodiment, by setting up the intermediate still area 610, the wastewater flowing out of the buffer area 603 can be allowed to stand for a second time in the intermediate still area 610, and then stand for a third time in the second still area 604. Because the suspended matter in the wastewater has been filtered multiple times at the front end of the buffer area 603, especially the filtration of dissolved matter, the still effect in the still area is increased.

[0079] Preferably, in order to increase the treatment efficiency of wastewater, the buffer area 603 is connected to the external vacuum device 12, and the vacuum device is introduced through a hose, which can quickly form a negative pressure in the buffer area 603. Combined with the adjustment of the constant flow valve, it is convenient for the waste liquid to enter the buffer area 603 from the first static area 602 and the liquid inlet area 601. Of course, before this operation, the first communication port 6031 needs to be blocked to avoid causing fluctuations in the water flow in the middle static area 610.

[0080] In the specific implementation, 40 tons / day of TCPP phosphate wastewater is treated, the organic phosphorus in the wastewater is TP1383 mg / L, TCPP4801 mg / L, NaCl4530 mg / L, TiO258 mg / L, PO1565 mg / L, COD8205.5 mg / L, and the water content is 95%. After the above steps, the effluent COD is ≤500 mg / L, and the organic phosphorus is ≤0.5 ppm. Figure 5 As shown in the data table of treated phosphate wastewater, it can be seen that converting phosphate wastewater into propylene oxide, sodium chloride, titanium dioxide and TCPP products and process soft water to realize the utilization of phosphate flame retardant wastewater not only eliminates pollution but also saves resources.

[0081] During the distillation process, when the operating pressure, reflux ratio, tower bottom, tower side and tower top temperatures reach certain conditions, increasing the number of pedals in the distillation tower 7 can make the PO4 and moisture content in the tower bottom liquid, the COD and TP indicators of the tower side soft water all show a downward trend. In this embodiment, the number of plates of the distillation tower 7 is 60.

[0082] In addition, in the recovery of PO at the top of the distillation tower, the main impurity in the recovered PO is water, which easily leads to the hydrolysis of phosphorus oxychloride, resulting in an increase in the consumption of phosphorus oxychloride raw materials, thereby affecting the production cost of TCPP products. Figure 4 As shown in the figure, as the mass fraction of water in the recovered PO decreases, the mass fraction of by-product NaCl increases, the consumption of raw material POCl3 decreases, and the mass fraction of PO increases. When the quality of the recovered PO is close to that of industrial PO, it has no obvious effect on the production of TCPP. Therefore, by controlling the mass fraction of water in PO during the distillation operation, the PO recovered from the top of the tower can be reused in the production of TCPP phosphate flame retardant.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for treating wastewater from the production of phosphate flame retardants, characterized in that: The following steps are included: Step 1: Pretreatment, the wastewater is passed into a grit chamber (1) to remove large solid particles and sediment; Step 2: Adjusting the pH value, passing the wastewater treated in step 1 into the regulating tank (3) through the first pump body (2), adding a regulator into the regulating tank (3), adjusting the pH value of the wastewater, and filtering; Step 3: sedimentation and separation, the wastewater treated in step 2 is passed into the first sedimentation tank (5) through the second pump body (4), a coagulant is added to the first sedimentation tank (5), fine suspended matter and difficult-to-degrade colloidal pollutants in the water are aggregated to form alum flocs, and the equipment is used to stir them to fully react to form larger flocs, and the flocs in the wastewater are separated once through the first sedimentation tank (5); The first sedimentation tank (5) is connected to a second sedimentation tank (6), and the second sedimentation tank (6) is used to perform secondary separation on the filtered water of the first sedimentation tank (5); Step 4: distillation, passing the wastewater treated in step 3 into a distillation tower (7) for continuous distillation, controlling the distillation temperature of each section in the tower, and collecting samples from the top, the middle and the bottom of the tower respectively; Step 5: Cooling and crystallizing, the high boiling products collected from the bottom of the distillation tower (7) in step 4 are passed into a condenser (8) for cooling and crystallization to obtain a mixture of NaCl and TiO2; Step 6: spraying, washing, filtering and refining the NaCl and TiO2 mixture in step 5 to obtain a TiO2 product; Step 7: Evaporation and crystallization: the filtrate in step 5 is passed into a rotary evaporator (10) for concentration and crystallization to obtain an industrial NaCl product; Step eight: extraction, collecting the filtrate in step six and adding a mixed extractant for extraction to recover the phosphate ester product, returning the remaining extract in this step to mix with the wastewater in step four and passing it into the distillation tower (7) for circulation treatment.

2. The method for treating wastewater from the production of phosphate flame retardants according to claim 1, characterized in that: The first sedimentation tank (5) comprises an inclined plate (501) arranged below the wastewater inlet, the inclined plate (501) being connected to a first grid (502), the inclined plate (501) dividing the first sedimentation tank (5) into a waste material tank and a filter tank, the filter tank being provided with an outlet.

3. The method for treating wastewater from the production of phosphate flame retardants according to claim 2, characterized in that: The second sedimentation tank (6) includes a liquid inlet area (601), a first static area (602), a buffer area (603), and a second static area (604) which are divided; The liquid inlet region (601) is provided with a liquid inlet (6011), the second static region (604) is provided with a liquid outlet (6021), and the liquid outlet (6021) is connected to the distillation tower (7); The buffer area (603) is connected to the first static area (602) and the second static area (604), the buffer area (603) is connected to the liquid inlet area (601) through a first connecting path, and the buffer area (603) is connected to the first static area (602) through a second connecting path; The inlet of the buffer area (603) is provided with a filter part (605), and the second static area (604) is provided between the buffer area (603) and the liquid inlet area (601). Wastewater flowing out of the liquid inlet area (601) passes through the buffer area (603) and enters the second static area (604) after being filtered by the filter part (605).

4. The method for treating wastewater from the production of phosphate flame retardants according to claim 3, characterized in that: The first communication path and / or the second communication path is provided with a first switch part (606); The first communication path and / or the second communication path is also provided with a second switch portion (607).

5. The method for treating wastewater from the production of phosphate flame retardants according to claim 3, characterized in that: The first communicating path and the second communicating path are both provided with a second grille (608), the first communicating path and the second communicating path are connected to a third communicating path, the third communicating path is connected to the inlet of the buffer area (603), and the third communicating path is provided with a third grille (609).

6. The method for treating wastewater from the production of phosphate flame retardants according to claim 3, characterized in that: An intermediate static area (610) is also provided between the buffer area (603) and the second static area (604); a second communication port (6041) communicating with the second static area (604) and a first communication port (6031) communicating with the buffer area (603) are provided in the intermediate static area (610); and the buffer area (603) is connected to an external vacuum device (12).

7. The method for treating wastewater from the production of phosphate flame retardants according to claim 2, characterized in that: In step three, a coagulant is added into the first sedimentation tank (5). The coagulant is lime, the CaO mass fraction is ≥ 80%-90%, the addition amount is 10-20 g / L, and the reaction time is 10-15 min.

8. The method for treating wastewater from the production of phosphate flame retardants according to claim 3, characterized in that: In step three, add flocculant PAM in the second sedimentation tank (6) at an amount of 0.5-1.0 mg / L and let stand for 30-35 minutes.

9. The method for treating wastewater from the production of phosphate flame retardants according to claim 1, characterized in that: In step 2, the pH value of the wastewater is adjusted to 12-13.

10. The method for treating wastewater from the production of phosphate flame retardants according to claim 1, characterized in that: The filter part (605) is provided with a reverse osmosis membrane.

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