Method for treating POSM production wastewater

Abstract

The invention relates to the technical field of industrial production wastewater treatment, and particularly discloses a treatment method of POSM production wastewater. The treatment method provided by the invention specifically comprises the following steps: carrying out pretreatment to convert heavy metal ions into precipitates, and carrying out mild oxidation on ultra-filtered clear liquid; carrying out wet catalytic oxidation; electrolytic oxidation is carried out under the condition that the current density is 1-10 A / dm < 2 >, and the hydraulic retention time is 10-60 min; the microcrystal material is filled through targeted adsorption, the liquid overflowing speed is 0.2-1 BV / H, and the adsorption temperature is 20-35 DEG C; the wastewater enters an MVR forced circulation system for evaporation, is sent to a forced circulation heat exchanger by a crystallization separator through a forced circulation pump and then returns to the crystallization separator; and performing pyrolysis coupling. The POSM wastewater is treated by adopting the scheme, mother liquor is not left, effluent COD (Chemical Oxygen Demand) is low and stable, condensate water and salt resources can be recycled, resource reutilization is realized, and the treatment cost is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of industrial wastewater treatment, and in particular to a method for treating POSM production wastewater. Background Art

[0002] The POSM process is to produce propylene oxide, benzene and ethylene by hydrogenation reaction under the action of a specific catalyst to generate intermediate products, which are then heated and cracked to finally obtain styrene and propane. This process is widely favored due to its flexible catalyst selection, high product yield and safe and reliable operation.

[0003] The characteristic of POSM co-production is that it can co-produce two important organic chemical products, styrene and propylene oxide, by combining the endothermic reaction of ethylbenzene dehydrogenation and the exothermic reaction of propylene oxidation, thus saving energy and operating costs. The disadvantage of this method is that the reaction is complicated and there are many by-products.

[0004] The main difficulty in treating POSM production wastewater lies in its high salinity, high COD, high temperature, high alkalinity and biological toxicity. Both at home and abroad, the comprehensive treatment of such high-concentration degraded organic wastewater has been highly valued and more stringent standards have been formulated. At present, incineration technology is mostly used to treat POSM production wastewater. Although this treatment process is relatively mature and has a high pollutant removal rate, the incineration of waste liquid will produce a large amount of nitrogen oxides and waste salts. If these nitrogen oxides and waste salts are not properly handled, they will pollute the atmosphere and soil.

[0005] In the prior art, invention patent CN 112624300 A discloses a method for treating wastewater from the production of propylene oxide, which includes contacting the wastewater with a wet oxidation heterogeneous catalyst to effectively reduce the COD in the wastewater from the production of propylene oxide. Although this treatment method can reduce the COD in the propylene oxide wastewater, it cannot achieve the level of condensate reuse and salt reuse.

[0006] Therefore, it is very necessary to develop cleaner, secondary pollution-free, and cost-effective treatment technologies. Summary of the invention

[0007] In order to solve the above technical problems, the present application provides a method for treating POSM production wastewater.

[0008] The present application provides a method for treating POSM production wastewater, which specifically comprises the following steps in sequence: pretreatment, wet catalytic oxidation, electrolytic oxidation, targeted adsorption, MVR, and thermal decomposition coupling; (1) Pretreatment: The wastewater enters the regulating tank, and after the water volume is adjusted and the water quality is balanced in the regulating tank, the heavy metal ions are converted into precipitates through the reaction of Na2S solution; then after ultrafiltration, the clear liquid enters the mild oxidation, and the retained concentrated liquid is centrifuged for dehydration. The dehydrated filter residue is transported out for disposal, and the centrifuged liquid returns to the reaction section; (2) Wet catalytic oxidation: the reaction temperature is 200℃~300℃, the reaction pressure is 3~10MPa, air or oxygen is used as the oxidant, the catalyst is one or more of copper, ruthenium, and cerium catalysts, the catalyst dosage is 0.5%~5%, and the catalytic oxidation time is 2~4h; (3) Electrolytic oxidation: The material of the electrolytic device is selected from diamond doped with boron or titanium substrate coated with graphene. The temperature of the liquid in the electrolytic oxidation device is lower than 60°C, and the current density is 1~10A / dm 2 , hydraulic retention time is 10~60min; (4) Targeted adsorption: Targeted adsorption fills microcrystalline materials, the liquid flow rate is 0.2~1BV / H, and the adsorption temperature is 20~35℃; (5) MVR: The wastewater enters the MVR forced circulation system for evaporation, and is pumped from the crystallizer to the forced circulation heat exchanger through a forced circulation pump and then returns to the crystallizer. The flow rate of the heat exchanger is 2-2.2 m / s; (6) Pyrolysis: Wastewater enters the pyrolysis device, first passes through the drying section, and then enters the pyrolysis section.

[0009] In the wastewater treatment method provided in the present application, step (1) is pretreatment: the wastewater from the combined production process of propylene oxide and styrene (POSM) first enters the regulating tank, and after the water volume is adjusted and the water quality is balanced in the regulating tank, it undergoes reaction precipitation to remove Cu in the wastewater. 2+ Cr 3+ 、Mo 4+Heavy metal ions such as ions are removed by moderate oxidation, and most of the organic matter in the wastewater is removed while reducing the pH value of the wastewater. Step (2) is wet catalytic oxidation, using air or oxygen as an oxidant, one or more of the precious metals such as copper, ruthenium, and palladium as catalysts, and metal oxidant fillers as enhanced dispersers to increase the contact area between oxygen and water and play a catalytic role at the same time. The wastewater is subjected to wet catalytic oxidation reaction at high temperature and high pressure to further remove organic matter in the wastewater. Step (3) is electrolytic oxidation: under the action of an external electric field, through physical and chemical effects, the organic pollutants in the wastewater are further efficiently purified. Step (4) is targeted adsorption: through the huge specific surface area and adsorption characteristics of the microcrystalline adsorption material, the organic matter in the wastewater is adsorbed on the adsorption material to achieve the purpose of removing organic pollutants in the wastewater. When the adsorption is saturated, the adsorption material is regenerated with alkali, and the regenerated liquid returns to the front end of the wet catalytic oxidation. Step (5) is MVR: targeted adsorption effluent enters the MVR system. In the MVR system, secondary steam is generated and compressed by a mechanical heat compressor. The temperature and pressure increase, the thermal enthalpy increases, and it is returned to be used as a heating source for the evaporator heating chamber, so that the feed liquid is maintained in a boiling state, thereby completing the evaporation and crystallization of the wastewater. The water vapor generated by evaporation is condensed into condensed water for reuse by a condensation device, and the mother liquor containing crystallized salt enters a pyrolysis device to further remove organic matter. Step (6) is pyrolysis: the MVR mother liquor is first dried at low temperature to evaporate most of the water therein, and then pyrolyzed at high temperature to further remove the organic matter in the salt, so that the crystallized salt reaches a purity that can be recycled.

[0010] Furthermore, the present application can recycle the main salts, such as Na2CO3, etc. Although the POSM co-production method has many by-products, they are all organic matter, with a high inorganic salt content and are relatively pure. The technology of the present application adopts pretreatment-wet catalytic oxidation-electrolytic oxidation-targeted adsorption-MVR-thermal decomposition coupling technology to fully remove organic matter in wastewater. First, the mild oxidation and wet catalytic oxidation in the pretreatment are used to remove most of the organic matter in the wastewater, and the large molecular organic matter is degraded into small molecular organic matter. Secondly, the electrolytic oxidation is run to further oxidize and decompose the organic matter in the wastewater into CO2 and other removal. Then, the small molecular organic matter is adsorbed on the surface or pores of the microcrystalline material through targeted adsorption, which greatly removes the organic matter in the wastewater. Finally, through MVR evaporation and pyrolysis technology, the organic matter in the product salt is further fully removed, so that the product salt reaches the organic matter concentration for recycling. The technical solution of the present application not only solves the problem of salt removal, but also can recycle and create economic value.

[0011] Furthermore, the present application can recycle the main water resources, remove impurities such as organic matter, SS, ammonia nitrogen and total nitrogen through pretreatment, wet catalytic oxidation, electrolytic oxidation and targeted adsorption technology, and then evaporate and condense through MVR. The condensed water produced can meet the reuse standards, thereby achieving the goals of clean production and energy conservation and emission reduction.

[0012] Preferably, in the pretreatment step, the parameters of the reaction of adding Na2S solution are as follows: the stirring speed is 50-200 rpm, the reaction time is 20-30 min; the speed of the centrifuge is 3000-5000 rpm, the liquid contact material is 316L, and the centrifugation time is 10-30 min; The ultrafiltration adopts tubular ultrafiltration, the inner diameter of the membrane tube is 5~8mm, the length of the membrane tube is 3~4m, the membrane pore size is 20~50nm, and the membrane material is PVDF; The reaction temperature of moderate oxidation is 140℃~200℃, the reaction pressure is 0.5~1.5MPa, air or oxygen is used as the oxidant, and there is no catalyst.

[0013] Preferably, the wet catalytic oxidation device is provided with a fixed bed, filled with a metal oxidant filler of φ4-10 mm as a reinforced disperser, and the filling density is 1.0-1.5 g / mL.

[0014] Preferably, in the electrolytic oxidation step, 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, and an online conductivity meter; 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 tank; the water outlet unit includes a water outlet pump, a reflux pump, and an online detection device; 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.

[0015] Preferably, in the targeted adsorption step, when the COD of the wastewater after adsorption is below 100 mg / L, it enters the MVR treatment system; when the COD of the wastewater after adsorption exceeds 100 mg / L, the microcrystalline material needs to be regenerated. During regeneration, fresh water and steam are introduced to heat the microcrystalline material adsorbent to above 100°C to regenerate it, and then it is purged with steam above 150°C. The regenerated liquid after purging enters the wet catalytic oxidation system.

[0016] Preferably, in the targeted adsorption step, the preparation method of the microcrystalline adsorbent is specifically as follows: Add 15-25 mol of silicon dioxide, 0.7-1.5 mol of aluminum oxide, and 2-4 mol of aluminum hydroxide into 1 L of water, mix well, and keep warm at 60-80°C for 2-6 hours to form a mixed solution; then crystallize at 120-140°C for 10-12 hours; then add 5-15 g of a synergist, mix well; and calcine at 600-800°C for 12-15 hours to obtain the product; The synergist is obtained by mixing bentonite and polylactic acid glycolic acid copolymer in a weight ratio of (1-3): (0.2-0.8).

[0017] The applicant has found through many experiments that the microcrystalline adsorbent obtained by dispersing silicon dioxide, aluminum oxide and aluminum hydroxide at specific concentrations in water, crystallizing them and then calcining them with enhancers as raw materials has unexpected effects in the wastewater treatment process.

[0018] In a specific embodiment, in the synergist, the weight ratio of the bentonite to the polylactic acid-co-glycolic acid copolymer can be 1:0.2, 1:0.5, 1:0.8, 2:0.2, 2:0.5, 2:0.8, 3:0.2, 3:0.5, 3:0.8.

[0019] Through experimental analysis, it can be known that the present application further improves the effect of wastewater treatment by using bentonite and polylactic acid glycolic acid copolymer in the above weight ratio as a synergist as a raw material for preparing a microcrystalline adsorbent.

[0020] Preferably, in the MVR, the secondary steam generated by the steam compressor enters from the air inlet of the heat exchanger, enters the crystallizer along the shell side of the heat exchanger, and enters the scrubber after exiting from the top of the crystallizer, where it absorbs the entrained foam. The secondary steam from the scrubber enters the steam compressor along the steam pipe; the temperature and pressure are increased in the steam compressor, and then it is supplied to the forced circulation evaporation for continued use; the whole process does not require the consumption of additional steam, and the evaporation and crystallization of the wastewater can be achieved; The condensate after evaporation and crystallization enters the condensate reuse pool, and the concentrated liquid enters the pyrolysis device from the bottom of the salt leg; When the evaporation capacity of the MVR forced circulation evaporator drops by about 10%, the liquid in the forced circulation evaporator is discharged to the pyrolysis device for further processing.

[0021] Preferably, the parameter conditions of the MVR are: evaporation temperature is 85-100°C, the diameter of the heat exchanger tube is 32mm×1.2mm, the liquid flow rate of the heat exchanger tube is 2-2.2m / s, the crystallizer gas velocity is <6m / s, the compressor inlet gas velocity is 25m / s, and the compressor outlet gas velocity is 30m / s.

[0022] Preferably, in the pyrolysis step, the temperature of the drying section is 100-200°C, the drying time is 0.5-2h, and the moisture content is dried to 10%-20%; the temperature of the pyrolysis section is 300-600°C, the pyrolysis time is 0.5-2h, and the COD content in the crystalline salt after pyrolysis is less than 30 mg / kg.

[0023] In a second aspect, the present application provides the application of the above-mentioned treatment method in the treatment of POSM production wastewater.

[0024] In summary, the technical solution of this application has the following effects: The present application adopts the pretreatment-wet catalytic oxidation-electrolytic oxidation-targeted adsorption-MVR-pyrolysis coupling technology to treat the wastewater from the joint production process of propylene oxide and styrene (POSM), which solves the shortcomings of the existing treatment process that produces difficult-to-treat secondary pollution and the condensed water and salt resources cannot be recycled. The pretreatment-wet catalytic oxidation-electrolytic oxidation-targeted adsorption-MVR-pyrolysis technology in the present application not only does not produce difficult-to-treat secondary pollution, no mother liquor is left, the effluent COD is low and stable, and the condensed water and salt resources can be recycled, which not only realizes the reuse of resources but also reduces the treatment cost.

[0025] This application uses a targeted adsorption microcrystalline adsorbent that mimics the microstructure of shells and corals, significantly increases the surface area and active site density through a multi-level pore structure, and enhances the selectivity and capture rate of specific pollutants; this structure not only improves the adsorption performance, but also reduces the amount of materials used. At the same time, the adsorbent has strong physical stability and chemical tolerance, ensuring reliability for long-term use. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart of the method for treating POSM production wastewater in the embodiment of this application. DETAILED DESCRIPTION

[0027] The present application is further described in detail below in conjunction with examples, comparative examples and performance testing experiments. These examples should not be construed as limiting the scope of protection claimed in the present application. Example Example 1

[0028] Example 1 provides a method for treating POSM production wastewater.

[0029] The process flow diagram of the treatment method of POSM production wastewater in Example 1 is as follows Figure 1 As shown, the process specifically includes performing the following steps in sequence.

[0030] The wastewater in Example 1 comes from POSM wastewater of a chemical company in Tianjin, with a water volume of 40t / h, a measured pH of 13.2, a COD of 118000mg / L, a total nitrogen of 200mg / L, a TDS of 50000~55000mg / L, and a Na2CO3 content of 25%~30%.

[0031] (1) Pretreatment: The wastewater from the combined production process of propylene oxide and styrene (POSM) first enters the regulating tank. After the water volume is adjusted and the water quality is balanced in the regulating tank, sodium sulfide is added to the reaction tank to precipitate heavy metal ions such as copper, chromium, and molybdenum. The ultrafiltration membrane is then used to separate the solid and liquid. The filtrate is then subjected to moderate oxidation at a temperature of 160°C and a reaction pressure of 1MPa, with air as the oxidant. The ultrafiltration concentrated solution is centrifuged for dehydration, the dehydrated residue is transported out for disposal, and the centrifuged solution is returned to the reaction section.

[0032] The parameters of the reaction with the addition of Na2S solution are as follows: the stirring speed is 150 rpm, the reaction time is 25 min, the speed of the centrifuge is 4000 rpm, the liquid contact material is 316L, and the centrifugation time is 20 min.

[0033] The ultrafiltration adopts tubular ultrafiltration, the inner diameter of the membrane tube is 6mm, the length of the membrane tube is 3m, the membrane pore size is 35nm, and the membrane material is PVDF.

[0034] The effluent COD is 35026 mg / L, the total nitrogen is about 31 mg / L, and the TDS is about 51016 mg / L.

[0035] (2) Wet catalytic oxidation: The reaction temperature of wet catalytic oxidation is 270℃, the reaction pressure is 8MPa, and the TiO2 filler with φ4~10mm is used as the catalyst fixed bed, the filling density is 1.5g / mL, and ruthenium is used as the catalyst. The mass ratio of catalyst to TiO2 filler is 1:100. Air is continuously introduced and catalytic oxidation is carried out for 2h. The COD of the effluent is about 3602mg / L, the total nitrogen is about 3.1mg / L, and the TDS is about 31008mg / L, of which the Na2CO3 content accounts for about 88%.

[0036] (3) Electrolytic oxidation: The temperature of the electrolytic oxidation device is lower than 60°C, the electrode material is diamond doped with boron, and the current density is 5A / dm 2 The hydraulic retention time of the electrolytic oxidation device is 25 minutes. After electrolytic oxidation, the effluent COD is about 1101 mg / L, the total nitrogen is about 2.5 mg / L, and the TDS is about 30123 mg / L, of which the Na2CO3 content accounts for about 96%.

[0037] (4) Targeted adsorption: The targeted adsorption system consists of 6 towers in parallel. During normal operation, 5 towers are used for adsorption and 1 tower is used for regeneration. Each tower is filled with 40m 3Microcrystalline adsorbent, total loading volume is 240m 3 , the liquid flow rate is 0.2BV / H. After targeted adsorption once (without regeneration), the effluent COD is 80.7mg / L, the total nitrogen is about 0.25mg / L, the TDS is about 28012mg / L, and the Na2CO3 content is about 99.6%.

[0038] The preparation method of the microcrystalline adsorbent is specifically as follows: Add 20 mol of silicon dioxide, 1 mol of aluminum oxide, and 3 mol of aluminum hydroxide into 1 L of water, mix well, and keep warm at 70°C for 4 hours to form a mixed solution; then crystallize at 130°C for 11 hours; then add 10 g of a synergist, mix well; and calcine at 700°C for 13 hours to obtain the product; The synergist is obtained by mixing bentonite (model YD-223, product number MR-3, 180-325 mesh; purchased from Tianjin Yandong Mineral Products Co., Ltd.) and polylactic acid-glycolic acid copolymer (product number S24482, performance parameters are: molecular weight: 10,000-20,000 PLGA 65:35, carboxyl end-capping; purchased from Shanghai Yuanye Biological Co., Ltd.) in a weight ratio of 2:0.5.

[0039] (5) MVR: The wastewater enters the MVR forced circulation system for evaporation, is pumped from the crystallizer to the forced circulation heat exchanger via a forced circulation pump, and then returns to the crystallizer. The flow rate of the heat exchanger is 2.1 m / s.

[0040] The secondary steam generated by the steam compressor enters from the air inlet of the heat exchanger, enters the crystallizer along the shell of the heat exchanger, and enters the scrubbing tower after coming out from the top of the crystallizer, where it absorbs the entrained foam. The secondary steam coming out of the scrubbing tower enters the steam compressor along the steam pipe; the temperature and pressure are increased in the steam compressor, and then it is supplied to the forced circulation evaporation for continued use; the whole process does not require the consumption of additional steam to achieve evaporation and crystallization of wastewater.

[0041] The condensate after evaporation and crystallization enters the condensate reuse pool, and the concentrated liquid enters the pyrolysis device from the bottom of the salt leg.

[0042] When the evaporation capacity of the MVR forced circulation evaporator drops by about 10%, the liquid in the forced circulation evaporator is discharged to the pyrolysis device for further processing.

[0043] The parameter conditions of MVR are: evaporation temperature is 95℃, heat exchanger tube diameter is 32mm×1.2mm, liquid flow rate in heat exchanger tube is 2.1m / s, crystal separator gas velocity is less than 6m / s, compressor inlet gas velocity is 25m / s, and compressor outlet gas velocity is 30m / s.

[0044] It produces about 5.7t / h of Na2CO3 concentrate with a solid content of 20%, of which the purity of Na2CO3 is above 99.6%. It produces about 35.3t / h of condensed water with a pH of 6-8, COD below 20mg / L, and TDS below 50mg / L, meeting the standards of "Water Quality for Industrial Water Used in Urban Wastewater Recycling" (GB / T 19923-2005).

[0045] (6) Pyrolysis: The 20% Na2CO3 concentrate first enters the drying section, where the temperature is 150°C and the drying time is 1 hour, until the moisture content is 10%; then it enters the pyrolysis section, where the temperature is 450°C and the pyrolysis time is 1 hour. The steam generated by drying and pyrolysis is recovered by heat, and the condensed water generated is recycled. After pyrolysis, about 1.14 t / h of crystalline salt with a COD of less than 30 mg / kg is generated, with a purity of more than 99.9%, meeting the salt recycling standards. Example 2

[0046] Example 2 provides a method for treating POSM production wastewater.

[0047] The method for treating POSM production wastewater in Example 2 specifically includes performing the following steps in sequence.

[0048] The wastewater in Example 2 comes from POSM wastewater of a petrochemical company in Guangxi, with a water volume of 7.5t / h, a measured pH of 13, a COD of 200000mg / L, a total nitrogen of 242mg / L, a TDS of 55000~60000mg / L, and a Na2CO3 content of 35%.

[0049] (1) Pretreatment: The wastewater from the combined production process of propylene oxide and styrene (POSM) first enters the regulating tank. After the water volume is adjusted and the water quality is balanced in the regulating tank, sodium sulfide is added to the reaction tank to precipitate the heavy metal ions such as copper, chromium, and molybdenum. The solid-liquid separation is then achieved using an ultrafiltration membrane. The filtrate is then subjected to moderate oxidation at a temperature of 200°C and a reaction pressure of 1MPa, with air as the oxidant. The ultrafiltration concentrated solution is centrifugally dehydrated, the dehydrated residue is transported out for disposal, and the centrifuged solution is returned to the reaction section.

[0050] The parameters of the reaction with the addition of Na2S solution are as follows: the stirring speed is 150 rpm, the reaction time is 25 min, the speed of the centrifuge is 4000 rpm, the liquid contact material is 316L, and the centrifugation time is 20 min.

[0051] The ultrafiltration adopts tubular ultrafiltration, the inner diameter of the membrane tube is 6mm, the length of the membrane tube is 3m, the membrane pore size is 35nm, and the membrane material is PVDF.

[0052] The effluent COD is about 61007mg / L, the total nitrogen is about 36mg / L, and the TDS is about 56009mg / L.

[0053] (2) Wet catalytic oxidation: The temperature of wet catalytic oxidation is 280°C, the pressure is 9 MPa, and the TiO2 filler with a diameter of 4-10 mm is filled as the catalyst fixed bed. The filling density is 1.5 g / mL. Ruthenium is used as the catalyst, and the mass ratio of the catalyst to the TiO2 filler is 1:100. Air is continuously introduced and the catalytic oxidation is carried out for 2 hours.

[0054] The effluent COD is about 5701 mg / L, the total nitrogen is about 3.6 mg / L, the TDS is about 33106 mg / L, of which the Na2CO3 content accounts for about 90%.

[0055] (3) Electrolytic oxidation: The temperature of the electrolytic oxidation device is lower than 60°C, the electrode material is diamond doped with boron, and the current density is 5A / dm 2 The hydraulic retention time of the electrolytic oxidation device is 25 minutes.

[0056] After electrolytic oxidation, the wastewater has an effluent COD of about 1402 mg / L, a total nitrogen of about 2.9 mg / L, and a TDS of about 31107 mg / L, of which the Na2CO3 content accounts for about 97%.

[0057] Among them, the electrolytic oxidation device includes an inlet unit, an electrolytic oxidation unit, a waste gas treatment unit, and an outlet unit; the inlet unit includes a sewage pump, an inlet tank, and an online conductivity meter; the electrolytic oxidation unit includes an 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 tank; the outlet unit includes an outlet pump, a reflux pump, and an online detection device.

[0058] (4) Targeted adsorption: The targeted adsorption system consists of three towers in parallel. During normal operation, two towers are used for adsorption and one tower is used for regeneration. Each tower is filled with 18m 3 The microcrystalline adsorbent (prepared in the same manner as in Example 1) has a total loading of 60 m 3 , the liquid flow rate is 0.21BV / H.

[0059] After one targeted adsorption, the effluent COD is lower than 85.6 mg / L, the total nitrogen is about 0.58 mg / L, the TDS is about 31007 mg / L, and the Na2CO3 content is about 99.7%.

[0060] (5) MVR: The wastewater enters the MVR forced circulation system for evaporation, is pumped from the crystallizer to the forced circulation heat exchanger via a forced circulation pump, and then returns to the crystallizer. The flow rate of the heat exchanger is 2.1 m / s.

[0061] The secondary steam generated by the steam compressor enters from the air inlet of the heat exchanger, enters the crystallizer along the shell of the heat exchanger, and enters the scrubbing tower after coming out from the top of the crystallizer, where it absorbs the entrained foam. The secondary steam coming out of the scrubbing tower enters the steam compressor along the steam pipe; the temperature and pressure are increased in the steam compressor, and then it is supplied to the forced circulation evaporation for continued use; the whole process does not require the consumption of additional steam to achieve evaporation and crystallization of wastewater.

[0062] The condensate after evaporation and crystallization enters the condensate reuse pool, and the concentrated liquid enters the pyrolysis device from the bottom of the salt leg.

[0063] When the evaporation capacity of the MVR forced circulation evaporator drops by about 10%, the liquid in the forced circulation evaporator is discharged to the pyrolysis device for further processing.

[0064] The parameter conditions of MVR are: evaporation temperature is 95℃, heat exchanger tube diameter is 32mm×1.2mm, liquid flow rate in heat exchanger tube is 2.1m / s, crystal separator gas velocity is less than 6m / s, compressor inlet gas velocity is 25m / s, and compressor outlet gas velocity is 30m / s.

[0065] It produces about 1.25t / h of Na2CO3 concentrate with a solid content of 20%, of which the purity of Na2CO3 is above 99.7%. It produces about 6.41t / h of condensed water, with a pH of 6-8, a COD of about 19mg / L, and a TDS of less than 50mg / L, meeting the standards of "Water Quality for Industrial Water Used in Urban Wastewater Recycling" (GB / T 19923-2005).

[0066] (6) Pyrolysis: 20% Na2CO3 concentrate first enters the drying section, the temperature of the drying section is 150℃, the drying time is 1h, and the moisture content is dried to 10%; then enters the pyrolysis section, the temperature of the pyrolysis section is 450℃, and the pyrolysis time is 1h. The steam generated by drying and pyrolysis is recovered by heat, and the condensed water generated is recycled. After pyrolysis, about 0.25t / h of crystalline salt with a COD of less than 30mg / kg is generated, and the purity is above 99.9%, which meets the salt recycling standard. Example 3

[0067] Example 3 provides a method for treating POSM production wastewater.

[0068] The wastewater in this embodiment is the same as that in Embodiment 1.

[0069] The method for treating POSM production wastewater in this embodiment is different from that in Embodiment 1 in that the preparation method of the microcrystalline adsorbent in step (4) is different, as shown below.

[0070] Targeted adsorption: The targeted adsorption system consists of 6 towers in parallel. During normal operation, 5 towers are used for adsorption and 1 tower is used for regeneration. Each tower is filled with 40m 3 Microcrystalline adsorbent, total loading volume is 240m 3 , the liquid flow rate is 0.2BV / H. After targeted adsorption once, the effluent COD is 192.1mg / L. When the COD of the wastewater after adsorption exceeds 100mg / L, the microcrystalline material needs to be regenerated. During regeneration, fresh water and steam are introduced to heat the microcrystalline material adsorbent to above 100°C to regenerate it, and then it is purged with steam above 150°C. The regenerated liquid after purging enters the front-end wet catalytic oxidation CWO treatment system. After targeted adsorption twice, the effluent COD is 99.8mg / L, the total nitrogen is about 0.65mg / L, and the TDS is about 31745mg / L, of which the Na2CO3 content accounts for about 99.6%.

[0071] The preparation method of the microcrystalline adsorbent is specifically as follows: Add 20 mol of silicon dioxide, 1 mol of aluminum oxide, and 3 mol of aluminum hydroxide into 1 L of water, mix well, and keep warm at 70°C for 4 hours to form a mixed solution; then crystallize at 130°C for 11 hours; and calcine at 700°C for 13 hours. Example 4

[0072] Example 4 provides a method for treating POSM production wastewater.

[0073] The wastewater in this embodiment is the same as that in Embodiment 1.

[0074] The method for treating POSM production wastewater in this embodiment is different from that in Embodiment 1 in that the preparation method of the microcrystalline adsorbent in step (4) is different, as shown below.

[0075] Targeted adsorption: The targeted adsorption system consists of 6 towers in parallel. During normal operation, 5 towers are used for adsorption and 1 tower is used for regeneration. Each tower is filled with 40m 3 Microcrystalline adsorbent, total loading volume is 240m 3 , the liquid flow rate is 0.2BV / H. After targeted adsorption once, the effluent COD is 130.8mg / L. When the COD of the wastewater after adsorption exceeds 100mg / L, the microcrystalline material needs to be regenerated. During regeneration, fresh water and steam are introduced to heat the microcrystalline material adsorbent to above 100°C to regenerate it, and then it is purged with steam above 150°C. The regenerated liquid after purging enters the front-end wet catalytic oxidation CWO treatment system. After targeted adsorption twice, the effluent COD is 91.3mg / L, the total nitrogen is about 0.37mg / L, and the TDS is about 29519mg / L, of which the Na2CO3 content accounts for about 99.5%.

[0076] The preparation method of the microcrystalline adsorbent is specifically as follows: Add 20 mol of silicon dioxide, 1 mol of aluminum oxide, and 3 mol of aluminum hydroxide into 1 L of water, mix well, and keep warm at 70°C for 4 hours to form a mixed solution; then crystallize at 130°C for 11 hours; then add 10 g of a synergist, mix well; and calcine at 700°C for 13 hours to obtain the product; The synergist is obtained by mixing bentonite (model YD-223, item number MR-3, 180-325 mesh; purchased from Tianjin Yandong Mineral Products Co., Ltd.) and polylactic acid-glycolic acid copolymer (item number S24436, performance parameters are: molecular weight: 10,000-20,000 PLGA 50:50, carboxyl end-capping) in a weight ratio of 2:0.5. Example 5

[0077] Example 5 provides a method for treating POSM production wastewater.

[0078] The wastewater in this embodiment is the same as that in Embodiment 1.

[0079] The method for treating POSM production wastewater in this embodiment is different from that in Embodiment 1 in that the preparation method of the microcrystalline adsorbent in step (4) is different, as shown below.

[0080] Targeted adsorption: The targeted adsorption system consists of 6 towers in parallel. During normal operation, 5 towers are used for adsorption and 1 tower is used for regeneration. Each tower is filled with 40m 3 Microcrystalline adsorbent, total loading volume is 240m 3 , the liquid flow rate is 0.2BV / H. After targeted adsorption once, the effluent COD is 132.9mg / L. When the COD of the wastewater after adsorption exceeds 100mg / L, the microcrystalline material needs to be regenerated. During regeneration, fresh water and steam are introduced to heat the microcrystalline material adsorbent to above 100°C to regenerate it, and then it is purged with steam above 150°C. The regenerated liquid after purging enters the front-end wet catalytic oxidation CWO treatment system. After targeted adsorption twice, the effluent COD is 89.3mg / L, the total nitrogen is about 0.49mg / L, and the TDS is about 29918mg / L, of which the Na2CO3 content accounts for about 99.7%.

[0081] The preparation method of the microcrystalline adsorbent is specifically as follows: Add 20 mol of silicon dioxide, 1 mol of aluminum oxide, and 3 mol of aluminum hydroxide into 1 L of water, mix well, and keep warm at 70°C for 4 hours to form a mixed solution; then crystallize at 130°C for 11 hours; then add 10 g of a synergist, mix well; and calcine at 700°C for 13 hours to obtain the product; The synergist is obtained by mixing bentonite (model YD-223, item number MR-3, 180-325 mesh; purchased from Tianjin Yandong Mineral Products Co., Ltd.) and polylactic acid-glycolic acid copolymer (item number S24479, performance parameters are: molecular weight: 10,000-20,000 PLGA 75:25, carboxyl end-capping) in a weight ratio of 2:0.5. Example 6

[0082] Example 6 provides a method for treating POSM production wastewater.

[0083] The wastewater in this embodiment is the same as that in Embodiment 1.

[0084] The method for treating POSM production wastewater in this embodiment is different from that in Embodiment 1 in that the preparation method of the microcrystalline adsorbent in step (4) is different, as shown below.

[0085] Targeted adsorption: The targeted adsorption system consists of 6 towers in parallel. During normal operation, 5 towers are used for adsorption and 1 tower is used for regeneration. Each tower is filled with 40m 3 Microcrystalline adsorbent, total loading volume is 240m 3 , the liquid flow rate is 0.2BV / H. After targeted adsorption once, the effluent COD is 121.1mg / L. When the COD of the wastewater after adsorption exceeds 100mg / L, the microcrystalline material needs to be regenerated. During regeneration, fresh water and steam are introduced to heat the microcrystalline material adsorbent to above 100°C to regenerate it, and then it is purged with steam above 150°C. The regenerated liquid after purging enters the front-end wet catalytic oxidation CWO treatment system. After targeted adsorption twice, the effluent COD is 96.3mg / L, the total nitrogen is about 0.48mg / L, and the TDS is about 28913mg / L, of which the Na2CO3 content accounts for about 99.6%.

[0086] The preparation method of the microcrystalline adsorbent is specifically as follows: Add 20 mol of silicon dioxide, 1 mol of aluminum oxide, and 3 mol of aluminum hydroxide into 1 L of water, mix well, and keep warm at 70°C for 4 hours to form a mixed solution; then crystallize at 130°C for 11 hours; then add 10 g of a synergist, mix well; and calcine at 700°C for 13 hours to obtain the product; The synergist is obtained by mixing bentonite (model YD-223, item number MR-3, 180-325 mesh; purchased from Tianjin Yandong Mineral Products Co., Ltd.) and polylactic acid-glycolic acid copolymer (item number S33142, performance parameters are: molecular weight: 10,000-20,000 PLGA 65:35, hydroxyl terminated) in a weight ratio of 2:0.5. Example 7

[0087] Example 7 provides a method for treating POSM production wastewater.

[0088] The wastewater in this embodiment is the same as that in Embodiment 1.

[0089] The method for treating POSM production wastewater in this embodiment is different from that in Embodiment 1 in that the preparation method of the microcrystalline adsorbent in step (4) is different, as shown below.

[0090] Targeted adsorption: The targeted adsorption system consists of 6 towers in parallel. During normal operation, 5 towers are used for adsorption and 1 tower is used for regeneration. Each tower is filled with 40m 3 Microcrystalline adsorbent, total loading volume is 240m 3 , the liquid flow rate is 0.2BV / H. After targeted adsorption once, the effluent COD is 142.1mg / L. When the COD of the wastewater after adsorption exceeds 100mg / L, the microcrystalline material needs to be regenerated. During regeneration, fresh water and steam are introduced to heat the microcrystalline material adsorbent to above 100°C to regenerate it, and then it is purged with steam above 150°C. The regenerated liquid after purging enters the front-end wet catalytic oxidation CWO treatment system. After targeted adsorption twice, the effluent COD is 96.1mg / L, the total nitrogen is about 0.58mg / L, and the TDS is about 29731mg / L, of which the Na2CO3 content accounts for about 99.6%.

[0091] The preparation method of the microcrystalline adsorbent is specifically as follows: Add 20 mol of silicon dioxide, 1 mol of aluminum oxide, and 3 mol of aluminum hydroxide into 1 L of water, mix well, and keep warm at 70°C for 4 hours to form a mixed solution; then crystallize at 130°C for 11 hours; then add 10 g of a synergist, mix well; and calcine at 700°C for 13 hours to obtain the product; The synergist is obtained by mixing bentonite (model YD-223, item number MR-3, 180-325 mesh; purchased from Tianjin Yandong Mineral Products Co., Ltd.) and polylactic acid-glycolic acid copolymer (item number S33143, performance parameters are: molecular weight: 10,000-20,000 PLGA 65:35, ester end-capping) in a weight ratio of 2:0.5. Example 8

[0092] Example 8 provides a method for treating POSM production wastewater.

[0093] The wastewater in this embodiment is the same as that in Embodiment 1.

[0094] The method for treating POSM production wastewater in this embodiment is different from that in Embodiment 1 in that the preparation method of the microcrystalline adsorbent in step (4) is different, as shown below.

[0095] Targeted adsorption: The targeted adsorption system consists of 6 towers in parallel. During normal operation, 5 towers are used for adsorption and 1 tower is used for regeneration. Each tower is filled with 40m 3Microcrystalline adsorbent, total loading volume is 240m 3 , the liquid flow rate is 0.2BV / H. After targeted adsorption once, the effluent COD is 119.4mg / L. When the COD of the wastewater after adsorption exceeds 100mg / L, the microcrystalline material needs to be regenerated. During regeneration, fresh water and steam are introduced to heat the microcrystalline material adsorbent to above 100°C to regenerate it, and then it is purged with steam above 150°C. The regenerated liquid after purging enters the front-end wet catalytic oxidation CWO treatment system. After targeted adsorption twice, the effluent COD is 89.3mg / L, the total nitrogen is about 0.51mg / L, and the TDS is about 29210mg / L, of which the Na2CO3 content accounts for about 99.6%.

[0096] The preparation method of the microcrystalline adsorbent is specifically as follows: Add 20 mol of silicon dioxide, 1 mol of aluminum oxide, and 3 mol of aluminum hydroxide into 1 L of water, mix well, and keep warm at 70°C for 4 hours to form a mixed solution; then crystallize at 130°C for 11 hours; then add 10 g of a synergist, mix well; and calcine at 700°C for 13 hours to obtain the product; The synergist is obtained by mixing bentonite (model YD-223, item number MR-3, 180-325 mesh; purchased from Tianjin Yandong Mineral Products Co., Ltd.) and polylactic acid-glycolic acid copolymer (item number S24482, performance parameters are: molecular weight: 10,000-20,000 PLGA 65:35, carboxyl end-capping) in a weight ratio of 0.5:2. Example 9

[0097] Example 9 provides a method for treating POSM production wastewater.

[0098] The wastewater in this embodiment is the same as that in Embodiment 1.

[0099] The method for treating POSM production wastewater in this embodiment is different from that in Embodiment 1 in that the preparation method of the microcrystalline adsorbent in step (4) is different, as shown below.

[0100] Targeted adsorption: The targeted adsorption system consists of 6 towers in parallel. During normal operation, 5 towers are used for adsorption and 1 tower is used for regeneration. Each tower is filled with 40m 3 Microcrystalline adsorbent, total loading volume is 240m 3 , the liquid flow rate is 0.2BV / H. After targeted adsorption once (without regeneration), the effluent COD is 79.9mg / L, the total nitrogen is about 0.26mg / L, the TDS is about 28422mg / L, and the Na2CO3 content is about 99.6%.

[0101] The preparation method of the microcrystalline adsorbent is specifically as follows: Add 20 mol of silicon dioxide, 1 mol of aluminum oxide, and 3 mol of aluminum hydroxide into 1 L of water, mix well, and keep warm at 70°C for 4 hours to form a mixed solution; then crystallize at 130°C for 11 hours; then add 10 g of a synergist, mix well; and calcine at 700°C for 13 hours to obtain the product; The synergist is obtained by mixing bentonite (model YD-223, product number MR-3, 180-325 mesh; purchased from Tianjin Yandong Mineral Products Co., Ltd.) and polylactic acid-glycolic acid copolymer (product number S24482, performance parameters are: molecular weight: 10,000-20,000 PLGA 65:35, carboxyl end-capping; purchased from Shanghai Yuanye Biological Co., Ltd.) in a weight ratio of 1:0.8. Example 10

[0102] Example 10 provides a method for treating POSM production wastewater.

[0103] The wastewater in this embodiment is the same as that in Embodiment 1.

[0104] The method for treating POSM production wastewater in this embodiment is different from that in Embodiment 1 in that the preparation method of the microcrystalline adsorbent in step (4) is different, as shown below.

[0105] Targeted adsorption: The targeted adsorption system consists of 6 towers in parallel. During normal operation, 5 towers are used for adsorption and 1 tower is used for regeneration. Each tower is filled with 40m 3 Microcrystalline adsorbent, total loading volume is 240m 3 , the liquid flow rate is 0.2BV / H. After targeted adsorption once (without regeneration), the effluent COD is 81.8mg / L, the total nitrogen is about 0.28mg / L, the TDS is about 28183mg / L, and the Na2CO3 content is about 99.6%.

[0106] The preparation method of the microcrystalline adsorbent is specifically as follows: Add 20 mol of silicon dioxide, 1 mol of aluminum oxide, and 3 mol of aluminum hydroxide into 1 L of water, mix well, and keep warm at 70°C for 4 hours to form a mixed solution; then crystallize at 130°C for 11 hours; then add 10 g of a synergist, mix well; and calcine at 700°C for 13 hours to obtain the product; The synergist is obtained by mixing bentonite (model YD-223, product number MR-3, 180-325 mesh; purchased from Tianjin Yandong Mineral Products Co., Ltd.) and polylactic acid-glycolic acid copolymer (product number S24482, performance parameters are: molecular weight: 10,000-20,000 PLGA 65:35, carboxyl end-capping; purchased from Shanghai Yuanye Biological Co., Ltd.) in a weight ratio of 3:0.2.

[0107] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for treating POSM production wastewater, characterized in that: Specifically, the following steps are carried out in sequence: pretreatment, wet catalytic oxidation, electrolytic oxidation, targeted adsorption, MVR, and thermal decomposition coupling; (1) Pretreatment: The wastewater enters the regulating tank, and after the water volume is adjusted and the water quality is balanced in the regulating tank, the heavy metal ions are converted into precipitates through the reaction of Na2S solution; then after ultrafiltration, the clear liquid enters the mild oxidation, and the retained concentrated liquid is centrifuged for dehydration. The dehydrated filter residue is transported out for disposal, and the centrifuged liquid returns to the reaction section; (2) Wet catalytic oxidation: the reaction temperature is 200℃~300℃, the reaction pressure is 3~10MPa, air or oxygen is used as the oxidant, the catalyst is one or more of copper, ruthenium, and cerium catalysts, the catalyst dosage is 0.5%~5%, and the catalytic oxidation time is 2~4h; (3) Electrolytic oxidation: The material of the electrolytic device is selected from diamond doped with boron or titanium substrate coated with graphene. The temperature of the liquid in the electrolytic oxidation device is lower than 60°C, and the current density is 1~10A / dm 2 , hydraulic retention time is 10~60min; (4) Targeted adsorption: Targeted adsorption fills microcrystalline materials, the liquid flow rate is 0.2~1BV / H, and the adsorption temperature is 20~35℃; (5) MVR: The wastewater enters the MVR forced circulation system for evaporation, and is pumped from the crystallizer to the forced circulation heat exchanger through a forced circulation pump and then returns to the crystallizer. The flow rate of the heat exchanger is 2-2.2 m / s; (6) Pyrolysis: Wastewater enters the pyrolysis device, first passes through the drying section, and then enters the pyrolysis section.

2. The method for treating POSM production wastewater according to claim 1, characterized in that: In the pretreatment step, the parameters of the reaction of adding Na2S solution are as follows: the stirring speed is 50-200 rpm, the reaction time is 20-30 min; the speed of the centrifuge is 3000-5000 rpm, the contact material is 316L, and the centrifugation time is 10-30 min; The ultrafiltration adopts tubular ultrafiltration, the inner diameter of the membrane tube is 5~8mm, the length of the membrane tube is 3~4m, the membrane pore size is 20~50nm, and the membrane material is PVDF; The reaction temperature of moderate oxidation is 140℃~200℃, the reaction pressure is 0.5~1.5MPa, air or oxygen is used as the oxidant, and there is no catalyst.

3. The method for treating POSM production wastewater according to claim 1, characterized in that: The wet catalytic oxidation device is provided with a fixed bed, which is filled with a metal oxidant filler of φ4-10 mm as a reinforced disperser with a filling density of 1.0-1.5 g / mL.

4. The method for treating POSM production wastewater according to claim 1, characterized in that: In the electrolytic oxidation step, 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, and an online conductivity meter; 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 tank; the water outlet unit includes a water outlet pump, a reflux pump, and an online detection device; 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.

5. The method for treating POSM production wastewater according to claim 1, characterized in that: In the targeted adsorption step, when the COD of the wastewater after adsorption is below 100 mg / L, it enters the MVR treatment system; when the COD of the wastewater after adsorption exceeds 100 mg / L, the microcrystalline material needs to be regenerated. During regeneration, fresh water and steam are introduced to heat the microcrystalline material adsorbent to above 100°C to regenerate it, and then it is purged with steam above 150°C. The regenerated liquid after purging enters the wet catalytic oxidation system.

6. The method for treating POSM production wastewater according to claim 1, characterized in that: In the targeted adsorption step, the preparation method of the microcrystalline adsorbent is specifically as follows: Add 15-25 mol of silicon dioxide, 0.7-1.5 mol of aluminum oxide, and 2-4 mol of aluminum hydroxide into 1 L of water, mix well, and keep warm at 60-80°C for 2-6 hours to form a mixed solution; then crystallize at 120-140°C for 10-12 hours; then add 5-15 g of a synergist, mix well; and calcine at 600-800°C for 12-15 hours to obtain the product; The synergist is obtained by mixing bentonite and polylactic acid glycolic acid copolymer in a weight ratio of (1-3): (0.2-0.8).

7. The method for treating POSM production wastewater according to claim 1, characterized in that: In the MVR, the secondary steam generated by the steam compressor enters from the air inlet of the heat exchanger, enters the crystallizer along the shell side of the heat exchanger, and enters the scrubber after exiting from the top of the crystallizer. The entrained foam is absorbed in the scrubber, and the secondary steam from the scrubber enters the steam compressor along the steam pipe; the temperature and pressure are increased in the steam compressor, and then the forced circulation evaporation is continued; the whole process does not require the consumption of additional steam, and the evaporation and crystallization of the wastewater can be achieved; The condensate after evaporation and crystallization enters the condensate reuse pool, and the concentrated liquid enters the pyrolysis device from the bottom of the salt leg; When the evaporation capacity of the MVR forced circulation evaporator drops by about 10%, the liquid in the forced circulation evaporator is discharged to the pyrolysis device for further processing.

8. The method for treating POSM production wastewater according to claim 1, characterized in that: The parameter conditions of the MVR are: evaporation temperature is 85-100°C, heat exchanger tube diameter size is 32mm×1.2mm, heat exchanger tube liquid flow rate is 2-2.2m / s, crystal separator gas speed is <6m / s, compressor inlet gas speed is 25m / s, compressor outlet gas speed is 30m / s.

9. The method for treating POSM production wastewater according to claim 1, characterized in that: In the pyrolysis step, the temperature of the drying section is 100-200°C, the drying time is 0.5-2h, and the moisture content is dried to 10%-20%; the temperature of the pyrolysis section is 300-600°C, the pyrolysis time is 0.5-2h, and the COD content in the crystalline salt after pyrolysis is less than 30mg / kg.

10. Use of the treatment method according to any one of claims 1 to 9 in the treatment of POSM production wastewater.

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