Refining treatment and concentration recovery method for carbonate wastewater of carbonization-process white carbon black

Abstract

The invention discloses a carbonation method white carbon black carbonate wastewater refining treatment and concentration recovery method which comprises the following steps: conveying carbonate wastewater to a first reaction tank for flocculent precipitation, and removing precipitates, SiO2 and heavy metal ions to obtain a reaction solution; filtering the reaction liquid through a plate frame to obtain clear filtrate; carrying out microporous filtration and resin tower treatment on the clarified filtrate to obtain a refined solution; treating the refined solution by a hollow fiber membrane to separate a concentrated solution and a dialysate, and returning the concentrated solution to the microporous filter; concentrating the dialysate through a high-pressure reverse osmosis membrane device to obtain a high-pressure reverse osmosis concentrated solution and dialysate, and treating the dialysate through a low-pressure reverse osmosis membrane device for recycling; after the high-pressure reverse osmosis concentrated solution is converted into a sodium carbonate solution through a wet decomposition tower, a concentrated solution and dialysate are separated out through a high-pressure nanofiltration membrane device; the concentrated solution is subjected to MVR concentration and drying, anhydrous sodium carbonate is obtained, and dialysate returns to the high-pressure reverse osmosis membrane device. According to the method, gradient removal of carbonate wastewater pollutants and efficient recovery of resources are realized.

Description

Technical Field

[0001] This invention relates to the field of chemical high-salt wastewater treatment, and in particular to a method for refining, concentrating and recovering carbonate wastewater from carbonation process for precipitated silica. Background Technology

[0002] The wastewater generated during the carbonization process of precipitated silica is complex, containing high concentrations of sodium carbonate (Na₂CO₃), sodium bicarbonate (NaHCO₃), and soluble and insoluble silica (SiO₂), along with small amounts of suspended particles and various divalent and higher-valent metal ions (such as calcium, magnesium, iron, and aluminum). This type of wastewater is not only highly saline and alkaline, but the presence of SiO₂ colloids and metal ions also causes severe membrane fouling, scaling, and efficiency reduction problems for traditional membrane separation and evaporation concentration technologies. Currently, the industry mostly uses acid-base neutralization flocculation and sedimentation processes to treat this type of wastewater. While these processes can remove some suspended solids, they cannot effectively separate soluble salts, resulting in a high environmental risk even after treatment. Directly using evaporation and crystallization to recover sodium carbonate often leads to impurity accumulation, affecting product purity and increasing energy costs. Summary of the Invention

[0003] In view of this, the purpose of this invention is to propose a method for refining, concentrating, and recovering carbonate wastewater from the carbonation process of precipitated silica, thereby solving the problems of refining, concentrating, and fully recovering production wastewater containing sodium carbonate and sodium bicarbonate.

[0004] To achieve the above-mentioned technical objectives, the technical solution adopted by this invention is: a method for refining, treating, concentrating, and recovering carbonate wastewater from carbonation process precipitated silica, comprising:

[0005] Carbonate wastewater is transported to the first reaction tank, where flocculant is added to react and cause SiO2 and heavy metal ions to form flocculated precipitates, yielding a reaction solution.

[0006] The reaction solution is fed to a plate and frame filter for circulating filtration to obtain a clear filtrate.

[0007] The clarified filtrate is sent to the second reaction tank, filtered through a microporous filter, and then enters the resin tower to remove metal impurities, thus obtaining a purified liquid.

[0008] The purified liquid is fed to a hollow fiber membrane for colloidal filtration to obtain a hollow fiber membrane concentrate and a hollow fiber membrane dialysis solution.

[0009] The hollow fiber membrane concentrate is returned to the microporous filter;

[0010] Hollow fiber membrane dialysis solution is fed into a high-pressure reverse osmosis membrane device for concentration to obtain high-pressure reverse osmosis liquid with a TDS of 7% to 9%. The high-pressure reverse osmosis liquid includes high-pressure reverse osmosis concentrate and high-pressure reverse osmosis dialysis solution.

[0011] The high-pressure reverse osmosis effluent is fed to a low-pressure reverse osmosis membrane unit for processing to obtain low-pressure reverse osmosis liquid, which includes low-pressure reverse osmosis concentrate and low-pressure reverse osmosis effluent. The low-pressure reverse osmosis concentrate is returned to the high-pressure reverse osmosis membrane unit, and the low-pressure reverse osmosis effluent is reused in the carbonization process of silica production line.

[0012] The high-pressure reverse osmosis concentrate is fed to a wet decomposition tower, where sodium bicarbonate in the high-pressure reverse osmosis concentrate is converted into sodium carbonate to obtain wet decomposition liquid;

[0013] The wet decomposition liquid is fed to a high-pressure nanofiltration membrane device for processing to obtain high-pressure nanofiltration liquid, which includes high-pressure nanofiltration concentrate and high-pressure nanofiltration dialysate.

[0014] The high-pressure nanofiltration concentrate was used as the feed liquid for the MVR concentration unit. After MVR concentration and drying, anhydrous sodium carbonate was finally obtained.

[0015] In addition, the high-pressure nanofiltration dialysis solution is returned to the high-pressure reverse osmosis membrane unit for reuse.

[0016] In some embodiments, carbonate wastewater is transported to a first reaction tank, and a flocculant is added to the first reaction tank to react, causing SiO2 and heavy metal ions to form flocculated precipitates, yielding a reaction solution comprising:

[0017] The carbonate wastewater is transported to the first reaction tank, and the reaction temperature is controlled at 40℃~60℃, and the pH is 9.0~10.5.

[0018] Add 0.05%–0.1% (by liquid mass) of polyaluminum sulfate to the first reaction tank as a flocculant, and stir for 40–80 minutes to allow suspended solids, SiO2, and heavy metal ions to form flocs and settle. The residual concentration of the reaction solution is: Ca 2+ <10mg / L, Mg 2+ <10mg / L, Fe 3+ <5mg / L, Al 3 + <5mg / L, SiO2 <50mg / L.

[0019] In some embodiments, the reaction solution is fed to a plate and frame filter for circulating filtration to obtain a clear filtrate, comprising:

[0020] The reaction solution is delivered to a plate and frame filter device at a pressure of 0.3MPa to 0.5MPa, the filtration temperature is controlled at 40℃ to 60℃, and the filter cloth with a pore size of 150 mesh to 200 mesh is used for filtration.

[0021] When the turbidity of the filtrate is >10 NTU, the filtrate is returned to the inlet of the plate and frame filter for circulation filtration.

[0022] When the turbidity of the filtrate is ≤10 NTU, it is output as clarified filtrate.

[0023] In some embodiments, the clarified filtrate is conveyed to a second reaction vessel, filtered through a microporous filter, and then enters a resin tower to remove metal impurities, yielding a purified liquid comprising:

[0024] The clarified filtrate is transferred to the second reaction vessel, and the reaction temperature is controlled at 40℃~60℃. Precision filtration is performed using a microporous filter with a pore size of 0.5μm~1.0μm, and the operating pressure is 0.1MPa~0.3MPa.

[0025] The filtered liquid is passed through a resin tower containing chelating resin at a flow rate of 2 BV / h to 4 BV / h, and the operating temperature of the resin tower is controlled at 40℃ to 60℃.

[0026] After treatment in the resin tower, a refined liquid is obtained, and the residual metal ion concentration in the refined liquid reaches: Ca 2+ <1 mg / L, Mg 2+ <1 mg / L, Fe 3+ <0.5mg / L, Al 3 + <0.5mg / L, turbidity of purified solution <2NTU.

[0027] In some embodiments, the purified liquid is fed to a hollow fiber membrane for colloidal filtration to obtain a hollow fiber membrane concentrate and a hollow fiber membrane dialysis solution, comprising:

[0028] The purified liquid is delivered to the hollow fiber membrane device at an operating pressure of 0.1MPa to 0.3MPa. The hollow fiber membrane device is equipped with a hollow fiber membrane layer, and the operating temperature of the hollow fiber membrane device is controlled at 30℃ to 40℃.

[0029] The reflux ratio of the hollow fiber membrane concentrate is adjusted to 5% to 10% to obtain a hollow fiber membrane concentrate with a solid content of 0.1% to 0.2% and a colloid removal rate of ≥95%. At the same time, a hollow fiber membrane dialysis solution with turbidity <0.5 NTU and SDI value <3 is obtained.

[0030] The hollow fiber membrane dialysis solution is fed into a high-pressure reverse osmosis membrane unit for concentration to obtain a high-pressure reverse osmosis liquid with a TDS of 7% to 9%. The high-pressure reverse osmosis liquid includes a high-pressure reverse osmosis concentrate and a high-pressure reverse osmosis dialysis solution, comprising:

[0031] The hollow fiber membrane dialysis solution is transported to the high-pressure reverse osmosis membrane unit, and the operating pressure is controlled at 5.5MPa~6.5MPa, and the operating temperature is 30℃~40℃.

[0032] High-pressure reverse osmosis membrane elements are used, and the membrane surface flow velocity of the high-pressure reverse osmosis membrane elements is controlled at 1.0 m / s to 1.5 m / s;

[0033] By adjusting the reflux ratio of the high-pressure reverse osmosis liquid to 20%–40%, a high-pressure reverse osmosis concentrate with a TDS of 7%–9% is obtained, along with a high-pressure reverse osmosis precipitate with a conductivity of <2000 μS / cm.

[0034] In some embodiments, the high-pressure reverse osmosis solution is fed to a low-pressure reverse osmosis membrane unit for processing to obtain a low-pressure reverse osmosis liquid, including:

[0035] The high-pressure reverse osmosis solution is transported to the low-pressure reverse osmosis membrane unit, and the operating pressure is controlled at 1.5MPa~2.5MPa, and the operating temperature is 30℃~40℃.

[0036] By adjusting the reflux ratio of the low-pressure reverse osmosis liquid to 10%–30%, a low-pressure reverse osmosis effluent with a conductivity of <500 μS / cm is obtained, and a low-pressure reverse osmosis concentrate with a TDS of 2%–3% is also obtained.

[0037] When the membrane flux of the low-pressure reverse osmosis membrane element drops to 80% of the initial value, chemical cleaning is performed using a citric acid solution with a pH of 2.0 to 4.0. The cleaning cycle is 10 to 15 days, each cleaning session lasts 60 to 90 minutes, and the cleaning pressure is 0.2 MPa to 0.3 MPa.

[0038] In some embodiments, the high-pressure reverse osmosis concentrate is fed to a wet decomposition tower to convert sodium bicarbonate in the high-pressure reverse osmosis concentrate into sodium carbonate, yielding a wet decomposition solution, comprising:

[0039] The wet decomposition tower adopts a packed tower structure with a packing height of 3m to 5m. The packing type is Pall rings or stepped rings, and the packing specifications are DN25 to DN38.

[0040] The reaction temperature in the wet decomposition tower is controlled at 95℃~100℃, the pressure inside the tower is 0.05MPa~0.1MPa, and the reaction residence time is 45min~90min;

[0041] A flow rate of 0.5 m³ / s is introduced into the wet decomposition tower. 3 / min~1.0m3 Saturated steam was supplied at a rate of / min, and the pH value at the end of the decomposition reaction was controlled to be 10.5-11.5 to obtain a wet decomposition solution with a sodium bicarbonate conversion rate of ≥98% and a sodium carbonate concentration of 7wt%-10wt% in the wet decomposition solution.

[0042] The converted wet decomposition liquid is cooled to 30℃~40℃ by a heat exchanger and then transported to a high-pressure nanofiltration membrane device.

[0043] In some embodiments, the wet decomposition solution is fed to a high-pressure nanofiltration membrane device for processing to obtain a high-pressure nanofiltration liquid, which includes a high-pressure nanofiltration concentrate and a high-pressure nanofiltration dialysate, comprising:

[0044] The wet decomposition solution is transported to the high-pressure nanofiltration membrane unit, and the operating pressure of the high-pressure nanofiltration membrane unit is controlled at 6.5MPa~7.5MPa and the operating temperature is 30℃~40℃.

[0045] By adjusting the reflux ratio to 50%–70%, a high-pressure nanofiltration concentrate with a sodium carbonate concentration of 13%–15% is obtained, along with a high-pressure nanofiltration dialysis solution with a TDS of <4%.

[0046] In some embodiments, the high-pressure nanofiltration concentrate is used as the feed liquid for the MVR concentration device, and after MVR concentration and drying, anhydrous sodium carbonate is finally obtained, comprising:

[0047] The high-pressure nanofiltration concentrate is transported to the MVR concentration unit. The compression ratio of the MVR concentration unit is 1.0 to 2.5, the steam compressor speed is 3000 rpm to 10000 rpm, the evaporation temperature is controlled at 95℃ to 110℃, and the operating pressure is -0.09 MPa to 0.06 MPa.

[0048] The high-pressure nanofiltration concentrate was evaporated and concentrated to a solid content of 25-30%, and then centrifuged to obtain sodium carbonate monohydrate crystals. The centrifuge speed was controlled at 1000-3000 rpm and the separation time was 1-3 min.

[0049] Sodium carbonate monohydrate crystals are fed into a fluidized bed dryer, and the drying temperature is controlled at 150℃~180℃ for 30min~60min, finally obtaining anhydrous sodium carbonate product with a purity ≥98%.

[0050] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0051] This invention provides a method for the purification, concentration, and recovery of carbonate wastewater from the carbonation process of precipitated silica. The method includes: conveying carbonate wastewater to a first reaction tank for flocculation and precipitation, causing SiO2 and heavy metal ions to form flocculated precipitates to obtain a reaction solution; filtering the reaction solution through a plate and frame filter to obtain a clarified filtrate; processing the clarified filtrate through microfiltration and a resin tower to obtain a purified solution; separating the purified solution into a concentrate and a dialysate through a hollow fiber membrane, with the concentrate returned to the microfiltration filter; concentrating the dialysate through a high-pressure reverse osmosis membrane device to obtain a high-pressure reverse osmosis concentrate and a dialysate, with the dialysate treated by a low-pressure reverse osmosis membrane device for reuse; converting the high-pressure reverse osmosis concentrate into a sodium carbonate solution through a wet decomposition tower, and then separating the concentrate and dialysate through a high-pressure nanofiltration membrane device; concentrating and drying the concentrate using an MVR to obtain anhydrous sodium carbonate, with the dialysate returned to the high-pressure reverse osmosis membrane device. This method achieves cascaded removal of pollutants from carbonate wastewater and efficient resource recovery. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a schematic diagram of the method and apparatus system described in the specific implementation. Detailed Implementation

[0054] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Please see Figure 1 This embodiment provides a method for refining, concentrating, and recovering carbonate wastewater from carbonation process precipitated silica, including:

[0056] Carbonate wastewater is transported to the first reaction tank, where flocculant is added to react and cause SiO2 and heavy metal ions to form flocculated precipitates, yielding a reaction solution.

[0057] The reaction solution is fed to a plate and frame filter for circulating filtration to obtain a clear filtrate.

[0058] The clarified filtrate is sent to the second reaction tank, filtered through a microporous filter, and then enters the resin tower to remove metal impurities, thus obtaining a purified liquid.

[0059] The purified liquid is fed to a hollow fiber membrane for colloidal filtration to obtain a hollow fiber membrane concentrate and a hollow fiber membrane dialysis solution.

[0060] The hollow fiber membrane concentrate is returned to the microporous filter;

[0061] Hollow fiber membrane dialysis solution is fed into a high-pressure reverse osmosis membrane device for concentration to obtain high-pressure reverse osmosis liquid with a TDS of 7% to 9%. The high-pressure reverse osmosis liquid includes high-pressure reverse osmosis concentrate and high-pressure reverse osmosis dialysis solution.

[0062] The high-pressure reverse osmosis effluent is fed to a low-pressure reverse osmosis membrane unit for processing to obtain low-pressure reverse osmosis liquid, which includes low-pressure reverse osmosis concentrate and low-pressure reverse osmosis effluent. The low-pressure reverse osmosis concentrate is returned to the high-pressure reverse osmosis membrane unit, and the low-pressure reverse osmosis effluent is reused in the carbonization process of silica production line.

[0063] The high-pressure reverse osmosis concentrate is fed to a wet decomposition tower, where sodium bicarbonate in the high-pressure reverse osmosis concentrate is converted into sodium carbonate to obtain wet decomposition liquid;

[0064] The wet decomposition liquid is fed to a high-pressure nanofiltration membrane device for processing to obtain high-pressure nanofiltration liquid, which includes high-pressure nanofiltration concentrate and high-pressure nanofiltration dialysate.

[0065] The high-pressure nanofiltration concentrate was used as the feed liquid for the MVR concentration unit. After MVR concentration and drying, anhydrous sodium carbonate was finally obtained.

[0066] In addition, the high-pressure nanofiltration dialysis solution is returned to the high-pressure reverse osmosis membrane unit for reuse.

[0067] In this embodiment, the wastewater from the carbonization process for producing precipitated silica is collected and transported to the first reaction tank. Flocculants are added to remove precipitates, SiO2, and heavy metal ions. The clarified filtrate, obtained through a plate and frame filter, then enters the second reaction tank. Deep removal of metal impurities is achieved by sequentially passing the filtrate through a microporous filter and a resin tower. The refined liquid is separated by a hollow fiber membrane, and the dialysis liquid undergoes cascade treatment using a high-pressure reverse osmosis membrane device and a low-pressure reverse osmosis membrane device for water reuse. The concentrated liquid is converted by a wet decomposition tower and then separated by a high-pressure nanofiltration membrane device to obtain sodium carbonate concentrate. Finally, anhydrous sodium carbonate is obtained through an MVR concentration device and drying.

[0068] Furthermore, the apparatus system used in this embodiment to implement the above method includes: a first reaction vessel, a second reaction vessel, a plate and frame filter device, a microporous filter device, a resin tower, a hollow fiber membrane device, a high-pressure reverse osmosis membrane device, a low-pressure reverse osmosis membrane device, a wet decomposition tower, a high-pressure nanofiltration membrane device, and an MVR concentration device.

[0069] The first reaction vessel is used to complete the flocculation and sedimentation reaction and is equipped with a stirring system; the plate and frame filter can be equipped with a circulation pipeline and an online turbidity monitoring system, and adopts a corrosion-resistant frame structure and a replaceable filter cloth design; the resin tower is a column-type device filled with chelating resin, equipped with a multi-layer distributor and a backwashing system; preferably, the wet decomposition tower is a tower-type device with built-in Pall ring packing; the high-pressure nanofiltration membrane device is equipped with a high-pressure resistant membrane shell and a variable frequency feed pump; the MVR concentration unit is an evaporation system with an integrated steam compressor.

[0070] Furthermore, the system also includes a drying device, which is a fluidized bed dryer. Preferably, the fluidized bed dryer is equipped with a hot air circulation system and a temperature gradient control device for dehydration and drying to obtain anhydrous sodium carbonate product.

[0071] This embodiment constructs a complete carbonate wastewater treatment system through gradient reactions in multi-stage reactors, synergistic purification by plate and frame filtration and resin towers, tiered separation by hollow fiber membranes and reverse osmosis membranes, efficient conversion by wet decomposition towers, and energy-saving concentration by MVR thickeners. Suspended solids and heavy metals are effectively removed through flocculation and sedimentation in the first reactor, followed by cyclic filtration by the plate and frame filtration unit to ensure clarity. Subsequent deep purification by the resin tower ensures the safe operation of the subsequent membrane system. The combination of hollow fiber membranes and dual-stage reverse osmosis membranes achieves both colloid removal and water reuse. The wet decomposition tower efficiently converts sodium bicarbonate into sodium carbonate, providing qualified raw materials for subsequent concentration. Finally, the combination of high-pressure nanofiltration membrane devices and MVR thickeners achieves efficient recovery of sodium carbonate. The entire process system, through internal material circulation design and tiered energy utilization, maximizes resource recovery while ensuring treatment effectiveness, forming a complete "treatment, recovery, and reuse" closed-loop system, achieving a balance between environmental and economic benefits.

[0072] In some embodiments, carbonate wastewater is transported to a first reaction tank, and a flocculant is added to the first reaction tank to react, causing SiO2 and heavy metal ions to form flocculated precipitates, yielding a reaction solution comprising:

[0073] The carbonate wastewater is transported to the first reaction tank, and the reaction temperature is controlled at 40℃~60℃, and the pH is 9.0~10.5.

[0074] Add 0.05%–0.1% (by liquid mass) of polyaluminum sulfate to the first reaction tank as a flocculant, and stir for 40–80 minutes to allow suspended solids, SiO2, and heavy metal ions to form flocs and settle. The residual concentration of the reaction solution is: Ca 2+ <10mg / L, Mg 2+ <10mg / L, Fe 3+ <5mg / L, Al 3+ <5mg / L, SiO2 <50mg / L.

[0075] In this embodiment, by controlling the operating parameters of the first reaction vessel (reaction temperature of 40℃~60℃, pH range of 9.0~10.5) and optimizing the flocculant dosage (polyaluminum sulfate 0.05%~0.1%), the reaction time of Ca was reduced to 40min~80min. 2+ Mg 2+ Fe 3+ This process achieves efficient removal of metal ions such as Al3+ and SiO2. The process conditions ensure sufficient floc formation while avoiding excessive reagent consumption, resulting in a residual concentration of Ca in the reaction solution. 2+ <10mg / L, Mg 2+ Purification standard of <10mg / L.

[0076] In some embodiments, the reaction solution is fed to a plate and frame filter for circulating filtration to obtain a clear filtrate, comprising:

[0077] The reaction solution is delivered to a plate and frame filter device at a pressure of 0.3MPa to 0.5MPa, the filtration temperature is controlled at 40℃ to 60℃, and the filter cloth with a pore size of 150 mesh to 200 mesh is used for filtration.

[0078] When the turbidity of the filtrate is >10 NTU, the filtrate is returned to the inlet of the plate and frame filter for circulation filtration.

[0079] When the turbidity of the filtrate is ≤10 NTU, it is output as clarified filtrate.

[0080] In this embodiment, by optimizing the operating parameters of the plate and frame filter (pressure 0.3MPa~0.5MPa, temperature 40℃~60℃) and using filter cloth with a pore size of 5μm~10μm, efficient solid-liquid separation was achieved within a 10min~30min filtration cycle. Using 10NTU turbidity as the filtration control standard ensured both filtrate quality and energy waste caused by over-filtration. The filtration mode in this embodiment stably controlled the filter cake moisture content between 55% and 65%, while ensuring the quality of the filter cake with a SiO2 content ≥35wt%, creating favorable conditions for subsequent resource utilization.

[0081] This embodiment significantly improves filtration efficiency through the synergistic effect of pressure and temperature. The circulating filtration mechanism effectively solves the problem of unstable filtrate quality in traditional filtration processes, providing high-quality clarified filtrate with turbidity ≤10 NTU for subsequent refining processes, and ensuring the continuous and stable operation of the entire wastewater treatment system.

[0082] In some embodiments, the clarified filtrate is conveyed to a second reaction vessel, filtered through a microporous filter, and then enters a resin tower to remove metal impurities, yielding a purified liquid comprising:

[0083] The clarified filtrate is transferred to the second reaction vessel, and the reaction temperature is controlled at 40℃~60℃. Precision filtration is performed using a microporous filter with a pore size of 0.5μm~1.0μm, and the operating pressure is 0.1MPa~0.3MPa.

[0084] The filtered liquid is passed through a resin tower containing chelating resin at a flow rate of 2 BV / h to 4 BV / h, and the operating temperature of the resin tower is controlled at 40℃ to 60℃.

[0085] After treatment in the resin tower, a refined liquid is obtained, and the residual metal ion concentration in the refined liquid reaches: Ca 2+ <1 mg / L, Mg 2+ <1 mg / L, Fe 3+ <0.5mg / L, Al 3 + <0.5mg / L, turbidity of purified solution <2NTU.

[0086] In this embodiment, by precisely controlling the reaction temperature to 40℃~60℃, and using a 0.5μm~1.0μm microporous filter for precision filtration at an operating pressure of 0.1MPa~0.3MPa, suspended particles were effectively removed. By using a flow rate of 2BV / h~4BV / h through the chelating resin tower and maintaining a contact time of 20~40 minutes at 40℃~60℃, deep removal of residual metal ions was achieved.

[0087] This embodiment achieves a Ca2+ level in the purified liquid. + Mg2 + <1 mg / L, Fe3 + The resin achieves an extremely high purity standard of Al3+ < 0.5 mg / L while maintaining an excellent turbidity of < 2 NTU. Through multi-parameter synergistic optimization of temperature, flow rate, and contact time, the resin's working efficiency is ensured while its service life is extended. This provides a high-quality purified solution that meets the feed water requirements for subsequent membrane treatment systems, effectively preventing membrane fouling and ensuring the long-term stable operation of the entire process system.

[0088] In some embodiments, the purified liquid is fed to a hollow fiber membrane for colloidal filtration to obtain a hollow fiber membrane concentrate and a hollow fiber membrane dialysis solution, comprising:

[0089] The purified liquid is delivered to the hollow fiber membrane device at an operating pressure of 0.1MPa to 0.3MPa. The hollow fiber membrane device is equipped with a hollow fiber membrane layer, and the operating temperature of the hollow fiber membrane device is controlled at 30℃ to 40℃.

[0090] The reflux ratio of the hollow fiber membrane concentrate was adjusted to 5% to 10% to obtain a hollow fiber membrane concentrate with a solid content of 0.1% to 0.2% and a colloid removal rate of ≥95%. At the same time, a hollow fiber membrane dialysis solution with turbidity <0.5 NTU and SDI value <3 was obtained.

[0091] The hollow fiber membrane dialysis solution is fed into a high-pressure reverse osmosis membrane unit for concentration to obtain a high-pressure reverse osmosis liquid with a TDS of 7%–9%. The high-pressure reverse osmosis liquid includes high-pressure reverse osmosis concentrate and high-pressure reverse osmosis dialysis solution, including:

[0092] The hollow fiber membrane dialysis solution is transported to the high-pressure reverse osmosis membrane unit, and the operating pressure is controlled at 5.5MPa~6.5MPa, and the operating temperature is 30℃~40℃.

[0093] By adjusting the reflux ratio of the high-pressure reverse osmosis liquid to 20%–40%, a high-pressure reverse osmosis concentrate with a TDS of 7%–9% is obtained, along with a high-pressure reverse osmosis precipitate with a conductivity of <2000 μS / cm.

[0094] In this embodiment, hollow fiber membrane treatment at an operating pressure of 0.1MPa–0.3MPa and an operating temperature of 30°C–40°C achieved a colloid removal rate of ≥95%, resulting in a high-quality dialysate with a turbidity of <0.5 NTU. Subsequently, deep concentration was performed using a 100Da–200Da reverse osmosis membrane element under high pressure of 5.5MPa–6.5MPa and an operating temperature of 30°C–40°C. A reflux ratio of 20%–40% was controlled to ensure a concentration effect of 7%–9% TDS while maintaining dialysate quality with a conductivity of <2000 μS / cm.

[0095] This embodiment effectively solves the risk of colloidal substances fouling the reverse osmosis membrane by precisely matching the parameters of the two-stage membrane treatment, and achieves the dual goals of high-efficiency concentration and water purification. It provides a stable source of feed liquid for subsequent wet decomposition and MVR systems. At the same time, the system energy consumption is optimized by controlling the reasonable reflux ratio, demonstrating the comprehensive advantages of membrane separation technology in wastewater treatment.

[0096] In some embodiments, the high-pressure reverse osmosis solution is fed to a low-pressure reverse osmosis membrane unit for processing to obtain a low-pressure reverse osmosis liquid, including:

[0097] The high-pressure reverse osmosis solution is transported to the low-pressure reverse osmosis membrane unit, and the operating pressure is controlled at 1.5MPa~2.5MPa, and the operating temperature is 30℃~40℃.

[0098] By adjusting the reflux ratio of the low-pressure reverse osmosis liquid to 10%–30%, a low-pressure reverse osmosis effluent with a conductivity of <500 μS / cm is obtained, and a low-pressure reverse osmosis concentrate with a TDS of 2%–3% is also obtained.

[0099] When the membrane flux of the low-pressure reverse osmosis membrane element drops to 80% of the initial value, chemical cleaning is performed using a citric acid solution with a pH of 2.0 to 4.0. The cleaning cycle is 10 to 15 days, each cleaning session lasts 60 to 90 minutes, and the cleaning pressure is 0.2 MPa to 0.3 MPa.

[0100] In this embodiment, the operating parameters and cleaning and maintenance scheme of the low-pressure reverse osmosis membrane treatment process are defined in detail. High-efficiency separation is achieved through precise control of the operating pressure (1.5MPa–2.5MPa) and the operating temperature (30℃–40℃). Using a reflux ratio adjustment of 10%–30% ensures the production of high-quality dialysate with a conductivity <500μS / cm while maintaining the quality of the concentrate with 2%–3% TDS. The membrane cleaning scheme in this embodiment uses a citric acid solution with pH 2–3 at a pressure of 0.2MPa–0.3MPa for periodic cleaning, effectively solving the membrane fouling problem and extending the cleaning cycle to 10–15 days, significantly improving the service life of the membrane elements.

[0101] This embodiment significantly reduces energy consumption while ensuring treatment effectiveness through the synergistic optimization of pressure, temperature, and flow rate. The high-quality dialysis solution produced can be directly reused in the production line, realizing the efficient recycling of water resources. The membrane maintenance scheme ensures the long-term stable operation of the system, providing an important guarantee for the sustainability of the entire wastewater treatment process.

[0102] In some embodiments, the high-pressure reverse osmosis concentrate is fed to a wet decomposition tower to convert sodium bicarbonate in the high-pressure reverse osmosis concentrate into sodium carbonate, yielding a wet decomposition solution, comprising:

[0103] The wet decomposition tower adopts a packed tower structure with a packing height of 3m to 5m. The packing type is Pall rings or stepped rings, and the packing specifications are DN25 to DN38.

[0104] The reaction temperature in the wet decomposition tower is controlled at 95℃~100℃, the pressure inside the tower is 0.05MPa~0.1MPa, and the reaction residence time is 45min~90min;

[0105] A flow rate of 0.5 m³ / s is introduced into the wet decomposition tower. 3 / min~1.0m 3 Saturated steam was supplied at a rate of / min, and the pH value at the end of the decomposition reaction was controlled to be 10.5-11.5 to obtain a wet decomposition solution with a sodium bicarbonate conversion rate of ≥98% and a sodium carbonate concentration of 7wt%-10wt% in the wet decomposition solution.

[0106] The converted wet decomposition liquid is cooled to 30℃~40℃ by a heat exchanger and then transported to a high-pressure nanofiltration membrane device.

[0107] In this embodiment, the structural parameters and operating conditions of the wet decomposition tower are specifically defined. A Pall ring or stepped ring packed tower with a packing height of 3m to 5m is used, under reaction temperatures of 95 to 105°C and pressures of 0.05MPa to 0.1MPa, in conjunction with a 0.5m... 3 / min~1.0m 3 The introduction of saturated steam per minute ( / min) achieved a high-efficiency conversion of sodium bicarbonate to ≥98%. Optimized reaction residence times of 45-90 min, combined with endpoint pH control of 10.5-11.5, ensured a wet decomposition liquid concentration of 7-10 wt% sodium carbonate. The packed tower structure design effectively increased the gas-liquid contact area, improving mass transfer efficiency, while precisely controlled reaction parameters guaranteed conversion rates while avoiding excessive energy consumption. Cooling to 30-40℃ via a heat exchanger met the feed temperature requirements of the subsequent high-pressure nanofiltration membrane and enabled heat recovery.

[0108] In this embodiment, the wet decomposition process achieves high-efficiency conversion within a compact equipment space through systematic optimization of structural parameters and operating conditions, providing sodium carbonate solution with concentration requirements for subsequent resource recovery, and realizing the cascade utilization of energy through reasonable temperature control.

[0109] In some embodiments, the wet decomposition solution is fed to a high-pressure nanofiltration membrane device for processing to obtain a high-pressure nanofiltration liquid, which includes a high-pressure nanofiltration concentrate and a high-pressure nanofiltration dialysate, comprising:

[0110] The wet decomposition solution is transported to the high-pressure nanofiltration membrane unit, and the operating pressure of the high-pressure nanofiltration membrane unit is controlled at 6.5MPa~7.5MPa and the operating temperature is 30℃~40℃.

[0111] By adjusting the reflux ratio to 50%–70%, a high-pressure nanofiltration concentrate with a sodium carbonate concentration of 13%–15% is obtained, along with a high-pressure nanofiltration dialysis solution with a TDS of <4%.

[0112] In this embodiment, high-efficiency separation was achieved through high-pressure operation of 6.5MPa to 7.5MPa and temperature control of 30℃ to 40℃. By precisely adjusting the reflux ratio of 50% to 70%, both a high-pressure nanofiltration concentrate with a sodium carbonate concentration of 13% to 15% was produced, and a high-quality dialysate with TDS < 4% was obtained.

[0113] This embodiment effectively controls the risk of membrane fouling while ensuring separation efficiency through the synergistic effect of high-pressure operating conditions and a suitable temperature range. The optimized membrane surface flow rate ensures mass transfer efficiency while avoiding increased energy consumption due to excessively high flow rates, and the reflux ratio setting achieves the optimal balance between product concentration and recovery rate. This high-pressure nanofiltration process provides the subsequent MVR system with feed liquid that meets the concentration requirements, and the reuse of dialysate enables material recycling. The overall system parameters ensure both treatment effectiveness and operational economy, demonstrating the comprehensive advantages of membrane separation technology in resource recovery.

[0114] In some embodiments, the high-pressure nanofiltration concentrate is used as the feed liquid for the MVR concentration device, and after MVR concentration and drying, anhydrous sodium carbonate is finally obtained, comprising:

[0115] The high-pressure nanofiltration concentrate is transported to the MVR concentration unit. The compression ratio of the MVR concentration unit is 1.0 to 2.5, the steam compressor speed is 3000 rpm to 10000 rpm, the evaporation temperature is controlled at 95℃ to 110℃, and the operating pressure is -0.09 MPa to 0.06 MPa.

[0116] The high-pressure nanofiltration concentrate was evaporated and concentrated to a solid content of 25%–30%, and then centrifuged to obtain sodium carbonate monohydrate crystals. The centrifuge speed was controlled at 1000 rpm–3000 rpm and the separation time was 1 min–3 min.

[0117] Sodium carbonate monohydrate crystals are fed into a fluidized bed dryer, and the drying temperature is controlled at 120-150℃ for 30-60 minutes to obtain anhydrous sodium carbonate product with a purity ≥98%.

[0118] In this embodiment, the operating parameters of the MVR concentration and subsequent drying processes are specifically defined. An MVR concentration device with a compression ratio of 1.0–2.5 and a rotation speed of 3000 rpm–10000 rpm is used to achieve efficient concentration at an evaporation temperature of 95°C–110°C and an operating pressure of -0.09 MPa–0.06 MPa, increasing the solid content of the solution to 25%–30%. Then, centrifugation at 1000 rpm–3000 rpm is performed for 1 min–3 min to obtain qualified sodium carbonate monohydrate crystals. The subsequent fluidized bed drying process is carried out at 150°C–180°C for 30 min–60 min to finally obtain anhydrous sodium carbonate product with a purity ≥98%.

[0119] This embodiment achieves energy-efficient utilization through optimized MVR operating parameters. Precisely controlled evaporation conditions ensure concentration efficiency while preventing component damage, while staged centrifugation and drying processes ensure the crystal morphology and purity of the product. The systematic configuration of the entire process parameters enables the complete transformation from wastewater concentrate to high-purity product. The scientific matching of operating conditions at each stage ensures product quality while optimizing energy consumption, fully demonstrating the synergistic improvement of resource recovery and energy efficiency.

[0120] By adopting the above technical solutions, the present invention differs from the prior art and has the following beneficial effects:

[0121] This invention achieves efficient removal of suspended solids, heavy metal ions, and SiO2 from carbonate wastewater through gradient sedimentation in multi-stage reaction tanks, combined with circulating filtration of a plate and frame filter and deep purification of a resin tower. The tiered combination of hollow fiber membranes with high-pressure and low-pressure reverse osmosis membranes not only achieves fine filtration of colloidal substances but also enables the tiered recycling of water resources. The wet decomposition tower, through optimized packing structure and reaction parameters, efficiently converts sodium bicarbonate into sodium carbonate, providing qualified raw materials for subsequent treatment. The high-pressure nanofiltration membrane device, under precisely controlled operating conditions, achieves efficient concentration and separation of the sodium carbonate solution. Finally, through energy-saving evaporation of the MVR concentration unit and precise temperature control of the fluidized bed dryer, the carbonates in the wastewater are converted into high-purity anhydrous sodium carbonate product.

[0122] The aforementioned technical solution, through internal material circulation design and tiered energy utilization, ensures efficient pollutant removal while maximizing resource recovery. It solves both wastewater treatment problems and the recovery and utilization of valuable components, achieving a balance between environmental and economic benefits. Parameter optimization and system integration of each treatment unit guarantee treatment effectiveness while reducing operating energy consumption, providing an efficient and reliable technical solution for the resource-based treatment of carbonate wastewater from the carbonation process of precipitated silica.

[0123] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0124] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute all or part of the steps of the methods of various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0125] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for refining, concentrating, and recovering carbonate wastewater from the carbonation process of precipitated silica, characterized in that, include: Carbonate wastewater is transported to the first reaction tank, where flocculant is added to the first reaction tank to react, causing SiO2 and heavy metal ions to form flocculated precipitates, thus obtaining a reaction solution. The reaction solution is fed to a plate and frame filter for circulating filtration to obtain a clear filtrate. The clarified filtrate is transported to the second reaction tank, filtered through a microporous filter, and then enters the resin tower to remove metal impurities, thereby obtaining a purified liquid. The purified liquid is fed to a hollow fiber membrane for colloidal filtration to obtain a hollow fiber membrane concentrate and a hollow fiber membrane dialysis solution. The hollow fiber membrane concentrate is returned to the microporous filter; Hollow fiber membrane dialysis solution is fed into a high-pressure reverse osmosis membrane device for concentration to obtain high-pressure reverse osmosis liquid with a TDS of 7% to 9%. The high-pressure reverse osmosis liquid includes high-pressure reverse osmosis concentrate and high-pressure reverse osmosis dialysis solution. The high-pressure reverse osmosis effluent is fed to a low-pressure reverse osmosis membrane unit for processing to obtain a low-pressure reverse osmosis liquid, which includes a low-pressure reverse osmosis concentrate and a low-pressure reverse osmosis effluent. The low-pressure reverse osmosis concentrate is returned to the high-pressure reverse osmosis membrane unit, and the low-pressure reverse osmosis effluent is reused in the carbonization process for silica production line. The high-pressure reverse osmosis concentrate is fed to a wet decomposition tower, where sodium bicarbonate in the high-pressure reverse osmosis concentrate is converted into sodium carbonate to obtain a wet decomposition solution. The wet decomposition liquid is transported to a high-pressure nanofiltration membrane device for processing to obtain a high-pressure nanofiltration liquid, which includes a high-pressure nanofiltration concentrate and a high-pressure nanofiltration dialysate. The high-pressure nanofiltration concentrate is used as the feed liquid for the MVR concentration device. After MVR concentration and drying, anhydrous sodium carbonate is finally obtained. In addition, the high-pressure nanofiltration dialysis solution is returned to the high-pressure reverse osmosis membrane unit for reuse.

2. The method for refining, concentrating, and recovering carbonate wastewater from carbonation-based precipitated silica according to claim 1, characterized in that, Carbonate wastewater is transported to a first reaction tank, where a flocculant is added to initiate a reaction, causing SiO2 and heavy metal ions to form flocculated precipitates, yielding a reaction solution comprising: The carbonate wastewater is transported to the first reaction tank, and the reaction temperature is controlled at 40℃~60℃, and the pH is 9.0~10.

5. Add 0.05%–0.1% (by liquid mass) of polyaluminum sulfate to the first reaction tank as a flocculant, and stir for 40–80 minutes to allow suspended solids, SiO2, and heavy metal ions to form flocs and settle. The residual concentration of the reaction solution is: Ca 2+ <10mg / L, Mg 2+ <10mg / L, Fe 3+ <5mg / L, Al 3 + <5mg / L, SiO2 <50mg / L.

3. The method for refining, concentrating, and recovering carbonate wastewater from carbonation-based precipitated silica according to claim 1, characterized in that, The reaction solution is fed to a plate and frame filter for circulating filtration to obtain a clear filtrate, comprising: The reaction solution is delivered to a plate and frame filter device at a pressure of 0.3MPa to 0.5MPa, the filtration temperature is controlled at 40℃ to 60℃, and the filter cloth with a pore size of 150 mesh to 200 mesh is used for filtration. When the turbidity of the filtrate is >10 NTU, the filtrate is returned to the inlet of the plate and frame filter for circulation filtration. When the turbidity of the filtrate is ≤10 NTU, it is output as clarified filtrate.

4. The method for refining, concentrating, and recovering carbonate wastewater from carbonation-based precipitated silica according to claim 1, characterized in that, The clarified filtrate is conveyed to a second reaction vessel, filtered through a microporous filter, and then enters a resin tower to remove metal impurities, yielding a purified liquid comprising: The clarified filtrate is transferred to the second reaction vessel, and the reaction temperature is controlled at 40℃~60℃. Precision filtration is performed using a microporous filter with a pore size of 0.5μm~1.0μm, and the operating pressure is 0.1MPa~0.3MPa. The filtered liquid is passed through a resin tower containing chelating resin at a flow rate of 2 BV / h to 4 BV / h, and the operating temperature of the resin tower is controlled at 40℃ to 60℃. After treatment in the resin tower, a refined liquid is obtained, wherein the residual metal ion concentration in the refined liquid reaches: Ca 2+ <1 mg / L, Mg 2+ <1 mg / L, Fe 3+ <0.5mg / L, Al 3 + <0.5mg / L, turbidity of purified solution <2NTU.

5. The method for refining, concentrating, and recovering carbonate wastewater from carbonation-based precipitated silica according to claim 1, characterized in that, The purified solution is fed to a hollow fiber membrane for colloidal filtration to obtain a hollow fiber membrane concentrate and a hollow fiber membrane dialysis solution, comprising: The purified liquid is delivered to the hollow fiber membrane device at an operating pressure of 0.1MPa to 0.3MPa. The hollow fiber membrane device is equipped with a hollow fiber membrane layer, and the operating temperature of the hollow fiber membrane device is controlled at 30℃ to 40℃. The reflux ratio of the hollow fiber membrane concentrate is adjusted to 5% to 10% to obtain a hollow fiber membrane concentrate with a solid content of 0.1% to 0.2% and a colloid removal rate of ≥95%. At the same time, a hollow fiber membrane dialysis solution with turbidity <0.5 NTU and SDI value <3 is obtained. The hollow fiber membrane dialysis solution is fed into a high-pressure reverse osmosis membrane unit for concentration to obtain a high-pressure reverse osmosis liquid with a TDS of 7% to 9%. The high-pressure reverse osmosis liquid includes a high-pressure reverse osmosis concentrate and a high-pressure reverse osmosis dialysis solution, comprising: The hollow fiber membrane dialysis solution is transported to the high-pressure reverse osmosis membrane unit, and the operating pressure is controlled at 5.5MPa~6.5MPa, and the operating temperature is 30℃~40℃. By adjusting the reflux ratio of the high-pressure reverse osmosis liquid to 20%–40%, a high-pressure reverse osmosis concentrate with a TDS of 7%–9% is obtained, along with a high-pressure reverse osmosis precipitate with a conductivity of <2000 μS / cm.

6. The method for refining, concentrating, and recovering carbonate wastewater from carbonation-based precipitated silica according to claim 1, characterized in that, The high-pressure reverse osmosis solution is transported to a low-pressure reverse osmosis membrane unit for processing to obtain a low-pressure reverse osmosis liquid, comprising: The high-pressure reverse osmosis solution is transported to the low-pressure reverse osmosis membrane unit, and the operating pressure is controlled at 1.5MPa~2.5MPa, and the operating temperature is 30℃~40℃. By adjusting the reflux ratio of the low-pressure reverse osmosis liquid to 10%–30%, a low-pressure reverse osmosis effluent with a conductivity of <500 μS / cm is obtained, and a low-pressure reverse osmosis concentrate with a TDS of 2%–3% is also obtained. When the membrane flux of the low-pressure reverse osmosis membrane element drops to 80% of the initial value, chemical cleaning is performed using a citric acid solution with a pH of 2.0 to 4.

0. The cleaning cycle is 10 to 15 days, each cleaning session lasts 60 to 90 minutes, and the cleaning pressure is 0.2 MPa to 0.3 MPa.

7. The method for refining, concentrating, and recovering carbonate wastewater from carbonation-based precipitated silica according to claim 1, characterized in that, The high-pressure reverse osmosis concentrate is fed to a wet decomposition tower, where sodium bicarbonate in the concentrate is converted into sodium carbonate to obtain a wet decomposition solution, comprising: The wet decomposition tower adopts a packed tower structure with a packing height of 3m to 5m, and the packing type is Pall rings or stepped rings with a packing specification of DN25 to DN38. The reaction temperature in the wet decomposition tower is controlled at 95℃~100℃, the pressure inside the tower is 0.05MPa~0.1MPa, and the reaction residence time is 45min~90min; A flow rate of 0.5 m³ / s is introduced into the wet decomposition tower. 3 / min~1.0m 3 Saturated steam was supplied at a rate of / min, and the pH value at the end of the decomposition reaction was controlled to be 10.5-11.5 to obtain a wet decomposition solution with a sodium bicarbonate conversion rate of ≥98%, wherein the sodium carbonate concentration in the wet decomposition solution was 7wt%-10wt%. The converted wet decomposition liquid is cooled to 30℃~40℃ by a heat exchanger and then transported to a high-pressure nanofiltration membrane device.

8. The method for refining, concentrating, and recovering carbonate wastewater from carbonation-based precipitated silica according to claim 1, characterized in that, The wet decomposition solution is fed to a high-pressure nanofiltration membrane device for processing to obtain a high-pressure nanofiltration liquid. The high-pressure nanofiltration liquid includes a high-pressure nanofiltration concentrate and a high-pressure nanofiltration dialysate, comprising: The wet decomposition solution is transported to the high-pressure nanofiltration membrane unit, and the operating pressure of the high-pressure nanofiltration membrane unit is controlled at 6.5MPa~7.5MPa and the operating temperature is 30℃~40℃. By adjusting the reflux ratio to 50%–70%, a high-pressure nanofiltration concentrate with a sodium carbonate concentration of 13%–15% is obtained, along with a high-pressure nanofiltration dialysis solution with a TDS of <4%.

9. The method for refining, concentrating, and recovering carbonate wastewater from carbonation-based precipitated silica according to claim 1, characterized in that, The high-pressure nanofiltration concentrate is used as the feed liquid for the MVR concentration device. After MVR concentration and drying, anhydrous sodium carbonate is finally obtained, comprising: The high-pressure nanofiltration concentrate is transported to an MVR concentration unit, wherein the compression ratio of the MVR concentration unit is 1.0 to 2.5, the steam compressor speed is 3000 rpm to 10000 rpm, the evaporation temperature is controlled at 95℃ to 110℃, and the operating pressure is -0.09 MPa to 0.06 MPa. The high-pressure nanofiltration concentrate was evaporated and concentrated to a solid content of 25%–30%, and then centrifuged to obtain sodium carbonate monohydrate crystals. The centrifuge speed was controlled at 1000 rpm–3000 rpm and the separation time was 1 min–3 min. Sodium carbonate monohydrate crystals are fed into a fluidized bed dryer, and the drying temperature is controlled at 150℃~180℃ for 30min~60min, finally obtaining anhydrous sodium carbonate product with a purity ≥98%.

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