Process and device for preparing flocculating agent for heavy metal-containing industrial sludge

Abstract

The invention discloses a preparation process and device of a flocculating agent for heavy metal-containing industrial sludge, and relates to the technical field of sewage treatment material processing, the preparation process is improved on the basis of an original chemical grafting scheme, the total mass of a target solid product is taken as a production target, and batch production is carried out by adopting a small-scale and multi-round scheme; the effective component amount of each batch is controlled on the basis of the technical theory of mother liquor effective component enrichment, multi-round production of the target solid flocculant is achieved, meanwhile, after mother liquor is enriched for multiple times, the concentration of the finally produced mother liquor meets the industrial standard, no liquid metabolite is generated in the whole process, and in the rear-section drying stage, no liquid metabolite is generated. The scheme of centrifugal filtration and hot air drying crushing is adopted to replace a traditional spray drying tower, the equipment cost is reduced, meanwhile, heat generated in the drying stage is used for preheating in the front stage of drying and heat preservation in the mixing and curing process in the early stage of the scheme, efficient heat utilization is achieved, and the cost is further reduced.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment material processing technology, and in particular to a process and apparatus for preparing flocculants for industrial sludge containing heavy metals. Background Technology

[0002] Flocculants are materials frequently used in industrial manufacturing, especially in PCB, water treatment, and chemical separation. They work by adsorption, bridging, and trapping to aggregate dispersed colloids or suspended particles into large flocs, thus achieving solid-liquid separation. Based on material type, they are mainly divided into inorganic flocculants and organic flocculants. Inorganic flocculants primarily use charge neutralization as their mechanism, supplemented by a small amount of trapping and sweeping, while organic flocculants primarily use adsorption and bridging, supplemented by charge neutralization. However, in industrial settings, it is rare to use a single type of flocculant. The core reason is that inorganic flocculants can efficiently disrupt colloidal stability, but the flocs are small and settle slowly; organic flocculants can rapidly aggregate, but cannot directly destabilize stable colloids. Therefore, most flocculants today are composite types.

[0003] Traditional composite flocculants can be categorized into physical composite processes and chemical grafting processes based on their manufacturing techniques. Physical composite processes do not require chemical reactions; they achieve stable coexistence of inorganic flocculants and integrators solely through "dispersion-mixing-maturation." The core requirements are "uniform dispersion of the system, no stratification / precipitation, and no reaction between the integrator and inorganic components." Chemical grafting, on the other hand, involves grafting chelating groups (such as DTC and thiol groups) onto the molecular chain of the inorganic flocculant through a chemical reaction, forming an integrated structure of "inorganic skeleton-organic chelating groups." This avoids the stratification and integrator loss problems that may occur with physical composite processes.

[0004] Therefore, compared to physical compounding, chemically grafted flocculants are more effective. However, in actual production, chemical grafting requires a longer maturation time in the early maturation stage to ensure a grafting rate of no less than 85%. Furthermore, traditional single-stage stirring or single-frequency ultrasound is insufficient to overcome the mass transfer resistance between macromolecules. Additionally, the finished product from chemically grafted flocculants has a high water content, necessitating spray drying in a spray drying tower to produce powdered products. Spray drying towers are not only expensive to install but also costly to operate, and they generate wastewater. Moreover, existing mother liquor reuse technologies often employ fixed static proportions, lacking real-time monitoring and dynamic adjustment of mother liquor composition fluctuations, which can easily lead to product quality loss after multiple cycles. Furthermore, existing heat recovery methods only address sensible heat exchange, resulting in significant waste of latent heat of water vapor. Therefore, this paper provides a flocculant preparation process and apparatus for industrial sludge containing heavy metals. Summary of the Invention

[0005] The purpose of this invention is to provide a process and apparatus for preparing flocculants for industrial sludge containing heavy metals, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a process for preparing a flocculant for industrial sludge containing heavy metals, comprising the following steps:

[0007] S1. A first-order flocculant solution is prepared by mixing the solvent with the base phase and then adding the functional phase.

[0008] S2. Accelerated maturation: Under the synergistic catalytic effect of fluid dynamics cavitation and multi-frequency ultrasound, the reaction activation energy is reduced and microscopic mass transfer is enhanced. Weak hydrogen bonds are formed in solution, and the basic phase and function are combined.

[0009] S3. Adding a coagulant accelerator allows the flocculant base phase to combine with the functional product for precipitation;

[0010] S4. Filtration and separation form a mother liquor containing flocculant and wet flocculant for later use;

[0011] S5. Mother liquor reinjection: After the concentration is measured in real time by an online near-infrared spectrometer, the PLC control system dynamically calculates and adds water to prepare a second-order flocculant based on a feedforward-feedback algorithm. This process is repeated until the raw materials are exhausted, resulting in wet flocculant and mother liquor containing flocculant. The process is repeated multiple times by increasing the concentration, so that the concentration of the mother liquor gradually increases to close to the concentration of the aqueous flocculant.

[0012] S6. Wet flocculant is dehydrated and dried to produce solid flocculant product and water vapor. The water vapor is deeply recovered through a heat pump system. The heated heat medium is used for temperature adjustment in the second round of operation S1. After condensation into water, it is used for S5 mother liquor preparation.

[0013] The flocculant mother liquor in S7 and S5 is converted into an aqueous flocculant product by fine-tuning the concentration.

[0014] Preferably, in step S1, the base phase is an inorganic flocculant, which is used to provide a network skeleton for the final product flocculant; the functional phase is a small molecule chelating agent, which is grafted onto the molecular chain of the inorganic flocculant using a chemical grafting composite process to form an integrated structure of "inorganic skeleton + organic compound groups".

[0015] Preferably, the base phase is formed by filtering PAFC stock solution through a 200-mesh filter and then mixing it with water. The functional phase is formed by mixing STDC stock solution and PEG and then adding it to the base phase. The base phase and functional phase are stirred and mixed using a low-speed, high-shear method to promote full contact between the base phase and the functional phase. Both the base phase and the functional phase are added in a supersaturated ratio so that the total content of effective components in the maturation solution after maturation in step S2 is ≥22%.

[0016] Preferably, in step S2, the ripening process shortens the ripening cycle by adjusting the ripening reaction conditions, including:

[0017] S21. pH adjustment: Before aging, the pH of the mixture is adjusted to 6.0~6.5 by adding 5% hydrochloric acid or sodium hydroxide solution. During the process, the aging solution is mixed by spraying and stirring.

[0018] S22. Pressure adjustment: Before aging, increase the pressure inside the reaction vessel to 0.12~0.15MPa;

[0019] S23, Air replacement: The stability of SDTC is improved by replacing the air in the reactor with ammonia, and the pressure is kept stable during the curing process;

[0020] S24. Temperature control: The temperature is maintained at 28~32℃ by introducing a circulating heat transfer medium into the container jacket.

[0021] S25. Low-frequency continuous stirring is used during the maturation period to promote system circulation;

[0022] S26. Synergistic treatment of fluid dynamics cavitation and multi-frequency ultrasound: By setting up a Venturi cavitation device in the reaction vessel and configuring a multi-frequency (20kHz and 40kHz alternating) ultrasound generator, the fluid dynamics cavitation generated by high-speed fluid passing through the Venturi tube and the "cavitation effect" of ultrasound are superimposed and coupled to generate high-density microbubbles. When these bubbles burst, they release local extreme high temperature and high pressure energy, which greatly accelerates the diffusion of PAFC and SDTC molecules, reduces the activation energy of chemical grafting reaction, and promotes the rapid formation of hydroxyl-amino hydrogen bonds. Ultrasonic vibration can break up local molecular aggregation and make weak interactions more uniform.

[0023] After aging, the mixture must be measured to have a zeta potential of +15mV to +20mV.

[0024] Preferably, in step S3, 0.05% to 0.1% by mass of anionic PAM is added to the matured composite liquid. First, the mixture is stirred at high speed of 200 r / min for 5 min to ensure uniform dispersion of PAM. Then, it is stirred at low speed of 50 r / min for 15 min to promote floc aggregation. Finally, the mixture is allowed to stand and settle for 2 to 4 hours to form an upper layer of mother liquor and a lower layer of dense solid precipitate, wherein the solid water content is about 80% to 85%.

[0025] Preferably, in step S4, the upper mother liquor and the lower dense solid precipitate are all injected into the filtration device for solid-liquid separation. After the machine is stopped, the bottom solid product is discharged and the upper mother liquor is collected. The upper mother liquor is filtered through 500 mesh and 1500 mesh to remove impurities, and then the pH is adjusted to 6.0~6.5.

[0026] Preferably, in step S5, the mother liquor produced by the first-order flocculant is used as a solvent, and the concentration is reduced by adding water. It should be noted that when preparing the second-order flocculant, the characteristic absorption peak intensities of PAFC and SDTC in the reinjected mother liquor are obtained in real time by an online near-infrared spectrometer, and a partial least squares (PLS) quantitative correction model is established to output the effective component concentration data in real time. The PLC control system dynamically adjusts the mass ratio of PAFC+SDTC+PEG in the fresh raw material to the reinjected mother liquor according to the concentration data. It needs to be controlled at 1:0.8~1:1.2 to ensure that the effective component concentration of the mixed system is ≤12%~15% and avoid excessive viscosity affecting dispersion and grafting.

[0027] Preferably, in step S6, the wet flocculant is dried using a dryer with a preheating section at the front end. The tail gas undergoes non-contact heat exchange through the drying exhaust gas. Simultaneously, the exhaust gas enters the evaporator end of the heat pump latent heat recovery unit to extract the latent heat released by water vapor condensation. After raising the temperature of the heat medium, it enters S1 and S2 for temperature adjustment, achieving deep and efficient heat recovery in a stepped manner. Finally, powder flocculant is directly produced, which is then screened and packaged for storage. The water in the exhaust gas is condensed and recovered for use in the mother liquor preparation in step S5.

[0028] A flocculant preparation apparatus for industrial sludge containing heavy metals, comprising:

[0029] The reactor is equipped with a stirrer that is rotatably installed inside the reactor, a heat-insulating jacket installed in the side wall of the reactor, a Venturi cavitation evacuator installed inside the reactor, and a multi-frequency ultrasonic transducer array installed on the outer wall.

[0030] A horizontal screw centrifuge is provided with a discharge pipe between it and the reaction vessel. Dry material outlet and liquid outlet are respectively installed on both sides of the bottom end of the horizontal screw centrifuge.

[0031] A box-type drying and pulverizing integrated machine has a feeding hopper installed at one end, a screw conveyor installed between the feeding hopper and the dry material outlet, and a discharge hopper installed at the other end of the box-type drying and pulverizing integrated machine;

[0032] The mother liquor mixing tank is equipped with a water inlet pipe between itself and the liquid outlet. A condensation return pipe is installed between the mother liquor mixing tank and the box-type drying and pulverizing integrated machine. A return injection pipe is installed between the mother liquor mixing tank and the reaction vessel. An online near-infrared spectroscopy probe is installed inside the mother liquor mixing tank and connected to a PLC intelligent proportioning control cabinet.

[0033] The heat pump latent heat recovery unit has its evaporator end connected to the gas path where the condenser return pipe is located, and its condenser end connected to the heat transfer medium circulation loop of the insulation jacket.

[0034] Preferably, the stirrer is a turbine stirrer, and a servo motor for driving the stirrer to rotate is fixedly installed on the top of the reactor.

[0035] A preheating and insulation sleeve is provided on the box-type drying and pulverizing integrated machine near the feeding end. A forced airflow return pipe is installed between the end of the box-type drying and pulverizing integrated machine and the preheating and insulation sleeve. A connecting pipe is installed between the end of the preheating and insulation sleeve and the insulation jacket. The condensation return pipe is installed at the bottom end of the preheating and insulation sleeve.

[0036] The technical effects and advantages of this invention are as follows:

[0037] 1. The flocculant preparation process for industrial sludge containing heavy metals is an improvement on the original chemical grafting scheme. In the front-end feeding stage, the total mass of the target solid product is used as the production target. Small-scale, multi-round batch production is carried out. During the production process, based on the technical theory of "enrichment of effective components in mother liquor" and combined with the dynamic monitoring and feedback mechanism of online near-infrared spectroscopy (NIR), the effective component content of each batch is precisely controlled in a closed loop. This completely solves the "black box" problem of component accumulation and fluctuation in multiple batches, thereby realizing the multi-round production of target solid flocculant. At the same time, after multiple enrichment of mother liquor, the concentration of the final batch of mother liquor produced meets the industry standard for the effective component concentration of "liquid flocculant", thus achieving no liquid metabolite generation throughout the process.

[0038] 2. In the preparation process of the flocculant for industrial sludge containing heavy metals, since the weight of each batch is small in the later drying stage, a scheme of centrifugal filtration + hot air drying and pulverization is adopted to treat solid powder flocculants, thereby replacing the traditional spray drying tower. This achieves cost control. At the same time, heat is generated in the drying stage, and by introducing heat pump latent heat recovery technology, the latent heat of water vapor that was originally lost with the exhaust gas is deeply extracted and its grade is improved. This heat is used for preheating in the drying stage and for heat preservation in the early mixing and maturation process, thereby achieving efficient utilization of heat in a closed loop, further reducing costs. The overall energy consumption can be reduced by more than 30%.

[0039] 3. The flocculant preparation device for heavy metal-containing industrial sludge is used in the following way: a Venturi cavitation device is installed inside the reactor, and a multi-frequency ultrasonic generator is installed on the outer wall. The basic phase and solvent are pre-mixed in the reactor, and then the functional phase is added. Then, through stirring and mixing, positive pressure holding, fluid dynamic cavitation and multi-frequency ultrasonic synergistic treatment are carried out, and the internal air is replaced by forced nitrogen gas. The extreme microenvironment generated by the collapse of cavitation bubbles breaks the mass transfer resistance, thereby reducing the original 18 hours required for the maturation reaction to 6-83-4 hours, thus achieving rapid maturation, increasing the grafting rate to over 95%, greatly shortening the maturation cycle and improving the output efficiency. Attached Figure Description

[0040] Figure 1 This is an overall flow chart of the preparation process of the flocculant for industrial sludge containing heavy metals according to the present invention;

[0041] Figure 2 This is an overall structural diagram of the flocculant preparation device for heavy metal-containing industrial sludge according to the present invention;

[0042] Figure 3 This is a cross-sectional view of the internal structure of the reactor of the present invention.

[0043] In the diagram: 1. Reactor; 12. Servo motor; 13. Discharge pipe; 14. Backfill pipe; 15. Insulation jacket; 16. Agitator; 17. Venturi cavitation device; 18. Multi-frequency ultrasonic transducer array; 2. Horizontal screw centrifuge; 22. Dry material outlet; 23. Water inlet pipe; 3. Box-type drying and pulverizing integrated machine; 32. Feed hopper; 33. Discharge hopper; 34. Forced airflow return pipe; 35. Preheating insulation jacket; 36. Connecting pipe; 37. Condensate return pipe; 4. Mother liquor mixing tank; 5. Screw elevator. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example 1: This embodiment of the invention provides, as follows Figure 1 The process for preparing a flocculant for industrial sludge containing heavy metals, as shown, includes the following steps:

[0046] S1. After mixing the solvent and the base phase, a functional phase is added to prepare a first-order flocculant solution. The base phase is an inorganic flocculant, which is used to provide a network skeleton for the final product flocculant. The functional phase is a small molecule chelating agent, which is grafted onto the molecular chain of the inorganic flocculant using a chemical grafting composite process to form an integrated structure of "inorganic skeleton + organic functional group". The base phase is formed by filtering PAFC stock solution through a 200-mesh filter and then mixing it with water. The functional phase is formed by mixing STDC stock solution and PEG and then adding it to the base phase. The mixture is stirred and mixed using a low-speed, high-shear method to promote full contact between the base phase and the functional phase. Both the base phase and the functional phase are added in a supersaturated ratio so that the total content of effective components in the matured solution after step S2 is ≥22%.

[0047] S2, accelerates aging, weak hydrogen bonds are formed in the solution, the basic phase and the function are combined, and the aging process is shortened by adjusting the aging reaction conditions, including:

[0048] S21. pH adjustment: Before aging, the pH of the mixture is adjusted to 6.0~6.5 by adding 5% hydrochloric acid or sodium hydroxide solution. During the process, the aging solution is mixed by spraying and stirring.

[0049] S22. Pressure adjustment: Before aging, increase the pressure inside the reaction vessel to 0.12~0.15MPa;

[0050] S23, Air replacement: The stability of SDTC is improved by replacing the air in the reactor with ammonia, and the pressure is kept stable during the curing process;

[0051] S24. Temperature control: The temperature is maintained at 28~32℃ by introducing a circulating heat transfer medium into the container jacket.

[0052] S25. Low-frequency continuous stirring is used during the maturation period to promote system circulation;

[0053] S26. Ultrasonic treatment: By configuring an ultrasonic generator on the reaction vessel, the "cavitation effect" of ultrasound is used to generate microbubbles. When these bubbles burst, they release local energy, which accelerates the diffusion of PAFC and SDTC molecules and promotes the rapid formation of hydroxyl-amino hydrogen bonds. Ultrasonic vibration can break up local molecular aggregation and make weak interactions more uniform.

[0054] After aging, the mixture must be measured to have a zeta potential of +15mV to +20mV.

[0055] S3. Add a coagulant to allow the flocculant base phase and functional product to precipitate. Add 0.05% to 0.1% by mass of anionic PAM to the matured composite liquid. First, stir at high speed of 200 r / min for 5 min to ensure uniform dispersion of PAM. Then, stir at low speed of 50 r / min for 15 min to promote floc aggregation. Then, let it stand and settle for 2 to 4 hours to form an upper mother liquor and a lower dense solid precipitate, in which the solid water content is about 80% to 85%.

[0056] S4. Filtration and separation form a mother liquor containing flocculant and wet flocculant for later use. The upper mother liquor and the lower dense solid precipitate are all injected into the filtration equipment for solid-liquid separation. After the machine is stopped, the bottom solid product is discharged and the upper mother liquor is collected. The upper mother liquor is filtered through 500 mesh and 1500 mesh to remove impurities. Then the pH is adjusted to 6.0~6.5.

[0057] S5. Mother liquor reinjection: After measuring the concentration, water is added to prepare the second-stage flocculant. This process is repeated until the raw materials are exhausted, resulting in wet flocculant and mother liquor containing flocculant. The process is repeated multiple times by increasing the concentration, gradually increasing the concentration of the mother liquor to close to that of the aqueous flocculant. In practice, the mother liquor produced from the preparation of the first-stage flocculant is used as a solvent, and the concentration is reduced by adding water. It is important to note that the mass ratio of PAFC+SDTC+PEG in the fresh raw materials to the reinjected mother liquor should be controlled at 1:0.8~1:1.2 during the preparation of the second-stage flocculant to ensure that the concentration of the effective components in the mixed system is ≤12%~15%, avoiding excessively high viscosity that could affect dispersion and grafting.

[0058] S6. The wet flocculant is dehydrated and dried to produce solid flocculant and water vapor. The water vapor is used for temperature control in the second round of operation S1. After condensation, it is used for mother liquor preparation in S5. The wet flocculant is dried using a dryer with a preheating section at the front end. The tail gas is dried through non-contact heat exchange, and then the generated medium-low temperature tail gas enters S1 and S2 for temperature control, achieving efficient heat recovery. Finally, powder flocculant is directly produced, which is then screened and packaged for storage. The water in the tail gas is condensed and recovered for use in mother liquor preparation in step S5.

[0059] The flocculant mother liquor in S7 and S5 is converted into an aqueous flocculant product by fine-tuning the concentration.

[0060] Working principle: This method improves upon the original chemical grafting scheme. In the front-end feeding stage, the total mass of the target solid product is used as the production target. Small-scale, multi-round batch production is carried out. During the production process, the amount of effective components in each batch is controlled based on the technical theory of "enrichment of effective components in mother liquor". This enables multi-round production of the target solid flocculant. After multiple enrichments of the mother liquor, the concentration of the final batch of mother liquor produced meets the industry standard for the effective component concentration of "liquid flocculant", thus achieving no liquid metabolites generated throughout the process.

[0061] Furthermore, in the later drying stage, since each batch is relatively small, a solution of centrifugal filtration + hot air drying and pulverization is adopted to treat solid powder flocculants, thereby replacing the traditional spray drying tower and achieving cost control.

[0062] Meanwhile, the heat generated during the drying stage is used for preheating in the pre-drying stage and for heat preservation in the early mixing and maturation processes, thereby achieving efficient heat utilization and further reducing costs.

[0063] Example 2, as follows Figure 1 As shown, based on the technical theory of Example 1, a detailed explanation will now be given using a specific input-output experiment. The total dry material volume in this experiment was 1000 kg, and the effective components were ≥90% (total proportion of PAFC + SDTC).

[0064] Grafting assurance: The effective ingredient concentration in a single mixing system is ≤12% to avoid insufficient grafting due to high concentrations;

[0065] Basic parameter settings

[0066] Reactor specifications: 10m³ (effective volume 9m³, with 1m³ reserved for safety space), with a fixed total processing capacity of 9m³ per batch;

[0067] Fresh raw material benchmark formulation (designed for every 4.5m³ of fresh mixed liquid, with an effective ingredient concentration of 10.4%) Component specifications Single batch feed amount (4.5m³) Effective ingredient contribution.

[0068] In the PAFC stock solution, (AL2O3≥10%, Fe³⁺≥3%), the mass percentage is 26%, and the single batch feed amount is 1125kg, of which PAFC contains 112.5kg of effective ingredients;

[0069] The effective content of SDTC powder is ≥90%; the single batch feed amount is 135kg, of which 121.5kg is SDTC effective ingredient;

[0070] PEG-6000 (dispersant), single batch dosage 9kg, not included in the effective ingredient count;

[0071] Deionized water (pH 6-8), free of impurities, single batch feed amount 3231kg;

[0072] Key conversion parameters: 90% retention rate of centrifugal filtration (90% of the effective components enter the dry material, and 10% enters the mother liquor circulation); moisture content of the dry material ≤5%; effective component of the liquid flocculant ≥15%.

[0073] The detailed operation plan (4-batch cycle, achieving 2000kg+ dry material with no wastewater) is designed as follows: Through 4-batch cycle, the mother liquor is fully re-added in each batch (9m³ total processing capacity = fresh mixed liquor volume + previous batch mother liquor volume). The concentration of the mother liquor is monitored in real time by an online spectrometer, and the amount of fresh raw material to be added is dynamically calculated by PLC. The concentration of the mother liquor is gradually enriched. After the final batch of dry material is produced, the remaining mother liquor, regardless of whether the concentration meets the standard, is used as a liquid flocculant base (if it does not meet the standard, dry material is added to adjust it), thus achieving full water conversion.

[0074] Detailed steps

[0075] Batch 1

[0076] 1A. Raw material pretreatment (30 min)

[0077] PAFC stock solution is filtered through a 200-mesh filter to remove mechanical impurities;

[0078] SDTC wet addition preparation: 135kg SDTC + 675kg deionized water are pulped for 15min to form 810kg pulp;

[0079] Adjust the pH of the deionized water to 6.5 for later use;

[0080] 1B. Mixing stage (150 min)

[0081] Heat to 38℃; add 3231kg ​​of deionized water to a 10m³ reactor, start stirring (300r / min), add 1125kg of PAFC stock solution in 3 batches (375kg each batch, 15min interval), stir for 45min to form the basic phase;

[0082] Maintain a rotation speed of 350 r / min, add SDTC slurry in 6 batches (135 kg per batch, 10 min interval), and stir for 60 min;

[0083] Add 9 kg of PEG-6000 and stir for 30 min to obtain 4.5 m³ of fresh mixture (10.4% active ingredient).

[0084] 1C. Maturation stage (8h 3h)

[0085] Adjust the pH of the mixture to 6.2 and the viscosity to 30 mPa·s;

[0086] Turn on the fluid dynamics cavitation circulation pump and multi-frequency ultrasound (20kHz and 40kHz alternating, 1200W, continuous for the first 2 hours + ultrasound for 30 minutes every 2 hours) + low-speed stirring (60r / min) + slight positive pressure (0.13MPa, ammonia protection), and mature at 28-30℃ for 8 hours (thanks to the synergistic enhancement of mass transfer by cavitation and ultrasound, the maturation time is greatly shortened).

[0087] Endpoint test: zeta potential +15mV, no stratification after standing for 2 hours, effective ingredient concentration 10.2% (minor moisture evaporation), grafting rate reached 96.5%;

[0088] 1D. Flocculation and sedimentation + centrifugal filtration (120 min)

[0089] Add 0.08% anionic PAM (4.5m³ x 0.08% = 3.6kg), stir at high speed for 5 minutes + stir at low speed for 15 minutes, and let stand and settle for 70 minutes;

[0090] After filtration, 450 kg of wet solid material with a moisture content of 65% and 4.05 m³ of mother liquor (40.5 kg of active ingredient with a concentration of 10%) were obtained. The solid material was put into a dryer, continuously dried, and then pulverized to obtain 157.5 kg of dry material with a concentration of 90.5% and 142.5 kg of active ingredient. The mother liquor was filtered through a 500-mesh precision filter (turbidity 3 NTU), and the pH was measured to be 6.0 and the viscosity to be 28 mPa·s. The mother liquor was then stored for later use.

[0091] Batch 2, First full-volume re-addition of mother liquor (4.05 m³ of mother liquor + 4.95 m³ of fresh mixed liquor, total 9 m³)

[0092] 2A. Pretreatment of mother liquor (45 min)

[0093] Take 4.05 m³ of mother liquor from batch 1 (total volume, 4050 kg, effective ingredient 40.5 kg), filter through a 500 mesh, and adjust the pH to 6.3 with 5% NaOH solution (add 2.8 kg NaOH solution dropwise); scan in real time using an online near-infrared spectrometer, establish a PLS model, and output the current effective ingredient concentration as 10.0%; the viscosity is detected at 28 mPa-s (meets the standard), add 0.41 kg PEG-6000 (to replenish mother liquor loss), and stir evenly;

[0094] 2B. Adjustment of fresh mixed liquor (to match the amount of mother liquor, total 9m³)

[0095] The PLC control system scales up the mother liquor concentration data based on the online spectral feedback, dynamically calculates and prepares 4.95 m³ of fresh mixed liquor (to supplement the insufficient volume of mother liquor to 9 m³).

[0096] Components Adjusted feed rate (4.95 m³) Active ingredient amount PAFC stock solution 1237.5kg (1125kg x 1.1) 123.75kg SDTC powder 1485kg (135kg x 1.1) 133.65kg PEG-6000 9.9kg (9kg x 1.1) - Deionized water 3554.1kg (3231kg ​​x 1.1) - total 4950kg (4.95m³) 257.4 kg (concentration 10.4%)

[0097] 2C. Mix + mature + filter (5h30min)

[0098] The pretreated mother liquor and fresh mixed liquor were pumped into the reactor, totaling 9 m³ (9000 kg). The effective component concentration after mixing was approximately 3.31% (40.5 + 257.4) ÷ 9000 x 100% (far below 12%, with no grafting issues).

[0099] 2D. Following the curing parameters of batch one, the effective ingredient concentration after curing is 12.5%. After filtration, 900 kg of wet solid material is obtained, and after drying, 315 kg of dry material is obtained, of which 284.5 kg of effective ingredient has a concentration of 90.3%. 8.1 m³ of mother liquor is also obtained (101.3 kg of effective ingredient with a concentration of 12.5%, which will be used entirely in batch three).

[0100] Batch 3: Second full addition of mother liquor (8.1 m³ of mother liquor + 0.9 m³ of fresh mixed liquor, total 9 m³)

[0101] 3A. Pretreatment of mother liquor (45 min)

[0102] Take 8.1 m³ of the mother liquor from batch 2 (total volume, 8100 kg, effective ingredient 101.3 kg), filter it through a 500 mesh, and test the pH=6.4 (compliant) and viscosity 32 mPas (compliant). In real time, the SDTC content was detected by online near-infrared spectrometer to be 1.3% and the PAFC effective ingredient to be 11.2%, with the ratio conforming to 97:2.5:0.3. Add 0.81 kg of PEG-6000 and stir evenly.

[0103] 3B. Fresh Mixture Adjustment (0.9m³, replenished to 9m³): The PLC control system reduces the volume according to the baseline formula ratio to prepare 0.9m³ of fresh mixture.

[0104] Components Adjusted feed rate (0.9 m³) Active ingredient amount PAFC stock solution 225kg (1125kg x 0.2) 22.5kg SDTC powder 27kg (135kg x 0.2) 24.3kg PEG-6000 1.8kg (9kg x 0.2) - Deionized water 646.2kg (3231kg ​​x 0.2) - total 900kg (0.9m³) 46.8 kg (concentration 10.4%)

[0105] 3C, Mixing + Cooking + Filtering (5h30min)

[0106] The total effective component after mixing is 101.3 + 46.8 = 148.1 kg, with a concentration of approximately 1.65%. After aging, the effective component concentration is 15.2% (meeting the qualified standard for liquid flocculants). After filtration, 900 kg of wet solids are obtained (315 kg of dry material, 285 kg of effective components, and a concentration of 90.5% are obtained after drying) and 8.1 m³ of mother liquor (123.2 kg of effective components, with a concentration of 15.2%, which is used entirely in batch four).

[0107] Batch 4: Third full addition of mother liquor (8.1 m³ of mother liquor + 0.9 m³ of fresh mixed liquor, totaling 9 m³, with dry materials meeting standards for finalization).

[0108] 4A. Pretreatment of mother liquor (45 min)

[0109] Take 8.1 m³ of the mother liquor from batch 3 (total volume, 8100 kg, effective ingredient 123.2 kg), filter it through a 500 mesh, and test the pH=6.3 and viscosity 33 mPas, which meet the standards; online spectroscopy confirms that the concentration is stable; add 0.81 kg of PEG-6000 and stir evenly.

[0110] 4B. Preparation of fresh mixed solution (0.9 m³, 3 in the same batch)

[0111] Feeding quantities: 225 kg PAFC stock solution, 27 kg SDTC powder, 1.8 kg PEG-6000, 646.2 kg deionized water, and 46.8 kg active ingredients.

[0112] 4C. Mix + mature + filter (10h 30min 5h 30min)

[0113] The total effective component after mixing is 123.2 + 46.8 = 170 kg, with a concentration of 1.89%. After maturation, the effective component concentration is 18.0% (qualified liquid flocculant). This filtration process increased the centrifugal speed of the centrifuge equipment, thereby improving...

[0114] The dry material output rate was increased, resulting in 616 kg of wet solid material after filtration (212.5 kg of dry material after drying, 191.5 kg of effective ingredients, concentration of 90.1%) and 8.5 m³ of mother liquor (153 kg of effective ingredients, concentration of 18.0%, which can be used as a qualified liquid flocculant).

[0115] The following is a summary of various input and production data for four batches.

[0116] batch Mother liquor re-addition volume (m³) Fresh mixed liquor volume (m³) Dry feed output (kg) Concentration of active ingredients in dry materials (%) Mother liquor output (m³) Mother liquor concentration (%) 1 0 4.5 157.5 90.5 4.05 10.0 2 4.05 4.95 315 90.3 8.1 12.5 3 8.1 0.9 315 90.5 8.1 15.2 4 8.1 0.9 172.5 90.1 8.5 18.0 total - 11.25 1000 ≥90.0 8.5 18.0

[0117] Four batches of dry material were separated by fine-tuning the centrifugation parameters to improve the dry material separation rate.

[0118] In this scheme, the total processing capacity of each batch is fixed at 9m³ of effective volume in a 10m³ reactor. The amount of fresh raw material is adjusted by reverse calculation of the mother liquor volume + fresh mixed liquor volume = 9m³ to ensure full utilization of the mother liquor. Before re-addition, the concentration and volume of the mother liquor are measured using an online near-infrared spectrometer and a high-precision flow meter, and controlled by a PLC closed loop to avoid residue or quality control failure due to volume or concentration deviations. During mother liquor transfer, the pipeline is flushed with the mother liquor of this batch, and the flushing liquid is fully introduced into the reactor, with no residue or waste. During centrifugal filtration, the effective component content of the mother liquor is tested for each batch to ensure that the retention rate is stable at 90%. If the retention rate decreases, the centrifugal speed is finely adjusted. The drying temperature is 70~80℃, the drying time is 3 hours, and the moisture content is tested for each batch to ensure ≤5%. If the dry material output of the previous batch is insufficient, the amount of fresh raw material can be appropriately increased in subsequent batches. This ensures a total dry material output of 1000kg and a liquid flocculant output of 8.5m³, thereby achieving the effect of zero wastewater generation.

[0119] This solution employs a four-batch cycle, with a fixed total processing capacity of 9m³ as its core. The amount of fresh mixed liquor in each batch is adjusted in reverse to ensure full reuse of the mother liquor from the previous batch. By stabilizing the filter press rejection rate and drying parameters, the total amount of dry material is guaranteed to be 2000kg with an effective component content of ≥90%. Regardless of whether the final mother liquor concentration meets the standard, it is adjusted to meet the standard by adding dry material. All added water is converted into liquid flocculant, with no wastewater generated. The solution features quantifiable parameters, controllable operation, high degree of intelligence, and extremely low energy consumption, making it suitable for small and medium-sized industrial production and meeting green production requirements.

[0120] Example 3, as follows Figure 2 As shown, this embodiment provides a flocculant preparation device for industrial sludge containing heavy metals, comprising:

[0121] The reactor 1 is equipped with a stirrer 16 rotating inside the reactor 1, a heat insulation jacket 15 is installed in the side wall of the reactor 1, a Venturi cavitation 17 is installed inside the reactor 1, and a multi-frequency ultrasonic transducer array 18 is installed on the outer wall.

[0122] A horizontal screw centrifuge 2 is connected to a reactor 1 by a discharge pipe 13. Dry material outlet 22 and liquid outlet 23 are installed on both sides of the bottom end of the horizontal screw centrifuge 2.

[0123] The box-type drying and pulverizing integrated machine 3 has a feeding hopper 32 installed at one end, and a screw conveyor 5 installed between the feeding hopper 32 and the dry material outlet 22. The box-type drying and pulverizing integrated machine 3 has a discharge hopper 33 installed at the other end.

[0124] The mother liquor mixing tank 4 is connected to the liquid outlet 23 by a water inlet pipe 23. The mother liquor mixing tank 4 is connected to the box-type drying and pulverizing integrated machine 3 by a condenser return pipe 37. The mother liquor mixing tank 4 is connected to the reaction vessel 1 by a return pipe 14. The mother liquor mixing tank 4 is equipped with an online near-infrared spectroscopy probe 41 and is connected to a PLC intelligent proportioning control cabinet 42.

[0125] The heat pump latent heat recovery unit 6 has its evaporator end connected to the gas path where the condenser return pipe 37 is located, and its condenser end connected to the heat transfer medium circulation loop of the insulation jacket 15.

[0126] The stirrer 16 is a turbine stirrer, and a servo motor 12 for driving the stirrer 16 to rotate is fixedly installed on the top of the reactor 1.

[0127] A preheating and insulation sleeve 35 is provided on the box-type drying and pulverizing integrated machine 3 and near the feeding end. A forced airflow return pipe 34 is installed between the end of the box-type drying and pulverizing integrated machine 3 and the preheating and insulation sleeve 35. A connecting pipe 36 is installed between the end of the preheating and insulation sleeve 35 and the insulation jacket 15. A condensation return pipe 37 is installed at the bottom end of the preheating and insulation sleeve 35.

[0128] Working Principle: This device is an apparatus for performing the preparation method proposed in Example 1. It includes a reaction vessel 1, a horizontal screw centrifuge 2, a box-type drying and pulverizing integrated machine 3, a mother liquor mixing tank 4, a screw conveyor 5, and a heat pump latent heat recovery unit 6. During operation, the fluid inside the reaction vessel 1 undergoes intense hydrodynamic cavitation via a Venturi cavitation device 17. Simultaneously, a multi-frequency ultrasonic generator array 18 is installed on the outer wall. The basic phase and solvent are pre-mixed in the reaction vessel 1, and then the functional phase is added. Through stirring and mixing, positive pressure maintenance, cavitation and ultrasonic synergistic treatment, and forced nitrogen gas to replace the internal air, the microjets generated by the cavitation effect and local high temperature and pressure break down the intermolecular mass transfer resistance, thereby reducing the original 18 hours required for the ripening reaction to 6-83-4 hours (depending on the viscosity of the material during the reaction), thus achieving rapid ripening. The ripened material is then injected into the horizontal screw centrifuge 2, and the process is adjusted... The centrifugal speed is used to control the dehydration rate of the dry material. The dry material is then fed into the box-type drying and pulverizing machine 3 through the screw conveyor 5 for drying. During drying, the powder material produced at the end is ground and sieved for packaging. At the same time, high-temperature water vapor is produced at the end. The water vapor enters the jacket of the preheating section at the front end of the box-type drying and pulverizing machine 3 to preheat the material. Then the water vapor enters the evaporator end of the heat pump latent heat recovery unit 6 to extract its latent heat of condensation. After the water vapor condenses, it is injected into the mother liquor mixing tank 4 through the condensation return pipe 37. At this time, the online near-infrared spectral probe 41 monitors the concentration of the mother liquor in real time and transmits the data to the PLC intelligent proportioning control cabinet 42. The system automatically calculates and mixes the mother liquor separated by the horizontal screw centrifuge 2 to prepare the next stage of mother liquor. The latent heat extracted by the heat pump unit 6 is used to heat the heat transfer medium. The heated medium enters the insulation jacket 15 of the reactor 1 to keep the early mixing and stirring and the later maturation process in the reactor 1 warm.

[0129] The final output is the target quantity of dry flocculant and by-product liquid flocculant, with all products produced and no wastewater generated. At the same time, small-batch production is achieved through a small-volume, multi-batch approach, eliminating the need for a spray drying tower. Furthermore, the introduction of intelligent closed-loop control and a deep energy-saving network results in lower overall equipment costs, more stable operation, and extremely low energy consumption, making it suitable for small to medium-sized production.

[0130] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process and apparatus for preparing flocculants for industrial sludge containing heavy metals, characterized in that, Includes the following steps: S1. A first-order flocculant solution is prepared by mixing the solvent with the base phase and then adding the functional phase. S2. Accelerated maturation: Under the synergistic catalytic effect of fluid dynamics cavitation and multi-frequency ultrasound, the reaction activation energy is reduced and microscopic mass transfer is enhanced. Weak hydrogen bonds are formed in solution, and the basic phase and function are combined. S3. Adding a coagulant accelerator allows the flocculant base phase to combine with the functional product for precipitation; S4. Filtration and separation form a mother liquor containing flocculant and wet flocculant for later use; S5. Mother liquor reinjection: After the concentration is measured in real time by an online near-infrared spectrometer, the PLC control system dynamically calculates and adds water to prepare a second-order flocculant based on a feedforward-feedback algorithm. This process is repeated until the raw materials are exhausted, resulting in wet flocculant and mother liquor containing flocculant. The process is repeated multiple times by increasing the concentration, so that the concentration of the mother liquor gradually increases to close to the concentration of the aqueous flocculant. S6. Wet flocculant is dehydrated and dried to produce solid flocculant product and water vapor. The water vapor is deeply recovered through a heat pump system. The heated heat medium is used for temperature adjustment in the second round of operation S1. After condensation into water, it is used for S5 mother liquor preparation. The flocculant mother liquor in S7 and S5 is converted into an aqueous flocculant product by fine-tuning the concentration.

2. The flocculant preparation process for heavy metal-containing industrial sludge according to claim 1, characterized in that, In step S1, the base phase is an inorganic flocculant, which is used to provide a network skeleton for the final product flocculant; the functional phase is a small molecule chelating agent, which is grafted onto the molecular chain of the inorganic flocculant using a chemical grafting composite process to form an integrated structure of "inorganic skeleton + organic compound groups".

3. The process for preparing a flocculant for heavy metal-containing industrial sludge according to claim 2, characterized in that, The base phase is formed by filtering PAFC stock solution through a 200-mesh filter and then mixing it with water. The functional phase is formed by mixing STDC stock solution and PEG and then adding it to the base phase. The base phase and functional phase are stirred and mixed using a low-speed, high-shear method to promote full contact between the base phase and the functional phase. Both the base phase and the functional phase are added in a supersaturated ratio so that the total content of effective components in the maturation solution after step S2 is ≥22%.

4. The process for preparing a flocculant for heavy metal-containing industrial sludge according to claim 1, characterized in that, In step S2, the ripening process shortens the ripening cycle by adjusting the ripening reaction conditions, including: S21. pH adjustment: Before aging, the pH of the mixture is adjusted to 6.0~6.5 by adding 5% hydrochloric acid or sodium hydroxide solution. During the process, the aging solution is mixed by spraying and stirring. S22. Pressure adjustment: Before aging, increase the pressure inside the reaction vessel to 0.12~0.15MPa; S23, Air replacement: The stability of SDTC is improved by replacing the air in the reactor with ammonia, and the pressure is kept stable during the curing process; S24. Temperature control: The temperature is maintained at 28~32℃ by introducing a circulating heat transfer medium into the container jacket. S25. Low-frequency continuous stirring is used during the maturation period to promote system circulation; S26. Synergistic processing of fluid dynamics cavitation and multi-frequency ultrasound utilizes the superimposed coupling effect of fluid dynamics cavitation generated by high-speed fluid passing through a Venturi tube and the "cavitation effect" of ultrasound to produce high-density microbubbles. When these bubbles rupture, they release local extreme high temperature and high pressure energy, which greatly accelerates the diffusion of PAFC and SDTC molecules, reduces the activation energy of chemical grafting reaction, and promotes the rapid formation of hydroxyl-amino hydrogen bonds. Ultrasonic vibration can break up local molecular aggregation and make weak interactions more uniform. After aging, the mixture must be measured to have a zeta potential of +15mV to +20mV.

5. The process for preparing a flocculant for heavy metal-containing industrial sludge according to claim 1, characterized in that, In step S3, 0.05% to 0.1% by mass of anionic PAM is added to the matured composite liquid. First, the mixture is stirred at high speed of 200 r / min for 5 min to ensure uniform dispersion of PAM. Then, it is stirred at low speed of 50 r / min for 15 min to promote floc aggregation. After that, it is allowed to stand and settle for 2 to 4 hours to form "upper mother liquor + lower dense solid precipitate, wherein the solid water content is about 80% to 85%".

6. The flocculant preparation process for heavy metal-containing industrial sludge according to claim 5, characterized in that, In step S4, the upper mother liquor and the lower dense solid precipitate are all injected into the filtration device for solid-liquid separation. After the machine is stopped, the bottom solid product is discharged and the upper mother liquor is collected. The upper mother liquor is filtered through 500 mesh and 1500 mesh to remove impurities, and then the pH is adjusted to 6.0~6.

5.

7. The process for preparing a flocculant for heavy metal-containing industrial sludge according to claim 6, characterized in that, In step S5, the mother liquor produced by the first-order flocculant is used as a solvent, and its concentration is reduced by adding water. It should be noted that during the preparation of the second-order flocculant, the characteristic absorption peak intensities of PAFC and SDTC in the reinjected mother liquor are obtained in real time by an online near-infrared spectrometer, and a partial least squares (PLS) quantitative correction model is established to output the effective component concentration data in real time. The PLC control system dynamically adjusts the mass ratio of PAFC+SDTC+PEG in the fresh raw material to the reinjected mother liquor according to the concentration data, and the ratio needs to be controlled at 1. 0.8~1; 1.2, to ensure that the concentration of effective components in the mixed system is ≤12%~15%, and to avoid excessive viscosity affecting dispersion and grafting.

8. The process for preparing a flocculant for heavy metal-containing industrial sludge according to claim 7, characterized in that, In step S6, the wet flocculant is dried using a dryer with a preheating section at the front end. The tail gas undergoes non-contact heat exchange through the drying exhaust gas. Simultaneously, the exhaust gas enters the evaporator of the heat pump latent heat recovery unit to extract the latent heat released by water vapor condensation. After raising the temperature of the heat medium, it enters S1 and S2 for temperature adjustment, achieving deep and efficient heat recovery in a stepped manner. Finally, powder flocculant is directly produced, which is then screened and packaged for storage. The water in the exhaust gas is condensed and recovered for use in the preparation of the mother liquor in step S5.

9. A flocculant preparation apparatus for industrial sludge containing heavy metals, designed based on the flocculant preparation process for industrial sludge containing heavy metals according to any one of claims 1-9, characterized in that, include: The reactor (1) is equipped with a stirrer (16) rotating inside the reactor (1), and a heat-insulating jacket (15) is provided in the side wall of the reactor (1). A Venturi cavitation device (17) is also provided inside the reactor (1), and a multi-frequency ultrasonic transducer array (18) is provided on the outer wall of the reactor (1). A horizontal screw centrifuge (2) is provided with a discharge pipe (13) between it and the reactor (1). A dry material outlet (22) and a liquid outlet (23) are respectively installed on both sides of the bottom end of the horizontal screw centrifuge (2). A box-type drying and pulverizing integrated machine (3) is provided with a feeding hopper (32) at one end, a screw conveyor (5) is provided between the feeding hopper (32) and the dry material outlet (22), and a discharge hopper (33) is provided at the other end of the box-type drying and pulverizing integrated machine (3). The mother liquor mixing tank (4) is connected to the liquid outlet (23) by a water inlet pipe (23). A condenser return pipe (37) is connected between the mother liquor mixing tank (4) and the box-type drying and pulverizing integrated machine (3). A return pipe (14) is connected between the mother liquor mixing tank (4) and the reaction vessel (1). An online near-infrared spectroscopy probe is installed inside the mother liquor mixing tank (4). The mother liquor mixing tank (4) is connected to a PLC intelligent proportioning control cabinet for intelligent adjustment of mother liquor concentration. The heat pump latent heat recovery unit has its evaporator end connected to the gas path where the condenser return pipe (37) is located, and its condenser end connected to the heat transfer medium circulation loop of the insulation jacket (15).

10. The flocculant preparation device for heavy metal-containing industrial sludge according to claim 9, characterized in that, The stirrer (16) is a turbine stirrer, and a servo motor (12) for driving the stirrer (16) to rotate is fixedly installed on the top of the reactor (1). A preheating and insulation sleeve (35) is provided on the box-type drying and pulverizing integrated machine (3) and near the feeding end. A forced airflow return pipe (34) is installed between the end of the box-type drying and pulverizing integrated machine (3) and the preheating and insulation sleeve (35). A connecting pipe (36) is installed between the end of the preheating and insulation sleeve (35) and the insulation jacket (15). The condensation return pipe (37) is installed at the bottom end of the preheating and insulation sleeve (35).

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