Chemical flocculation process for advanced phosphorus removal from phosphorus-containing wastewater

Abstract

The present application relates to the technical field of water treatment, and discloses a chemical flocculation process for deep phosphorus removal of phosphorus-containing wastewater, which comprises the following steps: synchronously feeding the phosphorus-containing wastewater and a polyaluminum chloride solution into a high-frequency shearing reaction zone, adjusting the shearing rate and the hydraulic retention time, adding hydrogen ions according to the alkalinity of the wastewater to maintain the pH at 4.5-5.5, so as to form a multi-core hydroxyl complex; introducing the fluid into a secondary reaction zone, inducing the pH transition and homogeneous nucleation by jetting an alkaline regulator, and using the generated primary microflocs to capture phosphate to form a phosphorus-rich complex; and separating and collecting the precipitate. The present application changes the phosphorus removal mechanism from physical entrapment to chemical coordination bonding by interfering with the hydrolysis path of aluminum salt, simultaneously improves the phosphorus grade of the precipitate during deep phosphorus removal, and makes the precipitate have the secondary mineral resource recovery value, so as to achieve the resource comprehensive utilization of the wastewater treatment process.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and in particular relates to a chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater. Background Technology

[0002] Currently, the method of adding metal salt coagulants is used to treat phosphorus-containing wastewater. The metal salt coagulants undergo hydrolysis in the wastewater environment, generating hydrolysis products, which remove phosphate ions from the wastewater through adsorption and sweeping. When treating trace amounts of phosphate ions, the process efficiency is limited by the thermodynamic spontaneous trend. After the metal salt coagulant enters the water body, it undergoes rapid hydrolysis. The primary polynuclear hydroxy complex with high charge density exists only briefly and aggregates to form amorphous hydroxide gel with low charge density. This type of gel structure reduces the electrostatic attraction and chemical coordination efficiency of phosphate ions.

[0003] To ensure the total phosphorus concentration in the effluent meets standards, excessive dosage of chemicals is often used to compensate for the probability of microscopic collisions. This phosphorus removal mode, primarily based on physical sweeping, generates a large amount of chemical sludge. Due to the excessive inert metal components incorporated into the sludge, the phosphorus grade of the solid products falls below industrial recovery standards, hindering the recycling of phosphorus resources. Adding specific chelating agents or enhancing mechanical agitation can improve reaction conditions, but chelating agents are expensive and biotoxic. Simple physical agitation cannot intervene in the chemical process of metal ion hydrolysis. Existing processes lack effective constraints on the evolution of coagulant hydrolysis forms, failing to lock in highly active intermediate products. This uncontrolled hydrolysis sequence results in a strong coupling relationship between phosphorus removal efficiency, chemical consumption, and sludge production. Enhancing physical agitation or adding specific agents... Methods for intervening in the microscopic process of metal ion hydrolysis have limitations beyond reactor structure; control strategies also have limitations. For example, Chinese invention patent CN105836919A discloses a method for removing phosphorus from phosphorus-containing wastewater. After adjusting the pH to 6-9, ferric chloride and polyaluminum chloride are added sequentially. The generated iron hydroxyl compounds and aluminum salts are used for adsorption and bridging. However, this method is limited by the physical sweeping mechanism. After the reagents are added, the metal ions rapidly hydrolyze and collapse into amorphous hydroxide gels. The physicochemical barrier that blocks the hydroxyl bridging is not built at the molecular scale, resulting in the coordination orbitals being occupied by disordered spontaneous hydroxylation reactions. The uncontrolled hydrolysis pathway leads to low reagent utilization, and the final precipitate contains a large amount of inert metal components, which cannot improve the phosphorus grade of the product and does not meet the economic requirements for secondary recovery of phosphorus resources.

[0004] Therefore, how to reconstruct the kinetic boundary conditions of the coagulation reaction, achieve precise locking of the intermediate state of coagulant hydrolysis, and transform the phosphorus removal mechanism from physical sweeping to atomic-level exclusive coordination, thereby reducing chemical consumption while improving the phosphorus grade of the sludge, has become the technical problem to be solved by this invention. Summary of the Invention

[0005] This invention provides a chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater, comprising:

[0006] Step 101: The phosphorus-containing wastewater to be treated and a polyaluminum chloride solution with a basicity of 45% to 55% are simultaneously fed into the primary reaction zone of the inline high-frequency shear reactor via a variable frequency metering pump; the spatial average shear rate in the primary reaction zone is adjusted to 2500 / s to 3200 / s, and the hydraulic residence time of the mixed fluid in the primary reaction zone is controlled to be 500ms to 800ms; wherein, the initial alkalinity value of the phosphorus-containing wastewater to be treated is monitored in real time, and hydrogen ion solution is added to the primary reaction zone according to the initial alkalinity value to adjust the mixed fluid... With a value of 4.5 to 5.5, polyaluminum chloride forms a polynuclear hydroxy complex system within the primary reaction zone;

[0007] Step 102: The mixed fluid discharged from the primary reaction zone is introduced into the secondary reaction zone. An alkaline regulator is injected into the mixed fluid through an annular jet to control the pH transition of the mixed fluid within 20ms to 50ms. This induces global homogeneous nucleation of polynuclear hydroxy complexes in the phosphorus-containing wastewater to be treated to generate primary microflocs. The primary microflocs then combine with phosphate ions in the phosphorus-containing wastewater to form phosphorus-rich complexes.

[0008] Step 103: The mixed fluid discharged from the secondary reaction zone is introduced into the solid-liquid separation unit to separate and collect the high-density phosphorus-rich precipitate. By adjusting the sludge discharge frequency at the bottom of the solid-liquid separation unit, the total phosphorus mass fraction (calculated as phosphorus pentoxide) in the collected high-density phosphorus-rich precipitate is not less than 15%. The high-density phosphorus-rich precipitate is then recycled as an industrial phosphorus extraction raw material to achieve comprehensive resource utilization of the phosphorus-containing wastewater to be treated.

[0009] Preferably, in step 101, the basicity of the polyaluminum chloride solution is 48% to 52%; while the mixed fluid is maintained at... Under an environment with a value of 4.5 to 5.5, the initial solvation layer of polyaluminum chloride is broken by utilizing the high-frequency shear stress field of the primary reaction zone.

[0010] Preferably, in step 101, the primary reaction zone of the pipeline high-frequency shear reactor is provided with staggered shear stators and shear rotors, and the linear velocity of the shear rotors is controlled to be 25 m / s to 35 m / s to generate high-frequency pressure pulsation in the fluid channel.

[0011] Preferably, step 102 includes the following sub-steps: step 1021, adjusting the injection flow rate of the alkaline regulator to instantly raise the pH value of the mixed fluid from 4.5 to 5.5 to 7.5 to 8.5; step 1022, controlling the nucleation reaction time to 2s to 5s to complete the capture of free phosphate ions before the spontaneous aggregation of primary micro-flocs.

[0012] Preferably, in step 103, the solid-liquid separation unit is a high-inclined tube sedimentation tank, and the sedimentation load is set to 5 m³ / m²·h to 8 m³ / m²·h; the water content of the separated high-density phosphorus-rich precipitate is less than 80%.

[0013] Preferably, in step 101, the initial total phosphorus concentration of the phosphorus-containing wastewater to be treated is less than 0.5 mg / L, and the microscopic collision frequency between polynuclear hydroxy complexes and phosphate is increased by using a pipeline high-frequency shear reactor.

[0014] Preferably, in step 102, the fractal dimension of the nascent microfibrils at the moment of nucleation is 1.2 to 1.5.

[0015] Preferably, the process also includes a precipitate reflux step: a portion of the high-density phosphorus-rich precipitate collected in step 103 is refluxed as a contact medium to the inlet of the secondary reaction zone to induce accelerated nucleation of polynuclear hydroxy complexes.

[0016] Preferably, the high-density phosphorus-rich precipitate collected in step 103 is sent to a phosphate fertilizer production line or a thermal phosphoric acid production line as a secondary phosphate source to replace natural phosphate rock.

[0017] Compared with existing technologies, the chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater of the present invention has the following advantages:

[0018] 1. In the chemical flocculation of deep phosphorus removal from phosphorus-containing wastewater, the high-frequency fluid shear and acidic environment provided by the primary mixing zone are used to construct a physicochemical dual barrier at the kinetic level. This blocks the spontaneous hydroxyl bridging process of metal ions in the polyaluminum-iron precursor solution, locking the coagulant molecular structure into a metastable primary polynuclear hydroxyl complex stage with high positive charge density. This mechanism inhibits the disordered collapse reaction of the coagulant in neutral water, avoiding the generation of a large amount of amorphous hydroxide gel with low charge density and closed structure. By maintaining the highly active intermediate state of metal ions, the electrostatic neutralization and coordination binding efficiency between the coagulant and phosphate ions is improved. While achieving the goal of deep phosphorus removal, the dosage of metal salt agents is reduced, and the dry weight of redundant chemical sludge generated by the hydrolysis of ineffective agents is reduced.

[0019] 2. In the secondary nucleation zone, a step-gradient pH gradient introduced by annular jet induces global synchronous homogeneous nucleation of metastable polynuclear complexes in phosphorus-containing wastewater. Because the primary micro-flocs generated in this process have exposed active coordination empty orbitals, the core mechanism of phosphorus removal in the system changes from physical sweeping net capture that relies on collision probability in traditional processes to atomic-level exclusive chemical coordination bonding. This change in the nature of the reaction path means that the removal accuracy of trace phosphate in wastewater is no longer limited by the probability distribution of macroscopic physical collisions, effectively improving the capture capacity of low-concentration free phosphate and achieving stable compliance of total phosphorus concentration in the effluent.

[0020] 3. Because this invention achieves precise intervention in the hydrolysis path of coagulants through time constraints, it significantly reduces the doping ratio of ineffective metal hydroxides in the solid products, resulting in a leapfrog increase in the mass ratio of phosphorus in the precipitate. The discharged high-density phosphorus-rich precipitate is close to industrial-grade phosphorus-rich mineral sources in terms of physical morphology and chemical composition, thereby transforming the chemical sludge that originally needed to be dewatered and landfilled into industrial raw materials with secondary extraction value. This transformation reshapes the material flow of phosphorus-containing wastewater, achieving effective enrichment of phosphorus resources while completing water purification, and improving the comprehensive resource utilization value of the treatment system. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the metastable latching deep phosphorus removal and resource recovery process of the present invention;

[0022] Figure 2 This is a diagram illustrating the aluminum salt hydrolysis pathway intervention and atomic-level chemical coordination mechanism of this invention. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0024] It should be noted that all directional and positional terms used in this invention, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, bottom, transverse, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0025] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0026] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0027] A chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater includes:

[0028] Step 101: The phosphorus-containing wastewater to be treated and a polyaluminum chloride solution with a basicity of 45% to 55% are simultaneously fed into the primary reaction zone of the pipeline high-frequency shear reactor via a variable frequency metering pump; the spatial average shear rate in the primary reaction zone is adjusted to 2500 / s to 3200 / s, and the hydraulic residence time of the mixed fluid in the primary reaction zone is controlled to be 500ms to 800ms; wherein, the initial alkalinity value of the phosphorus-containing wastewater to be treated is monitored in real time, and hydrogen ion solution is added to the primary reaction zone according to the initial alkalinity value to adjust the pH value of the mixed fluid to 4.5 to 5.5, so that the polyaluminum chloride forms a polynuclear hydroxyl complex system in the primary reaction zone;

[0029] Step 102: The mixed fluid discharged from the primary reaction zone is introduced into the secondary reaction zone. An alkaline regulator is injected into the mixed fluid through an annular jet to control the pH transition of the mixed fluid within 20ms to 50ms. This induces global homogeneous nucleation of polynuclear hydroxy complexes in the phosphorus-containing wastewater to be treated to generate primary microflocs. The primary microflocs then combine with phosphate ions in the phosphorus-containing wastewater to form phosphorus-rich complexes.

[0030] Step 103: The mixed fluid discharged from the secondary reaction zone is introduced into the solid-liquid separation unit to separate and collect the high-density phosphorus-rich precipitate. By adjusting the sludge discharge frequency at the bottom of the solid-liquid separation unit, the total phosphorus mass fraction (calculated as phosphorus pentoxide) in the collected high-density phosphorus-rich precipitate is not less than 15%. The high-density phosphorus-rich precipitate is then recycled as an industrial phosphorus extraction raw material to achieve comprehensive resource utilization of the phosphorus-containing wastewater to be treated.

[0031] Preferably, in step 101, the basicity of the polyaluminum chloride solution is 48% to 52%; while the mixed fluid is maintained at a pH of 4.5 to 5.5, the initial solvation layer of polyaluminum chloride is broken by the high-frequency shear stress field of the primary reaction zone.

[0032] Preferably, in step 101, the primary reaction zone of the pipeline high-frequency shear reactor is provided with staggered shear stators and shear rotors, and the linear velocity of the shear rotors is controlled to be 25 m / s to 35 m / s to generate high-frequency pressure pulsation in the fluid channel.

[0033] Preferably, step 102 includes the following sub-steps: step 1021, adjusting the injection flow rate of the alkaline regulator to instantly raise the pH value of the mixed fluid from 4.5 to 5.5 to 7.5 to 8.5; step 1022, controlling the nucleation reaction time to 2s to 5s to complete the capture of free phosphate ions before the spontaneous aggregation of primary micro-flocs.

[0034] Preferably, in step 103, the solid-liquid separation unit is a high-inclined tube sedimentation tank, and the sedimentation load is set to 5 m³ / m²·h to 8 m³ / m²·h; the water content of the separated high-density phosphorus-rich precipitate is less than 80%.

[0035] Preferably, in step 101, the initial total phosphorus concentration of the phosphorus-containing wastewater to be treated is less than 0.5 mg / L, and the microscopic collision frequency between polynuclear hydroxy complexes and phosphate is increased by using a pipeline high-frequency shear reactor.

[0036] Preferably, in step 102, the fractal dimension of the nascent microfibrils at the moment of nucleation is 1.2 to 1.5.

[0037] Preferably, the process also includes a precipitate reflux step: a portion of the high-density phosphorus-rich precipitate collected in step 103 is refluxed as a contact medium to the inlet of the secondary reaction zone to induce accelerated nucleation of polynuclear hydroxy complexes.

[0038] Preferably, the high-density phosphorus-rich precipitate collected in step 103 is sent to a phosphate fertilizer production line or a thermal phosphoric acid production line as a secondary phosphate source to replace natural phosphate rock.

[0039] Example 1: This technical solution is applied to the deep phosphorus removal process of phosphorus-containing wastewater with a total phosphorus concentration of 0.5 mg / L. Under this condition, the phosphorus-containing wastewater to be treated has a high initial alkalinity, and the target phosphorus removal requirement is that the total phosphorus in the treated effluent is less than 0.05 mg / L. The phosphorus-containing wastewater to be treated and a polyaluminum chloride solution with a basicity of 45% to 55% are simultaneously fed into the primary reaction zone of a pipeline high-frequency shear reactor via a variable frequency metering pump. The initial alkalinity value of the phosphorus-containing wastewater to be treated is obtained by real-time monitoring by online sensors. Hydrogen ion solution is added to the primary reaction zone to maintain the pH value of the mixed fluid at 4.5 to 5.5. The shear rotor linear velocity of the pipeline high-frequency shear reactor is simultaneously adjusted to 25 m / s to 35 m / s, thereby generating a high-frequency stress field with a spatial average shear rate of 2500 to 3200 m / s in the primary reaction zone. The shear rate induces intense fluid boundary layer stripping and local high-frequency pressure pulsation within the stator-rotor interlaced microchannels. When the pulsating negative pressure is lower than the fluid's saturated vapor pressure, micron-sized cavitation bubbles are generated. The impact microjets released when the cavitation bubbles collapse transiently generate nanosecond-level extreme energy densities. This energy scale successfully transcends the scope of macroscopic fluid dynamics, tearing and acting on the initial hydration molecular layer of aluminum ions, which is only angstrom-level away. The mechanical stripping force severs the microscopic dipole coordination bonds between the central ion and the water molecule group. The high-frequency stress field breaks the initial solvation layer of polyaluminum chloride. Combined with the acidic environment of the primary reaction zone, the disordered hydroxyl bridging process of aluminum ions is suppressed, allowing polyaluminum chloride to form a metastable primary polynuclear hydroxyl complex system with a high positive charge density in the primary reaction zone. The hydraulic residence time of the mixed fluid in the primary reaction zone is set to 500 ms to 800 ms.

[0040] A mixed fluid carrying a metastable primary polynuclear hydroxyl complex system is introduced into an adjacent secondary reaction zone. A 0.1 mol / L sodium hydroxide solution is injected under high pressure into the fluid through an annular jet unit within the secondary reaction zone as an alkaline regulator. By adjusting the injection flow rate of the alkaline regulator, a pH transition is controlled within 20 to 50 ms, causing the pH value of the mixed fluid to increase stepwise from 4.5 to 5.5 to 7.5 to 8.5. This pH transition rate disrupts the thermodynamic stability of the metastable primary polynuclear hydroxyl complex system, inducing global homogeneous nucleation of the polynuclear hydroxyl complex in the phosphorus-containing wastewater to generate high specific surface area primary microflocs. Before aggregation, these primary microflocs interact with… Phosphate ions in the phosphorus-containing wastewater to be treated are linked by chemical coordination bonds to form phosphorus-rich complexes. The mixed fluid discharged from the secondary reaction zone is introduced into a high-inclined tube sedimentation tank for solid-liquid separation. The sedimentation load of the high-inclined tube sedimentation tank is set to 5 m³ / m²·h to 8 m³ / m²·h. High-density phosphorus-rich precipitates are collected at the bottom of the separation zone. By adjusting the sludge discharge frequency, the total phosphorus mass fraction (calculated as phosphorus pentoxide) in the collected high-density phosphorus-rich precipitates reaches more than 15% and the water content is less than 80%. The high-density phosphorus-rich precipitates are used directly as a secondary phosphate rock source for downstream industrial phosphorus extraction. This process solves the technical problem of low phosphorus grade in sludge and difficulty in resource utilization caused by excessive addition of reagents in traditional processes by intervening in the hydrolysis path of alumina salt.

[0041] Example 2: This experiment was conducted on a pilot-scale continuous operation platform with a processing capacity of 10 m³ / h. The total phosphorus concentration of the phosphorus-containing wastewater to be treated was set at 0.52 mg / L. A sinusoidal disturbance with a frequency of 1 Hz and an amplitude of 10% of the total alkalinity of the influent was introduced at the inlet to simulate alkalinity fluctuations in an industrial setting. Sensors used for data acquisition included an online pH meter with a range of 0 to 14 and an accuracy of 0.01, and an online particulate matter size analyzer based on the principle of laser diffraction with a sampling frequency of 20 Hz. All data obtained in this experiment came from the aforementioned physical experimental platform. In the parameter settings of the primary reaction zone, the value of the key parameter, spatially averaged shear rate, depends on the Reynolds number of the mixed fluid and the turbulent energy dissipation rate. This parameter setting needs to balance the breaking efficiency of the initial solvation layer of polyaluminum chloride and the system energy consumption. When the dynamic viscosity of the mixed fluid is at... At that time, the linear velocity of the shear rotor of the pipeline high-frequency shear reactor was set to 30 m / s. By calculating the relationship between the flow channel geometry and the rotation speed, the spatial average shear rate in the primary reaction zone was determined to be 2800 / s. In conjunction with injecting hydrogen ion solution into the fluid to make the pH value 5.0, the hydraulic residence time of the mixed fluid through the primary reaction zone was set to 650 ms.

[0042] During the operation of the secondary reaction zone, an alkaline regulator is injected into the fluid through the annular jet unit to induce a pH transition. The duration of the pH transition depends on the nucleation rate of the polynuclear hydroxyl complex and the diffusion rate of the alkaline regulator. This parameter is set to balance the formation density of primary microflocs and the ineffective precipitation caused by local supersaturation of the reagent. When the high-charge state of the polynuclear hydroxyl complex at the outlet of the primary reaction zone is measured... When the component content is higher than 80%, the injection pressure of the alkaline regulator is set to 0.35 MPa, causing the mixed fluid to produce a pH step from 5.0 to 8.0 within 35 ms. The average median particle size of the generated primary micro-flocs is observed using an online particulate matter size analyzer. The pH transition time in the secondary reaction zone is 3.6 μm, controlled by the matching of the physical pipe section length and the axial velocity parameters of the fluid in the mixing zone. During equipment commissioning and operation, the axial velocity of the mixed fluid in the main pipe is used as the reference. Based on the target transition time range of 20ms to 50ms, the effective mixing tube length between the annular jet injection component and the downstream online pH probe was calculated and fixed. Maintain axial flow velocity and effective mixing pipe section length Under constant conditions, the injection pressure of the alkaline regulator is gradually increased in a fixed step gradient of 0.05 MPa, while simultaneously monitoring the feedback value of the downstream online pH probe until the feedback value first enters and stabilizes within the set range of 7.5 to 8.5. The critical injection pressure at this point is extracted as the benchmark for formal operation control. The calibration engineering procedure restricts the global homogeneous nucleation process of polynuclear hydroxy complexes within a defined spatial and temporal boundary. In this debugging and control loop, the online pH probe with a second-level physical response is only used to capture the final downstream macroscopic pH after the fluid has undergone complete mixing and reached a spatiotemporal steady state. The system's operating logic does not rely on this probe to capture or directly feed back the millisecond-level transient transition micro-process. Since the system is in a continuous and quantitative steady flow state, this steady-state pH feedback value, combined with the fixed effective mixing geometry of the pipe section and the constant axial flow velocity, cleverly constitutes a feedforward extrapolation rule that utilizes spatial mapping time. This ensures that the transition time in the core reaction section is compressed within a preset extremely short time window of twenty to fifty milliseconds without challenging the physical response limits of conventional sensors.

[0043] To verify the technical effectiveness, three control systems were set up. Control group 1 used stirred coagulation without applying a space-averaged shear rate and without inducing pH jumps in the confined space. Control group 2 applied a space-averaged shear rate of 2800 / s, but changed the pH adjustment method from a step increase to a slow adjustment to 8.0. The experimental groups used the method claimed in this invention. When the influent total phosphorus was 0.52 mg / L, the measured total phosphorus in the effluent of control group 1 was 0.118 mg / L, and the total phosphorus mass fraction (calculated as phosphorus pentoxide) in the collected precipitate was 4.62%. The measured total phosphorus in the effluent of control group 2 was 0.083 mg / L, and the phosphorus pentoxide mass fraction in the precipitate was 8.15%. The total phosphorus content in the effluent of the experimental group remained stable at 0.031 mg / L. The total phosphorus content (calculated as phosphorus pentoxide) in the collected high-density phosphorus-rich precipitate reached 18.46% and the water content was 76.3%. When the space-average shear rate decreased to 2300 / s, the total phosphorus content in the effluent increased to 0.092 mg / L. When the space-average shear rate increased to 4000 / s, the total phosphorus content in the effluent was 0.029 mg / L, but the system energy consumption increased by 42.5% and the phosphorus pentoxide content in the precipitate decreased to 13.2%. The above experimental group data confirmed that the defined parameter range enabled the phosphorus-containing wastewater treatment products to be converted into resources with industrial recovery value.

[0044] Example 3: For industrial phosphorus-containing wastewater treatment with alkalinity fluctuations, the pH transition time required to induce global homogeneous nucleation of the metastable primary polynuclear hydroxyl complex system needs to be determined using a parameter calibration method based on nucleation kinetics response. The phosphorus-containing wastewater to be treated serves as the initial reaction state. The chemical potential of phosphate ions within the wastewater is constrained by the concentrations of bicarbonate and hydroxide ions in the water. When a 0.1 mol / L sodium hydroxide solution is introduced into the secondary reaction zone as an alkalinity regulator, the local saturation within the mixed fluid increases. The calibration process includes preparing initial alkalinity ranges from 50 mg / L to 300 mg / L. Multiple wastewater samples with a concentration of mg / L were analyzed in the metastable primary polynuclear hydroxyl complex fluid produced in the primary reaction zone. The injection pressure was adjusted using an annular jet unit, with the injection pressure increased from 0.15 MPa in 0.05 MPa increments to 0.5 MPa. Simultaneously, the response time curve of the mixed fluid in the secondary reaction zone as the pH value jumped from 5.0 to 8.0 was monitored. An online particulate matter size analyzer was used to capture the outbreak point of primary microflocs. When the injection pressure was adjusted to 0.35 MPa, the fluid completed the pH transition within 35 ms. At this point, the number of primary microflocs generated increased from [amount missing]. leap to This indicates that the hydroxyl bridging process inside the multinucleated intermediate is inhibited by the instantaneously activated coordination reaction. At this critical state of microfloc eruption, the forward small-angle scattered light intensity distribution data can be obtained synchronously using the laser diffraction hardware array at the bottom of the aforementioned online particulate matter size analyzer. Based on the Rayleigh-Debye-Gans theory of static light scattering, the characteristic spectral model in the double logarithmic coordinate system is extracted. By performing real-time slope calculation on the linear band in the low vector region of the spectrum, the fractal dimension value of the nascent microfloc at the moment of nucleation can be deduced online. The system controls the alkali injection flow rate to keep the fractal dimension constant within the low value range of 1.2 to 1.5, to confirm that the microfloc exhibits a highly loose branched physical topology at this stage, thereby ensuring that all high-energy coordination empty orbitals inside are exposed to phosphorus-containing wastewater without dead angles.

[0045] The precipitate obtained after solid-liquid separation was characterized by fingerprint features. Fourier transform infrared spectroscopy was used to scan the product powder at a wavenumber of 1080. An antisymmetric stretching vibration peak of phosphate was observed at 540. A characteristic signal attributable to Al-OP bending vibration was detected, confirming that phosphate ions have entered the inner coordination layer of the polynuclear hydroxyl complex. The wavenumber was 1080 when the pH transition duration exceeded 100 ms. The peak intensity at that location decreased by more than 60%, accompanied by 970 The appearance of characteristic peaks in aluminum-oxygen octahedral polymerization indicates that the low-rate increase in alkalinity leads to the closure of active coordination sites due to the spontaneous hydroxylation collapse of aluminum ions. The 20ms to 50ms transition time range determined according to the calibration procedure induces highly coordinated primary micro-flocs in the wastewater, resulting in a total phosphorus mass fraction (based on phosphorus pentoxide) of over 18.2% in the final collected high-density phosphorus-rich precipitate. This procedure establishes a mapping relationship between transition kinetic parameters and product phosphorus grade, realizing the property transformation of wastewater treatment products from amorphous hydroxide sludge to standard industrial phosphorus extraction raw materials. The metastable primary polynuclear hydroxyl complexes generated in the primary reaction zone possess specific small angles. The characteristic peak position of X-ray scattering corresponds to aluminum hydrolysis polymer clusters with particle sizes between 2 nm and 5 nm. When the spatial average shear rate is set to 2800 / s and the pH is maintained at 5.0, the coordination environment of aluminum atoms undergoes a transition from a six-coordinate metastable state to a low-coordinate state by breaking the solvation layer. This microstructure releases a large number of active empty orbitals during the pH transition in the secondary reaction zone, thereby inducing chemical coordination capture of phosphate ions at the nucleation sites rather than simple physical sweeping. Experimental results show that when the mass proportion of polymers with high charge density in the reagent components increases from 20% to over 85%, the mass fraction of phosphorus pentoxide in the final precipitate exhibits a nonlinear jump from 5.2% to 18.8%, confirming the decisive role of polynuclear intermediates in improving the phosphorus grade of the product.

[0046] Example 4: In an industrial site where a deep phosphorus removal process for phosphorus-containing wastewater is deployed, a mapping benchmark between the variable frequency metering pump speed and the mass flow rate of polyaluminum chloride solution is established using a multi-point material balance method. The basicity of the polyaluminum chloride solution is set to 50%. The frequency of the variable frequency metering pump is increased from 10Hz to 50Hz in 5Hz increments. At each steady state of frequency, the liquid discharged from the outlet is weighed using an electronic scale, and the average value is taken three times. This is used to construct a linear regression function between flow rate and speed. At the same time, the dynamic viscosity of the polyaluminum chloride solution at different shear rates under this basicity is measured to ensure that the shear stress generated by the spatial average shear rate in the range of 2500 / s to 3200 / s is sufficient to break the solvation layer.

[0047] During the commissioning phase before the system is connected to the phosphorus-containing wastewater to be treated, the online pH meter is calibrated at two points using a standard buffer solution. The initial compensation coefficient for hydrogen ion replenishment flow rate is determined based on the total alkalinity range of the phosphorus-containing wastewater to be treated. In the calibration process, a 1.0 mol / L hydrochloric acid solution is used as an acid regulator. The acid regulator is added to simulated wastewater samples with initial alkalinities of 100 mg / L, 200 mg / L, and 300 mg / L. The acid consumption curve when the mixed fluid decreases to pH 5.0 is recorded. The resulting response matrix is ​​loaded into the control unit of the pipeline high-frequency shear reactor. When faced with a 10% alkalinity fluctuation disturbance, the control unit corrects the pulse frequency of the variable frequency metering pump in real time based on feedback from the online sensor, so that the acidic environment in the primary reaction zone is maintained within the preset process range.

[0048] Example 5: In a high-load deep phosphorus removal operation where the initial total alkalinity of the phosphorus-containing wastewater fluctuates between 300 mg / L and 500 mg / L, the physical parameters of the primary reaction zone of the pipeline high-frequency shear reactor were set using the gap calibration method, specifically the radial shear gap between the shear rotor and stator. The value ranges from 0.0008m to 0.0012m. Based on the laminar flow shear model, when the linear velocity of the shear rotor is 30m / s, the value can be calculated using the formula... Determine the space-average shear rate within the first-order reaction zone; where, The space-average shear rate, To shear the rotor linear velocity, For radial shear gaps, in specific fluid micro-element calculations, the values ​​directly calculated by the above theoretical model are only the local theoretical peak shear rate at extremely narrow shear gaps. Since the internal volume of the pipeline-type primary reactor not only includes the gap region of the densely meshed stator and rotor, but also widely distributed rotor channels and edge channels, the actual geometric proportion coefficient of the micro-element volume experiencing high shear stress to the total working volume is approximately 10% through three-dimensional volume fraction weighted integration calculations in internal fluid dynamics. After physical suppression by this geometric reduction factor, the total space experienced by the mixed fluid within the entire turbulent reaction channel... The average effective shear rate essentially falls back and remains constant within the aforementioned macroscopic parameter control range of 2500 / s to 3200 / s. This radial shear gap, while maintaining the flux of the mixed fluid, generates a shear stress field sufficient to break the initial solvation layer of polyaluminum chloride, allowing aluminum atoms to maintain a metastable polynuclear hydroxyl complex morphology during the 650 ms hydraulic residence time in the primary reaction zone. The system control unit adjusts the operating parameters in real time based on the burst point of the primary micro-flocs, and obtains the number concentration of micro-flocs in the secondary reaction zone using an online particulate matter size analyzer. And establish quantity concentration versus time The first derivative determination logic, when the determination The value exceeds the preset nucleation rate threshold. At that time, the control unit linearly compensated the injection pressure of the annular jet unit from 0.35 MPa to 0.42 MPa; among which, This refers to the number concentration of microflocs. For reaction time, As a nucleation rate threshold, this adjustment logic enables the mixed fluid to complete the transition from an acidic microenvironment to an alkaline environment within 35 ms. After solid-liquid separation and drying, the high-density phosphorus-rich precipitate collected by the leap was found to contain 18.6% phosphorus pentoxide by X-ray fluorescence spectrometry. This solid product was then used as a secondary phosphate rock source in downstream industrial phosphorus extraction production lines.

[0049] The dehydration procedure for high-density phosphorus-rich precipitates established during solid-liquid separation is based on the integrity index of crystal growth. The sedimentation load and settling rate of primary micro-flocs in the high-inclined tube sedimentation tank are also considered. satisfy Physical constraints; among which, For the settling rate, This refers to the inlet water flow rate. The effective projected area of ​​the sedimentation tank is defined by the fact that the particles generated by global homogeneous nucleation have a compact mineral phase structure. By adjusting the sludge discharge frequency, the sludge concentration at the bottom of the thickening zone is maintained above 45 g / L. This ensures that the solid product obtained through subsequent plate and frame filter press processes has a stable moisture content below 80% and does not undergo secondary dissolution of phosphorus. This phosphorus-rich complex with high crystallinity directly matches the industrial grade requirements of phosphate rock in terms of component properties. The sludge discharge frequency at the bottom of the solid-liquid separation unit depends on the feedback interlocking control of the physical density of the bottom layer of the thickening zone. The system is arranged in the solid... The sludge concentration meter at the bottom of the liquid separation unit extracts the concentration value of the settled sludge in real time. The control unit compares the concentration measurement value with the set 45g / L action threshold logic. When the concentration measurement value reaches or exceeds the action threshold, it issues an opening command to the sludge discharge pump to execute the underflow discharge operation. When the concentration measurement value does not reach the action threshold, it locks the sludge discharge circuit and extends the residence time of the sediment at the bottom, forcing the micro-flocs to undergo secondary gravity compaction at the bottom of the sedimentation tank. This eliminates the physicochemical risk of secondary phosphorus dissolution in subsequent processes caused by phosphorus-rich complexes under high moisture content conditions. Mechanical interception and... The state feedback mechanism constitutes the hardware constraint for controlling the mass fraction of phosphorus pentoxide in the final high-density phosphorus-rich precipitate. Within the macroscopic operating cycle of continuously establishing a dense bottom blanket state and relying on the aforementioned frequency of alternating feedback, this relatively low sludge discharge trigger frequency effectively forces the formation and stacking of a high-resistance suspended sludge interception blanket in the extremely deep region at the bottom of the sedimentation tank. Utilizing the continuous hydraulic reverse flow resistance at the bottom of the high-inclination tube assembly, extremely intense dynamic liquid-phase washing is applied to the primary particles mixed within the sludge mass; based on the microscopic mineral density of different substances... Due to the differential effect, the relatively low-density, ineffective, amorphous aluminum hydroxide inert gel is easily stripped away by the rising scouring flow and carried back to the upper clear liquid tank. Meanwhile, the main core of the phosphorus-rich complex, which has a dense internal lattice and a relatively high specific gravity, is selectively and firmly retained in the bottom bed due to its gravitational settling potential. It is this spontaneous micro-hydraulic beneficiation mechanism, which is entirely dependent on the change in the mechanical sludge discharge rhythm, that continuously removes the base impurities that interfere with subsequent chemical purity analysis from the physical level, thereby enabling the total phosphorus analyte after dehydration to fully realize a high-grade improvement in composition.

[0050] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater, characterized in that, include: Step 101: The phosphorus-containing wastewater to be treated and a polyaluminum chloride solution with a basicity of 45% to 55% are simultaneously fed into the primary reaction zone of the inline high-frequency shear reactor via a variable frequency metering pump; the spatial average shear rate in the primary reaction zone is adjusted to 2500 / s to 3200 / s, and the hydraulic residence time of the mixed fluid in the primary reaction zone is controlled to be 500ms to 800ms; wherein, the initial alkalinity value of the phosphorus-containing wastewater to be treated is monitored in real time, and hydrogen ion solution is added to the primary reaction zone according to the initial alkalinity value to adjust the mixed fluid... With a value of 4.5 to 5.5, polyaluminum chloride forms a polynuclear hydroxy complex system within the primary reaction zone; Step 102: The mixed fluid discharged from the primary reaction zone is introduced into the secondary reaction zone. An alkaline regulator is injected into the mixed fluid through an annular jet to control the pH transition of the mixed fluid within 20ms to 50ms. This induces global homogeneous nucleation of polynuclear hydroxy complexes in the phosphorus-containing wastewater to be treated to generate primary microflocs. The primary microflocs then combine with phosphate ions in the phosphorus-containing wastewater to form phosphorus-rich complexes. Step 103: The mixed fluid discharged from the secondary reaction zone is introduced into the solid-liquid separation unit to separate and collect the high-density phosphorus-rich precipitate. By adjusting the sludge discharge frequency at the bottom of the solid-liquid separation unit, the total phosphorus mass fraction (calculated as phosphorus pentoxide) in the collected high-density phosphorus-rich precipitate is not less than 15%. The high-density phosphorus-rich precipitate is then recycled as an industrial phosphorus extraction raw material to achieve comprehensive resource utilization of the phosphorus-containing wastewater to be treated.

2. The chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater according to claim 1, characterized in that, In step 101, the basicity of the polyaluminum chloride solution is 48% to 52%; while the mixed fluid is maintained at... Under an environment with a value of 4.5 to 5.5, the initial solvation layer of polyaluminum chloride is broken by utilizing the high-frequency shear stress field of the primary reaction zone.

3. The chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater according to claim 1, characterized in that, In step 101, the primary reaction zone of the pipeline high-frequency shear reactor is equipped with staggered shear stators and shear rotors. The linear velocity of the shear rotors is controlled to be 25 m / s to 35 m / s to generate high-frequency pressure pulsation in the fluid channel.

4. The chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater according to claim 1, characterized in that, Step 102 includes the following sub-steps: Step 1021, adjusting the injection flow rate of the alkaline regulator to instantaneously raise the pH value of the mixed fluid from 4.5 to 5.5 to 7.5 to 8.5; Step 1022, controlling the nucleation reaction time to 2s to 5s to complete the capture of free phosphate ions before the spontaneous aggregation of primary micro-flocs.

5. The chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater according to claim 1, characterized in that, In step 103, the solid-liquid separation unit is a high-inclination tube sedimentation tank, and the sedimentation load is set to 5 m³ / m²·h to 8 m³ / m²·h; the water content of the separated high-density phosphorus-rich precipitate is less than 80%.

6. The chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater according to claim 1, characterized in that, In step 101, the initial total phosphorus concentration of the phosphorus-containing wastewater to be treated is less than 0.5 mg / L. The microscopic collision frequency between polynuclear hydroxy complexes and phosphate ions is increased by using a pipeline high-frequency shear reactor.

7. The chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater according to claim 1, characterized in that, In step 102, the fractal dimension of the nascent microfibrils at the moment of nucleation is 1.2 to 1.

5.

8. The chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater according to claim 1, characterized in that, It also includes a precipitate reflux step: a portion of the high-density phosphorus-rich precipitate collected in step 103 is refluxed back to the inlet of the secondary reaction zone as a contact medium to induce the accelerated nucleation of polynuclear hydroxy complexes.

9. The chemical flocculation process for deep phosphorus removal from phosphorus-containing wastewater according to claim 1, characterized in that, The high-density phosphorus-rich precipitate collected in step 103 is sent to a phosphate fertilizer production line or a thermal phosphoric acid production line as a secondary phosphate source to replace natural phosphate rock.

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