Method and system for synergistic dewatering and solidification of high-water-content, salt-containing sludge and resource utilization thereof

Abstract

The application discloses a kind of high water content, salt-containing sludge's synergic dewatering solidification and resource utilization method and system, comprising: slurry pretreatment: alkali activation straw fiber is added to sludge and is dry mixed and wet mixed;Mechanical-electrodialysis synergic dewatering: the slurry after pretreatment is first carried out mechanical pressure dewatering, then coupling electrodialysis is carried out desalination dewatering, and dewatered sludge is obtained;And the voltage self-adaptive control algorithm is used to adjust the voltage size that electrodialysis is applied;Targeted solidification: composite solidifying agent is added to dewatered sludge and stirred into shape, realizes the triple salt solidification mechanism of chemical locking, physical adsorption, channel plugging, and the shaped solidified body is obtained after curing.The application realizes the rapid drop of water content, improves the dechlorination rate, significantly shortens the processing cycle, and solves the problems of slow dewatering, high energy consumption of high-salt sludge.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization, and in particular to a method and system for the synergistic dehydration, solidification and resource utilization of high water content and saline sediment. Background Technology

[0002] Silt from estuaries and coastal ports not only has a high water content but also a high salinity. Currently, it is mainly treated through near-shore dumping, landfilling, land reclamation, and traditional resource utilization (such as low-grade building materials). However, existing methods still have the following problems:

[0003] (1) Difficult to dewater: Traditional dewatering methods for high water content sediment (water content > 80%) are costly and time-consuming.

[0004] (2) Risk of salt migration: High salt content can cause salt to be released after direct solidification, which may damage the structure or pollute the environment.

[0005] (3) Resource bottlenecks: Salt inhibits microbial activity and limits compost utilization; chloride salts corrode steel bars and restrict their application in building materials.

[0006] (4) Secondary pollution: The large amount of chemical solidifying agent added can easily lead to the leaching of heavy metals or soil compaction. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention proposes a method and system for the synergistic dehydration, solidification, and resource utilization of high-moisture and saline sediment.

[0008] The specific technical solution is as follows:

[0009] A method for synergistic dewatering, solidification, and resource utilization of high-moisture, saline sediment includes the following steps:

[0010] S1. Mud pretreatment: Alkali-activated straw fibers are added to the bottom mud, and dry and wet mixing are carried out in sequence.

[0011] S2. Mechanical-Electrodialysis Co-dehydration: The pretreated sludge is first mechanically dehydrated to obtain a homogenized sludge cake; then electrodialysis is coupled to further desalinate and dehydrate the sludge cake to obtain dehydrated bottom sludge; the electrodialysis is achieved through an anode pressure platform and a cathode conductive filter cloth. A directional voltage is applied to this area to drive chloride ions to precipitate from the anode to achieve desalination, and water molecules to precipitate from the cathode to achieve dehydration; a voltage adaptive control algorithm is set so that when the resistivity of the sludge cake is within a set threshold range, the control voltage decreases exponentially as the resistivity of the sludge cake increases;

[0012] S3. Targeted solidification: Add a composite solidifying agent to the dewatered sediment and stir to form a solidified body, thereby achieving a triple salt fixation mechanism of chemical locking, physical adsorption, and channel blocking. After curing, a solidified body is obtained.

[0013] Furthermore, S1 is specifically implemented through the following sub-steps:

[0014] S1.1: After cutting the straw, soak it in a 2-2.5% NaOH solution at 60-65℃ for 2-3 hours, with a solid-liquid ratio of 1:10;

[0015] S1.2: Wash the soaked straw with deionized water until neutral and dry it to constant weight to obtain alkali-activated straw fiber;

[0016] S1.3: Add alkali-activated straw fiber at a ratio of 0.3~0.8% of the wet mud mass, and dry mix at 70~90 rpm to increase the porosity to 35~50%;

[0017] S1.4: Add atomized water to increase the moisture content of the wet mud, and perform wet mixing at 40~60 rpm to promote particle flocculation.

[0018] Furthermore, in S2, multiple radial guide channels originating from the center are formed on the upper surface of the anode pressure platform. The guide channels converge at the collection port at the center of the anode pressure platform, and the collection port is connected to the concentrate collection tank through a pipe.

[0019] The upper surface of the anode pressure platform is covered with an anion exchange membrane, the cathode conductive filter cloth is arranged above the anion exchange membrane, and the homogenized mud cake is arranged between the anion exchange membrane and the cathode conductive filter cloth; the pressure roller is arranged above the cathode conductive filter cloth to provide mechanical pressure to prevent the collapse of the water channel pores inside the mud cake; the distance between the pressure roller and the anode pressure platform is adapted to the thickness of the homogenized mud cake.

[0020] A directional DC electric field is applied to the area where the anode pressure platform is located, driving chloride ions to penetrate the anion exchange membrane, accumulate on the surface of the anode pressure platform, and be collected through the guide channel into the concentrate collection tank; at the same time, sodium ions and water molecules are driven to penetrate the cathode conductive filter cloth and be collected.

[0021] Furthermore, the anode bearing platform is formed by embedding titanium-coated ruthenium mesh electrodes into the middle of the steel structure to form an electrode plate on the surface of the anode bearing platform, thereby achieving a uniform distribution of the electric field.

[0022] Furthermore, in S2, the threshold range corresponding to the resistivity of the mud cake is (R c R f ), where R c To trigger the attenuation resistivity threshold, R f To determine the final resistivity; when the resistivity of the cake is within this threshold range, the voltage decreases exponentially with increasing resistivity of the cake:

[0023] At time t, the voltage V(t) is the product of the initial voltage V0 and a natural exponential function, where the exponential part of the natural exponential function is the product of the negative voltage decay coefficient k0 and a composite term; the composite term is the resistivity measurement R0 at the trigger decay and the trigger decay resistivity threshold R. c The difference, plus the product of the resistance growth coefficient α and the integral of the ratio of the square of the voltage value to the square of the resistivity from 0 to t;

[0024] The resistivity is the sum of the resistivity measurement R0 at the time of triggered decay and the resistance increase at time t; the resistance increase at time t is the product of the resistivity growth rate γ and t.

[0025] The resistivity growth rate γ is the product of the resistance growth coefficient α and the square of the initial current density;

[0026] The initial current density is the quotient of the product of the initial voltage V0, the resistivity measurement value R0, and the distance between the pressure roller and the anode bearing platform.

[0027] Furthermore, in S2, for equal amounts of mud or mud cake, the dewatering times of the two stages must satisfy the following: the mechanical dewatering time T1 is greater than or equal to the electrodialysis desalination dewatering time T2, and the difference is within a set threshold range.

[0028] Furthermore, the mechanical dehydration time T1 is the ratio of the amount of water dehydrated to the sum of the pressure term and the skeleton term; the amount of water dehydrated is the difference between the initial moisture content and the target moisture content; the pressure term is the product of the pressure efficiency coefficient and the average mechanical pressure to the power of 0.8; and the skeleton term is the product of the skeleton strengthening coefficient and the amount of alkali-activated straw fiber added.

[0029] The electrodialysis desalination and dehydration time T2 is calculated by multiplying the reciprocal of the product of the basic attenuation coefficient k1 and the resistivity growth rate γ by the initial voltage V0 and the minimum safe voltage V. min The natural logarithm of the ratio, multiplied by the trigger decay resistivity threshold R c With termination resistivity R f The ratio is then added to the safety time to obtain the final result.

[0030] Furthermore, in step S3, the composite curing agent comprises: sulfoaluminate cement, modified diatomaceous earth, nano-alumina, and sodium polyacrylate; the mass of the composite curing agent accounts for 8-10% of the dry mud mass.

[0031] Add sodium polyacrylate solution to the dehydrated bottom mud, stir until the mud particles are coated, then add the composite curing agent in three batches, control the water-cement ratio to be 0.28-0.32, and perform strong stirring at 120 rpm or higher to form the mixture.

[0032] Furthermore, the triple salt fixation mechanism includes:

[0033] The sulfoaluminate cement hydrates to form ettringite, chemically locking chloride ions into insoluble Friedel salts; the nano-alumina accelerates ettringite nucleation, thus shortening the initial setting time.

[0034] The modified diatomaceous earth utilizes 2-50nm micropores to physically adsorb free ions, while simultaneously providing a silicon source to react with cement to generate CSH gel.

[0035] The sodium polyacrylate forms a hydrophobic film, blocking capillary water absorption channels.

[0036] A system for the synergistic dehydration, solidification, and resource utilization of high-moisture and saline sediment, used to realize the synergistic dehydration, solidification, and resource utilization method of the high-moisture and saline sediment, includes: a pretreatment unit, a synergistic dehydration and desalination unit, a targeted solidification unit, and a control unit;

[0037] The pretreatment unit is used to achieve dry and wet mixing of alkalized straw fibers and bottom mud;

[0038] The synergistic dehydration and desalination unit includes a belt filter press mechanical dehydration device and an electrodialysis desalination and dehydration device connected in sequence. The electrodialysis desalination and dehydration device includes: a pressure roller, an anode pressure platform, a cathode conductive filter cloth, an anion exchange membrane, and a concentrate collection tank. Multiple radial guide channels originating from the center are formed on the upper surface of the anode pressure platform, converging at a collection port at the center of the anode pressure platform. The collection port is connected to the concentrate collection tank via a pipe. The upper surface of the anode pressure platform is covered with an anion exchange membrane, the cathode conductive filter cloth is arranged above the anion exchange membrane, and the homogenized sludge cake is arranged between the anion exchange membrane and the cathode conductive filter cloth. The pressure roller is arranged above the cathode conductive filter cloth to provide mechanical pressure and prevent the collapse of the pores in the water-conducting channels inside the sludge cake.

[0039] The curing unit includes a high-powered mixer and curing equipment for targeted curing.

[0040] The control unit includes a PLC system and a real-time resistance monitoring module. The PLC system has a built-in voltage adaptive regulation algorithm and a time synchronization control method for the two dehydration stages.

[0041] In the voltage adaptive control algorithm, when the voltage applied during the electrodialysis stage is greater than the minimum safe voltage and the resistivity of the sludge cake is less than the termination resistivity, the PLC system extends the processing time to solve the monitoring error problem, including compensating for sensor drift in the real-time resistance monitoring module; when the voltage applied during the electrodialysis stage is less than or equal to the minimum safe voltage, or the resistivity of the sludge cake is greater than or equal to the termination resistivity, the system operation is immediately terminated.

[0042] The two-stage dehydration time synchronization control method ensures that the dehydration time of the two stages meets the following conditions: the mechanical dehydration time T1 is greater than or equal to the electrodialysis desalination time T2, and the difference is within the set threshold range.

[0043] The beneficial effects of this invention are:

[0044] (1) The present invention proposes a dynamic synergistic dehydration and desalination process of mechanical-electrodialysis: coupling mechanical pressure dehydration and intelligent pressure-regulating electrodialysis, and operating synchronously under the support of straw skeleton, achieving a rapid decrease in moisture content while improving dechlorination rate, significantly shortening the treatment cycle, and solving the problems of slow dehydration and high energy consumption of high-salt mud.

[0045] (2) This invention proposes a voltage adaptive control algorithm driven by resistance: a voltage exponential decay model is proposed in the electrodialysis stage to dynamically match the change of sludge cake resistance, effectively prevent local overheating and maintain efficient ion migration, and ensure the stability and safety of dehydration and desalination.

[0046] (3) The present invention proposes a triple salt fixation mechanism: by using a composite curing agent, the salt fixation rate of the solidified body is significantly improved through the synergistic effect of chemical locking, physical adsorption and channel blocking, the curing cycle for the compressive strength to meet the standard requirements is shortened, and the bottleneck of salt resource utilization is broken. Attached Figure Description

[0047] Figure 1 This is a flowchart of a method for the synergistic dehydration, solidification, and resource utilization of high-moisture and saline sediment in an embodiment of the present invention.

[0048] Figure 2 This is a schematic diagram of the device structure for mechanical-electrodialysis synergistic dehydration in an embodiment of the present invention, wherein (a) is an overall schematic diagram and (b) is a partial enlarged view.

[0049] Figure 3 This is a schematic diagram illustrating the principle of electrodialysis desalination and dehydration in an embodiment of the present invention.

[0050] Figure 4 This is a top view of the anode bearing platform in an embodiment of the present invention.

[0051] Figure 5 In the targeted curing process of this invention, Cl - A schematic diagram showing the change in dissolution rate over time.

[0052] In the diagram, 1 is the pressure roller, 2 is the anode pressure platform, 3 is the cathode conductive filter cloth, 4 is the anion exchange membrane, 5 is the guide groove, 6 is the collection port, and 7 is the concentrate collection tank. Detailed Implementation

[0053] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The objectives and effects of the present invention will become clearer as a result. The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0054] This embodiment proposes a method for the synergistic dewatering, solidification, and resource utilization of high-moisture and high-salinity sediment, specifically targeting high-moisture (≥80%) and high-salinity (Cl) sediments generated from river and port dredging and industrial sludge. - ≥1%) sediment is treated with a synergistic technology of dewatering, desalination and solidification to achieve harmless and resource-based utilization of sediment.

[0055] like Figure 1 As shown, a method for the synergistic dewatering, solidification, and resource utilization of high-moisture and saline sediment involves pretreatment of the sediment followed by a three-stage synergistic gradient dewatering process: mechanical dewatering, electrodialysis desalination, and composite solidification. The method specifically includes the following steps:

[0056] S1: Collect the mud slurry formed from high-moisture and saline bottom sediment and pretreat it, specifically through the following sub-steps:

[0057] S1.1: Agricultural waste straw (such as rice and corn straw) is widely available and inexpensive. The straw is cut into short fibers of 0.5-2mm using a hammer mill. The cut straw is then soaked in a 2-2.5% NaOH solution at 60-65℃ for 2-3 hours (solid-liquid ratio 1:10, i.e., 1kg straw: 10L 2% NaOH solution) to destroy the cellulose crystal structure and expose the active hydroxyl groups, thereby increasing its specific surface area by 2.5-3.5 times.

[0058] S1.2: The soaked straw is repeatedly washed with deionized water until neutral, and then dried at 80~90℃ to constant weight to obtain alkali-activated straw fiber.

[0059] S1.3: Add alkali-activated straw fiber at a ratio of 0.3~0.8% of the wet mud mass, and dry mix it using a twin-shaft paddle mixer (70~90 rpm, 10 min) to increase the porosity to 35~50% and form water-conducting channels.

[0060] S1.4: Add a small amount of atomized water (adjust the moisture content of the wet mud to 83~87%) for wet mixing (40~60 rpm, 5 min) to reduce the absolute value of the bottom mud potential and promote particle flocculation.

[0061] S2: Mechanical-Electrodialysis Synergistic Dewatering: Based on traditional belt filter presses, mechanical dewatering is coupled with electrodialysis technology to achieve sludge dewatering and desalination. Specifically, the pretreated sludge is first dewatered to a moisture content ≤60% using a mechanical pressure of 0.5-1.0 MPa. Then, a low-pressure (0.18~2 MPa) electrodialysis system is coupled with intelligent voltage-regulating electrodialysis (initially 15V, dynamically reducing the pressure exponentially when the sludge resistivity is within a set threshold range), simultaneously achieving a moisture content ≤40% and desalination of sludge. - Removal rate ≥ 85%. This step is achieved through the following two consecutive implementation phases:

[0062] Phase 1 (Mechanical Dehydration): Based on, for example... Figure 2 The belt filter press mechanical dewatering device shown has two layers of membrane cloth forming a conveying channel, which surrounds multiple pressure rollers 1. Pretreated slurry is introduced between the two layers of membrane cloth. Under the linear pressure of 0.5-1.0 MPa provided by the pressure rollers 1, the free water is rapidly discharged based on the porous water-conducting skeleton of alkali-activated straw fibers, reducing the water content of the slurry from the initial ≥80% to ≤60%, and initially forming a homogenized slurry cake (thickness deviation ≤12%). This provides a stable conductive interface for the subsequent electrodialysis stage, ensuring that the electric field energy can efficiently drive ion migration in the subsequent electrodialysis stage, and also preventing excessive free water from causing power loss and electrode short circuits.

[0063] The methods for controlling the moisture content at this stage are as follows:

[0064] The moisture content prediction model after dehydration is established as follows:

[0065]

[0066] In the formula, W f The predicted moisture content after mechanical dehydration is given by K, where W0 is the initial moisture content; P The pressure efficiency coefficient is between 0.3 and 0.35, and the unit is... P represents the average mechanical pressure, ranging from 0.5 to 1.0 MPa; K f The skeletal reinforcement coefficient ranges from 0.1 to 0.12, with units of... ;F v The amount of alkali-activated straw fiber added is 3~8 kg / t wet mud; T1 is the mechanical dewatering time.

[0067] To verify the accuracy of the prediction model and ensure that the moisture content of different sediment types after the first stage of dewatering is ≤60%, different initial moisture contents W0 (80%, 85%, 90%), different average mechanical pressures P (0.5MPa, 0.8MPa, 1.0MPa), and different amounts of activated straw fiber added F were tested. vA multi-factor variable experiment was conducted under different organic matter content (8%, 15%, 20%), pH values ​​(6.0, 7.5, 9.0), and dehydration times (T1) (10 min, 15 min, 20 min) at different rates (3 kg / t, 5 kg / t, 7 kg / t), as well as different pH values ​​(8%, 15%, 20%). A total of 27 groups were included, as shown in Table 1 below. K was taken as... P =0.35, K f =0.12. Based on the experimental results, a reasonable combination scheme can be given for each variable, and the accuracy of the prediction model reaches 98%.

[0068] Table 1 Experimental Design

[0069]

[0070] The accuracy of the prediction model in predicting moisture content was verified, and the key factors affecting the accuracy of the prediction were analyzed. The results of each group are shown in Table 2 below. Among them, the dehydration effect of groups 3, 6, 8, 15, 18 and 26 met the standard.

[0071] Table 2. Accuracy of moisture content prediction and analysis results for each group.

[0072]

[0073] The second stage (electrodialysis desalination and dehydration): [e.g.] Figure 2 , Figure 3 As shown, the electrodialysis desalination and dehydration unit is immediately following the belt filter press mechanical dehydration unit, and includes: a pressure roller 1, an anode pressure platform 2, a cathode conductive filter cloth 3, an anion exchange membrane 4, and a concentrate collection tank 7. The anode uses a titanium-coated ruthenium (Ti / RuO2) mesh electrode (1.5mm) embedded in the middle of the steel structure to form the electrode plate on the surface of the anode pressure platform 2, achieving a uniform electric field distribution. Figure 4 As shown, the surface of the anode pressure platform 2 has multiple radial guide grooves 5 with a width of 4-6 mm and a depth of 2-3 mm. The guide grooves 5 converge at the collection port 6 in the center of the anode pressure platform 2. The collection port 6 is connected to the concentrate collection tank 7 through a pipe. The concentrate collection tank 7 is equipped with a peristaltic pump to increase the collection speed of the concentrated chlorine solution.

[0074] The surface of the anode pressure platform 2 is covered with an anion exchange membrane 4, and the cathode conductive filter cloth 3 is arranged above the anion exchange membrane 4. In this embodiment, the cathode conductive filter cloth 3 is made of stainless steel conductive filter cloth (pore size 50μm) and serves as the cathode, simultaneously undertaking drainage and charge conduction. The homogenized mud cake is located between the anion exchange membrane 4 and the cathode conductive filter cloth 3. The pressure roller 1 is arranged above the cathode conductive filter cloth 3. Under low pressure conditions, the distance between the pressure roller 1 and the anode pressure platform 2 is dynamically adjustable (20~30mm) to adapt to different homogenized mud cake thicknesses.

[0075] During electrodialysis, while maintaining a mechanical pressure of 0.18~0.2MPa to prevent the collapse of the internal water-conducting channels in the mud cake, an initial 15V directional DC electric field is applied to drive Cl... - The solution is enriched and extracted through the anion exchange membrane 4, forming a high-salt concentrate in the anolyte region. Then, under the action of a peristaltic pump, the concentrate flows through a guide channel to the collection port 6 (5) and enters the concentrate collection tank 7. Simultaneously, Na... + As water molecules migrate towards the cathode, the acidic water at the cathode is enriched, exported, and then refluxed (not shown in the figure), which can be used to clean filter cloths, etc.

[0076] By aligning the direction of electroosmotic flow with the migration path of anions, and by using residual mechanical pressure to suppress concentration polarization in the electrode region, the anion exchange membrane 4 in the anode region continuously captures chloride ions and exports the enriched solution, achieving simultaneous and efficient dehydration and desalination. The entire process is 50% shorter than the traditional process cycle.

[0077] As the moisture content of the mud cake decreases further, the resistivity increases. A voltage adaptive control algorithm is set to ensure the effectiveness and efficiency of electrodialysis desalination and dehydration while preventing localized overheating. When the resistivity of the mud cake is within a set threshold range, the voltage applied during the electrodialysis desalination and dehydration stages should decrease exponentially with increasing resistivity, as shown in the following expression. Ultimately, this ensures that the moisture content of the mud cake is ≤40%, and the Cl... - Removal rate ≥ 85%; set threshold range (R c R f ), where R c To trigger the attenuation resistivity threshold, R is between 480 and 500 Ω•cm. f The final resistivity is between 1000 and 1500 Ω•cm.

[0078]

[0079] In the formula, V(t) is the voltage at time t, controlled between 8 and 15V, and V0 is the initial voltage; k0 is the voltage decay coefficient, between 0.001 and 0.0012; R(t) is the resistivity at time t, and R0 is the resistivity measurement value when trigger decay; α is the resistance growth coefficient, which varies with the electrical characteristics of different sludge, between 0.18 and 0.21; γ is the resistivity growth rate, between 28 and 42; J0 is the initial current density, and d is the distance between the pressure roller 1 and the electrode plate.

[0080] Furthermore, the specific method for time synchronization control of the mechanical dewatering and electrodialysis desalination stages is as follows: To achieve efficient dewatering and desalination and synergistic effects between the two stages, for equal amounts of slurry or mud blocks, the mechanical dewatering time T1 must be greater than or equal to the electrodialysis desalination time T2, and the difference must be within a set threshold range. If T1 < T2, the filter cake will remain for too long, causing moisture redistribution, pore closure, and a sharp drop in electrodialysis efficiency. If T1 > T2, and the difference exceeds the set threshold range, the electrodialysis unit will be idle for too long, waiting for upstream material supply, increasing energy consumption. Specifically, T1 is controlled within the range of 10-20 minutes to avoid energy overload.

[0081] The mechanical dehydration time T1 can be calculated using the following formula:

[0082]

[0083] In the formula, ∆W is the amount of water removed. If the target moisture content after dehydration is 0.6, then ∆W = W0 - 0.6, where W0 is the initial moisture content. For stress terms, This is a skeleton item.

[0084] The desalination and dehydration time T2 of electrodialysis can be calculated by the following formula:

[0085]

[0086] In the formula, k1 is the basic attenuation coefficient, which is between 0.0295 and 0.035; V0 is the initial voltage, V min Minimum safe voltage; ∆t s For safety, the time should be between 3 and 5 minutes.

[0087] Furthermore, the safety time ∆t s Determined based on organic matter content: If the organic matter content is less than 15%, then ∆t s =3min; if the organic matter content is within the range of 15~20%, then ∆t s =4min; if the organic matter content is greater than 20%, ∆t s =5min. When the voltage drops to V min Or the resistivity increases to R f When this happens, the system immediately terminates operation, at which point ∆t s Automatically expired.

[0088] That is, if the requirement T1≥T2 is to be satisfied, then the following formula must be satisfied:

[0089]

[0090] As can be seen from the moisture content control method in the first stage, T1 is basically a constant value according to a specific combination scheme. If T1 < T2, the moisture content can be controlled by reducing the initial voltage V0, increasing the distance d between the pressure roller and the electrode plate, and increasing the termination resistivity R. f Increase the safety time ∆t s accomplish.

[0091] Table 3 Adjustment plan when T1 > T2

[0092]

[0093] S3: Targeted Solidification: A composite solidifying agent is used to achieve salt fixation and strength enhancement in dewatered sediment through a three-tiered synergistic mechanism of "chemical locking (Friedel salt), physical adsorption (diatomaceous earth micropores), and channel blocking (PAA hydrophobic membrane)" (hereinafter referred to as triple salt fixation). The composite solidifying agent is a mixture of sulfoaluminate cement, modified diatomaceous earth, nano-alumina, and sodium polyacrylate, wherein the mass of the mixture accounts for 8-10% of the dry sediment mass (calculated based on the initial moisture content and the predicted moisture content after dewatering). The solidified body generated by triple salt fixation has a compressive strength ≥6.2 MPa and a Cl... - With a leaching rate of <0.02%, it can be used as a building material raw material.

[0094] The principle of triple salt fixation by the composite curing agent is as follows: Sulfoaluminate cement (60-75%) hydrates to generate ettringite (hereinafter referred to as AFt phase), chemically locking chloride ions into insoluble Friedel salt (3CaO•Al2O3•CaCl2•10H2O); nano-alumina (3-5%) accelerates the nucleation of the AFt phase, shortening the initial setting time to 45 min. Modified diatomaceous earth (20-35%) utilizes 2-50nm micropores to physically adsorb free ions (adsorption capacity ≥35mg Cl). - / g), while providing a silicon source to react with cement Ca(OH)2 to generate CSH gel. On this basis, sodium polyacrylate (hereinafter referred to as PAA, molecular weight 8000-12000) is added at a rate of 0.3-0.8% to form a hydrophobic film (contact angle >90%), blocking capillary water absorption channels, and the triple protection increases the salt fixation rate to >95%.

[0095] In specific implementation, first dewater the sediment (moisture content ≤40%, Cl) obtained by mechanical-electrodialysis co-dewatering. - Add PAA solution to the clay (≤0.3%) and stir for 2 minutes to coat the clay particles. Then add the composite curing agent in three batches (total amount accounts for 8% of the dry clay mass), controlling the water-cement ratio at 0.28-0.32 and stirring vigorously at ≥120 rpm to form the clay. After curing at 25℃ for 72 hours (electroaluminate characteristic peaks 2θ=9.1°, 15.8°) and natural drying for 7 days, the solidified body forms a dense structure (porosity <15%), and the compressive strength reaches 6.2 MPa after 7 days. Figure 5 As shown, 30 days Cl - The dissolution rate is less than 0.02% (less than the 0.05% limit in GB / T 23486), and no salt frost precipitation occurs after 10 dry and wet cycles.

[0096] At the microscopic level, this process uses AFt lattice expansion (theoretical capacity 1.5 mol / kg cement) and diatomaceous earth adsorption to synergistically capture salts; at the macroscopic level, it uses PAA hydrophobic film and hydration network to block migration paths, simultaneously achieving a strength leap (28-day strength exceeding 7 MPa) and zero-pollution conversion (no chemical leaching waste liquid), meeting the requirements of highways and first-class roads (extremely heavy and extra-heavy traffic).

[0097] To realize the above-mentioned method for synergistic dewatering, solidification and resource utilization of high water and salinity sediment, this embodiment also proposes a system for synergistic dewatering, solidification and resource utilization of high water and salinity sediment, which includes: a pretreatment unit, a synergistic dewatering and desalination unit, a targeted solidification unit and a control unit.

[0098] The pretreatment unit includes a twin-shaft paddle mixer for dry and wet mixing of alkalized straw fibers with bottom mud.

[0099] The co-processing dehydration and desalination unit includes, for example: Figure 2 The belt filter press mechanical dewatering device and the electrodialysis desalination and dewatering device shown are described. The electrodialysis anode is a titanium-coated ruthenium mesh electrode connected to a concentrate collection tank, and the cathode is a stainless steel conductive filter cloth.

[0100] The curing unit includes a high-powered mixer and curing equipment.

[0101] The control unit includes a PLC system and a real-time resistance monitoring module. The PLC system incorporates a voltage adaptive regulation algorithm and a time synchronization control method for the two dehydration stages. In the PLC control system, when the voltage is greater than V... min And the resistivity is less than R f At the same time, the PLC system is controlled to extend the processing time by 3 to 5 minutes, mainly to solve the monitoring error problem, including the sensor drift (±10%) of the compensation resistor real-time monitoring module.

[0102] This invention targets high water content (≥80%) and high salt content (Cl). -The challenge of disposing of sediment with a moisture content of ≥1% is addressed through a unique "straw skeleton pretreatment - mechanical electrodialysis synergistic dehydration and desalination - triple salt fixation and solidification" technology chain, achieving efficient resource utilization. Alkali activation of straw fibers (0.6% wet mud ratio) provides high porosity (35-50%), laying the foundation for water and electricity conductivity. A synergistic process of mechanical dehydration (0.5-1.0MPa) and electrodialysis desalination (15V→8V dynamic voltage regulation coupled with 0.2MPa low voltage) is employed, adaptively adjusting the electrodialysis voltage and the two-stage dehydration time to reduce the moisture content to ≤40% while simultaneously achieving Cl... - Removal ≥85%, cycle shortened by 50%. After dewatering, the sediment is treated with a composite solidifying agent (8-10% of dry sediment mass), employing a triple salt-fixing mechanism of "chemical locking (Friedel salt) - physical adsorption (diatomaceous earth micropores) - channel blocking (PAA hydrophobic membrane)," resulting in a solidified body with a 7-day compressive strength of 6.2 MPa and a 30-day Cl- content... - The dissolution rate is <0.02% (solid salt rate >95%), which solves the risk of salt migration and the product meets the standard requirements.

[0103] It will be understood by those skilled in the art that the above descriptions are merely preferred examples of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for the synergistic dewatering, solidification, and resource utilization of high-moisture, saline sediment, characterized in that, Includes the following steps: S1. Mud pretreatment: Alkali-activated straw fibers are added to the bottom mud, and dry and wet mixing are carried out in sequence. S2. Mechanical-Electrodialysis Co-dehydration: The pretreated sludge is first mechanically dehydrated to obtain a homogenized sludge cake; then electrodialysis is coupled to further desalinate and dehydrate the sludge cake to obtain dehydrated bottom sludge; the electrodialysis is achieved through an anode pressure platform and a cathode conductive filter cloth. A directional voltage is applied to this area to drive chloride ions to precipitate from the anode to achieve desalination, and water molecules to precipitate from the cathode to achieve dehydration; a voltage adaptive control algorithm is set so that when the resistivity of the sludge cake is within a set threshold range, the control voltage decreases exponentially as the resistivity of the sludge cake increases; S3. Targeted solidification: Add a composite solidifying agent to the dewatered sediment and stir to form a solidified body, thereby achieving a triple salt fixation mechanism of chemical locking, physical adsorption, and channel blocking. After curing, a solidified body is obtained.

2. The method for synergistic dewatering, solidification, and resource utilization of high-moisture and saline sediment according to claim 1, characterized in that, S1 is specifically implemented through the following sub-steps: S1.1: After cutting the straw, soak it in a 2-2.5% NaOH solution at 60-65℃ for 2-3 hours, with a solid-liquid ratio of 1:10; S1.2: Wash the soaked straw with deionized water until neutral and dry it to constant weight to obtain alkali-activated straw fiber; S1.3: Add alkali-activated straw fiber at a ratio of 0.3~0.8% of the wet mud mass, and dry mix at 70~90 rpm to increase the porosity to 35~50%; S1.4: Add atomized water to increase the moisture content of the wet mud, and perform wet mixing at 40~60 rpm to promote particle flocculation.

3. The method for synergistic dewatering, solidification, and resource utilization of high-moisture and saline sediment according to claim 1, characterized in that, In S2, multiple radial guide channels starting from the center are opened on the upper surface of the anode pressure platform. The guide channels converge at the collection port at the center of the anode pressure platform, and the collection port is connected to the concentrate collection tank through a pipe. The upper surface of the anode pressure platform is covered with an anion exchange membrane, the cathode conductive filter cloth is arranged above the anion exchange membrane, and the homogenized mud cake is arranged between the anion exchange membrane and the cathode conductive filter cloth; the pressure roller is arranged above the cathode conductive filter cloth to provide mechanical pressure to prevent the collapse of the water channel pores inside the mud cake; the distance between the pressure roller and the anode pressure platform is adapted to the thickness of the homogenized mud cake. A directional DC electric field is applied to the area where the anode pressure platform is located, driving chloride ions to penetrate the anion exchange membrane, accumulate on the surface of the anode pressure platform, and be collected through the guide channel into the concentrate collection tank; at the same time, sodium ions and water molecules are driven to penetrate the cathode conductive filter cloth and be collected.

4. The method for synergistic dewatering, solidification, and resource utilization of high-moisture-content and saline sediment according to claim 3, characterized in that, The anode bearing platform is formed by embedding titanium-coated ruthenium mesh electrodes into the middle of the steel structure to form an electrode plate on the surface of the anode bearing platform, thereby achieving a uniform distribution of the electric field.

5. The method for synergistic dewatering, solidification, and resource utilization of high-moisture-content and saline sediment according to claim 3, characterized in that, In S2, the threshold range corresponding to the resistivity of the mud cake is (R c R f ), where R c To trigger the attenuation resistivity threshold, R f To determine the final resistivity; when the resistivity of the cake is within this threshold range, the voltage decreases exponentially with increasing resistivity of the cake: At time t, the voltage V(t) is the product of the initial voltage V0 and a natural exponential function, where the exponential part of the natural exponential function is the product of the negative voltage decay coefficient k0 and a composite term; the composite term is the resistivity measurement R0 at the trigger decay and the trigger decay resistivity threshold R. c The difference, plus the product of the resistance growth coefficient α and the integral of the ratio of the square of the voltage value to the square of the resistivity from 0 to t; The resistivity is the sum of the resistivity measurement R0 at the time of triggered decay and the resistance increase at time t; the resistance increase at time t is the product of the resistivity growth rate γ and t. The resistivity growth rate γ is the product of the resistance growth coefficient α and the square of the initial current density; The initial current density is the quotient of the product of the initial voltage V0, the resistivity measurement value R0, and the distance between the pressure roller and the anode bearing platform.

6. The method for synergistic dewatering, solidification, and resource utilization of high-moisture and saline sediment according to claim 1, characterized in that, In S2, for equal amounts of mud or mud cake, the dewatering time in the two stages must meet the following requirements: the mechanical dewatering time T1 is greater than or equal to the electrodialysis desalination dewatering time T2, and the difference is within the set threshold range.

7. The method for synergistic dewatering, solidification, and resource utilization of high-moisture-content and saline sediment according to claim 6, characterized in that, The mechanical dehydration time T1 is the ratio of the amount of water dehydrated to the sum of the pressure term and the skeleton term. The amount of water dehydrated is the difference between the initial moisture content and the target moisture content. The pressure term is the product of the pressure efficiency coefficient and the average mechanical pressure to the power of 0.

8. The skeleton term is the product of the skeleton strengthening coefficient and the amount of alkali-activated straw fiber added. The electrodialysis desalination and dehydration time T2 is calculated by multiplying the reciprocal of the product of the basic attenuation coefficient k1 and the resistivity growth rate γ by the initial voltage V0 and the minimum safe voltage V. min The natural logarithm of the ratio, multiplied by the trigger decay resistivity threshold R c With termination resistivity R f The ratio is then added to the safety time to obtain the final result.

8. The method for synergistic dewatering, solidification, and resource utilization of high-moisture and saline sediment according to claim 1, characterized in that, In step S3, the composite curing agent comprises: sulfoaluminate cement, modified diatomaceous earth, nano-alumina, and sodium polyacrylate; the mass of the composite curing agent accounts for 8-10% of the dry mud mass. Add sodium polyacrylate solution to the dehydrated bottom mud, stir until the mud particles are coated, then add the composite curing agent in three batches, control the water-cement ratio to be 0.28-0.32, and perform strong stirring at 120 rpm or higher to form the mixture.

9. The method for synergistic dewatering, solidification, and resource utilization of high-moisture and saline sediment according to claim 8, characterized in that, The triple salt fixation mechanism includes: The sulfoaluminate cement hydrates to form ettringite, chemically locking chloride ions into insoluble Friedel salts; the nano-alumina accelerates ettringite nucleation, thus shortening the initial setting time. The modified diatomaceous earth utilizes 2-50nm micropores to physically adsorb free ions, while simultaneously providing a silicon source to react with cement to generate CSH gel. The sodium polyacrylate forms a hydrophobic film, blocking capillary water absorption channels.

10. A system for the synergistic dewatering, solidification, and resource utilization of high-moisture and saline sediment, used to implement the method for the synergistic dewatering, solidification, and resource utilization of high-moisture and saline sediment as described in any one of claims 1-9, characterized in that, include: Pretreatment unit, synergistic dehydration and desalination unit, targeted curing unit, control unit; The pretreatment unit is used to achieve dry and wet mixing of alkalized straw fibers and bottom mud; The synergistic dehydration and desalination unit includes a belt filter press mechanical dehydration device and an electrodialysis desalination and dehydration device connected in sequence. The electrodialysis desalination and dehydration device includes: a pressure roller, an anode pressure platform, a cathode conductive filter cloth, an anion exchange membrane, and a concentrate collection tank. The upper surface of the anode pressure platform has multiple radial guide channels originating from the center, converging at a collection port at the center of the anode pressure platform. This collection port is connected to the concentrate collection tank via a pipe. The upper surface of the anode pressure platform is covered with an anion exchange membrane, the cathode conductive filter cloth is arranged above the anion exchange membrane, and the homogenized sludge cake is arranged between the anion exchange membrane and the cathode conductive filter cloth. The pressure roller is arranged above the cathode conductive filter cloth to provide mechanical pressure and prevent the collapse of the pores in the water-conducting channels within the sludge cake. The curing unit includes a high-powered mixer and curing equipment for targeted curing. The control unit includes a PLC system and a real-time resistance monitoring module. The PLC system has a built-in voltage adaptive regulation algorithm and a time synchronization control method for the two dehydration stages. In the voltage adaptive control algorithm, when the voltage applied during the electrodialysis stage is greater than the minimum safe voltage and the resistivity of the mud cake is less than the termination resistivity, the PLC system extends the processing time to solve the monitoring error problem, including the sensor drift of the compensation resistor real-time monitoring module. The system operation shall be terminated immediately if the voltage applied during the electrodialysis stage is less than or equal to the minimum safe voltage, or if the resistivity of the sludge cake is greater than or equal to the termination resistivity. The two-stage dehydration time synchronization control method ensures that the dehydration time of the two stages meets the following conditions: the mechanical dehydration time T1 is greater than or equal to the electrodialysis desalination time T2, and the difference is within the set threshold range.

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