A method for rapid dewatering of high-moisture-content dredged sludge using a combination of flocculation and plate and frame filter press

Abstract

This invention designs a method for rapid dewatering of high-moisture-content dredged sludge enhanced by flocculation combined with plate and frame filter press, comprising the following steps: Step S1, sending the sludge slurry to a sedimentation tank for slag removal; Step S2, the sludge after slag removal flows by gravity into a thickening tank; Step S3, pumping the sludge at the bottom of the thickening tank to a conditioning tank via a small cutter suction dredger; Step S4, adding a skeleton material to the sludge in the conditioning tank before it enters the plate and frame filter press; Step S5, conveying the sludge with the skeleton material to the plate and frame filter press for dewatering. This application provides a method for rapid dewatering of high-moisture-content dredged sludge enhanced by flocculation combined with plate and frame filter press, employing a process flow of environmentally friendly dredging + sedimentation tank + thickening tank + equalization tank + plate and frame filter press dewatering. The sludge dredged by the environmentally friendly cutter suction dredger undergoes sedimentation and impurity removal, sludge thickening, chemical conditioning, filter press dewatering, and sludge cake conveying, ultimately forming a sludge cake with low moisture content.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of sludge dewatering, and particularly relates to a flocculation combined plate-and-frame filter press reinforced high-moisture-content dredged sludge rapid dewatering method. BACKGROUND

[0002] The dredged sludge (the sludge is not limited to the dredged sludge of rivers, lakes and reservoirs, and also includes shield slurry, cast-in-place slurry and engineering waste slurry of underground continuous wall construction) has the characteristics of high water content, high clay content, low non-draining strength, large compressibility and small permeability, and is difficult to be directly utilized due to poor engineering properties. Most of these sludges are directly disposed by being piled in a yard. The dredged sludge in the yard is very slow in self-weight deposition, consolidation and dewatering, and often contains heavy metals, nutrient salts and organic pollutants. With the extension of time, these pollutants will be precipitated, causing soil pollution and groundwater pollution and destroying the ecological environment. The traditional yard disposal method is gradually restricted due to the slow natural drainage consolidation and the occupation of a large amount of land resources.

[0003] A small water body bottom mud routine maintenance dredging method is disclosed in Chinese patent CN109354376B: including step 1, pre-adding aluminum salt particles and alkaline mineral powder to the bottom mud area, and raking the bottom mud for pre-flocculation treatment; step 2, bonding the rigid fibers into loose block-shaped elastic aggregates, and spraying cationic flocculants; step 3, throwing the elastic aggregates into water to make them sink freely, and covering the bottom of the water with the elastic aggregates; step 4, dragging and raking the elastic aggregates back and forth to make them roll on the bottom mud surface, a large amount of floating sludge is aggregated on the elastic aggregates, and gradually dewatered and compacted underwater due to mechanical movement, becoming sludge balls with a density much higher than that of the floating sludge; and step 5, raking the sludge balls, and dragging and raking them to move them out of the water and onto the shore when they are compressed to be obviously difficult to deform. Although the flocculation material is used, the flocculation effect of the flocculant used is poor, and the sludge balls are compressed by raking, which obviously leads to poor compression effect.

[0004] A river and lake sludge modified dewatering system is disclosed in Chinese patent CN216785966U, which comprises a stirring device, a first feeder, a homogenizing tank, a slurry pump, a second feeder and a plate-and-frame filter press. The discharge port of the stirring device is communicated with the homogenizing tank, the discharge port of the first feeder is communicated with the stirring device, and the first feeder contains lime. The discharge port of the homogenizing tank is communicated with the inlet of the slurry pump through a pipeline, the discharge port of the second feeder is communicated with the pipeline, and the second feeder contains a flocculant. The discharge port of the slurry pump is communicated with the inlet of the plate-and-frame filter press. The flocculant used contains lime, which will cause serious environmental pollution.

[0005] In view of the problem of low dewatering rate of plate-and-frame filter press dewatering by using a single flocculation conditioner, it is urgent to design a sludge dewatering method to realize the technical effect of efficient dewatering. SUMMARY

[0006] In order to solve the problems of low efficiency, long dehydration time and high water content after dehydration in the prior art, the present application designs a flocculation combined with plate and frame filter press reinforced high water content dredged sludge rapid dehydration method to reduce the dehydration rate of sludge.

[0007] The flocculation combined with plate and frame filter press reinforced high water content dredged sludge rapid dehydration method comprises the following steps:

[0008] Step S1, send the sludge to the sedimentation tank for deslagging;

[0009] Step S2, the deslagged slurry flows into the thickening tank by itself;

[0010] Step S3, the slurry at the bottom of the thickening tank is pumped to the conditioning tank by a small cutter suction dredger;

[0011] Step S4, before the slurry in the conditioning tank enters the plate and frame filter press, add a skeleton material;

[0012] Step S5, the slurry with the added skeleton material is sent to the plate and frame filter press for dehydration.

[0013] Preferably, in the step S1, the sedimentation mode in the sedimentation tank includes natural sedimentation, setting a grid at the entrance of the slurry into the sedimentation tank, and being equipped with a deslagging machine during pipeline transportation.

[0014] Preferably, in the step S2, the bottom of the thickening tank is designed with an inverted slope with a slope of 12%-15%.

[0015] Preferably, the bottom of the thickening tank is designed with a sludge taking port, and a small cutter suction dredger is arranged at the sludge taking port.

[0016] Preferably, in the step S3, the two treatment methods of the upper clear liquid in the thickening tank are:

[0017] Method one: the upper clear liquid flows into the overflow area, the SS value of the supernatant is detected, if the SS value meets the discharge standard, the pump is started to transport the water in the overflow area to the residual water treatment area;

[0018] Method two: the upper clear liquid flows into the overflow area, the SS value of the supernatant is detected, if the SS value does not meet the discharge standard, continue to sediment until the SS value of the supernatant meets the discharge standard, then start the pump to transport the water in the overflow area to the residual water treatment area.

[0019] Preferably, in the step S3, the conditioning tank includes a medicament stirring tank, a slurry conditioning tank, a medicament stirrer, a slurry stirrer and a dosing pump.

[0020] The medicament stirring tank is communicated with the mud conditioning tank through a medicament feeding pump;

[0021] A medicament stirring machine is arranged in the medicament stirring tank.

[0022] A mud stirring machine is arranged in the mud conditioning tank.

[0023] Preferably, the water used in the medicament stirring tank is tail water filtered by a plate-and-frame filter press.

[0024] Preferably, the medicament stirring machine and the mud stirring machine both adopt screw belt stirring paddles.

[0025] Preferably, the addition of the skeleton material is as follows:

[0026] The mud in the conditioning tank is passed through an S-shaped pipe from top to bottom, and a medicament injection head of skeleton material is arranged in the pipeline of the S-shaped pipe.

[0027] Preferably, the length of each pipeline of the S-shaped pipe is 10 m.

[0028] Five medicament injection heads are arranged on the uppermost branch pipeline of the S-shaped pipe.

[0029] Flow switches are arranged at the feeding port and the discharging port of the S-shaped pipe to control the inflow and outflow of mud.

[0030] The advantages and effects of the present application are as follows:

[0031] 1. The present application improves the concentration tank and arranges a slope of 12%-15% at the bottom of the tank. The mud is concentrated in the mud taking port, and most of the soil particles are deposited after a long time of sedimentation, thereby forming mud with high concentration on the slope and sliding to the mud taking port for concentration, which enhances the concentration effect of the mud.

[0032] 2. A composite flocculant designed in the present application is prepared by compounding chitosan and APAM 1800 million molecular weight anionic polyacrylamide. The mass concentration of chitosan is 1.4 ‰, and the mass concentration of APAM is 1 ‰. Here, the mass concentration is the mass ratio of solid particles to distilled water. V1 (chitosan) : V2 APAM = 1 : 1. The addition sequence is to add chitosan first and then add anionic polyacrylamide. According to this concentration, water is added to the medicament stirring tank for stirring and dissolution. The concentration of the flocculant is controlled in real time by a monitoring system. The medicament stirring tank is equipped with a concentration monitoring device. The concentration of the medicament stirring zone is monitored in real time according to the monitoring data to control the water inflow. The flocculant can make smaller clay particles form larger flocs, accelerate the separation of mud and water, and quickly and effectively remove SS value, COD, BOD, ammonia nitrogen, etc. in residual water.

[0033] 3、The skeleton material of the plate and frame filter press proposed in the application can strengthen the flocculation dewatering effect of the preceding steps, the skeleton material is added by a multi-point injection in the pipeline, and a S-shaped pipe mixing mode is adopted. The mud slurry generates turbulent flow effect due to the inconsistency between the flow direction and the bending direction of the pipeline during the flow in the S-shaped bent pipe, the turbulent flow has strong mixing effect to mix the skeleton material and the conditioned mud slurry uniformly; the mud slurry with the added skeleton material has large particle size of the mud slurry particles during the plate and frame filter pressing process, the pore structure is formed, the drainage channel is increased, the dewatering resistance is reduced, and the water flow is accelerated. Meanwhile, the addition of the plate and frame filter pressing skeleton material can improve the tail water quality, so that the dewatering water quality meets the discharge standard. Some heavy metals, organic matter, nitrogen, phosphorus and other nutrient salts can also be stably kept in the mud cake.

[0034] 4、The application proposes a sawtooth diaphragm filter plate design. Compared with ordinary filter plates, the sawtooth diaphragm has one more row of convex sawtooth diaphragms on the shape. When the pressing medium is passed through the back side of the diaphragm (such as compressed air), the pressing pressure is 130-150 MPa. These convex sawtooth diaphragms will bulge towards the filter chamber, and the filter cake will be subjected to secondary pressing. During secondary pressing, the convex sawtooth diaphragms of the left and right filter plates are deeply inserted into the mud cake, increasing the drainage channel, and the moisture content of the filter cake can be 5-10% lower than that of ordinary diaphragm filter plates.

[0035] 5、The application returns the tail water of the plate and frame filter pressing to the medicament stirring tank, fully utilizes the effective components in the tail water, and can promote the flocculation and precipitation of the mud slurry. The tail water formed by the plate and frame filter pressing contains a large amount of residual dissolved substances. After the tail water is collected in the washing tank, the washing liquid is used to wash the filter cloth of the filter press first. The water after washing the filter cloth of the plate and frame filter press is returned to the washing tank through the liquid outlet pipeline. After the washing work is completed, the tail water stored in the washing tank is sent to the medicament stirring tank by the water pump to dissolve the flocculant.

[0036] 6、The application provides a flocculation combined plate and frame filter pressing reinforced high-moisture-content dredged sludge rapid dewatering method. An environmental dredging + sedimentation tank + concentration tank + homogenizing tank + plate and frame filter press dewatering technological process is adopted. The mud slurry dredged by the environmental dredging cutter suction dredger is subjected to sedimentation and impurity removal, mud slurry concentration, medicament conditioning, filter pressing dewatering, and mud cake conveying, and finally forms a mud cake with a moisture content of less than 40%. The method can be used in large-scale dredging slurry treatment of rivers, lakes, seas, reservoirs, ports, channels and the like.

[0037] 7、The application proposes a set of flocculant pre-conditioning, adding skeleton material, using zigzag diaphragm filter plate of plate and frame filter technology. The improved process first passes through the compressed double electric layer and adsorption bridge effect of flocculant, promotes the small solid particles in the slurry to coagulate together to form larger flocs, and precipitates the water adsorbed between particles due to charge, to facilitate subsequent filter pressing. In view of the unsatisfactory effect of single use of flocculation conditioner on plate and frame filter dewatering, it is very important to further find a skeleton building agent that can release the water of the sludge on the basis of flocculation conditioning. By adding such inorganic inert materials as fly ash, phosphogypsum and the like to build the "skeleton" in the sludge dewatering process, the dewatering rate of the plate and frame filter press dewatering process is improved, and the water content of the sludge cake is reduced. By using the skeleton building agent in combination, the dosage of the flocculant can be appropriately reduced, and the construction cost is effectively controlled. The zigzag diaphragm filter plate increases the zigzag drainage plate on the basis of the ordinary diaphragm filter plate, increases the drainage channel of the slurry in the filter pressing process, and further reduces the water content of the sludge cake.

[0038] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, the contents of the description can be implemented, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following will be described in detail with the preferred embodiments of the present application and the accompanying drawings.

[0039] According to the detailed description of the specific embodiments of the present application in the following text combined with the drawings, those skilled in the art will more clearly understand the above and other purposes, advantages and characteristics of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creating any creative labor. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual proportion.

[0041] Figure 1 The flow chart of the flocculation combined plate and frame filter reinforced high water content dredged sludge rapid dewatering method provided by the present application;

[0042] Figure 2 The optimization flow chart of the flocculation combined plate and frame filter reinforced high water content dredged sludge rapid dewatering method provided by the present application;

[0043] Figure 3 The plan view of the sludge concentration tank provided by the present application;

[0044] Figure 4 The schematic diagram of the medicament stirring area and the slurry conditioning area provided in the present application is shown in the following figure:

[0045] Figure 5 The schematic diagram of the skeleton material adding system provided in the present application is shown in the following figure:

[0046] Figure 6 The schematic diagram of the skeleton material multi-point injection provided in the present application is shown in the following figure:

[0047] Figure 7 The schematic diagram of the plate-frame filter press provided in the present application is shown in the following figure:

[0048] Figure 8 The schematic diagram of the sawtooth diaphragm filter plate provided in the present application is shown in the following figure:

[0049] The figure shows the following: 1, concentration pool; 2, sludge taking port; 3, small cutter suction dredger; 4, overflow area; 5, residual water treatment area; 6, medicament stirring pool; 7, slurry conditioning pool; 8, medicament stirrer; 9, slurry stirrer; 10, medicament adding pump; 11, S-shaped pipe; 12, medicament injection head; 13, concentration monitoring device; 14, skeleton material; 15, sawtooth diaphragm filter plate; 16, air compressor; 17, pneumatic diaphragm pump; 18, gas storage tank; 19, pressure gauge; 20, thrust plate; 21, filter plate; 22, filter chamber; 23, water outlet groove; 24, hydraulic pump; 25, sludge outlet pipeline; 26, flow meter; 27, slurry pump. DETAILED DESCRIPTION

[0050] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. In the following description, specific details such as specific configurations and components are provided only to help a comprehensive understanding of the embodiments of the present application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. In addition, descriptions of known functions and structures are omitted in the embodiments for clarity and conciseness.

[0051] It should be understood that the "one embodiment" or "the embodiment" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, "one embodiment" or "the embodiment" appearing throughout the specification does not necessarily mean the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner.

[0052] Furthermore, reference numerals and / or letters may be repeated in different examples within this application. Such repetition is for the purpose of simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0053] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" in this article describes another type of relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after it are in an "or" relationship.

[0054] In this article, the term "at least one" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, "at least one of A and B" can mean: A exists alone, A and B exist simultaneously, or B exists alone.

[0055] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion.

[0056] Example 1

[0057] This embodiment mainly introduces the basic design of a method for rapid dewatering of high-moisture-content dredged sludge enhanced by flocculation combined with plate and frame filter press. Please refer to the flowchart for the design process. Figure 1 This includes the following steps:

[0058] Step S1: Send the sludge slurry to the sedimentation tank for slag removal;

[0059] Step S2: The sludge after slag removal flows by gravity into thickening tank 1;

[0060] Step S3: Pump the sludge at the bottom of the thickening tank 1 to the conditioning tank via a small cutter suction dredger 3.

[0061] Step S4: Before the sludge in the conditioning tank enters the plate and frame filter press, add skeleton material 14;

[0062] Step S5: The slurry with added skeleton material 14 is transported to a plate and frame filter press for dewatering.

[0063] Furthermore, in step S1, the sedimentation methods in the sedimentation tank include natural sedimentation, setting up a screen at the inlet of the sedimentation tank for the sludge, and equipping the pipeline with a slag removal machine during the pipeline transportation process.

[0064] Furthermore, in step S2, the bottom of the concentration tank 1 is provided with a slope of 12%-15%.

[0065] Furthermore, the bottom of the thickening tank 1 is designed with a sludge inlet 2, and a small cutter suction dredger 3 is installed at the sludge inlet 2. Please refer to the specific design. Figure 3 .

[0066] Furthermore, in step S3, the two methods for treating the supernatant in the concentration tank 1 are as follows:

[0067] Method 1: Flow the supernatant into the overflow zone 4, test the SS value of the supernatant, and if the SS value meets the discharge standard, start the pump to transport the water in the overflow zone 4 to the waste water treatment zone 5.

[0068] Method 2: Flow the supernatant into overflow zone 4 and test the SS value of the supernatant. If the SS value does not meet the discharge standard, continue sedimentation until the SS value of the supernatant meets the discharge standard. Then, start the pump to transport the water from overflow zone 4 to waste water treatment zone 5.

[0069] Furthermore, in step S3, the conditioning tank includes a chemical mixing tank 6, a mud conditioning tank 7, a chemical mixer 8, a mud mixer 9, and a dosing pump 10; for specific design details, please refer to [reference needed]. Figure 4 .

[0070] The chemical mixing tank 6 and the mud conditioning tank 7 are connected by a dosing pump 10.

[0071] A pharmaceutical mixer 8 is installed in the pharmaceutical mixing tank 6;

[0072] The mud conditioning tank 7 is equipped with a mud mixer 9.

[0073] Furthermore, the water used in the reagent mixing tank 6 is derived from the tailwater filtered by the plate and frame filter press.

[0074] Furthermore, both the reagent mixer 8 and the mud mixer 9 employ ribbon-type agitators.

[0075] Furthermore, for the specific design of the skeleton material 14, please refer to [reference needed]. Figure 5 The method for adding is as follows:

[0076] The sludge in the conditioning tank is passed through a top-to-bottom S-shaped pipe 11. Inside the S-shaped pipe 11, a reagent injection head 12 made of skeleton material 14 is installed. For specific design details, please refer to [reference needed]. Figure 6 .

[0077] Furthermore, the length of each layer of the S-shaped pipe 11 is 10m;

[0078] Five agent injection heads 12 are installed on the uppermost branch pipe of the S-shaped pipe 11;

[0079] The inlet and outlet ports of the S-shaped tube 11 are equipped with flow switches to control the flow rate of mud entering and exiting.

[0080] This application improves the thickening tank by setting the bottom slope of the tank to 12%-15%. The design concentrates the mud in the mud intake port. After a long period of sedimentation, most of the soil particles are deposited on the slope to form a high-concentration mud and slide towards the mud intake port for thickening, thereby enhancing the mud thickening effect.

[0081] This application recycles the tailwater from plate and frame filter presses to a chemical mixing tank, fully utilizing the effective components in the tailwater and promoting sludge flocculation and sedimentation. The tailwater from plate and frame filter presses contains a large amount of residual dissolved substances. After the tailwater is collected in a washing tank, the washing liquid is first used to clean the filter cloth of the filter press. The water used to wash the filter cloth is then returned to the washing tank through the outlet pipe. After the washing process is completed, a water pump sends the tailwater stored in the washing tank to the chemical mixing tank to dissolve the flocculant.

[0082] This invention provides a method for rapid dewatering of high-moisture-content dredged sludge enhanced by flocculation combined with plate and frame filter press. The process involves environmentally friendly dredging, sedimentation tank, thickening tank, homogenization tank, and plate and frame filter press dewatering. The sludge dredged by an environmentally friendly cutter suction dredger undergoes sedimentation and impurity removal, sludge thickening, chemical conditioning, filter press dewatering, and sludge cake transportation, ultimately forming a sludge cake with a moisture content of less than 40%. This method can be used for large-scale dredging sludge treatment in rivers, lakes, seas, reservoirs, ports, and waterways.

[0083] If the moisture content of the mud cake is less than 40%, it can be mixed with coal in a certain proportion and used as fuel for combustion; it can also be mixed with other materials and used as building materials for making bricks, cement and other construction.

[0084] Example 2

[0085] Based on Example 1 above, this example mainly introduces the optimized design of a method for rapid dewatering of high-moisture-content dredged sludge enhanced by flocculation combined with plate and frame filter press. Please refer to [reference needed]. Figure 2 , Figure 2 The optimized flow chart of the flocculation-combined plate and frame filter press enhanced rapid dewatering method for high moisture content dredged sludge provided in this application specifically includes:

[0086] Step S1: Send the sludge slurry to the sedimentation tank for slag removal;

[0087] Step S2: The sludge after slag removal flows by gravity into thickening tank 1;

[0088] Step S3: Pump the sludge at the bottom of the thickening tank 1 to the conditioning tank via a small cutter suction dredger 3.

[0089] Step S4: Before the sludge in the conditioning tank enters the plate and frame filter press, add skeleton material 14;

[0090] Step S5: The slurry with added skeleton material 14 is transported to a plate and frame filter press for dewatering.

[0091] Furthermore, the specific method of step S1 is as follows: Using environmentally friendly dredging equipment, the sludge is pumped through pipelines to a sedimentation tank. If the dredging area is far from the sludge treatment center, a shuttle boat is needed to transport the sludge. Sedimentation can be achieved through natural sedimentation, installing a screen at the sludge inlet, or using a slag remover during pipeline transport. Its main function is to remove medium gravel ≥5mm and larger stones, as well as various types of garbage. The settled impurities include larger stones, aquatic plants, phytoplankton, and domestic waste. This waste is transported by conveyor belt to a waste disposal site for treatment by the sanitation department. The sludge after slag removal flows by gravity into the thickening tank 1.

[0092] Furthermore, the specific method of step S2 is as follows: the sludge after slag removal flows by gravity into the thickening tank 1, with a slope of 12%-15% at the bottom. When the slope exceeds 15%, the sludge stays on the slope for too short a time and slides quickly into the mud intake 2. At this time, the water content of the sludge in the mud intake 2 is still higher than 100%. When the slope is less than 12%, the sludge particles settle slowly under gravity, and the thickening time is prolonged. Although the water content of the sludge in the mud intake 2 is lower than 85%, the thickening cycle is greatly extended, reducing construction efficiency. The bottom of the tank is designed with a mud intake 2, and a small cutter suction dredger 3 is equipped in the tank. The thickening tank 1 is the main sedimentation area for fine sludge particles. After a long period of sedimentation, the sludge deposits on the slope to form a thick sludge layer and slides towards the mud intake 2 for thickening. The thickened sludge in the mud intake 2 is pumped to the conditioning tank by the small cutter suction dredger 3 through the mud discharge pipe 25, which positively promotes the continuous sliding and accumulation of the thick sludge layer towards the mud intake 2. The supernatant flows into overflow zone 4, where the suspended solids (SS) value is tested. If the SS value meets the discharge standards, the pump is activated to transport the water from overflow zone 4 to waste water treatment zone 5. If the SS value does not meet the standards, sedimentation continues until the SS value of the supernatant meets the discharge standards. The sludge in overflow zone 4 is then pumped to the conditioning tank. Overflow zone 4 primarily serves to further settle fine sludge particles within the tank, reducing the pollutant content in the waste water and alleviating the pressure on the waste water treatment system.

[0093] Further, the specific method of step S3 is as follows: the sludge from the thickening tank 1 is pumped to the conditioning tank via a small cutter suction dredger 3. The entire conditioning system includes a chemical mixing tank 6, a sludge conditioning tank 7, a chemical mixer 8, a sludge mixer 9, and a dosing pump 10. The entire sludge conveying system is connected by pipelines. The water in the chemical mixer 8 tank comes from the tailwater filtered by the plate and frame filter press. Because the tailwater contains residual flocculant, it is re-infused into the chemical mixing tank 6 to achieve full utilization of the chemical. The dosing pump 10 transports the prepared chemical to the homogenization tank of the sludge conditioning tank 7, where the flocculant and sludge are thoroughly mixed by the sludge mixer 9. Both the chemical mixer 8 and the sludge mixer 9 use a ribbon agitator. This ribbon agitation structure facilitates more thorough contact between materials and ensures low-resistance movement of the mixed materials within the mixing tank.

[0094] Most flocculants are in the form of solid particles or powders and need to be dissolved in advance to prepare a solution. Based on indoor graduated cylinder experiments, this technology proposes a composite flocculant: chitosan and APAM (18 million molecular weight anionic polyacrylamide) are compounded, with a chitosan mass concentration of 1.4‰ and an APAM mass concentration of 1‰; V1 (chitosan):V2 APAM = 1:1; the addition order is to add chitosan first, followed by anionic polyacrylamide.

[0095] Comparative Example 1: Synthetic Organic Polymer Flocculant

[0096] Synthetic organic polymeric flocculants were used to condition the concentrated sludge. The synthetic organic polymeric flocculant was APAM with a molecular weight of 18 million, and mass concentrations of 0.4‰, 0.6‰, 1.0‰, 1.5‰, and 2.0‰, respectively, stirred at 100 rpm for 3 minutes. All prepared flocculant solutions were used within 2 hours. A 500 ml glass graduated cylinder was used for the indoor experiments. 400 ml of well-stirred dredged sludge and 100 ml of flocculant solution were poured into a beaker and stirred until homogeneous, preparing a 500 ml mixture. 400 ml of this mixture was poured into the graduated cylinder, guided by a glass rod during pouring to avoid air bubbles affecting the test results. After pouring, the cylinder was sealed with plastic wrap to prevent water loss. After one week of static observation, observation was stopped when the mud-water interface height no longer showed significant changes. Relevant experimental data on sludge settling volume and mud-water interface height changes at different time points were recorded. After the experiment, the turbidity and pH of the residual water were measured. The experimental results showed that when the sludge sedimentation stabilized after 7 days, using 0.6‰ APAM alone resulted in the highest settling value, with the mud-water interface height as low as 190 ml, a pH of 8.24, and an overlying water turbidity of 28.33 NTU.

[0097] Comparative Example 2: Using natural organic polymer flocculants

[0098] Natural organic polymeric flocculants were used to condition the concentrated sludge. The natural organic polymeric flocculant was chitosan (CTS), with mass concentrations of 1.0‰, 1.3‰, 1.5‰, 1.8‰, and 2.0‰, stirred at 200 rpm for 3 minutes. All prepared flocculant solutions were used within 2 hours. A 500 ml glass graduated cylinder was used for indoor experiments. 400 ml of well-stirred dredged sludge and 100 ml of flocculant solution were poured into a beaker and stirred until homogeneous, preparing a 500 ml mixture. 400 ml of this mixture was poured into the graduated cylinder, guided by a glass rod to prevent air bubbles from affecting the experimental results. After pouring, the cylinder was sealed with plastic wrap to prevent water loss. The cylinder was allowed to stand for one week. Observation was stopped when the sludge-water interface height no longer changed significantly. The sludge settling volume and the change in the sludge-water interface height were recorded at different times. The turbidity and pH of the residual water were measured after the experiment. The experimental results show that when the mud sedimentation is stable after 7 days, the sedimentation value is the largest when 1.8‰ chitosan is used alone, the mud-water separation interface is as low as 175 ml, the pH value is 8.24, and the turbidity value of the overlying water is 11.11 NTU.

[0099] Comparative Example 3: Compound Flocculant

[0100] Based on indoor graduated cylinder experiments, this technology proposes a composite flocculant conditioning formula. Chitosan (CTS) with mass concentrations of 1.4‰, 1.8‰, and 2.2‰, and APAM (18 million molecular weight anionic polyacrylamide) with mass concentrations of 0.2‰, 0.6‰, and 1.0‰ were used in nine compounding experiments. The ratio of chitosan to APAM was 1:1, and the addition order was chitosan first, followed by APAM. A 500ml glass graduated cylinder was used for the indoor experiments. 400ml of well-stirred dredged sludge and 50ml of chitosan solution were poured into a beaker and mixed for 2 minutes. After complete mixing, 50ml of APAM solution was poured into the beaker and mixed until homogeneous, preparing a 500ml mixture. 400ml of this mixture was poured into the graduated cylinder, using a glass rod to guide the flow during pouring to avoid air bubbles affecting the experimental results. After completion, the cylinder was sealed with plastic wrap to prevent water loss. After one week of static observation, observation was stopped when the height of the mud-water separation interface no longer showed significant changes. The sedimentation volume of the sludge and the changes in the mud-water interface height were recorded at different times. After the experiment, the turbidity and pH of the residual water were measured. The results showed that with a chitosan concentration of 1.4‰ and an APAM concentration of 1‰, the sedimentation value at the mud-water separation interface was the highest, as low as 184 ml, the pH value was 8.27, and the turbidity of the overlying water was 6.37 NTU. With this compound flocculant dosage, reducing the dosage of chitosan and APAM by half achieved the same sedimentation results as the single-component experiment, with even lower turbidity. The pH value of the residual water met the requirements of the "Integrated Wastewater Discharge Standard" GB8978-19966-9, thus complying with the discharge standards.

[0101] According to this compound concentration, the flocculant is poured into the mixing tank 6, water is added, and the mixture is stirred and dissolved. The concentration of the flocculant is controlled in real time by the monitoring system. The mixing tank 6 is equipped with a concentration monitoring device 13, which monitors the concentration in the mixing zone in real time based on the monitoring data and controls the influent flow rate.

[0102] The homogenization tank is equipped with a mud concentration monitoring device 13, which monitors the amount of flocculant added in real time based on the monitoring data, ensuring system stability and saving material addition. The mud pump 27 is equipped with a flow meter 26 and a pressure gauge 19 to detect the mud feed rate and feed pressure, so that the flow rate of the dosing pump 10 and the mud feed flow rate are coordinated to maximize construction efficiency.

[0103] Furthermore, the specific method of step S4 is as follows: before the sludge conditioned by flocculant enters the plate and frame filter press for filtration, inorganic inert materials such as fly ash, phosphogypsum, and sawdust can be added to construct the "skeleton" in the sludge dewatering process, thereby improving the dewatering rate of the plate and frame filter press and reducing the moisture content of the sludge cake.

[0104] The method of adding skeleton material 14 is to spray it at multiple points in the pipeline. This spraying method can make skeleton material 14 mix evenly with the feed mud and prevent the agent from being carried away by the feed mud when spraying at one point and not fully contacting and mixing with the mud.

[0105] Mixing method: Top-down S-shaped pipe 11. Each layer of the S-shaped bend is 10m long. Five agent injection heads 12 are installed on the uppermost branch pipe. Flow switches are set at the inlet and outlet ports to control the flow rate of the slurry. The diameter of the bend is 4-6D, where D is the pipe diameter. The S-shaped bend is a continuous bend with a large degree of tortuosity. During the flow of the slurry in the S-shaped bend, turbulence is generated due to the inconsistency between the flow direction and the bend direction of the pipe. The turbulence has a strong mixing effect, which mixes the skeleton material 14 and the conditioned slurry evenly. On the other hand, it prolongs the flow path and increases the mixing time between the agent and the slurry.

[0106] The skeleton material 14 includes material A, material B, and material C. Material A has a content of 20-30 wt%, material B has a content of 30-40 wt%, and material C has a content of 40-50 wt%. Material A contains fly ash, phosphogypsum, and zeolite powder, with fly ash, phosphogypsum, and zeolite powder each containing 30-40 wt%. Material B contains sodium carboxymethyl cellulose and calcium lignosulfonate, with sodium carboxymethyl cellulose containing 50-60 wt% and calcium lignosulfonate containing 40-50 wt%. Material C contains calcium chloride and ferric sulfate, with calcium chloride containing 40-50 wt% and ferric sulfate containing 50-60 wt%. All of the above materials are solid powders with a particle size between 35 mesh and 65 mesh (0.25 mm-0.5 mm). Mixing them into the slurry can increase the particle size. Assume that the optimal dosage of skeleton material 14 is c (kg / m³) obtained from indoor tests, the pipe flow velocity is q (m / s), the introduction time is t (s), and the pipe cross-sectional area is A (m³). 2 The mass of the added skeleton material 14 is cqtA kg. The skeleton material 14 proposed in this technology can enhance the flocculation and dewatering effect of the aforementioned steps. During the plate and frame filter press process, it increases the particle size of the sludge particles, forms a porous structure, increases drainage channels, reduces dewatering resistance, and accelerates water outflow. Simultaneously, adding the plate and frame filter press skeleton material 14 can improve the quality of the effluent, ensuring that the dewatered water meets discharge standards. It also helps stabilize some heavy metals, organic matter, nitrogen, phosphorus, and other nutrients within the sludge cake. Indoor test results show that after adding the skeleton material 14, the d50 (median particle size of the sludge) increases to 1.3 times the original particle size.

[0107] For example, in the pilot project area of ​​ecological dredging in Chaohu Lake, the silt particles are mainly small clay particles, with a d50 (median particle size of silt) of about 14.27 μm, and the average proportion of particles smaller than 16 μm reaches 58.55%. For fine silt particles, the proportion of particles larger than 16 μm is less than 20%, resulting in a significant decrease in the production capacity of plate and frame silt mills.

[0108] In indoor experiments, sludge of different particle sizes was mixed in different proportions and then subjected to plate and frame dewatering tests to determine the effect of sludge particle size on the dewatering efficiency of the plate and frame dewatering system. The feeding time was kept constant at 20 min, the pressing time at 15 min, and the flocculant formulation was standardized.

[0109] Table 1. Effect of sludge particle size on the dewatering efficiency of plate and frame filter press.

[0110]

[0111] Experimental results show that as the sludge particle size increases from 100% fine to 100% coarse, under the same conditions, the sludge thickness increases by 10%, the weight increases by 18.9%, and the moisture content decreases by 1.5%. This indicates to some extent that increasing the particle size of the feed sludge can effectively reduce the moisture content of the sludge cake and increase its thickness. The addition of plate and frame filter press skeleton material 14 can solve the problem of small particle size and poor dewatering effect in the original sludge.

[0112] Furthermore, for the specific design of step S5, please refer to [reference needed]. Figure 3 The specific method is as follows:

[0113] After adding the skeleton material 14 into the S-shaped sludge conveying pipe, the uniformly mixed sludge is transported by the filter press feed pump pneumatic diaphragm pump 17 to a 600 square meter plate and frame filter press. Figure 6 The dehydration process is carried out with a stable feed pressure of 100-120 MPa, a pressing pressure of 130-150 MPa, and a filter press opening cycle that can generally be controlled within 1.5 hours. The plate and frame filter press mainly consists of a frame, filter plates 21, filter cloth, hydraulic pump 24, and supporting components such as a diaphragm pump, air compressor 16, and air tank 18. The filter plates 21 and the filter cloth sandwiched between them are arranged alternately to form filter chambers 22. At the start of filtration, the slurry, under the feeding pressure of the feed pump, enters each filter chamber 22 through the feed inlet of the thrust plate 20 and the pressing plate, and is filtered through the filter cloth. Solids remain in the filter chamber 22 to form a filter cake, while the liquid is discharged through the liquid outlet channel. To further reduce the moisture content of the filter cake, compressed air can be introduced through the air inlet. The air permeates the filter cake layer and carries away some of the moisture. Alternatively, compressed air can be introduced into the inner cavity of the diaphragm filter plate 21 to compress the filter cake, thereby reducing the moisture content.

[0114] After diaphragm pressing, the moisture content of the filter cake can be effectively reduced, and the filter cake can also be separated from the filter cloth, making it easier to remove the filter cake. Compared with ordinary filter presses, the moisture content of the filter cake can usually be reduced by 10-30%.

[0115] The filter press system separates homogenized slurry with a feed concentration of 15% into a slurry cake with a moisture content of ≤40% and tailwater with a turbidity value of less than 20 NTU through a series of processes including feeding, pressing, depressurization, backflushing, and unloading. Air compressor 16 provides compressed air to power the diaphragm pump and diaphragm filter plates 21. The compressed air is mainly used for feed pressure, pressing of the diaphragm filter plates 21, and pneumatic valve operation. Additionally, after the filter press process, the compressed air can be used for backflushing to return any remaining slurry and gas in the pipeline to the slurry storage tank, ready for the next filter press cycle. This prevents wet slurry from contaminating the slurry cake or filter cloth surface when the plate and frame filter press is opened. A schematic diagram of the backflushing system is shown below. Figure 7 .

[0116] Wastewater recycling systems, such as Figure 7 The tailwater generated by plate and frame filter press contains a large amount of residual dissolved substances. After the tailwater is collected in the washing tank, the washing liquid is first used to clean the filter cloth of the filter press. After the filter cloth of the plate and frame filter press is washed, the water is returned to the washing tank through holes C and D. After the filter press washing is completed, the tailwater stored in the washing tank is sent to the chemical mixing tank 6 by the water pump to dissolve the flocculant.

[0117] The sawtooth diaphragm filter plate 15 design is described in detail below. Figure 8 When a pressing medium (such as compressed air) is introduced behind the diaphragm, the pressing pressure reaches 130-150 MPa. These movable diaphragms then bulge towards the filtration chamber, meaning the filter cake is subjected to high-pressure compression again after the filtration process. The filtration process equipped with diaphragm filter plates 21 results in a filter cake moisture content that is 10-30% lower than that of ordinary filter plates 21, saving significant subsequent costs. This technology uses a sawtooth diaphragm, such as... Figure 8 This special diaphragm design allows for deeper insertion into the sludge cake during air intake, increasing drainage channels. The sludge cake filtered using the sawtooth diaphragm filter plate 15 has a 5-10% lower moisture content than that filtered using a regular diaphragm filter plate 21. The insertion depth is greater than 0.5d (d is the thickness of the filter chamber 22). The inclination of the insertion point into the filter plate 21 should be 3-5% to facilitate rapid downward collection of the filtrate under gravity. The middle layer is made of rigid PVC board, and the sawtooth protrusions on the surface are made of polypropylene filter cloth. The pore size of the filter cloth depends on the particle size of the sludge and must meet the following requirements: 90 ≤2-3D 85 And O 50 ≤10-12D 50 ;O 90 O 50D represents the pore size value corresponding to 90% and 50% of the filter cloth pores being smaller than a certain pore size. 85 D 50 This refers to the particle size corresponding to 85% and 50% of soil particles smaller than a certain size in the mud. The design drawing of the sawtooth diaphragm filter plate 15 is shown below. Figure 8 As shown.

[0118] According to the "Standard for Geotechnical Testing Methods" GB / T50123-2019, the moisture content W0 (%) before entering the filter press is measured. The concentration of the slurry after conditioning, detected by the concentration detection equipment in the conditioning tank, is c (kg / m³). The flow velocity in the slurry inlet pipe is v (m / s), the feeding time is T (s), and the cross-sectional area of ​​the inlet pipe is A (m²). Therefore, the slurry volume is vTA (m³), and the slurry mass is cvTA (kg), denoted as M0 (kg). After filtration, the mass M1 (kg) of the filter cake is weighed, and the moisture content W1 (%) of the cake is measured. Q is the effluent mass during the filtration process.

[0119]

[0120] Q= -

[0121]

[0122] Water flow rate (kg / s)

[0123] The mass of effluent (kg) during the measurement period (i.e., during the filter press process)

[0124] Time for measuring water flow rate (s)

[0125] Effective insertion length of diaphragm plate (m)

[0126] Filter chamber 22, height m

[0127] The hydrodynamic viscosity ratio is determined based on the water temperature during the test.

[0128] From this, we can obtain Assuming there are N saw blades, the insertion depth of each saw blade is... l = L / n And the insertion depth must be greater than 0.5d (d is the thickness of filter chamber 22). The serrated plate spacing d is (1 / 10-1 / 8). .

[0129] The invention ultimately yields filter-pressed mud cakes, which can be used in foundation pit and mine backfilling projects, urban landscaping soil, dike and embankment protection projects, land reclamation projects, and port and wharf projects. If the moisture content of the mud cake is less than 40%, it can be mixed with coal in a certain proportion for combustion; it can also be mixed with other materials for use as building materials such as brick and cement.

[0130] The above description is merely a preferred embodiment of the present invention and does not limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any changes, modifications, substitutions, integrations, and parameter alterations to these embodiments within the spirit and principles of the present invention, achieved through conventional substitutions or by achieving the same function without departing from the principles and spirit of the present invention, fall within the scope of protection of the present invention.

Claims

1. A flocculation combined with plate-and-frame pressure filtration enhanced high-moisture-content dredged sludge rapid dewatering method, characterized in that, It comprises the following steps: Step S1, the sludge slurry is sent to the sedimentation tank for deslagging; Step S2, the deslagged slurry flows into the thickening tank by itself, the bottom of the thickening tank is designed with an inverted slope with a slope of 12%-15%; Step S3, the slurry at the bottom of the thickening tank is pumped to the conditioning tank by a small cutter suction dredger, the conditioning tank comprises a reagent mixing tank, a slurry conditioning tank and a reagent feeding pump, the reagent mixing tank is in communication with the slurry conditioning tank through the reagent feeding pump, a reagent mixer is arranged in the reagent mixing tank, and a slurry mixer is arranged in the slurry conditioning tank, the reagent feeding pump feeds the prepared composite flocculant in the reagent mixing tank to the slurry conditioning tank, and the composite flocculant and the slurry are fully stirred and mixed uniformly by the slurry mixer; The mass concentration of the composite flocculant chitosan is 1.4 ‰, and the mass concentration of APAM is 1 ‰; The chitosan:APAM = 1:1, and the adding sequence is to add chitosan first and then add anionic polyacrylamide; Step S4, before the slurry in the conditioning tank enters the plate and frame filter press, a skeleton material is added, the slurry in the conditioning tank passes through an S-shaped pipe from top to bottom, a reagent injection head of the skeleton material is arranged in the pipeline of the S-shaped pipe, and the length of each layer of the pipeline of the S-shaped pipe is 10 m; Five reagent injection heads are installed on the uppermost layer of the branch pipe of the S-shaped pipe; Flow switches are arranged at the inlet and outlet ports of the S-shaped pipe to control the inlet and outlet slurry flow; Step S5, the slurry with the added skeleton material is transported to a plate-and-frame filter press for dewatering, the plate-and-frame filter press comprises a filter chamber, and the filter chamber contains a plurality of zigzag diaphragm filter plates, and the calculation formula of the effective insertion length L of the zigzag diaphragm filter plate is: M0 = cvTA; wherein q is the water flow rate, Q is the mass of water measured, t is the time during which the water flow rate is measured, and Δh is the height of the filter chamber, is the ratio of the hydrodynamic viscosity coefficient, W0 is the moisture content of the slurry before entering the filter press, c is the concentration of the conditioned slurry, v is the flow rate of the slurry in the pipeline, T is the feeding time, A is the cross-sectional area of the feeding pipeline, M0 is the mass of the slurry entering the filter press, M1 is the mass of the filter cake after the filtration, and W1 is the moisture content of the filter cake after the filtration.

2. The flocculation combined with plate-and-frame pressure filtration enhanced high-moisture-content dewatering method of dredged sludge according to claim 1, characterized by, In step S1, the sedimentation mode in the sedimentation tank comprises natural sedimentation, a grid is arranged at the inlet of the slurry into the sedimentation tank, and a deslagging machine is arranged in the pipeline during transportation.

3. The flocculation-combined plate-and-frame pressure filtration enhanced high-moisture-content dewatering method of dredged sludge according to claim 2, characterized by, The bottom of the thickening tank is designed with a sludge taking port, and a small cutter suction dredger is arranged at the sludge taking port.

4. The flocculate combined plate-and-frame pressure filtration enhanced high-moisture-content dewatering method of the dredged sludge according to any one of claims 1 or 2, characterized by, In step S3, the treatment method of the supernatant in the thickening tank is: Method one: the supernatant flows into an overflow area, the SS value of the supernatant is detected, if the SS value meets the discharge standard, the water in the overflow area is pumped and transported to a residual water treatment area; Method two: the supernatant flows into an overflow area, the SS value of the supernatant is detected, if the SS value does not meet the discharge standard, the supernatant is continuously deposited until the SS value of the supernatant meets the discharge standard, and then the water in the overflow area is pumped and transported to a residual water treatment area.

5. The flocculation-combined plate-and-frame pressure filtration enhanced high-moisture-content dewatering method of dredged sludge according to claim 3, characterized by, The water source of the reagent mixing tank is the tail water filtered out by the plate and frame filter press, the tail water filtered by the plate and frame filter press contains a large amount of residual dissolved substances, after the tail water is collected in a washing tank, the tail water stored in the washing tank is pumped to the reagent mixing tank by a water pump after the washing work of the filter press is completed, to dissolve the flocculant.

6. The flocculation-combined plate-and-frame pressure filtration enhanced high-moisture-content dewatering method of dredged sludge according to claim 4, characterized by, Both the reagent mixer and the slurry mixer adopt screw belt type stirring paddles.

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