A low-cost sludge dewatering process using a high-pressure belt machine

Abstract

The invention discloses a low-cost sludge dewatering process using a high-pressure belt machine, and relates to the technical field of sludge dewatering. The process comprises S1, adding a ferric chloride agent in a pretreatment stage to destroy the sludge colloidal structure; S2, adding lime powder in a conditioning stage to adjust pH and construct a porous skeleton structure; S3, adding a polyacrylamide agent in a flocculation stage to form dense flocs; S4, performing mechanical dewatering using a high-pressure belt filter press in the dewatering stage; S5, recovering filtrate for redissolution of the agent; and S6, performing dynamic linkage optimization of agent addition and filter press parameters through a dynamic agent addition algorithm of a control system. The process effectively reduces agent usage, improves sludge dewatering effect, reduces sludge dewatering treatment costs, and realizes the recycling of resources. The process solves the technical problems of excessively high agent costs, low reliability of agent ratio combinations, and insufficient process adaptability in existing sludge dewatering processes.

Description

Technical Field

[0001] The invention relates to the technical field of sludge dewatering, and in particular to a high-pressure belt machine low-cost sludge dewatering process. Background Art

[0002] With the acceleration of my country's urbanization process and the increasingly stringent environmental protection policies, the amount of sewage treatment has increased rapidly, and the amount of sludge generated has also continued to grow. As a by-product of the sewage treatment process, the treatment and disposal of sludge has become an important issue in the field of environmental protection. In order to achieve the harmlessness, reduction and resource utilization of sludge, sludge dewatering technology plays a key role in practical applications. The quality of dewatering effect not only directly affects the economy and environmental protection of subsequent sludge disposal, but also becomes one of the technical bottlenecks restricting the development of the environmental protection industry.

[0003] Currently, sludge dewatering technologies primarily utilize belt filter presses, centrifugal dewatering, and plate and frame filter presses. Belt filter presses are widely used due to their high processing capacity and continuous operation. In recent years, high-pressure belt presses (i.e., belt filter presses), as a new type of high-efficiency sludge dewatering equipment, have demonstrated superior sludge dewatering performance due to their higher dewatering pressure and compression capacity.

[0004] Chemical methods remain the mainstream approach for sludge modification. Their core focus is on modifying sludge properties and enhancing dewatering performance through the addition of chemical agents. PAM (polyacrylamide), a commonly used organic polymer flocculant, is widely used due to its excellent flocculation properties. However, PAM is relatively expensive, and its cost accounts for 30%-40% of the total sludge dewatering treatment cost, becoming a major constraint on technological advancement.

[0005] To reduce costs and improve dewatering efficiency, the technology for sludge dewatering has shifted toward the combined use of agents, leveraging the synergistic effects of inorganic and organic agents, particularly the combined use of ferric chloride, lime, and PAM. Ferric chloride has strong bridging adsorption capacity, which facilitates the formation of sludge flocs; while lime regulates the acidity and alkalinity of sludge and strengthens its structure, further improving dewatering performance. Existing technical research has shown that the "PAM + ferric chloride + lime" combination exhibits a strong synergistic effect in conventional dewatering equipment, effectively improving dewatering efficiency and reducing PAM usage in the sludge dewatering process.

[0006] However, the application of this combination of agents in high-pressure belt dewatering processes is still rare, and there is a lack of verification and ratio optimization, which restricts the application of the inorganic and organic agent combination of PAM+ferric chloride+lime in actual sludge dewatering projects.

[0007] Technical problems of existing technologies:

[0008] High cost of chemicals: Traditional sludge dewatering processes are highly dependent on expensive single chemicals (such as PAM), resulting in excessively high treatment costs;

[0009] The synergistic mechanism is unclear: Although ferric chloride and lime have been found to have a synergistic effect, the ratio and mechanism of action between them and PAM in the high-pressure belt conveyor process are still unclear;

[0010] Insufficient process adaptability: The "PAM+ferric chloride+lime" reagent combination is mostly developed for other dehydration equipment. It does not take into account the gradient pressure field and filter belt shearing effect unique to high-pressure belt machines, and cannot effectively guide engineering practice.

[0011] In summary, it is found that the existing technology has at least the following technical problems:

[0012] The existing sludge dewatering process has technical problems such as high reagent cost, low reliability of reagent ratio combination and insufficient process adaptability. Summary of the Invention

[0013] The purpose of the present invention is to provide a low-cost sludge dewatering process using a high-pressure belt machine to solve the technical problems of the existing sludge dewatering process, such as high reagent cost, low reliability of reagent ratio combination and insufficient process adaptability.

[0014] The various technical effects that can be produced by the preferred technical solutions among the various technical solutions provided by the present invention are described in detail below.

[0015] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0016] The present invention provides a low-cost sludge dewatering process using a high-pressure belt conveyor, comprising the following steps: S1, a pretreatment stage: adding ferric chloride to the sludge to be treated, and before adding, the ferric chloride needs to be prepared into a ferric chloride solution, and impurities are filtered to obtain a decontaminated ferric chloride solution; wherein the amount of the solute ferric chloride added is 0.5%-1.5% of the dry solid mass of the sludge, and mechanical stirring is performed for 30-60 seconds to uniformly mix the ferric chloride with colloidal particles in the sludge to generate an electrical neutralization reaction, thereby destroying the colloidal structure of the sludge;

[0017] S2, conditioning stage: after the ferric chloride reaction is completed, lime powder is added at a dosage of 2%-4% of the dry solid mass of the sludge, the sludge pH is adjusted to alkaline, and mechanical stirring is performed for 30-60 seconds to promote the formation of a porous skeleton structure in the sludge and enhance the stability of the filter cake structure;

[0018] S3, flocculation stage: After the completion of step S2 above, polyacrylamide is added to the sludge. Before adding, the polyacrylamide needs to be prepared into a polyacrylamide solution, and impurities are filtered to obtain a polyacrylamide solution after impurities are removed. The amount of solute polyacrylamide added is 0.1%-0.3% of the dry solid mass of the sludge, and mechanical stirring is performed for 1-2 minutes to form dense flocs through bridging adsorption, thereby improving the flocculation effect;

[0019] S4, dehydration stage: the sludge after the above treatment is transported to the high-pressure belt filter press, and mechanical dehydration is performed by setting the pressure gradient, filter belt speed and extrusion time to control the moisture content of the dehydrated filter cake to below 75%;

[0020] S5. Filtrate recovery and re-dissolution: After the sludge is dehydrated, the filtrate is recovered from the filtrate tank, and the filtrate conductivity is controlled to be below 2000 μS / cm before being used for the ferric chloride dissolution process in step S1;

[0021] S6. Control system linkage: Through the dynamic dosing algorithm based on the dry solid content of sludge, the dosage of the reagent is adjusted, and the dehydration parameters of the high-pressure belt filter press are adjusted in conjunction to achieve dynamic coordinated optimization of the reagent and dehydration parameters.

[0022] In one embodiment, in the sludge treatment tank, the order of adding the ferric chloride solution, lime powder and polyacrylamide solution is: first add the ferric chloride solution, then add the lime powder, and finally add the polyacrylamide solution.

[0023] In one embodiment, in step S1, the proportion of ferric chloride in the ferric chloride solution is 10%-15%.

[0024] In one embodiment, the addition of lime powder adjusts the pH value of the sludge to 9.5-11.

[0025] In one embodiment, in step S2, the lime powder is 200-400 mesh calcium hydroxide.

[0026] In one embodiment, in step S3, the proportion of polyacrylamide in the added polyacrylamide solution is 0.1%-0.3%.

[0027] In one embodiment, in step S3, the added polyacrylamide is anionic polyacrylamide with a molecular weight of 8-10 million.

[0028] In one embodiment, in step S4, the dehydration pressure applied by the high-pressure belt filter press is operated in the order from low pressure to high pressure, and the pressure gradient is applied in sequence from the set first gradient to the third gradient, and the sludge is gradient dehydrated at a filter belt running speed of 2.5-4.5 m / min and a squeezing time of 150-200 s.

[0029] In one embodiment, the dynamic dosing algorithm is: Q = α × S + β × C + γ × P; wherein Q is the total agent cost coefficient, S is the sludge dry solid content, C is the filter cake moisture content, P is the real-time monitored filtrate conductivity, and α, β, and γ are correction coefficients.

[0030] The beneficial effects of the present invention are as follows:

[0031] This technical solution provides a low-cost sludge dewatering process suitable for high-pressure belt conveyors. By optimizing the combination ratio and staged dosing sequence of the reagents "ferric chloride, lime, and PAM," and combining it with the high-pressure belt conveyor operating parameters for dynamic coordinated control of the process, it achieves multiple advantages in terms of reagent usage cost, sludge dewatering effect, process adaptability, and stability:

[0032] (1) Significantly reduce the cost of using chemicals. Through the synergistic effect of inorganic chemicals ferric chloride and lime and organic flocculant polyacrylamide, the dosage of PAM is effectively reduced while ensuring the dehydration effect of sludge treatment, and the unit sludge treatment cost is reduced by more than 4%, breaking through the existing technology's dependence on high-priced single chemicals.

[0033] (2) Improve the dehydration effect and filter cake performance. The optimized reagent addition ratio and sequence significantly improve the sludge structure. The filter cake is compact and easy to peel off from the filter mechanism, effectively reducing the moisture content of the filter cake to below 75%. At the same time, its compressive strength is increased to above 20kPa, providing convenient conditions for subsequent incineration or landfill.

[0034] (3) Enhance process adaptability and operational stability. In step S6, a dynamic dosing algorithm and a control system linkage mechanism are used to adjust the dosage of the agent in real time according to the dry solid content of the sludge, and accurately match the operating parameters of the high-pressure belt machine, such as gradient pressure, filter belt speed, and extrusion time, to avoid the dehydration performance degradation caused by load fluctuations or manual adjustment errors, thereby improving the stability and adaptability of the overall sludge dewatering process.

[0035] (4) Improve resource recycling efficiency. The filtrate recovery process in step S5 realizes the reuse of part of the water resources and dissolved reagents. The filtrate is reused in the ferric chloride dissolution process through conductivity control, further reducing water consumption and reagent preparation costs, which has good environmental benefits.

[0036] (5) Through the composite process of “segmented conditioning, dynamic reagent ratio, and control system linkage”, the operating characteristics of the high-pressure belt conveyor are systematically optimized and designed, providing a new technology route for sludge dewatering that is replicable, popularizable, and low-cost for engineering practice.

[0037] In summary, this technical solution solves the technical problems existing in existing sludge dewatering technologies, such as high cost, unclear mechanism and poor process adaptability. It has the technological advancement and industrial application value of reducing the cost of using chemicals, improving sludge dewatering effects and improving process adaptability and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the implementation. Obviously, the drawings described below are only some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 It is a schematic diagram of the process flow of the low-cost sludge dewatering process using a high-pressure belt machine according to the present invention. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0041] In a specific embodiment, a low-cost sludge dewatering process using a high-pressure belt machine is provided, which includes S1, adding ferric chloride as a reagent in the pretreatment stage and destroying the colloidal structure of the sludge; S2, adding lime powder in the conditioning stage to adjust the pH and construct a porous skeleton structure; S3, adding polyacrylamide as a reagent in the flocculation stage to form dense flocs; S4, using a high-pressure belt filter press for mechanical dewatering in the dewatering stage; S5, recovering the filtrate for redissolution of the reagent; S6, dynamically linking and optimizing the reagent addition and filter press parameters through the dynamic reagent addition algorithm of the control system; effectively reducing the reagent dosage, improving the sludge dewatering effect, reducing the sludge dewatering treatment cost, and realizing the recycling of resources; effectively solving the technical problems of the existing sludge dewatering process, such as excessively high reagent cost, low reliability of reagent ratio combination, and insufficient process adaptability.

[0042] The first implementation of a low-cost sludge dewatering process using a high-pressure belt machine Figure 1 As shown, the method includes the following steps: S1, pretreatment stage: adding ferric chloride to the sludge to be treated, and before adding, the ferric chloride needs to be prepared into a ferric chloride solution, and the impurities are filtered to obtain the impurity-removed ferric chloride solution; wherein, the addition amount of the solute ferric chloride is 0.5%-1.5% of the dry solid mass of the sludge, and mechanical stirring is carried out for 30-60 seconds to uniformly mix the ferric chloride and the colloidal particles in the sludge to generate an electrical neutralization reaction, thereby destroying the colloidal structure of the sludge.

[0043] S2, conditioning stage: After the ferric chloride reaction is completed, lime powder is added at a dosage of 2%-4% of the dry solid mass of the sludge, the pH of the sludge is adjusted to alkaline, and mechanical stirring is performed for 30-60 seconds to promote the formation of a porous skeleton structure in the sludge and enhance the stability of the filter cake structure.

[0044] S3, flocculation stage: After the completion of the above step S2, polyacrylamide is added to the sludge. Before adding, the polyacrylamide needs to be made into a polyacrylamide solution, and impurities are filtered to obtain a polyacrylamide solution after impurities are removed. The amount of solute polyacrylamide added is 0.1%-0.3% of the dry solid mass of the sludge, and mechanical stirring is performed for 1-2 minutes to form dense flocs through adsorption by bridging action, thereby improving the flocculation effect.

[0045] S4, dehydration stage: the sludge after the above treatment is transported to the high-pressure belt filter press, and mechanical dehydration is carried out through the set pressure gradient, filter belt speed and extrusion time, so that the moisture content of the dehydrated filter cake is controlled below 75%; and the compressive strength of the dehydrated filter cake reaches at least 20kPa; the dehydrated filter cake is discharged from the mud outlet.

[0046] S5. Filtrate recovery and re-dissolution: After the sludge is dehydrated, the filtrate is recovered from the filtrate tank, and the filtrate conductivity is controlled to be below 2000 μS / cm before being used for the ferric chloride dissolution process in step S1.

[0047] S6. Control system linkage: The goal is to reduce the cost of chemical reagents by 4%. By collecting the sludge parameters monitored and fed back, and based on the dynamic dosing algorithm of the sludge dry solid content, the chemical usage, chemical cost, sludge pretreatment effect, sludge conditioning effect, and sludge dewatering effect are balanced by calculation. The chemical dosage is dynamically adjusted during the continuous operation of the sludge dewatering process, and the dewatering parameters of the high-pressure belt filter press are adjusted in linkage, so as to achieve dynamic coordinated optimization of the chemical and dewatering parameters.

[0048] by Figure 1 As shown, when implementing the various steps of the high-pressure belt low-cost sludge dewatering process, and the process is in the startup stage, steps S1 to S5 need to be implemented in sequence in S1 to S5, and at the same time, the data of parameters S, C and P are detected before step S1, after step S4 and after step S5, and reserved for use when implementing step S6; before adding ferric chloride to the sludge to be treated in step S1, it is necessary to first detect the parameter S sludge dry solid content, and after obtaining the data of parameter S, it is returned to the controller for storage and reserved for use when starting step S6; after step S1 is completed; after the sludge is dehydrated in step S4, the discharged filter cake is detected, and the parameter C filter cake moisture content is obtained, and after obtaining the data of parameter C, it is returned to the controller for storage and reserved for use when starting step S6; when recovering the filtrate from the filtrate tank in step S5, the parameter P filtrate conductivity is detected, and after obtaining the data of parameter P, it is returned to the controller for storage and reserved for use when starting step S6.

[0049] When executing step S6, in each cycle step from S1 to S5, dynamic process parameters can be obtained according to the dynamic dosing algorithm, wherein the dynamic process parameters include the dynamic dosage of the reagent in steps S1 to S3 and the dynamic dehydration parameters in step S4; when performing steps S1 to S4, the dynamic process parameters given in step S6 are followed to achieve the purpose of dynamic coordinated optimization of the reagent and dehydration parameters in step S6, so that the sludge dewatering treatment process can dynamically adjust the reagent dosage and dehydration parameters according to the state of the sludge input into the treatment tank, and finally achieve the low-cost sludge dehydration process of the high-pressure belt machine to achieve better sludge dehydration effect with low-cost dehydration investment.

[0050] The dynamic dehydration parameters are obtained by optimizing the original basic dehydration parameters according to the latest adjusted reagent dosage of steps S1 to S3 in the process step cycle. The purpose is to apply the optimal dehydration parameters to the sludge in the current cycle in accordance with the latest adjusted reagent ratio in the current cycle, so that the dehydration effect of the sludge in the dehydration step can achieve the expected better dehydration effect.

[0051] Among them, in the sludge treatment tank, the order of adding ferric chloride solution, lime powder and polyacrylamide solution is: first add ferric chloride solution, then add lime powder, and finally add polyacrylamide solution.

[0052] Specifically, regarding the concentration control of the ferric chloride solution in the above steps, in step S1, the proportion of ferric chloride in the ferric chloride solution is 10%-15%.

[0053] During application, after the ferric chloride solution is added to the sludge, the absolute value of the zeta potential of the sludge is controlled to be reduced to <5mV, which is used to destroy the stability of the sludge colloidal structure; when the zeta potential approaches zero, the van der Waals force between the colloidal particles dominates, the sludge colloid quickly leaves the steady state, and forms dense flocs, laying the foundation for the subsequent conditioning of lime and PAM; by adding ferric chloride solution, the high charge density of Fe 3﹢ After the ions neutralize the negative charge on the surface of the sludge colloid, the flocs are more easily captured by the bridging effect of polyacrylamide (PAM) in the subsequent flocculation stage. The mechanical strength of the formed flocs is improved and can withstand the shear force of the high-pressure belt machine; and the dosage of PAM can be reduced by 20%-30%, saving the cost of adding chemicals.

[0054] The role of adding lime powder to the sludge in the above step S2 is to adjust the pH value of the sludge to 9.5-11.

[0055] Specifically, in step S2, the lime powder added to the sludge is 200-400 mesh calcium hydroxide.

[0056] When used, 200-400 mesh calcium hydroxide is added to the sludge to reduce the sludge resistance to 1×10 12 m / kg or less, so that the sludge dehydration effect in step S4 is better, and the PAM dosage in step S3 can be further reduced.

[0057] Regarding the concentration control of the polyacrylamide solution in the above steps, in step S3, the proportion of polyacrylamide in the added polyacrylamide solution is 0.1%-0.3%.

[0058] The added polyacrylamide is anionic polyacrylamide with a molecular weight of 8-10 million.

[0059] During application, the timing of adding the polyacrylamide solution is controlled to be completed within 1-2 minutes after the addition and stirring of the lime powder in step S2. Then, mechanical stirring is started to increase the flocculation speed, so that the sludge forms dense flocs faster and with better formation effect.

[0060] Regarding the dehydration parameters set for the above-mentioned high-pressure belt filter press, in step S4, the dehydration pressure applied by the high-pressure belt filter press is operated in the order from low pressure to high pressure, and the pressure gradient is applied in sequence from the set first gradient to the third gradient, and the sludge is gradient dehydrated at a filter belt running speed of 2.5-4.5m / min and a squeezing time of 150-200s.

[0061] During application, the first pressure gradient is: 0.4-0.6MPa, the second pressure gradient is: 0.7-0.9MPa, the third pressure gradient is: 1.0-1.2MPa, and the time ratio of the first to third pressure gradients is 1:1.5:2; so that the sludge is gradually pressurized during the dehydration process and the pressure holding time is increased to achieve progressive dehydration. The water in the center of the sludge aggregation gradually seeps out, avoiding water entrapment, increasing the dehydration amount of the sludge, and reducing the water content of the filter cake.

[0062] The low-cost sludge dewatering process of the high-pressure belt machine achieves multiple advantages in terms of reagent usage cost, sludge dewatering effect, process adaptability and stability by optimizing the combination ratio and staged addition sequence of "ferric chloride, lime, and PAM" and combining the operating parameters of the high-pressure belt machine for dynamic coordinated control of process treatment.

[0063] Significantly reduce the cost of using chemicals. Through the synergistic effect of inorganic chemicals ferric chloride and lime and organic flocculant polyacrylamide, while ensuring the dehydration effect of sludge treatment, the dosage of PAM is effectively reduced, and the unit sludge treatment cost is reduced by more than 4%, breaking the existing technology's dependence on high-priced single chemicals.

[0064] The dehydration effect and filter cake performance are improved. The optimized reagent addition ratio and sequence significantly improve the sludge structure. The filter cake is compact and easy to peel off from the filter mechanism, effectively reducing the moisture content of the filter cake to below 75%. At the same time, its compressive strength is increased to above 20kPa, providing convenient conditions for subsequent incineration or landfill.

[0065] To enhance process adaptability and operational stability, in step S6, a dynamic dosing algorithm and a control system linkage mechanism are used to adjust the dosage of chemicals in real time according to the dry solid content of the sludge, and accurately match the operating parameters of the high-pressure belt machine, such as gradient pressure, filter belt speed, and extrusion time, to avoid dehydration performance degradation caused by load fluctuations or manual adjustment errors, and improve the stability and adaptability of the overall sludge dewatering process.

[0066] Improve resource recycling efficiency. The filtrate recovery process in step S5 realizes the reuse of part of the water resources and dissolved reagents. The filtrate is reused in the ferric chloride dissolution process through conductivity control, further reducing water consumption and reagent preparation costs, and having good environmental benefits.

[0067] Through the composite process of "segmented conditioning, dynamic reagent ratio, and control system linkage", the equipment operation characteristics of the high-pressure belt conveyor are systematically optimized and designed, providing a new technology route for sludge dewatering that is replicable, popularizable, and low-cost for engineering practice.

[0068] In summary, this technical solution solves the technical problems existing in existing sludge dewatering technologies, such as high cost, unclear mechanism and poor process adaptability. It has the technological advancement and industrial application value of reducing the cost of using chemicals, improving sludge dewatering effects and improving process adaptability and stability.

[0069] As one of the optional implementations

[0070] The specific setting of the above-mentioned dynamic dosing algorithm is: Q=α×S+β×C+γ×P.

[0071] Among them, Q is the total reagent cost coefficient, S is the dry solid content of sludge, C is the moisture content of filter cake, P is the real-time monitored filtrate conductivity, and α, β, and γ are correction coefficients.

[0072] When applied, the formula reflects the synergistic effect of three key process parameters S, C and P on the total reagent cost coefficient Q through linear combination: First, it is assumed that the reagent cost is approximately linearly related to the sludge properties, dewatering effect and filtrate quality, which is convenient for engineering implementation and real-time control; the correction coefficients α, β and γ of each parameter S, C and P are clearly defined to characterize their influence on the total cost.

[0073] Among them, the parameter S, the dry solid content of sludge, directly determines the dosage of the reagent and is the basis for cost calculation. For example, the dosage of the solute ferric chloride is 0.5%-1.5% of the dry solid mass of the sludge, the dosage of lime powder is 2%-4% of the dry solid mass of the sludge, and the dosage of the solute polyacrylamide is 0.1%-0.3% of the dry solid mass of the sludge.

[0074] Specifically, the sludge dry solid mass is the parameter S of the sludge in the treatment tank measured by the sensor before the addition of the reagent in step S1, and the sludge dry solid mass means the initial solid load of the sludge, that is, the dry solid content in the total mass of the original sludge. It should be noted that parameter S and parameter C belong to different stages and cannot be directly correlated. There is no mathematical constraint relationship between the two.

[0075] Parameter C, the moisture content of the filter cake, directly reflects the dehydration effect. When the moisture content is high, the dosage of the agent needs to be increased to improve the dehydration effect. Conversely, when the dehydration rate reaches the dehydration target, the dosage of the corresponding agent can be gradually reduced through automatic control to further save costs.

[0076] Parameter P is the real-time conductivity of the filtrate. By monitoring the ion concentration of the filtrate, high conductivity may indicate a large amount of residual reagents and may also lead to equipment corrosion risks. It is necessary to judge the ion concentration of the filtrate based on the monitored conductivity, control the conductivity of the recovered filtrate, and thus control the ion concentration of the recovered filtrate. This can achieve the purpose of using the recovered filtrate for subsequent sludge dehydration to reduce costs and avoid corrosion of the sludge treatment equipment.

[0077] Step S6 realizes dynamic, refined and flexible control of process cost through dynamic dosing algorithm. Before realizing dynamic control, it is necessary to run only steps S1 to S5 at the process startup, and obtain the basic startup data required for running step S6 by collecting the actual operation data of process steps S1 to S5. The specific method for obtaining accurate data of sludge dewatering is as follows: after completing 2-3 cycles of steps S1 to S5, the orthogonal test method, response surface analysis method and online potential monitoring are used to analyze and obtain the sludge dry solid content, filter cake moisture content and filtrate conductivity, and input this data into the dynamic dosing algorithm in step S6. The method automatically calculates and generates the optimized agent dosage ratio and the process parameters of steps S1 to S5, and then feeds back the optimized agent dosage ratio and the process parameters of steps S1 to S5 to continue the implementation; after the optimized agent dosage ratio and the process parameters of steps S1 to S5 are fed back to the cycle of steps S1 to S5 for 5-6 times, the cycle is continuously run for at least 3 times and the obtained sludge dry solid content, filter cake moisture content and real-time conductivity parameters are recorded each time for analysis and comparison. After observing that the sludge dry solid content, filter cake moisture content and real-time conductivity parameters are stable, the agent dosage ratio and the process parameters of steps S1 to S5 are fixed, and the cycle of steps S1 to S5 is continued.

[0078] Through orthogonal experiments or response surface analysis, the S, C and P parameters and reagent cost data under different working conditions are collected to establish a "multivariate linear regression model" that is, Qactual = α×S+β×C+γ×P+ Perform analysis; in the model =Qactual-Qforecast, It is used to supplement the treatment cost changes caused by factors such as sludge composition fluctuations, unpredictable process disturbances, ambient temperature and equipment aging that are not considered in the model, so as to avoid overfitting of the model and loss of generalization ability during the modeling process;

[0079] By collecting the experimental data of the previous drug ratio and testing the model, we found that the model fitting degree is relatively high, and it is determined that α×S+β×C+γ×P plays a major role in the model. In addition, when fitting the model, the least squares fitting coefficient is used to make the prediction error Minimize; therefore, in engineering applications, the cost control of chemical addition and sludge dewatering affected by chemicals can be completed only by Q=α×S+β×C+γ×P.

[0080] Under the premise of ensuring the moisture content of the filter cake (C≤75%) and equipment safety (P≤2000μS / cm), the optimal range of α, β and γ was solved with the goal of minimizing the reagent cost. During the solution, the initial values ​​of the correction coefficients α, β and γ were determined by collecting the experimental data of the previous reagent ratio and fitting through the orthogonal analysis method. The initial values ​​of the correction coefficients α, β and γ were normalized, and the effects of the sludge dry solid content S, the filter cake moisture content C, and the filtrate conductivity P on the total reagent cost coefficient Q were verified again through experiments. The values ​​of the correction coefficients α, β and γ were adjusted to limit the influence of each factor on the total reagent cost coefficient Q in the sludge dewatering process. Finally, the actual operating optimal value range of the correction coefficients α, β and γ was obtained, which is 0.25-0.35 for α, 0.15-0.25 for β, and 0.05-0.15 for γ.

[0081] In engineering verification, it was found that when α=0.3, β=0.2, and γ=0.1, the comprehensive cost and dehydration effect are optimal, and the calculation formula is: Q=0.3S+0.2C+0.1P.

[0082] Among them, when the process is running, step S6 is performed before step S1, that is, before adding ferric chloride, the dry solid content of the sludge is detected online; after the high-pressure dehydration is completed in step S4 to form the filter cake, the moisture content of the filter cake is detected online at the mud outlet; in step S5, when the filtrate is discharged into the filtrate tank, the conductivity of the filtrate is detected online.

[0083] During application, the dry solid content of sludge can be measured by infrared water separator, the moisture content of filter cake can be measured by microwave moisture sensor, and the conductivity can be measured by electrical wire conductivity probe.

[0084] In the dynamic reagent dosing algorithm, the total reagent cost coefficient Q per unit sludge dewatering treatment is dynamically calculated based on real-time detection data and compared with the target maximum cost limit, which can trigger the adjustment of the reagent dosage.

[0085] Through the PID adjustment unit, the dosage of each agent is accurately controlled:

[0086] When the Q value increases, increase the dosage of ferric chloride linearly in proportion. Calculate the dosage of ferric chloride according to the dosage formula of ferric chloride: W=K1×Q×S.

[0087] When the S value increases, adjust the amount of lime powder added. According to the lime powder addition formula: W=K2×Q× .

[0088] When the C value increases, the dehydration effect is poor, and the dosage of PAM is automatically increased. According to the PAM dosage formula: W=K3×Q×(1-C).

[0089] Among them, K1, K2, and K3 are synchronized with the dosage ratio of ferric chloride, lime powder, and PAM, that is, K1=0.5-1.5, K2=2-4, and K3=0.1-0.3.

[0090] When the P value rises to greater than 2000μS / cm, the filtrate needs to be purified to reduce the trivalent iron ions and chloride ions in the filtrate, reduce the conductivity to below 2000μS / cm, and reduce the weight of the correction coefficient γ to the lowest 0.05 to reduce the consumption of new ferric chloride reagent.

[0091] When the S value increases, the filter belt running speed of the high-pressure belt filter press can be optimized synchronously, and the filter belt running speed can be reduced to 2.0-4.0 m / min. After reducing the filter belt running speed, the extrusion time for sludge dehydration needs to be extended at the same time. On the basis of the 150-200s extrusion time in the above step S4, the extrusion time is extended by at least 30s, so that the extrusion time reaches 180-230s to dehydrate the sludge.

[0092] The technical features of the above embodiments may be combined arbitrarily. To simplify the description, not all possible combinations of the technical features in the above embodiments are described.

Claims

1. A low-cost sludge dewatering process using a high-pressure belt machine, characterized in that: The following steps are involved: S1. Pretreatment stage: Add ferric chloride to the sludge to be treated. Before adding, the ferric chloride needs to be made into a ferric chloride solution, and the impurities are filtered to obtain the impurity-removed ferric chloride solution. The amount of solute ferric chloride added is 0.5%-1.5% of the dry solid mass of the sludge. Mechanical stirring is carried out for 30-60 seconds to uniformly mix the ferric chloride with the colloidal particles in the sludge to produce an electrical neutralization reaction, thereby destroying the colloidal structure of the sludge. S2, conditioning stage: after the ferric chloride reaction is completed, lime powder is added at a dosage of 2%-4% of the dry solid mass of the sludge, the sludge pH is adjusted to alkaline, and mechanical stirring is performed for 30-60 seconds to promote the formation of a porous skeleton structure in the sludge and enhance the stability of the filter cake structure; S3, flocculation stage: After the completion of step S2 above, polyacrylamide is added to the sludge. Before adding, the polyacrylamide needs to be prepared into a polyacrylamide solution, and impurities are filtered to obtain a polyacrylamide solution after impurities are removed. The amount of solute polyacrylamide added is 0.1%-0.3% of the dry solid mass of the sludge, and mechanical stirring is performed for 1-2 minutes to form dense flocs through bridging adsorption, thereby improving the flocculation effect; S4, dehydration stage: the sludge after the above treatment is transported to the high-pressure belt filter press, and mechanical dehydration is performed by setting the pressure gradient, filter belt speed and extrusion time to control the moisture content of the dehydrated filter cake to below 75%; S5. Filtrate recovery and re-dissolution: After the sludge is dehydrated, the filtrate is recovered from the filtrate tank, and the filtrate conductivity is controlled to be below 2000 μS / cm before being used for the ferric chloride dissolution process in step S1; S6, control system linkage: through the dynamic dosing algorithm based on the dry solid content of sludge, the dosage of the chemical is adjusted, and the dehydration parameters of the high-pressure belt filter press are adjusted in conjunction with each other to achieve dynamic coordinated optimization of the chemical and dehydration parameters; In the sludge treatment tank, the order of adding ferric chloride solution, lime powder and polyacrylamide solution is: first add ferric chloride solution, then add lime powder, and finally add polyacrylamide solution; In step S1, the proportion of ferric chloride in the ferric chloride solution is 10%-15%; In step S2, the lime powder is 200-400 mesh calcium hydroxide; the addition of lime powder adjusts the pH value of the sludge to 9.5-11; In step S3, the proportion of polyacrylamide in the added polyacrylamide solution is 0.1%-0.3%; In step S3, the added polyacrylamide is anionic polyacrylamide with a molecular weight of 8-10 million; In step S4, the dehydration pressure applied by the high-pressure belt filter press is operated in the order from low pressure to high pressure, and the pressure gradient is applied in sequence from the set first gradient to the third gradient, and the sludge is dehydrated in a gradient manner at a filter belt running speed of 2.5-4.5 m / min and a squeezing time of 150-200 s; The dynamic dosing algorithm is: Q = α × S + β × C + γ × P; where Q is the total chemical cost coefficient, S is the sludge dry solid content, C is the filter cake moisture content, P is the real-time monitored filtrate conductivity, and α, β, and γ are correction coefficients. The dry solid content of the sludge, the moisture content of the filter cake, and the conductivity of the filtrate are analyzed and obtained, and this data is input into the dynamic dosing algorithm in step S6. The optimized dosing ratio of the dosing agent and the process parameters of steps S1 to S5 are automatically calculated and generated, and then fed back to steps S1 to S5 for continued implementation.

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