High-pressure belt conveyor low-cost sludge dewatering process

Abstract

The invention discloses a high-pressure belt conveyor low-cost sludge dewatering technology, and relates to the technical field of sludge dewatering, the technology comprises the following steps: S1, in a pretreatment stage, adding a ferric chloride agent and destroying a sludge colloid structure; s2, in the conditioning stage, lime powder is added to adjust the pH value, and a porous skeleton structure is constructed; s3, adding a polyacrylamide medicament in a flocculation stage to form a compact floc; s4, a high-pressure belt filter press is used for mechanical dehydration in the dehydration stage; s5, recovering the filtrate for redissolving the medicament; s6, performing dynamic linkage optimization of chemical dosing and filter pressing parameters through a dynamic chemical dosing algorithm of the control system; the dosage of chemicals is effectively reduced, the sludge dewatering effect is improved, the sludge dewatering treatment cost is reduced, and the cyclic utilization of resources is realized; the technical problems that an existing sludge dewatering technology is too high in agent cost, low in agent matching and combination reliability and insufficient in technology adaptability are solved.

Description

Technical Field

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

[0002] As a by-product in the sewage treatment process, the treatment and disposal of sludge have become an important topic in the environmental protection field; to achieve the harmless, reduction, and resource utilization of sludge, sludge dewatering technology plays a key role in practical applications; the quality of the 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 mainly include belt filter press, centrifugal dewatering, plate and frame filter press, etc. Among them, the belt filter press is widely used due to its advantages such as large processing capacity and continuous operation. In recent years, as a new type of high-efficiency sludge dewatering equipment, the high-pressure belt machine (i.e., the high-pressure belt filter press) has shown good treatment effects in sludge dewatering due to its higher dewatering pressure and pressing capacity.

[0004] In terms of sludge modification treatment, the chemical method is still the mainstream means, and its core lies in changing the sludge properties by adding chemical agents to enhance its dewatering performance. Among them, PAM (polyacrylamide), as a commonly used organic polymer flocculant, is widely used due to its good flocculation performance; however, the price of PAM is relatively high, and the chemical agent cost accounts for 30%-40% of the total cost of sludge dewatering treatment during application, becoming the main factor restricting the technology.

[0005] To reduce costs and improve dewatering efficiency, the technical path in the field of sludge dewatering has begun to turn to the combined use of agents, taking advantage of the synergistic effect of inorganic agents and organic agents, especially the combined use of ferric chloride, lime, and PAM; ferric chloride has strong bridging adsorption ability, which is beneficial to the formation of sludge flocs; lime can adjust the acidity and alkalinity of sludge and strengthen the sludge structure, thereby further improving the dewatering performance. Existing technical research shows that the combination of "PAM + ferric chloride + lime" has a good synergistic effect in conventional dewatering equipment, which can effectively improve the dewatering efficiency and reduce the dosage of PAM in the sludge dewatering process.

[0006] However, the application of this agent combination in the high-pressure belt machine dewatering process is still less at present, lacking verification and ratio optimization, which restricts the application of the combination of inorganic and organic agents of PAM + ferric chloride + lime in actual sludge dewatering projects.

[0007] Technical problems of the prior art: High chemical agent cost: The traditional sludge dewatering process has a high dependence on expensive single agents (such as PAM), resulting in too high treatment costs; Synergistic mechanism unclear: Although the synergistic effect between ferric chloride and lime has been discovered, the dosage ratio and mechanism of action between them and PAM in the high-pressure belt filter press process are still unclear; Lack of process adaptability: The chemical agent combination of "PAM + ferric chloride + lime" was developed mainly for other dewatering equipment, without considering the unique gradient pressure field and filter belt shearing effect of the high-pressure belt filter press, and thus cannot effectively guide engineering practice.

[0008] In summary, it is found that the existing technologies have at least the following technical problems: The existing sludge dewatering processes have technical problems such as excessively high chemical agent costs, low reliability of chemical agent dosage ratios, and lack of process adaptability. Summary of the Invention

[0009] The purpose of the present invention is to provide a low-cost sludge dewatering process for a high-pressure belt filter press to solve the technical problems of excessively high chemical agent costs, low reliability of chemical agent dosage ratios, and lack of process adaptability existing in the existing sludge dewatering processes.

[0010] The many technical effects that can be produced by the preferred technical solutions among the many technical solutions provided by the present invention are described in detail below.

[0011] To solve the above technical problems, the present invention provides the following technical solutions: The present invention provides a low-cost sludge dewatering process for a high-pressure belt filter press, including the following steps: S1. Pretreatment stage: Add ferric chloride to the sludge to be treated. Before adding, ferric chloride needs to be made into a ferric chloride solution, and impurities are filtered to obtain the ferric chloride solution after impurity removal; wherein, the dosage 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 ferric chloride with the colloidal particles in the sludge to undergo an electro-neutralization reaction and destroy the sludge colloidal structure; S2. Conditioning stage: After the action of ferric chloride is completed, add lime powder, and the dosage is 2% - 4% of the dry solid mass of the sludge, adjust the pH of the sludge to alkaline, and carry out mechanical stirring for 30 - 60 seconds to promote the formation of a porous skeleton structure of the sludge and enhance the structural stability of the filter cake; S3. Flocculation stage: After the completion of the above step S2, add polyacrylamide to the sludge. Before adding, polyacrylamide needs to be made into a polyacrylamide solution, and impurities are filtered to obtain the polyacrylamide solution after impurity removal; wherein, the dosage of the solute polyacrylamide is 0.1% - 0.3% of the dry solid mass of the sludge, and mechanical stirring is carried out for 1 - 2 minutes to form dense flocs through bridging adsorption and improve the flocculation effect; S4. Dewatering stage: Convey the sludge treated above to a high-pressure belt filter press, and carry out mechanical dewatering through the set pressure gradient, filter belt speed, and extrusion time to control the moisture content of the dewatered filter cake below 75%; S5. Filtrate recovery and redissolution: After sludge dewatering, the filtrate is recovered from the filtrate tank. After controlling the conductivity of the filtrate below 2000 μS / cm, it is used for the ferric chloride dissolution process in step S1. S6. Control system linkage: Through a dynamic dosing algorithm based on the dry solid content of the sludge, the dosing amount of the chemical agent is adjusted, and the dewatering parameters of the high-pressure belt filter press are linked and adjusted to achieve dynamic collaborative optimization of the chemical agent and the dewatering parameters.

[0012] In one embodiment, in the sludge treatment tank, the dosing sequence of the ferric chloride solution, lime powder, and polyacrylamide solution is as follows: First, the ferric chloride solution is dosed, then the lime powder is dosed, and finally the polyacrylamide solution is dosed.

[0013] In one embodiment, in step S1, the proportion of ferric chloride in the ferric chloride solution is 10% - 15%. In one embodiment, the addition of lime powder adjusts the pH value of the sludge to 9.5 - 11.

[0014] In one embodiment, in step S2, the lime powder is calcium hydroxide with a mesh size of 200 - 400.

[0015] In one embodiment, in step S3, the proportion of polyacrylamide in the dosed polyacrylamide solution is 0.1% - 0.3%.

[0016] In one embodiment, in step S3, the polyacrylamide added is an anionic polyacrylamide with a molecular weight of 800 - 10 million.

[0017] In one embodiment, in step S4, the dewatering pressure applied by the high-pressure belt filter press operates in the order of small pressure to large pressure, and the pressure gradient is applied sequentially from the set first gradient to the third gradient, and the sludge is subjected to gradient dewatering at a filter belt running speed of 2.5 - 4.5 m / min and an extrusion time of 150 - 200 s.

[0018] In one embodiment, the dynamic dosing algorithm is: Q = α×S + β×C + γ×P; where Q is the total chemical agent cost coefficient, S is the dry solid content of the sludge, C is the moisture content of the filter cake, P is the conductivity of the filtrate monitored in real time, and α, β, and γ are correction coefficients.

[0019] The beneficial effects of the present invention are as follows: This technical solution provides a low-cost sludge dewatering process applicable to high-pressure belt machines. By optimizing the dosing combination ratio and segmented dosing sequence of "ferric chloride, lime, PAM", and combining the dynamic collaborative control of the high-pressure belt machine operation parameters for process treatment, multiple advantages of chemical agent usage cost, sludge dewatering effect, process adaptability, and stability are achieved: (1) Significantly reduce the cost of reagent use. Through the synergistic effect of inorganic reagents ferric chloride and lime and organic flocculant polyacrylamide, on the premise of 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 through the dependence on high-cost single reagents in the existing technology.

[0020] (2) Improve the dehydration effect and filter cake performance. The optimized reagent dosage ratio and sequence significantly improve the sludge structure. The formed filter cake is dense and easy to peel off from the filtration mechanism. The moisture content of the filter cake is effectively reduced to below 75%, and at the same time, its compressive strength is increased to above 20 kPa, providing convenient conditions for subsequent incineration or landfill.

[0021] (3) Enhance the process adaptability and operation stability. In step S6, a dynamic dosing algorithm and a control system linkage mechanism are adopted to adjust the reagent dosage in real time according to the dry solid content of the sludge, and accurately match the operating parameters of the high-pressure belt filter, such as gradient pressure, filter belt speed, and extrusion time, to avoid the decline in dehydration performance caused by load fluctuations or manual adjustment errors, and improve the stability and adaptability of the overall sludge dehydration process.

[0022] (4) Improve the resource recycling efficiency. In the filtrate recovery process in step S5, partial reuse of water resources and dissolved reagents is achieved. 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.

[0023] (5) Through the composite process of "segmented conditioning, dynamic reagent ratio, and control system linkage", the equipment operation characteristics of the high-pressure belt filter are systematically optimized and designed, providing a new, replicable, popularizable, and low-cost sludge dehydration technology route for engineering practice.

[0024] In summary, the technical solution of the present invention solves the technical problems existing in the existing sludge dehydration technology, such as high cost, unclear mechanism, and poor process adaptability, and has the technical progressiveness and industrial application value of reducing the cost of reagent use, improving the sludge dehydration effect, and enhancing the process adaptability and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solution of the present invention, the drawings required for the implementation will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is a schematic flow chart of the low-cost sludge dehydration process of the high-pressure belt filter of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0028] A low-cost sludge dewatering process for a high-pressure belt machine is provided in the specific embodiments. This process includes: S1, adding ferric chloride medicament in the pretreatment stage to destroy the sludge colloid structure; S2, adding lime powder in the conditioning stage to adjust the pH and construct a porous skeleton structure; S3, adding polyacrylamide medicament in the flocculation stage to form dense flocs; S4, using a high-pressure belt filter press for mechanical dewatering in the dewatering stage; S5, recycling the filtrate for medicament redissolution; S6, dynamically linking and optimizing the medicament addition and filtration parameters through the dynamic medicament addition algorithm of the control system; effectively reducing the medicament dosage, improving the sludge dewatering effect, realizing the reduction of the sludge dewatering treatment cost, and realizing the recycling of resources; effectively solving the technical problems of high medicament cost, low reliability of medicament ratio combination, and insufficient process adaptability existing in the existing sludge dewatering process.

[0029] The first embodiment of the low-cost sludge dewatering process for a high-pressure belt machine is as Figure 1 shown, and includes the following steps: S1, pretreatment stage: adding ferric chloride to the sludge to be treated. Before adding, ferric chloride needs to be made into a ferric chloride solution, and impurities are filtered to obtain the ferric chloride solution after impurity removal; wherein, the dosage 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 make ferric chloride and the colloid particles in the sludge evenly mixed to undergo an electro-neutralization reaction, destroying the sludge colloid structure.

[0030] S2, conditioning stage: adding lime powder after the action of ferric chloride, with the dosage being 2%-4% of the dry solid mass of the sludge, adjusting the pH of the sludge to alkaline, and carrying out mechanical stirring for 30-60 seconds to promote the sludge to form a porous skeleton structure and enhance the stability of the filter cake structure.

[0031] S3, flocculation stage: adding polyacrylamide to the sludge after the completion of the above step S2. Before adding, polyacrylamide needs to be made into a polyacrylamide solution, and impurities are filtered to obtain the polyacrylamide solution after impurity removal; wherein, the dosage of the solute polyacrylamide is 0.1%-0.3% of the dry solid mass of the sludge, and mechanical stirring is carried out for 1-2 minutes to adsorb and form dense flocs through bridging action, improving the flocculation effect.

[0032] S4, dewatering stage: conveying the sludge treated above to a high-pressure belt filter press, and carrying out mechanical dewatering through the set pressure gradient, filter belt speed, and extrusion time, so that the moisture content of the dewatered filter cake is controlled below 75%; and the compressive strength of the dewatered filter cake reaches at least 20 kPa; the dewatered filter cake is discharged from the mud outlet.

[0033] S5. Filtrate Recovery and Redissolution: After sludge dewatering, the filtrate is recovered from the filtrate tank. After controlling the conductivity of the filtrate below 2000 μS / cm, it is used for the ferric chloride dissolution process in step S1.

[0034] S6. Control System Linkage: Aiming to reduce the chemical cost by 4%, by collecting and monitoring the feedback sludge parameters, and based on the dynamic chemical dosing algorithm of the sludge dry solid content, the chemical usage, chemical cost, sludge pretreatment effect, sludge conditioning effect, and sludge dewatering effect are calculated and balanced. During the continuous operation of the sludge dewatering process, the chemical dosing amount is dynamically adjusted, and the dewatering parameters of the high-pressure belt filter press are linked and adjusted to achieve the dynamic collaborative optimization of chemicals and dewatering parameters.

[0035] As Figure 1 shown, when implementing each step of the high-pressure belt machine low-cost sludge dewatering process, and during the start-up phase of the process, steps S1 to S5 need to be implemented in sequence according to the order of S1 to S5. At the same time, the data of parameters S, C, and P are detected before step S1, after step S4, and after step S5 for use when implementing step S6. Among them, before adding ferric chloride to the sludge to be treated in step S1, it is necessary to first detect the sludge dry solid content of parameter S, obtain the data of parameter S and then transmit it back to the controller for storage and use when starting step S6; after step S1 is completed; after dewatering the sludge in step S4, the discharged filter cake is detected, and the filter cake moisture content of parameter C is obtained. After obtaining the data of parameter C, it is transmitted back to the controller for storage and used when starting step S6; when recovering the filtrate from the filtrate tank in step S5, the filtrate conductivity of parameter P is detected, and after obtaining the data of parameter P, it is transmitted back to the controller for storage and used when starting step S6.

[0036] When implementing step S6, in each cycle of steps S1 to S5, the dynamic process parameters can be obtained according to the dynamic chemical dosing algorithm. The dynamic process parameters include the dynamic chemical dosing amounts in steps S1 to S3 and the dynamic dewatering parameters in step S4. When performing steps S1 to S4, operate according to the dynamic process parameters given in step S6 to achieve the purpose of dynamic collaborative optimization of chemicals and dewatering parameters in step S6, so that the sludge dewatering treatment process can dynamically adjust the chemical dosing amount and dewatering parameters according to the sludge state input into the treatment tank, and finally achieve the high-pressure belt machine low-cost sludge dewatering process to obtain better sludge dewatering effect with low-cost dewatering input.

[0037] The dynamic dewatering parameters are obtained by synchronously optimizing the original basic dewatering parameters according to the latest adjusted chemical dosing amounts in steps S1 to S3 during the process step cycle. The purpose is to apply the best dewatering parameters to the sludge in the current cycle in cooperation with the latest adjusted chemical ratio in the current cycle, so as to make the dewatering effect of the sludge in the dewatering step reach the better dewatering effect of the expected dewatering.

[0038] Among them, in the sludge treatment tank, the dosing sequence of ferric chloride solution, lime powder, and polyacrylamide solution is as follows: first add ferric chloride solution, then add lime powder, and finally add polyacrylamide solution.

[0039] 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%.

[0040] 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 decrease to < 5 mV to destroy the stability of the colloidal structure of the sludge; when the Zeta potential approaches zero, the van der Waals force between colloidal particles dominates, and the sludge colloid quickly deviates from the steady state and forms dense flocs, laying a foundation for the subsequent conditioning of lime and PAM; by adding ferric chloride solution, using Fe 3﹢ ions with a high charge density, after neutralizing the surface negative charge of the sludge colloid, in the subsequent flocculation stage, the flocs are more easily captured by the bridging action of polyacrylamide (PAM, polyacrylamide), and the mechanical strength of the formed flocs is improved, which can withstand the shear force of the high-pressure belt filter; and the dosage of PAM can be reduced by 20% - 30%, saving the dosing cost of the chemical agent.

[0041] Regarding the role of adding lime powder to the sludge in the above step S2, the addition of lime powder adjusts the pH value of the sludge to 9.5 - 11.

[0042] Specifically, in step S2, the lime powder added to the sludge is calcium hydroxide with a mesh size of 200 - 400.

[0043] During application, after adding calcium hydroxide with a mesh size of 200 - 400 to the sludge, the specific resistance of the sludge is reduced to below 1×10 12 m / kg, making the dehydration effect of the sludge better in step S4, and the dosage of PAM in step S3 can also be further reduced.

[0044] 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%.

[0045] Among them, the added polyacrylamide is anionic polyacrylamide, and its molecular weight is 8 million - 10 million.

[0046] During application, the dosing timing of the polyacrylamide solution is controlled as follows: within 1 - 2 minutes after the addition and stirring of lime powder in step S2 are completed, the addition is completed, and then mechanical stirring is started to increase the flocculation speed, making the speed of forming dense flocs of the sludge better and the forming effect better.

[0047] 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 operates in the order from small pressure to large pressure, and the pressure gradient is applied in sequence from the set first gradient to the third gradient, and the sludge is dehydrated in gradients at a filter belt running speed of 2.5 - 4.5 m / min and an extrusion time of 150 - 200 s.

[0048] When in application, among them, the first pressure gradient is: 0.4 - 0.6 MPa, the second pressure gradient is: 0.7 - 0.9 MPa, the third pressure gradient is: 1.0 - 1.2 MPa, and the time ratio of the application of the first to the third pressure gradients is 1:1.5:2; enabling the sludge to be gradually pressurized during the dehydration process and increasing the pressure holding time, achieving progressive dehydration, and the water in the sludge agglomeration center gradually seeps out, avoiding trapped water, increasing the sludge dehydration amount, and reducing the water content of the filter cake.

[0049] The low-cost sludge dehydration process of the high-pressure belt machine realizes multiple advantages of reagent usage cost, sludge dehydration effect, process adaptability and stability by optimizing the reagent combination ratio and segmented dosing sequence of "ferric chloride, lime, PAM" and combining with the dynamic collaborative control of the high-pressure belt machine operation parameters.

[0050] Significantly reduce the reagent usage cost. Through the synergistic effect of the inorganic reagents ferric chloride and lime and the organic flocculant polyacrylamide, on the premise of ensuring the dehydration effect of sludge treatment, effectively reduce the dosage of PAM, reduce the unit sludge treatment cost by more than 4%, and break through the dependence on high-cost single reagents in the existing technology.

[0051] Improve the dehydration effect and filter cake performance. The optimized reagent dosing ratio and sequence significantly improve the sludge structure, the filter cake is formed densely and is easy to peel off from the filtering mechanism, effectively reduce the water content of the filter cake to below 75%, and at the same time increase its compressive strength to above 20 kPa, providing convenient conditions for subsequent incineration or landfill.

[0052] Enhance the process adaptability and operation stability. In step S6, adopt the dynamic dosing algorithm and the control system linkage mechanism, adjust the reagent dosing in real time according to the sludge dry solid content, and accurately match the operation parameters of the high-pressure belt machine, such as gradient pressure, filter belt speed, extrusion time, avoid the decline of dehydration performance caused by load fluctuations or manual adjustment errors, and improve the stability and adaptability of the overall sludge dehydration process.

[0053] Improve the resource recycling efficiency. In the filtrate recovery process in step S5, partial water resources and dissolved reagents are reused. The filtrate is recycled to the ferric chloride dissolution process through conductivity control, further reducing water consumption and reagent preparation cost, and having good environmental benefits.

[0054] Through the composite process of "segmented conditioning, dynamic reagent ratio, and control system linkage", the equipment operation characteristics of the high-pressure belt machine are systematically optimized and designed, providing a new technical route for sludge dewatering that is replicable, popularizable, and low-cost for engineering practice.

[0055] In summary, the present technical solution solves the technical problems existing in the existing sludge dewatering technologies, such as high cost, unclear mechanism, and poor process adaptability, and has the technical progressiveness and industrial application value of reducing the reagent usage cost, improving the sludge dewatering effect, and enhancing the process adaptability and stability.

[0056] As an optional implementation method The specific setting of the above dynamic reagent dosing algorithm is: Q = α × S + β × C + γ × P.

[0057] Among them, Q is the total reagent cost coefficient, S is the sludge dry solid content, C is the filter cake moisture content, P is the filtrate conductivity monitored in real time, and α, β, and γ are correction coefficients.

[0058] When applying, the formula reflects the synergistic effect on the total reagent cost coefficient Q by linearly combining the three key process parameters S, C, and P: First, assume that the reagent cost has an approximate linear relationship with the sludge properties, dewatering effect, and filtrate quality, which is convenient for engineering implementation and real-time control; clarify that the correction coefficients α, β, and γ of the parameters S, C, and P characterize their influence degrees on the total cost.

[0059] Among them, the parameter S, the sludge dry solid content, directly determines the dosing amount of the reagent and is the basis for cost calculation. For example, the dosing amount of solute ferric chloride is 0.5% - 1.5% of the sludge dry solid mass, the dosing amount of lime powder is 2% - 4% of the sludge dry solid mass, and the dosing amount of solute polyacrylamide is 0.1% - 0.3% of the sludge dry solid mass.

[0060] Specifically, the sludge dry solid mass is the parameter S of the sludge in the treatment tank measured by the sensor before starting to dose the reagent in step S1. The meaning of the sludge dry solid mass is that the sludge initial solid load is the dry solid content in the total mass of the original sludge. It should be noted that the parameter S and the parameter C belong to parameters in different stages and cannot be directly related, and there is no mathematical constraint relationship between the two.

[0061] The parameter C, the filter cake moisture content, directly reflects the dewatering effect. When the moisture content is high, it is necessary to increase the dosing amount of the reagent to improve the dewatering effect. On the contrary, when the dehydration rate reaches the dehydration target, the dosage of the corresponding reagent can be gradually reduced through automatic control to further save costs.

[0062] Parameter P: the real-time conductivity of the filtrate. By monitoring the ion concentration in the filtrate, high conductivity may indicate a large amount of chemical residue, and high conductivity may pose a risk of equipment corrosion. It is necessary to judge the ion concentration of the filtrate based on the monitored conductivity, control the conductivity of the recycled filtrate, and thus control the ion concentration of the recycled filtrate, so as to realize the use of the recycled filtrate for subsequent sludge dewatering to reduce costs and avoid corrosion of sludge treatment equipment.

[0063] Step S6 realizes the dynamic, refined and flexible control of the process cost through the dynamic dosing algorithm. Before realizing the dynamic control, that is, only steps S1 to S5 need to be run during the process startup, and by collecting the actual operation data of process steps S1 to S5, the basic startup data required for running step S6 is obtained. The specific method for obtaining accurate data for sludge dewatering is as follows: after cycling steps S1 to S5 2 - 3 times, use the orthogonal test method, response surface analysis method and on-line potential monitoring to analyze and obtain the sludge dry solid content, filter cake moisture content and filtrate conductivity. Input this data into the dynamic dosing algorithm in step S6, automatically calculate and generate the optimized chemical dosing ratio and process parameters of steps S1 to S5, and then feedback them to steps S1 to S5 for continued implementation; after feedback the optimized chemical dosing ratio and process parameters of steps S1 to S5 to steps S1 to S5 for 5 - 6 cycles, then continuously cycle and run at least 3 times and record the obtained sludge dry solid content, filter cake moisture content and real-time conductivity parameters 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, fix the chemical dosing ratio and process parameters of steps S1 to S5, and continue to cycle and run steps S1 to S5.

[0064] Through orthogonal test or response surface analysis, collect the S, C and P parameters and chemical cost data under different working conditions, and establish a "multiple linear regression model", that is, Q actual = α×S + β×C + γ×P + for analysis; among them, in the model = Q actual - Q predicted, is used to supplement the changes in treatment costs caused by factors such as sludge composition fluctuations, unpredictable process disturbances, environmental temperature and equipment aging that are not considered in the model, and to avoid the model overfitting and losing generalization ability during the modeling process; By collecting the previous chemical dosing ratio experimental data, the model degree is tested, and a relatively high model fitting degree is obtained. It is determined that α×S + β×C + γ×P plays a major role in the model, and when fitting the model, the least squares method is used to fit the coefficients, which can make the prediction error minimized; so in engineering applications, only Q = α×S + β×C + γ×P is needed to complete the control of chemical dosing and the cost affected by chemicals in sludge dewatering.

[0065] On the premise of ensuring the moisture content of the filter cake (C ≤ 75%) and equipment safety (P ≤ 2000 μS / cm), with the goal of minimizing the chemical cost, solve the optimal ranges of α, β, and γ; during the solution, by collecting the data of previous chemical proportioning experiments, fit and determine the initial values of the correction coefficients α, β, and γ through the orthogonal analysis method, and normalize the initial values of the correction coefficients α, β, and γ. Then, verify the influence of each factor such as the sludge dry solid content S, the moisture content of the filter cake C, and the conductivity of the filtrate P on the total chemical cost coefficient Q through experiments again, and limit the influence of each factor on the total chemical cost coefficient Q in the sludge dewatering process by adjusting the values of the correction coefficients α, β, and γ. Finally, obtain the actual optimal operating value ranges of the correction coefficients α, β, and γ. The value range of α is 0.25 - 0.35, the value range of β is 0.15 - 0.25, and the value range of γ is 0.05 - 0.15.

[0066] And it is found in the engineering verification that when α = 0.3, β = 0.2, and γ = 0.1, the comprehensive cost and dewatering effect are optimal, and the calculation formula is: Q = 0.3S + 0.2C + 0.1P.

[0067] Among them, during the process operation, in step S6, before step S1, that is, before adding ferric chloride, the sludge dry solid content is detected online; after the high-pressure dewatering in step S4 is completed to form a 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.

[0068] When in application, the sludge dry solid content can be detected by an infrared moisture analyzer, the moisture content of the filter cake can be detected by a microwave moisture sensor, and the conductivity can be detected by a wire conductivity probe.

[0069] In the dynamic chemical dosing algorithm, according to the data detected in real time, the total chemical cost coefficient Q for unit sludge dewatering treatment is calculated dynamically and compared with the target maximum cost limit value, which can trigger the adjustment of the chemical dosing amount.

[0070] Through the PID adjustment unit, accurately control the dosing amount of each chemical: When the Q value increases, linearly increase the dosing amount of ferric chloride in proportion. According to the ferric chloride dosing amount formula: W = K1 × Q × S, calculate the dosing amount of ferric chloride.

[0071] When the S value increases, adjust the dosing amount of lime powder. According to the lime powder dosing amount formula: W = K2 × Q × .

[0072] When the C value increases, the dewatering effect is poor, and automatically increase the dosing amount of PAM. According to the PAM dosing amount formula: W = K3 × Q × (1 - C).

[0073] Among them, K1, K2, and K3 are synchronized with the dosing ratios of ferric chloride, lime powder, and PAM, i.e., K1 = 0.5 - 1.5, K2 = 2 - 4, and K3 = 0.1 - 0.3.

[0074] When the P value rises above 2000 μS / cm, it is necessary to purify the filtrate, reduce the ferric ions and chloride ions in the filtrate, lower the conductivity to below 2000 μS / cm, and reduce the weight of the correction factor γ to the lowest 0.05 to reduce the consumption of the new ferric chloride reagent.

[0075] When the S value increases, the running speed of the filter belt of the high-pressure belt filter press can be optimized synchronously, reducing the running speed of the filter belt to 2.0 - 4.0 m / min. After reducing the running speed of the filter belt, it is necessary to extend the extrusion time for sludge dewatering at the same time. Based on the extrusion time of 150 - 200 s in step S4 above, the extrusion time should be extended by at least 30 s, so that the extrusion time reaches 180 - 230 s to dehydrate the sludge.

[0076] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described.

Claims

1. A low-cost sludge dewatering process for a high-pressure belt machine, characterized in that it includes the following steps: S1. Pretreatment stage: Add ferric chloride to the sludge to be treated. Before adding, ferric chloride needs to be made into a ferric chloride solution, and impurities are filtered to obtain the ferric chloride solution after impurity removal. Among them, the dosage of ferric chloride as the solute is 0.5%-1.5% of the dry solid mass of the sludge, and mechanical stirring is carried out for 30-60 seconds to make ferric chloride and the colloidal particles in the sludge evenly mixed to undergo an electro-neutralization reaction, destroying the sludge colloid structure; S2. Conditioning stage: After the action of ferric chloride is completed, add lime powder, and the dosage is 2%-4% of the dry solid mass of the sludge. Adjust the pH of the sludge to alkaline, and carry out mechanical stirring for 30-60 seconds to promote the formation of a porous skeleton structure of the sludge and enhance the structural stability of the filter cake; S3. Flocculation stage: After the above step S2 is completed, add polyacrylamide to the sludge. Before adding, polyacrylamide needs to be made into a polyacrylamide solution, and impurities are filtered to obtain the polyacrylamide solution after impurity removal. Among them, the dosage of polyacrylamide as the solute is 0.1%-0.3% of the dry solid mass of the sludge, and mechanical stirring is carried out for 1-2 minutes to form dense flocs through bridging adsorption, improving the flocculation effect; S4. Dewatering stage: Convey the sludge treated above to a high-pressure belt filter press, and carry out mechanical dewatering through the set pressure gradient, filter belt speed and extrusion time, so that the moisture content of the dewatered filter cake is controlled below 75%; S5. Filtrate recovery and redissolution: After sludge dewatering, recover the filtrate from the filtrate tank. After controlling the conductivity of the filtrate below 2000 μS / cm, it is used for the ferric chloride dissolution process in step S1; S6. Control system linkage: Through a dynamic dosing algorithm based on the dry solid content of the sludge, adjust the dosing amount of the medicine, and linkage-adjust the dewatering parameters of the high-pressure belt filter press to achieve dynamic collaborative optimization of the medicine and dewatering parameters.

2. The low-cost sludge dewatering process for a high-pressure belt machine according to claim 1, characterized in that in the sludge treatment tank, the dosing order of 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.

3. The low-cost sludge dewatering process for a high-pressure belt machine according to claim 2, characterized in that in step S1, the proportion of ferric chloride in the ferric chloride solution is 10%-15%.

4. The low-cost sludge dewatering process for a high-pressure belt machine according to claim 2, characterized in that the addition of lime powder adjusts the pH value of the sludge to 9.5-11.

5. The low-cost sludge dewatering process for a high-pressure belt machine according to claim 4, characterized in that in step S2, the lime powder is calcium hydroxide with a mesh size of 200-400.

6. The low-cost sludge dewatering process for a high-pressure belt machine according to claim 2, characterized in that in step S3, the proportion of polyacrylamide in the added polyacrylamide solution is 0.1%-0.3%.

7. The low-cost sludge dewatering process for a high-pressure belt machine according to claim 6, characterized in that in step S3, the added polyacrylamide is anionic polyacrylamide, and the molecular weight is 8 million - 10 million.

8. The low-cost sludge dewatering process of the high-pressure belt machine according to claim 1, characterized in that in step S4, the dewatering pressure applied by the high-pressure belt filter press operates in the order of small pressure to large pressure, and the pressure gradient is applied in sequence from the set first gradient to the third gradient, and the sludge is subjected to gradient dewatering at a filter belt running speed of 2.5-4.5 m / min and an extrusion time of 150-200 s.

9. The low-cost sludge dewatering process of the high-pressure belt machine according to claim 1, characterized in that The dynamic dosing agent algorithm is: Q = α×S + β×C + γ×P; where Q is the total dosing agent cost coefficient, S is the sludge dry solid content, C is the filter cake moisture content, P is the filtrate conductivity monitored in real time, and α, β, and γ are correction coefficients.

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