A method for treating filtrate of a plate-and-frame filter by sectioning and shunting

Abstract

The application discloses a kind of plate and frame filter press filtrate segmented flow treatment methods, belong to solid-liquid separation technical field, to the transition pressure P2 of filter low pressure stage to high pressure into slurry stage with plate and frame filter press, variable coefficient k is introduced to build filter cake forming pressure judging value P3, by comparing filter cake forming pressure judging value and plate and frame filter press when feeding main pipe pressure, filtrate is segmented and flows control.The filtrate judging method disclosed in the application does not need to install turbidimeter, time sequence control, can realize accurate automatic flow only relying on the pressure signal of filter press, effectively reduce waste water treatment drug consumption, improve water resource utilization, improve plate and frame filter press system operating efficiency.

Description

Technical Field

[0001] This invention belongs to the field of solid-liquid separation technology, specifically relating to a method for segmented diversion and treatment of filtrate from a plate and frame filter press. This method can be used in fields such as industrial wastewater resource utilization and desulfurization wastewater treatment. Background Technology

[0002] Plate and frame filter presses are core dewatering equipment in power plant desulfurization, chemical, and mining wastewater treatment systems. In conventional operation, during the initial low-pressure feeding stage, the filter cloth does not form a filter cake layer, and a large number of fine gypsum particles and sludge particles penetrate the filter cloth, generating a large amount of highly turbid and high-solids-content wastewater. When the pressure increases and the system enters a stable filtration stage, a dense filter cake layer is formed between the filter plates of the filter press, which can effectively trap fine solid particles, resulting in clear effluent with virtually no impurities. The filtrate after filtration varies throughout the entire process.

[0003] Traditional processes collect high-turbidity, high-solids wastewater and clean water together, but lack the problem of filtrate separation and diversion, which has serious drawbacks: (1) The clear filtrate water that can be directly reused is polluted by the previous dirty water and must be treated with chemicals, resulting in high consumption of chemicals and high operating costs; (2) A large amount of low-turbidity clean water enters the wastewater triplet, diluting the concentration of chemicals and increasing the treatment load of the water treatment system.

[0004] Most existing improvement solutions rely on manual timing control or turbidity meter monitoring. Manual timing control wastes a lot of manpower and is prone to high solids content filtrate entering the clear water tank due to human error, causing dirt accumulation, blockage, and scaling in pipelines and containers, which poses a safety hazard to the system. Turbidity meter monitoring is prone to contact with slurry for a long time, which can easily cause adhesion and blockage. It requires frequent flushing and replacement of the contacts, resulting in high maintenance and poor reliability.

[0005] Currently, the industry lacks a mature process for segmented flow of filtrate that relies on the equipment's native pressure parameters and variable coefficient control logic. Summary of the Invention

[0006] To address at least one of the problems in existing technologies, such as high load on filtrate mixed water treatment, high chemical consumption, and difficulty and susceptibility to failure in the later installation of monitoring equipment, this invention discloses a segmented diversion treatment method for filtrate from a plate and frame filter press. Based on the filter press's factory-designed pressure P2 and a variable coefficient k, a judgment value P3 is constructed. The pressure signal P1 of the feed header during the low-pressure stage of the plate and frame filter press is collected in real time. P3 is used as the standard for filtrate diversion treatment. Based on the comparison between P3 and P1, it is determined whether a feed filter cake has formed, and the filtered filtrate is then diverted.

[0007] To achieve the purpose of the invention, the following technical solution is provided: This invention discloses a method for segmented diversion of filtrate from a plate and frame filter press. The method constructs a filter cake forming pressure judgment value by combining the filter press's baseline design pressure with a variable coefficient. By comparing the filter cake forming pressure judgment value with the feed header pressure during the operation of the plate and frame filter press, the filtrate is controlled to be segmented and diverted.

[0008] Furthermore, the method for segmented and diverted filtrate treatment in the plate and frame filter press includes the following steps: S1. Based on the variable coefficient k and the pressure value P2 of the plate and frame filter press transitioning from the low-pressure stage to the high-pressure stage, calculate the filter cake forming pressure judgment value P3 according to the formula P3=P2×k. S2. Real-time acquisition and monitoring of the feed header pressure P1 during plate and frame filter press operation; S3. The filtrate is diverted according to the comparison values ​​of P3 and P1. When P1 < P3, the feed filter cake is not yet formed, and the filtered filtrate enters the wastewater treatment system for further treatment. When P1 ≥ P3, the feed filter cake is formed, and the filtered filtrate enters the clean water recovery unit for storage and reuse. The preferred wastewater treatment system is a wastewater triplet tank, and the clean water recovery unit is a clean water tank.

[0009] Furthermore, the variable coefficient k is determined based on the feed slurry concentration, filter cloth type, filter cloth aging degree, and filter press differences. The range of k is 0.03~0.13, thereby achieving adaptive correction of the control threshold.

[0010] Furthermore, the pressure P1 of the feed header pipe during the operation of the plate and frame filter press is continuously monitored; When P1≤P2, the plate and frame filter press is in the low-pressure mud feeding stage. Determine the magnitude of P1 and P3, and perform the above-mentioned segmented diversion treatment method for the filtrate of the circulating plate and frame filter press. When P1 > P2, the plate and frame filter press enters the high-pressure sludge feeding stage, and the filtrate is continuously transported to the clean water recovery unit. After a single filtration operation is completed, the filtrate pipeline is cleaned.

[0011] The technical solution proposed in this invention, a segmented and diverted filtrate treatment method for plate and frame filter presses, addresses the industry pain points of traditional plate and frame filter presses where filtrate is collected and treated uniformly during operation. This results in the mixing of high-turbidity filtrate water in the initial stage of low-pressure feeding with clean water in subsequent stages, which easily leads to wastewater treatment reagent waste, increased wastewater treatment volume, low wastewater resource reuse rate, and decreased system operating efficiency. This method was developed through experiments that fully considered comprehensive factors such as differences in plate and frame filter presses, slurry concentration, filter cake formation process, filter cloth type, and filter cloth aging degree. During the low-pressure mud feeding stage, the filter cloth has not formed a stable filter cake transition layer, and a large number of fine particles in the slurry pass through the filter. The filtrate has a high solids content and high turbidity, and cannot be directly reused. It must be collected and sent to the wastewater system for treatment. As the pressure P1 of the feed header of the plate and frame filter press gradually increases, a dense and stable filter cake layer gradually forms on the surface of the filter cloth during the filtration process. This layer can effectively trap solid particles. The filtrate at this stage has extremely low impurities and stable water quality, which meets the reuse standards of the production system. It can be directly fed into the clean water tank for production makeup water and equipment flushing water reuse. However, the exact point of divergence could not be determined, and it was unclear whether the filtrate should enter the wastewater triplet tank or the clear water tank. Therefore, a variable coefficient k was introduced through experiments. Based on P3=P2×k, the cake formation judgment value P3 was calculated to determine the divergence point. When P1<P3, the filter cloth did not form a stable filter cake layer, the filtrate had a high solid content and high turbidity, and the filtrate was collected and sent to the wastewater system for treatment and could not be directly reused. When the pressure P1>P3, the filter cake was formed in the filter plate cavity, which could effectively intercept solid particles, and the filtrate water quality was stable and could be directly entered into the clear water tank for reuse.

[0012] This invention breaks through the traditional approach of segmented control of filtrate in plate and frame filter presses. It is the first to use a benchmark design pressure combined with variable coefficients to construct a judgment value, forming an automatic segmented control strategy for filtrate water. The solution is fully consistent with the filter cake film formation mechanism of the equipment, requires no external water quality testing equipment, has strong anti-interference ability, outstanding energy saving and consumption reduction benefits, and has high industrial promotion value.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The plate and frame filter press filtrate segmentation and diversion method disclosed in this invention introduces a variable coefficient k and calculates the cake formation judgment value P3 as the filtrate diversion standard. This eliminates the filtration changes caused by changes in feeding method and filter cloth state, accurately matching the actual filter cake film formation law of the plate and frame filter press. This achieves precise diversion, allowing high-solids-content filtrate to enter the wastewater system and clear filtrate to be directly reused. The variable coefficient k can be dynamically corrected based on the feed slurry concentration, filter cloth, plate and frame filter press model, etc., making it widely applicable.

[0014] 2. The filtrate is processed in segments and by separate flow. No timing module, online turbidity monitoring instrument, or suspension monitoring equipment is required throughout the process. The system uses signals collected by the filter press pressure transmitter and relies on a DCS program to implement the decision-making logic. No modifications to the filter press structure are necessary; fully automatic segmented flow switching can be achieved using only the existing pressure transmitter. It is unaffected by equipment interlock protection, operating time, or water quality test data.

[0015] 3. The segmented diversion treatment method for filtrate from a plate and frame filter press disclosed in this invention accurately separates high-solids wastewater from clear water, significantly reducing the consumption of chemicals in subsequent treatment. Qualified filtrate no longer enters the wastewater system, reducing water treatment chemical consumption by more than 30%. It also reduces the load on the wastewater system, allowing a large amount of clean water to be directly reused, significantly reducing the amount of water treated by the wastewater treatment system and contributing to the water balance of the desulfurization system. Furthermore, it boasts high operational reliability, eliminating the need for easily clogged or malfunctioning turbidity monitoring probes and utilizing only the equipment's built-in pressure signal, making it suitable for complex industrial slurry environments. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of an automatic filtrate diversion control method for a plate and frame filter press according to the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Unless otherwise specified, all raw materials used in the following examples were purchased commercially.

[0019] Unless otherwise specified, the methods used in the following embodiments are conventional operating methods in the art.

[0020] This embodiment provides a method for segmented diversion of filtrate from a plate and frame filter press. The filter press base design pressure is combined with a variable coefficient to construct a filter cake forming pressure judgment value. By comparing the filter cake forming pressure judgment value with the feed header pressure during the operation of the plate and frame filter press, the filtrate is controlled to be segmented and diverted.

[0021] Taking the desulfurization plate and frame filter press system of a coal-fired power plant as an example, the filter press filtration process includes the following steps: S1. Based on the variable coefficient k and the pressure value P2 of the plate and frame filter press transitioning from the low-pressure stage to the high-pressure stage, calculate the filter cake forming pressure judgment value P3 according to the formula P3=P2×k. In this embodiment, the variable coefficient k is determined based on the feed slurry concentration, filter cloth type, filter cloth aging degree, and filter press differences. k is 0.08. The pressure value P2 for the transition from low pressure stage to high pressure stage of the plate and frame filter press is 0.6MPa. The filter cake forming pressure judgment value P3 is calculated according to the formula P3=P2×k and is 0.048MPa. The judgment value P3 is entered into the DCS control system. S2. Real-time acquisition of the feed header pressure P1 during plate and frame filter press operation; S3. Based on the comparison values ​​of P3 and P1, the filtrate is diverted for further treatment. When P1 < P3, the feed filter cake is not yet formed, and the filtered filtrate enters the wastewater triplet for further treatment. When P1 ≥ P3, the feed filter cake is in the forming stage, and the filtered filtrate enters the clean water tank for storage and reuse. In this embodiment, when the plate and frame filter press starts feeding, and the pressure P1 of the feed main pipe is less than 0.048MPa during operation, the pipeline from the filtrate water to the wastewater treatment system is automatically opened and the pipeline from the filtrate water to the clear water tank is closed. All the high solids content filtrate is sent to the wastewater triplet for further treatment. When the feed pressure continues to rise until the feed main pipe pressure P1 > 0.048MPa during operation, the interlock triggers the pipeline switching, shutting off the pipeline from the filtrate water to the wastewater treatment system and opening the pipeline from the filtrate water to the clear water tank, so that the clear filtrate is transported to the clear water tank for storage and reuse.

[0022] During the operation of the plate and frame filter press, the pressure P1 of the feed header pipe is continuously monitored. When P1 ≤ 0.6 MPa, the plate and frame filter press is in the low-pressure mud feeding stage. It is necessary to determine the magnitude of P1 and P3 and carry out the above-mentioned segmented diversion treatment method for the filtrate of the circulating plate and frame filter press. When the plate and frame filter press is running, the pressure P1 of the feed header continuously rises to P1>0.6MPa, the equipment enters the high-pressure sludge feeding stage, the filter cake layer is stably formed, and the clear filtrate continuously flows into the clean water tank to supply water to the desulfurization system and flush the equipment; a single filter press cycle ends.

[0023] After on-site application, the wastewater treatment volume of the system was reduced by about 35%, the consumption of wastewater agents such as lime slurry, coagulant aid, and organic sulfur decreased by 40%, the clean water reuse rate was significantly improved, and the water balance control of the desulfurization system continued to improve.

[0024] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for segmented and diverted treatment of filtrate from a plate and frame filter press, characterized in that, The filter cake forming pressure judgment value is constructed by combining the filter press benchmark design pressure with a variable coefficient. By comparing the filter cake forming pressure judgment value with the feed header pressure during the operation of the plate and frame filter press, the filtrate is controlled in segments and by diverting it.

2. The method for segmented diversion and treatment of filtrate from a plate and frame filter press as described in claim 1, characterized in that, Includes the following steps: S1. Based on the variable coefficient k and the pressure value P2 of the plate and frame filter press transitioning from the low-pressure stage to the high-pressure stage, calculate the filter cake forming pressure judgment value P3 according to the formula P3=P2×k. S2. Real-time acquisition and monitoring of the feed header pressure P1 during plate and frame filter press operation; S3. Based on the comparison values ​​of P3 and P1, the filtrate is diverted for further processing. When P1 < P3, the feed filter cake is not yet formed, and the filtered filtrate enters the wastewater treatment system for further processing. When P1 ≥ P3, the feed filter cake is in the forming stage, and the filtered filtrate enters the clean water recovery unit for storage and reuse.

3. The method for segmented diversion and treatment of filtrate from a plate and frame filter press as described in claim 2, characterized in that, The variable coefficient k is determined based on the feed slurry concentration, filter cloth type, filter cloth aging degree, and filter press differences. The range of k is 0.03~0.13, which realizes adaptive correction of the control threshold.

4. The method for segmented diversion and treatment of filtrate from a plate and frame filter press as described in claim 2, characterized in that, Continuous monitoring of the feed header pressure P1 during plate and frame filter press operation; When P1≤P2, the plate and frame filter press is in the low-pressure mud feeding stage. Determine the magnitude of P1 and P3, and perform the above-mentioned segmented diversion treatment method for the filtrate of the circulating plate and frame filter press. When P1 > P2, the plate and frame filter press enters the high-pressure sludge feeding stage, and the filtrate is continuously transported to the clean water recovery unit. After a single filtration operation is completed, the filtrate pipeline is cleaned.

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