In sludge dewatering treatment, plate and frame filter presses are widely used due to their advantages such as high dewatering efficiency and controllable solid content in the mud cake. However, in actual operation, the three major problems of "excessively long sludge feeding time", "sludge cake adhering to the filter cloth" and "frequent clogging of the filter cloth" have always been plaguing the enterprise. These problems not only increase the operating costs, but also lead to a reduction in the effective working hours of the equipment and a sharp increase in the frequency of maintenance. This article deeply analyzes the causes of pain points and provides systematic solutions from three dimensions: sludge conditioning, equipment optimization, and process innovation.
I. Symptom of the Problem: Dual constraints of efficiency and cost
The time of entering the mud is too long
When the sludge feeding time of a single cycle exceeds 2 hours and the equipment utilization rate is less than 60%, it directly leads to:
Limited processing capacity: The daily processing scale cannot meet the standard, and additional backup equipment needs to be activated.
Rising energy consumption: When air compressors and feed pumps operate inefficiently for a long time, the electricity consumption per ton of water increases by 15% to 20%.
The mud cake adheres to the filter cloth
The mud cake has a strong binding force with the filter cloth, making it difficult to unload the cake, which is manifested as:
Frequent manual intervention: High-pressure water gun flushing or manual removal is required, and a single cleaning takes more than 30 minutes.
Intensified damage to the filter cloth: Mechanical peeling causes deformation of the pore size of the filter cloth, shortening its service life by 40%.
The clogging of the filter cloth has intensified
After running for 3 to 5 cycles, the water permeability of the filter cloth drops by more than 50%, which is manifested as:
The filter pressure surges: To maintain the dehydration efficiency, the feed pressure needs to be continuously increased to above 1.8MPa.
Turbid filtrate: Blockage causes tiny particles to penetrate the filter cloth, and the SS in the filtrate exceeds the standard.
Ii. Pain Point Tracing: The "Triple Superposition" of Sludge Characteristics, Equipment Operating Conditions, and Improper Operation
One. "Inherent Defects" in sludge characteristics
Excessive viscosity: The extracellular polymer (EPS) content in the excess sludge exceeds 3000mg/L, forming a colloidal structure.
Too fine particle size: The median particle size of sludge particles is less than 20μm, which is prone to clogging the pores of the filter cloth.
Strong hydrophilicity: With a high proportion of organic matter, hydrophilic groups such as hydroxyl groups on the cell surface make it difficult to remove water.
Two. "Acquired imbalance" of equipment operating conditions
Defects in the feeding system: The flow pulsation of the single-screw pump is large, resulting in uneven distribution of sludge in the filter press chamber.
Improper selection of filter cloth: The pore size does not match the particle size of the sludge (for example, the pore size of the filter cloth is 30μm and the particle size of the sludge is 25μm);
The back-blowing device is missing: The high-pressure air back-blowing system is not configured, and the residual sludge accelerates clogging.
Three. Improper operation: "Artificial magnification"
Disordered dosing of chemicals: The dosing points of PAC and PAM overlap, forming "jelly-like" flocs.
The filtration pressure curve is rather rough: The segmented pressure increase strategy was not designed based on the characteristics of the sludge, and the initial high pressure led to the rapid sealing of the filter cake.
Insufficient cleaning and maintenance: The filter cloth cleaning cycle is more than 24 hours, and the residual sludge is difficult to remove after solidification.
Iii. Technological Breakthrough: The Innovative Path from "Single-point Improvement" to "System Optimization"
Innovation in sludge conditioning
Significantly improve the consistency and thickness of the mud cookies, with a fast response speed. This is a modified polymer product with multiple functions, which can replace the traditional conditioning process in the deep dewatering of sludge. It can truly achieve convenient use, energy conservation and consumption reduction, lower the cost of solid waste treatment, not change the nature of sludge, have no impact on ph and organic matter, and have no side effects. It has the characteristics of being versatile and comprehensive.
Two. Equipment upgrade and transformation - Enhance feeding efficiency and filter cloth lifespan
Optimization of the feeding system
Replacing the single-screw pump with a diaphragm pump reduces the flow pulsation by 80% and makes the sludge distribution more uniform.
Add a static mixer to ensure that the chemicals and sludge are thoroughly mixed (the mixing time is less than 5 seconds).
Intelligent management of filter cloth
Customized double-layer composite filter cloth (surface polyester + bottom polypropylene), balancing filtration accuracy (20μm) and wear resistance;
Install a high-pressure air back-blowing device and automatically back-blow at the end of each cycle, reducing the residual sludge by 70%.
Three. Precise control of process parameters - Constructing an efficient filtration pressure curve
Segmented voltage boosting strategy
Initial stage (0-5 minutes) : Pressure 0.3MPa to ensure uniform sludge filling of the filter chamber;
Mid-term pressure increase (5-15 minutes) : The pressure gradually rises to 1.0MPa to promote water migration;
Final pressure holding (15-20 minutes) : The pressure is stabilized at 1.5MPa, and the pressure holding time is extended to 10 minutes to completely remove the internal moisture.
Dynamic adjustment of feeding speed
Adjust the feed flow rate in real time according to the sludge concentration (for example, the flow rate is 4L/min when the concentration is 5%, and 2.5L/min when the concentration is 8%) to avoid local overload.
Iv. Case Evidence: See Practical Results from Data
Case 1: Sludge treatment project of a certain food processing plant
Problem: The sludge feeding time for a single cycle is 2.5 hours. The sludge cake adheres to the filter cloth and needs to be cleaned manually.
Solution: Add sludge enhancer (6kg/t dry sludge), optimize the filtration curve, and upgrade the diaphragm pump + double-layer filter cloth;
Effect:
The sludge feeding time was shortened to 1.2 hours and the equipment utilization rate increased by 52%.
The cleaning frequency of the filter cloth has been reduced from three times a day to twice a week, and its service life has been extended to six months.
Case 2: A sewage treatment plant in a certain chemical industrial park
Problem: The clogging of the filter cloth caused the filtration pressure to soar to 2.0MPa, and the SS in the filtrate exceeded the standard.
Solution: Add a high-pressure air back-blowing device and adjust the PAC/PAM dosing point;
Effect:
The filtration pressure was stabilized at 1.3MPa, and the SS of the filtrate was reduced to below 80mg/L.
The electricity consumption per ton of water has decreased by 18%, and the annual electricity bill savings exceed 100,000 yuan.
V. Future Outlook: Intelligence and Sustainability Advancing in Parallel
With the integration of AIoT technology into the sludge treatment field, the intelligent filter press system can monitor the filter chamber pressure and filtrate turbidity in real time through sensors and dynamically adjust the process parameters. Meanwhile, the increase in calorific value of low-viscosity mud cakes (10%-15%) provides a new path for co-incineration power generation, further reducing the treatment cost.
Conclusion
The problems of "slow sludge feed, sticky sludge cake and clogging filter cloth" in plate and frame filter presses are essentially a systematic contradiction among the nature of the sludge, the working conditions of the equipment and the operation management. Through innovative technologies such as sludge efficiency enhancers, combined with refined equipment transformation and process optimization, enterprises can not only achieve efficient and stable operation, but also open a new chapter in the resource utilization of sludge, finding the best balance between environmental protection and benefits.