How to debug the filter press - sludge filter press

                          How to debug the filter press - sludge filter press

In recent years, urban sewage treatment plants have been constructed on a large scale, and the sludge produced in the process of sewage treatment has also become a new source of environmental pollution. If the treatment is not timely, it will cause secondary pollution. These sludges have high moisture content, odor, etc. The deep dehydration of these sludges has become one of the key treatment objects. The study found that after adding polyacrylamide [1] to the sludge of the sewage plant, it was fully stirred, mixed and tempered, and then the sludge was dehydrated with a diaphragm filter press [2], and the sludge filter cake with a moisture content of ≤ 60 could be achieved. , to achieve sludge reduction and harmlessness; and the diaphragm filter press has obvious advantages such as mature technology, low moisture content, and low energy consumption. Therefore, the diaphragm filter press is selected as the sewage dehydration equipment in this paper.

Sewage Treatment Automatic Filter Press Filters

The sewage treatment plant mentioned in this paper has a water treatment volume of 20,000 m3/h, and adopts coarse screen + fine screen and cyclone grit chamber + improved Carrousel 2000 oxidation ditch (selective zone, anaerobic zone, anoxic zone and aerobic zone ) + secondary settling tank + intermediate lifting tank + high density tank + cloth filter tank + ultraviolet disinfection tank + Pasteur metering tank to purify the sewage. 18918-2002) Class A standard. Sludge dewatering system consists of: sludge feeding screw pump, diaphragm filter press [3], squeeze water tank, squeeze water pump, flushing water tank, flushing water pump, blow-off gas storage tank, instrument gas storage tank, freeze dryer, air compressor machine, sludge hopper, electromagnetic flowmeter, pressure sensor, pneumatic valve, manual valve, etc. Thesludge feeding screw pump pumps the sludge into the membrane filter press to fill up the entire filter cavity.When it reaches 9Mpa, the equipment stops filtering, and the squeeze water pump injects the filling expansion (the medium is water) into the pressing system of the membrane filter press. 2 elastic membranes in the,The entire elastic membrane of the pressing system will bulge, making the pressure act on the filter cake. As the pressure continues to increase, the liquid in the filter cake that can pass through the filter cloth will be pressed out, so as to realize the secondary dehydration of the filter cake and make the filter cake The moisture content of the cake is lower. The automation control center is the brain of the entire sludge dewatering system, which controls the normal operation of the sludge dewatering system. Its components: stainless steel control cabinet, man-machine interface, PLC, frequency converter, components, switches, program software, etc. It has "manual" and "automatic" operation modes, and has remote monitoring and operation functions. During automatic operation, all commands and work steps of the membrane filter press will be operated according to the design parameters, and the automatic operation process is as follows:

1. Switch the rotary switch to the automatic position, press the "Start" button switch, the hydraulic pump station will start to compress the compression plate, and it will stop automatically when the set pressure is reached.

2. After the hydraulic pump station is started, the pneumatic feed valve will be automatically opened within 3 seconds. After the feed valve is opened, the sludge feed screw pump will start, and the sludge will be pumped into the filter press for filtration. When the set pressure is reached, the filter press enters the pressure maintaining state.

3. After holding the pressure, it enters the pressing state, the pressing pneumatic valve is opened, and medium water is injected into the pressing system for tympanic pressing. When the set pressing parameters are reached, the pressing pneumatic valve is automatically closed.

4. Open the blow-off pneumatic valve to empty the medium water in the filter plate.

5. After the filter press is finished, it enters the unloading step. The pull plate trolley pulls the filter plates apart one by one, and manually shovels the mud. After all the filter plates are unloaded, the pull plate trolley returns to its original position and enters the next cycle.

1. Before the commissioning starts, all equipment manufacturers in the sludge dewatering system need to be present, such as screw pumps, filter presses, dosing systems, electrical automation systems, compressed air systems and other relevant personnel, to conduct joint commissioning to ensure that the sludge dewatering system Successfully completed the commissioning and running work.

2. Debugging tools: wrench, screwdriver, multimeter, cutting machine, welding machine, level and other tools.

3. The electrical connection work should be done by an electrician. The wiring of power supply, motor, etc. is correct, and the direction of rotation is consistent with the arrow in the direction of rotation.

4. Before the operation of the sludge feeding screw pump, the pipeline in front of the pump must be cleaned, and the particles larger than 3mm must be cleaned.

5. Check the sludge feeding screw pump, diaphragm filter press, squeeze water tank, squeeze water pump, flushing water tank, flushing water pump, blow off gas storage tank, instrument gas storage tank, freeze dryer, air compressor, sludge hopper, Whether the electromagnetic flowmeter, pressure sensor, pneumatic valve and manual valve are installed completely and meet the design requirements.

6. Check all pipelines in the sludge dewatering system, whether the flanges and valve bolts are tight, and whether the welding points are intact, so as to avoid water leakage during operation.

7. Pressure vessels, pump, air compressor, etc. are all installed and in good condition.

8. Check whether the filter press frame is kept horizontal vertically and horizontally, and the vertically and horizontally must be kept horizontal.

9. Check whether the legs of the thrust plate of the diaphragm filter press are fixed, whether the legs of the machine base are in a state of free displacement, check whether the opening of the flap and the position of the pit are correct, and ensure that the edge of the pit does not block the opening of the flap. Check whether the filter press frame is kept horizontal vertically and horizontally, and the vertically and horizontally must be kept horizontal. Check whether the installation of each process pipeline is strictly in accordance with the construction drawings.

10. Check whether the installation quantity and arrangement sequence of the filter plates of the diaphragm filter press are correct, and arrange the filter plates strictly according to the specified process configuration, and do not arrange them randomly. Check whether the matching filter plate balance pads are installed. The installation condition of the filter cloth, the membrane distribution, and the pore size sequence are consistent, the single filter cloth is installed correctly, the cloth lock nut is fastened, and all the filter cloths are flat and without folds.

11. Check whether the hydraulic system is installed correctly, the oil brand name is accurately implemented, the oil pipe connection is accurate, and the high-pressure oil pipe connection is ensured to be beautiful and free from dead bends.

12. Check whether the small accessories in each part of the main body of the equipment are missing or damaged.

13. Check whether the voltage used by the electrical system matches the on-site voltage. Be sure to notify the on-site customer supervisor of the power supply before powering on to prevent electric shock accidents. When preparing to power on, ensure that all distribution switches in the electric cabinet are in the off state, and a professional electrician uses a multimeter to measure the U/V/W/N phase sequence of the incoming main line is correct, and it is necessary not to blindly power on.

14. Chemical preparation: according to the nature of the sewage, select the appropriate product model through a small test in advance to ensure that the chemical is sufficient; use neutral, low-hardness water that does not contain suspended substances and inorganic salts to prepare a 0.2% concentration of PAM solution 2 hours in advance, The prepared solution should not be stored for a long time, it is best to prepare it immediately after use, and the solution should not be stored for more than 24 hours.

(1) Check the whole machine

1. Inspection of the electrical system: whether the components are installed according to the design requirements, and whether the wiring of all wiring ports is correct.

2. Add about 300L of 25# anti-wear hydraulic oil to the hydraulic station. 3. Check the filter plate and check whether the filter cloth is installed properly. The filter cloth should be neat and free of wrinkles; check whether the filter plate faucet is installed correctly.

4. Check again whether the installation of all pipelines and valves is correct and reasonable, and it must be the same as the construction drawing.

5. Check whether the sludge in the sludge conditioning tank has been prepared and whether the air compressor gas has been prepared.

 (2) The hydraulic system debugs the jog motor, and the time is not allowed to exceed 3 seconds. Observe whether the steering is consistent with the steering marked on the plunger pump. When the equipment is not fed, first adjust the upper limit of the electric contact pressure gauge on the oil cylinder to 5MPa and the lower limit to 2MPa, and open the exhaust valve at the high pressure chamber to exhaust. Then discharge the filter plate, the offset of the filter plate should not exceed 5mm, otherwise the sealing surface of the filter plate will be reduced, causing damage to the filter plate and leakage of filtrate. Then adjust the upper limit of the electric contact pressure gauge on the oil cylinder to 10MPa, adjust the lower limit to 7MPa, and perform compaction to check the stress points of the filter press and whether there are any abnormalities on both sides of the main beam; finally, the electric contact on the oil cylinder The upper limit of the pressure gauge is adjusted to 14MPa, and the lower limit is adjusted to 12MPa for compaction; if there are no other abnormal conditions, the material can be fed.

(3) The filter part is debugged, the compression plate and the diaphragm plate are kept under pressure. Open the feed valve, start the screw pump for sludge feed, open all the faucets on the filter plate, and observe whether the filtrate of the faucet is discharged and whether the feed pressure increases, and control the pressure within the set value. Due to the capillary phenomenon of the filter cloth, the filtrate was slightly turbid at the beginning of filtration. After 4-5 minutes of filtration in the undercurrent model, the feed valve can be slowly opened, and the overflow valve can be opened. When the feed pressure rises to the set pressure, stop feeding when the filtrate flows out very little. Turn on the squeeze water pump to pump medium water into the squeeze system in the filter plate to squeeze out the water in the filter chamber. After the set pressing time is reached, open the pressure relief pneumatic valve to release the pressure of the squeeze system to 0Mpa. (4) Debugging of the washing stand Check whether the installation of the washing stand is correct, visually inspect the electrical connection is smooth and beautiful, check whether the signal connection is complete, the proximity switch limit of all washing systems, and manually measure the signal in advance to ensure accurate feedback, each step The steering of the motor is adjusted accurately, and the connection of each washing hose is visually inspected. The main beam of the washing must be horizontal, and the top screws of the middle legs are all fastened in place. The rear wrench is tightened and the forward and backward signal screws are tightened.

(5) Debugging of the flap. The opening limit and closing limit of the flap limit are installed accurately in advance and the hand measurement signal is correct. Check that the turning of the flap motor is correct, and the connection of the high-pressure oil pipes of the upper and lower flaps is correct. Start the motor to drive the flap. Adjust the closing position of the upper flap, adjust the closing limit position of the upper flap accurately and tighten it with a wrench, and then adjust the closing position of the lower flap so that the overlap between the two flaps does not exceed 1cm, and the most It is best to be in the shape of the largest roof ridge. Adjust the opening position after the closing position is adjusted. Reasonably adjust the limit position according to the size of the pit and fasten it. The principle of opening form should be as vertical as possible at 90°.

(6) Operation steps of automatic filtering mode In the automatic mode, press the [Program Start] button, and the filter press will automatically run in sequence according to the process sequence: loosening, pulling the pull plate, pressing, holding the pressure cycle and waiting. The details are as follows: 1. Release: "Release" is turned on, the motor of the pump station starts, the solenoid valve is released to open, the pressing plate retreats to the starting point, and enters "take plate" after reaching the starting point. 2. Plate pulling and unloading: "Plate taking" and "plate pulling" are automatically activated alternately for unloading. When unloading, according to the need, you can pull the "pause" to continue unloading, and then pull the "pause" again. After the unloading is completed, the trolley returns to the limit position of the trolley, stops the unloading action, and enters the "pressing step". 3. Compression: Start the hydraulic pump station, and the compression plate moves forward to the set position. When the set pressure is reached, the motor of the hydraulic pump station stops moving forward and keeps the pressure at the set value. At this time, the pneumatic sludge feeding screw pump Start feeding.

(7) Parameter setting The details of parameter setting are shown in the table.

(1) The sludge feeding screw pump cannot be started in automatic mode. Check the pressure sensor, automatic control system, and inverter for incorrect wiring or parameter settings, and troubleshoot the problem, and find out that it is caused by a problem with the inverter parameter setting. It is concluded that the parameters of screw pumps produced by different operating processes and different manufacturers are set differently by the same frequency converter.

(2) Dosing amount of flocculant polyacrylamide. The dosage of polyacrylamide should be added in an appropriate amount according to the sludge concentration. If the dosage is not enough, it cannot meet the pressure filtration requirements of the dehydrator, and the water content of the pressed mud cake is too high to form; if the dosage is too high, the effect will not be obvious. And cause the consumption to increase, affect the passing capacity of the filter press at the same time, affect the filter press effect and cause the blockage to the filter cloth. Add 0.2% PAM flocculant to 1m3 of excess sludge, and the optimal dosage is 0.05m3.

(3) The feed pressure rises to the set pressure, the feed is stopped and the feed pneumatic valve is closed, causing the valve cover of the check valve behind the sludge feed pump to break and the sludge to splash.

1. Reason 1: The upper limit of the feed pressure is set too high, and the quality of the check valve is defective. In this regard, the upper limit of the feed pressure is set to 0.9MPa, and the check valve is replaced. Conclusion: feed again and reach the set pressure, stop feeding and close the feed pneumatic valve, the valve cover of the check valve is still broken and the sludge splashes, the problem is not solved, look for other reasons;

   2. Reason 2: When the feed pressure reaches the upper limit, the feed pneumatic valve is closed, but the sludge feed pump does not stop immediately, causing the pressure to rise instantaneously, exceeding the pressure of the check valve, causing the valve cover of the check valve to rupture. For this, set the stop time of the sludge feed pump, when the stop signal is received, the sludge feed pump will stop running within 5S. It is concluded that feeding again reaches the set pressure, stops feeding and closes the feeding pneumatic valve, the valve cover of the check valve is not broken, and the problem is solved. During the commissioning period, all equipment manufacturers in the sludge dewatering system need to arrive at the site, and cooperate with the membrane filter press manufacturer to carry out system commissioning, and solve problems in a timely manner; when the equipment is running, it is not only necessary to consider the parameter settings of a single equipment, but the entire set of sludge dewatering The parameters of the system should be set reasonably to ensure the normal operation of the system. Strengthen the training of operators and management personnel, strengthen the operation and maintenance of equipment, keep in mind and master the intractable diseases that occur in the membrane filter press, analyze and deal with the problems in the first place, and ensure the normal operation of the sludge dewatering system. And use it properly to give full play to the role of the diaphragm filter press, the moisture content of the filter cake is ≤ 60%, responding to the reduction of sludge, and also laying a solid foundation for the company to achieve energy conservation and environmental protection goals.

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