Application of Ultrasonic Vibration Box in Cleaning Ceramic Filter

The ceramic filter is a new type of high-efficiency and energy-saving solid-liquid separation equipment, which is widely used in mining production processes. The ceramic filter plate is the core component of the ceramic filter. The composite porous ceramic is used as the new filter medium. The ceramic filter plate must be cleaned in time and effectively to exert the maximum production efficiency of the ceramic filter. The application of the ultrasonic cleaning vibration box in the ceramic filter realizes the cleaning effect that cannot be achieved by conventional cleaning equipment and solvents. The vibration box and pickling form a combined cleaning system, which fully ensures the smoothness of the ceramic plate's micropores and the high efficiency of filtration.

 

The main cleaning process of ceramic filter

The cleaning of ceramic filter plates can be divided into physical methods and chemical methods. Physical methods include backwash, ultrasonic cleaning; chemical methods include oxidizer, acid-base cleaning, etc. Generally, it is adopted according to the difference of the ceramic filter plate material, the type of dirt, and the degree of contamination.

1. Backwashing

The positive pressure of compressed air leaks out from the inside of the filter plate to remove the remaining filter cake and the fine particles in the micropores on the surface of the ceramic sheet caused by the gap between the filter plate and the scraper. If the backwash pressure is too high, the filter plate is easy to be damaged. If the backwash pressure is too small, the backwash power is insufficient, generally controlled at about 0.15MPa.

 

2. Pickling

The system is mainly composed of acid storage tanks, acid pumps, cleaning pipelines, etc. Generally, about 1% of dilute nitric acid is used to chemically clean and dissolve fine particles and scales. It is combined with ultrasonic cleaning to form a combined cleaning device to promote chemical Cooperating with physical action, the liquid is continuously emulsified and dispersed, and the rate of the chemical reaction is greatly promoted.

3. Ultrasonic cleaning

It including an ultrasonic generator, ultrasonic vibration box, and related connecting cables. In the combined cleaning stage after the ceramic filter is stopped, the ultrasonic generator sends out a high-frequency signal, which is converted into a high-frequency mechanical oscillation wave by the ultrasonic transducer and continuously impacts the ceramic filter plate, so that the dirt on the surface of the ceramic filter plate and the gap is rapid peel off, achieve the purpose of quickly dredging the micropores and purifying the surface of the filter plate.

 

In the normal dehydration operation of the ceramic filter, a large number of fine particles will remain on the surface and micropores of the ceramic filter plate after the vacuum slurry suction, dehydration drying, and discharge procedures. The filter plate will enter the backwash area for cleaning after each filtration cycle, but long-term operation only relying on backwashing cannot completely remove the fine calcium carbonate, calcium sulfate, and other chemicals. Therefore, after running for a period of time, it will automatically enter the combined cleaning process according to the present time. The ultrasonic vibration plate in the cleaning tank starts to work, and the attachments on the surface of the filter plate are mechanically removed. At the same time, an appropriate amount of dilute is added to the cleaning tank. The nitric acid and clean water are mixed and driven into the filter plate through the distribution head, and the clogging in the micropores of the filter plate is washed from the inside to the outside. Through the interaction of ultrasonic cleaning, chemical cleaning, and backflushing water cleaning, the high efficiency of subsequent filtration operations is guaranteed, and the filter plate is restored to its pre-filtration performance. Generally, there are two to four ultrasonic cleaning and chemical cleaning for about half an hour every day as needed.

 

Ultrasonic cleaning of the ceramic filter plate

The ultrasonic cleaning system of the ceramic filter is mainly composed of an ultrasonic power supply, an ultrasonic vibration box, and accessory cables. The vibration box is installed in the cleaning tank on both sides of the filter plate. The bottom is the outlet from a hollow tube, and the power cord is connected to the ultrasonic power generator from the tube.  The nozzle has a silk thread, which is fixed and sealed with a nut. When cleaning, there is a certain level of water inside the tank. When the ultrasonic vibration plate is working, the liquid is vibrated to generate tens of thousands of tiny vacuum bubbles. These bubbles are generated and grown in the negative pressure zone formed by the longitudinal propagation of the ultrasonic wave. The positive pressure zone closes rapidly. In this process called the cavitation effect, the small bubbles can generate instantaneous high pressure exceeding atmospheric pressure when they are closed. The instantaneous high pressure continuously generated impacts the surface of the ceramic plate like a series of small explosions. The dirt on the surface of the ceramic plate and the gap can be quickly peeled off, and the ceramic filter plate that needs to be cleaned can be purified and dredged. Ultrasonic cleaning and chemical cleaning cooperate to dissolve some solid matter attached to the ceramic filter plate and completely separate it from the filter medium. Nevertheless, many factors affect the cleaning effect of the ultrasonic vibration box, mainly including:

1. Frequency range

Generally, low frequency is used for dirt that is difficult to clean and has larger particles; high frequency is suitable for delicate cleaning occasions. Therefore, according to the different ore properties and the pollution of the ceramic plate, the frequency generated by the ultrasonic generator can be adjusted appropriately to ensure the best cleaning effect of the filter plate.

 

2. Power density

Depending on the frequency, it is generally chosen to be around 0.5-1.5W/cm2. If the power is too small, the cleaning will not be clean, while the cleaning effect is good if the power is too large, but it may damage the ceramic filter plate.

 

3. The temperature of the cleaning fluid

Generally, at 20 to 50 degrees Celsius, the cavitation effect is best. The too-high liquid temperature will cause the generated bubbles to interrupt the sound wave, but weaken the ultrasonic wave, and may cause damage to the vibration box.

 

4. The viscosity of the cleaning fluid

Choose a clear liquid with low viscosity. A cleaning solution that is turbid or contains too much-suspended matter will absorb the energy of ultrasonic waves and reduce the effect of ultrasonic waves.

 

Installation method of ultrasonic cleaning vibration box

According to different installation forms, ultrasonic cleaning boxes can be divided into two types: plug-in type and lifting type.

 

1. Plug-in ultrasonic cleaning vibration box

The plug-in ultrasonic cleaning vibration box is composed of a vibration box, screw rod, nut, etc. The screw rod is welded on the vibration box, and the vibration box is installed between two ceramic filter plates. The screw rod is inserted into the fixed short connection in the groove body and is fixed by two upper and lower nuts. The installation height of the screw rod is adjusted to ensure that the vibration box is located on the running track of the ceramic filter plate. In the joint cleaning stage, the ceramic filter plate makes a low-speed circular motion with the rotation of the rotor and passes through the working area of the ultrasonic vibration box in turn. The mechanical wave emitted by the ultrasonic vibration box is transmitted into the liquid and acts on the ceramic filter plate through the liquid to complete the cleaning work.

 

2. Lifting ultrasonic cleaning vibration box

The lifting device is composed of an ultrasonic vibration box, a lifting rod, a lifting device, and upper and lower limit switches, etc. The vibration box and the lifting rod are rigidly connected. When the ceramic filter is in normal operation, the lifting device drives the lifting rod and the ultrasonic vibration box to rise and stops at the upper limit switch, and the vibration box is lifted and kept above the liquid level of the tank. When parking and entering the combined cleaning phase, the lifting device drives the lifting rod and the ultrasonic vibration box to descend and stops at the lower limit switch, and the vibration box enters and remains below the liquid level of the cleaning liquid. At this time, the ultrasonic starts to work, the ceramic filter plate moves in a low-speed circular motion with the rotation of the rotor, and sequentially passes through the working area of the ultrasonic vibration box. The ultrasonic wave penetrates the fine gaps and small holes, and the inside of the complex-shaped micropores of the ceramic filter plate is cleaned. With the cyclic rotation of the rotor, the surface and micropores of the ceramic filter plate are gradually cleaned. After cleaning, the ceramic filter enters the next normal start-up procedure, and the ultrasonic vibration box is raised above the liquid level of the tank again.

 

It is not difficult to see from the above structure that the plug-in ultrasonic vibrating box is submerged below the liquid level for a long time, and many materials filtered by the ceramic filter are very corrosive, which may cause cracks in the vibrating box shell and liquid penetration into the box. Causes short circuit or overload of the electrical circuit. Besides, the vibration box is fixed in the slurry tank, which increases the difficulty of disassembly and maintenance. The fixed installation position itself makes the tank form many dead corners, which is not easy to wash. The lift-type ultrasonic vibration box has obvious advantages. It only enters the cleaning tank when needed. At the same time, it is very convenient to replace, disassemble, and rinse, which greatly improves the stability and reliability of the ceramic filter system. However, the complex structure of the lifting ultrasonic vibration box and the higher degree of automation will inevitably lead to an increase in the manufacturing cost of the ceramic filter. Enterprises should choose their own ultrasonic cleaning program according to their own conditions.