The application potential of diaphragm filter press in the field of sludge treatment is huge

First, the composition of the filter press

The filter press belongs to the filtration and separation machinery, which is the process equipment to separate the liquid and solid in the suspension. The working principle of the filter press is to use the pressure pump to inject the suspension slurry into the hydraulic system by the vertical arrangement of multiple filter plates. In the multiple closed filter chambers formed by pressing, a pressure difference is formed between the two sides of the filter cloth, and the liquid in the filter chamber is discharged out of the filter press through the filter cloth adjacent to the filter plate along the filtrate confluence channel, and the dehydrated solid impurities Then it is trapped in the filter chamber to form a filter cake, and the adjacent filter plates are separated by a plate pulling machine. The filter cake in each filter chamber falls off under the action of gravity or a rapping device to realize the separation of solid phase and liquid phase. The filter is composed of frame part, pull plate part, filter part, hydraulic part and electrical part.

2. Classification of filter presses

Because filter presses are widely used in many industries such as environmental protection, minerals and processing, chemical industry, food, medicine, etc., and are affected by different sites, different operating environments, and different customer requirements for filtration effect, filtration area, and filter cake moisture content, resulting in There are many product models and parameters of the filter press, so it is difficult to achieve standardized production and measurement.

According to industry standards, filter presses can be divided into ultra-large, large, medium and small filter presses according to the size of the filtration area of ​​a single filter plate; According to the filter plate pressing method, it can be divided into manual pressing, mechanical pressing, hydraulic pressing and automatic filter press.

3, the development history of filter press

According to the different filter plates, the filter press has experienced three stages: plate and frame filter press, box filter press and diaphragm filter press. The filter press emerged in the 1980s. This filter is still in use today.

In the 1990s, reinforced polypropylene filter plates appeared in China, which mainly solved the problems of corrosion resistance, high temperature resistance and high pressure resistance of the filter plates. The reinforced polypropylene diaphragm filter plates are divided into combined type and integral fusion welding type, and integral fusion welding type. The diaphragm filter plate has a higher pressing pressure and a longer service life. China began to enter the stage of mass use in 2005. At present, the mainstream product in the filter press market is the diaphragm filter press.

4, the technical characteristics of the diaphragm filter press

When dealing with fine-grained materials, the diaphragm filter press not only has a good retention effect, but also can obtain a lower moisture content of the filter cake. Due to the high filtration pressure of the diaphragm filter press, a dense filter cloth can be selected, so that the filter cloth can retain The filter cake layer can be filtered to obtain a clear filtrate and a filter cake with low moisture content, which is difficult to achieve with vacuum filters, belt presses and centrifuges.

The filtration stage of the diaphragm filter press is the pump pressure differential filtration. The pump pressure differential filtration is positive pressure, and the realized pressure differential can be as high as 4MPa. Compared with the negative pressure filtration of the vacuum filter of 0.1MPa, the filtration pressure is large, and the Low consumption; the second stage of the filtration of the diaphragm filter press is the diaphragm pressing filtration. The material after the first filtration is subjected to 2 diaphragm pressing, and the residual liquid is squeezed out by squeezing the volume of the filter chamber to realize the deep separation of solid and liquid.

5. Application fields and potential of diaphragm filter press

Various filter presses and supporting equipment are widely used in environmental protection (municipal domestic sewage sludge, industrial wastewater sludge, tap water sludge and river, lake and reservoir dredging sludge treatment), minerals and processing (non-ferrous metals, non-metallic ores, metal tailings) ), chemical, food and pharmaceutical fields.

According to Weber Consulting, at present, in the field of sludge dewatering, the membrane filter press can reduce the moisture content of sludge to 40-58% at one time, and the dewatering effect is similar to that of the chamber filter press (with a moisture content of 75-80%). Compared with the centrifugal press (75-83 percent moisture content) and the centrifuge (75-80 percent moisture content), the dewatered sludge treated by the diaphragm filter press is comparable to the belt press and centrifuge. Compared with the dewatered sludge after treatment, the volume is reduced by more than 50%, and the dewatered sludge is solid, which reduces the stacking, the "secondary pollution" of the leachate during transportation, and effectively realizes the sludge reduction. With the improvement of sludge treatment and disposal requirements, sludge treatment will become one of the potential application fields of diaphragm filter presses.