Structural principle

The structure of the press filter is composed of three parts:

1. Frame: refers to the basic parts of the press filter and both ends are the thrust plate and holddown joint which connects with the beams on both sides. The beams are used to support the filter plate, filter frame and holddown plate.

a. Thrust plate: connects with the support and place one end of the press filter on the foundation. Feeding port is reserved in the middle of the thrust plate with four holes on the four angles, among which, the two holes in the upper side are the inlet of the washing liquid or the press gas while the two in the lower side are either the underflow structure or the filtrate outlet.

b. Holddown plate: used to press the filter plate and filter frame while the roller wheels on both sides are used to support the press plate to roll on the track of the beam.

c. Beam: refers to the bearing member. Rigid poly vinyl hydrogen, polypropylene, stainless steel cladding and new type anti-corrosion coating etc. can be selected according to the anti-corrosion environment of the environment used.

2. Press mechanism: manual press, machinery press and hydraulic press.

a. Manual press: means that the spiral machinery jack drives the press plate to press the filter plate.

b. Machinery press: press mechanism is composed of overload protector reducer, counter gear, lead screw and the fixed screw. When pressing tightly, the motor will be rotate on a clockwise basis, driving the reducer and counter gear to make the screw rotate in the fixed screw pair and promoting the press plate to press the filter plate and filter frame. When the pressing force is bigger and bigger, the load current of the motor will increase; when it increases to the current value set by the protector, it will reach the maximum pressing force. The motor will cut off the power and stop rotating. Since the screw and screw pair owns the reliable self-lock spiral angle, it is able to guarantee the pressing status during the working process. When returning, the motor will rotate on a reverse basis and it will return and stop when the lock block in the press plate contacts the stroke switch.

c. Hydraulic press: the composition of the hydraulic press mechanism consists of the hydraulic station, cylinder, piston, piston rod and the Haff flange card connected by the piston rod and the press plate. The structural composition of the hydraulic station is: motor, oil pump, selector valve of the pressure adjusting of the overflow valve, pressure meter, oil circuit and oil tank. When the hydraulic press mechanism presses, the hydraulic station is responsible for supplying high-pressure oil while the piston cavity formed by the cylinder and piston fills with the oil. When the pressure is larger than the friction resistance operated in the press plate, the press plate will slowly press the filter plate; when the pressing force reach the pressure value set by the overflow valve and displayed by the indicator of the pressure meter, filter plate, frame and plate of the filter frame and the filter plate van-type will be pressed tightly and the overflow valve will start unloading. At this time, the motor power will be cut off and the pressing action is finished. When returning, the selector valve will change the direction and the pressure oil comes into the rod end chamber of the cylinder. When the oil pressure is able to overcome the friction resistance of the press plate, the pressure plate will start to return. When the hydraulic press belongs to the automatic pressure protection, the pressing force is controlled by the pressure meter in the electrical contacts. Set the pointer of the upper and lower limit to the value requested by the process. When the pressing force reaches the upper limit of the pressure meter, the power will be cut off and the oil pump will stop supplying oil. Since the oil circuit system probably produces inner and outer leakage, resulting in the decrease of the pressing force, when it reduces to the pointer of the lower limit of the pressure meter, the power will be connected and the oil pump will start supplying oil. When the pressure reaches the upper limit, the power will be cut off and the oil pump will stop supplying oil. The circulation in such type will guarantee the effect of the pressing force during the process of filtering the materials.

 Filtering mechanism

The filtering mechanism consists of the filter plate, filter frame, filter cloth and the press diaphragm. Filter cloth is used to cover on both sides of the filter plate. When the pressure diaphragm needs allocating, one group of filter plate includes the diaphragm plate and the side plate. Rubber diaphragm is used to cover on both sides of the substrate of the diaphragm plate while filter cloth is covered outside the diaphragm. The side plate belongs to the common filter plate. The materials come into different filter rooms by means of the feeding hole of the thrust plate and the solid particles are closed in the filter room since diameter is larger than the aperture of the filter media (filter cloth). The filtrate outflows from the outflow liquid hole at the lower part of the filter plate. When the filter cake needs draining, beside the diaphragm press is used, compressed air or steam are adopted to enter from the washing port. The flow eliminates the moisture in the filter cake to reduce the moisture content in it.

1. Filter mode: the outflow mode of the filtrate includes the free current and undercurrent filter.

a. Free current: nozzle is established in the outflow liquid hole at the lower part of each filter plate and the filtrate directly outflows from the nozzle.

b. Undercurrent: outflow liquid channel hole is established in the lower part of each filter plate. the outflow liquid hole of several filter plats connect one outflow liquid channel and discharged by the pipelines connected by the outflow liquid holes in the lower part of the thrust plate.

2. Washing way: when the filter cake needs washing, there is free current bidirectional washing and single washing or undercurrent bidirectional washing and single washing.

a. Single washing of the free current is, the washing liquid enters from the washing hole of the thrust plate, runs through the filter cloth and filters cake, and finally outflows from the non-hole filter plate. at this time, the outflow liquid nozzle of the hole plate will be in closed status while that of the non-hole plate will be in the start status.

b. The bidirectional washing of the free current is washing for twice is carried out after the washing liquid comes into the washing inlet hole on both sides from the upper side of the thrust plate, that means the washing liquid washes on one side following with the other. The washing inlet and outlet are in diagonal direction, therefore, it is also called bidirectional cross washing.

c. Single washing of the undercurrent is, the washing liquid enters the hole plate from the washing inlet hole of the thrust plate, runs through the filter cloth and filter cake, and finally outflows from the non-hole plate.

d. Bidirectional washing of the undercurrent means the washing liquid carries out washing for twice after entering the two washing inlets from both sides of the upper of the thrust plate, which means wash is executed from one side first following with the other. The washing inlet and outlet are in diagonal direction, therefore, it is also called bidirectional cross washing.

3. Filter cloth: filter cloth mainly refers to the filter media. The selection and application of the filter cloth exerts a decisive function for the filtering effect. The proper materials and aperture of the filter cloth shall be selected according to the PH value of the filter materials, solid particle and other factors so as to guarantee low filtering cost and high filtering efficiency. Under aplication, the filter cloth shall be ensured evenly with smooth aperture and without unfolding.

 Filter cloth, materials and performance parameter