Filter Press Working Principle

Filter press can be divided into plate and frame filter press and recessed chamber filter press. As a solid-liquid separation equipment, it has been used in industrial production for a long time. It has good separation effect and wide adaptability, especially for the separation of viscous and fine materials.

Structure principle

The structure of the filter press consists of three parts

1.Frame: the frame is the basic part of the filter press, with thrust plate and pressing head at both ends. The two sides are connected by girders, which are used to support the filter plate, filter frame and pressing plate.

A.Thrust plate: it is connected with the support, and one end of the filter press is located on the foundation. The middle of the thrust plate of the box filter press is the feeding hole, and there are four holes in the four corners. The upper two corners are the inlet of washing liquid or pressing gas, and the lower two corners are the outlet (subsurface flow structure or filtrate outlet).

B. Hold down plate: it is used to hold down the filter plate and filter frame, and the rollers on both sides are used to support the hold down plate rolling on the track of the girder.

C. Girder: it is a load-bearing component. According to the anti-corrosion requirements of the environment, it can be coated with rigid PVC, polypropylene, stainless steel or new anti-corrosion coating.

2, Pressing style: manual pressing, mechanical pressing, hydraulic pressing.

A.Manual pressing: screw mechanical jack is used to push the pressing plate to press the filter plate.

B. Mechanical pressing: the pressing mechanism is composed of motor (equipped with advanced overload protector), reducer, gear pair, screw rod and fixed nut. When pressing, the motor rotates forward to drive the reducer and gear pair to make the screw rod rotate in the fixed screw, and push the pressing plate to press the filter plate and filter frame. When the pressing force is larger and larger, the load current of the motor increases. When it reaches the maximum pressing force set by the protector, the motor cuts off the power supply and stops rotating. Because the screw rod and the fixed screw have reliable self-locking screw angle, it can reliably ensure the pressing state in the working process. When it returns, the motor reverses. When the pressing block on the pressing plate touches the travel switch, it retreats Back to stop.

C. Hydraulic pressing: the hydraulic pressing mechanism is composed of hydraulic station, oil cylinder, piston, piston rod and hydraulic station connected by piston rod and pressing plate, including motor, oil pump, relief valve (regulating pressure) reversing valve, pressure gauge, oil circuit and oil tank. When the hydraulic pressure is pressed mechanically, the hydraulic station supplies high-pressure oil, and the element cavity composed of oil cylinder and piston is full of oil. When the pressure is bigger than the friction resistance of the pressing plate, the pressing plate slowly presses the filter plate. When the pressing force reaches the pressure value set by the relief valve (indicated by the pointer of the pressure gauge), the filter plate, filter frame (plate frame type) or filter plate (recessed chamber type) are pressed, and the relief valve starts to press When unloading, cut off the power supply of the motor and complete the pressing action. When returning, the reversing valve reverses and the pressure oil enters the rod cavity of the oil cylinder. When the oil pressure can overcome the friction resistance of the pressing plate, the pressing plate begins to return. When the hydraulic pressing is automatic pressure maintaining, the pressing force is controlled by the electric contact pressure gauge. The upper limit pointer and lower limit pointer of the pressure gauge are set at the values required by the process. When the pressing force reaches the upper limit of the pressure gauge, the power supply is cut off and the oil pump stops supplying power. The pressing force decreases due to the internal and external leakage of the oil system. When the pressure gauge reaches the lower limit pointer, the power supply is connected When the pressure reaches the upper limit, the power supply is cut off and the oil pump stops supplying oil, so as to achieve the effect of ensuring the pressing force in the process of filtering materials.

3. Filtering structure

The filtering structure is composed of filter plate, filter frame, filter cloth and membrane squeezing. Both sides of the filter plate are covered by filter cloth. When membrane squeezing is needed, a group of filter plates is composed of membrane plate and chamber plate. The two sides of the base plate of the membrane plate are covered with rubber/PP diaphragm, the outer side of the diaphragm is covered with filter cloth, and the side plate is the ordinary filter plate. The solid particles are trapped in the filter chamber because their size is larger than the diameter of the filter medium (filter cloth), and the filtrate flows out from the outlet hole under the filter plate. When the filter cake needs to be pressed dry, in addition to diaphragm pressing, compressed air or steam can be introduced from the washing port, and the air flow can be used to wash away the moisture in the filter cake, so as to reduce the moisture content of the filter cake.

(1) Filtration mode: the way of filtrate outflow is opened type filtration and closed type filtration.

A. Open flow filtration: a water nozzle is installed on the bottom outlet hole of each filter plate, and the filtrate directly flows out from the water nozzle.

B. Closed flow filtration: the bottom of each filter plate is provided with a liquid outlet channel hole, and the liquid outlet holes of several filter plates are connected to form a liquid outlet channel, which is discharged by the pipe connected with the liquid outlet hole under the thrust plate.

(2) Washing method: when the filter cake needs washing, sometimes it needs one-way washing and two-way washing, while it needs one-way washing and two-way washing.

A. The open flow one-way washing is that the washing liquid enters successively from the washing liquid inlet hole of the thrust plate, passes through the filter cloth, then passes through the filter cake, and flows out from the non perforated filter plate. At this time, the liquid outlet nozzle of the perforated plate is in the closed state, and the liquid outlet nozzle of the non perforated plate is in the open state.

B. The open flow two-way washing is that the washing liquid is washed twice successively from the washing liquid inlet holes on both sides above the thrust plate, that is, the washing liquid is washed from one side first and then from the other side. The outlet of the washing liquid is diagonal with the inlet, so it is also called two-way cross washing.

C. The one-way flow of undercurrent polyester is that the washing liquid enters the perforated plate successively from the washing liquid inlet hole of the thrust plate, passes through the filter cloth, then passes through the filter cake, and flows out from the non perforated filter plate.

D. Undercurrent two-way washing is that the washing liquid is washed twice successively from the two washing liquid inlet holes on both sides above the stop plate, that is, the washing liquid is washed from one side first, and then from the other side. The outlet of the washing liquid is diagonal, so it is also called undercurrent two-way cross washing.

(3) Filter cloth: filter cloth is a kind of main filter medium. The selection and use of filter cloth plays a decisive role in the filtration effect. When selecting, appropriate filter cloth material and pore size should be selected according to the pH value of filter material, solid particle size and other factors, so as to ensure low filtration cost and high filtration efficiency. When using, filter cloth should be smooth without discount and pore size unblocked.

With the development of modern industry, the mineral resources are exhausted day by day, and the mined ore has been faced with the situation of “poor, fine and miscellaneous”. Therefore, people have to grind the ore finer and separate the “fine, mud and clay” materials from solid-liquid. Nowadays, in addition to the high requirements of energy saving and environmental protection, enterprises put forward higher and wider requirements for solid-liquid separation technology and equipment. Aiming at the social needs of mineral processing, metallurgy, petroleum, coal, chemical industry, food, environmental protection and other industries, the application of solid-liquid separation technology and equipment has been promoted, and the breadth and depth of its application field is still expanding.


Post time: Mar-24-2021