Membrance Filter Press

In 1853, the filter press was invented in England for oil filtration. The main development of filter press technology began in the middle of the 20th century. In 1958, the Japanese successfully developed the world's first automatic horizontal filter press to improve the removal efficiency of filter cake and reduce the moisture content of filter cake. Later, a diaphragm filter plate filter press was developed in Japan to reduce the moisture in the filter cake. The advantages of diaphragm filter press increase the opportunities of filter press in various industrial applications. Filter presses were often used to extract sugar from sugar beets and sugarcane and to dry pulp in the late 19th century and beyond. Now, the world's largest filter press manufacturing base and application market are in China.

The basic types of filter press include: plate and frame filter press, chamber filter press, membrane filter press, etc. According to the different compression methods and automation, the types of filter presses include: program-controlled automatic plate pulling filter press, hydraulic compression filter press, mechanical compression filter press, Jack compression filter press, manual screw compression filter press, etc. If different filter plate materials are considered, the filter press can also be divided into PP filter plate filter press, cast iron filter plate filter press and stainless steel filter plate filter press.

Filter press usually uses filter cloth as filter medium, which is made of polypropylene filter cloth, non-woven fabric, cotton cloth, etc. filter paper board, cotton pulp board or filter membrane can also be used as filter medium as required. Generally, the cake thickness of plate and frame filter press can reach 50 mm, but in extreme cases, it can be increased to 200 mm. The box filter press (concave filter press) can form a filter cake with a thickness of 30-40mm.

Before using the filter press for filtration, if the solid suspension has precipitated, the mixed liquid needs to be pretreated, which can improve the performance of the filter press because it increases the porosity of the filter cake, thus speeding up the filtration speed. The size of floc can be controlled by changing temperature, concentration and pH value. In addition, if the filter cake is impermeable and not conducive to the flow of filtrate, filter aids can be added in the pretreatment process to increase the porosity of the filter cake, reduce the resistance of the filter cake and obtain a thicker filter cake. However, the filter aid needs to be able to be removed from the filter cake by physical or chemical treatment. A common filter aid is diatomite, with a porosity of 0.85.