The main difference between diaphragm filter press and ordinary box filter press is that a layer of semi-automatic diaphragm filter press composite rubber plate elastic membrane diaphragm is installed between the filter plate and the filter cloth. During the operation, when the feeding is finished, the high-pressure fluid medium can be injected between the filter plate and the diaphragm. At this time, the whole diaphragm will bulge and press the filter cake, so as to realize the further dehydration of the filter cake, that is, press filtration. The first is positive pressure dehydration, also known as pulp dewatering, that is, a certain number of filter plates are closely arranged in a row under the action of strong mechanical force, and a filter chamber is formed between the filter plate surface and the filter plate surface. The filtering material is sent into the filter chamber under strong positive pressure. The solid part of the filter material entering the filter chamber is intercepted by the filter medium (such as filter cloth) to form filter cake, and the liquid part is discharged through the filter medium With the increase of positive pressure, solid-liquid separation is more thorough. However, considering the energy and cost, too high positive pressure is not cost-effective.