Filter Characteristics Research on Deep Dehydration of Sludge in Van Membrane Filter Press

With the large-scale construction of urban sewage treatment plants in China, the sludge produced has become a new source of environmental pollution, these sludge has high moisture content and other problems, so the deep dehydration of these sludge has become one of the key research topics. It is found that the sludge cake with low water content can be formed and the sludge reduction can be achieved after the municipal sludge is modified by medicine and the sludge is dehydrated by the compartment diaphragm filter press. In this paper, the sludge filtration process and filtration characteristics of the chamber diaphragm filter press are studied by the method of simulation and experiment. The main work is as follows:

1. Establish the physical model of a single filter chamber of the compartment diaphragm filter press, and establish the mathematical model of the solid-liquid two-phase flow field of sludge in a single filter chamber by using the standard 71-account model, mixed model and porous media model in the CFD simulation software Fluent. In order to simulate the supply conditions of solid-liquid two-phase flow, the model established above was used to simulate the velocity distribution, pressure distribution and concentration distribution of the solid-liquid two-phase flow field in a single filter chamber of the compartment diaphragm filter press. The pressure drop change law at both ends of the filter cake, the formation law of the filter cake and the basic flow law of the sludge two-phase flow in the filter chamber were obtained.

3. Simulation analysis under different filtration pressure. The velocity distribution in the filter chamber and the change of the water content of the filter cake under different filtration pressure were studied.

4. Simulation analysis under different feeding methods. The formation rule of filter cake and uniformity of filter cake were studied by comparing the feeding mode of sludge from the center of filter chamber with that from the upper part of filter chamber. The results showed that the feeding mode from the center of chamber filter press was better than that from the upper part of filter chamber.

5, Determine the best thickness of the chamber filter press. The water content of filter cake formed under different thickness of filter chamber and the mass production rate of filter cake per unit time were studied. It was found that the optimal thickness of filter chamber was 12mm.

6, the filter performance of the van diaphragm filter press was tested, and the experimental results were compared with the simulation results, and the maximum error was found to be less than 10%, verifying the correctness of the simulation results; The water content of the cake is further reduced by pressing and dewatering after the feed is terminated. At the same time, the process also finds a suitable starting time point for pressing. The research results of this paper can be used to guide the design and use of compartment diaphragm filter press.