Simulation And Experiment Study On Purify Performance Of Surface Filter Media Of Bag Filters

Particles deposit continuously on the surface of filter or inside filter media during dust filtration process and may cause filter clogging if they are not removed timely. The pressure drop of filtration and energy consumption would increase or even the filtration process can not conduct if the filter media are completely clogged. The properties of filter media and operation paramers are very important to the dust removal.The objectives of this study were: 1) to find way to enhance dust particles collection efficiency of filter media, 2) to optimize filtration process parameters to reduce pressure drop of filtration and 3) to develop new filter media. To achieve these goals, theoretical calculations, experimental examinations and simulation were carried out. The main research work and findings are as follows:(1) A mathematic model describing dust concentration change with time and space was established, based on the law of mass conservation in a bag house. The general theoretical solutions of collection efficiency were obtained on the conditions of steady or non-steady filtration processes. It is found that the logarithm formula was only a specific solution of the mathematical equation. Experimental results of this work were in agreement with the theoretical calculations.(2) The factors affecting filtration were examined and a statistical model to predict collection efficiency of filter was put forward, which is a useful tool for calculation of overall removal efficiency of dust.(3) An empirical model and a theoretical model describing pressure drop of filtration on the conditions of steady or non-steady filtration processes have also been established in this work. Using experimental set-up of filtration performance measurement, we set up the filtration performance database of filter media made in China.(4) The visual simulation program of particle deposition on filtration media has been developed, which can be used to choose or design filter media for the interest of reducing laboratory work.(5) The correlations of dust collection capacity of fiber and fiber diameters as well as fiber intervals have been investigated by means of the visual simulation program. Based on the simulation results of collection efficiency and pressure drop of filtration for different particle diameters and fiber diameters, the novel gradient filter media were developed.(6) Using fractural theory, we studied the geometry characteristics of dust cake for single-disperse and multi- disperse dust particles. The fractural dimension can be used to describe complicated shape of dust cake. In addition, it can also be used to study the relationship of porosity and dust diameter. The fractural dimension could ne used to control filtration processes.(7) The novel gradient filtration media have been utilized in the dust removal of power plants burning coal successfully, showing better filtration performances (higher efficiency and lower pressure drop than traditional membrane-covered filter media).