Filtering gases contg. very fine particle e.g. of iron oxide - with precoat of coarse particles formed on external walls of filter sleeve to prevent silting up

摘要

Filtration of a gas contg. very small solid particles of microscopic and sub-microscopic size is described. The filter appts. comprises sleeve or pocket filters through which the gas passes, an inlet for the gas, an outlet for the purified gas and a hopper for the collection of the solid particles. Coarser particles are introduced in such a way that they form a layer on the external walls of the filter sleeves, preventing the silting up of the filter cloth by the small particles and the subsequent pressure loss across the filter. Used to filter the gas being emitted from a chamber in which such operations as the use of a blowpipe on steel ingots and the cutting a metal sheets with an oxygen flame are being carried out. These operations produce iron oxides of 0.01 to 5 mu particle size. The filter allows the evacuation of the gas into the atmos. The build-up of a precoat to prevent the silting up to the filter cloth reduces the loss of gas pressure across the filter.