Dust removal from air in systems of pneumatic transport of loose raw materials

Abstract

A new method proven under production conditions is proposed for fine cleaning of air in systems of pneumatic transport of loose materials consisting of the use of filters made of porous metals. A production scheme is considered for a test-industrial unit and operating parameters are recommended.Bag filters are used for dust removal from air in pneumatic transport systems. However, these filters have marked disadvantages: the flat walls of the casing are designed for a pressure of 2.5 -3.0 kPa; valves for changing the direction of the air stream do not provide sufficient sealing; switching of the valve position and shaking of filter bags is accomplished from a mechanical drive which leads to rapid wear of the rubbing parts and breakdown of the filter operating regime; the method for feeding the dust and gas stream does not provide preliminary separation and it does not avoid stirring of dust settling in a bunker [1 -3]. The operating efficiency of these filters established, for example, in a pneumatic transporter for alumina from silo towers to a bunker in separate firing of chamotte for high-alumina articles, is 94%. The residual dust content after filters exceeds health standards.Dust removal by a wet method under these conditions is undesirable in view of the development of deposits that are difficult to remove and there is an insufficient degree of cleaning. Therefore there is interest in experimental verification of the possibility of using granular filters with a bonded structure, in particular filters made of porous metals [3] exhibiting high strength, insensitivity to sharp variations in pressure in the network, and high catching capacity [4 -6]. The layout of an experimental device of such a filter in a pneumatic transported for alumina from a silo tower into a bunker of shown in Fig. 1.The dust and gas stream is taken from the industrial gas conduit 1 and it enters cyclone 2 of the TsN-15 type used as the first cleaning stage. Dust captured in the cyclone is removed through bunker 3, and the dust and gas stream containing highly dispersed fractions of alumina enters the cylindrical body of the cermet filter 4 intended for fine gas cleaning. Direct feed of the dust and gas stream is possible from an industrial gas conduit into the filter through a bypass pipe. The filtering elements 5 used are six welded cylinders with a diameter 90 and a height 600 mm with a wall thickness of 5 mm made from nickel powder of the fraction 0.1 -0.2 mm. In order to reduce the degree of pore blockage