Device for holding a granular catalyst

Claim 1

In a converter for catalytic conversion of exhaust gas from internal combustion engines comprising a housing closed by an upper and a lower end plate, said upper end plate being provided near its periphery with a plurality of apertures for delivering purified gas to a gas outlet flanged to said housing's upper end, said lower end plate being centrally penetrated by a gas inlet being provided with an extension reaching into the interior of said housing; said housing being provided with an inner metal collar being secured substantially perpendicular to said upper end plate and within said extension of said gas inlet, respectively; an inner perforated tube being disposed slidably within the inner metal collar to accommodate axial relative movement between the inner perforated tube and the inner metal collar, said housing being further provided with an outer perforated tube, an outer metal collar and a middle metal collar spaced apart from one another and being secured substantially perpendicularly to said upper and to said lower end plate, respectively; the outer perforated tube being arranged slidably between the outer metal collar and the middle metal collar for accommodating relative axial movement between the outer perforated tube and the outer and middle metal collars; said outer perforated tube being slidable on said housing's inside wall by means of at least one spacer being secured substantially perpendicular to the periphery of said outer perforated tube to accommodate relative axial movement between the spacer and the housing; said inner and said outer perforated tube being spaced apart with respect to one another forming an annular space therebetween, and said annular space being filled by catalyst granules forming a bed; said outer perforated tube and said inner perforated tube, respectively, being made up of perforated sheet metal having a wire mesh secured to its catalyst-facing side; the improvement according to which said perforated sheet metal has a thickness of 0.7 to 2 mm, said wire mesh with meshes 0.5 to 2 mm wide being provided with openings equal to 10 to 90% of the width of the openings of said perforated sheet metal, and being produced from wires having a diameter of 0.5 to 1.5 mm.