Catalytic converter module

Abstract

A catalytic converter module ( 16 ) houses two catalyst units ( 26,36 ) which are geometrically arranged in a serial manner. An exhaust gas stream (X) is processed in two parallel sub-streams which follow respective paths: a first path (A) which passes through the first catalyst unit ( 26 ) and bypasses the second catalyst unit ( 36 ), and a second path (B) which bypasses the first catalyst unit ( 26 ) and passes through the second catalyst unit ( 36 ). This enables exploitation of a catalyst having an effective area larger than that of the module housing 17 thus allowing the module ( 16 ) to be incorporated conveniently into available volumes whilst maintaining a low back pressure.

1 . An exhaust stack for installation on a tractor, the exhaust stack comprising a catalytic converter module comprising an elongate housing having a length along which an exhaust stream passes between an inlet and an outlet, a first and a second catalyst unit arranged one above the other within the length of the housing and spaced from one another, and a passive exhaust stream dividing element which divides and directs the exhaust stream into two mutually exclusive paths, a first path which passes through the first catalyst unit and bypasses the second catalyst unit, and a second path which bypasses the first catalyst unit and passes through the second catalyst unit. 
     
     
         2 . An exhaust stack according to  claim 1 , wherein the first and second paths are mutually coaxial along the lengths of the first and second catalyst units. 
     
     
         3 . An exhaust stack according to  claim 2 , wherein the second path bypasses the first catalyst unit around the outside thereof and the first path bypasses the second catalyst unit around the outside thereof. 
     
     
         4 . An exhaust stack according to  claim 1 , wherein each catalyst unit is radially offset in mutually different directions from a longitudinal centre line of the elongate housing. 
     
     
         5 . An exhaust stack according to  claim 4 , wherein the respective radial offset of the catalyst units is in mutually opposing directions. 
     
     
         6 . An exhaust stack according to  claim 5 , wherein each catalyst unit abuts an inner surface of the elongate housing. 
     
     
         7 . An exhaust stack according to  claim 6 , wherein each catalyst unit is secured to the inner surface of the elongate housing. 
     
     
         8 . An exhaust stack according to  claim 5 , wherein at least one of the catalyst units are integrated into the elongate housing. 
     
     
         9 . An exhaust stack according to  claim 1 , wherein the dividing element is perforated and so that a portion of the exhaust stream passing through perforations is directed into one of the first and second paths. 
     
     
         10 . An exhaust stack according to  claim 9 , wherein the dividing element comprises a diverging cone-shaped element which covers the upstream end of the first catalyst unit so that the portion of the exhaust stream passing through the perforations is directed into the first path. 
     
     
         11 . An exhaust stack according to  claim 9 , wherein the dividing element comprises a converging cone-shaped element which covers the inlet so that the portion of the exhaust stream passing through the perforations is directed into the second path. 
     
     
         12 . An exhaust stack according to  claim 1 , wherein part of the second path is defined between outer walls of the first catalyst unit and inner walls of the housing. 
     
     
         13 . An exhaust stack according to  claim 1 , further comprising transition means to guide the first path from a downstream end of the first catalyst unit around the second catalyst unit and to guide the second path into an upstream end of the second catalyst unit. 
     
     
         14 . An exhaust stack according to  claim 13 , wherein the first and second paths are mutually coaxial along the lengths of the first and second catalyst units, and wherein the transition means comprises a conical collar connected to the downstream end of the first catalyst unit and has a profile at a downstream end which seals with the inner wall of the housing so as to direct the first path outwardly and around the second catalyst unit. 
     
     
         15 . An exhaust stack according to  claim 14 , wherein the transition means further comprises a cone-shaped cap which covers the upstream end of the second catalyst unit, and pipes connect holes within the walls of the collar and cap to direct the second path into the second catalyst unit. 
     
     
         16 . An exhaust stack according to  claim 13 , wherein each catalyst unit is radially offset in mutually different directions from a longitudinal centre line of the elongate housing, and wherein the transition means comprises an internal wall attached to the downstream end of the first catalyst unit and the upstream end of the second catalyst unit and provides a sealed barrier between the first and second paths. 
     
     
         17 . according to  claim 1 , further comprising combining means connected to the downstream end of the second catalyst unit which combines the first and second paths upstream of the outlet. 
     
     
         18 . An exhaust stack according to  claim 16 , wherein the combining means comprises a collar which has a profile at a downstream end which seals with the inner wall of the housing and comprises holes through which the second path passes. 
     
     
         19 . An exhaust stack according to  claim 1 , wherein the housing is substantially cylindrical. 
     
     
         20 . An exhaust stack according to  claim 1 , wherein the first and second catalyst units have a substantially equal volume. 
     
     
         21 . An exhaust stack according to  claim 1 , wherein the passive dividing element is designed so that the gas flow through each of the first and second paths is substantially equal. 
     
     
         22 . An exhaust stack according to  claim 1 , wherein each catalyst unit is radially offset in mutually different directions from longitudinal centre line if the elongate housing, and wherein the first catalyst unit is radially offset in a direction towards the rear of the tractor and the second catalyst unit is radially offset in a direction towards the front of the tractor. 
     
     
         23 . An exhaust stack according to  claim 1 , wherein the elongate housing is curved in the longitudinal direction. 
     
     
         24 - 33 . (canceled) 
     
     
         34 . An exhaust emissions treatment system comprising an internal combustion engine, an exhaust and an exhaust stack connected to the exhaust, the exhaust stack comprising a catalytic converter module comprising an elongate housing having a length along which an exhaust stream passes between an inlet and outlet, a first and second catalyst unit arranged one above the other within the length of the housing and spaced from one another, and a passive exhaust stream dividing element which divides and directs the exhaust stream into two mutually exclusive paths, a first path which passes through the first catalyst unit and bypasses the second catalyst unit, and a second path which bypasses the first catalyst unit and passes through the second catalyst unit. 
     
     
         35 . A system according to  claim 34 , wherein the engine is a diesel engine. 
     
     
         36 . A system according to  claim 35 , further comprising between the engine exhaust and exhaust stack, a particulates filter and reductant injection means. 
     
     
         37 . A system according to  claim 36 , further comprising a nitrogen oxide sensor located within the housing upstream of the outlet. 
     
     
         38 . A vehicle comprising an internal combustion engine, an exhaust and an exhaust stack connected to the exhaust, the exhaust stack comprising a catalytic converter module comprising an elongate housing having a length along which an exhaust stream passes between an inlet and an outlet, a first and second catalyst unit arranged one above the other within the length of the housing and spaced from one another, and a passive exhaust stream dividing element which divides and directs the exhaust stream into two mutually exclusive paths, a first path which passes through the first catalyst unit and bypasses the second catalyst unit, and a second path which bypasses the first catalyst unit and passes through the second catalyst unit. 
     
     
         39 . An agricultural tractor according to  claim 38   
     
     
         40 . A tractor according to  claim 39 , wherein the exhaust stack is substantially aligned with a cab front pillar so that a line-of-sight of the driver intersects both the pillar and stack.