Frame elements for containing monoliths

An element frame for holding monoliths containing catalysts in a flow of exhaust gases from a combustion source, the element frame comprising:

• two pairs of opposing walls, wherein the walls form a rectangular or square shape,
• an interior formed by the two pairs of opposing element frame walls,
• an inlet end and an outlet end through which the flow of exhaust gases can pass,
• at least one locking element,
• at least one mat, and
• at least one monolith comprising
• a monolith inlet and a monolith outlet through which the flow of exhaust gases can pass,
• four sides, and
• a plurality of catalyst cells characterized as flow passages through which the flow of exhaust gases can pass and containing at least one catalyst effective in reducing the concentration of one or more gases in the exhaust gas,
• wherein the at least one monolith is positioned within the interior formed by the two pairs of opposing frame element walls in such a way as to allow passage of the flow of exhaust gases into the inlet end of the element frame and the monolith inlet, through the plurality of catalyst cells, and out of the monolith outlet and the outlet end of the element frame,
• wherein the at least one mat and the at least one monolith are positioned in the interior of the element frame so that there is at least one mat between the monolith and each adjacent wall,
• wherein each locking element extends across the inlet end or outlet end of the element frame and being connected to two opposite sides of the element frame, and
• wherein:
• (a) parts of the element frame at the inlet end and outlet end of the element frame are bent toward the interior of the element frame and comprise one or more cut-outs;
• and/or
• (b) the locking elements comprise one or more cut-outs,
• such that the one or more cut-outs of the element frame and/or the at least one locking element reduce the surface area of the respective element frame and/or the at least one locking element that would otherwise block the flow of exhaust gas, such that the one or more cut-outs increases the number of catalyst cells in the at least one monolith that are directly exposed to the flow of exhaust gas.