A cyclonic reactor vessel comprising: a shell; a primary cyclonic separation device disposed within the shell and having an outlet; a plurality of secondary cyclones, said secondary cyclones being disposed within the shell, and each of said secondary cyclones having a body, an inlet and an outlet; wherein the outlet of the primary cyclonic separation device is connected to the inlet of at least one secondary cyclone such that a fluid stream may flow from the outlet of the primary cyclonic separation device into the inlet of the at least one secondary cyclone; a first plenum having a skirt and a floor forming a sealed annular chamber within the shell, wherein the first plenum is supported within the shell by attachment to the shell; a second plenum having an outlet tube for removing gasses from within the shell, a skirt and a floor and having a smaller volume than a volume of the first plenum; and a secondary cyclone support system comprising at least one mechanism selected from the group consisting of: (a) attachment of the outlet tube of each secondary cyclone to the skirt and/or floor of the first plenum and (b) a first set of hanger straps extending from the first plenum skirt and/or first plenum floor and/or secondary cyclone outlet pipe to the body of each secondary cyclone, wherein the first set of hanger straps are substantially vertically placed within the shell such that the angle between the first set of hanger straps and a plumb line suspended from a point of attachment of the first set of hanger straps to the first plenum is equal to or less than 30°; and wherein the outlets of the plurality of secondary cyclones are fluidly connected to the second plenum. a shell; a primary cyclonic separation device disposed within the shell and having an outlet; a plurality of secondary cyclones, said secondary cyclones being disposed within the shell, and each of said secondary cyclones having a body, an inlet and an outlet; wherein the outlet of the primary cyclonic separation device is connected to the inlet of at least one secondary cyclone such that a fluid stream may flow from the outlet of the primary cyclonic separation device into the inlet of the at least one secondary cyclone; a first plenum having a skirt and a floor forming a sealed annular chamber within the shell, wherein the first plenum is supported within the shell by attachment to the shell; a second plenum having an outlet tube for removing gasses from within the shell, a skirt and a floor and having a smaller volume than a volume of the first plenum; and a secondary cyclone support system comprising at least one mechanism selected from the group consisting of: (a) attachment of the outlet tube of each secondary cyclone to the skirt and/or floor of the first plenum and (b) a first set of hanger straps extending from the first plenum skirt and/or first plenum floor and/or secondary cyclone outlet pipe to the body of each secondary cyclone, wherein the first set of hanger straps are substantially vertically placed within the shell such that the angle between the first set of hanger straps and a plumb line suspended from a point of attachment of the first set of hanger straps to the first plenum is equal to or less than 30°; and wherein the outlets of the plurality of secondary cyclones are fluidly connected to the second plenum.