horizontal tee joint interconnection in fig1 a riser reactor 1 is shown having a relatively open perpendicular communication with a relatively horizontal tee joint discharge conduit 2 fluid and solid materials pass upwardly through the riser reactor on either side of riser reactor 3a and 3b and pass into open communication with horizontal tee joint horizontal tube 2 having sides 4a and 4b while it is shown that side 4a and 4b interconnect with side 3b and 3c at a substantially perpendicular relationship this angle may actually be an acute angle of between 89 u00b0 and 75 u00b0 with respect to a vertical axis of riser reactor tube 1 a large portion of the fluid and solid material in a conventional riser reactor equipped with a horizontal tee joint interconnection flows into open communication with the horizontal tee joint conduit a small but important portion will pass upwardly and contact imperforate top 3d and descend as a backflow alongside either conduits 3e or 3c this backflow along sidewall 3e 3a results in an undue and undesirable pressure drop in the riser reactor thereby preventing upflow of the fluid and solid materials the solution to this backflow problem i e a reduction in the pressure drop in the riser reactor 1 is placement of fluid injection means 5 which preferably penetrates sidewall 3e 3a or is at least situated juxtaposed thereto the fluid injection means can be a nozzle bank of nozzles valves fog nozzle multiple perforations or contoured aperatures with compressed inert fluid either vapor or liquid being forced therethrough the fluidizatin means for admission of a vapor or fluid is preferably a bank of retrofitted gas injection nozzles in intercommunication with fluid access reservoir 7 via supply conduit 9 the fluid injection means.