dynamic bed of hot particles 176 is spiraled about zone 158 in direction 164 that follows the pitch of blades 172 and the tangential feed from burner 188 as shown in fig5 the hot fluid 170 is fed to the blade zone between the blades 172 in the spaces 174 between blades 172 and the slant of blades 172 causes the fluid stream to have a similarly angular pitch as shown by the arrows above the array of blades 172 the particles fed to the device form dynamic bed 176 that travels in the direction of the fluid stream restrained by the geometry of the path of the peripheral blade zone 158 this is fully discussed in u s pat no 4 479 920 supra the fluid may be at a temperature higher than 1400 u00b0 c preferably at a temperature of from about 100 u00b0 c to about 1400 u00b0 c most preferably from about 150 u00b0 c to a temperature less than about 1400 u00b0 c measured by thermocouples 182 as the hot fluid flows around the particles suspending them and vaporizing petroleum adhering to the particles the fluid is generally combustion gases that emanate from the burner however the burner assembly that issues the hot gases in a spiral direction into the array of blades 172 may be fitted with injection sites downstream of the burner so that.