Process and apparatus for rapidly cracking a hydrocarbon feed followed by rapid separation of the cracked gases from the particulate solids including a cracking reactor having offset orifices and at least two opposed inlet nozzles in the same plane, an entrained bed heater having an array of fuel inlet nozzles in a plane at the bottom of the heater and axially directed air inlet nozzles, and a separator assembly for separating particulate solids from the gaseous products thus produced.