. "However, the system is particularly well adapted for use in the Thermal Regenerative Cracking (TRC) process.As seen in FIG. 1, the composite solids quench boiler 2 of the invention is comprised essentially of a quench exchanger 4, a fluid bed-quench riser 6, a cyclone separator 8 with a solids return line 10 to the fluid bed-riser 6 and a line 36 forthe delivery of gas to the fluid bed-quench rise" . . . .