Abstract: A bed comprising fluidized particulate material and having a resistivity (.rho.) between 10.sup..sup.-1 and 10 ohm m is heated in a reaction chamber by means of an induction coil surrounding said chamber. The heat is generated in the bed itself by passing an alternating current through said coil. There is maintained between the least cross dimension (d) of the bed area and the penetration depth (.delta.) of the inductive field a ratio determined by the relationshipd/.delta. = k (0.54 - 0.35 .sup.. 10 log .rho.)where k is a numerical value between 0.2 and 1.5.

Abstract: A bed of coke or other material having a resistivity within the range of between 10.sup..sup.-4 and 10 ohm m is heated in a reaction chamber by means of an induction coil surrounding said chamber. The heat is generated in the bed itself by passing through said coil an alternating current having a frequency of at most ten times the mains frequency. There is maintained between the least cross dimension (d) of the bed area and the penetration depth (.delta.) of the inductive field a ratio determined by the relationship ##EQU1## WHERE K IS A NUMERICAL VALUE BETWEEN 1.1 AND 1.5.