1,195,637. Heating fluidized beds. FALCONBRIDGE NICKEL MINES Ltd. 11 Sept., 1968 [14 Sept., 1967], No. 43117/68. Heading F4B. [Also in Division C1] A fluidized bed reactor is heated by the combustion of an explosive mixture of gases (e.g. a mixture of natural gas or propane and air) the gases being delivered by separate fans 20, 21 to a common header 18 outside the shell of the reactor, and feeding the mixture to the hearth of the reactor by conduits 22 having parts outside the shell so that the gaseous mixture is maintained below its ignition temperature. The arrangement is such that the velocity of delivery of the gases is above the flame propagation speed of the gaseous mixture, and restrictions may be formed in each conduit to increase the gas velocity. To prevent diffusion within the refractory hearth of the lining, the delivery end of each conduit may be surrounded by a sleeve embedded in the hearth and secured to the reactor shell. The conduits 22 are preferably made of soft metal, so that they can be crimped to cut off gas flow in the case of a blockage. The reactor is used for the production of metal oxides from high melting point chlorides, and the bed may be formed of particles of the same or a different oxide. To start up the reactor, the mixture of gases is ignited prior to feeding the bed particles to the reactor. Material, such as non-volatile chlorides, is fed pneumatically to the bottom of the bed through an inlet 15, or delivered through an inclined feed pipe 23. A solution of chloride, which may be the liquor from a pickling bath is sprayed on to the top of the bed from a pipe 24. Product granules are discharged from a pipe 16, undersized granules being returned through a feed pipe 27, and dust and hydrogen chloride are recovered from the waste gases. The reactor may be used to regenerate spent moulding acid. The gas delivery conduits may be capped, or may taper upwardly, or may diverge from a restricted bottom part, or a restriction may be formed at the base of the conduit by allowing it to project into the header (Fig. 7, not shown).