Abstract: A method for regulating the quantity of circulating solids in a circulating fluidized bed reactor system, whereby a solid flow/gas flow mixture leaving the fluidized bed reactor is fed tangentially into at least one cyclone separator for separation of the solid from the gas flow. The gas flow that is exhausted via a gas outflow opening of the cyclone separator. The solid that has been separated in the cyclone separator is reintroduced into the fluidized bed reactor via a recirculation line. A partial quantity of the solid flow quantity 'is diverted from the wall of the cyclone separator by means of a jet blast of at least one gaseous free jet formed by the nozzle into the gas outflow opening.