NOVELTY - The process comprises feeding a deposition gas comprising hydrogen and a silicon monomer into an internal region such as a heating zone of a fluidized bed reactor (105), and concurrently feeding an etching gas into the heating zone of the reactor through a surrounding region. The surrounding region is present between the internal region and a wall of the fluidized bed reactor. The deposition gas is derived from a vent gas stream (104) from a Siemens reactor (102). The vent gas stream from the Siemens reactor is separated to form a portion of the deposition gas and etching gas.    USE - The process is useful for the production of polycrystalline silicon.    ADVANTAGE - The process is capable of efficiently producing the polycrystalline silicon with less consumption of energy and minimized by-products, and prevents the silicon deposits from forming on the walls of the fluidized bed reactor.    DETAILED DESCRIPTION - The process comprises feeding a deposition gas comprising hydrogen and a silicon monomer into an internal region such as a heating zone of a fluidized bed reactor (105), and concurrently feeding an etching gas into the heating zone of the reactor through a surrounding region. The surrounding region is present between the internal region and a wall of the fluidized bed reactor. The deposition gas is derived from a vent gas stream (104) from a Siemens reactor (102). The vent gas stream from the Siemens reactor is separated to form a portion of the deposition gas and a portion of the etching gas, after leaving the Siemens reactor and before entering the fluidized bed reactor. The deposition gas is supplemented with an additional chlorosilane species. The silicon produced by the Siemens reactors is used for integrated circuits and/or solar cells. The vent gas stream comprises trichlorosilane, silicon tetrachloride, hydrogen, hydrochloric acid and silicon powder. Silicon powder is removed from the vent gas stream before feeding the vent gas stream as the deposition gas to the fluidized bed reactor. The process further comprises feeding a second vent gas stream from the fluidized bed reactor to a recovery system, recovering silicon tetrachloride, converting the silicon tetrachloride to trichlorosilane, and feeding the trichlorosilane to the Siemens reactor or the fluidized bed reactor. An INDEPENDENT CLAIM is included for a fluidized bed reactor.    DESCRIPTION OF DRAWING(S) - The figure shows a flow diagram of a process for the production of polycrystalline silicon.    Siemens feed gas stream (101)    Siemens reactor (102)    Polycrystalline silicon rod (103)    Vent gas stream (104)    Fluidized bed reactor. (105)