Heating of fluidized bed reactor by microwaves

A method for preparing polycrystalline silicon in a fluidized bed reactor comprising:

• providing in said reactor at least one reaction zone and at least one heating zone, said at least one reaction zone and said at least one heating zone being separated by a partition preventing fluid communication and lateral penetration of particles therethrough;
• introducing silicon seed particles into said reaction zone to form a bed of silicon particles;
• introducing a reaction gas comprising a silicon source material into said reaction zone and thereby fluidizing said silicon particles in said reaction zone;
• introducing silicon particles into said heating zone;
• introducing a carrier gas into said heating zone and thereby fluidizing said silicon particles in said heating zone;
• heating said silicon particles in said heating zone by introducing microwave energy into said heating zone;
• providing open communication between an upper section of said heating zone and said reaction zone;
• mixing said silicon particles at an upper section of said heating zone with said silicon particles of said reaction zone for transferring the heat of said heating zone to said reaction zone via said upper section of said heating zone, whereby said silicon source material is thermally decomposed and/or reduced to silicon metal on said silicon particles at a reaction temperature sufficient to produce polycrystalline silicon;
• and
• removing unreacted fluidizing gases and reaction by-product gases from said reactor.

A method of operating a fluidized bed reactor in which a reaction gas comprising a source material is brought into a fluidized-bed relationship with seed particles on which said source material is to be deposited, comprising the steps of:

• providing a fluidized bed reactor vessel having a reaction zone and a heating zone, said at least one reaction zone and said at least one heating zone being separated by a partition preventing fluid communication and lateral penetration of particles therethrough;
• providing seed particles in said reaction zone and in said heating zone;
• introducing a carrier gas into said heating zone;
• introducing a reaction gas comprising a source material into said reaction zone;
• heating said particles in said heating zone by introducing microwave energy into said heating zone;
• effecting a fluidized-bed relationship in said reaction zone between said particles and said reaction gas;
• effecting a fluidized-bed relationship in said heating zone between said particles and said carrier gas;
• providing open communication between an upper section of said heating zone and said reaction zone;
• heating said particles in said reaction zone to a reaction temperature by effecting particle mixing at an upper section of said heating zone with said particles of said reaction zone for transferring the heat of said heating zone to said reaction zone via said upper section of said heating zone to thermally decompose and/or reduce said source material as a deposit on said seed particles.