Circulating fluidized bed steam generator having means for minimizing mass of solid materials recirculated

An apparatus for minimizing mass flow of solid material recirculated in a steam generator circulating fluidized bed which comprises:

• means defining a steam generator with combustion system in which minimum recirculation of solid materials is carried out;
• a fluid coolant circuit as part of said steam generator having serially connected economizer, waterwalls and superheater and wherein a steam drum may optionally be disposed between said waterwalls and said superheater;
• means for combustion of a solid fuel in association with inert solid particles within a vertical reactor/furnace, presence of said inert solid particles in said means for combustion suppressing said combustion temperature;
• the walls of said vertical reactor/furnace comprising portion/s of said fluid coolant circuit;
• first inlet means for combustion air located in the bottom portion of said reactor/furnace for partially combusting and fluidizing said solid fuel and inert particles;
• second inlet means for admission of supplemental air/gas flow to said reactor/furnace at level/s above said first inlet means adapted to entrain a substantial portion of said solid fuel and inert material particles in a flue gas stream produced by said means for combustion and to maintain velocity of said flue gas stream at said reactor/furnace outlet in a range of from 16 to 25 feet per second and at rated conditions of said steam generator;
• means for separating particles of solid materials in said flue gas from said flue gas downstream of said reactor/furnace as substantially inert material;
• means for recycling said separated particles to said means for combustion and for association with said solid fuel;
• means for removing said substantially inert material from said solid material recirculation circuit including means for regulation of the mass flow rate of said solid materials recirculated through said reactor/furnace outlet;
• means to cool said circulating solid materials after said reactor/furnace outlet and before recycle to said means for combustion;
• said means to cool said circulating solid materials having cooling capacity sufficient to maintain said reactor/furnace combustion temperature in a range of from 1,400.degree. F. to 1,750.degree. F. when the ratio of said mass flow rate of said solid materials to said flue gas at said reactor/furnace outlet and at rated conditions of said steam generator is in a range of from 6:1 to 2:1.