Method for producing aggregate used in hardening compositions, predominantly concretes, a fluidized-bed kiln for calcining mineral stock by means of same method, and an aggregate produced by same method

In a fluidized-bed kiln for calcining mineral stock incorporating a hearth and burners fitted into said hearth;

• the improvement consisting in that said burners are uniformly distributed over the entire area of said hearth and each of said burners is a gas/air nozzle comprising inner and outer coaxial vertical tubes, said inner tube having a central gas channel and said inner and outer tubes defining between them an annular air channel, a cone-shaped cap fitted into the upper end of said inner tube, and a diffuser fitted into the upper end of said outer tube, said cone-shaped cap having a central passage extending vertically therethrough in communication with said gas channel for directing vertical outflow of gas, and said cone-shaped cap and said diffuser defining between them an annular passage in communication with said air channel and extending upwardly at an angle to the vertical for directing outflow of air upwardly at an angle to the vertical.

In a fluidized-bed kiln for calcining mineral stock incorporating a hearth perforated for the admission of air and burners for the admission of gaseous fuel;

• the improvement consisting in that said burners are fitted into said hearth of said kiln uniformly over its entire area and each of said burners is a gas nozzle projecting upwards and comprising a vertical tube having a central gas channel, and a cone-shaped cap fitted into the upper end of said tube, said cone-shaped cap and the wall of said tube defining between them an annular passage in communication with said gas channel and extending at an angle to the vertical for directing outflow of gas upwardly at an angle to the vertical.