Fluidized bed gas distribution nozzle with the following features in its functional position: - a gas inlet pipe, having • an inner surface, • an outer surface, • a lower end section adapted to receive gas from an associated gas source, • an upper end section, • a plurality of openings formed in the gas inlet pipe, each opening extending form the inner surface of the gas inlet pipe to the outer surface of the gas inlet pipe, - a gas distribution cap connected or connectable to the gas inlet pipe, having • an upper top, • a lower bottom arranged at a vertical distance below said upper top and surrounding the gas inlet pipe, • a peripheral wall having an inner surface and an outer surface and extending between said upper top and said lower bottom, • outlets within the peripheral wall extending from the inner surface of the peripheral wall to the outer surface of the peripheral wall, wherein the gas distribution cap can be connected at least in a first position and in a second position to the gas inlet pipe, wherein in the second position the gas distribution cap at least partly closes at least some of the openings, wherein the second position and the first positions is a predetermined connecting position, characterized in that the gas inlet pipe and the gas distribution cap are mechanically embodied to provide the first predetermined connecting position and the second predetermined connecting position, so that a respective predetermined connecting position is uniquely identified by a respective mechanical feature of the gas inlet pipe and its corresponding mechanical feature of the gas distribution cap. - a gas inlet pipe, having • an inner surface, • an outer surface, • a lower end section adapted to receive gas from an associated gas source, • an upper end section, • a plurality of openings formed in the gas inlet pipe, each opening extending form the inner surface of the gas inlet pipe to the outer surface of the gas inlet pipe, • an inner surface, • an outer surface, • a lower end section adapted to receive gas from an associated gas source, • an upper end section, • a plurality of openings formed in the gas inlet pipe, each opening extending form the inner surface of the gas inlet pipe to the outer surface of the gas inlet pipe, - a gas distribution cap connected or connectable to the gas inlet pipe, having • an upper top, • a lower bottom arranged at a vertical distance below said upper top and surrounding the gas inlet pipe, • a peripheral wall having an inner surface and an outer surface and extending between said upper top and said lower bottom, • outlets within the peripheral wall extending from the inner surface of the peripheral wall to the outer surface of the peripheral wall, • an upper top, • a lower bottom arranged at a vertical distance below said upper top and surrounding the gas inlet pipe, • a peripheral wall having an inner surface and an outer surface and extending between said upper top and said lower bottom, • outlets within the peripheral wall extending from the inner surface of the peripheral wall to the outer surface of the peripheral wall, the gas distribution cap can be connected at least in a first position and in a second position to the gas inlet pipe, wherein in the second position the gas distribution cap at least partly closes at least some of the openings, wherein the second position and the first positions is a predetermined connecting position, characterized in that the gas inlet pipe and the gas distribution cap are mechanically embodied to provide the first predetermined connecting position and the second predetermined connecting position, so that a respective predetermined connecting position is uniquely identified by a respective mechanical feature of the gas inlet pipe and its corresponding mechanical feature of the gas distribution cap.