Method for the pneumatic injection of metered quantities of powdered substances into a chamber at a variable pressure

A method for injecting metered quantities of a powdered material at separate injection points within a chamber at variable pressure, comprising:

• forming a primary pneumatic stream, said primary pneumatic stream comprising the powdered material and a propellant gas;
• splitting the primary pneumatic stream into a plurality of secondary pneumatic streams;
• directing the secondary pneumatic streams through separate respective conduits to respective separate injection points, each conduit including a first tuyere disposed upstream of the respective injection point, and each first tuyere having an inlet end and an outlet end and defining a constricted flow passage between the inlet end and the outlet end;
• wherein each secondary pneumatic stream exhibits a first tuyere outlet pressure at the outlet end of its respective first tuyere;
• and acting on the outlet pressure of each respective first tuyere at a point downstream of the respective first tuyere and upstream of the respective injection point to influence the transport conditions within each respective conduit.