A device for metering one or more powders in order to produce a flow of the one or more powders and of a carrier gas at a given volume flow rate, the device comprising:
- at least a first source adapted to supply a first flow including a first powder and a first carrier gas at a volume flow rate substantially equal to the given volume flow rate;
- a source of a carrier gas adapted to supply an adjustment carrier gas flow at a volume flow rate substantially equal to the given volume flow rate;
- an outlet junction for sending the flow of the one or more powders and of carrier gas;
- at least a first proportional valve including an inlet connected to the first source to receive the first flow, a first outlet for selectively sending a volume percentage X1 of the first flow to the outlet junction, and a second outlet adapted to send a volume percentage 100−X1 of the first flow, the percentage X1 being between 0% and 100% inclusive and representative of a setting of the first proportional valve;
- an adjustment proportional valve including an inlet connected to the source of the carrier gas by a first connecting line to receive at least a fraction of the adjustment carrier gas flow, a first outlet adapted to send a volume percentage Y of the fraction, and a second outlet adapted to send a volume percentage 100−Y of the fraction, the percentage Y being between 0% and 100% inclusive and representative of a setting of the adjustment proportional valve;
- a control system adapted to control at least the first proportional valve and the adjustment proportional valve and configured so that the flow of the one or more powders and of carrier gas has a volume flow rate substantially equal to the given volume flow rate;
- at least a first recycling system for recycling at least a part of the first flow;
- at least a first recycling junction connected, upstream, to the second outlet of the first proportional valve to receive the percentage 100−X1 of the first flow and to the first outlet of the adjustment proportional valve to receive the percentage Y of the fraction and, downstream, to an inlet of the first recycling system, the control system being configured so that the inlet of the first recycling system receives a volume flow rate substantially equal to the given volume flow rate;
- and
- an aspiration and filtration system connected to an outlet of the first recycling system and a member for regulating a head loss between the first recycling system and the aspiration and filtration system, the member being adapted so that a pressure in the outlet junction and a pressure in the first recycling junction are substantially equal to one another.