Method and device for spraying a pulverulent material into a carrier gas

1. A device for spraying a pulverulent material into a carrier gas comprising:

a pressurized carrier gas inlet

a sonic throat convergent-divergent nozzle communicating with said pressurized carrier gas inlet

a pulverulent material feed communicating with a negative pressure zone,

means for expanding the carrier gas connected to said sonic throat convergent-divergent nozzle receiving the pressurized carrier gas and terminating in said negative pressure zone and

an outlet structure of said pulverulent material entrained by said carrier gas outside the negative pressure zone, wherein said pulverulent material in said carrier gas has a flow rate,

wherein the device for spraying further comprises a device for adjusting the flow rate of said pulverulent material in said carrier gas comprising a bypass circuit of said carrier gas equipped with a member for adjusting the amount of bypassed carrier gas, said bypass circuit comprising a carrier gas sampling structure placed upstream of said negative pressure zone of said carrier gas to bleed of an amount of sampled carrier gas and an orifice for reintroducing said amount of sampled carrier gas, wherein the orifice is located in said negative pressure zone, said sonic throat convergent-divergent nozzle being arranged to maintain, downstream, a constant flow rate of carrier gas entraining a predefined amount of pulverulent material.

2. The device as claimed in claim 1 , further comprising an injector communicating on the one hand with said sonic throat convergent-divergent nozzle and on the other hand with said expansion means and said negative pressure zone, said injector comprising at least one contraction zone.

3. The device as claimed in claim 1 , in which a smallest diameter of said sonic throat convergent-divergent nozzle is less than the diameter of each element downstream of said sonic throat convergent-divergent nozzle.

4. The device as claimed in claim 1 , in which said member for adjusting is a needle valve.

5. The device as claimed in claim 2 , in which said orifice is placed upstream of said contraction zone of said injector.

6. The device as claimed in claim 1 , in which said negative pressure zone is connected to a divergent passage, itself connected to said outlet of said pulverulent material entrained by the carrier gas.

7. The device as claimed in claim 6 , in which said outlet of pulverulent material entrained by said carrier gas is a tubular orifice comprising the divergent passage in which a first casing surrounds at least said outlet tubular orifice and in which a second casing surrounds a flexible hose leading to a spray nozzle connected to said outlet, the two casings being joined together.

8. The device as claimed in claim 7 , further comprising a thermofusible wire connected on the one hand to a trigger which comprises an open carrier gas flow position and a closed carrier gas blocking position and on the other hand, in said second casing, said thermofusible wire being arranged to maintain said trigger in the open position.

9. The device as claimed in claim 7 , in which said first and said second casings are joined to one another by return means having a predefined return force.

10. The device as claimed in claim 9 , further comprising a thermofusible wire connected on the one hand to a trigger which comprises an open carrier gas flow position and a closed carrier gas blocking position and on the other hand, between said first and second casings said thermofusible wire being arranged to maintain said trigger in the open position.

11. The device as claimed in claim 2 , in which a smallest diameter of said sonic throat convergent-divergent nozzle is less than the diameter of each element downstream of said sonic throat convergent-divergent nozzle.

12. The device as claimed in claim 2 , in which said adjusting member is a needle valve.

13. The device as claimed in claim 3 , in which said adjusting member is a needle valve.

14. The device as claimed in claim 2 , in which said negative pressure zone is connected to a divergent passage, itself connected to said outlet of said pulverulent material entrained by the carrier gas.

15. The device as claimed in claim 3 , in which said negative pressure zone is connected to a divergent passage, itself connected to said outlet of said pulverulent material entrained by the carrier gas.

16. The device as claimed in claim 4 , in which said negative pressure zone is connected to a divergent passage, itself connected to said outlet of said pulverulent material entrained by the carrier gas.

17. The device as claimed in claim 8 , in which said first and said second casings are joined to one another by return means having a predefined return force.