Chemical-looping combustion method with dilute phase removal of ashes and fines in the oxidationzone and plant using same

1. A method for chemical-looping combustion of a hydrocarbon feedstock of solid particles, wherein an oxygen-carrying material circulates in form of oxygen-carrying material particles, comprising:

contacting hydrocarbon feedstock particles with the oxygen-carrying material particles in a reduction zone R 0 ,

contacting oxygen-carrying material particles from reduction zone R 0 with an oxidizing gas stream in a reactive oxidation zone R 1 ,

separating fly ashes, oxygen-carrying material fines and the oxygen-carrying material particles within a mixture from zone R 1 by dilute phase elutriation in a dilute phase separation zone S 2 so as to discharge through a discharge line a gaseous effluent comprising the major part of the fly ashes and of the oxygen-carrying material fines, and to send a particle stream comprising the major part of the oxygen-carrying material particles to reduction zone R 0 , the driving force required for dilute phase elutriation in the dilute phase separation zone S 2 being provided by the oxidizing gas stream coming from the reactive oxidation zone R 1 .

2. A method as claimed in claim 1 , wherein the oxygen-carrying material particles are circulated in a loop in the reactive oxidation zone R 1 by means of a line allowing to recycle a stream of oxygen-carrying particles sedimented in the dense fluidized phase, from the bottom of the dilute phase separation zone S 2 to the lower part of the reactive oxidation zone R 1 .

3. A method as claimed in claim 1 , wherein heat is recovered in the dense fluidized phase formed in the bottom of the dilute phase separation zone S 2 by means of a heat exchanger E 3 .

4. A method as claimed in claim 1 , wherein an additional oxidizing gas stream is fed to the top of the reactive oxidation zone R 1 so as to maintain a gas velocity ranging between 30 and 300% of the mean terminal settling velocity of the oxygen-carrying material fines of diameter ranging between 50 and 150 μm.

5. A method as claimed in claim 1 , comprising:

carrying out deep separation of the ashes, the oxygen-carrying material fines and the oxygen-carrying particles in a dedusting zone S 4 in order to discharge a gas stream containing the major part of the ashes and the oxygen-carrying material fines, and a particle stream containing the major part of the oxygen-carrying material particles that is sent through a delivery line to the reduction zone R 0 .

6. A method as claimed in claim 5 , comprising:

carrying out dense phase elutriation separation in a dense phase elutriation separation zone S 5 arranged downstream from the dedusting zone S 4 and fluidized by a non-reducing gas allowing to separate the fly ashes from the oxygen-carrying material particles in the particle stream containing the major part of the oxygen-carrying material particles from the dedusting zone S 4 in order to send a particle stream rich in oxygen-carrying material particles to reduction zone R 0 and to discharge a gas stream rich in fly ashes.

7. A method as claimed in claim 6 , wherein a particle stream comprising part of the oxygen-carrying material particles separated in dense phase elutriation separation zone S 5 is recycled to the oxidation zone R 1 .

8. A method as claimed in claim 6 , wherein heat is recovered in the dense fluidized phase of separation zone S 5 by means of a heat exchanger E 6 .

9. A plant for carrying out chemical-looping redox combustion of a solid hydrocarbon feedstock according to the method as claimed in claim 1 , said plant comprising at least:

a reduction zone R 0 ,

an oxidation zone comprising a reactive zone R 1 provided with feed means supplying oxygen-carrying material particles coming from reduction zone R 0 and feed means supplying oxidizing fluidization gas, and a dilute phase elutriation separation zone S 2 arranged above reactive zone R 1 , of significantly larger diameter than the reactive zone R 1 so as to slow down the mixed phase coming from the reactive zone R 1 and provided with feed means allowing to feed a mixed phase comprising gas and particles coming from the reactive zone R 1 ,

a discharge line for discharging a transported phase rich in ashes and fines,

a line for recycling a particle stream rich in oxygen-carrying material particles to the reduction zone R 0 .

10. A plant as claimed in claim 9 , comprising a heat exchanger E 3 in the dense fluidized phase formed in the bottom of the dilute phase elutriation separation zone S 2 .

11. A plant as claimed in claim 9 , comprising a line for recycling a stream comprising oxygen-carrying particles from the bottom of the dilute phase elutriation separation zone S 2 to the lower part of the reactive zone R 1 .

12. A plant as claimed claim 9 , comprising a dedusting zone S 4 provided with an intake line for receiving a transported phase coming from the dilute phase elutriation separation zone S 2 , rich in ashes and fines, a discharge line allowing to discharge a gas stream containing the major part of the ashes and the fines, and a transport line for carrying to the reduction zone R 0 a particle stream comprising the major part of the oxygen-carrying material particles.

13. A plant as claimed in claim 12 , comprising a dense phase elutriation separation zone S 5 arranged downstream from the dedusting zone S 4 , receiving through the inlet thereof a particle stream comprising the major part of the oxygen-carrying material particles and comprising a line allowing delivery of a fluidization gas, a transport line for carrying a particle stream rich in oxygen-carrying material particles to the reduction zone R 0 , and a line for discharging a gas stream rich in fly ashes.

14. A plant as claimed in claim 13 , comprising a line coming from the dense phase elutriation separation zone S 5 for recycling to the reactive zone R 1 a particle stream comprising part of the solid particles separated in the dense phase elutriation separation zone S 5 .

15. A plant as claimed in claim 13 , comprising a heat exchanger E 6 within the dense fluidized phase in the dense phase elutriation separation zone S 5 .