Method and installation for beneficiation of fly ash particles by flash combustion

1. A method for beneficiation of fly ash particles, the method comprising:

determining the heat value of the fly ash particles;

comparing the heat value of the fly ash particles with a minimum heat value K;

feeding an inlet of a combustor with a feed material comprising the fly ash particles and, in case the heat value is lower than the minimum heat value K, fuel in sufficient quantity to assure that the heat value of the feed material is greater than or equal to the minimum heat value K;

supplying an upstream airflow to the combustor so as to carry the feed material in suspension from the inlet to an outlet of the combustor;

operating the combustor at a temperature of at least 700° C.; and

collecting beneficiated fly ash particles from the airflow at the outlet of the combustor.

2. A method for beneficiation of fly ash particles according claim 1 , wherein the minimum heat value K is in the range of 600 to 1000 cal/g.

3. A method for beneficiation of fly ash particles according to claim 1 , wherein the step of determining the heat value comprises measuring the carbon and sulfur contents of the fly ash particles.

4. A method for beneficiation of fly ash particles according to claim 1 , wherein the fuel is coal.

5. A method for beneficiation of fly ash particles according to claim 4 , wherein the coal is ground to an average particles size in the range of 50 to 200 μm.

6. A method for beneficiation of fly ash particles according to claim 1 , wherein average temperature in the combustor is measured and controlled to between 700 to 800° C.

7. A method for beneficiation of fly ash particles according to claim 6 , wherein temperature of the combustor is controlled by regulating the feeding rate of the feed material and/or by regulating the minimum heat value K.

8. A method for beneficiation of fly ash particles according to claim 1 , wherein average temperature in the combustor is controlled modifying the flow rate of the airflow supplied to the combustor in cases where fly ash particles have a heat value higher than 1300 cal/g.

9. A method for beneficiation of fly ash particles according to claim 1 , wherein the flow rate of the airflow supplied to the combustor is controlled so that the mean residence time of the feed material in the combustor is less than 1 minute.

10. A method for beneficiation of fly ash particles according to claim 9 , wherein the flow rate of the airflow supplied to the combustor is controlled so that the mean residence time of the feed material in the combustor is between about 5 to 15 seconds.

11. A method for beneficiation of fly ash particles according to claim 1 , wherein the flow rate of the airflow and/or the feeding rate of feed material are controlled such as air is at least 30% in excess of the stoichiometric quantity of air for the oxidation of carbon to carbon dioxide.

12. A method for beneficiation of fly ash particles according to claim 1 , wherein the velocity of the airflow through the combustor ranges from 1 meters/second to 3 meters/second.

13. A method for beneficiation of fly ash particles according to claim 1 , wherein the airflow is preheated to a temperature in the range of from 400 to 600° C. before being supplied to the combustor.

14. A method for beneficiation of fly ash particles according to claim 13 , wherein the airflow is preheated by an heat exchange with airflow outgoing from the combustor, before being supplied to the combustor.

15. A method for beneficiation of fly ash particles according to claim 1 , wherein fly ash particles are selected and prepared to have a particle size distribution represented by a d50 in the range of 50 to 200 microns.