PROCESS AND APPARATUS FOR MAKING A MINERAL MELT

Abstract

The invention relates to a method of making a mineral melt, the method comprising providing a circulating combustion chamber which comprises an upper zone, a lower zone and a base zone, injecting primary particulate fuel and particulate mineral material and primary combustion gas into the upper zone of the circulating combustion chamber, thereby at least partially combusting the primary particulate fuel and thereby melting the particulate mineral material to form a mineral melt and generating exhaust gases, injecting into the lower zone of the circulating combustion chamber, through at least one first burner, secondary combustion gas and gaseous fuel and secondary particulate fuel, wherein the secondary combustion gas and gaseous fuel and secondary particulate fuel are injected via a single first burner, wherein the amount of secondary combustion gas injected via each first burner is insufficient for stoichiometric combustion of the total amount of gaseous fuel and secondary particulate fuel injected via that first burner, and injecting tertiary combustion gas into the lower zone of the circulating combustion chamber, through at least one tertiary combustion gas injector, whereby the tertiary combustion gas enables completion of the combustion of the gaseous fuel and the secondary particulate fuel, separating the mineral melt from the hot exhaust gases so that the hot exhaust gases pass through an outlet in the circulating combustion chamber and the mineral melt collects in the base zone. The invention also relates to apparatus suitable for use in the method.

Claims

1. A method of making a mineral melt, the method comprising providing a circulating combustion chamber in which suspended particulate materials and gas circulate in a system which is or approaches a cyclone circulation system, the circulating combustion chamber comprising an upper zone, a lower zone and a base zone, injecting primary particulate fuel and particulate mineral material and primary combustion gas into the upper zone of the circulating combustion chamber, thereby at least partially combusting the primary particulate fuel and thereby melting the particulate mineral material to form a mineral melt and generating exhaust gases, injecting into the lower zone of the circulating combustion chamber, through at least one first burner, secondary combustion gas and gaseous fuel and secondary particulate fuel, wherein the secondary combustion gas and gaseous fuel and secondary particulate fuel are injected via a single first burner, wherein the amount of secondary combustion gas injected via each first burner is insufficient for stoichiometric combustion of the total amount of gaseous fuel and secondary particulate fuel injected via that first burner, and injecting tertiary combustion gas into the lower zone of the circulating combustion chamber, through at least one tertiary combustion gas injector, whereby the tertiary combustion gas enables completion of the combustion of the gaseous fuel and the secondary particulate fuel, separating the mineral melt from the hot exhaust gases so that the hot exhaust gases pass through an outlet in the circulating combustion chamber and the mineral melt collects in the base zone.

2. A method according to claim 1, additionally comprising the step of making mineral fibres from the mineral melt by flowing the collected mineral melt through an outlet in the base zone to centrifugal fiberising apparatus and forming fibres.

3. A method according to claim 1 wherein the secondary and/or tertiary combustion gas is oxygen-enriched air which contains at least 30%, preferably at least 35%, more preferably at least 50% oxygen by volume.

4. A method according to claim 1 wherein the secondary and/or tertiary combustion gas is oxygen-enriched air which contains at least 70% oxygen by volume.

5. A method according to claim 1 wherein the secondary and/or tertiary combustion gas is pure oxygen.

6. A method according to claim 1 wherein the tertiary combustion gas injector is a burner or a lance.

7. A method according to claim 1 wherein there is provided a tertiary combustion gas injector for each first burner.

8. A method according to claim 1 wherein the secondary particulate fuel is solid.

9. A method according to claim 1 wherein the secondary particulate fuel is powdered coal.

10. A method according to claim 1 wherein the secondary particulate fuel is coke fines.

11. A method according to claim 1 wherein at least 50% by weight of the particulate fuel particles are of size at least 100 microns.

12. A method according to claim 1 wherein the amount of secondary combustion gas injected via each first burner is in the range of 95 to 110% of the amount sufficient for stoichiometric combustion of the gaseous fuel injected through that first burner.

13. A method according to claim 12 wherein the amount of secondary combustion gas injected via each first burner is in the range of 100 to 105% of the amount sufficient for stoichiometric combustion of the gaseous fuel injected through that first burner.

14. A method according to claim 1 wherein the amount of tertiary combustion gas injected via each tertiary combustion gas injector is at least 95% of the amount sufficient for stoichiometric combustion of the secondary particulate fuel injected through an associated first burner.

15. A method according to claim 14 wherein the amount of tertiary combustion gas injected via each tertiary combustion gas injector is in the range of 100 to 105% of the amount sufficient for stoichiometric combustion of the secondary particulate fuel injected through an associated first burner.

16. A method according to claim 14 wherein the total amount of primary and tertiary combustion gas is in the range of 100 to 105% of the amount sufficient for stoichiometric combustion of the first particulate fuel, the gaseous fuel and the secondary particulate fuel.

17. Apparatus for making a mineral melt according to claim 1, comprising a circulating combustion chamber arranged such that suspended particulate materials and gas circulate in a system which is or approaches a cyclone circulation system, the circulating combustion chamber comprising a cylindrical top section, a bottom section and a base section, wherein the circulating combustion chamber comprises inlets in the top section for primary particulate fuel, particulate mineral material and primary combustion gas, at least one dual oxy-fuel burner in the bottom section for injection of secondary particulate fuel, gaseous fuel and secondary combustion gas at least one tertiary combustion gas injector in the bottom section for injection of tertiary combustion gas an outlet for exhaust gases and an outlet in the base section for allowing release of mineral melt.

Description

FIGURES

[0096] FIG. 1 is an illustration of a vertical cross-section of apparatus which is suitable for use in the present invention.

[0097] FIG. 2 is a schematic top view cross-section of the bottom section (lower zone) of an apparatus which is suitable for use in the present invention.

[0098] FIG. 1 shows a circulating combustion chamber 1 which comprises a top section 2, a bottom section 3 and a base section 4. Primary particulate fuel and particulate mineral material are introduced through inlet 5, with primary combustion gas being introduced through inlet 6 which concentrically surrounds inlet 5. The primary particulate fuel is ignited and burns in the upper section 2 and is collected in the base section 4 as a melt pool 7. The hot exhaust gases pass through the flue gas outlet 8 at the top of the combustion chamber.

[0099] Secondary particulate fuel and gaseous fuel and secondary combustion gas are injected through dual oxy-fuel burners 9 and form a flame in the bottom region 3 which acts to heat the melt pool 7.

[0100] Tertiary combustion gas is introduced through combustion gas lances 10 in the bottom region 3, which aids stabilisation of the flame generated by each dual oxy-fuel burner, and also aids burn-out of the fuel in this region.

[0101] The melt flows through siphon 11 to fiberising equipment 12 where it is formed into fibres.

[0102] As shown in FIG. 2, the gaseous fuel (e.g. natural gas) and secondary particulate fuel (e.g. particulate coal) are introduced via a dual oxy-fuel burner 9, the gaseous fuel being supplied through inlet 13 and the secondary particulate fuel being supplied through inlet 14. The combustion gas (e.g. oxygen) is supplied via the same dual oxy-fuel burner 9 through the inlet 15, and is sufficient for stoichiometric combustion of the gaseous fuel only.

[0103] The dual oxy-fuel burner generates a flame 16. This has a first combustion zone 17 in which the gaseous fuel combusts.

[0104] The associated tertiary combustion gas injector is a gas (e.g. oxygen) lance 10. The inlet for the tertiary combustion gas is downstream of the inlets of the dual oxy-fuel burner 9, in the direction A of circulating movement within the chamber. This allows the combustion of the secondary particulate fuel in a second combustion zone 18. It also allows completion of the combustion of the primary particulate fuel.