Process of and apparatus for making mineral fibers
The present invention relates to a method of making mineral fibers, comprising providing a circulating combustion chamber ( 1 ) which comprises a top section ( 2 ), a bottom section ( 3 ) and a base section ( 4 ), injecting primary fuel, particulate mineral material and primary combustion gas into the top section of the circulating combustion chamber and combusting the primary fuel thereby melting the particulate material to form a mineral melt and generating exhaust gases, separating the mineral melt from the exhaust gases wherein the exhaust gases pass through an outlet ( 8 ) in the circulating combustion chamber and the mineral melt collects in the base section of the circulating combustion chamber, injecting secondary fuel, which comprises liquid or gaseous fuel, and secondary combustion gas into the bottom section of the circulating combustion chamber to form a flame in the bottom section which heats the melt, and flowing a stream of the collected melt through an outlet ( 15 ) in the base section to a centrifugal fiberising apparatus and forming fibers. The present invention also provides an apparatus for use in the method of the invention.
1. A method of making mineral fibers, comprising
providing a circulating combustion chamber which comprises a top section, a bottom section and a base section,
injecting primary fuel, particulate mineral material and primary combustion gas into the top section of the circulating combustion chamber and combusting the primary fuel thereby melting the particulate material to form a mineral melt and generating exhaust gases,
separating the mineral melt from the exhaust gases wherein the exhaust gases pass through an outlet in the circulating combustion chamber and the mineral melt collects as a melt pool in the base section of the circulating combustion chamber,
injecting secondary fuel and secondary combustion gas into the bottom section of the circulating combustion chamber, above the melt pool, to form a flame in the bottom section which heats the melt, and
flowing a stream of the collected melt through an outlet in the base section to a centrifugal fiberizing apparatus and forming fibers.
2. A method according to claim 1 , wherein the secondary fuel comprises liquid or gaseous fuel.
3. A method according to claim 1 , wherein the secondary fuel is selected from the group consisting of an alcohol, propane, methane, natural gas and mixtures thereof.
4. A method according to claim 1 wherein the secondary fuel comprises coal or oil, which makes up less than 50% of the total secondary fuel by volume.
5. A method according to claim 1 wherein the secondary fuel comprises a solid fuel.
6. A method according to claim 5 wherein the secondary fuel comprises between 70 and 90% solid fuel.
7. A method according to claim 1 wherein the secondary combustion gas is pure oxygen.
8. A method according to claim 1 wherein the secondary fuel and secondary combustion gas are introduced through at least two burner inlets so that immediately after entry to the circulating combustion chamber, the secondary fuel combusts to form a flame.
9. A method according to claim 8 wherein the burner inlets are positioned in the lower half of the bottom section of the circulating combustion chamber.
10. A method according to claim 1 wherein the proportion of secondary combustion gas and secondary fuel is such that there is insufficient secondary combustion gas to enable the secondary fuel to undergo complete combustion.
11. A method according to claim 1 wherein the proportion of secondary fuel and secondary combustion gas is such that there is more than sufficient secondary combustion gas to enable the secondary fuel to undergo complete combustion.
12. A method according to claim 8 wherein the circulating combustion chamber comprises a burner inlet in the bottom section and at least one further inlet for additional secondary combustion gas.
13. A method according to claim 1 wherein the outlet in the base section is a siphon.
14. A method according to claim 1 wherein the primary fuel is a particulate carbonaceous fuel.
15. A method according to claim 1 wherein the primary fuel is a mixture of a particulate carbonaceous fuel, and one or more gaseous fuels selected from the group consisting of propane, methane, natural gas, and a combination of two or more of these.
16. A method according to claim 1 wherein the primary combustion gas is oxygen enriched air or pure oxygen.
17. Apparatus for use in making mineral fibers comprising
a circulating combustion chamber comprising a substantially cylindrical top section, a bottom section having a lower portion defining a melt collection zone, and a base section wherein the circulating combustion chamber comprises
inlets in the top section for primary fuel, particulate mineral material and primary combustion gas,
inlets for secondary fuel and secondary combustion gas located above the melt collection zone in the bottom section,
an outlet for exhaust gases,
an outlet in the base section and
centrifugal fiberizing apparatus, wherein the outlet in the base section leads to the centrifugal fiberizing apparatus.
18. Apparatus according to claim 17 , wherein the bottom section of the circulating combustion chamber is frustoconical.
19. Apparatus according to claim 17 wherein the outlet in the base section is a siphon.
20. The method of claim 1 wherein the secondary fuel comprises coal.
21. A method according to claim 1 wherein the primary fuel is coal.