GAS-BURNING FURNACE

Abstract

The present invention provides an apparatus and a method for operating a cyclone combustion furnace using gaseous fuel.

Claims

1. A method of making mineral melt, the method comprising: providing a cyclone furnace, particulate mineral raw material, gaseous fuel, and oxidising agent; injecting gaseous fuel into the furnace at one or more first injection ports; injecting oxidising agent into the furnace at one or more second injection ports; injecting mineral raw material into the furnace at one or more third injection ports, wherein the gaseous fuel, oxidising agent and mineral raw material are all injected into the top of the furnace; and allowing the gaseous fuel to combust with the oxidising agent, thereby melting the mineral raw material, wherein each first injection port is spaced at an angular separation from the one or more second injection ports such that no first injection port is at an angular separation of less than 20 degrees from any of the second injection ports, measured about a vertical axis through the centre of the cyclone furnace.

2. The method according to claim 1, wherein each second injection port is integrated with a third injection port.

3. The method according to claim 1, wherein each first injection port is spaced at an angular separation from the one or more third injection ports such that no first injection port is at an angular separation of less than 20 degrees from any of the third injection ports, measured about a vertical axis through the centre of the cyclone furnace.

4. The method according to claim 1, to claim wherein the gaseous fuel injected through the one or more first injection ports provides at least 40% of the energy in the furnace, preferably at least 50%.

5. The method according to claim 1, wherein the furnace comprises a body and a lid and wherein the first injection ports traverse the lid.

6. The method according to claim 1, wherein the furnace comprises a body having a body wall and a lid, the body comprising a top section, a central section and a bottom section, wherein the second and third injection ports traverse the top section of the body wall.

7. The method according to claim 5, wherein each of the one or more first injection ports is positioned at an angle of from 30 to 90 degrees from the lid of the furnace.

8. The method according to claim 1, wherein the mineral raw material has a composition in wt % of: SiO.sub.2: 30 to 51; Al.sub.2O.sub.3: at least 14, 15, 16 or 18, not more than 35, 30, 26 or 23; CaO: 8 to 30; MgO: 2 to 25; FeO (including Fe.sub.2O.sub.3): 4 to 15; FeO+MgO: 10 to 30; Na.sub.2O+K.sub.2O: up to 10; CaO+Na.sub.2O+K.sub.2O: 10 to 30; TiO.sub.2: up to 6; TiO.sub.2+FeO: 4 to 18; B.sub.2O.sub.3: up to 5; P.sub.2O.sub.5: up to 8; and others: up to 8.

9. The method according to claim 1, wherein the oxidising agent is air, oxygen, or oxygen-enriched air, preferably oxygen-enriched air.

10. A cyclone furnace for melting mineral raw material, the cyclone furnace comprising: a furnace body; a furnace lid; one or more first injection ports for injecting gaseous fuel into the furnace; one or more second injection ports for injecting oxidising agent into the furnace; and one or more third injection ports for injecting mineral raw material into the furnace, wherein the furnace body comprises a top section, a central section and a bottom section, each first injection port is spaced at an angular separation from the one or more second injection ports such that no first injection port is at an angular separation of less than 20 degrees from any of the second injection ports, measured about a vertical axis through the centre of the cyclone furnace, and wherein each of the first, second and third injection ports are configured to inject the gaseous fuel, oxidising agent and mineral raw material, respectively, into the top of the furnace.

11. The cyclone furnace according to claim 10, wherein each second injection port is integrated with a third injection port.

12. The cyclone furnace according to claim 10, wherein each first injection port is spaced at an angular separation from the one or more third injection ports such that no first injection port is at an angular separation of less than 20 degrees from any of the third injection ports, measured about a vertical axis through the centre of the cyclone furnace.

13. The cyclone furnace according to claim 10, wherein the furnace comprises a body wall and a lid and wherein the first injection ports traverse the lid.

14. The cyclone furnace according to claim 13, wherein each of the one or more first injection ports is positioned at an angle of from 30 to 90 degrees from the lid of the furnace.

15. The cyclone furnace according to claim 10, wherein the furnace comprises a body wall and a lid, the body wall comprising a top section, a central section and a bottom section, wherein the second and third injection ports traverse the top section of the body wall.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0040] FIG. 1 shows a schematic top view of a furnace in accordance with the invention.

[0041] FIG. 2 shows a schematic vertical cross section of the upper portion of a furnace in accordance with the invention.

[0042] FIG. 3 shows a schematic view of a furnace in accordance with the invention.

DETAILED DESCRIPTION

[0043] An exemplary furnace in accordance with the invention is illustrated in the figures.

[0044] FIG. 1 shows a schematic top view of a furnace 1. Gaseous fuel injection ports 2 traverse the lid 3 of the furnace, which comprises an exhaust outlet 4 in the centre. Mineral raw material and oxidising agent (such as air or oxygen-enriched air) are injected into the furnace together via injection ports 5 located at the top of the side body wall of the furnace 1. The top of the furnace 1 being generally cylindrical, there exists a single, continuous side body wall.

[0045] The gaseous fuel injection ports 2 are spaced apart at equal angular distance from one another. The angular separation between the gaseous fuel injection ports 2 is shown as angle A in FIG. 1. In this case it is 90? because there are four such injection ports 2, equally spaced around the circumference of the furnace. The injection ports 5 for mineral raw material and oxidising agent are spaced at equal angular distance from one another. The angular separation between the injection ports 5 is shown as angle B in FIG. 1. In this case it is 90? because there are four such ports 5, equally spaced around the circumference of the furnace. It will be seen that each injection port 5 is spaced apart at an angular distance of at least 20 degrees from the nearest gaseous fuel injection port 2. The angular separation between each injection port and the closest gaseous fuel injection port 2 is shown as angle C and in this embodiment is about 45?. The angular separation is measured about a point in the centre of this schematic top view.

[0046] The mineral raw material, oxidising agent and gaseous fuel are injected tangentially into the furnace 1 and move in a circulating flow, at or approaching a cyclone system. The location and angle of the gaseous fuel injection ports 2 means that the gaseous fuel is injected into the stream of oxidising agent and mineral raw material, facilitating slower mixing and energy release such that the mineral raw material melts with the combustion of the gaseous fuel.

[0047] FIG. 2 shows a cross-sectional side view of a furnace 1 in accordance with the invention. Mineral raw material and oxidising agent (usually air, oxygen, or oxygen-enriched air) are injected together through port 5. Specifically, in this embodiment the oxidising agent enters through inlet 5a and mineral raw material through inlet 5b, and the two components enter the top section 1a of the furnace 1 together. Alternatively (not shown) the raw material may be injected through the lid 3 at a position adjacent the inlet for the oxidising agent. If oxygen-enriched air is used as the oxidising agent, this may be achieved by injecting oxygen into the air stream at inlet 5a.

[0048] The general direction of the flow of materials inside the furnace 1 is also shown in FIG. 2. The oxidising agent and the mineral raw material provide a stream into which gaseous fuel is injected via port 2, which traverses the lid of the furnace. Each of the injection ports 2 is positioned at an angle D of from 30 to 90 degrees from the lid of the furnace. This allows for delayed mixing so that the energy release from the burning of the fuel can melt the mineral raw material, whilst allowing the fuel to combust without being drawn out of the exhaust 4 prior to combustion. The circulating flow continues as the mineral material melts and falls down the furnace to the central section 1b and on to the bottom section 1c (not shown in FIG. 2).

[0049] FIG. 3 shows a schematic of the exterior of the furnace 1. The generally cylindrical top section 1a, the generally frustoconical central section 1b and the generally cylindrical bottom section 1c are shown. The ports 5 for mineral raw material and oxidising agent and the ports 2 for gaseous fuel are located at the top of the furnace 1. Specifically, the gaseous fuel ports 2 traverse the furnace lid 3 and the ports 5 for mineral raw material and oxidising agent traverse the side body wall of the top section 1a of the furnace 1.

[0050] Additional heating apparatus such as further burners or electrodes can be implemented in the central section 1b and/or in the bottom section 1c, to heat and refine the melted mineral material. However, the primary fuel source is gaseous fuel and the energy to melt the mineral material is provided by the gaseous fuel that is injected at or near the top of the furnace 1.

[0051] In the bottom section 1c, an outlet 6 is provided for the mineral melt. In FIG. 3, the outlet 6 takes the form of a siphon. The outlet 6 could alternatively be provided in the base of the furnace 1 (not shown).

[0052] The mineral melt may be transported to a fiberizing apparatus such as internal centrifugation (spinning cup) or external centrifugation (cascade spinner) apparatus. There the mineral melt is converted into fibres in conventional manner and can then be formed into mineral fibre products, also in conventional manner.