GB2427261A - Fuel Injector for a Glass Melting Furnace - Google Patents

Abstract

A fuel injector 33 associated with an oxygen feed 32 injects fuel 26 and oxygen into a melting chamber 12 of a furnace. The furnace may be a glass melting furnace (10 fig 1), and the fuel and oxygen may be delivered by the injector which has a nozzle 36, 40, for causing mixing of the fuel and oxygen fed from ports 46, 48, respectively. The injector has a fuel passageway 34 through which the fuel is passed, and an oxygen passageway 38 may surround the fuel passageway. The oxygen feed may have more than 50mol% oxygen and may include inert gas or air. The fuel may be a solid, liquid, or gaseous fuel, and an atomising medium (58 fig 5) may be fed to the injector to assist in mixing the fuel and oxygen feed. The injector can be fitted to the wall 16 of a conventional preheated air regenerative glass melting furnace, either as an additional burner or as a replacement for an existing type. The furnace can then operate in either a pre-heated air combustion mode or an oxygen feed assisted combustion mode, and when operating in the oxygen feed assisted combustion mode the air preheating system can be isolated and/or maintained.

Description

FUEL INJECTOR

The present invention relates to a fuel injector for, and a method of injecting fuel and oxygen into, a glass melting furnace. In the furnace, glass is melted to produce molten glass for the production of new glass.

Conventional glass melting furnaces use highly preheated air and feed it through a port (or a channel) leading into a combustion or melting chamber of the furnace. Fuel for combustion with the heated air also is injected into the melting chamber, through another port, or through various ports. The ports are usually positioned beneath the air port, but sometimes they are placed to the sides of the air port, or within the sides of the air port.

The fuel is introduced into the melting chamber in such a way that it mixes with the air, and combusts within the melting chamber.

It is occasionally necessary to cut off, or to reduce, the flow of hot air. For example, this may occur when the air preheating system is being repaired or where it is necessary to reduce pollutants from the furnace, i.e. to control the combustion. Flowever, cutting off or reducing the flow of hot air stops or reduces the rate of glass production since the combustion will stop, or get less intense, and the temperature in the furnace will drop.

Further, because of the temperature drop, there will be an inevitable lag time for the furnace to reobtain its full operation temperature once the hot air resumes its full flow rate.

Methods of heating the furnace during these "down-time" periods have been developed.

However, they still result in a temperature drop for the furnace. Therefore they do not allow the production of glass to continue at its usual rate, thereby resulting in financial loss for the glass maker. However, they do reduce the down-time and lag time.

The present invention aims further to reduce the above problems.

The present invention provides a glass melting furnace fitted with a fuel injector and an oxygen feed, wherein the oxygen feed is a feed of oxidant (usually a gas) having more than S0mol% oxygen (this should be more than 50% oxygen by volume and mass when at both room temperature and atmospheric pressure). Room temperature is about 20 c.

Atmospheric pressure is about 1 bar.

In normal use, the oxygen feed is passed through the fuel injector.

The furnace might not comprise a hot air feed. However, it is not always essential for there to be no hot air feed. In fact the apparatus or method of the invention may be used, for example, to supplement an existing, or perhaps inadequate, hot air feed.

Since the oxygen feed is a feed of gas having more than SOmol% oxygen, it is more oxygen rich than air. Air usually comprises about 2Omol% oxygen.

Preferably the oxidant is a feed of a gas having at least SOmol% oxygen. More preferably, however, it has greater than 8Omol% oxygen, and perhaps even more than 9Omol% oxygen, or pure oxygen, but it is preferably a mixture of pure oxygen and air or pure oxygen and inert gas. This keeps the cost of the oxidant down. However, in most situations, the oxidant composition will be more a matter of what can be sourced, i.e. what is available. It should be noted, however, that that low oxygen concentrations may result in the need for a larger injector in order to inject sufficient oxidant, and this may lead to an impracticably large injector.

Preferably the injector comprises a central fuel line and an annular oxygen line surrounding the fuel line. If the fuel is a liquid, between the fuel line and the oxygen line, a second annular line may be provided. Preferably the second annular line is for feeding an atomising medium for atomising the fuel to help mix the fuel with the oxygen feed. This provides an efficient combustion.

Preferably the fuel line is for feeding a liquid, a gaseous fuel or a powdered solid fuel into the furnace.

The present invention is intended to allow the melting of glass to continue at full or near full production rates in a glass melting furnace during a reduced hot air feed, during a stopped hot air feed, or in a glass melting furnace not fitted with a hot air feed. It allows the furnace to be fired by burning the fuel in an environment that is more oxygen rich than hot air. Alternatively, the present invention uses the oxygen feed to supplement the hot air in situations where the hot air flow has to be, or is wanted to be, reduced. Yet further, the use of the oxygen feed allows at least similar efficiencies in the furnace to be achieved as compared to conventional hot air fed furnaces.

The present invention also provides a method of fuelling a glass melting furnace comprising injecting fuel and an oxygen feed into the melting chamber of the furnace. As before, the oxygen feed is a feed of gas having more than SOmol% oxygen. However, more preferably it is at least 80%mol oxygen, and most preferably more than 9Omol% oxygen.

Preferably the step of injecting is carried out under conditions of pressure and fuel/oxygen mixing that produce combustion of said fuel and oxygen in a region of the melting chamber such that the inner surface of the melting chamber is not at a higher temperature than during conventional firing. For example, the point of combustion might be spaced at least about 1cm, preferably at least about 5cm and most preferably at least about 10cm, from any inner surface of the melting chamber, although the distance can vary from application to application, for example depending on the size of the melting chamber.

The fuel and oxygen feed will usually be injected simultaneously. This may be done by a single injector, but more usually it would be done by multiple injectors.

The method may be carried out in the furnace described above, or using the injector as described above.

Preferably the oxygen feed is fed into the furnace at the same temperature as the fuel, or at a temperature that is not substantially increased compared to that of the fuel, i.e. within 100 C, or more preferably within 50 C of the temperature of the fuel. Preferably the oxygen feed is at a temperature of between 0 and 100 C. The prior art preheated air feed would have usually been preheated to a temperature well in excess of 500 C before injection into the melting chamber through the air port.

The present invention also provides a method of injecting oxygen and fuel into (or a method of heating) a conventional regenerative glass furnace having a preheated air supply port or channel, wherein both oxygen and fuel are injected into the furnace through one or more injector ports positioned to the side, underneath or above, or in a sidewall of, the preheated air supply port or channel of the conventional regenerative glass furnace.

The preheated air supply port is usually provided in a sidewall or endwall of the melting chamber. The location of each injector port, therefore, also is preferably provided in the sidewall or endwall of the melting chamber, and preferably adjacent the preheated air supply port. Preferably the position for the location of each injector port is the same position as used in a conventional regenerative glass furnace for conventional fuel injectors. Preferably the location of each injector port of the invention is in one of the injector ports used in the conventional regenerative glass furnace for each conventional fuel injector.

Preferably the method uses a combined fuel and oxygen injector, as opposed to separate injectors for the oxygen and the fuel. The preferred design for the injector is such that it can be fitted to the furnace using a conventional fuel injector port. Preferably the injector can simultaneously inject both the fuel and the oxygen into the melting chamber of the furnace through the injector port. In this manner, the combined injector can be a retrofit product. Further, positioning it there should avoid overheating of adjacent refractories since the prior art furnaces will already be designed to have fuel injected into the furnace in the area of the or each injector port.

The injector preferably consists of a passage through which the oxygen passes and a second passage within the oxygen passage through which the fuel is passed. Preferably the second passage is within the oxygen passage. The two passages may or may not be concentric. The two passages may or may not be cylindrical.

Preferably the oxygen passage tenninates in a nozzle - the oxygen nozzle. Preferably the oxygen nozzle can control the velocity of the injection of the oxygen - it may be adjustable. Suitable nozzles will be known to skilled persons since they will have been used for other high temperature applications.

Preferably the fuel passage terminates in a nozzle - the fuel nozzle. Preferably the fuel nozzle is suitable for delivering a gaseous fuel. When a gaseous fuel is fed to the fuel passage, preferably the fuel nozzle can regulate the gas velocity, or the gas plume characteristics, as the gas exits the fuel nozzle. Alternatively, the fuel nozzle may be suitable for liquid fuels. When a liquid fuel is fed to the fuel passage, preferably the fuel nozzle can regulate the liquid flow velocity, or liquid plume characteristics, as the fuel exits the fuel nozzle. Alternatively, the fuel nozzle may be suitable for powdered solid fuels carried in a fluid (gas or liquid). When a powdered fuel is fed to the fuel passage, preferably the fuel nozzle can regulate the powder flow velocity, or powder plume characteristics, as the fuel exists the fuel nozzle.

Suitable fuel nozzles will be known to skilled persons since they will have been used for other high temperature applications.

Preferably, the or each nozzle can be adjusted for altering or adjusting the position within, or beyond, the nozzle whereat the oxygen and fuel will mix. This allows the point of combustion within the furnace to be controlled. Preferably the point of combustion lies inside the melting chamber, and away from the sidewall of the melting chamber.

Preferably this point lies at a position sufficiently far away from the sidewall of the melting chamber to avoid overheating. This may be, for example, 10mm away from the sidewall, although the optimal distance will depend upon the application in question - i.e. the size of the melting chamber and the oxygen concentration of the oxidant. A skilled person in the art will be able to determine an appropriate distance for example by trial and error.

If liquid fuel is used, preferably the fuel passage terminates at its distal end with a liquid atomiser for producing a spray of small liquid particles. This atomiser can also be used to determine where the oxygen and fuel mix. Suitable liquid atomisers will also be known to skilled persons since they will have been used for other high temperature applications.

The fuel passage may be provided with a fuel line and an atomiser line, the atomiser line being a passage for an atomising medium. Preferably, liquid fuel will pass along the fuel line, and, upon exiting it, it will then mix with atomising medium expelled from the atomiser line - the atomising medium will have passed along and out of its own passage.

The mixing at that exit point will cause the atomisation of the liquid fuel for spraying the fuel in a more combustion friendly manner into the oxygen feed.

Preferably the mixing of the fuel with the oxygen occurs beyond the oxygen nozzle.

One or more of the liquid atomiser, the fuel passage, the fuel line, the atomiser line or the passage for the oxygen may be protected by a water jacket.

The present invention also provides a furnace system for melting glass, said system comprising a melting chamber having a first inlet therein for a preheated air feed and a second inlet associated with the first inlet for a fuel feed; an air preheater for supplying preheated air to the first inlet; a fuel injector for supplying fuel to the furnace through the second inlet when the furnace is in a preheated-air combustion mode; and a fuel-and- oxygen injector for supplying both fuel and an oxygen-enriched combustion gas to the furnace through the second inlet when the furnace is in an oxygen combustion mode.

The furnace system might be such that when the fuel-and-oxygen injector is not operating, the furnace system can still operate - i.e. in a conventional mode.

Preferably said injectors are demountable from said second inlet to permit rapid switching between said modes.

The present invention allows full or more probably near full rate production of glass to be maintained in a furnace when a hot air feed is either not provided or when it has been reduced. Further, the invention can usually achieve this with similar efficiency to fully operational conventional furnaces.

The injector of the present invention also provides a simple replacement component for existing conventional burner systems. It allows a quick and low cost conversion of existing furnaces into furnaces of the present invention.

In preferred embodiments of the invention, prior art fuel delivery systems and fuel or gas control systems are fitted, when needed. Further, in furnaces that are retrofitted with the injector of the present invention, the pre-existing fuel delivery and control systems in the furnace can also usually be retained.

Preferably the plume, jet, spray or cone of fuel and oxygen being ejected from the injector can be targeted directly into the furnace, perhaps perpendicular to the sidewall, rather than across the sidewall of the furnace. This should help the combustion to develop within the furnace in such a maimer that the sidewall refractories are not overheated.

Usually, the combustion produced by the present invention has a heat release pattern in the furnace that will be similar to conventional firing systems. Therefore, no significant changes are required in the operation or control of a furnace when it is using the present invention, as compared to conventional furnaces.

Finally, most aspects of the present invention may be used in, or by simply converting, conventional furnaces. The use of an oxygen rich gas feed to fire the furnace will often improve the efficiency of the furnace. Further, it will often lower the output of pollutants from the furnace.

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figures 1 and 2 show prior art arrangements for fuel injectors in glass melting furnaces; Figure 3 shows a preferred combined fuel and oxygen injector of the present invention in a sidewall of a furnace; Figure 4 shows the preferred injector using a gaseous fuel for retrofitting in existing furnaces; and Figure 5 shows an alternative injector of the present invention for use with liquid fuels.

Referring to Figure 1, a section through part of a prior art glass melting furnace 10 is shown. The furnace 10 comprises a melting chamber 12 at the bottom of which molten glass 14 collects. In the sidewall 16 of the melting chamber 12, an air port 18 is formed, through which hot air 20 can be fed into the melting chamber 12.

Below the air port 18, an injector port 22 is provided for a fuel injector 24. The fuel injector 24 is for injecting fuel 26 into the melting chamber 12. The fuel 26 mixes with the hot air 20 and combusts for heating or firing the melting chamber 12 so that the glass 14 within the melting chamber 12 will melt.

In the variation shown in Figure 2, instead of positioning the injector port 22 below the air port 18, two injector ports 22 are provided in the sidewalls 28 of the air port 18, each with a fuel injector 24 positioned therein. The injector ports 22 can inject fuel 26 directly into the stream of the preheated air 20. A flame 30 then forms within the melting chamber 12 as the mixed preheated air 20 and fuel 26 enter the melting chamber 12.

With the present invention as shown in Figures 3, 4 and 5, instead of using preheated air 20, an oxygen feed 32 is used. It is that oxygen feed 32 that is mixed with the fuel 26 for combustion in the melting chamber 12. The oxygen feed 32, therefore, replaces or supplements the hot air feed to provide a more efficient combustion - there is usually no need to preheat the oxygen feed, unlike air.

As shown in Figures 3 and 4, a preferred injector 33 comprises a fuel line 34 connected to a fuel source (not shown). The fuel line 34 is preferably a circular pipe having a nozzle 36 at the distal end thereof, i.e. at the end of the injector that is nearest, or within, the furnace.

This fuel nozzle 36 comprises inturned flanges, which in use will form a plume, a jet, a cone or a spray of fuel as it is ejected from the fuel line 34.

An oxygen line 38 surrounds the fuel line 34. This oxygen line 38 defines an annular space through which the oxygen feed passes.

At the distal end of the oxygen line 38, another nozzle 40 is provided. This second nozzle also comprises inturned flanges. It produces a plume, a jet or a cone 44 of oxygen. The oxygen nozzle 40 surrounds the fuel nozzle 36 at the end of the fuel line 34 so as to mix the plume, jet, cone or spray 42 of fuel with the plume, jet or cone 44 of oxygen.

The injector 33 has a fuel inlet port 46 in communication with the fuel line 34 for connecting the fuel line 34 to the source of fuel. The injector 33 also has an oxygen inlet port 48 in communication with the oxygen line 38 for connecting the oxygen line 38 to an oxygen supply (not shown). In the embodiment shown, the fuel inlet port 46 extends axially from the proximal end of the injector 33, whereas the oxygen inlet port 48 extends sideways from (or perhaps perpendicular to) the proximal end of the injector 33.

In the sidewall 16, i.e. the burner block, of the melting chamber 12, an injector port 22, similar to that shown in Figure 1, is provided. As shown, it has a tapered entrance for the injector to fit into (although the taper is not essential) and a tapered outlet facing into the melting chamber 12. The entrance is provided on the outside of the sidewall 16.

The oxygen nozzle 40 is adapted to attach into the entrance. A tight fit or seal is not essential. However, the nozzle can form a seal between the injector 33 and the sidewall 16 if it is connected tightly, perhaps with a screw fit (not shown).

The distal-most end of the oxygen nozzle 40, in this inserted position, will aim the plumes, jets, cones or sprays 42, 44 of the oxygen feed and fuel into arid through the tapered outlet of the injector port 22 so as to mix in the chamber 12, and such that neither the oxygen feed nor the fuel will contact the sidewall 16 as the fuel and oxygen feed enter the melting chamber 12. Upon entering the melting chamber 12, however, the heat within the melting chamber will cause the mixed fuel and oxygen feed to combust, thereby heating the glass 14 within the melting chamber 12.

The point which the flame develops is shown in Figure 3 as a dotted line 49. This point can be controllable by changing the design of the nozzles.

Referring now to Figure 4, the same gas injector 33 as shown in Figure 3 is again shown.

Further description thereof, therefore, is not required. However, it is removed from the furnace, and may be retrofitted into injector ports of prior art furnaces for converting those prior art furnaces into furnaces of the present invention.

Referring now to Figure 5, an alternative oil injector 50 is shown. The injector 50 again comprises an oxygen line 38 with an oxygen nozzle 40 and an oxygen inlet port 48.

However, in place of the previously described fuel line 34, a composite fuel and atomiser feed line is provided. That composite fuel and atomiser feed line comprises an internal fuel line 52 surrounded by an atomiser tube 54. The atomiser tube 54 is provided with a nozzle 56 much like the fuel nozzle 36 for the previous embodiment. However, the atomiser nozzle 56 is shown in its preferred positioned - distal to the oxygen nozzle 40 of the oxygen line 38.

The fuel line 52, which is positioned inside the atomiser tube 54 in this embodiment, does not comprise a nozzle. However, it, combined with the nozzle 56 of the atomiser tube 54, allows atomisation and mixing of the fuel and oxidant.

If desired, the fuel line may also comprise an intumed nozzle.

The fuel line 52 is adapted to receive liquid fuel. Further an atomising medium is adapted to be passed along the atomiser tube 54 from another supply source (not shown). As the liquid fuel 26 exits the fuel line 52, it mixes with the atomising medium 58 that it encounters inside the atomiser nozzle 56. This mixing, together with the action of the nozzle 56, causes a mixed liquid or fluid plume, jet, cone or spray 60 to exit the atomiser nozzle 56. That mix then gets surrounded by the plume, jet, cone or spray 44 of the oxygen feed exiting the oxygen nozzle 40 50 as to mix therewith within the melting chamber 12 - the injector 50 will be fitted to the furnace for injecting the mix of fuel, atomising medium and oxygen feed through the injector port 22 in the sidewall 16 of the melting chamber 12 into the melting chamber for combustion.

By using the injectors of the present invention, which use the oxygen feed and the fuel, the need for a hot air source in a glass melting furnace can be reduced or entirely removed.

The present invention has been described above purely by way of example. It should be noted, however, that modifications in detail may be made within the scope of the invention as defined in the claims appended hereto.

Claims (29)

1. A glass melting furnace fitted with a fuel injector and an oxygen feed, wherein the oxygen feed is a feed of gas having more than 5Omol% oxygen.

2. The furnace of claim 1, wherein the oxygen feed and the fuel injector pass through a single aperture in the wall of the furnace.

3. The furnace of claim 2, wherein the aperture is an aperture of the furnace that would normally used for conventional fuel injection.

4. The furnace of any one of the preceding claims, wherein the oxidant gas has at least SOmol% oxygen and more preferably more than 8Omol% oxygen.

5. The furnace of any one of the preceding claims, wherein the oxidant gas is a mixture of pure oxygen and air or pure oxygen and inert gas.

6. The furnace of any one of the preceding claims, wherein the injector comprises a fuel line and an oxygen line surrounding the fuel line.

7. The furnace of claim 6, the injector comprising a further line for feeding an atomising medium for atomising the fuel to help mix the fuel with the oxygen feed.

8. A method of heating a glass melting furnace comprising injecting fuel and an oxygen feed into the melting chamber of the furnace, wherein the oxygen feed is a feed of gas having more than 5Omol% oxygen.

9. A method according to claim 8, wherein the step of injecting is carried out under conditions of pressure and fuel/oxygen mixing that produce combustion of said fuel and oxygen in a region of the melting chamber that does not cause overheating of the furnace refectories in the melting chamber.

10. The method of claim 8 or claim 9, carried out in the furnace of any one of claims 1 to 7.

11. The method of claim 8, 9 or 10, wherein the fuel and oxygen feed are injected simultaneously by a single injector.

12. A method of heating a conventional regenerative glass furnace having a preheated air supply port or channel, wherein both oxygen and fuel are injected into the furnace through one or more of the furnace's conventional injector ports positioned to the side, underneath or above, or in a sidewall of, the preheated air supply port or channel of the conventional regenerative glass furnace.

13. The method of claim 12, wherein the preheated air supply port is provided in a sidewall of the melting chamber and the location of each injector port also is provided in the sidewall of the melting chamber, adjacent the preheated air supply port.

14. The method of claim 12 or 13, carried out together with the method of any one of claims 8 to 11.

15. The method of any one of claims 12 to 14, carried out using one or more combined fuel and oxygen injector for injecting the oxygen and fuel into the furnace.

16. The method of any one of claims 12 to 15, wherein the location of each injector port is in an injector port of the conventional regenerative glass furnace, as formerly used for a conventional fuel injector.

17. A furnace system for melting glass, said system comprising: a melting chamber having a first inlet therein for a preheated air feed and a second inlet associated with the first inlet for a fuel feed; an air preheater for supplying preheated air to the first inlet; a fuel injector for supplying fuel to the furnace through the second inlet when the furnace is in a preheated-air combustion mode; and a fuel-and-oxygen injector for supplying both fuel and an oxygen-enriched combustion gas to the furnace through the second inlet when the furnace is in an oxygen feed assisted combustion mode.

18. A furnace system according to claim 17, wherein said injectors are demountable from said second inlet to permit rapid switching between said modes.

19. The furnace system of claim 17 or claim 18, wherein the injector is for simultaneously injecting both fuel and an oxygen feed into a melting chamber of a glass melting furnace, the injector comprising a passage through which the oxygen feed passes and a second passage through which the fuel is passed, the injector comprising a nozzle for causing mixing of the fuel and the oxygen feed.

20. The furnace system of claim 19, wherein the second passage is within the oxygen passage.

21. The furnace system of claim 19 or claim 20, wherein the oxygen passage terminates in a nozzle.

22. The furnace system of any one of claims 19 to 21, wherein the fuel passage terminates in a nozzle.

23. The furnace system of claim 22, wherein the fuel passage comprises a fuel line and an atomiser line, the atomiser line being a passage for an atomising medium.

24. The furnace system of any one of claims 19 to 23, wherein one of the passages is protected by a water jacket.

25. The furnace system of any one of claims 19 to 24, fitted into the furnace of any one of claims 1 to 7.

26. The method of any one of claims 8 to 16, carried out using the furnace system of any one of claims 17 to 25.

27. A method of fuelling a glass melting furnace substantially as hereinbefore described with reference to Figure 3, 4 or 5 of the accompanying drawings.

28. A combined fuel and oxygen feed injector substantially as hereinbefore described with reference to Figure 3, 4 or 5 of the accompanying drawings.

29. A glass melting furnace substantially as hereinbefore described with reference to Figure 3, 4 or 5 of the accompanying drawings.