Patent Application
20100307196
The inventive embodiments relate to melting glass batch materials.
The melting of glass by combustion processes, in particular high efficiency melting, may include submerged combustion, wherein the flame is injected via burners mounted below the glass melt level. A similar effect may be created by impinging a high velocity flame downward onto and penetrating into the liquid bath, as practiced in an electric arc furnace (EAF) for the steel industry.
Conventional glass melting from above depends upon the transfer of heat from above the glass surface and by heat transferred by the liquid glass flowing under the unmolten batch material. The rate at which this heat is transferred from above the glass is dependent largely upon radiation from the crown material which imposes an upper limit on the amount of heat transferred and thus the production rate of the furnace. Heat transfer to the upper surface of the glass melt may be augmented by the nature of the combustion process itself, i.e. highly radiative flames and impinging flames can also increase the heat transfer rate at the glass melt. In such systems combustion space and exhaust gas temperatures can be high and result in high NOx emissions and heat losses in the exhaust gas. Glass melting from below the melt is dependent upon the glass temperature below the batch and its movement.
Submerged combustion provides for intimate contact of the combustion gases with the glass melt. Furthermore, submerged combustion creates agitation to the glass bath, which provides better mixing between undissolved batch material and molten glass. Both factors contribute to more rapid melting and lower exhaust gas temperatures.
However, submerged combustion burners and their integration into the side or bottom of the melter below the molten glass level present problems for burner maintenance and repair, operation, monitoring, and localized wear.
For a more complete understanding of the present embodiments, reference may be had to the following detailed description of the embodiments taken in conjunction with the drawing figures, of which:
By impinging the surface of the glass with a supersonic combusting jet such that the combusting jet displaces a surface of the glass melt and penetrates into the melt, the benefits of submerged combustion (better heat transfer, high efficiency, low NOx, better mixing, rapid melting) are achieved without the need for a burner or injector to be placed below the glass level.
A further embodiment is the inclusion (by injection or otherwise) of glass forming batch material in the supersonic combusting jet or flame in such a manner that the solid material is directly injected into the body of the glass melt rather than floating on the surface. This further enhances the penetration of the supersonic combusting jet into the melt, and the mixing of the batch and glass material.
The process of creating a submerged combustion effect by impingement of a high momentum supersonic combusting jet from above and its penetration into a bath of liquid glass may include the burner and flame jet disposed vertically or angled with respect to a surface of the glass bath, or injecting glass forming batch material concurrently with the supersonic combusting jet into the glass bath.
Penetration of the high momentum supersonic combusting jet into the glass bath produces a shearing action sufficient to enhance the solution rate of the glass forming batch material. Melting of the glass forming batch material proceeds more quickly, and/or at a lower temperature than occurs in a comparable conventional glass melting furnace.
Referring to
An injection system of the inventive embodiment is shown generally at 16 and includes a burner 18 or injector device (for the sake of brevity referred to as a “burner”) mounted to a crown 20 of the furnace 10. The burner 16 is arranged with its exhaust 22 or discharge outlet perpendicular to a surface 24 of the glass bath 12 or alternatively, disposed at an angle other than perpendicular with respect to surface 24 of the glass bath 12, as shown by the broken line 26. The burner 16 is constructed to provide a supersonic flame jet 28 to contact and displace the glass bath 12 such that the jet 28 penetrates into the bath 12 up to a depth indicated as “D” of approximately one-half a depth of the glass bath 12. The supersonic flame jet 28 can penetrate typically from one foot (0.305 meter) to three and one-half feet (0.991 meter) into the glass bath 12. As shown in
Referring to
A high pressure nozzle 34 or Laval nozzle supplies an oxidant such as an oxygen stream 36 about the fuel nozzle 31 for providing oxygen to mix with the fuel. Regardless of whether the fuel and oxygen streams are mixed internal to the burner 16 or external to the burner 16, the result of the mixing is that the supersonic jet 28 results for contacting and penetrating into the glass bath 12.
Referring to
The supersonic combusting jets 28,40 of
The fuel and oxidant streams 32,36 can be arranged co-axial or as separate streams proximate each other.
The burner 16 can be water-cooled, such as with a water jacket (note shown) for those occasions when the streams are mixed within the burner.
If the solid glass material feed is included in the fuel stream 32, a central passage 42 or channel such as shown in
Mixing of the fuel stream 32 and the oxygen stream 36 is done with sufficient force such that said streams 32,36 interact to produce the supersonic jet streams 28,40.
The penetration of a high momentum supersonic flame jet 28,40 into the glass bath 12 produces a shearing action sufficient to enhance the solution rate of the glass forming batch material. Melting of the glass forming batch material in the bath 12 proceeds more quickly, and/or at lower temperatures than occurs in a comparable conventional glass melting furnace. The burner 16 therefore provides for an increased melt rate, reduced melter size necessary for the melt operation, improved efficiency due to lower exhaust gas thermal losses, lower NOx due to lower temperatures, and elimination of submerged burners and complications associated therewith.
It will be understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make many variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the present embodiments as described and claimed herein. It should be understood that the embodiments described above are not only in the alternative, but may be combined.
