Patent Application
20110011134
The present embodiments are related to bubbling with gas in a glass bath of a melter.
Bubbling with gases, typically air, is a common practice in glass melting as it is used to reinforce convection currents within the glass bath or melt for improving melter performance. Further increases in performance may be achieved by bubbling with a pair of reactive gases, such as hydrogen and oxygen, in glass baths to improve refining, grain dissolution and reduce foam through controlled micro-explosions that result in a shock wave permeating the glass bath. Such gases are introduced through separate lines or conduits disposed indiscriminately with respect to a bottom of the melter to be in communication with the glass bath for introduction of the gases into the glass bath. The arrangement of existing gas passages is not conducive to the controlled mixing of the bubbles and explosions thereof with respect to the melt in the glass bath.
In a column of rising bubbles the location at which bubbles come together is difficult to predict, as it is strongly influenced by local conditions at a tip of each distinct bubbler, which may itself influence local conditions depending upon installation of the bubbler. A bubble will enlarge as it rises through the glass melt, due to a decrease in pressure exerted on the bubble by the remaining head of glass melt above and a rise in bubble temperature as it moves through the hot glass. As a bubble expands, its edges become closer to adjacent bubbles and, in the case of separate reactive hydrogen and oxygen bubbles, contact occurs causing the explosive reaction between the hot gases within the bubbles.
For any given glass being melted, the glass properties such as density, temperature and viscosity, all impact bubble formation. For example, viscosity is sensitive to temperature changes. Flow rate effects bubble formation diameter and separation, with higher flow rates tending to form larger bubbles. These factors influence the bubble separation frequency, a bubble's diameter and the bubble's ascent velocity through the melt, as larger bubbles rise at a faster rate. In addition, bubble diameter and velocity can be influenced by neighboring or adjacent bubbles. The initial distance between bubbles is important, as it influences not only the initial lateral edge-to-edge distance of a plurality of bubbles but also, bubble-to-bubble flow interference.
Accordingly, control over the hydrogen and oxygen bubble interaction location is desirable because (1) if the bubbles do not contact each other within the melt, no micro explosions will occur, which is desirable; and (2) if the bubbles come together at a position too close to a bottom of the melt in the furnace, shock waves that result may disturb the layer of slowly moving or quiescent glass bounding the refractory bottom of the furnace, thus exacerbating refractory 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:
Referring to
The injector 10 may be constructed as a separate integral unit which is mounted or releaseably mounted into a bore 18 of a furnace bottom 20. The injector may be mounted within a refractory bubbler block which is constructed integral with the bottom of the furnace or melter. The injector 10 may also be cast as a portion of the furnace bottom 20, such as for example if the furnace is constructed of modular parts joined together. With either construction, at least one passageway 22 is formed in the injector 10 for providing oxygen, while at least one passageway 24 is formed in the injector 10 for providing hydrogen.
A controller 26 is connected by control lines 28 to control valves 30 or other types of bubble initiators. The control valves 30 are mounted to gas supply lines which are connected to respective ones of the passageways 22, 24, to emit bubbles through the passageways 22, 24 at a select frequency for such emissions, which are discussed further below. A gas supply line 23 is connected to a high pressure oxygen (O2) source. A gas supply line 25 is connected to a low pressure O2 source. A gas supply line 27 is connected to a high pressure hydrogen (H2) source; while a gas supply line 29 is connected to a low pressure H2 source.
The gas supply lines 23, 25, 27, 29 (collectively referred to as “23-29”) to the injector 10 can operate continuously or in a pulsating manner, by the controller 26 controlling the valves 30. The injector 10 operates by the controller 26 switching a gas supply to the injector 10 from a low or holding pressure phase, to a high pressure phase. During the low pressure phase, the pressure is such that the gas inhibits molten glass from the glass bath 12 from flowing into the passageways 22, 24 by maintaining a bubble cap 22A at the passageway exit as shown in
As shown in
Passageway 122 provides oxygen; while passageway 124 provides hydrogen to the injection 110 for distribution into the glass bath 112. A top edge 114 or surface of the injector 110 as shown in
By controlling the initial bubble separation and separation frequency in the embodiment, this will improve the control over the location at which separate bubbles of hydrogen and oxygen will come together in the glass bath 12, 112, thus reducing risk that (i) the bubbles will not meet within the bath and thus have no beneficial influence on the process, and the bubbles do not interact too close to the furnace bottom causing refractory deterioration; and (ii) a single bubbler arrangement for the delivery of both hydrogen and oxygen reduces the number of holes within the bottom of a glass furnace and ensures accurate, reliable bubble center-to-bubble center distances.
The injector 10, 110 may be water cooled. That is, for example, the bore 18 may include a space or further passageway for providing a fluid jacket surrounding the injector 10, 110. The injector may also include a space in which the cooling fluid is disposed and circulated. Water can be circulated through the space. While the cross section of the embodiment of
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.
