JPS606900B2 - glass electric melting furnace - Google Patents

Description

[Detailed description of the invention] The present invention relates to an electric glass melting furnace.

Various types of electric glass melting furnaces have been developed in which electricity is applied directly to the glass through electrodes that are in contact with or immersed in the molten glass, and the glass is melted only by the generated Joule heat.

A rod-shaped body of molybdenum or tin oxide is usually used as the electrode, and the electrode bar is inserted into the furnace from the side wall or bottom of the furnace. However, when it is necessary to apply large amounts of power to the glass, the use of rod-shaped electrodes becomes inappropriate because the current density on the surface of each electrode rod becomes excessive. On the other hand, there is also a type of electric melting furnace that uses plate-shaped electrodes and arranges the plate-shaped electrodes along opposite longitudinal sides of a square or rectangular furnace to generate a current uniformly between both electrode slopes. known (see USP 289,947 degrees). In this type of electric melting furnace, glass raw materials are fed onto the surface of the molten glass in the melting section, and after being sequentially melted and refined downward, the glass passes through a throat provided at the bottom of the riser and rises. The working part is reached by a first-class flow path.

In order to prevent unmelted and/or unfined glass from penetrating downward and reaching the working area, the furnace is operated with a so-called "thermal barrier" having a maximum temperature at a level near the top of the plate electrode. However, in this type of furnace, inhomogeneous or bubbly molten glass often descends along the inner wall of the furnace and reaches the working area, which can lead to defects in the product. Such difficulties are unavoidable in electric melting furnaces that sequentially melt and refine glass in all directions.

The object of the present invention is to provide an all-electric glass melting furnace that does not have the above-mentioned disadvantages, and in particular uses plate-shaped electrodes.
To provide an electric melting furnace of a type that melts and refines glass horizontally.

Therefore, the electric glass melting furnace according to the present invention has a plurality of plate-shaped electrode groups disposed along both side walls and immersed in the molten glass, and has a melting furnace that melts the glass by directly applying electricity to the molten glass. It consists of a tank, a narrow neck part that is connected to the melting tank and guides the molten glass downstream, and a downstream tank that is connected to the neck part and into which the molten glass flowing out from the melting tank flows. A hot spot is provided near the neck by immersing the molten glass and placing a plate-shaped electrode thereon and heating the molten glass by directly applying current to the molten glass. It is characterized by providing a glass flow adjusting member made of a refractory and immersed in the glass.

In conventional horizontal glass melting furnaces, a throat structure is used to prevent unmelted or unfined glass from the melting tank from flowing into the downstream tank (which functions as a flow path for fining, temperature adjustment, or forming machines). It is common practice to provide a mechanical barrier such as the .

In the present invention, a neck structure is adopted in place of the throat, an electrode is installed here, and the glass in this part is heated by electricity to form a so-called hot spot and produce a thermal barrier effect.

Therefore, the forward flow of glass advancing at the bottom of the melting tank rises at this hot spot and returns to the melting tank again,
It will not flow directly into the downstream tank. A second feature of the furnace of the present invention is that a glass flow adjustment member made of a refractory material and whose lower end is immersed in molten glass is provided near the center of the melting tank along the direction of glass travel. In an all-power glass melting furnace, covering the entire surface of the melting furnace with a layer of raw material having a certain thickness is not only thermoeconomically effective but also essential for obtaining high quality glass. In the furnace of the present invention, the return flow of the thermal convection generated at the neck portion directly pushes the zero raw material layer in the melting tank, causing an exposed portion to appear in the raw material layer, disrupting the thermal balance and keeping the temperature constant. In order to avoid impossibility of retention, the glass flow adjusting member is provided in the center where the return flow is strongest. The glass flow regulating member is covered with a heat-resistant and corrosion-resistant metal plate, such as molybdenum, to prevent erosion due to convection.

It is effective to use this metal plate as the center electrode and generate a current between it and the plate-like electrode of the melting tank, since it allows the use of a multiphase AC power source. 0 The invention will now be described with reference to the accompanying drawings.

FIG. 1 is a plan view of an example of an electric glass melting furnace according to the present invention, FIG. 2 is a longitudinal sectional view thereof, and FIG. 3 is a plan view of another example of the electric melting furnace. , FIG. 4 shows a longitudinal section thereof. FIG. 5 is a plan view of still another example of the electrode melting furnace, and FIG. 6 is a longitudinal sectional view thereof. In FIGS. 1 and 2, 1 is a melting tank, 2 is a neck section which is a narrow connecting groove installed in front of the melting tank, and 3 is a downstream tank following the neck section. A frit feeder 5 is provided at the frit inlet 4 at the rear end of the melting tank, and feeds the frit into the surface of the molten glass 6 in a layered manner.

Reference numerals 7 and 8 indicate three pairs of plate-shaped electrodes that are immersed in the molten glass and arranged to face each other along both walls in the middle direction of the melting tank.

In the center of the melting tank, a glass flow adjusting member 9 consisting of six refractory blocks is installed in the direction in which the glass travels, that is, along the center line in the longitudinal direction of the tank, with its lower end lower than the level 11 of the glass. It is installed so that it is submerged in glass so that it faces downwards.

By installing the glass flow adjusting member 9, the return flow a from the hot spot formed in the neck portion does not proceed through the surface layer in the center of the melting tank, and does not directly push back the glass raw material layer.

Furthermore, although there is a glass layer with many bubbles, a so-called foam layer, below the frit layer, the presence of the member removes the frit layer from the central region of the melting tank, so that bubbles are not caught up in the return flow. Reduces the risk of being exposed. The depth of penetration into the glass of the glass flow adjustment section should be a value that exceeds the frit layer and the foam layer below it, and should be determined based on the temperature difference between the melting tank and the neck and other conditions.

The glass flow adjusting member is preferably covered with a metal plate having excellent heat resistance and corrosion resistance, such as molybdenum, and further preferably, this metal plate is used as a central electrode.

Two pairs of plate-shaped electric plates 12 and 13 arranged in the depth direction along both side walls of the neck part 2 are placed facing each other, and the molten glass at the bottom to middle part of the neck part is energized and strongly heated. A so-called hot spot, the highest temperature castle, will be set up in this area.

Thus, a turning point of convection appears in this hot spot, and the forward flow b moving forward in the bottom layer of the melting tank rises here.
A part becomes the forward flow c flowing on the surface layer of the downstream tank 3, and the rest is combined with the return flow a flowing backward on the surface layer of the melting tank. Return flow a
By strongly maintaining , the glass raw material layer (not shown) covering the glass surface of the melting tank is prevented from advancing from the melting tank to the neck part, and the forward flow c in the downstream tank constituting the glass to be formed is prevented. Prevents unmelted or non-uniform glass from being mixed in. d indicates a return flow that moves backward through the bottom layer of the downstream tank. A wider downstream tank 3 following the neck part 2
is provided.

Depending on the operating conditions such as the type of glass to be melted, this downstream tank 3 may be used as a so-called fining tank to further clarify the glass, and may also be used as an adjustment tank (working tank) to adjust the temperature of the glass to a temperature suitable for molding. It can also be used as a cooling tank. Moreover, it can also be used simply as a flow path for guiding glass to a molding machine. 14 indicates the outlet of the downstream tank.

Reference numerals 15 and 16 indicate plate-shaped electrodes that are immersed in the glass and placed opposite to each other along both side walls near the inlet of the downstream tank.

One to several pairs of plate-shaped electrodes may be further provided downstream of the downstream tank, and an electric heater may be suspended from the bottom to provide indirect heating. The bottom of the downstream tank is stepped up, ie located above the bottom of the neck. Reducing the depth of the glass makes it easier to degas, and since strong convection is not required in the downstream tank, making it shallower makes it easier to keep warm.5 The plate electrodes 7 and 8 of the melting tank are connected to a power source, A single-phase power source 301 is connected, and similarly, the plate-shaped electromagnetic devices 12 and 13 at the neck portion are connected to the single-phase power source 31, and the plate-shaped electrodes in the downstream tank are connected to the single-phase power source 32, respectively.

In the embodiment shown in FIGS. 3 and 4, a barrier hole is provided at the center of each of the six glass flow adjustment members 9, and six central electrodes 10 are arranged in a row downward from the top of the tank. Arranged in

The lower end of the central electrode 10 is immersed in molten glass so that the lowermost end is approximately at the same level as the lowermost ends of the plate electrodes 7 and 8.

The center electrode is preferably round rod-shaped for reasons of mounting support or replacement, but it may also be square rod-shaped or flat plate-shaped. By installing the central electrode, as will be described later, it is possible to use multiphase AC power, which has a higher power utilization rate, instead of single-phase AC power. The connection method with the power supply in this case will be explained.

The plate electrodes 7 and 8 and the center electrode 10 of the melting tank are connected to a two-phase AC power source 33.

In this example, the power supply is a so-called Scott-connected transformer that converts three-phase to two-phase using two single-phase transformers, where U, V, and W are three-phase AC power supplies. TM indicates a throne transformer, and TT indicates a T-seat transformer.
The plate-shaped electrode 7 is connected to the u terminal on the secondary winding side of the TM and the plate-shaped electrode 8
are respectively connected to the terminal on the secondary winding side of TT. On the other hand, the central electrode 10 is connected to a neutral terminal o, which is a combination of the terminals of the secondary windings of TM and TT having the same polarity. In this way, a current can be generated at a uniform current density throughout the entire melting tank, and heat can be generated. Figures 5 and 6 are
Still another embodiment of the electric melting furnace of the present invention is shown, in which the neck part 2 gradually expands inward toward the front, and the front end is in the same interior as the downstream tank.

The figure shows two pairs of plate electrodes 17 and 18 arranged vertically along both side walls of the neck portion, and three pairs of plate electrodes 19 and 20 arranged vertically in parallel thereto. This applies a large amount of power to the glass to further strengthen the formation of hot spots at the neck.
Furthermore, by applying a large amount of electric power between the plate electrodes 21 and 22 placed at the downstream tank inlet, two hot spots are formed near the neck and the clarification tank inlet, as shown in FIG. Fining is becoming more effective in these areas. In FIG. 7, plate-shaped electrodes 23 and 24 are provided along both side walls of the neck portion, and a third plate-shaped electrode 25 is further provided on the step-up wall surface between the neck portion 2 and the downstream tank 3. It will be done.

Preferably the three electrodes are arranged symmetrically.
In such an arrangement, each electrode is connected to a three-phase AC power source 34.
is connected to.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an example of an electric glass melting furnace according to the present invention, and FIG. 2 is a longitudinal sectional view thereof. FIG. 3 is a plan view of another example of the electric glass melting furnace according to the present invention, and FIG. 4 is a longitudinal sectional view thereof. Fifth
The figure shows a plan view of another example of an electric melting furnace, and FIG. 6 shows a longitudinal cross-sectional view thereof. FIG. 7 shows another example of the arrangement of electrodes in the neck portion. DESCRIPTION OF SYMBOLS 1... Melting tank, 2... Neck part, 3... Downstream tank, 4... Glass raw material input port, 5
... Glass feeder, 6... Molten glass, 7,8
... Plate electrode, 9... Glass flow adjustment member, 10... Center electrode, 11... Glass level 12, 13...Plate electrode, 14...Glass outlet, 15, IS...Plate electrode, 17,18...Plate electrode, 19,20,21,22...Plate electrode, 23,
24, 25... Plate electrode, 30, 31, 32... Single phase AC power supply, 33... Two phase AC power supply, 34... Three phase AC power supply. Tano drawing, 2 drawings of rhombus, 3 drawings of grass, 4 drawings of rhombus, 4 drawings of hair, 4 drawings of hair, 5 drawings of hair

Claims (1)

[Scope of Claims] 1. A melting tank that has a plurality of plate-shaped electrodes arranged along both side walls and immersed in the molten glass and melts the glass by directly applying electricity to the molten glass, and a melting tank that is connected to the melting tank to melt the glass. It consists of a narrow neck part that guides the molten glass downstream, and a downstream tank that is connected to the neck part and into which the molten glass flowing out from the melting tank flows.A plate-shaped electrode is placed in the neck part and immersed in the molten glass. A hot spot is provided near the neck by directly applying electricity to the glass to heat it, and a glass flow adjustment member made of a refractory material whose lower end is immersed in the molten glass is placed near the center of the melting tank along the direction in which the glass travels. An electric glass melting furnace characterized by being provided with a member. 2. The electric glass melting furnace according to claim 1, wherein the glass flow adjusting member is covered with a heat-resistant and corrosion-resistant metal. 3. The electric glass melting furnace according to claim 1, wherein a central electrode is installed in the glass flow adjusting member in contact with the molten glass, and a current is generated between the center electrode and the plate electrode of the melting tank. 4. The electric glass melting furnace according to claim 1, wherein the bottom of the downstream tank is located above the bottoms of the melting tank and the neck portion. 5. The electric glass melting furnace according to claim 1, wherein in the downstream tank, at least one pair of plate-shaped electrodes are disposed facing each other along both side walls thereof and immersed in the molten glass. 6. Electric melting of glass according to claim 3, wherein the plate electrode and center electrode of the melting tank are connected to a multi-phase AC power source, and the electrode of the network portion is connected to a single-phase or multi-phase AC power source. Furnace.