JPS6284217A - Glass melting furnace - Google Patents

Abstract

PURPOSE:To prevent a salt from being volatiled and enable a continuous taking-out processing to be performed when a compound containing a large amount of salt is processed to form a state of glass by a method wherein a molten glass discharging port is arranged at a bottom part of melting tank, a molten salt flow passage is formed near a surface of liquid, a heating electrode for performing a direct heating of the glass and an electrolysis electrode for the molten salt are provided. CONSTITUTION:AC power is supplied to a molybdenum electrode 5 near a bottom part of a furnace, and after a glass temperature is increased, a silicon carbide heater 7 located on the upper part of a melting tank 1 is removed. At first, a raw compound containing no salt is continuously supplied to the upper part of the melting tank and a height of the molten glass in the melting tank is increased to a desired value. Then, a glass flowing-out pipe 3 made by Inconel Inc. located at the bottom part of the melting tank is heated by an electric furnace 4 which is provided with the silicon carbide heater 7 and a thermocouple 8, respectively. The temperature is kept constant, thereby a normal or regular operation for making a continuous flowing-down of a specified amount of glass is continued while the upper surface of the melting tank is covered with a cold raw material. Thus, the carbon electrode 6 located at the upper part of the melting tank is inserted into the glass. DC electric power is supplied and then a polarization phenomenon is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION A1 Technical Field of the Invention The present invention relates to a glass melting furnace, and more particularly to a glass melting process for the continuous vitrification of non-vitrifying salt-rich mixtures, such as waste materials. A single melting tank that can continuously take out the salts that do not become glass components out of the furnace while preventing them from volatilizing into the atmosphere, and continuously take out only the glass melt from the bottom of the melting tank. The present invention relates to a glass melting furnace. It also includes a method of electrolyzing the molten salt that accumulates in the upper part of the melting tank, thereby converting the cations in the salt, which were in a non-vitrified form, into a vitrified form.

B. Prior Art and Problems It is well known that vitrification of waste is more effective than other treatment methods in reducing volume and preventing elution of harmful components. Conventionally, when general industrial waste is vitrified, the composition of the waste always fluctuates compared to the raw materials used for ordinary glass melting, and the substances it contains are salts that are difficult to vitrify (e.g. There are differences such as sometimes existing in the form of sulfides, chlorides, etc.). Taking common salt as an example of a salt that is difficult to vitrify, most of the salt evaporates without being decomposed because the surface of the molten glass is always at a high temperature in a normal melting method. In addition, because the amount of salt dissolved in glass is small, it has been difficult to vitrify waste containing a large amount of chloride while eliminating volatilization.

C0 Purpose of the Invention The present invention has been made in view of the current situation, with the aim of vitrifying a mixture 1, such as waste, containing a salt (e.g. chloride) that dissolves in a small amount in glass.
In addition to preventing volatilization of the molten salt, the salt that does not dissolve in the glass (which becomes molten salt when melted) is continuously taken out of the furnace, or the alkali components in the molten salt are introduced into the glass as glass components. On the other hand, it has the advantage that the molten glass can be continuously flowed out using a simpler method than in a normal glass melting furnace.

Structure of the D0 invention: In other words, the glass melting furnace of the present invention has an outlet for the molten glass at the bottom of the melting tank, a flow path for the molten salt near the liquid surface of the molten glass, and the glass melting furnace directly enters the melting tank. It is characterized by providing a heating electrode for heating and an electrode for electrolysis of molten salt.

E. Example Example 1 Hereinafter, the present invention will be explained by examples.

FIG. 1 is a sectional view showing the structure of the glass melting furnace of the present invention.

The melting tank (2) is equipped with a molten salt outlet (2) on the side wall of the furnace, an Inconel glass outlet pipe (2) at the bottom of the furnace, and an electric furnace (2) for heating (2). A total of two pairs of electrodes are installed in the melting tank ■, one pair each on the upper and lower stages, but the one pair of electrodes near the bottom of the furnace is made of metal molybdenum, and this electrode uses AC power to heat the glass. Connected to equipment that can be supplied. In addition, the upper pair of electrodes ■ are made of carbon, and these electrodes are mainly used for electrolysis, and are designed to prevent polarization during electrolysis. It is connected to a power supply device which is constructed so that power (reversing) can be supplied repeatedly and the intervals between these can be adjusted by means of a timer.

Between the melting tank ■ and the molten salt outflow part ■, a throat [phase] of the molten salt flow path that connects the melting tank ■ and the molten salt outflow part ■ is provided at a position slightly higher than the installation position of the carbon electrode. ing. In addition, the electric furnace that heats the melting tank ■, the upper part of the molten salt outflow part ■, and the Inconel glass outflow tube is equipped with a silicon carbide heating element ■ and a thermocouple ■. A thermocouple ■ is inserted into the glass.

The glass melting furnace of the present invention is operated as follows.

First, glass cullet with a basic composition that does not contain salt is placed into the melting tank ■ to a height where the electrode ■ can be inserted.
Electricity is applied to the silicon carbide heating element (■) at the top of the melting tank to gradually raise the temperature of the furnace. Next, after the input cullet has been sufficiently softened, a molybdenum electrode (2) is inserted into the glass melt, and AC power is supplied to the electrode. After the glass temperature rises further by applying electricity to this electrode, the silicon carbide heating element at the top of the melting tank is removed, and a raw material mixture that does not contain salt is continuously fed to the top of the melting tank using an automatic raw material feeder. death,
After raising the height of the molten glass in the melting tank to a predetermined value,
The Inconel glass outflow pipe (2) installed at the bottom of the melting tank is heated in an electric furnace (2), and by keeping the temperature constant, a certain amount of molten glass is continuously flowed downward. After the outflow of molten glass reaches a stable state, the amount of power input to the electrodes and the amount of glass outflow are adjusted so that steady operation can be continued in which the glass flows out while covering the top surface of the melting tank with cold raw materials.Next, The carbon electrode installed at the top of the melting tank is inserted into the glass, and the 5i
O263, Na 2025, CaO10, Al 20
32 (wt%) of soda and lime glass with a basic composition of 100% and 5% and 10.20% of common salt were added to the furnace, respectively. It was used continuously for about 3 days.

When raw materials containing salt were put into the furnace, a cold raw material layer was formed on the surface of the melting tank and a molten salt layer was formed below it, but this molten salt was transferred between the melting tank ■ and the molten salt outlet ■. It passed through the throat [phase] in between and continuously flowed out from the molten salt outlet 0. In the steady operation state of the furnace, raw materials are supplied to the upper part of the melting tank, glass is flowed out from the lower part of the melting tank, and molten salt is taken out of the furnace from the molten salt outflow section. I was able to do it continuously. While melting raw materials containing salt, continuous operation was performed with the top surface of the melting tank always covered with cold raw materials, so almost no salt volatilization from the surface of the melting tank was observed.

F0 Effects of the Invention In the present invention, when vitrifying a compound containing a large amount of salt that is difficult to vitrify, for example, common salt, the salt can be prevented from volatilizing and can be taken out continuously. ,
This is thought to be due to the following reasons.

Even if a compound containing salt is added to the top of the melting tank.

In this type of electric furnace, which directly heats the glass melt with the electrode, the glass can be melted below while the upper surface of the melting tank is always covered with cold raw material. It is possible to eliminate the volatilization of glass components that occurs during vitrification. In addition, a vitrification reaction is actively occurring between the raw material layer and the glass melt at the bottom of the melting tank, but since the salt in the compound has a lower specific gravity than the molten glass, it separates from the glass liquid and melts the glass. It accumulates between the upper surface of the glass and the lower part of the raw material layer. By forming a molten salt channel [phase] at the position of this accumulated layer, the molten salt could be continuously taken out of the furnace. To achieve this, it was necessary to control the amount of glass flowing downward through the glass outflow tube (1) and to keep the glass melt level constant.

Separately, in this experiment, an electrode for molten salt electrolysis was installed above the melting tank The following effects were observed by using electrolysis in combination with repeated electrolysis: - direct current (positive/negative reversal) - alternating current.

In other words, the expansion coefficient and softening point of the outflow glass were investigated, but 1
The expansion coefficient of the basic glass without salt is ll0XIO'
/”C<, the softening point was 569°C, but the basic glass 1
The outflow glass obtained from the raw material with 20 parts of common salt added to 00 parts has an expansion coefficient of 125 x 10' and a softening point of 558 °C. Compared to the base glass, the expansion coefficient is large and the softening point is lower. Was.

This behavior is consistent with that when the amount of Na20 in the glass increases. This increase in Na2Q in the glass is caused by supplying DC power to the carbon electrode installed in the upper part of the melting tank, which causes a part of the molten salt to be electrolyzed, and at the cathode, the 10 Na in the molten salt becomes metallic Na, and further It is thought that this is due to the fact that it was oxidized to Na2O and dissolved in the glass.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an outline of an embodiment of the present invention. ■ Melting tank, ■ Molten salt outflow section, ■ Inconel glass outflow tube, ■ Electric furnace, ■ Molybdenum electrode, ■ Carbon electrode, ■ Silicon carbide heating element, ■ Thermocouple, ■ Thermocouple, [Phase] Molten salt channel , O molten salt outlet patent applicant Director of the Agency of Industrial Science and Technology Tatsu Todoroki Designated agent Ryozo Hayami, Director of the Osaka Institute of Industrial Science and Technology No change in the content of the engraving of the drawing) Akira 1st procedural amendment band (method) % formula % 2 , Name of the invention Glass melting furnace 3, Relationship with the case of the person making the amendment Patent applicant address 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo Name (114) Director of the Agency of Industrial Science and Technology Tatsu 4, Designated agent Address: 1-8-31 Midorigaoka, Ikeda City, Osaka Prefecture Shipping date:
January 28, 1986

Claims (2)

[Claims] (1) A glass melting furnace consisting of a single tank, characterized in that an outlet for molten glass is provided at the bottom of the melting tank, and a flow path for molten salt is formed near the liquid surface of the molten glass. (2) The glass melting furnace according to claim 1, wherein the melting tank is provided with a heating electrode for directly heating the glass and an electrode for electrolyzing the molten salt.