JPH07113582A - Heat insulating furnace for aluminum melt - Google Patents

Abstract

PURPOSE:To reduce the time required for raising the temperature of a crucible and energy consumption costs. CONSTITUTION:A heat insulating furnace for aluminum melt comprises a crucible 3 capable of containing the aluminum melt, a furnace body 1 supporting the crucible 3 in a surrounding relationship and a pair of burners 5, 6 facing free space 2 defined between the crucible 3 and the furnace body 1 and alternately effecting the supply of combustion air and the discharge of combustion gas through a thermal storage matter. A partition wall 20 is provided in the free space 2 in order to partially separate the pair of the burners 5, 6 from each other. The combustion gas of high temperature flows around the partition wall 20 and is prevented from taking short pass to exhaust line so that the combustion gas is made to flow around the crucible before being discharged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten aluminum heat insulation furnace. More specifically, the present invention relates to improvement of a heating and heat retaining structure of a molten aluminum heat retaining furnace.

[0002]

2. Description of the Related Art As shown in FIG. 4, an aluminum molten metal heat insulation furnace supports a crucible 101 by surrounding a graphite crucible 101 with a furnace body 102 lined with a refractory heat insulating material so as to support the crucible 101. The heater 104 provided on the inner wall surface heats the crucible 101 to keep the molten aluminum 103 in the crucible 101 at a predetermined temperature, for example, 700 ° C. or higher (see Japanese Utility Model Publication No. 5-26476).

[0003]

However, in the conventional aluminum molten metal heat insulation furnace, the inside of the furnace and the crucible are heated to a predetermined temperature and kept at a constant temperature by the electric heater 104 installed on the wall surface and having a high energy cost. Running costs will be high. Further, since the electric heater has poor heating efficiency and cannot raise the temperature inside the furnace, there is a problem that it takes time to raise the temperature to a predetermined temperature inside the furnace.

An object of the present invention is to provide an aluminum molten metal heat insulation furnace which has a short heating time and a low energy consumption cost.

[0005]

In order to achieve the above object, a molten aluminum heat insulation furnace of the present invention comprises a crucible for containing molten aluminum, a furnace body surrounding and supporting the crucible, a crucible and a furnace body. An aluminum molten metal heat insulation furnace provided with a free space between the two and at least a pair of burners for alternately supplying combustion air and discharging combustion exhaust gas via a heat storage body, and a pair of them in the free space. A partition wall is provided to partially partition the burners.

In the molten aluminum heat insulation furnace of the present invention, an emergency heater for heating the side wall surface of the crucible is installed on the inner wall surface of the furnace body.

[0007]

Therefore, when the temperature inside the furnace is raised to a temperature suitable for keeping the temperature of the molten aluminum, heat is obtained by burning the burner in the free space around the crucible. Combustion of the burner, a pair of burners are burned alternately, when high-temperature combustion exhaust gas is passed through the heat storage body on the other burner side and exhausted,
The sensible heat is directly recovered by heat exchange in the heat storage body. Then, the heat recovered in the heat storage body is used for preheating for supplying combustion air with extremely high temperature efficiency by direct heat exchange, and is returned to the furnace again. The temperature of the combustion air at this time is
Since the temperature can be set to a high temperature close to the temperature of the combustion exhaust gas flowing out to the heat storage body, combustion can be maintained with a small amount of fuel by using this high temperature combustion air, and the temperature in the furnace can be rapidly raised. Also,
Due to the partition wall provided in the free space between the crucible and the furnace body, the high temperature combustion exhaust gas bypasses the partition wall and flows around the crucible along the crucible to be heated and then exhausted. Prevent short passes.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 and FIG. 2 show one embodiment of the molten aluminum heat insulation furnace of the present invention. This molten aluminum heat insulation furnace has a furnace body 1 in which, for example, a steel plate casing is lined with a refractory heat insulating material.
And a crucible 3 made of graphite, which is housed so as to be suspended in the center of the furnace body 1, and a heat storage type burner system 4 serving as a heat source. In this embodiment, one system of the regenerative burner system 4 is provided, but two or more systems may be installed.

The furnace body 1 surrounds and supports the crucible 3 containing the molten aluminum, and keeps the crucible 3 and its surroundings at a temperature suitable for keeping the temperature of the molten aluminum. For example, as shown in FIG. It has a bottomed cylindrical shape and is provided so as to suspend the crucible 3 in the center. The crucible 3 is provided such that the upper flange portion 3 a is placed on the furnace body 1 and the portion below the flange is inserted into the furnace body 1. Then, the bottom of the furnace body 1 is provided so as to form a free space 2 under a suspended crucible 3.
Further, a partition wall 20 is provided in the free space 2 portion, and the furnace body is partitioned into a C shape. Further, an emergency electric heater 21 is installed on the inner wall surface of the furnace body 1. As the electric heater 21, for example, a ribbon heater is adopted.
The inside of the furnace body 1 is sealed by a crucible 3, and the crucible 3 is covered with a lid (not shown).

In the free space 2 portion of the bottom of the furnace body 1, at least one system of regenerative burner system 4 is arranged. In the case of the present embodiment, a pair of burners 5 and 6 constituting the system are arranged with the partition wall 20 interposed therebetween. The heat storage type burner system 4 is not particularly limited in its structure and combustion method, but in the present embodiment, a duct in which a heat storage body is incorporated is connected to a burner body to integrate the heat storage body and the burner. Combining two units and burning them alternately,
What is provided so that exhaust gas can be discharged through a burner and a heat storage body which are stopped and not burned is used.
For example, as shown in FIG. 3, a combustion air supply system 8 for supplying combustion air and a combustion gas exhaust system 9 for discharging combustion gas to the heat storage bodies 7, 7 of the two burners 5, 6, respectively. Can be selectively connected by interposing a four-way valve 10 to supply combustion air to one of the burners 5 (or 6) through the heat storage body 7, while the other burner 6 (or 5) can store the heat storage body 7 It is provided so as to discharge the combustion gas through. Combustion air is supplied by, for example, a push-in fan or the like (not shown), and combustion exhaust gas is sucked from the furnace by exhaust means such as an induction fan (not shown) and discharged into the atmosphere. Further, the fuel supply system 11 is selectively and alternately connected to one of the burners 5 and 6 via a three-way valve 12 to supply fuel. The fuel nozzle 15 is embedded in, for example, the burner throat portion of the burner body 14, only the injection port is opened to the inner peripheral surface of the burner throat, and is provided so as not to be exposed to the combustion gas when passing through the inside. . In the case of this embodiment,
The four-way valve 10 for switching the path of the combustion exhaust gas and the combustion air and the three-way valve 12 for switching the flow path of the fuel are shown as a method of simultaneously switching the flow path by a single actuator 13, but the invention is not particularly limited to this. is not. For example, three-way valve 1
The two-way valve 10 and the four-way valve 10 may be separately controlled to be switched. A part of the combustion air and the fuel is distributed to the pilot burner gun 16. In the figure, reference numeral 14 is a burner body, 16 is a pilot burner gun, 17 is a flame detector, and 18 is a pyro-burner ignition transformer. Although not shown in each line, each solenoid valve for controlling the flow of fluid is shown. , Manual valves, etc. are installed.

A line 19 for supplying steam is connected to the line 8 for supplying combustion air. This steam is used to suppress an increase in NOx emission value due to preheating of combustion air, and the same effect can be obtained even if water is used.

Further, as the heat storage bodies 7, 7, it is preferable to use a material having a large heat capacity and a high durability in spite of a relatively low pressure loss, for example, a cylindrical body having a large number of honeycomb-shaped cell holes formed of ceramics. In this case, when heat is recovered from the combustion exhaust gas, even if the exhaust gas falls below the acid dew point temperature, the sulfur content in the fuel and its chemically modified substances are captured in the ceramics, and the exhaust system ducts, etc. located downstream are subject to low-temperature corrosion. There is nothing to do. Of course, it is not particularly limited to this, and other heat storage bodies such as ceramic balls and nuggets may be used.

According to the molten aluminum heat retaining furnace configured as described above, the crucible 3 is held at a temperature suitable for keeping the molten aluminum in the following manner.

First, the starting fuel is supplied to alternately burn the pair of burners 5 and 6 to warm the heat storage bodies 7 and 7 and the furnace body 1 to some extent. Then, when the temperature inside the furnace reaches a predetermined temperature, the startup operation is switched to full-scale operation.
One burner of the heat storage type burner system 4, for example, the burner 5
Is burned, the combustion gas after being used for heating the crucible 3 in the combustion chamber 2 is exhausted from the burner throat of the other burner 6 which is stopped through the combustion gas exhaust system 9. That is, in the other burner 6, the fuel supply system 11 for the burner 6 is closed by the three-way valve 12 and connected to the combustion gas exhaust system 9 by switching the four-way valve 10.
It is used as an exhaust passage for combustion exhaust gas without combustion.
The crucible 3 is heated by flame and radiant heat of combustion gas. Here, since the combustion air supplied to the burner 5 is preheated by direct contact with the heat storage body 7 for a short time and then supplied into the burner body 14, the combustion air has a high temperature (about 1000 ° C.) close to the exhaust gas temperature. Therefore, the fuel nozzle 1
When mixed with the fuel injected from No. 5, a small amount of fuel burns stably and a high-temperature combustion gas is obtained. Moreover, since the temperature of the combustion air changes immediately with the increase or decrease of the combustion amount, the responsiveness of the temperature adjustment of the combustion gas is good. Therefore, the temperature inside the furnace and the crucible 3 can be rapidly raised to the heat retention temperature.
The switching between combustion and exhaust is performed, for example, at an interval of 10 seconds to 2 minutes, preferably within about 1 minute, and most preferably at an extremely short interval of about 10 to 40 seconds. In this case, heat exchange is performed with high temperature efficiency. The switching may be performed when the combustion gas discharged via the heat storage body 7 reaches a predetermined temperature, for example, about 200 ° C. In this case, since the flame position changes frequently, the heat pattern in the combustion chamber can be made more uniform, and uneven heating and uneven heating can be reduced.

When the inside of the furnace reaches a temperature suitable for keeping the temperature of the molten aluminum, for example, 800 to 900 ° C., the combustion of the burner system 4 is throttled to such an extent that the temperature suitable for keeping the temperature of the molten aluminum in the crucible 3 can be maintained. In an emergency such as an accident in the fuel gas supply system or when the burner operator cannot attend, the burner system 4 is stopped and the electric heater 21 keeps the inside of the furnace warm.

It should be noted that the above embodiment is one example of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, although not shown, it is possible to install a pair of burners so as to face the free space around the side wall surface of the crucible 3 and partition the burners with a partition wall.
Further, the heat storage type burner system 4 of the present embodiment is configured such that one set of burners 5 and 6 is alternately burned by two sets, but the present invention is not particularly limited to this, and the burners to burn may be the same. The heat storage type burner system having a structure in which the flow of the combustion exhaust gas and the combustion air for the heat storage body is relatively switched by rotating the heat storage body itself between the combustion gas exhaust system and the combustion air supply system. But good.

A four-way valve is illustrated in this embodiment as a flow path switching means for selectively connecting the combustion air supply system and the combustion gas exhaust system to the heat storage body, but is not particularly limited to this. Instead of this, a combination of four solenoid valves or another type of flow path switching valve may be used.

[0019]

As is clear from the above description, the molten aluminum heat insulation furnace of the present invention uses a combustion air supplied from a combustion air recovered by a heat storage body to recover the heat of combustion exhaust gas to a high temperature. Since it is burned to heat the inside of the furnace to a temperature suitable for keeping the temperature of the molten aluminum, the set temperature inside the furnace can be increased with a small amount of fuel, and the amount of heat transfer can be increased to shorten the heating time. The running cost can be reduced. Moreover, the partition wall provided in the free space around the crucible causes the high-temperature combustion exhaust gas to bypass the partition wall and flow around the crucible along the crucible before being exhausted, so that the high-temperature combustion exhaust gas is short-circuited. You can prevent the pass. Therefore, it is possible to contribute to the improvement of thermal efficiency and energy saving by recovering the exhaust heat, and it is possible to reduce the energy cost as a whole to about 1/4 as compared with the conventional temperature rise / heat retention by the electric heater. Moreover, when compared with the conventional aluminum molten metal heat insulation furnace using an electric heater, the thermal efficiency can be increased and the energy consumption can be reduced, so that about 40% of the CO ₂ generated to obtain that amount of energy can be obtained. It can be reduced to a great extent and can greatly contribute to the improvement of the global environment.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a molten aluminum heat insulation furnace of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a schematic principle view showing one embodiment of a heat storage type burner system applied to the molten aluminum heat insulation furnace of the present invention.

FIG. 4 is a schematic view showing a conventional molten aluminum heat insulation furnace.

[Explanation of symbols]

 1 furnace body 2 combustion chamber 3 crucible 4 heat storage type burner system

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[Procedure amendment]

[Submission date] January 20, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryoichi Tanaka 2-53, Shirute, Tsurumi-ku, Yokohama-shi, Kanagawa Japan Furnace Industries Co., Ltd. (72) Inventor Matsuo Shibata, 2-chome, Tsurumi-ku, Yokohama-shi, Kanagawa No. 53 within Japan Furnace Industry Co., Ltd.

Claims (2)

[Claims] 1. A crucible containing molten aluminum, a furnace body surrounding and supporting the crucible, a free space between the crucible and the furnace body, and a heat storage body for combustion. An aluminum molten metal heat insulation furnace comprising at least a pair of burners for alternately supplying air and discharging combustion exhaust gas, characterized in that a partition wall for partially partitioning the pair of burners is provided in the free space. Aluminum molten metal heat insulation furnace. 2. The molten aluminum heat retaining furnace according to claim 1, wherein an emergency heater for heating the side wall surface of the crucible is installed on the inner wall surface of the furnace body.