JPS6221907Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention improves thermal efficiency by injecting high-temperature heated air at high speed into the furnace of an aluminum melting furnace to cause forced convection and promote convective heat transfer of high-temperature gas inside the furnace. This relates to an aluminum melting furnace. A typical example of an aluminum melting furnace is a direct heating type reverberatory furnace. The thermal efficiency of such reverberatory furnaces is generally about 16 to 18%, and the highest one is said to be at most 21%, and in fact, about 79 to 84% is not effectively used as exhaust gas and heat radiation loss. is lost. The reason for this is that in conventional melting, the combustion gas ejected from the burner stalls and its convection stagnates, and the combustion gas that stays in the vicinity of the ceiling wall in particular is mixed with the raw materials to be melted such as aluminum ingots and aluminum waste. One example is loss of contact. Incidentally, conventionally, a furnace in which a burner and an air jet port are respectively provided is known, for example, from Japanese Utility Model Publication No. 55-46801 or Japanese Utility Model Application Publication No. 119143/1983, and in the case of the former, the combustion gas Keep the temperature as low as possible
In order to suppress the generation of _NO The burner is placed horizontally on the side wall near the hearth, and the combustion gas from the burner is blown away by air jetted from a high-speed jet nozzle to equalize the temperature inside the furnace. It did not focus on the fact that after being ejected from the burner, it gradually stalls and tends to stay near the ceiling wall surface, resulting in low heating efficiency and wasted thermal energy. The present invention was developed in view of these conventional drawbacks, and the high-temperature gas that remains inside the furnace, particularly on the furnace ceiling wall, is blown out by high-temperature air that is jetted out at high speed from an air jet nozzle that is installed downward on the ceiling wall. The objective is to increase convective heat transfer efficiency with the raw material to be melted, improve heating efficiency of the raw material to be melted, and at the same time achieve energy savings. The present invention will be described in detail below based on examples and drawings. In FIG. 1, reference numeral 1 denotes a furnace body constructed of refractory bricks, and a melting tank 2 is provided at the bottom.
Reference numerals 3 and 3 denote combustion gas injection holes formed by burner tiles arranged on one side wall of the furnace body 1, and the combustion gas is blown diagonally downward into the furnace from the burner attached here. The melting tank 2 is provided with a molten metal outlet at the bottom and a raw material input port 4 at one side of the top, and the raw material input port 4 is shielded from the inside of the furnace by a door 5 that can be opened and closed. Note that 6 is an exhaust hole penetrated through one side wall of the furnace main body 1, and 7 is an exhaust gas exhaust pipe erected in communication with the exhaust hole 6. Reference numerals 8 and 8 designate air injection nozzles installed through the ceiling wall of the furnace body 1. These air injection nozzles 8, 8 are connected to a high-temperature, high-pressure air heater 10 via a heat-insulating pipe 9 (a heat-resistant tube covered with a heat-insulating cover), and the air pressure is 1.9 to 2.0.
Kg/cm ² , the ejection temperature of air injection nozzles 8, 8 is 850
℃ (regular use) to 900℃ (maximum), and this high temperature air is jetted out almost directly below the inside of the furnace at a jetting speed of Matsuha 1. FIG. 2 is a longitudinal cross-sectional view of this air injection nozzle, which allows cooling air to be supplied to the outer periphery 12 of the core tube 11 through which high-temperature air flows in order to protect the core tube from high temperatures. In the aluminum melting furnace configured in this way,
Raw materials such as aluminum ingots or aluminum scraps are inputted from the raw material input port 4, and the combustion gas from the burner is injected from the injection holes 3, 3 to generate a bright flame. Heat radiation also heats the inside of the furnace,
The raw materials mentioned above are melted, and the molten water is stored in a melting tank 2 and heated. When heating the inside of the furnace like this, the high-temperature air injected into the furnace from the air injection nozzles 8, 8 especially entrains and mixes the high-temperature atmospheric gas around the bright flame that stays on the ceiling wall side, and flows in the direction indicated by the arrow. By causing convection, for example, when the gas temperature at the top of the furnace is 1150℃, the spray mixing temperature at the surface of the molten metal can be set to 1120℃, eliminating the temperature difference in the furnace and speeding up the heating and melting of the input raw materials. Moreover, the temperature of the molten water in the melting tank 2 can be raised in a short time. In such convective heat transfer, the heat transfer coefficient increases in proportion to the mass velocity to the 0.77 to 0.79 power, so the convection velocity of the gas in the conventional furnace is increased by 1.2
~1.5m/s (1.35m/s on average), the thermal efficiency can be improved as shown in the following table. As is clear from the table below, when the speed increases by four times, the thermal efficiency actually increases by 1.96 times. This improvement in the effective heat amount is due to a decrease in the film coefficient between the gas and the surface of the molten metal.

[Table] In addition, when the temperature of the furnace rises, high-temperature gas can be forced to convect toward the bottom of the furnace when the raw materials start melting, which has a large energy-saving effect on the temperature rise process inside the furnace from low to high temperatures. is obtained. In the illustrated embodiment, air injection nozzles are provided at two locations, but of course, in the case of a large-sized device, a large number of air injection nozzles may be provided. As is clear from the detailed explanation of the embodiments above, the aluminum melting furnace of the present invention has the following features:
An air injection nozzle is installed on the ceiling wall of the furnace body, and high-temperature air is injected into the furnace from the nozzle at a high speed to cause forced convection within the furnace, particularly promoting convection of high-temperature gas that remains near the ceiling wall. This significantly increases convective heat transfer efficiency, thereby contributing to energy savings, and the high temperature accelerates the melting of raw materials, improving the productivity of molten metal, making it possible to economically produce molten aluminum. has advantages.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of an aluminum melting furnace showing an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of its air injection nozzle. 1... Furnace body, 2... Melting tank, 3, 3... Injection hole for combustion gas, 4... Raw material inlet, 8, 8... Air injection nozzle.

Claims (1)

[Scope of utility model registration request] An aluminum melting furnace equipped with a burner on the furnace wall and heating and melting raw materials to be melted such as aluminum ingots in the furnace using combustion gas from the burner,
An aluminum melting furnace characterized in that an air injection nozzle is installed on the ceiling wall of the furnace so as to face substantially directly downward, and high temperature air is ejected from the air injection nozzle at a high speed.