Melting furnace

Abstract

The melting furnace in the present invention includes: a preheating tower (12) including therein a preheating chamber (12b); a melting chamber (14); a combustion chamber (16); and a combustion burner (18). An exhaust gas branch tube (20) through which an upper portion of the preheating chamber (12b) and the combustion chamber (16) are in communication is provided inside a furnace body that forms the preheating tower (12) and that is made from a refractory material. A heat exchange loop tube passage (22) enclosing the preheating chamber (12b) is provided to an upper portion of an inside of the furnace body as the preheating tower (12). The heat exchange loop tube passage (22) is mounted with an outside air introducing means (24) for introducing outside air. A connection nozzle (26) through which the heat exchange loop tube passage (22) and the exhaust gas branch tube (20) are communicably connected is mounted therebetween. The connection nozzle (26) is formed in a shape of a funnel having an inner diameter decreased toward the exhaust gas branch tube (20) side and has an end that has a smallest diameter and that is oriented to an opening on the combustion chamber (16) side of the exhaust gas branch tube (20).

Description

melting furnace

[0001] The present invention relates to a melting furnace used for melting non-ferrous metals such as aluminum, and more particularly to a melting furnace having a raw material preheating tower.

[0002] A conventional melting furnace of this type is described in the following Patent Document 1 (Japanese Patent Publication No. 02-053708). This conventional technology is configured as follows: In a non-ferrous metal melting furnace equipped with a preheating tower, a melting chamber is provided below the preheating tower, and a combustion chamber is provided adjacent to the preheating tower, its lower part communicates with the melting chamber, and the upper furnace body is equipped with a burner that produces combustion gas. An exhaust gas branch pipe is also provided to circulate a portion of the raw material preheating exhaust gas from the preheating tower to the combustion chamber.

[0003] This technology is said to be able to stabilize the temperature of the combustion gas, stabilize the furnace conditions, and save thermal energy.

[0004] Special Publication No. 02-053708

[0005] However, the above-mentioned prior art has the following problem. Specifically, a fan installed midway through the exhaust gas branch pipe is used to directly draw in a portion of the raw material preheating exhaust gas and return it to the combustion chamber. However, in this configuration, the sensible heat of the raw material preheating exhaust gas is significantly dissipated as it flows through the exhaust gas branch pipe, making it extremely difficult to maximize the energy-saving effect achieved by heat recovery. Therefore, the main object of the present invention is to provide a melting furnace that can achieve stable energy-saving effects even when the filling rate of the melting material (raw material) in the preheating tower is low by maximizing the utilization efficiency of the sensible heat of the raw material preheating exhaust gas.

[0006] To achieve the above object, the present invention provides a melting furnace 10 configured as follows, as shown in Figures 1 and 2. Specifically, the melting furnace 10 includes a preheating tower 12 having a preheating chamber 12b disposed therein, a melting chamber 14 connected to the lower part of the preheating tower 12, a combustion chamber 16 adjacent to the preheating tower 12 and communicating at its lower part with the melting chamber 14, and a combustion burner 18 mounted within the combustion chamber 16 for heating and melting the material introduced into the melting chamber 14. A flue gas branch pipe 20 is provided within the refractory furnace body forming the preheating tower 12, connecting the upper part of the preheating chamber 12b with the combustion chamber 16. A heat exchange loop duct 22 is provided in the upper part of the preheating tower 12, surrounding the preheating chamber 12b. An outside air introduction means 24 is attached to the heat exchange loop duct 22 for introducing outside air. Between the heat exchange loop pipe 22 and the exhaust gas branch pipe 20, a connecting nozzle 26 is attached to connect the two together. The connecting nozzle 26 is formed in a funnel shape with its inner diameter decreasing toward the exhaust gas branch pipe 20, and its narrowest tip is directed toward the opening of the exhaust gas branch pipe 20 on the fuel chamber 16 side.

[0007] In the present invention, the material to be melted in the melting chamber 14 is melted with a high-temperature combustion flame from the combustion burner 18, and the resulting exhaust gas, retaining its residual heat, rises within the preheating tower 12 as raw material preheating exhaust gas E. When outside air is introduced into the heat exchange loop duct 22 using the outside air introduction means 24, the internal air preheated within the heat exchange loop duct 22 is supplied into the exhaust gas branch pipe 20 via the connecting nozzle 26. This connecting nozzle 26 is formed in a funnel shape whose inner diameter decreases toward the exhaust gas branch pipe 20, and its narrowest tip is directed toward the opening of the exhaust gas branch pipe 20 on the fuel chamber 16 side. Therefore, the internal air, whose velocity has increased due to the Venturi effect, is discharged toward the opening of the exhaust gas branch pipe 20 on the combustion chamber 16 side. This generates negative pressure at the opening on the preheating chamber 12b side, which is the upstream end of the exhaust gas branch pipe 20, and part of the raw material preheating exhaust gas E within the preheating chamber 12b is drawn into the exhaust gas branch pipe 20. The raw material preheated exhaust gas E sucked into the exhaust gas branch pipe 20 is returned to the combustion chamber 16 through this exhaust gas branch pipe 20, but since the exhaust gas branch pipe 20 is installed inside the furnace body of the preheating tower 12, the loss of latent heat contained in the raw material preheated exhaust gas E can be minimized.

[0008] In the present invention, it is preferable to attach a workpiece holder 28 made of a cylindrical sleeve to the preheating chamber 12b, leaving a gap g between the preheating chamber 12b and the wall surface where the upstream end of the exhaust gas branch pipe 20 opens. In this case, the durability of the furnace body forming the preheating chamber 12b is increased and the preheating efficiency of the workpiece can be further improved. Furthermore, due to the Venturi effect, the flow velocity of the raw material preheating exhaust gas E passing through the gap g toward the opening in the wall of the preheating chamber 12b, which is the upstream end of the exhaust gas branch pipe 20, increases. As a result, the velocity of the raw material preheating exhaust gas E moving through the exhaust gas branch pipe 20 also increases, and the loss of latent heat from the raw material preheating exhaust gas E while flowing through the exhaust gas branch pipe 20 can be more effectively prevented.

[0009] According to the present invention, by maximizing the utilization efficiency of the sensible heat of the raw material preheating exhaust gas, it is possible to provide a melting furnace that can exhibit stable energy-saving effects even when the filling rate of the material to be melted (raw material) in the preheating tower is low.

[0010] 1 is a longitudinal sectional view showing a main part of a melting furnace according to an embodiment of the present invention; FIG. 2 is a cross-sectional view showing a main part, focusing on a preheating tower, of the AA cross-section view in FIG.

[0011]

[0023] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a longitudinal cross-sectional view of a melting furnace 10 according to one embodiment of the present invention. As shown in this figure, the melting furnace 10 according to this embodiment is a so-called hand-held melting furnace that holds molten aluminum obtained by melting raw materials (materials to be melted) for aluminum casting, and roughly includes a preheating tower 12, a melting chamber 14, a combustion chamber 16, and a molten metal holding chamber 30.

[0012] The preheating tower 12 is the uppermost part of the furnace body, which has a material inlet 12a at its top and a preheating chamber 12b inside. The furnace body is formed by lining the inner surface of an outer frame (steel shell) made of sufficiently strong steel plates with a thick refractory material such as firebricks or castable refractory. A material inlet opening / closing damper 12c is attached to the material inlet 12a at the top of the preheating tower 12, and a furnace pressure adjustment damper 32 is attached to the approximate center of the inlet opening / closing damper 12c, which automatically opens and closes depending on the pressure inside the preheating chamber 12b. The melting chamber 14 is connected to the lower part of the preheating tower 12.

[0013] The melting chamber 14 is a section for heating and melting the raw material to be melted, which is the raw material fed through the material inlet 12a, by the flame of a combustion burner 18 (described later), and its floor is formed as an inclined floor 14a. Next to this melting chamber 14, a combustion chamber 16 is provided adjacent to the preheating tower 12 so that the lower parts of the chambers communicate with each other.

[0014] The combustion chamber 16 is a section in which a combustion burner 18 attached to its upper side is operated to produce a high-temperature combustion flame and combustion exhaust gas. The combustion flame and combustion exhaust gas produced in the combustion chamber 16 are supplied to the melting chamber 14 and preheating chamber 12b. In the illustrated embodiment, the combustion chamber 16 and the melting chamber 14 are installed on a platform floor 34. A molten metal holding chamber 30 is provided adjacent to the platform floor 34 and communicates with the combustion chamber 16 via a molten metal communication portion 36.

[0015] The molten metal holding chamber 30 is a place where the heated and melted molten metal is maintained at a constant temperature until it is used. An immersion heater (not shown) is attached to this molten metal holding chamber 30 to maintain the molten aluminum in the chamber at a constant temperature, and a molten metal drain port 38 is opened at a position away from the molten metal communication part 36. Note that the method of keeping the molten aluminum warm is not limited to the method using the immersion heater described above, and any holding and heating method can be used, such as direct flame heating using liquid or gas fuel, immersion heating using gas fuel or electricity, or electrical radiation heating.

[0016] In the melting furnace 10 of the present invention having the above-described components, an exhaust gas branch pipe 20 is provided inside the refractory furnace body forming the preheating tower 12, connecting the upper part of the preheating chamber 12b with the combustion chamber 16. This exhaust gas branch pipe 20 can be formed by embedding a metal pipe made of stainless steel or the like inside the furnace body of the preheating tower 12. Alternatively, this exhaust gas branch pipe 20 can be formed as part of the refractory structure using a refractory construction method. In the illustrated embodiment, as shown in FIG. 2 , a pair of front and rear exhaust gas branch pipes 20 are provided inside the furnace body of the preheating tower 12 located above the combustion chamber 16. However, the number of exhaust gas branch pipes 20 is not limited to this and may be one, three, or more. A heat exchange loop duct 22 is provided above the exhaust gas branch pipe 20 in the upper part of the furnace body of the preheating tower 12.

[0017] The heat exchange loop duct 22 is a member for preheating outside air supplied by an outside air introduction means 24 (described later) using sensible heat accumulated within the furnace body. In this embodiment, a square metal pipe made of stainless steel or the like is formed into a rectangular loop and embedded in the upper part of the furnace body of the preheating tower 12 so as to surround the preheating chamber 12b, thereby forming the heat exchange loop duct 22. The outside air introduction means 24 is connected to this heat exchange loop duct 22, and a connecting nozzle 26 is interposed between the heat exchange loop duct 22 and the exhaust gas branch pipe 20, connecting the two.

[0018] The outside air introduction means 24 is for supplying outside air to the heat exchange loop duct 22, and includes an outside air introduction nozzle 24a communicating with the heat exchange loop duct 22 and a blower 24b for supplying outside air to the outside air introduction nozzle 24a. Note that this blower 24b can also be used in combination with a burner combustion blower (not shown) attached to the combustion burner 18.

[0019] The connecting nozzle 26 is a nozzle for connecting the heat exchange loop duct 22 and the exhaust gas branch pipe 20 in communication with each other, and is formed in a funnel shape whose inner diameter decreases toward the exhaust gas branch pipe 20, with its narrowest tip directed toward the opening of the exhaust gas branch pipe 20 on the fuel chamber 16 side.

[0020] Here, with regard to the positional relationship between the outside air introduction nozzle 24a and the connecting nozzle 26, as shown in Figure 2, it is preferable to arrange them so that the outside air introduced from the outside air introduction nozzle 24a does not flow directly to the connecting nozzle 26, but flows through the heat exchange loop duct 22 before reaching the connecting nozzle 26.

[0021] In the melting furnace 10 of this embodiment, a melt material holding member 28 is attached to the preheating chamber 12b with a gap g between it and the wall surface where the upstream end of the exhaust gas branch pipe 20 is opened. This melt material holding member 28 is made of a heat-resistant metal such as stainless steel and is configured as a cylindrical sleeve body with open top and bottom, and is installed as needed. Since this melt material holding member 28 is installed with a gap g between it and the wall surface of the exhaust gas branch pipe 20, its upper end is formed in a flange shape.

[0022] When using the melting furnace 10 configured as described above, the inlet opening / closing damper 12c is opened and the melt material, which will be the raw material for molten aluminum, is introduced through the material inlet 12a. The inlet opening / closing damper 12c is then closed, and the combustion burner 18 is ignited to generate a combustion flame. The melt material in the melting chamber 14 is heated and melted by the combustion flame, flows down the floor surface of the inclined floor 14a, and passes through the combustion chamber 16, the molten metal communication section 36, and is held in the molten metal holding chamber 30. Furthermore, exhaust gas generated by the combustion burner 18 rises within the preheating tower 12 as raw material preheating exhaust gas E and preheats the melt material stored in the preheating chamber 12b from the top of the melting chamber 14.

[0023] In the melting furnace 10 of this embodiment, as described above, the material to be melted in the melting chamber 14 is melted by the high-temperature combustion flame generated by the combustion burner 18, and the resulting exhaust gas having residual heat rises within the preheating tower 12 as raw material preheated exhaust gas E. The outside air introduced into the heat exchange loop duct 22 by the outside air introduction means 24 is preheated by the sensible heat of the refractory material as it circulates around the heat exchange loop duct 22 and is then supplied into the exhaust gas branch pipe 20 through the connecting nozzle 26. The connecting nozzle 26 is formed in a funnel shape whose inner diameter decreases toward the exhaust gas branch pipe 20, and its narrowest tip is directed toward the opening of the exhaust gas branch pipe 20 on the fuel chamber 16 side. Therefore, the preheated outside air (i.e., the internal air in the heat exchange loop duct 22) whose velocity increases due to the Venturi effect is discharged toward the opening of the exhaust gas branch pipe 20 on the combustion chamber 16 side. As a result, negative pressure is generated at the opening on the preheating chamber 12b side, which is the upstream end of the exhaust gas branch pipe 20, and a portion of the raw material preheating exhaust gas E in the preheating chamber 12b is drawn into the exhaust gas branch pipe 20. The raw material preheating exhaust gas E drawn into the exhaust gas branch pipe 20 passes through the exhaust gas branch pipe 20 and is returned to the combustion chamber 16. However, since the exhaust gas branch pipe 20 is provided inside the furnace body of the preheating tower 12, loss of latent heat in the raw material preheating exhaust gas E can be minimized.

[0024] Furthermore, since the melt material holding member 28 is attached inside the preheating chamber 12b, the flow velocity of the raw material preheating exhaust gas E passing through the gap g toward the opening in the wall of the preheating chamber 12b, which is the upstream end of the exhaust gas branch pipe 20, increases due to the Venturi effect, making it possible to increase the speed of the raw material preheating exhaust gas E moving inside the exhaust gas branch pipe 20. As a result, the loss of latent heat from the raw material preheating exhaust gas E when it flows through the exhaust gas branch pipe 20 can be prevented even more effectively.

[0025] In the above embodiment, the outside air introduction means 24 introduces outside air around the blower 24b into the heat exchange loop duct 22. However, a burner with a built-in heat exchanger (exhaust heat recovery burner) may be used as the combustion burner 18, and the heat-recovered exhaust gas may be supplied to the blower 24b of the outside air introduction means 24. Additionally or separately, it is also possible to capture the combustion waste gas (raw material preheating exhaust gas E) discharged from the furnace top through the furnace pressure adjustment damper 32 and supply it to the blower 24b. This can further reduce the energy consumption rate of the melting furnace 10. Of course, various other modifications are possible within the scope of those skilled in the art.

[0026] 10: melting furnace, 12: preheating tower, 12a: material inlet, 12b: preheating chamber, 14: melting chamber, 16: combustion chamber, 18: combustion burner, 20: exhaust gas branch pipe, 22: loop duct for heat exchange, 24: outside air introduction means, 26: connecting nozzle, 28: material holding member to be melted, g: gap.

Claims

1. A melting furnace including a preheating tower (12) having a preheating chamber (12b) therein, a melting chamber (14) connected to the lower part of the preheating tower (12), a combustion chamber (16) adjacent to the preheating tower (12) and communicating at its lower part with the melting chamber (14), and a combustion burner (18) attached within the combustion chamber (16) for heating and melting the material to be melted introduced into the melting chamber (14), comprising: an exhaust gas branch pipe (20) provided within a furnace body made of a refractory material forming the preheating tower (12) and communicating the upper part of the preheating chamber (12b) with the combustion chamber (16); a heat exchange loop duct (22) provided within the upper part of the furnace body of the preheating tower (12) and surrounding the preheating chamber (12b); and outside air introduction means (24) for introducing outside air into the heat exchange loop duct (22); a connecting nozzle (26) for connecting the heat exchange loop duct (22) and the exhaust gas branch pipe (20) in communication with each other, the connecting nozzle (26) being formed in a funnel shape with an inner diameter that decreases toward the exhaust gas branch pipe (20), and the tip of the connecting nozzle (26) with the smallest diameter being directed toward an opening of the exhaust gas branch pipe (20) on the fuel chamber (16) side.

2. The melting furnace of claim 1, wherein a melt material holding member (28) consisting of a cylindrical sleeve body is attached to the preheating chamber (12b) with a gap (g) between it and the wall surface on which the upstream end of the exhaust gas branch pipe (20) is opened.