Melting furnace

Abstract

The melting furnace of the present invention comprises: a preheating tower (12) having a preheating chamber (12b) disposed therein; a melting chamber (14); a combustion chamber (16); and a burner (18). An exhaust gas branch pipe (20) is disposed inside a furnace body made of a refractory material forming the preheating tower (12) and connecting the upper part of the preheating chamber (12b) with the combustion chamber (16). In addition, an annular heat exchange pipe (22) surrounding the preheating chamber (12b) is disposed in the upper part of the furnace body of the preheating tower (12). An external gas introduction component (24) for introducing external gas is installed in the heat exchange annular pipe (22). Furthermore, a connecting nozzle (26) is installed between the heat exchange annular pipe (22) and the exhaust gas branch pipe (20) to connect the two. The connecting nozzle (26) is formed into a funnel shape whose inner diameter decreases toward the exhaust gas branch pipe (20) side, and the end of the connecting nozzle (26) with the smallest diameter faces the opening on the fuel chamber (16) side of the exhaust gas branch pipe (20).

Description

Technical Field

[0001] The present invention relates to a melting furnace for melting nonferrous metals such as aluminum, and in particular to a melting furnace with a raw material preheating tower. Background Art

[0002] Among such melting furnaces, there is a melting furnace described in Patent Document 1 (Japanese Patent Publication No. 02-053708) listed below. This prior art is configured as follows.

[0003] In a nonferrous metal melting furnace equipped with a preheating tower, a melting chamber is provided at the lower part of the preheating tower, a combustion chamber is provided adjacent to the preheating tower, the lower part of the combustion chamber is communicated with the melting chamber, and a burner for generating combustion gas is installed on the upper furnace body. In addition, an exhaust gas branch pipe is provided for circulating a part of the raw material preheating exhaust gas from the preheating tower to the combustion chamber.

[0004] According to this technology, the temperature of the combustion gas can be stabilized, and furnace conditions can be stabilized and thermal energy can be saved.

[0005] Prior Art Literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Publication No. 02-053708 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, the above-mentioned prior art has the following problem. That is, a part of the raw material preheating exhaust gas is directly sucked by a fan installed in the middle of the exhaust gas branch pipe and returned to the combustion chamber. However, in the case of this method, when the raw material preheating exhaust gas flows through the exhaust gas branch pipe, the sensible heat of the raw material preheating exhaust gas is significantly diffused, and it is difficult to maximize the energy saving effect based on heat recovery.

[0010] Therefore, a main object of the present invention is to provide a melting furnace which can achieve a stable energy-saving effect even when the filling rate of the melted 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.

[0011] Solutions to Solve Problems

[0012] In order to achieve the above-mentioned problems, the present invention is as follows Figure 1 and Figure 2 As shown in FIG. 1 , the melting furnace 10 is constructed as follows.

[0013] That is, a melting furnace includes: a preheating tower 12 having a preheating chamber 12b disposed therein; a melting chamber 14 disposed in connection with the lower portion of the preheating tower 12; a combustion chamber 16 adjacent to the preheating tower 12 and communicating with the melting chamber 14 at its lower portion; and a burner 18 installed in the combustion chamber 16 for heating and melting a material to be melted put into the melting chamber 14. An exhaust gas branch pipe 20 for communicating the upper portion of the preheating chamber 12b with the combustion chamber 16 is disposed inside a furnace body made of a refractory material forming the preheating tower 12. In addition, a heat exchange annular duct 22 is disposed in the upper portion of the furnace body of the preheating tower 12, which surrounds the preheating chamber 12b. An external gas introduction member 24 for introducing external gas is installed in the heat exchange annular duct 22. Moreover, a connecting nozzle 26 is installed between the heat exchange annular duct 22 and the exhaust gas branch pipe 20 to connect the two. The connecting nozzle 26 is formed in a funnel shape whose inner diameter decreases toward the exhaust gas branch pipe 20 side, and the top end of the connecting nozzle 26 with the smallest diameter faces the opening on the fuel chamber 16 side of the exhaust gas branch pipe 20.

[0014] In the present invention, the material to be melted in the melting chamber 14 is melted by the high-temperature combustion flame generated by the burner 18, and the waste gas with the remaining heat rises in the preheating tower 12 as the raw material preheating waste gas E. Therefore, when the external gas is introduced into the heat exchange ring duct 22 using the external gas introduction means 24, the internal gas preheated in the heat exchange ring duct 22 is supplied to the waste gas branch pipe 20 via the connecting nozzle 26. However, since the connecting nozzle 26 is formed in a funnel shape whose inner diameter decreases toward the waste gas branch pipe 20 side, and the end of the connecting nozzle 26 with the smallest diameter faces the opening on the combustion chamber 16 side of the waste gas branch pipe 20, the internal gas whose velocity is increased by the Venturi effect is discharged toward the opening on the combustion chamber 16 side of the waste gas branch pipe 20. As a result, a negative pressure is generated at the opening on the preheating chamber 12b side, which is the upstream end of the waste gas branch pipe 20, and a part of the raw material preheating waste gas E in the preheating chamber 12b is sucked into the waste gas branch pipe 20. Then, the raw material preheating exhaust gas E sucked into the exhaust gas branch pipe 20 returns to the combustion chamber 16 through the exhaust gas branch pipe 20, but since the exhaust gas branch pipe 20 is arranged in the furnace body of the preheating tower 12, the latent heat loss of the raw material preheating exhaust gas E can be minimized.

[0015] In the present invention, it is preferable that a melted material holding member 28 composed of a cylindrical sleeve body is installed in the preheating chamber 12 b with a gap g between the wall surface of the upstream end opening of the exhaust gas branch pipe 20 and the melted material holding member 28 .

[0016] In this case, the durability of the furnace body forming the preheating chamber 12b can be improved, and the preheating efficiency of the melted material as the raw material can be further improved. In addition, due to the Venturi effect, the flow velocity of the raw material preheating exhaust gas E flowing through the gap g toward the opening of the wall surface of the preheating chamber 12b which is the upstream end of the exhaust gas branch pipe 20 increases, and the speed of the raw material preheating exhaust gas E moving in the exhaust gas branch pipe 20 can also be increased, and the latent heat loss of the raw material preheating exhaust gas E when flowing through the exhaust gas branch pipe 20 can be further effectively prevented.

[0017] Effects of the Invention

[0018] According to the present invention, a melting furnace can be provided which can achieve a stable energy-saving effect even when the filling rate of the melted 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a longitudinal sectional view showing the main part of the melting furnace according to one embodiment of the present invention.

[0020] Figure 2 Yes means Figure 1 A diagram of the main parts centered on the preheating tower in the AA cross-sectional view. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present invention will be described using the drawings. Figure 1 1 is a longitudinal sectional view of a melting furnace 10 according to an embodiment of the present invention. As shown in the figure, the melting furnace 10 according to the present embodiment is a so-called manual melting furnace for holding molten aluminum metal obtained by melting raw materials (melted materials) for aluminum casting, and generally includes a preheating tower 12, a melting chamber 14, a combustion chamber 16, and a molten metal holding chamber 30.

[0022] The preheating tower 12 is formed at the uppermost part of the furnace body, and the furnace body is provided with a material inlet 12a at the upper part, and a preheating chamber 12b is provided inside. Here, the furnace body is formed by stretching refractory materials such as refractory bricks and castings inside the inner surface of the outer frame (steel shell) formed of a steel plate with sufficient strength in a thick wall shape. An inlet switch damper 12c is installed at the material inlet 12a at the upper end of the preheating tower 12, and a furnace pressure adjustment damper 32 that automatically opens and closes according to the pressure in the preheating chamber 12b is installed in the approximate center of the inlet switch damper 12c. In addition, a melting chamber 14 is connected to the lower part of the preheating tower 12.

[0023] The melting chamber 14 is a portion for heating and melting the raw material, i.e., the melted material, which is fed from the material feeding port 12a by the flame of the burner 18 described later, and its bottom surface is formed by an inclined bed 14a. In addition, a combustion chamber 16 is provided next to the melting chamber 14 so as to be adjacent to the preheating tower 12 and communicate with the melting chamber 14 at the bottom.

[0024] The combustion chamber 16 is a part that generates high-temperature combustion flames and combustion exhaust gas by operating the burner 18 installed on the upper side thereof. The combustion flames and combustion exhaust gas generated in the combustion chamber 16 are supplied to the above-mentioned melting chamber 14 and the preheating chamber 12b. In addition, in the illustrated embodiment, the combustion chamber 16 and the above-mentioned melting chamber 14 are arranged on a stand 34. And, at a position adjacent to the stand 34, a molten metal holding chamber 30 is provided that is connected to the combustion chamber 16 via a molten metal connecting portion 36.

[0025] The molten metal holding chamber 30 is a place for holding the molten metal after heating and melting at a certain temperature until use. An immersion heater (not shown) is installed in the molten metal holding chamber 30 to keep the aluminum molten metal in the chamber at a certain temperature, and a molten metal extraction port 38 is opened at a position away from the molten metal connecting portion 36. In addition, the heat preservation method of the aluminum molten metal is not limited to the method using the above-mentioned immersion heater, and any holding heating method such as direct flame heating using liquid-gas fuel, immersion heating using gas fuel-electricity, and radiation heating using electricity can also be applied.

[0026] In the melting furnace 10 of the present invention having the above-mentioned parts, an exhaust gas branch pipe 20 is provided inside the furnace body made of refractory material forming the preheating tower 12, which connects the upper part of the preheating chamber 12b with the combustion chamber 16. The exhaust gas branch pipe 20 can be formed by burying a metal pipe made of stainless steel or the like in the furnace body of the preheating tower 12. In addition, the exhaust gas branch pipe 20 can also be formed as a part of the refractory structure by a refractory construction method. In the illustrated embodiment, as shown in FIG. Figure 2 1 shows a case where a pair of exhaust gas branch pipes 20 are provided in the furnace body of the preheating tower 12 located above the combustion chamber 16, but the number of exhaust gas branch pipes 20 is not limited thereto, and may be 1 or more than 3. In addition, a heat exchange annular duct 22 is provided in the upper part of the furnace body of the preheating tower 12 above the exhaust gas branch pipe 20.

[0027] The heat exchange annular duct 22 is a member for preheating the external air supplied by the external air introduction member 24 described later by utilizing the sensible heat accumulated in the furnace body. In the present embodiment, a metal square tube made of stainless steel or the like is formed into a rectangular ring shape and buried in the upper part of the furnace body of the preheating tower 12 so as to surround the preheating chamber 12b to form the heat exchange annular duct 22. The external air introduction member 24 is connected to the heat exchange annular duct 22, and a connecting nozzle 26 is interposed between the annular duct 22 and the exhaust gas branch pipe 20 to connect the two.

[0028] The external gas introduction member 24 is used to supply external gas to the heat exchange annular duct 22, and includes an external gas introduction nozzle 24a connected to the heat exchange annular duct 22 and a blower 24b for supplying external gas to the external gas introduction nozzle 24a. In addition, the blower 24b can also be shared with a burner combustion blower (not shown) attached to the burner 18.

[0029] The connecting nozzle 26 is a nozzle used to connect the heat exchange annular duct 22 and the exhaust gas branch pipe 20. It is formed in a funnel shape with its inner diameter decreasing toward the exhaust gas branch pipe 20 side, and the end of the connecting nozzle 26 with the smallest diameter is opened toward the fuel chamber 16 side of the exhaust gas branch pipe 20.

[0030] Here, regarding the positional relationship between the external gas introduction nozzle 24a and the connection nozzle 26, Figure 2 As shown, it is preferable that the external gas introduced from the external gas introduction nozzle 24 a does not flow directly to the connection nozzle 26 , but reaches the connection nozzle 26 after flowing through the heat exchange annular duct 22 .

[0031] In the melting furnace 10 of the present embodiment, a melted material holding member 28 is installed in the preheating chamber 12b with a gap g between the wall surface of the exhaust gas branch pipe 20 and the upstream end opening. The melted material holding member 28 is formed of a heat-resistant metal such as stainless steel, and is composed of a cylindrical sleeve body opened at the top and bottom, and is provided as needed. In addition, since the melted material holding member 28 is provided with a gap g between the wall surface of the exhaust gas branch pipe 20, its upper end is formed into a flange shape.

[0032] When the melting furnace 10 configured as described above is used, the melted material to be the raw material of the aluminum molten metal is introduced from the material introduction port 12a by opening the introduction port opening and closing damper 12c. Then, the introduction port opening and closing damper 12c is closed, and the burner 18 is ignited to generate a combustion flame. Then, the melted material in the melting chamber 14 is heated and melted by the combustion flame, flows down along the bed surface of the inclined bed 14a, and is held in the molten metal holding chamber 30 from the combustion chamber 16 through the molten metal connecting portion 36. In addition, the exhaust gas generated by the burner 18 rises in the preheating tower 12 as the raw material preheating exhaust gas E, and preheats the melted material stored in the preheating chamber 12b from the upper part of the melting chamber 14.

[0033] As described above, according to the melting furnace 10 of the present embodiment, the material to be melted in the melting chamber 14 is melted by the high-temperature combustion flame generated by the burner 18, and the exhaust gas having the remaining heat rises in the preheating tower 12 as the raw material preheating exhaust gas E. Therefore, the external gas introduced into the heat exchange annular duct 22 by the external gas introduction means 24 is preheated by the sensible heat of the refractory material by circling in the heat exchange annular duct 22, and is supplied into the exhaust gas branch pipe 20 through the connecting nozzle 26, which is formed in a funnel shape whose inner diameter decreases toward the exhaust gas branch pipe 20 side, and the end of the connecting nozzle 26 which becomes the smallest diameter faces the opening of the combustion chamber 16 side of the exhaust gas branch pipe 20, so that the above-mentioned preheated external gas (=internal gas in the heat exchange annular duct 22) whose velocity is increased by the Venturi effect is discharged toward the opening of the combustion chamber 16 side of the exhaust gas branch pipe 20. Then, 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 part of the raw material preheating exhaust gas E in the preheating chamber 12b is sucked into the exhaust gas branch pipe 20. Then, the raw material preheating exhaust gas E sucked into the exhaust gas branch pipe 20 returns to the combustion chamber 16 through the exhaust gas branch pipe 20, but since the exhaust gas branch pipe 20 is provided in the furnace body of the preheating tower 12, the latent heat loss of the raw material preheating exhaust gas E can be minimized.

[0034] Furthermore, since the melted material holding member 28 is installed in the preheating chamber 12b, the raw material preheating exhaust gas E passes through the gap g toward the opening of the wall surface of the preheating chamber 12b, which is the upstream end of the exhaust gas branch pipe 20, and its flow velocity increases due to the Venturi effect, so that the speed of the raw material preheating exhaust gas E moving in the exhaust gas branch pipe 20 can be increased. As a result, the latent heat loss of the raw material preheating exhaust gas E when flowing in the exhaust gas branch pipe 20 can be further effectively prevented.

[0035] In the above embodiment, the external air around the blower 24b is introduced into the heat exchange annular duct 22, but a heat exchange built-in burner (waste heat recovery burner) may be used as the burner 18 to supply the heat-recovered exhaust gas to the blower 24b of the external air introduction unit 24. In addition or separately thereto, the combustion exhaust gas (raw material preheating exhaust gas E) discharged from the furnace top through the furnace pressure adjustment damper 32 may be captured and supplied to the blower 24b. Thus, the unit energy consumption in the melting furnace 10 can be further reduced.

[0036] Furthermore, it is of course possible to make various changes within the scope that can be conceived by those skilled in the art.

[0037] Description of Reference Numerals

[0038] 10: melting furnace; 12: preheating tower; 12a: material inlet; 12b: preheating chamber; 14: melting chamber; 16: combustion chamber; 18: burner; 20: exhaust gas branch pipe; 22: annular duct for heat exchange; 24: external gas introduction component; 26: connecting nozzle; 28: melted material holding member; g: gap.

Claims

1. A melting furnace, comprising: A preheating tower (12) having a preheating chamber (12b) disposed therein; a melting chamber (14) connected to the lower portion of the preheating tower (12); a combustion chamber (16) adjacent to the preheating tower (12) and connected to the melting chamber (14) at its lower portion; and a burner (18) installed in the combustion chamber (16) for heating and melting a material to be melted put into the melting chamber (14), characterized in that: The melting furnace comprises: An exhaust gas branch pipe (20) is arranged inside a furnace body made of refractory material forming the preheating tower (12) and connects the upper part of the preheating chamber (12b) with the combustion chamber (16); A heat exchange annular pipe (22) is arranged in the upper part of the furnace body of the preheating tower (12) and surrounds the preheating chamber (12b); an external gas introduction component (24) for introducing external gas into the heat exchange annular pipe (22); and A connecting nozzle (26) connects the heat exchange annular pipe (22) with the exhaust gas branch pipe (20), and the connecting nozzle (26) is formed into a funnel shape whose inner diameter decreases toward the exhaust gas branch pipe (20) side, and the top end of the connecting nozzle (26) with the smallest diameter faces the opening on the fuel chamber (16) side of the exhaust gas branch pipe (20).

2. The melting furnace according to claim 1, characterized in that: In the preheating chamber (12b), a melted material holding member (28) composed of a cylindrical sleeve body is installed with a gap (g) between the wall surface of the preheating chamber (12b) opening at the upstream end of the exhaust gas branch pipe (20).

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