Industrial furnace heating structure

Abstract

To provide a heating structure of an industrial furnace, which is excellent in heating efficiency and which makes a fan life long.SOLUTION: A heating structure of an industrial furnace comprises a recuperator 50 which is provided in an exhaust passage 51, into which ordinary temperature air supplied from an air blower 60 is taken before it reaches an air heater 11 and a burner 21, and which preheats the ordinary temperature air by exhaust heat from a furnace body 10. In the case of low output, a first on-off valve 12 is opened, and second and third on-off valves 22 and 25 are closed so that a material T to be heated can be heated by the air supplied from the air heater 11. In the case of high output, the first, second and third on-off valves 12, 22 and 25 are opened to add heating by the burder 21.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heating structure for an industrial furnace used for heat treating metals and non-ferrous metals. [Background technology]

[0002] 2. Description of the Related Art Electric furnaces that use electricity as a heat source exist as furnaces for heat treating metals and non-ferrous metals (see, for example, Patent Document 1). The electric furnace shown in Patent Document 1 is provided with a cooling fan on the outside of the furnace body, and this cooling fan has a cooling function of supplying outside air to the inside of the furnace body and dissipating the heated air inside the furnace body to the outside.

[0003] As such a conventional electric furnace, for example, the one shown in Figures 4 and 5 is known. The electric furnace shown in Figure 4 has metal heaters 31 provided on the left and right sides inside the furnace body 30, and a rotary fan 32 provided in the upper center of the furnace body 30. The air inside the furnace body 30 is heated by these metal heaters 31, and the heated air is circulated by the rotary fan 32 to heat the material T to be heated.

[0004] 5 has an air heater 41 attached to the outside of the furnace body 40, and external air is heated through the air heater 41 and taken into the furnace body 40, and the heated air heats the material to be heated T. The heated air is discharged to the outside of the furnace body 40. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-137781 A Summary of the Invention [Problem to be solved by the invention]

[0006] The electric furnaces of the prior art shown in Patent Document 1 and in Figs. 4 and 5 all use electricity as a heating source, and are therefore highly desirable from the standpoint of carbon neutrality.

[0007] However, there is a demand for further improvement in the heating efficiency of all of these electric furnaces. That is, the electric furnace shown in Patent Document 1 has a cooling function using a cooling fan, which naturally reduces the heating efficiency.

[0008] In addition, the electric furnace shown in Fig. 4 heats the air inside the furnace body 30 with metal heaters 31 installed on the left and right sides inside the furnace body 30, and circulates it with a rotary fan 32, so the agitation effect of the heated air is insufficient, and there are problems with heating efficiency. In addition, the heated air always acts on the material T from a fixed direction, which causes problems with heating efficiency. These problems are particularly noticeable when the shape of the material T is complex.

[0009] In addition, since the rotary fan 32 in this electric furnace is installed inside the furnace body 30, which is at high temperature, it is prone to damage such as deformation and vibration due to loss of impeller balance, and there are also problems in that it has a short lifespan.

[0010] 5, the air outside the furnace body 40 (i.e., air at room temperature) is heated by the air heater 41, and the heated air is discharged after acting on the material to be heated T. Therefore, it is necessary to constantly heat the air at room temperature to the required high temperature. Therefore, energy loss is large and heating efficiency is low.

[0011] Furthermore, since electric furnaces use electricity as a heat source, there is a problem that it is difficult to use them in cases where high output is required, such as in high-temperature heat treatment furnaces or heating furnaces.

[0012] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a heating structure for an industrial furnace which is excellent in heating efficiency and has a long fan life. [Means for solving the problem]

[0013] In order to achieve the above object, the heating structure of the industrial furnace of the present invention is an industrial furnace (1) that circulates air inside a furnace body (10) to heat a material (T), an air heater (11) provided on the outer side of the furnace body (10) for heating the air and blowing the air into the furnace body (10); a burner (21) provided on a side surface of the furnace body (10) for heating the air; an air blower (60) that takes in room temperature air and sends it to the air heater (11) and the burner (21); an exhaust passage (51) connecting an exhaust stack (100) provided outside the furnace body (10) to the furnace body (10); a recuperator (50) provided in the exhaust passage (51) and taking in room-temperature air blown from the air blower (60) before it reaches the air heater (11) and the burner (21), and preheating the room-temperature air with exhaust heat from the furnace body (10); a first on-off valve (12) provided between the recuperator (50) and the air heater (11); a second on-off valve (22) provided between the recuperator (50) and the burner (21); a third on-off valve (25) provided in a path through which gas fuel is sent to the burner (21); During low output, the first on-off valve (12) is opened and the second on-off valve (22) and the third on-off valve (25) are closed to heat the material to be heated (T) with air blown from the air heater (11), and during high output, the first on-off valve (12), the second on-off valve (22), and the third on-off valve (25) are opened to additionally heat the material by the burner (21).

[0016] Here, the symbols in parentheses indicate corresponding elements or items in the drawings and in the detailed description to be described later. Effect of the Invention

[0017] According to the industrial furnace of the present invention, an air heater is used at low output, and at high output, heating by a burner is added to this, making the heat source a hybrid, so that the furnace can also be used in high-temperature heat treatment furnaces and heating furnaces.

[0018] In addition, a recuperator is used to preheat room temperature air using the exhaust heat from the furnace body, and the preheated air is then sent to the air heater and burner, resulting in excellent heating efficiency and energy savings. Furthermore, since the air blower for blowing air is provided outside the furnace body, breakdowns due to the influence of heat can be reduced and the life of the furnace can be extended, compared to when the air blower is provided inside the furnace body.

[0021] In this way, a hybrid heat source configuration in which an air heater is used at low output and a burner is added to this at high output, and a recuperator is also used, is not described at all in the above-mentioned patent documents. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 is a front view showing the heating structure of the industrial furnace according to the embodiment of the present invention, illustrating the state at low output. [Diagram 2] FIG. 2 is a front view showing the heating structure of the industrial furnace according to the embodiment of the present invention, illustrating the state at high output. [Diagram 3] FIG. 4 is a front view showing a heating structure of an industrial furnace according to another embodiment of the present invention. [Figure 4] FIG. 1 is a front view showing the configuration of an electric furnace according to a conventional example. [Diagram 5] FIG. 13 is a front view showing an electric furnace according to another conventional example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The heating structure of an industrial furnace 1 according to an embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 shows the structure at low output, and Figure 2 shows the structure at high output.

[0024] The heating structure of the industrial furnace 1 according to this embodiment is a hybrid type heat source that uses electric heating from an air heater 11 and flame heating from a burner 21 as heat sources, and circulates air inside the furnace body 10 to heat the material T to be heated placed inside the furnace body 10. The material T to be heated may be placed in a fixed state, or may be placed in a movable (rotatable, etc.) state.

[0025] The heating structure of this industrial furnace 1 includes an air heater 11, a first on-off valve 12, a burner 21, a second on-off valve 22, a third on-off valve 25, a recuperator 50, an exhaust passage 51, a first passage 52, a second passage 53, a third passage 54, a fourth passage 55, a blower 60, a thermocouple sensor 71, and a temperature indicating regulator 72.

[0026] The air heater 11 is provided on the outer side (here, the right side) of the furnace body 10, and heats air by electricity and blows it into the furnace body 10. A part of the room temperature air blown from the air blower 60 is sent to the air heater 11 via a first on-off valve 12 as air for the air heater.

[0027] The burner 12 is installed on the side (here, the right side) of the furnace body 10 so that a flame is sprayed below the hot air blown into the furnace from the air heater 11, and the air circulating inside the furnace body 10 is heated by the fire. The burner 12 takes in gas as fuel and combustion air, and the gas is connected via a flowmeter 27 that measures the amount of gas, a regulating valve 26, and a third on-off valve 25, while the combustion air is connected via a flowmeter 24 that measures the amount of gas, a regulating valve 23, and a second on-off valve 22. The combustion air is room temperature air blown from the air blower 60, and the air excluding the air for the air heater is sent via the second on-off valve 22.

[0028] The exhaust passage 51 connects the exhaust tower 100 provided outside the furnace body 10 to the lower part of the furnace body 10, and a recuperator 50 is provided in the middle of the exhaust passage 51. A furnace pressure damper 56 is provided between the recuperator 50 and the exhaust tower 100. Room temperature air is sent to the recuperator 50 from an air blower 60 through a first passage 52, and the first passage 52 is provided with a flow meter 63 for measuring the amount of room temperature air blown from the air blower 60, a regulating valve 62, and an air on-off valve 61. In addition, a second passage 53 is connected to the recuperator 50, and the second passage 53 branches into a third passage 54 which is connected to the air heater 11 side, and a fourth passage 55 which is connected to the burner 21 side (the combustion air supply side).

[0029] The recuperator 50 is a heat exchanger for recovering exhaust heat. The room temperature air blown from the air blower 60 through the first passage 52 is taken in before it reaches the air heater 11 and the burner 21. The room temperature air taken in by the recuperator 50 is preheated by the exhaust heat sent from the furnace body 10 through the exhaust passage 51. The preheated air is sent to the air heater 11 through the second passage 53 and the third passage 54 as air heater air, and to the burner 21 through the second passage 53 and the fourth passage 55 as combustion air.

[0030] The thermocouple sensor 71 is a thermometer installed inside the furnace to measure the temperature inside the furnace, and the temperature is sent to a temperature indicator / regulator 72 installed outside the furnace, which controls the air heater 11 so that the temperature approaches a pre-input target set value. This control may be a control to turn the air heater 11 on and off, or a proportional control (phase control) that varies the output proportionally, and is not particularly limited.

[0031] The heating structure of this industrial furnace 1 uses different heat sources at low and high output. That is, at low output, the heat source is an air heater 11 as shown in Fig. 1, and at high output, heating by a burner 21 is added to this as shown in Fig. 2.

[0032] (Low power operation) At low power, the heating structure of the industrial furnace 1 can be operated as follows. That is, in the heating structure of this industrial furnace 1, the first on-off valve 12 is opened, and the second on-off valve 22 and the third on-off valve 25 are closed, and the material to be heated T is heated with air blown from the air heater 11. At this time, room temperature air is not sent directly from the air blower 60 to the air heater 11 as air for the air heater, but the room temperature air is preheated by the exhaust heat from the furnace body 10 using the recuperator 50, and the preheated high-temperature air is sent to the air heater 11. This provides excellent heating efficiency and energy savings.

[0033] In addition, since the air blower 60 for blowing air is provided outside the furnace body, breakdowns due to the influence of heat can be reduced and the life span can be extended, compared to when the air blower 60 is provided inside the furnace body 10.

[0034] (High power operation) Next, at high power, the heating structure of the industrial furnace 1 can be operated as follows. That is, in addition to opening the first on-off valve 12, the second on-off valve 22 and the third on-off valve 25 are also opened to add heating by the burner 21, and the material to be heated T is heated by the flame from the burner 21 in addition to the air blown from the air heater 11. At this time, the air for the air heater sent to the air heater 11 and the combustion air sent to the burner 21 are not room temperature air sent directly from the air blower 60, but high temperature air that has been preheated by the exhaust heat from the furnace body 10 using the recuperator 50, resulting in excellent heating efficiency and energy savings.

[0035] According to this, at the time of high output, heating by the air heater 11 is added to heating by the burner 21, so that the temperature inside the furnace can be instantly raised to a high temperature, which is effective.

[0036] As shown in FIG. 3, the burner 21 may be omitted and the material to be heated T may be heat-treated only by the air heater 11. In this case, too, a recuperator 50 is provided in the exhaust path 51, and room temperature air blown from an air blower 60 is taken in before it reaches the air heater 11, and the room temperature air is preheated using the exhaust heat from the furnace body 10, and the preheated high temperature air is sent through the second passage 53 as air for the air heater. As a result, even if heating is performed only by the air heater 11, an industrial furnace with excellent heating efficiency can be provided. [Explanation of symbols]

[0037] 1. Industrial furnace 10 Furnace body 11 Air heater 12 First shutoff valve 21 Burner 22 Second shutoff valve 23 Regulating valve 24 Flow meter (for combustion air) 25 Third shutoff valve 26 Regulating valve 27 Flow meter (for gas fuel) 30 Furnace body 31 Metal heater 32 Rotating Fan 40 Furnace body 41 Air heater 50 Recuperator 51 Exhaust passage 52 First aisle 53 Second aisle 54 Third aisle 55 Fourth aisle 56 Furnace pressure damper 60 Air Blower 61 Air on-off valve 62 Regulating valve 63 Flow meter (for normal temperature air) 71 Thermocouple sensor (thermometer) 72 Temperature indicator controller 100 Exhaust tower

Claims

[Claim 1] An industrial furnace in which air is circulated inside the furnace body to heat a material to be heated, An air heater provided on the outer side of the furnace body to heat the air and blow it into the furnace body; A burner provided on a side surface of the furnace body for heating the air; an air blower that takes in room temperature air and blows it to the air heater and the burner; An exhaust passage connecting an exhaust tower provided outside the furnace body to the furnace body; A recuperator is provided in the exhaust passage, and takes in room temperature air blown from the air blower before it reaches the air heater and the burner, and preheats the room temperature air with exhaust heat from the furnace body; A first on-off valve provided between the recuperator and the air heater; A second on-off valve provided between the recuperator and the burner; a third on-off valve provided in a path through which gas fuel is sent to the burner; said first on-off valve being opened and said second on-off valve and said third on-off valve being closed during low output to heat said material to be heated with air blown from said air heater, and said first on-off valve, said second on-off valve and said third on-off valve being opened during high output to additionally heat said material with said burner.

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