JPS6356288B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a direct-fired heating furnace.

Conventionally, in direct-fired heating furnaces that heat materials such as steel and copper alloys, if air enters through the door or other gaps used to charge the materials, the materials will be oxidized and the materials will be heated. An oxide film is formed on the surface of the object. Therefore, when steel materials, copper alloys, etc. are subjected to processing such as rolling or pressing after heating, the oxide film adheres to the product or is press-fitted into the product, causing defective products.

In order to eliminate such drawbacks and heat the inside of the furnace in a non-oxidizing state, the heating furnace should be of an indirect heating type or an electric heating type. need to be heated. However, when the object to be heated is copper or a copper alloy, the blackness of the surface of the object to be heated is small;
The radiant heat increases the heating time and therefore increases the size of the heating furnace. In addition, such indirect heating or electric heating increases equipment costs and operating costs.

An object of the present invention is to solve the above-mentioned technical problems and provide a direct-fired heating furnace that can heat in a non-oxidizing state.

In the present invention, a preheating zone 6, a heating zone 7, and a soaking zone 8 are formed in this order from the charging port 2 of the heated object 10 toward the discharge port 3 along the conveyance direction of the heated object 10, and the charging port 2, an exhaust pipe 11 for discharging combustion exhaust gas is provided, a heating burner 9 is provided in the heating zone 7 and the soaking zone 8, and an ejection hole 13 is provided in the heating zone 7 and the soaking zone 8. Main body 1 and pipe line 15 for supplying flammable gas to jet hole 13
a flow rate control valve 16 interposed in the pipe line 15; a carbon monoxide concentration detector 18 provided in the furnace body 1 at a position close to the discharge port 3 to detect the carbon monoxide concentration; It is characterized by including means 19 for adjusting the opening degree of the flow rate control valve 16 in response to the output from the carbon oxide concentration detector 18 so that the carbon monoxide concentration in the furnace body 1 becomes a predetermined value. It is a direct-fired heating furnace.

Embodiments of the present invention will be described below with reference to the drawings. The drawing is a sectional view of one embodiment of the present invention. The furnace body 1 of this direct-fired heating furnace is formed long in the horizontal direction, and a charging port 2 is formed at one end (the right end in the drawing), and at the other end (the left end in the drawing). A discharge port 3 is formed. These charging port 2 and discharge port 3 are provided with doors 4 and 5, respectively, which are vertically displaceable. Inside the furnace body 1, a preheating zone 6, a heating zone 7, and a soaking zone 8 are set in order from the charging port 2 toward the discharge port 3. A plurality of heating burners 9 are provided in the heating zone 7 and the soaking zone 8.

The object to be heated 10 such as steel material or copper alloy is inserted into the charging port 2
It is then charged into the furnace body 1 and continuously conveyed within the furnace body 1 toward the discharge port 3 by a conveying means (not shown). Pre-heating zone 6, heating zone 7 and soaking zone 8
The heated object 10 is discharged from the discharge port 3. On the other hand, the combustion exhaust gas from the heating burner 9 flows in a direction opposite to the conveyance direction of the object to be heated 10 and is discharged from an exhaust pipe 11 provided at the upper part of the furnace body 1 near the charging port 2 .

In such a direct-fired heating furnace, when air enters the furnace body 1 from the outside, the object to be heated 10 reacts with oxygen in the air, and an oxide film is formed on the surface of the object to be heated 10 . Moreover, such an oxidation reaction is accelerated when the heated object 10 is at a high temperature.

In the direct-fired heating furnace as described above, it is possible to maintain the inside of the furnace body 1 in an oxidation-free state by adjusting the ratio of fuel and air in the heating burner 9 to prevent oxidation. However, in order to control the temperature inside the furnace body 1, it is difficult to maintain a constant air-fuel ratio in response to changes in the combustion amount of each heating burner 9, and it is difficult to maintain a constant air-fuel ratio in response to changes in the combustion amount of each heating burner 9. It is difficult to regulate the amount of fuel supplied. Furthermore, if the air supplied to each heating burner 9 is kept below the theoretical air amount, unburned gas and soot will be generated, which is undesirable from the point of view of energy saving and environmental pollution. If a damper 12 is provided in the middle of the exhaust pipe 11 to prevent air from entering from the outside and a slight positive pressure is maintained inside the furnace body 1, the amount of air entering from the outside can be suppressed. When the objects 10 to be heated are charged into or discharged from the furnace body 1, when the doors 4 and 5 are opened, combustion gas is discharged from the upper part of the charging port 2 and the discharge port 3, and air is discharged from the lower part accordingly. invades. Therefore, the intrusion of outside air cannot be prevented by controlling the pressure inside the furnace.

Therefore, in the present invention, a portion where air enters the furnace body 1 from the outside and where the heated object 10 is relatively high temperature, that is, in this embodiment,
A plurality of ejection holes 13 are provided at the lower part of the heating zone 7 and the soaking zone 8. Moreover, these blowholes 13
is provided at the lower part of the heating zone 7 and the soaking zone 8. Gas supply pipes 14 each having a check valve 14a are connected to the ejection holes 13, and these gas supply pipes 14 are commonly connected to a pipe line 15. Conduit 1
5 includes a flow control valve 16 and a solenoid valve 17, and is connected to a combustible gas supply source (not shown). In this way, combustible gas such as natural gas, city gas, liquefied petroleum gas, etc. is fed into the furnace body 1 from each blowout hole 13 .

As described above, when flammable gas is introduced into the furnace body 1, when there is air that has entered the furnace body 1 from the outside, the flammable gas is combusted by reaction with oxygen in the air. Therefore, the inside of the furnace body 1 becomes a non-oxidizing atmosphere. Moreover, since each jet hole 13 is provided in the heating zone 7 and the soaking zone 8, even if the air-fuel ratio of the heating burner 9 deviates slightly and there is excess air, the excess air will react with the combustible gas. consumed by. Note that the heat generated by the combustion of the flammable gas is used to heat the object to be heated 10.

The amount of combustible gas sent from the nozzle 13 is
The amount is set so that no oxygen exists in the furnace body 1. In other words, unless flammable gas is introduced in excess of the amount of oxygen that has entered the furnace body 1, the furnace body 1
Although the atmosphere inside the exhaust pipe 1 will not be non-oxidizing, if excess flammable gas is introduced, unburned gas will be generated and the exhaust pipe 1
Soot may be generated from 1.

Therefore, in order to maintain the atmosphere within the furnace body 1 in an optimal non-oxidizing state, a detector 18 is provided to detect the concentration of carbon monoxide in the atmospheric gas within the furnace body 1. This detector 18 is provided in a soaking zone 8 in the vicinity of the discharge port 3 in the furnace body 1, and its detected carbon monoxide concentration value is inputted to the control means 19.
The control means 19 compares a preset carbon monoxide concentration, for example, about 0.5 to 1%, with the carbon monoxide concentration detected by the detector 18, and determines that the carbon monoxide concentration in the furnace body 1 is equal to the set value. Adjust the opening degree of the flow rate control valve 16 so that

The solenoid valve 17 is set to open when the temperature in the portion where the jet hole 13 is provided, that is, in the heating zone 7 and the soaking zone 8, reaches the ignition temperature of the combustible gas, for example, approximately 800° C. or higher. .

When the door 5 at the outlet 3 is opened,
The pressure inside the furnace body 1 decreases, air enters from the outside, and the carbon monoxide concentration decreases, but the opening degree of the flow rate control valve 16 increases in response to the decrease in the carbon monoxide concentration, and air flows from the jet hole 13. The flow rate of the ejected combustible gas increases, and the carbon monoxide concentration within the furnace body 1 is maintained at the set value. Furthermore, when the door 5 is opened, the amount of air entering from the outside decreases, so the carbon monoxide concentration increases, and the flammable gas flow rate decreases accordingly. Moreover, when the door 5 is opened, air entering from the outside enters from the lower part of the exhaust port 3, but since the jet hole 13 is provided at the lower part of the furnace body 1, the incoming air immediately reacts with the flammable gas. consumed.

At the charging port 2, air also enters the furnace body 1 when the door 4 is opened. Since the temperature 10 is relatively low, the amount of oxidation of the heated object 10 is negligibly small.

As described above, according to the present invention, the ejection holes 13 are provided in the heating zone 7 and the soaking zone 8 in the furnace body 1,
Carbon monoxide is supplied to this jet hole 13 via a flow rate control valve 16 interposed in a pipe 15, and a carbon monoxide concentration detector 18 is provided near the outlet 3 of the object to be heated 10. The opening degree of the flow rate control valve 16 is adjusted so that the carbon monoxide concentration detected by the detector 18 reaches a predetermined value, so that the inside of the furnace body is maintained in an almost oxidation-free state. Therefore, oxidation of the heated object 10 can be prevented. Furthermore, the combustion heat of the combustible gas ejected from the ejection holes 13 is used to heat the object to be heated 10, which greatly contributes to energy saving.

[Brief explanation of drawings]

The drawing is a sectional view of one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Furnace body, 13...Ejection hole, 16...Flow control valve, 18...Detector, 19...Control means.

Claims (1)

[Claims] 1 The object to be heated 1 along the conveyance direction of the object to be heated 10
A preheating zone 6, a heating zone 7, and a soaking zone 8 are formed in this order from the charging port 2 to the discharge port 3, and an exhaust pipe 11 for discharging combustion exhaust gas is provided near the charging port 2. The heating zone 7 and the soaking zone 8 are provided with heating burners 9, and the heating zone 7 and the soaking zone 8 are provided with a furnace body 1 having a jet hole 13, and a pipe line 15 that supplies combustible gas to the jet hole 13.
a flow rate control valve 16 interposed in the pipe line 15; a carbon monoxide concentration detector 18 provided in the furnace body 1 at a position close to the discharge port 3 to detect the carbon monoxide concentration; It is characterized by including means 19 for adjusting the opening degree of the flow rate control valve 16 in response to the output from the carbon oxide concentration detector 18 so that the carbon monoxide concentration in the furnace body 1 becomes a predetermined value. Direct-fire heating furnace.