JP2605198B2 - Low NOx combustion method in rolling furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low NOx combustion method in a rolling furnace used for hot rolling of steel or the like.

[0002]

2. Description of the Related Art As a conventional low NOx combustion technique in a rolling furnace or the like, a method using a low NOx burner, an exhaust gas denitration method for selectively reducing NOx by mixing ammonia gas or the like into exhaust gas, and the like are known. There is.

[0003]

In the former method, NOx is used.
There is a limit to the reduction, and the latter has a problem that equipment is required, and cost and operation cost are required. On the other hand, conventionally, no special measures have been taken in a rolling furnace to suppress the oxidation of the material to be rolled. The present invention has been made in view of the above points, that is, it is an object of the present invention to rationally utilize the structure of a rolling furnace, reduce NOx, and suppress oxidation of a material to be rolled. .

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, there is provided a combustion zone constituting a solitary tropical zone, a heating zone and a pre-tropical zone from a front side to a rear side in a transport direction of a material to be rolled. In a rolling furnace having a combustion gas passage between the soaking zone and the heating zone, and between the heating zone and the pre-tropical combustion chamber, a burner is provided for each of the combustion gas passages. A low NOx combustion method is proposed in which fuel gas is ejected from a fuel gas nozzle installed on the upstream side toward a material to be rolled to form a reducing atmosphere region on the downstream side.

[0005]

The combustion gas in the solitary combustion chamber flows through the combustion gas flow path into the combustion chamber forming the heating zone, and then the combustion gas in this combustion chamber flows through the combustion gas flow path and forms the pre-tropical combustion chamber. Flows into. And it is discharged from this combustion chamber through a flue. On the other hand, the material to be rolled is heated while being sequentially transferred through the combustion chambers forming the pre-tropical zone, the heating zone, and the solitary zone.

In the above operation, since the fuel gas ejected from the fuel gas nozzle provided on the upstream side of the combustion gas flow path between the combustion chambers forms a reducing atmosphere region on the downstream side thereof, Generated on the upstream side
Is reduced and denitrated, and oxidation of the material to be rolled is suppressed.

[0007]

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram showing a configuration of a rolling furnace to which the low NOx combustion method of the present invention is applied. In this figure, reference numeral 1 denotes a rolling furnace, which is provided with combustion chambers 2, 3, and 4 constituting a solitary zone, a heating zone, and a pre-tropical zone, respectively, adjacent to each other. , 6 and 7, and narrowed combustion gas passages 8, 9 between the soaking zone and the heating zone and between the heating zone and the pre-tropical combustion chambers, that is, between the combustion chambers 2, 3 and between the combustion chambers 3, 4. Is provided. Reference numeral 10 denotes a material to be rolled, such as steel, that is, a billet. The material to be rolled 10 is transferred from the pre-tropical combustion chamber 4 side to the combustion chamber 2 via the combustion chamber 3. Combustion chambers 3 and 4 in the pre-tropical and heating zones
It is configured to correspond to both sides of the material 10 to be rolled, and therefore, the combustion gas flow path 9 between the burners 6, 7 and the combustion chambers 3, 4 is also configured to correspond to both sides of the material to be rolled 10. . on the other hand,
The combustion chamber 2 forming the soaking zone is formed only on one side of the material to be rolled 10. On the downstream side of the pre-tropical combustion chamber 4, there is provided a combustion gas channel 12 connected to the flue 11,
The combustion gas passages 12 are also configured to correspond to both sides of the material to be rolled 10.

Fuel gas nozzles 13 and 14 for ejecting fuel gas toward the material to be rolled 10 are provided upstream of the combustion gas passages 8 and 9, respectively. The fuel gas nozzles 14 are configured to correspond to both sides of the material 10 to be rolled.

FIG. 2 is an enlarged view of a portion of the combustion gas flow path 8 which is partially cut away. In this embodiment, the fuel gas nozzle 13 has a plurality of nozzles 15 arranged in the width direction of the combustion gas flow path 8. , And each nozzle 15 has an ejection port having a flat shape in the width direction. Of course, the shape of the injection port is appropriately circular or the like, and a single fuel gas nozzle 13 is used.
Alternatively, it may be constituted by a plurality of slit nozzles which are long in the width direction. These fuel gas nozzles can be configured such that the ejection direction is variable. When the fuel gas nozzle 13 is composed of a plurality of nozzles 15 installed in the width direction of the combustion gas flow path 8, the effective diameter, pitch, etc. of the respective ejection ports are determined by the fuel gas ejected from each of the materials 10 to be rolled.
Are set so as to be distributed in a predetermined uniform state in the vicinity of. For example, as a setting example, the pitch between the nozzles 15 is set to 1/4 or less of the height of the combustion gas passage 8 and the effective diameter of each nozzle 15 is set to 1/100 of the height of the combustion gas passage 8.
The following settings are possible. On the other hand, fuel gas nozzle 1
The speed at which the fuel gas is ejected from the material 3 is not interrupted by the combustion gas flowing through the combustion gas flow path 8 and the material to be rolled 1
The speed is set to a predetermined speed or more, for example, five times or more the average flow velocity of the combustion gas so as to reach the zero surface. Although the configuration and conditions of the fuel gas nozzle for the combustion gas flow path 8 have been described above, it is needless to say that these configurations and conditions also apply to the combustion gas flow path 9.

The operation of the present invention in the above configuration will be described below with reference to a specific example. First, the combustion gas in the solitary combustion chamber 2 by the burner 5 flows into the combustion chamber 3 constituting the heating zone through the combustion gas flow path 8, and at the same time, the fuel gas nozzle of the combustion gas flow path 8 Fuel gas ejected from 13 flows in. The burner 6 in the combustion chamber 2
Is supplied to the combustion together with the fuel gas and air supplied to the fuel cell.

The amount of fuel gas and the amount of air supplied to the burner 5 are set so as to be in the same air ratio range as in normal combustion, for example, 0.8 to 1.1. The burner 6 determines the amount of fuel gas and air supplied to the burner 5, the flow rate of fuel gas supplied in the combustion gas flow path 8, and the amount of air and fuel gas supplied from the burner 6 itself. The calculated air ratio is set so as to be in the above-described normal air ratio range of 0.8 to 1.1.

On the other hand, the amount of fuel gas supplied from the fuel gas nozzle 13 is calculated based on the ratio of the amount of fuel gas supplied to the burner 5 and the amount of air supplied to the burner 5. It is set to be 0.9. This fuel gas amount is 10 times of the fuel gas amount supplied to the burner 5.
~ 20%.

The combustion gas in the combustion chamber 3 burned under the above conditions flows into the pre-tropical combustion chamber 4 together with the fuel gas through the combustion gas passage 9 in the same manner as described above. Then, in the combustion chamber 3, the fuel gas and the air supplied to the burner 7 are used for combustion. At this time, the amount of fuel gas and the amount of air supplied to the burner 7 and the amount of fuel gas supplied from the fuel gas nozzle 14 are set based on the air ratio calculated in the same manner as described above.

In the above operation, NOx generated in each of the combustion chambers 2 and 3 is reduced to the reducing atmosphere regions 16 and 1 formed by the fuel gas ejected from the fuel gas nozzles 13 and 14.
At 7, reduction and denitration reduce NOx. In the reducing atmosphere regions 16 and 17, the oxidation of the material to be rolled 10 is suppressed, so that the quality after rolling is improved.

[0015]

As described above, the present invention is provided between the combustion chambers constituting the rolling furnace structure, that is, the soaking zone, the heating zone, and the pre-tropical zone, so as to be narrowed to prevent interference between the combustion chambers. NOx by rationally using the combustion gas flow path
In addition, there is an effect that the quality can be improved by reducing the amount of oxidation and suppressing oxidation of the material to be rolled.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a rolling furnace to which a low NOx combustion method of the present invention is applied.

FIG. 2 is an enlarged perspective view of a main part of FIG. 1 with a part cut away.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolling furnace 2, 3, 4 Combustion chamber 5, 6, 7 Burner 8, 9, 12 Combustion gas flow path 10 Material to be rolled 11 Flue 13, 14 Fuel gas nozzle 15 Nozzle 16, 17 Reduction atmosphere area

Claims (6)

(57) [Claims] 1. A combustion chamber comprising a solitary zone, a heating zone, and a pre-tropical zone, respectively, are provided from the front side to the rear side in the transport direction of the material to be rolled. And, in a rolling furnace provided with a narrow combustion gas flow path between the heating zone and the pre-tropical combustion chamber, the fuel gas is directed from the fuel gas nozzle installed on the upstream side of the combustion gas flow path toward the material to be rolled. Low NOx combustion method in a rolling furnace characterized by forming a reducing atmosphere region on the downstream side by squirting. 2. The low NOx combustion method in a rolling furnace according to claim 1, wherein the fuel gas nozzle comprises a plurality of nozzles installed in a width direction. 3. The low NOx combustion method in a rolling furnace according to claim 1, wherein the fuel gas nozzle is constituted by a slit-shaped nozzle elongated in the width direction. 4. The fuel gas nozzle according to claim 2 or 3,
Low NOx combustion method in a rolling furnace characterized by variable ejection direction 5. The low NOx combustion method according to claim 1, wherein
In the combustion gas flow path, the amount of fuel gas ejected from the fuel gas nozzle is such that the air ratio calculated from the amount of fuel gas and the amount of fuel gas and air supplied up to that time is 0.7 to 0.
9. A low NOx combustion method in a rolling furnace, wherein the method is set to be 9. 6. The low NOx combustion method according to claim 1, wherein
The amount of fuel gas and the amount of air supplied to the burner are set such that the air ratio calculated from the amount of fuel gas and the amount of air supplied to the combustion chamber is 1.0 to 1.1. NOx combustion method in furnace