JPH0114514B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an atmosphere control method for a tunnel furnace in which an oxidizing flame firing zone and a reducing flame firing zone are coupled in the furnace.

Problems to be Solved by the Prior Art and the Invention When firing high-grade white porcelain, for example, in a tunnel furnace, it is heated to about 1000°C in an oxidizing atmosphere and then heated to an even higher temperature in a reducing atmosphere. In the tunnel furnace that performs this kind of firing, the firing zone is divided into an oxidizing flame firing zone in the first half and a reducing flame firing zone in the latter half.In the oxidizing flame firing zone, the fuel is completely combusted from the burner. An oxidizing flame firing zone is formed by injecting excess air in excess of the amount necessary and sufficient for complete combustion of the fuel from the burner, and in the reducing flame firing zone, less air than is necessary for complete combustion of the fuel is injected from the burner. However, in a tunnel furnace, the temperature gradually rises from the entrance to the highest temperature part of the firing zone, and the temperature reaches the highest temperature. In order to create a temperature gradient in the furnace in which the temperature gradually decreases from the temperature section to the carry-out port, multiple blowers are arranged to create an airflow from the carry-out port side to the carry-in port side. If no partition means is provided between the firing zone and the reducing flame firing zone, the above airflow will cause reducing gases such as CO gas to flow from the reducing flame firing zone to the oxidizing flame firing zone, and the atmosphere in the oxidizing flame firing zone will change. This will cause the color tone of the fired product to change and lead to defective products.

For this reason, conventionally, a plurality of inlets were formed on the wall between the oxidation flame firing zone and the reduction flame firing zone, and air outside the furnace or air heated using the furnace heat was blown in from the jets by a blower. An air curtain was formed between the oxidation flame firing zone and the reduction flame firing zone to prevent reducing gases such as CO gas from flowing from the reduction flame firing zone to the oxidation flame firing zone. Since the air is blown in by a blower, the upper limit of the temperature of the air is several hundred degrees Celsius, and it is impossible to make it higher than that. The temperature inside the furnace decreases, and the object to be fired, which was heated to approximately 1000℃ in the oxidizing flame firing zone, is rapidly cooled, and then enters the reduction flame firing zone where it is rapidly heated to over 1000℃, causing the object to be fired to cool down. Not only is there a risk of cracks and fractures occurring in the furnace, but additional fuel is required to maintain the temperature inside the furnace, which reduces thermal efficiency.To avoid this, it is recommended to reduce the amount of air blown. In this case, it becomes impossible to maintain a desired atmosphere, and it becomes difficult to bake a good product.

SUMMARY OF THE INVENTION An object of the present invention is to provide an atmosphere control method for a tunnel furnace that eliminates these drawbacks and allows a desired atmosphere to be maintained without lowering the temperature inside the furnace.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a tunnel furnace body in which a pre-heating zone P, a firing zone Q, and a cooling zone R are sequentially formed inside from the carry-in port at the left end to the carry-out port at the right end. Of these, the firing zone Q is divided into an oxidizing flame firing zone Qa on the loading port side and a reducing flame firing zone Qb on the loading port side. Burners that blow out excess air along with fuel are placed on both sides of the furnace wall to maintain an oxidizing atmosphere, and in the reduction flame firing zone Qb,
Burners that eject air with fuel in an amount smaller than that required for complete combustion of the fuel are placed on both sides of the furnace wall to maintain a reducing atmosphere, and between the oxidizing flame firing zone Qa and the reducing flame firing zone Qb. As shown in Fig. 2, a total of four burner mounting holes 2, two on the top and bottom, are formed facing each other in the furnace walls on both sides of the furnace. A burner tile 3 having a combustion flame outlet is fitted in the burner tile 3, and a burner tile 3 is fitted with a burner tile 3 having a sufficient amount to completely burn unburned gas such as CO gas flowing from the reduction flame firing zone Qb to the oxidation flame firing zone Qa. A burner 4 is installed that blows out excess air together with fuel to form a high-temperature air curtain of about 1000°C in which combustion gas and excess air are mixed between the oxidation flame firing zone Qa and the reduction flame firing zone Qb. The unburned gas flowing from the reduction flame firing zone Qb to the oxidation flame firing zone Qa mixes with excess air ejected from the burner 4 and is completely combusted.

Structure and effects of the invention As specifically explained in the above embodiments,
In the tunnel furnace atmosphere control method of the present invention, an oxidizing flame firing zone and a reducing flame firing zone are coupled in the furnace, and an air flow from the reducing flame firing zone side to the oxidizing flame firing zone side is formed in the furnace. Unburnt gas flowing from the reduction flame firing zone to the oxidation flame firing zone by the air flow from a burner disposed on the wall between the oxidation flame firing zone and the reduction flame firing zone of a tunnel furnace where The gist is to eject combustion gas containing a sufficient amount of excess air for complete combustion in the form of an air curtain that partitions the oxidizing flame firing zone and the reducing flame firing zone, Since the unburned gas flowing into the firing zone mixes with the excess air ejected from the burner and burns almost completely, the oxidizing atmosphere in the oxidizing flame firing zone is not disturbed and the furnace temperature does not drop. This has the effect of not only making it possible to bake a good product without changing the color tone of the fired product or causing cracks or cracks, but also improving thermal efficiency.

[Brief explanation of drawings]

FIG. 1 is a horizontal sectional view of an embodiment of a tunnel furnace for implementing the present invention, and FIG. 2 is an enlarged sectional view taken along the line A--A in FIG. 1: Furnace body, 4: Burner, Qa: Oxidation flame firing zone,
Qb: reduction flame firing zone.

Claims (1)

[Claims] 1. The oxidation flame firing of a tunnel furnace in which an oxidation flame firing zone and a reduction flame firing zone are coupled in the furnace, and an air flow from the reduction flame firing zone side to the oxidation flame firing zone side is formed in the furnace. A burner disposed on the wall between the belt and the reduction flame firing zone generates an amount sufficient to almost completely burn the unburned gas flowing from the reduction flame firing zone to the oxidation flame firing zone by the air flow. A method for controlling an atmosphere in a tunnel furnace, characterized in that combustion gas containing excess air is ejected in the form of an air curtain that partitions the oxidizing flame firing zone and the reducing flame firing zone.