JPS6089524A - Method for protecting conveying roll of direct firing clean heating furnace - Google Patents

Abstract

PURPOSE:To prevent corrosion on the surface of inlet side roll of direct firing clean heating furnace and to improve the working efficiency of equipment, the cost of the roll, yield, etc. by blowing a gas having the dew point lower than the dew point of waste gas to said roll thereby preventing condensation on the surface of the roll. CONSTITUTION:A cover 10 is disposed to ain inlet side roll 2 which is cooled in contact with a steel strip 7 of an ordinary temp. carried into a direct firing clean heating furnace and gaseous N2 or air having the dew point lower than the dew point if the waste gas is blown between the roll 2 and the cover 10 from a blow pipe 11. The dew point on the surface part of the roll 2 is thus decreased, by which the condensation on the surface of the roll 2 is surely prevented and the corrosion of the roll 2 surface is lessened. The improved working efficiency of the equipment is thus resulted from the decreased frequencies of exchanging the roll and the improved yield is obtained resulting from the decreased product flaws, by which the cost of the roll is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for protecting conveyor rolls in a direct-fired non-oxidizing furnace.

[Prior art]

Examples of direct-fired non-oxidizing furnaces include continuous zinc-melting equipment,
It is installed along with reduction furnaces and cooling furnaces in continuous annealing equipment, etc.

However, as shown in Fig. 1, such a non-oxidation furnace 1
, sequentially roll 3,
4,5.6 Transport the Nyofu steel strip 7.

After being subjected to heat treatment, it is led to the next reduction furnace 8.

In such a non-oxidizing furnace, generally, as shown in the figure,
The burner 9 completely burns the gas etc. and heats the copper strip 7.
The exhaust gas is discharged from the copper belt 7 person side 10 and exhaust gas heat 3
The copper strip 7 is completely preheated at 00 to 800°C. The entrance roll 2 is in constant contact with the steel strip 7 at room temperature, and the roll surface is cooled to a temperature of 30 to 50°C.

Therefore, the dew point of the non-oxidizing furnace exhaust gas is 50 to 70°C, the roll surface is always in a state of condensation, and furthermore, if the fuel in the non-oxidizing furnace is a sulfur-containing fuel such as coke oven gas, the condensed water contains sulfur. Containing acid condenses and corrodes the roll, which can cause stains or scratches on the belt.

In order to prevent deposits from adhering to the hearth roll surface in the high temperature (heating) section of the furnace, it has been proposed to maintain the roll surface at a low temperature, as disclosed in, for example, Japanese Patent Publication No. 49-29043. However, the inlet of a direct-fired heating furnace (
The condition of the roll surface in a low-temperature atmosphere (such as during preheating) is different from the high-temperature part described above, and therefore, regular roll replacement is required, but this has a negative impact on equipment operating rate, roll cost, yield, etc. However, no technology has been specifically disclosed to overcome these drawbacks.

[Purpose of the invention]

The present invention has been made to advantageously solve these drawbacks.

[Structure 1 of the Invention] The gist of the present invention is a method for protecting the conveyor roll of a direct-fired non-oxidizing furnace, which is characterized by spraying a gas with a dew point lower than the exhaust gas dew point onto the inlet roll of the direct-fired non-oxidizing furnace. It is something to do.

That is, in the present invention, as described above, a low dew point gas is sprayed onto the inlet roll, and as the gas, for example, N2f gas, air, etc. can be used. That is, the inlet roll is exposed to the exhaust gas of the non-oxidizing furnace, and a gas with a lower dew point than this exhaust gas dew point is blown onto the roll.

The method of spraying is to direct a low dew point gas spray nozzle to the roll and spray, or as shown in Figure 2, to lower the dew point of the cover 10 roll 2 surface as shown in the entrance roll 2&C and to the roll 2. As a result, it can be prevented.

〔Effect of the invention〕

According to the present invention, it is possible to reliably prevent dew condensation on the roll surface and reduce corrosion on the roll surface, thereby reducing the frequency of roll replacement, improving the operating rate of equipment, reducing product defects, and increasing yield. Since the roll cost can be improved and the roll cost can be reduced, the industrial benefits are extremely large.

〔Example〕

Next, examples of the method of the present invention will be listed together with comparative examples.

Example 1) Steel strip size 0.8 x 1500 mn2) Threading speed 100 mpm 3) Inlet steel strip temperature 3 (1 4) Non-oxidizing furnace fuel Coke oven generated gas 5) Combustion gas amount 1000 Nm3/Hr6) Exhaust gas Temperature 400℃ 7) Exhaust gas amount 6000 Nm' / I (r8) Exhaust gas dew point +60℃ 9) S content in exhaust gas 10 ppm 10) Distance between roll covers (Figure 2) 30 Solution 11) Low dew point gas and blowing amount N2 gas 300 Ntn'ATr
12) Low dew point gas dew point -40°C When carried out in this manner, the results described below were obtained.

Comparative Example A test was carried out under the same conditions as in the above example without blowing low dew point gas onto the roll, but the results were as follows.

As described above, according to the present invention, the Q

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the main parts of a direct-fired non-oxidizing furnace, and FIG. 2 is an explanatory diagram showing an embodiment of the present invention. Figure 1 Figure 2 Figure 2

Claims (1)

[Claims] A method for protecting a conveyor roll of a direct-fired non-oxidizing furnace, characterized by spraying a gas with a dew point lower than the exhaust gas dew point onto the inlet roll of the direct-fired non-oxidizing furnace to prevent dew condensation.