JPH04276013A - Method for operating batch type heating furnace - Google Patents

Abstract

PURPOSE:To easily and economically heat a steel material without oxidation by imperfectly burning a fuel in a first heating furnace at the specific air ratio to heat the steel material and executing after-burning to the burning gas in a second heating furnace. CONSTITUTION:Two sets of batch type heating furnaces 1, 5 connected with ducts 9 are arranged. In the first heating furnace 1, the fuel is burnt through burners 3 at 0.3-0.8 air ratio, and by this method, the steel material is heated without oxidation. The burning gas 4 incorporating unburnt part generated in the first heating furnace 1, is introduced into a second heating furnace 5 through the above-mentioned ducts 9, and at this time, the burning gas 4 is burnt at >=1.0 air ratio and burnt exhaust gas 8 after after-burning is exhausted to a chimney. By this method, the steel material 7 having no problem to the oxidation of surface is preheated, and the steel material 2 can be heated without oxidation and also the special heat recovery device and safety measures for chimney are eliminated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of operating a batch heating furnace.

0002

[Prior Art] When heating steel materials in a batch heating furnace, the air ratio m = 1.05 and O2% in the combustion exhaust gas is 1.
Since heating is carried out in a combustion atmosphere where the concentration is around 5%, there is a problem that the yield is reduced due to scale generation on the surface of the steel material, oxidation of grain boundaries, etc.

0003

[Problems to be Solved by the Invention] As a heating method for preventing oxidation during heating of steel materials as described above, heating is performed in an incomplete combustion atmosphere in which coke oven gas is combusted at an air ratio m = approximately 0.45. There is an equilibrium theory direct fire reduction heating method. However, although this method suppresses oxidation of steel, the thermal efficiency of the furnace is very low at approximately 20%, compared to 60% for a general heating furnace, and equipment costs such as heat recovery equipment and safety measures are extremely high. There is a problem.

[0004] The present invention solves the above-mentioned problems of the prior art, and is capable of heating steel without oxidizing it, and moreover, it is a batch process that does not require special heat recovery equipment or safety measures such as a flue. The purpose is to provide a method for operating a type heating furnace.

[0005]

[Means for Solving the Problems] A method for operating a batch-type heating furnace according to the present invention uses two batch-type heating furnaces,
In the first batch heating furnace, the fuel and air ratio is 0.3~
0.8 to heat the steel material, and the combustion gas generated in the first batch heating furnace is passed through a duct connecting the first batch heating furnace and the second batch heating furnace to the second batch heating furnace. In the second batch heating furnace, the combustion gas is combusted at an air ratio of 1.0 or more to heat the steel material.

[0006]

[Operation] The method of operating a batch heating furnace according to the present invention is as follows:
Two batch-type heating furnaces are used; in the first batch-type heating furnace, fuel is burned at an air ratio of 0.3 to 0.8 to heat the steel material; The combustion gas is introduced into the second batch heating furnace through a duct connecting the first batch heating furnace and the second batch heating furnace, and the combustion gas is introduced into the second batch heating furnace. air ratio 1
．． The steel is heated by combustion at temperatures above 0.

[0007] When operated in this manner, the steel material can be heated without oxidizing it, and the combustion exhaust gas containing unburned parts generated by heating the steel material is afterburned and used for residual heat of the steel material. Thermal efficiency of the furnace does not decrease.

Furthermore, since the combustion exhaust gas containing unburned parts is afterburned and the unburned parts are combusted, safety measures such as special heat recovery equipment and flues are not required.

[0009] Note that the air ratio in the first batch heating furnace is 0.
．． The reason why it is set to 3 or more is because if it is less than this, the flame temperature for heating the steel material cannot be obtained, and the reason why it is set to 0.8 or less is because the air ratio and scale thickness ratio (air ratio 1.
This is because, as can be seen in the graph showing the relationship between the scale thickness and the scale thickness when the thickness is 100%, if the thickness is less than this, the amount of scale generated will decrease rapidly.

[0010] Furthermore, the air ratio of the second batch type heating furnace is set to 1.
．． The purpose of setting the value to be 0 or more is to perform afterburning, so it is necessarily 1.0 or more.

[0011]

[Embodiment] A method of operating a batch type heating furnace according to an embodiment of the present invention will be explained with reference to FIG. FIG. 1 is a layout diagram showing the arrangement of a batch-type heating furnace used when implementing a method for operating a batch-type heating furnace according to an embodiment of the present invention. In the operating method of a batch heating furnace according to one embodiment of the present invention, a steel material 2 that is not to be oxidized is heated in a first batch heating furnace 1, and a coke oven gas is fed into an air ratio m=0.3 to 0.
Heat in the incomplete combustion atmosphere used in step 8. and,
Combustion gas 4 containing an unburned portion generated in the first batch heating furnace 1 is introduced into the second batch heating furnace 5 through a duct 9, and this combustion exhaust gas 4 is subjected to afterburning by an afterburning burner 6. Then, the steel material 7 whose surface oxidation is not a problem is preheated. The combustion exhaust gas 8 after afterburning is then diffused into the atmosphere through the chimney.

The graph in FIG. 2 shows the scale loss of steel materials in the first batch heating furnace.
When steel material weighing about 6 tons is charged and heated,
This is a comparison with the case of heating using the conventional method. Conventional 2%
It can be seen that when heating with this method, almost no scale loss occurs even though there was some scale loss.

[0013] If afterburning is not performed in the second batch heating furnace, the fuel consumption rate will be 112 x 103 kc.
It will cost extra al/T.

[0014] In the operating method of a batch-type heating furnace according to one embodiment of the present invention, as described above, the steel material can be heated without oxidizing it, and the combustion gas containing the unburned portion of the heated steel material can be removed after heating. Since other steel materials are heated by burning, the thermal efficiency of the heating furnace does not decrease. Furthermore, since the combustion gas including the unburned portion is completely combusted, there is no need for heat recovery equipment or safety measures.

[0015]

[Effects of the Invention] According to the present invention, it is possible to heat a steel material without oxidizing it without reducing the thermal efficiency of the heating furnace, without requiring special heat recovery equipment or safety measures.

[Brief explanation of the drawing]

FIG. 1 is a layout diagram showing the arrangement of a batch-type heating furnace used when implementing a method for operating a batch-type heating furnace according to an embodiment of the present invention.

FIG. 2 is a graph showing changes in scale loss.

FIG. 3 is a graph showing the relationship between air ratio and scale thickness ratio.

[Explanation of symbols]

1 First heating furnace 2 Steel material 3 Burner 4 Combustion exhaust gas including unburned parts 5 Second heating furnace 6 Burner for afterburning 7 Steel material 8 Combustion exhaust gas after afterburning 9 Duct

Claims (1)

[Claims] Claim 1: Using two batch-type heating furnaces, the first
In batch type heating furnaces, the fuel to air ratio is 0.3 to 0.
8 to heat the steel material, and the combustion gas generated in the first batch heating furnace is passed through a duct connecting the first batch heating furnace and the second batch heating furnace to the second batch heating furnace. A method for operating a batch-type heating furnace, characterized in that the steel material is heated by introducing the combustion gas into a batch-type heating furnace, and in a second batch-type heating furnace, the combustion gas is combusted at an air ratio of 1.0 or more.