JP2000119742A - Method for heating furnace and preparation of protecting atmosphere in furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute the heating of a furnace and the generation of combustion exhaust gas used for protecting atmosphere in the furnace with a gas combustion radiation tube disposed in the furnace. SOLUTION: A combustion nozzle 6 and a heat-storage body 7 are fitted to both ends of the gas combustion radiation tube 4 arranged in the furnace, and when the heat-storage body is thermally saturated with the combustion exhaust gas (e) exhausted from the tube, the combustion nozzle for jetting the combustion gas is changed from the one side to the other side and the combustion gas E jetted and burned from the combustion nozzle is changed into for heating the furnace or for generating the protecting atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION As a protective atmosphere in a furnace used for bright heating of metals, a modified gas of a mixture of hydrocarbon and air is used. The present invention relates to a method of heating a furnace and a method of producing a furnace protective atmosphere, which can provide a furnace protective atmosphere of the type described above simply and inexpensively by using a gas combustion radiant tube installed in the furnace.

[0002]

2. Description of the Related Art As a heat source of a heating furnace filled with a protective atmosphere, a gas combustion radiant tube is frequently used. Has been made more efficient. That is, the furnace is heated by the radiant heat of the combustion gas burned by the fuel injection means at one end in the pipe, and the combustion exhaust gas is discharged from the other end of the pipe. At the time of this discharge, the heat energy of the combustion exhaust gas is captured by a heat storage body made of ceramic or the like at the other end and stored.

[0003] Instead of the combustion by the combustion injection means at one end, the combustion gas is subsequently burned by the combustion injection means at the other end. At this time, the heat energy stored in the heat storage body at the other end is burned. It will help to preheat the gas.

As described above, the combustion by the combustion injection means at both ends is alternately performed, and such combustion is repeated in a short time, so that the heat energy stored in the heat storage unit is useful for preheating the next combustion gas, A high rate of energy saving will be achieved.

On the other hand, the protective atmosphere filling the inside of the heating furnace is generally created by a protective atmosphere generating furnace independent of the heating furnace.

[0006]

Therefore, by using a combustion radiant tube having a fuel injection means and a heat storage body at both ends of the above-mentioned type, the furnace is efficiently heated and a protective atmosphere for the furnace is produced. I researched what I can't do.

[0007]

According to the present invention, one of a pair of repetitive and alternating combustions by the above-mentioned pair of combustion injection means burns at the oxygen ratio in a region where the fuel gas is completely burned, thereby maximizing the combustion. The furnace is heated in order to generate heat, and on the other hand, the fuel gas is burned at the oxygen ratio in the region where the exhaust gas is reducible to iron and copper, and used for non-oxidizing bright heat treatment of iron and copper. The resulting reducing protective atmosphere is produced.
Hereinafter, the method of the present invention will be described with reference to the drawings.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a heating chamber 1 surrounded by a furnace wall 2 made of a heat insulating material, a pair of combustion radiation tubes 4, 5 are attached below a conveyor belt 3 circulating in the furnace. Although not shown in this embodiment, a pair of combustion radiation tubes extend in the longitudinal direction of the furnace even above the belt 3. Each radiation tube 4,
5 had an inner diameter of 114 mm and a length of 5000 mm.

At both ends of each combustion radiation tube, a fuel gas injection nozzle 6 and an annular air-permeable heat storage element 7 made of ceramics for capturing and storing thermal energy of combustion exhaust gas are attached.

In FIG. 1, a nozzle 6 on the left side of an upper combustion radiation tube 4 has a primary combustion gas D for heating a furnace.
(Methane gas: 6.7m ³ / h and air: 63.8m ³ /
h) was burned. At this time, the temperature around the radiation tube 4 was kept at 1000 ° C. The primary combustion exhaust gas d of the primary combustion gas D was discharged outside the furnace through the heat storage body 6 on the right. The composition of the primary combustion exhaust gas d was moisture, carbon dioxide, and nitrogen, and it was recognized that the combustion was almost completely completed.

When the primary combustion exhaust gas d passes through the heat storage element 6 on the right hand, the heat is transferred to the heat storage element 6 to lower the temperature, and
43 ° C.

The heat storage body 6 was saturated after 30 seconds. At this time, the direction of gas injection was reversed by a control device (not shown) as shown in the combustion radiation tube 4 in the upper part of FIG. That is, the right-hand nozzle in the upper combustion radiation tube 4 of FIG.
(Methane gas: 14.61 m ³ / h and air: 83.58
m ³ / h), and the gas burned after being preheated in the heat storage body 7 on the right. The composition of the secondary combustion exhaust gas e is:
Moisture: 13.2%, hydrogen: 13.4%, carbon dioxide: 5.
1%, carbon monoxide: 8.2%, and nitrogen: 60.1%, methane was not detected, and it could be used as a protective atmosphere for non-oxidizing heating of copper.

The thermal energy of the secondary combustion exhaust gas e is captured and stored by the heat storage body on the left side of the radiation tube 4 in the upper part of FIG. 2, and the temperature when taken out of the furnace is 237 ° C.
Met.

The secondary combustion gas E is sent from the right-hand nozzle to the lower combustion radiation tube 5 in FIG. 1 and burned in the tube, and then the secondary combustion exhaust gas e is obtained through the left-hand regenerator 7. . The heat storage element 7 on the left hand was saturated by the secondary combustion exhaust gas e, and after 30 seconds, its gas injection and combustion direction were reversed as shown in the lower combustion radiation tube 5 in FIG.

When the secondary combustion exhaust gas e obtained as described above was cooled to 5 ° C. to remove water, the composition was as follows: water: 0.8%, hydrogen: 15.2%, carbon dioxide: 6.
1%, carbon monoxide: 9.2%, and nitrogen: 68.7%. When heated or cooled to 200 ° C. or less in this protective atmosphere, sufficient reducing property for performing a brilliant heat treatment of steel is obtained. It was found that the gas composition had

In this embodiment, the combustion radiation tubes 4, 5
In either case, the combustion using the primary combustion gas D and the secondary combustion gas E was performed alternately. However, if necessary, for example, in one of the combustion radiation tubes 5, the combustion using only the primary combustion gas may be performed at any one of the nozzles at both ends. Good.

[0017]

The method of the present invention is as described above,
Without using a protective atmosphere generating furnace independent of the heating furnace, an excellent effect of heating the furnace and generating a protective atmosphere in the furnace can be easily and economically obtained only by the gas combustion radiation tube provided in the furnace.

[Brief description of the drawings]

FIG. 1 is one embodiment of a heating furnace suitable for carrying out the method of the present invention, and is an explanatory plan sectional view showing a pair of combustion radiation tubes provided in a heating chamber of the furnace and a combustion mode thereof. .

FIG. 2 is an explanatory plan view similar to FIG. 1, showing an inverted combustion mode of the radiant tube.

[Explanation of symbols]

 1-furnace heating chamber 2-furnace wall of heat-insulating material 3-conveyor belt 4-gas combustion radiation tube 5-different combustion radiation tube 6-combustion injection nozzle 7-ceramic regenerator E-mainly for heating furnace Primary combustion gas e-Combustion exhaust gas of primary combustion gas D-Secondary combustion gas whose main purpose is to create a protective atmosphere d-Combustion exhaust gas of secondary combustion gas

Claims (4)

[Claims] 1. A plurality of gas combustion radiant tubes each having a fuel injection means and a heat storage body at both ends are mounted in a furnace, and at least one of the gas combustion radiant tubes generates heat for heating the furnace. The combustion of the target gas is performed by the combustion injection means at one end, and the combustion of the gas for the purpose of changing the protective atmosphere in the furnace is performed by the combustion injection means at the other end, and the combustion of these gases is performed alternately. A method for heating a furnace and producing a protective atmosphere in the furnace. 2. The furnace according to claim 1, wherein the amount of air during combustion of the gas for the purpose of transforming the protective atmosphere in the furnace is adjusted so that a desired amount of hydrogen is present in the obtained protective atmosphere. For heating and producing a protective atmosphere in the furnace. 3. A partial pressure of nitrogen in the obtained protective atmosphere is reduced by replacing a part or all of air for combustion of a gas for the purpose of transforming the protective atmosphere in the furnace with oxygen. The method of heating the furnace and producing a protective atmosphere in the furnace according to the description. 4. The furnace heating and furnace protective atmosphere according to claim 1, wherein moisture is removed from the furnace internal protective atmosphere obtained by the combustion of gas by the other end of the combustion injection means to enhance its reducibility. Manufacturing method.