JP2006137965A - Metal-heating furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal-heating furnace which is provided with a burner that uses the pressure of supplied gaseous fuel for the energy of atomizing oil, thereby eliminates the need of installing a boiler for generating vapor for atomization or vapor, needs to install few number of burners therein, secures an adequate atmosphere in the furnace to reduce the production of scale, and achieves an adequate and uniform heating condition to save energy. <P>SOLUTION: This metal-heating furnace has the gas atomization burner 1 for introducing the gaseous fuel of a medium for atomizing liquid fuel arranged so that the formed flame can direct toward a material 13 to be heated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a metal heating furnace, and more particularly to a metal heating furnace provided with a relatively large-capacity gas atomizing burner that atomizes and burns liquid fuel using a supply pressure of a combustible gas.

Conventional heating furnaces for heating metals such as steel generally use liquid fuels such as oil or gaseous fuels such as city gas and LPG, but both fuels have advantages as fuels for heating furnaces. There are disadvantages.
The gas fuel has the characteristics that the brightness of the flame is low but the atomizing medium is unnecessary, the flame shape can be formed relatively freely, and the operation at a low air ratio is also possible.

On the other hand, the liquid fuel requires an atomizing medium for atomizing the liquid. As the atomizing medium, air or steam is generally used, but steam is often used for a relatively large-capacity burner such as a metal heating furnace.
Therefore, when the atomizing steam flows into the furnace, the moisture ratio in the combustion gas (in the furnace atmosphere) increases, and the steel material has an atmosphere that is more easily oxidized. However, in the high temperature range, the brightness of the flame is high, and it can be said that it works favorably from the viewpoint of heat transfer. On the other hand, the uniformity of the flame temperature tends to be slightly inferior.

  In view of the problems of the conventional metal heating furnace, the present invention eliminates the need for an atomizing steam and a boiler for generating the steam by using the supply pressure of the gaseous fuel for the atomizing energy of the oil. To provide a metal heating furnace that can achieve energy saving by reducing the generation of scale by reducing the number of installed burners, reducing the generation of scale, and realizing a good and uniform heating state. Objective.

  In order to achieve the above object, a metal heating furnace of the present invention includes a gas atomizing burner that introduces gaseous fuel as an atomizing medium for liquid fuel in a metal heating furnace including a burner that atomizes and injects liquid fuel. It arrange | positions so that a flame may be formed toward a heating material.

  In this case, after the combustion gas reaches the top of the furnace through the upper part of the furnace, the lower part of the furnace is divided into two hands while being heated, and the flue gas from the lower part of the gas atomizing burner is turned over. It can be exhausted.

  Further, the gas atomizing burner can maintain the heat quantity ratio between the gas body fuel and the liquid fuel at a constant value, and can control the furnace temperature by changing the heat input quantity.

  Further, the gas atomizing burner can maintain the supply amount of the gaseous fuel constant and change the supply amount of the liquid fuel to control the temperature of the furnace.

  According to the metal heating furnace of the present invention, in the metal heating furnace provided with the burner for atomizing and injecting the liquid fuel, the gas atomizing burner for introducing the gaseous fuel as the atomizing medium of the liquid fuel is directed toward the material to be heated. Since it is arranged so that a flame is formed, it is possible to form a long flame with high brightness in the furnace, to form a heating furnace with uniform furnace temperature, and to perform gas atomized combustion. By doing so, compared with steam atomized combustion, it is low NOx, the atmosphere in the furnace has a low moisture ratio, and therefore operation with reduced scale generated on the surface of the steel material is possible, and further, excess steam is generated in the furnace Therefore, the heating time of the furnace can be greatly shortened, a good and uniform heating state can be realized, and significant energy saving can be achieved at low cost.

  In addition, after the combustion gas reaches the top of the furnace through the upper part of the furnace, the lower part of the furnace is reversed in two hands while heating the material to be heated, and is exhausted from the flue below the gas atomizing burner. By doing so, the temperature distribution in the furnace can be made more uniform.

  Further, the gas atomizer burner controls the furnace temperature by increasing / decreasing only the liquid fuel by maintaining the heat quantity ratio between the gas body fuel and the liquid fuel at a constant value and changing the heat input to control the furnace temperature. be able to.

  In addition, the gas atomizer burner maintains the supply amount of the gaseous fuel constant, changes the supply amount of the liquid fuel and controls the temperature of the furnace, for example, the supply amount of the liquid fuel becomes almost zero. However, it is possible to burn the burner with the gaseous fuel, and as a result, it is possible to obtain a great merit that a large turndown ratio can be obtained as the burner.

  Hereinafter, embodiments of the metal heating furnace of the present invention will be described with reference to the drawings.

1 to 2, the metal heating furnace of the present invention will be described using a soaking furnace as an example.
This soaking furnace is a soaking furnace provided with a burner that atomizes and injects liquid fuel, and the flame is directed toward the material 13 to be heated by the gas atomizing burner 1 that introduces gaseous fuel as the atomizing medium of the liquid fuel. It is disposed at one end of the furnace body 2 so as to be formed.

As shown in FIGS. 1A and 1B, the atomizer chip 3 of the gas atomizer burner 1 is a gas body fuel (city gas or LPG or the like) for atomizing oil (C heavy oil) from the central atomizing medium inlet 4. ) At a pressure of 0.05 MPa to 0.2 MPa.
On the other hand, the oil supplied from the oil inlet 5 is supplied to the mixing chamber 6 through a plurality of oil communication pipes 7 at a pressure of 0.01 MPa to 0.3 MPa.
By dividing the communication pipe 7 into a plurality of parts, a good oil atomization state can be obtained only by setting the pressure of the atomizing medium to about 0.1 MPa. The atomizer tip 3 can be easily manufactured by dividing it into two parts and finally integrating them by welding.

When the oil and the gas fuel are mixed in the mixing chamber 6, the oil atomized into fine particles is ejected from the mixing chamber 6 together with the gas fuel that is an atomizing medium, and the atomized oil is The combustion air is continuously burned by the combustion air from the air outlet 8 supplied to the burner.
Since this atomized oil does not contain steam as in the prior art, a higher flame temperature is obtained. That is, it is not necessary to heat excess water vapor to a high temperature range of the flame temperature (about 1500 ° C.), so that the heating time is significantly shortened.
In FIG. 1C, 9 indicates an atomizing medium connection port, 10 indicates an oil connection port, 11 indicates a combustion air connection port, and 12 indicates a burner tile.

  Moreover, since the atomized oil and the gaseous fuel of the atomizing medium are ejected from the mixing chamber 6 at the same time, and the gaseous fuel that is easy to burn is burned first, the atomized oil that is burned thereafter is a kind of self-exhaust gas. Low NOx can be realized with the same effect as circulation.

Furthermore, by using gas body fuel as the atomizing medium, it is easy to form a long flame length while having a uniform temperature distribution as compared with the steam spray burner. It was not necessary to attach a large number of burners to one furnace in order to ensure, and it was easy to ensure a uniform temperature distribution.
In addition, since a uniform temperature distribution has been realized, it is possible to shorten the heating time (processing time for one cycle) for bringing the entire heated material to a predetermined temperature, realizing energy saving and processing per day. Increases in volume are also possible.

In the soaking furnace of the present embodiment, as shown in FIG. 2, one burner 1 (or a plurality if necessary) is attached so that the injection direction is the longitudinal direction of the furnace. In this case, in order to obtain a good temperature distribution in the longitudinal direction of the furnace, a burner capable of forming a long flame is required.
As shown in FIGS. 2 (a) and 2 (b), the combustion gas that has reached the top of the furnace through the upper part of the furnace is reversed in two at the lower part of the furnace while heating the material 13 to be heated. The air is exhausted from the flue 14 below the burner 1. By forming this flow, a more uniform temperature distribution can be obtained. The combustion air is heat recovered by an exhaust gas heat exchanger (not shown) and returned to the burner 1 to save energy.

Next, FIG. 3 shows the temperature control method of the soaking furnace.
FIG. 3A shows a control example of gas body fuel / oil proportional control, which is a method of changing the supply amount of the gas body fuel of the atomizing medium in proportion to the oil supply amount, and has a relatively low turndown ratio. This method is applied when the size of the image can be small.
This is because if the atomizing medium itself falls below a certain supply amount, it becomes impossible to atomize the oil. Of course, if the ratio of the supply amount of the gaseous fuel that is the atomizing medium is taken large, A large down ratio can be obtained.

FIG. 3B shows an example in which the supply amount of the gaseous fuel is kept constant at 5% to 15% with respect to the input heat amount, and the oil pressure (the supply amount of oil) is increased / decreased. Above the load b point, the supply amount of the gaseous fuel of the atomizing medium is maintained at a constant value, and the burner load correspondence is a method corresponding to the change in the supply amount of oil.
In this case, the supply amount of the atomizing medium needs to be an amount capable of obtaining a good spray at the point c which is the maximum amount of oil.
When turn-down at point b or below is required, it is possible to cope with furnace temperature control by changing only the gaseous fuel that is the atomizing medium.
Therefore, if this control method is adopted, a much larger turndown can be obtained as compared with a burner burned by the conventional steam spray method, and it becomes possible to follow more precise temperature control.

  As described above, the metal heating furnace of the present invention has been described by taking the soaking furnace as an example, but the present invention is not limited to the structure described in the above embodiment, and the structure is appropriately changed without departing from the gist thereof. can do.

  The metal heating furnace of the present invention eliminates the need for an atomizing steam or a boiler for generating steam by utilizing the supply pressure of gaseous fuel for the atomizing energy of oil, and is a good furnace with a small number of mounting burners. Heating of metals such as steel soaking furnaces, such as a soaking furnace, can achieve energy savings by securing a medium atmosphere and reducing the generation of scale, realizing a good and uniform heating state. It can use suitably for the use of a furnace, for example, the metal heating furnace used for the heating performed prior to rolling of steel materials.

An example of the metal heating furnace of the present invention is shown, (a) is a front view of a burner tip, (b) is a sectional side view thereof, and (c) is a sectional side view of the burner. The same Example is shown, (a) is a sectional side view, (b) is a sectional plan view, (c) is a sectional front view. The temperature control method of the Example is shown, (a) is a graph when gas and oil are input in proportion, (b) is a graph when changing the supply amount of oil while keeping the gas supply amount constant. It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas atomizer burner 2 Furnace body 3 Atomizer chip 4 Atomization medium (gas body fuel) inlet 5 Oil inlet 6 Mixing chamber 7 Oil communication pipe 8 Air outlet 9 Atomization medium (gas body fuel) connection port 10 Oil connection port 11 Combustion air Connection port 12 Burner tile 13 Heated material 14 Flue

Claims (4)

  In a metal heating furnace equipped with a burner that atomizes and injects liquid fuel, a gas atomizing burner that introduces gaseous fuel as an atomizing medium for liquid fuel is disposed so that a flame is formed toward the material to be heated. A metal heating furnace characterized by that.   After the combustion gas reaches the top of the furnace through the upper part of the furnace, the lower part of the furnace is inverted in two hands while heating the material to be heated, and exhausted from the flue below the gas atomizer burner. The metal heating furnace according to claim 1, wherein   3. The metal heating furnace according to claim 1, wherein the gas atomizing burner controls the furnace temperature by maintaining a calorie ratio of the gas body fuel and the liquid fuel at a constant value and changing a heat input amount. 4.   3. The metal heating furnace according to claim 1, wherein the gas atomizing burner controls the furnace temperature by maintaining the supply amount of the gaseous fuel constant and changing the supply amount of the liquid fuel.

Images