JPS59157218A - Heating furnace - Google Patents

Abstract

PURPOSE:To provide improved efficiency in heat transmission and economized energy by heating an object to be heated by the radiation heat of open radiant tube burners and the radiation heat from air permeable solid materials generated when the combustion flame of said burners and the waste gas thereof flow through the air permeable solid materials. CONSTITUTION:An object 4 to be heated is placed on beams 2, 3, moves in an arrow direction, and is heated by the combustion flames and waste gas of burners 5. While the bottom surface side of the object 4 is heated by the radiation heat and combustion flames of open radiant tube burners 7, a part of the waste gas thereof is passed through air permeable solid materials 9a by the suction effect of an ejector 13 and is deprived of its heat by the materials 9a. The heat is converted to radiation heat which is then irradiated to the bottom surface of the object 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a heating furnace that can efficiently heat steel materials.

With the development of continuous casting technology, the cross-sectional size of cast steel materials generally tends to be smaller in thickness and larger in width.
Correspondingly, the width of heating furnaces is also increasing.

On the other hand, the heating temperature of the steel material must be strictly controlled because it affects the quality of the rolled material, and in particular, it is essential to uniformly control the temperature distribution in the width direction of the steel material.

By the way, conventional metal heating furnaces heat steel materials using direct-fired burners or radiant tube burners, but in the case of direct-fired burners, burners are installed on both sides of the furnace to give a high blowing speed. However, the combustion flame did not reach the center of the furnace in the width direction, and the steel material could not be heated uniformly. In addition, in the case of a radiant tube burner, uniform heating of steel materials can be achieved, but N
It is necessary to take measures to suppress the amount of Ox, and for this reason, Tokukai Sho! ;/-/! ;073≠ publication and JP-A-52-73
As shown in G72G, a so-called self-recirculating radiant tube burner that mixes a part of the exhaust gas into the combustion air of the burner is also known, but even in that case, if the exhaust gas temperature is high, The combustion temperature was high and did not contribute much to reducing the amount of NOx.

On the other hand, a so-called oven radiant tube burner has also been proposed, in which a radiant tube is connected to the flame outlet of the burner and its tip is opened in the furnace, but in this too, the radiant tube is lengthened to improve temperature distribution. If this is attempted, the combustion temperature inside the radiant tube will rise significantly and the amount of NOx will increase significantly.As a countermeasure, the preheating temperature of the combustion air in the burner will be lowered, but an exhaust gas denitrification device will have to be installed. The former measure generally preheats the combustion air using heat from the exhaust gas from the burner, resulting in less energy-saving effects, while the latter measure has the drawback of increasing installation costs. For this reason, as shown in Japanese Patent Application Laid-Open No. 57-1211211, this oven radiant tube burner is arranged at regular intervals in the width direction of the kiln bed in an IF+j flow to make the temperature distribution in the short width direction uniform. However, since the kettle bed is equipped with a scale trough, and a walking beam furnace is equipped with a beam drive device to place and move the steel material, piping equipment for the burner, its fuel oil, combustion air, etc. must be installed. This poses a problem in terms of operation and maintenance.

In view of the above, the present invention achieves uniform heating of steel materials, an increase in heat transfer efficiency to preparations, energy saving, and NO
In order to achieve this goal, an oven radiant tube burner is installed in the furnace, and an air-permeable solid made of porous ceramic material is placed relative to the object to be heated in the furnace. A part of the exhaust gas in the furnace is made to flow through the air-permeable solid material, and the exhaust gas is recirculated to the burner.

Embodiments of the present invention will be described below with reference to the drawings for a walking beam furnace. In the figure, 1 is a furnace, 2 and 3 are fixed beams and movable beams on which the object to be heated 4 is placed and moved, and 5
is a normal burner attached to the side wall 6 of the furnace 1, and a plurality of burners are arranged on the upper surface side of the object to be heated 4 in the furnace. 7 is furnace 1
This is an oven radiant tube burner attached to the side wall 6 of the oven, and the burner is composed of a burner part 7a and a radiant tube 7b connected to the flame outlet thereof, and a tip 8 of the radiant tube 7b.
is open. A plurality of oven radiant tube burners are arranged on the lower surface side of the object to be heated 4. In addition, 9 is a breathable solid, and the breathable solid here is a heat-resistant material such as ceramic or gold R formed into a porous, net-like, honeycomb-like, fibrous, etc. form, so that combustion exhaust gas can easily pass through it. It refers to a solid that has air permeability. In the embodiment shown in FIGS. 1 and 2', a through hole 10 is provided in the side wall 6 at an obliquely lower portion of the oven radiant tube burner 7, and an exhaust duct is inserted into the through hole from the outer wall of the furnace. 11 is inserted through the exhaust duct, and the proximal opening of a cylindrical air-permeable solid 9a with a closed tip is connected to the furnace opening side of the exhaust duct. The air-permeable solid 9a is disposed so as to face the object 4 over substantially the entire width of the lower surface thereof, as shown in the figure. Further, the base end of the exhaust duct 11 communicates with the burner section 7a via a circulation vibrator, and the circulation vibrator is provided with an ejector 13 for forcibly sucking exhaust gas from the exhaust duct 1-11. 14 is a recuperator disposed within the cylindrical part of the breathable solid 9a, and the recuperator 1
Combustion air is introduced into the oven radiant tube burner 7 through a supply roll to preheat the combustion air and can be supplied to the oven radiant tube burner 7 through a communication pipe 16.

In the heating furnace configured in this way, the object to be heated 4 is
2.3 and moves in the direction of the arrow, and is heated by the combustion flame and exhaust gas of the burner 5.

At this time, the lower surface of the object to be heated 4 is heated by the radiant heat and combustion flame of the oven radiant tube burner 7, while a part of the exhaust gas flows through the air permeable solid 9a by the suction action of the ejector 13, thereby increasing the air permeability. Since it is guided into the solid, heat is taken away by the breathable solid 9a at that time, and the heat is converted into radiant heat and is irradiated onto the lower surface of the object to be heated 4.

Therefore, the lower surface of the object to be heated 4 is covered with a breathable solid material 9 over the entire width.
receives radiant heat irradiation from a. On the other hand, the exhaust gas that has flowed through the breathable solid 9a lowers its own temperature as it flows through, and further preheats the combustion material via the recuperator 14 and supplies it to the oven radiant tube burner 7 at a low temperature (
Since the fuel is recycled (recirculated), the generation of NOx is suppressed.

The embodiment shown in FIG.
A plurality of through holes 17 penetrating from the surface to the inner surface of a are bored,
The air supply pipe 18 is guided through the air-permeable solid body 9a, and its tip is branched to communicate with the through hole 17, and a hat-shaped cap 19 is placed over the tip, so that the air flows around the periphery of the cap 19. The jets are ejected from one jet that is formed radially. In this way, the exhaust gas from the oven radiant tube burner 7 is mixed with air on the surface of the air-permeable solid 9a, and as a result, unburned substances in the exhaust gas are combusted and secondary combustion occurs. Efficiency is further improved. If the air-fuel ratio of the burner 7 is kept below the stoichiometric air-fuel ratio, combustion is regulated in the burner 7 and the generation of NOx is suppressed, and at the same time, radiant heating by the air permeable solid 9a is promoted and the object to be heated 4 is average of
The heating properties are further improved.

In the embodiment shown in FIG. 11 and FIG. 22.
In addition, a piece of breathable solid material 9b is provided on the hearth 21 at a position close to both walls in the width direction of the furnace in an inclined manner so as to face the object to be heated 4, and a sealing frame material is placed around the solid material 9b. n, the lower surface side of each breathable solid 9b is communicated via an exhaust pipe U, and the exhaust gas flowing through each breathable solid 9b is guided to the exhaust duct 11. Even if the air-permeable solid body 9b is used, the object to be heated 4 can be irradiated with radiant heat.

Incidentally, in each of the above embodiments, a case has been described in which a breathable solid is provided on the lower surface side of the object to be heated 4, but the invention is not limited to this.
It goes without saying that a similar means may be provided on the upper surface of the object to be heated 4. In addition, in each of the above embodiments, all of the exhaust gas that has flowed through the breathable solid 9 is recirculated to the oven radiant tube nozzle 7. However, the present invention is not limited to this, and a portion of the exhaust gas may be recirculated.

As is clear from the above description of the embodiments, the present invention is directed to the combustion flame of an object to be heated to the width of the oven radiant tube burner, and the combustion flame generated when the exhaust gas flows through the gas permeable solid. It is a device that heats by radiant heat, and in particular, it is possible to heat the object over the entire width by solid heat radiation not only from an oven radiant tube burner but also from a breathable solid. When the gas flows through the gas, the air-permeable solid recovers heat and the heat is used to heat the objects to be heated.This increases the efficiency of heat transfer to the objects to be heated, and improves the width of the furnace. Variations in temperature distribution are reduced, promoting uniform heating over the entire width of the object to be heated, and contributing to energy savings. In addition, since the exhaust gas is recirculated to the burner after lowering its temperature, the generation of NOx can be suppressed, which has significant industrial effects.

[Brief explanation of drawings]

The drawings relate to the present invention; FIG. 1 is a longitudinal cross-sectional view showing one embodiment, FIG. 2 is an enlarged cross-sectional view showing the main part thereof, and FIG. 3 is a cross-sectional view showing another embodiment. Figure 5 is a cross-sectional view showing another embodiment, and Figure 5 is a cross-sectional view taken along the line X--X in Figure 11. 1...furnace, 4...heated object, 7...oven radiant tube burner, 8...opening, '9 (
9a. 9b)...Breathable solid. Patent applicant: Daido Steel Co., Ltd.;,'(","j-"t'/

Claims (1)

[Claims] 1. An oven radiant tube burner is provided in the furnace, and an air-permeable solid made of porous ceramic material is provided to face the object to be heated in the furnace, so that exhaust gas in the furnace can be removed. A heating furnace characterized in that the exhaust gas is recirculated to the burner, with a portion flowing through the gas permeable solid material. 2. The heating furnace according to claim 1, characterized in that unburned substances in exhaust gas are combusted by supplying air to the surface of the breathable solid. 3. The heating furnace according to claim 1 or 2, wherein an oven radiant tube burner and a permeable solid are provided at the lower part of a billet support beam in a walking beam furnace.