TW201910710A - Switching furnace and its modification method - Google Patents

Abstract

This invention provides for a rotary hearth furnace and a remodeling method of a rotary hearth furnace capable of efficiently obtaining energy conservation effect in a regenerative burner and equalizing a temperature distribution by improving a stirring of a furnace gas in a furnace, and further increasing a possible number of burners through an increase of a burner equipping space by a utility of a ceiling part and securing more combustion rate than the conventional system. A rotary hearth furnace l having a rotary hearth 2 in a furnace (F) structured in a form of encirclement by at least a cylindrical outer periphery wall part 5 and a ceiling part 6, wherein the rotary hearth furnace includes a regenerative ceiling burner 7 being provided at the ceiling part and having a crater toward an inside of the furnace, and a regenerative wall burner 8 being provided at the outer periphery wall part, having a crater directed to the inside of the furnace from a tangential direction of the outer periphery wall part, and being burned alternately with the regenerative ceiling burner.

Description

   Rotary hearth furnace and its transformation method   

The present invention relates to a rotary hearth furnace and a method for reforming the same. Based on the premise of using a regenerative burner, the energy-saving effect of the furnace can be fully exerted while the agitation of the furnace gas in the furnace is improved to uniformize the temperature distribution in the furnace. With the proper configuration of the burner, the number of units that can be set is increased to ensure a sufficient combustion capacity.

Conventionally, as a constituent of a rotary hearth furnace, the "Rotary Hearth Furnace" of Patent Document 1 is known. In addition, regarding such a rotary hearth furnace, in regard to the generation of ambient gas in the furnace, Patent Document 2 "Agglomerates of Raw Materials for the Production of Reduced Iron" is known. Patent Document 2 is constituted by arranging a plurality of burners on the outer peripheral wall portion of the rotary hearth furnace, generating flames into the furnace, and exhausting from a single exhaust port of the top wall portion.

In addition, as disclosed in the "Heating Furnace" of Patent Document 3, the technique of alternately burning a regenerative burner is used, and in the "Nonferrous Metal Dissolving Furnace Device" of Patent Document 4, the regenerative combustion type The burner is configured by being disposed on a cylindrical furnace wall.

    [Prior technical literature]         [Patent Literature]    

Patent Document 1: Japanese Patent No. 5841296

Patent Document 2: Japanese Patent Laid-Open No. 2013-14791

Patent Document 3: Japanese Patent Laid-Open No. 2012-112588

Patent Document 4: Japanese Patent Laid-Open No. 7-71879

Regarding the generation of the ambient gas in the furnace, in Patent Document 2, since the distances from a plurality of burners to a single exhaust port are different, there is a problem of uneven temperature distribution in the furnace.

In Patent Document 4, the adjacent regenerative burners are alternately burned alternately with each other. Therefore, the heat generated by the flame of the burner having the combustion mode is immediately attracted by the burner of the adjacent exhaust mode, and not only cannot be obtained. The energy saving effect may also cause the problem of uneven temperature distribution in the furnace.

In addition, if a plurality of burners are arranged only around the peripheral wall portion or the cylindrical furnace wall in Patent Document 2 or Patent Document 4, there is a lack of agitation of the furnace gas in the furnace, and the furnace cannot be sufficiently secured. The issue of uniformity of internal temperature distribution. In addition, if a burner is provided only around the outer peripheral wall portion or the furnace wall, there is a problem that burners cannot be installed in the surrounding space to ensure the required number of burners.

The present invention was created in view of the above-mentioned conventional problems, and its purpose is to provide a rotary hearth furnace and a method for reforming the same. The premise is to use a regenerative burner as a premise, which can improve the furnace gas in the furnace while giving full play to its energy saving effects. It can make the temperature distribution in the furnace uniform, and use the top wall to increase the installation space of the burner, so as to increase the number of burners that can be installed, so as to ensure a larger combustion volume than conventional.

The rotary hearth furnace of the present invention is a furnace provided with a rotary hearth in a furnace formed by being surrounded by at least a cylindrical outer peripheral wall portion and a ceiling wall portion; A regenerative top wall burner facing the inside of the furnace; a regenerative peripheral wall burner provided with an outer wall portion facing the furnace from a tangential direction and alternately burning with the top wall burner .

It is characterized in that the above-mentioned top wall burner is a burner generating a swirling flame.

It is characterized in that the flame mouth portion of the peripheral wall burner is oriented in a direction opposite to the direction of the swirling flame of the top wall burner along the outer peripheral wall portion.

It is characterized in that the top wall burner and the peripheral wall burner are provided in the same number, the top wall burner is arranged at equal intervals in the rotation direction of the rotary hearth, and the peripheral wall burner is arranged Between the adjacent top wall burners.

It is characterized in that the flame mouth portion of the top wall burner is formed so as to expand toward the inside of the furnace.

The transformation method of the rotary hearth furnace of the present invention is characterized in that the following transformations are performed: a regenerative top wall burner is installed on the top wall portion of the existing rotary hearth furnace, and the flame mouth portion is directed to the furnace; In the regenerative peripheral wall burner which alternately burns with the top wall burner, the flame mouth portion is directed into the furnace from a tangential direction thereof.

In the rotary hearth furnace and its transformation method of the present invention, while fully exerting the energy-saving effect, the agitation of the furnace gas in the furnace can be improved to uniformize the temperature distribution in the furnace, and the top wall portion is used to increase the space for the burner. By increasing the number of burners that can be installed, a larger combustion capacity can be ensured.

1‧‧‧ Rotary Hearth Furnace

2‧‧‧ Rotary Hearth

3‧‧‧furnace

4‧‧‧Inner peripheral wall

5‧‧‧ peripheral wall

6‧‧‧ top wall

7‧‧‧ Regenerative top wall burner

7a‧‧‧Flame mouth of top wall burner

7b, 8b‧‧‧‧Burner body

7c, 8c ‧‧‧ heat storage unit

8‧‧‧ Regenerative Peripheral Wall Burner

8a‧‧‧Flame mouth of peripheral wall burner

9‧‧‧ exhaust system

9a‧‧‧ exhaust valve

9b‧‧‧Exhaust throttle

9c‧‧‧chimney

9d‧‧‧ chimney

9e‧‧‧Exhaust manifold

9f‧‧‧ exhaust pipe

10‧‧‧Gas supply system

10a‧‧‧Air supply blower

10b‧‧‧Air supply throttle

10c‧‧‧Air supply valve

10d‧‧‧Gas supply manifold

10e‧‧‧Air supply pipe

11‧‧‧ cylindrical space

12‧‧‧ Fuel Supply System

12a‧‧‧ fuel nozzle

12b‧‧‧ fuel supply pipe

12c‧‧‧ Fuel on-off valve

13‧‧‧Nozzle flow path

13a‧‧‧1st side

13b‧‧‧ 2nd side

13c‧‧‧3rd side

13d‧‧‧Top

13e‧‧‧ Underside

14‧‧‧Walking Department

15‧‧‧ opening

16‧‧‧Expanding space

Dc‧‧‧The gas flow of the furnace gas during the combustion of the top wall burner

Dw‧‧‧Circular wall burner when burning

Ec‧‧‧Exhaust of top wall burner

Ew‧‧‧Exhaust

F‧‧‧ Inside the furnace

f‧‧‧ fuel gas

Mc‧‧‧ Flame of Top Wall Burner

Mw‧‧‧Flame of the perimeter burner

R‧‧‧ Rotation direction of rotary hearth

X‧‧‧ the central axis of the cylindrical space

FIG. 1 is a perspective view schematically showing a preferred embodiment of a rotary hearth furnace and a reforming method thereof according to the present invention.

FIG. 2 is a top cross-sectional view illustrating the combustion state of the rotary hearth furnace shown in FIG. 1 and a top wall burner.

3 (A) and (B) are explanatory diagrams illustrating the main parts of the top wall burner applied to the rotary hearth furnace shown in FIG. 1.

FIG. 4 is an explanatory diagram showing the equipment layout of the rotary hearth furnace shown in FIG. 1 when the top wall burner is in the combustion mode and the peripheral wall burner is in the exhaust mode.

5 is a top cross-sectional view illustrating the combustion state of the rotary hearth furnace shown in FIG. 1 and a peripheral wall burner.

FIG. 6 is an explanatory diagram showing the equipment layout of the rotary hearth furnace shown in FIG. 1 when the peripheral wall burner is in the combustion mode and the top wall burner is in the exhaust mode.

FIG. 7 is a side cross-sectional view showing a modified example of the top wall burner applied to the rotary hearth furnace of the present invention.

Hereinafter, a preferred embodiment of the rotary hearth furnace and the method for reforming the same according to the accompanying drawings will be described in detail. FIG. 1 is a perspective view schematically showing a preferred embodiment of the rotary hearth furnace of the present embodiment, and FIG. 2 is a top sectional view illustrating the combustion state of the rotary hearth furnace shown in FIG. 1 and being a top wall burner. 3 is an explanatory diagram illustrating the main part of the top wall burner applied to the rotary hearth furnace shown in FIG. 1, and FIG. 4 is a diagram showing the equipment layout of the rotary hearth furnace shown in FIG. 1 when the top wall burner is in a combustion mode 5. An explanatory diagram when the peripheral wall burner is in the exhaust mode. FIG. 5 is a top cross-sectional view illustrating the rotary hearth furnace shown in FIG. 1 and the combustion state of the peripheral wall burner. FIG. 6 is a view showing the rotary hearth furnace shown in FIG. 1. The layout of the equipment is an explanatory diagram when the peripheral wall burner is in the combustion mode and the top wall burner is in the exhaust mode.

As shown in FIGS. 1 and 2, the rotary hearth furnace 1 according to this embodiment is configured as a ring-shaped rotary hearth furnace 2 that is horizontally driven to the right or left by being covered with a furnace body 3 from above. The furnace body 3 is composed of a cylindrical inner peripheral wall portion 4, a cylindrical outer peripheral wall portion 5, and an annular top wall portion 6. The inner peripheral wall portion 4 is provided so as to be located in an annular shape. Inside the inner periphery of the hearth hearth 2, the outer peripheral wall portion 5 is arranged outside the outer periphery of the hearth hearth 2, and the top wall portion 6 is straddled above the hearth hearth 2 and is arranged on its outer periphery. Between the upper end portion of the wall portion 5 and the upper end portion of the inner peripheral wall portion 4, a rotary hearth 2 is provided in the furnace F formed by the furnace body 3 partition.

The object to be heated (not shown) is placed on the rotary hearth 2 from the entrance (not shown) provided at the outer wall portion 5 and is heated while rotating while rotating, and then set on the outer wall portion 5 by itself. Take out the exit (not shown).

The top wall portion 6 is provided with at least one thermal storage type top wall burner 7 in the present embodiment. The plurality of top wall burners 7 are arranged at equal intervals in the rotation direction of the rotary hearth 2 (shown by arrows R in the figure). In the example shown in the figure, four top wall burners 7 are arranged at 90 ° intervals. As shown in FIG. 3, the top wall burner 7 is arranged such that the flame mouth portion 7 a penetrates the top wall portion 6 and faces the inside of the furnace F, whereby the flame Mc is directed downward from the top wall portion 6.

At least one peripheral wall burner 8 is provided on the peripheral wall portion 5 below the top wall portion 6 and has a plurality of thermal storage type burners in this embodiment. The plurality of peripheral wall burners 8 are the same as the top wall burners 7 and are arranged at equal intervals in the rotation direction of the rotary hearth 2. In relation to the top wall burner 7, the peripheral wall burner 8 has the same number as the top wall burner 7, and is arranged at a position intermediate the top wall burners 7 adjacent to each other in the direction of rotation of the rotary hearth 2. . In the example shown in the figure, four peripheral wall burners 8 are arranged alternately with four top wall burners 7 at 90 ° intervals.

In addition, the top wall burner 7 is positioned above, while the peripheral wall burner 8 is positioned below it. As shown in FIG. 2, the peripheral wall burner 8 is configured such that the flame mouth portion 8 a is connected to the outer peripheral wall portion 5 from a tangential direction of the plane circular shape, thereby directing the flame Mw in a direction along the outer peripheral wall portion 5. Each of the top wall burner 7 and the peripheral wall burner 8 provided in the same number is a group, and alternately burns in a group.

The top wall burner 7 and the peripheral wall burner 8 are both thermal storage burners. The regenerative burner itself is well-known, as shown in Figs. 1, 2, and 4 to 6, and includes: burner bodies 7b and 8b, which have flame mouth portions 7a and 8a that open toward the furnace F; and a heat storage unit 7c and 8c are directly connected to the burner bodies 7b and 8b on the side opposite to the flame mouth portions 7a and 8a.

The top wall burner 7 and the peripheral wall burner 8 of the rotary hearth furnace 1 of this embodiment are alternately and repeatedly switched to spray flames Mc and Mw from the burner bodies 7b and 8b to the flame F in the furnace F The combustion mode in which the furnace F is heated and the furnace mode in which the furnace gas F is used as exhaust gases Ec and Ew are discharged from the flame mouth portions 7a and 8a. The furnace gas filled in the furnace F due to the combustion operation of the burners 7 and 8 becomes exhaust gas Ec and Ew when discharged from the furnace F. Therefore, in the following description, the exhausted furnace gas is referred to as exhaust gas Ec , Ew.

When the regenerative burner is in the exhaust mode, the exhaust gases Ec and Ew discharged from the furnace F are circulated to the heat storage units 7c and 8c, whereby the exhaust heat of the exhaust gases Ec and Ew is stored in the heat storage units 7c and 8c. The exhaust gas passing through the heat storage sections 7c and 8c is discharged to the exhaust system 9 after being cooled. Then, if the operation self-exhaust mode is switched to the combustion mode, the air supply function of the air supply system 10 having the air supply blower 10a is used. The combustion air is caused to flow toward the heat storage sections 7c, 8c, and the exhaust air Ec, Ew stored in the heat storage sections 7c, 8c is used to preheat (heat) the combustion air.

Then, the preheated combustion air is supplied to the burner bodies 7b, 8b, and is mixed with the supplied fuel gas f through a fuel nozzle 12a provided near each of the flame mouth portions 7a, 8a and burned, thereby burning. The burner bodies 7b and 8b can generate flames Mc and Mw by using the energy-saving operation of exhaust heat.

In the case of using a regenerative burner, the regenerative burner is such that the temperature in the furnace does not change with the switching of the combustion mode and the exhaust mode operation mode, in at least one pair, that is, by the top wall The burner 7 is used in combination with the peripheral wall burner 8.

The combustion mode and exhaust mode are connected between a pair of regenerative burners. When any one of the regenerative burners (for example, the top wall burner 7) is used as the combustion mode, the other regenerative burner (for example, The peripheral wall burner 8) is operated in the exhaust mode, and when the former is switched to the exhaust mode, the latter is switched to the combustion mode, and is alternately operated and controlled at a certain time interval (for example, one minute interval).

The heat storage sections 7c and 8c of each burner 7 and 8 use the flame-exposure section 7a and 8a side facing the furnace F as the exhaust inlet side (combustion air outlet side), and will be the same as the flame-exposure section 7a and 8a. The opposite side is the exhaust outlet side (combustion air inlet side).

Therefore, in each of the heat storage sections 7c and 8c of the regenerative burner, preheating is performed in the following manner, that is, when in the exhaust mode, the exhaust Ec, Ew goes from the flame mouth sections 7a, 8a to the heat storage section 7c And 8c circulate and are discharged to the exhaust system 9 from the exhaust outlet side of the heat storage sections 7c and 8c. In addition, in the combustion mode, the combustion air flows from the air supply system 10 to the exhaust outlets of the heat storage sections 7c and 8c. It is supplied from the side and flows from the heat storage sections 7c and 8c toward the flame mouth sections 7a and 8a.

In the rotary hearth furnace 1 of the present embodiment, the top wall burner 7 and the peripheral wall burner 8 are respectively provided with a burner body 7b and 8b, which have flame mouth portions 7a and 8a that open toward the furnace F, and a heat storage portion. 7c, 8c, which are connected to the burner bodies 7b, 8b on the opposite sides of the flame mouth portions 7a, 8a; the fuel supply system 12, which is provided adjacent to the burner bodies 7b, 8b and faces the flame mouth portions 7a, 8a Injects fuel mixed with combustion air to generate fuels such as flames Mc, Mw, and fuel gas f, fuel nozzles 12a, fuel supply pipes 12b connected to the fuel nozzles 12a to supply fuel f, and fuel supply pipes 12b provided to control fuel The supply and stop of fuel f is constituted by an on-off valve 12c (in the figure, it is opened with a blank display and closed with a black display); a gas supply system 10 having a supply air blower 10a for supplying combustion air, and a supply for adjusting the supply amount The air throttle damper 10b, and the air supply valve 10c that can be opened and closed to control the supply and stop of combustion air (in the figure, it is opened with a blank display and closed with a black display), and is used to exhaust the heat storage sections 7c and 8c. Supply combustion air at the exit side; and exhaust System 9, which has an exhaust valve 9a that controls the discharge and discharge of exhaust Ec and Ew, and can be opened and closed freely (open in the figure with a blank display and closed with a black display), and an exhaust throttle valve that adjusts the exhaust volume 9b, and the exhaust gas Ec, Ew in the furnace F is discharged to the flue 9c through the flame mouth portions 7a, 8a, and the exhaust gas Ec, Ew flowing out from the exhaust outlet side of the heat storage portions 7c, 8c is circulated. The flue 9c is connected to the chimney 9d.

Specifically, the air supply system 10 is a gas supply header 10d and a self-supply header 10d provided with an air supply blower 10a and capable of supplying combustion air to both the top wall burner 7 and the peripheral wall burner 8. A plurality of air supply pipes 10e provided separately to supply the combustion air to the heat storage sections 7c and 8c of the top wall burner 7 and the peripheral wall burner 8 and the above-mentioned air supply valve 10c provided in each air supply pipe 10e .

In detail, the exhaust system 9 is an exhaust manifold 9e and a self-exhaust manifold that are connected to the flue 9c and can discharge exhaust Ec and Ew from both the top wall burner 7 and the peripheral wall burner 8 9e is provided separately, and exhaust pipes 9f for exhaust gases Ec and Ew are exhausted from each of the heat storage sections 7c and 8c of the top wall burner 7 and the peripheral wall burner 8, and the above exhaust gas is provided in each exhaust pipe 9f. It is constituted by a valve 9a.

The air supply valve 10c is opened in the combustion mode in both the top wall burner 7 and the peripheral wall burner 8 and is used to supply combustion air to the burner bodies 7b and 8b through the heat storage sections 7c and 8c. The ports 7a and 8a are closed in the exhaust mode to stop the supply of combustion air.

The exhaust valve 9a is opened in the exhaust mode, whether in the top wall burner 7 or the peripheral wall burner 8, and is used to exhaust the exhaust Ec, Ew of the furnace F through the heat storage sections 7c, 8c. The flame mouth portions 7a and 8a of the main bodies 7b and 8b are discharged, and are closed in the combustion mode to stop the discharge of the exhaust gases Ec and Ew. In the operation of the rotary hearth furnace 1, the air supply blower 10a is normally operated.

The fuel on-off valve 12c, whether in the top wall burner 7 or the peripheral wall burner 8, is opened in the combustion mode to supply fuel f to the fuel nozzle 12a, and is closed in the exhaust mode. Used to stop the supply of fuel f.

As illustrated in FIG. 4, in the top wall burner 7 in the combustion mode, the exhaust valve 9 a is closed and the air supply valve 10 c is opened. The combustion air sent by the air supply function of the air supply system 10 is self-supplied. The air supply manifold 10d of the gas system 10 flows to the heat storage section 7c through the air supply valve 10c of the air supply pipe 10e, and is supplied from the heat storage section 7c to the flame mouth portion 7a of the burner body 7b.

Then, the fuel on-off valve 12c of the fuel nozzle 12a is opened, and the fuel f is supplied from the self-fuel supply pipe 12b to the flame mouth portion 7a to form a flame Mc. When the inside of the furnace body 3 is above the auto-ignition temperature of the fuel f, it will ignite naturally, but when the temperature is lower than that, it can be ignited by a spark plug or an igniter (not shown).

On the other hand, in the peripheral wall burner 8 in the exhaust mode, the exhaust valve 9a is opened and the air supply valve 10c is closed, and the exhaust Ec in the furnace F is directed from the burner 8a of the burner body 8b toward the heat storage section. 8c circulates, and the heat storage section 8c is discharged from the exhaust pipe 9f toward the exhaust manifold 9e of the exhaust system 9 through the exhaust valve 9a.

The top wall burner 7 is also provided as a swirling flame generating type burner that generates a swirling type flame Mc from the top wall portion 6 in a furnace directly below it. As shown in FIG. 3, the top wall burner 7 is formed in a cylindrical shape with a cylindrical space 11 defined inside the burner portion 7a side of the burner body 7b. FIG. 3 (A) is a side cross-sectional view of the periphery of the flame mouth portion 7a of the top wall burner 7, and FIG. 3 (B) is a cross-sectional view taken along the arrow A-A in FIG. 3 (A). The cylindrical space 11 constitutes a combustion chamber that generates a flame Mc using the fuel f from the fuel nozzle 12a.

In addition, the burner body 7 b has a nozzle flow path 13 opened at an upper portion of the cylindrical space 11. The nozzle flow path 13 includes a first side surface 13a formed by a plane that is in contact with the cylindrical surface of the cylindrical space 11 and a second side surface 13b that is opposed to the first side surface 13a and extends parallel to the first side surface 13a. And a third side surface 13c formed by a plane extending at an angle of 90 ° from the second side surface 13b and contacting the cylindrical space 11.

In addition, the top surface 13d of the nozzle flow path 13 is continuous with the top surface of the cylindrical space 11 and the bottom surface 13e of the nozzle flow path 13 is parallel to the top surface. That is, the top surface 13 d and the bottom surface 13 e of the nozzle flow path 13 are planes that intersect perpendicularly to the central axis X of the cylindrical space 11.

The nozzle flow path 13 is constituted by a walking aid portion 14 and an opening portion 15. The walking aid portion 14 is defined by a first side surface 13 a and a second side surface 13 b, and its cross section is a certain slit shape. The opening portion 15 is The first side surface 13a and the third side surface 13c are defined by two joint surfaces of the cylindrical space 11 that cross each other at an angle of 90 ° or less. The other end of the nozzle flow path 13 is in communication with the heat storage section 7c. The fuel nozzle 12 a is opened toward the cylindrical space 11.

The combustion air is blown in from the nozzle flow path 13 along the cylindrical inner wall of the burner body 7 b forming the cylindrical space 11 in a tangential direction, and a spirally swirling air flow is formed in the cylindrical space 11. The flame Mc formed by the combustion of the fuel f supplied from the fuel nozzle 12a is spirally extended along the swirling airflow. The flame Mc ejected from the flame mouth portion 7a toward the furnace F is formed by a swirling airflow to form a vortex-shaped flame flow that spreads over the entire circumference toward the radially outer side. The flame Mc diffuses into an umbrella shape while swirling.

In contrast, the peripheral wall burner 8 generates a flame Mw that travels straight from the flame mouth portion 8 a. As shown in FIG. 5, the flame Mw of the peripheral wall burner 8 runs along the peripheral wall portion 5. The flame Mw of the peripheral wall burner 8 is a long flame with a long straight line from the flame mouth portion 8a to the front end of the flame. On the other hand, the flame Mc of the top wall burner 7 is from the flame mouth portion 7a by the swirling action. A short flame with a short straight line to the front of the flame.

Thereby, since the distance between the object to be heated and the flames Mc and Mw placed on the rotary hearth 2 can be ensured, it is possible to prevent the flames Mc and Mw from contacting the object to be heated to a high temperature or to heat the object to be heated. Objects cause damage. In addition, the entire furnace body 3 can be miniaturized.

As shown in FIG. 2, the flame mouth portion 8a of the peripheral wall burner 8 faces the direction opposite to the direction of the flame Mc of the top wall burner 7 swirling in the furnace F along the outer wall portion 5. That is, it can be understood by referring to FIG. 5 and also referring to FIG. 2 that if the peripheral wall burner 8 and the top wall burner 7 are burned at the same time, the flame mouth portion 8a of the peripheral wall burner 8 is caused to face the peripheral wall burner. The direction in which the flame Mw of 8 and the flame Mc of the top wall burner 7 collide at the inner side of the outer peripheral wall portion 5. In fact, since the peripheral wall burner 8 and the top wall burner 7 alternately burn, there is no collision between the flames Mc and Mw.

In other words, due to the relationship between the group of peripheral wall burners 8 and the top wall burner 7 that are alternately burned, when the flame Mc of the top wall burner 7 is viewed from the position of the outer wall portion 5, when the flame Mc turns to the left, The flame mouth portion 8a of the peripheral wall burner 8 is provided on the right side of the observed position, and when the flame Mc turns to the right, it is provided on the left side.

Then, as shown in FIG. 2 and FIG. 5, the furnace gas (exhaust gas) of F in the furnace becomes a single-direction air flow toward the top wall burner 7 when the surrounding wall burner 8 burns (in FIG. 5, arrows indicate (Dw indicates). On the other hand, during the combustion of the top wall burner 7, it becomes an airflow (indicated by the arrow Dc in FIG. 2) in the opposite direction to the peripheral wall burner 8, and the top wall is repeatedly switched. The alternate combustion of the burner 7 and the peripheral wall burner 8 allows the furnace gas to repeatedly flow in the forward and reverse directions.

In this way, since the furnace gas repeatedly flows in the forward and reverse directions, the direction of the flame Mw of the peripheral wall burner 8 can be set either in the direction of the rotating direction R of the rotary hearth 2 or in the same direction as the The direction of rotation R is opposite to the direction of rotation, and either direction is acceptable. Similarly, as long as the above-mentioned relationship is ensured with the peripheral wall burner 8, the turning direction of the flame Mc of the top wall burner 7 may be right-handed or left-handed.

Next, the operation of the rotary hearth furnace 1 according to this embodiment will be described. As shown in FIGS. 2 and 4, during the operation of the rotary hearth furnace 1, if the top wall burner 7 is in the combustion mode and the peripheral wall burner 8 is in the exhaust mode, the combustion air heated in the heat storage section 7 c is used. The flame Mc generated with the fuel f from the fuel nozzle 12a at the flame mouth portion 7a of each top wall burner 7 will spread from a plurality of locations toward the furnace F to form a swirling flow of short flames, and the swirling flame generates The furnace gas continues to diffuse toward F in the furnace.

The furnace gas subjected to the swirling action is distributed throughout the entire furnace F on the periphery of the outer wall portion 5 in a single direction along the circumferential direction of the furnace body 3 (in the opposite direction on the periphery of the inner wall portion 4), and as an exhaust Ec Each of the flame mouth portions 8 a of the plurality of peripheral wall burners 8 provided outside the peripheral wall portion 5 below the top wall portion 6 is discharged.

Next, if the top wall burner 7 is changed to the exhaust mode and the peripheral wall burner 8 is switched to the combustion mode, as shown in FIG. 5 and FIG. 6, the long flame generated by the flame mouth portion 8 a of each of the peripheral wall burners 8 is switched. The flame Mw, which travels straight, spreads toward the furnace F along the peripheral wall portion 5, and the furnace gas generated by this long flame continuously diffuses toward the furnace F.

The furnace gas is distributed around the periphery of the outer wall portion 5 along the circumference of the furnace body 3 in the direction opposite to that of the top wall burner 7 when burning, and the side is provided as exhaust Ew on the upper side of the outer wall portion 5. Each of the flame mouth portions 7a of the plurality of top wall burners 7 of the top wall portion 6 is discharged. Moreover, whenever the mode is switched between the top wall burner 7 and the peripheral wall burner 8, the gas flow of the furnace gas is repeatedly switched to top-down, bottom-up, and repeatedly around the outer wall 5 Repeatedly switch to the opposite direction.

With this three-dimensional stirring effect, the temperature of F in the entire furnace can be uniformized, and the furnace gas can contact the object to be heated from all directions, and the entire object to be heated can also be uniformly heated.

In the rotary hearth furnace 1 of this embodiment, the top wall portion 6 is provided with a thermal storage type top wall burner 7 having a flame mouth portion 7a facing the furnace F, and the outer wall portion 5 is provided with a flame mouth portion 8a. It is a regenerative peripheral wall burner 8 that faces the inside of the furnace F from its tangential direction and alternately burns with the top wall burner 7. Therefore, during the operation of the rotary hearth furnace 1, the peripheral wall burner 8 and the top wall burner 7 alternately burn. The furnace gas in the furnace F repeatedly flows from the top wall portion 6 to the outer peripheral wall portion 5 below it, and from the outer wall portion 5 to the top wall portion 6 above it, and along the outer wall portion 5 The air flow is also repeatedly switched to the opposite direction, which can promote the stirring effect of the furnace gas F in the furnace. Thereby, the temperature distribution in the furnace can be made uniform.

In addition, the flame Mc generated in the top wall burner 7 does not directly face the flame mouth portion 8a of the peripheral wall burner 8, but flows from the top wall portion 6 along the top surface. In addition, the flame Mw and Exhaust Ew is not directly directed toward the flame mouth portion 7a of the top wall burner 7 of the top wall portion 6, but is directed toward the circumferential direction of the outer peripheral wall portion 5. Therefore, the flames Mc and Mw do not easily contact the rotary chamber. The object to be heated on the hearth 2 can prevent the flames Mc and Mw from coming into contact with the object to be damaged. In addition, the exhaust gas Ec and Ew of the top wall burner 7 and the peripheral wall burner 8 can be prevented from being immediately discharged from the adjacent flame mouth portions 7a and 8a, and the energy saving effect of the thermal storage burner can be fully exerted.

Since the regenerative burner is installed on the top wall portion 6 and the outer peripheral wall portion 5, it is possible to ensure that the installation space of the burner is enlarged to the top wall portion 6 as compared with the case where the burner is installed only on the outer wall portion 5. , Can obtain the layout that increases the number of burner equipment, so as to ensure a greater combustion capacity than conventional.

Since the top wall burner 7 is a swirling flame generating burner, the furnace gas is not only stirred by flowing up and down between the top wall portion 6 and the peripheral wall portion 5, but also by the swirling flame Mc of the top wall burner 7, Can further promote stirring.

The direction of the flame mouth portion 8a of the peripheral wall burner 8 is in a direction opposite to the swirling flame Mc of the top wall burner 7 in the direction of the outer peripheral wall portion 5, and along with the swirling flow of the top wall burner 7 The furnace gas flowing in the outer peripheral wall portion 5 flows smoothly as the exhaust Ec toward the flame mouth portion 8a of the peripheral wall burner 8 facing the direction in which it flows, and can be smoothly discharged. In addition, it is accompanied by the peripheral wall burner. The furnace gas flowing at the flame Mw of 8 and flowing along the outer peripheral wall portion 5 can also flow into the flame mouth portion 7a of the top wall burner 7 without any obstacle as the exhaust gas Ew and can be smoothly discharged.

The top wall burners 7 and the peripheral wall burners 8 are provided in the same number. The top wall burners 7 are arranged at equal intervals in the rotation direction R of the rotary hearth 2 and the peripheral wall burners 8 are arranged adjacent to each other. The top wall burners 7 are in the middle of each other, and the arrangement of the burners 7 and 8 is equalized as a whole of the rotary hearth furnace 1. Therefore, from the viewpoint of the burner arrangement, the temperature distribution in the furnace can be appropriately uniformized.

FIG. 7 is a side cross-sectional view showing a modified example of the top wall burner 7 of the rotary hearth furnace 1 used in the above embodiment. In this modification, in order to increase the radius of rotation of the swirling flame Mc, the flame mouth portion 7a of the top wall burner 7 is formed so as to expand toward the interior F of the furnace.

That is, as shown in the figure, a diameter expanding portion is formed in the flame mouth portion 7a, and the diameter expanding portion is used to define a diameter expanding space 16 that expands from the cylindrical space 11 toward the inside of the furnace F. The cylindrical space 11 and the enlarged diameter space 16 constitute a combustion chamber. The expanded diameter space 16 is configured to increase the diameter expansion rate toward the F side in the furnace.

If the flame Mc (swirling air flow) generated in the cylindrical space 11 reaches the expanding diameter space 16, the turning radius of the swivel air flow will gradually increase with its shape. Then, the swirling airflow that reaches F in the furnace forms a vortex-shaped airflow that spreads radially outward and spreads along the top wall portion 6 to the entire periphery. Thereby, the flame Mc in appearance is diffused into an umbrella shape. In this way, since the swirling flow of the flame Mc of the top wall burner 7 is enlarged, the uniformity of the temperature distribution in the furnace can be further promoted, and the flame Mc can be more difficult to contact the object to be heated.

In addition, for example, in the case where the rotary hearth furnace of Patent Document 2 is an existing furnace, if a regenerative top wall burner 7 is added to the furnace, and the peripheral wall burner is replaced with a regenerative peripheral wall burner 8, Then, even if it is a rotary hearth furnace that has been set, the same function and effect as those of the rotary hearth furnace 1 of the above embodiment can be obtained.

Claims (6)

    A rotary hearth furnace is a furnace provided with a rotary hearth in a furnace formed by being surrounded by at least a cylindrical outer peripheral wall portion and a top wall portion; A regenerative top wall burner facing the inside of the furnace; a regenerative peripheral wall burner having a flame opening portion facing the furnace from a tangential direction and alternately burning with the top wall burner in the outer peripheral wall portion.         The rotary hearth furnace according to claim 1, wherein the above-mentioned top wall burner is a burner generating a swirling flame.         According to the rotary hearth furnace of claim 2, wherein the flame mouth portion of the peripheral wall burner is oriented in a direction opposite to the direction of the swirling flame of the top wall burner along the outer peripheral wall portion.         The rotary hearth furnace according to any one of claims 1 to 3, wherein the top wall burner and the peripheral wall burner are provided in the same number, and the top wall burner is arranged in the rotary hearth furnace at equal intervals. In the direction of rotation of the bed, the peripheral wall burners are arranged between the adjacent top wall burners.         The rotary hearth furnace according to any one of claims 2 to 4, wherein the flame mouth portion of the top wall burner is formed so as to expand toward the inside of the furnace.         A method for rebuilding a rotary hearth furnace is characterized in that the following transformations are performed: a regenerative top wall burner is installed on the top wall portion of the existing rotary hearth furnace, and the flame mouth portion is directed to the furnace; The regenerative peripheral wall burner in which the top wall burner alternately burns, directs the flame mouth portion from the tangential direction toward the inside of the furnace.