JP2006029729A - Melting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a melting furnace capable of making efficient the heating of a charging member compatible with the prevention of the excessive heating of a furnace wall by directing combustion gas injected from a burner toward the center of the furnace as much as possible. <P>SOLUTION: This melting furnace has a hearth 1a capable of loading the charging member and the cylindrical furnace wall 1b erected from the hearth. A plurality of main burners 2 are arranged at predetermined heights from the hearth 1a across an interval along the peripheral direction of the furnace wall 1b. A plurality of auxiliary burners 3 are arranged at predetermined heights from the hearth 1a or at positions higher than the height along the peripheral direction of the furnace wall 1b. Two or more auxiliary burners 3 are arranged between two adjacent main burners 2 among the plurality of main burners 2. Arrangement pitchs (L) of two or more auxiliary burners 3 are set to twice the radius (R) of the flame of combustion gas injected from the auxiliary burner 3 or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a melting furnace for melting a charging material (for example, a metal scrap material) charged in a furnace with heat of combustion gas injected from a burner.

  Conventionally, a gas cupola, a type of melting furnace, is equipped with a grate and a refractory bed at the bottom of the furnace body, and a charging material (object to be melted) is placed on it, so that the temperature of the charging material is high evenly. (See, for example, Patent Document 1). However, as long as a grate or a refractory bed is used, it is difficult to raise the combustion temperature (and hence the melting ability and the hot water temperature) due to the fire resistance performance of these constituent materials as a bottleneck.

  For this reason, the charging material is placed directly on the hearth and a plurality of burners are arranged on a cylindrical furnace wall surrounding the periphery of the charging material, and flames (ignition high-temperature combustion gases) injected from the burners are applied to the charging material. A method of melting is proposed. For example, as in the melting furnace shown in FIGS. 1 and 2, three burners 2 are arranged along the circumferential direction of the furnace wall 1b with respect to the cylindrical furnace wall 1b at a predetermined height from the hearth 1a. Install at intervals (ie 120 ° intervals). The reason why each burner 2 is installed at a slightly higher position than the hearth 1a is to prevent the melt of the charging material from entering the burner 2 or blocking the burner 2. Further, the heating power of the burners 2 is set so that the combustion gas from each burner 2 can reach the center of the furnace body (that is, the core axis z).

  In such a melting furnace, as a result of the combustion gas flow 21 injected horizontally from each of the three burners 2 colliding with the core, the upflow 22 mainly along the core axis z and the two types of downflows 23 and 24 are obtained. And give rise to In particular, of the two types of downward flows, the first downward flow 23 that returns toward the injection source burner 2 is blocked from rising along the furnace wall 1 b by the horizontal combustion gas flow 21 from the injection source burner 2. Since it is guided again to the core, it circulates in a vortex between the core axis z and the injection burner 2 below the horizontal combustion gas flow 21. On the other hand, the second downward flow 24 flowing on the opposite side to the injection source burner 2 reaches the furnace wall 1b on the opposite side to the injection source burner 2 along the furnace floor 1a, and is perpendicular to the furnace wall 1b. Ascending combustion gas flow 25 (wall upward flow) is generated.

  The wall rising flow 25 that vertically rises along the furnace wall 1b only rises along the furnace wall 1b as there is nothing to block the vertical rise, and the center of the hearth 1a on which the charging material is placed. It is not suitable for. That is, the wall surface upward flow 25 is released to the upper part of the furnace without being effectively used for melting the charging material. In addition, the high-temperature combustion gas flows along the furnace wall 1b, so that the furnace wall 1b tends to overheat. For this reason, in order to protect the furnace wall 1b from heat, there was a dilemma that the combustion temperature (and consequently the melting capacity and the hot water temperature) had to be suppressed to some extent in consideration of the heat resistance limit of the furnace wall 1b.

Japanese Examined Patent Publication No. 1-4554 (cupola with refractory bed)

  An object of the present invention is to provide a melting furnace capable of achieving both efficient heating of a charging material and prevention of overheating of a furnace wall by directing combustion gas injected from a burner to the core as much as possible.

  The invention according to claim 1 is a hearth having a hearth on which a charging material to be melted can be placed, a substantially cylindrical furnace wall substantially upright from the hearth, and a predetermined height (h1) from the hearth. A plurality of first burners arranged at intervals along the circumferential direction of the furnace wall, and a plurality of the first burners at a position higher than the predetermined height from the hearth And a plurality of second burners arranged along the circumferential direction of the furnace wall so that at least one exists between two adjacent first burners.

  In this melting furnace, at least a part of the combustion gas injected from each first burner toward the center (core) of the furnace body changes its direction in the vicinity of the core, and moves from the core to the core wall along the hearth. It tends to flow toward and rise along the furnace wall. However, each of the second burners arranged in the circumferential direction of the furnace wall at a height equal to or higher than the first burner causes an upward flow of the combustion gas along the furnace wall by the combustion gas injection flow. Deflection towards the core. In particular, since there is at least one second burner between two adjacent first burners, the upward flow of combustion gas along the furnace wall located between the two adjacent first burners is surely directed toward the core. It is done. Therefore, according to this melting furnace, by the combustion gas injection from the second burner, most of the combustion gas injected from the first burner can be directed to the core to efficiently heat the charging material on the hearth, It is possible to prevent overheating of the furnace wall due to the upward flow of combustion gas along the furnace wall.

  According to a second aspect of the present invention, in the melting furnace according to the first aspect, two or more second burners are disposed in the circumferential direction of the furnace wall between two adjacent first burners of the plurality of first burners. The arrangement pitch (L) of these two or more second burners is set to be not more than twice the flame radius (R) of the combustion gas injected from the second burner. It is characterized by.

  According to this configuration, the arrangement pitch (L) of two or more second burners arranged between two adjacent first burners and arranged in the circumferential direction of the furnace wall has a flame radius of the combustion gas injected from the second burner. It is set to be twice or less of (R). For this reason, at the time of the combustion gas injection of the second burner, the combustion gas of one second burner and the combustion gas of the adjacent second burner contact or overlap in the outermost peripheral region of the respective combustion gas flows. As a result, a combustion gas flow group is formed in which the combustion gas flows injected from two or more second burners are continuously adjacent to each other without a gap, and the gas flow from the bottom to the top along the furnace wall is blocked. The Therefore, it is possible to effectively prevent the upward flow of the combustion gas along the furnace wall from passing through the jet flow from the second burner and rising as it is along the furnace wall.

  According to a third aspect of the present invention, in the melting furnace according to the first or second aspect, each of the plurality of first burners has a horizontal or depression angle with respect to a virtual horizontal plane (P1) at an installation height of the first burner group. It is provided so as to be directed in the direction of θ1).

  When the first burner is provided so as to be oriented in a direction that is horizontal or at a depression angle (θ1) with respect to the virtual horizontal plane (P1), injection is performed from each first burner toward the center (core) of the furnace body. At least part of the generated combustion gas turns around the core, flows along the hearth from the core toward the reactor wall, and further rises along the furnace wall. The probability of generating is high. Therefore, the need to be solved by the present invention is great.

  According to a fourth aspect of the present invention, in the melting furnace according to the first, second, or third aspect, each of the plurality of second burners is horizontal with respect to a virtual horizontal plane (P2) at the installation height of the second burner group. It is provided so as to be directed in the direction of the elevation angle (θ2).

  Combustion gas along the furnace wall by the combustion gas injected by each second burner by providing the second burner so as to be oriented in a direction that is horizontal or at an elevation angle (θ2) with respect to the virtual horizontal plane (P2). The effect of deflecting the upward flow of the gas toward the core is effectively exhibited.

  A fifth aspect of the invention is the melting furnace according to any one of the first to fourth aspects, wherein after the first burner is injected toward the center of the furnace body, the direction is changed along the hearth and further adjacent. The flow of the combustion gas rising along the furnace wall between the two first burners is deflected toward the center of the furnace body by the combustion gas injected from each second burner. This expresses the action or function of the present invention.

  According to the melting furnace described in each claim, the combustion gas that is going to rise along the furnace wall derived from the combustion gas injected from the first burner is made to the core as much as possible by the combustion gas injected from the second burner. Therefore, both the efficient heating of the charging material and the prevention of overheating of the furnace wall can be achieved.

Hereinafter, some embodiments of the present invention will be described with reference to the drawings.
3-5 illustrate a melting furnace according to one embodiment. This melting furnace has an upright cylindrical furnace body 1, three main burners 2 as first burners, and 15 auxiliary burners 3 as second burners. The burners 2 and 3 in this embodiment are combustion gas injection pipes that inject high temperature combustion gas (that is, flame) in an ignition state based on gas or liquid fuel and auxiliary combustion gas (for example, air). The heating power of the main burner 2 is set to be larger than the heating power of the auxiliary burner 3, and the flame length when each main burner 2 injects a flame alone is larger than the radius (D / 2) of the furnace body 1. The firepower is set to be long.

  The furnace body 1 includes a substantially horizontal hearth 1a on which a charging material (not shown) as an object to be melted can be placed, a cylindrical furnace wall 1b upright from the hearth 1a, and a charge in the furnace body. Is provided at least with a carry-in port (not shown) for carrying in, and a carry-out port (not shown) for carrying the melted material from the hearth 1a out of the furnace body. In addition, the diameter D of the upright cylindrical furnace body 1 is set to 200 to 800 mm, for example. It goes without saying that the distance (D / 2) from the core axis z extending in the vertical direction at the center of the hearth 1a to the furnace wall 1b is uniformly equal over the entire circumference.

  The three main burners 2 are arranged at equiangular intervals (that is, 120 ° intervals about the core axis z) along the circumferential direction of the furnace wall 1b at a position of height h1 from the hearth 1a. Usually, the height h1 is smaller than the radius (D / 2) of the furnace body 1. On the other hand, the fifteen auxiliary burners 3 are arranged along the circumferential direction of the furnace wall 1b at a height h2 from the hearth 1a. The height h2 is equal to the height h1 (h1 = h2) or larger (h1 <h2). In the melting furnace of FIGS. 3 to 5, a total of 18 burners including the main burner 2 and the auxiliary burner 3 are equiangularly spaced along the circumferential direction of the furnace wall 1b (that is, 20 ° intervals about the core axis z). ). That is, there are five auxiliary burners 3 between two main burners 2 adjacent to each other along the circumferential direction of the furnace wall 1b, and these auxiliary burners 3 are arranged at intervals of 20 °.

  Both the main burner 2 and the auxiliary burner 3 are installed radially in plan view so that the respective injection ports are directed to the core axis z, but the mounting angles of the burners in the vertical direction are slightly different. That is, each of the main burners 2 is installed so as to be oriented in the horizontal direction or the depression angle θ1 direction with respect to the virtual horizontal plane P1 at the mounting height h1 of these main burner groups (the main burner 2 shown in FIG. 4 is horizontal). Direction, ie the direction of θ1 = 0 °). The maximum value of the depression angle θ1 is preferably a value that satisfies tan θ1 = 2 · h1 / D.

  On the other hand, each of the auxiliary burners 3 is installed so as to be oriented in the horizontal direction or the elevation angle θ2 direction with respect to the virtual horizontal plane P2 at the mounting height h2 of these auxiliary burner groups (the auxiliary burner 3 shown in FIG. 4 is horizontal). Direction, ie the direction of θ2 = 0 °). A preferable angle range of the elevation angle θ2 is 0 ° to 30 °. When the elevation angle θ2 is smaller than 0 °, the combustion gas injected from the auxiliary burner 3 has a relationship of directly colliding with the combustion gas flow that is going to rise vertically along the furnace wall 1b, and the gas flow in the furnace is reduced. It will cause disturbance. If the elevation angle θ2 is larger than 30 °, the effect of deflecting the combustion gas flow that is going to rise vertically along the furnace wall 1b to the core axis z by the combustion gas injected from the auxiliary burner 3 is not preferable.

  Further, as shown in FIG. 5, the arrangement pitch L of the auxiliary burners 3 in the circumferential direction of the furnace wall 1 b is less than twice the flame radius R (indicated by a broken line) of the combustion gas injected from each auxiliary burner 3. Is set to Since the flame radius R of the combustion gas injected from the burner varies depending on the injection amount and injection pressure of fuel or the like, it is difficult to uniquely define the relationship between the flame radius R and the radius of the burner injection port. The flame radius R has a spread of about 2 to 4 times the radius of the burner nozzle.

  In the melting furnace of the present embodiment, the combustion gas flow 21 injected from the three main burners 2 collides with the core, and as a result, the upflow 22 along the core axis z and the two types of downflows 23 and 24. (See FIG. 4). Of the two types of descending flows, the first descending flow 23 returning to the injection main burner 2 is blocked from rising along the furnace wall 1b by the combustion gas flow 21 from the injection main burner 2. Since it is again guided to the core, it circulates in a vortex between the core axis z and the injection source burner 2 below the combustion gas flow 21. On the other hand, the second downward flow 24 flowing on the side opposite to the injection main burner 2 reaches the furnace wall 1b on the side opposite to the injection main burner 2 along the furnace floor 1a, and along the furnace wall 1b. Try to rise vertically.

  However, in this embodiment, each auxiliary burner 3 arranged in the circumferential direction of the furnace wall 1b at the height h2 causes the combustion gas flow to rise along the furnace wall 1b by the combustion gas injection flow. It is separated from the furnace wall 1b and deflected toward the core axis z. In particular, there are five auxiliary burners 3 between two adjacent main burners 2, and furthermore, the arrangement pitch L of these five auxiliary burners 3 is 2 of the flame radius R of the combustion gas injected from the auxiliary burner 3. Due to being set to be equal to or less than twice, the combustion gases of the adjacent auxiliary burners 3 contact or overlap in the outermost peripheral region of each combustion gas flow. As a result, a combustion gas flow group is formed in which the combustion gas flows injected from the five auxiliary burners 3 are continuously adjacent to each other without a gap, and the gas flow from the bottom to the top along the furnace wall 1b is blocked. The For this reason, the situation where the combustion gas flow which is going to rise along the furnace wall 1b located between the two main burners 2 is prevented from rising along the furnace wall 1b as it is, and is injected from each auxiliary burner 3. The induction of the combustion gas ensures that the combustion gas flow along the furnace wall 1b is directed to the core axis z.

  Thus, according to the present embodiment, the combustion gas that is going to rise along the furnace wall 1b derived from the combustion gas injected from the main burner 2 is directed to the core as much as possible by the combustion gas injected from the auxiliary burner 3. You can make it. For this reason, while being able to heat the charging material on the hearth 1a efficiently, the overheating of the furnace wall 1b resulting from the upward flow of the combustion gas along the furnace wall 1b can be prevented.

  Moreover, according to this embodiment, since the rise of the combustion gas along the furnace wall 1b can be prevented, it is not necessary to suppress the combustion temperature (and hence the melting capacity and the hot water temperature) in consideration of the heat resistance limit of the furnace wall 1b. . Therefore, it is possible to improve the combustion temperature by using high-concentration oxygen gas (for example, 100% concentration oxygen) as an auxiliary combustion gas for the main burner 2 or the like, such as steel scrap that is difficult to melt in an air combustion furnace. The charging material can also be melted.

(Modification) The embodiment of the present invention may be modified as follows.
The arrangement height of the auxiliary burner 3 may be set in multiple stages. For example, as shown in FIG. 6, among the five auxiliary burners 3 arranged between the two main burners 2, three are installed at the height h2, and the remaining two are installed at the height h3 (h2 <h3). . Even if the adjacent auxiliary burners 3 have different heights as described above, the combustion gas flow from the auxiliary burners 3 has a relationship in which the flame diameters (2R) of the combustion gases injected from the auxiliary burners 3 substantially overlap. The shielding effect of the upward flow along the furnace wall 1b and the induction effect on the core axis z by the group are sufficiently exhibited.

  As shown in FIG. 7, the main burner 2 may be installed at a downward mounting angle (a depression angle θ1) so that the injection port of the main burner 2 is directed toward the center point of the hearth 1a. At this time, the relationship of tan θ1 = 2 · h1 / D is substantially established. The obliquely downward combustion gas flow 21 injected from the main burner 2 reaches the furnace wall 1b located on the opposite side of the main burner 2 as the injection source along the hearth la and rises vertically along the furnace wall 1b. In this case as well, the combustion gas flow 25 is deflected toward the core axis z by the combustion gas injected from the auxiliary burner 3 as described above.

  As shown in FIG. 8, all the burners arranged along the circumferential direction of the furnace wall 1 b may be the main burner 2. That is, the main burner 2 may be designed so as to serve as the first burner and the second burner or to share the roles. In FIG. 8, a total of 16 main burners 2 are arranged at equiangular intervals (that is, 22.5 ° intervals). For example, four main burners 2 (2A) arranged at 90 ° intervals are the first ones. When it is regarded as one burner, the remaining 12 main burners 2 (2B) arranged at intervals of 22.5 ° can be regarded as second burners. The melting furnace configured as shown in FIG. 8 can achieve the same operations and effects as the above embodiment.

The top view which shows the outline of the burner arrangement | positioning of the melting furnace in a prior art example. The radial direction longitudinal cross-sectional view of the lower part of the melting furnace in a prior art example. The top view which shows the outline of the burner arrangement | positioning of the melting furnace in one Embodiment. The radial direction longitudinal cross-sectional view of the lower part of the melting furnace shown in FIG. The figure shown in the state which expand | deployed some furnace walls of the melting furnace shown in FIG. The figure shown in the state which expand | deployed some furnace walls in the example of a change. The radial direction longitudinal cross-sectional view of the lower part of the melting furnace in the example of a change. The top view which shows the outline of the burner arrangement | positioning of the melting furnace in the example of a change.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Furnace body, 1a ... Hearth, 1b ... Furnace wall, 2 ... Main burner (1st burner), 3 ... Auxiliary burner (2nd burner), 2A ... Main burner (1st burner), 2B ... Main burner ( Second burner), z ... core axis.

Claims (5)

A furnace body having a hearth capable of placing a charge as a melting object and a substantially cylindrical furnace wall substantially upright from the furnace floor;
A plurality of first burners arranged at intervals along the circumferential direction of the furnace wall at a predetermined height (h1) from the hearth;
Arranged along the circumferential direction of the furnace wall so that at least one exists between two adjacent first burners of the plurality of first burners at a position higher than the predetermined height from the hearth. A melting furnace comprising a plurality of second burners.   Between two adjacent first burners of the plurality of first burners, two or more second burners are arranged along the circumferential direction of the furnace wall, and the arrangement pitch of these two or more second burners (L) is set so that it may become 2 times or less of the flame radius (R) of the combustion gas injected from a 2nd burner, The melting furnace of Claim 1 characterized by the above-mentioned.   Each of the plurality of first burners is provided so as to be oriented in a horizontal or depression angle (θ1) with respect to a virtual horizontal plane (P1) at the installation height of the first burner group. The melting furnace according to claim 1 or 2.   Each of the plurality of second burners is provided so as to be oriented in a direction that is horizontal or an elevation angle (θ2) with respect to a virtual horizontal plane (P2) at the installation height of the second burner group. The melting furnace according to claim 1, 2 or 3.   A flow of combustion gas that is injected from each first burner toward the center of the furnace body, then changes direction along the hearth and rises along the furnace wall between two adjacent first burners, The melting furnace according to claim 1, wherein the gas is deflected toward the center of the furnace body by the combustion gas injected from each of the second burners.

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