JPS5830520B2 - Preheating device using exhaust gas and melting furnace attached to it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a melting furnace such as a reverberatory furnace, which has a preheating tower for preheating melted raw materials using the calorific value of combustion exhaust gas.

In conventional melting furnaces, a certain amount of heat is recovered in a packed column type preheating tower, but this causes many functional and economical problems.

To explain in detail, FIG. 1 shows an aluminum melting furnace of an aluminum tie-casting factory, in which the outer shell of a rectangular tower melting furnace body 51 is an iron shell, and the inner surface is lined with a refractory material and a heat insulating material.

The preheating tower 1 is installed upright at the end of the melting furnace body 51, and has an outer shell made of iron and an interior lined with a refractory material and a heat insulating material.

The melting section 2 is the bottom of the preheating tower 1 and the space above it, and the tap hole 3 is a tap hole provided at the bottom side of the melting furnace body 51.

The preheating ingot 4 and the return material 5 (return material) are filled in the preheating tower 1.

A skip hoist 6 is used to charge the ingot 4 and return material 5 to the top of the preheating tower 1.

A plurality of melting burners 7 are installed at the bottom side of the preheating tower 1,
The temperature increasing burner 8 is located at a position where a flame is applied to the material to melt it, and the temperature increasing burner 8 is installed facing downward on the ceiling of the furnace body 51, and injects flame onto the hot water surface 10 to raise the temperature.

The temperature increasing zone 9 is a spatial zone in which the temperature of the molten metal is raised at the furnace atmosphere temperature.

The holding chamber 11 refers to the leakage sound in the lower part of the melting furnace main body 51.

15 is an exhaust stack at the top of the preheating tower 1.

The ingot 4 and the return material 5 are carried by a skip hoist 6 (/
c from the top of the preheating tower 1 and is filled.

The melting burner 7 is ignited and the material at the bottom of the tower is melted by this high temperature combustion flame.

The molten aluminum flows down the sloping bottom of the tower and enters the holding chamber 11.
to go into.

The melting temperature of aluminum alloy is around 580°C, but for die casting, it is necessary to raise the temperature to 700 to 750°C. .

In this case, looking at the phenomenon inside the preheating tower 1, the combustion exhaust gas from the melting burner 7 and the temperature increasing burner 8 passes through the preheating tower 1 and is discharged from the exhaust pipe 15 to the outside of the furnace.

When the exhaust gas passes through the preheating tower 1, it preheats the return material 5 and the ingot 4, but the flow of the exhaust gas does not flow uniformly in the irregularly packed preheating tower 1, so there is little resistance. Flow through space.

Therefore, only the material in contact with that space is heated by the exhaust gas.

At this time, the pieces of the return material 5 having a small heat capacity are rapidly heated and eventually melt.

In this way, the area that becomes the exhaust gas passage becomes more and more efficient, and only the area around this passage is heated.
Other parts are less likely to be preheated by exhaust gas.

The so-called blowhole causes a phenomenon in which the heat transfer area of the exhaust gas to the material rapidly decreases, and the exhaust gas reaches the exhaust stack 15 while remaining at a high temperature.

Thus, the heat recovery efficiency of the preheating tower 1 rapidly decreases.

In addition, there is a problem in that partial melting by heating causes melting and crosslinking phenomena.

In addition, in this type of method in which the material is directly heated by the melting burner 7, partial melting is performed by the high temperature flame, so the melted material is vaporized and evaporates, resulting in a material loss of 3-6%, so-called metal loss, which is extremely It is uneconomical.

In addition, the vaporized material is deposited and fixed on the inner wall of the furnace.
This not only reduces the internal volume of the furnace, but also narrows the working opening and burner opening, leading to a risk of blockage.

FIG. 2 shows another example in which the preheating tower 1 is a vertical tower, and the melting section 2 is the bottom of the preheating tower 1 and the space above it, and the tapping port 3
is a tap hole attached to the bottom side of the heating furnace 53.

Reference numeral 52 denotes a connecting pipe between the bottom side of the preheating tower 1 and the heating furnace 53, and the bottom portion forms a runner for the molten metal flowing down from the melting section 2, leading the molten metal to the heating furnace 53.

The melting burner 7 is connected to the bottom side of the preheating tower 1 and the connecting pipe 52.
There are several installed on the sides of the

Reference numeral 8 designates one or more temperature increasing burners installed on the side surface of the temperature increasing furnace 53.

4 is an ingot block filled with 10 preheating towers, and 5 is a filled return material.

6 is a skip hoist that supplies the return material 5; 12 is a return material hopper; 13 is an electromagnetic feeder that supplies the return material 5 from the hopper 12 to the preheating tower 1 through a switching chute 14;
54, the ingot block is switched through the chute 14;
This is an ingot charging machine that charges 11 preheating towers.

Reference numeral 15 denotes an exhaust pipe, which is attached to the top side of the preheating tower 1.

The melted material ingot is charged into the preheating tower 1 via the switching chute 14 by the ingot charging machine 54 while remaining in the block shape.

The return material 5 is supplied to a return material hopper 12 by a skip hoist 6, and is filled into the preheating tower 1 via a switching chute 14 by an electromagnetic feeder 13 attached to the lower part of the hopper.

The melting burner T is ignited, and high-temperature combustion flame is directly blown onto the material at the bottom of the preheating tower 1 to melt it.

The molten aluminum flows down the sloping bottom of the tower and into the connecting pipe 5.
It passes through the runner no. 2 and enters the holding furnace 53.

The temperature of the molten metal remaining in the holding furnace 53 is raised by the temperature raising burner 8.

In this case, the combustion exhaust gas from the melting burner 7 and the temperature increasing burner 8 passes through the preheating tower 1 and is discharged from the exhaust pipe 15 to the outside of the furnace.

When passing through the preheating tower 1, it comes into contact with the return material 5 and the ingot 4 and preheats them, but since the ingot 4 is packed in a block shape, the exhaust gas passes only through the surface of the block and heats only the surface. As a result, heat transfer to the ingot 4 becomes extremely inefficient.

In addition, since it is filled in the form of an ingot block, only the surrounding return material 5 is ventilated, and the return material 5 is well preheated and eventually melted. This results in a decrease in thermal efficiency.

Further, since the melting burner 7 at the bottom of the preheating tower 1 directly melts, the same drawbacks as in the above example occur.

These drawbacks are due to irregular filling of the material, but
It is almost impossible to fill the preheating tower regularly.

The present invention solves various drawbacks of these conventional melting furnaces, and the material is stored in a preheating tower in an orderly manner.

FIG. 3 and subsequent figures show embodiments of the present invention.

In FIG. 3, the preheating tower 1 is installed perpendicularly to the end side of a rectangular melting furnace body 51, and the bottom of the tower forms a surface inclined toward the furnace body.

As can be seen in FIG. 5, the furnace body 51 and the preheating tower 1 are arranged in an L-shape.

The melting section 2 is the bottom of the preheating tower 1 and the space above it, and the tapping port 3 is connected to the heating burner 8 at the bottom of the end side of the furnace body 51.
be installed near.

In FIG. 4, the upper end of the skip hoist 6 has reached the return material input door 40 on the upper side of the preheating tower 1.

In FIG. 3, the melting burner 7 is attached downward to the side surface of the furnace body 51 facing the preheating tower 1, and the temperature raising burner 8 is attached downward to the longitudinal end surface of the furnace body 51.

The temperature rising zone 9 is a flame combustion space of the temperature rising burner 8 of the furnace body 51.

Reference numeral 10 indicates the level of the molten metal when the molten metal is held at the bottom of the furnace body 51, and the holding tank 11 is a place where the molten metal at the bottom of the furnace body 51 is held.

The inclined surface 16 at the bottom of the preheating tower 1 is a dry hearth,
Above it is a holding stand 17, which has two seats arranged parallel to each other and having a rectangular cross section and a substantially horizontal upper surface.

The temperature measuring nozzle 20 is inserted into the upper space of the melting section from the side of the preheating tower.

There are three shelves in the preheating cylinder 1, which are used to preheat the returned materials.
They are a first holding shelf 23, a second holding shelf 24, and a third holding shelf 25.

As the plane of the third holding shelf 25 is shown in FIG.
Each holding shelf has a fork shape and is inserted into the interior through openings in both side walls of the preheating tower 1, and its tips are in contact with each other.

Reference numeral 56 is a drive unit that uses an air cylinder to move in and out of the fork-shaped shelf in the horizontal direction.

Each holding shelf is arranged in the middle of the preheating tower 1 with a suitable space between them.

A temperature measuring nozzle 29 is attached to the side surface of the preheating tower to measure the temperature in the upper space of the third holding shelf 25.

30 is a butterfly damper installed in the upper exhaust pipe 31/I of the preheating tower 1; 132 is a fan damper installed inside the bypass piping from the upper side of the preheating tower; 33 is installed in the bypass piping system; The induced fan 34 is a pipe connecting the induced fan outlet and the exhaust pipe.

Next, a support beam 21 for mechanically charging the ingot 4 is installed in the melting section 2 at the bottom of the preheating tower 1.

An opening/closing door 554 is formed on the outside of the lower part of the preheating tower 1, and the bases of two parallel beams of the support beam 21 are connected, so that the support beam 21 can move in and out of the preheating tower 1 and move up and down.

The support beam drive mechanism 36 moves the support beam 21 vertically and horizontally as shown by the dotted line 35 like a forklift, and a gap 60 is provided in the lower side wall of the preheating tower so that the support beam 21 can move up and down. When the support beam 21 is stopped, the gap is closed.

As shown in FIG. 7, a push plate 57 with a convex cross-section is arranged on the inner surface of the lower part of the preheating tower, and a push mechanism 37 for horizontally driving the push plate 57 is driven by an air cylinder 59 via a drive rod 58. be.

An inspection and work door 38 is provided on the side of the furnace body opposite to the heating burner 8 .

A return inlet door 40 is provided on one side of the upper part of the preheating tower 1 (FIG. 4).

To mechanically charge the melted material ingot 4 during operation, first place it on the support beam 21 outside the preheating tower in steps 10.11.
As shown in FIG. 12, the ingots are loaded in the form of a group of orthogonally stacked ingots 22.

The opening/closing door 55 is opened, and the support beam drive mechanism 36 charges the fuel into the preheating tower through the opening.

Next, the ingot group 22 loaded by the drive mechanism 36 is lowered, and the ingot group 22 is loaded onto the holding table 17ζ, and in this state it becomes the ingot group 18 for melting, and the support beam 21 is moved horizontally backward by the drive mechanism 36. Then, the ingot group is loaded again onto the support beam 21 that has been extracted from the inside of the preheating tower, and the ingot group 22 for preheating is lifted vertically and horizontally moved from the ingot charging port in the same manner as described above.
It will be established as

On the other hand, the return material 5 is charged into the preheating tower by the skip hoist 6 through the return material membrane inlet door 40.

The charged return material 5 is loaded onto the third holding shelf 25 and becomes the third preheated return material 28.

Next, the air cylinder 56 of the holding shelf 25 is actuated to move the forked holding shelf 25 to both sides and open it.

At this time, the second holding shelf 24 at the lower stage of the third holding shelf 25 is in a closed state.

The third preheated return material 28 is dropped onto the second holding shelf 24 and held, and becomes the second preheated return material 27 .

In the same operation, the second preheated return material 27 is transferred to the first preheated return material 26.
and moves onto the first holding shelf 23.

Furthermore, by the same operation, the first preheated return material 26 becomes the melted return material 19 and is moved onto the melting ingot group 18.

This movement is performed before the preheating ingot 22 is loaded into the preheating tower.

When loading the ingot 4 manually (in this case, the support beam 21
Instead of the above operation, the ingot group 18 is assembled at the bottom of the preheating tower 1.

Next, the melting burner 7 and the temperature increasing burner 8 are ignited.

Combustion heat from the flames of both burners is consumed to raise the temperature inside the furnace, and the cooled exhaust gas is transferred to the holding table 17 at the bottom of the preheating tower.
The ingot group 18 loaded on the ingot group 18 is heated, and the exhaust gas passing through that space heats the return material 19 for melting, and then preheats while passing through the space of the preheating ingot group 22, and then placed above it. The returned materials 26, 27, and 28 on the first, second, and third holding shelves are preheated and ascended.

During this time, the temperature of the exhaust gas gradually decreases and reaches a temperature of about 120° C. through the exhaust stack 31, and is either dissipated into the atmosphere or guided to the next stage dust collector and removed.

Due to the continued combustion of burner 7.8, the temperature inside the furnace is 800~9.
00'C! When this is reached, the lower ingot group 18 and the return material 19 gradually begin to melt, and the molten metal flows down the slope of the dry hearth 16 and begins to stay in the holding tank 11.

The flame of the temperature-raising burner 8 heats the molten metal surface 10 of the holding tank 11 and raises the temperature of the molten metal to a predetermined temperature.

The melting burner 7 also applies its flame to the molten metal surface 10 to assist in raising the temperature of the molten metal, and its combustion exhaust gas joins the temperature raising burner 8 and flows into the preheating tower 1.

The melting burner 7 heats the surface of the molten metal and passes the exhaust gas through the molten material without directly blowing the flame onto the molten material. Therefore, the molten material is not heated to a high temperature, and the molten material is vaporized. No evaporation occurs.

Therefore, there was almost no material loss, that is, metal loss, which was only about 0.7%, which was less than a fraction of that of conventional furnaces.

Further, when most of the melting ingot group 18 and the return material 19 have been melted and a portion of the melted material remains on the holding table 17, the air cylinder 59 of the pushing mechanism 37 moves the pushing plate 57 to the drive rod. 58, the remaining melted material is pushed into the molten metal from above the dry hearth 16, and the top of the dry hearth is cleaned.

After the preheating ingot group 22 is moved to the position of the melting ingot group 18 by the same operation as in the next startup, the first holding shelf 23 is opened by the drive device, and the first preheating return material 26 is transferred to the ingot group 18. drop it on top.

Next, the first holding shelf 23 is closed, the second holding shelf 24 is opened, and the second preheated return material falls onto the first holding shelf, and by the same operation, the third preheated return material is transferred to the second holding shelf, The new return material is put into the third holding shelf 25 by the skip hoist 6 □40
It is introduced after

The preheating ingot group 22 is then inserted into the position shown in the figure.

By properly arranging the ingots to be melted and the ingots to be preheated to form a uniform spatial arrangement, the hot gas for melting and preheating can uniformly pass through.

Since the return material 5 is separated into each shelf stage, uneven flow of exhaust gas is corrected, and by moving the preheating stage, uniformity of preheating is promoted.
The hot gas itself can undergo sufficient heat exchange and reach the exhaust stack 31.

Because heat exchange occurs between the hot gas and the preheating material in this way,
Partial dissolution, no dissolution and therefore blockage of gas passages,
There is no material cross-linking phenomenon, and the operation is extremely smooth and continuous.

Furthermore, since the preheated material is uniformly preheated during melting, there are no lumps in the melting part and the material melts quickly, resulting in very good results in shortening and controlling the melting time.

Furthermore, in order to increase the thermal efficiency of this melting furnace, the temperature measurement nozzle 29 measures the exhaust gas temperature after preheating, and if the temperature exceeds a predetermined temperature, the combustion of the melting burner is throttled or stopped, and the exhaust gas is A control mechanism may be provided to prevent heat loss.

In addition, by controlling the damper 32 of the induction fan and the furnace pressure in conjunction so that the furnace pressure is equal to or slightly higher than atmospheric pressure, cooling due to the inflow of atmospheric cold air into the furnace and diffusion of hot air outside the furnace are suppressed. be able to.

The induced fan 33 is used when the pressure loss in the preheating section and the melting section is large and cannot be handled by the suction force of the exhaust stack alone.

When an induced fan is not required, the pressure inside the furnace is adjusted by the damper 30.

In addition, the inspection, work □ 38, insertion door 39, and input door 40 have a convex structure as shown in the figure so that they can be folded down to improve airtightness and prevent hot air from leaking to the outside.

Although not shown in the drawings, the opening is provided with an air curtain system to block heat inside and outside the furnace and prevent gas from flowing in and out when the door is opened, thereby increasing the thermal efficiency of the furnace.

According to the present invention, the fuel consumption for melting can be drastically reduced to about one third of that of a conventional reverberatory furnace.

Additionally, metal loss due to material vaporization has been drastically reduced to just a few minutes.

There are no troubles caused by vapor deposition on the inner wall of the furnace due to vaporization, and the life of the furnace can be greatly extended.

In addition, when the operation is stopped (there is no need to melt the holding material in the preheating tower), the volume of the furnace can be greatly reduced.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views showing conventional examples of aluminum melting furnaces, Figures 3 and below are cross-sectional views showing embodiments of the present invention, and Figures 8 to 10 are partial detailed explanatory views. be. 1... Preheating tower, 7... Melting burner 8
...Temperature rising burner, 17...Holding stand,
21... Support beam, 23... First holding shelf, 24... Second holding shelf, 25... Third holding shelf, 36...・Support beam drive mechanism, 51...
・Furnace body.

Claims (1)

[Claims] 1. A melting furnace having a preheating tower in which a plurality of fork-shaped shelves are arranged inside an exhaust gas preheating tower installed upright in the furnace body, and a drive mechanism for moving the fork-shaped shelves in the horizontal direction is provided. . 2 A multi-stage fork-like shelf is installed inside the flue gas preheating tower installed upright in the furnace body, and a drive mechanism is provided to move the fork-like shelf in the horizontal direction, and the fork-like shelf is supported at the lower part of the preheating tower below the fork-like shelf. A melting furnace that has a preheating tower in which beams are arranged and a drive mechanism that moves the support beams vertically and horizontally.