JPH0816589B2 - Circulation reburning reverberatory furnace - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly applied to food cans, automobiles,
The present invention relates to a circulating reburning reverberatory furnace for melting aluminum scrap used in electric trains and the like.

[0002]

2. Description of the Related Art In recent years, aluminum has been widely used in food cans, household products, automobiles, trains, etc., and the amount of aluminum scrap produced has also increased significantly.
In general, scrapped aluminum is once melted, then made into an ingot or the like and reused. Thus, conventionally, a reverberatory furnace using heavy oil as a fuel has been used for melting aluminum scrap. That is, the reverberatory furnace is configured by disposing a heavy oil burner on one side wall of a box-shaped furnace body having a scrap charging port and a tapping port, and a burner flame and reflection from a ceiling or a wall heated by the flame. The heat is used to melt the aluminum scrap that has been charged into the furnace body from the scrap charging port. Further, the combustion gas in the furnace body is discharged through the flue immediately from the exhaust port formed on the other side wall facing the burner of the furnace body, and dust etc. is collected by the bag filter provided in the middle of the flue. After being removed, it is discharged into the atmosphere from the chimney.

[0003]

However, a conventional reverberatory furnace (capacity: 5 ton to 10 ton) using heavy oil as fuel is used.
Has a structure in which the hot combustion gas in the furnace body is immediately discharged to the outside through the flue, so its thermal efficiency is 15
It was as low as -25%, and there was a problem that a large amount of heavy oil was required. For example, about 230 to 250 liters of heavy oil was required to make 1 ton of aluminum hot water. As a result, there was a problem that the price of recycled aluminum soared. In addition, many aluminum scraps contain impurities such as various paints, oil, and vinyl that generate soot (black smoke) due to incomplete combustion. There was a problem that it burned completely and a large amount of soot (black smoke) was generated. Particularly, when the scrap was charged, the impurities were incompletely burned, and a large amount of soot was generated. As a measure for preventing soot, there is a method of preliminarily pretreating aluminum smoke that generates soot before melting. That is, it is a method of appropriately sizing scrap, burning it in a kiln, and passing the smoke through a reburning furnace to treat soot. However, this method is not very practical because it uses a considerable amount of fuel only in the pretreatment and also has the drawback of shortening the life of the bag filter for treating the exhaust gas. Further, in the conventional reverberatory furnace, a large amount of air tends to be supplied into the furnace in order to suppress the generation of soot and smoke. As a result, there is a problem that the amount of oxygen in the furnace becomes large, so-called aluminum oxidation loss increases, and the product yield decreases. For example, in a conventional reverberatory furnace of about 10 tons, it is necessary to extract slag about 8 to 9 times while supplying scrap. In addition, in the conventional reverberatory furnace, since the amount of soot and dust in the exhaust gas is large and the exhaust gas temperature is relatively high, there is a problem that the dust collector becomes significantly large.

The present invention was devised in order to solve the above problems, and its purpose is to improve thermal efficiency and energy saving, and to reduce oxidation loss during melting to improve product yield. Another object of the present invention is to provide a recirculating combustion type reverberatory furnace capable of significantly suppressing the generation of soot and smoke.

[0005]

According to the present invention , a burner is provided on one side wall of a box-shaped furnace main body having a material charging port and a tapping port, and a material charged into the furnace main body from the material charging port is provided. ,
In the reverberatory furnace that melts by the flame of the burner and the reflected heat from the ceiling and walls heated by the flame, the bar of the box-shaped furnace body
The combustion gas inlet in the side wall of the person who has disposed over Na, a combustion gas outlet on the other side wall you face the combustion gas inlet,
Form material inlets on the front wall or rear wall, respectively, and use the furnace
Extend the hearth of the body outside the material input port
And a flue for combustion gas circulation for recirculating the combustion gas discharged from the combustion gas outlet between the combustion gas inlet and the combustion gas outlet into the furnace body. thereby forming a second burner to the combustion gas circulation flue in the vicinity of the combustion gas inlet, combustion of the combustion gas circulation flue
Secondary air injection nozzles are provided in the middle of the burning gas outlet, and an opening / closing door is provided at the material inlet.
A hood is installed above the material receiving pit to operate the furnace
Part of the combustion gas from the furnace is received through the material inlet.
It can be discharged into the pit and released into the atmosphere through the hood.
It is an basic arrangement of the invention and.

[0006]

The aluminum scrap charged into the furnace body from the material charging port is gradually melted by the flame of the burner and the reflected heat from the ceiling or wall of the furnace body heated by the flame. On the other hand, the high-temperature combustion gas in the furnace body is discharged from the combustion gas outlet, flows into the combustion gas circulation flue, returns to the inside of the furnace through the combustion gas inlet, and is burned again by the burner. Further, when soot is often generated when scrap is thrown in, secondary air is ejected from the secondary air blowing nozzle into the combustion gas circulation flue. The combustion gas is sent to the combustion gas inlet side by this secondary air, and is mixed with the secondary air in the combustion gas circulation flue and returned to the furnace body for re-combustion, or the combustion gas inlet port. 2 in the vicinity
After reburning by the next burner, it is returned to the inside of the furnace body from the combustion gas inlet. In this reverberatory furnace, the high temperature combustion gas is recirculated into the furnace body by the combustion gas circulation flue, so that the thermal efficiency is improved. As a result, the amount of fuel used is small and energy can be saved. Further, since the combustion gas is circulated and re-combusted, incomplete combustion in the furnace body is prevented and soot and smoke are reduced. In addition, since the combustion gas is circulated with the secondary air supply reduced as much as possible, the inside of the furnace is not in an oxygen excess state, the generation of slag is reduced, and the number of times of slag extraction is reduced. It will be excellent in workability. Then, when the scrap is melted and a certain amount of hot water is accumulated in the hearth of the furnace body, this is taken out from the hot water outlet. Incidentally, the slag floating on the surface of the hot water is properly taken out from the material charging port and the hot water discharging port. If impurities such as paint and oil contained in scrap are incompletely burned and a large amount of soot (black smoke) is generated, an appropriate amount of oxygen is blown into the furnace body from the oxygen blowing nozzle. As a result, soot and dust are reburned by this oxygen. As a result, the generation of soot and smoke at the time of scrap input is reduced, and there is no concern about air pollution. The combustion gas in the furnace body is discharged to the outside of the furnace through the gap between the material inlet opening / closing door and the molten metal surface, collected in the hood, passes through the flue, and is filtered by the bag filter to remove dust, etc. Emitted into the atmosphere.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 and 2 are schematic vertical cross-sectional views of a circulating reburning type reverberatory furnace according to an embodiment of the present invention, in which 1 is a furnace body and 2
Is a burner, 3 is a flue for circulating combustion gas, 4 is a secondary burner,
Reference numeral 5 is a secondary air blowing nozzle, and 6 is an oxygen blowing nozzle.

The furnace body 1 comprises a left side wall 1a, a right side wall 1b, a front wall 1c and a rear wall 1 which are made of refractory material such as refractory bricks.
It is formed in a box shape by d, the ceiling 1e and the hearth 1f, and the material inlet 7 is formed in the front wall 1c, and the tap 8 is formed in the lower portion of the rear wall 1d. Further, a combustion gas inlet 9 is provided on the left side wall 1a of the furnace body 1, and a combustion gas outlet 1 is provided on the right side wall 1b facing the combustion gas inlet 9.
0 is formed respectively. A fireproof opening / closing door 11 for opening / closing the material inlet 7 is provided on the outer surface of the front wall 1c, and the opening / closing door 11 is moved up and down by an appropriate driving device (not shown). Has been done. A material receiving pit 16 is provided on the outside of the opening / closing door 11 for facilitating the introduction of scrap, and a gap of about 5 to 10 cm is always provided between the hot water A and the lower end surface of the opening / closing door 11. Is provided. Further, on the outer surface of the right side wall 1b, there is provided an adjusting door 12 for opening and closing the combustion gas outlet 10 and changing the opening area thereof. The adjusting door 12 is an appropriate driving device (not shown). It is designed to move up and down. Two burners 2 are arranged on the left side wall 1a forming the combustion gas inlet 9 so that flames flow from the combustion gas inlet 9 side to the combustion gas outlet 10 side. As the burner 2, a heavy oil burner that uses A heavy oil as a fuel is used. The combustion gas circulation flue 3 is the combustion gas outlet 1
For recirculating the combustion gas discharged from 0 into the furnace body 1, and is formed by connecting the combustion gas outflow port 10 and the combustion gas inflow port 9 with a refractory rectangular tubular duct 13. To be done. One secondary burner 4 is arranged in the combustion gas circulation flue 3 in the vicinity of the combustion gas inlet 9 so that the flame flows toward the combustion gas inlet 9. As with the burner 2, a heavy oil burner that uses A heavy oil as fuel is used for the secondary burner 4. The secondary air blowing nozzle 5 is disposed in the middle of the combustion gas circulation flue 3 so that the combustion gas discharged from the combustion gas outlet 10 flows favorably and smoothly to the combustion gas inlet 9 side. And is connected to a blower (not shown) via a pipe or the like. A pair of oxygen injection nozzles 6 are provided on the rear wall 1d of the furnace main body 1 and are for uniformly injecting oxygen into the furnace main body 1, and are connected to an oxygen supply source (not shown) via a pipe or the like. It is connected. In FIG. 2, 14 is a hood arranged above the material inlet 7, and 15 is a flue connecting the hood 14 and a chimney (not shown).

Next, the operation of the circulating reburning type reverberatory furnace will be described. When melting aluminum scrap, first of all, a predetermined amount of aluminum ingot (10
In the case of a ton furnace, about 1.5 to 2 ton) is charged and the burner 2 is actuated to melt it to form so-called bottom hot water. As a result, the temperature in the furnace rises to about 800 degrees. next,
Aluminum scrap is charged into the material receiving pit 16 and is pushed into the furnace body 1 from the material feeding port 7 by a pushing machine (not shown). Although it depends on the type of scrap, in the case of an empty can or the like, it takes about 40 minutes to push 1 ton of material. The aluminum scrap thrown into the furnace body 1 burns the flame of the burner 2 and the ceiling 1e and walls 1a, 1 of the furnace body 1 heated by the flame.
It is gradually melted by the reflected heat from b, 1c and 1d. On the other hand, high temperature combustion gas in the furnace body 1 (about 800 degrees near the combustion gas outlet 10 and about 7 degrees near the combustion gas inlet 9)
00 degrees) is discharged from the combustion gas outlet 10, flows into the combustion gas circulation flue 3, and is returned from the combustion gas inlet 9 into the furnace. When a large amount of soot is generated at the time of feeding the raw material, etc., the flue 3 for combustion gas circulation from the secondary air blowing nozzle 5
An appropriate amount of secondary air is ejected into the inside, and the combustion gas is satisfactorily and smoothly sent to the combustion gas inlet 9 side by the secondary air. Then, after being mixed with secondary air in the combustion gas circulation flue 3 and re-combusted by the secondary burner 4 near the combustion gas inlet 9, it is circulated from the combustion gas inlet 9 into the furnace body 1. . The opening area of the combustion gas outlet 10 is variable by the adjusting door 12 and has an opening area corresponding to the amount of combustion gas generated. When a predetermined amount of raw material is sequentially charged and the level of the hot water A in the furnace rises to a constant value (about 40 to 50 cm), the hot water outlet 8 is opened and the hot water A is taken out. The time required to take out the hot water A greatly varies depending on the shape of the taken-out product, and normally 2.5 to 6 hours is required to take out 10 tons of the hot water A. Further, during the hot water discharge, the burner 2 is intermittently operated for about 10 minutes per hour in order to maintain the hot water temperature. Further, the slag generated by the oxidation of aluminum during the melting of scrap and the removal of hot water is a material inlet 7 or a hot water outlet 8.
From the above, it is appropriately scraped out of the furnace (smelting of 10 tons, scraping 4 to 5 times during hot water discharge), and then carried out to an aluminum squeezing device. During the operation of the reverberatory furnace, the combustion gas in the furnace is discharged to the outside of the furnace through the gap between the opening / closing door 11 of the material inlet 7 and the molten metal surface, collected in the hood 14 and passed through the flue 15 to the flue
After dust and the like are removed by a bag filter (not shown) provided in the middle of 5, the product is discharged from the chimney into the atmosphere.
The pressure difference between the inside and outside of the furnace is set to be very small, and it is not said that a large amount of combustion gas is discharged outside the furnace during the operation of the furnace. The molten metal surface temperature in the material receiving pit 16 is maintained. In this reverberatory furnace, the high-temperature combustion gas is recirculated into the furnace body 1 by the combustion gas circulation flue 3, so that the thermal efficiency is significantly improved. As a result, the amount of fuel used is small and energy can be saved. Further, since the combustion gas is circulated, the secondary air is mixed with the combustion gas, and the secondary air is re-combusted by the secondary burner 4, incomplete combustion in the furnace body 1 is prevented and soot and smoke are reduced. . In addition, since the excessive supply of air is suppressed, the generation of slag is reduced, the number of times of slag extraction is reduced, and the workability is excellent. Further, when impurities such as paint and oil contained in the scrap are incompletely burned and a large amount of soot (black smoke) is generated, oxygen is blown into the furnace body 1 from the oxygen blowing nozzle 6 and reburned. By doing so, less soot is generated and there is no concern about air pollution.

Although a pair of oxygen blowing nozzles 6 are arranged on the rear wall 1d in the above embodiment, the position of the oxygen blowing nozzle 6 is not limited to that of the above embodiment. , Front wall 1c, left and right side walls 1a, 1b or ceiling 1e
May be arranged in any number, and the number thereof is arbitrary.

[0011]

As described above, in the recirculation combustion type reverberatory furnace of the present invention, the combustion gas outlet and the combustion gas inlet are formed in the furnace body, and the space between the combustion gas outlet and the combustion gas inlet is formed. A flue for circulating combustion gas is formed in the furnace, and the high-temperature combustion gas generated in the furnace main body is recirculated into the furnace main body through the flue for circulating combustion gas. The thermal efficiency will be greatly improved compared to the conventional reverberatory furnace. As a result, the amount of fuel used is small and energy can be saved. According to the result of the actual test using the 10 ton type reverberatory furnace, the conventional reverberatory furnace required about 250 l / ton of fuel oil for melting and tapping aluminum scrap, whereas the conventional reverberatory furnace of the present invention In case of reverberatory furnace, the required fuel amount is about 150 l / ton
This results in a fuel saving of about 40%. Further, when soot is relatively often generated when the raw material is charged, the combustion gas is circulated, secondary air is appropriately mixed therein, and the secondary burner reburns it. Incomplete combustion in the furnace body is prevented and soot generation is reduced. Furthermore, the circulation of combustion gas is as close to natural circulation as possible so that the inside of the furnace is not in an excess air state, so the generation of slag due to the oxidation of aluminum is reduced, and the number of times slag is extracted is reduced. It has excellent properties.
According to the actual test using the 10 ton type reverberatory furnace, the product yield is about 3% because the generation of slag is reduced.
It has been proven to improve. In addition, when impurities such as paint and oil contained in scrap are incompletely burned and a large amount of soot (black smoke) is generated, oxygen is blown from the oxygen blowing nozzle to easily reburn soot. can do. As a result, it is possible to reduce the generation of soot and smoke for any scrap raw material, to avoid the risk of air pollution, and to significantly reduce the size of the dust collector.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a circulating reburning type reverberatory furnace according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line EE of FIG.

[Explanation of symbols]

1 is a furnace body, 2 is a burner, 3 is a flue for circulating combustion gas, 4
Is a secondary burner, 5 is a secondary air blowing nozzle, 6 is an oxygen blowing nozzle, 7 is a material inlet, 8 is a hot water outlet, 9 is a combustion gas inlet, 10 is a combustion gas outlet, 11 is an opening / closing door,
16 is a material receiving pit.

Claims (1)

[Claims] 1. A burner is disposed on one side wall of a box-shaped furnace body having a material charging port and a hot water discharging port, and the material charged into the furnace body from the material charging port is heated by a burner flame and a flame. in reverberatory furnace to dissolve the reflected heat from ceiling and walls, the combustion <br/> combustion gases inlet in the side wall of who were provided with burner box-shaped furnace body, the combustion gas inlet the other <br/> sidewall combustion gas outlet you face, the material inlet in the front wall or rear wall
While forming each, the hearth of the furnace main body of the material input port
A material receiving pit of appropriate size is formed by extending outward.
In addition, a flue for combustion gas circulation for recirculating the combustion gas discharged from the combustion gas outlet into the furnace body is formed between the combustion gas inlet and the combustion gas outlet, and the combustion gas flow is formed. the inlet secondary burners to the combustion gas circulation flue in the vicinity of the secondary air blow nozzles each provided in the middle of the combustion gas flow outlet side of the combustion gas circulation flue, further the material input
An opening / closing door is provided at the mouth and above the material receiving pit
A hood is installed in the furnace to remove some of the combustion gas from the inside of the furnace during operation.
The material is discharged to the material receiving pit through the material input port and the hood
A circulating reburning reverberatory furnace characterized by being released into the atmosphere via