JPH06300455A - Melting furnace - Google Patents

Abstract

PURPOSE:To provide a melting furnace capable of displaying an excellent effect from the aspects of economical efficiency, labor reduction, environmental pollution, working environment and quality. CONSTITUTION:The melting furnace is lined with a refractory body 11 and is provided with a cylindrical furnace body 4 made rotatable about the horizontal axis B and a burner 5 for melting the material R to be melted charged into the furnace body 4 by burning fluid fuel with oxygen.

Description

Detailed Description of the Invention

[0001]

This invention relates to melting furnaces.

[0002]

2. Description of the Related Art As a melting furnace for melting a material to be melted such as cast iron, a vertical cylindrical cupola made of a refractory material such as brick is conventionally used. Coke and material to be melted were alternately laminated, and air was blown from the tuyere below to blow coke to melt the material to be melted.

[0003]

However, such a cupola has the following problems.

Thermal efficiency and melting efficiency due to coke combustion are low.

[0005] The refractory material is greatly worn out due to use, and a lot of labor is required for repair.

The amount of exhaust gas is large, and SO ₂ , NO in exhaust gas
The dust concentration of _X and CO ₂ is high.

[0007] It is difficult to automate the operation and requires many operation personnel.

Therefore, an object of the present invention is to provide a melting furnace that solves the above problems (1) to (3).

[0009]

In order to achieve the above object, the present invention provides a cylindrical furnace body lined with a refractory body and driven to rotate around a horizontal axis, and a fluid containing oxygen. A burner that burns fuel to melt the material to be melted charged in the furnace body.

The oxygen purity is set to 99.99% or more.

The fluid fuel is any one of methane, propane, butane and kerosene.

The air-fuel ratio of oxygen and fluid fuel is 0.5 to 1.5.
Set to.

[0013] SiO ₂ -Al ₂ O, including the SiO ₂ 90% ~95%
A refractory body consisting of _three types of acid amorphous refractory material and having its surface ceramicized by firing treatment.

The flame temperature of the burner is 1800 ° C to 2800 ° C.
Set to.

The rotation cycle of the furnace body is 1 to 2 minutes.

[0016]

[Function] Since the burner burns the fluid fuel with oxygen, the flame temperature is high, and the heat of the refractory is transferred to the material to be melted by the rotation of the furnace body. Therefore, the heat efficiency and the melting efficiency are higher than those of the cupola. Can be obtained.

In addition, combustion using oxygen causes the exhaust volume to decrease sharply compared to air combustion, and SO ₂ , NO _X , CO _{2 in} exhaust gas
Has a very small dust concentration and has little adverse effect on the environment.

Further, since the refractory body is made into a ceramic by firing treatment using an acid amorphous refractory material of the SiO ₂ —Al ₂ O ₃ system, it can be used continuously for a long period of time, and the labor of daily maintenance is reduced. Significantly reduced.

Further, in the melting work step, unmanned operation from charging of raw materials to tapping can be performed by using a computer or the like.

Further, by controlling the air-fuel ratio of oxygen and fluid fuel with a computer or the like, the atmosphere in the furnace can be freely adjusted to be oxidizing and reducing, and the molten metal melt is As the body rotates, it mixes appropriately, so
It enables refining and melting of cast iron.

[0021]

The present invention will be described in detail below with reference to the drawings showing the embodiments.

FIG. 1 is a side view of an embodiment of the melting furnace according to the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a cross-sectional view of the essential parts thereof. It is used for producing cast iron, spheroidal graphite cast iron, alloy cast iron such as hardened and hardened resist, and other non-ferrous metals.

In the melting furnace, the furnace body 4 having the cylindrical body 1 and the conical conical parts 2 and 3 connected to both ends of the body 1 and the fluid fuel is burned with oxygen to form the furnace body 4. Burner 5 for melting the material R to be melted, such as cast iron.
And a chimney-shaped exhaust path 6 for escaping combustion exhaust gas to the outside, and an injector 7 such as a skip or a conveyor for introducing the material R to be melted into the furnace body 4.

The furnace body 4 is rotatable about a horizontal axis A on a supporting member 9 which is erected on a fixed portion 8 such as the ground, and is orthogonal to the axis A and has a horizontal axis. The furnace body 4 is rotatably supported around B and is configured to be rotatable around the axis A at a predetermined angle by a drive mechanism including a fluid pressure cylinder, a motor and the like (not shown). Moreover, it is configured to be rotatable around the axis B at a predetermined rotation cycle.

The rotation and rotation of the furnace body 4 are controlled by a computer or the like, and are automatically performed in accordance with predetermined conditions (rotation speed, inclination angle, etc.) and order.

The furnace body 4 is constructed by lining the inner peripheral surface of a steel plate outer peripheral wall 10 with a refractory body 11. The refractory body 11 has a thickness of about 30 cm in the furnace body 4 having a capacity of 3 t, for example. .

The refractory body 11 contains 90% to 95% of SiO _2.
SiO ₂ -Al ₂ O ₃ -based acidic monolithic refractory material (e.g. size 0
mm to 10 mm) is used, and the compounding ingredients are adjusted by the service temperature.

Specifically, a core (not shown) is inserted into the outer peripheral wall 10 of the furnace body 4, and the acidic amorphous refractory material is poured between the core and the outer peripheral wall 10 to solidify the mixture. After being dried to drive out moisture, the surface (the inner surface of the refractory body 11) is made into ceramic by heating it to 1600 ° C. or higher by firing treatment.

The one end opening 12 of the furnace body 4 serves as a burner mounting port, and the other end opening 13 of the furnace body 4 serves as a charging port for the material R to be melted, an exhaust gas outlet and a slag discharge port. Reference numeral 17 denotes a tap hole that is provided through the conical portion 2 of the furnace body 4 and is closed except when tapping.

The burner 5 has a vertical axis C (shown in FIG. 2).
It is attached to the arm 14 that can swing around,
By horizontally swinging the burner 5, the burner 5 can be attached / detached to / from the one end opening 12 of the horizontal furnace body 4.

FIG. 4 shows an example of the internal structure of the burner 5. This burner 5 is a triple pipe, and an oxygen supply port 16 is provided on the outer periphery of the central fluid fuel injection port 15, and water is flown outside it. It is cooling.

As the fluid fuel, any one of methane, propane, butane and kerosene is used, and the purity of oxygen is set to 99.99% or more. Further, the flame temperature of the burner 5 is set to 1800 ° C to 2800 ° C.

The air-fuel ratio of oxygen to fluid fuel is 0.5 to 1.
It is set to 5 and the air-fuel ratio in this range is controlled by a computer. Here, in the present invention, it is defined that the fluid fuel completely burns when the air-fuel ratio is 1.0.

Therefore, if the burner 5 is burned with an air-fuel ratio of less than 1.0, oxygen becomes insufficient, and the atmosphere in the furnace body 4 becomes reductive, and if the burner 5 is burned with an air-fuel ratio of more than 1.0, oxygen is released. As the number increases, the atmosphere inside the furnace body 4 becomes oxidative.

Next, an example of the melting operation process of the melting furnace shown in FIG. 5 will be described.

When the operation is started, as shown in FIGS. 1 and 3, after the horizontal furnace body 4 is preheated by the burner 5 as required, the burner 5 is removed from the one end opening 12 and the iron lid or the like is removed. Is covered with.

Next, as shown in FIG. 6, the furnace body 4 has an axis A.
After turning around and tilting, a predetermined amount of a material to be melted such as cast iron or steel scrap and a raw material such as a slag forming agent are charged into the furnace body 4.

As the slag forming agent, for example, 1.65% silica sand or 2% SiC of the material to be melted is added, and SiO ₂ 91%,
In a melting furnace using a refractory material containing Al ₂ O ₃ 6.5%, SiO ₂ 68.5
%, Al ₂ O ₃ 5.0%, CaO 0.5%, FeO 15.8%, MnO 7.
5% slag 3% to 3.5% is produced by dissolution.

After charging the raw materials, as shown in FIG.
Returns to a horizontal shape, and the other end opening 13 is connected to the exhaust passage 6 for communication.

Further, as shown in FIG. 3, a burner 5 is attached to the one end opening 12 of the furnace body 4 for automatic ignition.

Then, the furnace body 4 rotates about the axis B,
The melting of the materials R to be melted is started.

The rotation cycle of the furnace body 4 is set to 1 to 2 minutes, and the heat of the refractory body 11 heated by the burner 5 is transferred to the material R to be melted in the lower portion by the rotation of the furnace body 4. In this way, the rotating refractory body 11 serves as a heat medium, and high heat efficiency can be maintained.

Moreover, the melted melt is appropriately mixed by the rotation of the furnace body 4, and the length and temperature of the flame of the burner 5, the degree of oxidation / reduction of the atmosphere in the furnace body 4, etc. are in the operating stage-- ─ For example, since it is automatically adjusted according to the preheating period, melting period, molten metal holding period (including component adjustment and temperature rise),
Cast iron can be refined and melted, and a uniform and high-quality cast iron material can be obtained.

In the burner 5, oxidative combustion is preferable in the preheating period, and reducing combustion is preferable in the melting period and the molten metal holding period. By adjusting the degree of oxidation of the flame of the burner 5, the oxidation of Fe It is possible to suppress and reduce C and Si loss. Further, by adjusting the flame, it is possible to remove the oil adhering to the Dalai powder and the Zn of the zinc steel sheet which has recently been increasing as a dissolved material.

Next, when the melting is completed, temperature measurement and analysis are performed, and as a result, if necessary, for example, when steel scrap is used as the material to be melted, a carbonizing agent such as graphite. Alloys such as C, Si, and Mn are added to adjust the composition.

If the component adjustment is not necessary, the burner 5 is stopped, the burner 5 is removed from the opening 12 at one end, and the tap hole 17 is further opened. As shown in FIG. Four
Incline and pour hot water.

When the tapping is completed, the furnace body 4 is rotated around the axis A and becomes vertical, and the slag remaining in the furnace body 4 is discharged from the other end opening 13, and thereafter, as shown in FIG. The furnace body 4 returns to the horizontal state, and the melting work process is completed.

These melting work steps are controlled by a computer or the like, and unmanned operation from charging of raw materials to tapping is possible.

Regarding the temperature of each part, the inside of the furnace body 4 is
1550 ℃ ~ 1650 ℃, hot water discharge 1450 ℃ ~ 1550 ℃, exhaust gas 1200
℃ ~ 1300 ℃, outside the furnace body 4 (steel plate) is about 250 ℃.

In the exhaust gas component, CO ₂ is 30% to 50%,
CO is 25% to 45%. Table 1 shows the results of comparison of NO _X emissions between air combustion and oxyfuel combustion, and it can be seen that oxyfuel combustion is significantly reduced compared to air combustion.

[0051]

[Table 1]

Further, in the melting furnace of the present invention, the amount of exhaust gas during melting work decreases sharply compared to air combustion, and coke is not used, so the dust concentrations of SO ₂ , NO _X and CO _{2 in} the exhaust gas are
It is less than 1/10 of the cupola and has little adverse effect on the environment. Even if an exhaust gas treatment facility is not required, or even if it is provided, it has a small capacity and is simple, and cost is not required.

[0053] As an example of a dust generation amount, whereas in the cupola is ^{0.5g / m 3 ~ 6.2g / m} 3, the average 0.19 g / m ³ in the present invention, extremely small.

Tables 2 and 3 exemplify the time required for the melting operation for each capacity of the melting furnace of the present invention and the production amount thereof.

[0055]

[Table 2]

[0056]

[Table 3]

Tables 4 and 5 exemplify the amounts of oxygen and fluid fuel used for each capacity of the melting furnace of the present invention, and Table 6 shows the loss of auxiliary materials.

[0058]

[Table 4]

[0059]

[Table 5]

[0060]

[Table 6]

Further, Table 7 shows that the dissolution time and oxygen content by volume when different fluid fuels from those in Tables 4 and 5 are used.
The amount of fluid fuel used is illustrated. The fuel consumption other than methane is about 0.4 x H for propane, about 0.32 x H for butane, and about 0 for kerosene, where H is the methane consumption in Table 7.
Each consumption amount is 88 × H, and the oxygen consumption amount for these fuel consumption amounts is the same as the numerical value in Table 7.

[0062]

[Table 7]

Further, in the melting furnace of the present invention, as described above, the refractory body 11 is made into a ceramic by a firing treatment using an acid amorphous refractory material of the SiO ₂ —Al ₂ O ₃ system, so that it can be continuously used for a long period of time. It can be used, the labor of daily maintenance is greatly reduced, and the refractory material and work cost for repairing the furnace body 4 (refractory body 11) can be reduced.

Table 8 exemplifies the maintenance contents of the furnace body 4 (refractory body 11) in the melting furnace having a capacity of 8 tons.
The body 1 can initially use 200 batches continuously, the conical parts 2 and 3 can use 50 batches continuously, and 600 to 800 batches can be continuously used until the total replacement. Note that small erosion points are repaired hot or cold after tapping every time.

[0065]

[Table 8]

Table 9 exemplifies the contents of the total reassignment work, the work time, and the required number of days.

[0067]

[Table 9]

In the melting furnace of the present invention, since the burner 5 burns the fluid fuel with (pure) oxygen, the flame temperature can be raised to about 2850 ° C. On the other hand, in air combustion, the flame temperature is up to 1870 ℃,
It is possible to shorten the melting time, achieve a high melting temperature and save fuel. For example, the melting temperature of cast iron can be 1600 ° C or higher, and the temperature rising rate up to 1400 ° C is 7 to 10 ° C / min.

Moreover, the length of the flame of the burner 5 can be easily adjusted, and the thermal efficiency can be improved by blowing the flame in a short spiral shape, and the refractory body 11 serves as a heat medium as described above. High thermal efficiency can be maintained.

As a result, as shown in Table 10, in the present invention, higher melting efficiency can be obtained as compared with the cupola and the induction electric furnace. The melting efficiency of each induction furnace is a numerical value that includes the efficiency of the power plant.

[0071]

[Table 10]

Table 11 compares the total cost with the cupola and induction electric furnace. The melting furnace of the present invention is superior in terms of furnace maintenance cost and operator labor cost to the cupola, and compared with the induction electric furnace. It is excellent in terms of energy cost and equipment (depreciation) cost, and has the lowest total cost than any of them.

[0073]

[Table 11]

Thus, the melting furnace of the present invention is economical,
Not only does it show excellent effects in terms of labor saving, pollution, work environment, and quality, but it can also use bad steel scrap as a raw material.
It can also be used as a recycling furnace for the ever-increasing amount of steel scrap.

[0075]

Since the present invention is constructed as described above, it has the following great effects.

Since the burner 5 burns the fluid fuel with (pure) oxygen, the flame temperature is high, and the furnace body 4 is rotated to transfer the heat of the refractory body 11 to the material to be melted. Compared with the above, high thermal efficiency and melting efficiency can be obtained, and shortening of melting time, high melting temperature and fuel saving are realized.

Moreover, since the combustion using oxygen causes the exhaust volume to decrease sharply compared to the air combustion, and coke is not used,
The dust concentration of SO ₂ , NO _X , CO _{2 in} the exhaust gas is less than 1/10 of that of cupola, and it has little adverse effect on the environment. Even if exhaust gas treatment equipment is unnecessary or installed, it is simplified with a small capacity and cost is reduced. Does not hang.

Further, since the refractory body 11 is made into a ceramic by a firing treatment using an acid amorphous refractory material of the SiO ₂ —Al ₂ O ₃ type, it can be used continuously for a long period of time, and the labor of daily maintenance is required. Is greatly reduced, and the refractory material for repairing the furnace body 4 and the repair work cost can be reduced.

Further, in the melting work step, unmanned operation from charging of raw materials to tapping can be performed by using a computer or the like, and the number of operating personnel can be greatly reduced.

Further, by controlling the air-fuel ratio of oxygen and fluid fuel with a computer or the like, the atmosphere in the furnace body 4 can be freely adjusted to be oxidizing and reducing and the molten metal melted can be adjusted. Since the furnace body 4 is appropriately mixed by rotation, the cast iron can be refined and melted, and a uniform and high-quality cast iron material can be obtained.

Moreover, in the melting furnace of the present invention, bad steel scrap can be used as a raw material, and can also be utilized as a recycling furnace for an increasing number of steel scraps.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a plan view.

FIG. 3 is a sectional view of a furnace body.

FIG. 4 is a side view showing the internal structure of the burner.

FIG. 5 is a flowchart of a melting work process.

FIG. 6 is an explanatory diagram of a melting work process.

FIG. 7 is an explanatory diagram of a melting work process.

FIG. 8 is an explanatory diagram of a melting work process.

[Explanation of symbols]

 4 Furnace body 5 Burner 11 Refractory material R Dissolved material B Shaft center

Claims (7)

[Claims] 1. A cylindrical furnace body 4 lined with a refractory body 11 and driven to rotate around a horizontal axis B, and a fluid fuel is burned with oxygen to be charged into the furnace body 4. And a burner 5 for melting the melted material R thus melted. 2. The melting furnace according to claim 1, wherein the purity of oxygen is set to 99.99% or more. 3. The melting furnace according to claim 1 or 2, wherein the fluid fuel is any one of methane, propane, butane, and kerosene. 4. The melting furnace according to claim 1, wherein the air-fuel ratio of oxygen to the fluid fuel is set to 0.5 to 1.5. 5. The SiO ₂ -Al ₂ containing a SiO ₂ 90% ~95%
5. The melting furnace according to claim 1, wherein the refractory body 11 is composed of an O ₃ -based acidic amorphous refractory material and whose surface is made ceramic by a firing treatment. . 6. The flame temperature of the burner 5 is 1800 ° C. to 2800 ° C.
The melting furnace according to claim 1, claim 2, claim 3 or claim 4, wherein 7. The melting furnace according to claim 1, wherein the rotation cycle of the furnace body 4 is set to 1 minute to 2 minutes.