JP2002357386A - Method of melting aluminum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of melting aluminum by which the production of aluminum can be increased easily as necessary by using an already existing aluminum melting furnace. SOLUTION: A fuel supply path (4) and a combustion air supply path (7) are connected to a burner (3) provided in the aluminum melting furnace and an additional oxygen injecting path (10) is communicatively connected to the path (7). The quantity of oxygen in combustion air is increased by 1-2% by reducing the quantity of the combustion air supplied to the combustion air supply path (7) from the quantity of combustion air calculated on the basis of the quantity of fuel flowing through the fuel supply path (4) and, at the same time, adding oxygen from the additional oxygen injecting path (10) to the combustion air supply path (7) by the quantity corresponding to the quantity of oxygen in the reduced combustion air. The fuel is burnt by using the oxygen- enriched air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of melting aluminum, and more particularly to a method of melting aluminum capable of improving production efficiency.

[0002]

2. Description of the Related Art Aluminum is generally melted by using a flame generated when a liquid fuel or a gaseous fuel is burned by a burner and its radiant heat. In this case, it has been considered that in the dissolution of aluminum, oxygen-enriched combustion like the dissolution of other metals cannot be used due to the property of the aluminum material that the formation of aluminum oxide is promoted during the dissolution.

For this reason, combustion air is supplied so that oxygen does not become excessive.
% Of the inert nitrogen gas removes the heat of combustion and is discharged outside the furnace, causing a problem of large heat loss.

A method utilizing oxygen-enriched air for dissolving aluminum having such a basic problem has recently been proposed (Japanese Patent Laid-Open No. 4-293740). In this method, oxygen-enriched combustion air is supplied to a burner attached to an aluminum melting furnace so that oxygen in the total air flow is 25 to 40%, and the amount of exhaust gas is reduced to remove nitrogen gas. The heat efficiency is improved by reducing the amount of heat.

[0005]

The aluminum melting technique using oxygen-enriched air has the advantage of being able to obtain a high combustion temperature, but has the advantage of being too hot and damaging the furnace wall. Therefore, there is a problem that the generation of NOx increases. In particular, when the oxygen enrichment ratio (volume% of oxygen in the total combustion air) exceeds 25%, the amount of NOx tends to increase by 2.5 to 3 times as compared with standard air (oxygen 21%).

Therefore, when oxygen-enriched air is used, the aluminum melting furnace must be formed to have a structure that can withstand a high combustion temperature, and high-performance exhaust gas treatment equipment must be facilitated. There was a problem that the capital investment amount was large.

[0007] It is an object of the present invention to provide a method for melting aluminum that can easily increase the production as needed using an existing aluminum melting furnace.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention relates to a combustion air supply passage connected to a combustion burner provided in an aluminum melting furnace. And the amount of combustion air supplied to the combustion air supply passage is reduced from the amount of combustion air calculated based on the amount of fuel flowing through the fuel supply passage, and the decrease The amount of oxygen in the combustion air is reduced by 1 to 2% by adding an amount of oxygen corresponding to the amount of oxygen in the combustion air from the addition oxygen injection passage to the combustion air supply passage.
It is characterized in that the fuel is burned using the oxygen-enriched air by increasing the amount.

[0009]

According to the present invention, the amount of combustion air supplied to the combustion air supply passage is reduced from the amount of combustion air calculated based on the amount of fuel flowing in the fuel supply passage, and the reduced combustion air supply amount is reduced. Since the amount of oxygen corresponding to the amount of oxygen in the air is added, and the amount of oxygen in the combustion air is increased by 1 to 2%, the fuel is burned using combustion air. Although it rises, the amount of exhausted gas is not different from the case where normal combustion air is used, and the amount of NOx generated can be suppressed by the decrease in the absolute amount of nitrogen.

[0010]

FIG. 1 is a schematic system diagram of an aluminum melting furnace embodying the present invention, in which a combustion burner (3) is arranged on a side wall (2) of a furnace body (1). The combustion burner (3) blows out combustion air from around a fuel gas such as propane gas, mixes the air and fuel gas at the same time as the spraying, ignites the mixed gas to form a combustion flame, and The heat of combustion of the flame melts the aluminum to be melted such as an ingot housed in the furnace.

A fuel supply passage (4) connected to the combustion burner (3) is extended from a fuel gas storage container (5), and a fuel amount adjusting valve (6) is provided in the fuel supply passage (4). Is interposed. Further, a combustion air supply passage (7) connected to the combustion burner (3) is led out of a blower (8), and an air amount adjusting valve (9) is interposed on the way.

An oxygen injection passage (10) is connected to the combustion air supply passage (7) downstream of the air amount adjusting valve (9). The addition oxygen injection path (10) is provided with an addition oxygen metering valve (11). Reference numeral (12) denotes an oxygen storage container as a supply oxygen source.

[0013] A fuel amount adjusting valve disposed in the fuel supply path (4)
(6), air amount adjusting valve arranged in combustion air supply path (7)
(9) The addition oxygen metering valve (11) arranged in the addition oxygen injection passage (10) is opened and closed based on the output from the control device (13).

In this case, the control device (13) calculates a fuel supply amount from a required heat amount in the furnace, and calculates a necessary combustion air amount based on the calculated fuel supply amount. Then, the air amount adjusting valve (9) is adjusted to an opening for supplying an amount of the supply air in the combustion air supply passage (7) at a predetermined rate smaller than the calculated required air amount, and The addition oxygen metering valve (11) is adjusted to an opening for supplying the same amount of oxygen gas as the oxygen content in the reduced air amount.

Therefore, the required amount of oxygen is secured, but the amount of oxygen in the reduced air is reduced by the amount of nitrogen in the air. In this case, the control device (13) calculates the reduction in the amount of combustion air and the amount of oxygen to be added so that the oxygen enrichment rate is about 1 to 2 vol% (22 to 23% in total ratio).
In this case, the amount of gas sent into the furnace is kept constant by circulating part of the furnace gas. As described above, when oxygen is replenished in an amount corresponding to the amount of oxygen in the reduced amount of combustion air, energy loss due to exhaust gas can be suppressed by an amount corresponding to a decrease in the amount of nitrogen discharged as exhaust gas. The energy that did not become available can be used for melting aluminum. Further, since the space in the furnace occupied by the nitrogen gas is reduced, a large amount of fuel can be blown, and effective use of heat energy can be achieved.

In the above-described embodiment, the fuel using propane gas has been described. However, liquid fuel such as heavy oil or light oil can be used as fuel in addition to liquefied petroleum gas such as butane gas.

According to the method of the present invention, the amount of thermal energy in the furnace is adjusted by adjusting the supply amount of combustion air and the supply amount of oxygen for addition. The productivity can be increased even with the equipment as it is, and the operation with increased productivity can be performed only for a certain period of time or only for a certain period of a day. Can be enhanced.

[0018]

According to the present invention, the amount of combustion air supplied to the combustion air supply passage is reduced from the amount of combustion air calculated on the basis of the amount of fuel flowing in the fuel supply passage, and the reduced combustion air supply amount is reduced. Since the amount of oxygen calculated from the amount of oxygen in the air is added, and the amount of oxygen in the combustion air is increased by 1 to 2%, the fuel is burned using the combustion air. Rises, but the amount of exhausted gas is no longer the same as when using normal combustion air,
As the absolute amount of nitrogen decreases, the generation amount of NOx can be suppressed. This reduces the amount of heat energy taken out by the exhaust gas, enables high-efficiency production, and improves productivity.

Further, since the total amount of combustion air blown into the furnace and the amount of exhaust gas obtained by the reaction between oxygen and fuel is the same as in the case of normal combustion, the pressure in the furnace increases due to the combustion. This is no different from the case of normal combustion, and a sufficient residence time of the gas can be ensured to ensure sufficient heat conduction to the substance to be dissolved (aluminum).

[Brief description of the drawings]

FIG. 1 is a schematic system diagram of an aluminum melting furnace embodying the present invention.

[Explanation of symbols]

3: combustion burner, 4: fuel supply path, 7: combustion air supply path, 10: addition oxygen injection path.

Claims (3)

[Claims] 1. A fuel supply passage (4) and a combustion air supply passage (7) are connected to a combustion burner (3) provided in an aluminum melting furnace, and oxygen for addition is supplied to the combustion air supply passage (7). The injection path (10) is connected in communication to reduce the amount of combustion air supplied to the combustion air supply path (7) from the amount of combustion air calculated based on the amount of fuel flowing in the fuel supply path (4). At the same time, an amount of oxygen corresponding to the reduced amount of oxygen in the combustion air is added from the addition oxygen injection passage (10) to the combustion air supply passage (7), thereby reducing the oxygen amount in the combustion air by one. A method for dissolving aluminum, characterized in that the oxygen-enriched air is used to burn fuel by increasing the amount by 2%. 2. The fuel supplied to the fuel supply path (4) is LPG.
2. The method for dissolving aluminum according to claim 1, which is a gaseous fuel. 3. The method according to claim 1, wherein the fuel supplied to the fuel supply path is a liquid fuel.