KR20010019662A - A method for increasing scrap melting rate in electric furnace - Google Patents

Abstract

PURPOSE: A method for promoting smelting of scrap iron during operation of an electric furnace is provided to promote smelting of scrap iron, thereby decreasing a basic unit of electric power by increasing heating value of aluminum dross higher using peroxidation free liquid oxygen together with aluminum dross. CONSTITUTION: In an operation method for an electric furnace comprising smelting and refining by conducting charged scrap ore, a method for promoting smelting of scrap iron during operation of an electric furnace comprises the processes of feeding 12 to 48 kg of aluminum dross briquette per ton of charged scrap ore before charging the scrap ore, charging and conducting the scrap ore, and supplying 45 to 75 wt.% of liquid oxygen per aluminum dross briquette until the scrap ore is completely smelted. Therefore, a smelting time of scrap ore and a basic unit of electric power can be reduced during operation of an electric furnace.

Description

A METHOD FOR INCREASING SCRAP MELTING RATE IN ELECTRIC FURNACE}

The present invention relates to a method for promoting the dissolution of scrap metal in an electric furnace, and more particularly, to a method for promoting dissolution of scrap iron using aluminum dross and liquid oxygen.

In general, in the furnace operation, scrap iron is first charged into the furnace at about 75 of the total loading amount, and then melted first, and then the remaining about 25 scraps are charged again and then melted. In this dissolution and refining process, gas oxygen and carbon are supplied to the upper part of the molten steel to accelerate dissolution while conducting electricity by setting an appropriate power pattern for each step in order to shorten the operation time.

When carbon and oxygen are supplied to the electric furnace, the dissolution time can be shortened by the exothermic reaction as follows.

C + ½O ₂ = CO ΔH ° ₂₉₈ = -26.42 μs / mole- C

That is, the calorific value in the reaction caused by the solid carbon and the gaseous oxygen supplied to the molten steel is 2200 kW at 25 ° C. and 2340 kW at 1500 ° C. per kg of carbon, which is converted into electrical energy (1KWH / 860 kW). In this case, it corresponds to 2.6KWH and 2.7KWH, respectively.

Therefore, in the related art, by discharging gaseous oxygen and carbon powder having a flow rate of 25 to 60 Nm3 / hr per ton of scrap metal on the molten steel during energization, the melting time is shortened through the reaction of the reaction formula (1) to reduce power consumption. . In connection with this technique, various lances and nozzles have been proposed to promote the reaction of carbon and gaseous oxygen. However, in order to supply carbon and oxygen according to the conventional method, not only expensive equipment such as a separate lance and dispenser is required, but also the ratio of the injected gas oxygen used to oxidize C components by encountering obstacles such as scrap iron charged into the furnace. As a result of lowering and oxidizing scrap metal, it causes various problems due to peroxidation. For example, there is a decrease in tapping error rate, or an increase in the amount of slag and an increase in the amount of deoxidizer and alloying material consumed in subsequent deoxidation. This is because the supplied oxygen forms iron oxide by reaction with the iron scrap as well as the dissolution accelerator.

On the other hand, Japanese Laid-Open Patent Publication No. 55-125219 has proposed a technique of using a substance containing another type of carbon component as a dissolution accelerator. The proposed dissolution accelerator uses semi-coke, anthracite, iron, and lignic acid as caking agents, and mostly carbon powder as a dissolution accelerator, thereby inducing exothermic reactions as shown in the reaction formula (1). The raw unit is reduced and the dissolution time is shortened. The dissolution accelerator contains iron, but there is no mention of its action, so details are not known. However, if it is assumed that the iron helps the combustion of C, which acts as a dissolution accelerator, it can be considered that iron is once oxidized to Fe ₂ O ₃ and then reacted as in Scheme (2). However, since the reaction of reaction formula (2) is an endothermic reaction, dissolution is inhibited as a whole even if the combustion of C increases.

C + ⅓Fe ₂ O ₃ = ⅔Fe + CO ΔH ₂₉₈ = 39.35㎉ / mole- C

Furthermore, since the oxygen injected for the combustion of the C component included in the dissolution accelerator oxidizes the scrap iron due to obstacles such as scrap iron charged into the furnace, various problems due to peroxidation are still not solved.

In order to solve this problem, the present inventors have proposed a dissolution accelerator containing aluminum and solid oxygen (iron oxide) (Korean Application No. 1998-57623). This prior art solves the problem caused by peroxidation by using solid oxygen, while the metal aluminum has a high calorific value, as well as exothermic reaction may occur even at the bottom of the furnace where the oxygen injection from the top is not smooth. It has a technical meaning.

2Al + Fe ₂ O ₃ = Al ₂ O ₃ + 2Fe ΔH ₁₅₀₀ = -105.0 ㎉ / mole

2Al + FeO = Al ₂ O ₃ + 3Fe ΔH ₁₅₀₀ = -113.9㎉ / mole

As can be seen from the reaction formula (1) and the reaction formula (3) or (4), it can be seen that the metal aluminum is four times larger than the conventional carbon.

The present inventors have completed and proposed the present invention through a series of research projects for developing a method that can reduce the power source unit while maximizing the advantages of the prior art.

The present invention is to provide a dissolution promoting method that can reduce the power unit by promoting the dissolution of scrap iron by using a liquid oxygen without the risk of peroxidation with aluminum dross to increase the calorific value of aluminum dross. .

Dissolution promotion method of the present invention for achieving the above object, in the electric furnace operation method comprising the electricity to melt and refining the charged scrap metal, 12 to 48 kg per tonne of aluminum dross briquettes before loading the scrap metal After charging, the steel is charged and energized to supply 45 to 75 parts by weight of liquid oxygen to the aluminum dross briquettes until the melting of the scrap is completed.

Hereinafter, the present invention will be described in detail.

The inventors of the present invention, when reacting aluminum with gaseous oxygen (Scheme (5)), compared with the calorific value obtained by reacting aluminum with solid oxygen (Fe ₂ O ₃ or FeO), that is, 105, 114 kPa ((3) It is noted that a calorific value of about four times higher can be obtained.

2Al + 2 / 3O ₂ = Al ₂ O ₃ ΔH ₁₅₀₀ = -400 μs / mole

However, since gaseous oxygen oxidizes the charged scrap metal, its application is not preferable. Therefore, the present inventors have confirmed through experiments that the newly applied liquid oxygen as a combustor of aluminum dross can optimize the calorific value of aluminum dross without fear of peroxidation of charged scrap metal, thereby completing the present invention.

The aluminum dross used as a dissolution accelerator in the present invention is a by-product generated during the production of aluminum, and usually contains 50 to 80 metallic aluminum, which acts as a heat generating source as in Scheme (5). In addition, aluminum dross is ductile, and each shape is a block shape and a sharp edge shape, it is possible to be molded into briquettes without adding a separate binder has the advantage that the automatic injection through the hopper. The aluminum dross applied to the present invention preferably has a size of 2.67 mm or less. The bulk aluminum dross having a size exceeding 2.67 mm not only reduces the formability (compressive strength) after the production of briquettes, but also has a low value as a by-product because it is expensive because of its separate use. In the present invention, aluminum dross briquettes are injected into the electric furnace before charging the scrap metal, wherein the input amount is 12 to 48 kg per ton of scrap metal in consideration of the power source unit and the amount of iron oxide.

On the other hand, the present invention is characterized in that by injecting the aluminum dross briquettes and charging the scrap iron as described above to supply liquid oxygen until the dissolution of scrap iron is completed to burn the dissolution promoter. Since the liquid oxygen can easily move to the bottom of the furnace through the gap between the scrap metal charged in the furnace, the liquid oxygen reacts with the aluminum dross introduced as a dissolution accelerator in the entire furnace. In general, oxygen has a high activity and promotes dissolution as well as tends to oxidize scrap metal to form iron oxide, but the aluminum dross of the present invention has a greater binding force with oxygen than conventional carbon-based dissolution accelerators. The amount of oxygen used to oxidize scrap is reduced. Therefore, there is no concern about the peroxide caused by the use of gaseous oxygen as in the prior art.

In the present invention, it is preferable to supply the liquid oxygen at an arbitrary speed until dissolution is completed rather than supplying the liquid oxygen collectively. More preferably, it is supplied at a uniform speed. This is to uniformly use the calorific value of aluminum dross generated by the reaction with liquid oxygen until the dissolution of scrap iron is completed.

Liquid oxygen in the present invention is determined according to the amount of aluminum dross. That is, considering the power source unit and the amount of iron oxide is supplied in an amount corresponding to 40 to 75 parts by weight of aluminum dross briquette input. After the melting of the scrap iron according to the present invention is completed, carbon powder and gaseous oxygen can be supplied through a lance according to the existing dissolution promotion method.

Hereinafter, the embodiment of the present invention will be described in more detail.

(Example)

The aluminum dross briquette, which is a dissolution promoter, is charged into the furnace at a predetermined ratio with the scrap iron and supplied with liquid oxygen at a constant ratio to the aluminum dross weight while conducting melting to melt the molten steel. The amount of power source consumed to reach and the amount of iron oxide formed in this process were investigated. At this time, the amount of iron oxide is a value calculated by analyzing the amount of slag and the iron oxide content in the slag due to the iron oxide formation.

Table 1 shows an invention example in which the weight ratio of aluminum dross to liquid oxygen is 2: 1, a comparative example in which gaseous oxygen is charged with aluminum dross instead of liquid oxygen, and a conventional example in which iron dross is used with iron oxide as solid oxygen. It shows the power source unit and the iron oxide formation amount according to the aluminum dross input.

Psalm Number Aluminum drop dose (㎏ / ton) Oxygen Oxygen input ratio (part by weight) Power source unit Iron Oxide () Input quantity (㎏ / ton) Kinds Comparative Example 1 0 0 Liquid oxygen － 100 100 Comparative Example 2 4 2 50 98 120 Comparative Example 3 8 4 50 98 122 Inventive Example 1 12 6 50 95 125 Inventive Example 2 24 12 50 92 127 Inventive Example 3 36 18 50 88 125 Inventive Example 4 48 25 50 85 131 Comparative Example 4 60 30 50 82 162 Comparative Example 5 70 35 50 80 178 Comparative Example 6 12 6 Gaseous oxygen 50 97 165 Comparative Example 7 24 12 50 94 171 Comparative Example 8 36 18 50 91 187 Comparative Example 9 48 25 50 88 195 Conventional Example 1 12 6 Solid oxygen (iron oxide) 50 99 132 Conventional Example 2 24 12 50 97 141 Conventional Example 3 36 18 50 95 163 Conventional Example 4 48 25 50 92 171

As shown in Table 1, increasing the aluminum dross input reduces the power source unit. In the case of Comparative Examples (1), (2), and (3) in which the aluminum dross dose is less than 12 kg / ton, the amount of power source savings is insignificant. Therefore, it is preferable to control the aluminum dross dose more than that. On the other hand, if the liquid oxygen use ratio is constant, the iron oxide concentration in the slag will be at a similar level, but in the case of Comparative Examples (4) and (5) where the aluminum dross dose exceeds 48 kg / ton, the aluminum dross usage increases. Since the amount of slag formed is increased to increase the total amount of iron oxide, that is, the loss of iron as a valuable metal, the amount of aluminum dross is preferably limited to 48 kg or less per tonne of scrap iron.

In Comparative Examples (6) to (9) using gaseous oxygen in Table 1, the effect of reducing power source unit was smaller than that of the invention example using liquid oxygen, and the amount of iron oxide generated was rather increased.

In addition, the conventional examples (1) to (4) in which iron oxide was charged with aluminum dross as solid oxygen also had smaller power source-saving effect and increased iron oxide generation amount compared to the invention example.

As such, when the liquid oxygen of the present invention is used, it can be seen that the amount of iron loss due to the reduction of the power source unit used for the scrap iron and the generation of iron oxide is reduced as compared with the conventional gas and solid oxygen.

Next, Table 2 below shows the experimental results of dissolving the aluminum dross dose at 24 kg per ton of scrap iron and changing the input ratio of liquid oxygen.

Psalm Number Aluminum drop dose (㎏ / ton) Liquid Oxygen Input (㎏ / ton) Oxygen input ratio (part by weight) Power source unit Iron Oxide () Comparative Example a 0 0 － 100 100 Comparative Example b 24 4.8 20 98 110 Comparative Example c 24 7.2 30 98 112 Inventive Example a 24 9.6 40 95 116 Inventive Example b 24 12 50 92 127 Inventive Example c 24 15.6 65 90 141 Inventive Example d 24 18 75 88 149 Comparative Example d 24 19.6 80 85 193 Comparative example 24 21.6 90 82 225

From Table 2, it is possible to determine the proper ratio of the liquid oxygen to the aluminum dross of the present invention. As shown in Table 2, when the aluminum dross input was constant at 24 kg / ton, the power source unit decreased as the liquid oxygen input increased, but the liquid oxygen was less than 40 parts by weight of the aluminum dross briquettes (a), In (b) and (c), the amount of power source unit savings is insignificant, and therefore, it is preferable to control the liquid oxygen input amount more than that. On the other hand, as the amount of liquid oxygen input increases, the amount of iron oxide formed increases. In particular, in the case of Comparative Examples (d) and (e) where the liquid oxygen use ratio exceeds 75 parts by weight of aluminum dross briquettes, the total amount of iron oxide, that is, oil Since the loss of iron, which is a metal, is increased, it is preferable to control the liquid oxygen to 75 parts by weight or less of aluminum dross briquettes.

According to the present invention as described above, it is possible to promote the melting of scrap metal in the electric furnace to reduce the melting time and power source unit of scrap during operation of the electric furnace.

Claims (1)

In an electric furnace operation method comprising energizing, melting and refining charged scrap, in which 12 to 48 kg of aluminum dross briquettes are charged per ton of scrap metal before charging the scrap metal, the scrap metal is charged and energized. How to accelerate the dissolution of scrap iron in the operation of an electric furnace, characterized in that for supplying 45 to 75 parts by weight of liquid oxygen to the aluminum dross briquette until completion.