DE1771144B1 - PROCESS FOR PRODUCING A BODY PRODUCED FROM MELT IN THE ARC FURNACE, ALUMINUM OXYDE-CONTAINING MELT, WITH REDUCED POROSITY AND / OR STAINING - Google Patents

Description

according to consumer wishes - between a lot further limits changeable than those of the stones, which practically only consist of aluminum oxide.

The unwanted constituents present in a melt containing aluminum oxide can cause the Be the cause of porosity, stratification and discoloration in the resulting product as well as the reason for annoying side effects - when using it - result. It is therefore Such processes are also known which use gas-generating additives to unite the entire melt Generate stirring gas stream.

The material of the cast stones containing aluminum oxide which is melted in the arc furnace in some cases The spongy-pore structure is transferred from the furnace electrodes into the melt Carbon content causes; the content of dissolved gas also still plays a role.

As a result of the possible differences between the carbon content and the aluminum oxide-containing melt Reactions, e.g. B .:

Al ₂ O ₃ + 3C ==== 2Al + 3CO CO 2 Al ₂ O ₃ + 9C ==== Al ₄ C ₃ ^ -6CO + 6CO Al ₂ O ₃ + Al ₄ C ₃ - 6Al + 3CO f 6CO 3 Al ₂ O ₃ + C = # = 2 (AlO • Al ₂ O ₃ ) + 6CO 8 Al ₂ O ₃ + 6C === (3 Al ₂ O • 5 Al ₂ O ₃ ) 6 Al ₂ O ₃ + 9C = S- (4 A1 ₂ O _; 3 Al ₄ C ₃ ) - 3 Al ₂ O ₃ + 9C = # = (Al ₂ O ₃ ■ Al ₄ C ₃ ) +

SiO ₂ + 2
SiO ₂ + C

=== Si + 2 CO

==? = SiO + CO

Those created in this way as well as those dissolved in the melt. Gases and vapors are cause of solidification Stone castings between the growing crystals in the melting phase bubbles, which cause the porosity of the cast stones. This porosity is for individual stone compositions characteristic and occurs as a coherent network of pores. Glass melt flow, slag and others Melts and solutions that come into contact with the porous stones usually penetrate quite a bit deep into the pore canals of this one. Because of the increased contact area between the porous Stone structure and the corrosive melt is an increased wear compared to stone dense structure detectable.

The invention, which is aimed at preventing the formation of a porous structure in aluminum oxide-containing, cast blocks is based on the following train of thought:

^{The oxygen-containing compound or a mixture of such compounds, which are reducing below 180O 0} C and which is largely reduced during the formation of reaction products volatile below 180O 0 C, or a mixture of such - appropriately the oxides of zinc, of cadmium , magnesium, lead, antimony or their aluminum oxide-containing compounds and / or their ^{inorganic or organic salts, heated up to 150O 0} C without residue, transforming into oxide and gaseous decomposition products - reduce or prevent the porosity of the structure of the aluminum oxide-containing molded bricks after sufficient exposure time, whereby their structural density and density increase.

On one melted in an electric arc furnace through the one made from carbon or graphite electrodes Alumina-containing melt contaminated with carbon content will be some when using the above-mentioned and, for example, selected oxidizing additives in possible reaction equations shown in the sequence:

gases and vapors are created inside the cast stones - until they are completely solidified. Similar reactions are also produced in the presence of those contaminating or otherwise adding to the clay Oxides possible, e.g. B .:

9 ZnO + Al ₄ C ₃
PbO + Sb ₂ O ₅ + 6 C

6 MgO + (3 Al ₂ O 5 Al ₂ O ₃ )
MgCO ₃ + 2 C
(MgC ₂ O ₄ · 2 H ₂ O) + C

9 ZnO + Al ₄ C ₃

9 Zn (steam)
+ 2 Al ₂ O ₃
+ 3 CO (gas)

Pb (steam)
+ 2 Sb (steam) + 6 CO (gas)

6 mg (steam)
+ 8 Al ₂ O ₃

==== Mg (steam)
+ 3 CO (gas)

===== Mg (steam)
+ CO ₂ (gas)
+ 2 CO (gas)
+ 2H ₂ O
(Steam)

===== 9 Zn (steam)
+ 2 Al ₂ O ₃
+ 3 CO (gas)

ZnSO ₄ + 4 (AlO · Al ₂ O ₃ ) =====

PbO + Sb ₂ O ₅ + 6 C

3 PbSO ₄ + 4 Al

Zn (steam)

+ 6 Al ₂ O ₃

+ SO ₂ (steam)

===== Pb (steam)
+ 2 Sb (steam) + 6 CO (gas)

===== 3 Pb (steam)
+ 2 Al ₂ O ₃
+ 3 SO ₂ (gas)

From the above equations it can be seen that various additions during their reduction the various forms of the from the electrodes of the electric arc furnace in the aluminum oxide-containing melt Effectively oxidize the charcoal. Some of the reaction products escape from the melt in gaseous state. The reducing effects created in the aluminum oxide-containing melt Melt products are also oxidized by the oxidizing additives - during their reduction.

As a result of the above and similar reactions, the carbon content of in the electric arc furnace molten oxide melts are reduced to the extent that the interaction with Aluminum oxide and other oxides occurring gas development fails. The requirement for one The gas-free state of the melt is the sufficient reduction in its carbon content. One sufficient reduction of the coal content occurs only after a corresponding period of exposure to the An oxidizing agent, because the last stage of the reaction becomes more and more sluggish.

The desired reduction in the coal

5 6

content causing exposure time of the oxy- (ZnO) - introduced and continuously melted, dationsmittel amounts to depending on the equal- 10 to 120 minutes. The safeguarding of the desired effect of the oxidation melting time of the oxidizing agent is - from 5 means 45 minutes to a 50 to 150 ° C above its task in the furnace - heated to about the melting point temperature.
10 mins. Although the dimensions are common in ovens. .

gen those present in the melt, due to the tempera- e ι s ρ ι e

differences in temperature and electrodynamic forces. In the melting tank of the arc furnace

If currents caused the distribution of the molten material to accelerate the uniformly mixed oxidizing agent in batches, further time is required _{for this - consisting of 78 parts by weight of alumina (Al 2} O _3). 6 parts by weight of sodium carbonate (Na ₂ CO ₃ ), 2 parts

By reducing the concentration of the active agent, additional components by weight from the rest also decrease the rate of reaction. The time required to achieve the desired level in magnesite (MgCO ₃ ) as an oxidizing agent - the reaction process involved - can therefore be quite long. brings. After the last meltdown has taken place, this period of time applies - due to the fact that the Möllerpartie, 3 parts by weight of melt are added for operational reasons in the furnace of zinc oxide (ZnO) for a longer period of time. After the meltdown has ended, the lingers - as secured. the latter, the melt is carried out and for the purpose

The reduction in the duration of action of the active 20 secure the effect of the oxidant 40 Mistoffes is only by increasing its concentration nutes to a temperature of 50 to 150 ⁰ C above but feasible, whereby a product completely melting point temperature heated. m

deviating type (spinel stone) can arise. . ■ λ λ

The implementation of the invention, in the example 4

Alumina-containing melt introduced and 25 into the melting tank of the electric arc furnace is a mixture evenly mixed after its oxidation effect - consisting of excess remaining in the _{molded stone material - 99.2 percent by weight of alumina (Al 2} O ₃ ) and 0.8 Gezelner additives - reduce to the Weight of the weight percent lead acetate (Pb / CH ₃ COO / ₂ ■ 3 H ₂ O) - · based on cast stones - also in proportionately introduced and continuously melted down. After small quantities of the last batch of batches melted down beyond the level that was brought about, there is a decrease in porosity, the attack on the stones caused by the melt for the purpose of rapid mixing of the small iron oxide melts. Lead acetate additive and to ensure its effect. In the following we shall lay down the invention. After that it becomes the most effective possible

such examples represent the generation of mold- removal of its remaining excess the stones from alumina-containing melts by means of 35 melt, from the time the last one was added illustrate the method according to the invention. Möllerpartie counted, 45 minutes on one

. . with 50 to 150 ⁰ C above the melting point

^{B e 1 s} P ^{1 e [J} temperature heated.

In 3000 kg one produced in an electric arc furnace. -rc

Melt whose analytically determined composition 40 e 1 s ρ 1 e 1

Settlement 94 percent by weight Al ₂ O ₃ , 5 percent by weight in the melting tank of the electric arc furnace

Na ₂ O and 1 percent by weight of other constituents, in parts 300 kg of alumina (Al ₂ O ₃ ) are introduced and held, are continuously melted down by sprinkling on the surface of the; carried hereinafter - ■ scattered in 1 to melt the like, based on the weight of the latter, 0.5 ° / ₀ 2 cm thick layer on the melt surface ™ (ie, 15 kg) of lead sulfate _(PbSO4) as Oxidant 45 - the Addition of 700 kg of a uniformly entered. After the lead-mixed mixture, consisting of 384 kg of zinc sulfate additive, has been melted down, the melt in the furnace is oxide (ZnO), 276 kg of alumina (Al ₂ O ₃ ), 17 kg of pure and to ensure the effectiveness of the quartz sand and 23 kg of sodium carbonate (Na ₂ CO ₃ ). Oxidizing agent for 50 minutes on a 50 to then the melt - for the purpose of securing the

150 ⁰ C above the melting point temperature 50 Effect of the oxidizing agent - heated by the addition. counting from the last batch of batches, 10 minutes

During the duration of the melting, the graphite electrodes may be heated to a temperature that is ^{50 to 150 ° C. above the melting point in all examples listed for a long time.}
Do not immerse the arc furnace in the melt, _R. . ,

but only at a short distance above their upper 55 B e 1 s ρ 1 e 1 0

area can be adjusted. This causes the through into the melting tank of the arc furnace

the oxidizing agent introduced into the melt initially in batches prevents a uniformly mixed caused - ■ useless excess electrode consumption - mixture - consisting of 63 parts by weight of alumina. (Al ₂ O ₃ ), 26 parts by weight of magnesium oxide (MgO) -

B is π ie 1 2 ^{6o em} g ^etra S ^{en UQ} d continuously melted down. After this

The last batch of batches is still being melted down

A mixture of 7 parts by weight of alumina (Al ₂ O ₃ ) and 6 parts by weight of zinc oxide (ZnO) are added to the furnace _{- consisting of 68 parts by weight of alumina (Al 2} O _3). From the time the 24 parts by weight of quartz sand has been melted with at least 99.5 _{parts by weight of the latter mixture, weight percent SiO 2} content, 1 part by weight additional to ensure the effectiveness of the oxidizing agent, the constituents from the remaining mixture components melt for 15 minutes at a temperature and heated as oxidizing agent 7 parts by weight of zinc oxide 50 to 150 ⁰ C above the melting point.

In all of the above-described exemplary embodiments - on cast aluminum oxide-containing Stones of known composition - the most expedient types of application of an oxidizing Addition set out according to the invention.

This method according to the invention enables the porosity, which greatly reduces the durability of the cast, refractory bricks, to be reduced to a tolerable level and / or the discoloration thereof caused by reducing substances to be eliminated. The reduction in porosity and the reduction in the intensity of the discoloration of the stones caused by the presence of reducing substances not only extends their useful life, but also gives rise to other advantages. So z. B. cause the reducing impurities getting into the glass flow through the formation of bubbles. The occurrence of rejects due to such glass defects does not occur when using tub blocks according to the invention.
The chemical resistance of the stones to individual substances can also be increased if the circumstances in which the stones are to be used are also taken into account when selecting the appropriate oxidizing agent.

ίο The reduction in the discoloration of individual corundum products (Abrasives) improve their quality and usability.

The above examples only serve to illustrate the method according to the invention in more detail; it is However, it should be noted in this regard that the field of application of the invention is not limited by this.

209523/386

Claims (1)

taking used material of furnace construction. As their patent claims: Areas of application apply: construction as well as Lining material in industrial furnaces with high 1. Process for producing one from in the internal temperature. Arc furnace of molten aluminum oxide 5 Especially as the inner lining of molten glass Melt-produced body with furnace is one that is chemically less resistant to the flow of glass melt Porosity and / or discoloration due to furnace construction material which is in contact with it especially to reduce their content of outstanding molten glass not contaminated, advantageous, elementary carbon from the furnace electrodes The higher internal temperature required in high-performance furnaces or the temperature caused by the action between coal and io determines the further development of the Aluminum oxide-containing melt also resulted in desirable properties of furnace linings Reaction products, thereby materials. To increase the fire resistance in indicates that additives have been added to the furnace lining materials for from 10 to 20 minutes Long-acting, none must be mixed in the melt, with the substance of the furnace lining Additive in an amount of 0.5 to 15 stones, thin liquid that occurs at operating temperature 44 percent by weight on the aluminum oxide-containing melt with a viscosity similar to glass flux. Melt-based, appropriately oxygen-containing This condition corresponds to z. B. a predominantly off Compounds of cadmium, lead, antimony and corundum and spinel crystals built up over zinc and / or their mixture is introduced. mainly made of molten aluminum oxide 2. The method according to claim 1, characterized in that - with 2 to 10% MgO content · - drawn that the even distribution of the cast, highly refractory substance (USA.-Patent 2 019 208 - oxygen-containing additive by stirring before from 1933 ). % Start of the exposure period is secured. The use of aluminum 3. The method according to claim 1 or 2, characterized in that the oxide-containing, cast bricks in up to 1300 ⁰ C, that the oxygen-containing additional 25 heated preheating, forging and pusher furnaces as the material in the production of the aluminiumoxydhalti- material of the furnace base; in the latter, the mixture used in the melt can be added in the desired form bricks as components of the pusher-furnace rails vertem ratio. be turned. Generally increases at higher levels 4. The method according to claim 1 or 2, characterized in that the reactivity of the refractory temperatures, the total amount of 30 bricks compared to the various, oxygen-containing additive in the furnaces at once in the input materials. In all these desired proportions in the aluminum oxide cases, the melt contained on the surface of the steel blocks is introduced. standing iron oxides (FeO, Fe ₃ O ₄ and Fe ₂ O ₃ ) 5. The method according to claim 1 or 2, thereby causing a rapid destruction of the aluminiumoxydgekennzeich.net, that the oxygen-containing additive- 35 containing stones. It should therefore improve the fire resistance of the Substance in several parts and in the desired stones by their melting point increasing additives Weight ratio in the alumina can be improved. This goal was achieved by the EntSmmelze is introduced. winding of the MgO-rich stones achieved. It is considered 6. The method according to claim 1 or 2 and 3 or known that the resistance to certain chemi-4 or 5, characterized in that in the 40 see attacks and the fire resistance of aluminum melt different, oxygen-containing additional oxide-containing stones with higher, advertising inserted in the direction of the rising MgO thermodynamic efficiency additive and the higher temperature - - 25 to 45 ° / ₀ materials in order of increasing MgO content increases the like. (Spinel stones). The thermal shock resistance of Alu- ^ 7. The method according to claim 6, characterized in 45 miniumoxydsteinen with a higher MgO content is im draws that in a melt, which is also magne- general · - because of the MgO content siumoxide contains, nor one or more acid-induced strong increases in thermal expansion substances Zinc compound (s) added value - quite unfavorable. (will). To extend the oven trips as well as for the purpose of 8. The method according to claim 6, characterized in 50 increasing the resistance to very different, shows that the oxidizing agents in the demands occurring in industrial furnaces (high Shape of their with others, preferably in temperature, erosion, chemical agents, ab-stone material Even existing oxides formed, heat shocks, etc.) were made by the producers th connections are introduced. refractory bricks within the last 30 years 55 numerous, quite different in their composition, cast stones containing alumina developed. To meet the requirements for the various stones containing aluminum oxide The invention is a method of reducing 60 operational demands to create and right the porosity and / or discoloration of one out of different desires in terms of quality Electric arc furnace to meet molten, alumina-containing, the introduction of various Melt produced body. Add additives to the aluminum oxide-containing melt. The whipped produced from molten alumina. The most commonly used additives are: Due to their high melting point, cast stones are SiO ₂ , Na ₂ O, Cr ₂ O ₃ , ZrO ₂ , B ₂ O ₃ , MgO and TiO ₂ . point of their substance, because of their great strength The properties of the additives mentioned and their resistance to abrasion and to holding alumina-containing stones are through the attack by high-temperature melts an additional - the appropriate selection of the former - the