DE1471452A1 - Process for the treatment of refractory materials - Google Patents

Description

Homburg-Aitona

.J * ll ** - Ub «r-Stra6 · 21 Succeeded in disclosure

File number P 1471 452.4

Applicant: SHINAGAWA I ¹ IKE BRICK CO., LTD.

New Ohtemachi Bldg., No. 4, 2-chome, Ohtemachi, Chiyoda-ku, Tokyo, Japan

Process for the treatment of refractory materials

The invention relates to a method of treatment Refractory materials made of magnesia, magnesia-chromium, silica, alumina, silica-alumina and zircon, which are impregnated be provided with a chromium oxide precipitate.

The term refractory materials means prefabricated, i.e. already finished refractory bricks and other refractory items that have been annealed. ™

In general, annealed refractory bricks and the like have gates that can be used in both closed and closed spaces be in an open form. These pores are harmful in that they cause the brick to corrode. Comes namely the refractory brick with a liquid phase, such as molten steel slag or molten steel, in contact, then this penetrates into the pores of the brick.

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As a result, the refractory brick is considerably corroded, and it is formed by the expansion and contraction of the brick Hoists that reduce its strength considerably at high temperatures.

Attempts have already been made to reduce the pores in refractory materials by regulating the particle size, Heating to high temperatures and the addition of binders, however, could achieve satisfactory results can hardly be achieved. If the proportion of pores is reduced too much, the resistance to temperature changes will also decrease degraded.

A cast brick made by melting refractories at high temperatures in an electric furnace shows although it is a favorable reduction in the proportion of lorries, it is very expensive to manufacture and, moreover, has only one low resistance to temperature changes.

It is also already known to reduce the proportion of pores in refractory bricks in that aie brick with impregnated with a fire-resistant fabric. For example refractory bricks made in one of the usual processes impregnated with tar, so that-coal as Precipitation is deposited, which, however, burns in an oxidizable atmosphere, whereby the scope of application is severely restricted. It has also been proposed to use a refractory manufactured by the usual method Impregnate bricks with an aqueous α-chroic acid solution. The high toxicity of chromic acid leads to aeren a

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used in the industrial manufacture of refractory bricks to great dangers.

The inventor has now found that refractory Substances with a low percentage of pores, high mass density and long service life can be obtained by the fact that these Substances impregnated with one of the following compounds, such as ammonium, magnesium, potassium and sodium chromate and dichromate and then this compound is decomposed to chromium (III) oxide under the action of heat.

For a treatment according to the method according to the invention Suitable refractories are those made from magnesia, magnesia-chromium, silica, alumina, silica-alumina as well Zircon made.

The impregnation of refractories with one of the above-mentioned compounds can be carried out in such a way that either the refractory object is immersed in an aqueous solution of this compound or the aqueous solution under it Pressure or by boiling is forcibly introduced into the refractory article. Here the connection can take place in aqueous solution can also be used in the molten state.

According to one implementation of the method according to the invention is an aqueous ammonium dichromate solution under reduced pressure at normal temperature forcibly introduced into a prefabricated refractory brick, this one then dried at a temperature of 100 to 150 ° C and

then at a temperature of 300 to 400 ° C until decomposition of ammonium dichromate heated. The reaction in this case is represented by the following formula:

(NH ₄ ) ₂ Cr ₂ 0 ₇ Cr ₂ O ₃ + N _{2 +} 4H ₂ O (I)

According to another embodiment of the invention In the process, an aqueous potassium dichromate solution is forced into a prefabricated refractory brick and this then at a temperature of 400 to 500 ° C in a reducible atmosphere until decomposition of potassium dichromate heated. The reaction is represented here by the following formula:

K ₂ Cr ₂ O ₇ + 20 ν ^Cr 2 ° 3 + ^Κ 2 ⁰⁰ 3 ^{+ G0} ^ ¹¹ ^

According to a further embodiment of the invention ^ mass procedure is a mixture of theoretical quantities aqueous potassium dichromate solution and aqueous ammonium chloride solution at room temperature in a prefabricated refractory Bricks are introduced, this is trocitnet and then at a temperature of 400 to 500 ° C until it decomposes heated by sodium dichromate. The reaction will be in this Case represented by the following formula:

Na ₂ Cr ₂ O ₇ + NH ₄ CI ^ Cr ₃ O ₅ + 2NaCl + N ₃₊ 4H ₃ O (II3J

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According to a further embodiment of the invention In the process, a basic refractory brick is impregnated with an aqueous magnesium chromate solution and then exposed to a temperature of 700 to 800 ° 0. The reaction is shown here by the following formula »

2MgCrO ₄ Or ₂ O ₃ + 2MgO +
^

In this case, the formation of Or ₂ O, MgO and for the \ W basic brick very favorable.

The chromium (III) oxide, which is deposited in the pores as described above, differs from the odorous oxide which is used in the refractory material
Chromite ore is contained has considerable activity and its melting point is over 2200 ° 0, so that its fire resistance is excellent. ·

In refractory magnesia and magnesia tubing bricks, the precipitated chromium (III) oxide can easily be made to react with _Λ Reaction with iron oxide, so that a
brinell (FeO.Or ₂ O,), which counteracts the penetration of a liquid phase in the bricks to a high degree and thus increases the brick's resistance to corrosion.

The method according to the invention is suitable for refractory basic bricks, such as magnesia and Magneaiachrome bricks, for silica bricks, for alumina bricks, ittr
oilica clay bricks and for zirconium bricks, because there
is oxide neutral.

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The method according to the invention can be used once or repeatedly. The amount of chromium (III) oxide precipitate can be regulated by the number of impregnations. The achievable in one application of the inventive traversed amount of deposited chromium (III) -oxyd is in a fired Magneaiaziegel 1.4 wt. I "with a pore ratio of 15 $ 1.9 wt. $ With a pore ratio of 2Ο5έ and 2, 8 wt. # With a porosity of $ 50.

W The non-refractory substances formed during the decomposition of chromate and bichromate, such as potassium carbonate and sodium chloride in the above reaction formulas (II) and (III), can be easily removed from the brick by washing.

The deposition of chromium (III) oxide is preferred carried out within the entire brick, but can also only done on the surface within an outer layer of 10 to 20 mm thickness.

^ The present invention is now intended to follow

The following examples are explained in more detail without wishing to restrict the scope of the invention thereby. Example 1

A fused magnesia brick made by any of the conventional methods was placed in a vacuum impregnation apparatus given that for 30 minutes on a reduced pressure of 20 mmHg. was held. Then an aqueous 40 ^ ige Magneeiumchromatlöeung supplied and the brick with this

^: impregnated. The ao impregnated brick was

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temperature of 100 ° C and then dried in a heating oven at a temperature of 700 to 800 ° C until complete Decomposition of magnesium chromate into chromium (III) oxide and Magnesium oxide heated. The Qhrom (III) oxide and the magnesium oxide were evenly distributed in the pores of the brick.

The physical and chemical properties of a brick treated once in this way compared to an untreated one Bricks are shown in Table 1 below.

Table 1

brick treated f% untreated impregnated amount At 165O ° C Or ₂ O ₃ (*) 2.0 not softened 0 Porosity (? S) 16.3 19.5 barrel density « 2.89 6 mm 2.79 Compressive strength (kg / om) 650 640 Softening point 0.5 mm (max.) under load Tp 1535 ⁰ O (2 kg / om ² ) Corroion test with smack «1 9 mm [Corrosion test with attall.iron · 2 3 - 5 mm

• 1 corrosion depth at. Exposure of hearth furnace slag for 6 hours at a temperature of 1600 ⁹ O in a small electric rotary furnace.

«2 Sohiohtdiefe the brick up to the one reaction with Iron took place, ale 15 g of iron in a 20x20X20 mm crucible formed from bricks at a

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Temperature of 1500 ⁰ C were heated for two hours in an oxidizable atmosphere. .

The above table clearly shows the effectiveness of the chromium (III) oxide lower floor in terms of a reduction in porosity and an increase in bulk density, as well as the superiority of the treated brick compared to the untreated brick in terms of corrosion resistance, with iron penetration into the brick being significant Mas.se cannot be determined.
Example 2

An alumina brick manufactured by one of the customary methods was used in the apparatus mentioned in Example 1 treated with an aqueous 40% ammonium dichromate solution, then at a temperature of 300 to 320 ° C until complete Decomposition of ammonium dichromate heated. The ammonium dichromate turned into green (or dark green) chromium (III) oxide converted, which was uniformly distributed in the pores of the brick.

The following table 2 shows the physical and chemical properties of one of the treatments described here twice subjected brick compared to one here untreated Brick.

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Table 2

brick treated untreated [impregnated amount
IL / X nV / 7 \ r ° J 4.8 0 porosity 21.6 25.7 ! Seating density 2.84 2.62 \ Compressive strength
| (kg / om ^z ) 655 640 corrosion test
bit slag ♦! 4 mm 16 mm j

* 1 corrosion depth for 5 hours exposure to hearth furnace slag with a temperature of 1600 ⁰ C in a small rotary electric furnace.
Example 3

A manufactured in a conventional manner silica-alumina brick was? & Kaliumbiohromatlö aqueous watered with a mixture of 50 ^ 45 ^ and ung aqueous Natriumbichromatlösung and then heated in .One reducing atmosphere at a temperature of 400 to 500 ⁰ C. Potassium dichromate and sodium dichromate were decomposed into chromium (III) oxide as well as potassium and sodium carbonate. The potassium and sodium carbonate formed were then waxed out.

The results of the corrosion tests with Sohlaoke and metallic Iron for treated and untreated bricks that are im

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Meaning of the note to Table 1 ssu are to be understood, shows the following table 3.

Table 3

brick treated untreated corrosion test with
Sohlacke (1500 ° E / 2 hours)
iorroeionstest with
netall. iron
(1600 ° 0/1 hour) 13 mm
5 mm 30 mm
20 mm

Example 4

A magnesia-chrome brick produced in the usual way was poured with an aqueous 60% ammonium chromate solution and initially heated until the ammonium chromate decomposed in ammonium dichromate and ammonia. The tile was then heated again, until the decomposition of ammonium bichromate to green chromium (IIl) -oxyd at a temperature of 300 to 32O ⁰ C.

The results obtained essentially corresponded to those given in Example 1.
Example 5

A zirconium brick made by a conventional process was treated with an aqueous 50% ammonium dichromate solution watered and then at a temperature of 300 to 320 until the decomposition of ammonium dichromate to chromium (III) oxide heated.

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The zirconium brick treated in this way was used as a nozzle in the corrosion test and then showed a corrosion depth of about 0.5 mm, while an untreated zirconium brick had a corrosion depth of about 5 mm untreated brick Example 6

Example 2 was repeated using a silica brick in place of the alumina brick.

The following! Table 4 shows the physical and chemise The properties of a silica brick once subjected to the treatment described above in comparison with one Untreated brick,

Table 4

brick treated untreated impregnated Meng "
torgO, ^) 2.6 0 porosity (j6) 19.5 21.0 «Aesendiohte 1.95 1.85 pruokfestigkait (kg / om ² ) 155 160 Compressive strength under "
Exposure to heat (kg / cm
ι 1400 ⁵ O) 46 38 torrosion test / aohlaoke
(1600 0/3 hours «) 8 on 12 mm iorrosloneteat / Eieen
(1500 ° E / 2 hours) 1.5 au » 7 mm

Example 7

Particles were of a size in mm of magnesia 1-3 immersed in an aqueous 40? £ strength Magnesiumchromatlösung, then boiled for 60 minutes, then dried and exposed to a temperature of 700 to 800 ⁰ C. The magnesium chromate was decomposed and settled in the pores of the magnesia clinker as chromium (III) oxide and magnesium oxide.

The physical properties of the treated magnesia clinker in comparison with untreated magnesia clinker are shown in Table 5 below.

Table 5

Magnesia clinker treated untuned Water absorption
W. 5.5 7.0 Porosity ($) 16.4 20.2 Mas «final 2.99 2.90 Apparent density 3.59 3.64

From the treated magnesia clinker vvurae according to a conventional one Method made of a magnesia brick. The physical properties of the brick thus obtained show uie following table 6.

Table 6

Magnesia brick ^T 1
^T 2
3 from treated
Magnesia clinker from untreated
Magnesia clinker Porosity (56) Hours.) 11.1 10.0 Mass density 2.93 2.93 Compressive strength
(kg / onr) 620 600 Softening point [
under load V
(2 kg / cm2) J. 1576 ⁰ C
166O ⁰ C
towards HOO ⁰ C
1494 ⁰ C
1608 ⁰ C Corrosion test /
Slag (1600 C / 6 11 mm 19 πιπί

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Claims (6)

1 · Process for the treatment of refractory materials, characterized in that open pore-proof refractories Substances with a compound such as ammonium, magnesium, or potassium Sodium chromate or dichromate impregnated and then two decomposition of this compound to form chromium (III) oxide Be subjected to heat treatment. 2. The method according to claim 1, characterized in that the refractory materials are prefabricated refractories Brick bind. 35. The method according to claim 1, characterized in that the refractory materials are already annealed Refractories are involved. 4. The method according to claim 2 or 3f, characterized in that that the prefabricated bricks or the fire- solid substances made of magnesia, magnesia-chromium, silica, alumina, silicon-alumina and zircon are made. 5. The method naoh claim 1, characterized in that a prefabricated magnesia brick with magnesium chromate impregnated and then used to decompose the magnesium chromate is subjected to a heat treatment to form chromium (HI) oxide. 6. The method according to Patentanapruoh 1, daduroh characterized, that a prefabricated alumina brick is impregnated with ammonium dichromate and then to decompose the ammonium biohromatB to Uhrom (III) oxide is subjected to a heat treatment. 809901/0682 New U.it-laj.-n _: ..t-; iAt «, 2N-.ic *