DE2011805B2 - Process for the production of refractory magnesia chromite and chromite magnesia bricks - Google Patents

Description

The invention relates to a method for the production of refractory magnesia chromite and chromite magnesia bricks from a sintered material that is produced by burning together chromium oxide-containing substances and magnesite or other natural or synthetic magnesium compounds that are present in the fire Deliver periclase, was obtained.

Processes of this type are already known in large numbers. In one of these known processes, chromium oxide-containing substances, in particular chrome ore, are mixed with magnesite, optionally sintered magnesite, or other natural or synthetic magnesium compounds that produce magnesium oxide during firing and, preferably after shaping into briquettes or stones, at temperatures of at least 1700 ⁰ C sintered without melting, whereupon this sintered material, which is usually referred to as simultaneous sintering, is granulated and, if necessary after the addition of sintered magnesite, is shaped into stones. The characteristic of this procedure consists in the combination of measures that

a) for the production of the sintered material, the chromium oxide-containing substances have a grain size of 0 to 6 mm, preferably 0 to 4 mm,

at least 65%, preferably at least 80% of the chromium oxide-containing substances in a grain size of more than 0.12 mm are present,

b) whereas the magnesite or the magnesium oxide supplying substances have a grain size below 0.12 mm, preferably at most 0.10 mm, and

c) the sintered material has a silica content of at most 5.5%, preferably 4.5%, and

d) has a lime-silica ratio of at most 0.6, preferably at most 0.35.

In another prior art method using a simultaneous sintering material is used to manufacture unfired, refractory bricks and masses from magnesia achromite and chromite magnesia the set for the production of the sintered material to a molar lime-silica ratio of at most 0.6, preferably at most 0.35, and a silica content of the sintered material of at most 5.5%, preferably at most 4.5%. In the on the two The sintered materials obtained and also in the stones obtained from them are the listed ways Periclast particles bound directly to the chromium oxide-containing particles, and there is thus a so-called direct bond.

It has now been found that when using starting materials with low silica contents for the production of the simultaneous sintering material with simultaneous use of the chromium oxide-containing Substances in certain grain sizes Magnesate chromite and chromite magnesite stones with a direct Binding can also be obtained with molar lime-silica ratios above 0.6, which compared to the known stones made of simultaneous sintering material has an increased resistance against slag migration and in particular an infiltration of CoO-rich slags.

Accordingly, the invention relates to a method for the production of refractory magnesia chromite and Chromite magnesia stones, with chromium oxide-containing substances, in particular chrome ore, in one grain size from 0 to a maximum of 6 mm, preferably a maximum of 4 mm, with fine-grained magnesite, if necessary Sintered magnesia, or other fine-grained, natural or synthetic pericals that form when fired Magnesium compounds with a grain size of less than 0.20 mm, preferably not more than 0.12 mm, which, based on the fired state, contain less than 95%, suitably less than 93%, MgO, mixed and, preferably after shaping into briquettes or stones, at temperatures

20 805

of at least 1750 ° C, expediently at least 1850 ° C, are sintered without melting and then this sintered material, which has a content of 5 to 40 ⁰ Zo, in particular 20 to 30%, Cr ₉ O ₃ , granulated and, optionally after the addition of Sintered magnesia, being shaped into stones. The essence of this procedure is that

a) for the production of the sintered material at least 20 ⁰ Zo, at most 80 ⁰ Zo, the chromium oxide-containing substances have a grain size of less than 0.12 mm,

b) the sintered material has a silica ^{content of at most 2.5 0} Zo, a lime content of at most 4 ⁰ Zo and

c) has a molar lime-silica ratio of over 0.6 to 2.5.

With regard to feature a) it should be noted that to fulfill it under certain circumstances, e.g. B. when using a fraction of chromite or other chromium oxide-containing substances from 0 to 2 or 0 to 4 mm, plus z. B Chrome ore flour from. must be added below 0.12 mm.

Preferably, the sintered material should have a silica content of at most 1.5 ⁰ O.

If sintered magnesia is added to the granular sintered material for the production of refractory bricks, such an addition is made in amounts of at most 35 ⁰ zo, based on the refractory mixture. When producing unfired sieves using magnesium sulfate as a binding agent, only limited amounts of fine-grained sintered magnesia are allowed in the sintered material, namely at most 8 ⁰ Zo, preferably 3 to 5 ⁰ Zo, based on the refractory mixture, sintered magnesia with a grain size of at most 0.12 mm can be added. Any sintered magnesia that is also added must have a grain size of over 0.12 mm.

The invention is explained in more detail using the following examples:

example 1

72 ⁰ Zo magnesite with a core size of 0 to 0.12 mm was mixed with 28 ⁰ Zo chromium ore concentrate from 0 to 1 mm, 20 ⁰ Zo flue dust produced by burning magnesite, hereinafter referred to as "flue dust" for short, and 4 ⁰ Zo saturated kieserite solution mixed, and the mixture was formed into briquettes, which were fired at 1850 ° C for about 3 hours in a rotary or shaft furnace.

The composition of the raw materials and the simultaneous sinter obtained were as follows (the abbreviation »CZS« means the lime-silicic acid weight ratio):

Ma Chrome ore Simultaneously gnesite concentrate sinter ( ⁰ Zo) ( ⁰ Zo) SiO ₀ 0.02 1.89 1.01 ⁰ zo Fe ₂ O., 2.99 15.44 10.16 ⁰ zo Al ₂ Oi, 0.57 14.01 6.62 ° / o Cr ₂ Ol, 0.00 53.94 24.70 ⁰ zo CaO 0.57 0.07 0.84 per cent MgO 44.85 14.65 56.67 ⁰ zo Loss on ignition 51.00 + 0.16 + 0.04 ⁰ zo CZS 0.83 Kornraiimeewicht 3.38 gZcm ³

The sintered material was crushed and ground, and ⁰ mm 67 Zo of this material with a grain size of 0.3 to 3 and 33 ⁰ Z _n having a particle size between 0 and 0.12 mm were added I ⁰ Zo treckener sulfite waste liquor and 1, 6 ⁰ Zo water formed into stones, which after the fire at 1580 ° C had the following properties:

Volume weight (RG) 3.23 gZcm ³

ίο porosity 16.2 ⁰ Zo

Cold compressive strength (KDF) 490 kpZcm ²

Pressure fire resistance (DFB) to 1535 ° C

ta 1675 ° C

eat> 1700 ° C

Sunk 0.9 ⁰ zo

Hot Flexural Strength (HBF) at

126O ⁰ C 120kpZcm ²

B e i s ρ i e 1 2

72 ⁰ Zo magnesite with a grain size of 0 to 0.12 mm were ^{mixed with 28 0} Zo chrome ore concentrate from 0 to 0.5 mm, 20 ⁰ Zo flue dust and 4 ⁰ Zo saturated kieserite solution, and the mixture was shaped into briquettes, which at 2000 ° C for about 3 hours in a rotary or shaft furnace. The starting materials and the sintered material obtained had the following composition:

Ma Chrome ore Simultaneously gnesite concentrate sinter ( ⁰ Zo) C / o) SiO ₂ 0.05 1.03 0.97 ⁰ zo Fe ₂ O ₃ 2.61 28.80 17.24 ⁰ zo AI.O, 0.20 17.65 9.52 ⁰ zo Cr ₂ O ₃ 0.00 45.95 25.40 ⁰ Zo CaO 1.35 0.06 1.29 ⁰ zo MgO 45.79 6.51 45.58 ° / o Loss on ignition 50.00 + 1.67 + 0.14 ⁰ zo CZS 1.33 Grain density 3.38 g / cm ³

Mm from a mixture of 67 ⁰ Zo of the sintered material in a grain size of 0.3 to 3, 33 ° / o of the sintered material with a grain size of 0 mm to 12, 1.1 ° / o dry sulfite waste liquor and l, 8 ° / o Stones were formed in water and burned at 1560 ° C.

The properties of the stones obtained were as follows:

RG 3.25 g / cm ³

Porosity 18.2 ⁰ zo

KDF 461 kpZcm ²

DFBio 1475 ⁰ C

ta 171O ⁰ C

t " > 1720 ° C

Decreased 0.6 per cent

HBF at 1260 ° C 94 kpZcm *

Example 3

72 ⁰ zo of magnesite with a grain size of 0 to 0.12 mm were mixed with 28% chrome ore concentrate from 0 to 0.12 mm

0.5 mm, 18% fly ash and 4% saturated kieserite solution mixed and the mixture became briquettes deformed, which were fired at 2150 ° C for about 3 hours in a shaft furnace.

The composition of the raw materials and the sintered material obtained were as follows:

Ma Chrome ore Simultaneously gnesite concentrate sinter (%) (Vo) SiO ₂ 0.18 0.65 0.48 ° / o Fe, O, 1.84 18.20 10.28 ° / o Αφ ", 0.11 12.70 5.85 ° / o CuO \ 0.00 55.04 24.75 ° / o Cab ' 0.80 0.07 0.94% MgO 45.67 13.12 57.70 ⁰ zo Loss on ignition 51.40 0.22 0.00 », Ό C / S 1.96 KRG 3,4OgZCm ³

A mixture of 67% sintered material from 0.3 to 3 mm, 33% sintered material from 0 to 0.12 mm, 1% dry sulphite waste liquor and 1.8% water were formed into stones that were burned at 1580 ° C. These stones had the following properties:

RG 3.20 g / cm '

Porosity 17.0%

KDF 518kp / cm ²

DFB t _B > 1700 ° C

Decreased 0.4%

HBF at 1260 ° C 102 kp / cm ²

Example 4

72% magnesite from 0 to 0.12 mm was mixed with 28% chrome ore from 0 to 4 mm, 20% fly ash and 4% saturated kieserite solution were mixed, and the mixture was formed into briquettes, which at 1950 ° C were fired in a rotary or shaft furnace for about 3 hours.

The composition of the raw materials and the simultaneous sintering material were as follows:

Ma Chrome ore Simultaneously gnesite concentrate sinter (Vo) C / o) SiO " 0.18 1.72 0.91% Fe "Ö, 1.84 15.96 8.76% AUO ₁ 0.11 12.94 5.31% cr; o _s 0.00 55.54 22.30% CaO 0.45 0.19 0.63% MgO 45.87 13.65 62.09% Loss on ignition 51.55 - 0.23 0.00% C / S 0.69 Grain density 3.40 g cm ³

The sintered material was crushed and milled, and 67% of this material mm with a grain size of 0.3 to 3 and 33% a grain size between 0 and 0.12 mm were marked "on 1% dry spent sulfite liquor and 1.5 ⁰ Zo water deformed into stones that were fired at 1580 ° C and then had the following properties:

RG 3.18g'cm3

Porosity 17.2%

KDF 50? kp'cm ²

DFBfß> 1700'C

Decreased 0.4%

HBF at 1260 ° C 98 kn c ™ ²

Example 5

72% magnesite with a grain size of 0 to 0.12 mm were made with 28% chrome ore from 0 to 4 mm. 20% fly dust and 4% saturated kieserite solution mixed, and the mixture was shaped into briquettes, which were stored at 2050 ° C in a rotary or shaft furnace were burned for about 3 hours.

The starting materials and the SimuHan ^ ntermaterinl had the following composition:

Ma- Chrome Ore- Simuiian-

gnesite concentrate sinter ( ⁰ O) ("O)

0.15 2.84 1.08%

Fe _n O ₃ 2.40 14.68 8.30%

AKO ₃ 0.45 9.63 3.97%

CnA, 0.00 54.50 19.08%

Cab '1.15 0.15 1.71%

MgO 44.85 16.55 65.45%

Loss on ignition 51.00 1.65 0.41 ". C / S 1.59 Grain density 3.39 g / cm ³

From a mixture of 67% of the sintered material with a grain size of 0.3 to 3 mm, 33% of the sintered material a grain size of 0 to 0.12 mm, 1% dry sulphite waste liquor and 1.6% water Stones shaped and fired at 1570 ° C. These stones had the following properties:

RG 3.19 g / _cm s

Porosity 17.5%

KDF 528 kp'cm =

DFBr _n > 1700 ° C

Decreased 0.4%

HBF at 1260 ° C 98 kp.'cm *

Example 6

72% magnesite with a grain size of 0 to 0.12 mm from the composition given in Example 5 were mixed with 28% chromium ore from 0 to 4 mm from the analysis given in Example 4, 20 ⁰ Zn fly ash and 4% saturated kieserite solution, and the mixture was formed into briquettes which were about fired for 3 hours at 2000 C ⁿ in a rotary or shaft furnace.

The obtained sintered material was crushed and ground; 67% of this material with a grain size of 0.3 to 3 mm and 28% of a grain size of 0 to 0.12 mm were mixed with 5% sintered magnesia powder with a grain size of 0 to 0.12 mm with the addition of 0.63% boric acid, 0 mixed 5% dry spent sulfite liquor and 2.0% magnesium sulfate solution of 29 ° to 30 ° be and deformed to stones which were dried at 180 ⁰ C.

The composition of the sinler material and the sintered magnesia powder added thereto were as follows:

The shafts obtained:

Stones had the following properties

Simultaneous sintering of sintered magnesia

Fe "Ö ₃ AlA Cr _n O ₃

CaO '

Grain density

0.73%

8.74 "Vo

4.14 ", O 16.65%>

1.73 "/ o 68.01" / o

2.37

3.40 g / cm »

2.4 3.8 0.6 0.0 1.8 91.4

RG 3.08g / cm3

Porosity 11.8 ⁰ zo

KDF 654 kgf / cm ²

Inter-zone strength (ZZF)

after fire at 800 ° C 225 kp / cm ²

ZZF after fire at 1000 ° C ... 305 kp / cm ²

KDF after tunnel furnace fire .... 578 kp / cm ²

DFBr _{/ f} > 1700 ° C

Sunk O ⁰ Zo

HBF at 1260 ° C 103 kp / cm ^:

Claims (4)

Patent claims: 1. A process for the production of refractory magnesia achromate and chromium magnesia bricks, whereby chromium oxide-containing substances, in particular chromium ore, in a grain size of 0 to a maximum of 6 mm, preferably a maximum of 4 mm, with finer-grain magnesite, optionally sintered magnesia or other finer-grain, natural or synthetic, during firing Periclase-forming magnesium compounds with a grain size of less than 0.20 mm, preferably not more than 0.12 mm, which, based on the fired state, contain less than 95 * 70, advantageously less than 93% MgO, mixed and, preferably after deformation into briquettes or Stones, % ei temperatures of at least 175O ⁰ C, eweckmälüji at least 185O ⁰ C, are sintered without smelting and then this sinter material, which has a content of S to 40%, in particular 20 to 30% Cr ₂ O ₃ , granulated and, if necessary after the addition of sintered magnesia, the stones are made, so I knew η et that a) for the production of the sintered material at least 20%, at most 80% of the chromium oxide-containing Substances have a grain size of less than 0.12 mm, b) the sintered material has a silica content of at most 2.5% and a lime content of a maximum of 4% and c) has a molar lime-silica ratio of over 0.6 to 2.5. 2. The method according to claim 1, characterized in that that the sintered material has a silica content of at most 1.5%. 3. The method according to claim 1 or 2, characterized in that the chromium oxide-containing substances have a grain size of 0 to a maximum of 2 mm. 4. The method according to any one of claims 1 to 3, characterized in that the grained Sintered material at most 35%> Sintered magnesia, be added to the refractory mixture. !>. Method according to claim 4, characterized in that that the grained sintered material in the manufacture of unfired stones under Use of magnesium sulfate as a binder at most 8%, preferably 3 to 5%, based on on the refractory mixture, fine-grain Siriter magnesia with a grain size of at most 0.12 mm can be added.