FR2553404A1 - BODIES OR REFRACTORY MASSES IN PARTICULAR FOR COATING OVENS OR CONTAINERS FOR MOLTEN METALS AND THEIR USE - Google Patents

Abstract

THE INVENTION CONCERNS REFRACTORY BODIES OR MASSES, IN PARTICULAR FOR THE COATING OF FURNACES OR CONTAINERS FOR MELTED METALS BASED ON ALUMINUM SILICATES, ALUMINUM OXIDE, SILICON DIOXIDE, ZIRCONIUM SILICATE AND CARBIDE OF SILICON, WITH THE USUAL ADDITIVES AND BINDERS AS A BASE MIXTURE, TO WHICH ARE ADDED, DURING THE PREPARATION, FROM 0.5 TO 40 BY WEIGHT OF BARIUM SULPHATE TO FORM CELSIAN (BAO-ALO-2SIO) AND 3 A 25 PARTS BY WEIGHT OF CALCIUM FLUORIDE, RELATED TO 100 PARTS BY WEIGHT OF ADDED BARIUM SULPHATE. THESE BODIES OR MASSES ARE USED FOR THE COATING OF ALUMINUM MELTING KILNS, STEEL CAST POCKETS, ROTATING CEMENT KILNS, LUNGE INCINERATION KILNS, GLASSWARE BASIN OVEN CHAMBERS AND HIGH RANGES.

Description

Refractory bodies or masses, in particular for coating ovens or

  The invention relates to the preparation of refractory bodies or masses with good resistance to corrosion by molten metals. According to the German patent 28 42 176 of the applicant, we already know masses which, high content of bauxite-based alumina, chemically harden and their use in the form of molded bodies intended for the coating of aluminum appliances melted, which were prepared with an addition of 3 to 30% by weight of finely divided barium sulphate. According to German Patent 28 35 934, refractory bodies based on aluminum oxide or aluminosilicates containing 0 5 to 30% by weight of barium sulphate and a phosphate binder for aluminum smelting furnaces Ceramic masses based on celsian

  (Ba O A 12 03 2 Si 02) are known according to DE-PS 536 779.

  The object of the present invention is the preparation of molded bodies or refractory masses, in particular as a coating for furnaces or containers for molten metals based on aluminum silicates, aluminum oxide, silicon dioxide, zirconium silicate and silicon carbide, additives and binders customary as a starting mixture, to which is added, during manufacture, barium sulfate to form celsian (Ba 0 A 12 03 2 Si 02) by ceramic firing between 1100 and 1600 C with the components present or added in sufficient quantity, which require a cooking temperature

  and have improved properties of cold compressive strength and corrosion resistance.

  Surprisingly, it has been discovered that by adding calcium fluoride to the starting mixture of the refractory masses or bodies these advantageous properties can be obtained. Therefore, the present invention relates to refractory bodies or masses of the type mentioned, which are characterized in that 0.5 to 40% by weight of barium sulphate and 3 to 25 parts by weight are added to the dry starting mixture. weight of calcium fluoride, based on 100 parts by weight of the added barium sulfate. According to various variants, it is possible to add to the dry starting mixture from 0.5 to 30% by weight of barium sulfate,

preferably from 5 to 20% by weight.

  The addition of calcium fluoride to the starting mixture can be obtained by the addition of a barium sulfate which contains as impurity calcium fluoride within the limits

  of proportions indicated above.

  6 to 14 parts by weight of calcium fluoride, based on 100 parts by weight, can be added to the starting mixture.

weight of added barium sulfate.

  The firing of the refractory bodies or masses is carried out between 1100 and 1450 ° C. for the starting mixtures based on silicates with aluminum oxides and with bauxite, between 1200 ° and 1600 ° C. for mixtures based on aluminum oxide / corundum. or base of zirconium oxide and between 1200 and 1550 C for

  mixtures based on silicon dioxide and silicon carbide.

  The refractory bodies and masses can be prepared from a mixture of 90 to 98% by weight of bauxite, 2 to 10% by weight of calcined alumina and phosphoric acid and of

  aluminum phosphate as added binders.

  The base or starting materials for the refractory bodies or masses according to the present invention are aluminum oxide, aluminum silicates, silicon carbide, zirconium silicate and silicon dioxide. Suitable mixtures of these basic materials corresponding to the usual refractory know-how can be used. Aluminum oxide can be used as sintered corundum, calcined bauxite with 4 to 7% by weight of Si O 2 and in a smaller amount of calcined aluminum oxide The term "aluminum silicates" should be understood to mean the aluminum silicates usually used in the refractory field, in particular sintered mullite, sillimanite or andalusite, kaolin fireclay, refractory fireclay and fire clay. For the silicon dioxide material it may be quartzite

  refractory and in particular quartz finely ground.

  The term "refractory bodies" should be understood to mean the usual refractory moldings, in particular bricks. The term "refractory masses" includes masses in different forms of application, for example compressed or cast masses (but it also includes the dry masses, that is to say the masses delivered dry to the user,

  which are added with the amount of water needed to be transformed by the user).

  The term "barium sulphate" should be understood to mean chemically prepared barium sulphate, such as, for example, precipitated barium sulphate, as well as natural barite Naturally such barite may contain the usual impurities, in so far as is not

  inconvenient for the final refractory product.

  The barium sulfate added to the starting mixture forms with the components A 12 03 and Si O 2 present in sufficient quantity by ceramic firing between 1100 and 1600 ° Celsius (Ba OA 112 03 2 Si 02), the formation of which can be verified by X-ray examination To obtain the most complete formation possible of celsian with simultaneously good properties of the bodies or masses cooked, the firing must be carried out between 1100 and 1450 ° C for mixtures based on silicates aluminum oxides and of bauxite, between 1200 and 1600 C for mixtures based on aluminum oxide / corundum or based on zirconium oxide and between 1200 and 1550 C for mixtures based on silicon dioxide and silicon carbide. In addition to the BaO component which is derived from barium sulphate, the necessary components A 12 03 and SiO 2 must be provided by finely divided materials containing A 12 03 and / or SiO 2 in order to prepare the celsian compounds. masses or refractories As material containing A 12 03 and / or Si O 2 it is possible to use finely divided corundum, calcined alumina, refractory clay, fine aluminum silicates, finely divided quartz and silicas By reaction of finely divided components between them, celsian is formed in the matrix of bodies and

  masses, which contributes to the formation of the ceramic bond 10 and the development of strength.

  The calcium fluoride added according to the invention to the starting mixture may be chemically prepared calcium fluoride as well as natural fluorinated spar, which in this latter case may also contain the usual impurities. Some naturally occurring barium sulphates already contain calcium fluoride as an impurity. Since these barium sulphates contain about 3 to 25 parts by weight of calcium fluoride as an impurity per 100 parts, they can also be used for However, it is also possible when the barium sulphate used does not contain enough calcium fluoride to add to the starting mixture the necessary amounts of pure calcium fluoride or fluorspar, to obtain the desired amounts of calcium fluoride.

  proportions of calcium fluoride in the barium sulfate required according to the invention.

  The base materials are used with the usual particle size dispersions, for example for a maximum size of 3 mm with 20% by weight below 0.09 mm, 15% by weight of 0.09-0.5 mm, 20% However, depending on the nature of the starting material and the type of use of the molded body or the refractory mass, it is also possible to choose between 0.5 to 1 mm and 45 to 30% by weight. thinner mixtures with an upper limit of, for example, 0.2 mm. Barium sulphate and calcium fluoride

  advantageously used in the form of a powder, that is to say

  with a particle size of less than 0.09 mm and preferably less than 0.04 mm Also products containing A 12 03 and / or Si O 2 which react with the BaO compound to form celsian should be used with a particle size of less than 0.09 mm and preferably less than 0.04 mm The amount of these latter fine materials is determined from the stoichiometric composition of celsian, depending on the base material and is easily determined for each composition by some 10 tests and X-ray celsian determination in the cooked masses The role of the base material in the formation of

  Celsian, for example in the case of base material such as chamotte or quartz, is to involve in the reaction coarse grains which contain A 1203 and / or Si O 2, during the formation of celsian.

  During the preparation of the bodies and masses according to the invention, it is possible to use the usual inorganic binders, for example sodium phosphate, sodium polyphosphate, aluminum phosphate, sodium silicate or organic binders, for example methylcellulose or laundry. sulphite, synthetic resin binder or tar pitch As aluminum phosphate exists in dry and solid form, this chemical binder is particularly suitable for the manufacture of dry masses, because otherwise they would not have storage stability sufficient, ie a sufficient storage life When organic binders are used, there is no risk of premature mass pick-up, if the masses are delivered in the wet state, c that is, already with water, it may be advantageous to use a fungicide to prevent mold growth. The bodies or masses according to the present invention have a high resistance to attack by molten metals and / or slags and to the attack by infiltration of corrosive gases and alkaline salts by using the bodies or masses according to the invention. invention based on aluminum oxide and

  Aluminum silicates have been found after testing in aluminum melting furnaces for improved durability and virtually no infiltration by metals and slags.

  These bodies or masses are moreover advantageous in the coating of rotary kilns, incineration furnaces of garbage, in the filling of glass furnace furnaces and blast furnaces. The invention is explained in more detail.

  detail with the aid of the following non-limiting examples.

  The granular refractory materials of the starting mixture are presented with their main

  chemical composition in Table 1.

  In the examples of Tables 2 and 4, a barite powder containing no calcium fluoride with about 88% by weight of Ba 504 and 12% by weight of SiO 2 is used. In addition, a barium powder containing calcium fluoride (referred to as barium sulfate (F) in Tables 2 and 4) with about 81% by weight of BaSO 4, 12% by weight

  weight of Ca F 2, 6% by weight of Si O 2 and one of calcium fluoride.

  From the mixtures, the bodies which are baked after drying are molded at a pressure of between 80 and 100 N / mm 2. For the mixtures which are bound to the pitch, the moldings are annealed in the known manner at 350 ° C. For these moldings 25 celsian formation only occurs in the refractory k

  industrial commissioning and the corresponding temperatures.

  The refractory bodies based on calcined bauxite according to Examples 1 to 3 (Tables 2 and 3) reach, after firing 30 to 1300, 1400 and 1450 C, a high resistance to cold compression of 200 to 290 N / mm 2. In Comparative Examples 4 and 5 without calcium chloride content with barium sulfate, a maximum of 80 N / mm 2 cold compressive strength is obtained after baking at 1400 C. Based on aluminum oxide or bauxite contain, as cooking phases, corundum, celsian and mullite as mineral phases. The mineral phases are shown in Table 3 by abbreviations for some examples: K = corundum, C = celsian, M = mullite and 5 in the order of decreasing levels Thus Examples 1, 2 and 3 show that as the cooking temperature increases and the barium sulfate content increases, the mullite content decreases in favor of the celsian At temperatures in higher cooking temperatures, for example at 1500 C, the celsian content decreases in the bauxite-based

  celsian passes largely in the vitreous phase of binder.

  The bodies according to Example 2 baked at 1400 or 1450 C are, because of their particularly good resistance to CO

  (600 C / 100 hr control in a gas stream of CO), especially suitable for use in blast furnace lining.

  The refractory bodies according to the present invention

  Chamotte base (Example 8) already reached after cooking at 1200 C a resistance to cold compression of 120 N / mm 2.

  These bricks are distinguished by good resistance to alkaline products during the crucible test for 5 hours at 1100 C in the presence of potassium carbonate. Also, they are very resistant after a crucible test at 800 C for more than 72 hours. hours with respect to corrosion and

  infiltration of an aggressive split aluminum aluminum-silicon-zinc alloy).

  In Example 9 is presented a mass of storage stable chamotte which, thanks to the use of dry binder,

  can be made suitable for transformation by adding water.

  In Examples 10 and 11, a starting mixture based on andalusite (Table 3) shows the possibility of using, according to the invention, calcium fluoride besides barium sulfate or barium sulfate. containing

calcium fluoride.

  Examples 12 to 17 (Table 4) with materials based on quartz, silicon carbide, silicate

  zirconium present in sufficient quantities already present or added components of calcined A 12 03 (A 12 03) and Si O 2 (pyrogenic Si O 2) to form celsian.

Table 1:

  A 12 Bauxite about Corundum envirol Andalousite about Chamotte A 1203 calcined Silicon carbide (99% Si C) Zirconium silicate Quartz n n n

99 60

If O 2 Zr O 2 fi 6 C 0.5 39 48

<0.5

0.6

34 65

99 1.8 0.2 1.3

  Ti O 2 Fe 203 (wt.%) 2.5-3 1.5-2 0.1 approx 1 2.0 1

0.1 0.2

0.3

Table 2:

  % by weight 1 2 3 4 u, v

90

  Corundum 0-3 mm Bauxite calc 0-3 mm 95 95 Andalousit 0-3 mn Chamotte, 0-3 nm A 12 i 3 calcined S 5 Barium sulphate + 10 Barium sulphate ') + 5 Calcium fluoride + 1, Phosphate of aluminum + 0.5 + 0, Phosphoric acid (m) e I ++ 3.0 + 3, Carbon black pitch (Softening point 60-650 C) Water Cooking C 1300 1300

95 95

5

100

5

+ 10 + 20

5

+ 20 + 10

+ 10 + 10

+ 10 + 10

+ 10 + 0 +

0.5 3.0

+ 0.5 + 3.0

+ +

+ 1 + 0.5 + 1.5 + 3.0 + 2.0 +

1.5 2.0

+ 0.5 + 4 + 3.0

+ 1,2

+ 4 + 4

o + 4 + 4 + 5

1400 1300

1480 1480 1200

1400 14 uu ui gold

Table 3:

properties

1 2

2 3 4 5 5 6 7

  (Example with :) Barium sulphate (F) by weight Barium sulphate% by weight Cooking C Bulk density gm 3 Compressive density 2 cold heading N / mm Value DYB-ta C Mineral composition (corundum, celsian, mullite)

5 10 10 20

10

20 20

2.98 260

1400 1300 1400 1450

2.97 3.03 3.08 3.0 (

215 240 290 200

K, C, M K, C, M K, C, Trao M K, C

2.97 80

2.84 40

1400 1480

2.82 3.07 55 250

K, C, M

3.15,295

  _X K, C * DFB = Resistance to sag under hot load ru n m Lnl Lfl J.8

Table 4:

  Quartz O 3.5 nl 95 Silicate zir O 0.5 mn conlum Silicon carbide 0 3 nn clum A 1203 calcined 5 Si O 2 pyrogen Barium sulphate + 10 Barium sulphate (F) Calcium fluoride + 1 Phosphate d aluminum + 1 Phosphoric acid (80% in vol) + 4 Sulphite laundry, in dry Cooking C 1400

12 1 A

1 r 16; g 5 1 t *

92 92

92 92

5 5

3 3

+ 10

+ 10 + 10

+ 1

+ 1 + 2 + 1

+ 4 + 2 + 4

+ 0.5 + 0.5 1400 1450 1450

3 + 10

+ 10

+ 2 + 2 + 0.5 1360

+ 1 + 3 + 1 + 0.5 1360

na U 1 n

Claims (7)

  1 Refractory bodies or masses, in particular used as coating for furnaces or containers for molten metals based on aluminum silicates, aluminum oxide, silicon dioxide, zirconium silicate and silicon carbide, conventional additives and conventional binders such as starting mixture, to which is added, during manufacture, barium sulfate to form celsian (Ba OA 1203-2 Si 02) by ceramic firing between 1100 and 1600 C with the components present or added in sufficient quantity, characterized in it is added to the dry starting mixture of 0.5 to 40% by weight of barium sulphate and 3 to 25 parts by weight of calcium fluoride, based on 100 parts by weight added barium sulfate.   2 Bodies or refractory masses according to claim 1, characterized in that 0.5 to 30% by weight of barium sulphate is added to the dry starting mixture. preferably from 5 to 20% by weight.   3. The refractory body or mass according to claim 1, characterized in that a barium sulphate is added to the starting mixture which contains as impurity calcium fluoride within the limits of proportions indicated in FIG. claim 1.   4 Refractory bodies or masses according to claim 1 or 2, characterized in that 6 to 14 parts by weight of calcium fluoride are added to the starting mixture.   to 100 parts by weight of the added barium sulfate.   Bodies or refractory masses according to Claim 1, characterized in that the firing is carried out between 1100 30 and 1450 C for the starting mixtures based on silicates with aluminum oxides and bauxite, between 1200 and 1600 C for the mixtures based on aluminum oxide / corundum or zirconium oxide base, and between 1200 and 1550 C for the blends   based on silicon dioxide and silicon carbide.   6 Refractory bodies or masses according to any one of   of the preceding claims, characterized in that they are   prepared from a mixture of 90 to 98% by weight of bauxite, 2 to 10% by weight of calcined alumina and acid   phosphoric acid and phosphate as added binders.   7 Use of bodies or masses according to one   any of the preceding claims, for coating   aluminum smelting furnaces and steel ladles to protect them from attack by molten metals and / or slags and for the coating of rotary kilns, incineration furnaces waste and for the lining of glasshouse furnace chambers against attack by corrosive gases that seep into and alkaline salts.   8 Use of the bodies or masses according to any one of claims 1 to 6 for coating   refractory with high CO resistance for blast furnaces.