DE1211980B - Process for the manufacture of silica stones - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C04b

German class: 80 b -8/06

Number: 1211980

File number: B 73726 VI b / 80 b

Filing date: October 2, 1963

Opening day: March 3, 1966

The invention relates to a method for the production of silica bricks from strongly renewable ones Quartzites, especially from rock quartzites.

The well-known silica stones made from rock quartzites have the disadvantage of being grainy at around 1680 ° C, without visible melting phenomenon to disintegrate, so that they are as vaulted stones in highly stressed Siemens-Martin furnaces and are only suitable to a limited extent as electric furnace cover stones. This disadvantage is due to the property of rock quartzites, as a result of fine to coarse crystalline structure and the resulting unfavorable distribution of the accessory mineral components with loosening of the grain and -Destructuring strong regrowth.

The same disadvantages have a product that one after in the German patent 582 446 procedure described. Silica stones are supposed to be produced by mixing of crushed silica-rich raw materials, such as quartzite or quartz sand, with unslaked lime and Water, shaping and burning the mass, whereby the unslaked lime only with part of the raw materials, namely fine or finely ground quartz or sand, is mixed with heating, whereupon the Rest of the quartzite or sand is added. During the extinguishing of the lime can over the sand-lime mixture steam can be passed through at normal or elevated pressure.

Therefore, silica stones made of cement quartzite, its structure, are mainly used today is microcrystalline to X-ray amorphous, and in which the accessory mineral components are therefore cheaper These silica stones soften with melting phenomena in the temperature interval of 1700 up to 1720 ° C. In the steel mills they slowly drip off under the high thermal loads, an appearance that is quite desirable.

However, the known world supply of cement quartzites is becoming depleted, while rock quartzites are queuing in large deposits. The invention arose in the search for methods from Rock quartzites od. Like. Silica stones to produce, which completely replace the well-known silica stones made of cement quartzite are equivalent.

The inventive method is characterized in that the at least in its larger Grain fractions at temperatures above 575 ° C prebaked quartzite with water and hydrated lime mixed, formed into a rough stone, hydrothermally pre-hardened at temperatures above 165 ° C and only then is burned in a manner known per se.

Process for the production of silica stones

Applicant:

Höganäs-Billesholms Aktiebolag,
Häganäs (Sweden)

Representative:

Dipl.-Phys. N. Eilers, patent attorney,

Frankfurt / M., Am Römerhof 35

Named as inventor:
Kjell Yngve Björklund, Höganäs;
Karl-Johan Leander, Hälsingborg (Sweden);
Dipl.-Ing. Rudolf Rasch, Frankfurt / M.

This process creates an X-ray amorphous silica phase at the same time generated by calcium silicate hydrates that are the same or even better than these silica stones Imparts properties than are known from the best cement quartzites. By pre-burning the quartzite crystallites are shattered, whereby a porous, small crystalline product is obtained. This product now has the advantage that when the quartzite is treated with milk of lime in a wet pan or wet mixer and the subsequent pre-curing in the autoclave to the inside of the Porous particles of basalt cement (X-ray amorphous silica) are formed, which have the desired properties has, namely conversion into tridymite and cristobalite in the conventional production firing process with little regrowth, with little increase in porosity and with high compressive strength and pressure fire resistance.

The individual stages of the process according to the invention are explained in more detail below.

1. Pre-firing of the quartzite

The rock quartzite is pre-fired to loosen up the structure through the low-high quartz transformation. You can either use the rock quartzite in the delivered piece form in the kiln or first break it up finely and only the grain fractions over 0.1 mm or if necessary also only pre-burn the grain fractions over 0.5 mm

609 510/381

nen. Pre-firing can take place at temperatures up to over 1450 ° C. In all cases must in all Quartzite particles the limit of the transformation range from deep to high quartzite, namely the Temperature of 575 ° C must be exceeded.

2. Processing

The silica mass is made in a conventional manner from the prefired, lumpy quartzite or the re-mixed coarse and fine grain fractions in the wet pan or wet mixer with additives treated with water and hydrated lime or milk of lime. The addition of lime should be 7% of the silica mass not exceed, on the other hand not fall below 0.5%. A lime additive has proven to be the most beneficial between 3.5% and 5.5%. During processing, the silica mass can still be made finest Add quartz flour up to a proportion of 25%. The properties of the silica stones are improved, if up to 3% titanium dioxide is added during the preparation of the silica mass. Most economical is an addition of 1% titanium dioxide, since a further increase in the addition does not result in an equal improvement the silica stones do more.

Furthermore, adhesives such as sulphite waste liquor or molasses can also be added to the silica mass. However, the moldings show good green stability even without this addition.

3. Shaping

The moldings are produced from the silica mass in a conventional manner with machine tools or hand presses or on vibrators.

4. Hydrothermal pre-hardening

After shaping, the briquettes are placed in a steam-fed autoclave and pre-cured there at temperatures above 165 ° C. The most economical way to work in the temperature range between 180 and 225 ° C at vapor pressures between 10 and 20 atü. The length of time the pre-curing is measured so that the product of the internal pressure of the autoclave and the Time is at least 65 atmospheric hours (pressure in atmospheres, time in hours). In other temperature and pressure ranges, the guide value for the number of atmospheric hours also changes.

5. Burning

The pre-cured moldings removed from the autoclave are in conventional Fired at temperatures of around 1400 to 1500 ° C. Heating up and cooling down can be done with the pre-hardened moldings take place faster than with the moldings made of cement quartzite. They are too pre-cured briquettes are much less sensitive to fluctuations in the firing temperature than Cement quartzite moldings.

Claims (10)

Patent claims: 1. Process for the production of silica stones from strongly renewable quartzite, in particular Rock quartzite, characterized in that at least in its larger grain fractions Quartzite pre-fired at temperatures above 575 ° C with water and Lime hydrate mixed, formed into a rough stone, hydrothermal at temperatures above 165 ° C is pre-hardened and only then fired in a manner known per se. 2. The method according to claim 1, characterized in that the quartzite portion to be prebaked is pre-fired above 1450 ° C. 3. The method according to any one of claims 1 and 2, characterized in that only the Grain fractions over 0.1 mm, preferably over 0.5 mm, are pre-burned. 4. The method according to any one of claims 1 to 3, characterized in that the stone molding hydrothermally hardened at temperatures between 180 and 225 ° C. 5. The method according to claim 4, characterized in that the hydrothermal pre-hardening Vapor pressures between 10 and 20 atmospheres can be used. 6. The method according to claim 5, characterized in that the pressure during such Period of time is maintained that the product from pressure in atü times time at least 65 atmospheric hours. 7. The method according to any one of claims 1 to 6, characterized in that the lime additive during processing between 0.5 and 7%, preferably 3.5 to 5.5%, of the silica mass amounts to. 8. The method according to claim 7, characterized in that the quartzite mass during processing Finest quartz flour is added up to a proportion of 25%. 9. The method according to claim 7 or 8, characterized in that the silica mass is added in amounts of up to 3%, preferably 1 ⁰ Io, during processing. 10. Method according to one of the claims? to 9, characterized in that the silica mass is processed with adhesive, such as molasses or sulphite liquor, can be added. Considered publications:
German patent specification No. 582 446. 609 510/381 2.66 © Bundesdruckerei Berlin