DE4319163A1 - Spinel-containing, cement-bonded shaped body and process for producing spinel-containing shaped bodies - Google Patents

Abstract

The invention relates to a spinel-containing, cement-bonded shaped body for aluminous cement clinker (high-alumina cement clinker), which can also be used as building materials, containing oxides of aluminium, magnesium and silicon and, if desired, further coarse aggregates, where as fine filler use is made of a high-alumina residue from the workup of salt slags in the aluminium industry, which contains at least the following constituents, based on the weight of the dried substance: 55-70% of Al2O3, 7-10% of MgO, 6-9% of SiO2, 2-5% of CaO, 1.5-2.5% of F, 1.5-2.5% of Fe2O3 and 7-11% loss on ignition and where MgO is mineralogically present as spinel MgO.Al2O3 and CaO is mineralogically present as fluorspar (fluorite) CaF2. <IMAGE>

Description

The invention relates to spinel-containing, cement-bound Shaped body consisting of a mixture of cementitious Raw material and a fine-grained filler, containing Silica and alumina and, if necessary, further coarse granular aggregates, as well as a method for producing Position of spinel-containing moldings by mixing CaO or CaO-containing raw materials with a clay-containing content or fillers and sintering or melting Temperatures above 1100 ° C.

According to US Patent 4,330,336, a dross from the Alumi niumindustrie for the production of an alumina cement ver applies. It is the scabies as a raw material for the fire a cement clinker used, but not as a filler added to a cement-bound building material. Also, the Use of high-alumina residue from the Aufar processing of salt slag not described.

Patent DE-AS 20 27 250 claims a method for Her refractory calcium-magnesium alumina cements using natural and artificial raw materials. High alumina residual material from the salt slag work is not mentioned. While this one already Spinel contains MgO.Al₂O₃ is according to DE-AS 20 27 250 the spinel phase only when sintering or melting the Alumina cement clinker formed. The use of high clay-containing residue from the work-up of salt slag for subsequent admixture as a filler a ground cement clinker or cement is not described.  

Also from the literature are alumina cements with spinel content known (M. Jung: Silikattechnik 27 (1976) 7, 224-226). As with DE-AS 20 27 250 spinel is, however, off finally part of a cement clinker and not Component of a filler.

In the patents DE 27 31 612 and DE 27 59 908 Cement mixtures and concrete compositions will bean with a fine-grained filler which are silicon oxide, chromium oxide, titanium oxide, zirconium oxide and alumina can act. Also L. Zaigeng u. a. (Stahl and Eisen Special (1992) 10, 149-152), that silica, alumina and chromium oxide in fire solid concrete compositions as fine fillers ver be used. On a filler with a together tion corresponding to a high-alumina residue from the salt slag processing give both sources no indication.

A problem with the known method is that the spinel phase formed during sintering is not is homogeneously distributed in the shaped body. Especially at large shaped bodies arise due to the difference temperature distribution and composition Inhomo properties in the distribution of spinel phases. This must either by very complex mixing processes or by long treatment times are compensated.

Object of the present invention is therefore, the Nach Parts of the known spinel-containing moldings ver to avoid and to offer a procedure that already at relative low temperatures and short treatment times homogeneous formation of the spinel phase over the cross section the molded body guaranteed.  

The object is achieved by the in the Claims specified features solved. As essential Thought of the invention is considered that high tone Residual residues from the workup of salt the aluminum industry in connection with a CaO carrier to a valuable and in its properties excellent alumina cement clinker can be fired.

In the following the invention with reference to several off guide examples explained in more detail. It shows

Fig. 1 is a cross section through an inventive, spinellhaltigen shaped body,

Fig. 2 process flow in the inventive method.

For the following examples, the following are together stated:

Residue "OXITON": Chemical composition Oxiton-Ts in (%) based on dry matter

Alumina cement: trade name "SECAR 51" from Lafarge Fondu International in Neuilly-sur-Seine, France, Sintered corundum: commercial tabular earth.

The exact composition of the mortar mixtures are in Table 1 given. So the mortar consists according to example 1 of pure cement (SECAR 51), while in the examples 2 and 3 according to the following procedure:

High-alumina soil ("OXITON") and clay cement ("SECAR 51") were in the weight ratio 1: 3 (Example 2) or 1: 1 (Example 3) weighed, and to mixed with a mortar. The water content became like that adjusted that a good processable consistency existed.

The solidification times, beginning and end, were determined by means of Vicat needle determined.

For the preparation of specimens, the mortar was in forms of dimensions 10 × 10 × 60 mm by means of a vibrating table vibrated. After moist storage of 3 days, the Flexural strength and compressive strength measured.

The results, compared to pure cement "SECAR 51", shows Table 1.

Investigations on a concrete molding

To produce concrete, the mixtures listed in Table 2 were used
high-alumina residue (OXITON)
Alumina cement (SECAR 51) and
Sintered Corundum (TABULAR TONERDE)
Weighed, mixed and added mixing water as needed.

When molding into test specimens with the dimensions 160 × 40 × 40 mm was compacted by vibrating table. After 3 Wet storage days were the flexural strength and the Compressive strength measured.

The results are shown in Table 2.

Table 1

mortar mixtures

Of particular note is the constant bending strength at high residue levels. This retains the value of 7 N / mm², although the compressive strength decreases.  

Table 2

concrete mixtures

To illustrate the method according to the invention were Examples 4 and 5 below are performed.

example 4

115 g dried, hochtonerdigerhaltiger residue "OXITON" and 75 g of limestone flour "20 m" (Rhenish lime steinwerke, Wülfrath) were in a tumble mixer "Turbula" (Maschinenfabrik Willi Bachofen, Switzerland) 30 min mixed dry for a long time. Subsequently, with the addition of 5% of a 1% solution of methylcellulose in water produced a press-ready granules. At a pressing pressure of 50 N / mm, uniaxial tablets were pressed of 24 mm  Diameter and 7 mm height. After drying at 110 ° C / 12 h a green density of 1.6 g / cm³ was determined. In one electrically heated laboratory furnace (Naber, Bremen) was with a heating rate of 300 km / h Sintered 1200 ° C / 1 h holding time. The tablets were in switched off the oven slowly to room temp within 12 h cooled.

The following minerals were analyzed by X-ray diffraction analysis determined phases:

Spinel | 28% corundum <1% C₂AS 32% C₁₂A₇ 32% CA 8th%

example 5

The cement clinker was produced as in Bei game 1 described, but the clinker by Ab was cooled in water from room temperature.

The X-ray diffraction analysis revealed:

Spinel | 27% corundum <1% C₂AS 5% C₁₂A₇ 25% CA 6% glass phase 37% (difference)

example 6

For the production of a building material, located in the Building and civil engineering industry can be 5-10% Residue (OXITON), 10-15% Portland cement and residual gravel or chamotte in the usual grain size composition are processed. A resulting concrete shows after setting a bending strength of 8-10 N / mm² at one pressure strength of 40-50 N / mm².

A particularly interesting application is the Lining of smelting furnaces. These are usually simple chamotte with a relatively coarse grain size used. These consist mainly of silicon dioxide and about 30% alumina.

It is now possible, the durability of the furnace lining against aggressive smelting such as aluminum and Magnesium melts thereby improve that

• - either a fine-grained filler according to the invention in the form of the high alumina residual material according to Claim 1 in the production of fireclay added is mixed, wherein the content of the filler is about 15-35% can be.
• - or you coat the already existing fireclay Clothing with a coating containing the invention proper residue in a binder phase. The Binder can be hydraulically off at room temperature bind, provided that a cement phase in the appropriate Composition arises. It can also be chemical when, for example, aluminum phosphates as  Binders are used. The binding takes place then at temperatures of about 200 ° C. As another Binder phase is still alumina into consideration, the at temperatures above 800 ° C a ceramic Binding with the residue is received. In all cases is advantageously already in the residue used existing spinel phase. It then arises resistant coating to aggressive melts, the reduction of the silicon oxide content of Chamotte during the electrolysis or during the Remelting of light metal alloys largely prevented.

Claims (5)

1. Spinellhaltiger, cementitious molded body, consisting of a mixture of cementitious raw material and a fine-grained filler containing silica and alumina and, if necessary. Further coarse granular additives, characterized in that the fine-grained filler is a hochtonerdehaltiger residue from the workup of salt slag of the aluminum industry containing at least the following constituents, based on the weight of the dried substance: 55-70% Al₂O₃,
7-10% MgO,
6-9% SiO₂,
2-5% CaO,
1.5-2.5% F,
1.5-2.5% Fe₂O₃ and
7-11% loss on ignition while mineralogically MgO as spinel MgO.Al₂O₃ and CaO as Flußspat CaF₂ present. 2. Spinel-containing, cement-bound solid after Claim 1, characterized, that the filler in an amount of 15-35%, bezo to the sum of cement and residue. 3. Spinellhaltiger, cementitious filler according to any one of the preceding claims, characterized in that

• a) the proportion of spinel MgO.Al₂O₃8-10 wt .-% based on the effective binder content of the total mixture is and
• b) the spinel-containing phase is homogeneously distributed in the volume fraction of the cement phase.

4. A process for the preparation of spinel-containing moldings by mixing CaO or CaO-containing raw materials with alumina-containing additives or fillers and sintering or melting at temperatures of above half 1100 ° C, characterized in that spinel-containing residues from the workup of Salt slags of the aluminum industry are used as aggregate substances, being added as spinel MgO.Al₂O ₃ in a proportion of 25-30% and then the mixture of the shaped body is sintered or melted until the content of free CaO max. 0.5%. 5. The method according to any one of the preceding claims, characterized, that a relationship with the targeted training of a Spinel phase of 1: 3 (spinel phase: cement phase) is set.