METHOD FOR MAKING MAN-MADE VITREOUS FIBRES

Abstract

The invention provides methods of making man-made vitreous fibres (MMVF), comprising providing an electric furnace having molybdenum electrodes, providing mineral raw material, wherein the mineral raw material comprises (a) particulate material that comprises metallic aluminium and (b) other mineral component, introducing the mineral raw material into the furnace, melting the mineral raw material to form a mineral melt, and forming MMVF from the mineral melt, with the benefit of reduced shrinkage of consolidated MMVF products.

Claims

1. A process for making man-made vitreous fibres (MMVF) which comprise at least 3 wt % iron oxides determined as Fe.sub.2O.sub.3, comprising providing an electric furnace having molybdenum electrodes, providing mineral raw material, wherein the mineral raw material comprises (a) material that comprises metallic aluminium and (b) other mineral component, introducing the mineral raw material into the furnace, melting the mineral raw material to form a mineral melt, and forming MMVF from the mineral melt.

2. The process according claim 1, wherein the material that comprises metallic aluminium comprises from 0.5 to 10 wt % metallic aluminium.

3. The process according to claim 1, wherein the material that comprises metallic aluminium further comprises from 50 to 90 wt % aluminium oxide.

4. The process according to claim 1, wherein the material that comprises metallic aluminium is particulate, and wherein 90 wt % of the particles are smaller than 1 mm

5. The process according to claim 1, wherein the material that comprises metallic aluminium is alu-dross.

6. The process according to claim 4, wherein from 5 to 30 wt % of the mineral raw material is alu-dross.

7. The process according to claim 1, wherein the material that comprises metallic aluminium comprises from 45 to 100 wt % metallic aluminium.

8. The process according to claim 7, wherein the mineral raw material comprises from 0.05 to 10 wt % of the material that comprises from 45 to 100 wt % metallic aluminium

9. The process according to claim 7, wherein the material that comprises metallic aluminium is aluminium granulate.

10. The process according to claim 9, wherein the aluminium granulate has average granule diameter of no greater than 3 mm.

11. The process according to claim 1, wherein the mineral raw material comprises from 0.1 to 0.5 wt % metallic aluminium.

12. The process according to claim 1, wherein the MMVF have a content of oxides, as wt. %, as follows: SiO.sub.2 35 to 50 Al.sub.2O.sub.3 12 to 30 TiO.sub.2 up to 2 Fe.sub.2O.sub.3 3 to 12 CaO 5 to 30 MgO up to 15 Na.sub.2O 0 to 15 K.sub.2O 0 to 15 P.sub.2O.sub.5 up to 3 MnO up to 3 B.sub.2O.sub.3 up to 3.

13. The process according to claim 1, wherein the MMVF have a content of oxides, as wt. %, as follows: SiO.sub.2 39-55% Al.sub.2O.sub.3 16-27% CaO 6-20% MgO 1-5% Na.sub.2O 0-15% K.sub.2O 0-15% R.sub.2O (Na.sub.2O+K.sub.2O) 10-14.7% P.sub.2O.sub.5 0-3% Fe.sub.2O.sub.3 (iron total) 3-15% B.sub.2O.sub.3 0-2% TiO.sub.2 0-2%.

14. The process of claim 1, wherein the MMVF have a ratio of Fe(II):Fe(III) of above 2, such as above 3.

15. The process of claim 1, further comprising consolidating the MMVF to form a consolidated product comprising the MMVF.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0095] FIG. 1 shows a typical electric furnace which may be used in the process of the present invention.

[0096] FIG. 2 shows an arrangement of electrodes in a cross-section of FIG. 1.

DETAILED DESCRIPTION

[0097] Exemplary methods in accordance with the invention will now be described with reference to FIGS. 1 and 2.

[0098] An electric furnace 1 is illustrated schematically in FIGS. 1 and 2. Mineral raw material is introduced to the furnace 1 via one or more inlets 2, 3 and forms a layer 4 on top of a melt pool 5. The mineral raw material is melted by Joule heating, facilitated by molybdenum electrodes 6. The electrodes 6 are illustrated in FIGS. 1 and 2 as protruding from the sidewalls 7 of the furnace 1. The electrodes may be emerging from the top in other configurations provided that the electrodes are protected from the air. Alternatively, the electrodes may emerge from the bottom of the furnace. Various options for basic setup of an electric glass-melting tank furnace are generally known in the art.

[0099] Material that comprises metallic aluminium may be pre-mixed with the other mineral component and introduced to the furnace 1 as a uniform mineral charge via one or more inlets 2, 3. This option might be preferable when alu-dross is used as the material that comprises metallic aluminium.

[0100] Alternatively, the material that comprises metallic aluminium may be introduced to the furnace 1 separately from the remaining mineral material. For example, the material that comprises metallic aluminium may be introduced to the furnace 1 via inlet 2 and the other mineral material may be introduced to the furnace 1 via separate inlet 3. This option might be preferable when aluminium granulate or blocks are used as the material that comprises metallic aluminium.

[0101] Optional outlet 8 formed in the base 9 of the furnace 1 may be used to tap metallic iron, if it is formed. Preferably metallic iron is not formed in the process and so outlet 8 may not be needed.

[0102] Mineral melt from the melt pool 5 exits the furnace 1 via melt outlet 10. Melt outlet 10 is illustrated as being formed in the sidewall 7 of the furnace 1 but may equally be formed in the base 9.

[0103] On exiting the furnace 1, mineral melt may optionally be subject to fining processes. Alternatively, the mineral melt may be transported directly to a fiberizing apparatus 11 to form man-made vitreous fibres (MMVF). Either internal centrifugation or external centrifugation may be used and so the details of fiberizing apparatus 11 are not shown. Suitable fiberizing apparatuses are known to those skilled in the art.

[0104] MMVF formed at apparatus 11 may be collected and stored, or they may be directly processed into a consolidated product at processing line 12 (details not illustrated).

[0105] Flue gas exit 13 is shown provided in the top of the sidewall 7 of furnace 1. However, it may also be provided in the top of the furnace, in setups known to those skilled in the art.

[0106] alu-dross

Test Method

[0107] The area shrinkage of a consolidated MMVF product may be measured according to the following test method:

[0108] 1) cutting, measuring and weighing test specimens from product test unit;

[0109] 2) selecting representative test specimens from test unit;

[0110] 3) removing binder at 590° C.;

[0111] 4) sintering test specimens at 1000° C. +/−20° C. for 30 minutes; and

[0112] 5) Measure area of sintered test specimen.

[0113] The shrinkage is measured as a % reduction in surface area of each product. The major face of each product that is measured for shrinkage is equivalent to the major face that would be apparent in a finished product. For example, the reduction in length and width of a slab, but not its thickness, is measured.