# US 11,440,847 B2 · Method for producing a porous sintered magnesia, backfill for producing a heavy-clay refractory product with a granulation from the sintered magnesia, product of this type, and method for the production thereof, lining of an industrial furnace and industrial furnace

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- Number: US 11,440,847 B2
- Document ID: US11440847B2
- Status: Granted
- Kind: B2
- Application number: 16/646,409
- Filed: 2018-09-13
- Published: 2020-09-03
- Granted: 2022-09-13
- Earliest claimed: 2017-09-15
- Assignees: Refratechnik Holding GmbH
- Applicants: Refratechnik Holding GmbH
- Inventors: Hans-Jürgen Klischat; Robert Plummer; Carsten Vellmer; Holger Wirsing
- Web page: https://patentgrep.com/patent/US11440847B2

## CPC

- C04B 35/043: Refractories from grain sized mixtures
- C04B 35/0435: {containing refractory metal compounds other than chromium oxide or chrome ore}
- C04B 35/03: based on magnesium oxide, calcium oxide or oxide mixtures derived from dolomite
- C04B 35/626: Preparing or treating the powders individually or as batches {(pigments for ceramics C09C1/0009); preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B}
- C04B 35/6264: {Mixing media, e.g. organic solvents}
- C04B 35/63: using additives specially adapted for forming the products {, e.g.. binder binders}
- C04B 35/66: Monolithic refractories or refractory mortars, including those whether or not containing clay {(making or repairing of linings F27D1/16)}
- C04B 38/00: Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof (treating slag with gases or gas generating material C04B5/06 {; expanded graphite C04B35/536})
- C04B 38/0058: {open porosity}
- C04B 35/62605: {Treating the starting powders individually or as mixtures}
- C04B 38/0051: {characterised by the pore size, pore shape or kind of porosity}
- C04B 38/0054: {the pores being microsized or nanosized}
- C04B 2235/3208: Calcium oxide or oxide-forming salts thereof, e.g. lime
- C04B 2235/3217: Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
- C04B 2235/3222: Aluminates other than alumino-silicates, e.g. spinel (MgAl2O4)
- C04B 2235/3241: Chromium oxides, chromates, or oxide-forming salts thereof
- C04B 2235/3244: Zirconium oxides, zirconates, hafnium oxides, hafnates, or oxide-forming salts thereof
- C04B 2235/327: Iron group oxides, their mixed metal oxides, or oxide-forming salts thereof
- C04B 2235/3418: Silicon oxide, silicic acids or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint
- C04B 2235/3445: Magnesium silicates, e.g. forsterite
- C04B 2235/404: Refractory metals
- C04B 2235/50: Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
- C04B 2235/5436: micrometer sized, i.e. from 1 to 100 micron
- C04B 2235/5463: Particle size distributions
- C04B 2235/604: Pressing at temperatures other than sintering temperatures
- C04B 2235/606: Drying
- C04B 2235/6562: Heating rate
- C04B 2235/6567: Treatment time
- C04B 2235/70: Aspects relating to sintered or melt-casted ceramic products
- C04B 2235/77: Density
- C04B 2235/96: Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
- C04B 2235/9607: Thermal properties, e.g. thermal expansion coefficient
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE

## Abstract

A method for producing a granular material from sintered magnesia by sintering of pressed articles, in particular pellets, from MgO powder, preferably from caustic MgO powder, and subsequent mechanical comminution of the pressed articles, the sintering being carried out in such a way that the granular material has a grain porosity (total porosity), according to DIN EN 993-1:1195-04 and DIN EN 993-18:1999-01, of from 15 to 38 vol %, preferably 20 to 38 vol %. Also, a batch for producing a coarse ceramic, refractory, shaped or unshaped product containing the porous sintered magnesia, to such a product produced from the batch and to a method for its production, to a lining, in particular a working casing and/or a backing, of a large-volume industrial furnace, the lining, in particular the working casing and/or the backing, having at least one such product, as well as to such an industrial furnace.

## Claims

### Claim 1

A method for producing a granular material of sintered magnesia, comprising:
sintering of pressed articles of MgO meal, the MgO meal having a grain size ≤200 μm, and
subsequently mechanically comminuting the pressed articles to provide a granular material,
wherein the sintering takes place in such a way that the granular material has a grain porosity (total porosity) according to DIN EN 993-1:1995-04 and DIN EN 993-18:2002-11 of 15 to 38 vol % and a grain compression strength, based on DIN 13055-2016-11 (10 mm instead of 20 mm), of 10 to 30 MPa,
wherein the sintering takes place at a maximum temperature between 1100-1600° C. and wherein a firing duration at the maximum temperature is between 0.5 h to 7 h.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the sintering takes place at a maximum temperature between 1200-1600° C.

### Claim 3 (depends on 1)

The method according to claim 1, wherein sintering takes place in such a way that the granular material has a grain bulk density, according to DIN EN 993-1:1995-04 and DIN EN 993-18:2002-11, of 2.20 to 2.85 g/cm3.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the pressed articles have a bulk density according to DIN 66133:1993-06 of 1.8 to 2.3 g/cm3.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the pressed articles have a porosity, according to DIN 66133:1993-06, of 32 to 52 vol %.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the MgO meal comprises at least 88 wt % MgO, determined by x-ray fluorescence analysis according to DIN 12677:2013-02.

### Claim 7 (depends on 1)

The method according to claim 1, wherein the MgO meal has a particle size distribution having at least one of following values, determined using laser granulometry according to DIN ISO 13320:2009:
d90 between 80 and 100 μm; d50 between 5 and 15 μm; or d10 between 1 and 3 μm.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the pressed articles consist, relative to their dry mass, of at least 96 wt % of MgO meal.

### Claim 9 (depends on 1)

The method according to claim 1, wherein the granular material made of sintered magnesia is produced without the use of burnout materials.

### Claim 10 (depends on 1)

The method according to claim 1, wherein the sintering takes place in such a way that the granular material made of sintered magnesia has an average pore diameter d50 of 0.1 to 10 μm, determined according to DIN 66133:1993-06.

### Claim 11 (depends on 1)

The method according to claim 1, wherein the granular material made of sintered magnesia has a grain compression strength, based on DIN 13055-2016-11 (10 mm instead of 20 mm), of 11 to 25 MPa.

### Claim 12 (depends on 1)

The method according to claim 1, further comprising: producing a batch from
at least one granular material made of the granular material of sintered magnesia.

### Claim 13 (depends on 12)

The method according to claim 12, wherein the batch comprises
a dry material mixture having or consisting of:
a) at least one coarse granular material made of the sintered magnesia the at least one coarse granular material and having a grain size >200 μm,
b) at least one powdered granular material made of magnesia the at least one powdered granular material having a grain size ≤200 μm, and, an
additive to the dry material mixture and, at least one liquid, or solid, binder for refractory materials.

### Claim 14 (depends on 13)

The method according to claim 13, wherein the batch consists of at least 90 wt % of binder and the dry material mixture, relative to the total mass of the batch.

### Claim 15 (depends on 13)

The method according to claim 13, wherein the dry material mixture comprises ≥50 wt % of the coarse granular material made of the sintered magnesia.

### Claim 16 (depends on 13)

The method according to claim 13, wherein the coarse granular material made of the sintered magnesia has a maximum grain size ≤8 mm.

### Claim 17 (depends on 13)

The method according to claim 13, wherein the dry material mixture further comprises a further granular material, and wherein the further granular material is selected from the group consisting of: magnesium aluminate spinel, bauxite, alumina, hercynite, pleonaste, chromium ore, pleonastic spinel, zirconium oxide, olivine, and/or forsterite.

### Claim 18 (depends on 13)

The method according to claim 13, wherein the dry material mixture further comprises a further granular material having a maximum grain size ≤8 mm.

### Claim 19 (depends on 16)

The method according to claim 16, wherein the dry material mixture further comprises a further granular material and wherein a grain distribution of the further granular material is steady.

### Claim 20 (depends on 1)

The method according to claim 1, further comprising: coarse ceramic, refractory, shaped or unshaped product from the granular material of sintered magnesia.

### Claim 21 (depends on 12)

The method according to claim 12 further comprising: forming a coarse ceramic, refractory, shaped or unshaped product, from the batch.

### Claim 22 (depends on 20)

The method according to claim 20, wherein the product comprises a green, shaped body.

### Claim 23 (depends on 20)

The method according to claim 20, wherein the product comprises a tempered shaped body.

### Claim 24 (depends on 20)

The method according to claim 20, wherein the product comprises a fired shaped body.

### Claim 25 (depends on 24)

The method according to claim 24, wherein the fired shaped body has a thermal conductivity according to the hot-wire (parallel) method according to DIN 993-15:2005-14 of 4.0 to 6.0 W/mK at 300° C., 3.0 to 5.0 W/mK at 700° C. and 2.0 to 3.5 W/mK at 1000° C.

### Claim 26 (depends on 24)

The method according to claim 24, wherein the fired shaped body comprises an open porosity of 22 to 45 vol %, determined according to DIN 993-1:1995-4.

### Claim 27 (depends on 24)

The method according to claim 24, wherein the fired shaped body has an average value of the pore diameter distribution d50, determined according to DIN 66133:1993-06, of 0.5 to 10 μm.

### Claim 28 (depends on 23)

The method according to claim 23, wherein the fired shaped body has a bulk density of 1.9 to 2.9 g/cm3 determined according to DIN 993-1:1995-04.

### Claim 29 (depends on 24)

The method according to claim 24, wherein the fired shaped body has a cold compression strength according to DIN EN 993-5:1998-12 of 30 to 100 MPa.

### Claim 30 (depends on 24)

The method according to claim 24, wherein the fired shaped body has a cold bending strength according to DIN EN 993-6:1995-04 of from 2 to 18 MPa.

### Claim 31 (depends on 23)

The method according to claim 23, wherein the fired shaped body has a gas permeability according to DIN EN 993-4:1995-04 of from 0.2 to 8 nPm.

### Claim 32 (depends on 13)

The method according to claim 13, further comprising the steps of:
a) mixing the dry material mixture with the at least one binder, water or both to form a plastic mass, and,
b) shaping of the plastic mass to form a green shaped body.

### Claim 33 (depends on 32)

The method according to claim 32, wherein the shaped body is fired at a temperature of 1200 to 1800° C.

### Claim 34 (depends on 20)

The method according to claim 20 further comprising: forming a lining in a large-volume industrial furnace from the product.

### Claim 35 (depends on 34)

The method according to claim 34, wherein the lining has a working casing that comprises the at least one product.

### Claim 36 (depends on 35)

The method according to claim 35, wherein the working casing is installed in a one-layer or a multilayer masonry structure.

### Claim 37 (depends on 34)

The method according to claim 34, wherein the lining has an insulating backing that comprises the at least one product.

### Claim 38 (depends on 34)

The method according to claim 34, further comprising: forming the lining in a cement kiln installation, a lime shaft kiln or lime rotary kiln, a magnesite or dolomite kiln, or a heating kiln or a kiln for energy production or a kiln for steel production or a kiln of the nonferrous metal industry.

### Claim 39 (depends on 1)

The method according to claim 1, wherein the pressed articles are pellets.

### Claim 40 (depends on 1)

The method according to claim 1, wherein the pressed articles are made of caustic MgO meal.

### Claim 41 (depends on 1)

The method according to claim 1, wherein the sintering takes place in such a way that the granular material has a grain porosity (total porosity) according to DIN EN 993-1:1995-04 and DIN EN 993-18:2002-11 of 20 to 38 vol %.

### Claim 42 (depends on 1)

The method according to claim 1, wherein the firing duration at the maximum temperature is 2 h to 6 h.

### Claim 43 (depends on 1)

The method according to claim 1, wherein the sintering takes place at a maximum temperature between 1200-1550° C.

### Claim 44 (depends on 1)

The method according to claim 1, wherein the sintering takes place at a maximum temperature between 1200-1500° C.

### Claim 45 (depends on 1)

The method according to claim 1, wherein sintering takes place in such a way that the granular material has a grain bulk density, according to DIN EN 993-1:1995-04 and DIN EN 993-18:2002-11, of 2.20 to 2.75/cm3.

### Claim 46 (depends on 1)

The method according to claim 1, wherein the pressed articles consist, relative to their dry mass, of 100 wt %, of MgO meal.

### Claim 47 (depends on 1)

The method according to claim 1, wherein the pressed articles contain no magnesite meal.