[go: up one dir, main page]

GB2218978A - Ceramic coatings - Google Patents

Ceramic coatings Download PDF

Info

Publication number
GB2218978A
GB2218978A GB8812486A GB8812486A GB2218978A GB 2218978 A GB2218978 A GB 2218978A GB 8812486 A GB8812486 A GB 8812486A GB 8812486 A GB8812486 A GB 8812486A GB 2218978 A GB2218978 A GB 2218978A
Authority
GB
United Kingdom
Prior art keywords
coating
oxide
coating material
furnace
emissivity
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB8812486A
Other versions
GB8812486D0 (en
Inventor
R Iain Campbell Alexander
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
MORGAN MATERIALS TECHNOLOGY LI
Original Assignee
MORGAN MATERIALS TECHNOLOGY LI
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by MORGAN MATERIALS TECHNOLOGY LI filed Critical MORGAN MATERIALS TECHNOLOGY LI
Priority to GB8812486A priority Critical patent/GB2218978A/en
Publication of GB8812486D0 publication Critical patent/GB8812486D0/en
Publication of GB2218978A publication Critical patent/GB2218978A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/63Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
    • C04B35/632Organic additives
    • C04B35/636Polysaccharides or derivatives thereof
    • C04B35/6365Cellulose or derivatives thereof
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/03Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on magnesium oxide, calcium oxide or oxide mixtures derived from dolomite
    • C04B35/04Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on magnesium oxide, calcium oxide or oxide mixtures derived from dolomite based on magnesium oxide
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/66Monolithic refractories or refractory mortars, including those whether or not containing clay
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/80Optical properties, e.g. transparency or reflexibility
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3205Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
    • C04B2235/3206Magnesium oxides or oxide-forming salts thereof
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3205Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
    • C04B2235/3208Calcium oxide or oxide-forming salts thereof, e.g. lime
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30Constituents and secondary phases not being of a fibrous nature
    • C04B2235/34Non-metal oxides, non-metal mixed oxides, or salts thereof that form the non-metal oxides upon heating, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3427Silicates other than clay, e.g. water glass
    • C04B2235/3436Alkaline earth metal silicates, e.g. barium silicate
    • C04B2235/3454Calcium silicates, e.g. wollastonite

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Furnace Housings, Linings, Walls, And Ceilings (AREA)
  • Compositions Of Oxide Ceramics (AREA)

Abstract

A refractory coating material for lining furnaces comprises a low emissivity, high reflectivity coating material formed from an oxide ceramic having a total emissivity of less than 0.45 and, preferably, over part at least of the infra-red range, a spectral emissivity of less than 0.25. Particular examples of materials shown are magnesium oxide and a calcium oxide/ china clay mixture.

Description

CERAMIC COATINGS This invention relates to ceramic coating materials for furnaces.
It has been shown that low emissivity (high reflectivity) coatings can improve the energy efficiency of furnaces during the heating-up phase (Metals and Materials, January 1988, pages 25-27). However, the material used (platinum) is not cost effective.
The present invention provides a low emissivity, high reflectivity, coating material for lining furnaces, comprising an oxide ceramic having a total emissivity of less than 0.45. Preferably, over part at least of the infra-red range, the ceramic has a spectral emissivity of less than 0.25.
Preferably the oxide ceramic comprises a white, heavy grade, magnesia.
Advantageously, the coating is chosen and engineered so that any mismatch between the base material of the coating and that of the substrate furnace lining is minimised so as to prevent crazing and/or spalling of the coating. Factors to be considered in such a choice include: whether the coefficients of thermal expansion of substrate and coating are matched; and, whether substrate and coating are likely to react at their interface to form an adherent layer.
This invention is illustrated by way of the following non-limitative examples: Example 1 The coating system comprised a two-part mixture; Component A, the dry powdered component; Component B, the liquid binder component.
Component A comprised magnesium oxide (Pennine Darlington Magnesia Limited - Darlington, Durham, Grade P014/200, 88% < 325 mesh, 98.5% MgO, packed density 0.50 g/cm3). This was ball milled for a period of half an hour to give a finely comminuted solid powder.
Component B comprised a 1W/o solution of a medium molecular weight hydroxypropyl-methyl cellulose (CELACOL 5000 [trade markl - Supplier: Courtaulds Chemicals Limited, Derby).
50 g of Component A was added to 130 ml of Component B slowly with constant mechanical stirring over a period of 5 - 10 minutes, so that Component A was thoroughly wetted by the liquid Component B. A smooth suspension of paint like consistency resulted, which could be applied while still fluid by any suitable method (e.g. brushing, spraying, rolling) to the desired substrate.
In comparative trials a furnace lined with lightweight alumino silicate brick, was operated through four heating and cooling cycles, before having a coating of between 200 - 300pm thickness of the above material applied to the alumino silicate brick. A further four heating and cooling cycles were carried out at the same heating rate, to the same soak temperature.
The results of these trials in terms of the energy consumption of the furnace, as measured by a standard electricity meter, and as recorded by a power transducer (Rochester Instrument Systems, Dartford), are given in Table 1. The relative power/energy efficiencies of this coating and that of the idealised platinum lining, are shown in Table 2.
It is believed that the magnesium coating and alumino silicate brick may react above 1000"C at their interface to form a spinel which improves adherence of the coating.
Example 2 The coating preparation procedure of Example 1 was repeated, except that the magnesium oxide of Component A was replaced by a 40 w/o calcium oxide (BDH Chemicals Limited - Poole, GPR grade), 60 w/o china clay (English China Clay International Limited, Grade GTY) mixture.
A similar energy performance trial was carried out as in Example 1, and the relative power/energy efficiencies of this coating are given in Table 3.
Use of calcium oxide alone is not satisfactory due to its slaking tendency. This hydration leads to degradation by "fluffing up" in a very short period of time.
Combination with china clay overcomes this problem and leads to a stable coating.
The material of Example 1 had a total emissivity of 0.42 and had a minimum emissivity in the infra-red range of 0.15. The comparable figures for Example 2 were 0.43 and 0.2 respectively.
TABLE1 : SMALL FURNACE RUNS AT 1200 C, 15 HOURS SOAK, 2 HOURS TO TEMPERATURE (SiC BRICK LOAD)
E N E R G Y C O N S U M P T I O N ( k W h ) Power (kW) required During Ramp During 15 hour soak Total During Soak Electricity Electricity Electricity After After After Rochester Meter Rochester Meter Rochester Meter 5 hrs 10 hrs 15 hrs 1 2.38 3.15 15.33 19.62 17.71 22.77 - - Standard 2 2.40 3.10 15.27 19.57 17.67 22.67 0.968 0.956 0.954 Brick 3 2.36 3.14 15.29 19.90 17.65 23.04 0.964 0.972 0.956 Walls 4 2.42 3.15 15.29 19.85 17.71 23.00 0.984 0.972 0.972 Same 1 2.36 3.01 14.84 19.19 17.20 22.20 0.934 0.923 0.923 Brick coated 2 2.34 3.02 15.10 19.24 17.44 22.26 0.962 0.945 0.936 with MgO/Cel 3 2.36 2.99 15.00 19.43 17.36 22.42 0.967 0.937 0.943 4 2.34 2.98 14.83 19.12 17.17 22.10 0.956 0.937 0.925 TABLE 2 MEAN ENERGY AND POWER REQUIREMENTS AND RELATIVE EFFICIENCIES OF CERTAIN 'COATING' SYSTEMS C O N T R O L L E D R A M P S Y S T E M
Relative Furnace lined with:- Relative Furnace lined with: Energy Energy Measurements Standard Requirement Standard Requirement Platinum MgO/Cel Brick (Std.Brick = 1) Brick (Std.Brick = 1) Energy Consumption (kWh) During heat up:- 3.46 3.21 0.93 3.14 3.00 0.96 During soak::- 21.01 20.76 0.99 19.74 19.25 0.98 Power (kW) required during soak After (hours) 5 1.052 1.040 0.99 0.972 0.954 0.98 10 1.040 1.031 0.99 0.966 0.936 0.97 15 1.040 1.033 0.99 0.961 0.932 0.97 TABLE 3.
Mean Energy and Power Requirements and Relative Efficiencies of a CaO/Clay Coating
Furnace Lined With Relative Energy Requirement Measurements Standard Brick Standard CaO/ Designed Factor of 1 Brick Clay Energy Consumption (kWh) During heat up Rochester 2.55 2.48 0.97 Electricity 3.14 3.10 0.99 During soak Rochester 15.05 14.74 0.98 Electricity Meter 18.72 18.46 0.99 Power (kW) Required During Soak After (hours) 4 0.990 0.980 0.99 8 0.978 0.963 0.98 12 0.976 0.961 0.98

Claims (9)

  1. CLAIMS 1. A low emissivity, high reflectivity, coating material for lining furnaces comprising an oxide ceramic having a total emissivity of less than 0.45.
  2. 2. A coating material as claimed in claim 1 and having over part at least of the infra-red range, a spectral emissivity of less than 0.25.
  3. 3. A coating material as claimed in claim 1 or claim 2, in which the oxide ceramic predominantly comprises a white, heavy grade, magnesium oxide.
  4. 4. A coating material for lining furnaces as claimed in claim 1 or claim 2 in which the oxide ceramic comprises a calcium oxide/china clay mixture.
  5. 5. A coating material as claimed in any preceding claim in which the material is chosen so that mismatch between coating and furnace wall material is minimised so as to reduce crazing and/or spalling of the coating.
  6. 6. A coating material as claimed in claim 5 in which the oxide material is chosen to react with the furnace wall material so as to bond with the furnace at the interface between furnace and coating.
  7. 7. A coating material substantially as described.
  8. 8. A suspension of oxide material in liquid for use in preparation of a coating, as claimed in any of claims 1 to 7.
  9. 9. A furnace, including a coating as claimed in any of claims 1 to 7.
GB8812486A 1988-05-26 1988-05-26 Ceramic coatings Withdrawn GB2218978A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8812486A GB2218978A (en) 1988-05-26 1988-05-26 Ceramic coatings

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8812486A GB2218978A (en) 1988-05-26 1988-05-26 Ceramic coatings

Publications (2)

Publication Number Publication Date
GB8812486D0 GB8812486D0 (en) 1988-06-29
GB2218978A true GB2218978A (en) 1989-11-29

Family

ID=10637577

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8812486A Withdrawn GB2218978A (en) 1988-05-26 1988-05-26 Ceramic coatings

Country Status (1)

Country Link
GB (1) GB2218978A (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1272845A (en) * 1969-03-12 1972-05-03 Foseco Int Magnesia-containing refractory dressings
GB1315543A (en) * 1970-05-11 1973-05-02 Foseco Int Casting of metal ingots

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1272845A (en) * 1969-03-12 1972-05-03 Foseco Int Magnesia-containing refractory dressings
GB1315543A (en) * 1970-05-11 1973-05-02 Foseco Int Casting of metal ingots

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"Refractories" by J.H. C *
and p. 279 *

Also Published As

Publication number Publication date
GB8812486D0 (en) 1988-06-29

Similar Documents

Publication Publication Date Title
US4943544A (en) High strength, abrasion resistant refractory castable
EP0584335B1 (en) Sprayable refractory composition
JPH01160883A (en) Light fire-proof composition of fused silica
CA2410075A1 (en) Process for making chemically bonded composite hydroxide ceramics
GB2100744A (en) Heat-resistant inorganic composition
WO1995015932A1 (en) Chromium-free brick
US3084060A (en) Process of coating a refractory body with boron nitride and then reacting with aluminum
JPH01500331A (en) Method for spraying a fire-resistant layer onto a surface and the coating layer produced thereby
US4622070A (en) Fibrous composite material for fused aluminum
JPS61295277A (en) Abrasion resistant refractory composition
KR20020022453A (en) compositions of ceramics for extreme infrared radiation
GB2218978A (en) Ceramic coatings
WO2011115352A1 (en) Unshaped refractory composition added with alumina sol binder
EP1264810A1 (en) Monolithic refractory for waste pyrolysis furnace and waste pyrolysis furnace using the same
US3775139A (en) Non-ferrous refractory composition having improved resistance to molten non-ferrous metals and slags
Chan et al. Effect of Cr2O3 on slag resistance of Al2O3–SiO2 refractories
JPS61117168A (en) refractory composition
JPH01239049A (en) Binder
Chakraborty et al. Performance of conventional CSZP-based ceramic coating on oxidation of carbon–carbon composites
TORIYAMA et al. Effect of Mixed Addition of Al2O3 and SiO2 on Mechanical Strength of Sintered β-Tricalcium Phosphate
JPH10316476A (en) Thermal insulation castable
JPS54161503A (en) Repairing method for wall of refractory vessel
Chan et al. Bonding matrix for bauxite-based, high-alumina torpedo ladle brick for lower temperature firing
JP2006327842A (en) Insulating refractory material for microwave firing furnace
US3754949A (en) Protective coating for materials exposed to molten aluminum and its alloys

Legal Events

Date Code Title Description
WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)