Corrosion resistant ceramic media
OwnerXueren Caoinventor
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Abstract
The present invention relates to novel ceramic media or ceramic media coatings comprising mainly magnesia, silicon dioxide, and alumina, with forsterite and spinel as the dominant crystalline phases, which show high resistance to alkali attack at high temperature. Ceramic materials having these characteristics are particularly well suited for use as heat-exchange media in regenerative thermal oxidizers (RTOs) for the wood process industry.
Claims33
1) An alkali-resistant material comprising:
- to 80% by weight of MgO;
- to 50% by weight of SiO2;
- to 30% by weight Al2O3;
- and
- 1 to 10% by weight Fe2O3, CaO, and alkali oxides.
9) A process for the production of an alkali-resistant ceramic body comprising the steps of:
- a) grinding together a mixture comprising 0% to 50% by weight of light magnesia, 0% to 85% by weight of roasted magnesia, 10% to 60% by weight of ceramic clay, 0% to 15% by weight of limestone, 0% to 3% by weight of water glass, 0% to 3% by weight of carboxymethyl cellulose, 0% to 30% by weight of talc, and 0% to 30% by weight of calcium or barium carbonate to a particle size of less than 50 microns for 80% of the particles;
- b) mixing the ground mixture with water to produce a paste containing less than 30% by weight of water;
- c) shaping the paste to a desired shape;
- d) drying the shaped product at a temperature greater than 100 degrees centigrade to make it suitable for firing in a kiln;
- and
- e) firing the dried shaped product in a kiln at 1,250 to 1,450 degrees centigrade.
10) A process for coating a conventional ceramic body with an alkali-resistant ceramic coating comprising the steps of:
- i) preparing an alkali resistant ceramic coating by grinding together 75% to 85% by weight of roasted magnesia, 5% to 10% by weight of ceramic clay, 0% to 15% by weight of limestone, 0% to 2% by weight of water glass, and 0.5% to 2% by weight of carboxymethyl cellulose to a particle size of less than 40 microns for 80% of the particles;
- ii) mixing the ground mixture with water to produce a paste containing less than 30% by weight of water;
- iii) applying a coating of the alkali resistant material paste to the surface of the conventional ceramic body;
- iv) drying the coated ceramic body at a temperature greater than 100 degrees centigrade;
- and
- v) firing the dried coated ceramic body in a kiln at 1,200 to 1,400 degrees centigrade.
11) An alkali-resistant ceramic body comprising:
- to 80% by weight of MgO;
- to 50% by weight of SiO2;
- 5 to 30% by weight Al2O3;
- and
- 1 to 10% by weight Fe2O3, CaO, and alkali oxides.
24) A ceramic body coated with an alkali-resistant material, the alkali resistant coating comprising:
- to 80% by weight of MgO;
- to 50% by weight of SiO2;
- 5 to 30% by weight Al2O3;
- and 1 to 10% by weight Fe2O3, CaO, and alkali oxides.
Dependencies are inferred from the claim text.