Refractories ©2009 Dr. B. C. Paul Credit is given to “Industrial Minerals” (SME), Geology.com, Yuprocks.com, Geology.about.com, Glendale Community College, The Robitics Institute- Carnegie Melon, Tasaclips.com, Webmineral.com, gc.maricopa.edu, rocks- rock.com, Cochise Community College, mii.org, USGS

What Are Refractories Linings put in equipment to withstand high temperatures –Many devices are made of metal –But the temperatures inside the vessels would melt the metal –They must be lined with something that takes a lot of heat without breaking up or melting Base brick ingredient in clay –Flint clays or Kaolin with fusion temp over 425C Low alkali content helps with temp resistance

Alumina Refractories Alumina refractories hold shape at higher pressure and take more heat. –Mix incorporates Bauxite Kyanite Sillimanite Andalusite –Raw materials are calcined at high temperature –Action forms mixtures of silica and mullite glass –Glass is ground and dry pressed into form of bricks

Bauxite gibbsite, Al(OH)3 boehmite, AlO(OH) diaspore, AlO(OH) Really a combination of oxides and Hydroxides S.G Hardness 1-3

Kyanite Al 2 SiO 5 S.G Hardness 4-7 Streak - White

Sillimanite Same composition- Different crystal form than Kyanite

Andalusite Same composition as Kyanite and Sillimanite Different crystal structure.

What Are Alumina Refractory Raw Materials Worth Record is for Kyanite About $240/ton

Magnesia Refractories They are not easily eaten by molten slags Raw materials –Magnesite –Brucite –Dolomite –Olivine –Serpentine (with extra step) Calcine them to make MgO magnesia –Can be used as a chemical but –Fired to Perclase makes a very resistant refractory

Magnesite MgCO 3 S.G Hardness 3.5-4

Brucite Mg(OH) 2 S.G Hardness 2.5-3

Dolomite CaMg(CO 3 ) 2 S.G Hardness Limestone with a partial replacement of Calcium with magnesium.

Olivine Peridot (gem quality Olivine) Forsterite = Mg 2 SiO 4 Olivine (Chrysolite) = (Mg,Fe) 2 SiO 4 Fayalite = Fe 2 SiO 4 Olivine is a solid solution with variable amounts Of iron and magnesium S.G. 3.2 – 4.2 Hardness 6.5-7

Serpentine ((Mg, Fe) 3 Si 2 O 5 (OH) 4 )MgFe Si OOH Hydrous magnesium iron silicate One mineral variation is Asbestos S.G Hardness 2.5-3

Value of Magnesia (MgO) Around $500/$600/ton (this price does Require Processing of The raw material)

Other Refractories Zircon based –Fine ground pressed into bricks often used in borosilicate glass manufacture Zirconia –Ultra high melting point 2710 C Artificial minerals – Silicon Carbide (also an abrasive) –Made from coke (a carbon source) and sand (a silicon source) with sawdust and salt –Cook the mix at about 2200 C –Refractory very good at resisting oxidation