Typical iron slurry, preparation

Limonite and saprolite are typically mined and processed through slurry preparation plants separately. The high iron goethite component of the ore is generally very fine, so there are ore bodies where separation can be achieved based on sizing. In any event, it is preferable to have some saprolite contamination of limonite, as saprolite will leach in the high acid conditions of the limonite leach, but the same cannot necessarily be said of limonite in the saprolite leach. 

Iron-based catalysts are used in both LTFT and HTFT process mode. Precipitated iron catalysts, used in fixed-bed or slurry reactors for the production of waxes, are prepared by precipitation and have a high surface area. A sihca support is commonly used with added alumina to prevent sintering. HTFT catalysts for fluidized bed apphcations must be more resistant to attrition. Fused iron catalysts, prepared by fusion, satisfy this requirement (Olah and Molnar, 2003). For both types of iron-based catalysts, the basicity of the surface is of vital importance. The probability of chain growth increases with alkali promotion in the order Li, Na, K, and Rb (Dry, 2002), as alkalis tend to increase the strength of CO chemisorption and enhance its decomposition to C and O atoms. Due to the high price o Rb, K is used in practice as a promoter for iron catalysts. Copper is also typically added to enhance the reduction of iron oxide to metallic iron during the catalyst pretreatment step (Adesina, 1996). Under steady state FT conditions, the Fe catalyst consists of a mixture of iron carbides and reoxidized Fe304 phase, active for the WGS reaction (Adesina, 1996 Davis, 2003). 

The production method of the porous sintered plaque includes a dry method and a wet method. With respect to the dry method, carbonyl nickel powder is spread to a Ni wire grid with a sieve or the like, adjusted to a predetermined thickness, and then sintered at 800-1,000° [Celsius] in a reducible gas atmospheres, such as hydrogen gas or butane reformed gas. With respect to the wet method, carbonyl nickel powder, a binder such as CMC or MC, and water are mixed to prepare a slurry. The slurry is applied to a nickel-plated iron thin sheet (perforated sheet) which has an open area ratio of about 50 %, and the thickness is adjusted in a scratching pcrtimi. Then, after drying with a drying furnace, it is sintered at a temperature of 800-1,000° [Celsius] in a reducible gas atmosphere. The typical porosity of the porous sintered plaque is 80-87 %. 

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