Geological Variations in Marble Deposits - Implications for the Mining of Raw Material for Ground Calcium Carbonate Slurry Products
Doctoral thesis
Permanent lenke
http://hdl.handle.net/11250/228440Utgivelsesdato
2001Metadata
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Sammendrag
Hustadmarmor AS is the world’s largest producer of ground calcium carbonate (GCC) slurry products for the paper industry, with an annual production of approximately 2.5 million tonnes. The raw material is calcite marble, which is produced by Hustadkalk AS from its own and other mines it co-operates with in Norway.
All mineral deposits possess geologically derived variations. These may be variations in texture, mineralogy and geochemistry, and are the result of changes in the depositional environment, deformation, metamorphism and metasomatism.
Variations in the properties of the raw material affect the product quality, as well as the behaviour of the mineral dressing process. This means that the quality of mineral products depends both on the properties of the raw material and the mineral dressing process, in this case grinding, flotation and micronisation.
This work deals with the aspects of product quality and mineral dressing process behaviour that are related to geological variations in the marble deposits.
The objective has been to:
• Enable mines to produce a stable feed of raw material with predictable and predefined properties.
• Minimise the influence of geologically derived variations on the mineral dressing process and product properties.
• Ensure optimal exploitation of deposits within the limits of the product- and process requirements.
The various types of marble occurring in the deposits that are in production have been described. The influence of different types of raw material on the behaviour of the mineral dressing process and product characteristics has been investigated.
Three primary requirements, which the raw material must comply with, have been defined:
• Product requirement: from the raw material it must be possible to manufacture products which meet customer specifications, i.e. quality.
• Process requirement: it must be possible to manufacture quality products from the raw material within technical and economical limits.
• Environmental requirement: it must be possible to manufacture quality products from the raw material in a manner which is acceptable to society.
Based on the primary requirements, control parameters for the production of raw material have been selected. These are tappi whiteness of product, silicate reagent consumption in the flotation and flotation loss.
A method for measuring the control parameters is provided by a laboratory simulation of the mineral dressing process. The method has been standardised and implemented in a system for production control based on sampling and analysis of cuttings from production drilling, and subsequent blending of raw material.
It has been demonstrated that the level of the control parameters are distributed differently in the various deposits. This means that the same requirements should not be specified for all deposits, as this would unnecessarily reduce the raw material basis. Instead, individual specifications should be made for each deposit, such that the exploitation of each deposit is optimised within the limits of a master specification.
Further, it has been shown that geological variations in calcite marble deposits can be handled during the mining process, and that minimising variations in the properties of the raw material can stabilise both the mineral dressing process and the properties of the ground calcium carbonate slurry products.