1. Introduction

The minerals processing industries constitute the largest annual tonnage manufacturers on a worldwide basis, of which some 1500millon tonnes per annum of minerals are processed at temperatures in excess of 1000^oC. The general term for high temperature (<800^oC) processing of material is [GLOSS]calcination[/GLOSS], and the term bears no relationship to the particular chemical or physical changes that are effected in the kiln. Over 80% of this production is dedicated to the manufacture of cements which consumes >5000PJ.p.a. of primary energy, mainly in the form of [GLOSS]coal[/GLOSS].

2. Minerals processing

Typical industries that fall within the minerals processing sector include:

·          Cement

·          Lime

·          Alumina

·          Magnesite

·          Chromium and titanium dioxide

Other related operations, such as:

·          dead burnt petroleum coke production and

·          metal ore fines roasting

may also be considered within this sector as they use similar technologies. 

Whilst the individual process thermodynamics and chemistry requirements are different for the type of minerals being processed there are some basic similarities in the process cycles and equipment used. Counter-current flow of process material and process gases tends to be a common design feature, whereby the feed of raw material is preheated/pre-processed by the flue gases from the primary furnace(s). The primary furnace(s) calcine the product, heat being supplied by direct contact with a diffusion flame. The combustion air to the furnace is generally preheated by contact with the product material in a cooler. Table 1 summarises these processes and the furnace technologies they use.  These industries are described in more detail in linked Combustion Files (see bottom of this text for the links).

Table 1 Major industries in the minerals processing sector

Sources

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