Development of Simple Techniques for Calculating the Extent of Coal Cleaning-part 1: Estimating Coal Liberation Characteristics

ABSTRACT

The extent of coal cleaning is primarily dependent on three core factors: (1) coal liberation, (2) coal washability, and (3) separator performance. The most important factor that determines the extent of coal cleaning is the liberation of organic matter from mineral matter. In the past, various methods for estimating coal liberation characteristics have been used by different researchers such as fractionation method, macroscopic and microscopic techniques, advanced image analysis techniques, and methods based on float-sink data of coal. Some of these methods do not precisely represent coal liberation, some are purely qualitative, and some involve expensive equipment, extensive testing, and cumbersome mathematical analysis. Moreover, other than float-sink analysis, these techniques are not applicable to the original coal size range being treated in a coal preparation plant. This paper presents a critical review of previous work related to the assessment of coal liberation and proposes a simple mathematical expression for quantifying coal liberation characteristics. The proposed method is exclusively based on float-sink data and thus applicable to any coal size range being treated in gravity-based separators. The proposed method was applied to estimate and compare liberation characteristics of coals belonging to different countries of the world by using their published float-sink data.

KEYWORDS:

• Coal liberation
• float-sink
• degree of liberation
• world coal liberation
• coal liberation classes