Development of simple techniques for determining the extent of coal cleaning-part 2: Estimating coal washability characteristics and separator performance

ABSTRACT

The extent of coal cleaning is primarily dependent upon three core factors; (1) coal liberation, (2) coal washability, and (3) separator performance. The first factor has been dealt with in part 1. This part focuses on the second and third core factors. Coal washability data are typically generated by the standard float-sink test. Many researchers have proposed different washability indices based on float-sink data to describe coal amenability to washing, but most of these involve cumbersome mathematical calculations while relying on an error-prone graphical technique. Probable error (Ep) is generally used to represent coal separator efficiency but its calculation requires float-sink analysis of both feed and separator products. This paper proposes a simple equation for quantitative estimation of the degree of coal washing based on the feed coal washability data, clean coal yield, and ash. The proposed equation was applied to quantify and compare the washability characteristics of coals from different countries and provides an alternative method for measuring separator efficiency (in percentage).

KEYWORDS:

• Float-sink
• coal washability
• degree of washing
• separator performance
• world coal washability