Optimizing coal feed in a Brazilian thermal power plant:: A case study

The rapid increase in thermal power generating capacity in Brazil hers resulted in the production of huge quantities of brown coal of high ash content. Current estimates indicate that coal ash production in Brazil is likely to reach 4 million tons per year by 2005. In view of the need to burn this type of fuel to the maximum possible extent, a rational use of coal is vitally important. However, the coal from Candiota (a coal nine in southern Brazil) contains calcium-bearing compounds that damage equipment, causing process stoppages; this coal may become cost ineffective unless the noncombustible material and its content is controlled. This article reports on tire results of the comminution characteristics of coal combustion feed and of industrial tests, which demonstrate the urgent need for optimizing particle size distribution to preclude the presence of calcareous material. Hard calcium-based minerals display a crushing behavior that differs from coal particles, requiring their screening and elimination from the,feed. Examples of the overall situation, screening optimization, and the beneficiation process at the Candiota power plant are discussed in terms of fragmentation, particle size analysis, type of screen, and economic benefits.