Coal quality improvements affect positively the overall electricity generation efficiency of coal-fired power plants, decrease operation and maintenance costs and reduce the environmental. Natural gamma radiation, due to the presence of trace amounts of uranium and thorium in coal, can be used as a reliable indicator of its ash content. This work aims to present the results from an ash content measurement system, tested for Greek lignite and demonstrated for Polish coal. The applied measuring technology is the natural gamma radiation emission, which provides the advice with simplicity and safety since there is no radioactive source. Results obtained so far show that the accuracy of ash content determination being approximately 1.5-2.0% of ash for coarse coal and even better for fine particles, while the accuracy is not essential influenced by the moisture content and the chemical composition of coals.

Keaywords : Ash, Coal, Gamma radiation, On-line analysis