Scholarly record

A PROCESS FLOW FOR EXTRACTION OF UNBURNED CARBON FROM BOTTOM ASH - ECONOMICAL AND ENVIRONMENTAL ASSESSMENT

Mihai Cruceru

Abstract

Economic analysis was performed for a new process that will be adapted to an existing coal-fired power plant process in order to recycle bottom ash with the objective of obtaining synthetic graphite. Synthetic graphite is a valuable raw material with many industrial applications. It can replace successfully natural graphite, saving capital and environmental costs associated to graphite extraction. Bottom ash resulting from combustion of low quality lignite at a Romanian coal-fired power plant contains significant amounts of unburned carbon. This large value is caused by many factors, such as the high humidity value of the raw coal delivered to the plant, advanced wear of the coal mills and large variability of the coal quality. As the unburned carbon reduces significantly the economic efficiency of the power generation, solutions to improve the process were investigated. Recycling of the bottom ash to the purpose of obtaining synthetic graphite is a new technology that can be adapted to the existing process with little technological difficulties and low capital costs. The main advantage of the proposed recycling technology is the fact that it does not influence the existing process flow. It was found that the proposed process flow could be implemented with minimum capital costs resulting in both profit and saving of environmental costs.

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