Estimation of potential savings from reducing unburned combustible losses in coal-fired systems

Abstract

A potentially significant loss emanates from the combustion of coal fuels is usually called as the unburned carbon loss. All coal-fired steam generators and coal-fired vessels inherently suffer from efficiency debit attributable to unburnt carbon. The aim of this study is to develop a simple-to-use predictive tool which is easier than existing approaches, less complicated with fewer computations and suitable for engineers to determine the approximate potential savings resulting from reducing unburned coal fuel loss. The proposed method determines the benefits of reducing the combustible losses in terms of annual fuel savings for coal-fired units as a function of percent combustibles in ash, achievable percent combustibles in ash, unit design heat output and average fuel cost. Results show that the proposed predictive tool has a very good agreement with the reported data with average absolute deviation percent being around 1.77%. The proposed method is superior owing to its accuracy and clear numerical background, wherein the relevant coefficients can be retuned quickly for various cases. The developed tool can be of immense practical value for the utility engineers to have a quick check on the benefits of reducing the combustible losses in terms of annual fuel savings for a coal-fired unit for wide range of operating conditions without the necessity of any pilot plant set up and experimental/plant trials. In particular, practice engineers would find the methodology to be user friendly involving transparent calculations with no complex expressions for the design and operation of coal-fired systems such as furnaces and boilers.