Online Analysis and Coal-Fired Power Plant
AUTHOR: Hermine Nalbandian
DATE: September 2005
Online analysis can play a major role in minimising not only generation costs (fuel cost) but also operational issues at a coalfired power plant. The technology is accepted and widely used in the coal producing sector but its application, until recently, remained somewhat sporadic in power generating plants. However, the demand for electricity at the lowest possible cost while meeting environmental compliance (minimising emissions) has led more utilities to examine the benefits of knowing coal quality characteristics and properties in real time.
Online analysers in power plants can provide real time data on parameters such as ash and moisture content as well as elemental composition of the coal, thus showing variations in coal quality as they occur. Some analysers are mainly used to optimise coal blend to keep within emission guidelines without using excessive amounts of premium priced, low sulphur coals. A number of real time, pulverised-coal flow measurement instruments are now commercially available. Some have already been installed at demonstration and/or at commercial scale at a number of pulverised coal-fired power plants in several countries including Australia, Canada, Denmark, Finland, Germany, Japan, Republic of Korea, Portugal, Spain, South Africa, the UK and the USA. However, there are no commercially-proven devices currently available for online split control of coal flow in response to a flow meter. Work continues to develop such devices.
In-duct/boiler-outlet gas monitoring systems are being evaluated at some coal-fired plants while online carbon in fly ash gauges are regularly used not only to ascertain the saleability of the combustion products but also to optimise carbon burnout, maximise the efficiency of the mills and control the amount of overfire air. The performance and accuracy of online analysers depend strongly on initial installation, calibration, subsequent maintenance and application environment. Applying online analysis in a coal-fired power plant involves extensive planning, preparation and evaluation prior to the installation and continued monitoring and maintenance after installation.