Close monitoring of coal milling with the XO particle sizer from Xoptix Ltd, safeguards coal from being over milled and helps keep NOx emissions levels to a minimum.
Xoptix Ltd, based in Worcestershire, England, have developed the in-line particle sizer XO to maintain optimum coal milling production. As world coal sources vary greatly in fuel properties and loading profiles, uncontrolled combustion conditions force operators to apply boiler settings, which are conservative and far from ideally tuned. Particle sizing technology from Xoptix has been developed for coal milling and is based on over 30 years of knowledge of laser diffraction, which can be used to determine particle size. 

With the XO inline particle sizer installed to monitor milling production, over milling and under milling can be easily and quickly be detected with real-time measurements, and the process can be adjusted accordingly. If the coal is excessively coarse due to under milling, then there will be higher levels of un-burnt carbon in the ash. This will adversely affect the efficiency of the process and create a less saleable by-product. Conversely coal feed which is milled too fine produces areas of high temperature which lead to higher levels of NOx emissions and flame instability. This results in loss of efficiency incurred by unnecessarily over grinding of the fuel. An optimum particle size distribution between these two extremes is highly desirable to ensure that power generation costs and emissions are kept to a minimum.

Richard Graves explains the importance of accurate milling to control NOx emissions, “Our XO particle sizer helps coal mills to ensure optimization of milling, which helps save production costs, but also reduces NOx emissions too. We place great importance on producing green technology that helps the environment and this ethos will always remain firmly rooted at the heart of the Xoptix culture.”
Generally coal should be pulverized until 92% is smaller than 74 microns and ideally there should be less than 2% greater than 300 microns. Xoptix Limited design, manufacture and distribute particle sizing products for process applications and are proud of their heritage in laser diffraction technology.  The sizing of particles from 0.1 to 3000 micron is made easy with a robust and stable unit, with real-time inline monitoring to optimise processes.

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