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Mill Optimisation

Mill Optimisation

Importance of Milling

Influence on Mill Performance on Combustion and Boiler Performance

Milling performance is critical in controlling the combustion process in the boiler.

Coal pf fineness influences:

  • ignition delay;  
  • combustion efficiency;
  • particle erosion;
  • loss on ignition (and hence coal costs);
  • value of ash and ability to dispose / sell;
  • emission levels;
  • boiler slagging and fouling;
  • potential damage to superheater tubes from combustion delay.

Need for Testing

  • Mill maintenance costs are one of the highest maintenance costs in a coal fired power station;
  • Testing allows a change to 'condition based' maintenance (from set mill operating hours) which in HRL's experience can increase time between minor / major mill overhauls by up to 10%;
  • Optimising milling performance can reduce coal consumption and therefore costs;
  • Testing can help detect mill performance issues early and can help direct / target maintenance activity.

Broader HRL Mill Performance Capability

The EUcoalsizer fits into the broader mill performance service offer to assist in optimising mill performance.

  • Measurement of pf flow per burner duct microwave technology;
  • Coal flow balancing (e.g. by adjustment of values on PF pipes);
  • Check / calibration of coal flow obtained from volumetric or gravimetric coal feeder to mill and check on mill capacity limits (and assessment of reason for limits);
  • Mill power consumption (per unit of coal throughput) including as a check on classifier recirculation rates;
  • CFD modelling of milling system to solve flow related issues;
  • Adjustment of classier vane setting or redesign to adjust pf fineness;
  • Mill condition and inspection;
  • Measurement of pressure drop across mill / classifier;
  • Mill performance as a function of load / coal throughput;
  • Measurement of PA flow / auxiliary air / mill seal air flowrate;
  • Comparison of measurements against station instruments;
  • 'Clean' (no coal flow) testing to measure air flow distribution to burners;
  • Assessment of individual mill performance and recommendations for maintenance, physical modifications, or operational changes;
  • Measurement of mill inlet / outlet temperature, and check on temperature stability;
  • Testing of mill performance following major overhaul to demonstrate performance gain and to help optimise future overhaul scope of work;
  • Assessment of materials, failure analysis, requirement for repair or replacement.

Introducing the EUcoalsizer

EUcoalsizer Features

  • Measures (in real time) pf particle size distribution (PSD), coal and air flow;
  • Provides spatially resolved (2D) readings;
  • Allows real time coal : air flow tuning and adjustment of coal feeders / mill control settings;
  • Requires larger 3" ports to be installed.

Benefits of EUcoalsizer

  • Cost of testing is dramatically reduced.  Testing is conducted by a single operator;
  • The cost competitiveness allows regular e.g. quarterly or bi-annual testing of all mills;
  • This in turn facilitates moving to a 'condition based' maintenance program and hence a reduction in mill maintenance cost, as well as prioritising mill maintenance to optimise combustion performance;
  • Allows milling performance to be characterised following a change in coal supply (or evaluation of suitability of a particular coal supply);
  • Allows real-time assessment of changes to mill operation and settings on pf size and hence adoption
  •  of a mill operation optimisation program;
  • Optimising mill performance can result in reduction in coal consumption, carbon in ash and allows full benefit to be obtained from combustion tuning.

What Our Clients Say

"For certain alleged foreign matter complaints in our products we need not only the analytical services provided by the lab there at HRL, but particularly the expert opinion of scientists such as Greg Richards to give an independent opinion on the ...

Andrew Penncuick
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