We take pride in our coordinated approach of applying experience and first principles to properly balance and set up coal mills.
We have separate programs for ball tube mills and ball or roller-type mills. We have extensive experience with the EL, MB, MBF, and MPS, and also with CE (Alstom) mills and the Riley BTM. Although we can step into the process to help our clients at any stage in mill improvement, our complete First Principles Program includes the following for all coal pulverizers:
All Coal Mill First Principles Programs Include the Following:
- Obtain a full range of applicable fuel analyses as well as necessary drawings, dimensions and data on the boiler, burners, classifiers, coal conduits, mills, feeders and fans.
- Perform mill internal inspections, looking for wear, erosion, corrosion, inappropriate modifications, missing or broken parts, or non-functioning parts. Inspection includes classifier outlet cylinder vs classifier vane height, classifier roof and cone, classifier blades, and outlet restrictions.
- Properly test the mills, or obtain proper mill test data.
- Seal air minimization, usually involving seal pressure control modifications.
- Certain mill modifications and repeat testing may be recommended at this time if fineness and fuel balance are significantly off.
- Test and determine accurate PA flow and “K” factor. Correct if required.
- Calculate minimum primary air (PA) flow based upon plant elevation, coal conduit I.D. and quantity of coal conduits.
- Correct mill PA/Fuel Flow curve if necessary based upon minimum PA flow and fuel classification.
- Test and reconfigure hot and tempering air damper characterization for a constant combined flow coefficient.
- Calculate burner nozzle velocity.
- Calculate burner secondary air velocities (inner and outer, as applicable).
- Recommend burner and air register specific re-sizing if necessary.
- Reconfigure and/or tune controls as necessary to accommodate new settings.
Additional Program Components for EL, HP, MB, MBF, MPS, & Alstom Mills:
- Inspection includes pyrites sweepers, and tires, throat rings.
- Redesign reject valves, throat rings, classifier vanes, and other internal components as necessary for fuel and application.
- Perform mill dribble tests to determine minimum throat velocity & minimum PA flow.
- Perform mill response tests to evaluate proper balance of mill primary air/fuel ratio at high load.
- Implement additional correction to mill PA/Fuel Flow curve if necessary based upon mill response tests.
Additional Program Components for Ball Tube Mills:
- Inspection includes liners, inlet & outlet boxes, bypass (aux. air) dampers, hot & cold air dampers, rating damper, ball charge, ball classification, reject valves, and crusher/driers.
- Ball classification evaluation and recommendation.
- Ball charge (ie, inches below the trunion) evaluation and recommendations.
- Ball charging procedure review and recommendations.
- Inlet/Outlet box modifications, if necessary, often changing area proportion, division plate angle or adding a “tail” to the division plate.
- Bypass damper inspection and modification, moving the pivot point off center to help with turndown.
- Bypass damper characterization modification.
- Rejects valve modification for positive action and external confirmation and adjustment.
- Crusher drier overhaul recommendations, placing them back in service and proper adjustment.