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Lafarge Corporation, Concrete Example of Industrial Efficiency

This project involved the installation of sectionalized grinding chambers in the raw mill and finish mill #1 (of two finish mills) and the installation of a variable frequency drive (VFD) on the 250 HP cement slurry discharge pump.

Cement storage and loading silos Raw cement grinding mill 2,500 HP finish cement mill motor
Cement storage and
loading silos
Raw cement
grinding mill
2,500 HP finish
cement mill motor

Lafarge Corporation Case Study Summary

Under baseline conditions, the raw and finish mills were large, single-section cylindrical mills where solid steel grinding balls of all sizes were mixed together to crush the cement ingredients. This caused inefficiency in the grinding process by expending energy and time tumbling large grinding balls to impact cement material already pulverized and, conversely, tumbling light-weight grinding balls to impact raw, coarse material, to little avail.

By matching the size of the grinding media with the coarseness of the cement ingredients in each of the new grinding chambers, grinding efficiency was increased. Consequently, the energy consumption of the 2,000 and 2,500 HP electric motors powering the raw mill and finish mill #1 significantly decreased.

In addition to the measured energy savings on the raw mill and finish mill #1, there were unanticipated energy savings from finish mill #2 as a result of improved efficiency and product quality from the upgraded raw mill.

Eighty-one percent of Lafarge's non-energy benefits were the result of reduced O&M expenses which included a longer motor life of the slurry pump, and reduced cost of replacing the steel balls used as grinding media. The remaining 19% included reductions in sulfur dioxide (SO2) and nitrous oxide (NOX) emissions due to improved cement kiln stability and lower operating temperatures.

Lafarge Corporation Project Information

Location: 5400 W. Marginal Way S.W.
Description: Installation of sectionalized grinding chambers and variable speed drive
Annual Energy Savings: 4.3 million kWh/Year or 63.8 MWh over project life
Annual Energy Cost Savings: $161,250
Peak Demand Savings: 446 kW
Non-Energy Impacts: $27,500/yr. in reduced O&M, 78% reduction
in SO 2 emissions, 40% reduction in NO x emissions
Payback to Customer: 1.1 years
Project Cost: $753,838
SCL Incentive Amount: $575,509

For more information on this City Light customer, please visit the Lafarge Corporation Leaving City of Seattle public network website. For more information on Seattle City Light's projects in partnership with industry, please contact David Rodenhizer by e-mail at or call David at 206.684.3209.

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