Industrial Utility Efficiency

# Systems Approach Cuts Fabric Mill Energy Costs

A large fabric mill has implemented an energy management system based on the ISO 50001 standard to track their compressed air system efficiency.  As a result of information gained from this system, and measures learned in some recent compressed air training, the company has reduced their compressed air system costs while at the same time achieving increased fabric production output. The savings were gained by not only optimizing the supply side of the system, but by also addressing the end uses.

### Background

The large fabric mill is located in Asia and is one of four integrated textile-manufacturing facilities owned and operated by a private company. Mill 2, the subject of this article, produces about 5.5 million yards of fabric annually.

The compressed air system consists of ten large turbo compressors ranging in size from 375 kW to 500 kW.  Two smaller rotary compressors were used for seal air duty for the turbo compressors and other auxiliary uses.  The age of the turbo compressors varied, with some units over twenty years old.

The compressed air is conditioned using refrigerant style dryers.  Starting in 2008 the company started replacing their dryers with units with inverter drives to save energy, and improving environmental impact because these dryers contain non-ozone depleting refrigerants.

### Overhaul Underperforming Air Compressors

The energy management system the company implemented tracks the air compressor energy and compressed air output.  Energy meters were installed on each compressor to track power consumption.  In addition, vortex flow meters were installed to measure air output.  The output of these meters is then used to calculate the efficiency of each compressor in kWh/Nm3.

When analyzing the data, two air compressors in particular were identified as low performers and scheduled for inspection.  During subsequent overhauls a number of internal defects were found and corrected.  After the work was done, as shown in Figure 4,  it was found the  efficiency of both compressors improved by about 10 percent - saving 69,000 kWh per month totaling \$70,000 per year. Since overhaul costs were about \$72,800, the payback for this measure is slightly over one year.

One of the facility's compressors was identified as a low performer but it was too expensive to repair, with estimates totaling \$154,000. Since the cost of a new compressor was \$186,000 the decision was made to replace the unit.  The new air compressor is 16 percent more efficient that the old unit and therefore saves energy per unit output.  This compressor saves an estimated 64,565 kWh per month worth \$65,600 per year in savings. Simple payback on the complete project costs is 3.1 years. ### Conclusion Savings Results Using the energy management system the company was able to track the resulting savings from energy conservation measures. ##### Figure 6: Improvements have reduce cost and increased productivity. Click here to enlarge. An important part of this successful project was the initial tracking of the plant electricity costs through the energy management system. Both the reduction of compressed air consumption and optimization of the air compressors reduced the overall compressed air system costs significantly. This company has not only reduced their electricity costs but has also experienced increased product output volumes due to the replacement of inefficient and outdated equipment. These improvements increase plant profitability and reduce production costs. Energy efficiency measures have reduced the consumption of compressed air by 64,800 m3/day and increased compressor system efficiency, resulting in 5,532,800 kWh per year in decreased energy consumption leading to annual savings of \$468,000 per year.  This calculates to 21% savings.

For more information visit the Compressed Air Challenge® website or contact Ron Marshall, Marshall Compressed Air Consulting, tel: 204-806-2085, email: ronm@mts.net.