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Compressed Air Systems in Glass Industry

In glass manufacturing, forming of containers as well as for the forming of other specialty glass products are the main consumers of compressed air, although compressed air may be used throughout the plant for tools. In the US, electricity use for the forming section of the container glass industry is estimated to be 105 kWh/t, out of which a large part is for compressed air. In some plants, compressed air may represent as much as 3% of plant's overall energy use. Due to its extremely low efficiency (around 10% efficiency from the point of generation to the point of use), compressed air is one of the most expensive forms of energy, and therefore, requires particular attention for optimization. 

Improvements in compressed air systems are usually not very expensive, and for some measures the returns can be very high. In this section, measures that can improve the efficiency of the compressed air systems in glass industry are listed. Additional information on compressed air systems can also be found here

Compressed Air Systems in Glass IndustryTechnologies & Measures

Technology or MeasureEnergy Savings PotentialCO2 Emission Reduction Potential Based on LiteratureCostsDevelopment Status
Replacing Compressed Air by Alternative SourcesQuantitative information not available. Four cases studies in the U.S. glass industry estimate an average payback period for replacing compressed air with other applications of 5 months (Worrell et al., 2008. p.33) Commercial
Energy Recovery for Air DryingQuantitative information not available. Quantitative information not available. Commercial
Turning Off Unnecessary AirQuantitative information not availableQuantitative information not availableQuantitative information not availableCommercial
Natural Gas Engine Driven CompressorsGas fired compressors but may have lower overall operating costs depending on the relative costs of electricity and gas. In a Nestle plant payback times for a gas engine driven compressor estimated to have a payback time as low as 2.6 year with heat recovery (with 75% efficiency) and 4.2 years without heat recovery (Worrell et al., 2008. p.36)Commercial
Compressed Air System Monitoring

As a rule of thumb, every 2 psi pressure rise resulting from resistance to flow can increase compressor energy use by 1% (Worrell et al., 2008. p.31-32).

Commercial
Using Properly Sized RegulatorsCommercial
Inlet Air Temperature ReductionAs a rule of thumb, each temperature reduction of 3°C (5°F) will save 1% compressor energy (Worrell et al., 2008. p.34). A payback period of two to five years has been reported for importing fresh air.

Industrial case studies have found an average payback period for importing outside air of less than 1.7 years, but costs can vary significantly depending on facility layout (Worrell et al., 2008. p.34).

Commercial
Maintaining Lowest Possible Air Pressure and Quality

US flag An analysis of several U.S. case studies in the fiber, flat, and specialty glass industries shows an average payback period for using lower pressure of less than 3 months (Worrell <em>et al.</em>, 2008. p.37).

Commercial
Improved Load Management

Replacing single- stage compressors with two-stage compressors typically provides a payback period of two years or less 

US flag Case studies in the US show an average payback period for optimally sizing compressors of about 1.2 years (Worrell et al., 2008. p.34)

Commercial
Adjustable Speed Drives for Compressor MotorsImplementing adjustable speed drives in rotary compressor systems can save 15% of the annual energy consumption

A Glasuld glass wool insulation manufacturing plant in Denmark, realized electricity savings of 200 MWh/y (a 29% reduction) by installing an ASD on its main compressor (Worrell et al., 2008. p.37).

A container glass manufacturer in the UK was able to save 31 200 kWh/year by implementing ASD in one of four compressors in the plant. Total savings that could be achieved by implementing ASDs in all compressors were estimated to be 83 100 kWh/year (Worrell et al., 2008. p.35).
The payback period of installing an ASD in a Danish glass wool insulation plant was 3 years(Worrell et al., 2008. p.37).

For the plant in the UK, the installation of ASD saved US $2 820 and resulted in a payback time of around 3.5 years (Worrell et al., 2008. p.35).

Commercial
System Modification in Response to increased Pressure DemandQuantitative information not availableQuantitative information not availableQuantitative information not availableCommercial
Heat Recovery from CompressorsIt has been estimated that approximately 50,000 Btu/hour of recoverable heat is available for each 100 cfm of compressor capacity.

Heat recovery from large water-cooled compressors can make 20% of the annual compressor energy use available for space heating (Worrell et al., 2008. p.36).

Payback periods are typically less than one year.

Two case studies in the specialty and fiber glass industries in the US estimate the payback period for this measure is less than 6 months (Worrell et al., 2008. p.36)

Commercial
Leak ReductionOverall, a 20% reduction of annual energy consumption in compressed air systems is projected for fixing leaks;

A compressor operating 2,500 hours per year at 87 psi with a leak diameter of 0.5 mm is estimated to lose 250 kWh per year; 1 mm to lose 1,100 kWh per year; 2 mm to lose 4,500 kWh per year; 4 mm to lose 11,250 kWh per year.

An audit in a glass plant in the US found that leaks accounted for 20% of the compressed air usage in the plant (Worrell et al., 2008. p.32).

An analysis of several U.S. case studies in the fiber, flat, container, and specialty glass industries shows an average payback period for leak reduction of less than 4 months (Worrell et al., 2008. p.32)Commercial
Compressed Air ControlsEnergy savings for sophisticated compressor controls have been reported at around 12% annually;

Advanced multi-master compressor controls are expected to deliver energy savings of about 3.5% where applied. (Worrell et al., 2008. p.35)
The typical payback for start/stop controls is one to two years (Worrell et al., 2008. p.34).

Commercial
Compressed Air System MaintenanceCommercial
Maximizing the Allowable Pressure Dew Point at air IntakeAs rule of thumb desiccant dryers are considered to consume 7 to 14% of the total energy of the compressor, whereas refrigerated dryers are considered to consume 1 to 2% as much energy as the compressor (Worrell et al., 2008. p.37).Commercial
Pressure Drop MinimizationOn positive displacement compressors for each 2 psi of differential caused by flow resistance connected drive energy of connected power increases by 1% (Worrell et al., 2008. p.34).

US flag Audits of industrial facilities found that the payback period is typically shorter than 3 months for this measure (Worrell et al., 2008. p.34).

Commercial
Properly Sized Pipe DiametersIncreasing pipe diameters typically reduces compressed air system energy consumption by 3% (Worrell et al., 2008. p.35) Commercial

Compressed Air Systems in Glass Industry Publications

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