Industrial Utility Efficiency

# Food Processing Plant Eliminates 734 scfm with Nozzle Upgrade

This food & beverage plant is a large (500,000 sq ft) meat processing plant with twenty packaging lines and nine palletizers. The compressed air system is supplied from three separate rooms with seven individual lubricant-cooled, single and two-stage rotary screw compressors. The plant has four blower purge desiccant dryers designed to deliver a - 40°F pressure dewpoint.

### Current System Summary

Annual plant electric costs for compressed air production, as operating today, are $230,640 per year. If the electric costs of$32,640 associated with operating ancillary equipment, such as dryers are included, the total electric costs for operating the air system are $263,100 per year. These estimates are based upon a blended electric rate of$0.06 /kWh.

The air system operates 8,760 hours per year. The load profile or air demand of this system is relatively stable during all shifts. Overall system flow ranges from 2,554 acfm during production to 1,903 acfm during sanitation. The system pressure runs from 96 to 100 psig in the headers during production.

### Open Blows

Due to article space limitations, we will only outline the compressed air flow-reduction project focusing on installing venturi nozzles on blow-off air locations.

With open blows, turbulent compressed air blasts straight out of the pipe or tube. It not only wastes huge amounts of compressed air, but also violates OSHA noise and dead ended pressure requirements.

Air jets and air flow-inducing nozzles used in place of open blows can reduce noise level, lower compressed air use, and most often improve blow-off operation in both productivity and quality.

Air Power USA, Inc. has developed the following data over time. It is relative to specific standard products available in the industry. A test of one nozzle may vary somewhat from another nozzle of the same manufacturer, but not significantly. Below are some important points to remember:

• In blow-off, thrust from pressure (psig), is required to loosen the objects to be removed.
• Thrust dissipates very rapidly once the air has left the “blow-off” device.
• In blow off, volume of total air (cfm), compressed air plus induced air, is critical to carrying the blown-off material away within the air stream.
• Use expensive compressed air only as a last resort; mechanical, hydraulic, etc., will always be more energy economical and often safer.
• All blow-off air should be regulated to the lowest effective pressure – higher pressure means higher flow, which may not be heeded; higher pressure air costs more to produce.  Blower pressure air is cheaper.
• Use Venturi air amplifier nozzles whenever and wherever possible – properly selected and applied for needed thrust and volume, this will usually reduce blow-off air at least 50%, freeing up more air flow for other more valuable applications.
• All blow-off air should be shut off (automatically) when not needed for production.
• When blower-generated air is available or apparently economically feasible, always compare the net energy cost to alternatives.
• There is substantial potential savings to install automatic compressed air shut-off at various points using blow-off air.  This will shut off the compressed air whenever the line stops or the product flow is interrupted.  It will automatically blow again when needed, as sensed. If the plant does not have a current PLC or electric eye system in place, we recommend choosing something similar to the Exair Model Electric Eye Controller, which is economical and simple to install.

Table 2: High-pressure blow-off air locations

### Summary

Reducing average compressed air consumption was the key to improving the efficiency of this food processing plant. Spending time examining compressed air leaks and the packaging equipment allowed our team to find the major compressed air flow-reduction opportunities. The compressed air equipment was in good working order. The controls on the air compressors and the compressed air dryers simply needed to be used to their full potential.

Table 3. Summary of Key Compressed Air System Parameters and Projected Savings