Industrial Utility Efficiency

Food Industry Factory Saves $154,000 in Annual Energy Costs The Facility This food industry factory, located in California, was spending \$386,533 annually on energy to operate their compressed air system. This system assessment detailed eleven (11) project areas where yearly energy savings totaling \$154,372 could be found with a investment of \$289,540. A local utility energy incentive, paying 9 cents/kWh, provided the factory with an incentive award of \$159,778. This reduced the investment to \$129,762 and provided a simple ROI of ten months on the project.

This project represents a true “supply and demand-side assessment”. The demand-side work identified significant opportunities to reduce compressed air consumption in blow-off air applications and in leaks. Due to article length space constraints, this article will detail how the factory reduced compressed air consumption by over 841 cfm.

It is important to note, that the supply-side, of the compressed air system, had to be modified in order to turn the reduced compressed air consumption into energy savings. A new variable speed drive air compressor and a compressor control automation system was required to turn the reduced compressed air demand into energy savings.

Supply-Side System Overview

The “specific power” rating of the current system was 5.27 cfm/kW. This energy efficiency metric means that for every one kW consumed, the air compressors generate 5.27 cfm (cubic feet per minute) of compressed air flow.

The air system operates 8,760 hours per year. The load profile or air demand of this system varies during the day based on production cycles (not shifts) – 55% of the time two compressors meet the demand while 45% of the time three compressors meet the expanded demand. Overall system flow ranges from an average of 2,591 acfm during two-compressor periods to 3,258 during three-compressor periods. The system pressure runs from 103 to 104 psig in the headers during production.

The #1 and #2 300 horsepower air compressors run as primary lead air compressors and the #3 air compressor runs as the trim (lag) unit. All the existing air compressors are sequence controlled and are rotated in sequence on a scheduled interval.

When doing system assessments, the energy savings estimates depend, in part, on the air compressor capacity control system effectively translating lower air use into reduced electric cost. The currently installed air compressors have this type of unloading controls-but they are oversized. It was necessary to install a smaller (150 hp) variable speed drive air compressor to improve the specific power of the system to 5.68 cfm/kW. Additionally, the existing piping system will allow the controls to accomplish their goals.

Project #1: Leak Identification and Repair

A partial survey of compressed air leaks was conducted at the plant and 43 leaks were identified, quantified, and logged. Potential savings totaled 245 cfm for the 43 leaks that were identified. We recommend an ultrasonic leak locator be used to identify and quantify the compressed air leaks in an ongoing manner. The plant already has such a leak detector in house. Some of the areas surveyed in the leak study included a great deal of high background ultrasound noise that shields many of the smaller leaks. In continuing the leak management program, plant staff should perform leak detection during non-production hours in order to eliminate some of the high ultrasonic background noise.

Project #3: Use Venturi Air Nozzles for Blow-off Air

This food industry plant can save substantial energy by installing venturi nozzles in four open blow areas. The following open blow projects are based on using stainless steel nozzles rather than the usual nylon composite nozzles. In total, these four open blow projects can save an average 440 cfm over all shifts at a cost of \$6,000. 1. Whey area, northeast corner, tube blowing out 25 cfm – use 9 cfm amplifier nozzle and automatic solenoid shut off valve for half the time. Savings are 19 cfm all the time. Cost is \$800.
2. Yamamoto filler room, line #1 there are 4 open blows of 25 cfm each all the time – add regulator (\$200) and amplifier nozzles (\$200) at 12 cfm each and automatic solenoid shut off valve (\$750) for half the time. Savings are 76 cfm all shifts. Cost is \$1,200.
3. Yamamoto filler room, line #2 four directional wedge nozzles at 32 cfm each used to fold plastic bag flaps could be replaced with amplifying wedge nozzles and regulated air to 80 psig and then use only 16 cfm each. Operate 20 hours a day. Savings are (32-16) times 4 nozzles at 20/24 hours = 52 cfm all shifts. Cost is \$1,000. 4. Block cheese room uses 4*4 wedge nozzles at 32 cfm each used to blow water off the cheese (512 cfm). Operate 80% of time. Replace with 4*1 air knives each using 36 cfm, or 144 total cfm. Savings are [(512-144) x 80%] = 294 cfm all shifts. Installed cost is \$3,000.

Project #5: Tank Agitation

This food industry factory has nine (eventually twelve) cleaning tanks which need agitation for maximum cleaning to occur. Cleaning takes place at night with each wash tank being agitated for about 2 hours.

The plant has built air lines with about forty-one 1/8” holes drilled every couple of inches for blowing compressed air into the water. Generally these lines are submerged only 24” and therefore have about 1 psig of water pressure on them. Thus low pressure air will work just as effectively to agitate the water, instead of using regulated but still much higher pressure compressed air.

We suggest the plant use these same lines in the same wash tanks, but beta test use of a small 7 psig blower to feed the system instead of hooking up to the compressed air system. This blower will require an electric hookup, but it appears service is available nearby each wash tank. The blower probably can fit under each tank so that it is out of the way.

 Current air flow with compressed air 13 cfm per hole (1/8” regulated to 60 psig) times 41 holes times 2 hours/24 hours 45 cfm Compressed air flow with blower air 0 cfm Total air flow saved 45 cfm Recoverable savings from air flow reduction \$110.70/cfm yr Annual electric cost savings from flow reduction \$4,981/year Total estimated cost of project (blower and installation) \$5,000 To be fair in the analysis, the blower will consume electricity. This will depend on the blower, but it will be in the range of 1 kW. This will cost 1 kW * 2 hours/day * 365 days/year * \$0.08/kWh = \$58 annually to operate. In other words, the blower solution is about 85 times more energy efficient than using compressed air. If this project is completed the utility company rebate will be calculated on the net energy savings (\$4,981 less \\$58). Once this beta approach proves successful, modify all 9 (or 12 once line #3 comes online) wash tanks. The energy savings and the utility rebate will scale up arithmetically.

Conclusion

This project is a good example of the opportunities that exist in a modern factory to significantly reduce compressed air consumption. It is also a good example of the fact that simply reducing compressed air demand doesn’t guarantee energy savings. In fact, it is usually the case that the supply-side system (the air compressors) must be reconfigured to deliver the energy savings.

Contact Hank van Ormer; tel: 740-862-4112, www.airpowerusainc.com