Industrial Utility Efficiency

# A Food Processing System Assessment

 Where: North America Industry: Food Issues: Excessive Operating Costs Audit Type: Supply and Demand Side
 System Assessment Win/Win Results Energy Savings per Year: $214,907 Project Investment:$68,350 Simple ROI: 3.8 months Reduction in Energy Use: 2,540,700 kWh Equivalent C02 Emissions: 1,811.5 metric tons Equivalent C02 for Homes: 240 homes Equivalent C02 for Vehicles: 332 vehicles

### Project #1: Centrifugal Compressor Room:

Enlarge Air Compressor Inlet & Discharge Piping

The three centrifugal air compressors were upgraded with Air Relief designed Control Systems by Allen Bradley. The benefits of the control system upgrade, however, are negated by low inlet pressure of 12.2 psia into the #3 Centac. This is due to 40 feet of 10” inlet pipe (there is no significant loss with the filter). The effect of 12.2 psia inlet pressure on the #3 Centac is dramatic. This is causing a 15% reduction in efficiency of the machine. This corresponds to 319 scfm less air flow or a corresponding 61.8 kW more to deliver the same air from another source. This equates to \$45,979 in unnecessary energy costs. Calculations: (100 x 12.2/14.8 = .85 or a 15% reduction in flow; 2,128 scfm x .85 = 1,809 scfm, a loss of 319 scfm; specific power = 1,809/412.2 = 4.39 scfm/kW. This is a 15% reduction from design of 5.16 scfm/kW. The project will replace the 10” x 40’ air inlet pipe to the #3 Centac which is restricting inlet pressure to 12.2 psig with 12” x 4’ line, which will restrict a negligible amount. The compressor will now deliver about 319 scfm more air at full load. This is a 15% gain in flow. The value of the lost air is 15% of full load kW or 412.2 kW = 61.8 kW recovered during 7,440 hours/production/year. The current 6” compressor discharge piping size and design will not allow all three centrifugals to run effectively without severe restrictions, which would preclude all units to be able to stay at full load and feed the plant. This piping will be replaced with 8” pipe. This action, coupled with lowering the air demand, can have a major impact in eliminating any effects of this choke in the interconnecting piping. This will allow us to reduce system pressure and compressor discharge pressure. The #3 Centac will now be the most power efficient of the three centrifugals and from an energy standpoint should always run base load. ### Project #2: Centrifugal Compressor Room: Pressure Drop from the Desiccant Dryer and After-filter The plant has run for several months continuously at 85 psig to 89 psig system pressure due to the plugged dryer and dryer after-filter. The desiccant dryer is a 4900 scfm Pneumatic Products internally heated desiccant air dryer with the AMLOCÆ energy saving control system. This is a high quality dryer which solved the moisture problems in the facility since it was installed many years ago. Today, however, there is 14 to15 psid loss of pressure across the 4900 scfm desiccant dryer system (including filters) in the compressor room. We are only flowing about 3000 scfm at 89 to 90oF compressed air to this dryer which is about a 50% moisture load and 60% plus capacity load. We would expect full performance and a total of 4-5 psid of lost pressure with proper filtration. There is 8-10 psid of lost pressure in the after filter, which is being caused by extreme contamination from desiccant dust. The desiccant is over three years old and has been topped off about every six months. In our opinion, the desiccant should be changed every two to at least three years, in an internal heated dryer depending on what is happening. The AMLOCÆ purge control is on but the dryer is cycling (switching) every four hours. At these load conditions, we would expect this cycle time or switching time to be in the 10- to 12-hour range. Properly running we would expect to run the dryer about 30 to 35% of the time during the year with the correctly working AMLOCÆ energy saving control system. The annualized electrical energy cost to run the dryer today is: 44.25 kW X .10 X 8760 = \$38,763 per year.

This project will service this PPC dryer by completely replacing the desiccant, replace the pre- and after-filters, and get the AMLOC purge control working normally.

### Project #5: Replace or modify open blow-offs with Venturi amplifiers

Regardless of application, there are several guidelines that should always be applied to compressed air being used for open blow off:

• Use high pressure only as a last resort
• All blow off air should be regulated
• All blow off air should be regulated to the lowest effective pressure—higher pressure means higher flow, which may not be needed
• Use Venturi air amplifier nozzles whenever and wherever possible—this will usually reduce blow off air at least 50%, freeing up more air flow for other applications
• All blow-off air should be shut off (automatically) when not needed for production.

Plants with many 1/8 and 1/4 inch lines running as blow off on units will use approximately 10 and 25 cfm each, respectively, at 60 psig.

One savings approach is to use an air amplifier, which requires less compressed air. Air amplifiers use “Venturi” action to pull in significant amounts of ambient air and mixing it directly into the air stream, which amplifies the amount of air available at the point of use. Air amplifiers have amplification ratios up to 25:1. Using 10 cfm of compressed air can supply up to 250 cfm of blow off air to the process and generate a savings of a 15 cfm compressed air per 1/4-inch blow off. Savings may be available using 1/8-inch lines, but the cost effectiveness will not be as great.

During this system assessment, we identified sixty-seven (67) locations where open blows should be replaced with Venturi amplifiers. We provided the client with a detailed list. The locations included a Mixer, Bin Cleaning, Sheeting Machine, Packaging Filler, Bucket Conveyor, and the James Cartoner knife tower. Timer controls are also needed to optimize usage.

 Total average scfm reduction for this project 344 cfm Recoverable electrical energy cost (scfm/yr) $150.29/scfm Total project electrical energy cost recoverable$51,700/year Estimated cost to implement \$6,900

### Conclusion

The overall strategy for improving this air system centered on improving specific power of the #3 Centac and reducing over-all demand with compressed air savings projects. Other savings projects done that we don’t have room to detail in this article included:

 Replace 3 timer drains with level activated units in Power House 6.2 scfm Move vacuum break on Venturi generators from the vacuum line to the air line 157 scfm Replace air driven vibrators with electric driven 160 scfm Replace air hoists with electric 28 scfm Replace open blow with Venturi amplifiers or modify 344 scfm