Industrial Utility Efficiency    

End Uses

In this series we covered some very common issues in the Compressed Air Generation or “Supply Side” with regard to misapplying some capacity controls and installing different types of air compressors with piping and/ or orientation. These can preclude any reduction in compressed air demand on the production side from effectively translating lower air usage into a commensurate level input energy.
A flour based frozen foods manufacturer orders a compressed air efficiency audit. The audit establishes the cost of compressed air at $0.27/1000 cubic feet. The study finds the 116 pulse jet dust collectors represent the greatest opportunity for compressed air demand reduction and energy cost savings. A dust collector optimization study/service is suggested and the customer agrees to proceed. In this facility, pulse jet dust collectors are used to filter dust from raw materials entering the plant, for conveying and mixing of ingredients, and for the final packaged finished products leaving the plant.  
In the last ten years, the design of pneumatic systems has changed dramatically, mainly due to developments in the technologies that create them. Pneumatic manufacturers’ online tools for sizing components have evolved, the fieldbus systems are ever-changing, component designs are constantly improving, and network devices such as the Industrial Internet of Things (IIoT) have reshaped the industry. All these advances play a large role in optimizing the efficiency of pneumatic systems, but the age-old practice of routine maintenance must not be overlooked. This article will focus on proper air compressor sizing, proper pneumatic component sizing and predictable preventative maintenance. 
One of the most common problems in plants is low air pressure. One of the most common solutions is to purchase new air compressors. Often this advice leads to a poor return on investment with the company’s hard-earned money. Often the issues are related to demand, distribution, or both. Solving the wrong problem can be expensive from a capital and operating cost perspective. Determining root cause analysis may cost more up front, but will save tens if not hundreds of thousands of dollars long term.
A zinc producer spends an estimated $516,000 annually on electricity to operate the air compressors in a compressed air system at its north American plant.  The current average electric rate, at this plant, is 5 cents per kWh, and the compressed air system operates 8,760 hours per year. This system assessment recommended a group of projects able to reduce these energy costs by fifty-one percent (51%) to an annualized $270,000.  The simple payback of the project was 15 months – without taking into account potential incentive dollars from the local utility.
A meat processor, located in Canada, hired a consultant to assess their compressed air system as part of a company-wide energy conservation effort. The assessment and analysis showed, despite having a modern compressed air system using a VSD air compressor and pressure/flow control, the system was running inefficiently and had significant levels of leakage and inappropriate use.
An electronics manufacturer with a very large compressed air system recently had a compressed air audit done in their plant to assess system efficiency. The audit discovered the system had been designed to be extremely efficient, yet some previously undetected problems were causing less than optimal operation. Despite being located in a tropical environment, this plant utilizes heat recovery to help reduce the overall energy consumption.
Parrheim Foods, a division of Parrish and Heimbecker, is an innovative starch, protein and fiber mill situated in Saskatoon, Saskatchewan, Canada.  The plant has improved system efficiency and reduced production problems by addressing some problems with the consumption of compressed air by their reverse pulse baghouse cleaning operations.  This effort has allowed them to turn off one of their 100 hp air compressors, saving significant electricity costs.
A chemical plant spends an estimated $587,000 annually on electrical energy to operate their compressed air system. In addition, the plant has an expenditure on rental air compressors of equal or greater size - but this will not be covered in this article. The plant was built in the 1940s and modernized in the 1970s. The plant generates its own power and serves many processes. The average cost per kWh is $0.0359.
Compressed air is used as a convenient and often necessary source of air flow to perform blow-offs, cooling, or drying.  And since compressed air is a costly utility, a frequent recommendation in this magazine and audits is to reduce the compressed air use by using high efficiency engineered nozzles.  Using these nozzles is a good practice as they are designed in a way that uses the compressed air to accelerate the surrounding air to deliver the same mass transfer effect as a standard nozzle (or tube) with a much larger orifice.
At a Midwest window manufacturing plant, the cooling process for the plastic frame pieces, after leaving the extruder, was critical to process productivity and quality. Too much cooling air (or not enough cooling air) would generate scrap and rejected product. The plants’ 17 extruders and 55 separate blow-offs in these lines had similar cooling stations at the cooling boxes. They consisted of about three hoses at each exit frame angled down to the extruded piece moving past it. The compressed air flow was controlled by a manual control valve set by an operator. The operator used his experience to control the flow delivered and thereby control the product quality.