Industrial Utility Efficiency    

Air Compressors

There are many choices of compressor technology and types of controls that can be used for variable demands. Some examples are rotary screw compressors with inlet valve control: variable speed drives: load/unload control; or centrifugal compressors with variable inlet guide vanes. However, in many cases, the efficiency of the overall compression process can be reduced significantly during lower flow demands, leading to more power per unit of air flow being delivered. It is very important to evaluate different available options and see how a plant can run most efficiently.
Compressed Air Best Practices® Magazine interviewed Dr. Jay Varadaraj, (Managing Director) of ELGi Equipments Ltd. ELGi today is one of the world’s leading manufacturers of air compressors. Like most companies, however, it started with one ambitious person. My grandfather, Lakshminaickenpalayam Govindaswamy (this where the “L” and “G” in ELGi come from) was a bus driver for the British in 1918. He purchased one bus and proceeded to build a fleet peaking at 300 buses. He believed he was in the transportation business so he entered the airline business ultimately withdrawing however when this industry was nationalized.  
Boeing Canada Winnipeg (BCW) has been recognized with the best improvement project of 2013 within the Boeing enterprise worldwide. A cross-functional project team including BCW staff, Manitoba Hydro technical support, and design engineers from Alliance Engineering Services, Inc. used innovative high-pressure storage to reduce the required size of their air compressors and save substantial utility energy and demand charges.
Most of us understand each individual has a unique DNA combination. Compressed air is very similar, each compressed air system should be uniquely designed so the system performs in harmony. Properly managing the compressed air system requires an investigative audit to understand the nuances of the system and identify the most effective solution(s) for efficiency. Not investigating the system, before selecting improvements, would be like consenting to surgery without having an exam. Yet, this frequently occurs in businesses operating compressed air systems.
Northwest Pump & Equipment was founded in 1959 - opening three branches on the same day in Portland, Seattle and Spokane. The business focus was to distribute petroleum equipment for the oil and gas market – primarily to service stations and oil jobbers. In-ground fuel tanks, hoists, lubrication equipment, lighting, farm pumps, air compressors and other gas pumping equipment were our primary product lines back when there were “Full-Service Gas Stations”. Over the years, this successful business model was expanded so the Company did business in California, Hawaii, Washington, Alaska, Arizona, Nevada, Idaho, and Montana.
This is a corn mill processing cornstarch, sugar, and other byproducts. Ambient air is contaminated with extremely high levels of dust due to the manufacturing processes and material handling. Average electric rates at the plant are $0.04 / kWh. The actual plant electric cost for compressed air production is $553,630 per year.
This glass bottle production plant had a complete compressed air audit in 2001 and 2002 at which time many successful projects reduced and stabilized the demand at 3,148 scfm at 95 psig for the high pressure system air and 9,300-9,500 scfm at 58 psig for the low pressure system. Successful application of an oversized 7,200-scfm rated cycling refrigerated dryer completely dried up the high-pressure air, allowing the removal of several non-performing desiccant dryers and savings in direct kW and purge air.
Not long ago most air compressors were controlled with mechanical pressures switches, relays and gauges. The setup of these units, especially when attempting to coordinate multiple compressors could be a frustrating and fruitless experience because often, no sooner than the controls were correctly adjusted, some sort of mechanical gremlin would throw something out of adjustment again.
Energy conservation measures (ECM) associated with compressed air have received a significant amount of attention over the years, mostly due to a reasonably short financial return compared with other energy consuming equipment. Over time many of the corrective actions put forward to reduce compressed air energy consumption have been simplified with the goal of encouraging action. Although this is done with the best of intentions, sometimes simplifications and generalizations do not necessarily lead to positive results. One of the most common energy conservation measures for compressed air that leverages best practice calculations involves reducing system pressure. It is the objective of this series of articles to highlight some of the more common issues associated with estimating energy conservation resulting from changing system pressure.
The rise in energy prices is an unwelcome reality in today’s manufacturing and business environment. And while the rate of price increases for natural gas, heating oil and electricity may vary from year to year, the upward trajectory is clear. Energy cost reduction strategies are vital to staying competitive. Compressed Air Best Practices® Magazine recently discussed heat recovery, from industrial compressed air systems, with the Compressed Air and Gas Institute’s (CAGI) Technical Director, Rick Stasyshan and with CAGI member – Werner Rauer of Kaeser Compressor. Their inputs should provide you with some insight in energy-saving technology.
When compressed air is generated, heat is inevitably produced as a by-product. Anyone looking to enhance efficiency can use this heat and increase the efficiency of compressors to about 95 percent as a result. To achieve this, there are easy-fit heat exchangers which can be fitted to existing air compressor stations. This investment often pays for itself within less than a year.