Industrial Utility Efficiency    

Compressor Controls

A large chemical plant in Celje, Slovenia, planned to retrofit a kiln used to produce titanium dioxide. To make space for the new equipment related to the retrofit, the plant needed to relocate its high-pressure compressed air system feeding an adjacent pressing process used to dry the material before firing it in the kiln. However, a comprehensive compressed air audit using cloud-based software showed the plant did not need to relocate the system.
This building products factory spent an estimated $240,000 annually on energy to operate the compressed air system at their Midwestern facility. This figure will increase as electric rates rise from their current average of 7.8 cents per kWh. The set of projects recommended, by the system assessment, reduced these energy costs by an estimated $104,336 or 43% of current use. Project costs totalled $73,000, representing a simple payback period of 8 months.
Air Demand Increase of 43% Results in Only a 5% Energy Cost Increase Compressed air is an expensive medium; yet, many compressed air systems are wastefully managed with minimal system transparency. Capturing essential system performance data and monitoring critical air quality data is not only eye opening, it enables future investments in compressed air systems to be fact-based and traceable.
“I don’t understand. I attended the Compressed Air Challenge® Fundamentals and Advanced courses. I read every article and book I could find on improving the efficiency of compressed air systems. I developed great ideas about how to reduce my compressed air consumption. We fixed leaks, “right-sized” filters to reduce pressure drop, changed piping, moved some processes to shifts that used less compressed air, bought low consumption nozzles and educated our entire workforce. We did all of this work and I still have six out of six compressors running. Reducing my air consumption does not appear to have reduced my air production!”  
The Trinity Mirror Group print works on Oldham is one of the UK’s largest newspaper printers. The nine presses in the facility produce around 1million papers every day, including the Independent, the Daily Mirror and a range of local, regional and sports titles. Printing on this scale does not come cheap in energy terms, however. The plant’s annual electricity bill is in the order of £1.5millon. With energy prices on the rise, and a strong desire to improve environmental performance and reduce its carbon footprint, the plant’s management has recently embarked on a project to cut energy use substantially.
It has been my experience that more than 50% of industrial air users don’t control their air compressor resources effectively. As a result, a tremendous amount of energy is wasted. When my firm does audits of plant energy consumption, it’s not unusual for us to encounter installations with large numbers of independently-controlled compressors that are all running at different pressure settings and different loads.
Treating compressed air as a true utility and outsourcing the entire process is a growing trend in the industry. If a plant does not generate their own power, provide their own water or deliver their own natural gas, then why not treat compressed air requirements in the same manner? This article will use a recent project as a case study to show the benefits one factory received by making the decision to outsource compressed air like a utility.
While control storage was originally an integral component of a reciprocating air compressor installation, this article will only briefly explore that application. The content of this article will focus instead on rotary screw installations since the rotary screw air compressor has essentially replaced the reciprocating as the compressor of choice in industrial applications. It should also be noted that in compressed air systems where reciprocating and rotary screw air compressors are operating together, control storage should always be utilized.
The U.S. Department of Energy estimates that air compressors use as much as 10% of all electricity generated in the United States. Further, the DOE calculates that as much as 50% of this energy is wasted. Compressed air leaks alone account for 25-30% of compressed air use.
The objective of a compressed air management system is to improve the Key Performance Indicator (KPI) of “Energy Intensity” as it relates to compressed air. This translates into improving the ratio between the volume of product shipped and the net electricity (kWh) consumed by the compressed air system. How many thousand bottles, per compressed air kWh consumed, were shipped this month?
Pneumatic air cylinders play a major role in allowing a modern sawmill to produce at the high-speed production rates required. Stable air pressure is critical to allow the air cylinders to respond in a timely manner and avoid any production delays.