The objective of this article is to look at typical industrial wastewater agitation processes and share various energy saving compressed air/blower projects that have worked well over the years. These basic fundamentals are a good starting point to begin the evaluation of a project idea. There are three primary uses of compressed air in all wastewater treatment applications. This article will focus on agitation and movement of materials.
Operating the vacuum system at higher levels (then necessary) affects the needed volumetric flow to compensate for leaks. This required compensation of volume (ACFM) must be added to the nominal production flow demand. The ambient air leak into the system will expand to the highest vacuum level, which is known as the “Expansion Ratio.”
What is vacuum as used in the manufacturing/industrial sector? The clearest answer is – a contained space with gaseous pressures much less than surrounding atmospheric pressure. Atmospheric pressure (ATM) is expressed in many units of measure. At room temperature a cubic foot of contained air at sea level – the random movement and molecular impact on the walls of the containment vessel equal a force of 14.7 psia for every square inch of the walls.
This article reviews two common pneumatic conveying system types and the importance for each operating plant to know their design and operating parameters particularly conveying air flow velocity and particle velocity profile.
In open end pipe line suspension flow, or dilute phase pneumatic conveying, proper particle velocity is critical to continuing productivity and product quality. Until recently, measurement of actual particle velocity within the pipe has not been practical outside the laboratory. The plant operating personnel depend on a much less accurate metric - estimating the conveying air velocity in the pipe and relating that to particle velocity.
Air-driven Venturi vacuum generators have long been a viable option for fast-response, localized, vacuum-powered systems. Through the last decade, they were considered convenient and flexible solutions with quick response time. However, they were not regarded as energy efficient, probably due to their use of compressed air. Extensive product development with this equipment — particularly the crucial system accessories — often makes the selection of the most energy-efficient items difficult for many localized operations.
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.
The object of this article is to look at some very typical industrial water treatment processes and various compressed air and energy savings projects that have worked well for our clients over the years. The basic fundamentals with regard to compressed air usage are similar to municipal water treatment – a good starting point.
In many manufacturing operations, a very significant compressed air use is pneumatic conveying of many types of materials such as cement, fly ash, starch, sugar, salt, sand, plastic pellets, oats, feeds, etc. Often these are systems that use high-pressure air (100 psig class) reduced to lower pressures (15 psig, 45 psig). This creates an air savings opportunity.
This factory currently spends $735,757 annually on the electricity required to operate the compressed air system at its plant. The group of projects recommended in the system assessment will reduce these energy costs by an estimated $364,211 (49% of current use). Estimated costs for completing the recommended projects total $435,800. This figure represents a simple payback period of 14.4 months.
