Volatile Organic Compounds
When the Environmental Protection Agency was formed, in1970, it used its congressional mandate to issue all sorts of regulations regarding the discharge of contaminants into the land, water and air of this country. Over the years, air pollution has been one of the key areas where the Agency has put in place stringent requirements to control the emission of VOCs or Volatile Organic Compounds. Today the mandates of this government agency require extensive steps be taken to curtail their release by all operators of tank farms, chemical plants, refineries, fermentation plants and landfill operations. As a result of these regulations the Bio-Mass utilization industry was born.
Since VOCs are gases, the only way to provide control and movement to process it is to use compressors. In most instances, the collection and initial transport can be done with blowers or other dynamic displacement compressors, because the pressure ratios required are low (typically under 1 BAR). But the EPA mandates call for not just collection but process of the gas into a harmless form. For most gaseous pollutants, higher pressure ratios and thus positive displacement compressors were required.
Two-Stage Rotary Vane Vapor Recovery Unit
Vapor Recovery Unit System Feeding Flare
Vapor Recovery Units Are Introduced
These new types of compressor applications were referred to as VRU’s or Vapor Recovery Units. When the challenge came to the compressor industry, the first response was to put forth those compressor designs that were currently working in similar applications. This meant large bore distance piece reciprocating compressors were the selection of choice. But large cylinders were required because the higher volume gas flows were at low pressure and this meant big displacement cylinders were necessary to handle the gas. Not only did these compressors require very expensive castings but they also needed a large number of valves per cylinder. Valves, which due to the corrosive nature of the gas stream, were often very expensive to replace.
Just as the industrial air compressor market had shifted away from large reciprocating compressors to rotary designs, the VRU building companies also went in that direction. Hy-Bon Engineering of Midland, Texas pioneered the development of rotary gas compressors and developed their own line of rotary vane units designed with the capability to use both grey iron or stainless steel castings. Others like Harley Industries of Tulsa used the existing Allis Chalmers Ro-Flow vanes for their gas compressor units.
With the emergence of the flooded rotary screw compressor as the industrial air standard, compressor manufacturers such as Sullair entered the gas market by creating their own dedicated Process and Gas Compressor Division, based in Houston, Texas. This group was followed by independent packagers of Le-Roi, Mycom and Gardner Denver gas screws as they sought opportunities in the growing field of Vapor Recovery.
Subscription users only!
Subscribers are able to view the whole article. Please register/subscribe (it's free and easy) to read all articles.