Why collect the vapor stream? The components of vented vapors are harmful to the environment, as well as the employees that work around them. They consist primarily of methane plus volatile organic compounds (VOCs), hazardous pollutants (HAPs or BTEX) and volatile natural gas liquids (NGLs). The vapors are sourced from heater treaters, flash gas separators, vapor recovery towers (VRTs) or crude oil and produced water storage tanks. The higher BTU content (BTUs/cu. ft) of the vapor stream can be an additional revenue source, allowing the operator to not only recover the cost of the rotary screw used to capture the vapors, but also increase return on the asset. The rotary screw compressor is one of the few rental equipment lease operating expenses that can payout beyond a breakeven point and contribute to lease profits.
How to collect the vapor stream? Install a properly sized, single stage rotary screw compressor with an auto-start feature and 100% turndown. If the compressor experiences downtime, then the vapor stream is diverted to a flare stack or combuster. Lost vapors equal lost revenue. Multi-Stream is a unique application, in that the compressor suction can be taken from any two of the source points, but primarily from the VRT and the storage tanks. As shown on the attached Fig.1 below, the vapors from the VRT and the storage tank vapors are being collected as a Multi-Stream application (patented by Flogistix LP) and switched to the sales line by a precise programmable logic controller (Flogistix Logix PLC) located on the rotary screw compressor skid. As the pressure drops below the set point of the VRT, the compressor begins taking suction from the tank vapor collection piping. When the VRT pressure rises to the set point, the suction again switches to the VRT. Two separate vapor sources are covered by a single rotary screw compressor for the price of one. To find out more, please visit www.flogistix.com.
Figure 1 Multi-Stream VRU