Two-Stage Vapor Recovery Units
Nichols Engineering Two-Stage VR Unit has a recovery efficiency of 93% of saturated inlet
gasoline vapor. The 2-Stage VR Unit emissions are 67 mg/l or 0.164 gal/1000g with
saturated inlet gasoline vapor. The systems meet the EPA 80 mg/l standard, no longer in
effect, with vapor return from service stations. In
larger terminals, >2M gal/day, serving mandated Service Station Stage I accounts, the
system shows higher economic returns than a 1-Stage VRU, both with a Burner.
2-Stage units are more complicated than the 1-Stage unit, but
still much simpler than carbon and refrigeration units. These units have again
typically only two motors and various pressure and flow control valves. The two-stage sliding vane compressor has a first-
and second-stage compressor with a common motor and the absorber fuel supply
pump has the second motor. A 300 cfm system has 120 nameplate hp. Maintenance
costs are dramatically lower than any carbon or refrigeration unit in operation
as the systems only run when they are processing vapor.
are very effective for large terminals with Stage 1 and minimal diesel loading. The advantages of increased efficiency are often
outweighed by lower capital cost, simplicity and decreased operating and maintenance costs
of the 1-Stage VR Unit. Both single and 2-Stage VR Units use a tail gas burner. Burner
outlet emissions to less than 0.5% of inlet vapor volume, less than 5 mg/l, and/or more
than 99+% efficiency.
To Print This Page, Please Orientate Your Printer To