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R. A. Nichols Engineering

Vapor Collection, Storage & Processing Specialists for the Petro/Chemical Industry Since 1975.

 

 

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AEH system 3.jpg (13338 bytes)Two-Stage Vapor Recovery Units

 R. A. 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 The systems meet the EPA 80 mg/l standard, no longer in effect, with vapor return from service stations.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.

AEH system 1.jpg (27372 bytes)              2-Stage units 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.

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