Hypotheses:

Vapor inlet concentration : 40 % Volume if vapour return from service station Average outlet concentration : 2g / Nm3
Average MW : 65 (Gasoline vapours)

Calculation:

Mass of hydrocarbons at inlet per m3 = 0.4 x 65 / 22.40 x 10-3 = 1160,7 g/m3 Masse of hydrocarbons recovered 1158.7 g / m3 of inlet vapour.

The recovery rate:

The effective recovery rate is 1,49 liter per m3 of inlet vapour Vapor recovery rate : 99,9%

An accurate measurement of the recovered product is very hard to achieve:

Measurement of increase of volume in day tank
Restricted by accuracy of the level meter device, tank shall be dedicated to the unit

Measurement of inlet flow and concentration
Indirect system – restricted by flow and concentration fluctuation, meters accuracy, MW changes

Measurement of the differential between absorbent inlet and outlet
Meters accuracy