Vapour recovery and equipment
During loading of bulk liquid tankers or barges, the liquid introduced displaces vapours from previous cargoes that still exist in the tank and those vapours generated by the current cargo loading. The vapours of certain cargoes contain volatile organic compounds (VOCs) that include hydrocarbons, oxygenated hydrocarbons, and organic compounds containing nitrogen or sulphur.
Oil and petrol are valuable commodities. Their vapours lead to the formation of ground level ozone, an air pollutant that triggers a variety of health problems including aggravated asthma, reduced lung capacity, and increased susceptibility to respiratory illnesses like pneumonia and bronchitis. Vapour recovery can capture an amount of vapour equivalent to 10-15 gallons of petrol and oil each time an average tanker truck unloads. During a year, that amounts to 5 million gallons of petrol that potentially could be recovered, or in other words, 37.5 million pounds (18,750 tons) of VOCs not emitted into the air.
In the simplest of terms, vapour recovery is transferring vapours from the storage tank being filled with petrol to the tanker truck that is being emptied of petrol. The first stage of the vapour recovery process collects vapours when underground or aboveground petrol storage tanks are being filled.
