| 摘要 |
Emission to atmosphere of the vapor of a volatile liquid, such as gasoline, displaced from a receiving tank being filled with the liquid from a liquid storage tank of a liquid dispensing system, is reduced by conveying the displaced vapor from the receiving tank to the storage tank and cooling the vapor and the liquid in the system to a reduced vapor pressure which the system can sustain without vapor emission. In one described embodiment, the displaced vapor is returned directly to the storage tank, and the vapor and liquid in the storage tank are cooled by recirculation of the tank vapor through a cooling circuit, such as a refrigeration circuit. In a second described embodiment, the displaced vapor from the receiving tank and recirculating vapor from the storage tank are combined and returned to the storage tank through the cooling circuit. Within the flow path of the displaced vapor from the receiving tank is a normally closed pressure responsive valve which opens to permit flow of the displaced vapor into the dispensing system only when the vapor pressure in the receiving tank exceeds atmospheric pressure so as to prevent air leakage into the dispensing system. The vapor pressure in a storage tank located above ground is regulated to balance the vapor and atmospheric pressures in such a way as to avoid breathing of the tank in response to atmospheric temperature changes. |
