| 摘要 |
<p>Apparatus is provided for reducing the pressure in a volatile organic chemical (VOC) tank ullage (11) whilst minimising emissions of VOC vapours into the atmosphere. The apparatus comprises a separation module (44) having an inlet (48) for receiving vapours from the tank, an outlet (42) connected to vent pipe (21) for depleted/retentate and an outlet (46) for permeate separated from inlet (48) and outlet (42) by a membrane (18) permeable to VOC's. A pump (19) draws VOC's through the membrane whilst a vapour extractor (17) causes vapour from the ullage (11) to flow across the membrane (18). The flow of vapour across the membrane is controlled by controller (45) in dependance, at least in part, on the pressure sensed in the underground tank by sensor (23), and the concentration of VOC's in vent pipe (21) detected by VOC detector (24). The vapour flow is controlled such as to act to minimise emissions by maximising residence time in proximity to the membrane (18).</p> |
