DEOXYGENATION OF COAL SEAM GAS PRODUCED ASSOCIATED WATER FOR MANAGED AQUIFER RECHARGE UTILISING MEMBRANE TECHNOLOGY

摘要

During coal seam gas (CSG) production water isrnseparated from gas. This associated water (AW) canrnthen be re-injected into a suitable aquifer. This processrnis called managed aquifer recharge (MAR).rnPrior to reinjection deoxygenation can be required tornreduce dissolved oxygen (DO) in the water. This projectrnwas concerned with the design, build, and commissionrnof a de-oxygenation plant to reduce the DO content tornbelow a concentration of 0.5 mg.L-1 in nine mega-litresrnper day (MLD) and a pressure of 2500 kPa.rnThe plant pumping system incorporated eightrnmultistage centrifugal 90 kW variable speed drivern(VSD) pumps operating in both series and parallelrnbringing the flow from a low pressure 30 kPa onto arnhigher pressure of above 2500 kPa.rnAt the heart of the de-oxygenation plant are gasrntransfer membranes. The membranes consist ofrnhydrophobic hollow fibres that allow the water to flowrnaround them and a gas stream to flow inside them.rnPlant operating analysis showed the importance ofrnvacuum line integrity to the process and that the purityrnof the N2 sweep gas and vacuum pressure were vital tornhigh-end performance.rnResults on site showed the plant could reach below therntarget DO level of less than 0.5 mg.L-1 to as low as 0.1rnmg.L-1 and that flows could range from 35 kL/hr to 400rnkL/hr at pressures ranging from 2000 – 2500 kPa.