Presentation on theme: "air lifting mechanisms for oxidation in underground mines"— Presentation transcript:
1 air lifting mechanisms for oxidation in underground mines Bruce Leavitt PE PG, Consulting HydrogeologistWashington, PennsylvaniaPrepared in conjunction with West Virginia Universityunder a grant fromthe Office of Surface MiningApplied Science Research Program
2 In Situ Aeration Net alkaline mine drainage. Oxidize ferrous iron in mine drainage.Fe H2O O2 = Fe(OH)3 + 2 H+Reaction rate proportional to pH.Lower reagent cost than hydrogen peroxide.Design parameters unknown.Potential for carbon dioxide removal.
11 Test Procedure Adjust dock height to less than ¼ inch from overflow Measure depth to diffuser.Warm up blower.Measure and adjust air flow. (before and after test)Read Magnehelic.Open 4 inch ball valve in dam.Close bypass valve & time tank filling.Pump produced water back into lake.
21 Oxygen Mass Transfer Comparison at 14 cfm Pipe DiameterAeration stoneWell ScreenImprovementinchgrams / minutepercent124.143.5516.6105.033.3848.884.873.0559.663.412.0169.6
22 Air Lift OperationAll air flows used in this testing can be achieved with a ¾ hp high-pressure regenerative blower. (smaller units are possible)At $0.10 / kW hr the daily cost of operation would be $1.34 or $ per year.A ¾ hp high-pressure regenerative blower can be purchased for $700.00
23 ConclusionsThe use of low pressure air to create flow in a zero static head setting has been demonstrated.The volume of water moved with such a small volume of air surpassed expectations.Five cubic feet of air per minute is able to generate 200 gallons per minute of water flow.Oxygen transfer to the produced water only achieved 25 percent to 30 percent saturation under the best conditions.
24 Conclusions continued In most tests, there is not a significant difference between the DO produced by the well screen and the stone diffuser at the same depth.There is a tendency for the shallower depth setting to produce a higher DO than the deeper setting.Based on the calculated oxygen delivery to the mine, between 23.8 and 35.1 grams of iron per minute can be oxidized. This rate of iron oxidation is equal to 75.6 to pounds iron per day.
25 Conclusions continued Based on these tests the 8 inch riser with stone diffusers is the most economical configuration.Construction of a large diameter borehole may be expensive, but the cost of equipment and it’s operation is low.Borehole maintenance will be required.
30 2010 JOINT MINING RECLAMATION CONFERENCE 27th Annual Meeting of the American Society of Mining and Reclamation 12 Annual PA Abandoned Mine Reclamation Conference 4th Annual Appalachian Regional Reforestation Initiative Mine Land Reclamation Conference