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air lifting mechanisms for oxidation in underground mines. Bruce Leavitt PE PG, Consulting Hydrogeologist Washington, Pennsylvania. Prepared in conjunction with West Virginia University under a grant from the Office of Surface Mining Applied Science Research Program. In Situ Aeration

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air lifting mechanisms for oxidation in underground mines
air lifting mechanisms for oxidation in underground mines

Bruce Leavitt PE PG, Consulting Hydrogeologist

Washington, Pennsylvania

Prepared in conjunction with West Virginia University

under a grant from

the Office of Surface Mining

Applied Science Research Program

slide2

In Situ Aeration

      • Net alkaline mine drainage.
      • Oxidize ferrous iron in mine drainage.
      • Fe2+ + 2.5 H2O + 0.25 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.
air lift test design
Air Lift Test Design

Flow Testing

4 pipe diameters (12”, 10”, 8”, and 6”)

2 diffusers

Multiple air flow rates

Oxygen Transfer Testing

High volume low DO source

Same pipe diameters and diffusers

diffusers
Diffusers

Sintered glass diffuser

medium bubble

2 inch dia. #10 well screen

large bubble

test procedure
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.

water production
Water Production

Drain Closed

Drain Open

sulfur run borehole
Sulfur Run Borehole

Closing the Ball Valve

oxygen concentration
Oxygen Concentration

Squares are set about 4 feet

Diamonds are set about 3 feet

air lift operation1
Air Lift Operation

All 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 $490.00 per year.

A ¾ hp high-pressure regenerative blower can be purchased for $700.00

conclusions
Conclusions

The 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.

conclusions continued
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 111.4 pounds iron per day.

conclusions continued1
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.

slide30

2010 JOINT MINING RECLAMATION CONFERENCE

27th Annual Meeting of the American Society of Mining and Reclamation12 Annual PA Abandoned Mine Reclamation Conference 4th Annual Appalachian Regional Reforestation Initiative Mine Land Reclamation Conference