United States
Environmental Protection Agency
Air and Radiation
April 1998
      EPA Coalbed Methane Outreach Program Technical Options Series
       Appin Power Plant, New South Wales, uses mine ventilation air as combustion air in its 1C engines
                        (Photo courtesy of Energy Developments Limited)

        Significantly increases overall output of internal combustion (1C) engines

        Use in 1C engines is commercially proven at the Appin Power Plant, New South
        Wales, Australia

        Potentially economical for use in gas turbines in cases where the coal mine can
        supply gob gas or other low cost methane as the primary fuel

        Reduces overall emissions of methane, a potent greenhouse gas

Ventilation Air Use in Internal Combustion Engines
       Iining of underground coal deposits releases large quantities of methane  into the mine
       workings, which mines must remove by diluting the methane with large volumes of air.
       Many gassy mines, like the Appin and Tower Collieries in New South Wales, Australia, also
drain methane by drilling  boreholes into the coal seams and surrounding strata in advance of
mining. The mines then pipe this methane to the surface.
In the past,  the Appin and Tower Collieries  emitted to the atmosphere most of their drained
methane and all  of the methane contained in the ventilation air.   In 1996, however, Energy
Developments Limited (EDL) began maximizing the use of this methane when they installed coal
mine methane-powered generating plants at Appin and Tower.  There are 54 one-MW internal
combustion (1C) engines at Appin, and 40 such engines at Tower. The project sells most of the
resulting power to a local utility grid, and sells a portion to BHP Steel for use at the mines.

The Appin and Tower power plants use all of the gas produced during methane drainage
operations at both mines, lowering their greenhouse gas emissions. The Appin Colliery also uses
methane from its ventilation air as feed air to the 1C engines. This is the first project in the world to
commercially use mine ventilation air.  The mine uses electric vacuum pumps to route ventilation
air through its upcast shaft, then ducts it to a filtration system to remove particulates before piping it
as a supplementary fuel to the generator sets.
1                HOLES DRILLED IN
                ROCK MO COAL STMJA
              Use of methane at the Appin Colliery for power generation in 1C engines

Some Facts About the  Use  of  Mine  Ventilation  Air at the Appin  Power

- Use of methane from ventilation air as fuel increases overall plant output by 7 to 10%

  Appin can use 2,295 ft3 (65  m3) of ventilation air per second to produce 4-8 MW of electricity
   (depending on the methane content of the ventilation air)

  Ventilation air supplied to the engines typically contains 0.5 to 1.0 percent methane

  Appin recovers up to 1,306 mcf (37,000 m3) of methane per day from ventilation air

Ventilation Air Use in Gas Turbines

       Gas turbines, like 1C engines, require air to combust fuel and produce heat. Ventilation
       air can supply most or all of the combustion air required, while methane that the mine
       drains can supply the primary fuel.  A gas turbine is a simple device that consists of an
       air compressor, combustors, a power turbine, and an electric generator.  Gas turbines
are less capital intensive than coal-fired power plants, and are available in a large range of
sizes.  Ideally, the mine should locate the gas turbine adjacent to the mine's ventilation exhaust
shaft in order to minimize the transportation cost of the ventilation air.
                          Fuel Compressor
        (Coal Mine
               Duct to Compressor
                                    Shaft To
                                    Drive Compressor
                                                            Turbine Shaft

                                                                 To Generator
                                               Power Turbine
          Mine Ventilation
          Exhaust Shaft
            Schematic of Simple Cycle Gas Turbine Using Ventilation Air (Not to Scale)

The combustion air requirements of a gas turbine depend on its generating capacity.  The
combustion air required for simple cycle gas turbines is approximately 353 ft3 (10 m3) per hour
of air per kW of installed turbine capacity, based on manufacturer operating and design data
for turbines in the 1 to 100 MW size range, The more complex combined cycle plants require
slightly lower air flows.

Preliminary estimates indicate  that ventilation air containing 0.5% methane would supply 4-
12% of a turbine's energy requirements, depending  on operating pressures, temperatures,
model  selected,  and  other  site-specific  conditions.  Northwest  Fuel  Development,  Inc.
demonstrated the technique in the early 1990's, using an air mixture of 0.5% to 1.5% methane
in the combustion air, and proved that the turbine used less fuel than it would with ambient air
as combustion air.  At  present,  EPA  is  further researching the potential for using coal mine
methane, and coal mine ventilation air, in gas turbines.

For More Information.
 Changing electricity markets, coupled with environmental concerns associated with emissions
 ot greenhouse gases to the atmosphere,  are  prompting coal and electricity producers
 worldwide to take a new look at the methane contained in mine ventilation air.  Using this
 methane as combustion air for internal combustion engines and gas turbines enhances the
 productivity and economics of gas-fired power projects, while reducing emissions of methane
 to the atmosphere.

 To obtain more information about using coal mine methane as combustion air in gas engines
 at the Appin Power Project, contact:

 Mr. William Lazarus
 General Manager
 Energy Developments
 P.O. Box 535
 Richlands, QLD 4077
 Tel:    (61) (7)  3275 5555
 Fax:   (61) (7)  321 7 0733

 To obtain more information about gas turbines, contact:

 Solar Turbines,  Incorporated
 600 East Crescent Avenue, Suite 305
 Upper Saddle River, NJ 07458
 Tel:    (201)825-8200
 Fax:   (201)825-8454
Or contact EPA's Coalbed Methane Outreach Program for information about this and other
profitable uses for coal mine methane.
 Coalbed Methane Outreach Program
 401 M Street, SW (6202J)
 Washington, DC 20460 USA
       (202) 564-9468 or (202) 564-9481
 Fax:   (202) 565-2077
 e-mail: fernandez.roger@epa.gov

   R  O  6  R A M
 The mention of products or services in this case study does not constitute an endorsement by EPA.