A gantry stacker is the preferred means to provide this, at least for WICET stage one.

The approach was proposed by Aurecon Hatch, which also put together the design.

As yet a builder for the gantry stacker has not been appointed.

The WICET owners, which include Aquila Resources, Bandana Energy, Caledon Resources, Cockatoo Coal, Northern Energy Corporation, Wesfarmers Curragh, Yancoal and Xstrata Coal wanted to be able to blend up to five different types of coal with very close tolerances.

Those eight companies have made capacity commitments totalling 27 million tonnes per annum.

This is not unusual. Rio Tinto has been doing this sort of thing with iron ore for years.

WICET also wanted to reduce the number of dozers it would need to run its stockpiles.

However, one of the problems faced with coal stockpiles is the dust created by dozer push operations.

The gantry stacker would allow WICET to halve the size of the dozer fleet it would need to operate a 25-30Mtpa facility, the size stage one is expected to be.

Aurecon Hatch consultant (mechanical) Jim Harrison said one of the key aims for the WICET terminal was to reduce its dust signature.

“They realised dozers were one of the main dust causers,” he said.

The gantry stacker operates on two rails, similar to a gantry crane.

However, following the gantry crane example, in the place of the hook there is a discharge chute for the coal.

The gantry stacker simply moves over the various stockpiles, adding the coal to each as required by its blend.

Harrison said the stacker would be fed by a 6000 tonne per hour conveyor.

It also has its own transformer and switch room and an umbilical cord for its power and water needs.

“The unit knows exactly to the millimetre where it is at any one time,” Harrison said.

“Its controllers can decide where it needs to go. It goes there, checks to see there’s nothing in its path, and then starts operating. A completely unmanned operation.”

There has only been one other gantry stacker built in the world. That was used in Los Angeles at the LAX coal terminal for a short time.

Harrison said the LA gantry stacker was about three quarters the size of the one Aurecon has designed for WICET.

At this stage only one of these gantry stackers will be required. However, there are plans for two more to be added in stage two of the terminal and a fourth to be put in with stage three.

Harrison said, however, that the proponents would reassess the gantry stacker situation as part of the planning for stage two.

WICET appointed Worley Parsons to provide procurement and construction services for stage one of the terminal earlier this year. It hopes to have final approval of the procurement and construction management contract in early 2011.