(Adds details and share moves from paragraph 3 onwards) June 21...

(Adds details and share moves from paragraph 3 onwards)

June 21 (Reuters) - Pilbara Minerals (PLS) , Australia's biggest independent lithium producer, said on Friday it could double its production capacity for lithium spodumene at its Pilgangoora operations in Western Australia.

A pre-feasibility study by the company determined production at Pilgangoora could increase to more than 2 million tons per annum (Mtpa), with the expansion expected to result in the first 10 years of annual production averaging about 1.9 Mtpa.

Pilbara is likely to make a potential investment decision regarding the expansion based on an outcome of a feasibility study expected in the December quarter of 2025.

The company expects to incur additional capital expenditure of A$1.2 billion ($799.20 million) for the construction of a new flotation plant to increase its production capacity. The new plant would be located adjacent to an existing Pilgan plant to leverage key existing synergies.

Shares in the lithium miner fell as much as 2.2% to A$3.130, while the broader mining sub-index .AXMM edged 0.4% higher.

($1 = 1.5015 Australian dollars)