BHP had promised to return all of the net proceeds from the $10.8 billion sale of its U.S. shale business to shareholders when the deal was announced in July.
Mitsui has said it will trim its thermal coal assets in the long term but would continue to invest in coking coal - a key raw material for steel-making.
Glencore expected to achieve annual cash savings of more than $300 million in its coal business by the end of 2018, but now it expects savings of more than $450 million by year-end.
The plants haven’t been running at full capacity after the court ruled last year that a change in regulations overseas couldn’t be a ground for increasing power prices.
Capital expenditure among the 10 largest metals and mining companies is forecast to advance to about $35 billion this year, the first annual rise since 2013.