MCPHERSON, Kan. (AP) -- A multi-million dollar upgrade is planned at the oil refinery at McPherson.

The National Cooperative Refinery Association refinery is the largest buyer of oil in Kansas. More than half of the 115,000 barrels of oil produced in the state every day goes through McPherson.

NCRA is owned directly by three farm cooperatives, the majority of it by CHS of St. Paul, Minn.

The Wichita Eagle reports (http://bit.ly/MVhDfk ) that the company is planning a $550 million replacement of its coker unit. That unit is used to process crude oil, mostly into gasoline and diesel oil.

Construction is expected to start early next year and be completed in 2015.