Reuters: Duke Energy Corp (DUK.N: Quote, Profile, Research) raised the cost estimate for its proposed clean-coal gasification plant in Indiana by $365 million, to $2.35 billion, in a filing with state regulators on Thursday. In a release, Duke said the increased cost would boost electric rates by 2 percent. Construction costs were already expected to raise rates 16 percent. In November, the Indiana Utility Regulatory Commission granted Duke permission to build the 630-megawatt …