Demand for coal in India is expected to remain strong, but China could soon turn more toward domestic sources, a report out Friday from Barclays notes. U.S. coal exporters, including Arch Coal (ACI) and Peabody Energy (BTU), were down 3.5% and 2%, respectively, in afternoon trading. The British bank said the global supply of coal climbed 10.5% in 2012. Indian exports are expected to climb next year as that country brings online new coal-fired