Ames Laboratory scientists hope soon to test a new filter that would let power plants cleanly burn what’s called “dirty” coal. Iver Anderson, a metallurgist at the Ames Lab, says “dirty” coal has high sulfur content.When “dirty” coal is burned, it can produce acid rain, as there’s presently no adequate filter to keep the sulfur from escaping as the coal is being burned. Anderson says the filter that’s being developed at the Ames Lab is made of “super alloys” — metals that are very tough.Anderson says the goal is to develop a rugged filter that can last for years in 850-degrees Celsius, which is how hot it gets when high-sulfur coal is burned in a power plant. Anderson hopes the filters, or at least part of them, can be tested in a research power plant in North Dakota later this year. Anderson says perfecting the filter is the last step to reaching the point where high-sulfur coal can be burned in power plants. Over half the coal deposits in the U-S have high sulfur content, and cannot be burned in power plants because of emission problems.