it is mostly the use of pure nitrogen that can help reduce the cost...

     A pair of new technologies could reduce the cost of capturing carbon dioxide from coal plants and help utilities comply with existing and proposed environmental regulations, including requirements to reduce greenhouse-gas emissions. Both involve burning coal in the presence of pure oxygen rather than air, which is mostly nitrogen. The basic idea of burning fossil fuels in pure oxygen is not new. The drawback is that it is more expensive than conventional coal plant technology, because it requires additional equipment to separate oxygen and nitrogen. The new technologies attempt to offset at least some of this cost by improving efficiency and reducing capital costs in other areas of a coal plant.
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