Lone Star's unique approach to environmental challenges [cement plant air pollution control]

Annually in the USA, 20 million t of cement clinker are still produced by wet process kilns. This is approximately 20% of all clinker produced in the USA. Conventional wisdom dictates that expansion of existing wet process kilns will occur via conversion to the dry process or by the abandonment of wet kilns in favor of completely new dry process lines. However, under increasingly stringent emissions requirements, this conventional wisdom is being challenged - particularly if the raw materials contain significant amounts of organic carbon and/or pyritic sulfur. This paper presents a case study of Lone Star's Greencastle, Indiana plant, at which, it is successfully demonstrated that the plant's increased clinker demands are much more cost-effectively achieved by a 'partial' conversion of the wet plant to a semi-dry process rather than a completely dry preheater/calciner process.