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1.1 Cemex Lyons Cement Plant <br />The Lyons plant was commissioned in 1969 and has been in continuous operation for over 33 <br />years producing portland cement. Limestone, shale, and sandstone are quarried in the Lyons <br />area and delivered to the plant. These minerals contain the necessary proportions of calcium, <br />silica, iron and alumina for creating the calcium silicates that is the active ingredient in portland <br />cement. Crushed limestone, shale and sandstone are precisely metered into ball mills which <br />pulverize it to a fine powder called raw or kiln feed. The kiln feed is introduced to the <br />preheater/precalciner that heats the material to over 1550 degrees F, calcining it (turning it to <br />lime), using a combination of waste heat from the kiln and additional fuel. This calcined <br />material is then fed into the rotary kiln. The rotary kiln is a 245 foot long, 14.5 foot diameter <br />rotating pipe. It is an effective mixer, conveyor and reaction chamber. Material is gradually <br />heated from 1550 degrees F to over 2600 degrees F. During this process the lime turns to <br />cement clinker with all the chemical properties of the finished product. Cement clinker is <br />typically a black granular material with the consistency of gravel. <br />The clinker from the kiln is metered into the finish mill along with a small fraction of gypsum. <br />The finish mill is a ball mill that pulverizes the clinker and gypsum into a very fine powder that <br />is the finished product -portland cement. <br />A combination of fuels is used in the Lyons preheater/precalciner and kiln system. Coal and <br />natural gas have been the most common. Tires and other materials have also been used. The <br />fuel choice is based on a combination of the fuel's cost and chemical composition. <br />1.2 Tire Derived Fuel Test <br />Cemex expressed an interest in evaluating tires as a kiln fuel source early in 2002. This fact <br />was widely communicated in Boulder County. Tires have been commonly used as fuel in <br />Europe, North America and other locations since the 1970's. They carry a high heat value and <br />are extremely volatile at high temperatures, properties important in industrial processes. <br />Community members frequently ask questions about how the process emissions change as <br />the fuel sources change. Extensive testing has accompanied the trial and startup of tire <br />derived fuels at most facilities. The experiences at most facilities have been that emissions <br />typically do not change a great deal. The concentrations of some elements and compounds go <br />up, and some go down by small amounts. Typically, there have not been large changes in <br />actual emissions, up or down. <br />7 <br />