02-06-2012, 01:48 PM
Portland Cement Manufacturing
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Process Description
Portland cement is a fine powder, gray or white in color, that consists of a mixture of
hydraulic cement materials comprising primarily calcium silicates, aluminates and aluminoferrites.
More than 30 raw materials are known to be used in the manufacture of portland cement, and these
materials can be divided into four distinct categories: calcareous, siliceous, argillaceous, and
ferrifrous. These materials are chemically combined through pyroprocessing and subjected to
subsequent mechanical processing operations to form gray and white portland cement. Gray portland
cement is used for structural applications and is the more common type of cement produced. White
portland cement has lower iron and manganese contents than gray portland cement and is used
primarily for decorative purposes. Portland cement manufacturing plants are part of hydraulic cement
manufacturing, which also includes natural, masonry, and pozzolanic cement. The six-digit Source
Classification Code (SCC) for portland cement plants with wet process kilns is 3-05-006, and the
six-digit SCC for plants with dry process kilns is 3-05-007.
Emissions And Controls
Particulate matter (PM and PM-10), nitrogen oxides (NOx), sulfur dioxide (SO2), carbon
monoxide (CO), and CO2 are the primary emissions in the manufacture of portland cement. Small
quantities of volatile organic compounds (VOC), ammonia (NH3), chlorine, and hydrogen chloride
(HCl), also may be emitted. Emissions may also include residual materials from the fuel and raw
materials or products of incomplete combustion that are considered to be hazardous. Because some
facilities burn waste fuels, particularly spent solvents in the kiln, these systems also may emit small
quantities of additional hazardous organic pollutants. Also, raw material feeds and fuels typically
contain trace amounts of heavy metals that may be emitted as a particulate or vapor.