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Introduction Cement has been manufactured at this location since 1903. Several thousand men were needed for construction and operation of the original plant. A large number of Polish, Slavic, Hungarian, and Italian immigrants were attracted to jobs here. They settled on plant property and formed the small community of ILASCO, named for the constituents necessary in the cement-making process: Iron, Limestone, Aluminum, Silica, Coal, and Oxygen. The original plant was expanded and improved through out its operating history until 1966, when the existing facility was constructed. At that time, one 622' x 16' kiln replaced sixteen small kilns and production was more than doubled. Today, the Hannibal kiln is the second longest cement kiln in the world, with annual production of over 600,000 tons of clinker. Continental's distribution network includes shipments from the production facility and terminals in St. Louis, and Bettendorf, Iowa. As with any industry, technological changes have occurred. At the time of our plant modernization, wet process kilns were the most common. Coal, the primary kiln fuel, was abundant and relatively inexpensive. With rising fuel costs, many plants have been built with low fuel consuming components known as pre-heaters and/or pre-calciners. In order to respond to an environmentally beneficial opportunity and remain competitive, Continental began using supplemental waste fuels for energy recovery as a direct replacement for coal in 1986. This usage increased over the next few years; and, in 1992, Continental acquired the assets of an on-site fuels recycler and formed MFR (Missouri Fuel Recycler). MFR rapidly expanded the use of waste fuels by adding two patented processes for handling solid waste. In 2005, Continental/MFR partnered with AES to form Green America Recycling. Today, Continental/GAR is recognized as an industry leader. This merger of operations has provided a new era of competitive cement operations and has proven to be environmentally beneficial. By replacing coal, a natural resource is preserved, and kiln stack emissions are much cleaner. Waste that would otherwise be incinerated is reused for energy; and we all benefit. |
Cement is made from common materials such as limestone, clay, silica, and iron ore. Principle raw materials are a blend of 92% limestone and 8% fire clay. The limestone is mined from quarries on Continental's 3,500 acre plant site at Hannibal. Clay is trucked in from reserves at our Owensville, MO operation, 120 miles southwest of the plant. Large limestone boulders are dumped into the primary crusher and broken into gravel sized particles. Clay is also introduced through the crusher, and the combined material is conveyed into one of five 2,000 ton storage silos. Feed requirements for the kiln are approximately 3,200 tons a day. Raw materials are selectively withdrawn from the storage silos, fed through the secondary crushing system, before introduction into the raw mill. In the 3,000 HP mill, 200 tons of steel balls reduce the crushed rock to a fine powder, and water is added to create a thin mud called "slurry". The slurry is then pumped to one of several blending and storage tanks, where it is kept in suspension with agitating mixers. Chemical composition is determined by x-ray and spectrophotometric analysis, and a precise mixture is blended to assure consistent quality for the cement making process. This feed is then introduced into the kiln through a system of pipes, pumps and mass flow meters. Continental's kiln is a cylindrically shaped industrial furnace, lined with heat resistant firebrick. The 622' x 16' kiln rotates approximately 68 revolutions an hour and has a production rate of 1,900 tons per day. Raw feed is introduced into the slightly inclined kiln at the cold feed end, and gradually moves toward the burning zone. As material passes through the kiln, physical and chemical changes occur. The entire process takes about 2.5 hours. The first section of the kiln is a large heat transfer unit hung with 260 tons of chain in the chain zone, water is evaporated and material temperature rises above 1,000°F. The feed then passes through the calcining zone, where carbon dioxide is disassociated from the limestone at 1650°F. Material temperatures rise to 2250°F in the burning zone, and the primary constituents (silica, iron, aluminum, and calcium) combine to form hydraulic silicates ("clinker"). Fuel requirements for the kiln, supplied by a combination of coal and waste material, are equivalent to approximately 22 tons of coal per hour, or in excess of 400 million BTU's per hour. Gas temperatures in the kiln are above 3,500°F. |
The intense heat of the kiln ensures destruction of any organics in the fuel, and metals are chemically bonded in the crystal structure of the clinker. An induced draft fan pulls a countercurrent air stream through the kiln. Gases from combustion, calcination, and water evaporation are drawn through a four-stage electrostatic precipitator (ESP) for particulate control and exhausted to the atmosphere through a 150-foot stack. The nerve center of the plant is the central control room where monitors and instrumentation allow operators to continuously control the entire manufacturing process. Redundant certified Continuous Emission Monitors (CEMs), installed on the kiln stack, provide a record of 02, CO, CO2, NOx, SO2, THC, and opacity. Automatic waste feed cut-offs, set by stack testing results and federal regulations, are in place to assure compliance. A cement kiln provides a perfect environment for safely processing cerain waste materials and recovering their energy value. |
Portland Cement from Clinker Clinker is discharged from the kiln into a cooler, where high volume/high pressure fans drive the heat from the material. Heated air is recycled back to the kiln for use as combustion air. After the clinker cools to approximately 150°F, it is delivered by a conveyor system to one of 12 storage silos. The plant has two 2,500 HP finish mills, that are each charged with steel grinding balls. Clinker is fed to the mills with about 5% gypsum to produce Portland cement. Each mill can produce 60 tons of cement per hour. After leaving the finish mill, the finely ground cement is fed into a separator system for final classifying before being transported to the storage and shipping silos for distribution. |