Cement Manufacturing Process 1.What is cement ? 2.History. 3.Overveiw of Cement Manufacturing process. 4.Overveiw of Kiln process. 5.Why burn wastes ?
Portland Cement . A hydraulic cement made by finely powderising the clinker produced by calcining to incipient fusion a mixture of argillaceous and calcareous materials. .Portland cement is a powder that is the active ingredient in concrete.
Concrete It is prepared by:- . Shovel powder…………Portland Cement . Shovels sand…………Mineral Aggregate . Shovels Rock………. Mineral Aggregate . Add water & mix. . It is ready to mend .
Concrete • Mixture of ingredients into a paste & triggers a chemical reaction – hydration. • Reaction forms a gel which coats & fills spaces between the stone/sand; • Hardens into a solid mass that gets stronger & stronger.
Concrete • The world’s most widely used building material. • Global production is 5 billion cubic yards per year (using approximately 1.25 billion tons of cement).
Concrete owes its strength and durability to one essential ingredient - Portland Cement.
Portland Cement • Limestone + Shale/Clay + Heat = Clinker + CKD + Exit Gas. • Material Temperatures Exceed 2700 degrees F • Pulverized Clinker + Gypsum = Portland Cement. • Cement is powder so fine that one pound contains 150 billion grains.
Portland Cement (cont’d) • Basic Chemical Components of Portland Cement: – Calcium (Ca) – Silicon (Si) – Aluminum (Al) – Iron (Fe) • Typical Raw Materials: – Limestone (CaCO3) – Sand (SiO2) – Shale, Clay (SiO2, Al2O3, Fe2O3) – Iron Ore/Mill Scale (Fe2O3)
Portland Cement (cont’d) Ca Ca O O Al2O SiO2 3 Ca Ca Ca Ca O O O O
History of Portland Cement • First cements produced by early Greeks and Romans from volcanic ash mixed with slaked lime. • This art was lost during the Middle Ages. • Portland cement developed in England by bricklayer Joseph Aspdin in early 1800’s. • Called “Portland” because concrete made with it resembled natural stone from the Isle of Portland.
History of Portland Cement • First rotary kiln designed to produce Portland cement patented in 1885 by Frederick Ransome. • First economical U.S. kilns developed by Atlas Cement Company in 1895. • Thomas A. Edison first developed long kilns (150 feet compared to 60 to 80 feet).
Types of Cement Processes • Wet Process. • Dry Process - 74% of cement produced. • Preheater/Precalciner Process.
Evolution of the cement Process • Wet process easiest to control chemistry & better for moist raw materials. • Wet process high fuel requirements - fuel needed to evaporate 30+% slurry water. • Dry process kilns less fuel requirements • Preheater/Precalciner further enhance fuel efficiency & allow for high production rates.
Cement Kilns • High temperature • Long residence time • Natural alkaline environment • CKD is only by-product of the process. • Thermal stability
Kiln Process Control • Critical Parameters: Fuel, Feed, Kiln Speed, Gas Flow • Kiln Temperatures - Burning Zone • Kiln Stability • Chemistry • Instrumentation
Why Burn Wastes? A cement kiln is a proven technology for recycling by beneficial REUSE of solid and hazardous wastes. The benefits are: – energy recovery – material recovery – economics – environmental preservation
Federal State Established Priorities for Industrial Waste Disposal • Reduction at the source. • Recycling • Energy recovery • Incineration • Stabilization • Landfill
Benefits of a recycling Program • Allows for reuse of waste materials. • Conserves virgin fuels & raw materials. • Regulated stringently for Environmental Protection.
Waste Recycling Process • Waste fuels are destroyed, releasing heat, water and carbon dioxide. • Solid materials are physically and chemically combined in the clinker product.
Cement Kilns Excellent Environment for Destroying &Recycling Wastes A Cement Kiln Provides: • 3,000degreeF + Flame • Long retention times of gasses and materials. • Stability of a large dependable industrial process. • Many inherent safeguards.
A Cement Kiln Is A Proven Technology For Beneficial REUSE of Otherwise Waste Materials The Benefits are: • Energy Recovery •Material Recovery
Recycling Programs Energy Replacement for Coal/Coke. • Liquid fuels. • Solid fuels. Material Replacement for Raw Materials (Limestone, Shale and Sand). • Solids/sludge slightly contaminated with metals. • Solids/sludge slightly contaminated with Organics.