Cement Manufacturers Association (CMA)

40 dealing with standard or alternative fuels, understanding kiln lining requirements and tire ring expansion is crucial. By leveraging specialized refractories, cement manufacturers can achieve better performance, longer lifespans, and cost- effective operations. Advancement in refractories for cement industry Refractories play a critical role in maintaining the integrity of cement kilns and other high- temperature equipment. Here are some key insights: Challenges Faced by the Cement Industry: 1. Usage of Alternative Fuels: Cement plants increasingly use cost-effective alternative fuels. 2. Adaptation to Wide Range of Raw Materials: The industry deals with diverse raw materials. 3. Higher Thermal Loading: Kilns operate at ever- increasing capacities, subjecting refractories to higher thermal loads. 4. Environmental Norms: Compliance with strict environmental norms is essential. Operating Parameters and Their Impact on Refractories: 1. Silica Modulus (SM): Affects coating formation. Low SM leads to wash-off, while high SM results in off-grade cement. 2. Alumina Modulus (AM): Influences coating stability. Low AM causes large ball formation, while high AM leads to a viscous state. 3. Liquid Phase (LP): Determines coating type— dense, fairly good, or porous. 4. Alkali Equivalent (AE): High AE requires alkali bypass provisions. 5. Alkali/Sulphate Ratio: Impacts coating due to coal composition. 6. Stress Factors on Refractories: • Thermal Stress: Includes thermal shocks, flame heat load, and overheat. • Mechanical Stress: Erosion, impact, and tension due to kiln ovality. • Chemical Stress: Redox reactions and corrosion from volatile alkali salts. Essentials of Good Quality Refractories: 1. High-quality raw materials: • Fireclay with low iron and alkali. • Imported low-iron Chinese bauxite. • Fused magnesia and high-sintered dolomite. • Synthetic materials like tabular alumina and mullite. • Efficient mixing machinery for raw material batches. Industry Growth and Sustainability: 1. The global refractory industry is expected to grow significantly, driven by core industries, technological advancements, and sustainability initiatives. 2. Automation and technology enhance refractory utilization within cement plants, ensuring optimal performance and longevity. Some special features of the refractories for critical area of the kiln: Preheater tower and TAD area: Extreme abrasion and impact is experienced in this area and where build up and coating occur- High density silicon carbide based compositions castables and plastics are the best solution for this area as the surface remains smooth and dust deposits can be moved very easily and maintained properly. Silicon carbide based material not only give a higher thermal conductivity but also thermal shock resistance is improved. The attack by alkali salts also is prevented as SiC% is maintained in such a way Calsilite, i.e. mono calcium silicate is formed, the mechanism being at the operating temp SiC get oxidised and the oxidation product SiO 2 first forms a self-glaze on the SiC grains which greatly reduces the coating built up. Burning zone and transition zones: These zones are divided in three areas: upper transition zone, sintering zone and lower transition zone. Upper and lower transition zone bricks are made out of high purity dead burnt magnesite and magnesia alumina spinel. In the lower transition zone, most severe conditions occur as clinker fluids are present, temperature is the highest and the coating is normally unstable and thin. Spinel bricks are fired basic products; miner logically mainly consists of spinel, and are distinguished by very high chemical resistance to alkalis, alkali salts and SO 3 . Their thermal shock resistance is also very high and after service these bricks present less disposal problems than magnesium chromite bricks. But refractories for burning zone or sintering zone