Cement Plant Parts | Kiln Cooler Preheater | ATF

Cement Plant Spare Parts: Heat-Resistant Alloys for the Pyro-Processing Line

The pyro-processing line is the thermal heart of a cement plant, converting raw meal into clinker through a sequence of preheating, calcining, and sintering stages where gas temperatures range from 350 degrees C at the top of the preheater tower to over 1 450 degrees C in the burning zone of the rotary kiln. Every component in this circuit — from cyclone dip tubes to kiln nose castings to clinker-cooler grate plates — must withstand some combination of high temperature, thermal cycling, abrasive particulate flow, and corrosive gas-phase alkali attack. ATF manufactures castings for the full pyro-processing line in heat-resistant alloys selected to match the specific thermal and mechanical conditions at each installation point.

Preheater cyclone components operate at gas temperatures of 350–880 degrees C and experience continuous erosion from raw meal carried in the gas stream at velocities of 15–25 m/s. Dip tubes, vortex finders, and splash plates are cast in heat-resistant chromium-nickel austenitic alloys. ATF's standard preheater alloy is a 25Cr-12Ni grade (ASTM A297 Grade HH) that maintains oxidation resistance up to 1 000 degrees C and resists sulphate- and chloride-induced hot corrosion. For lower cyclone stages where temperatures approach 900 degrees C and alkali condensation is more aggressive, we supply 25Cr-20Ni (HK-30) castings with controlled silicon content (1.5–2.0 % Si) to enhance resistance to alkali sulphate penetration along grain boundaries.

Kiln nose castings and kiln-hood components face the most extreme thermal conditions in the cement plant. The kiln nose ring and dam ring are positioned at the interface between the rotary kiln and the clinker cooler, where gas temperatures exceed 1 350 degrees C and the clinker bed temperature reaches 1 450 degrees C. ATF casts these components in HK-40 alloy (25Cr-20Ni, 0.40 % C) or in a proprietary 25Cr-35Ni-Nb grade with 1.0–1.5 % niobium that forms NbC precipitates to stabilise the austenite matrix against sigma-phase embrittlement during prolonged service above 900 degrees C. All kiln nose castings are supplied in the as-cast condition without post-weld repair to preserve microstructural integrity.

Clinker-cooler grate plates must remove heat from 1 400-degree C clinker while withstanding abrasion from tumbling clinker nodules and thermal fatigue from the continuous air-quench cycle. ATF manufactures grate plates in a 25Cr-12Ni heat-resistant grade for standard reciprocating grate coolers, and in a 28Cr-15Ni grade with 2.0 % tungsten for high-throughput modern coolers where grate-plate temperatures routinely exceed 1 100 degrees C. Grate plates are investment-cast or sand-cast with integral air nozzles sized to the cooler's specific air-distribution requirements. Each plate is hardness tested (typically 200–250 BHN at ambient, maintaining structural stability at elevated temperature) and dimensionally verified against the OEM slot pattern to ensure interchangeability.

Riser ducts, tertiary-air ducts, and kiln-inlet chambers are subject to heavy particulate erosion at moderate temperatures (600–900 degrees C). ATF supplies these areas with high-chrome overlay wear plates: a mild-steel substrate with a weld-deposited chromium-carbide overlay achieving 58–63 HRC. The overlay microstructure consists of primary Cr7C3 carbides in a martensitic matrix, providing outstanding sliding-abrasion resistance. For geometrically complex duct transitions, we supply pre-formed overlay plates laser-cut and rolled to match the duct curvature, enabling bolt-on installation that eliminates field welding. Standard overlay thickness is 8–10 mm on a 6–8 mm substrate, providing 3 000–5 000 hours of service depending on dust loading and velocity.