Cement
Build-up, coating and accretion
Also known as build-up, coating (cement), accretion, cement build-up.
Build-up, coating and accretion are interchangeable terms used in cement-industry vocabulary for accumulated deposits on the gas-path surfaces of a cement plant — preheater cyclones, calciner, kiln inlet, tertiary air duct, bypass system. Build-up is the leading single cause of unplanned cement-kiln stops.
Composition
Cement-plant build-up is dominated by:
- Alkali sulphates (K₂SO₄, Na₂SO₄)
- Alkali chlorides (KCl, NaCl)
- Calcium sulphate (CaSO₄)
- Sticky pre-calcined meal trapped in the matrix
The exact composition depends on raw-material chemistry, fuel chemistry, and where in the preheater-kiln system the deposit forms.
Why build-up matters
- Kiln stops when build-up blocks the gas path
- Lost clinker during the outage
- Operator hours to remove with hammer, lance, water
- Refractory damage from the cleaning operation
- HSE risk to operators working in the hot, confined gas-path
Active prevention
Sonic horns, air cannons and operator vigilance combine to prevent build-up from consolidating into kiln-stop conditions. The acoustic approach is the dominant preventive technology because it works continuously and causes no structural damage.
Related terms
Related terms
- Preheater towerA preheater tower is a vertical stack of cyclone separators that pre-heats raw meal with kiln exhaust gas before it enters the rotary kiln. The most fouling-prone section of any cement plant.
- Kiln-inlet ring and snowmanA snowman is a massive accretion at the cement kiln inlet that can completely block the gas path. Driven by sulphur and chloride cycles, intensified by alternative fuels.
- Sulphur, chloride and alkali cyclesSulphur, chloride and alkali cycles describe how volatile species evaporate from the kiln burning zone, condense in the cooler preheater, and recirculate. Their build-up drives kiln-stop fouling.
- Sonic hornA sonic horn is a pneumatically-driven low-frequency sound emitter (typically 60–400 Hz at 140–180 dB SPL) used to dislodge particulate fouling from boilers, ESPs, baghouses and process vessels.