Cement
Calciner
Also known as cement calciner, inline calciner, separate calciner, precalciner.
A calciner is the combustion chamber in a modern cement preheater tower where raw meal is pre-calcined — the endothermic CaCO₃ → CaO + CO₂ reaction is driven to ~90% completion — before the meal enters the rotary kiln. Calciners can be inline (placed in the kiln-riser gas path) or separate (a dedicated combustion chamber receiving tertiary air through a dedicated tertiary air duct).
AFR firing
Calciners are the dominant firing location for alternative fuels (RDF, SRF, TDF, sewage sludge). They tolerate variable-quality waste fuels better than the main kiln burner because residence time is longer and temperatures are lower. Cement plants targeting high thermal substitution rates (TSR) concentrate their AFR firing in the calciner.
Fouling
AFR firing in the calciner raises the chlorine and sulphur loading of the gas reaching the preheater cyclones above. This intensifies the build-up problem in the lower preheater stages and the kiln riser, driving the need for chloride bypass and active sonic-horn cleaning.
Cleaning
Sonic horns are mounted on calciner walls and on the calciner outlet to the preheater stage 5 cyclone, keeping the gas path free of the alkali coatings that accumulate at high AFR rates.
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.
- Preheater cycloneA preheater cyclone is one stage of a cement-plant preheater tower. Lower stages (stage 4-5) suffer the worst build-up and are the primary target for sonic-horn cleaning.
- Rotary kilnA rotary kiln is a long inclined rotating cylinder where preheated raw meal is burned at 1,450 °C to form clinker. The heart of every cement plant.
- Alternative fuelAlternative fuels (AFR) replace fossil fuel in cement kilns. They cut CO2 emissions and waste-disposal cost but increase chlorine, sulphur and alkali loading in the kiln gas.
- 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.