What fuel is used in a lime kiln?
Fuel for Lime Kilns
A lime kiln produces quicklime (CaO) by calcining limestone (CaCO₃) at high temperatures (900–1200°C). The primary fuels used include:
.Coal
Traditional fuel with low cost but high pollution, requiring desulfurization and dust removal equipment.
Fuel Properties:
Calorific Value: 5000–7000 kcal/kg (varies by coal type, e.g., bituminous coal, anthracite).
Ash Content: 10–30%, which may mix into the lime product, affecting purity.
.Natural Gas
Clean, efficient, and stable combustion, suitable for regions with strict environmental regulations.
Fuel Properties:
Calorific Value: 8000–9000 kcal/Nm³ (higher than coal).
Combustion Temperature: Up to 1400°C, with stable flames and no ash residue.
.Petroleum Coke
High calorific value but high sulfur content, requiring strict exhaust gas treatment.
Fuel Properties:
Calorific Value: 8000–8500 kcal/kg (higher than coal).
Sulfur Content: 3–7%, with ash content <1% (but contains metal impurities like vanadium (V) and nickel (Ni)).
.Biomass Fuel (e.g., wood chips, straw)
Renewable but with low calorific value and potential supply instability.
Types and Properties:
Common Types:
Wood chips (calorific value: 3500–4000 kcal/kg), rice husks (3000 kcal/kg), palm kernel shells (4500 kcal/kg).
Carbon-Neutral Attribute:
CO₂ emitted during combustion ≈ CO₂ absorbed during plant growth, recognized by the EU as a “zero-carbon emission fuel.”
.Alternative Fuels (e.g., waste tires, plastics)
Reduce carbon emissions but require preprocessing and specialized combustion technology.
Types and Preprocessing:
Common Types:
Waste tires (calorific value: 8000 kcal/kg), waste plastics (6000 kcal/kg), waste oil (10,000 kcal/kg).
Preprocessing Requirements:
Crushing: Tires must be shredded into particles <50 mm.
Sorting: Remove harmful substances like metals and chlorine (Cl) (e.g., PVC plastics must be eliminated).