Limestone kiln – calcination and the carbon cycle
Integrated ScienceChemical ReactionsAges 14–15
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Chemical Reactions
Load limestone into the kiln and adjust the kiln temperature: below about 825 °C the reaction barely proceeds, but from 900 °C upward CaCO₃ decomposes rapidly into CaO while CO₂ gas escapes through the chimney. The mass columns show the exact 100 kg limestone : 56 kg quicklime : 44 kg CO₂ ratio, and switching on slaking lets you watch CaO react with water to form Ca(OH)₂ and release heat. The carbon-cycle diagram alongside it adds up CO₂ from respiration, fossil-fuel burning and lime kilns, subtracts what photosynthesis absorbs, and displays the resulting atmospheric CO₂ concentration in ppm.
Lesson: Limestone extraction and the carbon cycle
What it shows
Thermal decomposition of limestone, CaCO₃ → CaO + CO₂, is the reaction behind lime and cement production. In this model it is negligible at or below 825 °C and speeds up as the kiln gets hotter. Mass is conserved: 100 kg of CaCO₃ gives 56 kg of quicklime and 44 kg of CO₂, the ratio of the molar masses. Slaking then turns CaO into Ca(OH)₂ in an exothermic reaction. A carbon-cycle panel shows atmospheric CO₂ in ppm rising with kiln emissions and fossil-fuel burning, while photosynthesis and the ocean store carbon.
How to use
Drag the Kiln temperature slider below 825 °C and note that the CaCO₃ column hardly changes, then raise it above 900 °C and watch the CaO and CO₂ columns grow. Change the Limestone mass and check that the columns keep the 100 : 56 : 44 ratio. Press Slaking: off to switch slaking on, and Load new batch to restart. Compare the ppm reading at low and high Regional fossil-fuel burning level.
Parameters you can change
- Kiln temperature 600–1200 °C
- Mass of limestone charged 10–200 kg
- Slaking: react CaO with water
- Regional fossil-fuel burning level Low, Medium, High
- Simulation speed 0.5–4 ×
Questions to explore
- What are the maximum masses of quicklime and CO₂ obtained by heating 150 kg of pure limestone?
- Why must a lime kiln be kept well above 825 °C for the decomposition to be useful?
- Which processes in the carbon-cycle panel add CO₂ to the atmosphere, and which take it out?
