Limestone kiln – calcination and the carbon cycle

Integrated ScienceChemical ReactionsAges 14–15

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.