When a mixture of limestone and clay is heated in a rotary kiln, cement is produced. burning a mixture of methane and air heats the kiln. carbon dioxide is one of the main gases give two reasons why. and give a reason why sulphur dioxide has a high percentage coming out of the kiln?

Carbon dioxide is a primary effluent gas because it is being generated in large amounts by:
1) The burning of methane which produces water vapor and carbon dioxide
2) The decomposition of limestone, CaCO₃ to CO₂ and CaO
Sulfur is contained within the clay and the high temperature and combustion conditions cause it to form Sulfur dioxide which exits the kiln.