Process for incorporating coal ash into cement clinker

A method of producing cement clinker with reduced emission of carbon dioxide from a charge of cement clinker raw ingredients comprising:

• i) providing a rotary cement kiln having a feed end and a discharge end;
• ii) establishing levels of at least calcium, silicon and aluminium for a cement clinker, based on a raw ingredient feed material comprising a source of calcium carbonate, a source of silicon and a source of aluminium,
• iii) providing a raw ingredient feed material formulation comprising said sources, in which a portion of said source of calcium carbonate is replaced by a coal ash while maintaining said level of calcium;
• iv) feeding said formulation into said kiln,
• v) exposing said formulation to elevated temperatures in said kiln, while feeding said ingredients in a direction from said feed end towards said discharge end, to calcine said source of calcium carbonate with formation of calcium oxide and liberation of carbon dioxide, and chemically combine and integrate said calcium oxide with said sources of silicon and aluminium, and said coal ash, as a cement clinker, and
• vi) discharging said cement clinker from said discharge end, whereby carbon dioxide emissions are reduced in proportion to the replacement of said source of calcium carbonate by said coal ash.