Process for calcining blending material with high activity by feeding outside kiln head and apparatus thereof

A process for making a cement clinker by feeding unground raw material outside of a kiln head comprising:

• a) feeding at least one unground raw material selected from the group consisting of coal gangue, oil shale, stone coal, clay, river and lake mud, waste muck, sewage sludge, and peat from outside the kiln head with a cement clinker from high temperature calcining from about 1250° C. to 1450° C. in a rotary kiln as the cement clinker is simultaneously entering a grate cooler via a kiln hood, the raw material forming an active cement component through low temperature calcining at a temperature from 700° C. to 1200° C. and has a thermal value of 100 KJ/kg to 12,000 KJ/kg;
• and
• b) cooling the low temperature calcined raw material that is mixed together with the high temperature calcined cement clinker to jointly form a cement clinker admixture.