Portland cement production process

摘要

In a Portland cement production process, the aluminate content of the product is either reduced by sulphur and/or sulphur-containing material addition or is increased by alkali and/or alkali-containing material addition before or during the production process. Preferably, the molar ratio between the alkali (equivalent) and the sulphur (equivalent) in the raw material is adjusted to exactly 1:1 to achieve a minimal aluminate content or is adjusted to 1.1-20:1 to achieve a greater than minimal aluminate content. The additives may be added to the rotary kiln in the form of sulphur-containing or alkali-containing raw materials, especially scrap tyres and/or sulphur-containing or alkali-enriched fuels, especially heating oil or waste oil. Also claimed is an apparatus for carrying out the above process, including an unit (4, 8, 9) for controlled supply of the additive to the raw material or to the partially processed raw material.