Abstract: This invention relates to a method to further enhance NOx reduction in rotary preheater mineral kilns by coupling the temperature control and gas composition uniformity afforded by the high temperature mixing with the use of chemical reducing agents. The chemical reducing agent or agents, generally chosen from ammonia or ammonia precursors, are introduced at a specific point in the rotary preheater kiln which has as an optimal temperature window to achieve the greatest reduction of NOx emissions.

Abstract: This invention relates to a method to further enhance NOx reduction in rotary preheater mineral kilns by coupling the temperature control and gas composition uniformity afforded by the high temperature mixing with the use of chemical reducing agents. The chemical reducing agent or agents, generally chosen from ammonia or ammonia precursors, are introduced at a specific point in the rotary preheater kiln which has as an optimal temperature window to achieve the greatest reduction of NOx emissions.

Abstract: Sulfur oxides have a strong affinity for free lime and readily form gypsum anhydrite. By utilizing 2200.degree. F or higher on-gas containing reduced quantities of sulfur to the preheat zone of a material treating apparatus, large quantities of sulfur can be removed from gases evolved in the rotary kiln. Utilizing lower sulfur content on-gas to preheat will substantially improve the ability of the system to lower both sulfur and alkali levels in the clinker. Substantially free lime in the form of fines is introduced into the kiln off-gas stream to form gypsum anhydrite which is removed and has the potential to be utilized as a by-product. Essentially all of the remaining gaseous sulfur that has not been absorbed by the lime bearing dust is absorbed by the free lime in the pellets in the preheat zone of a material treating apparatus.

Abstract: Sulfur oxides have a strong affinity for free lime and readily form gypsum anhydrite. By utilizing 2200.degree. F. or higher on-gas containing reduced quantities of sulfur to the preheat zone of a material treating apparatus, large quantities of sulfur can be removed from gases evolved in the rotary kiln. Utilizing lower sulfur content on-gas to preheat will substantially improve the ability of the system to lower both sulfur and alkali levels in the clinker. Substantially free lime in the form of fines is introduced into the kiln off-gas stream to form gypsum anhydrite which is removed and has the potential to be utilized as a by-product. Essentially all of the remaining gaseous sulfur that has not been absorbed by the lime bearing dust is absorbed by the free lime in the pellets in the preheat zone of a material treating apparatus.

Abstract: Variable dual orifices in the restricted portion of the flue between the kiln and the preheater provides a controlled bypass of 0 to 100% of the kiln gases around the preheater and prevents short circuiting of process materials from the precalciner and mixing chamber to the kiln and provides a means for adjusting the orifice and system pressures to thereby provide stability of operation and control over the entire range of bypass; positive isolation of kiln gases from preheater gases during 100 percent bypass operation is ensured.