Suspension Preheater Refractories
The modern cement plant incorporates a suspension preheater in the clinker production line to reduce energy consumption. Preheaters are a series of cyclone vessels and ducts that preheat the raw mix using the hot gases from the rotary kiln. Temperatures progressively increase as the kiln feed descends to the lower stages. Almost every suspension preheater includes a calciner vessel where additional fuel is burned to support the calcination process. Hot air to support combustion in the calciner is conveyed from the cooler through the refractory-lined tertiary air duct.
The upper stages of the suspension preheater utilize refractories based on fireclay and have approximately 40% alumina content. This type of refractory offers good abrasion resistance and insulating value. In the lower preheater ducts and cyclone stages, medium alumina content refractories are used in response to the high temperature. Alkali resistance is also important, and 50% to 60% alumina refractories are more appropriate.
Suspension Preheater Components
Most linings within the suspension preheater are comprised of two components: a dense working lining and an insulating layer. RescoCast 3, RescoCast 3-35, and, QuikLite 3 are commonly selected for the insulating layer. Gunite refractories are commonly used for maintenance in the upper preheater, including RescoCast 15GM, Progun 26LI and Progun 28LI.
Lower Suspension Preheater
In the lower preheater, shotcrete is the preferred installation method. EZ Cubed 3000 and Vibrocast 60Z PC are conventional low cement castables selected for the working lining within the lower preheater. Vibrocast 60Z PC contains zircon which provides a moderate amount of build-up resistance. QuikTurn castables are very popular selections for the lower preheater, including QuikTurn 60 PC and QuikTurn 60Z PC. QuikLite 3 is the companion insulation gunite for a QuikTurn lining. For severe build-up applications, EZ Cubed AZS and QuikTurn AZS PC are standards in the industry. QuikTurn AZS G provides a gunite selection in a severe build-up location.