Rotary sludge feed

Rotary Kiln Incinerators. The rotary kiln has been used to incinerate a large variety of Hquid and soHd industrial wastes. Any Hquid capable of being atomized by steam or air can be incinerated, as well as heavy tars, sludges, pallets, and filter cakes. This abiUty to accept diverse feeds is the outstanding feature of the rotary kiln and, therefore, this type of incinerator is often selected by the chemical and waste treatment industries. 

Wiper blades attached to the moving distribution duct scrape the bottom and the sides of the tank and discharge settled sludge into the built-in sump, for periodic purging. The variable speed gear motor drives the rotating elements and the scoop. Electrical current for the gear motor feeds from a rotary contact mounted on the central shaft. 

Probably the rotary horizontal kiln is the most versatile, since it allows a feed of lumps or fines of limestone or marble, or wet or dry calcium carbonate sludges (Fig. 7.1). The main component of this calcination system is a 2.5- to 3.5-m diameter by 45- to 130-m long firebrick-lined inclined steel tube. Heat is applied to the lower end of this via oil, gas, or coal burners [7]. The feed to be calcined is fed in at the top end. Slow rotation of the tube on its axis gradually moves the feed down the tube, as it tumbles countercurrent to the hot combustion gases. In this way, wet feed is dried in the first few meters of travel. Further down the tube, carbon dioxide loss begins as the temperature of the feed rises. By the time the solid charge reaches the lower, fired end of the kiln it reaches temperatures of 900-1,000°C and carbon dioxide evolution is virtually complete. Normally the temperature of the lower end of the kiln is not allowed to go much above this as it reduces the life of the kiln lining. It also adversely affects the crystal structure of the lime product since it produces a dead-burned or overburned lime. Overburned lime is difficult to slake to convert it to calcium hydroxide and raises... 

Relatively weak feedstones, such as shell deposits, and limestones that decrepitate, are unsuitable as feed to shaft kilns but may prove to be acceptable for rotary kilns. Long rotary kilns can also accept a wet feed, i.e., a sludge or filter cake of finely divided carbonate. 

FBCs And their primary application to feeds that are nonatomizable liquids, slurries, sludges, tars, and granular solids, with the potential for combusting liquids or gases in combination with these. Thus, in terms of feed form, FBCs are intermediate between the simple liquid injection incinerator and the rotary kiln. 

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