Kilns double-inclined

Cooling air is drawn into the bottom of the kiln, and a portion of this is withdrawn further up the kiln and is reinjected in the combustion chambers. The double incline creates a circuitous route for both the burden and combustion gases, which ensures a uniform distribution of heat that allows the feeding of material as small as 0.8 in. The top feed size is about 4 in. 

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The double-inclined kiln calcines even smaller si2ed stone of 1.88—3.75 cm and at reduced capacity with stone of only 0.63 cm minimum si2e. Most of these kilns operate using gaseous or oil fuels, including propane. An exception is the double-inclined kiln, which appears to operate at optimum efficiency with a mixture of fuel, ie, 60—75% natural gas or oil and 40—25% coke, although it can operate on 100% gas or oil. 

The double-inclined kiln incorporates two inclined sections in the calcining zone see Figure 6.13. The offset arches created by the inclines create a void on both sides of the kiln where fuel and preheated combustion air can be fired in combustion chambers. 

The multichamber shaft kiln is a variation of the double-inclined kiln. It consists of 4 or 6 alternating inclined sections in the calcining zone, which... 

The double-inclined kiln (design H in Table 16.1) is shown in Fig. 16.10. It is essentially rectangular in cross-section, but incorporates two inclined sections in the calcining zone. Opposite each inclined section, off-set arches create spaces into which fuel and preheated combustion air are fired via three combustion chambers. 

Three aspects are common to all shaft kiln designs, namely charging, drawing of the ore, and combustion. A shaft kiln is essentially a vertical refractory lined cylinder or ellipse. The ore is charged in at the top of the furnace, along with, in some cases, a solid fuel such as coke or anthracite coal. Other fuels such as natural gas and oil can also be employed. There are a number of different variants of shaft kilns, such as the mixed feed, traditional type and modern basic design, annular, parallel-flow regenerative, double inclined, and multichamber. 

Figure 6.13 Double-inclined shaft kiln. (Reproduced by permission of J.A.H. Oates and Wiley-VCH.)...

Figure 16.10. Cross-section of a double-inclined shaft kiln (a) upper combustion chamber (b) lower combustion chamber...

W. H61tje, Improvements in process technology in a double inclined lime shaft kiln , Zement Kalk Gips 9,1991,467 71 (En ish 11,1991,246-249). 

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