Traditional shaft kilns

Traditional shaft kilns operate continuously and are fired with fuel introduced into the calcining zone (see section 16.2.2). Various fuels have been used, including bituminous coal, producer gas, fuel oil and natural gas. 

Thus the properties of quicklime from a given kiln reflect the average properties of individual lumps, each of which has experienced a particular time-temperature history. Fig. 15.8 compares the distribution of particle densities for a light-burned quicklime from an annular shaft kiln, with a mean apparent density of 1.66 g/cm with that of a solid-burned quicklime from a coal-fired traditional shaft kiln with a mean apparent density of 2.15 g/cm. Table 15.4 presents some typical... 

In many countries, the widespread increase in the availability of natural gas at competitive prices in the 60s and 70s enabled many lime producers to extend the operating lives of their traditional shaft kilns. Natural gas brings three major advantages ... 

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. 

In traditional lime processing plants serving shaft kilns, the screened ROK lime then passed along a picking conveyor belt, where partially calcined lumps (sometimes called bullheads ) are removed, together with selected grades of lime. However, economic and social pressures have resulted in the phasing out of this activity in many countries. 

Traditional shaft-type kilns Conventional long wet, dry rotary kilns Fluidized-bed type kilns... 

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