Lime

Chemical lime is produced by the calcination of high-quality limestone which produces either high-calcium quicklime or dolomitic quicklime. Further treatment of high-calcium quicklime and dolomitic quicklime produces their hydrated counterparts. Figure 7.39.2 shows the chemical lime production process.

Table 7.39.3 shows typical analyses of the two types of quicklimes. The difference in chemical composition between high-calcium and dolomitic quicklimes results in varying reaction rates and reactivities when these materials treat the same wastewater. Figure 7.39.3 demonstrates the reaction rate characteristics of high-calcium and dolomitic lime (2% excess) at 25°C when reacted with 0.1N H2SO4.

The reaction rate curve for high-calcium lime in the figure was obtained with 2% excess lime. Lesser amounts of

TABLE 7.39.1 pH RANGES FOR VARIOUS WATER QUALITY CATEGORIES

Water Quality

pH Range

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