Lime in its basic form is not commonly used. The final application is almost always that of Ca(OH)2, Calcium Hydroxide(also known as hydrated lime). For economic reasons,on-site conversion of CaO, calcium oxide (also called quicklime or pebble lime) is preferred to purchasing hydrated lime. Quicklime requires only about 75% as much chemical by weight to obtain the same results; which translates to 75% less storage capacity, cost of handling, and freight. Additionally, Quicklime is less dusty and easier to handle. Quicklime is normally metered to the slaker by a gravimetric or volumetric feeder. However, because the weight of a given volume may vary 5 to 15% from the average, gravimetric feeders will compensate for changes in material bulk density and provide a more uniform and accurate flow to the slaker. Consideration should be given to the design of the lime storage bin to insure a constant flow of material to the feeder. Quicklime is discharged directly from the feeder into the inlet of the slaker. The lime feed rate is determined manually or automatically by the level of slurry in the slurry surge tank located directly beneath the slaker or by a demand signal from the process.
