hydrated lime and quicklime

The fact of adding water to the powdered quicklime, putting it in a kiln or oven, and then pulverizing it with water, lead to the reaction of CaO with H2O bringing the new chemical Ca(OH)2.

The difference between Calcium oxide and Calcium hydroxide is that CaO has a heavy density (1 g/cm³) and is more reactive than hydrated lime which has the density of 0,5 g/cm³.

It is necessary for calcium oxide (quicklime) to be slaked in a controlled environment because it can create heat that reaches up to 50 degrees Celsius. Calcium hydroxide, or hydrated lime, is already neutralized, so it will not undergo oxidation and can be mixed with water in our system, for water ph control, lime slurry addition, lime slurry mixes, soil rehabilitation and more.

How do you determine whether to use hydrated lime or quicklime?

Usually, lime is used in water and wastewater treatment as well as Flue gas Desulphurization. The choice of using hydrated lime or quicklime will depend on the feed rate that the process requires. Also the ‘’reactivity’’ of the powder will be a factor of choice.

For instance, in the sludge liming for sludge stabilization process, the Quicklime is more desired for its exothermic reaction where the increase of temperature will help to kill the pathogen existing in the sludge.

The best example is flue gas treatment, also known as Flue Gas Desulphurization, used in coal fire plants, cement industries, glass industries, and incinerators to reduce their HCl, Sox and Nox emissions. Some of these systems require hydrated lime to filter or catalyze the particles emitted after combustion, while other systems use quicklime..

To determine if hydrated lime or quicklime is more profitable, check the amount of powder needed for the process. For big consumptions of powder, quicklime will be the best powder to choose as the density (1g/cm³)  is twice the density of the hydrated lime (0,5 g/cm³) which reduces the storage and transportation costs.

On the other hand, quicklime requires a lime slaker due to its hydrophobic reaction with water. The aim of using a lime slaker is to convert the quicklime into hydrated lime by mixing it with water. The lime slaker has the ability to control the exothermic reaction during the transformation of the CaO into Ca(OH)2. The result will be a lime slurry ready to be injected into the process.

On the contrary, when the demand of lime consumption is low or medium, Hydrated lime is used. In fact, the equipment is simpler because this doesn’t require a lime slaker because there is no exothermic reaction. The scope can be reduced to a screw conveyor that feeds the powder directly into the preparation tank equipped with a slurry mixer, where water is added to match the requested lime slurry concentration (%).