Lime production from limestone

Limestone products are commonly used in industrial processes and are naturally occurring consisting of high levels of calcium, magnesium carbonate and minerals Lime is used in many industries to neutralize acid waste and as an alkali for chemical processes, in agriculture, soil stabilization, building, and industrial purposes such as cement and steel production.

Lime Production Process involves four steps

1. Mining or Quarrying

Limestone material is extracted carefully to maintain its purity in underground mines and quarries all over the world.

2. Stone Preparation

In this step, the limestone is crushed and screened to further wash and remove impurities

3. Lime Calcining (Conversion of limestone (CaCo3) to lime (CaO))

Limestone is a source of calcium carbonate and is heated to convert the calcium carbonate into calcium oxide. This process is generally carried out in large rotary kilns or vertical shaft kilns where high temperature is required. Quicklime is produced in the calcination process, which can be crushed depending on it's use.

4. Hydrating

In this step, hydrated also known as slaked lime is produced by reacting quicklime with water.CaO + H2O? Ca(OH)2

Applying Le Chatelier's Principle in the Production of Limestone:Limestone as a source of calcium carbonate (CaCO3) is created from lime as a source of calcium oxide (CaO) and carbon dioxide (CO2).

CaCO3(s) + heat CaO(s) + CO2(g) (?H = +178 kJ mol-1)

Kc = [CO2]1

The equilibrium constant expression is Kc = [CO2]1 since the concentration of the solids is constant which means that the only properties that can affect equilibrium is change to the concentration of carbon dioxide or heat. Since the enthalpy is positive, this makes the forward reaction endothermic, therefore 178kJ of heat energy is absorbed for every mole of calcium oxide produced.

Pressure:

When the reaction is carried in a ventilated lime kiln at normal atmospheric pressure, the pressure of carbon dioxide (CO2) is reduced, which consequently reduces the chances of a backwards reaction. In this process, only one mole of gas is formed, so the net of the moles increase in the formation of lime since there are no gaseous products, therefore by decreasing the pressure, it will favor the production of more carbon dioxide molecules, ultimately shifting towards the right (products) side and producing more lime.

Temperature:

Since the reaction is endothermic, this means that this reaction is favored by high temperatures. According to Le Chatelier's principle, by increasing the temperature of the system, the position of equilibrium will shift in the forward direction in order nullify the change, where more amounts of CaO and CO2 will be obtained and the concentration of CaCO3 will decrease at equilibrium.This means that the position of equilibrium will move to the right as to decrease the temperature again. However, if the temperature is reduced, the position of equilibrium will shift accordingly to counteract this change, so in other words, it will shift to the left to increase the temperature again.

In order to produce more lime for society in the industry, the reaction is manipulated so that the position of equilibrium is able to shift more to the right in order to produce more lime. By disrupting equilibrium for the sole purpose of producing more lime, society is able to benefit since lime can be used in several useful ways.

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