Carbon Sequestration Research Paper

Abstract

In today’s energy driven world, fossil fuels constitute the majority of our fuel resources. Burning of fossil fuels at such an enormous rate has increased the level of carbon dioxide in the atmosphere. Such high level of carbon dioxide emission into the atmosphere has started to take a toll on the delicate balance of gases in the atmosphere. There are efforts being made to develop a method of carbon sequestration that will effectively convert carbon dioxide in to carbonate minerals using alkaline earth oxides like calcium oxide (CaO), magnesium oxide (MgO). Since the start of the world mineralization has taken place naturally and at large scale but the naturally occurring mineralization reactions are too slow to balance out the high

Keywords: carbon dioxide, mineralization, carbon sequestration, calcium oxide, magnesium oxide. Introduction

In the below section of this paper I will briefly discuss the carbonation of CO2 in the form of inorganic carbonates, also known as mineral sequestration. I have also written about how CO2 mineralization methods can be used for the mitigation of the CO2 by human activities, steps involved in the whole carbonation process, how naturally occurring aquifers and artificially created aquifers can be used for the mineralization and the chemical reactions which take place during the fixation of carbon by this particular method.

Carbon dioxide mineralization

In the process of mineral carbonation, CO2 reacts with metal oxide forming insoluble carbonates of calcium and magnesium as these two are the most attractive metals. This type of reaction is called silicate weathering. The source of alkaline and alkaline-earth metals are the naturally occurring silicates these consume the atmospheric CO2. This process involves first, capturing of residual gases from various sources like industries and power plants then separating

These natural aquifers provide a good storage place for a long period of time and thus carbonation can take place naturally at a slow rate. However natural mineralization process is very slow, in order to overcome this shortcoming an artificially made reactor that are commonly known as accelerated mineral carbonation (these units are still in experimental phase) that speeds up the mineralization process can be used which immensely reduces the storage time.

Mineral carbonation can be schematized in Fig 1.

Fig 1 : Mineral Carbonation Schematic (Mazzotti, 2005)

Chemical reactions occurring during the mineral carbonation of CO2

When CO2 reacts with divalent metal oxides of calcium, magnesium, or iron the corresponding carbonate and some heat is formed, following is the chemical reaction chemical reaction:

Metal oxide + CO2 → MetalCO3 + heat energy

How much heat will be released depends upon the type of metal used (in all cases heat values are given per unit mol of CO2 and standard conditions 25°C and 0.1 MPa, Robie et al. 1978).

Following are some of the reactions that occur with various minerals during CO2 carbonation:

• Olivine:

Mg2SiO4 + 2CO2 → 2MgCO3 + SiO2 + 89 kJ mol–1CO2

•