Flue gas desulphurization using natural calcium based sorbents.
Power generation from coal combustion serves as a major source of energy however this process has detrimental environmental effects. SO₂ is a destructive pollutant and is oxidized with water vapour to form sulphuric acid which falls as acid rain causing corrosion to monuments, deforestation, soil erosion and destruction of the natural habitat. SO₂ emissions cause chronic respiratory diseases. The development and advancement in pollution control technologies is a pressing issue as environmental regulations become more stringent. The principal technology that is currently implemented is termed Flue Gas Desulphurization (FGD) and involves treating the flue gas before it is released into the atmosphere. Industries are constantly welcoming new research and development that would reduce their SO₂ emissions. As a result most companies are turning to sorbents to solve the major environmental crisis. In the work undertaken an effective test unit for sulphur dioxide capture was commissioned and recommended conditions for SO₂ removal were established. Four ESKOM sorbents were prepared and tested in the experimental set-up. These sorbents were then ranked according to their desulphurization efficiency. The effect of particle size on desulphurization efficiency was determined using four different size fractions and it was found that smaller particles have higher sulphur removal efficiency. The effect of the presence of CO₂ in the gas mixture was also determined by comparing the efficiencies obtained using two different flue gas mixtures. The chemical, physical and surface properties of each sorbent was also analysed and used to support the conclusions drawn from the ranking of the sorbents. A suitable model to represent the data set was also investigated and it was found that the simple shrinking core model best described the system investigated.