Flue Gas Desulfurization by Ammonia

توضیحات

Air pollution is caused by the presence of a mixture of suspended particles and gases whose concentration exceeds the standard limit and is harmful to human health, which can cause lung, heart and other diseases in humans in addition to the effect on global warming.

The most important pollutants produced by human beings are as following:

1) Carbon dioxide

2) Carbon monoxide

3) Sulfur oxides (SO_x)

4) Nitrogen oxides (NO_x)

5) Volatile organic compounds such as benzene, toluene, etc.

6) Toxic metals such as lead and mercury

7) Chlorofluorocarbons (the main cause of ozone layer destruction)

Sulfur dioxide and sulfur trioxide are the predominant gaseous oxides of sulfur in the atmosphere. More than 80% of sulfur oxides are produced during the combustion of fossil fuels, because almost all fossil fuels contain sulfur, and it enters the air in the form of sulfur dioxide during combustion. The amount of sulfur in fuels and petroleum products is different. Fuel oil contains between 2.5 and 3.5% and diesel between 0.5 and 1% of sulfur, but gasoline sulfur is insignificant and coal contains between 0.1 and 4% of sulfur. Sulfur dioxide is a non-flammable, non-explosive and colorless gas that can be felt by taste in concentrations of 0.3 to 1 ppm, and has a pungent and stimulating smell in concentrations above 3 ppm. Sulfur dioxide destructive effects are as following:

1) Production of acid rains and destruction of the entire biosphere, for example acidification of the soil causes drying of roots and destruction of forests

2) Absorption by the plant’s stomata and its poisoning due to regeneration

3) Intensification of corrosion of metals such as iron, steel, zinc, copper, etc. in the presence of moisture

4) Causing disease in humans as a result of inhalation, such as shortness of breath, severe cough, irritation of the eyes and respiratory tracts, and finally aggravation of cardiovascular, vascular and respiratory complications

Flue gas desulfurization (FGD) is a set of technologies used to remove sulphur compounds from the exhaust emissions of flue gases produced from industrial combustion at petrol refineries, chemical manufacturing industries, mineral ore processing plants, and power stations. This is done through the addition of absorbents, which can remove up to 95% of the sulphur dioxide from the flue gas.

Flue gas analysis is essential for evaluating air-to-fuel ratios in combustion for best efficiency. The kind of fuel consumed and the combustion circumstances at each plant define the particular composition of flue gas. Sulfur is one of the most unwanted and detrimental impurities. Thus, desulfurization is needed as a key process to removed undesired SO_x.