Sulphur in exhaust fumes – why is it dangerous

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Sulphur released into the atmosphere in the form of sulphur dioxide contained in exhaust fumes is one of the most dangerous products of combustion.

Sulphur dioxide is generated in the process of burning fossil fuels, mainly coal, crude oil, mazut, gasoline or natural gas. In the case of coal, sulphur exists mainly in the form of pyrite and organosulphur compounds. Sulphur content is one of the quality indexes of fuel. In the case of bituminous coal, the content of this substance usually does not exceed 1.5 per cent of the coal mass. However, fuel of a worse quality may contain it much more.

Why sulphur is so dangerous

The presence of sulphur in the environment is one of the reasons for acidity, which leads to gradual dying of plants.

High sulphur content in the air leads to acid rains. This phenomenon was first described by Robert Boyle in his book “A general history of the air” in 1692, where he called it “nitrous or salino-sulphurous spirits”.

Sulphur dioxide generated during the combustion process, combines with the water in the air to produce sulphurous acid (a traditional name of the sulphuric acid (IV), H2SO3). This is one of the strongest acids in nature. Together with rain, sulphurous acid goes into soil. This substance is toxic to people, animals and plants. In human body, such rain causes mainly respiratory diseases.

One of the most visible examples of devastation of the natural environment resulting from acid rain is the “dead forest” in the Jisera Mountains, where leafless tree trunks stretch over square kilometres of land. Another example is acidification of lake water, in which hardly any organisms are able to survive.

Acid rains also destroy buildings and constructions. Limestone contained in plasters undergoes a chemical reaction with the acid, which turns it into hydrated calcium sulphate, also known as gypsum. Then, due to the presence of water, it dissolves and flows down, which – among others – destroys the building’s façade and rinses the mortar from between the bricks.

Acid rains devasted natural environment as early as in 1980s. The introduction of the exhaust fume desulphurization technology was a milestone towards making industry, particularly, the energy industry, much cleaner and environment and human-friendly.

Another way of fighting emission of sulphur oxides is to install special filters which desulphurize exhaust fumes. Today’s most effective method is the so called “wet” method which in practice, reconstructs the process causing plaster erosion in residential buildings. Fumes containing sulphur dioxide, still in the production plant, go through a special filter with sprayed suspension of calcium and water. As a result, the process produces gypsum and the fumes are cleaned.

Now, nearly all gypsum used in the construction industry is used solely for fume desulphurization. One of the reasons why this method became so popular is due to the actions of the European Environment Agency thanks to which emission of sulphur in Europe between 1990 and 2011 dropped by 72 per centI)https://smoglab.pl/jeszcze-niedawno-mielismy-polsce-kwasne-deszcze-je-pamieta/.

No comfort for Polish power plants

From the perspective of the Polish industry, particularly the energy sector, the absence of modern desulphurization installations is a challenge. Therefore, multiple Polish energy companies (mainly power and heating plants) are forced to use, in their furnaces, low sulphur coal, which usually means they need to import high-quality fuel. These companies are also not able to use Polish high sulphur coal because they would emit much greater volumes of sulphur dioxide, exceeding the adopted standards.

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