Application of Science - Solutions to Acid Rain
Scientists have found strategies of reducing emissions, hence, reducing acid rain. Since the largest amount of sulfur dioxide is caused by coal fired power plants, scientists have found several ways in order to reduce the coal power plant pollution and emission of gases causing acid rain.
1. Scrubbers:
Firstly, Scientists have found the solution of smoke stack scrubbers. These scrubbers trap the sulfur dioxide (SO2) gases before they are emitted from the power plant and transform the gases into sludge and waste. The benefits of the smoke stack scrubbers are that they filter out and remove 80%-95% of the SO2 and turn it into waste, which means that only 20%-15% of the gases are released into the atmosphere. Therefore, acid rain will be reduced. The limitations of the scrubbers are that they are very expensive, therefore, many companies and power plants do not want to install these. Especially the installation of scrubbers into old power plants is very expensive. In addition, scrubbers increase the electric generating costs by 10-15%. Scrubbers are not very common due to their price, only a few amount of power plants use this technology. Another limitation is that the waste and sludge have to be disposed somewhere. The EPA estimates that only 30% of the waste is recycled and that the rest 70% are dumped into landfills.
1. Scrubbers:
Firstly, Scientists have found the solution of smoke stack scrubbers. These scrubbers trap the sulfur dioxide (SO2) gases before they are emitted from the power plant and transform the gases into sludge and waste. The benefits of the smoke stack scrubbers are that they filter out and remove 80%-95% of the SO2 and turn it into waste, which means that only 20%-15% of the gases are released into the atmosphere. Therefore, acid rain will be reduced. The limitations of the scrubbers are that they are very expensive, therefore, many companies and power plants do not want to install these. Especially the installation of scrubbers into old power plants is very expensive. In addition, scrubbers increase the electric generating costs by 10-15%. Scrubbers are not very common due to their price, only a few amount of power plants use this technology. Another limitation is that the waste and sludge have to be disposed somewhere. The EPA estimates that only 30% of the waste is recycled and that the rest 70% are dumped into landfills.
How do Scrubbers work?
Scrubbers function as filters of the gases that are produced in the combustion. The gases go through a liquid spray of water and lime, which is calcium hydroxide. The lime reacts with the sulfur dioxide gas, which produces a solid, calcium sulfate. From this reaction, a liquid sludge is produced.
2. Low Sulfur Coal:
An alternative technology is using coal that contains a lower percentage of sulfur, 0-1% of sulfur. High sulfur coal contains between 2-4% of sulfur. According to the Department of Energy, low sulfur coal reduces the SO2 emissions by approximately 85%. Low sulfur coal decreases the pollution and gases emitted from a coal power plant drastically, which reduces acid rain. The limitations of this type of coal is that it is more expensive than coal containing a normal amount of sulfur. Furthermore, low sulfur coal is not available in all regions. Therefore, the transport ocsts to the power plant have to be added on top of all of the other costs making this an expensive alternative to coal containing normal amounts of sulfur.
An alternative technology is using coal that contains a lower percentage of sulfur, 0-1% of sulfur. High sulfur coal contains between 2-4% of sulfur. According to the Department of Energy, low sulfur coal reduces the SO2 emissions by approximately 85%. Low sulfur coal decreases the pollution and gases emitted from a coal power plant drastically, which reduces acid rain. The limitations of this type of coal is that it is more expensive than coal containing a normal amount of sulfur. Furthermore, low sulfur coal is not available in all regions. Therefore, the transport ocsts to the power plant have to be added on top of all of the other costs making this an expensive alternative to coal containing normal amounts of sulfur.
3. Fluidized-bed combustion
According to Charles Ophardt, "In the system known as atmospheric fluidized-bed combustion, a turbulent bed of pulverized coal and limestone is suspended by an upward blast of air. The combustion chamber has many boiler tubes which convert water into steam. The turbulent mixing of coal and air allows the combustion to occur at a lower temperature which reduces the formation of nitrogen oxides. The limestone captures the sulfur oxides by converting them to calcium sulfate which is a solid rather than a gas."
This technology benefits from its efficiency. Firstly, it reduces the formation of nitrogen oxides by about 15-35% and 90% of the sulfur oxides are converted to a solid. Therefore, the amount of gaseous pollutants are decreased, therefore, the amount of acid rain is too. Fluidized-bed combustion does not only reduce the pollution, but it also increases the efficiency of the coal combustion by approximately 5% (Charles Ophardt).
According to Charles Ophardt, "In the system known as atmospheric fluidized-bed combustion, a turbulent bed of pulverized coal and limestone is suspended by an upward blast of air. The combustion chamber has many boiler tubes which convert water into steam. The turbulent mixing of coal and air allows the combustion to occur at a lower temperature which reduces the formation of nitrogen oxides. The limestone captures the sulfur oxides by converting them to calcium sulfate which is a solid rather than a gas."
This technology benefits from its efficiency. Firstly, it reduces the formation of nitrogen oxides by about 15-35% and 90% of the sulfur oxides are converted to a solid. Therefore, the amount of gaseous pollutants are decreased, therefore, the amount of acid rain is too. Fluidized-bed combustion does not only reduce the pollution, but it also increases the efficiency of the coal combustion by approximately 5% (Charles Ophardt).