September 4, 2011
Kristal Davis Fadtke
Using Clean Coal Technologies to Reduce Air Pollution
Air pollution is of pronounced concern in the media lately. Some of the effects of air pollution include the increase of carbon in the atmosphere which contributes to the global warming effect. The effects have been felt with record temperatures on the east coast and in the Midwestern United States this summer. One major contribution to the pollution is the use of coal to generate electricity. Approximately 50% of the power in the United States comes from coal fired electrical generation plants (UCSUSA, 2009). A typical 500 megawatt generation plant burns 1.4 million tons of coal per year (UCSUSA, 2009). Not only is the pollution evident from the exhaust stacks of the generation plant, there is the pollution created from the mining and transportation to the power-plant (UCSUSA, 2009). Because of the amount of air pollution generated, there needs to be a concentrated effort to use the newer clean technologies to reduce the impact on the environment. Air pollution is of great concern because of the widespread damage it can cause. The damage caused just from electricity generation from coal does not just affect the area where the power-plants are at. The effects are usually felt in other areas. This could be as simple as the next town downwind of the power-plant, or in some cases it can be other nations as pollution knows no boundaries (Berg & Hagar, 2007). Stories have shown that there is an increase in the ozone levels on the three states on the west coast, California, Oregon, and Washington. It has been shown that the ozone is carried over from Asia, as the countries there start to industrialize (CBSNews, 2010). Because the use of coal in electrical generation is considered the primary source of atmospheric pollution, there have been several technologies developed since the 1970s to reduce the pollution levels from the generation plants (Sen, 2010). These technologies for existing power-plants include both pre-combustion and post-combustion controls. These controls work to reduce the carbon, mercury, sulfur oxides, nitrogen oxides, and particulate matter exhausted from the plant (Sen, 2010). Most pre-combustion methods rely on physically cleaning the coal or upgrading the coal (Sen, 2010). This improves the commercial value as well as making a more ecologically friendly product. Post combustion technology works to scrub the mercury, nitrous oxides, sulfur oxides, and other pollutants out of the flue gasses (Sen, 2010). Several methods are used to accomplish this task. Pre-combustion cleaning of coal is the most effective way to reduce or remove the majority of trace elements from the coal. Drying the coal prior to transportation is one effective method of reducing the weight of coal so that more of the product can be shipped (Sen, 2010). This is usually performed at the mine site utilizing the sun by leaving the coal out in the open to allow the sun to dry the coal (Sen, 2010). This also can be done at the generation plant by heating the coal using the hot flue gasses. Low quality coal can be upgraded by cleaning. The most effective way this is accomplished is the utilization of gravity separators. These separate out the mineral content in the coal (Sen, 2010). This can reduce the sulfur oxide pollution by up to 40% and lower carbon dioxide pollution by 5% (Sen, 2010). Figure 1: Nitrogen removal Technologies (Sen, 2010)
Figure 1: Nitrogen removal Technologies (Sen, 2010)
Post-combustion treatment in existing power-plants is done by treating or scrubbing the pollutants out of the flue gasses. All of the primary pollutants, nitrous oxides and sulfur oxides can be greatly reduced or with some treatments, eliminated (Sen, 2010). Limestone gypsum is by far the most common system in use for scrubbing out the sulfur oxides (Sen,...