Acid Rain Effects Acid Rain  Elmhurst College
Acid Lake Effects Effects on Forests Acid Rain Solutions  Chemistry Department
Acid Soils and Effects Effects on Buildings    Virtual ChemBook

Coal Company Views:

Many coal companies in the Midwest may go broke and cause high unemployment rates among coal miners if power companies switch to low sulfur coat from the West.

The cost of this massive reduction in sulfur oxides could be as high as $21 billion a year with most of these costs borne by the consumer. Thousands of coal miners may pay a steeper price: their jobs.

The Edison Institute expects 10-15 percent electricity rate increases in several states. At ten particularly hard-hit utilities the rate increases may exceed 20%.

EPA Views:

The EPA calls the estimates made by electric power companies as excessive. The EPA estimates that the total cost of implementing the 1990 Clean Air act would be less than $4 billion a year. This translates to an increase of 1-1.5 % in consumer electric bills.

The installation of scrubbers on "old" plants is expensive, but the environmental costs of inadequately controlled emissions are also large. Many costs are hidden with synergistic effects of the stresses that acid puts on organisms.

Other sources suggest that the installation of scrubbers at exisitng electric power plants would raise electric bills by about 7%. This translates to $4.20 per month on a $60 per month bill or $8.40 /month on a $120 per month bill.

Acid Rain - Solutions

Progress in Controlling Emissions:

Some progress has already been made in slowing the emission of sulfur oxides. These decreases are the result of the 1975 Clean Air Act and and the 1990 Amendments.

In the Northeast there has been a steady decrease in the sulfate content of the air and rain. The rate of acidifying lakes has also slowed as well. To actually reverse the trend, the amount of acid rain will have to be reduced much further. Some scientist think that at least of 50 % reduction is required.

Solutions - Use Low Sulfur Coal:

The amount of sulfur oxides emitted by a power plant can be reduced by burning coal with a very low percentage of sulfur present. Low sulfur coal (0-1% sulfur) is surface mined in the Western states of Wyoming and Montana. Transportation costs are much higher.

High sulfur coal (2-4% sulfur) is currently mined in the Midwestern states of Illinois, Indiana, Ohio, West Virginia, and Kentucky. If a complete switch to low sulfur coal is made, many coal miners will lose jobs.


Solutions - Use Scrubbers:

Scrubbers remove 80-95 percent of the sulfur oxides. Certain types do not remove nitrogen oxides. They are costly to retrofit to existing power plants. They increase the electric generating costs by 10-15 %. Graphic on left.

Scrubbers are like "liquid" filters for the gases resulting from combustion. The exhaust gases are forced through a spray of water containing lime (calcium hydroxide). The sulfur dioxide gas reacts with the lime to produce a solid of calcium sulfate. Graphic on lower left.

The sulfur dioxide gas reacts with the lime to produce a solid of calcium sulfate. There are then problems in getting rid of the liquid sludge that is produced. Here it is pumped into a pond for temporary storage. Graphic below.


Solutions - Fluidized Bed Combustion:

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 process also burns the coal more efficiently by about 5 %. This process removes 90 % of the sulfur oxides and 15-35 % of the nitrogen oxides.

Limestone Injection - Multistage Burner

Limestone injection multiple burning is still in the development and testing stages. Crushed limestone is injected into a boiler burning powdered coal at lower than normal temperatures. The limestone combines with sulfur dioxide to produce a solid ash (mostly gypsum, calcium sulfate). This process removes 70 % of both sulfur and nitrogen oxides.