uent by washing with scrubbers. Sometimes, the particles will simply settle out before being emitted, in what are called settling chambers. Sometimes the gas is pushed through filters of cloth collectors. Other devices are even more sophisticated. The gas might be whipped around in a circular path, so that centrifugal force separates the particles. Those devices are called centrifugal separators. An other type of device is the electrostatic precipitators. This device delivers an electrical charge to the particles. An opposite charge is placed on a metal plate, and, because opposites attract, the particles will collect on the plate. Then the plate is cleaned off. Of course all these devices remove the particles, but once the particles have been removed the problem becomes how to dispose of the sludge. The toxicity of the material and its impact on the environment become new considerations. Internal Combustion Engine One of the greatest polluters on Earth is the automobile. Volatile organic compounds, nitrogen oxides and carbon monoxides are the major pollutants that come out of a car's exhaust. If the air-fuel mix is lean, there is a good deal of air and less fuel. The combustion temperature will be relatively high, which will favor the complete burning of the gases, and hydrocarbons will convert to water vapor and carbon dioxides. However if the mixture is not so lean, but richer with more fuel the temperature will be lower. Instead of completely burning the hydrocarbons with the oxygen, you end up with unburned hydrocarbons and carbon monoxide instead of carbon dioxide. So the conclusion here should be to have a very lean mix of air and fuel. The problem with that is the high temperature of efficient combustion. The oxygen and nitrogen in the air combine, resulting in a lot of nitrogen oxides. You may reduce the carbon-monoxide pollution in having a transformation to carbon dioxide, but on the other hand, you 're going to end up with m...
