In our society, almost everyone uses electricity everyday and takes it for granted. Very few people know about the impact that this has on our environment. Since most of our energy is provided by fossil fuels like oil and coal, a large amount of carbon dioxide and other pollutants like nitrogen oxides, sulfur dioxide are released into our atmosphere every day. There are two ways to lower the impact to the environment. One is to get people to use less energy, which is difficult since the people in our society is used to using copious amounts. The other way is to find more environmentally friendly methods of producing energy. Two relatively environmentally friendly source of power are Integrated Gasification Combined Cycle(IGCC) Power Plants and Fluidized Bed Combustion Power Plants.
Let us talk about IGCC Power Plants first. IGCC Power Plants use coal to generate energy, but in a more clean way than other methods involving coal. Generally, IGCC Power plants start off by feeding a hydrocarbon, like coal, through a high-temperature gasifier with air or oxygen produced in an air separation unit(ASU). The resulting synthetic gas(syngas) is then cooled, cleaned, and fired in a gas turbine. The exhaust from the turbine then goes through a heat recovery steam generator(HRSG) to produce the steam necessary to drive a steam turbine. Both the gas turbine and the steam turbine generate electric power. And since the gas is cleaned before it gets combusted in the gas turbine, very little pollutants are released into the environment.
Variations between different IGCC Power Plants are usually found in how the gasifier island, air separation unit, and power block are integrated. Current state-of-the-art designs make sure that the ASU gets 25-50% of its oxygen from the gas turbine compressor and the rest from another air compressor. It is generally preferred to carry out the gasification process under pressure in order to avoid losing too much power in the compression...