Coal has played a major role in electricity production ever since the first power plants were built in the world in the 1880's. The earliest power plant used hand feed wood or coal to heat boiler and produce steam. This steam was used in reciprocation steam engines which turned generators to produce electricity. In the 1920's Pulverized-coal firing was developed which brought advantages that included higher combustion temperatures, improved thermal efficiency, and a lower requirement for excess air for combustion. In the 1940's the cyclone furnace was developed which allowed the combustion of poorer grade coal with less ash production and greater overall efficiency. Improvements in efficiency have continued to occur throughout the years. But overall, electricity production from coal is based on the same methods started over 100 years ago, but the improvements in all areas have brought coal power to be the inexpensive power source used so widely today( Electricity from coal).
Coal Burning Power Plants 3
There are three predominate methods of burning coal to make steam, power turbine, and generate electricity. Most coal power plants either burn pulverized coal blown into a boiler or use cyclone furnaces to burn coal in a vortex of air. The current trend for new coal power plant is to use fluidized bed combustion which has a number of advantages over the other methods (Electricity from coal).
In the Pulverized coal system the coal burning has been pulverized into a fine powder stem, it will burn almost as easily and efficiently as a gas. The feeding rate of coal is according to boiler demand and the amount of air available for drying and transporting the pulverized coal fuel is controlled by computers. Pieces of coal are crushed between balls or cylindrical rollers that move between two tracks or "races". The raw coal is then fed into the pulverizer along with air heated to about 650 degrees F from the boiler. As the coal gets crushed by the rolling action, the hot air dries it and blows the usable fine powder out to be used as fuel. The powdered coal from the pulverizer is directly blown to a burner in the boiler. The burner mixes the powder coal in the air suspension with additional pre-heated combustion air and forces it out of a nozzle. Under operating conditions, there is enough heat in the combustion one to ignite all the incoming fuel (Coal Fired).
Coal Burning Power Plant 4
The Cyclone furnaces were developed after pulverized coal systems and require less processing of the coal fuel. The crushed coal feed is either stored temporarily in bins or transported directly to the cyclone furnace. The furnace is basically a large cylinder jacketed with water pipes that absorb the some of the heated to make steam and protect the burner itself from melting down. A high powered fan blows the heated air and chucks of coal into one end of the cylinder. At the same time additional heated combustion air is injected along the curved surface of the cylinder causing the coal and air mixture to swirl in a centrifugal "cyclone" motion. The whirling of the air and coal enhances the burning properties producing high heat densities and high combustion temperatures. The hot combustion gases leave the other end of the cylinder and enter the boiler to heat the water filled pipes and produce steam. Some slag remains on the walls insulating the burners and directing the heat into the boiler while the rest drains through...