Thermoelectric Power Plants: Operation, Impact, and Innovations
Thermoelectric Power Plant Operation
From the coal storage site, coal is placed on a conveyor belt and moved into a hopper that feeds the crushing mill, where it is converted into a fine powder to facilitate combustion. The coal dust is mixed with preheated air and injected into burners in the boiler, where combustion occurs. The heat of combustion heats water in pipes, producing steam. A superheater removes moisture and increases the temperature. The steam expands in the various bodies of the turbine. On leaving the steam turbine, it goes to the condenser, where it cools and condenses. The combustion gases in the boiler are sucked out of the fireplace and used to heat the combustion air. Precipitators retain as many solid pollutants as possible before the gases leave the chimney.
Environmental Impact of Thermal Power Plants
Air Pollution
The use of fossil fuels leads to the production of carbon dioxide and water vapor, causing the greenhouse effect. Poor combustion and fuels containing impurities cause the emission of sulfur oxides and nitrogen oxides, the main causes of acid rain. These compounds, together with the emission of hydrocarbons, solid particles, and heavy metals, are the triggers of photochemical fog.
Water Pollution
Thermal pollution is minimized by the use of cooling towers. In addition, the plant uses water for cleaning various elements. Water obtained from water treatment plants, the power boiler, steam from purges, etc., is chemically contaminated, so it requires a treatment system before being discharged into the water network.
Noise Pollution
We must avoid the noise of forced fans, purge valves, etc., affecting the environment, particularly if there are populations living near the central. To do this, the noisiest elements are isolated kilometers away, and acoustic screens are built.
New Technologies in Power Generation
- Fuel Desulfurization Systems: These systems transform sulfur oxides into soluble compounds that are easy to remove.
- Coal Gasification: This allows the exploitation of resources that are not profitable or technically feasible with traditional mining. Part of the process produces gas, a much less polluting fuel.
- Fluidized Bed Combustion: This is a coal combustion system within a specific temperature range, which allows most contaminants to remain with the combustion waste and not be emitted into the atmosphere. At the same time, performance increases as the coal presents more surface contact with the air during combustion.
- Combined-Cycle Power Plants: To avoid heavy dependence on oil in the energy sector and reduce the emission of contaminated particles, the current trend is to build combined-cycle plants using natural gas.
Combined-Cycle Power Plant Operation
The characteristic features of a combined-cycle power plant are a gas turbine with a compressor and a combustion chamber, a recovery boiler, and a steam turbine. High-pressure air from the compressor mixes with fuel gas in the combustion chamber and is burned. The combustion gases, at a temperature of 1300°C and high pressure, spread to the gas turbine and drive the compressor and generator. After the expansion process, the gases, which are about 800°C (a temperature high enough to seize the power they have), are sent to the recovery boiler. The recovery boiler has the same components as a conventional boiler to make the most of the power possible from the exhaust gases. The steam-water cycle is performed in any conventional power station so that the steam from the boiler drives a turbine generator group for more power.
Cogeneration Plants
Cogeneration plants produce energy using fuel and take the residual heat to obtain hot water for heating, steam, heated fluid, etc., depending on the needs of the area where the plant is located.