How do coal power plants affect the environment?
Think of them like cars
Coal fired power plants, in simple terms, are just a very large exhaust pipe. Similar to what you have on a car. Minor differences here and there, but overall very similar.
Coal fired power plants work by burning coal which is composed of mainly carbon. When burning the coal we have the ability to produce vast amount of energy which is one reason the world has had a hard time moving away from coal power.
However, just like many combustion reactions we burn coal and create gaseous compounds containing carbon and oxygen. The main gas emitted is Carbon dioxide. Others are also emitted such as sulfur compounds. They also produce soot which is the fine black dust-like material the comes from diesel trucks sometimes.
How all these affect the environment can be very different however, carbon dioxide and methane affect it similarly. These gases act as a blanket letting radiation and heat from the sun in and only letting a fraction back out to space. The heat will keep building in tandem with the more carbon you put in the atmosphere.
To environmental impacts. The most obvious impact would be the melting of the polar ice caps and the eventual sea level rise but other consequences exist. Some include reduced planetary solar reflection (albedo) from soot in the snow, ocean acidification from carbonic acid forming and large scale species extinction.