Boilers of the thermal power plants have tall chimneys.

Explanation

(i) The thermal power plants mainly use coal and natural gas as a fuel which have chemical energy.
(ii) The combustion of coal or natural gas result in the formation of various gases like carbon dioxide and sulphur dioxide, nitrogen oxide gas which are very dangerous and cause air pollution.
(iii) These gases and the produced soot can be hazardous if released at the normal height.
(iv) Tall chimney release them at a height in such a way that they disperse easily and do not sediment
(v) Therefore, the chimneys of boilers are much taller.