What can be a primary source of steam in a boiler system?

The primary source of steam in a boiler system is liquid water heated to its boiling point. In the boiler, water is subjected to heat generated by burning fuel or through other methods, causing the water to reach its boiling point and convert into steam. This process is central to the operation of the boiler, as the steam produced is used for various applications such as powering turbines, providing heat for industrial processes, or for heating spaces.

Liquid water is essential because, without it, the boiler would not have the necessary medium to produce steam. The transformation of water into steam is governed by principles of thermodynamics, where heat is absorbed to facilitate this phase change. Once water is heated to its boiling point, it begins to vaporize and create steam, which can then be harnessed for energy or heating purposes.

The other options, while they may have roles in certain systems, do not serve as primary sources of steam. For example, electrical power can be used to heat water, but it is not directly a source of steam; air compression does not produce steam as it involves compressing air rather than heating water; recycled flue gases may be utilized for heat recovery in some systems but are not a direct source of steam generation. Therefore, liquid water heated to