What is the purpose of an economizer in a boiler system?

The purpose of an economizer in a boiler system is to recover waste heat from combustion products. By capturing this waste heat, the economizer helps to preheat the boiler feedwater before it enters the boiler. This preheating process increases the overall efficiency of the boiler system because less energy is required to convert the preheated water into steam. Consequently, the system uses less fuel to achieve the desired steam output, leading to reduced operational costs and lower emissions.

The other choices do not accurately represent the role of an economizer. For instance, increasing steam pressure is typically achieved through other components in the boiler system, while enhancing the lifespan of boiler materials falls under maintenance and material selection rather than a specific function of the economizer. Storing excess steam is also not a function of an economizer, as steam storage is managed by different components designed specifically for that purpose. Thus, recovering waste heat is the essential function that distinguishes the economizer within the boiler system.