To guarantee the successful and efficient shell boiler operation, the user must:
1)Know the conditions, environment, and demand characteristics of the plant, and accurately specify these conditions to the boiler manufacturer.
2)Provide a boiler house layout and installation that promotes good operation and maintenance.
3)Select the control systems that allow the boiler to operate safely and efficiently.
4)Select the control systems that will support the boiler in supplying dry steam to the plant at the required pressure(s) and flowrate(s).
5)Identify the fuel to be used and, if necessary, where and how the fuel reserve is to be safely stored.
The term “boiler efficiency” is often substituted for thermal efficiency or fuel-to-steam efficiency. When the term “boiler efficiency” is used, it is important to know which type of efficiency is being represented. Why? Because thermal efficiency, which does not account for radiation and convection losses, is not an indication of the true boiler efficiency. Fuelto-steam efficiency, which does account for radiation and convection losses, is a true indication of overall boiler efficiency. The term “boiler efficiency” should be defined by the boiler manufacturer before it is used in any economic evaluation.
Excess air provides safe operation above stoichiometric conditions. A burner is typically set up with 15% to 20% excess air in higher firing ranges. Higher excess air levels result in fuel being used to heat the air instead of transferring it to usable energy, increasing stack losses and significantly decreasing efficiency. Boilers with lower excess air throughout the operating range have higher efficiencies.
