Figure 6: A generic boiler and steam distribution system

Figure 6: A generic boiler and steam distribution system

• Recover lost stack gas. A boiler’s stack or chimney allows the gases produced after fuel combustion to be exhausted into the atmosphere. The energy lost through the boiler stack is a function of exhaust gas temperature and excess air at the stage of fuel combustion. Typically, stack gas loss contributes to about 15 percent of a boiler’s energy loss. Energy from the stack can be recovered for preheating combustion intake air or preheating feed water before it enters the boiler. When water is pre-heated (utilising the energy in the stack gases) it needs less energy to be heated to form steam, thereby saving energy and making the boiler more energy-efficient.

• Use the warmest air possible for combustion intake. As a rule of thumb, a 1 percent increase in boiler efficiency is possible for each 20-degree-Celcius increase in intake air temperature for combustion. This air could be sourced from the area just below a facility’s roof, which will be warmer due to air temperature stratification.

• Key parts of the boiler, including fireside surfaces, waterside surfaces, the burner assembly and the stack, should be regularly maintained. This maintenance would include visual inspection for leaks or cracks in insulation and cleaning, as necessary.

• Seals, feed water pumps and safety valves should be systematically checked for water leaks and repaired, if necessary

• Eliminate steam leaks. Significant energy savings can be realised by locating and repairing leaks in live steam lines and in condensate return lines. By wasting steam through leaks in steam lines, increased boiler steam production is required to meet the system’s needs. In leaky condensate return lines, additional feed water is required to make up for condensate losses, as more energy is needed to heat this new, cooler feed water than what would be necessary to heat the preserved, warmer condensate. In this case, the need for water treatment also increases, as additional water is required to top up the system. Leaks most often occur at the fittings in the steam and condensate pipe systems. Energy and cost savings from the elimination of leaks depend on a boiler’s efficiency, the number