OCR Text |
Show Reference thermal efficiency is a value (%) assigned to boilers, according to fuel type, by agreement within the working group. The reference thermal efficiency is intended to be representative of boilers as they are likely to be operated in the absence of specific provisions for energy efficiency, and does not represent optimal tuning of a boiler. Assigned reference thermal efficiencies are listed in Table 7. Table 7 - Reference Thermal Primary Fuel Gaseous fuel Distillate oil Residual oil < 0.35% nitrogen Residual oil > 0.35% nitrogen Efficiencies for Boilers Reference Thermal Efficiency {%) 78 81 83 83 Actual thermal efficiency, for the purpose of the Guideline, is determined in accordance with stack loss methodologies (ref. 7, 8) or equivalent methods. This can be done by measuring combustion air temperature and stack temperature during a N O x emission test, and consulting nomographs, supplied with the Guideline, for determining dry flue gas loss and hydrogen loss. Actual Thermal Efficiency = 100% - Dry Flue Gas Loss - Hydrogen Loss For heaters, energy efficiency credits are based on combustion air preheat temperatures, heater exit temperatures and excess air. Table 8 presents a condensed version of one of three tables from the Guideline indicating the relationship among these three parameters in determining energy efficiency credits. Table 8 - Energy Heater Exit Temperature (°C) 1300 1100 800 500 Efficiency Credits for Heaters at 5 0 % Excess Air Combustion Air Preheat Temperature (°C) 100 1.15 1.08 1.06 1.04 200 1.31 1.21 1.16 1.12 300 1.42 1.31 1.23 1.19 400 1.50 1.39 1.30 1.25 500 1.56 1.45 1.36 The above efficiency credits are based on the reduction of fuel input that results from the corresponding level of combustion air preheat. The use of these efficiency credits will ensure that heaters operating with combustion air preheat emit no more N O x than similar heaters operating with no combustion air preheat. 9 |