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Show 9 3.4 POWER OUTPUT ALLOWANCE The Guideline targets were established from agreed upon basic NOx levels at a certain efficiency in each chosen size category, for gaseous and liquid fuels. Basa Emission Tarqets(ppmv) Size Base Eff. (%) Gas Fuel Liquid Fuel o - 3 MW 25 75 175 3 - 20 MW 25 35 65 Over 20 MW 30 25 65 These levels were then converted to an energy output basis using 1.7 g/GJCi t) per ppmv of NOx on gas fuel, and a 1.77 factor on liquid fue~. For example, for a large 30% efficient unit; 25 ppmv x (1/.30) x 1.7 = 142 g/GJC~t~t)' rounded to 140 g/GJ This Power Output Allowance relates the mass of NOx emitted to the number of GigaJoules or Megawatts of power output, and would apply to the normal operating conditions as determined by the regulatory authority. Since both air mass flow and ppmv of NOx tend to drop at reduced power, engines meeting a base rating emission ppmv level are expected to be able to achieve the grams/GJ criteria under most normal conditions. This Allowance based on thermal efficiency results in large base-loaded units, fired on natural gas, having to meet a full load NOx emission target of about 27-33 ppmv in simple cycle applications, and 37-42 ppmv in a combined cycle mode (see example in Guideline Appendix B). If it is demonstrated that exhaust thermal energy is then used for an additional proce'ss, a slightly higher emission level is available through the Heat Recovery Allowance. units in the size range of 3 to 20 MW have emission targets set about 70 percent higher (240 g/GJ). This level is thought to be technically feasible for the smaller dry-low NOx combustors. The overall emission targets generally reflect what was originally contemplated for simple cycle units in the NOx/VOC Plan (33 ppmv) , for the majority of power installed in the foreseeable future in Canada. Emission limits for liquid fuels are substantially higher for the following reasons: -liquids fuels such as No. 2 oil have higher local flame temperatures in their atomised droplet pattern, -many liquid fuels contain nitrogen compounds which contribute to NOx production, and -dry low-NOx control requires more research, and manufacturers are concentrating efforts on gas fuelled units which represent the majority of applications. |