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Show above. The absolute level of PNA emissions was low and the values were similar to those reported on conventional size boiler combustion tests with coal derived and petroleum fuels [13]. PNA emissions, although presently without limiting standards, are of environmental concern with aromatic fuels due to their known carcinogenic effects. The breakdown analysis of the PNA emissions from the gas turbine tests suggests that the emitted PNA was formed during the combustion process and it was not a product of incomplete combustion since the ring size was for all fuels nearly identical. If partial combustion of fuel-PNA were contributing significantly to the emissions, the distribution of the ring types in the emissions would have been different for the three fuels. VII. WATER INJECTION The EPA New Performance Standards vary with the fuel nitrogen content. For fuels with nitrogen levels below 0.15 percent, the standard is 75 vpm. As the FBN rises above 0.15 percent, the standard increases linearly until it reaches a maximum of 125 vpm at 0.25 percent FBN. Based on this Standard, EDS and the shale derived fuel would have to meet a limit of approximately 125 vpm at a thermal efficiency of 25 percent. These figures are on a dry basis at 15 percent oxygen in the exhaust gas, converted to ISO standard day conditions. Water injection tests demonstrated on the type 9 gas turbine, that for diesel a 0.7 water-to-fuel ratio and for EDS a 0.9 water-to-fuel ratio is required to meet the 75 vpm specifications. However, due to the allowance incorporated into the EPA Standard for FBN, the permissible 125 vpm NO emission limit can already be reached at an injection rate of 0.6 - 0.7 kg water per kg of fuel, i.e., at about the same rate as required for diesel oil. Reduction factors developed for various fuels at full load conditions, defined as the ratio of the amount of NO measured without water injection to that with water injection, are plotted as a function of water to fuel mass ratios in Figure 12. It appears from the graph that the efficiency of water injection has declined as the FBN increased in the test fuels. 1.4.10 |
