OCR Text |
Show 6 water condensed by mechanical refrigeration. All analyzers were calibrated prior to each experiment, with calibration gas introduced at the probe tip. Two types of fuel feeders were utilized for the tests. The original coal feeder was incapable of feeding an uninterrupted stream of fuel due to the bridging characteristics of the biomass materials. The coal feeder was replaced initially by a top-unloading variable volume feeder (Jenkins, 1990), which was used in the tests with the waste paper, woodstraw blend, and humus. Although the fuel feed was continuous, the device produced a characteristic fuel enrichment toward the end of each fuel batch. The bulk density of the milled waste paper was also sufficiently low that feed rates had to be kept low to avoid clogging the eductor, and equivalence ratios above 0.4 were not tested. The variable volume feeder was subsequently replaced with another custom feeder producing a continuous and steady fuel feed rate. This second feeder was used for the tests with wood and rice straw. Emission factors, f, expressing the mass of pollutant species produced per unit mass of dry fuel consumed were computed from the species concentrations and calculated instantaneous fuel mass flow rates derived by carbon balance. Equivalence ratio, t/J = AF slAF, was computed from the air-fuel ratio, AF, and the stoichiometric air-fuel ratio, AFs, determined from the elemental composition of the fuel. The stoichiometric air-fuel ratio was left uncorrected for the production of CO, such that the actual O:l concentration approached zero at equivalence ratios slightly less than 1. With some fraction, k, of the fuel carbon volatilized, the moist fuel feed rate was estimated as: 1- w . . a m/,moist = ma z -+c+d-b a We a =--(xco +xeo +xTHe) Wgas 2 b = (1- M)(1- Yash) c = (1- M)(1- k )YC [1] [2] [3] [4] |