OCR Text |
Show 2 ing the diffusion flame limit for pulverized fuels, acting as a complement to premixed flat flame burner experiments. The results of a recent experimental study of the devolatilization of pulverized coal in a well-characterized opposed-flow diffusion flame are reported here. The experiments have been performed on suspensions of 12 urn diameter coal particles at temperatures up to 1500 K and heating rates from 2000 to 20,000 K/s. The atmosphere surrounding the particles has been controlled, with varying concentrations of nitrogen, argon, propane and oxygen. Particular attention has been paid to the identification of individual gaseous nitrogen and sulfur species, and the rates at which they evolve during the early stages of coal combustion. EXPERIMENTAL FACILITY The experimental facility consists of an OFDF burner, coal preparation equipment, particle feeder, flame sampling system, chemical analysis train and a laser-Doppler anemometer [12,13,14]. The burner has an upper and lower section which can be separated anywhere between 5 and 25 mm, each with a 25 by 100 mm rectangular opening. Oxygen is brought in from below and passes through a sintered stainless steel plate to ensure a flat velocity profile. The upper half of the burner is formed from stainless steel plate and is constructed with a diverging and converging section. The design of the converging section is a compromise between an effort to form a flat gas velocity profile and to minimize coal particle build up on the wall. Three 16 mesh stainless steel screens are used to straighten the flow and reduce the scale of the turbulence. The edges of the flanges on both the upper and lower sections are |