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91Cf + -9f c,, = -If the Langmuir isotherm expression is used to describe the equilibrium relationship, Eq. 9 is given as Nitrogen Pollutant Formation in a Pulverized Coal Combustor: Effect of Secondary Stream SwirlConcentrations of NO, NH3, and HCN, together with coal particle burnout and gas composition, were measured during combustion of a bituminous coal. Control of incoming secondary gas swirl level and overall stoichiometric ratio led to significant reductions in nitrogen oxide pollutant concentration. In-situ measurements showed that coal particles were confined near the reactor center during rapid particle reaction. This took place in a locally fuel-rich environment, producing nearquantitative conversion of fuel-nitrogen to NH3 and HCN, with some NO. Subsequent gas phase reactions of these nitrogen species were identified as important in establishing the ultimate NO concentration. SCOPEIt has been shown (e.g., Pershing et al., 1975;Rees et al., 1980) that control of nitrogen oxide can be achieved through control of the pulverized coal mixing and combustion processes. It has also been shown (Pershing and Wendt, 1979) that oxidation of the nitrogen in the coal is the major source of the oxides of nitrogen, and that NO can be controlled through staging (Chen et al., 1980; Wendt, 1980). However, work is continuing to understand the NO formation and to further reduce NO levels. The objective of this work was to investigate the extent and causes of NO formation in the presence of secondary inlet air swirl level. Experiments were conducted in a cylindrical, laboratory N. S. Harding. Jr , is currently with Conoco, Inc., Library, PA. pulverized coal combustor (13.7 kg coal/h) with samples being withdrawn 145 cm aft of the fuel-inlet port. Pulverized coal and air were injected through a cylindrical primary port while the secondary air stream was injected in a swirling fashion surrounding the primary stream. Measurements were made on gas composition (Ar, CO, COz, CHI, Hz, Nz, Oz), elemental particulate composition (ash, C, H, N), and pollutant concentration (NO, NHs, HCN). Effects of secondary stream swirl, stoichiometric ratio, primary stream velocity and solids loading level, coal particle size, and secondary stream preheat temperature were tested on coal burnout and N-pollutant level. Experiments were also conducted at three swirl levels with gas-particulate samples obtained at various axial and radial positions. Resultant data provided NO concentration maps for interpreting the test results. July, 1982Page 573 AlChE Journal (Vd. 28, No. 4) CONCLUSIONS AND SIGNIFICANCEStoichiometric ratio (SR) and secondary swirl (S) significantly influenced N-pollutant concentrations. An 88% reduction in NO was obtained while operating fuel-rich (SR = 0.66) at high secondary swirl compared to fuel-lean operation (SR = 1.32) without a swirling secondary stream. A reduction in NO by a factor of nearly 4 was obtained through use of the lower SR value, while an additional factor of 2 was obtained through use of secondary swirl (F...

Dynamic growth of ash deposits was studied in a carefully controlled environment using high _peed video cameras and temperature controlled deposition probes. Deposition data are reported as a function of coal type, extent of particle burnout, and time. Five coals varying in rank from bituminous to lignite were tested. The coals were tested at conditions simulating three locations in a boiler: the near-flame region, the superheater region, and the convection pass. Details of deposit formation were monitored for 90 minutes for each coal at each test condition. A particularly interesting result is that particle capture efficiencies, the fraction of t]yash particles which adheres to the probe upon contact, have a strong time dependence, varying from near zero to near unity during deposit formation. Dependence of ash deposition on coal rank and location of the boiler is also discussed. Y ,lcurrently at Burns and Roe,