ACERC
Abstracts - 1997 |
ACERC
Abstracts - 1997 |
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Thrust Area 3: Pollutant Formation/Control and Waste Incineration |
Veranth, J.M.; Silcox, G.D.
and Pershing, D.W.
Environmental Science and Technology, 31:2534-539(1997). Funded by ACERC.
The gas, wall and bed temperatures in a hazardous wasted incineration kiln were studied using a commercially available, CFD-based, r4eacting flow code, which included radiation heat transfer. The model was compared to field measurements make on a co-current flow, 35 MW slagging rotary kiln. Cases were run to determine the sensitivity of the predictions to changes in the model assumptions and to simulate the normal variation in combustion inputs. The model predictions of the peak bed temperature, of the axial temperature profile, and of the gas temperature at the exit-plane were consistent with the measurement at a full-scale wasted incinerator during normal operation. The model and the field observations both indicate that the peak bed temperature occurs near the middle of the kiln and that the difference between the peak bed temperature and the exit-plane gas temperature depends on the inlet flow. The geometry of the transition between the kiln and the secondary combustion chamber and the fuel-to-air equivalence ratio have the greatest effect on the calculated temperature distribution. Modeling studies provide useful information such as the relationship between available measurements and the temperature at inaccessible locations inside a full-scale kiln.
Smoot, L.D.; Hill, S.C.
and Xu, H.
Progress in Energy and Combustion Science, (in press), 1997. Funded by
ACERC.
Reburning is a process whereby a hydrocarbon fuel is injected immediately downstream of the combustion zone to establish a fuel-rich zone in order to convert nitric oxide to HCN. The reburning fuel can be gaseous (e.g., natural gas), solid (e.g., coal char or wood) or liquid (e.g., residual oil. Typically, the amount of reburning fuel used is 10-30% of the total fuel. This technology is practiced commercially with nitric oxide reduction levels of 35-65%, depending on the type of scale of the boiler or combustion, the primary and reburning fuels and other variables. Current research and development are suggesting several advanced reburning concepts including injection of ammonia or urea aft of the reburning fuel injection. Nitric oxide reductions of over 90% are anticipated. In this mini-review, a review of reburning technologies, measurements and mechanisms is presented. Predictive methods for reburning are also discussed. Recent work on reburning, including development of a global reburning reaction rate, is summarized, and results of application of a comprehensive combustion model to reburning measurements are summarized.
Xu, H.; Smoot, L.D. and
Hill, S.C.
1997 Fall Meeting of the Western States Section/Combustion Institute,
Diamond Bar, California, October 23-24, 1997. Funded by ACERC.
Advanced reburning technology, which makes use of natural gas injection followed by ammonia injection, has proved to be and effective method for removal up to 85-95% of NO in pulverized, coal-fired furnaces. This paper reports the development of a 7-step, 11-species reduced mechanism for the prediction of nitric oxide concentrations for advanced reburning from a 312-step 50-species full mechanisms. The derivation of the reduced model is described in detail, including the selection of the full mechanism, the development of the skeletal mechanism and the selection of steady-state species. The prediction of the 7 step reduced mechanism are in good agreement with those of the full mechanism over a wide range of parameters, applicable to coal-based, gas-based, and oil-based combustion cases. Comparisons with three independent sets of experimental laminar data indicate that the reduced model correctly predicts observed trends, and H2O on NO reduction. The observed effects of CO on NH3 slip were also reliably predicted. Mechanistic considerations explain the roles of important radicals and species. Also, parametric studies of effects of CO2 and H2O have been performed with reduced mechanism. A maximum NO reduction exists, which strongly depends on the concentrations of CO, CO2, (NH3/NO)in, and temperature.
Brouwer, J.; Kemp, G.; Heap,
M.P.; Lighty, J.S.; Burton, B.; Sirdeshpande, A.; Inkley, D.; Pershing, D.W.;
Fisher, J. and Pisharody, S.
Western States Section of the Combustion Institute, Spring 1997
For the last two years, the University of Utah and Reaction Engineering International, in cooperation with Ames Research Center, have been developing a waste incineration system for regenerative life support systems. The system is designed to burn inedible plant biomass and human waste. The exhaust gas is currently designed to recycle back to the plant growth chamber and will eventually be recycled to the human chamber after passing through a Trace Contaminant Control System. The incineration system, a fluidized bed reactor, has been designed for a 4-person mission. This paper will detail the design of the components of this system. In addition, results will be presented from testing at the University of Utah. Presently, the unit has been shipped to Ames Research Center for more tests prior to delivery to Johnson Space Center for testing in a 90-day, 4-person test.
Lighty, J.S.; Burton, B.;
Sirdeshpande, A.; Inkley, D.; Pershing, D.W.; Brouwer, J.; Kemp, G.; Heap, M.P.;
Fisher, J. and Pisharody, S.
27th International Conference on Environmental Systems, Lake Tahoe, Nevada,
July 14-17, 1997
For the last two years, the University of Utah and Reaction Engineering International, in cooperation with NASA Ames Research Center (ARC), have been developing a waste incineration system for regenerative life support systems. The system is designed to burn inedible plant biomass and human waste. The goal is to obtain an exhaust gas clean enough to recycle to either the plant or human habitats. The incineration system, a fluidized bed reactor, has been designed for a 4-person mission. This paper will detail the design of the units. In addition, results will be presented from testing at the University of Utah. Presently, the unit has been shipped to Ames Research Center for more tests prior to delivery to Johnson Space Center for testing in a 90-day, 4-person test.
Lighty, J.S. and Veranth,
J.M.
Twenty-Seventh Symposium (International) on Combustion, The Combustion
Institute (1997)
The interaction between advances in combustion research, practical demonstrations of incineration technology, and changing regulations over the past 10 years is reviewed. The driving force behind changes in technologies for the incineration of hazardous and municipal waste is the changing regulatory climate. More stringent regulations create the need for better understanding of all aspects of the combustion process. In this review case studies are employed to demonstrate how recent advances in combustion have impacted the design and operation of memerators with special emphasis on pollutant minimization are methods for complying with proposed memerator emission standards for dioxins and furans the interaction of NOx and chlorine in incinerators and the environmental impact of solid residues from incinerators.
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