Nitrogen oxide abatement by distributed fuel addition

A screening study was performed on a laboratory scale downfired combustor to determine the effect of various variables on the effectiveness of the reburning process as a technique for NO{sub x} abatement. The objective was to define optimum conditions under which reburning can be used and to be able to compare the reburning performance of our combustor to that reported by others. For this purpose, a statistically designed parametric investigation was conducted to determine how a set of controlled variables (primary and secondary stoichiometric ratios, location of the reburn zone and primary fuel load) would affect the reduction in NO emissions in a classical reburning configuration. Also, the effects of other variables (NO in the primary zone, temperatures in the primary, reburn and burnout zones and the residence time in the reburn zone) were also investigated. No optimum configuration was identified in this study. Nevertheless, this study provides insight into the parameters associated with reburning

Interactions between trace metals, sodium and sorbents in combustion. Quarterly report No. 5, October 1, 1995--December 30, 1995

The proposed research is directed at an understanding of how to exploit interactions between sodium, toxic metals and sorbents, in order to optimize sorbents injection procedures,which can be used to capture and transform these metals into environmentally benign forms. The research will use a 17kW downflow, laboratory combustor, to yield data that can be interpreted in terms of fundamental kinetic mechanisms. Metals to be considered are lead, cadmium, and arsenic. Sorbents will be kaolinite, bauxite, and limestone. The role of sulfur will also be determined. The research is divided into the following five tasks: (1) combustor modifications; (2) screening experiments; (3) mechanisms; (4) applications and (5) mathematical modelling. Accomplishments for this past quarter are briefly described for tasks 1 and 2

Nitrogen oxide abatement by distributed fuel addition

The purpose of this project is to develop techniques for nitrogen oxides abatement by distributed fuel addition. The major nitrogen oxide of interest is Nitric Oxide (NO), a precursor to premature forest damage and to acid rain. Recently interest has also been evoked with respect to an additional oxide of nitrogen, namely Nitrous Oxide (N{sub 2}O). Therefore, abatement measures for NO{sub x} are being investigated to determine their influence on N{sub 2}O as well. This report briefly describes the significance of N{sub 2}O emissions to the environment and the urgent need to develop techniques that can reduce emissions of both NO and N{sub 2}O. Reburning through distributed fuel addition may be an effective technique for NO{sub x} (mainly NO) emission control as described in the previous quarterly report. Reburning may also be effective in reducing N{sub 2}O levels. A technique for N{sub 2}O measurement by gas chromatography/electron capture detection was developed during this quarter, and is described in this report. This analysis technique will be used in the proposed experimental study to investigate the effectiveness of reburning on N{sub 2}O control

Interactions between trace metals, sodium and sorbents in combustion. Quarterly report No. 4, July 1, 1995--September 30, 1995

The proposed research is directed at an understanding of how to exploit interactions between sodium, toxic metals and sorbents, in order to optimize sorbents injection procedures, which can be used to capture and transform these metals into environmentally benign forms. The research will use a 17kW downflow, laboratory combustor, to yield data that can be interpreted in terms of fundamental kinetic mechanisms. Metals to be considered are lead, cadmium, and arsenic. Sorbents will be kaolinite, bauxite, and limestone. The role of sulfur will also be determined

Integración de ecuaciones diferenciales rígidas de valor de contorno en problemas de combustión con cinética de reacción detallada

Detailed models of the flat, laminar, opposed jet diffusion flame involve the solution of the momentu, energy and species conservation equations coupled with stiff chemical kinetics. The problem has self similar solutions and can be solved through numerical integration of a set of second order, stiff, boundary valued, ordinary differential equations, each with a regular first order turning point arising from convection. Use of standard finite difference discretization (in the spatial domain) and expansion of the reaction rate source terms in a Taylor series abaut the backward iteration (in the temporal domain), lead to a matrix equation in which the coefficient matrix is a very large block tridiagonal matrix. It is also a band matrix and solution is obtained through LU descomposition. Instabiiities originating from the unevenly spaced grid and from diffusion of numerical errors towards the boundaries forced the use of a large number of equally spaced grid points which contrained the program to solution of relatively small kinetic problems (due to core storage limitations). This dilemma was resolved by developing a modified central difference discretization which assumes that the solution at a mesh point is given by the sum of exponentials. Using the new technique it was possible to obtain the solution of the opposed jet problem with 150 reactions and 70 species on the available CYBER 175 computer

Synergistic capture mechanisms for alkali and sulfur species from combustion

Due to the generation of a wide variety of pollutants during coal combustion, research on the development of a multifunction sorbent for adsorbing SO{sub 2} and alkali compounds simultaneously is ongoing at the University of Arizona. The current work focuses on the thermodynamic behavior of the reacting system for alkali adsorption especially in gas phase. The temperature and pressure effects on sodium species and on the system are intensively investigated under the simulated flue gas composition condition. The interaction of sulfur dioxide with sodium chloride vapor and some other system elements is also explored

Synergistic capture mechanisms for alkali and sulfur species from combustion

This report presents work done on a laboratory combustor in an attempt to identify mechanisms that govern the simultaneous capture of alkali and sulfur species using sorbent injection techniques. The mechanisms of capture fall into two broad categories i.e. Physical transport of alkali species (in vapor or condensed phase) to the sorbent surface and surface reaction between the alkali species and the sorbents. Water solubility, though not specific, has been used to get an indication of relative significance of these two broad mechanisms. It is assumed that the physically adsorbed alkali species on sorbents are predominantly water soluble while the chemically reacted alkali content is predominantly water insoluble. In order to infer possible dominant mechanisms, specific parameters has been varied during experimentation. Such parameters include, speciation, particle time-temperature history, and furnace burning conditions

Synergistic capture mechanisms for alkali and sulfur species from combustion

An aerosol reactor system has been designed and constructed for the systematic study of the mechanisms governing the possible synergistic capture of sulfur oxide and alkalis with aluminosilicates and lime (CaO). Actual particle dynamics found in coal combustor systems can be simulated, mass balances can be closed, and the system conditions are well controlled. The collection of hot reactive aerosol flows is performed utilizing an isokinetic probe