Characterization of Gas Reburning-Sorbent Injection Technology By-Products
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CHARACTERIZATION OF GAS REBURNING-SORBENT INJECTION TECHNOLOGY BY-PRODUCTS
SHAS V. MATTIGOD AND DHANPAT RAI Battelle, Pacific Northwest Laboratories, Richland, Washington 99352 U.S.A.
ABSTRACTr Three samples of fly ashes from pilot-scale tests of gas reburning and sorbent injection (GR-SI) technology were characterized physically, chemically, and mineralogically. Texturally, the samples consist of approximately 97% by weight of silt-size particles. Total chemical analysis showed that Al, Ca, C, Fe, Si, and S were the major elements, making up 56% of the total mass of the sample on average. Approximately 3% of the sample mass consisted of the elements Cl, Mg, P, K, Na, and Ti, and 0.4% consisted of trace elements. Major crystalline compounds found in these samples were lime (CaO), anhydrite (CaSO 4 ), and calcium carbonate (CaCO 3 ). Calculations show that these compounds constituted from 56 to 76% of the mass of the samples. The morphology and chemistry of particles in GR-SI samples were similar to those of particles in conventional coal fly ashes. The particles in the GR-SI samples consisted of fragments and spheres of varying sizes. Most of the particles were calcareous. Silicate and alumino-silicate particles were fewer in number, and iron-rich particles were rare. The EP test indicated that extract concentrations of Ag, As, Ba, Cd, Cr, Pb, and Se were well below the EPA regulatory levels. Predictions of leachate compositions from these types of fly ashes, if disposed of as a landfill at a midwestern U.S. site indicate, that during the first ten years the concentrations of Ca, SO 4 , Na, B,and OH would remain high. The concentrations of minor constituents (As, Ba, Cd, Cd, Cu, Cr, Fe, Ni, and Se) in the leachate are predicted to be at trace levels.
INTRODUCTION Much of the electric energy produced in the United States comes from the combustion of coal 111.Coal combustion results in a number of different kinds of solid and gaseous by-products. New ways to safely dispose of the solid products of conventional and new coal-combustion technologies could better protect the environment and could save disposal costs. The new coal-combustion technologies have been designed and developed to regulate gaseous emissions to meet current air quality standards [2]. One of the new coal-combustion technologies is gas reburning and sorbent injection (GR-SI). This technology is designed to reduce NO, and SO2 emissions significantly by using a two-stage process. In the first stage, NO, emissions are reduced by infusing natural gas downstream from the coal-combustion zone. In the second stage, the SO 2 content of the flue gases is reduced by injecting a sorbent either into the upper part of the combustion chamber or into the gases downstream from the boiler. The GR-SI process is estimated to remove about 70% of SO2, and reduce NO, emissions by approximately 60% [3]. The solid by-products resulting from new coal-combustion technologies must be evaluated for either use or safe disposal. One of the initial steps in evaluating them is
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