Studies of waste produced in pilot-plant testing using Fe(II)(center dot)EDTA and magnesium-enhanced lime for combined SO(sub 2)/NO(sub x) removal

摘要

A pilot-plant-scale study of combined sulfur dioxide/nitrogen oxides removal has been performed by the Dravo Lime Company at the Cincinnati Gas & Electric Company's Miami Fort Station in North Bend, Ohio. This study used Dravo's patented Thiosorbic(reg sign) lime process along with Argonne National Laboratory's (ANL's) patented ARGONOX ferrous(center dot)ethylenediaminetetraacetate anion (Fe(II)(center dot)EDTA) additive. For approximately nine months, scrubbing tests were collected and waste samples were collected. Waste testing at ANL involved two types of long-term chemical stability experiments. In one test, the gas-phase composition above several different samples was studied as a function of time. Significant changes were noted for both oxygen (0(sub 2)) and carbon dioxide (CO(sub 2)) gases. The other experiment involved solid-phase leaching and testing of gases the leachate for total nitrogen and for some nitrogen-containing species. Several types of tests were performed by the Dravo Lime Company. Particle size and shape of the solids were determined. Elemental analyses were performed using x-ray fluorescence, and moisture and residual EDTA were determined. Tests were conducted to determine if the waste solids could be stabilized using current treatment technology for stabilizing flue-gas desulfurization (FGD) solids. Tests of stabilization were conducted with addition of various amounts of fly ash and lime. Results showed the solids were easily stabilized. The US EPA Toxicity Characteristic Leaching Procedure (TCLP) and toxicity tests using Daphnia simplex and fat-head minnows were performed on solids both before and after stabilization. The TCLP results after stabilization were well within acceptable limits for heavy metals.