| A rotary-kiln simulator was used to develop a better understanding of how hazardous materials are removed from sorbent clays. Experimental results and associated numerical modeling on the combustion and desorption of toluene from a montmorillonite clay sorbent are presented. The purpose of these tests was to understand the mass and heat transfer characteristics of the material in a rotary kiln environment. The experiments were done in a batch mode, simulating a control volume of solids moving down the length of a full-scale rotary kiln, exchanging time for distance as the independent variable. Studies investigating the effect of oxygen concentration, charge size, rotational velocity, and kiln cavity temperature on the desorption rate were completed. Also, effects of water in the montmorillonite were examined. Two comprehensive models were developed to predict the thermal and mass desorption characteristics of the bed, respectively. Key conclusions of these studies were: (1) water exerts a profound effect on the solids thermal profile, (2) simple geometrical scaling between pilot and full-scale is not sufficient to allow prediction of full-scale performance; computer modeling is necessary to extrapolate to pilot-scale data, (3) radiation and convective heat transfer can both be of major importance depending on the thermal environment, and (4) desorption predictions were successfully completed using either experimental or predicted solids temperatures.; Another series of studies in the rotary kiln simulator was focused on NO{dollar}sb{lcub}rm x{rcub}{dollar} formation from nitrogenous waste constituents. These tests were performed to simulate materials (plastics, nylons, dyes, and process waste) usually destroyed in hazardous-waste incinerators. Four surrogate wastes, Aniline, Pyridine, Malononitrile, and Ethylenediamine, were absorbed onto the montmorillonite clay sorbent. The major results from the experiments were: (1) the percentage conversion of fuel nitrogen to NO{dollar}sb{lcub}rm x{rcub}{dollar} decreased as the weight percent of nitrogen in the hydrocarbon portion of the waste increased, (2) more NO{dollar}sb{lcub}rm x{rcub}{dollar} was formed at the higher fuel-nitrogen concentrations, and (3) there was good agreement between these laboratory results and previous field tests with other nitrogenous fossil fuels.; A detailed discussion regarding the design, construction and operation of the rotary-kiln simulator for research on the destruction of hazardous waste materials is presented in the Appendices. All facility calibration techniques and calculations in addition to data acquisition and reduction algorithms are also discussed there. |
