Document Type

Thesis

Date of Award

5-31-1990

Degree Name

Master of Science in Environmental Science - (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Joseph W. Bozzelli

Second Advisor

Richard B. Trattner

Third Advisor

Barbara B. Kebbekus

Abstract

Incineration processes are effective and sometimes efficient technologies for the remediation of contaminated solids which result in permanent destruction of most organic hazardous compounds. A less energy intensive, but more efficient process to remove contaminants from the soil is the application of heat and a flow of inert gas where the entire soil mass is not heated to incineration temperatures. This thermal treatment increases volatilization and often effects complete removal of organic compound depending on soil conditions and species volatility,

The goals of this research are to develop an understanding of the mass transport phenomena and adsorption thermodynamics that control the desorption of contaminants from sand specifically determining mass transfer coefficients, film mass transfer coefficients, and equilibrium constants for a series of target organic pollutants. We also determined particle size effects on each of the above parameters for the pollutant species. We compare these data with soil bed mass transfer parameters and heats of adsorption in view the of absence of intraparticle diffusion effects in sand bed. These parameters will yield a better understanding and allow calculation of required time, temperature, and flow veocity for the desorption process in incineration or thermal desorption processes.

The experiment is based on plug flow deposition of the target contaminant on a well characterized sand column monitoring its travel through the column at varied temperatures, flowrates, and sand particle sizes. Chromatographic response analysis on the results is used to calculate the heats of adsortion of organic materials onto the sand matrices in addition to axial dispersion and film mass transfer coefficients. We study these effects on particle sizes of the sand bed; at sieve #'s 30-35, 35-40, and 40-50.

The amount of contaminant remaining in the sand decreases with the increasing temperatures in the sand bed. We observe that the film mass transfer and dispersion coefficients decrease when the sand particle size increases. The following results have been obtained:

Particle Size I : Rp = 0.027cm

Particle Size II : Rp = 0.023cm

Particle Size III : Rp = 0.018cm Compound MolecularDiffusivity( Dm,cm2 / sec) Film Mass Transfer Coefficient (Kf,cm / sec) Dispersion Coefficient (Dz,cm2 / sec) /td> I II III I II III Methylene Chloride 0.122 4.41 5.09 6.43 2.47 6.54 9.04 Chloroform 0.117 4.26 5.08 6.51 2.51 2.92 4.12 1,1,1-trichloroethane 0.108 3.95 4.70 6.03 1.63 4.05 5.79 Benzene 0.122 4.45 5.30 6.80 5.40 7.96 9.06 Toluene 0.123 4.47 5.33 6.83 5.14 6.16 8.45 Tetrachloroethylene 0.134 4.89 5.82 7.47 3.25 3.98 4.11 Chlorobenzene 0.132 4.81 5.73 7.36 3.33 6.32 8.77 1.2,4-trichlorobenzene 0.154 5.61 6.68 8.57 4.74 6.53 17.65

These results can be then applied to thermal treatment of contaminated soils and will be utilized to obtain optimum operational conditions for sand decontamination experiments.

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