Date of Award

12-1-1980

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

Abstract

The exchange of sodium and other cations from lignite by hydrogen ion in an aqueous H2SO4 medium was investigated in a continuous counter- current ion exchange unit. This was studied as a function of solid residence time, solid/liquid mass ratio, initial acid concentration and lignite particle size.

Cations removal from lignite increased with an increase in residence time and in acid concentration and with a decrease in solid/liquid mass ratio and in particle size. The removal of sodium reached equilibrium values at 50 minutes residence time and for 0.4651 N solution concentration. Solid/liquid mass ratios of less than 1/2 produced no significant increase in sodium removal. Particle sizes of less than 35 mesh were not required to reduce the sodium content of the lignite to less than 5 percent of its initial content.

A theoretical model featuring film diffusion control was postulated for the removal of sodium from lignite. The experimental data were consistent with this model. An overall empirical correlation, based on the film diffusion model, relating the percent sodium removed from lignite, Y, to the solid residence time t, seconds, solid/liquid mass ratio P, initial acid concentration C, normality, and particle size rQ, centimeters, was obtained using a linear least-squares regression. Y = exp -0.160t0<316 c0*259 p0.241 _ 0.274. The least-squares fit had a multiple correlation coefficient of 0.860. Partial F statistics indicated that the heirarchy of the independent variables in predicting the dependent variable is acid concentration, solid residence time, particle size and solid/liquid mass ratio in decreasing contribution.

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