Removal of Sodium from Nerco Subbituminous Coal by Ion Exchange in a Continuous Countercurrent Unit Using an Aqueous Sulfuric Acid Medium
Date of Award
Master of Science (MS)
The removal of sodium and other ions (potassium, magnesium, calcium, and aluminum) from a Montana subbituminous coal by ion exchange, with the hydrogen ion from aqueous sulfuric acid, in a continuous countercurrent unit was investigated as a function of initial sulfuric acid concentration, coal particle size, liquid to solid mass ratio, and coal residence time.
The results from this investigation indicate that the ion exchange process in the continuous countercurrent unit is controlled by film diffusion. Experimental results also indicate that the sodium removal is directly proportional to the initial sulfuric acid concentration and coal residence time, inversely proportional to the coal particle diameter, and independent of the liquid to solid mass ratio, providing that there are enough hydrogen ions available in the exchange solution to attain maximum sodium removal at equilibrium for the particular coal particle size. Ninety percent of the original sodium could be removed at equilibrium from coal having a mean coal particle diameter of 0.814 mm (-10 x +48 mesh).
A theoretical model for an ion exchange process controlled by film diffusion was fitted to experimental data in order to predict the sodium removal from coal. The following equation was fitted at the 5 percent significance level.
Fraction of sodium removed = [1 - exp [((-3) (D) (C) (t))/((r0) (sigma) (C bar))]] where: D = self-diffusion coefficient for H -Na ion exchange within the 2 particle, cm /sec + 3 C = initial sulfuric acid concentration, meq H /cm t = time of ion exchange, sec r = mean coal particle radius, cm o 6 = film thickness, cm — +3 C = sodium ion content in the as-recieved coal, meq Na /cm P = fraction of sodium removed experimentally at equilibrium
The self-diffusion coefficient was found to be more sensitive to changes in the coal particle size than it was when any other operating parameter was varied.
Thorfinnson, Dennis B., "Removal of Sodium from Nerco Subbituminous Coal by Ion Exchange in a Continuous Countercurrent Unit Using an Aqueous Sulfuric Acid Medium" (1985). Theses and Dissertations. 3249.