27. Muthukumaran, Poongunran; Gupta, Ram
B. Sodium-Carbonate-Assisted
Supercritical Water Oxidation of Chlorinated Waste.
Abstract
Supercrit. water oxidn. (SCWO) is emerging as a promising technol. for the destruction of org. wastes. However, corrosion is a severe problem for chlorinated wastes because of the formation of HCl. Recently, it was proposed that the addn. of Na2CO3 significantly reduces the corrosion. This work examines the effect of Na2CO3 on the oxidn. kinetics of phenol and 2-chlorophenol in supercrit. water. The kinetics data in the absence of Na2CO3 are verified to conform to the literature data. New data in the presence of Na2CO3 show that the oxidn. is highly enhanced, which may be due to a combination of the catalytic effects of Na2CO3 and removal of HCl by Na2CO3. If all other kinetic parameters are unchanged, the activation energy of 2-chlorophenol decompn. decreases from 11.5 Kcal/mol without Na2CO3 to 2.44 Kcal/mol with Na2CO3. Similarly, a redn. from 10.4 to 7.5 Kcal/mol is obsd. for phenol. Na2CO3 plays a key role in reducing corrosion on the reactor walls by 1st neutralizing the acid and then providing a large surface area for adsorption of the pptd. corrosive compds. Because Na2CO3 is insol. in supercrit. water, it ppts. as fine particles with a large surface area. A new reactor design is proposed for obtaining fine Na2CO3 particles based on the supercrit. anti-solvent method; these fine particles provide a surface area that is several orders of magnitude larger than that of the reactor walls.
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