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Supercritical water oxidation of phenol and 2,4 dinitrophenol Perez, Ivette Vera

Abstract

The destruction kinetics of two model compounds has been investigated in the University of British Columbia (UBC) Supercritical Water Oxidation (SCWO) pilot plant. High concentrations of phenol (2.7% and 4% by weight) were oxidized at pressures of 24 to 26 MPa, temperatures of 666 to 778 K, and 0 to 39% oxygen excess. Phenol and Total Organic Carbon (TOC) conversions varied from 92 to 99.98% and 75 to 99.77% respectively. The second group of wastes studied contained 2,4 dinitrophenol (DNP). Two different solutions that simulated an aromatic nitration facility's wash-water were investigated. The first one contained 2.4% by wt. 2,4 dinitrophenol with 2% by wt. ammonium sulphate and simulated the final wash waters from the nitration plant with no sulphates elimination. The second solution contained 2.27% by wt. as ammonium dinitrophenol, with no sulphates. For the first DNP waste, at process conditions of 25 MPa, 780 K and 37% oxygen excess, 99.9996% destruction efficiencies were obtained for 2,4 dinitrophenol, and 99.92% for TOC. Mono-nitrophenols were detected as intermediates, but not in the liquid effluent, where residuals of ammonium bicarbonate and sulphates were detected. No NO[sub x] or CO was present in the gaseous effluent streams. This solution resulted to be very corrosive to the system. The second solution was treated at 22.9 ±0.1 MPa, 742-813 K and oxygen concentrations ranging from sub-stoichiometric to 69% excess. Destruction efficiencies for 2,4 dinitrophenol were 99.9996% in all cases (not detected). TOC destruction efficiencies ranged from 98.98 to 99.98%, while ammonia destruction ranged from 15 to 50%. Picric acid, mono-nitrophenols, ammonium carbonate and bicarbonate were detected as intermediates, but not in the liquid effluent. No CO or NO[sub x] was present in the effluent gas samples, except in cases with less than stoichiometric oxygen.

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