Supercritical water oxidation of phenol and 2,4 dinitrophenol

• Main Author: Perez, Ivette Vera
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/13638

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.