Supercritical water oxidation for energy production by hydrothermal flame as internal heat source. Experimental results and energetic study

The cooled wall reactor has been modified by adding an additional upper outlet of products at 500-700 °C to improve energy recovery and make possible energy generation with the supercritical water oxidation of different waste. Experimental and modeling results of the performance of this new reactor configuration are presented as well as a theoretical analysis of the energy recovery of the reactor compared to other supercritical water oxidation reactors. Different flow distributions were tested to find the best elimination conditions. Total organic carbon removal over 99.99% was obtained at room injection temperatures, when the fraction of products leaving the reactor in the upper effluent is lower than 70% of feed flow. The performance of the reactor was tested with the oxidation of a recalcitrant compound such as ammonia. Removals higher than 99% of N-NH4+ were achieved at temperatures near 700 °C. The behavior of the reactor working with feeds with up to 2.5% wt Na2SO4 could be injected in the reactor without plugging problems. Upper effluent always presented a concentration of salt lower than 30 ppm. Theoretical energetic analysis shows that the performance of this reactor is superior to other designs obtaining a maximum power efficiency of 27% (0.339 kW/kg-feed).