A Green Desuperheater For An Energetic Efficient Alternative To The Decompression Valve In Supercritical Water Hydrolysis Process. Cfd Simulation

The supercritical water hydrolysis (SCWH) of biomass (P=250 tiara & T=400 degrees C) allows directly obtaining sugars, which are high value products in the chemical industry, in reaction times lower than 0.2 s. The process is characterized by the high selectivity values which can be obtained controlling the reaction time. Reaction kinetics show that glucose degradation is only retarded at temperatures below 250 degrees C. Therefore, in the traditional SCWH process, degradation control is achieved expanding the hydrolysis stream in a valve which instantaneously cools down the products. Although the selectivity values obtained are greater than 96 %, the pressure is wasted on the valve expansion decreasing the global energetic efficiency of the process. In this paper a CFD simulation of a desuperheater which mixes the hydrolysis product with pressurized cooling water is presented. The temperature of the hydrolysis stream decreases below 250 degrees C in cooling times lower than 20 ins maintaining the pressure at 250 tiara and the selectivity value over 90 A,