Conversion of tar in a counter flow of supercritical water at a temperature varying along the reactor axis

Abstract

The article reports the conversion of tar (empirical formula CH_1.47N_0.01S_0.007) continuously introduced into a counter flow of supercritical water (SCW) at 30 MPa in a tubular reactor with a temperature gradient along its vertical axis (450°C at the top and 650°C at the bottom). The yields of liquid products and volatile (C₁–C₉) hydrocarbons are 41.4 and 28.4%, respectively, relative to the weight of tar supplied into the reactor. Methane is the major component (40.5 mol %) of the volatile products, and the liquid products are dominated by oils (74.4 wt %). Deasphaltization and desulfurization of tar conversion products are observed. The average rate of water decomposition calculated from the quantity of O atoms in the conversion products is 0.24 g/min. Use of counter flows of the reactants in combination with a temperature gradient along the reactor axis affords a higher yield of low-boiling hydrocarbons than in the case of SCW pumping through a tar layer.