Photocatalytic treatment of IGCC power station effluents in a UV-pilot plant

Abstract

The aim of this work is to improve the quality of water effluents coming from an Integrated Gasification Combined Cycle (IGCC) power station to meet with future environmental legislation. This study has been made using an homogeneous photocatalytic oxidation process (UV/Fe(II)/H 2O 2) in a pilot plant. The efficiency of the process was determined from the analysis of the following parameters: cyanides, formates and TOC content. In the first stage, a factorial experimental design allowed to determine the influence of operation variables (initial concentration of H 2O 2 and Fe(II), pH and temperature) on the degradation kinetics. pH was always kept in a value >9.5 during cyanides destruction to avoid gaseous HCN formation and lowered later to enhance formates degradation. Experimental kinetic constants were fitted using neural networks (NNs). Under the optimum conditions ([H 2O 2] = 1700 ppm, [Fe(II)] = 2 ppm, pH 2 after cyanides destruction, and T = 30 °C), it is possible to degrade 100% of cyanides in 15 min and 76% of formates in 120 min. The use of an homogeneous process with UV light can offer an economical and practical alternative to heterogeneous photocatalysis for the destruction of environmental pollutants present in thermoelectric power stations effluents, since it can treat very high flowrates using a lower H 2O 2 concentration. Furthermore, it does not require additional operations to recover the solid catalyst and regenerate it due to deactivation as occurs in heterogeneous catalysis.