Optimisation of SCR-DeNOx catalyst performance related to deactivation and mercury oxidation (Denopt) : final report

The Denopt project aimed at optimising existing and developing new SCRDeNOx catalysts applied at coal fired power plants. Special emphasis was put on catalyst deactivation and mercury oxidation, but nevertheless NOx reduction and SO2-SO3 conversion were considered, too. New catalysts for high dust application were produced and tested in extensive tests in lab-scale and bench-scale reactors. New promising materials like copper, manganese, iron and cerium were introduced into the catalyst material and their effects on mercury oxidation, DeNOx activity and SO2-SO3 conversion were determined. Some of the materials showed a mercury oxidation level almost twice as high at only slightly increased SO2-SO3 conversion compared to a commercial catalyst. As important parameters, the flue gas HCl content was identified. Furthermore, the interaction of DeNOx reaction and mercury oxidation was shown with a strong influence of flue gas ammonia concentration on mercury oxidation. A new approach of low temperature mercury oxidation catalysts with noble metal impregnation was tested and economically analysed, showing that noble metal catalysts are powerful mercury oxidation catalysts at high cost. The effect of deactivation was evaluated by mass balances of mercury, arsenic and phosphorous in power plants and showed the major effect and sinks of these materials, leading to a better understanding of measures against deactivation. A 3D CFD model was developed, implemented and calibrated, which includes relevant descriptions and their interactions for NOx-reduction, mercury oxidation and SO2-SO3 conversion. The model showed good correlation at validation with measurement data of full scale power plants and forms a good tool for power plant optimisation in the section boiler until downstream of the DeNOx catalyst.