High-temperature and high-concentration SCR of NO with NH3: Application in a CCS process for removal of carbon dioxide

摘要

This study investigates several commercial selective catalytic reduction (SCR) catalysts (A-E) for application in a high-temperature (approximately 525 °C) and high-concentration (5000 ppm NO) system in combination with CO2 capture. The suggested process for removing high concentrations of NO_x seems plausible and autothermal operation is possible for very high NO concentrations. A key property of the catalyst in this system is its thermal stability. This was tested and modelled with the general power law model using second-order decay of the BET surface area with time. Most of the materials did not have very high thermal stability. The zeolite-based materials could likely be used, but they too need improved stability. The SCR activity and the possible formation of the by-product N2O were determined by mea-surement in a fixed-bed reactor at 300-525 °C All materials displayed sufficiently high activity for a designed 96% conversion in the twin-bed SCR reactor system proposed. The amount of catalyst needed varied considerably and was much higher for the zeolithic materials. The formation of N2O increased with temperature for almost all materials except the zeolithic ones. The selectivity to N2 production at 525 °C was 98.6% for the best material and 95.7% for the worst with 1000ppm NO_x in the inlet; at 5000 ppm NO_x, the values were much better, i.e., 98.3 and 99.9%, respectively.