Prolonged campaign length of high pressure nitric acid plant by optimization of secondary catalyst design for N2O abatement

摘要

The combustion of ammonia on catalytic platinum gauzes is a fundamental step for the production of nitric acid. Although the desired product nitric oxide (NO) is obtained with a selectivity conventionally greater than 95% the formation of side products like nitrogen (N2) and especially nitrous oxide (N2O) are a particular drawback. Since N2O is condiered as a high potential greenhouse gas regional legislative regulations nitric acid producers are forced to shutdown plants or pay fines if the emission limit is exceeded. In our contribution we present the significant prolongation of primary catalyst campaign length of a high pressure nitric acid plant by optimization of our precious metal containing secondary catalyst for N2O abatement (HRSC++). We successfully managed to increase the catalyst N2O abatement performance and set-up a good alignment to the primary gauze catalyst life time. The given improvements are achieved despite retaining catalyst bed volume, allowable pressure drop and plant operation parameters. Due to the optimizations mentioned above the primary catalyst campaign length of the considered plant is increased from 40 to at minimum 80 days. Furthermore, the secondary catalyst lifetime is increased from typically 3 (at 40 days) to at least 4 (at 80 days) primary catalyst campaigns. Finally, we provided a significant drop in cost of ownership for the plant operator due to lower number of shutdowns for primary and secondary catalyst exchange causing less costs for gauze manufacturing and recycling as well as stop of nitric acid production for days.