N_2O ABATEMENT IN AN EU NITRIC ACID PLANT:A CASE STUDY

摘要

Nitrous oxide (N_2O) is an invisible gaseous by-product of the manufacture of nitric acid by the Ostwald process. It forms during the catalytic oxidation of ammonia over platinum/rhodium gauzes, the major product being nitric oxide gas (NO). Since nitrous oxide is a potent greenhouse gas with some three hundred times the effect of carbon dioxide, and nitric acid plants now represent the single largest industrial process source of the former gas, there is a need for technologies to lower nitrous oxide emissions from nitric acid plants.Responding to this need Uhde established a research and development programme to find a commercially viable method for removing nitrous oxide and NO_x from the tail gas of nitric acid plants. To gain practical long-term operating experience with possible catalysts, a catalyst test unit was designed and built, which could be connected to the tail gas section of a nitric acid plant. In a partnership with Uhde, Agrolinz Melamine International (AMI) provided the nitric acid plant access and all the support needed for the trouble free and continuous operation of the catalyst test unit. Based on the positive results obtained, a full-size nitrous oxide and NO_x abatement reactor was planned and constructed, and the first commercial scale implementation of the new process successfully started up in September 2003 at AMI, Linz, Austria. After one year of operation a consistent 98-99% of the tail gas nitrous oxide is being destroyed in the reactor and the NO_x concentration has been lowered from around 400 ppmv to 30 - 35 ppmv.