Nitrous oxide (N2O) is an unwanted by-product from nitric acid production, also known as “laughing gas,” that comes during the oxidation of the ammonia. It is 310 times more harmful green house gas emission than carbon dioxide and contributes to global warming.
Yara has spent more than EUR 20 million to develop the de-N2O catalyst technology and patented two technologies for secondary N2O abatement, i.e. the process by which the N2O is removed just after being formed in the catalyst basket. The company has put the technology to use at 12 out of its 25 nitric acid plants around the world and in 30 Clean Development Mechanism (CDM) and Joint Initiative (JI) projects around the world, mostly in China.
The technology has been able to reduce nitrous oxide emissions at nitric acid plants by 70–90% at a cost of about EUR 2 per CO2 equivalent. The current price for CO2 is about EUR 10 and is estimated by the EU to reach about EUR 30. The EU will include nitrous oxide from nitric acid plants in its emission trading system in 2013.
“This is a cheap way to reduce CO2 emissions compared to carbon capture and storage or cleaning the CO2,” said Tore Jenssen, Yara vice president of safety and environment. “It has been very profitable for Chinese companies.”
Earning Carbon Credits Around the Globe
Yara accounts for 35% of all CDM/JI projects at nitric acid plants worldwide and 50% of the market through a marketing joint venture with Johnson Matthey PLC Nobles Metals. If all plants were to use this technology, companies would be able to reduce their greenhouse gas emissions by 100m tonnes of CO2 equivalents per year.
The Yara de-N2O catalyst is a cerium oxide based catalyst with a cobalt compound as the active component for decomposing N2O to nitrogen and oxygen. The multi cored cylindrical pellets can be placed in the burner basket or on top of a partial rashig ring filling.
The N2O is removed just after being formed in the catalyst basket under the metal ammonia oxidation gauzes. A selective de-N2O catalyst is installed in the high temperature zone to promote N2O decomposition. Alternatively N2O is removed by homogenous thermal decomposition by enlarging the space between the catalyst gauze and the process gas cooler.
The technology has the potential to reduce Yara’s emissions from 10 million tons of CO2 equivalents per year in 2005 to 5 million tons in 2009 and a future potential to 3 million. The company has already exceeded its goal of reducing total greenhouse gas emissions from its existing plants by 25% in 2009 compared to 2004, thanks by and large to this technology.