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thyssenkrupp Uhde's state-of-the-art technology for the combined removal of N2O and NOX. It is capable of almost complete removal of nitrous oxide. NOX emissions can also be reduced to very low levels enabling an invisible stack plume to be easily achieved.
The industrial production of nitric acid (HNO3) produces nitrous oxide (N2O) as an undesired by-product, which is emitted into the atmosphere with the tail gas. Nitrous oxide is a potent greenhouse gas some 310 times stronger than carbon dioxide and is implicated in the destruction of the ozone layer.
Variant 1 is especially applicable for tail gas temperatures higher than approx. 425°C.
The central component is a reactor arranged between the final tail gas heater and the tail gas turbine, which contains two catalyst beds filled with iron zeolite catalysts operating at the same pressure and temperature, and a device for the intermediate addition of NH3. EnviNOx® variant 1 has recently been declared by the European Union authorities to be BAT (Best Available Technique) for permitting purposes within the EU. It has been in operation in the 1,000 metric tpd nitric acid plant of Agrolinz Melamine International (AMI) at Linz, Austria, since September 2003.
Process variant 2 is suitable for temperatures between around 300°C and 520°C.
With variant 2, N2O is removed by catalytic reduction over an iron zeolite with a hydrocarbon such as natural gas or propane. The first commercial-scale implementation of EnviNOx® process variant 2 came on stream in the fall of 2006 and is realized in the 1,830 metric tpd nitric acid plant of Abu Qir Fertilizers Co. in Egypt.
Today, thyssenkrupp Uhde ranks among the world's leading process plant licensors for the removal of nitrous oxide.
high N2O removal rates (up to 99%).
end-of-pipe technology (no contact with intermediate product stream or product).
availability of approved CDM methodology AM 0028 (suitable for all EnviNOx® variants).
non-toxic catalyst – simplifies handling and disposal. Long catalyst service life.