Air Monitoring 41


Haber-Bosch Ammonia Synthesis Process


Otswald Process for Nitric Acid Production


and nitrogen using heat from the combustion process prior to the cracked ammonia being fed to the burner.


Ammonia-fi red turbines are like those used with natural gas. The main changes are in the burner and the process control system, not the turbine itself. Control of NOx emissions in general, and especially nitrous oxide (N2


O) which is a very potent greenhouse gas is a focus of development in this area.


Minimising and monitoring nitrous oxide emissions


Partial cracking of 20% to 30% of the ammonia is a solution that several turbine OEMs are testing. The blend of ammonia, hydrogen and nitrogen seems to burn very well.


When using 20 to 20% of cracked ammonia blended with ammonia on a gas turbine, optimisation of the air:fuel ratio is important to ensure effi cient combustion with minimum emissions. Tests have shown that using a slightly oxygen rich fl ame, with an equivalence ratio of 0.8 to 0.9, can eliminate N2 emissions. As the equivalence ratio falls to 0.6 N2


O emissions


can rise to as much as 200 ppm by volume. At a ratio of 1.3, they would be around 50 ppm.


The National Institute of Advanced Industrial Science and Technology (AIST) is one of the largest public research organizations in Japan. They have conducted tests to validate the use of an ammonia natural gas blend for power generation on a small gas turbine. Co-fi ring ammonia with hydrocarbons changes the emissions footprint since CO and CO2


may be formed. In Japan, there is a large pilot project in planning which will co-


fi re ammonia onto unit 4 of the Hekinan coal fi red power plant.


The reduction in coal usage on this 1GWe unit will reduce CO2 emissions since the ammonia will be sourced as green or blue ammonia. It will be important to avoid N2


O emissions since N2 When co-fi ring ammonia with coal, or natural gas CO and CO2 O have overlapping peaks in the IR spectrum. The CO2 IR absorption peak is also very close to N2


The ISO 21258 (Stationary source emissions -Determination of the mass concentration of dinitrogen monoxide) has been developed to enable accurate measurement of N2


and potentially to analyse the CO2 O O


is an extremely potent greenhouse gas, about 250 times worse than carbon dioxide.


will


be present in the fl ue gas. This adds to the complexity of the CEM system because CO and N2


O. O in fl ue gas


streams. It confi rms NDIR as the reference method and draws attention to the need to convert CO to CO2


compensate for CO2


on a separate instrument or channel and then if required.


Commercial experience of CEM for nitrous oxide


Fortunately, there is relevant experience to draw on for N2 gas analysis. N2


O for many years. O fl ue O is a regulated greenhouse gas in the European


Emissions Trading Scheme (ETS) and is also regulated through US Greenhouse Gas (GHG) legislation. Nitric acid production has dealt with the challenge of CEM for N2


Commercial systems exist that can enable simultaneous N2O and NOx analysis. As an example, the Fuji CEMS from Fuji Electric uses NDIR for the N2


uses NDIR as the method for N2


O analysis. The SWG200 from MRU also O analysis.


MKS offers their MultiGas FTIR with capability for N2 generation turbines.


Ammonia may also be used as a fuel for aviation, maritime propulsion, and land-based mobility. In these cases, engine development and testing will require N2


O CEM systems and they


may also be required to be installed on ships to monitor maritime emissions.


The growth of low-carbon fuels for power generation and propulsion will introduce new CEM challenges. It will simultaneously open new opportunities for innovative solutions providers to serve this emerging market.


O analysis.


The Rosemount CT5100 quantum cascade laser gas analyser has also been used for research into N2


O emissions from power


Hekinan power plant, Japan


Author Contact Details Stephen B. Harrison • sbh4 GmbH • Address: Kranzlstraße 21, 82538 Geretsried, Germany • Tel: +49 (0)8171 24 64 954 • Email: sbh@sbh4.de • Web: www.sbh4.de


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