During combustion, NOx is released into the environment. The amount of NOx needs to be lowered so that you are in compliance with the legal requirement. In addition, you will need to ensure that you measure how much NO and NO₂ is produced whenever you take a reading. If you are using methods of NOx reduction, then you can expect to see as much as 50% NO₂.
Methods of NOx Reduction
Staged Combustion – Using this method, the main chamber will only burn some of the fuel. The rest will also burn up eventually and will produce just as much energy. This method tends to reduce how much temperature the main chamber has
Catalytic Converters – This device is for reducing the toxicity found in the various emissions that come out of the combustion process. Their work is to break down the nitrogen oxides so that they form separate oxygen and nitrogen particles.
Recirculation of Flue Gas – This is a method that brings down the flame’s temperature, thus reducing the amount of thermal NOx. Some of the exhaust gas is then re-circulated back into the process of combustion and cools the area.
Reduction of O₂ Level – By reducing how much O₂ is available for reacting with Nitrogen, you will also reduce the NOₓ. Mainly it is done via O₂ trim controls. This is a method that reduces NOₓ by as much as 10%, but it increases the amount of CO produced.
Low NOₓ Burners – here airflow is controlled using plates to create a more elongated flame. This then decreases the temperature, which in turn reduces how much NOₓ is to be found. CO may increase and should therefore be monitored closely.
Fuel oil with Low Nitrogen – These oils can have fifteen to twenty times less nitrogen than the standard oil. This reduces the emission of NOₓ. If you are using a No.2 oil, they can contribute between twenty and fifty percent of the NOₓ levels found.
Steam or Water Injection – The injection of either one lowers the flame’s temperature during combustion thus reducing the NOₓ produced.
Selective Catalytic Reduction (SCR) – here you add to the flue some type of reductant. Many times, it is ammonia. The ammonia and NOₓ react giving off N2 and H₂O.
Selective Non-Catalytic Reduction (SNCR) – here the reductant is added at the furnace top and usually it is urea. The reduction of NOₓ can be as high as 70%.
The other thing to consider if you are using a gas fired turbine is what we called Dry Low Emission. We are proud to be the FIRST company to successfully Commision Fuel Flex Bias DLE Technology in the field. Complete information on how it works as well as its history is in our next article.