Fuel NOx

Source Combustion of nitrogen-containing fuels (fuel NOx) or oxidation of atmospheric nitrogen during combustions at high temperatures. Transport is the main contributor, whereas in the industry sector, combustion installations are responsible for 1.5 X 106 t/yr released to ah and 58.3% of the total emissions from industry in Europe. 

Engine load NO c (ppm) (Thermofuel fuel) NOx (ppm) (conventional diesel)... 

N. Kudo, I. Study on prevention of fuel NOx formation, (in Japanese) Proceedings of the 13th Japan Heat Transfer Symposium, 197 V+2-Mf +... 

In reality, this very complicated process consists of hundreds of reactions. The hydrocarbon radicals are intermediate species formed during the combustion process. Prompt NOx is generally an important mechanism at lower-temperature combustion processes. Fuel NOx is formed by the direct oxidation of organo-nitrogen compounds contained in the fuel. It is given by the overall reaction ... 

Fuel NOx is not a concern for high-quality gaseous fuels like natural gas or propane, which normally have no organically bound nitrogen. However, fuel NOx may be important when oil, coal, or waste fuels that may contain significant amounts of organically bound nitrogen are used. 

The only solution for fuel NOx is hydrodenitrogenation. But there is no fuel NOx at all if a clean fuel like natural gas or petroleum fractions with low nitrogen content is being used. Only when burning coal, which may contain up to 2% bound nitrogen, a preferential formation of fuel NOx occurs. In all other cases and for all other fuels, the thermal mechanism is the main culprit for NOx emissions. 

Catalytic combustion has received an increasing interest as an ultra-low emission technology for gas turbines. The main advantage with catalytic combustion is the possibility to decrease, and for some fuels to increase, the fuel-to-air ratio beyond the limits of flammability. Hence the combustion process and the temperature evolution in a gas turbine combustion chamber can be better controlled and stabilized. This flexibility gives the possibility to reduce emissions of unwanted pollutants compared with conventional flame combustion. Depending on fuel characteristics, emissions such as thermal and fuel-NOx, CO and hydrocarbons as well as soot can be reduced to ultra-low levels. Other advantages are lower noise levels and less vibrations. 

ULECAT group NR 2.3 MW stationary Biomass diesel Ceramic NR + Dual fuel, reduction of fuel-NOx, no net COj from biomass 26. 146... 

The chemistry of the conversion of coke-bound nitrogen on the FCC catalyst into NOx, though not yet very clear, is analogous to the three modes of NO formation in ordinary combustion,namely thermal-NOx, prompt NOx and fuel-NOx- The conversion of fuel/coke nitrogen first to HCN and NH3 and then to NOx is schematically shown in Figure 8. 

Nitric oxide (NOx) is one of the main pollutants in combustion systems and rotary kilns are no exception particularly for pulverized fuel combustion. NOx formation depends on three factors, namely (i) the amount of nitrogen present in the fuel, (ii) the combustion temperature, and (iii) the stoichiometric conditions for the combustion reaction. Hence NOx production is classified into fuel NOx, thermal NOx, and prompt NOx. Some of the mechanisms for the formation of these species during pulverized coal combustion in rotary cement kilns have been described in commercial CFD packages (e.g., FLUENT, CINAR). 

Most models assume that the fuel-bound nitrogen that is released by the devolatilization of coal is in the form of HCN, or some instantaneous transforms of HCN, which in turn form the base species of NO formation. It is believed that the HCN not only contributes to fuel NOx formation but also to some destruction of NOx and that the net formation might depend on the chemical as well as the thermal state of the mixture. The global chemical reactions involved for coal flames might therefore be expressed as... 

Conventionally NO formation is divided into thermal NOx and fuel NOx, with the former coming from either the Zeldovich mechanism... 

In the flue gases of power installations with gas flow rates of 25,000—32,000 m /h, nitrogen oxides concentration is 400—800 mg/m, whereas the figures for installations with gas flow rates of 35,000—80,000 m /h are higher, 700—1500 mg/m [296]. Of the three major kinetic mechanisms of the formation of nitrogen oxides during the combustion of hydrocarbon fuels, thermal (Zeldovich mechanism), prompt (Fenimore mechanism) and fuel NOx, the major role in the combustion of natural gas belongs to the thermal mechanism [297], This mechanism, described by the two main reactions... 

The -11N2 can also handle the same rou fuel as the -13D. Peak metal temperatures, internal metallurgy, and fuel-treatment requirements are all quite similar. The single-burner design for this model can get NOx down to 42 ppm with water injection. An EV silo combustor (several fuel nozzles) option is available if the end user has gas or diesel fuel. NOx can then be reduced to 15 ppm when at base load on natural gas. 

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