• Journal of Hydrogen and New Energy
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• v.33 no.4
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• pp.400-412
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• 2022

Hydrogen with high chemical reactivity and combustion efficiency, is expected to reduce greenhouse gas and CO emission. However, there is a problem of increase in NOx emission due to hydrogen combustion. MILD combustion technology has been proposed to resolve NOx emission. In this study, the characteristics of MILD combustion and NOx formation by flue gas recirculation (KV) in CH₄-H₂ mixture were analyzed and predicted using 0D premixed combustion model. The ignition delay time became shorter as the hydrogen co-firing rate increased, and longer as the recirculation rate increased. For NOx emission, EINO decreased as the KV increased, but EINO increased as the hydrogen co- firing rate increased. In particular, EINO was predicted to increase significiently above 80% hydrogen. Through the pathway analysis of NO formation, it was found that the influence of N₂O intermediate route and NNH route was enhanced for hydrogen co-firing.

• Journal of the Korean Institute of Gas
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• v.11 no.1 s.34
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• pp.9-12
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• 2007

In this study, a new method of combustion characteristics have been proposed to reduce exhaust emissions in a diesel engine using four kinds of mixed fuel. Mixed fuels show four different torque ratios between diesel oil md natural gas, which are 4:0, 3:1, 2:2 and 1:3. In order to investigate the exhaust gas during combustion, exhaust gases are sampled by gas analyzer, for example NOx, Soot, CO, and HC, as the RPM changed. As a result, the NOx, CO, and HC concentrations of mixed fuel are higher than those of diesel oil only. However, the Soot concentration of mixed fuel is lower when diesel oil is burned.

• Journal of Institute of Convergence Technology
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• v.7 no.1
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• pp.15-18
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• 2017

As emission gas regulation of deisel vehicles is strengthened to Euro-6, It becomes difficult to deal with NOx regulated value mainly by EGR without additional after-treatment system. In addition, RDE(Real Driving Emissions) test will be introduced after september 2017. Therefore, It is essential to develop the after-treatment of diesel vehicles which reduce NOx emissions. It is possible to use DOC, DPF, LNT or DOC, DPF and SCR as a after-treatment system for reducing NOx. However, It is expected that the SCR will be applied widely because LNT alone does not have sufficient NOx purification efficiency. In this study, It tried to analyze the efficiency of reducing NOx emissions during the mode test by attaching a NOx sensor to test vehicle. As a result, It was confirmed that NOx emissions was significantly reduce through the after-treatment system from engine. And the NOx reduction efficiency of SCR was about 4.5 times better than DOC, DPF.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.225-232
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• 2012

A chemical reactor network (CRN) was developed for a lean premixed gas turbine combustor to predict the emission of pollutants such as NOx and CO. In this study, the predictions of NOx and CO emissions from lean premixed methane-air combustion in the gas turbine were carried out using CHEMKIN and a GRI 3.0 methane-air combustion mechanism, which includes the four NO formation mechanisms for various load conditions. The calculated results were compared with experimental data obtained from a modified test combustor to validate the model. The contributions of the four NO pathways were investigated for various load conditions. The effects of nonuniformity of the mass flux and of the equivalence ratio of the injector on the NOx formation were investigated, and a method of reducing the pollutant formation was suggested for the development of a sub-10 ppm gas turbine combustor.

• New & Renewable Energy
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• v.7 no.3
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• pp.67-73
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• 2011

MGT fuelled by landfill gas was tested to asses feasibility of its exhaust gas application for $CO_2$ enrichment. The exhaust gas was analyzed during start-up and normal operation with different MGT load conditions. Due to the changes of air/fuel ratio and combustion mode, $O_2$, $CO_2$, CO and NOx concentration were varied within wide ranges during the MGT start-up. Especially, NOx emissioin level was increased up to 20.01 ppmv. Different tendencies of $O_2$, $CO_2$, CO and NOx concentrations were observed with MGT output changes. $O_2$ and CO concentrations were shown to be decreased and NOx and $CO_2$ concentrations were shown to have opposite trends. NOx emission level (0.8~1.88 ppmv) was very low compared to other types of combustion based power generation equipment. Unburned hydrocarbon emission level was substantially decreased with MGT load increase. Especially, $C_2H_4$ concentration was below the detection limit(0.2 ppmv) around the nominal load condition. The exhaust gas from landfill gas fuelled MGT system was shown to be feasible for $CO_2$ fertilization. Concentrations of major components were within or below the maximum allowable ranges.

• Journal of Energy Engineering
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• v.22 no.2
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• pp.128-135
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• 2013

In order to estimate the combustion characteristics and the gas interchangeability for natural gas with various compositions per each production area, equivalent gas are using to replace natural gas. It is known that an equivalent gas has the same the heating value, the compression factor, the relative density, CO emission and the burning velocity as the original natural gas. However, it is not reported that the flame shape and thermal efficiency and NOx emission by real gas appliance. In this study, equivalent gas was examined the validation to replace natural gas. The CO emission the burning velocity and the flame temperature were reconfirmed, and the flame shape, the NOx emission and the thermal efficiency were numerically and experimentally investigated. As results, there was not a large difference between natural gas and equivalent gas. This result demonstrated that there was no problem using equivalent gas to replace natural gas.

• Journal of Energy Engineering
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• v.13 no.2
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• pp.144-151
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• 2004

Stabilization and reduction of combustion noise and NOx emission from dry low NOx combustor of GE MS7001F gas turbine were achieved. Dry low NOx gas turbines that adopt the lean premixed combustion technology frequently generate the flame instability and high NOx emissions if not adequately tuned. Dynamic pressure oscillation during the combustion mode transfer increased as ambient temperature decreased with frequency of 80㎐ and magnitude of 4-9 psi. Effects of both combustor tuning for uniform fuel flow with burner nozzles and fuel pre-filling into transfer fuel valves on stabilisation of the dry low NOx combustor were very significant. Dynamic pressure oscillation during the combustion mode change was decreased up to 2.5 psi. Also, NOx emission from GE7F DLN-1 combustor can be maintained as low as 35-43ppm (15% O$_2$) in base load operation of 150 MW.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.11
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• pp.1977-1983
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• 2000

SCR(selective catalytic reduction) pilot plant for reduction of the nitrogen oxides using diesel oil as a reductant was installed at the NG(natural gas) fired combined cycle and the activity of Pt(0.3%)/Zeolite catalyst was studied in real flue gas condition according to the amount of reductant. reaction temperature and space velocity. NOx conversion gradually increased with increasing the diesel oil concentration up to C/N ratio 5.5(C/N ratio: the ratio of the number of carbon atom to the number of NOx molecules included in the flue gas). Increasing the reaction temperature. NOx conversion increased and reached a maximum conversion of 50% at $190^{\circ}C$. NOx conversion did not changed with increasing the space velocity up to 18,500/hr and then gradually decreased. These results reveal the potential for diesel oil as a reductant for de-NOx SCR process.

• Journal of the Korean Institute of Gas
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• v.9 no.2 s.27
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• pp.50-55
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• 2005

The compositional and structural properties of alkali metal ion exchanged Y-zeolites have been investigated by la number of analytical techniques and their catalytic activities were tested for NOx reduction in combination with a non-thermal plasma. The NOx conversion data for LiY, NaY, KY and CsY were measured by chemiluminiscent NOx meter in the temperature range of 100 to $350^{\circ}C$. The initial activities of the catalyst at $150^{\circ}C$ increased in the order LiY < KY < NaY < CsY in alkali series. The activity of CsY and NaY were increased and showed maximum at $200^{\circ}C$ and then decreased in the plasma reactor, as the temperature increased. The activity of KY maintained same by $200^{\circ}C$ and then decreased, whereas the activity of LiY decreased with the increasing temperature. The CsY catalyst, which showed the highest activity in alkali metal series, exhibits a NOx conversion efficiency of $80\%$ between $170{\~}220^{\circ}C$.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.78-83
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• 2011

Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its high thermal efficiency and lower harmful emissions, including $CO_2$. Although the high octane value of natural gas increases engine output and efficiency due to the high compression ratio, this fuel is prone to such difficulties as a narrow limit of inflammability and a slow combustion speed in the lean burn operation domain, leading to unstable combustion and higher emissions of harmful exhaust gases. Hydrogen blended with natural gas can extend the lean burn limit while maintaining stable, efficient combustion and achieving lower NOx, hydrocarbon and green house gas emissions. In this study, the effect of hydrogen addition on an engine performance and NOx emission characteristics was investigated in a heavy duty natural gas engine. The results showed that thermal efficiency was increased and NOx emissions were reduced due to the expansion of lean operation range under stable operation. NOx emission can be significantly reduced with the retard of spark advance timing.