Influence of Pressure and Steam Dilution on NOx and CO Emissions in a Premixed Natural Gas Flame

Abstract

C h ris tia n O liv e r P a s c h e r e it1In flu en ce of Pressure and S team D ilu tio n on NOx and CO Em issions in a P rem ixed N atu ral Gas F lam eIn the current study, the influence o f pressure and steam on the emission formation in a premixed natural gas flame is investigated at pressures between 1.5 bar and 9 bar. A pre mixed, swirl-stabilized combustor is developed that provides a stable flame up to very high steam contents. Combustion tests are conducted at different pressure levels fo r equivalence ratios from lean blowout to near-stoichiometric conditions and steam-to-air mass ratios from 0% to 25%. A reactor network is developed to model the combustion process. The simulation results match the measured NOx and CO concentrations very well fo r all operating conditions. The reactor network is used fo r a detailed investigation o f the influence o f steam and pressure on the NOx formation pathways. In the experi ments, adding 20% steam reduces NOx and CO emissions to below 10 ppm at all tested pressures up to near-stoichiometric conditions. Pressure scaling laws are derived: CO changes with a pressure exponent o f approximately -0.5 that is not noticeably affected by the steam. For the NOx emissions, the exponent increases with equivalence ratio from 0.1 to 0.65 at dry conditions. At a steam-to-air mass ratio o f 20%, the NOx pressure expo nent is reduced to -0.1 to +0.25. The numerical analysis reveals that steam has a strong effect on the combustion chemistry. The reduction in NOx emissions is mainly caused by lower concentrations o f atomic oxygen at steam-diluted conditions, constraining the ther mal pathway. plants [1,2] but with lower installation costs and emission levels [3]. In contrast to the complex combined-cycle plants, ultra wet gas turbines have a substantially smaller footprint. Depending on the cycle configuration, short start-up times and excellent load control capabilities can be achieved. Furthermore, the high steam content allows for low-NOx, near-stoichiometric combustor oper ation and, thus, enables postcombustion CO2 capture at low cost, since the concentration of CO2 reaches the highest possible value for air breathing gas turbines after condensation of the steam. It was recently shown for a lean premixed and for a rich-quenchlean combustor, that steam dilution significantly reduces NOx

An Experimental Investigation on the NO and CO Emission Characteristics of a Swirl Convergent-divergent Nozzle at Elevated Pressure

“…As mentioned before [26], flame residence time t R has an important influence on NO formation. The flame residence time t R can be measured with a global flame residence time t g , which is defined as Equation (10). The t g has been used in some previous analyses for NO x formation [22,40,41], its definition is based on the consideration that the flame volume V f is proportional to L f 3 , as indicated by Equation 11:…”

“…The results revealed that the NO x exponent n changed from −0.18 to 1.6 for the tangential nozzle and from −0.77 to 0.61 for the axial nozzle as the equivalence ratio varied from 0.43 to 0.65. Göke et al [10] studied NO x and CO emissions for a premixed natural gas flame within a pressure range of 1.5-9.0 bar by performing experiments and simulations. They found that NO x increased and CO decreased with increasing pressure, the exponent for NO x emissions increased with equivalence ratio from 0.1 to 0.65 while the exponent for CO emissions was about −0.4 at lower temperatures and −0.5 at higher temperatures.…”

Comparative analysis of characteristics of liquid fuel combustion for various designs of oil-steam burners

“…Currently, the issue of environmentally friendly combustion of heavy hydrocarbons and substandard fuels for cheap energy production is relevant [1,2]. One of the promising approaches to reduce toxic products when burning liquid combustible waste is steam injection into the combustion zone as an effective way to suppress nitrogen oxides and soot formation [3,4].…”

Changes in chemical components of aerosol particles in different haze regions in China from 2006 to 2013 and contribution of meteorological factors

“…Since the aerosol particles and cloud (fog) droplets can influence atmospheric visibility (Watson, 2002), and in the ambient atmosphere no cloud (fog) can be formed if no hygroscopic aerosols can be activated to cloud condensation nuclei (CCN) or ice nuclei (IN) (Twomey, 1977;Seinfeld and Pandis, 1997), high loadings of aerosols not only affect climate change (Forster et al, 2007;Boucher et al, 2013) but also adversely influence weather (Wang et al, 2010;Pérez et al, 2006) and contribute to the occurrence of haze and fog events, both of which can be considered as types of aerosol pollution in present-day China (Zhang et al, 2013). Since there have been individual reports of persistent haze-fog events in January 2013 in central-eastern China, the change in aerosol particles and their chemical components are attracting special attention in this rapid economic growth and high population density area (H. Wang et al, 2015;Huang et al, 2014;Zhang et al, 2013;Guo et al, 2014;. However, questions were raised about what changes occurred to the major chemical components of aerosol in different haze areas in China during recent years, as well as why a big difference existed between 2013 and an adjacent year in the case of no significant changes in emission.…”