Ultra Low NOx Catalytic Combustion for IGCC Power Plants

The computational fluid dynamical software AVL-FIRE code was used for investigating the impact of multiply injection strategies and spray included angles on combustion and emissions in a marine diesel engine. The fuel injection parameters of spray included angle and pilot injection timing with pilot-main injection, as well as post injection ratio and post injection duration angle with pilot-main-post injection, were all investigated and optimized. The results indicate that retarding pilot injection timing with pilot-main injection declines high temperature region, resulting in a notable reduction in NOx emissions. Since fuel evaporation and burn are hampered by long spray penetration due to low temperature and pressure with pilot injection, a suitable spray included angle are used to offer more efficient air-fuel mixing process. A wider spray included angle simultaneously reduces soot emission and indicated specific fuel consumption (ISFC). Post injection fuel exerts impact on combustion process by causing a great disturbance to flow field during post combustion. Increasing post injection ratio from 4% to 10% at a small post injection duration angle great emission performance is achieved by simultaneous reduction in NOx and soot emissions while only using a slight consumption of ISFC. To summarize, the defeat of traditional NOx-soot trade-off occurs as both NOx and soot emissions are decreased with optimized multiple injection strategy and spray included angle. Particularly, there are respectively four cases with pilot-main injection and two cases with pilot-main-post injection, that achieve simultaneous reduction in NOx emissions, soot emission, and ISFC, compared to the prototype.

Simultaneous reduction of NOx emission and SOx emission aided by improved efficiency of a Once-Through Benson Type Coal Boiler

Atmospheric distribution of photochemical oxidants has been a subject of interest and concern not only because of their deleterious effects on human health and vegetation but also because of their crucial role in determining the chemical composition of the atmosphere. Several important issues related to the distribution and production of photochemical species are examined through an analysis of results obtained from applications of a comprehensive three‐dimensional regional scale photochemical model over the Northeast United States. The Regional Oxidant Model (ROM) is used to simulate the response of various photochemical species to specific anthropogenic emission strategies involving NOx, and hydrocarbon reductions for an episodic period during July 1988. Domain and temporal averages of predicted concentrations are examined for various species. Their relative influence on oxidant chemistry over the modeled domain is investigated. Further, spatial distributions of O3 with respect to those of NOx, NOy, and hydrocarbons over the modeled domain are examined and the variations in O3 levels for different chemical regimes classified by characteristic NOx/reactive organic gases and NOx/NOy ratios are investigated. Temporal trends in domain‐averaged concentrations indicate that the model replicates the expected diurnal trends in species concentrations. The relative benefits of reductions in NOx and hydrocarbon emissions on predicted O3 levels are also examined. In general, for this modeled domain, reductions in NOx emissions with or without reductions in hydrocarbon emissions have more impact on reducing predicted O3 levels compared to reductions only in hydrocarbon emissions.

New-particle nucleation within coal-fired power-plant plumes can have large effects on particle number concentrations, particularly near source regions, with implications for human health and climate. In order to resolve the formation and growth of particles in these plumes, we have integrated TwO-Moment Aerosol Sectional (TOMAS) microphysics in the System for Atmospheric Modelling (SAM), a large-eddy simulation/cloud-resolving model (LES/CRM). We have evaluated this model against aircraft observations for three case studies, and the model reproduces well the major features of each case. Using this model, we have shown that meteorology and background aerosol concentrations can have strong effects on new-particle formation and growth in coal-fired power-plant plumes, even if emissions are held constant. We subsequently used the model to evaluate the effects of SO2 and NOx pollution controls on newparticle formation in coal-fired power-plant plumes. We found that strong reductions in NOx emissions without concurrent reductions in SO2 emissions may increase new-particle formation, due to increases in OH formation within the plume. We predicted the change in new-particle formation due to changes in emissions between 1997 and 2010 for 330 coal-fired power plants in the US, and we found a median decrease of 19% in new-particle formation. However, the magnitude and sign of the aerosol changes depend greatly on the relative reductions in NOx and SO2 emissions in each plant. More extensive plume measurements for a range of emissions of SO2 and NOx and in varying background aerosol conditions are needed, however, to better quantify these effects.

Hydrogen serves as an optimal fuel for engines. Pure hydrogen engines do not generate carbon monoxide and hydrocarbon emissions; instead, they encounter significant nitrogen oxide emissions. Inner-engine control and outer-engine control are two methods to reduce NOx emissions. Outer-engine control primarily mitigates NOx emissions by selective catalytic reduction (SCR), a process that has been extensively researched. Nevertheless, there is a paucity of research about NOx emission regulation in pure hydrogen engines via internal engine management. This work utilised the closed homogeneous reactor (CHR) in Chemkin Pro to model the primary NOx emission control within pure hydrogen engines. The findings indicate that single exhaust gas recirculation (EGR) reduces NOx emissions by 45.3% at an EGR ratio of 20%, suggesting that the reduction in NOx emissions is not substantial. Nonetheless, EGR combined with lean burn reduces NOx emissions by 96.31% at a λ of 1.4 and an EGR ratio of 20%, resulting in ultra-low NOx emissions from pure hydrogen engines. In comparison to single EGR and EGR combined with lean-burn, SNCR is more effective for NOx emission control. An NH3 ratio of merely 10% can reduce NOx emissions by 96.32% in pure hydrogen engines, whilst a 15% NH3 ratio can attain zero NOx emissions in pure hydrogen engines without necessitating a high λ value or EGR ratio. It is essential to precisely regulate the NH3 ratio in the cylinder; otherwise, residual NH3 may be generated, leading to environmental pollution.

Meteorological variations impeded the benefits of recent NOx mitigation in reducing atmospheric nitrate deposition in the Pearl River Delta region, Southeast China

A wide experimental campaign was developed on an automotive turbocharged diesel engine, using two blends between diesel oil and waste cooking oil methyl esters (WCOME) and neat biodiesel. A conventional B7 diesel oil was considered as a reference fuel. The two blends, respectively, included 40 and 70% of WCOME, on a volumetric basis. The influence of biodiesel was analyzed by testing the engine in two part-load operating conditions, applying proper control strategies to the exhaust gas recirculation (EGR) circuit and rail pressure, to assess the interactions between the engine management and the tested fuels. The variable nozzle turbine (VNT) was controlled to obtain a constant level of intake pressure in the two experimental points. Referring to biodiesel effects at constant operating mode, higher WCOME content generally resulted in better efficiency and soot emission, while NOX emission was negatively affected. EGR activation allowed for limited NO formation but with penalties in soot emission. Furthermore, interactions between the EGR circuit and turbocharger operations and control led to higher fuel consumption and lower efficiency. Finally, the increase in rail pressure corresponded to better soot emission and penalties in NOX emission. Combining all these effects, the selection of EGR rate and rail pressure values higher than the standard levels resulted in better efficiency, NOX, and soot emissions when comparing blends and neat biodiesel to conventional B7, granting advantages not only with regard to greenhouse gas emissions. Combustion parameters were also assessed, showing that combustion stability and combustion noise were not negatively affected by biodiesel use. Combustion duration was reduced when using WCOME and its blend, even if the center of combustion was slightly shifted along the expansion stroke. The main contribution of this investigation to the scientific and technical knowledge on biodiesel application to internal combustion engines is related to the development of tests on diesel–biodiesel blends with high WCOME content or neat WCOME, identifying their effects on NOX emissions, the definition of integrated strategies of HP EGR system, fuel rail pressure, and VNT for the simultaneous reduction in NOX and soot emissions, and the detailed assessment of the influence of biodiesel on a wide range of combustion parameters.

Establishing a low-NOx and high-burnout performance in a large-scale, deep-air-staging laboratory furnace fired by a heavy-oil swirl burner

Combustion Air Humidification for NOx Emissions Reduction in Gas Boiler: An Experimental Study

In the current study, the influence of 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 premixed, swirl-stabilized combustor is developed that provides a stable flame up to very high steam contents. Combustion tests are conducted at different pressure levels for 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 for all operating conditions. The reactor network is used for a detailed investigation of the influence of steam and pressure on the NOx formation pathways. In the experiments, 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 of 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 of 20%, the NOx pressure exponent 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 of atomic oxygen at steam-diluted conditions, constraining the thermal pathway.

Small Diesel engines pose a very tough challenge of simultaneously meeting NOx and particulate matter (PM) emissions, without hampering performance and fuel consumption. Frequent revision in small diesel engines pose a very tough challenge of simultaneously meeting NOx and PM emissions, without hampering performance and fuel consumption. Frequent revision in emission norms for small diesel engines makes it further difficult, as they need to be upgraded in design and for combustion. These small, low-capacity engines are predominantly used in specific regions/countries where cost plays a major role and hence these engines lack a clear emission reduction strategy. It is required to develop an emission reduction strategy considering available technologies and cost implications. Current research work aims to develop a cost-effective emission reduction strategy by modifying the engine using conventional technologies. The present work is an experimental study of the effect of cylinder head Swirl, static injection timing (SIT), intake valve opening (IVO), and Exhaust gas recirculation (EGR) on a 0.4 l single-cylinder diesel engine's performance and emission. Baseline vehicle has HC+NOx and PM emission levels are 0.61 g/kM and 0.04 g/KM, respectively; which is higher considering existing and upcoming emission norms. The lower Swirl cylinder head, advanced IVO timings with retarded injection timings shows an 18% reduction in NOx emission with a 3% improvement in performance at the engine dynamometer. Different EGR rates were also studied and effects were analyzed on emission and fuel consumption and emissions. EGR rate of 25% with advanced IVO of 16° with SIT of 5° and 1.9 Swirl cylinder head had shown 48% improvement in HC+NOx emissions, 20% improvement in PM emission, and 11% improvement on CO emissions at the Chassis dynamometer.

Analysis of combustion and emissions characteristics of a DI diesel engine fuelled with diesel/biodiesel/glycerol tert-butyl ethers mixture by altering compression ratio and injection timing

NOx and PM emissions reduction on an automotive HSDI Diesel engine with water-in-diesel emulsion and EGR: An experimental study

While the absence of carbon makes ammonia (NH3) a promising alternative fuel, some challenges need to be addressed before commercial implementation in practical systems such as gas turbines or internal combustion engines. One potential obstacle is an increase in NOx and N2O emissions due to the fuel-bound nitrogen in ammonia. This study investigates the reduction of NOx emissions from NH3 combustion through staged combustion, incorporating features of exhaust gas recirculation, where two distinct ignition events occur at disparate conditions; a primary ignition that burns a rich fuel-air mixture prior to completing the combustion in a subsequent stage after the introduction of additional air. This process can be emulated in a constant volume combustion chamber (CVCC) by initially igniting a rich mixture, adding air to the combustion products, and then igniting a second time at a globally lean condition. This approach provides isolated insight into how changes in initial equivalence ratios affect the production of NOx emissions for both single-stage and 2-stage combustion. The experimental results indicate that a staged approach reduces NOx emissions, particularly in comparison to stoichiometric and lean ammonia combustion.

<strong class="journal-contentHeaderColor">Abstract.</strong> The reduction of fine particles (PM_2.5) and reactive N (N_r) and S (S_r) species is a key objective for air pollution control policies because of their major adverse effects on human health, ecosystem diversity, and climate. The sensitivity of global and regional N_r, S_r, and PM_2.5 to 20 % and 40 % individual and collective reductions in anthropogenic emissions of NH₃, NO_x, and SO_x (with respect to a 2015 baseline) is investigated using the EMEP MSC-W atmospheric chemistry transport model with WRF meteorology. Regional comparisons reveal that the individual emissions reduction has multiple co-benefits and small disbenefits on different species, and those effects are highly geographically variable. Reductions in NH₃ emissions are effective at decreasing NH₃ concentrations and deposition but much less so for NH₄⁺. A 40 % NH₃ emissions reduction decreases regional average NH₃ concentrations by 47&ndash;49 %, while sensitivities of NH₄⁺ concentrations decrease in the order Euro_Medi (Europe and Mediterranean, 18 %), East Asia (15 %), North America (12 %), and South Asia (4 %), reflecting the increasing regional ammonia-richness. A disbenefit is the increased SO₂ concentrations in these regions (10&ndash;16 % for 40 % NH₃ emissions reductions) because reduced NH₃ levels decrease SO₂ deposition by altering atmospheric acidity. The 40 % NO_x emissions reductions decrease NO_x concentrations in East Asia by 45 %, Euro_Medi and North America by ~38 %, and South Asia by 22 %, whilst decreases in fine NO₃^- are regionally reversed, which is related to enhanced O₃ levels in East Asia (and also, but by less, in Euro_Medi), and decreased O₃ levels in South Asia (and also, but by less, in North America). Consequently, the oxidation of NO_x to NO₃^- and of SO₂ to SO₄^2- is enhanced in East Asia but decreased in South Asia, which in East Asia causes a more effective decrease in NO_x and SO₂ but a less effective decrease in NO₃^- and even an increase in SO₄^2-; in South Asia it causes a less effective decrease in NO_x and an increase in SO₂ but a more effective decrease in NO₃^- and SO₄^2-. For regional policy making, it is thus important to reduce NH₃, NO_x and SO_x emissions together and/or go for stronger reductions to minimise such adverse effects in East Asia and Euro_Medi. Reductions in SO_x emissions are slightly more effective for SO₂ than SO₄^2-. A disbenefit is that SO_x emissions reductions increase NH₃ total deposition and ecosystem eutrophication (~12 % increase for 40 % emissions reduction). PM_2.5 mitigation in South Asia is most sensitive to 40 % SO_x reduction (3.10 &mu;g m^-3, 10 %) and least sensitive to NH₃ reduction (0.29 &mu;g m^-3, 1 %), which is because South Asia is so ammonia-rich that reducing NH₃ has little impact. The most effective measure for North America is reducing NO_x emissions with an 8 % (0.63 &mu;g m^-3) decrease in PM_2.5 in response to a 40 % reduction. In Euro_Medi, the sensitivities of PM_2.5 to 40 % individual emissions reductions range 5&ndash;8 % (0.55&ndash;0.82 &mu;g m^-3). In the UK and Scandinavia PM_2.5 is more sensitive to NH₃, in central Europe it is more sensitive to NO_x, while in the Mediterranean it is more sensitive to SO_x. In East Asia, reductions in SO_x, NO_x and NH₃ emissions are almost equally effective with PM_2.5 sensitivities to 40 % reductions of 7&ndash;8 % (1.89&ndash;2.33 &mu;g m^-3). Due to the varying contributions of SIA, PM_2.5 sensitivities to 40 % collective reductions in all 3 precursors decrease in the order East Asia (20 %), Euro_Medi and North America (17 %), South Asia (13 %). The geographically-varying non-linear chemical responses of N_r, S_r, and PM_2.5 to emissions reductions revealed by this work show the importance of both prioritising emissions strategies in different regions and combining several precursor reductions together to maximise the policy effectiveness.