Residual Fuel Oil Combustion Research Articles

Influence of Ambient Atmospheric Environments on the Mixing State and Source of Oxalate-Containing Particles at Coastal and Suburban Sites in North China

Photodegradation is a key process impacting the lifetime of oxalate in the atmosphere, but few studies investigated this process in the field due to the complex mixing and sources of oxalate. Oxalate-containing particles were measured via single-particle aerosol mass spectrometry at coastal and suburban sites in Qingdao, a coastal city in North China in the summer of 2016. The mixing state and influence of different ambient conditions on the source and photodegradation of oxalate were investigated. Generally, 6.3% and 12.3% of the total particles (by number) contained oxalate at coastal and suburban sites, respectively. Twelve major types of oxalate-containing particles were identified, and they were classified into three groups. Biomass burning (BB)-related oxalate–K and oxalate–carbonaceous particles were the dominant groups, respectively, accounting for 68.9% and 13.6% at the coastal site and 72.0% and 16.8% at the suburban site. Oxalate–Heavy metals (HM)-related particles represented 14.6% and 9.3% of the oxalate particles at coastal and suburban sites, respectively, which were mainly from industrial emissions (Cu-rich, Fe-rich, Pb-rich), BB (Zn-rich), and residual fuel oil combustion (V-rich). The peak area of oxalate at the coastal site decreased immediately after sunrise, while it increased during the daytime at the suburban site. However, the oxalate peak area of Fe-rich particles at both sites decreased after sunrise, indicating that iron plays an important role in oxalate degradation in both environments. The decay rates (k) of Fe-rich and BB-Fe particles at the coastal site (−0.978 and −0.859 h−1, respectively), were greater than those at the suburban site (−0.512 and −0.178 h−1, respectively), owing to the high-water content of particles and fewer oxalate precursors. The estimated k values of oxalate peak area for different ambient conditions were in the same order of magnitude, which can help establish or validate the future atmospheric models.

Source apportionment of PM2.5 at IMPROVE monitoring sites within and outside of marine vessel fuel sulfur emissions control areas

ABSTRACT Fuel sulfur emissions control areas have been established in a few marine coastal regions to reduce environmental impacts from combustion of high sulfur residual fuel oil (RFO). For example, in August of 2012, the U.S. began enforcing fuel sulfur limits on certain large commercial marine vessels up to 200 nautical miles (nm) of its coasts as part of a North American Emissions Control Area (NA-ECA), and in January of 2014, the U.S. began enforcing fuel sulfur limits on these vessels within up to 50 nm of Puerto Rico and the U.S. Virgin Islands as part of the U.S. Caribbean Sea ECA (USCAR-ECA). This work evaluates ECA effectiveness at reducing PM2.5 from combustion of RFO by using both spatial analysis, comparing PM2.5 source apportionment at IMPROVE monitoring sites largely impacted by air from either inside or outside of an ECA, along with temporal analysis, comparing RFO combustion impacts pre and post ECA enforcement at sites largely impacted by air from inside an ECA. Source apportionment was performed using Positive Matrix Factorization (PMF) on chemically speciated PM2.5 data from 2009 to 2018. Results for 7 coastal U.S. IMPROVE sites influenced by marine air masses within the NA-ECA showed an annual mean reduction of PM2.5 from RFO combustion of 79.0% (range, 60.2% to 91.5%) when comparing impacts from the pre-ECA (RFO average 2.7% S) period of 2009–2011 to the ECA 0.1% fuel S period of 2015–2018. In contrast, the Virgin Islands, Big Bend, and Baengnyeong Island South Korea IMPROVE sites were impacted by RFO combustion and were largely or wholly influenced by air masses from outside of an emissions control area. These sites saw a statistically significant 14.0% increase, a 21.0% decrease, or no statistically significant change, respectively, when comparing time periods pre and post ECA enforcement. Implications: This study performs source apportionment on PM2.5 monitoring data to identify 10 sites impacted by residual fuel oil combustion, mainly from marine vessel fuel use. The paper then evaluates the effects of enforcement of marine vessel fuel sulfur emissions control areas at reducing ambient impacts of this source on PM2.5. This study uses both temporal analysis of the source apportionment results, comparing source impacts before and after enforcement of marine vessel fuel sulfur emissions control areas, and spatial analysis, comparing source impacts between sites largely impacted or not impacted by airmasses originating inside of marine vessel fuel sulfur emissions control areas.

The effects of marine vessel fuel sulfur regulations on ambient PM2.5 at coastal and near coastal monitoring sites in the U.S.

In August of 2012 the U.S. began implementing fuel sulfur limits on certain large commercial marine vessels within 200 nautical miles (nm) of its coasts as part of a North American Emissions Control Area (NA-ECA). The NA-ECA limited fuel sulfur use in these vessels to below 1% in 2012 and to below 0.1% starting in 2015. This work uses ambient PM2.5 monitoring data from the U.S. IMPROVE network and Positive Matrix Factorization (PMF) receptor modeling to assess the effectiveness of the NA-ECA at reducing ambient PM2.5 from high-sulfur residual fuel oil (RFO) use. RFO combustion emissions of PM2.5 are known to have a fairly unique vanadium (V) and nickel (Ni) trace metal signature. To determine if IMPROVE sites were affected by residual fuel oil combustion, V and Ni data from 65 IMPROVE sites in coastal States of the U.S. were analyzed from 2010 to 2011, the two years prior to NA-ECA implementation. 22 of these IMPROVE sites had a V and Ni correlation coefficient (r2) greater than 0.65 and were selected for further analysis by PMF. The slopes of the correlations between V and Ni at these 22 sites ranged from 2.2 to 4.1, consistent with reported V:Ni emission ratios from RFO combustion. Each of the 22 IMPROVE sites was modeled independently with PMF, using the available PM2.5 chemical speciation data from 2010 to 2015. PMF model solutions for the 22 sites contained from 5 to 9 factors, depending on the site. At every site a PMF factor was identified that was associated with RFO combustion, however, 9 sites had PMF factors where RFO combustion was mixed with other aerosol sources. For the remaining 13 sites, PM2.5 from RFO combustion was analyzed for three time periods; 2010–2011 representing the time period prior to the NA-ECA implementation (pre-NA-ECA), 2013–2014 representing the time period where fuel sulfur was limited to 1.0% (NA-ECA 1.0% S), and 2015 representing the time period where fuel sulfur was limited to 0.1% (NA-ECA 0.1% S). All 13 sites indicated statistically significant reductions in the contribution of RFO combustion to PM2.5 between the pre-NA-ECA period and the two periods of fuel sulfur control. The average decrease in annual average PM2.5 from RFO combustion from the pre-NA-ECA to NA-ECA 1% S period was 50.2% (range, 29.0%–65.4%) and from the pre-NA-ECA to NA-ECA 0.1% S period was 74.1% (range, 33.0%–90.4%).

The effects of marine vessel fuel sulfur regulations on ambient PM2.5 along the west coast of the U.S.

This work uses PM2.5 data and Positive Matrix Factorization (PMF) modeling to explore the effects of two marine vessel fuel sulfur regulations along the west coast of the United States (US); California's (CA) Ocean-Going Vessel Clean Fuel Regulation (CA-CFR) implemented in July 2009 and the North American Emissions Control Area (NA-ECA) implemented in August 2012. Data from 31 chemically speciated PM2.5 monitors along the US west coast were analyzed and 9 sites with strong linear correlations between vanadium and nickel were selected for PMF modeling. The 9 sites were modeled independently and for 8 sites, 3 in CA and 5 in Washington State (WA), a well-defined factor linked to marine vessel residual fuel oil (RFO) combustion was identified. For these 8 sites, model results were subdivided into three time periods; a three year period prior to implementation of the CA-CFR, a three year period after the CA-CFR but prior to the NA-ECA, and a one year period after implementation of the NA-ECA. Marine vessel PM2.5 distributions were compared between the three time periods to determine if statistically significant reductions had occurred. Comparing marine vessel PM2.5 for the three years before and after CA-CFR implementation, all CA sites indicated statistically significant reductions, with reductions in annualized average marine vessel PM2.5 from 30 to 52% (0.09–0.78 μg/m3). Comparing marine vessel PM2.5 for the three years before NA-ECA implementation and the 1 year after, 2 of 5 WA sites indicated statistically significant reductions in annualized average impacts (45–50%, 0.12–0.23 μg/m3) and 1 of 3 sites in CA (46%, 0.04 μg/m3). These results demonstrate that marine vessel fuel sulfur regulations on the west coast of the US have been effective at reducing PM2.5 impacts from marine vessel RFO combustion at some locations, with the implementation of the CA-CFR showing more success than the NA-ECA. The greater observed success of the CA-CFR is, to some extent, probably the result of a longer 3-year implementation time compared to only 1 year for the NA-ECA.

Relating urban airborne particle concentrations to shipping using carbon based elemental emission ratios

This study demonstrates a novel method for testing the hypothesis that variations in primary and secondary particle number concentration (PNC) in urban air are related to residual fuel oil combustion at a coastal port lying 30 km upwind, by examining the correlation between PNC and airborne particle composition signatures chosen for their sensitivity to the elemental contaminants present in residual fuel oil. Residual fuel oil combustion indicators were chosen by comparing the sensitivity of a range of concentration ratios to airborne emissions originating from the port. The most responsive were combinations of vanadium and sulphur concentration ([S], [V]) expressed as ratios with respect to black carbon concentration ([BC]). These correlated significantly with ship activity at the port and with the fraction of time during which the wind blew from the port.The average [V] when the wind was predominantly from the port was 0.52 ng m−3 (87%) higher than the average for all wind directions and 0.83 ng m−3 (280%) higher than that for the lowest vanadium yielding wind direction considered to approximate the natural background. Shipping was found to be the main source of V impacting urban air quality in Brisbane.However, contrary to the stated hypothesis, increases in PNC related measures did not correlate with ship emission indicators or ship traffic. Hence at this site ship emissions were not found to be a major contributor to PNC compared to other fossil fuel combustion sources such as road traffic, airport and refinery emissions.

Chemical fingerprint and impact of shipping emissions over a western Mediterranean metropolis: Primary and aged contributions

An intensive monitoring campaign was carried out in the harbor of Barcelona (Spain) to quantify the contribution of primary shipping emissions (PSE) on PM10. Chemical composition of inorganic species, as well as OC and EC, was completed, and a source apportionment analysis by Positive Matrix Factorization was conducted. Among the 6 sources extracted, two were linked to harbor emissions: dusty materials released in different areas along the harbor and fuel–oil combustion. On average, harbor emissions accounted for 31% of the PM10 mass.Since the chemical signature of PSE was not determined neither their contribution was obtained, additional approaches were followed and mainly consisted in: 1) the evaluation of V/Ni and V/Cu ratios to identify those days affected by PSE; 2) the identification of the chemical components increasing under the influence of PSE; 3) the calculation of the daily and average PSE from their experimentally-determined chemical signature and the experimental concentrations of vanadium. As a result, the contribution of PSE was estimated in 0.84μgm−3 (2.7% of PM10) and the residual fuel–oil combustion factor (3.6μgm−3, 12% of PM10) was interpreted as aged shipping emissions.The present study splits the contribution of shipping emissions into primary and aged, and highlights the importance of atmospheric mixing and aging processes in western Mediterranean atmospheres. In the case of shipping emissions, the aged products were found to be dominant with respect to the primary ones even in the vicinity of the source.

A regional assessment of marine vessel PM2.5 impacts in the U.S. Pacific Northwest using a receptor-based source apportionment method

This work reports results from a receptor-based source apportionment analysis using the Positive Matrix Factorization (PMF) model on chemically speciated PM2.5 data from 36 urban and rural monitoring sites within the U.S. Pacific Northwest. The approach taken is to model each site independently, treats monitor datasets with a common data preparation protocol, and uses a common modeling protocol. Complementary data from two monitoring networks, the urban Chemical Speciation Network (CSN) and rural Interagency Monitoring of Protected Visual Environments (IMPROVE) Network, was modeled for the period of 2007–2011. 15 different factor types were found for CSN sites and 17 for IMPROVE sites, however many factors occurred at only a few locations. Only 3 factor types were common in both networks: sulfate/sulfur rich, nitrate rich, and soil. However, for coastal and near coastal monitoring sites there were three additional factors common in both networks: sea salt, aged sea salt, and residual fuel oil combustion (RFO). This work presents annual average PM2.5 mass impacts for all sites and factors found and the results for RFO are explored in greater depth. The association between RFO results and commercial marine vessel emissions is made based on similarities between factor chemical profiles and published emissions profiles, comparisons with emissions inventories, and the similarity in the spatial extent of RFO factor locations to that of the other marine aerosols identified in this study, sea salt and aged sea salt. All 14 monitoring sites with marine vessel RFO factors showed a seasonal cycle of mass impacts, with lower impacts in winter months (monthly average PM2.5 between 0.1 μg m−3 and 0.9 μg m−3 in January) and higher impacts in summer months (monthly average PM2.5 between 0.3 μg m−3 and 2.7 μg m−3 in August). These results set a baseline to measure progress in emissions reductions that are expected from implementation of the North American Emissions Control Area (ECA) beginning in August 2012.

Chemical characterization and source apportionment of fine and coarse particulate matter in Lahore, Pakistan

Lahore, Pakistan is an emerging megacity that is heavily polluted with high levels of particle air pollution. In this study, respirable particulate matter (PM 2.5 and PM 10) were collected every sixth day in Lahore from 12 January 2007 to 19 January 2008. Ambient aerosol was characterized using well-established chemical methods for mass, organic carbon (OC), elemental carbon (EC), ionic species (sulfate, nitrate, chloride, ammonium, sodium, calcium, and potassium), and organic species. The annual average concentration (±one standard deviation) of PM 2.5 was 194 ± 94 μg m −3 and PM 10 was 336 ± 135 μg m −3. Coarse aerosol (PM 10−2.5) was dominated by crustal sources like dust (74 ± 16%, annual average ± one standard deviation), whereas fine particles were dominated by carbonaceous aerosol (organic matter and elemental carbon, 61 ± 17%). Organic tracer species were used to identify sources of PM 2.5 OC and chemical mass balance (CMB) modeling was used to estimate relative source contributions. On an annual basis, non-catalyzed motor vehicles accounted for more than half of primary OC (53 ± 19%). Lesser sources included biomass burning (10 ± 5%) and the combined source of diesel engines and residual fuel oil combustion (6 ± 2%). Secondary organic aerosol (SOA) was an important contributor to ambient OC, particularly during the winter when secondary processing of aerosol species during fog episodes was expected. Coal combustion alone contributed a small percentage of organic aerosol (1.9 ± 0.3%), but showed strong linear correlation with unidentified sources of OC that contributed more significantly (27 ± 16%). Brick kilns, where coal and other low quality fuels are burned together, are suggested as the most probable origins of unapportioned OC. The chemical profiling of emissions from brick kilns and other sources unique to Lahore would contribute to a better understanding of OC sources in this megacity.

Vaporization and pyrolysis modelling of a single droplet of heavy fuel oil using continuous thermodynamics

This article presents modelling of vaporization and pyrolysis of a single droplet of heavy fuel oil in a high ambient temperature field using the principle of continuous thermodynamics. Continuous thermodynamics reduces the computational simulation load compared with discrete thermodynamics, without compromising the quality of prediction of the complex combustion behaviours of such multicomponent complex fuels. Heavy fuel oil is represented by four fuel fractions and each of these fractions are assigned a separate distribution function. The prediction shows that in the modelling of heavy fuel oil, both heating rate and composition are very important parameters in coke formation. Coke formation can lead to engine degradation and increased exhaust smoke. The developed model shows good agreement with experimental results obtained by other researchers. References Goldsworthy, L., CFD Modelling of residual fuel oil combustion in the context of marine diesel engines. International Journal of Engine Research , 2005, 7: pp. 181--199. Baert, R. S. G., A mathematical model for heavy fuel oil droplet vaporization and pyrolysis in a heavy temperature inert gas. Combustion Science and Technology , 1993, 90: pp. 125--147. Hallett, W. L. H and C. Grimwood. A simple continuous mixture droplet evaporation model with multiple distribution functions. in Combustion Institute, 2001. Canadian Section. Spring Meeting. Hallett, W. L. H., A simple model for the vaporization of droplets with large numbers of components. Combustion and Flame , 2000, 121(1-2): pp. 334--344. doi:10.1016/S0010-2180(99)00144-3 Chen, C. S. and M. M.EI-Wakil, Experimental and theoretical studies of burning drops of hydrocarbon mixtures. Proceedings for Instrumentation and Mechanical Engineers, 1969, 184 (Pt. 3J): pp. 95--108. Ikegami, M., G. Xu, K. Ikeda, S. Honma, H. Nagaishi, D. L. Dietrich, and Y. Takeshita, Distinctive combustion stages of single heavy oil droplet under microgravity. Fuel , 2003, 82(3): pp. 293--304. doi:10.1016/S0016-2361(02)00257-0 Shyu, R. R., C. S. Chen, G. O. Goudie, and M. M. El-Wakil, Multi-component heavy fuel drop histories in a high-temperature flow field. Fuel , 1972, 51(2): pp. 135--145. Tamim, J. and W. L. H. Hallett, A continuous thermodynamics model for multicomponent droplet vaporization. Chemical Engineering Science, 1995, 50(18): pp. 2933--2942. doi:10.1016/0009-2509(95)00131-N Lippert, A. M. and R. D. Reitz. Modelling of multicomponent fuels using continuous distributions with application to droplet evaporation and sprays. in International Fall Fuels and Lubricants Meeting and Explosion. 1997. Tulsa, Oklahoma, 972882. Lippert, A. M., D. W. Stanton, C. J. Rutland, W. L. H. Hallett, and R. D. Reitz, Multidimensional simulation of diesel engine cold start with advanced physical submodels. International Journal of Engine Research , 2000, 1(1): pp. 1--27. Hallett, W. L. H. and N. A. Clark, A model for the evaporation of biomass pyrolysis oil droplets. Fuel , 2006, 85(4): pp. 532--544. doi:10.1016/j.fuel.2005.08.006

Computational Fluid Dynamics Modelling of Residual Fuel Oil Combustion in the Context of Marine Diesel Engines

A simplified model is presented for vaporization and combustion of heavy residual based fuel oil in high-pressure sprays, in the context of marine diesel engines. The fuel is considered as a mix of residual base and cutter stock. The model accounts for multiple fuel components as well as limited diffusion rates and thermal decomposition rates within droplets by the use of straight-line relationships for the saturation pressure of combustible fuel vapour at the droplet surface as functions of droplet temperature. The energy required for decomposition of heavy molecules is accounted for. Combustion is modelled using a timescale that is the sum of a kinetic timescale based on a single-step reaction and a turbulent timescale based on turbulent mixing rates. The ignition timescale is based on a simple three-equation model. Cellwise ignition is employed. The heavy fuel oil model is applied to two different constant volume chambers that are used to test ignition and combustion quality of marine heavy fuel oil, using the computational fluid dynamics code StarCD version 3.2. Good agreement is shown between trends in measured and computed data including ignition delay, burn rate and spatial distribution of spray and flame parameters. The model is tested for two representative fuels, one with good ignition and combustion properties and one poor. Essentially only two parameters need to be changed to set the fuel quality. These are the ignition delay factor and the activation energy for the high-temperature kinetics. Further tuning of the model to specific fuels is possible by modifying the saturation temperature relationships.

Characterization of Fine Particulate Matter Produced by Combustion of Residual Fuel Oil

ABSTRACT Combustion experiments were carried out on four different residual fuel oils in a 732-kW boiler. PM emission samples were separated aerodynamically by a cyclone into fractions that were nominally less than and greater than 2.5 |j.m in diameter. However, examination of several of the samples by computer-controlled scanning electron microscopy (CCSEM) revealed that part of the PM2.5 fraction consists of carbonaceous cenospheres and vesicular particles that range up to 10 |j.m in diameter. X-ray absorption fine structure (XAFS) spectroscopy data were obtained at the S, V, Ni, Fe, Cu, Zn, and As K-edges and at the Pb L-edge. Deconvolution of the X-ray absorption near edge structure (XANES) region of the S spectra established that the dominant molecular forms of S present were sulfate (26-84% of total S) and thiophene (13-39% of total S). Sulfate was greater in the PM2.5 samples than in the PM25+ samples. Inorganic sulfides and elemental sulfur were present in lower percentages. The Ni XANES spectra from all of the samples agreed fairly well with that of NiSO4, while most of the V spectra closely resembled that of vanadyl sulfate (VO•SO4•xH2O). The other metals investigated (i.e., Fe, Cu, Zn, and Pb) also were present predominantly as sulfates. Arsenic was present as an arsen-ate (As+5). X-ray diffraction patterns of the PM2.5 fraction exhibit sharp lines due to sulfate compounds (Zn, V, Ni, Ca, etc.) superimposed on broad peaks due to amorphous carbons. All of the samples contain a significant organic component, with the loss on ignition (LOI) ranging from 64 to 87% for the PM2.5 fraction and from 88 to 97% for the PM2.5+ fraction. Based on 13C nuclear magnetic resonance (NMR) analysis, the carbon is predominantly condensed in graphitic structures. Aliphatic structure was detected in only one of seven samples examined.

Fine particle emissions from residual fuel oil combustion: Characterization and mechanisms of formation

Abstract : The characteristics of particulate matter (PM) emitted from residual fuel oil combustion in two types of combustion equipment were compared. A small commercial 732 kW rated fire-tube boiler yielded a weakly bimodal particulate size distribution (PSD) with over 99% of the mass contained in a broad coarse mode and only a small fraction of the mass in an accumulation mode consistent with ash vaporization. Bulk samples collected and classified by a cyclone indicate that 30% to 40% of the total particulate emissions were less than 2.5mum aerodynamic diameter (PM2.5). The coarse mode PM was rich in char, indicating relatively poor carbon burnout, although calculated combustion efficiencies exceeded 99%. This characteristic behavior is typical of small fire-tube boilers. Larger, utility-scale units firing residual oil were simulated using an 82 kW rated laboratory-scale refractory-lined combustor. Particulate matter emissions from this unit were in good agreement with published data including published emission factors. These data indicated that the refractory-lined combustor produced less total but more fine particulate emissions, as evident from a single unimodal PSD centered at <0.1 mum diameter. Bulk cyclone segregated samples indicated that here all the PM were smaller than 2.5 mum aerodynamic diameter, and loss on ignition (LOI) measurements suggested almost complete char burnout. These findings are interpreted in the light of possible mechanisms governing the release of organically bound refractory metals and may have particular significance in considering the effects of fuel oil combustion equipment type on the characteristic attributes of the fine PM emitted into the atmosphere and their ensuing health effects.

Literature review Magnesiumoxide as inhibitor of hot oil ash corrosion

The accumulation of mineral ashes from residual fuel oil combustion on surfaces of various metals and alloys causes fouling and corrosion which results from the formation of low melting point aggressive compounds by the reaction between vanadium pentoxides and sodium sulphates in steam boilers and gas turbines. This paper reviews investigations into the effects of adding magnesium oxide to inhibit this form of corrosion. It has been found that by adding magnesium oxide to fuel oil the melting point of deposits is considerably increased and the formation of sodium vanadate is inhibited by formation of the more stable magnesium vanadates. This effect has been studied in actual plant conditions as well as in laboratory tests using melts of different compositions. Determination of the optimum amount of chemical inhibitor to be added has also been studied using various techniques. Magnesium oxide is found to be a very effective additive in combating hot ash corrosion by counteracting the effects of SO3 in combustion gases and by increasing the melting points offuel ash constituents so as to increase their viscosity and thus reduce the diffusion of oxygen by up to an order of magnitude and thereby preventing the destruction of the protective oxide barrier film.

Literature review Magnesiumoxide as inhibitor of hot oil ash corrosion

The accumulation of mineral ashes from residual fuel oil combustion on surfaces of various metals and alloys causes fouling and corrosion which results from the formation of low melting point aggressive compounds by the reaction between vanadium pentoxides and sodium sulphates in steam boilers and gas turbines. This paper reviews investigations into the effects of adding magnesium oxide to inhibit this form of corrosion. It has been found that by adding magnesium oxide to fuel oil the melting point of deposits is considerably increased and the formation of sodium vanadate is inhibited by formation of the more stable magnesium vanadates. This effect has been studied in actual plant conditions as well as in laboratory tests using melts of different compositions. Determination of the optimum amount of chemical inhibitor to be added has also been studied using various techniques. Magnesium oxide is found to be a very effective additive in combating hot ash corrosion by counteracting the effects of SO3 in combustion gases and by increasing the melting points offuel ash constituents so as to increase their viscosity and thus reduce the diffusion of oxygen by up to an order of magnitude and thereby preventing the destruction of the protective oxide barrier film.

97/00546 Combustion-generated NO x and coke in heavy residual fuel oil combustion

97/00546 Combustion-generated NO x and coke in heavy residual fuel oil combustion

Combustion-Generated NOxand Coke in Heavy Residual Fuel Oil Combustion

Abstract This paper deals with the numerical modelling of heavy residual fuel oil combustion. Some results of combustion-generated nitric oxide and coke are presented. The emissions of both species are greatly affected by a gas temperature and thus the modelling of soot concentration, which affects radiation heat transfer is of vital importance. The calculated results of three combustion cases, the thermal inputs of which are 1.8,3.5 and 36 MW, respectively, are compared with the measured ones A simplified model of the formation and reduction of nitric oxide, in which hydrogen cyanide is an intermediate phase between the phases of fuel nitrogen and nitric oxide, is used. The amount of coke generated is described with the so-called residual carbon rate coefficient ξ which has in actual practice a non-linear relationship to the heavy residues and chemical structure of the fuel. In this study it is assumed that a fixed portion of vaporized fuel oil remains as coke, i.e. ξ has a constant value. The prediction...

Coatings and hardfacing alloys for corrosion and wear resistance in diesel engines

The potential for surface engineering solutions to increase the corrosion and wear resistance of diesel valves is examined with regard to operation in residual fuel oil combustion products. The environment in which the exhaust valve operates is discussed. The corrosion test is used to sort the 27 coating treatments and 16 hardfacing alloys examined. H ardfacing materials showing the greatest potential are also evaluated in hot wear tests. As reference materials, En 52 steel, Nimonic 80A, and Stellite 6 are included. Corrosion tests over the temperature range 500–700°C have shown that the surface treatments can be ranked in terms of their composition and expected metal surface temperature. Good corrosion resistance to residual fuel oil combustion products reflects primarily the content of the alloy, the base metal (Fe, Ni, or Co) being of secondary importance. Refractory metals (Ti, Nb, Ta, Mo, and W) and other minor alloying additions do not significantly alter the corrosion behaviour, unless they are present in large quantities. Hot wear tests (650°C, 80 MN m−2 contact pressure) of candidate hardfacing alloys have also demonstrated the importance of the Cr content of the alloy. This probably results from the ease of formation of a protective glaze, lowering the coefficient of friction and therefore the wear rate. Additions of refractory metals were beneficial. Since optimum wear resistant alloys contained high levels of Mo and vv: they were poor in terms of corrosion resistance. It is therefore necessary to balance wear resistance against corrosion resistance in the selection of materials for residual fuel oil service. Two coating systems, vacuum plasma sprayed Ni–50Cr and a chromised diffusion treatment appeared to have potential as valve surface treatments for improved corrosion resistance; and two hardfacing alloys, Tristelle TS2 and Colmonoy 8, offered balanced behaviour as seat materials with acceptable wear resistance and improved corrosion performance. These materials have been evaluated in the engine tests of three different diesel engine manufacturers.MST/3157

Thermochemical studies on hot ash corrosion of stainless steel 304 and inhibition by magnesium sulphate

The accumulation of mineral ashes from residual fuel oil combustion on stainless steel surfaces causes fouling and corrosion resulting from the formation of low melting aggressive compounds. TG, DTA and weight loss experiments were carried out to study the effect of added MgSO 4 in depressing hot ash corrosion on stainless steel 304. Magnesium sulphate raised the melting point of the ash and inhibited the formation of sodium vanadate by formation of the more stable magnesium vanadates. The techniques employed help in determining the optimum amount of the chemical inhibitor to be added. When excesses of MgSO 4 were used, the iron was further protected; however, attack by chromium was relatively increased.