Particulate emissions from large-scale medium-speed diesel engines: 1. Particle size distribution

This paper addresses particulate matter (PM) size distributions in large-scale diesel engine exhaust. The test engines were multivariable large-scale turbo-charged, after-cooled medium speed (~ 500 rpm, ~ 1 MW power per cylinder) direct injection diesel engines. Emissions measurements were carried out while burning heavy fuel (HFO) and light fuel (LFO) oils. Test modes for investigation were propulsion mode (marine) and generator mode (power plant), with load varying from 25 to 100%. PM was measured using a gravimetric impactor with four impactor stages plus a filter, classifying particles between 0.005 and 2.5 μm (aerodynamic diameter). The results show that HFO firing produces significantly higher PM emissions (more than factor of ~three on mass bases for high load operation) compared to LFO, especially for particles smaller than 0.5 μm. This is mainly due to higher ash-forming elements and sulphur content of HFO. For HFO, the fraction of the finest particles increases with load, more strongly for generator mode than for propulsion mode, with generator mode giving ~ 50% higher PM emissions than propulsion mode. With LFO firing, the largest amount of fine PM was emitted at the lowest load, for propulsion mode being lower and almost independent of load at higher loads, while for generator mode a steady decrease in emissions with increasing load is seen for all PM size classes measured.     

Emissions from large-scale medium-speed diesel engines: 2. Influence of fuel type and operating mode

This paper addresses gaseous emissions smoke (soot) and particulate matter in large-scale diesel engine exhaust. The test engine was a large-scale turbocharged, after-cooled mean speed ( 500 rpm) direct-injection diesel engine and the power per cylinder was about 1 MW. Emission measurements were carried out on burning heavy fuel (HFO) and light fuel (LFO) oils. The test modes for the investigation were a propulsion mode (marine application) and a generator mode (power plant application). Gaseous emissions were measured according to the IMO technical code, smoke (soot) emissions were determined optically and particulate matter (PM) was measured by gravimetric impactor designed for five size fractions. In comparison the emissions from HFO and LFO utilisations indicate slightly higher NO and CO emissions for HFO, while LFO gives clearly higher emissions of hydrocarbons (HC). Emissions of soot and CO appeared to correlate very well, being very high for both fuels throughout the propulsion mode and low load, otherwise being similar for both modes. PM emissions are more than three times higher with HFO than with LFO and appear to decrease with the load except for HFO during the generator mode where an increase of PM emissions with the load is seen. Some data on sampled particles is given.     

Emissions from large-scale medium-speed diesel engines: 1. Influence of engine operation mode and turbocharger

The operation of four – stroke diesel engines in either propulsion or generator mode application has a strong influence on gaseous, smoke (soot) and particulates emissions. Tests were made with a supercharged after-cooled large-scale diesel engine (mean speed  500 rpm, power per cylinder  1 MW) burning mainly heavy fuel oil. Gaseous emissions (NOx, CO, HC) were measured according to the IMO technical code, smoke (soot) emissions were determined optically and particulate matter (PM) was measured using a gravimetric impactor for five size fractions. Impact on gaseous emissions, smoke (soot) and PM was found when analysing the effects of the engine operating mode, fuel nozzle, start of injection (SOI), and load (speed). Results show that the exhaust emission was also highly dependent on the engine turbocharger system, especially the by-pass control, but was not affected by waste gate control. The gaseous and soot emissions were less for the generator mode in the total load region, decreasing with the load. PM emissions were found to decrease with the load for the propulsion mode, while showing an increase with the load for the generator mode.     

Emissions from large-scale medium-speed diesel engines: 3. Influence of direct water injection and common rail

The influence of direct water injection (DWI) on emissions from a multivariable large-scale (6–18 cyl, ~ 1 MW/cyl) diesel engine is reported, using a combined injection valve and nozzle that allows for injection of water and fuel oil into the cylinder. This method allows for injecting a relatively large amount of water without derating the engine power and NO_x emissions can be more than halved by DWI. Indeed DWI decreases combustion temperatures and NO_x emissions, but it gives somewhat increased (yet not problematic) emissions of CO, HC, soot (smoke) and particulate matter (PM), depending on the water injection timing and degree of incomplete combustion.     

Chemical characterization of particulate emissions from diesel engines: A review

This review examines the chemical properties of particulate matter (PM) in diesel vehicle exhaust at a time when emission regulations, diesel technology development, and particle characterization techniques are all undergoing rapid change. The aim is to explore how changes in each of these areas impact the others. Particle composition is of central interest to the practical issues of health effects, climate change, source apportionment, and aerosol modeling. Thus, the emphasis here is to identify the emerging questions and examine how they can be addressed. As regulations drive down the allowed tailpipe emission levels, advances in engine and aftertreatment technology have made it possible to substantially reduce PM emissions. Besides the reduction in level, new technologies such as diesel particulate filters (DPFs) and selective catalytic reduction (SCR) can also affect the physical and chemical properties of PM. This in turn introduces new analytical demands that must address not only the issue of sensitivity, but also of specificity. New methods of aerosol chemical analysis are described that address these needs, improve our understanding of particle composition, and provide critical insight into the current issues surrounding motor vehicle PM emissions and their environmental impact.     

Urea-SCR: a promising technique to reduce NOx emissions from automotive diesel engines

Urea-SCR, the selective catalytic reduction using urea as reducing agent, has been investigated for about 10 years in detail and today is a well established technique for DeNO_x of stationary diesel engines. It is presently also considered as the most promising way to diminish NO_x emissions originating from heavy duty vehicles, especially trucks.

The paper discusses the fundamental problems and challenges if urea-SCR is extended to mobile applications. The major goal is the reduction of the required catalyst volume while still maintaining a high selectivity for the SCR reaction over a wide temperature range. The much shorter residence time of the exhaust gas in the catalyst will lead to higher secondary emissions of ammonia and isocyanic acid originating from the reducing agent. Additional problems include the control strategy for urea dosing, the high freezing point of urea, and the long term stability of the catalyst.     

An investigation of the catalytic abatement of emissions from the combustion of diesel/bioethanol blends

In this study, we investigated the activity of pre-sulfated 1%Pt–2%Sn/γ–Al₂O₃ on the catalytic abatement of the combustion emissions of three fuels: pure diesel E(0), pure bioethanol E(100) and bioethanol blended diesel containing 10% bioethanol E(10). The emissions generated, by each blend combustion, were conducted continuously to the catalyst sample. The catalytic activity was determined by following the evolution of the outflow emissions concentrations by FTIR gas spectroscopy as a function of the catalyst temperature. Results showed that the addition of bioethanol to diesel may be necessary to enhance the catalytic oxidation of diesel unburned hydrocarbons and particulate matter on pre-sulfated 1%Pt–2%Sn/γ–Al₂O₃.     

Various strategies for reducing Nox emissions of biodiesel fuel used in conventional diesel engines: A review

Energy demand, decreasing fossil fuel reserves, and health-related issues about pollutants have led researchers to search for renewable alternative fuels to either partially or fully replace fossil fuels. Among many alternative fuels, biodiesel became one of the most popular choices due to similar properties to that of conventional diesel. Biodiesel produces slightly lower brake thermal efficiency compared to that of conventional biodiesel, but has an advantage of reduced emissions of CO₂, CO, HC, and smoke. However, biodiesel shows higher NOx emission which, when used in increased biodiesel market, may become a serious problem. Various strategies were attempted by different researcher to reduce NOx emissions. In this paper, various strategies, adapted for reducing NOx emissions of biodiesel fuel used in diesel engines for automobile applications, are reviewed and discussed. The strategies are grouped into three major groups, namely combustion treatments, exhaust after-treatments, and fuel treatments. Among various strategies discussed, fuel treatments, such as low temperature combustion, mixing fuel additives and reformulating fuel composition, reduce NOx emission without compromising other emission and performance characteristics and they seem to be promising for future biodiesel fuel.     

Chemical composition ofRumex crispus L. seed

Rumex crispus L. seeds harvested in Olavarría (Province of Buenos Aires, Argentina) were extracted with 60–80°C petroleum ether to render 6.0% (dry basis) of a lipid fraction with a 152.4 saponification value and 15.4% unsaponifiable matter. Fatty acid composition obtained by gas-liquid chromatography was: 14:0, 2.7; 16:0, 13.5; 16:1, 1.2; 18:0, 1.2; 18:1, 38.6; 18:2, 36.3; 18:3, 0.5; 20:0, 2.4; 20:2, 0.3; 22:0, 0.9; 22:1, 1.2; and 24:0, 1.2; with traces of 14:1, 15:1, 17:0, and 17:1. Residual meal contained 10.62% crude protein, with a low value of available lysine (3.31 g/16 g N). Ash, crude fiber, sugars, hydrolyzable carbohydrates, total and phytic acid phosphorus, calcium and residual lipids contents are reported here.     

Chemical composition of commercial cornicabra virgin olive oil from 1995/96 and 1996/97 crops

The chemical composition of commercial Cornicabra virgin olive oils (n=65) was studied, as was its relationship with oil quality and the influence of the extraction method and production year. The main characteristics of these olive oils were: oxidative stability 53 ± 24 h, mean polyphenol content 162 ± 57 mg/kg (as gallic acid), oleic acid 80.8 ± 0.9%, linoleic acid 4.6 ± 0.6%, and campesterol 4.3 ± 0.1%, which is peculiar to this variety. No clear differences in composition were observed with respect to the different extraction systems (dual-phase/triple-phase decanters and pressure), although oils produced by the dual-phase decanter showed higher oxidative stability and polyphenol content. There were significant differences in major fatty acids and sterols according to the production year.     

Auto-cyclic reactor: Design and evaluation for the removal of unburned methane from emissions of natural gas engines

A non-adiabatic fixed bed auto-cyclic reactor (ACR) consisting of two counter-current concentric compartments was designed and built for removing low concentrations of methane from exhaust gases from natural gas engines. The length was based on simulations by a simple heterogeneous one dimensional model using literature parameters and kinetic data, while the diameter was selected to assure a linear fluid velocity between 0.5 and 2 m/s. Its innovative design consists of a judicious combination of 14 longitudinal fins welded to the outlet part of inner reactor compartment to maximize the heat transfer to the inlet section and highly active pellet type catalyst filling the space between fins to lower the ignition temperature.The experimental ACR pilot unit was loaded by a combination of highly active laboratory prepared catalysts: palladium/alumina pellets and palladium/alumina coated cordierite monoliths. The efficiency of methane removal from air and from synthetic exhaust gas containing 7 vol% CO₂ and 14 vol% H₂O was evaluated under a wide range of operating conditions: temperature from 290 to 500 °C, methane concentration between 500 and 3800 ppm. The reactor performance was monitored in terms of axial temperature profiles and methane conversion both in transient and steady state conditions.Reproducible performance of the ACR was observed even after 1200 h of cumulative operation and complete methane removal was obtained at relatively low temperatures.To simulate the obtained experimental data, a heterogeneous one-dimensional model was developed to suit the final reactor configuration using actual laboratory determined kinetic data. The model described adequately the experimental temperature profiles and methane conversion when heat transfer between the reactor compartments and heat loss were taken into account.     

The white porcelains from Dehua kiln site of China: Part I. Chemical compositions and the evolution regularity

Dehua county in Fujian province of China has a long history of white porcelain production from the Song to Qing Dynasties. The development and flourish of Dehua porcelain has always been closely related to the export trade. In this part of the study, white porcelain samples of the Song to Qing Dynasties excavated from Wanpinglun, Qudougong, Zulonggong, Jiabeishan and Xingjiao kiln sites were analyzed to investigate chemical compositions of body and glaze and the evolution regularity in the course of time. The study demonstrates that the composition of Dehua body has similar evolution regularity through the Song to Qing Dynasties with Dehua glaze, and the samples of the Ming Dynasty have extraordinary high K₂O both in bodies and glazes.     

Novel mesoporous aluminosilicate supported palladium-rhodium catalysts for diesel upgrading: II. Catalytic activity and improvement of industrial diesel feedstocks

Bimetallic PdRh catalysts (molar ratio Pd/Rh = 1 and 2) were prepared by impregnation of a mesoporous aluminosilicate (molar ratio Si/Al = 10 and 20). These materials are destined to be used in industrial processes aiming to improve diesel quality by hydrogenation and ring-opening of aromatic components. The four catalysts were examined for their activity in hydrogenation of naphthalene and tetralin model feedstocks, at 6 MPa, including in the presence of sulfur containing compounds. The capacity of one of these catalysts to improve the quality of hydrogenated industrial light cycle oil containing ≤50 wt ppm of sulfur was evaluated in a pilot plant. In these industrial conditions, the catalyst has a higher catalytic activity at lower temperature than a reference state of-the-art catalyst, giving a seven-point improvement of the cetane number at 280–300 °C and with formation of less than 10% of non-selective cracking products.     

An analysis of the chemical composition,performance and structure of China Yixing Zisha pottery from 1573 A.D. to 1911 A.D.

Yixing Zisha pottery is one of the most representative and influential traditional tea sets in ancient and even contemporary China. Chemical and phase composition, microstructure and performance of Yixing Zisha pottery samples from the late Ming Dynasty to the late Qing Dynasty (1573 A.D.–1911 A.D.) unearthed for the first time in the Shushan Mountain Zisha pottery kiln sites in the western and southern hills of Shushan Mountain, Dingshu Town, Yixing City, China, were systematically analyzed. The chemical composition variations of Yixing Zisha pottery of the above-mentioned periods were studied. Porous structure of Yixing Zisha pottery body was discovered and the relationships among the unique performance of Yixing Zisha pottery, its raw material and the special technological process were discussed.     

Canarium schweinfurthii Engl.: Chemical composition of the fruit pulp

Canarium schweinfurthii Engl. (Burseraceae) is a wild tree found mostly in Africa, which produces fruit similar to olives and which is barely used. On a dry matter basis, the fruit pulp from Côte d’Ivoire (the Ivory Coast) was found to contain 5.6% protein, 30–50% fat, 8.2% starch, 11.8% cellulose and 8.3% ash (the highest mineral elements being potassium, 1.2% and calcium, 0.4%). The melting and solidification points of the extracted fat (44.5°C and 35.2°C, respectively) are higher than those of all the commercial and otherCanarium-species oils. This oil shows low iodine, peroxide and carotene values (36, 17 meq-g and 2 mg, respectively). The fatty acid composition of the oil revealed a high content of oleic (89.4%) or stearic (67.7–84.0%) acids in the liquid, semi-solid and solid forms of the oil. Consequently, the content of these two acids is much higher inCanarium schweinfurthii oil than in any other vegetable oil. The three forms (liquid, semi-liquid and solid) of the oil depend on the maturity of the fruit and these stages will be investigated further in future work.     

Exhaust emissions from a diesel powered vehicle fuelled by soybean biodiesel blends (B3-B20) with ethanol as an additive (B20E2-B20E5)

The effects of diesel oil-soybean biodiesel blends on a passenger vehicle exhaust pollutant emissions were investigated. Blends of diesel oil and soybean biodiesel with concentrations of 3% (B3), 5% (B5), 10% (B10) and 20% (B20) were used as fuels. Additionally, the effects of anhydrous ethanol as an additive to B20 fuel blend with concentrations of 2% (B20E2) and 5% (B20E5) were also studied. The emissions tests were carried out following the New European Driving Cycle (NEDC). The results showed that increasing biodiesel concentration in the fuel blend increases carbon dioxide (CO₂) and oxides of nitrogen (NO_X) emissions, while carbon monoxide (CO), hydrocarbons (HC) and particulate matter (PM) emissions are reduced. The addition of anhydrous ethanol to B20 fuel blend proved it can be a strategy to control exhaust NO_X and global warming effects through the reduction of CO₂ concentration. However, it may require fuel injection modifications, as it increases CO, HC and PM emissions.     

Chemical composition, angiotensin I-converting enzyme inhibitory, antioxidant and antimicrobial activities of essential oil of Tunisian Thymus algeriensis Boiss. et Reut. (Lamiaceae)

The present study describes chemical composition, angiotensin I-converting enzyme (ACE) inhibitory, antioxidant and antimicrobial activities of the essential oil of wild growing Thymus algeriensis Boiss. et Reut. (Lamiaceae), a traditional medicinal plant which is mainly endemic in Tunisia and Algeria. The essential oil from the fresh leaves and flowers of T. algeriensis were extracted by hydrodistillation and analysed by GC and GC/MS. Fifty-seven compounds were identified accounting for 97.71% of the total oil, where oxygenated monoterpenes constituted the main chemical class (44.85%). The oil was dominated by camphor (7.82%), 4-terpineol (7.36%), α-pinene (6.75%), 1,8-cineole (5.54%) and cis-sabinene hydrate (5.29%). The T. algeriensis essential oil was found to possess an interesting inhibitory activity towards ACE with an IC50 value of 150 μg/ml. The obtained results also showed that this oil can act as radical scavengers (IC₅₀ = 0.8 mg/ml) and displayed a lipid peroxidation inhibitory activity (IC₅₀ = 0.5 mg/ml) as evaluated by 2,2-diphenyl-1-picrylhydrazyl and β-carotene bleaching methods, respectively. Furthermore, the oil was tested for antimicrobial activity against six bacterial strains and two fungal strains. The inhibition zones and minimal inhibitory concentration values of microbial strains were in the range of 13.5-64 mm and 1-6 μl/ml, respectively. The oil exhibited remarkable inhibitory activity against fungal and Gram-positive bacteria strains.     

New anti-ablation candidate for carbon/carbon composites: Preparation,composition and ablation behavior of Y2Hf2O7 coating under an oxyacetylene torch

Y₂Hf₂O₇ possesses low thermal conductivity and high melting point, which make it promising for a new anti-ablation material. For evaluating the thermal stability and the potential applications of Y₂Hf₂O₇ on anti-ablation protection of C/C composites, Y₂Hf₂O₇ ceramic powder was synthesized by solution combustion method and Y₂Hf₂O₇ coating was prepared on the surface of SiC coated C/C composites using SAPS. Results shown that the coating exhibits good ablation resistance under the heat flux of 2.4?MW/m² with the linear and mass ablation rates are 0.16?μm?s^?1 and ?0.028?mg?s^?1, respectively, after ablation for 40?s. With the prolonging of the ablation time, the increasing thermal stress causes the increase of cracks. Moreover, the chemical erosion from SiO₂ and the physical volatilization of low temperature molten products aggravate failure of the Y₂Hf₂O₇ coating.     

Synthesis and catalytic properties of Ce0.6Zr0.4O2 solid solutions in the oxidation of soluble organic fraction from diesel engines

Ce_0.6Zr_0.4O₂ solid solutions were synthesized by co-precipitation, sol–gel like method, solution combustion and surfactant-assistant approaches, respectively. The catalytic properties of bulk and γ-Al₂O₃ supported Ce_0.6Zr_0.4O₂ solid solutions were studied for the oxidation of soluble organic fractions (SOF) from diesel engines by TG-DTA method. The physicochemical properties were characterized by XRD, BET surface area and pore distribution, SEM, TEM, and particle size distribution techniques. XRD and TEM results show that a Ce_0.6Zr_0.4O₂ solid solution was formed for samples as-prepared and heat-treated at 900 °C for 2 h in air. The co-precipitation derived Ce_0.6Zr_0.4O₂ has as high BET surface area as 153.71 m²/g by controlling preparation conditions. Notable is that the surface area and particle size for fresh Ce_0.6Zr_0.4O₂ ignited at 350 °C decreased little after a thermal treatment in air at 900 °C for 2 h. Furthermore, its bulk density is lowest. The commercial engine oil (SJ5W/40) for FAW-VOLKSWAGEN, which was used by Bora 1.9 TDI diesel cars in China market was substituted for SOF. The catalytic activity was evaluated by normalized peak areas and extrapolated onset temperatures of DTA curves. A computer program was developed by direct non-linear regression model for simulation of TG/DTG curves to determine the thermal processes and kinetic parameters. It is found that lube evaporation/decomposition and thermal decomposition (pyrolysis) were observed under a nitrogen atmosphere. Lube evaporation fractions were inhibited by Ce_0.6Zr_0.4O₂ and γ-Al₂O₃. While under an air atmosphere, namely, in the process of lube oxidation (combustion), evaporation/decomposition, low-temperature oxidation and high-temperature oxidation were distinguished. Ce_0.6Zr_0.4O₂ solid solutions are active catalysts for lube oxidation, in which the sample prepared by solution combustion has the highest activity, mainly due to the maintenance of the surface area and particle size upon sintering and its lowest bulk density. However, γ-Al₂O₃ is more like a support. There exists synergism between Ce_0.6Zr_0.4O₂ and γ-Al₂O₃: γ-Al₂O₃ adsorbs lube retaining it within its pore structure, whereas, Ce_0.6Zr_0.4O₂ solid solutions initiate oxidation reactions when light-off temperatures reach. The application of CeO₂-ZrO₂ solid solution prepared by solution combustion at lower temperature would be promising in diesel oxidation catalysts.