Catalytic activity of bed materials from industrial CFB boilers for the decomposition of N2O

The correlation between the catalytic activity towards N₂O decomposition and fuel type was studied for the bed materials sampled from the bottom bed of two industrial CFB boilers, a 12 MW_th and a 550 MW_th, burning biomass fuels and wastes, alone or as a mixture. It was found that the elemental composition of the surface of the bed material particles changed according to the composition of the ash from the parent fuel. The measured catalytic activity of the bed material samples increased with the amount of the catalytically active oxides (CaO, MgO, Fe₂O₃, Al₂O₃). In the case of limestone addition, the activity of the bed material was influenced by both the elemental composition of the fuel, and the ratio between lime and sulfated lime.     

Utilization of ethyl ester of waste vegetable oils as fuel in diesel engines

Jordan relies heavily on expensive and unreliable imported oil. Therefore, this study was initiated to investigate the potential of ethyl ester used as vegetable oil (VO; biodiesel) to substitute oil-based diesel fuel. The fuels tested were several ester/diesel blends including 100% ester in addition to diesel fuel, which served as the baseline fuel. Variable-speed tests were run on all fuels on a standard test rig of a single-cylinder, direct-injection diesel engine. Tests were conducted to compare these blends with the baseline local diesel fuel in terms of engine performance and exhaust emissions. The results indicated that the blends burned more efficiently with less specific fuel consumption, and therefore, resulted in higher engine thermal efficiency. Furthermore, the blends produced less carbon monoxide and unburned hydrocarbons than diesel fuel. The 100% ester fuel and the blend of 75:25 ester/diesel gave the best performance while the 50:50 blend consistently resulted in the lowest amounts of emissions over the whole speed range tested.     

Efficiencies of various esters of fatty acids as diesel fuels

Methyl esters of commercial grades of lauric, myristic, palmitic, stearic, linoleic and linolenic acids, as well as ethyl and butyl esters of oleic acid, were burned in a diesel engine to determine their efficiencies as fuels. Triolein and some common vegetable oils were burned as comparison fuels and No. 2 diesel fuel was used as a control. The fuels were tested in a single-cylinder direct-injection engine running at rated speed and load in short-term, performance engine tests. Specific fuel consumption and thermal efficiencies of the engine burning these fuels were then determined. Among the methyl esters of the saturated acids, thermal efficiency was inversely related to chain length of the fatty acid. Introduction of a double bond resulted in increased efficiency. Further increases in unsaturation had negligible effects on thermal efficiencies. Ethyl oleate had the highest thermal efficiency and butyl oleate had the lowest thermal efficiency of any of the ester fuels tested. Most of the ester fuels produced higher thermal efficiencies than did No. 2 diesel fuel. Triolein produced the lowest specific fuel consumption of the triglyceride fuels and peanut oil produced the lowest specific fuel consumption of the vegetable oils. The data suggest that ethyl esters of monounsaturated or short-chain fatty acids should make good alternative fuels and that they should be further evaluated in longterm engine tests.     

Emission Reduction of Regenerative Fuel Powered Co-Generation Plants with SCR- and Oxidation-Catalysts

Since the beginning of combustion engine development in this recent century various different fuels have been successfully tested. Diesel engines have been adapted to fuels made from mineral oils because of the rising importance and the cheapness in comparison to other fuels. On the other hand, it is possible to burn regenerative fuels in engines and achieve some significant advantages in comparison to fossil diesel fuel. This is, for example, a closed carbon dioxide (CO₂) cycle which causes no green house effect. It is possible to extract oil from various seeds like rapeseed. It is also possible to burn used oil from the food processing industry or waste grease and oil from food recycling companies. The great advantages: (1) food recycling oils can produce energy instead of use as animal food, and (2) as nobody knows exactly the consistency of the collected oils, poisonous pollution is possible. These regenerative fuels can be burned without any further processing in special adapted diesel engines, for example an Elsbett engine, or in precombustion engines with large swept volumes. Most researchers focused on operating diesel engines with regenerative fuels and reducing the emissions caring only about regulated exhaust components. In comparison to these studies it is necessary to learn more about the emissions beyond the exhaust regulations. Additionally emission reduction is possible by using an SCR-catalyst (selective catalytic reduction) to reduce the NO₂ combined with an oxidation-catalyst which reduces any kind of oxidisable emissions. The TU München, Lehrstuhl für Energie- und Umwelttechnik der Lebensmittelindustrie, operates a small co-generation plant with the ability of analysing the standard emission components (CO, NO₂, HC, particles, CO₂, O₂) and unregulated components (SO₂, NH₃, polycyclic aromatic hydrocarbons (PAH), aldehyde, ketone). The emissions show some significant differences in comparison to fossil diesel fuel which is caused by the diversity of each fuel. Results of an investigation on four different fuels (wastefat methyl ester (WME), rapeseed methyl ester (RME), rapeseed oil and diesel fuel) burned in a small co-generation plant with a SCR- and oxidation-catalyst will be presented. A comparison to the emissions before and after the catalysts will be shown additionally to the results of the different reduction potential of diesel fuel, methyl ester or untreated oils. The combination of regenerative fuel and catalyst shows good potential for reducing the emissions. Furthermore the use of regenerative fuels is a sustainable production of energy with an overall efficiency of almost 90%. Regenerative fuels based on vegetable oils and waste fat are a valuable form of energy and have some significant advantages in comparison to diesel fuel, like an almost closed carbon dioxide cycle, rapid biological decomposition and lower CO, HC and particle emissions. Regenerative fuels should also meet minimum standards discussed in the paper to avoid the risk of engine damage and to reduce emissions.     

Examination of the combustion conditions of herbaceous biomass

Power generation from biomass is a fairly new area, and boilers that utilize various types of biomass have in many cases experienced serious problems with slagging, fouling and corrosion of boiler tubes. Mineral matter in these fuels can deposit on the heat-exchanger surfaces in the boiler and generate an insulating layer, which will significantly reduce the degree of heat-transfer from flue gas to water and steam. Our investigations were focused on the slag characteristics of different kinds of herbaceous biomass fuels. Since there is usually a reducing atmosphere present in the direct combustion zone of modern low-NO_x firing systems, it is important to study mineral matter transformation of burned fuel residues in a reducing atmosphere. An excellent device for this type of study is the electric-resistance heated Bunte–Baum softening temperature testing instrument, which was used in this work. Ash chemical composition was analyzed via flame atomic absorption spectrometry and the microstructure of ash was determined using a scanning electron microscope. Crystalline compounds of the ashes were identified by using X-ray powder diffraction. This paper provides an overview of results on the combustion and slag characteristics of herbaceous biomass fuels. The results include chemical compositions, morphology and softening properties of these fuels, with special attention to switch grass and sunflower seed shell.     

Influence of Methanol–Biodiesel Blends on the Particulate Emissions of a Direct Injection Diesel Engine

In this study, Euro V diesel fuel, biodiesel, and methanol–biodiesel blends were tested in a 4-cylinder direct-injection diesel engine to investigate the combustion characteristics and particulate emissions of the diesel engine under five engine loads at the maximum torque engine speed of 1800 rpm. Compared with Euro V diesel fuel, biodiesel gives lower and earlier heat release rate. For the blended fuels, the peak heat release rate becomes higher and retarded. With regard to particulate mass concentration, biodiesel generates less than Euro V diesel fuel, while the blended fuels result in significant reduction especially at high engine loads. Compare with Euro V diesel fuel, the total particle number concentration of using biodiesel is always higher while the geometric mean diameter (GMD) of the particles is lower. With the blended fuel, the total number concentration and GMD decrease in comparison with pure biodiesel. Further analysis shows that the difference between the total number concentration of biodiesel and Euro V diesel fuel is in particles smaller than 50 nm rather than in the larger particles. The use of methanol–biodiesel blends, compared with biodiesel, could reduce the number concentration of all sizes. A comparison between the particulate mass emission and total particulate number concentration with the mass of fuel burned in the diffusion mode show that they are strongly related to each other, even for the blended fuel.     

Experimental investigation on particulate emissions of a direct injection diesel engine fueled with diesel–diethyl adipate blends

Euro V diesel fuel blended with 8.1%, 16.4%, 25% and 33.8% by volume of diethyl adipate (DEA), corresponding to 3%, 6%, 9% and 12% by mass of oxygen in the blended fuels, were tested on a 4-cylinder direct-injection diesel engine. Experiments were conducted under five engine loads at a steady speed of 1800 rev/min to investigate the effects of the blended fuels on combustion and particulate emission characteristics. The results indicate an increase in ignition delay and the amount of heat release in the premixed burning phase, while a decrease in both diffusive and total combustion duration with an increase in DEA in the fuel. Compared to the diesel fuel, the particulate mass concentration and the total number of particles are reduced significantly, whereas the proportion of soluble organic fraction (SOF) in the particles increases with increasing DEA in the fuel. The increase in SOF might increase the toxicity of the particles. Moreover, the geometric mean diameter (GMD) of the particles shifts towards smaller size. A diesel oxidation catalyst was used and found to further reduce both particulate mass and total number concentration. The results also show that the DOC could reduce the finer particles more effectively.     

The effects of fuel characteristics and engine operating conditions on the elemental composition of emissions from heavy duty diesel buses

The effects of fuel characteristics and engine operating conditions on elemental composition of emissions from twelve heavy duty diesel buses have been investigated. Two types of diesel fuels – low sulfur diesel (LSD) and ultra low sulfur diesel (ULSD) fuels with 500 ppm and 50 ppm sulfur contents respectively and 3 driving modes corresponding to 25%, 50% and 100% power were used. Elements present in the tailpipe emissions were quantified by inductively coupled plasma mass spectrometry (ICPMS) and those found in measurable quantities included Mg, Ca, Cr, Fe, Cu, Zn, Ti, Ni, Pb, Be, P, Se, Ti and Ge. Multivariate analyses using multi-criteria decision making methods (MCDM), principal component analysis (PCA) and partial least squares (PLS) facilitated the extraction of information about the structure of the data. MCDM showed that the emissions of the elements were strongly influenced by the engine driving conditions while the PCA loadings plots showed that the emission factors of the elements were correlated with those of other pollutants such as particle number, total suspended particles, CO, CO₂ and NO_x. Partial least square analysis revealed that the emission factors of the elements were strongly dependent on the fuel parameters such as the fuel sulfur content, fuel density, distillation point and cetane index. Strong correlations were also observed between these pollutants and the engine power or exhaust temperature. The study provides insights into the possible role of fuel sulfur content in the emission of inorganic elements from heavy duty diesel vehicles.     

Correlating the effects of ash elements and their association in the fuel matrix with the ash release during pulverized fuel combustion

During pulverized fuel combustion, inorganic elements such as alkalis, sulfur, chlorine, calcium and magnesium, as well as a range of minor elements are partly released into the gas phase. These gas-borne species can nucleate, coagulate and condense to form either aerosol particles or sticky layers on ash particles, leading to ash deposition and corrosion problems in power utilities. Furthermore, the fine aerosols can lead to harmful gaseous and particulate emissions. It is well documented that the mode of occurrence and the chemical speciation of ash forming elements in the coal/biomass structure are important for the release behavior of mineral components. In the presented work, this is investigated by performing quantitative elemental investigations of ash releases for two different coals (a Polish and a UK coal) and six diverse biomass fuels (Wood bark, Wood chips, Waste wood, Olive residue, Saw dust and Straw). The tests are performed within the Lab-scale Combustion Simulator (LCS) of the Energy Research Centre of the Netherlands (ECN). The operating conditions applied were that of a typical pulverized fuel (PF) fired boiler i.e. atmospheric pressure, high temperatures of 1400-1650 °C, and high heating rate of 10⁵ K/s. Gas phase elemental release of alkalis, sulfur, chlorine, calcium and magnesium has been quantified at relevant high carbon conversion levels. With the performed set of experiments several of the past observations from the literature are reconfirmed. In addition to this, based on the extensive data pool at hand, a simple but reliable (R² > 0.95) set of linear correlations have been proposed to predict the elemental release of potassium, sodium, chlorine and sulfur. It is also concluded that such linear expressions can be particularly effective for the prediction of elemental release from the fuels of similar characteristics, such as woody biomass.     

Porosity of refractory coatings with flame guniting of converters

Conclusions Coatings obtained from flame-guniting of the lining of converters using coke powder as the fuel have higher porosity which increases wear. The pores are formed in the place where the coke particles are burned out in the coating since their burning time is greater than their flight time from the nozzle to the lining.Translated from Ogneupory, No. 2, pp. 36–39, February, 1981.     

Influence of fuel ash composition on high temperature aerosol formation in fixed bed combustion of woody biomass pellets

In this work, the influence of fuel ash composition on high temperature aerosol formation during fixed bed combustion of woody biomass (two wood pellets and one bark pellets) were investigated experimentally in a laboratory reactor and theoretically through chemical equilibrium model calculations. For all fuels, the particle mass size distribution in the PM_2.5 region was bimodal, with one fine mode and one coarse mode. Early in the flame, the fine mode was dominated by particles from incomplete combustion and these particles were rapidly oxidised in the post flame zone. After the hot flame, the fine mode concentration and the particle diameter increases gradually when the temperature decreases due to condensation of vaporised inorganic matter, K, Na, S, Cl, and Zn. For two of the fuels also P could be found in the fine particles. The coarse mode consisted of carbon, refractory metals and considerable amount of alkali. Further, the initial fuel alkali concentration and the alkali to silicon ratio (K + Na)/Si influenced the amount of vaporised aerosol forming alkali matter. Finally, the present study shows that, combustion temperature and fuel ash composition is of major importance for the formation of high temperature aerosols in fixed bed combustion of woody biomass pellets.     

Particulate Emission Characteristics of a Compression Ignition Engine Fueled with Diesel–DMC Blends

The effect of fuel composition on the combustion characteristics and particulate emissions of a compression-ignition engine fueled with Euro V diesel fuel blended with dimethyl carbonate (DMC) was investigated experimentally. Blended fuels containing 4.48%, 9.07%, 13.78%, and 18.6% by volume of DMC, corresponding to 3%, 6%, 9%, and 12% by mass of oxygen in the blended fuels, were investigated. By analyzing the measured in-cylinder pressure data and the derived heat release rate, it is observed that the addition of DMC increases the ignition delay and the amount of heat release in the premixed combustion duration, but shortens both the diffusive burning duration and the total combustion duration. On the emission side, the smoke opacity, the particulate mass concentration as well as the total number of particulates are all reduced, while the proportion of soluble organic fraction (SOF) in the particulate is increased, by using the blended fuels. The geometric mean diameter of the particles shifts towards smaller size in comparison with that of the diesel fuel. The particulate mass concentration, the total number of particles and SOF can be further reduced by the use of diesel oxidation catalyst (DOC), while the particles shift towards larger geometric mean diameter for each fuel, indicating that the DOC could reduce the finer particles.     

Combustion of Energetic Fuel for Ducted Rockets (I)

Energetic solid fuels composed of modified GAP (glycidyl azide polymer) propellants were formulated in order to obtain optimized combustion characteristics for variable flow ducted rockets. Burning rate in a primary combustor and the combustion efficiency in a secondary combustor were studied and evaluated as a function of the mixture ration of fuel and air. The energetic fuels consisting of – N₃ groups in its chemical structure burned very rapidly even though the combustion temperature was low when compared with conventional solid propellants for rockets. The pressure exponent of the burning rate was optimized to gain wide range of mass generation rate. The combustion gases generated in the primary combustor burned very efficiently in a secondary combustor. The effective specific impulse of the ducted rockets was obtained to be about 780 s.     

Size and structural characterization of lignin-cellulosic fuels after the rapid devolatilization

The aim of this work is to develop and test a method for assessing the size and the morphology of biomass fuels and their chars. Severe thermal conditions (high temperature and heating rate) are programmed during the pyrolysis, focusing on characteristics of chars in combustion or gasification. An image analysis program is used to quantitatively study several scanning electron microscopy images of fuel and char samples. Distributions of results are obtained for a significant number of particles from a statistical point of view. Average values and the standard deviations of the distributions quantify the heterogeneous nature of the fuel and char particles, providing useful parameters for advanced modeling. Size, shape factors (aspect and roundness) and superficial parameters are defined and measured (or calculated) developing a procedure for a low time-consuming analysis. The structural variations caused by the fast release of a high amount of volatile products are evaluated comparing the results obtained on fuel and char particles. The results are discussed to assessing the suitability of the selected parameters and the possibility to quantify softening, melting, shrinking and fragmentation phenomena. The method is applied to two biomass fuels of different origin and chemical composition: wood pellets and olive residue.     

Morphology and composition of the fly ash particles produced in incineration of municipal solid waste

This paper describes the results of experiments using a pilot-scale, 140,000 Btu/h, solid fuel continuous feed laboratory incinerator. A synthetic fuel representative of the municipal solid waste in the United States was formulated and used in this research. The fuel contained Fe and SiO₂, and was doped with trace amounts of Al, Ni, Cr, Hg, and PbO. Experiments were performed with varying fuel–air ratio, and both gaseous and condensed products were collected and analyzed.This work focuses on the characterization of composition and morphology of fly ash particles captured in a fabric filter. Particle size distributions were obtained using optical microscopy and sieving. Atomic absorption (AA) was used to determine bulk compositions of the size-classified ash fractions. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used to study the morphology and surface compositions of the ash particles. It was observed that the fly ash particles have bimodal size distribution and, most interestingly, that the ash particles of different sizes have different elemental and phase compositions. Concentrations of Cr, Ni, and Fe were greater in the coarse particles (up to 1-mm diameter), whereas concentrations of Al and Si were higher in the finer particles (less than 75 μm). Maximum concentrations of Pb and Hg occurred in the 150–300-μm particles.It is suggested that if a correlation between the composition and size of the ash particles similar to that observed in this research exists in the products of industrial combustors, a technique of ash processing based on the particle size classification could be developed. Applying such a technique could result in the efficient and inexpensive removal of the lead- and mercury-rich particulates from the produced ash. The processed, environmentally benign ash portions will therefore be useful for a variety of the recycling-based manufacturing, and metal recovery processes.     

A PM 2.5 Inlet Impactor Designed for a High Flow Application

Two potential strategies for reducing diesel emissions are exhaust aftertreatment and the use of reformulated or alternative fuels. Little is yet known about the impact on ultrafine particle emissions of combining exhaust aftertreatment with such increasingly common fuels. This paper reports ultrafine particle size distribution measurements for a study in which the impact of such fuels on emissions from a heavy duty diesel engine employing different aftertreatment configurations was evaluated. Eight different fuels were tested: Canadian No. 1 and No. 2 diesel; low sulfur diesel fuel; two different ultra low sulfur diesel fuels (< 30 ppm S); Fischer-Tropsch diesel fuel; 20% biodiesel blended with ultra low sulfur diesel fuel; and PuriNO_x?. The fuels were tested in combination with four exhaust configurations: engine out, diesel oxidation catalyst (DOC), continuously regenerating diesel particle filter (CRDPF), and engine gas recirculation with CRDPF (EGR-DPF). In general, aftertreatment configuration was found to have a greater impact on ultrafine particle size distributions than fuel composition, and the effects of aftertreatment tended to be uniform across the entire particle size distribution. Steady state tests revealed complex behavior based on fuel type, particularly for PuriNOx. This behavior included bimodal particle size distributions with modes as low as 8–10 nm for some fuels. Unlike previous results for gravimetric PM from this study, no significant correlation for ultrafine emissions was found for fuel properties such as sulfur level.     

生物质燃油碳烟颗粒的形貌、结构与组分表征

通过微乳化工艺分别把不同含量的精制生物质裂解油与柴油进行混合(micro-emulsified biomass fuel, MEBF), 研究了该类燃油碳烟颗粒的形貌与结构, 并对其组分进行了表征。结果表明:该类燃油碳烟的一次颗粒形貌均为球形, 而且一次颗粒之间互相连接构成链状团聚物。同时, 精制生物质裂解油含量为20%(质量)(BS20)的混合油碳烟颗粒的平均粒径最小, 约为32 nm, 其他含量混合油碳烟颗粒的平均粒径均在38 nm左右。BS30石墨化程度高于其余碳烟, 且BS20颗粒表面C=O和C-O-C基团含量较高, 可能归因于混合油燃烧过程中复杂含氧组分的氧化程度不同。     

Potentiale regenerativer Festbrennstoffe und die Notwendigkeit der Charakterisierung ihres Brennverhaltens

Potentiality of Solid Regenerative Fuels and the Necessity of the Characterization of Combustion Processes Apart from coal, solid regenerative fuels will obtain increasing importance in overlapping fuel markets. The combustion process depends on the properties of the fuel and fuels can be characterized using standard analytical tests. These standard test methods are simplified and only valid for the specific fuel type. The transfer to other fuel types can not be made without further analytical tests. The development of new highly informative analytical methods is necessary to compare the different reactions of a combustion process by using fuels of different origin. A new analytical principle fulfils these demands. The main difference to common techniques is that it uses large fuel particles. This leads to a better statistical validation of the analytical results and information about the fragmentation behavior of large fuel particles can be gained. The definition of characteristic parameters enables the practical use of the analytical data.     

Comparison of particle emissions from an engine operating on biodiesel and petroleum diesel

Biodiesel is an alternative fuel with growing usage in the transportation sector. To compare biodiesel and petroleum diesel effects on particle emissions, engine dynamometer tests were performed on a Euro II engine with three test fuels: petroleum diesel (D), biodiesel made from soy bean oil (BS) and biodiesel made from waste cooking oil (BW). PM_2.5 samples were collected on Teflon and quartz filters with a Model 130 High-Flow Impactor (MSP Corp). Organic (OC) and elemental (EC) carbon fractions of PM_2.5 were quantified by a thermal-optical reflectance analysis method and particle size distributions were measured with an electrical low pressure impactor (ELPI). In addition, the gaseous pollutants were measured by an AMA4000 (AVL Corp). The biodiesels were found to produce 19-37% less and 23-133% more PM_2.5 compared to the petroleum diesel at higher and lower engine loads respectively. On the basis of the carbon analysis results, the biodiesel application increased the PM_2.5 OC emissions by 12-190% and decreased the PM_2.5 EC emissions by 53-80%, depending on the fuel and engine operation parameters. Therefore OC/EC was increased by three to eight times with biodiesel application. The geometrical mean diameter of particles from biodiesels and petroleum diesel had consistent trends with load and speed transition. In all the conditions, there is a shift of the particles towards smaller geometric mean diameter for the biodiesel made from waste oil.     

Performance of ZrC-Coated Particle Fuel in Irradiation and Postirradiation Heating Tests

The ZrC-coated UO₂ particle is a promising fuel for high-temperature gas-cooled reactors. Particle fuels with multiple layers of pyrolytic carbon and ZrC have been irratiation-tested to a maximum fast-neutron fluence exceeding 2 × 10²⁵/m² ( E < 29 fJ). In-reactor fission-gas release measured at a burnup of 1.5 at.% was minimal. The failure fraction by postirradiation examination was null for all samples. The ZrC-coated particles at 4 at.% burnup were postirradiation heated to 2400°C/min without failure until after 6000 s at the maximum temperature. It was found that the ZrC layer could sustain a large strain at such high temperatures. The behavior is in strong contrast with that of SiC of standard Triso coating, which is brittle to very high temperatures.