Effect of Flue Gas Recirculation on Multi-Cyclones Performance in Reducing Particulate Emission from Palm Oil Mill Boiler

The effect of recirculating the flue gas on the performance of a multi-cyclones unit as particulate collector in an actual plant scale was studied. The existing multi-cyclones unit was modified by connecting a recirculation duct between the inlet and outlet gas stream of the multi-cyclones attached with an external induced (ID) fan. The particulate samplings were done following the U.S. EPA method at boiler outlet (before multi-cyclones), stack (after multi-cyclones) and recirculation duct. Result shows that the amount of recirculated particulates increases with ID fan suction power. The collection efficiency increased slightly from 68% (0% or without recirculation) to 74% (at 11% recirculation) and dropped to 67% (at 17% recirculation). Moreover, the amount of the fine particulate size fraction emitted able to be reduced one fold at 11% recirculation flow rate. However, high amount of recirculated particulates results in re-entrainment of particulates into the outlet of the multi-cyclones, hence, results in increase of particulate emission in the stack.     

碳化硅增强铝基复合材料的力学性能和断裂机制

研究了碳化硅颗粒(SiCp)尺寸对用粉末冶金法制备体积分数为15%的SiCp/2009铝基复合材料力学性能和断裂机制的影响.结果表明,复合材料的强度随着SiCp尺寸的增大而减小,塑性则随着颗粒的增大而增大.当SiCp尺寸为1.5μm时,SiCp/2009A1复合材料的断裂主要以界面处撕裂和基体材料的开裂为主;当SiCp尺寸为20 μm时,复合材料的断裂主要以SiCp断裂为主;当SiCp尺寸处于两者之间时,SiCp/2009A1复合材料界面处撕裂和SiCp断裂的共同作用决定复合材料的断裂.     

Ambient air particulate concentrations and metallic elements principal component analysis at Taichung Harbor (TH) and WuChi Traffic (WT) near Taiwan Strait during 2004-2005

The purpose of this study is to characterize metallic elements associated with atmospheric particulate matter of total suspended particulate (TSP), fine particle (particle matter with aerodynamical diameter <2.5 microm, PM(2.5)), coarse particle (particle matter with aerodynamical diameter 2.5-10 microm, PM (2.5-10)) at the Taichung Harbor (TH) and WuChi Traffic (WT) sampling site of central Taiwan during March 2004 to February 2005. The result indicated the average total suspended particulate concentration in 1 year was 157.31 and 112.58 microg m(-3) at TH and WT sampling site, respectively. Fine particle (PM(2.5)) size was the dominant species at TH and WT sampling site. In TH sampling site, higher correlation coefficient was observed on total suspended particulates of metallic elements Fe and Zn. And in WT sampling site, higher correlation coefficients displayed on total suspended particulates of metallic elements Fe and Zn, Fe and Mn. Ambient airborne particle principal component analysis of metallic metals was used to identify the possible pollutant sources in this study. At the TH sampling site, 50.81% of the total variance of the data was observed in factor 1. Higher loading of Fe (0.86), Zn (0.79), Pb (0.76), and Mn (0.68) were contributed by traffic emission and the soil source. At the WT sampling site, factor 1 explained 53.74% of the total variance of the data and had high loading for Zn (0.86) and Cu (0.85), which were identified as industrial/traffic emission sources.     

Particle size distribution of polycyclic aromatic hydrocarbons in motorcycle exhaust emissions

The size distribution of polycyclic aromatic hydrocarbons (PAHs) in emission of a two-stroke carburetor motorcycle was studied. The exhaust gas from the test motorcycle was passed to a dilution tunnel and collected using a 10 cascade micro-orifice uniform deposit impactor (MOUDI) of 0.056-10 microm aerodynamic diameter fitted with aluminum substrates. All MOUDI substrates were analyzed for particulate mass and for PAHs by GC/MS. Most of the 21 analyzed PAHs have two significant modes that peak at <0.1 and 0.18-0.32 microm. For some PAHs, a third peak appears around 1.8 microm. MOUDI impactor samples show that 88.9% particulate and 89.6% PAH mass distributed smaller than 2.5 microm. Mass median diameters of PAHs are about 0.2 microm. Total benzo[a]pyrene toxic equivalency emission factor was 440+/-13.8 ng/km for the test motorcycle. An average of 90.3% of carcinogenicity is observed in particulate smaller than 1.0 microm. The results suggest that submicron particulates predominate in the exhaust from motorcycle and exhibit high carcinogenic potency for these particulate.     

Hypervelocity impact testing of micrometeorite capture cells in conjunction with a PVDF thin-film velocity/trajectory sensor and a simple plasma velocity detector

Five different small particle capture cell designs were evaluated for their ability to capture fragments and residue from 10–200 μm diameter glass projectiles and oblong olivine crystals impacting at 1–15 km/s in sufficient quantity for chemical and isotopic analyses. Aluminum multi-foils (0.1–100 μm thick with ≈10, 000 and 1800 μm spacing), foil covered germanium crystals, and 0.50 and 0.120 g/cm³ Aerogels, were positioned behind either multi-film (1.4–6.0 μm thick) polyvinylidene fluoride (PVDF) velocity/trajectory sensor devices of a simple wire-grid plasma velocity detector. All capture cells collected significant amounts of impactor debris behind the PVDF sensors from nominal 100 μm diameter glass projectiles and olivine crystals which struck the sensor at velocities up to 6.4 km/s. At velocities >8 km/s little or no debris penetrated the second PVDF film. Results were incolsive for velocities between 6.5 and 8 km/s. Plasma detector results showed identifiable impactor residue on Al foils for velocities up to 8.7 km/s and impact tracks with apparent debris imbedded in the Aerogels for velocities up to 12.7 km/s. Maximum foil penetration of glass spheres and olivine crystals were the same, but more particulate debris was associated with olivine crystal ipacts versus glass impacts. Foil spacing beyond one particle diameter had no effect on total penetration. Aerogels are identified as a capture cell media that warrants further investigation. The Al multi-foil capture cell with 100 μm net spacers is identified as the most effective of the other designs and offers the advantages of compact structure, low secondary ejecta from impacts, and easy recovery of impactor debris for analysis.     

喷射共沉积SiCp/Al复合材料的增强颗粒植入

对用喷射共沉积法制备颗粒增强复合材料中固体颗粒向金属基体的转移过程进行了计算.在考虑到颗粒所受到的拖曳力、表面力和密度差引起的浮力的条件下,推导出了增强颗粒植入沉积层的判据.以颗粒冲击沉积层液膜最小速度为表达形式的判据指出,颗粒的动能、直径和同金属的润湿条件对颗粒的植入有决定性的影响.     

Dry separation of fine particulate sand mixture based on density-segregation in a vibro-fluidized bed

Separation of fine particulate solid materials is one of most important unit operations in industry. Utilization of gas-solid fluidized beds has been considered where particulates are released from constraints due to contacts with surrounding particulates and segregation occurs according to density, size or combination of density and size. Addition of mechanical vibration to the gas-solid fluidized bed may improve dry solid separation. In this study, we investigated the dry separation characteristics of solid particulates using a vibro-fluidized bed especially focusing on the separation of fine particulate ores (≈100 μm) with small density differences. At first, we focused on the influence of fluidizing air velocity on the efficiency of segregation. Subsequently, the influence of vibration strength, vibration amplitude and frequency on segregation behavior was investigated. We found the density segregation does not occur with either gas-fluidization or vertical vibration alone. Only the combination of these effects produces density segregation. The fluidizing air velocity is an important factor to enhance the density-segregation of the particulates with small density difference.     

Colloidal and electrophoretic behavior of polymer particulates in suspension

The behavior of individual polymer chains in solvent has been reported in the literature and formed the basis of polymer dynamic understanding [S.R. Quake, H. Babcock and S. Chu, Nature 388 (1997) 151, T.T. Perkins, D.E. Smith and S. Chu, Science 276 (1997) 2016.]. However, thus far, the behavior of isolated particulate polymer or block polymer/copolymers in suspension has not been investigated. In the present work, it is found that classical colloidal theories that describe the particle behavior in suspension can be applied to polymer particulates/blocks. This, in turn, suggests many possibilities in materials processing including co-processing of composites via particulate or powder route to formulate complex microstructures. A polymeric material, polyetheretherketone (PEEK), was used to examine the colloidal behavior of polymer particulates in the present work. Zeta potential of the particulate suspension was measured and the electrostatic interaction of the particulates was examined by DLVO theory. The electrosteric effect between the charged particulates in suspension was also studied. Based on the findings, an optimum condition for a dispersed stable suspension was identified and applied to the electrophoretic deposition of PEEK particulates.     

MEASUREMENTS AND ANALYSIS OF THE PARTICULATE EMISSION FROM A DIRECT INJECTION DIESEL

For five different operating conditions of varying speed and load, measurements have been made of the particulate emissions using a mini-dilution tunnel operated at different dilution ratios and air temperatures. Particles were sized by electron microscopy and employment of interactive computer graphics.

Analysis of results leads to conclusions that the organic fraction of the particulates can be explained by either an adsorption or condensation interaction with the gas phase. Account must be taken of the multi-component nature of the organic species and that adsorption is multilayer in modeling these processes.     

喷雾共沉积SiCP/Al复合材料颗粒进入基体机制的研究

本文分析了喷雾共沉积颗粒增强金属基复合材料工艺中颗粒进入金属基体的动力学过程和可能机制,首次提出对于陶瓷颗粒/铝等非润湿系,颗粒将按射入机制进入基体;并由颗粒进入沉积层液膜的力学平衡关系,推导出颗粒按射入机制进入基体时,沉积前所需达到的临界速度表达式。在射入机制和大量实验的基础上,提出了一种新的颗粒加入方法即外部环孔式喷嘴注入法,解决了微细SiC颗粒在基体中分布不均匀、体积分数难以控制和提高等工艺难点,制出了W10 SiC颗粒在基体中分布均匀、体积分数达14.7vol%的SiC_P/Al复合材料。     

Characteristics of Air-Side Particulate Fouling Materials in Finned-Tube Heat Exchangers of Air Conditioners

ABSTRACT

Heat exchangers are used widely in residential, commercial, and industrial HVAC applications. Air-side particulate fouling in the heat exchangers of HVAC applications degrades the performance of cooling capacity, pressure drop across a heat exchanger, and indoor air quality. Indoor and outdoor air contaminants foul heat exchangers. The purpose of this study is to investigate the characteristics of the air-side particulate fouling materials in finned-tube heat exchangers of air conditioners. Air conditioners being used in the field such as inns, restaurants, and offices are collected in chronological order of use. The fouling materials attached on the evaporator heat exchangers consist of particulates and fibers. The particulates mainly originate from indoor dusts and the fibers are separated from clothes, bedclothes, papers, fur of pets, and so on. Typical fouling materials on the heat exchangers include fibers and dusts ranging from 6.6 to 20.9 μm in aerodynamic mean diameter.     

Analysis of mold flow and microstructures of die casting in Al alloy/SiC(p) composites

The report involves a study of the microstructure of tensile, impact and three-point bending samples of aluminum alloy/SiC_(p) composites produced by die casting. The results show that in impact samples, 80 m SiC particulates cluster along the left and right edges of the section vertical plane with the notch plane, and near the notch. In tensile and three-point bending samples, they were distributed uniformly in the matrix. Furthermore, porosities occurred near the notch in the impact samples. The 80 m SiC particulates will undergo settling in the shot biscuit. There exist arc and irregular shapes in the clustering section of the particulate. The dendrite arm spacing (DAS) is larger in this section. From the shot biscuit to the bending section of the sprue; the quantity of SiC particulate is less. The SiC particulate is clustered in the protrusive region where the injector pins are situated. We can decrease the porosity of die casting samples effectively by designing the overflow well in a wave shape. We can prevent the melt from adhering to the surface of the mold cavity, thermal cracking on the surface of die casting samples and wear on plungers using electroless nickel plating on the SiC particulate.     

针刺毡C/C复合材料磨擦制动压力和速度特性

用模拟刹车制动的摩擦试验机,研究探讨了一种针刺毡结构C/C复合材料在不同制动压力和制动速度下的摩擦磨损性能,并用扫描电子显微镜对摩擦表面进行了观察和分析。摩擦磨损机理由磨屑经挤压、剪切堆积在表面形成的磨屑层所决定。在5m/s制动速度或静态条件下,表面温度低(<150~200℃)吸附水气未脱附,其润滑作用导致了较低的摩擦系数值;当制动速度达到10m/s,摩擦使表面温度升高,达到了吸附水气脱附温度,引起摩擦系数急剧升高,达到了最大;此后,随制动速度及表面温度的继续升高,磨屑层间剪切强度降低,导致摩擦系数随之下降。在较高制动速度下,该种材料仍能保持较高的摩擦系数,显示出优良的高温高能摩擦性能。     

Experimental investigation of impact of diesel particulate filter on smoke and NO<Subscript>x</Subscript> emissions of a Euro-I compression ignition engine with active and off-board regeneration

Old engines (Euro III or earlier) produce more emissions, and it will be difficult to entirely stop their usage especially in developing and under-developed nations; hence, it is desired that appropriate emission reduction technologies are tested on such engines to analyze their feasibility and economical acceptability. While most such studies have been conducted on constant speed stationary engines and modern engines, this study tried to analyze the effectiveness of an uncoated wall-flow type ceramic diesel particulate filter on a Euro-I, water-cooled, direct injection, variable speed, compression ignition engine in a laboratory set-up in India. Also, this study focused on diesel particulate filter regeneration by two methods: active regeneration by diesel injection in the particulate filter using an electronic control unit and off-board regeneration by taking out and heating the diesel particulate filter in an electrical resistance furnace at 650 °C for 10 h. The results, in the form of smoke emission, NO_x emission and engine performance, obtained using both the regeneration methods were analyzed, and conclusions were drawn. It was found that using diesel particulate filter, particulate matter emissions (smoke) were almost entirely eliminated. It was also found that off-board regeneration had numerous advantages compared to active regeneration. Since a furnace would be needed for off-board regeneration, an exchange process for diesel particulate filter is suggested.     

Microstructure and properties of austenitic stainless steel reinforced with in situ TiC particulate

Austenitic stainless steel reinforced with 5 vol.% TiC particulate was in situ synthesized by in situ reaction during melting process successfully and its microstructure, mechanical properties as well as oxidation behavior were investigated. Microstructure observations revealed that in situ TiC particulates with an average size of 2–10 μm distributed uniformly in the matrix and the interface boundaries between TiC particulates and austenite matrix were clean without any impurities and contaminations. Addition of TiC particulates refined the grain structure of austenitic matrix, but did not cause formation of any new phases in microstructure. Beneficial effects of TiC addition to austenitic stainless steel on both mechanical properties and oxidation resistance were found. Both at ambient and elevated temperature, tensile strengths of the steel with TiC addition were notably higher than those of its matrix alloy, however, a decrease in ductility also appeared, as exhibited by other particulate reinforced alloys. Besides tensile strengths, creep resistance of austenitic stainless steel was also significantly increased by TiC addition at elevated temperature of 923 K. Oxidation test at 1073 K revealed that TiC addition to austenitic stainless steel raised the oxidation resistance of the steel remarkably.     

Burning characteristics and emission products related to metallic content in incense

This study mainly compared particulate emission factors of nine popular incense. The influence of metallic contents upon the burning rate, ash and particulate emission factors of combustion was discussed. The contents of Ca and K were the highest among all metallic elements in the raw materials of the incense (the geometric mean contents 8.7 and 2.5mgg(-1), respectively), followed by Al, Mg, Fe, Na (0.1-1.0mgg(-1)) and Ba, then Sr, Mn, Cu and Zn (<0.01-0.1mgg(-1)). Most calcium existed as inorganic salts, such as CaCO(3). Under the same burning conditions, the particulate generation rates are similar (0.50mgmin(-1)+/-9%) among different types of incense-the shorter the combustion duration of a stick, the lower the total suspended particulate emission. Additionally, with the same incense weight burned, the greater the emission of ash is, the lower the emission of suspended particulate. It is recommended that consumers select incense which produces more ash, hence less particulate, to minimize the threat to their' health. Additionally, when the total metallic content (with Ca as the major component) was lower than 2% of the raw materials, properly increasing the total metallic content (from 0.5 to 2.0%) can effectively reduce the level of particulates (about 40%) during the combustion.     

Doppler Microwave Cavity Monitor for Particulate Loading

A real-time particulate loading monitor using a multimode microwave cavity is described and analyzed. Microwave power in the cavity volume is scattered with a Doppler shifted frequency by particulates suspended in a gas flowing through the cavity. Detection of the scattered radiation by beating it with the nonscattered radiation provides an indication of the particulate loading. A proof-of-concept experimental setup is described with the obtained results. The monitoring system is not very sensitive to particulates smaller than 1 ?m. However, it is very well suited to operations where the effluent gas is under high pressure and temperature.     

Laser-produced lithium plasma as a narrow-band extended ultraviolet radiation source for photoelectron spectroscopy

Extended ultraviolet (EUV) emission characteristics of a laser-produced lithium plasma are determined with regard to the requirements of x-ray photoelectron spectroscopy. The main features of interest are spectral distribution, photon flux, bandwidth, source size, and emission duration. Laser-produced lithium plasmas are characterized as emitters of intense narrow-band EUV radiation. It can be estimated that the lithium Lyman-alpha line emission in combination with an ellipsoidal silicon/molybdenum multilayer mirror is a suitable EUV source for an x-ray photoelectron spectroscopy microscope with a 50-meV energy resolution and a 10-mum lateral resolution.     

激光熔覆TiCp／Ni基合金复合涂层中TiCp的行为

通过激光熔覆TiCp/Ni基合金复合涂层微观组织的研究表明,TiC颗粒在熔覆过程中表面发生部分溶解,当凝固时,溶解的部分TiC在残留TiC颗粒上重新外延生长析出,并与基体合金元素产生附加合金化,同时,TiC颗粒成为从激光熔体凝固各相优先形核的基底;TiC颗粒与凝固前沿间的相互作用控制其微观分布。     

On the thermal conductivity of bimodal SiC/A356 composites fabricated via powder metallurgy route

The present study investigates the thermal conductivity of bimodal SiC particulate distribution in aluminum matrix composites fabricated via powder metallurgy route. The effects of the SiC_p reinforcement size distribution and processing parameters such as sintering time and temperature on the thermal conductivity have been examined. The Box–Behnken experimental array was employed to identify the effects of selected variables on the thermal conductivity of the composite. A reasonable augmentation in the thermal conductivity was observed with an increase in sintering time and %volume fraction of fine SiC particulates. It has been demonstrated that the matrix doped with fine SiC particulates (37?µm) occupied interstitial positions and formed continuous SiC–matrix network resulting in minimizing the micropores that contributed for good thermal conductivity, that is, 235?W/mK. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were conducted to evaluate the microstructure architecture and interfacial phase formation.