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Now showing items 1 - 16 of 57

  • Pore Characteristics and Slurryability of Coal Blends

    Zhu, Jie-Feng   Wang, Jie   Liu, Jian-Zhong   Cheng, Jun   Wang, Zhi-Hua   Zhou, Jun-Hu   Cen, Ke-Fa  

    The pore characteristics and slurryability of two coal blends between Shigang anthracite coal and Huangling bituminous coal (SG/HL), and Guizhou anthracite coal and Xiaotun lean coal (GZ/XT), respectively, were investigated. The fractal dimensions of coal were calculated in the two regions of P/P-0 < 0.45 and P/P-0 > 0.45 and defined as D, and D-2, respectively. Upon an increase in the blending ratio of parent coal with smaller BET surface area (SBET) and total pore volume (TPV), the S-BET and TPV of coal blends monotonously decreased. D-1 was mainly related to the Smeso/macro(10-220 nm)/S-total and mineral phase within coal while D-2 was closely affected by the Vmeso(2-10 nm)/V-total. D-1 of SG/HL coal blends had no apparent linear correlation with the pore structure parameters whereas I), of GZ/XT coal blends changed linearly with the pore structure parameters. Both D-2 of SG/HL coal blends and that of GZ/XT coal blends changed linearly with the pore structure parameters. The slurry quality of coal water slurry (CWS) prepared from coal blends is comprehensively affected by the physicochemical properties and blending ratio of parent coals. Therefore, the maximum solid loading (MSL) and water separation ratio (WSR) of CWS prepared from coal blends do not always change linearly with the blending ratio of parent coal.
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  • Treating PCDD/Fs by combined catalysis and activated carbon adsorption.

    Ji, Sha-sha   Ren, Yong   Buekens, Alfons   Chen, Tong   Lu, Sheng-yong   Cen, Ke-fa   Li, Xiao-Dong  

    V2O5-WO3/TiO2 catalysts are used to destroy dioxins present in the gas phase, yet both their removal efficiency (RE) and destruction efficiency (DE) decrease with rising initial concentration (IC). Therefore, activated carbons (AC-1: based on lignite; AC-2: based on coconut shell) were mixed with the catalyst to tackle these high IC gases. A gas phase dioxin-generating system was used to supply three different stable IC-values. When the highest IC is used (20.5 ng I-TEQ Nm(-3)) without AC, at 200=C2=B0C, the RE and DE-value of PCDD/Fs reaches only 76% and 64%, respectively. At the same conditions, using a mix of catalyst and AC-2, these RE and DE-values rise to 90.1% and 82.0%, respectively. The mix catalyst/AC also shows better performance at low temperature (160 and 180=C2=B0C). The AC characteristics influence upon the adsorption and degradation abilities of the mixtures. Copyright =C2=A9 2013 Elsevier Ltd. All rights reserved.
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  • Ozone-enhanced oxidation of PCDD/Fs over V2O5-TiO2-based catalyst

    Ren, Yong   Chen, Tong   Cen, Ke-Fa   Ni, Ming-Jiang   Buekens, Alfons  

    The catalytic oxidation of PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) vapors was studied in a temperature range of 180-220 degrees C on a honeycomb V2O5-TiO2-based catalyst, in the presence and the absence of ozone. A stable dioxin-generating system was established to support the experimental program and this system could adjust the concentration of PCDD/Fs by injecting appropriate mother liquors. At 220 degrees C the removal efficiency(1) (RE) of PCDD/Fs reaches up to 97% and the degradation efficiency (DE) up to 90%. Both values diminish at lower operating temperatures. In the presence of ozone, however, these values rise to 99% and 98% at 220 degrees C. Especially at low temperatures the effect of ozone is obvious. Catalytic oxidation with ozone thus offers a low-temperature solution to achieve higher rates and low activation energies. The morphology and microstructure of the catalysts changes after ozone treatment and some of their characteristics seem closely related with DE-values. (C) 2013 Elsevier Ltd. All rights reserved.
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  • Instrumentation of rainbow refractometry:portable design and performance testing

    Wu, Xue-cheng   Li, Can   Cao, Kai-lin   Cao, Jian-zheng   Wu, Ying-chun   Chen, Ling-hong   Gao, Xiang   Grehan, Gerard   Cen, Ke-fa  

    Accurate measurement of various key parameters is indispensable for the characterization of spray droplets. Global rainbow refractometry shows great potential for its unique capability of measuring the refractive index (RI) of a droplet, but is still restricted to the laboratory. A portable design of a global rainbow refractometry instrument is implemented based on a new optical layout, with software developed as well. This instrument has four operation modes in its hardware design. Performance testing on the instrument consists of image quality, multi-working distance measurement, and measurement accuracy. The quality of the rainbow image is improved using the new system. The results of the multi-working distance measurement show that the measured refractive indices with working distances of 16, 25, and 30 cm are exact with a maximum deviation of about 2 x 10(-4), while the deviation is as large as 1.2 x 10(-3) at 50 cm, which is explained by the aberration from a long working distance (<=3D 32-35 cm). The measurement accuracy is verified further by ethanol-water spray droplets with volume concentrations of 0%-100%. The mean error of the RI measurement is about 2 x 10-4 at different concentrations. The measured mean droplet diameter has an accuracy of 2 mu m in the experiments. The rainbow refractometry instrument has great potential for in situ measurement of various sprays, i.e. spray combustion/pollutant removal in a large containment.
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  • Slurry characteristics and mechanism analysis of petroleum coke-coal water slurry

    Wang, Shuang-Ni   Liu, Jian-Zhong   Wang, Yi   Li, Ning   Cen, Ke-Fa  

    Petroleum coke-coal slurry (PCCS) was prepared by blending sub-bituminous coal with petroleum coke in different proportions. The rheology and stability of PCCS were studied, and the mechanism of dispersion and stability was analyzed. Results show that with the increase of the mass ratio of petroleum coke to Shenhua coal (alpha) in PCCS, the apparent viscosity of the slurry gradually increases, and the stability of the slurry decreases. Moreover, the contact angle also increases, indicating that the surface hydrophobicity was increased. When the alpha is 3:7, the fixed viscosity concentration of PCCS is above 60%, the fixed viscosity flow characteristic index is below 0.9, and the fixed segregation water rate is below 5%. Blending petroleum coke with Shenhua coal takes advantage of the complementary properties of the two materials and obtains PCCS with high concentration and improved stability.
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  • Novel Methods for Flame Pulsation Frequency Measurement with Image Analysis

    Wu, Ying-chun   Wu, Xue-cheng   Cen, Ke-fa   Wu, Ying-chun   Lu, Shou-xiang   Zhang, Jia-qing  

    To characterize the periodic pulsation of flame from the flame image sequence, several novel methods for flame pulsation measurement were introduced and demonstrated based on flame image analysis. Results show that moment function of flame image, such as weighted Euclidean distance and cross correlation coefficient, could represent the geometric and periodic flame pulsation; and that both the vertical and horizontal flame image slices (intersection of the cutting plane and the flame image sequence) evidently exhibit periodic texture resulted from flame oscillation. Flame pulsation frequency evaluated from flame image moment function, flame image slice and three-dimensional fast Fourier transform (FFT) is consistent and stable. For low instrument requirement and reliable performance, methods show great potential in flame diagnosis and monitor application.
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  • Slurry characteristics and mechanism analysis of petroleum coke-coal water slurry

    Wang, Shuang-Ni   Liu, Jian-Zhong   Wang, Yi   Li, Ning   Cen, Ke-Fa  

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  • Filtration combustion characteristics of low calorific gas in SiC foams

    Zheng, Cheng-Hang   Cheng, Le-Ming   Li, Tao   Luo, Zhong-Yang   Cen, Ke-Fa  

    This study investigated the combustion characteristics of low calorific gas in silicon carbide (SiC) foam. The temperature distribution, reaction zone, maximum temperature, and combustion wave propagation velocity were analysed at different inlet velocities, equivalence ratios of premixed gases, and pore densities. The temperature distribution near the reaction zone was determined by a time-based method. Super-adiabatic combustion was obtained in porous media under different conditions. The experimental results showed that higher temperatures were obtained in SiC foams of 30 pores per inch (PPI) than those measured for foam of 20 PPI. Increased equivalence ratio of premixed gases and pore density led to a thicker reaction zone and a higher preheating efficiency in the preheating zone. The combustion wave propagation velocity, which was less than 2 mm/s under these experimental conditions, was increased with increased inlet velocity and decreased equivalence ratio of premixed gases. The combustion wave propagation in foams of 20 PPI had the lowest velocity because of the good match of convection and radiation. (C) 2009 Elsevier Ltd. All rights reserved.
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  • Gas-Phase Elemental Mercury Removal by CeO(2) Impregnated Activated Coke

    Hua, Xiao-yu   Zhou, Jin-song   Li, Qiankun   Luo, Zhong-yang   Cen, Ke-fa  

    We have studied gas-phase elemental mercury (Hg(0)) capture by a CeO(2) loaded activated coke (AC) using a laboratory-scale fixed-bed reactor under simulated flue gas conditions. Through systematic investigation on the CeO(2) loading, temperature, and acid gases such as SO(2) and HCl, we have found that the Hg(0) capture capability of CeO(2)/AC was much higher than that of AC alone. Furthermore, we have successfully removed Hg(0) by CeO(2)/AC in the presence of SO(2), which is aimed at high-sulfur coal resources. The results showed that the coexistence of SO(2) and CeO(2) has significantly improved the Hg(0) removal efficiency. The Hg(0) capture capability of CeO(2)/AC was 50% higher than that of AC when the concentration of SO(2) was 500 ppm. As the SO(2) concentration increased to 5000 ppm, the Hg(0) capture capability decreased slightly, which indicates the important role of CeO(2) in Hg(0) oxidation and capture. In addition, X-ray photoelectron spectroscopy analysis demonstrates that the Hg captured by CeO(2)/AC was mainly in the forms of HgO and HgSO(4), and the presence of HCl resulted in a higher level of mercury oxidation at 120 degrees C.
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  • Theoretical Study on Destruction Mechanism of 2,3,7,8-TCDD by O(3) and NO(3)

    Wang, Zhi-hua   Wen, Zheng-cheng   Xu, Jiang-rong   Zhou, Jun-hu   Cen, Ke-fa  

    In order to improve the destruction efficiency of dioxins and also for developing new dioxin control technology, the destruction mechanisms of 2,3,7,8-tetrachlorodihenzo-p-dioxin (2,3,7,8-TCDD) by O(3) and NO(3), were investigated employing quantum chemical calculations. For involved reactions, the microcosmic reaction processes were analyzed and depicted in detail based on geometry optimizations made by the B3LYP/6-31G(d) method. At the same time, the reaction activation energies were also calculated at the MP2/6-311G (d,p)//B3LYP/6-31G(d) level. Configuration analysis indicated that 2,3,7,8-TCDD could be destroyed by O(3) and NO(3) in two different ways. The destruction of 2,3,7,8-TCDD by O(3) proceeded via the addition of O(3) and the cleavage of C=C while the destruction of 2,3,7,8-TCDD by NO(3) proceeded via the substitution of chlorine by NO(3). Calculated results show that, the activation energy of the destruction reaction of 2,3,7,8-TCDD by NO(3) (267.48 kJ/mol) is much larger than that of the destruction reaction of 2,3,7,8-TCDD by O(3) (51.20 kJ/mol). This indicated that the destruction of 2,3,7,8-TCDD by O(3) is much more efficient than that of 2,3,7,8-TCDD by NO(3). The reason why the activation energy for the destruction reaction of 2,3,7,8-TCDD by NO(3) is so large, is also discussed.
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  • A Ce-Cu-Ti oxide catalyst for the selective catalytic reduction of NO with NH3

    Gao, Xiang   Du, Xue-sen   Cui, Li-wen   Fu, Yin-cheng   Luo, Zhong-yang   Cen, Ke-fa  

    A Ce-Cu-Ti complex oxide catalyst for the selective catalytic reduction of NO with NH3 was prepared by coprecipitation method XRD and H-2-TPR reveal that the strong interaction between Ce and Cu results in the production of a new active oxygen species with high reducibility at low temperatures Compared with Ce-Ti oxide catalyst the Ce-Cu-Ti oxide catalyst produces better performance at the temperatures lower than 350 C and higher SO2-resistent ability H2O will reduce the SCR activity of Ce-Cu-Ti catalyst at low temperatures while promoting the catalyst performance at temperatures more than 350 C (C) 2010 Elsevier B V All rights reserved
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  • Low-temperature gasification of waste tire in a fluidized bed

    Xiao, Gang   Ni, Ming-Jiang   Chi, Yong   Cen, Ke-Fa  

    In order to recovery energy and materials from waste tire efficiently, low-temperature gasification is proposed. Experiments are carried out in a lab-scale fluidized bed at 400-800 degrees C when equivalence ratio (ER) is 0.2-0.6. Low heat value (LHV) of syngas increases with increasing temperature or decreasing ER, and the yield is in proportion to ER linearly. The yield of carbon black decreases with increasing temperature or ER lightly. When temperature is over 600 degrees C, characteristics of carbon black is similar. When temperature is over 700 degrees C, LHV of syngas rises up lightly with increasing temperature, which indicates that it hardly facilitates gasification any more. It is suitable for tire gasification when temperature is 650700 degrees C and ER is 0.2-0.4. Under this condition, LHV and yield of syngas are about 4000-9000 kJ/Nm(3) and 1.8-3.7 Nm(3) /kg, respectively; surface area and yield of carbon black lie in range of 20-30 m(3)/g and 550-650 g/kg, respectively. The carbon balance of these experiments achieves 85-95% when temperature is over 600 degrees C. (c) 2008 Elsevier Ltd. All rights reserved.
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  • Emission characteristics of volatile compounds during sludges drying process

    Deng, Wen-Yi   Li, Xiao-Dong   Wang, Fei   Zhu, Xiao-Wan   Lu, Sheng-Yong   Cen, Ke-Fa  

    The emission characteristics of volatile compounds (VCs) during municipal sewage sludge (MSS) and paper mill sludge (PMS) drying process were investigated through experiments conducted on a lab-scale tubular drying furnace and a pilot-scale paddle dryer, respectively. The result indicated that five kinds of VCs, i.e. CO2, NH3, C7H16 (n-heptane), volatile fatty acids (VFAs) and CH4 were emitted during the drying process. It was found that the NH3 and CO2 were the primary compound released from the MSS drying process. In the case of the PMS, the VFAs and CO2 were the main compounds released. The temperature and water content of sludge had great effects on the emission rates of NH3, C7H6, CO2 and VFAs. The pH and chemical oxygen demand (COD) of condensate from the paddle dryer were also studied. It showed that pH and COD of condensate from MSS were much higher than that from the PMS, and that the higher COD value of the MISS condensate interrelated to the higher ammonium and sulfur content of it. (C) 2008 Elsevier B.V. All rights reserved.
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  • Effects of different drying methods on the grinding characteristics of Ximeng lignite

    Zhu, Jie-Feng   Liu, Jian-Zhong   Wu, Jun-Hong   Cheng, Jun   Wang, Zhi-Hua   Zhou, Jun-Hu   Cen, Ke-Fa  

    Ximeng lignite (XL) was treated by using different drying methods, namely, conventional, microwave, and combination, to investigate their effects on the grinding characteristics of XL. The controlled mechanisms that improved the grindability of XL treated by different drying methods were analyzed with proximate analysis and scanning electron microscope. Results showed that the removal moisture and the physical structure damage induced by thermal stress or steam jet flow improved the grindability of treated XL. Microwave drying had the most remarkable effect on the grindability of XL. The increments in grindability of XL irradiated for 0.5 and 3 min were 44.03% and 200.45%, respectively. Compared with conventional dying, combined drying simultaneously improved grindability of XL, and reduced energy consumption. However, combined drying reduced the effects of microwave drying on the increment in the grindability of XL. Drying treatment for a short period could not effectively increase the mass fraction of finely ground product unless drying time was properly prolonged. According to the economy evaluation at lab scale, treatment of XL by microwave drying for a short period improved the grindability of treated XL and achieved a maximum energy saving of around 10% after a long period of the grinding process. (C) 2015 Elsevier Ltd. All rights reserved.
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  • Application of rainbow refractometry for measurement of droplets with solid inclusions

    Li, Can   Wu, Xue-cheng   Cao, Jian-zheng   Chen, Ling-hong   Grehan, Gerard   Cen, Ke-fa  

    Characterization of droplets with solid inclusions is of great research interest and has wide industrial applications. Reported here is a theoretical and experimental investigation of the measurement of droplets with solid inclusions using rainbow refractometry. A rainbow extinction model of a droplet with solid inclusions was deduced based on Beer-Lambert's Law. It takes into account the volume concentration, relative size, scattering efficiency of the solid inclusion, and liquid refractive index. An acoustic levitation system for a single droplet and a global rainbow instrumentation system for spray were integrated to study the effect of the H2O-CaCO3 suspension droplets on the rainbow signal and the measured parameters. The results showed that the rainbow encountered unusual disturbances, introduced by the solid inclusions, but its overall structure was not destroyed. Discoveries also included that for volume concentrations of 2.5% or less the CaCO3 particles with diameters below 41,im had little effect on the measured parameters of the host droplet. The extinction characteristic was also analyzed. The rainbow extinction model failed to quantity the volume concentration of CaCO3, but succeeded in its qualitative analysis. (C) 2017 Elsevier Ltd. All rights reserved.
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  • Destruction of PCDD/Fs by gliding arc discharges.

    Yan, Jian-hua   Peng, Zheng   Lu, Sheng-yong   Du, Chang-ming   Li, Xiao-dong   Chen, Tong   Ni, Ming-jiang   Cen, Ke-fa  

    PCDD/Fs have been become a serious issue because of their toxicological effects and associated adverse health implications. In this study, the gliding arc plasma was tested for treatment of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), which was synthesized from pentachlorophenol in atmospheric condition at 350 degrees C with or without the catalysis of CuCl2. From the experiment, we found that the destruction efficiency of PCDD/F homologues after gliding was discharge ranged from 25% to 79%. This result demonstrates that gliding arc plasma is an effective technology to decompose PCDDs/Fs in flue gas. A plausible degradation mechanism for PCDD/Fs by gliding arc was discussed. Finally, a multistage reactor structure of gliding arc was proposed to upgrade removal efficiency for PCDD/Fs.
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