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Laboratory-scale study of the suppression of PCDD/F emission during coal and MSW co-incineration

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Journal of Environmental Sciences 2007年第6期19卷 762-767页

作者： LU Sheng-yong YAN Jian-hua LI Xiao-dong NI Ming-jiang cen ke-fa State key Laboratory of Clean Energy Utilization Institute for Thermal Power Engineering Zhejiang University Hangzhou 310027 China

The experimental test of co-incinerating Chinese raw municipal solid waste （MSW） and coal in a laboratory-scale tubular reactor was first reported in present study, and the emission of normal gas components and the effects of the S/Cl molar ratio or coal mixing percentages on polychlorinated dibenzo-p-dioxins and dibenzofurans （PCDDs/Fs） emission were investigated and discussed. The results indicated that OCDD was the only PCDD homologues since others like TCDD-HpCDD was hardly detected, while as the categories of PCDF homologues were comparatively much more general. The amount of PCDD was much larger than that of PCDF in all operating conditions. Since ZPCDF/∑PCDD〈〈1, the dominant role of the precursor formation was proven in our experimental conductions. With increasing the coal addition to MSW （from 0 to 16%）, PCDD and PCDF were reduced considerably. Coal and MSW may suppress the PCDD/F emissions efficiently （over 95%） during the MSW incineration process. The PCDD/F suppression results of the present study could be helpful guidance to the industrial application of Chinese MSW and auxiliary coal co-incineration processes. The PCDD/F stack emission data of two industrial incinerators using co-incineration technology in China seem to have a great positive reduction of PCDDs/Fs.

关键词： co-incineration PCDDs/Fs suppression S/Cl molar ratio

Semi-analytical Monte Carlo simulation of laser-induced fluorescence propagation in an optically participating spray

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第7期8卷 1170-1178页

作者： CHEN Ling-hong ROZE Claude GARO Annie GIRASOLE Thierry cen ke-fa GREHAN Gérard State key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China Laboratoire d＇Electromagnétisme et Systémes Particulaires Universite ＆ INSA Rouen CORIA/CNRS UMR 6614 France

A semi-analytical Monte Carlo (SMC) simulation was developed to simulate the propagation of laser-induced fluo- rescence (LIF) in an optically participating spray, which simultaneously exhibits spectrally dependent emission, anisotropic scattering, absorption, and re-emission. The SMC simulation is described and then applied to an experimental configuration of a cloud of polydisperse droplets composed of water and sulforhodamine B dye. In the SMC simulation, the collected LIF flux on the remote receptor element is calculated as the global contribution from the emissive source, single, twice, … and nth collision events in any sequence. The effects on the fluorescence photons propagation of spray parameters like the dye concentration, droplets concentration, and droplets size are examined. Three spectral bands representing different optical properties are chosen to analyze the interference of absorption, scattering and re-emission on the detected LIF flux. The obtained spectral LIF flux distribution on the receptor demonstrates a “red shift” phenomenon.

关键词： Laser-induced fluorescence (LIF) Semi-analytical Monte Carlo (SMC) simulation Absorption Anisotropic scattering Re-emission Spray

Removal of PCDDs/Fs from municipal solid waste incineration by entrained-flow adsorption technology

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第11期7卷 1896-1903页

作者： YAN Jian-hua PENG Zheng LU Sheng-yong LI Xiao-dong cen ke-fa State key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

Entrained flow adsorption using activated carbon as the adsorbent is widely adopted for PCDDs/Fs-abatement in municipal solid waste incineration (MSWI) process. The effects of operating parameters including flue gas temperature, feeding rate of activated carbon, polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDDs/Fs) concentration at the inlet of the air pollution control device (APCD), filter materials, pressure drop on PCDDs/Fs removal efficiency are reviewed and commented upon in this paper. Evaluation on the various mechanistic models for entrained flow adsorption is carried out based on the computational simulation in terms of the actual operating condition and theoretical analysis. Finally, an advancement of en- trained flow adsorption in combination of dual bag filter is introduced.

关键词： PCDDs/Fs Entrained flow adsorption Operating parameters Mechanistic model Dual bag filters

Effect of oxidation treatment on the adsorption and the stability of mercury on activated carbon

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Journal of Environmental Sciences 2006年第6期18卷 1161-1166页

作者： HU Chang-xing ZHOU Jin-song LUO Zhong-yang HE Sheng WANG Guang-kai cen ke-fa State key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

Oxidation treatment on the adsorption and the stability of Hg on activated carbon （AC） was inrestigated. Both MnO2-AC and FeCl3-AC were produced during oxidation treatment. The measurement of modified AC＇s mercury adsorption capacity was conducted in a simulated coal-fired flue gas by adsorbing test apparatus. TCLP and column leaching methods were used to test the stability of mercury adsorbed on ACs. The results indicate that the oxidation treatment changed the pore structure of the AC and modified the carbon surface by creating chemical components such as MnO4^-, Mn^4＋, O, NO^3-, Fe^3＋, Cl^-, etc. The Hg sorption capacity on MnO2-AC or FeCl3-AC was about three times higher than that of untreated carbon. In addition, the mercury control cost of each of the formers was about the half cost of the untreated carbon. The stability of Hg absorption was studied, it found that mercury adsorbed on the oxidation treated AC was not better than that of untreated carbon. It could concluded that the insoluble form of Hg is very important to the stability of mercury adsorbed on AC. This study suggests that the FeCl3-AC is the best absorbent for Hg with high adsorption capacity, better Hg adsorption stability in leaching environment, and lower cost among the three ACs tested.

关键词： activated carbon oxidation treatment Hg adsorption stability

Fluidized-bed pyrolysis of waste bamboo

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第9期8卷 1495-1499页

作者： XIAO Gang NI Ming-jiang HUANG He CHI Yong XIAO Rui ZHONG Zhao-ping cen ke-fa key Lab. on Clean Coal Power Generation and Combustion Technology of Ministry of Education School of Energ3＂ and Environment Southeast University Nanjing 210096. China State key Lab. of Clean Energy Utilization College of Mechanical and Energy Engineering Zhejiang University Hangzhou 310027 China College of Lfe Science and Pharmaceutical Engineering Nanjing University of Technology Nanjing 210009 China

Bamboo was a popular material substituting for wood, especially for one-off commodity in China. In order to recover energy and materials from waste bamboo, the basic characteristics of bamboo pyrolysis were studied by a thermogravimetric analyzer. It implied that the reaction began at 190-210℃, and the percentage of solid product deceased from about 25% to 17% when temperature ranged from 400℃ to 700℃. A lab-scale fluidized-bed furnace was setup to research the detailed properties of gaseous, liquid and solid products respectively. When temperature increased from 400℃ to 700℃, the mass percent of solid product decreased from 27% to 17% approximately, while that of syngas rose up from 19% to 35%. When temperature was about 500℃, the percentage of tar reached the top, about 31%. The mass balance of these experiments was about 93%-95%. It indicated that three reactions involved in the process： pyrolysis of exterior bamboo, pyrolysis of interior bamboo and secondary pyrolysis of heavy tar.

关键词： Bamboo Pyrolysis Fluidized beds Syngas Tar

Study on pyrolysis and gasification of wood in MSW

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Journal of Environmental Sciences 2006年第2期18卷 407-415页

作者： NI Ming-jiang XIAO Gang CHI Yong YAN Jian-hua MIAO Qi ZHU Wen-li cen ke-fa Institute for Thermal Power Engineering State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

In order to develop municipal solid waste（MSW） pyrolysis/gasification and melting technology with low emission and high efficiency, it was planed that all the main components in MSW and some typical kinds of MSW were pyrolyzed/gasified to propose an expert system for raw MSW. In this paper, wood, which was a prevalent component in MSW, was pyrolyzed and gasified in fluidized-bed reactors at different apparent excess air ratios （EARs）, temperatures and fluidizing velocities. For pyrolysis, with tem- perature increasing from 400℃ to 700℃, the yield of pyrolysis char decreased while that of pyrolysis gas increased （in this paper respectively from 28% to 20% and from 10% to 35%）, and when temperature was 500℃, the yield of pyrolysis tar reached the highest, up to 38% in this paper. It was the optimum for gasification when temperature was 600℃ and apparent EAR was 0.4. Under the experimental conditions of this paper, gasification efficiency achieved 73%, lower heat value（LHV） reached 5800 kJ/（Nm^3） and yield of syngas was 2.01 Nm^3/kg. Lower fluidizing velocity was useful to upgrade gasification efficiency and LHV of syngas for wood gasification. Based on the results, the reactive courses and mechanism were analyzed respectively for wood pyrolysis and gasification.

关键词： wood pyrolysis gasification municipal solid waste(MSW)

Effects of inorganic chlorine source on dioxin formation using fly ash from a fluidized bed incinerator

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Journal of Environmental Sciences 2007年第6期19卷 756-761页

作者： LU Sheng-yong YAN Jian-hua LI Xiao-dong Ni Ming-jiang cen ke-fa DAI Hui-fen State key Laboratory of Clean Energy Utilization Institute for Thermal Power Engineering Zhejiang University Hangzhou 310027 China School of Medicine Zhejiang University Hangzhou 310058 China

Chlorine source is indispensable for polychlorinated dibenzo-p-dioxin and furan （PCDD/F） formation during municipal solid waste （MSW） incineration. Inorganic chlorine compounds were employed in this study to investigate their effects on PCDD/F formation through heterogeneous synthesis on fly ash surfaces. A fly ash sample obtained from a fluidized bed incinerator was sieved to different size fractions which served as the PCDD/F formation sources. The capability of different metal chlorides which facilitate the formation of PCDDs/Fs was found to follow the trends： Na 〈 Mg 〈 K 〈 AI 〈 Ca, when two particle fractions of 〉177 μm and 104-125 μm were used in the experiments. However, the capability of NaCI, MgCl2 and KCI did not seem much different from each other, whereas CaCl2 and AlCl3 were much more active in PCDD/F formation. NaCl and MgCl2 were relatively effective to produce more PCDDs, while KC1, AICl3 and CaCl2 generated more PCDFs during heterogeneous reactions occurring on fly ash. 2,3,7,8-TCDF was the most significant contributor to the toxicity of the PCDDs/Fs formed from inorganic chlorine sources. Decreasing the sizes of fly ash particles led to more active formation of PCDDs/Fs when NaCl was used as inorganic chlorine in the experiment. The highest PCDDs/Fs produced from particles with size 〈37 μm, while the lowest PCDDs/Fs produced from particles with size 〉177μm. The toxicity generally increased with decreasing size of the fly ash particles. The formation of PCDDs was mainly facilitated by the two size fractions, 104-125 μm and 〈37μm, while the formation of PCDFs was favored by the two other size fractions, 〉177 μm and 53-104 μm.

关键词： fly ash inorganic chlorine source PCDDs/Fs heterogeneous synthesis

Experimental and modeling study of de novo formation of PCDD/PCDF on MSW fly ash

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Journal of Environmental Sciences 2007年第1期19卷 117-122页

作者： LI Xiao-dong ZHANG Ji YAN Jian-hua cen ke-fa RYAN Shawn P GULLETT Brian K LEE Chunwai State key Laboratory of Clean Energy Utilization Institute for Thermal Power Engineering Zhefiang University Hangzhou 310027 China U.S. Environmental Protection Agency Office of Research and Development National Risk Management Research Laboratory E305-01 Research Triangle Park North Carolina 27711 USA

The effect of sulfur dioxide （SO2） on the formation of polychlorinated dibenzo-p-dioxins （PCDDs） and polychlorinated dibenzofurans （PCDFs） has been studied in an entrained-flow reactor （EFR） under simulated waste combustion conditions. A chlorination model based on conditional probability was employed to evaluate the homologue patterns of PCDDs and PCDFs. Results revealed that the presence of SO2 did not alter the formation pathway although SO2 suppressed PCDD/F formation. The prediction model of PCDF showed good agreement with the experimental data （R--0.95）, whereas the prediction for PCDDs did not correlate well with the experimental data. This may be explained because potential chlorination pathways play a significant role in PCDF formation, whereas PCDDs are mainly formed through condensation reactions. Furthermore, the result indicated that the steric hindrance during formation has more effects on PCDD than on PCDF due to the symmetric molecular structures of PCDDs.

关键词： PCDDs PCDFs de novo synthesis formation chlorination model sulfur dioxide air pollution waste combustion

Effects of Magnesium and Ferric Ions on Crystallization of Calcium Sulfate Dihydrate Under the Simulated Conditions of Wet Flue-gas Desulfurization

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Chemical Research in Chinese Universities 2008年第6期24卷 688-693页

作者： GAO Xiang HUO Wang ZHONG Yi LUO Zhong-yang cen ke-fa NI Ming-jiang CHEN Le-ming State key Laboratory of Clean Energy Utilization Institute of Thermal Energy and Power Engineering Zhejiang University Hangzhou 310027 P. R. China

The influences of magnesium and ferric ions in their different ratios on the rate of gypsum crystallization were studied under the conditions similar to those of wet flue-gas desulfurization（WFGD）. The results show that addition of both Mg^2＋ and Fe^3＋ increased induction time and decreased the growth efficiency up to 50% compared with the baseline（without impurities） depending on the concentration and the type of impurity. The effects of Mg^2＋ and Fe^3＋ on the surface energy and the rate of nucleation were estimated by employing the classical nucleation theory. The surface energy decreased by 8% and 14% with the addition of 0.02 mol/L magnesium or ferric ions, respectively, compared to the baseline. Mg^2＋ and Fe^3＋ made the growth rate of the （020）, （021） and （040） faces of gypsum crystal a much greater reduction, which leads to the formation of needle crystals compared to the baseline which favors the formation of plate or flakes. Furthermore, an edge detection program was developed to quantify the effects of impurities on the filtration rate of gypsum product. The results show that the inhibition efficiency of the presence of 0.02 mol/L Mg^2＋ and Fe^3＋ on the filtration rate of gypsum crystal ranges from 22% to 39%.

关键词： Calcium sulfate dihydrate Morphology Wet flue-gas desulfurization Filtration rate