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Emission characteristics and combustion instabilities in an oxy-fuel swirl-stabilized combustor

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第11期9卷 1582-1589页

作者： Guo-neng LI Hao ZHOU ke-fa cen State key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

This paper presents an experimental study on the emission characteristics and combustion instabilities of oxy-fuel combustions in a swirl-stabilized combustor. Different oxygen concentrations (Xoxy=25%～45%, where Xoxy is oxygen concentra- tion by volume), equivalence ratios (φ=0.75～1.15) and combustion powers (CP=1.08～2.02 kW) were investigated in the oxy-fuel (CH4/CO2/O2) combustions, and reference cases (Xoxy=25%～35%, CH4/N2/O2 flames) were covered. The results show that the oxygen concentration in the oxidant stream significantly affects the combustion delay in the oxy-fuel flames, and the equivalence ratio has a slight effect, whereas the combustion power shows no impact. The temperature levels of the oxy-fuel flames inside the combustion chamber are much higher (up to 38.7%) than those of the reference cases. Carbon monoxide was vastly produced when Xoxy>35% or φ>0.95 in the oxy-fuel flames, while no nitric oxide was found in the exhaust gases because no N2 participates in the combustion process. The combustion instability of the oxy-fuel combustion is very different from those of the reference cases with similar oxygen content. Oxy-fuel combustions excite strong oscillations in all cases studied Xoxy=25%～45%. However, no pressure fluctuations were detected in the reference cases when Xoxy>28.6% accomplished by heavily sooting flames which were not found in the oxy-fuel combustions. Spectrum analysis shows that the frequency of dynamic pressure oscillations exhibits randomness in the range of 50～250 Hz, therefore resulting in a very small resultant amplitude. Temporal oscillations are very strong with amplitudes larger than 200 Pa, even short time fast Fourier transform (FFT) analysis (0.08 s) shows that the pressure amplitude can be larger than 40 Pa.

关键词： Swirl Oxy-fuel Combustion instability Pollutant emissions

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CFD simulation with enhancement factor of sulfur dioxide absorption in the spray scrubber

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第11期9卷 1601-1613页

作者： Xiang GAO Wang HUO Zhong-yang LUO ke-fa cen State key Laboratory of Clean Energy Utilization Institute for Thermal Power Engineering Zhejiang University Hangzhou 310027 China

A model describing the absorption process of SO2 into limestone slurry with a spray scrubber is presented. Both the physical performance of the spray liquid in the scrubber and the involved chemical reactions are analyzed in the model. A con- tinuous concentration change of H+ was solved by iterative coupling using Matlab, and it was found that there was a remarkable influence on the concentration of the other elements in the process of SO2 absorption. The calculations show that the enhancement factor exponentially grows with an increasing value of pH and logarithmically decays with an increasing value of the driving force. To verify the accuracy of the model, experiments were also carried out, and the results suggest that the model, after combining the physical performance of the spray and the enhancement factor, can more precisely describe SO2 absorption in a spray scrubber. Furthermore, a commercial computational fluid dynamics (CFD) tool is used to perform several simulations which describe and clarify the effects of variables on SO2 absorption. The results of numerical simulation can provide a basis for further design and optimization of the scrubber.

关键词： SO2 absorption Limestone dissolution Enhancement factor Mass transfer Concentration profile

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A 3D numerical simulation of laser-induced incandescence of soot particles in coal combustion products

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第9期10卷 1320-1326页

作者： Ling-hong CHEN ke-fa cen Annie GARO Gerard GREHAN State key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China LESP UMR 6614/CORIA CNRS/Universite et INSA de Rouen Saint Etienne du Rouvray 76800 France

Laser-induced incandescence (LII) has received increasing attention as a potentially powerful technique for in-situ measuring of the volume fraction and primary size of soot particles in combustion systems. In this study, a 3D Monte Carlo simulation combined with a Mie equation was developed to analyze the influence of spectral absorption and scattering on the measured LII flux emitted by soot particles. This paper represents a first attempt to analyze soot measurement using the LII technique in coal combustion products. The combustion products of gases (CO2, N2), soot, and fly-ash particles, present between the location of laser-excited soot and the LII flux receiver. The simulation results indicated that an almost Beer-Lambert exponential decrease in LII flux occurred with an increase in the volume fraction of soot particles, while a nearly linear decrease occurred with an increase in the volume fraction of fly-ash particles. The results also showed that scattering effects of both soot and fly-ash particles on the LII flux could be neglected. Compared with the absorption of gases, a decrease of 20% of LII flux was observed with soot particles, and a decrease of 10% with fly-ash particles.

关键词： Laser-induced incandescence (LII) Soot Fly-ash 3D Monte Carlo Scattering Absorption

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NUMERICAL PREDICTION OF CROSS FLOW IN UNHEATED FURNACE

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Journal of Hydrodynamics 1991年第3期3卷 68-73页

作者： Jian-ren, fan Qiang, Hua ke-li, Zeng ke-fa, cen Zhejiang Univ Hangzhou China

This paper describes the results of a finite-difference solution for the three-dimensional flow field generated by a rectangular turbulent jet (secondary air) deflected by a main stream (primary air) in an unheated furnace. The essential properties of cross flow are discussed in the case of different shapes of the rectangular orifice, ratios of the secondary air injected velocity to the primary air velocity, and different injection angles. Last, two correlations equations are obtained and the numerical predictions are shown to demonstrate the good agreement with the experimental data.

关键词： Computers Applications Fluid Mechanics Furnaces Mathematical Models

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Quantum chemical study on the catalytic mechanism of Na/K on NO-char heterogeneous reactions during the coal reburning process

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第3期10卷 423-433页

作者： Zheng-cheng WEN Zhi-hua WANG Jun-hu ZHOU ke-fa cen State key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

Quantum chemical simulation was used to investigate the catalytic mechanism of Na/K on NO-char heterogeneous reactions during the coal reburning process. Both NO-char and NO-Na/K reactions were considered as three-step processes in this calculation. Based on geometry optimizations made using the UB3LYP/6-31G(d) method, the activation energies of NO-char and NO-Na/K reactions were calculated using the QCISD(T)/6-311G(d, p) method; Results showed that the activation energy of the NO-Na/K reaction (107.9/82.0 kJ/mol) was much lower than that of the NO-char reaction (245.1 kJ/mol). The reactions of NaO/KO and Na2O/K2O reduced by char were also studied, and their thermodynamics were calculated using the UB3LYP/6-31G(d) method; Results showed that both Na and K can be refreshed easily and rapidly by char at high temperature during the coal reburning process. Based on the calculations and analyses, the catalytic mechanism of Na/K on NO-char het-erogeneous reactions during the coal reburning process was clarified.

关键词： Catalytic mechanism Quantum chemistry Sodium Potassium Char NO

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Impact of individual acid flue gas components on mercury capture by heat-treated activated carbon

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2012年第9期13卷 700-708页

作者： Jian-ming ZHENG Jin-song ZHOU Zhong-yang LUO ke-fa cen State key Laboratory of Clean Energy Utilization Zhejiang UniversityHangzhou 310027China School of Mechanical Engineering Jimei UniversityXiamen 361021China

Elemental mercury capture on heat-treated activated carbon （TAC） was studied using a laboratory-scale fixed bed reactor. The capability of TAC to perform Hg0 capture under both N2 and baseline gas atmospheres was studied and the effects of common acid gas constituents were evaluated individually to avoid complications resulting from the coexistence of multiple components. The results suggest that surface functional groups （SFGs） on activated carbon （AC） are vital to Hg0 capture in the absence of acid gases. Meanwhile, the presence of acid gas components coupled with defective graphitic lattices on TAC plays an important role in effective Hg0 capture. The presence of HC1, NO2, and NO individually in basic gases markedly enhances Hg0 capture on TAC due to the heterogeneous oxidation of Hg0 on acidic sites created on the carbon surface and catalysis by the defective graphitic lattices on TAC. Similarly, the presence of SO2 improves Hg0 capture by about 20%. This improvement likely results from the deposition of sulfur groups on the AC surface and oxidation of the elemental mercury by SO2 due to catalysis on the carbon surface. Furthermore, O2 exhibits a synergistic effect on Hg0 oxidation and capture when acid gases are present in the flue gases.

关键词： Flue gases Mercury Activated carbon (AC)

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Simultaneous removal of ethyl acetate, benzene and toluene with gliding arc gas discharge

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第5期9卷 695-701页

作者： Zheng BO Jian-hua YAN Xiao-dong LI Yong CHI ke-fa cen State key Laboratory of Clean Energy Utilization Institute for Thermal Power Engineering Zhejiang University Hangzhou 310027 China

The simultaneous removal of ethyl acetate, benzene and toluene with relatively low or high initial concentration is studied using a laboratory scale gliding arc gas discharge (GA) reactor. Good decomposition efficiencies are obtained which proves that the GA is effective for the treatment of volatile organic compounds (VOCs) with either low or high concentration. A theoretical decomposition mechanism is proposed based on detection of the species in the plasma region and analysis of the decomposition by-products. This preliminary investigation reveals that the GA has potential to be applied to the treatment of exhaust air during color printing and coating works, by either direct removal or combination with activated carbon adsorption/desorption process.

关键词： Plasma Gliding arc gas discharge (GA) Volatile organic compounds (VOCs) Simultaneous removal Printing and coating process

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A quantum chemistry study on reaction mechanisms of SO_2 with O_3 and H_2O_2

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第9期10卷 1327-1333页

作者： Shu-dong JIANG Zhi-hua WANG Jun-hu ZHOU Zheng-cheng WEN ke-fa cen State key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

Reaction mechanisms of SO2 with O3 and H2O2 were investigated using quantum chemistry ab initio methods. Structures of all reactants, products, and transition states were optimized at the B3LYP/6-311G＋（3df,2p） level, and energy calculations were made at the G2M level. SO2 reactions with O3 and H2O2 occurred by O-abstraction and OH-abstraction by SO2, respectively, at length forming SO3＋O2 （3Eg） and H2SO4. For SO2＋O3 reactions the barrier height was predicted to be 9.68 kcal/mol with a rate constant of 3.61 × 10^-23 cm^3/（molecule.s） at 300 K, which is below the experimental upper limit. The rate constant predicted for this reaction accords well with the one provided by National Institute for Standards and Technology （NIST） in 250-500 K. For SO2＋H2O2 reactions the barrier height was predicted to be 62.39 kcal/mol with a rate constant of 2.48× 10^-61 cm^3/（molecule.s） at 300 K.

关键词： Sulfur dioxide Ozone Hydrogen peroxide Reaction mechanism Rate constant Quantum chemistry

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Absorption of NO_2 into Na_2S solution in a stirred tank reactor

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第3期10卷 434-438页

作者： Xiang GAO Rui-tang GUO Hong-lei DING Zhong-yang LUO ke-fa cen State key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China School of Energy Source and Environmental Engineering Shanghai University of Electric Power Shanghai 200090 China

To understand the absorption mechanism of nitrogen dioxide into a sodium sulfide solution, a stirred tank reactor with a plane gas-liquid interface was used to measure the chemical absorption rate of diluted nitrogen dioxide into sodium sulfide solution. The absorption rates under various experimental conditions were measured and the effects of experimental conditions on nitrogen dioxide absorption rate were discussed. The results show that, in the range of this study, nitrogen dioxide absorption rate increases with increasing sodium sulfide concentration, nitrogen dioxide inlet concentration, and flue gas flow rate, but decreases with increasing reaction temperature and oxygen content in flue gas.

关键词： Nitrogen dioxide Gas-liquid reaction Kinetics Absorption

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Occurrence of the Bunsen side reaction in the sulfur-iodine thermochemical cycle for hydrogen production

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第4期14卷 300-306页

作者： Qiao-qiao ZHU Yan-wei ZHANG Zhi YING Jun-hu ZHOU Zhi-hua WANG ke-fa cen State key Laboratory of Clean Energy Utilization Department of Energy EngineeringZhejiang University

This study aimed to establish a closed-cycle operation technology with high thermal efficiency in the thermochemical sulfur-iodine cycle for large-scale hydrogen production.A series of experimental studies were performed to investigate the occurrence of side reactions in both the H2SO4 and HI x phases from the H2SO4/HI/I2/H2O quaternary system within a constant temperature range of 323-363 *** effects of iodine content,water content and reaction temperature on the side reactions were *** results showed that an increase in the reaction temperature promoted the side ***,they were prevented as the iodine or water content *** occurrence of side reactions was faster in kinetics and more intense in the H2SO4 phase than in the HI x *** sulfur or hydrogen sulfide formation reaction or the reverse Bunsen reaction was validated under certain conditions.

关键词： Thermochemical sulfur-iodine cycle Hydrogen production Side reaction Sulfur Hydrogen sulfide

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