| 1. |
- Hesameddin, Fatehi, et al.
(författare)
-
LIBS measurements and numerical studies of potassium release during biomass gasification
- 2015
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 35:2, s. 2389-2396
-
Tidskriftsartikel (refereegranskat)abstract
- This paper reports on a joint numerical and experimental investigation of the release of potassium from biomass during gasification process. In this work, laser-induced breakdown spectroscopy (LIBS) was adopted to measure quantitatively the concentration of potassium from gasifying biomass. The effect of temperature on the potassium release is investigated in hot gas mixture of CO2, H2O with different concentration of O-2. A biomass thermochemical conversion model is employed to study the physical and chemical processes inside the particle. A sub-model is developed to simulate the various stages of potassium release during biomass conversion and to improve the chemical kinetic mechanism and chemical kinetic constants of the release rate. Two stages of the potassium release associated to devolatilization and char reaction and ash-cooking stages are proposed. The rate of release of potassium during char reaction and ash-cooking stages follows a first order Arrhenius expression as 2.5 X 10(5 +/- 0.2) exp (-266 X 10(3)/RT). The kinetics rate constants along with the reaction path appear to be able to predict the potassium release with an acceptable accuracy. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
|
|
| 2. |
- Wang, Z. H., et al.
(författare)
-
Effect of H-2/CO ratio and N-2/CO2 dilution rate on laminar burning velocity of syngas investigated by direct measurement and simulation
- 2015
-
Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 141, s. 285-292
-
Tidskriftsartikel (refereegranskat)abstract
- Laminar burning velocities of syngas/air premixed flames, varying with H-2/CO ratio (from 5/95 to 75/25) and N-2 or CO2 dilution rate (from 0% to 60%), were accurately measured using a Teflon coated Heat Flux burner and OH-PLIF based Bunsen flame method. Experiments were carried out at atmospheric pressure and room temperature, with fuel/air equivalence ratios ranging from fuel-lean to fuel-rich. Coupled with experimental data, three chemical kinetic mechanisms, namely GRI-Mech 3.0, USC Mech II and Davis H-2-CO mechanism, were validated. All of them can provide good prediction for the laminar burning velocity. The laminar burning velocity variations with H-2 and dilution gas contents were systematically investigated. For given dilution gas fraction, the laminar burning velocity reduction rate was enhanced as H-2/CO ratio increasing. Effects of the syngas components and equivalence ratio variation on the concentrations of radical H and OH were also studied. It appears that there is a strong linear correlation between the laminar burning velocity and the maximum concentration of the H radical in the reaction zone for syngas. This characteristic is exclusively different from that in methane air premixed flame. These findings indicated that the high thermal diffusivity of the H radical played an important role in the laminar burning velocity enhancement and affected the laminar burning velocity reduction rate under dilution condition. (C) 2014 Elsevier Ltd. All rights reserved.
|
|
| 3. |
- Wang, Z. H., et al.
(författare)
-
Investigation of combustion enhancement by ozone additive in CH(4)/air flames using direct laminar burning velocity measurements and kinetic simulations
- 2012
-
Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 159:1, s. 120-129
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of ozone additive on the enhancement of the burning velocity for premixed methane-air flames is investigated by both experimental measurements and kinetic simulations. Laminar burning velocities with and without O(3) were directly measured using the Heat Flux method. The O(3) molecules were introduced into the system by a dielectric-barrier-discharge ozone generator installed in the O(2) gas line, which provided prompt control of on/off of the O(3) feed into the system, enabling a precise comparison of the measured burning velocity with and without ozone additives. Noticeable burning velocity enhancement was observed at off-stoichiometric conditions rather than stoichiometric conditions. With 3730 ppm O(3) additive in the oxidizer, experimental data shows similar to 8% burning velocity increase in fuel-rich mixtures and similar to 3.5% burning velocity increase for the stoichiometric mixture. With 7000 ppm ozone additive in the oxidizer, maximum similar to 16% burning velocity increase was observed at fuel-lean conditions while similar to 9.0% was found at fuel-rich conditions. An O(3) kinetic mechanism involving 16 elementary reactions together with the GRI-Mech 3.0 was composed and validated through CHEMKIN calculations, which gives good predictions of the burning velocities with and without O(3) additives. Extra O radicals contributed by O(3) molecules in the pre-heat zone initiate and accelerate the chain-branching reactions and consequently increase the burning velocity. (C) 2011 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
|
|
| 4. |
- Wang, Z. H., et al.
(författare)
-
Investigation of flue-gas treatment with O-3 injection using NO and NO2 planar laser-induced fluorescence
- 2010
-
Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 89:9, s. 2346-2352
-
Tidskriftsartikel (refereegranskat)abstract
- Direct ozone (O-3) injection is a promising flue-gas treatment technology based on oxidation of NO and Hg into soluble species like NO2, NO3, N2O5, oxidized mercury, etc. These product gases are then effectively removed from the flue gases with the wet flue gas desulfurization system for SO2. The kinetics and mixing behaviors of the oxidation process are important phenomena in development of practical applications. In this work, planar laser-induced fluorescence (PLIF) of NO and NO2 was utilized to investigate the reaction structures between a turbulent O-3 jet (dry air with 2000 ppm O-3) and a laminar co-flow of simulated flue gas (containing 200 ppm NO), prepared in co-axial tubes. The shape of the reaction zone and the NO conversion rate along with the downstream length were determined from the NO-PLIF measurements. About 62% of NO was oxidized at 15d (d, jet orifice diameter) by a 30 m/s O-3 jet with an influence width of about 6d in radius. The NO2 PLIF results support the conclusions deduced from the NO-PLIF measurements. (C) 2010 Elsevier Ltd. All rights reserved.
|
|
| 5. |
- Wang, Z. H., et al.
(författare)
-
Investigation on elemental mercury oxidation mechanism by non-thermal plasma treatment
- 2010
-
Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 91:11, s. 1395-1400
-
Tidskriftsartikel (refereegranskat)abstract
- Converting elemental mercury into divalent compound is one of the most important steps for mercury abatement from coal fired flue gas. The oxidation of elemental mercury was investigated in this paper using dielectric barrier discharge (DBD) non-thermal plasma (NTP) technology at room temperature. Effects of different flue gas components like oxygen, moisture, HCl, NO and SO2 were investigated. Results indicate that active radicals including O, O-3 and OH all contribute to the oxidation of elemental mercury. Under the conditions of 5% O-2 in the simulated flue gas, about 90.2% of Hg-0 was observed to be oxidized at 3.68 kV discharge voltage. The increase of discharge voltage, O-2 level and H2O content can all improve the oxidation rate, individually. With O-2 and H2O both existed, there is an optimal moisture level for the mercury oxidation during the NTP treatment. In this test, the observed optimal moisture level was around 0.74% by volume. Hydrogen chloride can promote the oxidation of mercury due to chlorine atoms produced in the plasma process. Both NO and SO2 have inhibitory effects on mercury oxidation, which can be attributed to their competitive consumption of O-3 and O. (c) 2010 Elsevier By. All rights reserved.
|
|
| 6. |
- Weng, W. B., et al.
(författare)
-
Effect of N-2/CO2 dilution on laminar burning velocity of H-2-CO-O-2 oxy-fuel premixed flame
- 2015
-
Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 1879-3487 .- 0360-3199. ; 40:2, s. 1203-1211
-
Tidskriftsartikel (refereegranskat)abstract
- The dilution effect of N-2/CO2 on the laminar burning velocity of H-2-CO-O-2 mixtures was investigated. The dilution fraction of N-2 and CO2 in the unburned mixtures varied from 0% to 70% and 0%-50%, respectively, and H-2 content in H-2-CO fuels altered from 5% to 100%. All the studies were carried out at standard laboratory conditions (1 atm, 298 K) with equivalence ratio changing from 0.6 to 2.0. The Heat flux method and OH-PLIF (Planar Laser-Induced Fluorescence) based Bunsen flame method were employed to measure the laminar burning velocities. The Li mechanism was used in simulations, due to its good prediction of laminar burning velocities. Based on extensive experimental results, the correlations between dilution fraction and laminar burning velocity reduction rate were analyzed. It was found that, for a given dilution fraction, the reduction in laminar burning velocity is largely independent equivalence ratio and fuel H-2-CO mole fraction. This behavior does not extend to all fuels, e.g. methane. Exploiting the lack of dependence on equivalence ratio and fuel composition, a unified correlation equation was proposed which can be used to predict the laminar burning velocities of H2CO fuels for given fuel component, dilution rate and equivalence ratio. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
|
|
