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1.
V. Ratna Kishore Ringkhang MuchaharyAnjan Ray M.R. Ravi 《International Journal of Hydrogen Energy》2009
Global warming due to CO2 emissions has led to the projection of hydrogen as an important fuel for future. A lot of research has been going on to design combustion appliances for hydrogen as fuel. This has necessitated fundamental research on combustion characteristics of hydrogen fuel. In this work, a combination of experiments and computational simulations was employed to study the effects of diluents (CO2, N2, and Ar) on the laminar burning velocity of premixed hydrogen/oxygen flames using the heat flux method. The experiments were conducted to measure laminar burning velocity for a range of equivalence ratios at atmospheric pressure and temperature (300 K) with reactant mixtures containing varying concentrations of CO2, N2, and Ar as diluents. Measured burning velocities were compared with computed results obtained from one-dimensional laminar premixed flame code PREMIX with detailed chemical kinetics and good agreement was obtained. The effectiveness of diluents in reduction of laminar burning velocity for a given diluent concentration is in the increasing order of argon, nitrogen, carbon dioxide. This may be due to increased capabilities either to quench the reaction zone by increased specific heat or due to reduced transport rates. The lean and stoichiometric H2/O2/CO2 flames with 65% CO2 dilution exhibited cellular flame structures. Detailed three-dimensional simulation was performed to understand lean H2/O2/CO2 cellular flame structure and cell count from computed flame matched well with the experimental cellular flame. 相似文献
2.
在目前煤炭依然作为能源主体的背景下,控制燃煤污染物排放有着重要意义。基于CFD数值模拟,建立伴流燃烧器模型,控制燃料、氧化剂入口流量恒定,设计了O2/CO2、O2/N2氧化剂氛围中O2浓度在21%~40%内的多种工况,对煤粉燃烧特性及燃烧产生的污染物进行了研究。分析了不同工况下煤粉燃烧的温度分布、燃烧速率、碳烟、NOx的生成情况。结果显示,在O2/CO2、O2/N2两种氧化剂氛围中,随着O2浓度的上升,煤粉燃烧温度升高、燃烧速率增大,碳烟生成量均增加,同等O2浓度条件下,O2/CO2氛围的煤粉燃烧温度和燃烧速率均高于O2/N2氛围,碳烟生成量小于O2/N2氛围,且O2/CO2... 相似文献
3.
Nawadee Srisiriwat Supaporn Therdthianwong Apichai Therdthianwong 《International Journal of Hydrogen Energy》2009
Oxidative steam reforming of ethanol at low oxygen to ethanol ratios was investigated over nickel catalysts on Al2O3 supports that were either unpromoted or promoted with CeO2, ZrO2 and CeO2–ZrO2. The promoted catalysts showed greater activity and a higher hydrogen yield than the unpromoted catalyst. The characterization of the Ni-based catalysts promoted with CeO2 and/or ZrO2 showed that the variations induced in the Al2O3 by the addition of CeO2 and/or ZrO2 alter the catalyst's properties by enhancing Ni dispersion and reducing Ni particle size. The promoters, especially CeO2–ZrO2, improved catalytic activity by increasing the H2 yield and the CO2/CO and the H2/CO values while decreasing coke formation. This results from the addition of ZrO2 into CeO2. This promoter highlights the advantages of oxygen storage capacity and of mobile oxygen vacancies that increase the number of surface oxygen species. The addition of oxygen facilitates the reaction by regenerating the surface oxygenation of the promoters and by oxidizing surface carbon species and carbon-containing products. 相似文献
4.
为掌握煤半焦与生物质在O2/N2和O2/CO2条件下的混燃特性及其影响因素,采用全自动物理化学吸附仪获得了煤半焦-生物质混合燃料的孔隙结构,采用热重实验分析了两种燃料的混燃特性和反应动力学,通过多元线性回归法研究了燃料比、比表面积与混燃特性参数之间的关系。结果表明,O2/N2气氛下,掺混生物质可改善煤半焦的着火、燃尽及综合燃烧特性;O2/CO2气氛下,掺混生物质能改善煤半焦的着火特性,但会延迟其燃尽。混燃的活化能在低温区和高温区有显著差异,生物质掺混比增大,两个温区的活化能都降低;两种气氛下,低温区的活化能相近,但O2/CO2气氛下高温区的活化能显著高于O2/N2气氛下的。O2/N2气氛下孔隙结构对燃烧特性的影响更显著,而O2/CO2气氛下... 相似文献
5.
采用管式炉研究了在O2/CO2气氛下添加CaCO3对PM2.5(空气动力学直径小于2.5,μm的颗粒物)排放特性的影响.试验采用荷电低压撞击器(ELPI)采集和分析燃烧后的PM2.5.结果表明,添加CaCO3是燃烧过程中影响PM2.5生成的重要因素.添加CaCO3后,生成PM1的数密度和质量浓度均降低,而PM1-2.5的数密度和质量浓度均略有增加,PM2.5粒径分布均呈双峰分布,峰值点分别出现在0.2,μm和2.0,μm左右.随着CaCO3添加质量分数的增加,PM2.5中的S、Pb、Cu、Na和K几种元素的浓度呈下降趋势. 相似文献
6.
Ahmed Al-Fatesh Sunit Kumar Singh G.S. Kanade Hanan Atia Anis H. Fakeeha Ahmed A. Ibrahim Ahmed Mohamed El-Toni Nitin K. Labhasetwar 《International Journal of Hydrogen Energy》2018,43(27):12069-12080
Ni (2.5 wt%) and Co (2.5 wt%) supported over ZrO2/Al2O3 were prepared by following a hydrolytic co-precipitation method. The synthesized catalysts were further promoted by Rh incorporation (0.01–1.00 wt%) and tested for their catalytic performance for dry CO2 reforming, combined steam–CO2 reforming and oxy–CO2 reforming of methane for production of syngas. The catalysts were characterized by using N2 physical adsorption, XRD, H2–TPR, SEM, CO2–TPD, NH3–TPD, TEM and TGA. The results revealed that ZrO2 phase was in crystalline form in the catalysts along with amorphous Al oxides. Ni and Co were confirmed to be in their respective spinel phases that were reducible to metallic form at 800 °C under H2. Ni and Co were well dispersed with their nano-crystalline nature. The catalyst with 0.2% loading of Rh showed superior performance in the studied reactions for reforming of methane. This catalyst also showed good coke resistance ability for dry CO2 reforming reaction with 3.8 wt% of carbon formation during the reaction as compared to 11.6 wt% carbon formation over the catalyst without Rh. The catalyst performance was stable throughout the reaction time for CH4 conversions, irrespective of carbon formation with slight decline (~1%) in CO2 conversion. For dry CO2 reforming reaction, this catalyst showed good conversion for both CH4 and CO2 (67.6% and 71.8% respectively) with a H2/CO ratio of 0.84, while for the Oxy-CO2 reforming reaction, the activity was superior with CH4 and CO2 conversions (73.7% and 83.8% respectively) and H2/CO ratio of 1.05. 相似文献
7.
在水平管式炉上通过在线烟气分析仪研究了O2/CO2气氛下生物质混合比例、温度、燃烧气氛及氧浓度对生物质混煤SO2排放特性的影响规律。结果表明,O2/CO2气氛下,随着生物质混合比例的增大,生物质混煤SO2释放峰值减小,SO2排放完毕的时间减少,SO2的排放量降低;随着温度的升高,生物质混煤SO2的排放量增加。O2/CO2和O2/N2气氛下随着氧浓度的增大,生物质混煤SO2的排放量均增加。相同氧浓度时,O2/CO2气氛下生物质混煤SO2的排放量略小于O2/N2气氛下的情况,其降低幅度约为5%左右。 相似文献
8.
Yongfeng Liu Fenghuai WangYanhui Cao Mingxia GaoHongge Pan 《International Journal of Hydrogen Energy》2010
Complex hydrides and Metal–N–H-based materials have attracted considerable attention due to their high hydrogen content. In this paper, a novel amide–hydride combined system was prepared by ball milling a mixture of Na2LiAlH6–Mg(NH2)2 in a molar ratio of 1:1.5. The hydrogen storage performances of the Na2LiAlH6–1.5Mg(NH2)2 system were systematically investigated by a series of dehydrogenation/hydrogenation evaluation and structural analyses. It was found that a total of ∼5.08 wt% of hydrogen, equivalent to 8.65 moles of H atoms, was desorbed from the Na2LiAlH6–1.5Mg(NH2)2 combined system. In-depth investigations revealed that the variable milling treatments resulted in the different dehydrogenation reaction pathways due to the combination of Al and N caused by the energetic milling. Hydrogen uptake experiment indicated that only ∼4 moles of H atoms could be reversibly stored in the Na2LiAlH6–1.5Mg(NH2)2 system perhaps due to the formation of AlN and Mg3N2 after dehydrogenation. 相似文献
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12.
在沉降炉中进行了石灰石的脱硫特性研究.表明用20%O2+80%CO2的混合气体作助燃气时比用空气作助燃气时有较好的脱硫效果,并能减少NOx的排放,是一种新的能同时控制CO2,SO2和NOx三种污染物的好方法.图8参8 相似文献
13.
Wei Tao Hongwei Cheng Weilin Yao Xionggang Lu Qiuhua Zhu Guangshi Li Zhongfu Zhou 《International Journal of Hydrogen Energy》2014
Syngas production by CO2 reforming of coke oven gas (COG) was studied in a fixed-bed reactor over Ni/La2O3–ZrO2 catalysts. The catalysts were prepared by sol–gel technique and tested by XRF, BET, XRD, H2-TPR, TEM and TG–DSC. The influence of nickel loadings and calcination temperature of the catalysts on reforming reaction was measured. The characterization results revealed that all of the catalysts present excellent resistance to coking. The catalyst with appropriate nickel content and calcination temperature has better dispersion of active metal and higher conversion. It is found that the Ni/La2O3–ZrO2 catalyst with 10 wt% nickel loading provides the best catalytic activity with the conversions of CH4 and CO2 both more than 95% at 800 °C under the atmospheric pressure. The Ni/La2O3–ZrO2 catalysts show excellent catalytic performance and anti-carbon property, which will be of great prospects for catalytic CO2 reforming of COG in the future. 相似文献
14.
利用管式电阻炉在O2/CO2气氛和O2/N2气氛下对煤粉燃烧过程中NOx排放特性进行实验,研究在不同停留时间、炉内燃料/氧化学当量比、温度、氧浓度等因素对燃煤过程中NOx放特性的影响,并对这两种燃烧方式下NOx的排放特性进行对比。结果表明:在O2/CO2气氛下NOx的生成量要远远低于O2/N2气氛下NOx的生成量。随着停留时间的延长,NOx沿程释放特性是先增大后减少。随着燃料/氧化学当量比的增加,NOx排放浓度也呈现出先增加后降低的趋势。随着炉内温度的增加,2种气氛下NOx的排放浓度均增加。随着氧浓度的提高,NOx排放浓度增大。 相似文献
15.
Won-Jun Jang Dae-Woon Jeong Jae-Oh Shim Hyun-Seog Roh In Hyuk Son Seung Jae Lee 《International Journal of Hydrogen Energy》2013
Ni–Ce0.8Zr0.2O2 and Ni–MgO–Ce0.8Zr0.2O2 catalysts were investigated for H2 production from CO2 reforming of CH4 reaction at a very high gas hourly space velocity of 480,000 h−1. Ni–MgO–Ce0.8Zr0.2O2 exhibited higher catalytic activity and stability (CH4 conversion >95% at 800 °C for 200 h). The outstanding catalytic performance is mainly due to the basic nature of MgO and an intimate interaction between Ni and MgO. 相似文献
16.
采用反应分子动力学(ReaxFF MD)模拟方法研究了O2/CO2/H2O气氛下CO的燃烧。结果表明:根据化学平衡原理,高浓度CO2抑制CO的氧化,同时CO2在高温下参与反应CO2+H—→CO+OH,进一步抑制CO氧化。在较低温度条件下,较高浓度H2O的三体效应显著,抑制了CO氧化。另一方面,在较高温度条件下,H2O参与的H2O+H—→H2+OH和H2O+O—→OH+OH反应占据其化学作用的主导地位,进而促进CO氧化。随着O2浓度的增加,CO的氧化速度加快。 相似文献
17.
Jiasheng Wang Shumin Han Wei Zhang Dan Liang Yuan Li Xin Zhao Ruibing Wang 《International Journal of Hydrogen Energy》2013
A 2LiBH4–MgH2–MoS2 composite was prepared by solid-state ball milling, and the effects of MoS2 as an additive on the hydrogen storage properties of 2LiBH4–MgH2 system together with the corresponding mechanism were investigated. As shown in the TG–DSC and MS results, with the addition of 20 wt.% of MoS2, the onset dehydrogenation temperature is reduced to 206 °C, which is 113 °C lower than that of the pristine 2LiBH4–MgH2 system. Meanwhile, the total dehydrogenation amount can be increased from 9.26 wt.% to 10.47 wt.%, and no gas impurities such as B2H6 and H2S are released. Furthermore, MoS2 improves the dehydrogenation kinetics, and lowers the activation energy (Ea) 34.49 kJ mol−1 of the dehydrogenation reaction between Mg and LiBH4 to a value lower than that of the pristine 2LiBH4–MgH2 sample. According to the XRD test, Li2S and MoB2 are formed by the reaction between LiBH4 and MoS2, which act as catalysts and are responsible for the improved hydrogen storage properties of the 2LiBH4–MgH2 system. 相似文献
18.
Jinhua Wang Zuohua Huang Hideaki Kobayashi Yasuhiro Ogami 《International Journal of Hydrogen Energy》2012
Laminar burning velocities of CO–H2–CO2–O2 flames were measured by using the outwardly spherical propagating flame method. The effect of large fraction of hydrogen and CO2 on flame radiation, chemical reaction, and intrinsic flame instability were investigated. Results show that the laminar burning velocities of CO–H2–CO2–O2 mixtures increase with the increase of hydrogen fraction and decrease with the increase of CO2 fraction. The effect of hydrogen fraction on laminar burning velocity is weakened with the increase of CO2 fraction. The Davis et al. syngas mechanism can be used to calculate the syngas oxyfuel combustion at low hydrogen and CO2 fraction but needs to be revised and validated by additional experimental data for the high hydrogen and CO2 fraction. The radiation of syngas oxyfuel flame is much stronger than that of syngas–air and hydrocarbons–air flame due to the existence of large amount of CO2 in the flame. The CO2 acts as an inhibitor in the reaction process of syngas oxyfuel combustion due to the competition of the reactions of H + O2 = O + OH, CO + OH = CO2 + H and H + O2(+M) = HO2(+M) on H radical. Flame cellular structure is promoted with the increase of hydrogen fraction and is suppressed with the increase of CO2 fraction due to the combination effect of hydrodynamic and thermal-diffusive instability. 相似文献
19.
Effective nanoconfinement of 2LiBH4–MgH2 via simply MgH2 premilling for reversible hydrogen storages
Rapee Gosalawit–Utke Sophida Thiangviriya Payam Javadian Daniel Laipple Claudio Pistidda Nils Bergemann Christian Horstmann Torben R. Jensen Thomas Klassen Martin Dornheim 《International Journal of Hydrogen Energy》2014
To improve nanoconfinement of LiBH4 and MgH2 in carbon aerogel scaffold (CAS), particle size reduction of MgH2 by premilling technique before melt infiltration is proposed. MgH2 is premilled for 5 h prior to milling with LiBH4 and nanoconfinement in CAS to obtained nanoconfined 2LiBH4–premilled MgH2. Significant confinement of both LiBH4 and MgH2 in CAS, confirmed by SEM–EDS–mapping results, is achieved due to MgH2 premilling. Due to effective nanoconfinement, enhancement of CAS:hydride composite weight ratio to 1:1, resulting in increase of hydrogen storage capacity, is possible. Nanoconfined 2LiBH4–premilled MgH2 reveals a single–step dehydrogenation at 345 °C with no B2H6 release, while dehydrogenation of nanoconfined sample without MgH2 premilling performs in multiple steps at elevated temperatures (up to 430 °C) together with considerable amount of B2H6 release. Activation energy (EA) for the main dehydrogenation of nanoconfined 2LiBH4–premilled MgH2 is considerably lower than those of LiBH4 and MgH2 of bulk 2LiBH4–MgH2 (ΔEA = 31.9 and 55.8 kJ/mol with respect to LiBH4 and MgH2, respectively). Approximately twice faster dehydrogenation rate are accomplished after MgH2 premilling. Three hydrogen release (T = 320 °C, P(H2) = 3–4 bar) and uptake (T = 320–325 °C, P(H2) = 84 bar) cycles of nanoconfined 2LiBH4–premilled MgH2 reveal up to 4.96 wt. % H2 (10 wt. % H2 with respect to hydride composite content), while the 1st desorption of nanoconfined sample without MgH2 premilling gives 4.30 wt. % of combined B2H6 and H2 gases. It should be remarked that not only kinetic improvement and B2H6 suppression are obtained by MgH2 premilling, but also the lowest dehydrogenation temperature (T = 320 °C) among other modified 2LiBH4–MgH2 systems is acquired. 相似文献
20.
Jason R. Hattrick-Simpers James E. Maslar Michael U. Niemann Chun Chiu Sesha S. Srinivasan Elias K. Stefanakos Leonid A. Bendersky 《International Journal of Hydrogen Energy》2010
In situ Raman spectroscopy was used to monitor the dehydrogenation of ball-milled mixtures of LiNH2–LiBH4–MgH2 nanoparticles. The as-milled powders were found to contain a mixture of Li4BN3H10 and Mg(NH2)2, with no evidence of residual LiNH2 or LiBH4. It was observed that the dehydrogenation of both of Li4BN3H10 and Mg(NH2)2 begins at 353 K. The Mg(NH2)2 was completely consumed by 415 K, while Li4BN3H10 persisted and continued to release hydrogen up to 453 K. At higher temperatures Li4BN3H10 melts and reacts with MgH2 to form Li2Mg(NH)2 and hydrogen gas. Cycling studies of the ball-milled mixture at 423 K and 8 MPa (80 bar) found that during rehydrogenation of Li4BN3H10 Raman spectral modes reappear, indicating partial reversal of the Li4BN3H10 to Li2Mg(NH)2 transformation. 相似文献