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1.
《International Journal of Hydrogen Energy》2022,47(29):13815-13827
Partial gasification of coal char was conducted with addition of metal oxides for co-production of fuel gas and methane decomposition catalysts. Effect of the metal composition (Ni, Co and Fe based mono- or bi-metals) was investigated on the fuel gas production and the resultant catalyst surface and textural properties, morphology and performance in catalytic methane decomposition (CMD). Besides H2-rich fuel gas production (the combustion energy up to 11.03–23.42 MJ/kgchar) from the gasification, the gasification residue can directly serve as the effective and efficient catalyst for CMD. The Fe and Fe–Co composite oxides were found to be better among the mono- and bi-metallic oxides for the fuel gas production during the gasification, respectively. The Ni-based mono-/bi-metallic catalysts could display high and stable methane conversion (up to 80%) during the 600-min CMD test at 850 °C. Promotional role of the second metal in CMD was discussed on the carbon diffusion, metal mobility and reducibility, formation and growth of the deposited carbons. The formed carbon morphology after CMD was analyzed based on the Kirkendall effect and Tammann temperature and further correlated to the potential catalyst deactivation. 相似文献
2.
Impacts of char structure evolution and inherent alkali and alkaline earth metallic species catalysis on reactivity during the coal char gasification with CO2/H2O 下载免费PDF全文
In this work, we studied the effects of char structural evolution and alkali and alkaline earth metallic species (AAEMs) catalysis on the reactivity during the char gasification with CO2, H2O, and their mixture. The gasified chars with different carbon conversion levels were prepared, and their physicochemical structures were characterized via nitrogen adsorption and FT‐Raman techniques. The concentrations of AAEMs in different modes were obtained by the sequential chemical extraction method. The reactivities of the raw and gasified chars were analyzed by the thermogravimetric analysis. The gasification atmospheres had varied effects on the physicochemical structure of coal char. The gasified char obtained in the CO2 atmosphere had a lower aromatic condensation degree compared with that obtained in the H2O atmosphere, irrespective of the temperature. The impact of the atmospheres on the specific surface area of the char varied with the temperature because H2O and CO2 have different routes of development of pore structure with coal char. A large specific surface area facilitates the exposure and dispersion of more AAEMs on the surface of the channel, which is conducive to their contact with the gasification agent to play the catalytic role. Thus, the reactivity of the gasified char is well correlated with its specific surface area at different gasification temperatures. In the absence of AAEMs, the chemical structure of coal char becomes the dominant factor affecting the reactivity. 相似文献
3.
以成型松木颗粒为原料,进行低温热解,研究了热解温度和升温速率对生成的松木半焦产率及官能团的影响。以试验得到的松木半焦进行蒸汽气化试验,对比分析了温度对半焦重整气化形貌特征、比表面积和平均孔径的影响。研究表明:随着热解温度升高,松木半焦脂肪族结构峰消失转化为烃等小分子物质及气化气,进而降低半焦产率。升温速率升高,半焦产率呈先下降后升高的趋势,在800℃升温速率为30K/min时半焦产率最低。不同温度热解和蒸汽气化对比试验表明,温度相对较低时(500℃)热解和蒸汽气化半焦孔隙结构相近,随着温度的升高,蒸汽气化半焦结构发生明显变化,900°C时出现了更小的孔道结构且比表面积增加明显。蒸汽引入使松木半焦和水蒸气发生热解反应的同时发生了脱氢反应,气化半焦形貌出现熔融和烧结现象。 相似文献
4.
油页岩矿物质催化半焦燃烧特性及机理 总被引:1,自引:0,他引:1
利用微型流化床反应分析仪(MFBRA)研究了油页岩矿物质催化半焦燃烧特性,重点考察了半焦内部矿物质和外部页岩灰床料对半焦燃烧的催化作用,揭示了流化床反应器中半焦燃烧过程和机理。结果表明:内部矿物质和外部床料对半焦燃烧均具有明显催化作用,而两者共同催化效果最为显著。矿物质中CaO和Fe2O3对半焦燃烧具有催化活性,CaO催化作用强于Fe2O3。油页岩半焦燃烧反应活化能在60.41~78.97 kJ/mol之间,矿物质的催化作用会明显降低反应活化能。流化床反应器中,矿物质对半焦燃烧的催化作用主要表现在四个反应,即:挥发分裂解和燃烧、半焦表面炭燃烧、半焦内部炭燃烧以及一氧化碳燃烧。 相似文献
5.
He Yang Thomas H. Fletcher Yang Li Lijun Jin Sufen Li Yan Shang Haoquan Hu 《American Institute of Chemical Engineers》2020,66(2):e16834
The influence of changes in aliphatic structure on char surface area during coal pyrolysis was modeled, and the effect was introduced to a previous char surface area model for lignite pyrolysis established based on the chemical percolation devolatilization (CPD) model. The modified model can predict not only the N2 and CO2 char surface area during rapid pyrolysis of three lignites but also the CO2 char surface area of two high-volatile bituminous coals; the agreement of the modified model with experiments is improved at high temperatures. The decrease in aliphatic chain length can reduce adsorption positions around aromatic core, and decrease char surface area. When mass release is more than 55% at about 1,100 K, the predicted N2 char surface area starts to decrease with further generation of volatiles, and the increase of predicted CO2 char surface area with increasing generation of volatiles also become slow at the end of mass release. 相似文献
6.
针对高温烟气中煤焦的气化行为,本文采用FactSage 6.1计算了煤焦在高温烟气下的高温反应特性,并利用热重分析仪分析了煤焦气化行为。通过沉降炉实验进一步研究了不同温度、气体配比、粒径条件下气体产物的动态析出特性,同时计算了评价指标α、β、LHV值。结果表明:随着温度的升高,气体产物H2和CO的含量增加,β、α、LHV值增大,CH4和CO2的含量下降。在温度为1200℃时,β、α值分别由CO2/CO比为10∶70时的10.80%、5.21%增加到CO2/CO比为50∶30时的24.71%、41.06%。同时,随着CO2/CO比值的增大,高温烟气对煤焦气化反应抑制减弱。通过对比反应温度和粒径对煤焦气化反应的影响,得出反应温度远大于粒径对煤焦气化反应的影响。通过实验验证了向高温烟气中喷吹煤焦制备高品质可燃气体方法的可行性。 相似文献
7.
《International Journal of Hydrogen Energy》2021,46(70):34679-34688
The endless and dramatic increase of global energy demand makes it imperative to develop sustainable, affordable, and efficient materials to act as electrocatalysts in the clean energy technologies. Electrocatalysts based on coal chars are promising materials as they can be considered as value-added by-products from coal combustion contributing to industrial ecology and circular economy. Therefore, herein we report the application of three sets of coal char (char concentrates before and after carbonization and demineralized and graphitized char concentrates) obtained from four different countries (Portugal, Romania, Poland, and South Africa) as oxygen reduction reaction (ORR) electrocatalysts. All electrocatalysts presented moderate ORR activity with some showing selectivity for the indirect two-electron process while others for a mixed regime between the two- and four-electron process. Still, the positive results obtained are better or in some cases comparable to commercial graphene. Moreover, all electrocatalysts presented good tolerance to methanol poisoning. More importantly, the results of this study demonstrate that pristine coal chars are promising materials to prepare efficient ORR electrocatalysts which will be of great importance in the near future. 相似文献
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10.
Sunil K. Sharma 《Fire Technology》2003,39(3):247-260
Metal-based organic complexes (MBO) are a class of FRSS additives that comprise a transition metal and an organic ligand that cleaves at an elevated temperature thereby releasing the metal in a reactive state. They help in the formation of char and thus act as an effective smoke suppressant. Use of MBO complexes as flame retardant smoke suppressants, phosphate ester as a flame retardant and active filler as endothermic material is reported here as multicomponent FRSS systems. MBOs used in the present study are the chelates of pentanediono. They were used alone as well as in combination with aluminum trihydrate (ATH) as filler were used to impart flame retardancy and smoke suppression to poly vinylchloride. Their performance was measured in terms of flammability, smoke generation, char formation and evolution of combustion gases. MBOs of molybdenum and chromium were found to be very efficient flame retardant smoke suppressants. 相似文献