共查询到15条相似文献,搜索用时 359 毫秒
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研究了在采用甲烷化法去除重整氢气中CO的过程中,反应温度、CO浓度和CO2浓度对3个竞争反应即CO甲烷化反应、CO2甲烷化反应、逆变换反应(RWGS)的影响。实验结果表明,随着温度升高,CO、CO2甲烷化反应速率均增大,但CO甲烷化的选择性降低。CO浓度对CO甲烷化反应速率的影响在高温时较为明显,反应速率随CO浓度的升高而增大;CO对CO2甲烷化反应的影响在较低温度下较为显著,CO2甲烷化反应速率随CO浓度的升高而减小,表明CO对CO2的甲烷化具有抑制作用,因而随着CO浓度的升高,选择性增大。另一方面,CO2浓度对CO甲烷化反应几乎没有影响,而CO2甲烷化反应速率和RWGS反应速率均随CO2浓度的升高而增大,该趋势在高温下更加显著,并对3个竞争反应的宏观动力学进行了初步研究。 相似文献
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基于NiO载氧体的煤化学链燃烧实验 总被引:4,自引:2,他引:2
采用流化床反应器并以水蒸气作为气化-流化介质,研究了以NiO为载氧体在800~960℃内的煤化学链燃烧反应特性。实验结果表明,载氧体与煤气化产物在反应器温度高于900℃体现了高的反应活性。随着流化床反应器温度的提高,气体产物中CO2的体积浓度(干基)呈单调递增;CO、H2、CH4的体积浓度(干基)呈单调递减;煤中碳转化为CO2的比率逐渐递增,碳的残余率逐渐递减。反应器出口气体CO2、CO、H2、CH4的生成率随反应时间呈单峰特性,H2生成率的峰值远小于CO的峰值;且随反应器温度升高,CO2生成率升高,CO、H2、CH4的生成率降低。反应温度高于900℃时,流化床反应器NiO载氧体煤化学链燃烧在9 min之内就基本完成,CO2含量高于92%。 相似文献
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在循环流化床锅炉上耦合流化床热解反应器既可提供电力又副产热解油,明显提高煤的利用价值。在这个过程中,热解反应器通常利用自身产生的热解气作为流化介质。本文考察了模拟热解气反应气氛对流化床煤热解拔头制取热解油产率的影响,并利用TG-FTIR分析了焦油官能团组成及随TG温度的变化。针对锅炉用烟煤的实验结果表明:采用热解气作为反应气氛时焦油产率最大,相对无水无灰基煤达13%。反应气氛中H2和CO2的存在不利于焦油生成,但CO 和CH4的加入提高了焦油产率;H2的加入有利于焦油中酚羟基、羧基类化合物生成,同时也促进了脂肪族化合物的裂解;CH4的存在可以提高焦油中单环芳烃、脂肪族及酚羟基类化合物的含量。 相似文献
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基于热重和红外联用进行等温实验,探讨了化学链燃烧载氧体CaSO4在CO气氛下的还原反应特性。研究发现:温度对CaSO4还原反应历程和速率有显著的影响,在10%CO气氛下,温度低于900℃时,发生单一反应,CaSO4的还原产物只是CaS,气相产物为CO2;当温度高于950℃后,发生平行反应和连串反应组合成的多重反应,固体产物为CaS和CaO,而产物气中除了有CO2,还存在SO2和COS,且气相硫化物的析出以COS为主;随着反应温度的升高,CaSO4与CO反应速率显著增加,而目标产物CaS在固体产物中所占的摩尔分数呈下降趋势;基于钙基载氧体化学链燃烧中燃料反应器温度不宜高于950℃。 相似文献
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采用共沉淀法制备γ-Al2O3载体和不同Ce添加量的CeO2-Al2O3载体,然后用浸渍法制备Ni负载质量分数10%的Ni/γ-Al2O3和Ni/CeO2-Al2O3催化剂。在固定床微反装置中考察了反应温度、原料气配比和CH4空速等工艺条件对Ni/γ-Al2O3和Ni/Ce30Al70Oδ催化剂在甲烷自热重整制氢反应中催化性能的影响。结果表明,添加Ce的催化剂催化性能有较大提高,在Ni/Ce30Al70Oδ催化剂上,反应温度750 ℃时, CH4转化率94.3%,与Ni/Al2O3催化剂相比,提高20%。Ni/γ-Al2O3和Ni/CeO2-Al2O3催化剂的CH4转化率均随反应温度的升高而增大。原料气中n(O2)∶n(CH4)和n(H2O)∶n(CH4)的增加均能提高各催化剂的CH4转化率。但n(O2)∶n(CH4)和n(H2O)∶n(CH4)的变化对各催化剂的催化性能的影响不同。随着n(O2)∶n(CH4)的增大,产物中n(H2)∶n(CO)降低,n(CO2)∶n(CO+CO2)升高;而n(H2O)∶n(CH4)增大时,产物中n(H2)∶n(CO)和n(CO2)∶n(CO+CO2)均升高。随着CH4空速的增加,Ni/Al2O3催化剂上CH4转化率、n(H2)∶n(CO)和n(CO2)∶n(CO+CO2)均较大程度下降;而在Ni/Ce30Al70Oδ催化剂上,随着CH4空速的增加,CH4转化率、n(H2)∶n(CO)和n(CO2)∶n(CO+CO2)变化不大。 相似文献
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Hydrogen generation during the reaction of a coal/CaO mixture with high pressure steam was investigated using a flow-type reactor. Coal, CaO and CO reactions with steam, and CO2 absorption by Ca(OH)2 or CaO occurred simultaneously in the experiment. It was found that H2 was the primary resultant gas, comprising about 85% of the reaction products. CO2 was fixed into CaCO3 and CO was completely converted to H2. Pyrolysis of the coal/CaO mixture carried out in N2 was also examined. The pyrolysis gases were compared with gases produced by general coal pyrolysis. While general coal pyrolysis produced about 14.7% H2, 50.5% CH4, 12.0% CO and 12.0% CO2, the gases produced from coal/CaO mixture pyrolysis were 84.8% H2, 9.6% CH4, 1.6% CO2 and 1.1% CO. 相似文献
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在自行设计的加压密闭热解反应器中研究了大同煤中As、Pb、Cr、Cd和Mn等微量有害元素在氮气条件下随温度(300~700℃)、压力(0.1~4MPa)和停留时间的变化规律,同时也考察了热解气氛(氮气和氢气)的影响.结果表明:这5种元素的析出率均随热解温度的升高而升高,随停留时间的延长而增大;反应压力的升高抑制了微量元素的释放;长停留时间,氢气气氛有利于微量元素的挥发; 热解过程中As和Cd较其他3种元素表现了较强的挥发性. 相似文献
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在水平管式炉上研究了O2浓度、CO2浓度、温度及石灰石添加等各参数对O2/CO2气氛下徐州烟煤和龙岩无烟煤燃烧过程中SO2/NO排放特性的影响。结果发现,O2/CO2气氛下,烟煤和无烟煤燃烧SO2/NO的析出规律与空气气氛下不同,同等O2浓度下析出量比空气气氛下小。O2/CO2气氛下,随着O2浓度的提高,烟煤和无烟煤SO2/NO排放量均增大;随着CO2浓度的升高, SO2/NO排放量均减小。O2/CO2气氛下,石灰石添加对SO2排放的抑制作用低于空气气氛下;石灰石添加对NO的排放有一定减排作用。对煤灰的元素分析显示O2/CO2燃烧对SO2的抑制主要是由于煤灰的自固硫能力增强,而对NO的减排作用则是促进燃料N向其他含N气体的转换。 相似文献
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To reveal the effect mechanism of CO atmosphere on coal pyrolysis, a study on raw and demineralized lignite was carried out in a horizontal tube furnace under N2 and CO/N2 atmosphere. CO had a negligible effect on the char yield at low temperatures, whereas it enhances the char yield at temperatures higher than 550 °C. The release of tar was higher in the presence of CO above 450 °C because of more free radicals, which reduced low‐temperature crosslinking, and higher selectivity of hydroxyl groups to phenols in the CO‐containing atmosphere. The yields of CO2 and H2 increased, water and CO yields decreased under CO/N2 atmosphere. Light hydrocarbon gases were not affected by changing the reaction atmosphere. The difference between product yields from raw and demineralized coal confirmed that the catalysis of inherent minerals had a great catalytic effect on the water‐gas shift reaction and Boudouard reaction. 相似文献
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The volatilization behavior of fluorine in five Chinese coals was investigated during fluidized-bed pyrolysis and CO2-gasification at a temperature range of 500-900 °C. The effect of co-existed and added calcium on fluorine volatility during pyrolysis was also determined. With increasing pyrolysis temperature, the volatility of fluorine increases. However, the volatility is greatly dependent on the fluorine chemical forms occurred in coal. Except for Datong and Zhungeer coal, more than 65% of fluorine in other three coals occurs as the steady forms. Fluorapatite is not the major carrier of fluorine in the coals studied. Fluorine volatility is retarded by coexisting calcium during coal pyrolysis, indicating that at least part of the stable forms of fluorine in coal might occur as calcium fluoride or calcium fluoride with complex compounds which are stable even at high pyrolysis temperature. The addition of CaO and limestone can suppress the release of fluorine during pyrolysis. The effect of CaO is better than that of limestone. The volatility of fluorine of coal during CO2-gasification depends on not only the occurrence mode of fluorine, but also the gasification reactivity of the coal. Compared with N2 atmosphere, CO2 is more favorable to the release of fluorine from coal. 相似文献