Performance characteristics of a pilot-scale biomass gasifier using oxygen-enriched air and steam
Performance characteristics of a pilot-scale biomass gasifier using oxygen-enriched air and steam
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DOI：
10.1016/j.fuel.2012.09.033
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发表时间：
2013-01-01
期刊：
影响因子：
7.4
通讯作者：
Kong, Song-Charng
中科院分区：
文献类型：
--
作者：
Cuong Van Huynh;Kong, Song-Charng
本研究旨在研究以“富氧空气”和蒸汽的混合物作为气化剂的生物质气化系统的特性，以提高合成气的热值和可燃气体成分。本研究还旨在表征氧气和蒸汽气化对合成气燃烧中导致大量NOx排放的氨浓度的影响。实验是使用一个中试规模的加压鼓泡流化床气化炉进行的，其容量为每天5吨。在与蒸汽混合气化之前，向空气中加入纯氧。需要大量的蒸汽来控制系统在高氧水平下的反应性。富氧空气中的氧含量在干燥条件下为21.45 ~ 80vol .%，在湿条件下分别为21.30 ~ 40vol .%。床的温度保持在800摄氏度的所有测试。研究使用了三种不同的生物质原料，氮含量从0.05到1.4 wt.%不等（即，松树，枫橡木混合物和废弃的玉米种子）。合成气干组分使用微型气相色谱仪测量，而氨浓度和水分含量分别使用改进的IEA焦油议定书和卡尔费歇尔滴定法测量。结果表明，富氧空气和蒸汽气化有利于产生可燃气体成分，包括氢气、一氧化碳、甲烷和较轻的碳氢化合物。当氧气用量为40%时，松树、枫橡树和玉米种子的氢分别增加70%、47%和32%，而CO分别增加34%、18%和8.6%。总的来说，氧气和蒸汽气化对于低氮和低水分的原料是最有效的。合成气中氨氮和氮氧化物浓度随氧富集程度的增加而增加。对于所研究的原料，合成气的较低热值可提高43%。当含氧量从21%增加到40%时，松木、枫橡树和种子玉米的H-2/CO比值也分别从0.59增加到0.75、0.67增加到0.84和0.36增加到0.43。尽管有所改善，但H-2/CO比仍然适中。H-2/CO比适中的原因是在高氧和高蒸汽条件下合成气中含水量高，这表明在当前气化炉温度为800℃时，有大量未反应的蒸汽。版权所有。
This study is to investigate the characteristics of a biomass gasification system using mixtures of "oxygen-enriched air" and steam as the gasifying agent for increasing the syngas heating value and combustible gas constituents. This study also aims to characterize the effects of oxygen-and-steam gasification on ammonia concentration that can lead to significant NOx emissions from syngas combustion. Experiments are conducted using a pilot-scale, pressurized bubbling fluidized bed gasifier with a capacity of five tons per day. Pure oxygen is added to air before mixing with steam for gasification. A significant amount of steam is required to control the reactivity of the system at high oxygen levels. The oxygen content in the enriched air varies from 21, 45, to 80 vol.% on dry basis, corresponding to 21, 30, and 40 vol.% on wet basis respectively. The bed temperature is maintained at 800 degrees C for all tests. Three different biomass feed-stocks with nitrogen contents varying from 0.05 to 1.4 wt.% are used for study (i.e., pine, maple-oak mixture, and discarded seed corn). The syngas dry composition is measured using a microgas chromatograph while ammonia concentration and moisture content are measured using a modified IEA Tar Protocol and Karl Fischer Titration respectively. Results indicate that oxygen-enriched air and steam gasification favors the production of combustible gas components including hydrogen, carbon monoxide, methane, and lighter hydrocarbons. When 40% oxygen is used, hydrogen increases by 70%, 47%, and 32% for pine, maple-oak, and seed corn respectively, while CO increases by 34%, 18%, and 8.6% respectively. Overall, it is found that oxygen and steam gasification is most effective for feedstock with low nitrogen and moisture contents. Results also show that ammonia and NOx concentrations in syngas increase as oxygen enrichment increases. The lower heating value of syngas can increase by as much as 43% for the feedstock studied. When the oxygen level increases from 21% to 40%, the H-2/CO ratio also increases from 0.59 to 0.75, 0.67 to 0.84, and 0.36 to 0.43 for pine, maple-oak, and seed corn respectively. Despite the improvement, the H-2/CO ratio is still moderate. The moderate H-2/CO ratio is explained by the high water content in syngas at high oxygen and steam conditions, indicating a large amount of un-reacted steam at the current gasifier temperature at 800 degrees C. (C) 2012 Elsevier Ltd. All rights reserved.