Pilot-scale experimental and CFD modeling investigations of oxy-fuel combustion of Victorian brown coal
Pilot-scale experimental and CFD modeling investigations of oxy-fuel combustion of Victorian brown coal
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DOI：
10.1016/j.fuel.2014.12.026
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发表时间：
2015-03
期刊：
影响因子：
7.4
通讯作者：
Jian Zhang;Baiqian Dai;Ying Meng;Xiaojiang Wu;Jianwen Zhang;Xiang Zhang;Y. Ninomiya;Zhong-xiao Zhang;Lian Zhang
中科院分区：
文献类型：
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作者：
Jian Zhang;Baiqian Dai;Ying Meng;Xiaojiang Wu;Jianwen Zhang;Xiang Zhang;Y. Ninomiya;Zhong-xiao Zhang;Lian Zhang
本文介绍了在世界上第一次尝试的实验和模拟研究的富氧燃烧的维多利亚褐煤在一个3兆瓦的中试规模的设备。两个煤样具有不同的水分含量，湿（40重量%的水分）和空气干燥（24重量%的水分），进行了测试，在空气和氧气燃烧模式，氧气水平从27%（体积）到40%的炉。商业软件，FLUENT 13，被用来解释实验数据，考虑到一系列的验证细化子模型的氧燃料燃烧。模拟结果与实测的烟气温度分布和炉膛内的火焰照片吻合较好。正如已经证实的那样，对于干燥的维多利亚褐煤，在空气燃烧和氧-27%O2之间实现了相当相同的烟气温度分布。然而，对于含水量为42wt%的湿褐煤，在富氧燃料模式下，30%的O2对于匹配空气以实现相同的烟气温度分布是必不可少的。即便如此，在上述最佳改造条件下，无论煤中的水分含量如何，空气燃烧和氧气燃烧情况下的辐射传热和CO排放曲线仍然略有不匹配。湿煤富氧燃烧烟气中含有大量的CO2和H2O，烟气发射率较高，从而增加了烟气的辐射换热。在氧燃料模式下的CO排放浓度的提高，由于增强的C-CO2和C-H2O气化反应，容易发生在相对较低的温度维多利亚褐煤焦。一次气体中氧气含量不低于30%，这对于最大限度地减少CO2和蒸汽的大比热容引起的颗粒点火延迟也是至关重要的。对于烟道气性质，已经证实，在优化的氧燃料条件下，干燥烟道气中典型的CO2纯度达到约80%，其中过量氧气保持在104%，而蒸汽达到35%，相对于空气燃烧烟道气中的10%。通过将煤燃烧从空气燃烧模式转变为富氧燃料模式，对于湿煤和干煤的使用，烟气再循环比从48%变化到64%，这大大低于烟煤的文献结果。
This paper presents the first trial in the world for experimental and modeling investigation of oxy-fuel combustion of Victorian brown coal in a 3 MWthpilot-scale facility. Two coal samples with different moisture contents, wet (40 wt% moisture) and air-dried (24 wt% moisture), were tested in air- and oxy-firing modes with oxygen level varying from 27% (vol) to 40% in furnace. The commercial software, FLUENT 13, was employed to interpret the experimental data by taking into account a series of validated refined sub-models for oxy-fuel combustion. The modeling results showed reasonable agreement with the measurements of flue gas temperature profile as well asin-situflame photographs in furnace. As has been confirmed, a rather identical flue gas temperature profile was achieved between air-firing and oxy-27% O2for the dried Victorian brown coal. For the wet brown coal with 42 wt% moisture, 30% O2in oxy-fuel mode is however essential to match air to achieve an identical flue gas temperature profile. Even so, under above optimum retrofit conditions, the radiative heat transfer and CO emission profiles were still slightly mismatched between air-firing and oxy-firing cases regardless of the moisture content within coal. The radiative heat transfer was increased in wet coal oxy-firing because of the higher gas emissivity for the abundant CO2and H2O within the flue gas. The CO emission concentration in oxy-fuel mode was raised, due to the enhanced C–CO2and C–H2O gasification reactions that occurred readily at relatively low temperatures for Victorian brown coal char. The presence of no less than 30% oxygen in primary gas is also essential to minimise particle ignition delay caused by the large specific heat capacity of CO2and steam. For flue gas properties, it has been confirmed that, under the optimised oxy-fuel conditions, the typical CO2purity reached approximately 80% in dried flue gas, in which the excess oxygen remained at ∼4% whereas steam reached 35%, relative to 10% in air-firing flue gas. By shifting coal combustion from air-firing to oxy-fuel mode, the flue gas recirculation ratio varied from 48% to 64% for the use of wet and dried coals, which are considerably lower than the literature results for bituminous coal.