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Cogasification of sewage sludge in an updraft gasifier

机译：上浮式气化炉中污水污泥的气化

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摘要

Sewage sludge is the residue produced by the domestic or industrial wastewaters treatment plants. According to the principles of sustainability, several restrictions have been imposed on the conventional methods currently adopted for its disposal. The consequent need to develop alternative processes for the use of sewage sludge for energy purposes such as gasification requires experimental tests in order to quantify the potential energy recover from this waste, as well as to evaluate the optimum conditions for its gasification. In the present study, the gasification with air of dehydrated sewage sludge (20 wt.% moisture) mixed with conventional woody biomass was performed in a pilot scale updraft fixed-bed gasifier operating at atmospheric pressure. Attention was focused on the effect of the sewage sludge content and the equivalent ratio (ratio between the amount of air used and the stoichiometric air needed for combustion) on the product yields, gas composition and cold gas efficiency. The results obtained showed that it is possible to cogasify sewage sludge with wood pellets in pre-existing updraft fixed-bed gasification installations. However, at high sewage sludge content (≥ 70 w/w%) slagging and an excessive clinker formation may occur in the oxidation zone because of the high ash content and low ash fusion temperatures of the sludge making the gasification process unstable. In addition, the formation of an ash layer on the grate requires persistent ash discharge that introduces instabilities in the gasifier operating conditions. The rise in the equivalent ratio led to higher gas and carbon yields and cold gas efficiencies. At the optimal equivalent ratio of 0.25, compared with wood pellets gasification, the addition of sewage sludge with 20 wt.% moisture up to 70 w/w% gave rise to decreasing the dry gas yield from 1.56 to 1.07 Nm~3/kg of feedstock due to the higher moisture and ash content of sewage sludge and to moderate reductions of the gas lower heating value and cold gas efficiency from 5.8 to 4.9 MJ/Nm_(dry)~3 and from 60% to 55%, respectively.
机译：污水污泥是生活或工业废水处理厂产生的残留物。根据可持续性原则，对目前采用的常规处理方法施加了一些限制。因此，需要开发用于将污泥用于能源目的（例如气化）的替代方法，这需要进行实验测试，以量化从该废物中回收的潜在能量，并评估其气化的最佳条件。在本研究中，将脱水的污水污泥（水分含量为20 wt％）与常规木质生物质混合后，在空气中进行气化是在大气压下进行的中试规模上浮固定床气化炉中进行的。注意力集中在污水污泥含量和当量比（使用的空气量与燃烧所需的化学计量空气之间的比率）对产品收率，气体组成和冷气效率的影响上。所得结果表明，可以在已有的上升气流固定床气化装置中将污水污泥与木屑一起气化。然而，在高污泥含量（≥70 w / w％）的情况下，由于污泥的高灰分含量和低灰分熔化温度，会在氧化区产生结渣并形成过多的熟料，从而使气化过程不稳定。另外，在炉rate上形成灰烬层需要持续的灰烬排放，这会导致气化炉运行条件的不稳定。当量比的增加导致更高的天然气和碳收率以及冷气效率。在最佳当量比为0.25的情况下，与木屑气化相比，添加含水量为20 wt。％到70 w / w％的污水污泥会使干气产量从1.56 Nm〜3 / kg降低到1.06 Nm〜3 / kg由于污水污泥的水分和灰分含量较高，并且适度降低了气体，热值和冷气效率分别从5.8 MJ / Nm_（Nm_（干）〜3和60％降至55％）降低了。

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  • 来源
    《Fuel》 |2012年第2012期|p.486-491|共6页
  • 作者

    M. Seggiani; S. Vitolo; M. Puccini; A. Bellini;

  • 作者单位

    Department of Chemical Engineering, Industrial Chemistry and Material Science, University of Pisa, Largo Lucio Lazzarino 1, 56126 Pisa, Italy;

    Department of Chemical Engineering, Industrial Chemistry and Material Science, University of Pisa, Largo Lucio Lazzarino 1, 56126 Pisa, Italy;

    Department of Chemical Engineering, Industrial Chemistry and Material Science, University of Pisa, Largo Lucio Lazzarino 1, 56126 Pisa, Italy;

    Department of Chemical Engineering, Industrial Chemistry and Material Science, University of Pisa, Largo Lucio Lazzarino 1, 56126 Pisa, Italy;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    sewage sludge; gasification; updraft gasifier; energy recovery;

    机译：污水污泥;气化;上升气流气化炉;能量恢复;

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