Analysis of moisture diffusion and activation energy in superheated steam and hot air sludge thin layer drying

Sewage sludge is generated in waste-water treatment processes. The key step to treating sludge is dewatering. Dewatering of sludge by belt presses, filters, and centrifuges can lead to dry solids contents in the range of 15-25%. In order to study the effective diffusion coefficient and the activatio...

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Veröffentlicht in:Nong ye gong cheng xue bao 2013-01, Vol.29 (22), p.226-235
Hauptverfasser: Zhang, Xukun, Su, Zhiwei, Wang, Xuecheng, Ma, Yiguang
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Sprache:chi
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Zusammenfassung:Sewage sludge is generated in waste-water treatment processes. The key step to treating sludge is dewatering. Dewatering of sludge by belt presses, filters, and centrifuges can lead to dry solids contents in the range of 15-25%. In order to study the effective diffusion coefficient and the activation energy characteristics of the sludge layer in the process of superheated steam drying and hot air drying, an internal-circulation drying test-bed under normal pressure was built to carry out superheated steam drying and hot air drying tests on sludge layers with thicknesses of 4 mm and 10 mm respectively at the temperature range of 160-280[degrees]C. The test showed that when temperature exceeds 260[degrees]C, the effective diffusion coefficient of a sludge layer by superheated steam drying is greater than that created by hot air drying. Values obtained showed a linear increase in diffusion coefficients to temperature by superheated steam drying but a curve in hot air drying, suggesting the possibility of oxidati
ISSN:1002-6819
DOI:10.3969/j.issn.1002-6819.2013.22.026