The comparison of formation of ash contamination layers between on helically finned tube bank and on bare bank under gas solid two phase fluid is discribed.

从分析螺旋翅片管束受气固两相流冲刷时其表面上灰污层形成的机理着手，分析各种因数对灰污系数数值的影响。

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Coal ash is known to contain dangerous elements including arsenic, lead, and selenium, yet the TVA refused at first to issue any health warnings about contamination from the spill.

煤灰渣含有多种危险物质，包括砷、铅、硒等，然而田纳西流域管理局起先矢口否认煤灰渣中含有对健康有害的物质。

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Vitrification is the safest disposal method at present. Howevee, some harmful substance volatilized from fly ash in melting process, which caused second contamination.

熔融固化处理是安全的处理方法，但飞灰熔融过程中有有害物质挥发，造成二次污染。

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