Thermal Drying of Wastewater Sludge: Change in Drying Area Owing to Volume Shrinkage and Crack Development

Abstract

The drying of wastewater sludge with or without an artificial crack was monitored using an electronic balance and an X-ray micro-computerized tomography scanner (micro-CT). The drying rates for sludge cake without a crack was 50–60% of pure water test. With an artificial crack of triangular cross section whose orientation was parallel to (P-type) or normal to (N-type) the air flow, their peak drying rates would be higher than that of cake without a crack. Also, the drying rate of sludge cake with P-type crack was higher than that with N-type crack, being attributable to the additional surface yielded by artificial crack. Using the total surface area as a basis, the effective drying fluxes from sludge cake were noted to close to the water drying test.

Keywords:

• Drying
• Crack
• CT
• Fluxes

ACKNOWLEDGMENT

The National Scientific Fund supported this work through Grant No. 50136020. T. Tao is grateful to National Taiwan University for inviting him as an exchange student from November 2003 through March 2004.