Medium-Temperature Belt Dryers for Biosolids
Abstract:Drying saves biosolids transportation and disposal costs. A brief historical review about thermal biosolids drying technologies is provided. Main technical features of belt dryers are explained in comparison with drum, fluidized bed, contact and solar dryers. While most belt dryers were originally designed for low-temperature operation, medium or high temperature designs have now become more common. Advantages of higher temperature operation are smaller dryers, reduced exhaust air flows and improved odor control. Medium-temperature dryers can achieve disinfection and thus generate Class A biosolids, even if they are entirely operated with medium temperature heat of around 85 °C (185 °F) from CHP (Combined Heat and Power) systems. The time-temperature regime according to US-EPA Biosolids Rule 503 in belt dryers is explained. Results from the measurement of air and solids temperatures within a medium-temperature belt dryer are presented. Use of waste heat for sludge drying provides great economical and ecological advantages in comparison to direct use of fossil energy, such as natural gas. A list of some reference installations by several suppliers includes key technical data.
Document Type: Research Article
Publication date: January 1, 2011
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