Convective drying of sewage sludge layer in through-flow

Lipolt, Andraž (author), Širok, Brane (author), Hočevar, Marko (author), Novak, Lovrenc (author)

Drying of the sewage sludge layer was investigated in a convective laboratory dryer at air temperatures of 65 °C and 80 °C and air speeds of 0.53 m/s and 0.83 m/s. The sludge layer was formed by loading cylindrical extrudates on a grate of 0.5 m x 0.5 m size. The drying air was directed through the layer, as typically encountered in industrial belt dryers. Under such setup, the sludge layer structure and porosity significantly affect the air flow conditions and thus the drying rates. Shrinkage and cracking of the material during drying caused changes in the layer's porous structure, that affected the pressure drop and the drag force due to passing of air through the layer. The decreasing of drag force over time was modeled by a simple function that showed excellent agreement to the selected measured data. The sludge layer drying kinetics was determined by fitting the measured data to the most common drying models. Two models, the modified Nadhari and the Wang Singh model, were determined as most suitable for modeling of drying curves. The total drying time per kilogram of sludge was modeled as a function of drying air temperature, drying air velocity and initial sludge dry matter content. The coefficient of determination (R2) of the model is 0.944. Total drying times between 43 minutes per kilogram and 76 minutes per kilogram of sludge were obtained for the investigated range of drying air conditions.

• Language: English
• Keywords: wastewater sludge, thin-layer drying, porous layer, drying kinetics, drag force
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Place of publishing: Ljubljana
• Year: 2020
• Number of pages: Str. 481-493
• Numbering: Vol. 66, no. 9
• PID: 20.500.12556/RUL-119801
• UDC: 66.047.41(045)
• ISSN on article: 0039-2480
• DOI: 10.5545/sv-jme.2020.6717
• COBISS.SI-ID: 27998723
• Publication date in RUL: 11.09.2020

Record is a part of a journal

• Title: Strojniški vestnik
• Shortened title: Stroj. vestn.
• Publisher: Zveza strojnih inženirjev in tehnikov Slovenije [etc.], = Association of Mechanical Engineers and Technicians of Slovenia [etc.
• ISSN: 0039-2480
• COBISS.SI-ID: 762116

Secondary language

• Language: Slovenian
• Title: Konvektivno sušenje plasti odpadnega blata s tokom skozi plast
• Keywords: odpadno blato s čistilnih naprav, sušenje v tanki plasti, porozna plast, sušilna kinetika, sila upora, modeliranje

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: P2-0401
• Name: Energetsko strojništvo