Analysis of Drying Performance and Cost of Large-Capacity Sewage Sludge Dryer

Abstract

Purpose: This study aimed to develop a high-capacity dryer for high-water-content sewage sludge and to experimentally investigate the drying characteristics and cost. Methods: A dryer with a drying capacity of 5000 kg that uses electrically heated oil as a drying heat source was fabricated. Its performance was verified, and the drying cost was analyzed by performing experiments using sewage sludge collected in a sewage processing plant as an experimental material. Results: The drying experiment results showed an input water content of 82.0%, an average water content of 3.49% after drying, an average drying rate of 3.3%/h, and an average drying capacity of 130.05 kg/h. After drying, the combustible content of the sewage sludge increased as its water content decreased, whereas its ash content remained relatively constant. Before and after drying, the higher and lower heating values of the sewage sludge were inversely proportional to its water content. In particular, when the water content was 4% or less after drying, the average lower heating value was found to be 4340 kcal/kg. In the drying experiments, the average drying cost was found to be approximately 3.55 \/kg. Conclusions: The results of the drying experiments in which oil was used as a heat source to dry high-water-content sewage sludge indicated that the developed stirring-type dryer is sufficiently applicable to sewage sludge drying in terms of drying capacity, drying rate, and drying cost. ? 2021, The Korean Society for Agricultural Machinery.