Drying Performance of a Thermal Jet Dryer for Solid Waste with High Water Content

Naohito Hayashi*, Hideyuki Umehara**, Yoshiaki Asai** and Sohei Shimada***
* Department of Geosystem Engineering, Graduate School of Engineering, The University of Tokyo
** Dryer Gr., Environmental Development Division, Ebara Jitsugyo Co., Ltd.
*** Institute of Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo
+ Correspondence should be addressed to Naohito Hayashi:
Department of Geosystem Engineering, Graduate School of Engineering, The University of Tokyo
(7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656 )

Abstract
For the purpose of weight and volume reduction and recycling of solid waste with high water content, drying experiments were carried out with a combustion gas thermal jet dryer. Dehydrated cake of sewage sludge, bean curd refuse and dehydrated cake of waste water sludge from a dye works were used for drying experiments. The experimental parameters were temperature and the flow rate of thermal jet and the feed rate of samples. The thermal efficiency and volumetric heat transfer coefficient of the dryer were calculated to investigate the drying characteristics of the samples. The following results were obtained. (1)Drying performance of this machine depends much more on the disintegration characteristics than on the drying characteristics of the samples. (2)The highest value of volumetric heat transfer coefficient of the dryer was 4,000kcal/h . m3 . C[Celsius degree]. (3)The actual effective particle diameter of the dried product and average residence time of particles in the processing chamber were larger than the theoretical values by two orders, a result probably caused by the large number of collisions between particles. (4)There was a limited to the feed rate giving a good disintegration process. Increasing feed rate over this value decreased the drying performance.

Key words: thermal jet, solid waste with high water content, sludge, weight and volume reduction, drying