Document Type : Research Paper

Abstract

In order to study the fluidization behavior of grains, a laboratory fluidized bed dryer (FBD) was designed and developed. Forward blade centrifugal fan with 1.5 kW electric motor, was selected to be used based on the highest pressure loss calculated at minimum fluidization condition and airflow rate at terminal velocity of the selected grains (paddy, soybean, millet and barley). The dryer was constructed with cylindrical chamber (0.144m diameter and 0.3m height), and 3.3 kW electric heater (with seven elements). Gas distributor bedplates were selected from the physical properties of the grain samples and then fluidization characteristic curves of the samples were obtained. Fluidization uniformity and drying of the samples showed that the dryer works properly and drying time of paddy at fluidized bed condition was shorter than that at fixed bed condition. The fluidization experiment results of the samples showed that the deviation between calculated and experimental pressure loss and minimum fluidization velocity for millet and soybean were less than the other grains, because of high sphericity.

Keywords

- امیری چایجان، ر. 1379. طراحی و ساخت خشک‌‌کن بستر سیال آزمایشگاهی برای محصولات دانه‌‌ای
، پایان‌‌نامة کارشناسی ارشد مهندسی مکانیک ماشینهای کشاورزی. دانشکدة کشاورزی. دانشگاه تربیت مدرس. 141ص
2- Bleier, P. F. 1998. Fan handbook. NewYork:  McGrow-Hill, U. S. A.
3- Brooker, D. B., Bakker-Arkema, F. W. and Hall, C. W. 1992. Drying andstorage
of grains and oilseeds. New York: Van Nostrand Reinold, U. S. A.
4- DiMattia, D. G., Amyotte, P. R. and Hamdullahpur, F. 1996. Fluidized beddrying of large particles. Transactions of the ASAE. 39 (5), 1745-1750.
5- Krill, L. and Schmitt, W.  1997. Sugar drying and cooling in a fluidized beddrier. Zucker Indusrie. 122 (8), 585-603.
6- Kunii, D. and Levenspiel, O. 1991. Fluidization engineering. Stoneham:Butterworth- Heinemann, U. S. A.
7- Marcus, R. D., Leung, L. S. Klinzing, G. E., and Rizk, F. 1990. Pneumatic   conveying of solids. London: Chapman and Hall, U.K.
8- Mc Cabe, L. W., Smith, J. C. and Harriot, P. 1988. Unit operation of  chemical engineering. New York: Mc Grow Hill Book Company, U.S.A.
9- Perry, R. H. and Green, D. 1985. Perry’s chemical engineering handbook. Caledonia: Mc Graw-Hill, U. S. A.
10- Pliestic, S. 1995. The dependence of the BC492 hybrid maize grain beginning fluidization upon the grain moisture content and the air velocity during the drying process. Poljoprivredna Znadstvena Smotra. 60 (1), 5-25.
11- Prasad, B. V. S., Chandra, P. K. and Bal, S. 1994. Drying parboiled roughrice in stationary, semi-fluidized and fluidized conditions. Transactions of the ASAE.
37 (2), 589-
594.
12- Romankov, P. G. and Rashkovskaya, N. B. 1979. Drying in suspensionstate. Leningrad: Khimiya, Russia.
13- Stroshine, R. and Haman, D. 1994. Physical properties of agricultural materials andfood products. West Lafayette: Purdue University, U. S. A.
14- Strumilo, C. and Kudra, T. 1998. Drying: Principles, applications anddesign.New York: Hemisphere Publications, U. S. A.
15- Temple, S. J., Whittle, A. M. and Khumalo, F. R. 1996. Fluid bed drying oftea experimented work and practical implications. Proceedings of the 1stRegional Tea Research Seminar in Malawi, 136-143.