Classification of Convective Drum Dryers (Survey of Patents)
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CLASSIFICATION OF CONVECTIVE DRUM DRYERS (SURVEY OF PATENTS) I. O. Mikulionok
UDC 66.047.57:66.047.4/.5(048.83)
A classification of convective drum dryers of bulk materials used in chemical and food enterprises as well as enterprises that work with construction materials is proposed. A critical survey of the most characteristic designs of convective drum dryers developed by designers and inventors from the leading countries of the world is performed. Keywords: bulk materials, drum dryer, classification, design
Drum dryers are the among the most efficient and productive types of dryer equipment intended for processing bulk materials in the chemical and food enterprises as well as in enterprises that work with construction materials [1−3]. Drum dryers are characterized by simplicity of design, universality, high rate of mixing of material being dried, and reliability of operation, though they are distinguished by elevated consumption of energy (chiefly in the rotation of the drum) as well as in dust formation in the course of drying of brittle materials. A number of different methods of drying bulk materials are implemented in drum dryers, for example, with the use of a vacuum (Patents No. RU2120589C1, No. RU45018U1, and No. UA95451C2); radiation heat exchange (Inventor’s Certificate No. SU901774A1, Patent No. RU10448U1, and Claim No. WO2012/140305A1); induction heating (Patents No. RU2374580C1 and No. RU15622U1, along with Claims No. WO0107850A1 and No. WO2008/113338A2) [4]; contact heating (for example, with the use of indirect heating steam or electric heating elements; Patents No. US3852892A and No. 6415527B1, and No. CN107462031A, Claims No. WO98/02700A1, No. WO99/54674A1, and No. US2006242855A1). However, of all drum dryers, convective dryers are the most in demand. Through an analysis of the different designs of convective drum dryers we are led to propose the following classification of these types of dryers (Fig. 1). By type of heat-transfer agent (drying agent), we distinguish drum dryers with the use of heated air, flue gases, and mixtures of flue gases and free (cold) air [1, 3]. By relative direction of travel of the heat-transfer agent and material being dried, drum dryers are divided into those that function with parallel-current flow and counterflow, and in compound regimes. Parallel-current flow is used in the case of high initial humidity and/or low thermal stability of the material being dried, while counterflow is used where it is necessary to obtain maximally dehydrated product and/or with a level of high thermal stability of the material being dried [1]. In dryers with two sections of compound flow of the drying agent (along the length of the drum) the direction of travel of the heat-exchange agent in each section may be varied, which makes it possible to regulate the intensity of the drying process in general (Patents No. RU2159915C1 and No. RU2367864C1). By type of internal nozzle of drum, we distinguish between dryers with ascending impeller, sectional, distributive, and transfer nozzles alo
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