muktistage extractor control

E. Simeonov, J. Nedialcova 445 Journal of the Un iversity of Chemical Technology and Metallurgy , 41, 4, 2 006, 445-4 48 PROCESS CONTROL AND ESTIMATION OF MUL TISTAGE EXTRACTION USING CHARACTERISTIC FUNCTION APPROACH E. Simeonov, J. Nedialc ova University of Chemical Technology and Metallurgy 8 Kl. Ohridski, 1756 Sofia, Bulgaria E-mail: [email protected] ABSTRACT Kinetic experiments have been carried out, under three-stage led process of extraction according to the scheme crossed current, for the system tobacco leaves (Nicotiana tabacum L.) water. The solid phase is triple extracted and a fresh solvent is used for each stage. The experiments are obtained in a batch extractor with a propeller. The characteristic function for the experimental system is obtained from the kinetic curves. By using this function the basic design size (length) of solid liquid extractor is calculated. The new working speed (II and III stages) of solid stage transition in the extractor is also obtained, which is done by screws rpm and constant design sizes calculated from the kinetic curves for the Ist stage of the extraction. The obtained revolutions correspond to the necessary equilibrium time of extraction, which is the time of reaching the reference extraction degree of the extracted component. Keywords: solidliq uid extraction, kinetics, characteristic func tion, multistage extraction. Received 05 September 2006 Acce pted 12 November 2006 INTRODUCTION The efficiency of extraction installations is usually estimated by technological criteria the degree of extraction. According to the need of quality refining of raw materials and reaching high extraction degree, the solid phase refining is usually multistage and the num- ber of sta ges is defin ed for eac h partic ular case. It is well known that each experimental kinetic curve holds in hidden way all the factors that have an impact on the process of non-stationary diffusion extraction [1-4]. Kinetics by the characteristic function gives the opportunity in the common case for polydisperse aniso- tropic solid phase, the characteristic in the structure of solid particles and the value of the external diffusion resistance to be integrally found [3,6]. The use of the characteristic function gives pos- sibility not only to calculate but also to control the process [7] when the raw material is changed, the technological parameters of the multistage extraction. EXPERIMENTAL Kinetic experiments have been carried out, under three-stage led process of extraction according to the scheme crossed current for the tobacco leaves water system. The solid phase has been extracted three times and fresh solvent has been used for each stage. The experimental data have been obtained in a batch vessel extractor with a propeller under the following condi- tions: hydromodule î=0,02 m 3 /kg, temperature t=20 0 C and stirring revolutions n=7 s -1 , for which have been

muktistage extractor control

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