Mixing properties in loop reactor.

Abstract

Mixing process under batch operation was investigated by the impulse response method. A series solution of the dispersion model for recirculation flow is given and a simple procedure to determine the model parameter, Bodenstein number Bo, is proposed. Dimensions of the loop reactor used in most experiments are: inner diameter=10 cm, whole pipe length=280 cm and reactor volume=22 /. The impellers used are: pitched paddles of three different pitched angles and three different diameters, an axial flow pump-type impeller and a marine screw. Bodenstein number was converted into Peclet number, Pe, which in turn is correlated with the pipe Reynolds number, Rep. For the experimental range of i?^=2.5 x l03-2 x l05, Pe ranges over 3-16, which is 2-3 times that in a straight pipe. Geometry of the impeller does not affect the value of Pe for a given value of Rep. Pe in unbaffled condition is larger than that in baffled condition because of helical motion of fluid. The numberof circulations before the fluctuation decays below 1 % of average concentration is analytically found to be 0.134 Bo.

Bioreactors, Air‐lift Reactors

“…The coefficient M given by Verlaan et al is in exact agreement with the theoretical relationship derived by Murakami et al (118) for Bo Ͼ 50 and a degree of inhomogeneity, I ‫ס‬ 0.05. Equation 28shows that the circulation path, which enters in the definition of Bo, has a linear effect on the mixing time.…”

“…The latter is usually reported as the mixing time (t m ), the former as Bo or r 2 . Indeed, these parameters are interrelated, and knowledge of Bo or t m is sufficient for calculating, theoretically, the mixing time (108,118) based on the deviation of the envelope of the maxima in the response curve to a pulse, which is a measure of the degree of inhomogeneity. Verlaan et al (80) and Lin et al (119) correlated their results as follows:…”

Sparged loop reactors

“…Interfacial area has been estimated using Equation (4.4) with the assumption of constant Sauter mean bubble diameter. Blenke (1979) and Murakami et al (1982) have applied the axial dispersion model to the loop reactor and have derived equations relating the concentration at a fixed point and time. Murakami et al (1982) have obtained the following equation: The effective Peclet number for EL-ALR has been calculated using the additive property of variance (Levenspiel, 1972) for the case of series reactors.…”

“…Blenke (1979) and Murakami et al (1982) have applied the axial dispersion model to the loop reactor and have derived equations relating the concentration at a fixed point and time. Murakami et al (1982) have obtained the following equation: The effective Peclet number for EL-ALR has been calculated using the additive property of variance (Levenspiel, 1972) for the case of series reactors. Considering an EL-ALR to be made up of four parts: riser, downcomer, gas disengagement tank and bottom bend, the overall effective Peclet number was estimated using the following equation:…”

Effects of catalyst activity profiles on polyethylene reactor dynamics

“…In this study, both tubular loop and tank reactors are considered for HDPE production. Loop reactors usually operate at high recirculation rates that allow them to be modeled as a Ž stirred-tank reactor Murakami et al, 1982;Zacca and Ray, . 1993 .…”