Oxygen transfer to slurries treated in a rotating drum operated at atmospheric pressure

Abstract

The objective of this work was to determine (1) the effect of rotational speed (N) and lifters on the oxygen transfer coefficient (k (L)) of a mineral solution and (2) the effect of solids concentration of a slurry soil-mineral solution on k (L), at a fixed value N (0.25 s(-1)); in both cases the treatment was carried out in an aerated rotating drum reactor (RDR) operated at atmospheric pressure. First, the k (L) for the mineral solution was in the range 6.38 x 10(-4)-7.69 x 10(-4) m s(-1), which was of the same order of magnitude as those calculated for closed rotating drums supplied with air flow. In general, k (L) of RDR implemented with lifters was superior or equal to that of RDR without lifters. For RDR implemented with lifters, k (L) increased with N in the range 6.65 x 10(-4)-10.51 x 10(-4) m s(-1), whereas k (L) of RDR without lifters first increased with N up to N = 0.102 s(-1), and decreased beyond this point. Second, regarding soil slurry experiments, an abrupt fall of k (L) (ca. 50%) at low values of the solid concentration (C (v)) and an asymptotic pattern at high C (v) were observed at N = 0.25 s(-1). These results suggest that mass transfer phenomena were commanded by the slurry properties and a semi-empirical equation of the form Sh = f(Re, Sc) seems to corroborate this finding.

Power Consumption of Liquid and Liquid/Solid Systems in a Rotating‐Drum Bioreactor

“…Lifters in RDBs can enhance efficiently mass transfer and mixing performance [6,27]. Power consumption was tested with 4, 8, and 12 lifters (W B = 70 mm, V L /V = 0.7, a = 0°) mounted vertically to the RDB wall.…”

“…Many researches indicated that the RDB satisfied well the gas mass transfer demand for bioprocesses [6,18,19]. Nevertheless, power consumption is rarely investigated.…”

“…An appropriate environment for microbial growth includes sufficient dissolved oxygen, rapid carbon dioxide discharge [3], and low or suitable intensity of shear force [4]. Rotating-drum equipment is commonly used in the process industry for drying and mixing of solid particles and materials [5][6][7][8]. Due to the mild shear force it can provide, the application of a rotating-drum bioreactor (RDB) has been explored in shear-sensitive bioprocesses, e.g., plant cell culture [9,10], solid substrate fermentation [11][12][13], composting [14], bioremediation [6,15,16], and bioleaching processes [17][18][19].…”

“…Rotating-drum equipment is commonly used in the process industry for drying and mixing of solid particles and materials [5][6][7][8]. Due to the mild shear force it can provide, the application of a rotating-drum bioreactor (RDB) has been explored in shear-sensitive bioprocesses, e.g., plant cell culture [9,10], solid substrate fermentation [11][12][13], composting [14], bioremediation [6,15,16], and bioleaching processes [17][18][19]. According to the computational fluid dynamics (CFD) investigation by Jin et al [20], RDB is likely to have a less severe impact on microorganisms since the dissipation rate of turbulent kinetic energy and the maximum particle collision intensity in an RDBs are about one order of magnitude smaller than those in a stirred-tank bioreactor.…”

Design of a new rotating drum bioreactor operated at atmospheric pressure on the bioremediation of a polluted soil

“…The diameter of the RBD hole was 0.035 m; the bioreactors were equipped with four straight lifters. The effect of lifter type (straight versus helicoidal) on g TPH was It is worth highlighting that the critical value of the rotational speed in these RDBs was 1.96/s according to the formula published in Barrera-Cortés et al [22] and Perry and Chilton [23,.…”