Mass transfer in gas-liquid stirred reactor with various triple-impeller combinations

doi:10.1016/j.cjche.2015.12.008

Abstract

Abstract: The gassed power demand and volumetric mass transfer coefficient (k_Lα) were investigated in a fully baffled, dished-base stirred vessel with a diameter of 0.30 m agitated by five triple-impeller combinations. Six types of impellers (six-half-elliptical-blade disk turbine (HEDT), four-wide-blade hydrofoil impeller (WH) pumping down (D) and pumping up (U), parabolic-blade disk turbine (PDT), and CBY narrow blade (N) and wide blade (W)) were used to form five combinations identified by PDT+2CBY_N, PDT+2CBY_W, PDT+2WH_D, HEDT+2WH_D and HEDT+2WH_U, respectively. The results show that the relative power demand of HEDT+2WH_U is higher than that of other four impeller combinations under all operating conditions. At low superficial gas velocity (u_G), k_Lα differences among impeller combinations are not obvious. However, when u_G is high, PDT+2WH_D shows the best mass transfer performance and HEDT+2WH_U shows theworstmass transfer performance under all operating conditions. At high u_G and a given power input, the impeller combinations with high agitation speed and big projection cross-sectional area lead to relatively high values of kLa. Based on the experimental data, the regressed correlations of gassed power number with Froude number and gas flow number, and k_Lα with power consumption and superficial gas velocity are obtained for five different impeller combinations, which could be used as guidance for industrial design.

Key words: Stirred vessel, Gassed power, Mass transfer, Triple-impeller combination, Gas-liquid system

摘要： The gassed power demand and volumetric mass transfer coefficient (k_Lα) were investigated in a fully baffled, dished-base stirred vessel with a diameter of 0.30 m agitated by five triple-impeller combinations. Six types of impellers (six-half-elliptical-blade disk turbine (HEDT), four-wide-blade hydrofoil impeller (WH) pumping down (D) and pumping up (U), parabolic-blade disk turbine (PDT), and CBY narrow blade (N) and wide blade (W)) were used to form five combinations identified by PDT+2CBY_N, PDT+2CBY_W, PDT+2WH_D, HEDT+2WH_D and HEDT+2WH_U, respectively. The results show that the relative power demand of HEDT+2WH_U is higher than that of other four impeller combinations under all operating conditions. At low superficial gas velocity (u_G), k_Lα differences among impeller combinations are not obvious. However, when u_G is high, PDT+2WH_D shows the best mass transfer performance and HEDT+2WH_U shows theworstmass transfer performance under all operating conditions. At high u_G and a given power input, the impeller combinations with high agitation speed and big projection cross-sectional area lead to relatively high values of kLa. Based on the experimental data, the regressed correlations of gassed power number with Froude number and gas flow number, and k_Lα with power consumption and superficial gas velocity are obtained for five different impeller combinations, which could be used as guidance for industrial design.

关键词: Stirred vessel, Gassed power, Mass transfer, Triple-impeller combination, Gas-liquid system

Jinjin Zhang, Zhengming Gao, Yating Cai, Ziqi Cai, Jie Yang, Yuyun Bao. Mass transfer in gas-liquid stirred reactor with various triple-impeller combinations[J]. Chin.J.Chem.Eng., 2016, 24(6): 703-710.

Jinjin Zhang, Zhengming Gao, Yating Cai, Ziqi Cai, Jie Yang, Yuyun Bao. Mass transfer in gas-liquid stirred reactor with various triple-impeller combinations[J]. Chinese Journal of Chemical Engineering, 2016, 24(6): 703-710.

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