双环流气升式反应器流动及混合特性研究
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摘要
气升式反应器因其结构简单、良好的混合传热性能、便于操作等优点已广泛用于化工、生物化工等行业。国内外学者对其进行了广泛而深入的研究，其中包括从对物料的性质、反应器的操作条件、反应器的结构等方面考察气升式反应器的流体力学、传递性能等方面。
喷射环流反应器(JLR)因其高效的多相传递性能以及简单的设备结构、低能耗、易于操作等优点，已广泛应用于生物、环境化工过程中。对于喷射环流反应器的性能，多针对有氧过程，其研究对象多集中在细长型反应器上，其中对高径(H／D)比为7～12的反应器的研究约占70％以上，研究的重点侧重于气液传质效果，气体停留时间等。而对于适用于厌氧反应的低高径比反应器性能的研究报道则很少见。
气升式反应器在好氧发酵中已被大量采用，在厌氧反应领域的应用则很少见。目前，厌氧发酵中，以酒精发酵生产为例，应用较多的还是传统的无搅拌大型罐。这类反应器的总体特点是：结构简单，具有较低的高径比(一般H／D=1.1：1左右)。随着生产规模的大型化，其应用中存在的问题也日益暴露。
大型罐在酒精生产使用过程中，存在易积物、易染菌，浓度梯度差大等问题，同时在后发酵期又会因积料占去一定的罐容，使发酵时间被迫缩短从而引发原料的浪费与酒精产率的降低。
将喷射环流反应器应用于厌氧发酵，主要通过气液内循环使醪液搅动，减少滞留和染菌现象。其中由于在喷射过程中，气液混合强度很大，剪切力也很大，这对于消除细胞周围的代谢物抑制膜将十分有利。同时考虑到生产大型化发展趋势的要求，宜在内循环的基础上加入外循环以实现外冷，减少内部复杂冷却清洗装置，增加有效罐容。同时由于喷射自吸式环流反应器循环量与通气量的调节方便，结构形式简单易于实现连续化操作，对于厌氧发酵过程，所需的气量不大故而又可节约附加设备投资。
本文重点针对厌氧反应的特点，将喷射式双环流反应器用于厌氧发酵过程。对一种具有低高径比(H／D=1.67)的双环流气升式反应器的流动及混合性能进行了研究。主要考察导流简直径、外循环流量，通气量的变化对气含率、混合时间、循环液速及单位体积料液功耗的影响。由于喷射自吸式反应器在喷射过程中能耗损失较
大.因此我们采用通气和吸气两种不同的气体引入方式，将两种情况下反应器的流
动、混合及功耗情况进行研究。将二者进行经济性对比。为工业实际应用提供一定
参考。
本实验包括内、外两个循环通路。实验介质为:空气一水体系，气液比范围为
0.01一o.lm3(G)/mi可耐(L);外循环流范围为:通气情况2一6m3/h，吸气情况3一sm，瓜;
导流筒直径变化范围D‘/D。=0.733，0.76，0.787。
实验主要采用的测量方法:气含率的测量采用体积膨胀法:下降区循环液速、
混合时间的测量采用电导示踪迹法。泵有效功率的计算运用柏努力方程式求得。压
缩空气功率按绝热过程计算。
通过对实验结果进行分析和讨论，在实验范围内回归到得相应关联式。
实验范围内，不论是通气还是吸气情况，气含率与循环液速均随表观气速的增
大而增大。气含率受表观气速影响，其变化规律可用:一Ku霎或近似以直线
:=A十Bug关系描述。外循环流量对气含率影响不大。外循环流量较小时，气含率
随外循环流量增大而减小。循环液速随外循环流量的增大而增大。
混合时间随表观气速及外循环流量的增大而减小。吸气时的混合情况要好于通
气情况。功耗随表观气速及外循环流量的增大而增大。其主要取决于外循环流量的
大小。达到相同的混合效果时，吸气时所消耗的功率要远大于通气情况。导流筒尺
寸变化对气含率、混合时间及功耗的影响可通过一定的无因次关系反映。
Airlift reactor has been widely used in chemical industry, biological chemistry for their simple construction, good mixing ,good heat conducting performance, and easy to be operated compared with stirred tanks. It has been extensively studied by scholars at home and abroad, including trying to evaluate its hydrodynamics performance and transmitting capability from material character, operation condition, and constructions of the reactor.
Jet loop reactor(JLR) is a kind of multiphase reactors with high-efficient heterogeneous transmission performance, simple device structure, high heat and mass transfer rates, well mixing effects, low energy consumption and easy to be operated etc. It has been used in biology engineering and chemical environment industry extensively.
Most research of JLR's performance is focused on aerobiosis course. More than 70 percent of all the reactors studied were slightness, with ratio of height to diameter about 7-12. Focal points were particularly emphasized on mass transfer rates between gas and liquid and the time of gas held up. Few reports about the anaerobic reactors with low ratio of height to diameter can be found.
ALR has already been adopted in a large amount in the anaerobic fermentation, but fewer can be found during anaerobic fermentation In anaerobic fermentation, for example alcoholic fermentation, what are used more often present are still traditional large pots without blender apparatus. The overall characteristic of this kind of reactor is its simple constructions and of low ratio of height to diameter (often H/D=1.1:1). With the development of large-scale production, problems existing in its applications become increasingly day by day. While applied to alcohol production, large-scale pot is apt to accumulate materiel, easy to infect other bacteria and often of heavy concentration gradient. At the same time, materiel accumulation will occupy most effective space which tends to shorten fermentation time, cause waste of raw materials and reduce production rate alcohol.
While applied JLR to anaerobic fermentation, material can be stirred by inside
circulation of gas and liquid to reduce held up and infect other bacteria. During the course of jetting, gas and liquid are mixing strongly and shear strength becomes even heavy. Thus pays for dispel suppress membrane of metabolite near yeast cell. Consider requests of the development trend of large scale production meanwhile, outside circulation should be put into account in order to realize outside cooling on the basis of circulating inside, therefore, inside complicated cooling wash device could be reduced as a result, effective pot hold would increase. Meanwhile the flux of fluid and gas will be convenient to regulate when JLR are adopted. The reactor's structure becomes simple and easy to realize continuous production. Besides, in anaerobic fermentation not large amount of gas is needed, therefore investment for additional equipment will be reduced to some extent.
Considering the character of anaerobic reaction, one kind of double loop jet-air lift bioreactor is applied in anaerobic fermentation. Flow and mixing characteristic of one kind of double loop air lift bioreactor with low ratio of height to diameter ( H/D=1.67) are studied in this paper. How changes of diversion tubes diameter, flux of gas and outside circulation influence the total gas hold up, mixing time, liquid circulation speed and consumption of unit volume material are mainly studied in this paper. Considering that jet-inhale course consume more energy and of high loss, two kinds of different introducing ways of gas: inhale gas and ventilate gas are adopted. Flow and mixing effect of the two are compared. Economic contrast of them is carried on too, to offer for industry's practical application. The experiment includes two circulations, inside and outside circulation.
Air and water were used as gas and liquid phase; the volume ratio of gas to liquid is 0.01~0.1m3(G)/min/ m3 (L); volume of outside circulation flux is: ventilate gas: 2~6m3/h; inhale gas: 3~5m
喷射环流反应器(JLR)因其高效的多相传递性能以及简单的设备结构、低能耗、易于操作等优点，已广泛应用于生物、环境化工过程中。对于喷射环流反应器的性能，多针对有氧过程，其研究对象多集中在细长型反应器上，其中对高径(H／D)比为7～12的反应器的研究约占70％以上，研究的重点侧重于气液传质效果，气体停留时间等。而对于适用于厌氧反应的低高径比反应器性能的研究报道则很少见。
气升式反应器在好氧发酵中已被大量采用，在厌氧反应领域的应用则很少见。目前，厌氧发酵中，以酒精发酵生产为例，应用较多的还是传统的无搅拌大型罐。这类反应器的总体特点是：结构简单，具有较低的高径比(一般H／D=1.1：1左右)。随着生产规模的大型化，其应用中存在的问题也日益暴露。
大型罐在酒精生产使用过程中，存在易积物、易染菌，浓度梯度差大等问题，同时在后发酵期又会因积料占去一定的罐容，使发酵时间被迫缩短从而引发原料的浪费与酒精产率的降低。
将喷射环流反应器应用于厌氧发酵，主要通过气液内循环使醪液搅动，减少滞留和染菌现象。其中由于在喷射过程中，气液混合强度很大，剪切力也很大，这对于消除细胞周围的代谢物抑制膜将十分有利。同时考虑到生产大型化发展趋势的要求，宜在内循环的基础上加入外循环以实现外冷，减少内部复杂冷却清洗装置，增加有效罐容。同时由于喷射自吸式环流反应器循环量与通气量的调节方便，结构形式简单易于实现连续化操作，对于厌氧发酵过程，所需的气量不大故而又可节约附加设备投资。
本文重点针对厌氧反应的特点，将喷射式双环流反应器用于厌氧发酵过程。对一种具有低高径比(H／D=1.67)的双环流气升式反应器的流动及混合性能进行了研究。主要考察导流简直径、外循环流量，通气量的变化对气含率、混合时间、循环液速及单位体积料液功耗的影响。由于喷射自吸式反应器在喷射过程中能耗损失较
大.因此我们采用通气和吸气两种不同的气体引入方式，将两种情况下反应器的流
动、混合及功耗情况进行研究。将二者进行经济性对比。为工业实际应用提供一定
参考。
本实验包括内、外两个循环通路。实验介质为:空气一水体系，气液比范围为
0.01一o.lm3(G)/mi可耐(L);外循环流范围为:通气情况2一6m3/h，吸气情况3一sm，瓜;
导流筒直径变化范围D‘/D。=0.733，0.76，0.787。
实验主要采用的测量方法:气含率的测量采用体积膨胀法:下降区循环液速、
混合时间的测量采用电导示踪迹法。泵有效功率的计算运用柏努力方程式求得。压
缩空气功率按绝热过程计算。
通过对实验结果进行分析和讨论，在实验范围内回归到得相应关联式。
实验范围内，不论是通气还是吸气情况，气含率与循环液速均随表观气速的增
大而增大。气含率受表观气速影响，其变化规律可用:一Ku霎或近似以直线
:=A十Bug关系描述。外循环流量对气含率影响不大。外循环流量较小时，气含率
随外循环流量增大而减小。循环液速随外循环流量的增大而增大。
混合时间随表观气速及外循环流量的增大而减小。吸气时的混合情况要好于通
气情况。功耗随表观气速及外循环流量的增大而增大。其主要取决于外循环流量的
大小。达到相同的混合效果时，吸气时所消耗的功率要远大于通气情况。导流筒尺
寸变化对气含率、混合时间及功耗的影响可通过一定的无因次关系反映。
Airlift reactor has been widely used in chemical industry, biological chemistry for their simple construction, good mixing ,good heat conducting performance, and easy to be operated compared with stirred tanks. It has been extensively studied by scholars at home and abroad, including trying to evaluate its hydrodynamics performance and transmitting capability from material character, operation condition, and constructions of the reactor.
Jet loop reactor(JLR) is a kind of multiphase reactors with high-efficient heterogeneous transmission performance, simple device structure, high heat and mass transfer rates, well mixing effects, low energy consumption and easy to be operated etc. It has been used in biology engineering and chemical environment industry extensively.
Most research of JLR's performance is focused on aerobiosis course. More than 70 percent of all the reactors studied were slightness, with ratio of height to diameter about 7-12. Focal points were particularly emphasized on mass transfer rates between gas and liquid and the time of gas held up. Few reports about the anaerobic reactors with low ratio of height to diameter can be found.
ALR has already been adopted in a large amount in the anaerobic fermentation, but fewer can be found during anaerobic fermentation In anaerobic fermentation, for example alcoholic fermentation, what are used more often present are still traditional large pots without blender apparatus. The overall characteristic of this kind of reactor is its simple constructions and of low ratio of height to diameter (often H/D=1.1:1). With the development of large-scale production, problems existing in its applications become increasingly day by day. While applied to alcohol production, large-scale pot is apt to accumulate materiel, easy to infect other bacteria and often of heavy concentration gradient. At the same time, materiel accumulation will occupy most effective space which tends to shorten fermentation time, cause waste of raw materials and reduce production rate alcohol.
While applied JLR to anaerobic fermentation, material can be stirred by inside
circulation of gas and liquid to reduce held up and infect other bacteria. During the course of jetting, gas and liquid are mixing strongly and shear strength becomes even heavy. Thus pays for dispel suppress membrane of metabolite near yeast cell. Consider requests of the development trend of large scale production meanwhile, outside circulation should be put into account in order to realize outside cooling on the basis of circulating inside, therefore, inside complicated cooling wash device could be reduced as a result, effective pot hold would increase. Meanwhile the flux of fluid and gas will be convenient to regulate when JLR are adopted. The reactor's structure becomes simple and easy to realize continuous production. Besides, in anaerobic fermentation not large amount of gas is needed, therefore investment for additional equipment will be reduced to some extent.
Considering the character of anaerobic reaction, one kind of double loop jet-air lift bioreactor is applied in anaerobic fermentation. Flow and mixing characteristic of one kind of double loop air lift bioreactor with low ratio of height to diameter ( H/D=1.67) are studied in this paper. How changes of diversion tubes diameter, flux of gas and outside circulation influence the total gas hold up, mixing time, liquid circulation speed and consumption of unit volume material are mainly studied in this paper. Considering that jet-inhale course consume more energy and of high loss, two kinds of different introducing ways of gas: inhale gas and ventilate gas are adopted. Flow and mixing effect of the two are compared. Economic contrast of them is carried on too, to offer for industry's practical application. The experiment includes two circulations, inside and outside circulation.
Air and water were used as gas and liquid phase; the volume ratio of gas to liquid is 0.01~0.1m3(G)/min/ m3 (L); volume of outside circulation flux is: ventilate gas: 2~6m3/h; inhale gas: 3~5m
引文
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[2] McDuffie N G. Bioreactor design fundamentals, Butter worth-Heinemann, Boston,1991;
[3] Blenke H.,Ghose T K. Advances in Biochemical Engineering(13), Springer-Verleg,1979, 122;
[4] Siegel M H, Hallaile M, Merchuk J. A. Mizrahied. Advances in Biotechnological Processes (7), Alan R Liss, 1988, 79;
[5] 杨文选，尚龙安．化工机械，1990，17(3)：177-183；
[6] 刘辉，胡宗定．喷射环流反应器性能与模化[J] 化学工程，1996，24(1)：30-36；
[7] Havelka P, Linek V, Sinkule J, et al. Effect of the ejector configuration on the gas suction rate and holdup in ejector loop reactors[J]. Chem Eng Sci, 1997, 52: 1701-1713;
[8] Rene F Duveen. High performance gas liquid reaction technology[A]. The Royal Society of Chemistry, Applied Catalysis Group. New frontiers in reactor design[C]. Billingham: The Royal Society of Chemistry. 1988.1-14;
[9] Has-Jurgen Henzler. Design of ejectors for single-phase material systems[J]. Ger Chem Eng, 1986 (6): 292-300
[10] 黄秋云译 喷射器[M]．北京：科学出版社，1997．3；
[11] CAMC Dirix, K Vander Wiele, Mass transfer in jet loop reactors[J]. Chem Eng Sci, 1990, 45: 2333-2340;
[12] Jain D K, Patwari A V, M Bhagawantha Rao, et al. Liquid circulation characteristics in jet loop reactors[J] Can J Chem Eng, 1990, 68: 1047-1051;
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