内环流发酵反应器的能耗研究及传质强化

本文从传质和能耗两个方面对内环流发酵反应器进行了考察,强调评价内环流反应器的性能应综合考虑其传质效果和能量消耗。实验中首先研究了7种不同的气体分布器,发现多孔板型分布器在单位功耗下的传质效果最好;在此基础上,为了对内环流反应器进行强化,在其导流筒内加入了Kenics静态混合元件、螺旋叶片、弓形筛板三种内部构件。测定了其传质系数K_L(?)及液体循环时间、全塔压降等,还在其中进行了酵母培养实验。结果表明在导流筒中加入适当的内件后,环流反应器的性能可得到改善,几种内件中以弓形筛板效果最佳。     

喷射自吸式生化反应器气液传质的研究

<正> 一、前言 从宏观分析,生化反应器是非均质的包含物理传质过程的催化反应器,其催化剂为有生命活性的微生物菌体或酶。从微观概念出发,每一个微生物活细胞本身就是一个微型反应器。维持反应系统的气(氧)-液(水和营养基质、代谢产物)-固(微生物菌体)三相良好的混合与分散,尤其是较高的溶氧传质速率,是需氧生化反应器设计和放大的关键。在生化工程领域,通常以体积溶氧系数K_La和溶氧比能耗(P_W/V_L)/OTR表征气液传质效能。 我们在上文已介绍了喷射自吸式反应器的喷射吸气特性,并推导出吸气速率的数学表达式;本研究对喷射自吸式反应器的另一个重要特性——气液传质性能及其与反应器喷射     

双层桨自吸式反应器结构和性能参数的研究进展

双层桨自吸式反应器是为满足工业化发展而设计的新型组合式搅拌槽。因其兼有自吸式反应器耗能小和传统搅拌器传质性能高的优点,在食品发酵工业领域被广泛采用。文章主要介绍双层桨自吸式反应器的主要性能参数,包括气体吸入临界转速、功率消耗、气含率和体积溶氧系数。并从上层桨桨型、下层桨桨型、桨间距、有无定子等结构对双层桨自吸式反应器性能参数的影响进行综述。     

螺旋筛板气升式反应器在真菌发酵中的应用

在发酵工业中,性能优良的反应器能够起到增加产量和提高能量利用效率的作用。新研发的带有螺旋筛板的新型气升式反应器(airlift reactor with helical sieve plate,ALR-HSP),已经在空气-水实验中证实了其优良的传质特性。为研究反应器综合性能,选取2种具有代表性的真菌(高山被孢霉和毕赤酵母)在ALR-HSP中进行通风培养,分析发酵过程参数和产物组成并与经典气升式反应器(conventional airlift reactor,CALR)进行比较。结果显示:在高山被孢霉培养中,ALR-HSP内菌体的对数生长期的最大比生长速率较CALR提高30%,发酵结束后脂肪酸总量提高约40%;毕赤酵母培养中,ALR-HSP内菌体对数生长期的最大比生长速率较CALR提高20%,发酵结束后菌体浓度增长约20%。且在低通风量条件下,达到相同kLa,ALR-HSP的功率消耗比CALR减少50%。显示出螺旋筛板气升式反应器在耗氧生物培养过程中的优越传质特性和节能效益。     

自吸式生物反应器放大方法研究进展

自吸式反应器具有操作简单、传质性能好等优点,特别是不需要空气压缩机等附件,节省了供气机械的投资和运行,在化学工程、环境工程、生化工程中得到了越来越广泛的应用。自吸式反应器内涉及气液两相体系,这种两相流体流动过程中的混合、传热和传质等过程非常复杂,仍有大量问题需要理论解释。文章对自吸式生物反应器的临界转速、吸气速率、功率、气含率和传质系数的理论模型,以及经验公式进行综述,并对其CFD模拟研究进展做出概括,对于自吸式反应器的放大应用有一定的参考价值。     

下喷式液泵型生物反应器与通用发酵罐K_Lα对比及应用

下喷式液泵型生物反应器作为一种新型高效环流反应器,日益受到有关科研工作者的关注.测试了20L下喷式液泵型生物反应器在不同通风比(0.462,0.615,0.846)和不同循环液速(2.71,2.38,2.01,1.64L/min)下容积氧传递系数K_La的变化规律,并与3L搅拌式生物反应器BioFlo110作对比试验,找到一组能使两个反应器有相近容积氧传递系数(K_La≈173.2h~(-1))的操作条件.试验了_β-葡聚糖酶产生菌黑曲霉315(Aspergillus niger 315)在该反应器内的发酵代谢情况,并与3L搅拌式生物反应器BioFlo110作对比,试验结果表明该反应器产酶效率优于后者,且发酵时间缩短了6h,大幅度节省了能耗.     

新型搅拌桨组合在非牛顿流体中的传氧性能研究

为了研究新型搅拌桨组合在非牛顿流体中的传氧性能,在水和黄原胶溶液中,通过对体积传氧系数、气含率和功率的测定,对4种搅拌桨组合的传氧、气体分散和功率消耗性能进行比较。结果表明：在非牛顿流体中,抛物线圆盘桨＋翼型轴流桨＋翼型轴流桨耗能最少（Np≈1．7）,节能66％;在输入相同功率下传氧性能和气体分散性能明显好于其他三组桨,相对于小直径平直叶圆盘桨＋小直径平直叶圆盘桨＋小直径平直叶圆盘桨,体积传氧系数和气含率分别提高了45％、35％。因此,适用于非牛顿流体的组合桨,此研究结果可为工业用多层组合桨在非牛顿流体中的应用提供参考。     

新型自吸式气液搅拌釜气含率特性研究

分析了气体分散通道叶片角度、搅拌转速、介质黏度、桨叶组合对气含率的影响。研究结果表明,当气体分散通道叶片角度为30°时,在转速相同或输入相同的功率时,可以吸入更多的气体。气含率随搅拌转速和介质黏度的增大而增大。适宜的桨叶组合为六直叶圆盘桨+六叶上斜叶桨,该组合具有较高的气体吸入速率和气体分散能力,气含率较高。气含率与单位体积功耗的关系为ε∝(P_g/V)~(2.4),随单位体积功耗增大,气含率明显上升,气液分散效果更好,传质效率较高。     

真菌固定床反应器发酵L(+)-乳酸的初步研究

研究了在5L发酵罐中采用纤维床固定化技术发酵生产乳酸过程不同溶氧量和固定化面积对乳酸发酵过程的影响,测定了不同固定化面积发酵过程中的氧传质系数。在通气率为1.0vvm和固定化面积为400cm2条件下,产酸速率为2.13g/(L·h),发酵液中乳酸最终浓度为73.1g/L,L(+)-乳酸光学纯度为98.9%,证明提高发酵过程中菌体层内部溶氧传质系数有助于增加乳酸产率。乳酸发酵液浊度0.49NTU,显著改善发酵液的流体力学条件,为应用膜生物反应器技术连续发酵生产乳酸奠定了基础。     

影响聚丙烯塑料中抗氧剂BHT向食品中迁移规律因素研究

目的为降低食品包装材料对食品的污染风险,研究影响2,6-二叔丁基-4-甲基苯酚(butylated hydroxytoluene,BHT)向食品中迁移规律的因素并有效预测迁移量。方法研究了含BHT的聚丙烯母料的比表面积和模拟液的溶解度参数对BHT向模拟液中迁移规律的影响,并把Scatchard-Hilderbrand热力学理论模型预测平衡分配系数(D_(r0))与实验值(D_r)进行比较分析。结果模拟中BHT的浓度(C_t)与浸泡时间(t)符合C_t=a×(1-e~(-b×t))方程式,且塑料比表面积越大,迁移速率和迁移平衡分配系数(模拟液/塑料)越大;平衡分配系数(D_r)与比表面积(S)符合方程lnD_r=-2.944+2.157e~(-53.6S),平衡分配系数实验值与Scatchard-Hilderbrand热力学理论模型计算值随模拟液的溶解度参数变化趋势基本一致,实验值与计算值的比值随模拟液与聚丙烯的溶解度参数差值减小而增大。结论塑料的比表面积和模拟液的极性对Scatchard-Hilderbrand热力学理论预测聚丙烯中BHT向模拟液中迁移平衡分配系数有一定的影响,在向溶解度参数为7.0~13.0(cal/cm~3)~0.5范围内的模拟液中平衡分配系数的预测均有良好的适用性。     

Degradation of waste gas containing toluene in an airlift bioreactor

Suspension microorganisms in an internal-loop airlift bioreactor were utilized to treat waste gas containing toluene. The working volume of the reactor was 35 L, and the biomass concentration was 3 kg/m3. The gas pollutant flowed into the reactor from the bottom; it then transferred from the gas phase to the liquid phase and was degraded by the microorganisms suspended in the liquid phase. The microorganisms were able to degrade 50-90% of the inlet toluene when its concentration was from 0.5 to 10 g/m3, and the superficial gas velocity ranged from 0.15 to 1.23 cm/s. A comprehensive mathematical model was also developed to describe the overall degradation process of toluene in the internal-loop airlift bioreactor. The overall degradation process included gas flow, gas-liquid mass transfer, flow and dispersion of the liquid phase, and microbial kinetics. The hydrodynamic properties including the gas and liquid superficial velocities, the gas holdup, the volumetric mass transfer coefficients of toluene and oxygen, and the microbial kinetics were obtained for this model. The substrate inhibition theory was used to simulate the microorganism growth kinetics, and its kinetic constants were obtained experimentally. The penetration theory was used to predict the volumetric mass transfer coefficient. And the drift-flux theory was used to predict the hydrodynamic properties in each section (riser, gas-liquid separator, downcomer, and bottom) of the airlift bioreactor. The concentration distributions of toluene and oxygen in the airlift bioreactor and the removal efficiency of toluene predicted by the mathematical model agreed well with the experimental data.     

Computational fluid dynamics modeling of gas dispersion in multi impeller bioreactor

In the present study, experiments have been carried out to identify various flow regimes in a dual Rushton turbines stirred bioreactor for different gas flow rates and impeller speeds. The hydrodynamic parameters like fractional gas hold-up, power consumption and mixing time have been measured. A two fluid model along with MUSIG model to handle polydispersed gas flow has been implemented to predict the various flow regimes and hydrodynamic parameters in the dual turbines stirred bioreactor. The computational model has been mapped on commercial solver ANSYS CFX. The flow regimes predicted by numerical simulations are validated with the experimental results. The present model has successfully captured the flow regimes as observed during experiments. The measured gross flow characteristics like fractional gas hold-up, and mixing time have been compared with numerical simulations. Also the effect of gas flow rate and impeller speed on gas hold-up and power consumption have been investigated.     

气升式生物反应器

本文叙述了生物反应器的发展及气升式生物反应器的特点和应用,概述了设计中氧传递速率与空气分布器及上升管直径和长度之间的关系。     

DRYING of COFFEE BERRIES IN A VIBRATED TRAY DRYER OPERATED WITH SOLIDS RECYCLE and SINGLE‐STAGE1

A vibrated tray dryer was tested for drying coffee berries. It consists of a vertical chamber (0.33 m × 0.18 m × 1.30 m) provided with four trays. the trays are supported by a vibrated shaft. Experimental tests were carried out at a vibration amplitude of 1 mm and at a variable frequency. the process itself consisted of feeding the vibrated tray dryer with an initial mass of coffee berries: after leaving the dryer through the discharge channel, the berries were fed again to the top of the dryer by a bucket elevator (intermittent operation with recycle of the coffee berries). Drying tests were carried out with drying air velocity of 2.4 m/s. the drying air control temperature was related with the temperature of the coffee berries at the discharge (under 45C). the drying time required for coffee berries to reach 12.6% (wb) moisture was 28 h, initial mass (moisture of 67% wb) was 5.54 kg. In this work the influence of vibration in single‐stage drying is also shown. the single‐stage operation shows that vibration (besides promoting the conveyance of coffee berries) also reduces the time of drying.     

Solid-substrate fermentation of soybeans with Rhizopus spp.: comparison of discontinuous rotation with stationary bed fermentation

Tempe is a soybean food obtained by stationary solid-substrate fermentation using moulds (mainly Rhizopus spp.) as starter organism. Traditionally, tempe is fermented in static layer trays or wrapped packages. Due to heat and mass transfer limitations, gradients of temperature and gas atmosphere will result. Agitated fermentation can help to level heat and mass gradients, yielding better homogeneity. This type of process will not result in traditional tempe, but in individually fermented soybeans that could be processed into food ingredients. This report deals with the comparative effect of stationary versus agitated solid-substrate fermentation of soybeans on some chemical indices of substrate modification. For agitated solid-substrate fermentation, a 450-l size rotary-drum bioreactor was designed and constructed. Of two Rhizopus spp. tested, R. microsporus tolerated agitation quite well, as judged by changes of pH, amino nitrogen, ammonia, and soluble dry matter. The other species, R. oligosporus was strongly affected by agitation. This resulted in less pH increase (difference approx. 1.5 units), lower amino nitrogen levels (30-50% of levels in static fermentation), and lower levels of water-soluble non-lipid dry matter (30-50% of levels in static fermentation) with R. oligosporus agitated fermentation of soybeans controlled at 30 and 37 degrees C, compared to static fermentation at temperatures ranging between 25-35 and 30-40 degrees C, respectively.     

Air Inclusion Into a Model Cake Batter Using a Pressure Whisk: Development of Gas Hold-up and Bubble Size Distribution

ABSTRACT: This paper investigates the development of gas hold-up (that is, gas volume fraction) and bubble size distribution in a model cake batter, which is aerated in a pressure whisk. With increasing aeration time, the hold-up was found to pass through a maximum before approaching a uniform steady state value. A mathematical model that describes this profile has been developed. Bubble size distribution was found to be adequately described by a log normal distribution function with mean size varying between 20 and 50 μm. Higher pressures were found to increase hold-up and mean bubble size, whereas higher whisk speeds reduced the time required to achieve a given hold-up and the final mean bubble size.     

Effect of capsule circulation velocity on production of L-lysine by encapsulated Corynebacterium glutamicum in an airlift bioreactor

The effect of capsule circulation velocity and volumetric oxygen transfer coefficient on the production of L-lysine by encapsulated Corynebacterium glutamicum in an airlift bioreactor has been evaluated. A larger oxygen supply in the airlift bioreactor caused a more than 58% increase in L-lysine productivity compared to that in a shaking flask incubator. The quantity of L-lysine produced during 5 h of cultivation in the airlift bioreactor was suggested to increase with increasing circulation velocity of the capsule in the bioreactor rather than with an increase in volumetric oxygen transfer coefficient.     

The influence of agitation on aroma release

We have developed a new methodology for measuring aroma release by coupling together two high performance instruments, a proton-transfer-reaction mass spectrometer and closed-cell pressure-controlled rheometer. In this article we report the aroma release from aqueous solutions as a function of different agitation levels, in connection with the theoretical model of mass transfer across interfaces. Two aspects are described in more detail: (1) the use of model parameters to fit the aroma release curves, and (2) the underlying theoretical model in terms of the separate mass transfer coefficients for the liquid phase and the gas phase, including the dependency of these mass transfer coefficients on agitation.As expected from classical theories, the mass transfer coefficient for the liquid phase was found to correlate with agitation of the liquid phase following a power law relation. The overall aroma release was found to be related to a combination of factors: the thermodynamic equilibrium partition coefficient, as well as the mass transfer coefficient for the liquid phase (at low agitation levels) and the mass transfer coefficient for the gas phase (at high agitation levels).Industrial relevanceThe use of modelling based on the dynamics and mechanistic aspects of aroma release enables a better understanding of the aroma release in real life, and therefore a shorter development cycle for new products. Currently, many experimental studies on aroma release underexpose the need for understanding the dynamics and mechanistic aspects of mass transfer. The new methodology with more accurate measurements and more robust fitting is essential for obtaining experimental data that can be fitted with details of mass transfer models. Furthermore, the experimental system and approach can be used directly in an empiric way for the optimization of the aroma impact and profile of new food products.     

高效生物反应器处理脱墨废水

利用高效生物反应器(HCR)处理脱墨废水，通过反应器启动、运行、水力停留时间等方面的试验，得出用此反应器处理脱墨废水，对CODcr、BOD5、浊度等都取得了良好的去除效果。