Simultaneous degradation of atrazine and simazine by a binary culture of Stenotrophomonas maltophilia and Arthrobacter sp. in a two‐stage biofilm reactor

BACKGROUND: The impact of mixtures of chloro‐triazinic herbicides, such as atrazine and simazine, on aquatic ecosystems is of environmental concern. To study their biodegradation under various operational conditions, a binary community comprising Stenotrophomonas maltophilia and Arthrobacter sp. attached to the porous support of a packed bed reactor, was evaluated. RESULTS: The genetic analysis of the two atrazine‐degrading strains revealed that genes atzA, atzB, atzC are present in both bacteria, but only S. maltophilia possess atzD. Thus, by cultivating Arthrobacter sp. on these herbicides, cyanuric acid accumulation was observed. When the binary community was cultivated in the biofilm reactor, at all the loading rates probed, both herbicides were entirely removed. However, complete biodegradation of cyanuric acid was not achieved. CONCLUSIONS: Even with a two‐stage reactor, cyanuric acid was only partially removed. This fact could be attributed to the absence, in the second stage, of an easily degradable energy source, required by S. maltophilia for the uptake and cometabolic degradation of the recalcitrant heterocyclic ring. Responding to differences in nutritional conditions prevailing at each reactor stage, local differences in species' predominance were clearly detected by microbiological and molecular biology methods. Copyright © 2010 Society of Chemical Industry     

A continuous ultrasound‐assisted packed‐bed bioreactor for the lipase‐catalyzed synthesis of caffeic acid phenethyl ester

BACKGROUND: The focus of this paper is the ultrasound‐assisted synthesis of caffeic acid phenethyl ester (CAPE) from caffeic acid and phenyl ethanol in a continuous packed‐bed bioreactor. Immobilized Novozym^® 435 (from Candida antarctica) is used as the catalyst. A three‐level–three‐factor Box–Behnken design and a response surface methodology (RSM) are employed to evaluate the effects of temperature, flow rate, and ultrasonic power on the percentage molar conversion of CAPE. RESULTS: Based on ridge max analysis, it is concluded that the optimum condition for synthesis is reaction temperature 72.66 °C, flow rate 0.046 mL min^?1, and ultrasonic power 1.64 W cm^?2. The expected molar conversion value is 97.84%. An experiment performed under these optimal conditions resulted in a molar conversion of 92.11 ± 0.75%. The enzyme in the bioreactor was found to be stable for at least 6 days. CONCLUSIONS: The lipase‐catalyzed synthesis of CAPE by an ultrasound‐assisted packed‐bed bioreactor uses mild reaction conditions. Enzymatic synthesis of CAPE is suitable for use in the nutraceutical and food production industries. Copyright © 2011 Society of Chemical Industry     

Biochemical methane potential (BMP) of solid organic substrates: evaluation of anaerobic biodegradability using data from an international interlaboratory study

BACKGROUND: This paper describes results obtained for different participating research groups in an interlaboratory study related to biochemical methane potential (BMP). In this research work, all experimental conditions influencing the test such as inoculum, substrate characteristics and experimental conditions were investigated. The study was performed using four substrates: three positive control substrates (starch, cellulose and gelatine), and one raw biomass material (mung bean) at two different inoculum to substrate ratios (ISR). RESULTS: The average methane yields for starch, cellulose, gelatine and mung bean at ISR of 2 and 1 were 350 ± 33, 350 ± 29, 380 ± 42, 370 ± 36 and 370 ± 35 mL CH₄ g^?1 VS_added, respectively. The percentages of biotransformation of these substrates into methane were 85 ± 8, 85 ± 7, 88 ± 9, 85 ± 8 and 85 ± 8%, respectively. On the other hand, the first‐order rate constants obtained from the experimental data were 0.24 ± 0.14, 0.23 ± 0.15, 0.27 ± 0.13, 0.31 ± 0.17 and 0.23 ± 0.13 d^?1, respectively. CONCLUSION: The influence of inocula and experimental factors was nearly insignificant with respect to the extents of the anaerobic biodegradation, while the rates differed significantly according to the experimental approaches. Copyright © 2011 Society of Chemical Industry     

浅析反应罐制造中如何防止和减少焊接应力与变形

针对制盐企业卤水反应罐制造过程中,容易出现的焊接应力与变形对整台设备结构及安装带来的影响进行原因分析,并制定相应对策措施来防止和减少焊接应力与变形,从而提高反应罐制造质量水平。     

带耐火衬里高温反应器密封锥结构的设计

耐火衬里及支撑结构设计的可靠性是保证高温反应器壳体温度小于设计温度的关键因素。针对耐火衬里结构失效导致反应器壳体温度超过设计温度的问题,提出了一种双金属焊接的密封锥结构。该结构具有支撑金属衬里的作用以及将耐火材料与金属衬里之间的膨胀空间分割成多个密闭空间以阻止高温气体的流动,进而提高隔热可靠性。采用ANSYS软件中APDL语言建立了密封锥连接结构的有限元模型,通过研究密封锥不同角度以及厚度对计算结果的影响,得出了密封锥的最佳结构参数,并满足ASME标准的应力强度评定要求。模拟结果可为此类高温反应器耐火衬里结构的设计提供参考依据。     

不同形状催化剂的F—T合成宏观动力学

采用绝热固定床积分反应器,在工业条件下,对条形及片形Ｆｅ－Ｃｕ－Ｋ工业催化剂进行了Ｆ－Ｔ合成反应性及宏观动力学考查。在稳态下,用集总的方法,保持一定的轴向温度分布,求出不同形状催化剂的宏观动力学方程,与实验数据符合较好。     

醋酸反应釜的基本结构和日常维护

醋酸反应釜是醋酸系统的重点设备,反应釜由锆/钢复合材料焊接而成,主要由7个部件组成：电机、变速箱、机械密封、机轴、导流板、叶轮和轴套等。由于反应釜控制的温度和压力较高,所以对于特材设备的日常维护就显得尤为重要。根据不同部件的工作特点,重点阐述了反应釜顶部密封垫片的更换和变速箱的拆检以及回装时的注意事项等。     

我国烷氧基化装置的工艺进展和评述（续完）

正2.1.5第5代反应器第5代反应器是PREESS喷雾反应器和BUSS文丘里混合反应器的组合,是组合式烷氧基化反应器(见图8)。第5代工艺中也有单循环回路和双循环回路2种工艺,根据产品品种的不同而采用不同的工艺。在联泓集团昊达化学有限公司工程中,生产低增长比的产品时采用无小循环回路的单回路循环工艺,生产高增长比的产品时采用双回路循环工艺。