Gas-liquid as well as gas-liquid-solid bubble column reactors are extensively used in the chemical industry. This review evaluates the present state of the art for the estimation of "nonadjustable" parameters in bubble column reactors. All the pertinent literature concerning these parameters is discussed and the discussion is followed by re1evant.recommendations for their predictions. Literature on the modified bubble columns has beem incorporated. Finally, the inadequacies of the data in some areas of practical importance have been pointed out and the recommendations for future work are outlined. Y. T. SHAH SCOPEIt is well known that bubble column reactors have a wide range of applications such as absorption, catalytic slurry reactions, bioreactions, coal liquefaction etc. These reactors are preferred because of simplicity of operation, low operating costs, and ease with which liquid residence time can be varied. The vast literature makes it impossible to cover all the aspects of bubble column reactors in one review; therefore, we limit ourselves in this review to the parametric estimations in bubble column reactors. The only unified review on bubble columns was published by Mashelkar (1970). Since then, many articles have been published on different aspects of bubble columns, except for the estimations of non-adjustable parameters. This paper attempts to bring about a more complete and up-to-date review of this subject matter.In the introduction, a comprehensive list of processes in which bubble columns are used is presented. Bubble dynamics and flow regimes indirectly influence the scaleup and design of bubble column reactors; and hence, these aspects are discussed initially along with relevant recommendations. Nonadjustable parameters like phase holdup, gas-liquid interfacial area, interfacial mass transfer coefficients, dispersion coefficients and heat transfer coefficients have a direct bearing on the problems associated with the design of the bubble column reactors. A critical analysis of the available literature on each of these parameters is presented in conjunction with the recommendations for their estimation. Wherever possible, the literature on modified bubble columns pertaining to these parameters, is also outlined. Finally, suggestions for the future work on bubble columns are offered. CONCLUSIONS AND SIGNIFICANCEOver the past two decades, an extensive effort has been directed to the scaleup of bubble column reactors. Though easy to use, bubble columns are difficult to design because of the complexity of flow characteristics, and their unknown behavior under different sets of design parameters such as diameter, height, etc. The present review indicates that there are numerous methods available to evaluate the non-adjustable parameters; few of which are based on extensive collection of data.For water-like less viscous fluids, flow regime characteristics can be depicted with help of Richardson and Zaki's (1954) correlation. Unfortunately, no systematic effort has been made to study the effect of flu...

Summary: It is demonstrated that PET, which is usually regarded as ‘non‐biodegradable’, can effectively be depolymerized by a hydrolase from the actinomycete Thermobifida fusca. Erosion rates of 8 to 17 µm per week were obtained upon incubation at 55 °C. Lipases from Pseudomonas sp. and Candida antarctica did not degrade PET under comparable conditions. The influences of crystallinity, melting point, and glass transition temperature on the enzymatic attack on PET, PBT, and PHB are discussed.Outline of the degradation of PET.imageOutline of the degradation of PET.

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