Packed-bed Reactor

Palm stearin (POs) and palm kernel olein (PKOo) blends were modified by enzymatic interesterification (IE) to achieve the physical properties of margarine fats. POs and PKOo are both products of the palm oil industry that presently have limited use. Rhizomucor miehei lipase (Lipozyme IM 60) was used to catalyze the interesterification of oil blends at 60°C. The progress of interesterification was monitored by following changes in triacylglyceride composition. At 60°C interesterification can be completed in 5 h. Degrees of hydrolysis obtained through IE for all blends were decreased from 2.9 to 2.0 by use of dry molecular sieves. The solid fat contents of POs/PKOo 30:70 and 70:30 interesterified blends were 9.6 and 18.1 at 20°C, and 0 and 4.1 at 35°C, respectively. The slip melting point (SMP) of POs/PKOo 30:70 was 40.0°C before interesterification and 29.9°C after IE. For POs/PKOs 70:30, SMP was 47.7 before and 37.5°C after IE. These thermal characteristics of interesterified POs/PKOo blend ratios from 30:70 to 70:30 were comparable to those of commercial margarines. Results showed that IE was effective in producing solid fats with less than 0.5% trans.

The energy industry needs to take action against climate change by improving efficiency and increasing the share of renewable sources in the energy mix. On top of that, refrigeration, air-conditioning, and heat pump equipment account for 25–30% of the global electricity consumption and will increase dramatically in the next decades. However, some waste cold energy sources have not been fully used. These challenges triggered an interest in developing the concept of cold thermal energy storage, which can be used to recover the waste cold energy, enhance the performance of refrigeration systems, and improve renewable energy integration. This paper comprehensively reviews the research activities about cold thermal energy storage technologies at sub-zero temperatures (from around −270 °C to below 0 °C). A wide range of existing and potential storage materials are tabulated with their properties. Numerical and experimental work conducted for different storage types is systematically summarized. Current and potential applications of cold thermal energy storage are analyzed with their suitable materials and compatible storage types. Selection criteria of materials and storage types are also presented. This review aims to provide a quick reference for researchers and industry experts in designing cold thermal energy systems. Moreover, by identifying the research gaps where further efforts are needed, the review also outlines the progress and potential development directions of cold thermal energy storage technologies.

The disposal of 280 million tires generated each year in the U.S. is a great environmental problem. The tires take up large amounts of valuable landfill space and also present fire and health hazards. Tire-pyrolysis plants have been in operation for years, but the economics are poor, and most of these facilities have been shut down. This is mainly due to the low value of the end products, which are usually fuels (oil, pyrolysis gas, char). It is believed that reprocessing of waste tires into value-added products would improve the economic leverage. This study addresses reprocessing of oils derived from waste-tire pyrolysis into carbon black - a valuable feedstock for the manufacture of tires, other rubber products, paints, pigments, ink, powder coating, toner, etc. Such a process would form a recycling loop for the carbon black recovered from waste tires. The objective of this work was to demonstrate the feasibility of the proposed approach in a laboratory scale. More specifically, ...

Nowadays process safety is a key issue at the design and operation of a production process. Unfortunately, at the application of process hazard analysis (PHA) techniques the time aspect of operation and the dynamical behaviour of the process are neglected. This is due to the small number of easily available tools which can be applied to perform dynamical process simulation and dynamical analysis. However, in recent times dynamical models are increasingly applied to support the solution of any tasks related to process safety. Another problem that makes it difficult to take into account time, is the lack of a standardized concept and evaluation system to integrate the obtained information into the design procedure of safety integrated system (SIS). The aim of this article is to investigate the role of time in the design of process safety elements (PSEs), and to define the connection between the process and the time by using the process safety time (PST) term, as well as to give a methodology how PST can be designed based on the process simulator and applied in the development of PSEs. The developed methodology is based on dynamical analysis of the system and the possible safety actions. Based on this methodology, an algorithm has been developed to detect unsafe situations and to determine the necessary safety actions that can be used to avoid the undesired states of operation. The algorithm has been applied in the solution of an industrial problem related to reactor runaway.

In this study, a simple and effective technique for characterizing Michaelis–Menten apparent kinetic parameters in packed-bed immobilized enzyme reactors is presented. The apparent kinetic parameters of immobilized glucose oxidase on weak base ion exchanger resin (Duolite A 568) were determined for different substrate flow rates in a recirculation system and compared with those for soluble glucose oxidase. It was observed that, for the experimental conditions, the immobilized enzyme K′m values in a packed-bed reactor were less than the soluble enzyme Km value and were flow dependent. The value of K′m decreased with increasing flow rate.

The present research work deals with the performance of packed bed reactor for continuous H2 production using cane molasses as a carbon source. Maximum H2 production rate of 1.7 L L−1 h−1 was observed at a dilution rate and recycle ratio of 0.8 h−1 and 0.6, respectively which was corresponding to the lowest NADH/NAD+ ratio. This suggests that the utilization of NADH pool for H2 and metabolite production might lead to decrement in NADH/NAD+ ratio. Thus NADH/NAD+ ratio show inverse relation with hydrogen production. The substrate degradation kinetics was investigated as a function of flow rate considering the external film diffusion model. At a flow rate of 245 mL h−1, the contribution of external film mass transfer coefficient and first order substrate degradation constant were 55.4% and 44.6% respectively. Recycle ratio of 0.6 improved the hydrogen production rates by 9%. The viable cell count was directly proportional to the recycle ratio (within the range 0.1–0.6). Taguchi design showed the significant influence of the feed pH on continuous H2 production followed by dilution rate and recycle ratio. Thus environmentally friendly and cheaper solid matrix like coconut coir could be efficiently used for thermophilic continuous hydrogen production.

In this study, a novel continuous reactor has been developed to produce high quality methyl esters (biodiesel) from palm oil. A microporous TiO2/Al2O3 membrane was packed with potassium hydroxide catalyst supported on palm shell activated carbon. The central composite design (CCD) of response surface methodology (RSM) was employed to investigate the effects of reaction temperature, catalyst amount and cross flow circulation velocity on the production of biodiesel in the packed bed membrane reactor. The highest conversion of palm oil to biodiesel in the reactor was obtained at 70°C employing 157.04g catalyst per unit volume of the reactor and 0.21cm/s cross flow circulation velocity. The physical and chemical properties of the produced biodiesel were determined and compared with the standard specifications. High quality palm oil biodiesel was produced by combination of heterogeneous alkali transesterification and separation processes in the packed bed membrane reactor. © 2010 Elsevier Ltd.

http://ac.els-cdn.com/S0960852410014574/1-s2.0-S0960852410014574-main.pdf?_tid=74bcbdf2-025e-11e4-8ea3-00000aab0f27&acdnat=1404356723_f959262287254ffe4bce3abeee7084d9 
http://www.sciencedirect.com/science/article/pii/S0960852410014574

Gas-phase solar receivers can operate over a wider temperature range than receivers which use conventional liquid heat transfer media. However, due to their relatively poor heat transfer performance, gas-phase receivers require substantially more heat transfer area and/or higher flow rates to extract the same amount of heat which leads to more complicated designs (e.g. a porous-media absorber with small feature/pore size) and decreased reliability (e.g. internal temperature gradients and higher thermal stresses). Detailed numerical modelling techniques can help elucidate the fundamental heat and mass transfer mechanisms/interactions in such to help mitigate these risks and to create innovative, high-performance, designs. To collate the research efforts towards gas-phase receiver modelling, this paper systematically reviews—and critically compares—the latest numerical studies of various high-temperature gas-phase receiver designs. It was found that, from a numerical point of view, gas-phase receivers can be categorised by whether they contain a porous medium or not. This categorisation is crucial, because it dictates the numerical techniques needed to capture the underlying phenomena. This review also found that no standardised performance metrics are reported for gas-phase receivers. We suggest that a holistic figure of merit, such as the one developed by Lenert et al. (Lenert et al. 2012), be adopted in this field to merge all performance criteria for comparative evaluation. Overall, the present review is expected to serve as a guide for the development/enhancement of receiver designs based on linking best practices in simulation/modelling with the key features and limitations of gas-phase receivers.

In this study we focus our attention on a strategy to deal with packed-bed catalytic reactors in order to present an alternative methodology for the derivation of a new explicit equation for the determination of apparent kinetics coefficients for first order reactions. The Özdural–Alkan methodology, originally used in membrane separations, was followed during the analytical solution of the governing PDE of the system whose solution have resulted the explicit equation sought. The apparent kinetics coefficients obtained through the above-mentioned explicit equation were compared and verified with the numerical solution results of the same system where two different numerical techniques were employed independently. It was concluded that the proposed equation successfully predicts the apparent first order kinetics coefficient in recycling packed-bed catalytic reactors with the use of a single reservoir concentration measurement and the corresponding time data.