The effect of materials, process settings and screw geometry on energy consumption and melt temperature in single screw extrusion

YesPolymer extrusion is an energy intensive production process and process energy e ciency has become a key concern in the current industry with the pressure of reducing the global carbon footprint. Here, knowledge of the pattern of energy usage and losses of each component in the plant is highly useful in the process energy optimization. Moreover, it is essential to maintain the melt quality while improving the energy e ciency in polymer processing. In this work, an investigation was made on the total energy consumption, drive motor energy consumption, power factor and the melt temperature profile across the die melt flow (as an indication of the melt thermal quality) of an industrial scale extruder with three di erent screw geometries, three polymer types and wide range of processing conditions (altogether 135 di erent processing situations were observed). This aims to widen the knowledge on process energy and thermal behaviors while exploring possible correlation/s between energy demand and melt quality (in terms of melt temperature fluctuations across the melt flow). The results showed that the level and fluctuations of the extruder’s power factor is particularly dependent upon the material being processed. Moreover, it seems that there is a relation between the level of energy demand of the heaters and the level of melt temperature fluctuations. While the extruder specific energy consumption decreases with increasing screw speed, specific energy consumption of the drive motor may have either increasing or decreasing behavior. Overall, this study provides new insights in a wide range on process energy demand and melt thermal quality in polymer extrusion. Moreover, further research is recommended to establish strong correlation/s between process energy consumption and melt thermal quality which should help to enhance process control and hence the product quality in single screw polymer extrusion

Improving the Performance of Shell-and-Tube Heat Exchangers by the Addition of Swirl

Heat exchanger is a component which is used to transfer the heat from one medium to another efficiently. Generally, they occupy a large space compared to other components and such bulky designs are not attractive in the modern industrial applications due to several constraints. Therefore, it is invaluable to develop compact heat exchangers but with the improved performance. In this work, an investigation was made on the possibility of reducing the size of a shell-and-tube heat exchanger by addition of swirl. Swirl was generated by using a twisted-tape which inserted inside tube and the effects of these tapes on the heat transfer rate and pressure drop were theoretically studied. The results showed that a half-length regular spaced twisted-tape insert gave the lowest Nusselt number while a full-length twisted-tape insert gave the maximum Nusselt number and hence the highest rate of heat transfer. The length of the heat exchanger could be reduced by 13.3% with a full-length twisted tape and this would be result in 6.8% of reduction of the fabrication cost. Therefore, addition of swirl into the fluid flow should help to design compact and low cost heat exchanges with improved performance but the pressure drop increased leading to an increase of the required pumping power. A prototype shell-and-tube heat exchanger was designed and fabricated based on the theoretical results. Studies are underway to experimentally investigate the overall effectiveness of the use of twisted-tape inserts for enhancing the heat transfer rate by considering all the related benefits and drawbacks

Investigation of the process energy demand in polymer extrusion: A brief review and an experimental study

YesExtrusion is one of the fundamental production methods in the polymer processing industry and is used in the production of a large number of commodities in a diverse industrial sector. Being an energy intensive production method, process energy efficiency is one of the major concerns and the selection of the most energy efficient processing conditions is a key to reducing operating costs. Usually, extruders consume energy through the drive motor, barrel heaters, cooling fans, cooling water pumps, gear pumps, etc. Typically the drive motor is the largest energy consuming device in an extruder while barrel/die heaters are responsible for the second largest energy demand. This study is focused on investigating the total energy demand of an extrusion plant under various processing conditions while identifying ways to optimise the energy efficiency. Initially, a review was carried out on the monitoring and modelling of the energy consumption in polymer extrusion. Also, the power factor, energy demand and losses of a typical extrusion plant were discussed in detail. The mass throughput, total energy consumption and power factor of an extruder were experimentally observed over different processing conditions and the total extruder energy demand was modelled empirically and also using a commercially available extrusion simulation software. The experimental results show that extruder energy demand is heavily coupled between the machine, material and process parameters. The total power predicted by the simulation software exhibits a lagging offset compared with the experimental measurements. Empirical models are in good agreement with the experimental measurements and hence these can be used in studying process energy behaviour in detail and to identify ways to optimise the process energy efficiency

Organic Photochemistry: Remote Delivery of Reactive Oxygen Intermediates via a Heterogeneous Approach

Photosensitized oxidation reactions produce a number of intermediates species, which are generated in varying amounts over time. This complexity presents major challenges in the study of oxidation processes. Mechanistic efforts to separate and deliver reactive oxygen intermediates enable their controlled use in processes such as bacterial inactivation. This thesis describes a heterogeneous reaction approach taken to control the generation and delivery of reactive oxygen intermediates. The mechanistic details of photosensitized reactions were elucidated via synthetic, materials, and physical organic techniques to optimize the delivery of reactive oxygen intermediates. This thesis contains six chapters as described below. Chapter 1 gives a short background on molecular organic photochemistry, to provide a sense of the current state of photochemistry research, as well as an outline of the thesis. Chapter 2 describes a physical-organic study on the photodecomposition of dicumyl peroxide co-adsorbed with sensitizers 4,4¢-dimethylbenzil or chlorin e6 on dry silica. Dicumyl peroxide was decomposed by heterogeneous photosensitization under UV and white lamp irradiation and monitored by the desorption of products acetophenone, 2-phenylpropan-2-ol, and α-methylstyrene using 1H NMR spectroscopy and GC/MS. Dicumyl peroxide and sensitizer were co-adsorbed on silica in 1:4 up to 200:1 ratios, a high peroxide destabilization occurring in a ratio of about 10:1. This increased photodecomposition corresponds to sensitizer–peroxide distances of up to 6–9 Å on silica. Furthermore, a higher photostability of dicumyl peroxide was observed on silica than in a homogeneous acetonitrile solution, where the surface attenuated the diffusion of alkoxy radical geminate pairs apart from each other. A mechanism is proposed that explains how the sensitizer and peroxide separation distance, and geminate recombination of alkoxy radical pairs lead to higher and lower peroxide O–O bond homolysis efficiencies on silica, respectively. This biphasic system can thus serve both to destabilize and stabilize a peroxide; this may be of practical use in a surface used for the delivery of alkoxy radicals for bacterial disinfection. Chapter 3 describes the study of a new series of alkyl chain pterin conjugates using photochemical and photophysical methods, as well as theoretical DFT and solubility calculations. Reactivity patterns for the alkylation of pterin were examined both experimentally and theoretically. The theoretical calculations were carried out using density functional theory (DFT) methods. 2D NMR spectroscopy was used to characterize the pterin derivatives, clearly indicating that the decyl chains were coupled to either the O4 or N3 site on the pterin. At a temperature of 70 °C, the pterin alkylation regioselectively favored the O4 alkylation over the N3 alkylation. The O4 alkylation was also favored when using solvents in which the reactants had increased solubility, e.g., N,N-dimethylformamide and N,N-dimethylacetamide, rather than solvents in which the reactants had a very low solubility, e.g., tetrahydrofuran and dichloromethane. Two additional adducts were also obtained from an N-amine condensation of DMF solvent molecule as byproducts. In comparison to the natural product pterin, the alkyl chain pterins have reduced fluorescence quantum yields (ΦF) and enhanced singlet oxygen (1O2)quantum yields (Φ∆). The DMF-condensed pterins were found to be more photostable compared with the alkylated pterins bearing a free amine group. The alkyl chain pterins efficiently intercalate in large unilamellar vesicles; this is a good indicator of their potential use as photosensitizers in biomembranes. Our study serves as a starting point where the synthesis can be expanded to produce a wider series of lipophilic, fluorophilic, and photooxidatively active pterins. Chapter 4 describes the synthesis of new chlorin e6 silica conjugates and interfacial photooxidation studies. Porous silica and nonporous fumed silica were used as solid supports to evaluate the effect of solid supports on 1O2 production. Chlorin e6 conjugated silica was embedded on to superhydrophobic surfaces to generate bi- and triphasic photocatalytic systems. Finally, photooxidation efficiencies of interfacial systems were evaluated for applications in bacteria inactivation. Chapter 5 describes a photooxidation study on prenylsurfactants [(CH3)2C=CH(CH2)nSO3- Na+ (n = 7, 9, 11)] to probe the “ene” reaction mechanism of 1O2 at an air–water interface. Increasing the number of carbon atoms in the hydrophobic chain increased the regioselectivity for a secondary rather than a tertiary surfactant hydroperoxide, arguing for an orthogonal alkene on water. The prenylsurfactants and a photoreactor technique enabled a certain degree of interfacial control of the hydroperoxidation reaction on a liquid support, where the oxidant (airborne 1O2) is delivered as a gas. Chapter 6 is a review of literature techniques developed so far to understand the delivery of 1O2. This chapter strives to push the idea of 1O2 delivery further by examining two types of delivery: First, the transport of 1O2 in the presence of physical and chemical quenchers is described. Second, the transport of 1O2 by carrier compounds is described. Singlet oxygenation examples include endoperoxides and hydroperoxides