Extruder Configuration Research Articles

Effect of Extruder Configuration and Extrusion Cooking Processing Parameters on Selected Characteristics of Non-Starch Polysaccharide-Rich Wheat Flour as Hybrid Treatment with Xylanase Addition

The effects of a single-screw extruder configuration and processing variables such as conventional extrusion or hybrid treatments with xylanase were tested on the extrusion performance and selected characteristics of the developed non-starch polysaccharide-rich (NSP-rich) wheat flour. L/D 16 and 20 extruder configurations with various screw profiles were used. The interactions between processing variables (moisture content 23, 25, 27%; screw speed 40, 60, 80 rpm; xylanase level 0, 50, 100 ppm) were assessed to indicate energy consumption and the rheological properties of flour. The results showed that the possibility of obtaining enzyme-assisted extruded flour products derived from flours of varying characteristics depended on the processing conditions. The application of various extruder configurations and screw profiles showed significant effects on both processing behavior and rheological characteristics. The longer L/D 20 extruder configuration using a screw profile with mixing elements allowed us to obtain products with lower extrusion pressure (max. 20.8 bar) and energy requirements (max. SME = 33.1 kWh/kg) and better rheological properties (max. Hyd = 69.2%, less intensive starch gelatinization with max. C3 = 1.47 Nm) than the L/D 16 version. The extruded wheat flour was characterized by improved hydration properties and limited retrogradation tendency, especially when hybrid extrusion with xylanase was applied. This may lead to favorable results, as the newly developed enzymatic extrusion modification method produces NSP-rich wheat flour with specific techno-functional and rheological characteristics that can be seen as a potential “clean label” enhancer in bakery products. Our statistical analysis confirmed feed moisture and screw speed to be the variables with the most significant effect on wheat flour features.

Prediction of extruded aquafeed physical quality parameters through a dough viscosity model

AbstractA widely used dough viscosity model in food extrusion was adopted and employed for the analysis and prediction of extruded aquafeed physical quality parameters. The data for the analysis were collected from previously published articles. The analysis was based on the assumption that pellet physical quality parameters, such as bulk density, oil adsorption, hardness, and durability, are correlated to the dough viscosity property changes in the extrusion process. The physical qualities of feed were modeled using the modified viscosity model. The model was evaluated using the data collected from experiments conducted in three different pilot extrusion systems. The results showed that the new model has the capability to predict the physical quality parameters of extruded aquafeed pellets in the three studied scenarios. The absolute average deviations of the model regression for the pellet qualities were 8.5% for hardness, 4.8% for bulk density, 6.5% for oil adsorption, 15.7% for Holmen durability, and 0.7% for pellet diameter. The new model can correlate the physical qualities of aquafeed pellets across different recipes, extruder configurations, and systems.Practical ApplicationsFood or aquatic feed extrusion process operation heavily depends on the operator's experiences and is still a black‐box process. In this study, a dough viscosity model was applied to explain the relationship between extrusion variables and extruded pellet physical qualities. The new model can be used for a quantitative description of a feed formulation extrusion process and feed pellet quality optimization.

Extrusion Simulation for the Design of Cereal and Legume Foods.

A 1D global twin-screw extrusion model, implemented in numerical software, Ludovic®, was applied to predict extrusion variables and, therefore, to design various starchy products with targeted structure and properties. An experimental database was built with seven starchy food formulations for manufacturing dense and expanded foods made from starches, starch blends, breakfast cereals, pulse crop ingredients such as pea flour, fava bean flour, and fava bean starch concentrated, and wheat flour enriched with wheat bran. This database includes the thermal and physical properties of the formulations at solid and molten states, melt viscosity model, extruder configurations and operating parameters, and extruded foods properties. Using extrusion and viscosity models, melt temperature (T) and specific mechanical energy (SME) were satisfactorily predicted. A sensitivity analysis of variables at die exit was performed on formulation, extruder configuration, and operating parameters, generating the extruder operating charts. Results allowed the establishment of relationships between predicted variables (T, SME, melt viscosity) and product features such as starch and protein structural change, density and cellular structure, and functional properties. The extrusion operating conditions leading to targeted food properties can be assessed from these relationships and also the relationship between extrusion operating parameters and variables provided by simulation.

Process Behavior of Special Mixing Elements in Twin-screw Extruders

Abstract Tightly intermeshing, co-rotating twin-screw extruders are commonly employed for tasks requiring good mixing. The modular structure of both barrel and screw makes it possible to optimize the extruder configuration for a given task. Increasing demands on polymers have resulted in the development of more sophisticated mixing elements. In the framework of this investigation we looked at the pressure-throughput behavior of mixing elements in a conveying, reconveying and conveying-reconveying configuration. Furthermore, the local residence time distribution within those elements was investigated. We developed physical-mathematical models to describe the pressure – throughput behavior observed in the experimental investigations.

Analysis of Mixing in Corotating Twin Screw Extruders through Numerical Simulation

Abstract Mixing is a major ingredient in many industrial processes to obtain desired and uniform material properties. Nowadays, many materials, pigments, additives, gas or reactants, are mixed to create new products combining the characteristics of different raw materials to obtain specific product properties. The quality of the mixing, i.e. the uniformity of the mixture, is a key issue that will determine the morphology and the properties of the resulting compound [1, 2]. An insight in the physics of mixing is therefore necessary in order to achieve a good quality of mixing or maintain it when scaling equipment, for example. Such information can now be obtained through the numerical simulation of the transient flow in extruder components. To improve greatly the ease of obtaining such information, a new technique introduced in a finite elements software is presented. This technique simplifies the meshing, reduces the meshes needed and eliminates complex remeshing algorithms to simulate flow in screws, pumps and mixing devices. This technique is validated versus traditional simulation methods (i.e. conforming meshes). 3-D transient numerical simulations of two twin screw extruder configurations are then presented. A further quantitative comparison of their mixing behavior is developed as statistical information (of the RTD, deformations, dispersion, etc.) can be obtained to compare both configurations in a synthetic and quantitative way.

Theoretical and experimental investigation of alginate microtube extrusion for cell culture applications

A novel cell culture technology, consisting of hollow alginate tubes, OD ~550μm, ID ~450μm containing a cell suspension, provides stress-free conditions. Cells reach confluency in approximately ten days with cell densities of 0.5−1 billion cells per mL. Tubes are manufactured in a tri-axial needle extruder with three concentric flows. The cell suspension flows in the inner needle (N1), the alginate solution flows in the annulus between N1 and the second needle (N2) and a CaCl2 solution is the sheath fluid between the second and third needle (N3). Beyond the tip of N2, the sheath solution is in contact with the alginate and Ca2+ diffuses into the alginate solution and crosslinks it to form an alginate microtube around the core fluid. The cross-linked layer moves radially inwards like a front, starting at the sheath/annulus interface and ends at the annulus/core interface. A mathematical model is used to find the minimum length zC of direct contact between the CaCl2 solution and the alginate solution to complete the cross-linking. Experimental results support the theoretical findings that stable tubes can only be manufactured if the contact length exceeds zC. Experiments also show that the extruder configuration N3 > N2 is best for alginate tube manufacture.

Effects of particle size and moisture content of maize grits on physical properties of expanded snacks.

The main aim of this research was to investigate the effects of simultaneous changing of maize grits particle size and moisture content on some physical properties and microstructure of the expanded snacks produced by an industrial single screw extruder. Maize grits with different particle sizes of 212-299, 300-474, 475-680, 681-870, 871-1,016, and 1,017-1,070 μm and various moisture contents of 15, 16, 17, and 18% were used to manufacture puffed products. The samples produced with larger particle sizes and higher moisture content exhibited lower water absorption and water solubility indices and less expansion and crispiness than other samples. As microstructure results revealed, these samples showed more uneven surface and thicker cross-section. Overall, controlling both moisture content and particle size of maize grits had significant effects on the quality of the snacks. However, the impact of changing particle size on the snack properties was greater than changing the moisture content. This research has implications in food industry in production of puffed snacks using extrusion process. The results provide practical and green methods of improving the quality of the snacks by choosing the appropriate feed particle size and moisture content. The approach introduced in this paper is easy to impediment in the food industry without the need to change extruder configuration or adding to the list of ingredients and additives.

Study on the morphology development and dispersion mechanism of polypropylene/graphene nanoplatelets composites for different shear field

Four different screw configurations were designed to prepare polypropylene (PP) nanocomposites reinforced with graphene nanoplatelets (GNPs). The relationship between the shear field, the morphology development of GNPs in PP and the properties of PP/GNPs nanocomposites were investigated. Finite element method software, POLYFLOW, was used to quantify the shear flow field in the four screw configurations. The morphology development was analyzed by field-emission SEM and optical transmission microscopy. The dispersion mechanism of GNPs in the PP matrix under the effect of a shear field was simulated showing that left-handed kneading elements resulted into the longest residence time and the addition of mixing elements resulted in the highest shear stress. Calculation results showed that during the extrusion process, large GNPs agglomerates (above 40 μm) tend to be exfoliated into smaller ones by two dispersion mechanisms corresponding to rupture and erosion. Since the shear stress provided by the twin-screw extruder configuration was limited, small agglomerates (below 40 μm) would exfoliate to thin layers only by following an erosion mechanism. The erosion mechanism and GNPs migration resulted to be mainly affected by the residence time. By increasing the residence time, nanocomposites resulted to be better dispersed and the particle size distribution was more homogeneous. Moreover, we found that the more the GNPs agglomerates thickness can be reduced by exfoliation, the more connection can established within the GNPs network, resulting in higher electrical and thermal conductivities.

Natural Fibre/PA6 composites with flame retardance properties: Extrusion and characterisation

Abstract Replacing glass fibre by natural one in reinforcing engineering plastics for electronic industries has two pre-requirements. Firstly, the processing window should be defined for the engineering plastics of high melting temperature and the natural fibres of limited thermal stability. These processing parameters should be ensured in a stable extrusion procedure. Secondly, a flame retardant (FR) to meet the requirements such as in electronic industries. FR should be however minimised as much as possible to keep good mechanical properties. An optimisation is carried out for extruding thermoplastics like Polyamide 6 (PA6) with natural fibre like flax or kenaf and FR. Extruder configuration is adjusted to obtain a stable process up to 22.5 wt% fibre. Mechanical testing shows just a decrease of 10% in strength and 15–25% in impact strength after the addition of 20% FR.V-0 rating is obtained by 20% FR according to UL94 test. The cone calorimetry shows a reduction in heat release rate HRR to 50% after the application of FR. Also higher share of mineral FR is found feasible keeping UL94 V-0 flame retardance level.

Effect of extruder elements on fiber dimensions and mechanical properties of bast natural fiber polypropylene composites

ABSTRACTIllusions and facts about aspect ratio and the corresponding mechanical properties of the polypropylene flax are studied in this work. Selection of extruder elements controls significantly the fiber final dimensions. Hence, the load transfer efficiency can be improved. Different extruder layouts are tried. First and second trials investigate the mixing degree effect using kneading elements with eight and four kneading elements, respectively. The third and fourth trials keep four kneading blocks but differentiate in using multiprocessing element MPE and toothed elements, respectively. All the four configurations are tested at different shearing rates namely 100, 200, and 300 rpm and different fiber loadings 10, 20, and 30 wt %. Polypropylene (PP) with high flowing properties and slivers flax natural fibers are used. The output extruded strands are mechanically tested. The third and fourth configurations showed superiority to the normal kneading profiles regarding the mechanical properties. Samples of composites are withdrawn after each processing extruder element to study the effect of this element on the fiber dimension. Measurement of extracted fibers is carried out by two methods namely dynamic image analysis machine and secondly normal microscopic investigation. Weibull distributions are defined for fiber geometry distributions for the different locations on the extruder configuration. Also, the effect of the shear rate and the extruder configuration on the final dimensions of the fibers extracted from the composite. The results show the correlation between extruder configuration and fiber aspect ratio and hence the composite overall strength. However, further processing like injection molding erases the pre‐extrusion effect. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40435.

Shear effect in beta‐phase induction of polypropylene in a single screw extruder

ABSTRACTIn this work, we investigated the effect of four different configurations at the exit of a single‐screw extruder on the induction of beta phase in PP for four different rotational speeds. The configuration of a breaker plate with 120 orifices of 1‐mm diameter and 7‐mm length each, give the highest content of beta‐phase (56.92%), for a screw rotational speed of 20 rpm. It was due to the shear caused separation of the melt when it passes through the orifices of the breaker plate. The breaker plate of configuration 4 (breaker plate with the greatest number of orifices) provided the largest number of contacts between the melt and the orifice walls resulting in chain alignment. The results show that the beta‐phase can be induced in the polymer without any further additives, especially without any nucleating agents, but rather by using a special breaker plate configuration at the exit of the single‐screw extruder. The skin‐core structure of the polymer was only developed with one type of extruder configuration. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2932–2937, 2013

Regime map development for continuous twin screw granulation

A promising method for continuous wet granulation is to pass powdered solids and binder through a twin-screw extruder, usually, as in this case, with co-rotating screws. In the current work, the relationship between operating conditions and product granule properties has been investigated using the same materials (microcrystalline cellulose and polyethylene glycol) as in an earlier study of conventional batch granulation using a high shear mixer-granulator (Tu et al., 2009), enabling a direct comparison to be made. Two extruder configurations were used: with barrel diameter/length dimensions of 16mm/16mm and 16mm/64mm. Two regimes (granulation and extrusion) were recognised for the short mixing geometry, while three regimes (granulation, extrusion and blockage) were recognised for the long mixing geometry and the staggered geometry. The resulting regime maps suggest that optimal granulation (narrow granule size distribution and large mean granule size) can be achieved with a higher liquid-to-solid ratio and a higher screw speed. The uniformity of size distribution can be improved by reprocessing and/or more aggressive mixing.

Foam granulation: new developments in pharmaceutical solid oral dosage forms using twin screw extrusion machinery

This paper investigates foam granulation in a twin screw extruder as a new continuous wet granulation technique for pharmaceutical powder drug formulations. Foamed aqueous binder has a reportedly lower soak-to-spread ratio than drop or spray liquid addition in batch granulation. This work demonstrates a twin screw extruder configuration for foam granulation and subsequently compares the new approach against liquid injection in the granulation of α-lactose monohydrate with a methylcellulose binder. Trials were conducted at high powder output rates (20–40 kg/h) and high screw speeds (220–320 RPM) with two screw configurations. Process stability improved with the new technique allowing granulation with less binder. The extruded mass maintained a low exit temperature, being insensitive to operating conditions unlike the liquid injection approach, where temperatures rose significantly as flow rate increased. The particle size distribution by foam granulation reflected a more uniformly wetted mass with larger granule growth noted even for conditions where dry powder exited by liquid injection. Other factors were found similar between the two binder delivery methods such as consumed mechanical energy, as well as fracture strength and compressibility of produced granules.

Engineering an efficient two-phase local search algorithm for the co-rotating twin-screw extruder configuration problem

The twin-screw configuration problem arises during polymer extrusion and compounding. It consists in defining the location of a set of pre-defined screw elements along the screw axis in order to optimize different, typically conflicting objectives. In this paper, we present a simple yet effective stochastic local search (SLS) algorithm for this problem. Our algorithm is based on efficient single-objective iterative improvement algorithms, which have been developed by studying different neighborhood structures, neighborhood search strategies, and neighborhood restrictions. These algorithms are embedded into a variation of the two-phase local search framework to tackle various bi-objective versions of this problem. An experimental comparison with a previously proposed multi-objective evolutionary algorithm shows that a main advantage of our SLS algorithm is that it converges faster to a high-quality approximation to the Pareto front.

Application of evolutionary algorithms to the definition of the optimal twin‐screw extruder configuration for starch cationization

AbstractThe twin‐screw configuration problem (TSCP) involves defining the location of a set of predefined screw elements of a corotating twin‐screw extruder configuration to optimize different, often conflicting, objectives. A multiobjective optimization methodology based on Evolutionary Algorithms was developed and applied to solve the TSCP. This methodology is used in starch cationization case studies, involving different screw elements and screw lengths. The results obtained, taking into consideration various conflicting objectives, such as minimizing the specific mechanical energy and maximizing output and reaction efficiency, have physical meaning and thus validate the methodology. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

The11/2−[505]neutron extruder orbital inSm159

Excited states in $^{159}\mathrm{Sm}$, populated following the spontaneous fission of $^{252}\mathrm{Cf}$ have been studied by means of $\ensuremath{\gamma}$ spectroscopy, using the Gammasphere array. In $^{159}\mathrm{Sm}$ we have identified an isomeric level with a half-life of ${T}_{1/2}=116(8)$ ns at an excitation energy of 1276.8 keV and observed a rotational band on top of this isomer. On the basis of the observed properties of the isomer and the band on top of it we propose that the 1276.8-keV level in $^{159}\mathrm{Sm}$ corresponds to the $11/{2}^{\ensuremath{-}}[505]$ neutron extruder configuration. The new excitation scheme of $^{159}\mathrm{Sm}$ is compared to quasiparticle rotor model calculations.

Nylon 66/clay nanocomposite structure development in a twin screw extruder

AbstractNylon 66/clay nanocomposites were prepared in a Berstorff ZE25A UTX Ultra‐glide corotating twin screw extruder at 270°C. Two types of extruder configurations with different mixing sections were used. One comprised two kneading block sections in the screws (KB only) and the other had a combination of a multi‐process‐element (MPE) section and a kneading block section. Samples at eight different locations along the extruder screw were obtained and analyzed using scanning electron microscope and transmission electron microscope to examine the morphology development of clay inside nylon down the length of the extruder. It is found that the clay aggregates are quickly broken into smaller tactoids (micron size) and then even much smaller clay bundles (nanometer size) and single clay platelets in the first mixing section. The structure changes in the second mixing section are much less significant. X‐ray diffraction (XRD) analysis of the nanocomposite products showed small, or disappearance of, characteristic XRD (001) peaks, which indicates partial exfoliation, or complete exfoliation, respectively, of clay inside nylon matrix. Differential scanning calorimetry nonisothermal study shows that the crystallization temperature of the nanocomposites has increased around 17°C when compared with neat nylon 66. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Rubber Powder – A Perspective Filler of Thermoplastics

AbstractRubber powder, ground at ambient temperature, was compounded with polypropylene using only 16 L/D of a co‐rotating twin screw extruder. An optimum of extruder configuration and selected process parameters were found for compounds with a rubber filling rate of 50 wt.‐%. Restrictions of a reactive compounding were taken into account. The dispersion of the rubber powder is not a limiting process. A compound containing 70 wt.‐% rubber powder showed to be overfilled.

Physico-Mathematical Model for the Description of the Temperature Development and the Power Consumption in Co-Rotating Twin Screw Extruders

Abstract Tightly intermeshing, co-rotating twin-screw extruders are commonly employed for tasks requiring good mixing. The modular constitution of both barrel and screw makes it possible to optimise the extruder configuration for a given task. Even today this optimisation is frequently done by applying the “Trial and Error”-method. Physico-mathematical models enable the process engineer to predict the process behaviour of a chosen extruder configuration and to optimise existing extrusion processes. Increasing demands in mixing quality and efficiency of the processing unit result in efforts to optimise existing extruders with respect to those factors. For this reason knowledge concerning the temperature profile along the screw and the power consumption is essential. We present a new physico-mathematical model for the description of the temperature development. At stages where the analytical solution itself would result in a not satisfying degree of accuracy we used descriptions based on finite element simulation results to achieve the desired exactness. As a result we got a model to describe the temperature development in the screw channel and a model to describe the power consumption in different screw sections. Applying these models it is possible to optimise the process parameters and the screw configuration with only a minimum of preceding experimental investigations.

Non-Isothermal Modeling of Co-Rotating and Contra-Rotating Twin Screw Extruders

The quality of the mixing of different raw materials, i.e. the uniformity of the mixture, is a key issue that will determine the morphology and the specific product properties of the resulting compound [1,2]. Numerical simulation of flow in extruder components provides a new insight, both qualitative and quantitative, into those features. 3-D transient numerical simulations of twin screw extruder (TSE) configurations are presented. A special method, the mesh superposition technique (MST), has been introduced to provide a convenient way to model intermeshing TSEs without involving any remeshing complexity [3]. It has been validated in previous work for isothermal cases [4]. To account for the important non-isothermal effects, the method is compared against numerical and experimental results for additional, non-isothermal validation [5]. We present an analysis of different non-isothermal features that characterize the flow induced by a co-rotating as well as a contra-rotating configuration. Both cases are compared in terms of pressure profiles, temperature fields, resulting torque imposed on the screws and from a mixing point of view to illustrate a typical analysis of different TSEs and provide objective information to select the most appropriate configuration for specific process requirements.