Feed Screw Research Articles

Thermo-mechanical recycling via ultrahigh-speed extrusion of film-grade recycled LDPE and injection molding

The analysis of the mechanical recycling market in North America indicates that flexible packaging is the most significant end-use application of PE (i.e., > 40%), with a domestic recycling rate lower than 10%. Several technical barriers currently hinder film and flexible plastics recycling, including feedstock contamination, lack of stability and coordination in the supply chain, inefficient sorting, poor processing capabilities, and lack of end markets. In this work, we use ultrahigh-speed extrusion to modify the molecular weight of film-grade LDPE to promote its recycling via injection molding. The extrusion process is analyzed considering the effect of screw speed and feed rate on the rheology of the modified materials. The modified LDPE was injection molded using a novel pressure-controlled injection molding strategy. The tensile testing of the parts manufactured using the modified material showed a slightly reduced elastic response and significantly lower elongation at break. The sustainability analysis for the proposed combination of ultrahigh-speed extrusion and injection molding showed that the embodied energy is substantially lower than that obtained from the injection molding of the virgin LDPE. The energy saving can be converted to CO2 emissions showing that the proposed process could save 6 kg of CO2 for each kg of LDPE converted into an injection molded product.

Temperature field modeling and vibratory-thermal coupling analysis of ball screw feed system

Thermal deformation and dynamic response are essential factors affecting the accuracy of the ball screw feed system. In this paper, the temperature field model of the thermal network of the system and the axial dynamic model are established. The relationship between the heat generation of components and system response is analyzed by coupling models. The temperatures of related components are obtained by solving the thermal balance equations. The obtained temperatures are substituted into the dynamic model to investigate the response of the system considering the thermal effect. According to the displacement response of the system, the contact forces of the balls are calculated and substituted into the thermal network model to explore the influence of the response on heat generation. This work also gives a method to solve the relatively stable temperatures of vibratory-thermal coupling. The models of the system are verified by experiments, and the influences of related parameters on heat generation and the response of the system are also discussed.

Effects of Food Additives Treatment on the Texture of Artificial Rice prepared from Dried Cassava and Corn Flours Mixture

The purpose of this study is to understand how food additives like Sodium Tri-Polyphosphate (STPP), Guar Gum, and Glycerol Monostearate (GMS) affect the textures of synthetic rice (tiwul rice) produced using a twin screw extruder. 70% (w/w) dry cassava flour and 30% (w/w) corn flour were combined for the extrusion process. By adjusting the amounts of the extra ingredients guar gum, sodium tri poly phosphate (STPP), and glycerol monostearate, it was done in six different formulae (GMS). The moisture content of the raw material mixture was 30-35% (w/w) at the extrusion conditions the feeding screw motor speed was 5-6Hz, the screw speed of the extruder was 7.5-8.5Hz and the barrel temperature from zone 1 to 3 extruder was around 45-50°C. Tiwul rice that is produced with 0.5% GMS addition obtains several characteristics that are nearly similar with native rice, such as hardness, cohesiveness, adhesiveness, springiness, gumminess and chewiness texture.

Effects of protein formula and extrusion cooking conditions on the techno‐functional properties of texturised pea proteins

SummaryPea protein concentrate and isolate were blended to obtain protein blend formulas (PBFs) with three levels of protein content and investigated for their potential for developing texturised vegetable proteins (TVPs). PBFs were extruded at three screw speeds and two feed moisture contents to obtain TVPs. Nitrogen solubility index (NSI) and techno‐functional properties, i.e. water holding capacity, oil absorbance capacity, emulsion capacity and emulsion stability, of the raw materials and the TVPs were examined. Raising the protein content through PBF decreased NSI for both the raw formulas and the TVPs. Regardless of the PBF, extrusion processing substantially decreased NSI, but increased oil absorption capacity. Extrusion's impact on water holding capacity, emulsion capacity and stability was complex and might have been impacted by the protein content and source. Overall, PBF's impact on the techno‐functionality of TVPs was more pronounced than that of extrusion conditions. At higher PBF, the NSI, emulsion capacity and stability values of TVPs were negatively impacted, implying that high protein content does not equate to better TVP quality. Future, TVP techno‐functionality research should focus on a wider range of extrusion screw speed and feed moisture content or the effects of protein content and source.

Simulations of biomass compression-screw feeding using a compressible non-Newtonian constitutive model

There is global interest in the conversion of biomass into sustainable low-carbon-footprint fuels and chemicals as an alternative to non-renewable fossil feedstocks. Feeding biomass solids into pressurized reactors is one of the key steps in biomass conversion. Predicting mechanical failure and energy requirements for this step helps avoid upstream processing bottlenecks and enables efficient operation of a biorefinery. In this work, we developed a predictive computational model for biomass screw feeders that capture the highly viscous, non-Newtonian and compressible behavior of biomass slurries. Biomass compressible behavior is formulated by an equation of state and the non-Newtonian rheology is represented by a density-dependent viscosity model. Experimental data from two compression screw-feeder systems are presented as a validation for our model. Our model successfully predicted the location of the compressed biomass “plug”, biomass flow rate, and the required torque at different operating conditions for the experimental conditions studied in this work.

A laboratory-scale compression feed screw for characterizing continuous feeding of dense granular materials

Compression feed screws are commonly used in biorefineries for the continuous feeding of biomass feedstock into reactors. Developing methods to assess the feasibility of feeding granular materials in a compression feed screw is critical for reducing solids handling issues during operation. A laboratory-scale compression feed screw has been built to measure critical process parameters of the feeding operation, namely the driving torque and the mass flow rate. The process parameters of two granular materials, microcrystalline cellulose Avicel PH-200 and milled corn stover are measured using the laboratory-scale feeder. The results show that a larger torque is required to feed corn stover than Avicel PH-200, even though the former consists of more compressible particles. Further, the device can capture real-time fluctuations in the process parameters during operation. The laboratory-scale feeder can be used to compare the feeding of different granular materials and the measured parameters can be used to validate predictive models for a compression screw feeding process.

Гальваношламы – источник вторичных материальных ресурсов при получении пигментов-наполнителей для лакокрасочных изделий

Galvanic production occupies one of the first places according to the degree of negative impact on the environment due to the content of heavy metal ions which have toxic, carcinogenic and mutagenic properties. Finding an effective method of recycling and utilization of galvanic sludge will solve the problem of the steady growth of the cost of metals and minimize the negative impact on the environment, which is an important environmental task of great scientific and practical significance. This paper presents the results of studies on the extraction of iron oxide(III) Fe2O3 from ironcontaining galvanic sludge to use it as a filler pigment in the manufacture of paint (red iron oxide). At the initial stage, the original galvanic sludge was dissolved in distilled water to a creamy consistency, and then, sulfuric acid was gradually added until the pH value gradually decreased (pH 6.0–1.5), metal sulfates were obtained. Iron hydroxide(III) Fe(OH)3 was precipitated from filtered sulfate solutions with 40% NaOH alkali solution at pH 1.5–4.1. After preliminary drying at a temperature of ≈ 150 оС, heat treatment was carried out at 600±2 оС for 5–6 h, obtaining iron oxide(III) Fe2O3, which met the requirements of GOST 10503-71 “Oil paints, ready to use. Technical Conditions in terms of particle size, oil capacity, particle density and pH of aqueous extracts. The iron minium paint made on its basis also met the requirements of this GOST on parameters: viscosity, hiding power, drying time, etc. A schematic diagram is proposed for obtaining a filler pigment used for the production of paints and varnishes. The scheme uses a set and layout of equipment widely used in industry (conveyor, batchers, screw feeders, acid and alkali treatment baths, centrifuge, drying and roasting oven).

Dynamic analysis and modeling of ball screw feed system with a localized defect on the support bearing

Dynamic analysis and modeling of ball screw feed system with a localized defect on the support bearing

A Novel Approach to the Screw Feeder Design to Improve the Reliability of Briquetting Process in the Roller Press

The screw feeder design for the pre-compaction of bulk materials to be briquetted in a roll press is considered to increase the overall reliability. The relationship between the parameters of the screw feeder and its technological characteristics is investigated by the example of two fine-grained materials. A new mathematical model and design algorithm have been developed, which takes into account the properties of materials, the roller press parameters, the shape of the briquettes, and their deformation after compaction. The relationship between the pre-compaction pressure and the material stack height at the inlet is determined. The relations between the torque, the screw pitch, and the material stack height above the inlet, as well as the drive power and the screw pitch on productivity, are investigated. In experiments, using the proposed design, the compaction ratio of the peat increases by 22-27%, and hydrolyzed lignin – by 14-17%. The proposed approach allows for preventing drive overloading and ensures the reliable operation of pre-compaction devices for the roller presses.

Particle size and shape effect of Crumbler® rotary shear-milled granular woody biomass on the performance of Acrison® screw feeder: A computational and experimental investigation

Physical experiments and discrete element model (DEM) simulations are conducted to evaluate particle characteristics and operation parameter effects on screw feeding performance for rotary shear-milled Douglas fir. Three performance metrics are used: mass flow rate, shaft driving torque, and specific energy consumption. The impact of particle size, particle size distribution (PSD), shaft rotational speed (rpm), and hopper dimensions on the performance are investigated. All employed performance metrics reveal the superior flowability of the 2-mm particles in contrast to the larger 6-mm counterpart. Remarkably, wider PSD results in poorer flowability than the two mono-sized particles, proving the flowability enhancement achieved by narrower PSD of the woody feedstock. More importantly, DEM simulations unveil PSD-induced degradation in flowability is attributed to mechanical interlocking and particle segregation effects. Furthermore, higher shaft rpm causes higher mass flow rate at the cost of higher specific energy consumption due to viscous dissipation and changes in flow pattern.

Influence of nonlinearity of servo system electrical characteristics on motion smoothness of precision CNC machine tools

The ball screw feed system of CNC machine tools is a typical mechatronic motion mechanism. During the operation of the machine tool, not only the dynamic characteristics of the mechanical structure will affect its performance, but also the electrical characteristics of the servo system will affect the movement of the worktable, which will lead to displacement fluctuation and bring adverse effects on the precision of the machine tool and even the quality of the processed parts. Therefore, the electrical system and the mechanical system are strongly coupled to each other due to their high integration. In this paper, the fluctuation of current, torque, and displacement during the motion of the worktable is studied. Firstly, the mechatronic model of the ball screw feed system, which not only consists of all components of the feed system but also takes different nonideal characteristics of each component into consideration, is established to realize the physical simulation of the whole system. Then, with the consideration of the impacts of inverter dead zone, motor cogging torque, rotor mixed-eccentricity, winding asymmetry, and collecting error of feedback current, the frequency components of fluctuations caused by the nonlinear electrical characteristics of inverter and servo motor in the servo drive system are obtained. Finally, the influences of load, feedrate, servo parameters, and dynamic characteristics of mechanical structure on fluctuation are analyzed in the time domain and frequency domain. The phenomenon of displacement fluctuation of the worktable caused by the electrical characteristics of the servo system indicates that it is necessary and meaningful to build the integrated model to study the ball screw feed system from the view of the whole system.

Evaluation of the influence of material properties and process parameters on granule porosity in twin-screw wet granulation

In recent years, continuous twin-screw wet granulation (TSWG) is gaining increasing interest from the pharmaceutical industry. Despite the many publications on TSWG, only a limited number of studies focused on granule porosity, which was found to be an important granule property affecting the final tablet quality attributes, e.g. dissolution. In current study, the granule porosity along the length of the twin-screw granulator (TSG) barrel was evaluated. An experimental set-up was used allowing the collection of granules at the different TSG compartments. The effect of active pharmaceutical ingredient (API) properties on granule porosity was evaluated by using six formulations with a fixed composition but containing APIs with different physical–chemical properties. Furthermore, the importance of TSWG process parameters liquid-to-solid (L/S) ratio, mass feed rate and screw speed for the granule porosity was evaluated. Several water-related properties as well as particle size, density and flow properties of the API were found to have an important effect on granule porosity. While the L/S ratio was confirmed to be the dictating TSWG process parameter, granulator screw speed was also found to be an important process variable affecting granule porosity. This study obtained crucial information on the effect of material properties and process parameters on granule porosity (and granule formation) which can be used to accelerate TSWG process and formulation development.

Extrusion as a tool to enhance the nutritional and bioactive potential of cereal and legume by-products

Cereal and legume by-products obtained from primary food production industries pose an environmental and economic problem. Nevertheless, these residues can potentially yield value-added products due to their elevated content of dietary fiber, phytochemicals, vitamins, minerals, and residual levels of proteins, which makes them a suitable and heightened option for reutilization in human consumption. Several studies identify extrusion as an innovative technology to modify the technofunctionality and nutritional properties of cereal and legume by-products, resulting in the production of improved ingredients. This review focuses on studies that evaluate the effect of extrusion to improve the nutritional and bioactive potential of cereal and legume by-products. A revision of the extrusion process parameters that improve the profile and bioavailability of dietary fiber, proteins, and phenolic compounds, and minimize antinutritional factors associated to cereal and legume by-products was done. The composition of by-products and process parameters such as feed moisture, barrel temperature and screw speed influence the resulting effect of extrusion. Studies suggest that extruding composite feedstock containing cereal or legume by-products may limit the molecular modifications that trigger the nutritional improvements. Therefore, extrusion applied as a pretreatment represents an interesting and economic alternative to improve the profile and bioavailability of the nutrients found in cereal and legume by-products which might lead to the development of functional ingredients useful to produce foods aimed to prevent chronic diseases.

Detection of potential voids in the granulated bentonite mixture and concrete plug in the Full-scale Emplacement experiment using a parallel-wire cable as an extra-long TDR waveguide

For quality control of a concrete plug constructed for the Full-scale Emplacement (FE) experiment at the Mont Terri rock laboratory and to monitor the backfilling of granulated bentonite, a commercial parallel-wire cable designed for audio speakers was applied as an extra-long time-domain reflectometry (TDR) waveguide. A procedure for estimating the length and position of a potential air void was first established based on laboratory test results. Three cables with a length of 8.0 or 8.5 m were installed along the lined perimeter of the tunnel with a diameter of about 2.7 m. The first cable in the granulated bentonite detected the potential presence of two air voids, 0.79 and 1.17 m in length along the cable, on either tunnel shoulder. Their positions suggested that the voids could have resulted from the flow of granules on both sides of the single screw feeder used to backfill the uppermost portion of the tunnel. The second cable in the concrete plug detected a potential air void (0.98 m in length along the cable) at the tunnel crown likely to have formed when fresh concrete was cast. The third cable did not show any sign of an air void in the concrete at the tunnel crown, implying that the void detected by the second cable was likely localized. The cables were also used to monitor resin-based contact grout injection. The data before and after grout injection suggested that the grout did not seep into the granulated bentonite behind the concrete plug and sufficiently filled gaps in the vicinity of the injection lines. Although the outcome above suggests a promising possibility for observation, it is based on our interpretation of the acquired data. There is no direct observation as of yet, thus, our interpretation remains to be verified when dismantling the FE experiment.

Improving the processability of pharmaceutical powders using atomic layer coating

Functional coatings on Active Pharmaceutical Ingredients (API) are used in the pharmaceutical industry to enhance mechanical strength, enable controlled release, taste masking, reduce formulation complexity and/or to improve drug product stability. Current API coating technologies have many challenges related to coating uniformity and defects, leading to variations in drug performance. This paper discusses using an ultra-thin API coating technology adapted from the semiconductor industry that can address many of the shortcomings of current coating technologies commonly used in the pharmaceutical industry. We show that this technique can achieve uniform and conformal nano-coating on multiple APIs without impacting their specific surface area and particle size distribution. We demonstrate the processability enhancements achieved using these coatings. The improvement in the processability of coated API was compared against uncoated API in commercially relevant unit operations used in the pharmaceutical industry, such as a loss in weight screw feeder and rotary tablet press.

Study of the feeding performance of mesoporous silica in a loss-in-weight feeder

Accurate and reliable continuous feeding is essential for the continuous manufacturing of solid-dose pharmaceuticals to ensure the reproducible composition of the final product. Consistent feeding of cohesive powders is challenging and requires an understanding of the interplay between material properties and feeder configuration. This study presents the volumetric and gravimetric feeding behaviour of a cohesive pharmaceutical, excipient mesoporous silica, at low feed rates (< 0.6 kg/h) using a twin-screw loss-in-weight feeder. The study investigates how the screw pitch, screen type and gravimetric setpoint impact the feed factor and feed rate variability. Additionally, the flow function and bulk density of the fed and unfed silica samples were determined and related to the feeding process parameters. Volumetric experiments highlight inconsistent feed due to the poor screw flight filling at high screw speeds and for configurations with the larger pitch, coarse concave screw. Poor screw flight filling also resulted in an inverse relationship between screw speed and feed factor in volumetric mode. In gravimetric mode, feed variability, expressed as %RSD, was greatest at the lower gravimetric setpoints with minimal impact due to tooling configuration. Discharge screen set-up was identified as the parameter which had a significant effect on the bulk density and flowability of the powder post-feeding.

Promoting Pellet Feed Flow in a Screw Feeder with an Agitator

Promoting Pellet Feed Flow in a Screw Feeder with an Agitator

Twin-screw continuous mixing: Effect of mixing elements and processing parameters on properties of aerosol powders

Twin-screw continuous mixing was used to prepare aerosol powders containing 1% budesonide, 0.3% magnesium stearate, and 98.7% α-lactose monohydrate. The effect of mixing configuration was studied using three screw profiles containing either a combing element, 30° forward kneading element, or a 60° forward kneading element. The impact of screw speed, feed rate, and multiple passes through the mixer on powder quality was investigated. The impact of specific energy on aerosol performance was dependent on the mixing configuration, and high energy input was detrimental to FPF for the 30° kneading element. Control of content uniformity was demonstrated by varying the mixing element in the screw profile. Passing the material through the mixer multiple times improved the aerosol performance. The robust and tunable nature of twin-screw mixing makes it a process well suited for continuous manufacturing of aerosol powders.

Calculation of the Heat Flux from a Ball Screw Nut to the Nut Raceway

In the field of precision machining, temperature fluctuation tends to cause the most significant machining errors. In particular, heat, which is generated in the nut of the ball screw feed system during movement, can deform the screw shaft significantly. In order to calculate and evaluate the thermal deformation of the ball screw shaft, the rate of the heat transfer from the nut to the screw shaft must be known. This rate can be calculated by subtracting the heat transfer rate to the nut raceway from the heat generation rate of the nut. Hence, it is necessary to calculate the heat flux from the nut to the nut raceway. This paper introduces a novel method to calculate the heat flux from the nut to the nut raceway. The new approach also enables calculations for different operating conditions. Furthermore, an experimental setup is established to measure the temperature increase, from 0 to 180 s after the nut starts moving, for various operating conditions. It is then theoretically shown that the 0–180 s temperature increase/heat flux curves for the nut are “universal”, i.e., the curve remains unchanged for the different operating conditions. Subsequently, a thermal model using the finite element method (FEM) is developed to simulate the nut temperature increase over time, which is then compared with the experimental data. As a result, it becomes possible to determine the heat flux from the nut to the nut raceway and calculate the 0–180 s temperature increase/heat flux curve (ΔT˜0~180s,Training Data) for the training group. Finally, the heat flux from the nut to the nut raceway is calculated for ten different operating conditions in the test group using the 0–180 s temperature increase/heat flux curve of the training group (ΔT˜0~180s,Training Data). The corresponding temperature curves are then calculated by inputting the values of the heat fluxes into the FEM model. The highest root mean square error (RMSE) between the calculated and experimentally measured temperature increase was 0.16 °C for Test 7 (the error was 10.7%). This result indicates that the new method is valid and feasible for calculating the heat flux from a ball screw nut to the nut raceway.

DETERMINATION OF CONDENSABLE PARTICULATE MATTER RELEASED BY THE COMBUSTION OF SOLID FUELS IN LOW-POWER BOILERS

Despite significant emission control steps in recent decades, damage to air quality caused byparticulate matter with a diameter of 2.5 m or less is now a major concern on a global scale.Condensable particulate matters (CPM) due to their significant contribution to the totalconcentration of particulate matter and their small aerodynamic size (below 2.5 m) are now ofwidespread interest. CPMs produced in low-power solid fuel heating systems can be one of themain components of the total mass of fine particles present in the air we breathe. The operatingconditions of large power installations and small heating boilers differ significantly, therefore itis necessary to adapt the research methods adapted to industrial installations, to the low-powerboilers. In the tests, three fuels were combusted in two low-power boilers (18 kW boiler witha suction feeder and 5class 14 kW boiler with a screw feeder): bituminous coal, pine and sprucewood pellets and cereal straw pellets. An EPA 202 method was used to collect the CPM. Qualitativeand quantitative analyses of inorganic and organic CPM components were performed. Analysesof the inorganic part of the CPM included the determination of metals m.in Na, Ca, Fe, Mg, Al,K, and water-soluble ions, m.in SO42, Na+, K+ and Cl, while analyses of the organic part of theCPM comprised the determination of PAHs. Differences were observed in the amount of CPMgenerated depending on the fuel used and the type of low-power boiler used. CPM emissions arerelatively high and constitute a large part of total particulate matter, so the impact of CPM on theenvironment cannot be ignored and we should pay special attention to its research and control,especially from small solid fuel heating boilers.