Feed Screw Research Articles

Stability and storage properties of hydrocarbons obtained by pilot scale pyrolysis of real waste HDPE-PVC in tubular reactor

In this work the mixtures of real waste high-density polyethylene, low-density polyethylene, polypropylene and polyvinyl-chloride (PVC) were pyrolyzed in a pilot scale horizontal tubular reactor using different synthetic zeolite catalysts. Raw material was fed into the reactor through an electrically heated screw feeder, and then decomposed in the reactor. Products were separated into gases, pyrolysis oil and heavy fraction by atmospheric distillation. The yields of gases and pyrolysis oils can be significantly increased by using catalysts, but the catalyst properties were key parameter. For instance, Ni/ZSM-5 catalyst can increase the hydrogen content in gases and isomerize the carbon framework of hydrocarbons. Pyrolysis oils contained C5-C35 hydrocarbons; however their properties were modified by catalysts. An accelerated aging test was performed to follow the long term behavior of products. Pyrolysis oils were treated at 80 °C for 7 d, and then the stability of pyrolysis oils was assessed by evaluating the density, solid deposition and acid number. Unsaturated hydrocarbons in pyrolysis oils can agglomerate during the aging. On the other hand the catalysts can improve their properties. Pyrolysis oils obtained by thermo-catalytic pyrolysis resulted with less corrosion than in case of without catalysts.

Research on Thermal Deformation of Feed System for High-speed Vertical Machining Center

Thermal deformation is one of the most significant factors influencing the precision of NC machining. This paper studies the thermal deformation mechanism of ball screw feed system (BSFS) for high-speed vertical machining center. Based on the thermal condition of feed system, the temperature field model of BSFS is established. By changing machining parameters such as rotational speed, loads and the flow rate of coolant, different results of thermal deformation are obtained. By analyzing the effects of machining parameters, we get the influence factors of BSFS’s thermal deformation. This work can help us reduce thermal deformation effectively, and improve the precision of NC machining.

An Electromechanical Co-Simulation Model Based on Lumped Parameter Model of Ball Screw Feed Drive System

The continuous search for efficiency put forward higher requests to the machine tool for high speed and high acceleration, which makes the large-size and lightweight-designed feed drive system more likely to produce vibration during high-speed and high-acceleration feed operation. Ball screw feed system is the most widely used linear drive system in the field of industrial automation. Electromechanical Co-Simulation for ball screw feed drive dynamics is an important technique for solving vibration problems occurs in the feed motion. In view of the shortcomings of the current dynamic simulation model in the study of vibration of ball screw feed drive system, taking a ball screw feed drive system test bench as an example, an electromechanical co-simulation model based on the lumped parameter model of ball screw feed drive system was built up in this paper. Firstly, based on the axial and rotation vibration integrated dynamic modeling method of ball screws, the lumped parameter model of ball screw feed system was established. Secondly, through the integration of the simulation model of semi-closed-loop cascade control system and the lumped parameter model of ball screw feed drive system, an electromechanical co-simulation model was built up. Simulation result shows that, the co-simulation model of ball screw feed drive system can predict the vibration occurs in the feed operation caused by the servo controller, ball screw feed system or the coupling between them.

Positioning Behavior by Applying Ultrasonic Oscillation to Sliding Feed Screw

Positioning Behavior by Applying Ultrasonic Oscillation to Sliding Feed Screw

From benchtop to pilot scale–experimental study and computational assessment of a hot-melt extrusion scale-up of a solid dispersion of dipyridamole and copovidone

The aim of our work was to study and define a computationally-based adiabatic scale-up methodology for a hot-melt extrusion (HME) process to produce an amorphous solid dispersion (ASD). As a drug product becomes commercially viable, there is a need for scaling up the manufacturing process. In the case of HME used for the formation of ASDs, scale-up can be challenging due to the fundamental differences in how heat is generated in extruders of differing scale, i.e. conduction vs. viscous dissipation and the significant role heat generation plays in determining the final product attributes. Using a 30%w/w dipyridamole-in-copovidone formulation, 11 mm-, 16 mm- and 24 mm-diameter extruders with L/D 40, solid-state characterization tools, a geometric scaling equation, and Ludovic® twin-screw extrusion software, we compared the total imparted material energy, the conducted energy and the difference between barrel and melt temperature at die exit for various feed rates and screw speeds. Numerical simulation identified desirable adiabatic conditions at multiple extruder scales in agreement with the chosen scaling factor. With the use of computational tools, the energetics in an extrusion process can be evaluated and processing conditions can be selected to identify the most efficient scaling of a HME process.

Use of Batch Mixing To Investigate the Continuous Solvent-Free Mechanical Synthesis of OLED Materials by Twin-Screw Extrusion (TSE)

Mechanochemical synthesis has the potential to change the way in which chemistry is conducted, particularly with regard to removing or dramatically reducing the need for solvents. Recently, it has been demonstrated that mechanochemistry can be carried out continuously and on large scale through the use of twin-screw extrusion (TSE). TSE has successfully been applied to the synthesis of cocrystals, metal organic frameworks (MOFs), deep eutectic solvents (DESs), metal complexes, and organic condensation reactions. However, while TSE provides a route for mechanochemical synthesis to be developed into a continuous, high-volume manufacturing process, little is currently understood about how to best optimize the various process parameters involved. Herein, we investigate the use of a batch mixer that has been previously used in polymer processing, to optimize mechanochemical reactions performed by extrusion. In particular, reactions between 8-hydroxyquinoline (Hq) and metal acetate salts of zinc or aluminum to give quinolinate complexes Znq2·AcOH and Alq3·AcOH, which are of interest for organic light-emitting diode (OLED) applications, have been investigated. The manner in which the progress of the reaction correlates with the machine torque, temperature, and specific mechanical energy (SME) imparted by the batch mixer has been elucidated. Significantly, this knowledge enabled optimization of the mechanochemical reactions by TSE through the key parameters of screw speed, feed rate, temperature, and particle size.

Modeling and Optimization of Fiber Quality and Energy Consumption during Refining Based on Adaptive Neuro-fuzzy Inference System and Subtractive Clustering

Refining is a critical step in the manufacturing of medium-density fiberboard (MDF). To ensure fiber quality and control of the energy consumption during refining, proper production parameters, such as feeding screw revolution speed (SR), accumulated chip height (CH), opening ratio of the discharge valve (OV), and content of Chinese poplar (CP), are vital. These parameters were monitored and recorded in an MDF mill to investigate the relationships between the parameters and the fiber quality and energy consumption. In this study, fuzzy models of the fiber quality and the energy consumption during refining were established based on subtractive clustering and an adaptive neuro-fuzzy inference system (ANFIS). The fiber quality and energy consumption models demonstrated high prediction accuracy because their predictive mean relative errors were as low as 4.14% and 6.72%, respectively. The errors of fiber quality were optimized using the simulated annealing method, and the input parameters were obtained. Based on the energy consumption model, the minimum energy consumption was 41.51 kWh/t, on the premise of the minimum requirement of fiber quality. This study can be a guideline for MDF production management to improve fiberboard quality and reduce energy consumption.

Microalgal cell disruption via extrusion for the production of intracellular valuables

Abstract The objective of this study was to evaluate the effectiveness of extrusion on cell disruption of a marine alga Nannochloropsis oceanica with a single-screw extruder for the production of intracellular valuables. The effect of operating parameters including feed moisture (15–24%) and screw rotation speed (300–450 rpm) was also determined. Experimental results demonstrated that extrusion was effective in algal cell disruption indicated by direct observation of cell break-up through scanning electron microscope (SEM) and significant increases up to 94.3% and 68.7% in lipid and sugars yield, respectively between treatments and the control (no treatment). It was found that feed moisture (15%) generally improved cell disruption efficiency due to longer residence time of biomass in the extruder. Increasing screw rotation speed from 300 to 450 rpm tended to enhance cell disruption because of stronger shear forces on algae. However, the effectiveness was restricted by residence time of biomass in the extruder because a faster screw rotation speed resulted in a higher biomass flow rate. Thus, the optimal cell disruption was not always achieved at the fastest screw rotation speed; instead, it appeared at the levels depending on specific evaluation indicators (around 350 rpm), therefore the optimal conditions for algal cell disruption were obtained at about 15% of feed moisture and 350 rpm of screw rotation speed. This study also confirmed that extrusion was beneficial for the production of more valuables including polyunsaturated fatty acids (PUFA) and essential amino acids (EAA) from microalgae, for example up to 74.3% increase of PUFA and 20.5% increase of EAA after extrusion compared to the control.

Catalytic fast pyrolysis of corn stover in a fluidized bed heated by hot flue gas: Physicochemical properties of bio-oil and its application

Fast pyrolysis of corn stover was performed at temperatures in the range of 450°C-525°C in a fluidized bed. The chemical composition of the bio-oil acquired was analyzed by GC/MS, and its pH, kinetic viscosity and calorific values were determined. In the pyrolysis system used in this experiment, some improvements to former pyrolysis systems were done. Two screw feeders were used to prevent jamming the feeding system, and the condenser was equipped with some nozzles and a heat exchanger to cool quickly the cleaned hot gas into bio-oil. The results showed that the bio-oil yield increased with increasing pyrolysis temperature and then declined with a further increase in pyrolysis temperature. The highest bio-oil yield of 43.3 wt.% was obtained at 500°C with the dolomite as bed material. The char yield always decreased with the increase of temperature. The major chemical compounds of bio-oil included acetol, butanone, acetic acid, propionic acid, ethylene glycol, phenol, etc. Pyrolysis oil was completely immiscible in diesel, but homogeneous emulsions were obtained when mixing the pyrolysis oil, emulsifier with diesel in different ratios. Keywords: corn stover, pyrolysis, bio-oil, fluidized bed, hot flue gas, GC/MS DOI: 10.25165/j.ijabe.20171005.2473 Citation: Yang W, Fu P, Yi W M. Catalytic fast pyrolysis of corn stover in a fluidized bed heated by hot flue gas: Physicochemical properties of bio-oil and its application. Int J Agric & Biol Eng, 2017; 10(5): 226–233.

Adaptive real-time model on thermal error of ball screw feed drive systems of CNC machine tools

The positioning error of ball screw feed drive systems is mostly caused by thermal deformation of the ball screw shaft in machine tool feed systems. This paper presents an adaptive real-time model (ARTM) for predicting the temperature transient distribution and thermal error distribution of the ball screw shaft. FEM integrated with the Monte Carlo method is applied to determining the heat generation rates of two bearings, moving nut and two guides in the ball screw feed system. Then based on the data of the FEM calculations, an exponential function of the feed velocity and time is used to describe variation of the temperature difference between the measured surface point and the center of the kinematical pair with time. Finally, a numerical forecasting algorithm is developed to predict the thermal characteristics of the screw shaft and its effectiveness is verified by the experiments.

Effect of extrusion variables on antioxidant activity, total phenolic content and dietary fibre content of gluten‐free extrudate from germinated Chenopodium (Chenopodium album) flour

SummaryA Box‐Behnken design was used to study the effects of feed moisture content (18–20%), barrel temperature (115–135 °C) and screw speed (225–275 rpm) on the responses; antioxidant activity, total phenolics, dietary fibre, colour (L‐value), hardness, expansion ratio, water absorption index and overall acceptability for development of gluten‐free extrudate based on germinated Chenopodium album flour. Second‐order polynomial fitted model showed that temperature most significantly (P ≤ 0.05) affected the antioxidant activity (AoxA), total phenolics (TPC), expansion ratio, hardness and overall acceptability (OA). Antioxidant activity, total phenolic content and dietary fibre of extrudate varied from 11.56 to 15.93%, 56.77 to 81.28 mg/100 g and 18.65 to 22.06 g/100 g, whereas the lightness and hardness of extrudates ranged from 64.02 to 68.35 and 12.26 to 19.49 N, respectively. The results of this study validate the production of functional and acceptable snack product made from C. album flour by extrusion cooking.

Pilot scale steam-oxygen CFB gasification of commercial torrefied wood pellets. The effect of torrefaction on the gasification performance

Torrefaction is a promising biomass upgrading technology as it makes biomass more coal alike and offers benefits in logistics and handling operations. Gasification is an attractive thermochemical conversion technology due to its flexibility in the product gas end-uses. Therefore, it is valuable to investigate whether additional benefits are foreseen when torrefaction is coupled with gasification. Therefore, two commercial torrefied wood fuels and their parent materials are gasified at 800–850 °C under atmospheric steam-oxygen circulating fluidized bed gasification conditions and magnesite as bed material. The torrefied feedstocks consisted of wood residues torrefied by Topell at 250 °C (Topell black), and mixed wood and wood residues torrefied by Torrcoal at 300 °C (Torrcoal black). The gasification results show that torrefaction resulted in an increased gas quality, as it yielded higher H2 and CO contents, a decrease of the CO2 content, increased gas yield and a significant decrease of the total tar content for both feedstocks. For the Torrcoal samples, torrefaction resulted in a decrease in the carbon conversion efficiency (CCE). In addition, the cold gas efficiency (CGE) remained approximately the same due to the increase in the H2 and CO contents. The Topell samples showed an increase in the CCE and CGE upon torrefaction, but this could be attributed to a significant grinding in the screw feeder. It is generally concluded that both torrefied fuels may offer benefits as a feedstock for steam-oxygen blown circulating fluidized bed gasification, in particular in terms of gas quality and yield.

English

The aim of this study is to model screw feeder unit to handle granulated wet cassava to the flash dryer column. The knowledge of the flow behavior, physical and mechanical properties, rheology of the product and the geometrical characteristics of feeders unit were essential to evaluate the best conditions of handling granulated cassava based on the theory of virtual works. The effect of granular media strain on the rotational speed which is limited to 2 rps corresponding to the elastic limit of 30% was studied. With the same strain limit, maximum screw length of 1300 mm and the maximum residence time of 100 s in the bin were identified as the best area used to design the screw feeder unit and conduct the process operation. The modeling of the strain was based on the theory of virtual works or energies.   Key words: Modeling, virtual works, strain, screw feeder, cassava.

Effect of the screw–nut joint stiffness on the position-dependent dynamics of a vertical ball screw feed system without counterweight

The study on the position-dependent dynamic characteristics of a vertical ball screw feed system without counterweight is an important step in the enhancement of the structural performance of mini-type vertical milling machines. The ball screw is generally driven by a servomotor, which converts a rotary motion into a linear motion through a screw–nut pair. To assess the position-dependent dynamic characteristics of a vertical ball screw feed system subjected to the influence of the screw–nut joint stiffness, a variable-coefficient lumped parameter model of the system is developed. This model is established taking into account the screw–nut joint stiffness under three different strategies: (1) considering the preload and the weight of the spindle system, (2) considering the elastic deformation but ignoring the effect of the weight, and (3) a perfectly rigid model. The differences between the three models in predicting the position-dependent dynamic characteristics of the system are compared, revealing that the stiffness of screw–nut joint greatly affects the vibratory behavior of the spindle system in the transmission direction. A set of conducted experimental results demonstrate that the stiffness model under the preload and the weight of the spindle system is the most accurate model for the prediction of the position-dependent natural frequency and displacement response of the system with the spindle system position. Therefore, it is more suitable for structure design, performance simulation, and evaluation of a vertical ball screw feed system without counterweight.

Optimization of the control loops of the variable frequency induction motor drive of the flame reactor feed screw

In the paper the optimization of the control loops of the variable frequency induction motor drive for the feed screw of a flame reactor has been carried out to obtain required dynamic characteristics of the electric drive for known parameters of the plant. Simulation studies of basic control loops

WITHDRAWN: Estimation of powder mass flow rate in a screw feeder using acoustic emissions

WITHDRAWN: Estimation of powder mass flow rate in a screw feeder using acoustic emissions

Dynamic Thermal-Structure Coupling Analysis and Experimental Study on Ball Screw Feed Drive System of Precision Machine Tools

To improve the simulation accuracy of the thermal characteristic of ball screw feed drive systems, a dynamic thermal-structure coupling model, which considered the effect of the thermal contact conductance (TCC) of the solid joint on the accuracy of simulation results, was proposed to conduct thermal characteristic analysis of ball screw feed drive systems. The predictive model for TCC was proposed based on the micro morphology description of rough surfaces and the contact load distribution of solid joints. Then, the dynamic thermal-structure model of the ball screw feed drive system was established. To validate the effectiveness of the dynamic thermal-structure coupling model, thermal characteristic experiments of the ball screw feed drive system were conducted under different feed rates. The results showed that the simulation accuracy of temperature field and axial thermal elongation can be improved from 65% to 87% and from 70% to 85%, respectively.

Physical and hydration properties of expanded extrudates from a blue corn, yellow pea and oat bran blend

Extrudates were prepared from a blue corn, yellow pea and oat bran blend employing a twin-screw extruder. Response surface methodology was used to evaluate the effect of extrusion-cooking process independent variables: screw speed (SS, 300–400 rpm), die temperature (DT, 120–160 °C) and feed moisture content (FMC, 20–25%) on the system parameters (specific mechanical energy and product temperature), physical properties (sectional and specific longitudinal expansion indices, porosity, hardness and color attributes), hydration properties (water absorption and solubility indices, and pasting properties), microstructure and x-ray diffraction. Although, system parameters, physical and hydration properties were affected by SS and DT, the greatest effect was due to the FMC. Indicating this way lubricant effect as the preponderant factor controlling extrusion effects on raw material. Decreased FMC increased specific mechanical energy, expansion, soluble compounds; and decreased hardness, time to raw peak viscosity, raw peak, total setback and final viscosities. Data were also analyzed with a principal component analysis, showing that 74.67% of data variability can be explained defining two components corresponding to the 62.10% that was due to mechanical effect and 12.57% that was related to thermic effect. Conditions obtained for multiple optimization were: 158.64 °C, 371.98 rpm, 18.38% FMC.

Integrated modeling and analysis of ball screw feed system and milling process with consideration of multi-excitation effect

Abstract The present researches about feed drive system and milling process are almost independent with each other, and ignore the interaction between the two parts, especially the influence of nonideal motion of feed drive system on milling process. An integrated modeling method of ball screw feed system and milling process with multi-excitation effect is proposed in this paper. In the integrated model, firstly an analytical model of motor harmonic torque with consideration of asymmetrical drive circuit and asymmetrical permanent magnet is given. Then, the numerical simulation procedure of cutter/workpiece engagement during milling process with displacement fluctuation induced by harmonic torque is put forward, which is followed by the solving flow for the proposed integrated model. Based on the integrated model, a new kind of quality defect shown as contour low frequency oscillation on machined surface is studied by experiments and simulations. The results demonstrate that the forming mechanism of the contour oscillation can be ascribed to the multi-excitation effect with motor harmonic torque and milling force. Moreover, the influence of different milling conditions on the contour oscillation characteristics, particularly on surface roughness, are further discussed. The results indicate that it is necessary to explain the cause of the new kind of quality defect with a view of system integration.

The vibration frequency analysis of the screw feeding system with spring supports

Ball screw feeding system has wide application in machine tools, and its dynamic research is very important. The drive screw can be seen as a rotating Timoshenko beam under the pre-tension force. Considering the bearing stiffness, the boundary condition of the screw is spring supported. Also, considering the contact deformation between the screw and the worktable and the worktable moving, the screw is added an intermediate moving spring-mass system. Using boundary conditions and continuity conditions, the lateral and longitudinal frequency equations of the screw feeding system are derived considering the effect of gyroscope, the pre-tension force, the bearing stiffness, the contact between the worktable and the screw and the moving of the worktable. The effect of the system parameters on the natural frequency is studied. The diameter, the pre-tension force, the bearing stiffness, the contact stiffness and the rotational speed of the screw have effect on the vibration frequency and the frequency varies when the worktable moves along the screw from the left to the right end. This work supplies a base for designing the drive system to avoid resonance and to improve the stability of the system.