Extruder configurations

Figure 5.21 Twin-screw extruder configuration forthe transformation of raw agricultural products...

Throughput Screw speed Extruder configuration (screw/barrel)... 

The contribution to the overall scenario is summarized through the three process steps shown in Fig. 3.18. Suppose that the developer has finished processing the initial version of the extruder functional zones in the flowsheet editor. This information is sent, under the control of the process engine, to MOREX (step 1). MOREX receives the extruder configuration, along with material and process parameters via XML. The engineer, then, starts the... 

For the coarse estimation of extruder size and screw speed, simple mass and energy balances based on a fixed output rate can be used. For the more detailed design of a twin-screw extruder configuration it is necessary to combine implicit experience knowledge with simulation techniques. Theses simulation techniques cover a broad range from specialized programs based on very simple models up to detailed Computational Fluid Dynamics (CFD) driven by Finite Element Analysis (FEA) or Boundary Element Method (BEM). 

As it seems that the dispersive mixing of the additives could be improved by increasing the melt shear rate, in the video conference the 3D simulation expert proposes a modification of the screw configuration as well as the screw speed. This is accepted by the team leader, a new MOREX simulation is done and the compounding extruder configuration is fixed. 

Figure 23.7 Simplified diagrams of twin-screw extruder configurations. I = interaxis = separation (distance) between the screw axes D = screw diameters h — screw channei depth.

Figure 1 Twin-screw extruder configuration for the alkaline treatment of vegetable matter...

In addition to mass temperature, residence time also plays a decisive role. Fig. 4.6. Figure 4.7 shows the residence time distribution in various extruder configurations. A single screw channel provides poor axial mixing. In addition, there is a stagnant layer on the screw surface with a long residence time. In a twin-screw... 

Figure 4.7 Residence time distribution with various extruder configurations [590]...

Figure 4 Diagram of the twin screw extruder configuration used for processing ceramics at Brunei University.

Based on the shapes of the responses to step changes in controller output, and reasoning from the physical configuration of the extruder barrel, a reduced order dynamic model of the process was postulated. One can think of the Topaz program as order 80 (the number of nodes in the finite element subdivision), and the reduced model of order 4 (the number of dynamic variables). The figure below illustrates the model. 

Figure 11.6 illustrates the general configuration of a film blowing operation. Molten polymer from the extruder is pumped into an annular die, where it is distributed around a tubular melt channel before emerging vertically as a relatively thick-walled molten tube. The top of... 

When a polymer is extruded through an orifice such as a capillary die, a phenomenon called die swell is often observed. In this case, as the polymer exits the cylindrical die, the diameter of the extrudate increases to a diameter larger than the diameter of the capillary die, as shown in Fig. 3.9. That is, it increases in diameter as a function of the time after the polymer exits the die. Newtonian materials or pure power law materials would not exhibit this strong of a time-dependent response. Instead they may exhibit an instantaneous small increase in diameter, but no substantial time-dependent effect will be observed. The time-dependent die swell is an example of the polymer s viscoelastic response. From a simplified viewpoint the undisturbed polymer molecules are forced to change shape as they move from the large area of the upstream piston cylinder into the capillary. For short times in the capillary, the molecules remember their previous molecular shape and structure and try to return to that structure after they exit the die. If the time is substantially longer than the relaxation time of the polymer, then the molecules assume a new configuration in the capillary and there will be less die swell. 

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