Residence time and conversion in the extrusion of chemically reactive materials
Extrusion is one of the most versatile and energy-efficient processes for the manufacture of polymer products, including food, pharmaceuticals and plastics. Many functions including mixing, cooking and chemical reaction can be performed in an extruder. Here, twin-screw extruders offer improved control of the residence time distribution (RTD) and mixing in materials such as plastics, rubber and food. Based on the flow and the heat transfer characteristics obtained for a self-wiping, co-rotating twin-screw extruder, the residence time and chemical reaction are studied by tracking the particles. For normally starve-fed twin-screw extruders, the length of the completely filled section is calculated as function of the process variables using the coupling of the flow with the die. With a model of the solid conveying section, the RTD for the whole extruder is calculated for corn meal at different screw speeds and flow rates. The calculated variation of RTD with the screw speed and the flow rate yields good agreement with observations from many experiments. The variation of the fully filled section length, chemical conversion and mixing effectiveness are also obtained under different operation conditions. Most of the results are in qualitative agreement with experimental results and may be used as guidelines for extruder design and determination of optimal operating condition.
- Research Organization:
- Rutgers, State Univ. of New Jersey, New Brunswick, NJ (US)
- OSTI ID:
- 20002496
- Report Number(s):
- CONF-990805-; TRN: IM200002%%496
- Resource Relation:
- Conference: 33rd National Heat Transfer Conference NHTC'99, Albuquerque, NM (US), 08/15/1999--08/17/1999; Other Information: PBD: 1999; Related Information: In: Proceedings of the 33rd national heat transfer conference NHTC'99, by Jensen, M.K.; Di Marzo, M. [eds.], [1150] pages.
- Country of Publication:
- United States
- Language:
- English
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