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DETERMINATION OF RESIDENCE TIME DISTRIBUTION IN A TWIN-SCREW EXTRUDER BY

COLORIMETRIC METHOD

محاسبه توزیع زمان اقامت اکسترودر دو ماردون به روش رنگ سنجی

Amirreza Hasheminia, mohammadjavad Hafezi

Presenter: Amirreza Hashemininia

Paper Code: (imbpa15-00650046)

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Introduction

• Residence time

• Residence time distribution

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Introduction

Increasing use of twin-screw extruders (TSE)

Increasing importance of residence time

distribution (RTD)

Why?

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Introduction

• The importance of RTD of TSE on parameters such as :

• extrusion process characterization

• mixing conditions

• controlling chemical reaction time in the extruder

• scaling up extruders

• characterize the flow pattern

• And . . .

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Introduction

• A common method to obtain RTD for a chemical reactor:

Apply input and output data analysis of theactual measurement, it is possible to identifythe nature of the system. The change in theconcentration of the input flow, theconcentration of records and examine theoutput current

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Introduction

Color tracer such as

masterbatch

Output will be a color

distribution

What is the relationship together?

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Materials

• The polymer used in this project is LDPE 2420H. Also using red iron powder as tracer

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Experimental

• Extrution

• A twin-screw extruder with corotating screws

• screws speed= 120 rpm feeding rate= 15 rpm

• The temperature at the first barrel= 165°C

• The temperature at the sixth barrel= 175 °C

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Experimental

• colorimeterL* a* b* values were measured with a colorimeter. In the case, the red color intensity, C, was calculated as:

However, the value of b* did not contribute to the red color intensity, so c was simplified as:

Thus, the value of the redness, a*, was used as a measure of red color intensity of the concentration of tracer in the TSE

a* = value of redness

b* = value of blueness

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Experimental

• function of RTD

• By assuming the TSE as a chemical reactor and into pulse-type some of tracer , the RTD E is:

• The mean residence time (MRT): Mean time the material spent in the extruder can be described as:

C(t) = tracer concentration at time t

E(t) = fraction of the tracer ofinput which at time t from ofchemical reactor exits

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Experimental

•The preparation of masterbatch• The tracer used for determining the RTD was prepared by

production a masterbatch, Containing of LDPE 2420H and with Characterized 1 wt% Iron powder red

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Experimental

• The process of sampling

the tracer was added as a pulse

input

pure LDPE 2420H

15 rpm

120 rpm

steady state conditions

Samples were collected every 10 s for 7 min after adding the tracer.

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Experimental

• The preparation of samples for Calculation of intensity Color:

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Experimental

• By Using the mentioned assumptions and equations, graph E(t) versus time is as follows:

MRT≈160 s

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Conclusion

• By color value distribution can make it possible toachieve RTD and this method is a tailored protocolfor analysis TSE.

• Color value distribution has a direct relationship withRTD. It is sufficient that the intensity of colorsamples, linked to the concentration and by usingfrom this concentration, for each sample achievedE(t).

• With the help of graph E(t) versus time and MRT,control the extent of conversions and reactions ofthe compounds in the TSE.

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Refrences

• 1 Octave Levenspiel, Chemical reaction engineering -Third Edition, pp. 260-270

• 2. Residence Time Distribution Determination Using On-Line Digital Image Processing- S.Lee,,M.Hanna, D.Jonesa -(2009)

• 3. Residence time distribution in a corotating twin-screw extruder J.P. Puaux, G. Bozga, A. Ainser Chemical Engineering Science 55 (2000)