10/11/2011
2011 ACS Rubber Division180th Technical Meeting
Kneader Technology for the Direct Devolatilization of Temperature Sensitive Elastomers
Boyd T. Safrit, PhD, PEAndreas E. Diener, Dipl. Ing.
10/11/2011 – p. 2
Conventional Process
Polymerization exothermic Temperature control important Polymer temperature sensitive Viscosity increases with MW build
Solution polymerization Stirred tank reactors Steam stripping for solvent removal
10/11/2011 – p. 3
Conventional Process
Solution Polymerization
Stripping
Separation
Confectioning
Coagulation
Expeller
Expander
Belt dryer
Water / steam consumption, solvent recovery
Air handling and emissions
Plant footprint, maintenance
10/11/2011 – p. 4
Conventional vs. Direct Devolatilization
Solution Polymerization
Stripping
Separation
Confectioning
Coagulation
Expeller
Expander
Belt dryer
Main Evaporation
Finishing
10/11/2011 – p. 5
Kneader Technology
10/11/2011 – p. 6
Kneader Technology
10/11/2011 – p. 7
Main Evaporation
Cement feed of 75-90% solvent Maximum temperature of 100°C High energy duty for solvent evaporation
Back mixed kneader reactor Discharge target of 2-10% solvent High mechanical energy input
10/11/2011 – p. 8
Finishing
Pasty feed of 2-10% solvent Maximum temperature of 100°C High viscosity high mechanical energy
overheating of elastomer
Plug flow kneader reactor Discharge target of 200-2000 ppm solvent Process elastomer as crumbles (or pasty
phase)
10/11/2011 – p. 9
Two Step Process for Direct Devolatilization
Installed at Fraunhofer Gesellschaft, Schkopau, Germany
Part of larger semi works plant for polymer synthesis, production, and testing
10/11/2011 – p. 10
Main EvaporationExperimental
100 liter single shaft kneader reactor Residence time of 15 minutes Shaft speed of 50-80 RPM
ElastomerSolution
400 kg/hr10% BR100°C
PastyElastomer
Hot Oil80°C
300 mbar
Hot Oil
10/11/2011 – p. 11
FinishingExperimental
200 liter twin shaft kneader reactor Residence time of 30 minutes Shaft speed of 60 RPM
PastyElastomer
CrumblyElastomer
60 mbar
40 kg/hr
Hot Oil80°C
Hot Oil
10/11/2011 – p. 12
405060708090
100
1 2 3 4 5 6
Tem
pera
ture
(C
) Main Evaporation
Temperature Profile
Thermal Input
Mechanical Input
Thermal Output
Energy Required
Feed
10/11/2011 – p. 13
Main EvaporationEnergy Balance
SolventEvaporation
35 kW
27 kW (77%)mechanical energy
ElastomerSolution
300 mbar~65 °C (estimated)
400 kg/hr10% BR100°C
PastyElastomer44 kg/hr90% BR
97°C
8 kW (23%)thermal energy
10/11/2011 – p. 14
FinishingEnergy Balance
60 mbarDevolatilization0.5 kW
4.6 kWmechanical energy
PastyElastomer
40 kg/hr 1000 ppm Solvent87 °C
44 kg/hr90% BR
97°C
CrumblyElastomer
4.1 kWthermal energy
10/11/2011 – p. 15
FinishingImproved Mass Transfer Process
10/11/2011 – p. 16
FinishingImproved Mass Transfer Process
Finisher size Capacity final VOC total volatiles
7 liter 2.5 kg/hr < 10 ppm 5000 ppm
30 liter 30 kg/hr < 50 ppm 5000 ppm
100 liter 50 kg/hr < 50 ppm 5000 ppm
200 liter 50 kg/hr < 15 ppm 5000 ppm
BR in hexane Atmospheric pressure
10/11/2011 – p. 17
Comparison to Conventional Process
Energy Environment Flexibility Operation Footprint Quality
0
500
1000
1500
2000
2500
kW
h/t
[Ru
bb
er]
Stripping andconvective drying
Direct evaporation
Energy Consumption
24%
100%
10/11/2011 – p. 18
Conclusion
Conventional process for temperature sensitive elastomers Mature and proven technology Several key disadvantages
Two step process for direct devolatilization Kneader reactor technology Removes water from process Demonstrated process on semi works scale