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