bioethanol meeting, detmold, 2008 ethanol plant revamp … · vapour equilibrium curve ... -save...

Buss-SMS-Canzler GmbH Bioethanol Meeting, Detmold / B. Kaiser / April 20081

Bioethanol Meeting, Detmold, 2008

Ethanol Plant Revampand

Process Optimization by proven

Membrane Technology

Capacity Increase and Reduction of Energy Consumption


Content

• Ethanol separation• Rectification design and operation• Energy saving at rectification• Example:

Stand alone membrane dehydration system• Recycling permeate/regenerate to distillation• Integrated dehydration Systems• Example:

Cascade system• Project work sequence • Membrane selection

Membrane qualitiesMembrane modules

• Examples: Process optimisation/redesign

• Conclusion• Outlook


95908580756050403010 7020 1000

95

90

85

80

Ethanol in liquid (wt%)

75

70

60

50

40302010

Etha

nol i

n Va

pour

(wt%

)

Azeotrope (95.6 wt%)

0

100

Fermentation

Distillation

Dehydration

Possible Working range forMembranes

Working range for

Line of equalliquid/vapourconcentration

Alcohol-Water Vapour equilibrium curve

Traditional dehydrationtechnology

Ethanol Separation

80 w% Ethanol is proven working range for membranes


Rectification Design and Operation

No. of theoretical Stages

8 1612

1.0

2.0

3.0

0

4.0

4 20 24 28

15 wt.%8 wt.%5 wt.%

Water content in head product

Possible energy saving

Reb

oile

rEne

rgy

Energy consumption at rectification

5w% water vs 15w% water at column top


Feed:

55 w% Ethanol

99,5 w% Water

80 w% Ethanol

46%

44%

Energy Saving at Rectification

80 w% vs 93 w% Ethanol at top

93 w% Ethanol

Column theor. trays: 20 30

Heating energy: 240 528

Cooling energy: -226 -512

Existing rectification:

double capacity and produce 99,7w% Ethanol instead of 93w% Ethanol at same energy consumption


Reduction of Operating Costs:High Water Content to Dehydration

Use the advantage of high water content feed by use of Membranes

Case A:Stand alone dehydration systems

independent from raw Ethanol production

Case B:Integrated dehydration systems

connect to the vapour outlet of rectification/distillation


Stand Alone Membrane Dehydration System

Liquid Feed

Ethanol 99,7w% Water 99,9%

Raw Ethanol

Feed: 85w% Ethanol, liquidincluding recycle treatment

App. 0,72 kg steam / kg dehydrated Ethanol

Vapour compressionincluding recycle treatment

App. 0,44 kg steam / kg dehydrated ethanol

Compared to molecular sieve (top at 93w% Ethanol)

70 % saving heating energy at regenerate recycle

Revamp existing systems with membranes:-increase capacity-save heating energy-save cooling water consumption


Membrane

Molecular Sieve

Recycling of Regenerate/Permeate

Molecular Sieve - Membrane

Regenerate/permeate:Molecular sieve:

Flow: 52 % of Ethanol output, 19 w% Water, Qrec.=0,45 kW/kg ETOH

Membrane:

Flow: 46 % of Ethanol output, 67 w% WaterQrec.=0,13 kW/kg ETOH

31%

Regenerate

recycle energy

Ethanol 99,7w%

93 w% Ethanol

Rec

tifie

r Regenerate

Ethanol 99,7w%

Rec

tifie

r

80 w%Ethanol

Regenerate


Integrated Dehydration Systems

Complex Heat Integration in Complete Ethanol Plants

•Rectification is not isolated

•Heat is exchanged within theoverall plant

•Big variety of process designs

•Process redesign needed, e.g. pressure cascadee.g. vapour compressione.g. different heat integratione.g. modifying split rates at columns

•Membranes must fit to the pressure temperature conditions Others

Fermentation

Distillation

DryingRectification

Dehydration

Steam input


Integrated Dehydration UnitsExample: Heat integration by cascade systems

Cascade reuse of energy:

-pressure cascade up to 7 bar

Associated temperatures at 80/20w%

-Saturation = 140 °C

-plus 15°C superheat => 155 °C

-plus safety margin => 170 °C

Rec

tifie

r

Stri

pper

Traditional Dehydration

Stri

pper

1Membrane-Dehydration

Stri

pper

2

Rec

tifie

r

Original process

Membrane process (only1 alternative shown)


Upgrading Existing Ethanol Processes / Plants

Adopt

process design

Redesign

heat integration concept

Select Proper

Membranes

Check process design

Improved economy

Each plant is different specific considerations needed

-Low-, middle-, high pressure

Higher value product


Membrane SelectionDifferent membranes and modules

Flat membranes

Module type: „Sandwich“

Zeolite membranes

Module type:

„Shell & tube“

Capillary membranes

Module type: „Cartridge“

Courtesy Sulzer, Mitsui, WFX


Membrane SelectionQualities of different membranes

Flat Membranes Ceramic Membranes

Max. temperature

Typical op. Pressure

Chemical stability

Permeate vacuum

Cooling water

Cold water

Permeat solvent cont.

Sealings

Maintenance

Vacuum vessel

Capacity reserve:-Feed pressure-Sweep-Vacuum

Cost

Operation mode

App. 95-110°C

App. 1 barg

medium

>10 mbar abs

at stage 1

at stage 2

App. 15%

App. 4m per 1m²

difficult

needed

Capacity reserve:-no-difficult, inefficient-no

Low

VP + PV

App. 180°C

App. 5 barg

medium

>10 mbar abs

At stage 1

At stage 2

App. 10%

2 O-rings per tube (0,8 m²)

fair

-

Capacity reserve:-yes-no-no

Medium

VP + PV

App. 180°C

App. 5 barg

medium

>100 mbar abs

Yes, needs only 1 stage

-

App. 40%

2 rings per 130 m²

easy

-

Capacity reserve:-yes-yes-yes

high

VP

Conclusion: Select Membranes with regards to the overall circumstances

Capillary Membranes


Membrane SelectionOperational availability and maintenance

Flat Membranes Ceramic Membranes Capillary Membranes

Courtesy Sulzer, Mitsui, WFX

Accessibility

Operational availability

Easy access - ++ ++

Easy fault detection - - + ++

Easy replacement - - + ++

Continue production if faulty - - ++


Membrane Requirements

Mechanical and chemical qualities:• Mechanical strength up to 10 bar (depending on process)

• Temperature up to 180°C (depending on process)

• Tolerant to high water content (min 20w% water)• Tolerant to fusel oil• Solvent resistance (alcohols, heads: e.g.: acetate, cetone, toluene, organic acids, etc)• Chemical resistance app. pH 2-13

Operation, availability, maintenance:• Static operation, no cycling, no moving parts• Easy fault identification • Easy maintenance • Replacement without plant shut down• Continued production at lower capacity in case of failure• Normal cooling water required

Commercial:• Long warranty period on capacity and product quality• Purchase or leasing

All proven in industrial scale, but….

proper membranes must be selected


Original design with molecular sieve: 2,34 kg steam / kg ethanol 99,7w%

New design with membrane dehydration: 1,48 kg steam / kg ethanol 99,7w%

Saving 27% heating energy and NO additional equipment

reduction cooling water consumption

Optimization Cascade Process with Membranes

-Replace molecular sieve by membranes

-Rectification stops at 80w% ethanol

-Redesign heat integration

Stri

pper

1

Stri

pper

2

Rec

tifie

r

Hea

ds

Membrane


Conclusion

Membranes, properly selected, proved in industrial application:

•Reliable, long term operation

•Chemical resistance against byproducts/solvents

•Various raw material possible

•Easy to operate

•Simple to maintain

•Big potential for saving in heating energysaving cooling water consumptionreduce emissions


Stand alone dehydration systems:

Revamp with membranes for dehydrationIncrease capacity and reduce energy consumption

Existing raw ethanol plants:Upgrade existing equipment with membrane dehydration and produce higher value product i.e. Ethanol 99,7-99,95w% Ethanol combined with less energy consumption

New ethanol process designs:

Integrated membrane dehydration will reduce energy consumption significantlyConsider membranes at an early stage in process design and selection

Conclusion

Redesign and revamp of existing systems and processes

Low-, middle-, and high pressure processes

Debottle Necking:

Membranes can set free capacity for distillation / rectification / condensation,throughput


Outlook

Membrane feed with 50 w% water is under investigation of long term pilot testingEnergy saving will be increased even more

Producers and Engineering Companies are welcome

Visitors to reference plants are welcome

bioethanol meeting, detmold, 2008 ethanol plant revamp … · vapour equilibrium curve ... -save...

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