Prof. Dr.-Ing. M. Modigell

Dipl.-Ing. S. Engels

High Temperature Membrane Technology for Oxygen Production

Oxyfuel-Process

ASU

N2

airCO2

O2

O2 + flue gas

coalwater

steam

flue gas

OXYCOAL-AC Process

O2 + flue gas

coal

efficiency drop < oxyfuel

Principle of OTM-Membranes

• high permeation rate:jO2 > 3 Nml/(cm2min)

• as thin as possible activemembrane layer

Wagner-equation:

Concepts with and without Contact to the Flue Gas

CO2, CO, O2, H2O, SO2, NOx, dust

combustion

air

N2T = 850°C

flue gasT = 300°Cp = 1bar

p = 20bar

100 % O2T = 850°C

1

2

• higher total efficiency• higher permeation rate,smaller membrane area

• flue gas recirculation temperature 850°C• chemical stable membranes

• no contact between membrane and flue gas

• cold recirculation (~300°C)• lower permeation rate,

larger membrane area• complete heat input by air, heat

up of air to 850 °C

functional tests of membrane materialspermeation testseffects of flue gas components (CO2, SO2, CO, NOx, H2O ...)long term stability

high temperature joining methoddevelopment of joining methods between membrane (ceramic material)and module material (steel)

model development and scale-upheat and mass transfer across the membraneCFD-based optimisation and construction of industrial applicablemembrane modules

Research Topics

High Temperature Test Facilitygas mixing system

tubular oven(T<1050°C)

temperature: < 1050°Csweep gas: He, CO2, O2, CO, SO2 , NO, H2O

pressure: 0.01 - 1.5 bar absfeed gas: synthetic air / air

pressure: 1 - 25 bar abs

selected materials are tested

Ba0.5 Sr0.5 Co0.8 Fe0.2 O3-δ (BSCF)

Sr0.5 Ca0.5 Mn0.8 Fe0.2 O3-δ (SCMF)

La2NiO4

membrane geometrytubular: length up to 500 mm

diameter: 8 – 15 mm

discs: diameter: 10 -15 mm

joining methods

force fit by spring and gold sealing

Membrane Materiales

high temperature silver or glas brazing

• high permeation rate under ideal / inert conditions• 3 ml/(cm2min) feasible by means of thinner membranes(tested membrane thickness: 1 mm)

function of O2-partial pressure ratio

O2-

perm

eatio

n ra

te [m

l/cm

2 min

]

O2-

perm

eatio

n ra

te [m

l/cm

2 min

]

temperature [°C] Ln(PO2,Feed / PO2,Sweep) [-]

Ba0.5 Sr0.5 Co0.8 Fe0.2 O3-δ (BSCF)

temperature / absolute pressure

Only applicable for air separation without direct contact to the flue gas !

high permeation rate, but critical chemical stability against CO2

O2-

perm

eatio

n ra

te[m

l/cm

2 min

]

time [min] time [min]

O2-

perm

eatio

n ra

te[m

l/cm

2 min

]

CO2 - Stability BSCF

lower partial pressurelower permeation ratelarger membrane area

O2-

perm

eatio

n ra

te[m

l/cm

2 min

]

temperature [°C]

pO2-ratiowith sweepgas: 26with vacuum pump: 5

permeation rate (850°C, 20bar)2,05 ml/cm2min0,95 ml/cm2min

⎟⎟⎠

⎞⎜⎜⎝

⎛=

−

fluegasO

airOTK

MWagnerO p

pe

sTCj

Wagner

,

,

2

2

2ln

BSCF: without Contact to the Flue Gas

• lower permeation rate compared to BSCF

• stable against CO2, NO, slow decrease of permeation rate

• unstable against 360 ppm SO2

100% CO2

O2-

perm

eatio

n ra

te [m

l/cm

2 min

]

temperature [°C]

O2-

perm

eatio

n ra

te [m

l/cm

2 min

]

time [h]

SO2 stability

La2NiO4

temperature / absolute pressure

tested membrane material are unstable under Oxyfuel power plantconditions

interactions between steel and membrane material

new materials or chemical stable protective layers have to be developed

Measurements

OXYCOAL-AC(development of

power plant process,membrane modules)

MEMBRAIN HGF-Alliance(analysis and optimisation ofmembrane materials)

MEM-OXYCOAL(development of new membrane

materials)

Module Concept without Contact to the Flue Gas

because of the critical chemical stability membrane modules without contact to the flue gas have to be developed at first

(IWM RWTH Aachen)

membrane module(42 tubes, 0.5m length)

1m2-Membrane Module / High Temperature Sealing

(IWM RWTH Aachen)

high temperature silver brazing

BSCF

low pressure

perovskite

high pressure

casing

flance

baseplate

brazing socket

brazing

flancebrazing

10 x M33 screw

air

N2

O2(IWM RWTH Aachen)

high temperature silver brazing

BSCF

low pressure

perovskite

high pressure

casing

flance

baseplate

brazing socket

brazing

flancebrazing

10 x M33 screw

air

N2

O2

Test Plant for Prototype 1m2-Membrane Module

1 bar < Pair < 35 barToven < 1550°C

Tgas preheater = 850°C 0.01 bar < Ppermeat < 1 bar

gas fluxes: pressure:temperature:min/400

2 NCO lV =&

min/400 Nair lV =&

high temperature oven

gas preheaters

air compressor

cooling system

flux control,pressure control

Acknowledgment

The project MEM-BRAIN Alliance is supported by:Helmholtz-Gemeinschaft Deutscher Forschungszentren

The OXYCOAL-AC project is supported by:Bundesministerium für Wirtschaft und Technologie Federal State of NRW

RWE Power AG, E.ON Energie AG, Hitachi Power EuropeGmbH ,Linde AG, MAN Turbo AG, WS-Wärmetechnik GmbH

Thank you for your attention!