InGas 18 months meeting May, 20th/21st 2010 Paris, France

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Institut für Chemische VerfahrenstechnikD-70199 Stuttgart, Böblingerstr. 72

InGas 18 months meetingMay, 20th/21st 2010

Paris, France

WP B2.3: Exhaust heating/Catalyst concepts

Institute for Chemical Process Engineering of Stuttgart University, Germany

-USTUTT-

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• Heat exchanger experiments:– Setup for stationary heat exchanger experiments (ICVT)– Stationary results of ICVT prototype– Basic adaption of simulation model– Setup for stationary heat exchanger experiments (Delphi)– Stationary results of Delphi prototype

Activity outline

• Comparison experimental results ICVT/Delphi– Amplification factors– Pressure drop– Conversion behavior

• Conclusions/Outlook

• Appendix

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Setup for stationary hex experiments

FIC

Air

H2

CH4

FIC

FIC

TIR TIR

TIR

TC

Hood

TIR TIR TIR TIR

TIRTIRTIR

FID

General conditions:• Air flows up to 30 m3/h• CH4 conc. up to 5000

ppm • Inflow temperatures:

20 – 400 °C• Fuel lean operation• Hydrogen-assisted

heat up

PIR

PIR

Sensors:• 10 Thermocouples

(Type K)

• 2 pressure sensors

• THC analytics

Flowchart of test rig

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Positions of axially aligned Thermocouples

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Δ-Pressure measurement

Additional insulation was applied around the heat exchanger

Due to severe heat losses, the burner interface (tube) was heated during the second set of stationary experiments

32,5 cm

Setup for stationary hex experiments Sensor equipment of hex prototype (ICVT)

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Setup for stationary hex experiments Control loop for setpoint experiments

Tmax

FIC

PID

-+

CH4

Tset

Main advantages:

Stationary temperature profile is reached much faster

Approach:

Heuristic design of

controller parameters

i.e. analysis of step

response (of yCH4,in)

Resulting amplification factor is equal to system without control:

Without control Controlled system

= f(yCH4,in,Vair)

= const.

= const.

= f(yCH4,in,Vair)adT

TA

max

adT

TA

max

.

.

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1. Startup:• Inflow temperature @ 200 °C, Volume flow @ 12 m3/h

• H2 in air for fast ignition

• H2 + CH4 in air to further heat up the system

• CH4 in air until stationary point is reached

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# Constant parameters Varied parameters Target

I Tin, Tmax (setpoint) Air flow, yCH4 (control) Amplification factor

II Tin, yCH4 Air flow Amplification factor

III Air flow, Tmax (setpoint) Tin, yCH4 (control) Amplification factor

2. Stationary experiments performed:

3. Stationary experiments, modified (electrically heated burner interface):

• Repetition of 2.I and 2.III (II omitted due to inertia of system) Setpoint Ttube = Setpoint Tmax

Setup for stationary hex experiments Experimental procedure (ICVT)

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Stationary results of ICVT prototype Axial temperature: Experiments with active control

6 m3/h (GHSV: 24 000 1/h), Tin = 300 °C, Tset= 630 °C, yCH4,in= 3174 ppm (control)

Heat sink due to non-insulated connection tube

Tmax

TH,out

TC,in

TC,out

TH,in

inCinH

outHinHhex TT

TT

,,

,,

εhex = 91 %

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Stationary results of ICVT prototype Axial temperature: Experiments with active control

11 m3/h (GHSV: 44 000 1/h), Tin = 300 °C, Tset= 630 °C, yCH4,in= 3155 ppm (control)

Tmax

Tmax shifted to outflow channels

Smaller influence of heat sink

εhex = 84 %

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Stationary results of ICVT prototype Axial temperature: Experiments with active control

11 m3/h (GHSV: 44 000 1/h), Tin = 300 °C, Tset= 630 °C, yCH4,in= 3155 ppm (control)

Tmax

εhex = 81 %

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Stationary results of ICVT prototype

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• Catalyst activity is low and steadily decreasing (see later)

• Conversion is distributed over inflow- and outflow channels

• Mass transfer limitation Active surface needs to be

increased!

Experiments with active control

• Tmax = Tset = 660 °C

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Stationary results of ICVT prototype

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1. As can be seen in the previous results, the burner interface acts as a heat sink Coupling equation between inflow and outflow channel at U-turn:

ambwall

p

tube

outinTT

cmAk

TT

1,2,

Fitting parameter

2. The catalyst is less active than initially assumed: Mass transfer surface as well as kinetic parameters (act. energy, preexp. factor)

were modified

3. Global heat loss was increased by 3 %

4. Laminar pressure drop is accounted for by:

2

hdm

Cdzdp

Fitting parameter

Model adaptions I

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7 m3/h (GHSV: 28 000 1/h), Tin = 300 °C, yCH4,in= 3500 ppm

Heat sink caused by connection tube for burner

Stationary results of ICVT prototype Results with fitted model: no control, no heating

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Stationary results of ICVT prototype

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8 m3/h (GHSV: 33 000 1/h), Tin = 300 °C, Theat=Tmax=630 °C

Results with fitted model: control, heating

Heat sink relation set to 0 in model

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Stationary results of ICVT prototype

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Amplification factor is calculated as:

A is corrected by CH4 conversion (ΔTad referred to converted CH4)

adT

TA

max

Amplification factors

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Stationary results of ICVT prototype

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No heating, conversion

No heating, yCH4,in

Heating, conversion

Heating, yCH4,in

• Tmax is kept constant in both experimental runs (630 °C)

yCH4,in has to change with volume flow

Inverse shape as of A vs. volume flow

• Severe decay of catalyst activity between two runs

What happend to the catalyst?

Deactivation!

CH4 conversion and yCH4,in

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Stationary results of ICVT prototype

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Linear decay of conversion, leading to linear decay of Tmax

Thermal ageing is not likely. Spalling of washcoat?

Catalyst deterioration

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Stationary results of ICVT prototype

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Washcoat crumbs!

Due to non-fixed spacer structures (fins), the washcoat was mechanically not stable!

Catalyst deterioration

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Setup for stationary hex experiments

Fitting of additional Thermocouples (sliding through center channels)

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Δ-Pressure

measurement

Delphi hex at test rig

Additional insulation

Sensor equipment of hex prototype (Delphi)

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Setup for stationary hex experiments

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Positions of additional TCs

Inflow U-turn

outflow

Positions of TCs placed by Katcon

1* 2* 3*4 5

67

# Position [cm]

Type Diameter [mm]

1 7.5 K 1

2 15 K 1

3 22.5 K 1

*: 2 TCs of same type (redundance)

# Position [cm]

Type Diameter [mm]

Inflow 0 K 1

4 20 K 0.5

5 24 K 0.5

U-turn 30 K 1

6 28 K 0.5

7 26 K 0.5

outflow 0 K 1

Axial temperature measurement (Delphi)

(All positions measured from inflow end)

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1. Startup:• Inflow temperature @ 200 °C, Volume flow @ 11 m3/h

• H2 in air for fast ignition

• H2 + CH4 in air to further heat up the system

• CH4 in air until stationary point is reached

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# Constant parameters Varied parameters Target

I Tin, Tmax (setpoint) Air flow, yCH4 (control) Amplification factor

2. Stationary experiments performed:

Setup for stationary hex experiments Experimental procedure (Delphi)

Due to insulated burner interface, additional heating was not required!

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Stationary results of Delphi prototype Axial temperature: Experiments with active control

ICVT: 6 m3/h (GHSV: 24 000 1/h), Tin = 300 °C, Tset= 630 °C, yCH4,in= 3174 ppm (control)

Delphi: 7 m3/h (GHSV: 24 000 1/h), Tin = 278 °C, Tset= 630 °C, yCH4,in= 4041 ppm (control)

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Stationary results of Delphi prototype Axial temperature: Experiments with active control

ICVT: 11 m3/h (GHSV: 44 000 1/h), Tin = 300 °C, Tset= 630 °C, yCH4,in= 3155 ppm (control)

Delphi: 13 m3/h (GHSV: 44 000 1/h), Tin = 293 °C, Tset= 630 °C, yCH4,in= 3484 ppm (control)

Kink due to increased cell density!

Simulation result taken from DB2.5 report (m=15kg/h)..

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Stationary results of Delphi prototype Axial temperature: Experiments with active control

ICVT: 15 m3/h (GHSV: 60 000 1/h), Tin = 300 °C, Tset= 630 °C, yCH4,in= 3472 ppm (control)

Delphi: 18 m3/h (GHSV: 60 000 1/h), Tin = 297 °C, Tset= 630 °C, yCH4,in= 4379 ppm (control)

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Comparison exp. results ICVT/Delphi Amplification factors

Strong influence of axial heat conduction in wall material!

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Comparison exp. results ICVT/Delphi Pressure drop

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Comparison exp. results ICVT/Delphi Conversion behavior

Wrong measurement due to non-uniform mixing in U-turn section

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• Experiments with ICVT heat exchanger: Stationary profiles require long time experiments

(very slow system response) Experimental procedure with controlled Tmax is significantly faster

Insulation/Heating of top section is critical for hex performance Severe catalyst deterioration

• Experiments with Delphi heat exchanger: Results are comparable with ICVT heat exchanger Worse conversion behavior due to lower cell density (i.e. lower active surface) Much lower pressure drop than ICVT prototype Up to now no information regarding catalyst deterioration

Conclusions

• Fitting: Temperature profiles fit nicely Pressure profiles fit as well Fitting is not reliable due to severe catalyst deterioration

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• Dynamic experiments: ICVT prototype was damaged during first experimental attempt (see

Appendix) Heat up tests with fixed ICVT prototype Heat up tests with Delphi prototype

• Stationary experiments with Delphi heat exchanger: More experimental data to evaluate ageing/deactivation

Outlook

• Fitting: Fitting of stationary results obtained with Delphi hex Improvement of pressure relation Fitting of dynamic experiments as soon as data is available

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-Appendix-

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Characterization of burner system Thermal power output / Lambda of exhaust

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Characterization of burner system Mean temperature / Volume flow

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Damaged ICVT prototype

• Temperature in outflow channels was too high. Meltdown of channel ends due to compression of hex core Rapid heat accumulation / pressure increase

• Damage only at the very end of outflow channels Hex core was shortened and will be used again for heat up experiments

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PHASE I: Stationary tests without burner

• Heating up the system with high throughput of hot exhaust (~ 500°C) with low THC concentration (low amplification factor)

• Subsequently, different characteristic operating points in engine map are tested, i.e. low/middle/high load at low/middle/high rpm?

Testing different constant exhaust compositions @ λ = 1: Variation of H2 ,CO/CH4 ratio in exhaust

Can CH4 conversion be boosted by H2 / CO (similar tests at ICVT test bench?) ?

PHASE II: Dynamic tests without burner

• Can CH4 light-off be sped-up by increasing CO concentration in exhaust (+ flap) ?

• Simulating fuel shut-off under overrun conditions @ constant rpm (possible at test bench?) How long can system be kept above CH4 light-off ?

• λ spikes @ constant rpm+load: monitoring CH4 slip

Test program Delphi bench scale prototype

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PHASE III: Dynamic tests with burner

• Cold start @ constant rpm and burner mass flow

• Cold start under NEDC conditions

• Burner operation after cold start: Preventing extinction during fuel shut-off (overrun) @ high rpm Is addition of CH4 more effective ?

More details need to be defined after dynamic laboratory experiments!

For bench scale, a specifically designed burner system should be ordered (experience will

be gained during laboratory tests)

Test program Delphi bench scale prototype