Phone: 775-674-7129
Email: [email protected]
Curt Robbins
Assistant Research Engineer
S. Kent Hoekman
Amber Broch
Research Professor
Assistant Research Engineer
CO2 Recycling by Reaction with RenewablyGenerated Hydrogen
Goals/Objectives
Testing
Synthetic exhaust
gas (2% CO2 in N2)
was mixed with
renewably produced
H2 and heated to
roughly 200°C before
entering the
methanation reactor.
This project investigated a method to reduce GHG emissions from
the natural gas power generation sector. CO2 in exhaust can be
reacted with renewably produced H2 to generate CH4 that can be
recycled back into an engine or turbine, reducing greenhouse
emissions and increasing the engine/turbine efficiency.
8
Upper Catalyst
Temperature
250
H2 in (slpm)
6
200
% CH4 out
150
4
o
• Use renewably generated Hydrogen
With increasing H2
flow, the % CO2
decreased and CH4
increased. The
exothermic reaction
can also be seen at
the top of the graph.
350
300
Gas Flow Rates
• Reduce Greenhouse Gas (GHG) emissions
400
Lower Catalyst
Temperature
10
Temperature ( C)
• Demonstrate the recycle of CO2 into CH4 by reaction with H2
Results
12
100
2
50
% CO2 out
0
25
:0
30
:0
0
0
0
20
:0
15
:0
0
10
:0
0
0
05
:0
00
:0
0
0
Time
(min:sec)
Concept
H2 Inlet Line
Synthetic
Exhaust Inlet
Line
H2 Storage
Tanks
Preheater
Synthetic Exhaust
Flow Controller
Reactor (with
Heat Guard)
The exothermic Sabatier Reaction occurs at moderate temperatures
(<400 °C) over a Ni or Ru catalyst. Haldor Topsoe PK-7R Ni based
catalyst was used for this project.
The experiment was setup in DRI’s
renewable energy trailer. The reactor is a
0.55 L stainless steel reactor, with top to
bottom flow. A National Instruments
Compact Field Point unit controlled the
experiment. Exhaust gas analyzers
outside the trailer tested the gas stream
before and after the reactor.
18%
H2 utilization efficiency
is shown on the right.
While more CO2 is
reacted with higher H2
flow rates, the
efficiency of CO2
conversion per mole of
H2 used decreases.
H2:CO2 = 2:1
16%
H2:CO2 = 4:1
CO2 moles in- CO2 moles out
H2 moles in
Opening for inlet and
exhaust lines
Stoichiometric ratio
14%
12%
H2:CO2 = 6:1
10%
8%
6%
Maximum theoretical efficiency is 25%
4%
2%
0%
200
2%CO2 in N2
Catalytic Reactor
(Ni/AL2O3)
Solar Photovoltaic
CH4 + H2O
H2
H2O
Wind Turbines
H2
Storage
Electrolyzer
O2
Experiments were performed at various temperatures, flow rates, and
gas mixing ratios. In most cases, the synthetic exhaust gas flow rate was
held constant while varying the flow of H2. (Shown below, with H2 flow in
blue, N2/CO2 in red).
12
A Stuart KOH 5 kW
electrolyzer produced H2
through electrical power
generated from
photovoltaic panels and
wind turbines.
10
Steam
Boiler
H2 Flow (SLPM)
6.52 SLPM
50
40
4
Flue Gas
60
6.52 SLPM
6
Work
Output
Work
Output
80
81.5 SLPM
8
3.26 SLPM
Steam
Turbine
30
3.26 SLPM
20
2
Air
10
0
The Sabatier reaction can
be implemented in a
combined cycle power
plant reducing emissions
and increasing the
efficiency of the gas
turbine while supplying
heat for the boiler.
9.78 SLPM
70
Overall Scheme for CO2 Capture and Recycle in a Natural Gas Power Plant
0
Gas Turbine
CH4
Flue
Gas
O2
Sun
Wind
Nuclear
Hydro
CH4
H2
Electrolyzer
H2O
-60
0
20
40
Time (min)
Methanation
Reactor
Heat
Start data log
H 2 solenoid OFF
Preheat ON
Reactor Heat ON
225
250
275
300
325
350
Upper Catalyst Temperature
Conclusions
• A nickel-based catalyst is effective for reducing CO2 to CH4 using H2 at
moderate temperatures (300-350oC)
90
Synthetic Exhaust Flow (SLPM)
Synthetic
Exhaust
Start flow profile
when Cat. 1
reaches test
temperature
60
Preheat OFF
Reactor Heat
OFF
80
All gas flow OFF
END Test
• Approximately 60% conversion of CO2 was demonstrated at a
stoichiometric ratio of H2/CO2 of 4/1 and space velocity of 10,000 hr-1
• With renewably-produced H2, this CO2 recycle approach is effective in
reducing GHG emissions
Acknowledgements
Funding for this work was provided by Recycle CO2 Inc. We also
acknowledge the contributions of Alan Gertler, Rick Purcell, Larry Sheets
and Roger Jacobson from DRI.
375