Post on 24-Apr-2020
Small-scale Production of Renewable Ammonia
Mark HubertyUniversity of Minnesota-Twin Cities
Dr. Lanny Schmidt and Dr. Ed Cussler
September 30, 2008
2
Motivation
Current State of the Industry
• Centralized, capital intensive production
www.pfrengineering.com/new_page_3.htm
• Scale of 1000s ton/day
• Steam methane reforming
• Pre- and post-processing
– Sulfur removal, WGS, CO2 removal, methanation
• Equilibrium limited reaction
– Recycle
3
Motivation
http://www.fertilizerworks.com/html/market/TheMarket.pdf
4
Objective
Disperse, Small-scale Production
• Can we bring the anhydrous ammonia plant to
the farmer?
• Reduce transportation costs
• Utilize renewable sources of
hydrogen
– Reduce capital costs
• Implement alternative designs
– Economics of small scale, local ammonia
– Improved conversion
– Eliminate recyclehttp://www.nrel.gov/features/images/0508_photo_turbines_field.jpg
5
The Morris Project
University of Minnesota and IREE
• Renewable ammonia from wind
• 1.65 MW wind turbine for
electricity generation
• Electrolyzer for hydrogen
production
• Haber-Bosch chemistry for
ammonia synthesis
• 1 ton/day ammonia production
• Biomass gasifier
– Alternative renewable hydrogen production
www.morris.umn.edu
6
Reactor Engineering
Ammonia Process Flow Diagram
http://www.cheresources.com/ammonia.shtml
7
Reactor Engineering
Simultaneous Reaction and Separation
• Targets small-scale production on the co-op or
farm
• Requires innovative reactor and process
design
– Fed-batch reactor
– Absorbent bed
– Subsequent Swing Desorption
8
Reactor Engineering
• Alkaline earth halides e.g MgCl2– Three ammine complex formation steps
– Absorption of up to 6 ammonia molecules at low
temperature and high pressure
2 3 2 3
2 3 3 2 3
2 3 3 2 3
2
2 4 6
MgCl NH MgCl NH
MgCl NH NH MgCl NH
MgCl NH NH MgCl NH
→+ ⋅←
→⋅ + ⋅←
→⋅ + ⋅←
Decrease T,
Increase P
Absorbents
Elmoe, T.D, 2006. A high-density storage/delivery system based on Mg(NH3)6Cl2 for SCR-DeNOx in vehicles. Chemical Engineering Science
9
Reactor Engineering
Predicted Performance
550 600 650 700 750 8000.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
temperature (K)
nitro
gen c
onve
rsio
n
reaction
reaction and absorption
10
Reactor Engineering
Proposed Reactor Configuration
Step 1: Fed-Batch Charging
Step 2: Pressure Swing Desorption
Step 3: Ammonia Condensation
Feed compressed, pre-
heated gases at 400 oC
and 250 atm into combined
catalytic-absorbent bed
Vent to relieve pressure,
desorb ammoniaCondense liquid product
11
Reactor Engineering
• Temperature swing desorption
– Requires separate beds with independent
temperature control for catalyst preservation
– Expected to retain synergistic effect due to the limiting time scale of diffusion in the solid
• Recirculation reactor
– Convective transport benefit
Potential Alternative Configurations
12
Reactor Engineering
Experimental Set-up
13
Reactor Engineering
Our Preliminary Results
0 50 100 150 200 250 300 3500
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
time (hr)
nitro
gen c
onve
rsio
n
Long time scale
High conversion
14
Reactor Engineering
• Transport limitation by diffusion
• Particle size O(1mm)
• Implies diffusion O(10-9 )
aPt
D
dt
dP
π
=
Preliminary Results
2cm
s
15
Conclusions
• Future directions
– Structural stability and catalyst deactivation studies
– Investigation of transients, transport
– Economic analysis
• Opportunity for renewables utilization and
small-scale, disperse chemical production
– Reaction and separation implemented in the same
vessel at the same set of operating conditions
– Improved equilibrium conversions, transport
limitations