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

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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

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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

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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