Hideaki KobayashiInstitute of Fluid Science, Tohoku University, Japan

Japan-Norway Hydrogen SeminarNorwegian Embassy, February 28, 2017

Ammonia Combustion for Energy System

Energy carriers project to develop a value chain of CO2 free hydrogenAmmonia (NH3) is a potential energy carrier which can burn directly.

NH3

The Cross-ministerial Strategic Innovation

Promotion Program (SIP) “energy carriers”

Fuel NH3 CH4 C3H8 H2

Boiling point at 0.1 MPa(℃) - 33.3 - 161.6 - 42.1 - 252.9

Lower heating value (MJ/kg) 18.6 50.2 46.6 120 .4

Flammability limit (eq. ratio ) 0.63～1.40 0.50～1.69 0.51～2.51 0.10～7.17

Maximum burning velocity(m/s) 0.09 0.37 0.43 2.91

Ignition temperature ( ℃) 651 537 432 500

Maximum adiabatic flame temperature (℃) 1750 1970 2020 2120

Fuel NH3 CH4 C3H8 H2

Boiling point at 0.1 MPa(℃) - 33.3 - 161.6 - 42.1 - 252.9

Lower heating value (MJ/kg) 18.6 50.2 46.6 120 .4

Flammability limit (eq. ratio ) 0.63～1.40 0.50～1.69 0.51～2.51 0.10～7.17

Maximum burning velocity(m/s) 0.09 0.37 0.43 2.91

Ignition temperature ( ℃) 651 537 432 500

Maximum adiabatic flame temperature (℃) 1750 1970 2020 2120

Ammonia combustion fundamentalsAdvantages CO2 free combustion; 4NH3 + 3O2 2N2 + 6H2O Alternative fuel suitable to storage and transport Matured infrastructure of combustion facility

Challenge for applications Low combustion intensity High NOx emission Low radiation intensity

Laminar burning velocity and effects of pressure measure in IFS.

Properties of fuels and combustion characteristics with air0.7 0.8 0.9 1.0 1.1 1.2 1.30

2

4

6

8

10

(-)

S L (c

m/s

)

0.1 (Present)0.3 (Present)0.5 (Present)

Pi (MPa)

Ammonia

Zakaznov et al., 0.1 MPa

Takizawa et al., 0.1 MPaPfahl et al., 0.1 MPa

1916• Haber-Bosch process was established for fertilizer and

chemical ingredient1940’s

• A public bus with NH3 fueled engine was used in Europa1960’s

• Hypersonic experimental aircraft X-15 used NH3/LOxrocket motor to achieve Ma=6.72

• US army investigated NH3 gas-turbine, but it was given up because of very low combustion efficiency

1970’s • Atmospheric pollutant research on N-C-O-H chemistry

revealed thermal NO and prompt NO mechanisms2000’s

• NH3 as a hydrogen-energy carrier was noticed and “NH3Fuel Association” was established in US

A public bus which used ammonia/coal-gas engine in Belgium in 1942 (E. Kroch)

X-15 which used NH3/LOX rocket motor in 1960’s

http://history.nasa.gov/x15/cover.html

Brief history of ammonia combustion R&D

In 2015, AIST, Japan succeeded in 41.8 kW power generation using a NH3 single-fueled micro gas turbine for the first time.

Kurata et al., Proc. Combust. Inst., (2017).

The facility consists of a fuel-supply system, NH3 gas compressor, gas turbine, SCR NOx-reduction apparatus and loading equipment.

A 50 kW micro gas-turbine with a regenerative cycle is equipped.

NOx emission less than 10 ppm was achieved.

NH3 gas-turbine test facility in AIST

Vaporizer1 ton NH3 cylinderGas compressor

Loading equipment Gas turbineSCR

Gas turbinetest facility

The Fukushima Renewable Energy Institute,

AIST, Japan

NH3 fueled micro gas-turbine generates 41.8 kW power with low NO emission downstream of the SCR system.

NH3 ratio=0.5

Revolution: 80000 rpm

NH3/CH4/air fueled operation NH3/air fueled operation

Time [s]

Rev

olut

ion

[rpm

]

Rev

olut

ion

[rpm

]

Pow

er, F

uel c

onsu

mpt

ion

Pow

er, F

uel c

onsu

mpt

ionRevolution[rpm]

Power[kW]

Power[kW]

Kerosene[L/h]

Time [s]

Kerosene[L/h]

Revolution[rpm]

Upstream of SCR

NO emission in NH3/air operationThermal efficiency

Starting-up procedure and steady operation of the micro gas-turbine

Large scale vortexstructures Small scale vortex structures

The second invariant of the velocity gradient tensor

3-D numerical analysis using LES, Uin = 36.1 m/s, Swirl number = 0.675, Inlet temperature = 500 K, Equivalence ratio =1.0,Ammonia detailed chemistry by Miller （23 species, 98 elementary reactions)

Profiles of turbulence intensity

L=15

0 mm

Uxz(m/s)

D = 72 mmX

Z

Uprime(m/s)

D = 72 mm

L=15

0 mm

ZX

YNH3 (-)

Numerical analysis : Flow structure of the swirling flame

Large scale vortex motion extends residence time of reactants and produce stagnant region near the swirler.

L=15

0 mm

D = 72 mm

ZX

NO concentration corresponds to the NO profiles for 1-D premixed flame. Controlling equivalence ratio is effective for NO emission reduction.

Equivalence ratio: = 1.0 =1.25 =1.40

Flame structure calculated by 1-D

numerical simulation

=1.3

3-D numerical analysis : Effect of equivalence ratio on NO profiles

Chemical equilibrium Chemical

equilibrium

Heat release rate

Heat release ratea.u.

a.u.

D = 72 mm

L=15

0 mm

rz

NO [ppm] NO [ppm]NO [ppm]

rz

rz

=1.0

L=15

0 mm

L=15

0 mm

D = 72 mm D = 72 mm

Uin = 36.1 m/s, Inlet temperature = 500 K, Equivalence ratio =1.0

Ammonia (NH3) is a potential CO2 free fuel which can strongly burn using combustors in energy systems.

Ammonia fueled micro gas-turbine in AIST succeeded in power generation of 41.8 kW with small amount of NO emission less than 10 ppm downstream of SCR.

Combustion science and technology can derive solutions for combustion enhancement and NO emission reduction of ammonia direct combustion.

Summary

Acknowledgement

This work was supported by the Council for Science, Technology and Innovation (CSTI), the Cross-ministerial Strategic Innovation Promotion Program (SIP), “energy carrier” (Funding agency: Japan Science and Technology Agency (JST)).