Elizabeth Saade1, David E. Clough1, Carl Bingham2, Alan W. Weimer1

1 Department of Chemical and Biological Engineering University of Colorado at Boulder

2 National Renewable Energy Laboratory, Golden, CO

Modeling of a Solar-Thermal

Reactor for Synthesis Gas Production

May 15th, 2012

A control system will improve the operation of a solar-thermal reactor

H2 + CO + CO2

Steam Biomass

Operation of solar-thermal reactor is dependent on available sun

As the clouds cover the sun, the reactor will be cooled within 1 or 2 minutes

If the clouds are partially covering the sun the reactor can still operate

High Flux Solar Furnace at NREL (10 kW)

a

c

Reactor

Heliostat

Primary concentrator

How is the control system going to work?

PT

TT

FIC

FT

RC FIC

FT

Solar irradiation

MPC

Steam Carbon

H2 + CO + CO2

HT Solar

irradiation predictor

AT

Attenuator

Dynamic model of the reactor

DOMAIN:

H2 + CO + CO2

Carbon + Ar

Steam Reflective cavity

Single tube

35 c

m

9.8

cm

20 mm I.D.

Dynamic model of the reactor

STRATEGY:

≈

CARBON STEAM CARBON STEAM

H2 + CO + CO2

H2 + CO + CO2

CARBON STEAM

T1

T2

T1,OUT =T2,IN

front back

Conduction between disks

Irradiation from concentrator

Dynamic model of the reactor

EQUATIONS:

Model validation at NREL

Particle feeder

Attenuator

Secondary concentrator

Reactor

SiC tubes

Validation with no particles, just Ar

Some runs with particles

Used attenuator to test power levels (2, 3, 4, 5, 6 kW)

Recorded transients

Model validation during transients

Front Wall Temperature at the center of the tube:

3 kW

1258 K

1256 K τ= 85 s

Dynamic model of the reactor

CARBON STEAM GASIFICATION REACTION:

C(s) + H2O (g) CO (g) + H2 (g)

Considered also water-gas shift reaction:

CO(g) + H2O (g) CO2 (g) + H2 (g)

Kinetics taken from literature

Experimental runs at NREL to choose best-fitting kinetics

Carbon rate of reaction: 𝑟𝑐𝑎𝑟𝑏𝑜𝑛 =-(𝑟𝑐𝑜 + 𝑟𝑐𝑜2)

Dynamic model of the reactor

GASIFICATION KINETICS:

Dynamic model of the reactor

RESULTS FOR A PARTLY CLOUDY DAY

REFLECTIVE CAVITY ABSORBING CAVITY

τ=552 seconds τ=12 seconds

Summary

A simplified dynamic model was developed and implemented in MATLAB

Model was validated with experimental runs at NREL

The model will be used in a MPC algorithm to control flow rates in response to changes in solar irradiation

Error in the model is less than 5% in terms of the steady state temperatures

14 CSREES 68-3A75-7-605

Acknowledgements

Questions?