31/05/2012

Carbstone: A novel process for the production of construction materials from slags and CO2

Mieke Quaghebeur, Peter Nielsen, Ben Laenen, Dirk Van Mechelen, Evelyne Nguyen

31/05/2012 2 © 2012, VITO NV

Introduction: Carbstone

» Building materials high

strength

» No binder/additives needed

» Carbonates in-situ act cement

» Availability: annual production

» current inhibitors for reuse

» Environmental impact

» Stability

CO2

31/05/2012 3 © 2012, VITO NV

Production process: upscaling

» Dimensions of the Carbstone blocks;

» Purity of CO2-gas;

» Use of (semi)-industrial equipment;

31/05/2012 4 © 2012, VITO NV

Up-scaling dimensions Carbstone blocks

» Porosity (grain size distribution and compaction);

» Relation between process time and dimensions of

construction materials?

CO2

» Permeability of CO2-gas;

31/05/2012 5 © 2012, VITO NV

Up-scaling dimensions Carbstone blocks

0

20

40

60

80

100

120

0 200 400 600 800 1000

CO

2-u

pta

ke (%

of f

inal

up

take

)

Time (min)

3,5cm

10cm

» CO2-uptake for a small and large compact (BOS-slags) (20bar,

80°C);

» Conclusion: longer carbonation time required for large

versus small compact;

31/05/2012 6 © 2012, VITO NV

Up-scaling dimensions Carbstone blocks

» Large (25*10*10cm) BOS-compacts, varying compaction forces

(200-400 kg/cm2) carbonated during 2, 4, 8 and 16h (20bar, 80°C);

1a

1b

2a

2b

3a

3b

3c

4a

4b

5a

5b

31/05/2012 7 © 2012, VITO NV

Up-scaling dimensions Carbstone blocks

» Cross section of carbonated blocks (25*10*10cm) after 2h and 4h

carbonation (20bar, 80°C). Compaction: 200 kg/cm2 (31+/2 MPa).

31/05/2012 8 © 2012, VITO NV

Up-scaling dimensions Carbstone blocks

» Cross section of carbonated blocks (25*10*10cm) after 2h and 4h

carbonation (20bar, 80°C). Compaction: 300 kg/cm2 (39+/1 MPa).

» Clear carbonation front moves through block;

2h 4h

31/05/2012 9 © 2012, VITO NV

Up-scaling dimensions Carbstone blocks

» Carbonation of large blocks realised by controlling process

parameters (eg. grain size distribution, compaction, …);

6*6*3.5 cm 30*30*17 cm

31/05/2012 10 © 2012, VITO NV

Carbonation and purity of CO2 gas

CO2-balance:

» CO2-binding during production:

» -0,3 ton CO2/m3 carbstone

blocks

» CO2 produced during production:

» +0,14 ton CO2/m3 (energy

demand 200 kWh/m3)

31/05/2012 11 © 2012, VITO NV

Carbonation and purity of CO2 gas

» CO2-uptake versus time for BOS-slags carbonated at 20bar

with 20%, 50%, 77% and 100% CO2 (constant during reaction)!

0

20

40

60

80

100

120

0 200 400 600 800 1000

CO

2-u

pta

ke

(%

of

fin

al u

pta

ke

)

Time (min)

100%

77%

50%

20%

» Longer reaction times required when diluted CO2 used;

31/05/2012 12 © 2012, VITO NV

Carbonation and purity of CO2 gas

Input:

•77% CO2/23%N2

•20 bar

In autoclave:

•Uptake of CO2 by block;

•Fresh supply of gas

needed to keep 20bar;

•Decrease in CO2

concentration over time;

31/05/2012 13 © 2012, VITO NV

Carbonation and purity of CO2 gas

» Model constructed to predict CO2-concentration over time

and CO2-uptake over time;

31/05/2012 14 © 2012, VITO NV

Carbonation and purity of CO2 gas

» Validation of model by measurement of CO2-concentration

in autoclave;

31/05/2012 15 © 2012, VITO NV

Carbonation and purity of CO2 gas

» Carbonation time can be calculated based on purity of

the input CO2-gas;

206 min 557 min

359 min

31/05/2012 16 © 2012, VITO NV

Upscaling: use of (semi)-industrial equipement

31/05/2012 17 © 2012, VITO NV

Thank you!

31/05/2012 18 © 2012, VITO NV