presentation august 2011-08-30

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Measurements of the Quality of Cement Produced from

Looped Limestone

Charles Dean, Prof. Denis Dugwell and Dr. Paul Fennell*

Department of Chemical Engineering and Chemical Technology, Imperial College London.

Funded by EPSRC

IEA GHG Solid Looping Cycles Network, Vienna 2011.

*[email protected]



Presentation Outline

• Background to the Project

• Objectives

• Methods

• Some Results



Benefit to Cement Manufacture of Using Spent Sorbent

kg / tonne clinker

Assuming energy demand of 3.7GJ/tonne clinker, pet coke

use at calciner and bituminous

coal at kiln.

Data taken from: Alsop, P. A.,

2007, Cement Plant Operations

Handbook



kg / tonne clinker

Therefore possible to mitigate ~ ¾

cement CO2 emissions by using spent

sorbent from Ca-loop.

Assuming energy demand of 3.7GJ/tonne clinker, pet coke

use at calciner and bituminous

coal at kiln.

Data taken from: Alsop, P. A.,

2007, Cement Plant Operations

Handbook

Benefit to Cement Manufacture of Using Spent Sorbent



Cement Chemistry Overview

CaO is used to produce calcium silicates

→ upon hydration these crystals form an interlocking microstructure whichprovide the bonding strength.

KILN REACTIONS

900-1200 2CaO+SiO2 → 2CaO.SiO2 – ‘Belite’

CaO + Clay → Calcium Aluminates (‘Interstitial phases’)

1250-1500 CaO+2CaO.SiO2 → 3CaO.SiO2 – ‘Alite’

Final Proportions: ~ 60 % Alite, ~ 25 % Belite, ~ 15 % interstitials.

< 1 yr strength

> 1 yr strength



The Role of Trace Elements in Cement

e.g. Effect of MgO e.g. Effect of ZnO

Some elements are beneficial between certain limits, detrimental outside of those limits.

e.g. MgO > 2 %.

Formation of calcium silicates strongly influenced by trace elements in clinker:



Objectives of the Project

• To identify chemical changes in sorbent(concentration of trace elements) upon repeated

cycling under different conditions.→ Repeated cycling will lead to chemical and physical

changes in the sorbent. In particular combustion products and

ash from fuel use in calciner will potentially be retained in the

sorbent.

• To relate chemical changes in sorbent topossible changes in cement quality/composition.→ In this project, cement quality is being inferred from alite production (as the most prevalent phase).



Research Methodology

1. Produce sorbent using different fuelsand numbers of cycles.

2. Analysis of sorbent (ICP).

3. Production and analysis of clinkers(XRD).



Sorbent Production and Analysis



Sorbent Production – 3kW Spouted Bed Reactor

C O 2 c o n c e n t r a t i o n

15 % CO2 (balance air), 5 l/m, LongcalP25 limestone, 425 – 500 µ.

2g coal / cycle – based on modeling work(essentially is amount req’d at calciner

based on 30 % split fuel use).

Fluidising gas

Fuel

B e d T e m

p e r a t u r e ( ◦ C )

Time (s)



Sorbent Production – RDF Fuel Feeding System



Clinker Production and Analysis



Clinker Production

Once sorbent is removed from reactor:• Homogenised with other oxides in DI water then dried.

• Pressed into a brick using 100 atm pressure.

• Then fired in tube furnace at 1500°C for 2hrs.



Clinker Production

• The brick is then pushed directly from the furnace into an aircooled chamber – 25 l/m applied evenly across brick untilambient temp.

• This is to prevent decomposition of alite to belite which can take

place if clinker is allowed to cool at its own rate.



Methods – Qualitative Assessment of Clinkers

• First, qualitative assessment of phases present in the clinker – indicates that correct phases are present.

25 30 35 40

0

400

1600

3600

6400

I n t e

n s i t y

( c o u n t s )

Blue – Belite

Green – Alite

Pink - Interstitial

Alite

Belite

Interstitial phases



• % alite is achieved by mixing clinker samples with corundum(Al2O3) in 1:1 ratio. This enables changes in alite peaks to beconverted to % by comparing to corundum peak (using RIRvalue – taken from ICDD database).

Methods – Quantitative Assessment

Xa = (Ia/Ic)*(Irelc/Irela)*(Xc/RIR)26.5 27.0 27.5 28.0 28.5 29.0 29.5 30.0 30.52Theta (°)

0

100

400

900

1600

2500

I n t e n s i t y

( c o u

n t s )



Main Results -

% Alite



Main Results - % Alite – No Fuel & La Jagua Coal

C. Dean, D. Dugwell, and P.S. Fennell.

Energy & Environmental Science, 2011. 4(6): p. 2050-2053.

0

10

20

30

40

50

60

70

80

90

100

1 5 10 15

% A

l i t e

No. Cycles

No Fuel 2 g / cycle

All results average of 3 replicate experiments



Sorbent trace element levels after 5 cycles

5 cycles, La Jagua Colombian coal – 2 g / cycle

Average of 3 replicate experiments

**

Increase in most elements. However largest increase is Ba and Cr.

(Decrease in Mg and Sr – assume that other increases over-ride these losses).

↑

↓

La

Jagua

Long-

cliffe

5cyc

Sorbent

ppm ppm ppm

B 13.88 0.00 9.73

Ti 69.77 0.35 6.60

Zn 6.17 0.00 5.14

Ba 80.34 12.00 27.99

Cr 2.97 2.50 47.26

Cu 31.50 4.50 10.64

Ni 2.89 0.35 0.30

Mg 114.31 1500.00 1295.29

Mn 6.57 45.00 57.54

Sr 56.85 135.00 112.82

Elements Detrimental to Alite Formation

Elements Beneficial to Alite Formation



5 cycles, La Jagua Colombian coal – 2 g / cycle

Average of 3 replicate experiments

Drop in the level of trace element concentrations after 1 cycle indicates that

most elements are first lost before being replenished. This could explain drop

in % alite upon repeated cycling without fuel.

Sorbent trace element levels after 5 and 1 cycle

↑

↓

La

Jagua

Long-

cliffe

5cyc

Sorbent

1cyc

Sorbent

ppm ppm ppm ppm

B 13.88 0.00 9.73 9.81

Ti 69.77 0.35 6.60 0.00

Zn 6.17 0.00 5.14 4.87

Ba 80.34 12.00 27.99 6.59

Cr 2.97 2.50 47.26 3.82

Cu 31.50 4.50 10.64 13.76

Ni 2.89 0.35 0.30 0.00

Mg 114.31 1500.00 1295.29 1399.19

Mn 6.57 45.00 57.54 43.98

Sr 56.85 135.00 112.82 84.23



Conclusions on cement from cycled sorbent

Repeated cycling without fuel - appears to impact negatively onalite production. Trace element results after 1 cycle indicatethat this could be due to loss of impurities / trace elements.

For the case of La Jagua – repeated cycling appears to improvealite formation. Trace element results after 5 cycles indicatethis could be due to replenishment of impurities from fuel, esp.Ba and Cr.

However further work needed – esp. producing clinker from rawmaterials containing a more realistic baseline of trace elements(i.e. clay) to see if repeated cycling with fuel takes trace elementconcentrations past any ‘tipping points’.



Further Results –

Trace Element Partitioning



Partitioning of Trace Elements



Partitioning of Trace Elements after 5 cycles: RDF

0

50

100

150

200

250300

350

400

450

T i

T i

C u B V A

l

B a

C r

M n

F e

N a K S

Z n

S r

N i

M o

M g

P b P

C o

C d

A s

S b

% R e c o v e r e d

% Recovered in Solid Streams

Average of 3 repeats

• Heavier elements closer to 100 %.

• More volatile elements lost.

• Contamination from Ti and Cu.



Partitioning: Implications for Cement Manufacture

S

Na K

18,000ppm!

+148 %

+43 %

+ 579 %

20,000ppm!RDF

█ - Sorbent █ - Fly Ash █ - Fines █ - Lost

RDF Trace Element Conc.



Conclusions on RDF trace element partitioning

• Heavier elements / elements with lower boiling pointstend to reside in sorbent and therefore potentiallyalso in the cement. Volatile elements tend to collectin fines / fly ash or exit as gas.

• Partitioning shows that Na, K and S could causeproblems in use of RDF-derived sorbent, both incement application (i.e. aggregate/concrete) and in

Ca-loop / cement plant operation.

• Climafuel feeding: contamination issues needresolving before producing cement!



Thankyou

Questions

presentation august 2011-08-30

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