USE OF SECONDARY FUELS IN THE CEMENT MANUFACTURING:

A CASE STUDY

Dr. C. TSILIYANNIS1, I. FOTINOPOULOU1, Dr. M. GEORGIOPOULOU2 and Prof. G. LYBERATOS2

1ANION Environmental Ltd, Em. Lykoudi 26, 11141, Athens, Greece2National Technical University of Athens, Athens, Greece

4th International Conference on Sustainable Solid Waste ManagementCYPRUS 2016

Based on a stoichiometric balance of Alternative Fuels (AFs) combustion, the present study assesses the use of more than 20 distinct AFs, classified according to Eurocodes, in cement production

The operational efficiency and the emission rates in an actual dry process clinker plant are analyzed.

Alternative Fuels investigated in the Case Study (Decisions 2000/532/EC & 2014/955/EU)

CODE DESCRIPTION CODE (EUROPEAN LIST OF WASTE)

1 02 01 03 Plant tissue waste 2 02 01 04 waste plastics (except packaging)

3 03 01 05 sawdust, shavings, cuttings, wood, particle board and veneer other than those mentioned in 03 01 04

4 04 02 21 wastes from unprocessed textile fibres 5 04 02 22 wastes from processed textile fibres 6 12 01 05 plastics particles 7 13 05 07 * oily water from oil/water separators 8 13 05 08 * mixtures of wastes from grit chambers and oil/water separators 9 15 01 01 paper and cardboard packaging

10 15 01 02 plastic packaging 11 15 01 03 wooden packaging 12 16 01 03 end-of-life tyres 13 16 01 19 plastic 14 17 02 01 wood 15 19 08 05 sludges from treatment of urban waste water 16 19 12 01 paper and cardboard 17 19 12 04 plastic and rubber 18 19 12 07 wood other than that mentioned in 19 12 06 19 19 12 08 textiles

20 19 12 12 other wastes (including mixtures of materials) from mechanical treatment of wastes other than those mentioned in 19 12 11

21 19 12 11* other wastes (including mixtures of materials) from mechanical treatment of waste containing dangerous substances

22 19 02 03 / 19 02 04* premixed waste composed only of wastes marked as hazardous* or not

23 19 08 11* sludges containing dangerous substances from biological treatment of industrial waste water

24 19 08 12 sludges from biological treatment of industrial waste water other than those mentioned in 19 08 11

25 19 12 10 combustible waste (refuse derived fuel)

Cement plant investigated in Drepanon, Achaia, Greece

1.500.000 ton/year clinker, dry-process cement plant. 2 parallel kiln / precalciner / cyclone preheater lines. Current utilization of fossil fuels (70%Pet Coke and 30% Coal). Total Fuel Energy Demand: 4.600 TJ/year. Specific Energy Consumption (ε): 3.550 kJ/kg clinker.

Use of alternative fuels (AFs) for 30% thermal Pet Coke substitution is investigated in this work, leading to an energy mixture of Pet Coke 40%, Coal 30% and AF 30%.

Cement Plant Flow Diagram

Clinker Production

Air Pollution Control Systems

Cement Production/Packaging

Fuel Air Soil materials

Gypsum

Cement

Cleaned flue gas (off gas)

Flue gas

Clinker

Soil Mill

Cyclone Preheater, Precalciner, Rotary Kiln

Coal and Petcoke Mill

Rotary Kiln/ Calciner /Preheater and Soil Mill APCS

Fuel Mill APCS

Fuel Air Soil materials

Air

Air

Water Quen-cher

Flue gas flow

1-θ

θ

Compound operation Direct operation

Direct and compound operation diagram(mostly operated under compound mode)

Case study: Cement plant emission points and offgas flows (compound operation).

Main emission point is the kiln –soil mill APCS (2 stacks with a total of 577.000 Nm3/h offgas flowrate)

95.000 m3/h

Kiln/Soil Mill APCS

Kiln-soil mill offgasVksm=577.000 m3/h Mass fraction θ of kiln

fluegases

Fuel Mill APCS

Dusty air from Raw materials Homogenization silo

Soil Press APCS

20.000 m3/h

Homogen-ization silo APCS

35.000 m3/h

Clinker Cooler APCS

250.000 m3/h Dusty hot air from clinker cooler not used as combustion air

Mass fraction 1-θ of kiln fluegases

Mass fraction 1-θ of kiln fluegases

Schematic description of the method for assessing offgas emissions (compound)

K iln stoichiometry (Fuel Combustion) Ultimate as received

analysis of conventional and alternative fuels

Main kiln combustion fluegas flowrates: overall, CO2, O2 , N2 and H 2O (fraction θ of combustion fluegases)

Offgas flowrates(fraction θ of overall kiln f luegases + CO 2 lime + soil mill air + exhaust air draft)

Assume emitted concentrations at the standardized maximum limit

Actually emitted pollutant concentrations

actual emission rates (mg pollutant /sec) = actual releases to the environment

Soil mill air (fraction αsm of raw meal fluegases)

Exhaust air draft (fraction ψ of overall fluegas flowrate)

Clinker production Raw meal

Lime dissociation (fraction θ οf CO 2 lime)

Overall kiln fluegases’ f lowrates

Kiln Stoichiometry and Mass Balance

A. Fuel Combustion Stoichiometry

CxHyOzClwSvNu + (1+E) (x + φ + v -0,5 z) Ο2 + (1+E) 79/21 (x + φ + v -0,5 z)N2

x CO2 + 2φ H2O + (x + φ + v -0,5 z) E O2 + w ΗCl + v SO2 +

(0,5 u + (1+E) 79/21 (x + φ + v - 0,5 z)) N2 (1)

whereCxHyOzClwSvNu is the empirical formula of the fuel and

φ = 1/4 (y - w) if y > w (2)φ = 0 if y ≤ w (3)

The operation of the rotary kilns at high temperatures (>1.450 oC) is described by the reactions:

Kiln flue gas species’ flowrates under AF utilization (30% thermal petcoke substitution) without including the CO2 generated by lime dissociation

Kiln fluegases (combustion and lime dissociation)

0

100

200

300

400

500

600

700

800

Baseli

ne02

01 03

02 01

0403

01 05

04 02

2104

02 22

12 01

0513

05 07

*13

05 08

*15

01 01

15 01

0215

01 03

16 01

0316

01 19

17 02

0119

08 05

19 12

0119

12 04

19 12

0719

12 08

19 12

1219

12 11

*

19 02

03 / 1

9 02 0

4*19

08 11

*19

08 12

19 12

10

Fuels

SO2 x

4, H

Cl (t

n/ye

ar)

0

200 000

400 000

600 000

800 000

1 000 000

1 200 000

1 400 000

1 600 000

1 800 000

CO2 ,

H2O

, O2 ,

N2 (t

n/ye

ar)

SO2 HCl CO2 H2O O2 N2

B. Lime dissociation

CaCO3 CaO + CO2 (4)

mCO2,lime,0 = η MWCO2 (mclinker – fuel ash)0 (5)

VCO2,lime,ο = η 22.400 ( mclinker - fuel ash)0 (6)

Raw meal required = mCO2,lime (1+ η MWCO2 ) / η MWCO2 (7)

where

η =ζ /56*(1- MWCO2 ζ/56)-1 (8)

ζ= %w CaO in CaCO3 (9)

Kiln Stoichiometry and Mass Balance

C. Determination of offgas flow rates (main APCS, kiln-soil mill) From overall mass balances (AF- baseline):

Vk,sm = Vk,sm, 0 + Vk,sm, 0 {(1+ψ)θ Vfg MWfg - (1+ψ)θ Vfg, 0 MWfg,0 } /

{θ Vfg, 0 MWfg, 0 +θ VCO2,lime, 0 MWCO2 + υ αsm mCO2,lime,0 (1+ η MWCO2 ) / η MWCO2 + υ θ

ψ (mfg, 0 + mCO2,lime, 0 ) } (11)

where ψ = the mass fraction of induced air draft from main exhaust blower with respect to overall kiln flue gasesMW = molecular weightVfg = flue gas volumetric flow rate.

The actual pollutant emission rates are given by ri = xi,l/ SF (12) Where SF is the standardization factor,

Kiln Stoichiometry and Mass Balance

PP

TT

OHOSF s

ssmksmk ,2,2 ]%[100100

]%[211021

and xl denotes the standardized emission limit for any pollutant set by legislation.

Determination of standardization factor

Off gas water and oxygen concentrations are found in terms of fluegas, exhaust air draft and soil mill water and oxygen content

[H2O] = Vk,sm H2O =100 (VH2Ofg + Vpseudo air moisture + Vsoil mill air moisture ) / Vk,sm (14)

[O2] = Vk,sm O2 = 100 (V O2fg + Vpseudo air O2 + Vsoil mill O2) / Vk,sm (15)

Flue gas (Vfg) and offgas (Vksm) flowrates under AF utilization (30% thermal petcoke substitution)

Flue gas (Vfg) and offgas (Vk,sm) of conventional & secondary fuels in chimney

100 000

200 000

300 000

400 000

500 000

600 000

700 000

Baseli

ne02

01 03

02 01

0403

01 05

04 02

2104

02 22

12 01

0513

05 07

*13

05 08

*15

01 01

15 01

0215

01 03

16 01

0316

01 19

17 02

0119

08 05

19 12

0119

12 04

19 12

0719

12 08

19 12

1219

12 11

*

19 02

03 / 1

9 02

04*

19 08

11*

19 08

1219

12 10

Fuels

V fg,V

k,sm

(Νm

3 /h)

Vk,sm (Nm3/h)Vfg

Results

NOx emission rates based on maximum emission limit (800 mg/m3

under conventional fuel, 500 mg/m3, dry, 10%v O2 , under AF utilization) (AF: 30% thermal petcoke substitution)

ΝOx emissions based on maximum emission limit (baseline 800 mg/m3, AF 500 mg/m3, dry, 10% v.v. Ο2)

0

10 000

20 000

30 000

40 000

50 000

60 000

70 000

80 000

Baseli

ne02

01 03

02 01

0403

01 05

04 02

2104

02 22

12 01

0513

05 07

*13

05 08

*15

01 01

15 01

0215

01 03

16 01

0316

01 19

17 02

0119

08 05

19 12

0119

12 04

19 12

0719

12 08

19 12

1219

12 11

*

19 02

03 / 1

9 02 0

4*19

08 11

*19

08 12

19 12

10

Fuel

Act

ual N

Ox

offg

as e

mis

sion

rate

/ R

otar

y K

iln 1

& R

otar

y K

iln 2

(mg/

sec)

SO2 emission rates based on maximum emission limit (60 mg/m3 under conventional fuel, 50 mg/m3 under AF utilization,

dry, 10%v O2) (AF: 30% thermal petcoke substitution)

SO2 emissions based on maximum emission limit (baseline 60 mg/m3, AF 50 mg/m3, dry, 10% v.v. Ο2)

0

1 000

2 000

3 000

4 000

5 000

6 000

Baseli

ne02

01 03

02 01

0403

01 05

04 02

2104

02 22

12 01

0513

05 07

*13

05 08

*15

01 01

15 01

0215

01 03

16 01

0316

01 19

17 02

0119

08 05

19 12

0119

12 04

19 12

0719

12 08

19 12

1219

12 11

*

19 02

03 / 1

9 02 0

4*19

08 11

*19

08 12

19 12

10

Fuel

Act

ual S

O 2 o

ffgas

em

issi

on ra

te

/ Rot

ary

Kiln

1 &

Rot

ary

Kiln

2 (m

g/se

c)

TSP emission rates based on maximum emission limit (10 mg/m3 under conventional fuel, 30 mg/m3 under AF utilization, dry, 10%v O2, AF: 30% thermal petcoke substitution)

TSP emissions based on maximum emission limit (baseline 10 mg/m3, AF 30 mg/m3, dry, 10% v.v. Ο2)

0

500

1 000

1 500

2 000

2 500

3 000

3 500

Baselin

e02

01 03

02 01

0403

01 05

04 02

2104

02 22

12 01

0513

05 07

*13

05 08

*15

01 01

15 01

0215

01 03

16 01

0316

01 19

17 02

0119

08 05

19 12

0119

12 04

19 12

0719

12 08

19 12

1219

12 11

*

19 02

03 / 1

9 02 0

4*19

08 11

*19

08 12

19 12

10

Fuel

Act

ual T

SP o

ffgas

em

issi

on ra

te

/ Rot

ary

Kiln

1 &

Rot

ary

Kiln

2

(mg/

sec)

CO2 emission rates under AF utilization (30% thermal petcoke substitution)

CO2 emissions

0

50

100

150

200

250

Baseline

02 01 03

02 01 04

03 01 05

04 02 21

12 01 05

13 05 07

15 01 01

15 01 02

15 01 03

16 01 03

16 01 19

19 02 03

19 08 05

19 08 11

19 08 13 & 19 0

8 1419 12

0419 12

1119 12

12

CO

2 em

issi

ons

(m3 /tn

clin

ker)

Overall (with lime dissociation) and overall non biogenic CO2 emission rates under AF utilization (30% thermal petcoke substitution)

CO2 emissions

30 000

35 000

40 000

45 000

50 000

55 000

60 000

65 000

Baseline

02 01 0302 01 0403 01 0504 02 2104 02 2212 01 0513 05 07 *13 05 08 *

15 01 0115 01 0215 01 0316 01 0316 01 1917 02 0119 08 0519 12 0119 12 0419 12 0719 12 0819 12 1219 12 11*

19 02 03 / 19 02 0

4*19 08 11*

19 08 1219 12 10

Fuel

CO

2 offg

as e

mis

sion

rate

/ R

otar

y K

iln 1

& R

otar

y K

iln 2

(m3 /h

)

Total CO2 (m3/h) with lime dissociationNon Biogenic CO2 (m3/h) with lime dissociation

Thank you for your attention!