University of Edinburgh , School of Engineering, Edinburgh SCCS – Sco9sh Carbon Capture and Storage Centre TechnoEconomic Study for Carbon Capture from Cement Plants Dursun Can Ozcan, Hyungwoong Ahn, Stefano Brandani [email protected]
University of Edinburgh , School of Engineering, Edinburgh SCCS – Sco9sh Carbon Capture and Storage Centre
Techno-‐Economic Study for Carbon Capture from Cement Plants
Dursun Can Ozcan, Hyungwoong Ahn, Stefano Brandani
CO2 Emissions from Cement Industry
2
• Cement is a key construcIon material (3.78 billion tons in 2012)1 • Accounts for more than 5% of global emissions from staIonary sources2
• 50 -‐ 70% of the total emission accounts for calcinaIon of limestone in raw meal • More efficient thermal management has reduced CO2 emissions3 • EssenIal to deploy a carbon capture technology to reduce CO2 emission up to 90%
1 CW Group, Global Cement Volume Forecast Report, 2012. 2 IEA, Carbon Emission ReducIons up to 2050, 2009. 3 Hasanbeigi et al., Renewable and Sustainable Energy Reviews, 6220, 2012.
Cement Plant SimulaIon
3
• The base cement plant includes all the major units; raw mill, preheaters, pre-‐calciner, kiln and cooler
• It is crucial to idenIfy the chemical reacIons occurring in each unit and determine their conversion rate in order to have accurate mass and energy balances
• Technical opIons for carbon capture; calcium looping (Ca-‐looping) process, amine scrubbing , oxy-‐combusIon and indirect calcinaIon
Base Cement Plant – Mass Balance
4
Mass in (kg/s) Mass out (kg/s) Raw meal 52.41 Clinker 31.61 Air 99.55 Flue gas Fuel From fuel drying 4.30 Wet coal to pre-‐calciner 2.26 From raw mill 75.49 Wet pet-‐coke to kiln 1.18 Excess Air 44.00 Total in 155.40 Total out 155.40
o 1.66 kg/s of raw meal is required to produce 1 kg/s of clinker o The approximate chemical composiIon of clinker phases are esImated by Bogue equaIon1 o The CO2 generaIon intensity is around 0.8 ton CO2/ton clinker within the range of 0.65 – 0.92 ton CO2/ton cement given in the reference2
1 Bogue, R.H., 1929. I&EC 1(4), 192-‐197. 2 IEA, Tracking Industrial Energy Efficiency and CO2 Emissions; 2007.
Base Cement Plant – Energy Balance
5
Enthalpy in Enthalpy out Sensible Heat
*Heat by combusAon
Sensible Heat
Heat of ReacAon
Raw Meal 1.82 Clinker 5.12 Air 3.25 Flue gas Fuel From fuel drying 4.29 Wet coal to pre-‐calciner 0.12 216.58 From raw Mill 72.95 Wet pet-‐coke to kiln 0.05 139.25 Excess Air 45.77
Heat lost by radiaIon and convecIon 54.54
Overall heat of reacIon 178.4
(1.57 MJth/kg) Total in 361.07 Total out 361.07
o All the reacIons (decomposiIon of raw materials and clinkerizaIon) are carefully considered in the process simulaIon o The required thermal energy for unit clinker is esImated to be 3.13 MJ/ton clinker, similar to reported values, 2.9 – 3.4 MJ/ton clinker1
1 WBCSD, Cement Industry and CO2 performance; 2009.
Ca-‐looping Process
6
• Ca-‐looping agent (CaO) circulates between two reactors: * Carbonator: CO2 is captured by exothermic carbonaIon reacIon at ~650 °C * Calciner: CaCO3 is regenerated to CaO by endothermic calcinaIons reacIon at ~930 °C • CaO loses its capacity over the cycles and needs to be replaced with fresh sorbent • The purge stream from this system contains mainly CaO and can be used for cement producIon, lowering the variable cost associated with sorbent use
Charitos et al., Powder Technology,117, 2010 La Perada, Spain (1.7 MW pilot plant, www.caoling.eu)
Ca-‐looping Carbonator Model
7
• The rigorous carbonator model1: * CirculaIng fluidized bed (CFB) model operates in the fast fluidizaIon regime * ParIcle distribuIon part has been applied from K-‐L model2; lower dense region and upper lean region * The CO2 concentraIon at the exit has been esImated from the gaseous material balance by considering the first order kineIc law of carbonaIon degree
• All the mathemaIcal models have been solved in Matlab and implemented fully into UniSim®; -‐ Directly via a component object model (COM) interface3
-‐ As a standalone executable file using Matlab Compiler4
The schemaIc of carbonator–calciner reactor system (www.caoling.eu)
1Romano, M., CES,257, 2012 2Kunii and Levenspiel, FluidizaIon Engineering, 1991 3Microsoo, hpp://www.microsoo.com/com/default.mspx 4Matlab, hpp://www.mathworks.co.uk/products/compiler/
ImplementaIon of Carbonator Model
8
o SoluIon of all mathemaIcal models for the carbonator in Matlab
o The carbonator unit into the Unisim Design process simulaIon UniSim Design à Matlab à UniSim Design
UniSim User Unit OperaDon as a Carbonator The interface of carbonator in UniSim
Carbonator Model
• Stream properIes • Carbonator specificaIons
• Capture efficiency • Reactor volume • Pressure drop
9
SelecIon of a Feed Stream
0
10
20
30
40
CO
2 con
cent
ratio
n
(mol
e%)
1st Preheater 2nd Preheater 3rd Preheater 4th Preheater Precalciner Kiln Raw mill
0
200400
600
800
10001200
1400
1600
Tempe
rature [C
]
Gas
S olid
Raw Mill 1st Preheater 2nd Preheater 3rd Preheater 4th Preheater Pre-‐Calciner Kiln Cooler
Gas Flow ß
Solid Flow à
RelaDvely low (~22 vol%)
Higher CO2 concentraDon (~35 vol%)
Flue gas needs to be heated up to 650°C.
Flue gas temperature is around 650°C à no preheaDng is required.
* The flue gas temperature and CO2 mole fracFon varies over the cement process
R/M 1st PHE
2nd PHE
3rd PHE
4th PHE Pre-C Kiln Cooler
B/F
F/D
B/F
CoalPet Coke
Air Air Air
Secondary Air
Tertiary Air
Primary Air
Raw Meal
Collected Dust
Air
To Atmosphere
Carb CalCaCO3
CaO
PetCoke
CO2 Comp.
Oxygen
Make-upCaCO3
Steam Cycle
CompressedCO2
Purge
Qcarbonator
B/F
Clinker
Gas FlowSolid Flow
Excess Air
Heat stream
ASU
Excess Air
To Atmosphere
Cooling Air
Ca-‐looping Process IntegraIon
10
CSIC Ca-‐looping test facility (www.caoling.eu)
Post combusIon Amine Process
11
• The most convenIonal technology for carbon capture based on selecIve absorpIon of CO2 by the solvent (MEA) • A combined heat and power plant (CHP), which is required to supply stripper reboiler with low pressure steam, has been designed • A selecIve catalyIc reducIon (SCR) unit for NOx removal and a flue-‐gas desulfurizaIon unit (FGD) for SOx control are required
Flue GasLean Solvent
Rich Solvent / RefluxCooling Water Steam
CondensateWater Wash
Carbon Dioxide
Cement plant + CHPflue gas
Absorber Stripper
Water /Amine Makeup
CO2 product
CO2 depleted flue gas
Ahn et al., IJGGC,29, 2013
Oxy-‐combusIon
12
• In this opIon, pure oxygen is supplied to the reactor instead of air to obtain highly concentrated CO2
• However, the concern is technical uncertainty in operaIng a cement kiln under oxy-‐combusIon condiIons
• Therefore, an oxy-‐combusIon system was only applied to pre-‐calciner1 • The overall carbon capture rate is limited
1 IEA CO2 Capture in the Cement Industry, July 2008/3, 2008.
Indirect CalcinaIon
13
Limestone(CaCO3)
CaO Air Fuel
High Temperature Solid Stream
Flue GasCO2-rich
Gas
Calciner(930oC)
Combustor(1050oC)
Heat
• An external combustor is used to generate heat for the pre-‐calciner by separaIng CO2 produced by calcinaIon from combusIon gases1
• Heat requirement of calcinaIon is supplied by circulaIon of hot CaO between the combustor and pre-‐calciner
• Only capture the CO2 involved in calcinaIon but not from fuel combusIon • Moderate level of CO2 recovery are achievable
1 Rodriguez et al. ACS 2011, 50, 2126-‐2132.
Summary and Comparison
14
Authors IEA 1 IEA 1 Rodriguez et al. 2 This study
CO2 capture technology
Amine-‐based Oxy-‐combusIon Hot solid circulaIon Ca-‐looping
Type of integraAon
The flue gases from cement plant and a CHP plant are fed to the amine process
Oxy-‐calciner (convenIonal kiln) Indirect calcinaIon
Flue gases from the 3rd preheater stage
are sent to a carbonator.
Efficiencies (%) CO2 avoidance
74
61
33
92 -‐ 99
Results Net power producDon
Specific thermal energy
consumpDon (GJ/ton CO2 avoided)
CO2 avoided cost (€/ton CO2 avoided)
+ 9.2
107.4
-‐
1.95
40.2
+
N/A 9.0
-‐/+
2.5 – 3.0
25 – 45
1 IEA CO2 Capture in the Cement Industry, July 2008/3, 2008. 2 Rodriguez et al. ACS 2011, 50, 2126-‐2132.
Conclusion
15
• A way of capturing CO2 from cement plants by integraIng it with carbon capture processes has been invesIgated
• The cement plant simulaIon implemented in this study was in an agreement with those reported in the literatures
• The gas stream leaving the 3rd preheater was selected to be a feed suitable for Ca-‐looping capture unit since o it does not have to be preheated o it has a higher CO2 parIal pressure and lower total volumetric flow rate o a simpler design of steam cycle for heat recovery is possible
• Among the compared carbon capture processes, the CO2 capture target of 90% can be only achieved by Ca-‐looping and amine-‐based capture processes
• Lower specific energy consumpIon and cost per unit of CO2 avoided have been esImated for Ca-‐looping process compared to the amine-‐based capture configuraIon
16
Acknowledgements Financial Support o Turkish Ministry of EducaIon o EPSRC Science and InnovaIon Award, ‘Carbon Capture from Power Plant and Atmosphere’, EP/F034520/1
• Honeywell for providing the Unisim R400 sooware
Thank you
Ozcan D.C., Ahn H. and Brandani S. Process IntegraAon of a Ca-‐looping Carbon Capture Process in a Cement Plant. InternaDonal Journal of Greenhouse Gas Control, 2013, in press.