CO capture in cement plants by entrained flow reactors ...

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CO2 capture in cement plants by entrained flow reactors Calcium Looping process Matteo C. Romano1, Maurizio Spinelli1, Stefano Campanari1, Stefano Consonni1, Maurizio Marchi2, Giovanni Cinti2, Natale Pimpinelli2 1 Politecnico di Milano, Department of Energy 2 C.T.G. - Italcementi Group, Bergamo, Italy 6th HTSLCN meeting, 1-2 September 2015, Milan

Titolo dello schema 2

M.C. Romano

Summary

Background on Calcium Looping Process

Cement plant technology

Calcium looping process for low-CO2 cement production

The proposed plant concept

Simulation tools and assumptions

Results and comparison with oxyfuel capture

Conclusions & future developments


M.C. Romano

Calcium looping is one of the most promising «short term» CO2 capture technologies.

CaL is a mixed post-combustion + oxycombustion process using Calcium oxide (CaO) as CO2 sorbent forming calcium carbonate (CaCO3) through Carbonation reaction:

CaO(S)+CO2(G) CaCO3(S) ΔhR= - 179 kJ/mol

Carbonation reaction is exothermic and occurs at high temperature (650°C); reaction heat can be exploited to generate HP steam for a Rankine Cycle.

Sorbent is regenerated through the reverse Calcination reaction, which is endothermic. Heat can be provided burning a fuel in oxycombustion, releasing highly concentrated CO2.

The most mature application of this process is in power plants, based on 2 fluidized bed reactors.

Background – CaL process


M.C. Romano

Cement plant and related model

Clinker out

Raw meal* in

Gas out

Air in

Petcoke

65%

35%

CO2 80%

20%

Development of a cement plant model based on Italcementi 4000 tpd reference plant GS (POLIMI code) Cement plants are characterized by:

• high fuel consumptions: ~3.2 MJLHV/kgCK • high CO2 emissions (~850gCO2/kgCK) from fuel combustion and CaCO3 decomposition.

CaCO3 CaO+CO2

Calciner

* Mostly CaCO3 + additives like Fe2O3, Al2O3, SiO2, MgCO3


M.C. Romano

CO2 capture in cement plants by oxyfuel combustion

Full oxycombustion (i.e. oxyfiring in both calciner and rotary kiln):

very high capture rates possible

modification of the temperature profiles in the rotary kiln

high air in-leakages expected in the rotary kiln Partial oxycombustion (i.e. oxy-fired calciner, air-fired kiln):

no modification of the kiln temperatures

minor issues related to air in-leakages

maximum CO2 capture rate of 70-80%


M.C. Romano

Partial oxyfuel configuration

CO2 from rotary kiln fuel combustion and residual calcination in the kiln

rotary kiln

pre-calciner

clinkercooler

fuelinlet

fuelinlet

CO2 tostorage

CO2-richflue gas

rawmealinlet

O2

inlet

raw mealpreheater


M.C. Romano

rotary kiln

pre-calciner

clinkercooler

fuelinlet

fuelinlet

CO2 tostorage

CO2 freeflue gas

rawmealinlet

O2

inlet

raw mealpreheater

carbonator

The proposed concept of Ca-Looping cement plant (POLIMI-ITC patent)

1) The calciner is operated with oxycombustion.

2) Part of CaO is used as a sorbent for CO2 capture in kiln exhaust gases, using a carbonator placed in a proper position along the suspension preheater

3) Carbonator riser has to be longer than a conventional riser to ensure proper contact times and cooled by heat exchange surface


M.C. Romano

rotary kiln

pre-calciner

clinkercooler

fuelinlet

fuelinlet

CO2 tostorage

CO2 freeflue gas

rawmealinlet

O2

inlet

raw mealpreheater

carbonator

The proposed concept of Ca-Looping cement plant (POLIMI-ITC patent)

Why entrained flow carbonator? 1) Entrained flow hydrodinamics is

suitable for operation with small size particles (40-50 μm) typical of cement plants raw meal

2) The cement industry is experienced in entrained flow systems (calciner and suspension preheaters are entrained flow gas-solid reactor/contactors)


M.C. Romano

rotary kiln

pre-calciner

clinkercooler

fuelinlet

fuelinlet

CO2 tostorage

CO2 freeflue gas

rawmealinlet

O2

inlet

raw mealpreheater

carbonator

Simulation assumptions

- O2 content in the calciner oxidant to keep the same combustion temperature

Carbonator Outlet temperature (°C) 650.0 CO2 capture efficiency based on equilibrium CaO to CaCO3 conversion 29%

Calciner Reaction temperature (°C) 950.0 O2 molar fraction – calciner inlet 34%

- Kiln outlet gas increased by 90°C due to the increased calcination temperature;

- Waste heat recovered by a Rankine cycle net electricity export

Heat recovery steam cycle High temperature (>350°C) efficiency ~ 43% Low temperature (<350°C) efficiency ~ 30%

CO2 purification and compression CO2 separation efficiency ~ 95% Specific electric consumption (kJ/kg CO2) 404

ASU O2 purity 95% Electric consumption (kWh/t O2) 200

F0/FCO2=4.1


M.C. Romano

Simulation tools

GS code (developed at POLIMI Department of Energy): Modular structure: complex schemes can be reproduced by assembling

basic modules Efficiency of turbomachineries evaluated by built-in correlations

accounting for operating conditions and the machine size Stage-by-stage calculation of steam and gas turbines Chemical equilibrium Advanced devices: Fuel cells (PEM-SOFC-MCFC), membranes. Thermodynamic properties of gases NASA polynomials Thermodynamic properties of water/steam IAPWS-IF97

Aspen Plus: CO2 compression and purification


M.C. Romano

Results

State of the art cement plant

w/o CO2 capture

Partial oxyfuel cement plant

Calcium looping cement plant

Fuel input, kJLHV/kgclk 3231 3866 5573 Gross power production, MWe - 24.4 63.54 Auxiliaries, MWe -9.77 -31.87 -44.45 Net power output, MWe -9.77 -7.44 19.09 Net power output, kWhe/tclk -57.0 -43.4 111.4 CO2 capture efficiency, % - 81.9 95.4 CO2 emission, kg/tclk 854.8 174.2 40.8 CO2 avoided, % - 79.6 95.2 Equivalent(1) CO2 emission, kg/tclk 911.6 217.6 -70.3 Equivalent (1) CO2 avoided, % - 76.1 107.7 Equivalent (1) SPECCA(2), MJ/kgCO2 - 0.71 0.62

(1) Taking into account the CO2 emissions/credits from electric power import/export, considering external power generation by 35% efficiency coal plant

(2) SPECCA: specific primary energy consumption for CO2 avoided.


M.C. Romano

Results – sensitivity analysis

46.5%28.9%

18.1%

CaO conversion: 8.6%

40

60

80

100

120

140

160

180

5200

5400

5600

5800

6000

6200

6400

6600

30% 40% 50% 60% 70% 80%

Net

pow

er g

ener

ated

, kW

h/t cl

k

Fuel

con

sum

ptio

n, M

J LH

V/t c

lk

Calcined ray meal to the carbonator, %of the toal flow from the calciner

Effect of sorbent circulation rate: FCa/FCO2 between 2 and 11


M.C. Romano


46.5%

28.9%

18.1%

CaO conversion:8.6%

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

106%

107%

108%

109%

110%

111%

112%

113%

30% 40% 50% 60% 70% 80%

SPEC

CA,

MJ L

HV/k

g CO

2

Equi

vale

nt C

O2

avoi

ded

Calcined ray meal to the carbonator, %of the toal flow from the calciner

Effect of sorbent circulation rate: FCa/FCO2 between 2 and 11


M.C. Romano


Effect of carbonator efficiency

14.8%

19.5%

24.3%

CaO conversion:28.9%

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

86%88%90%92%94%96%98%

100%102%104%106%108%110%

40% 50% 60% 70% 80% 90% 100%

SPEC

CA,

MJ L

HV/k

g CO

2

CO

2av

oide

d

Carbonator CO2 capture efficiency

Direct CO2avoided

Equivalent CO2 avoided


M.C. Romano

Conclusions

A new plant configuration for the production of cement with CO2 capture by entrained flow reactors CaL process has been presented.

A distinctive feature of the process is the high integration level of the carbonator reactor in the suspension preheater of the cement plant.

The plant has a positive net power output. Simulations show the possibility to achieve a CO2 capture efficiency of up to 95%

and equivalent avoided emissions higher than 100% Even with moderate carbonator efficiencies (50%), the equivalent CO2 avoided

approaches 100%.

Romano, M.C., Spinelli M., Campanari S., Consonni S., Marchi M., Pimpinelli N., Cinti G., 2014. The Calcium looping process for low CO2 emission cement plants. The 6th International Conference on Applied Energy. Taipei, Taiwan. Marchi, M., Cinti G., Romano M.C., Campanari S., Consonni S., 2012. Improved process for the production of cement clinker and related apparatus (in Italian). Italian patent MI2012 A00382. Marchi, M., Cinti G., Romano M.C., Campanari S., Consonni S., 2012. Process and improved plant for the production of cement clinker (in Italian). Italian patent MI2012 A00383.


M.C. Romano

Research needs and future activities

Entrained flow carbonator testing and modelling: Reactor length Feasible solids-gas ratio Sorbent properties Heat transfer

Heat recovery steam cycle modelling

Work on this concept will be performed in the next 3½ years in the framework of the Horizon 2020 Cemcap project and compared with fluidized bed CaL and other capture technologies in cement plants.


M.C. Romano

Thank you for your attention !

http://www.energia.polimi.it/ http://www.gecos.polimi.it/

www.italcementigroup.com/

Contacts: [email protected]

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