Green House Gas reduction for iron and steel

1. CO2 ACCOUNTING AND
ABATEMENT: AN APPROACH FOR
IRON & STEEL INDUSTRY
Prof. P. K. Sen (IIT Kharagpur)
3/2/2013 NMD ATM 2012 1

2. • The iron and steel industry is a large energy
user in the manufacturing sector (7% of
worldwide anthropogenic CO2 emission)
• Approaches:
• Work out feasible solutions for CO2 reduction
leading to decrease of the specific CO2 emission
adopting a process optimization approach
• Radical changes of existing processes and
production routes can be considered to decrease
the CO2 emissions
• Pre-decarbonisation of process fuel to produce hydrogen
as the process reductant.
3/2/2013 NMD ATM 2012 2

3. Features of emission
accounting
 Important to understand the genesis of
CO2 emission in plants:
 Processing of raw materials require both
reductant (Carbon source) +energy
sourced from fossil fuels
 C+ O source products+energy+CO2
 The carbon source is partially gasified in
the primary iron making reactor
 Gives rise to Emissions related to process
and fuel gases producing energy
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4. Features of emission
accounting
C + O source energy+CO2
 The carbon source supplies energy in
addition to process fuel gases energy
 Purchase external energy?
 External energy generation for plant
involves CO2 generation elsewhere
and is added to plant emissions
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5. Features of emission
accounting
 Surplus fuel gases sold externally for
power generation contribute to emissions
elsewhere, Life Cycle Analysis Approach
for allocation of such emissions to plant
 Total emissions are estimated based on
fuel gas related emissions including
process emissions and energy related
emissions (purchased/generated)
 Additionally, energy chemicals and
carbonate emissions have to be added
further
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6.  Novel iron making process routes:
 Produce little by-product gases and meets the
process energy requirements through
import/generation of energy required
 When combined with Integrated plant using
conventional technology, one can profitably use
the by-product gases and meet substantially the
process energy requirements with some
import/generation of energy
 Careful energy balance required to
minimize emissions
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8. Emission comparisons based on
energy consumption
 Emission comparisons based on energy
considerations are often difficult to make
 Varied nature of fuel energy inputs (both
solid and gaseous) for individual process
steps and
 Different circuit configurations used
 Energy inputs such as steam , power can
have different emission factors depending
on how this energy is generated
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9. Typical emission profiles: energy
generation
Fuel Gas Energy T CO2 MWh/kNm3 T CO2 / T CO2/
(GJ/kNM3 ) /kNM3 MWh/T coal GJ MWh
(GJ/T ) T CO2/T T CO2 / TCO2/
coal GJ MWh
BF 3.684 0.872 0.353 0.237 2.475
BOF 7.433 1.379 0.711 0.186 1.938
C OVEN 16.72 0.755 1.6 0.045 0.472
COREX 8.40 1.50 0.804 0.179 1.870
N GAS 38.20 1.96 3.655 0.0514 0.535
STEAM 16.942 1.72 1.621 0.101 1.061
COAL
3/2/2013 NMD ATM 2012 9

10.  Example: energy loads and emissions for
individual process steps for given circuit
configurations (Papers by MIDREX)
 DR/EAF route using 80 percent DRI
and 20 percent scrap, which is a
typical ratio in natural gas-rich areas,
has significantly lower carbon
emissions than does the BF/BOF
method
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11.  Energy loads similar to conventional
process
 Emission advantage in such cases
emerges from the use of carbon lean fuel
 External electricity input attributed a
constant emissivity
 For identical specific energy
consumption, emission patterns for
conventional processes may differ
because of carbon rich fuel input
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12. Emission comparisons based on
Carbon flux approach
 Carbon flow model for emissions
comparison (Chunxia, Jl of Env
Sc.,2009)
 Calculation of CO2 emission is made
through carbon balance with the carbon
flow of fuels, raw materials and
products, byproducts, waste, etc.
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13. Typical carbon flow diagram
3/2/2013 NMD ATM 2012 13

14. Emission Accounting: Emission
comparisons based on Carbon flux
approach
 The major advantage of this approach it
allows visualization of carbon flow of the
fuel gases generated during processing
in addition to solid fuel usage
3/2/2013 NMD ATM 2012 14

15.  Total emission for process step=Fuel gas related
emission+ process gas emission
 Fuel gas related CO2 emissions for an
individual process step can be separately
estimated
 For a unit generating fuel gas (blast furnace,
coke oven, COREX etc.),CO2 content of the
process gas can be separately estimated
 If internal electricity generation is through fuel
gases and external carbon, carbon contribution to
emission can be separately worked out
 Steam, energy chemicals and carbonates are
separately considered (generation mode)
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16. Emission accounting
based on process
and fuel gases
 Emissions attributed to process and fuel
gases generated can be separately tracked
through measurements
 These emissions are likely to constitute
the major part of total emissions
 Analysis of Correlations of these emissions
with other emissions (direct energy
emissions ) allows process appraisal for a
given application
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17. Typical emission profiles of fuel gases
Fuel Gas Energy T C /kNM3 T CO2 T CO2 /
(GJ/kNM3) /kNM3 GJ
BF 3.684 0.238 0.872 0.237
BOF 7.433 0.376 1.379 0.186
C OVEN 16.72 0.206 0.755 0.045
COREX 8.40 0.410 1.50 0.179
N GAS 38.20 0.534 1.96 0.0514
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18. Case Study:
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19. Importance of carbon balance
 Net quantities of fuel gases based on
input carbon
 Estimation Approach assumes that there
are minimal discrepancies in carbon
balances
 Do the fuel gas quantities monitored
match predicted values from carbon
balance?
3/2/2013 NMD ATM 2012 19

20. Importance of carbon balance
 Is the plant losing fuel gas and energy ?
 Is the plant generating emissions not
related to process and fuel gases?
 Estimation of excess energy available
through fuel gases for „across the fence
transfer‟ is critically dependant on such
losses
 Such losses occur and these need to be
then assessed based on input carbon load
to the iron making complex
3/2/2013 NMD ATM 2012 20

21. Establishing a Carbon balance
(Example, Integrated Steel
Plant) COKE PLANT C-BALANCE
(Per ton hot metal basis)
Coke Oven Gas
(21.92 kg)
Coal Tar
(314.39 kg)
COKE PLANT (9.52 kg)
Coke
(262.22 kg)
BLAST FURNACE C-BALANCE
(Per ton hot metal basis)
Blast Furnace Gas
Coke (408.57 kg)
(385.17 kg)
Hot Metal
BLAST FURNACE (44.4 kg)
PCI
Dust Loss
(86.91 kg)
(5 kg)
OVER-ALL C-BALANCE
(Per ton hot metal basis)
Coke Oven Gas
(21.92 kg)
Coal
(314.39 kg)
COKE PLANT Tar
(5.97 kg)
Coke Breeze
(60.55 kg)
Coke Tar
(201.66 kg) (3.55 kg)
Blast Furnace Gas
External (408.57 kg)
Purchased Coke
Hot Metal
(183.5 kg) BLAST FURNACE (44.4 kg)
PCI
Dust Loss
(86.91 kg)
(5 kg)
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24. Fuel gas role in total emissions
 Utilization of BF gas downstream of iron
making for generating energy leads to
marked increase of emissions
 Is there a way of sequestering the CO2 of
the blast furnace gas profitably?
3/2/2013 NMD ATM 2012 24

25. How do process and fuel gas
emissions compare with other
emissions?
Process + Generated Energy External
Fuel Gas Energy Chemicals Electricity
+
carbonates
1 81.72% 2.86% 7.49% 7.94%
2 72.51% 19.47% 5.58% 2.44%
Process and Fuel gas related emissions
constitutes the major part of total CO2
emission in an integrated (BF-BOF) plant
3/2/2013 NMD ATM 2012 25

26. Spreadsheet model for optimal
fuel gas network
 For a given energy requirement, what is the
best combination of input fuel gases to
minimize fuel gas related emissions for a
chosen step?
 Developing predictive fuel gas generation
quantity for blast furnace, coke oven
 Semi-empirical model for coke oven based on coke
input
 Spread sheet model for blast furnace top gas yield
 Input thermal loads based on plant data
 Develop utilization network based on split
factors: minimize gas export
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27. Optimized plant parameters
 Plant operating parameters for
minimum fuel gas emission can be
proposed based on an ideal carbon
flow diagram exclusively on model
based material and energy balance
(Larsson,2007, Luleå University)
 Requires extensive model validation
3/2/2013 NMD ATM 2012 27

28.  Other emission sources can then be
computed to arrive at total emission
profile
 The predicted „optimal emission
pattern‟ with/without „plant parameter
prediction‟ needs to be reinforced with
systematic plant data collection on
carbon flows
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29. Comparison of Alternative routes
with Integrated plant iron making
section
 Alternative routes produce very little fuel
gas
 CO2 emissions were worked out (VATECH)
for MIDREX-DR plant, FINMET plant,
FINMET plant plus EAF, MIDREX plant
plus EAF ensuring that a representative C
balance has been obtained
 GHG emissions from imports of electricity,
steam or heat were also considered in this study
(Scope 2 emissions)
3/2/2013 NMD ATM 2012 29

30.  MIDREX plant producing HBI, process
related emissions have been reported as
0.556 T CO2/THM
 Integrated plant BF direct emissions : 0.88
T CO2/THM for BF producing hot metal
 Sintering and coke making are responsible for
almost half of the total direct process emissions
from BF
 Credit for energy export of the fuel gases
 Specific energy consumption lowered
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32. Abatement of emissions:
Reduction of intensity at source
 Use of analytical models
 Effective use of C-DRR diagrams
derived from two zone models in an
environment of blast furnace control
system
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35. Optimized Emissions vs. costs
 Optimization of emissions for a blast
furnace based on analytical models
vis-á-vis the input costs
(Saxen,2009,Mat.Manf.Process)
 A cost function (F1) which includes all inputs to
the furnace has been used
 CO2 emission function (F2) includes emissions
pertaining to those arising within the iron making
complex attributable to the blast furnace
operation with a chosen optimal shaft efficiency
 Pareto front
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36. 3/2/2013 NMD ATM 2012 36

37. Abatement of emissions:
Using sequestration
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38. • Industrial CO2 streams from fuel
combustion are typically smaller than a
standalone coal power plant CO2 stream
• Smaller scale may raise the cost per ton of
CO2 captured
• Process CO2 streams (such as blast
furnace stove combustion stream) are,
however, richer in CO2 (25-29%) as
compared to a thermal power plant CO2
stream
3/2/2013 NMD ATM 2012 38

39. Sequestration potential
assessment of a BF flue gas
source (An Example)
 Large world-scale complex refinery has
reported three largest point sources, all
about 1200 kt CO2 per year
 A typical blast furnace stack may emit
1790 kTPA, 3MTPA plant, larger than
the single refinery stack
3/2/2013 NMD ATM 2012 39

40. Typical scheme for a coastal
refinery
 The flue gas is bifurcated into two
streams to (a) enrich the flue gas, as
shown in the figure and (b) use the gas
in a slag sequestration scheme
 The products consisting of an enriched
gas stream is transported via pipelines
for oceanic disposal along with a
carbonate bearing residue which is used
during gas injection for pH control
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41. 3/2/2013 NMD ATM 2012 41

42. Total CO2 of Blast Furnace exit flue gas = 223.8 tph = 5371.2 tpd
CO2 CO2
Capture feed % share
CO2 lost (tpd) captured
Processes of CO2
(tpd) (tpd)
Mineralogic 411.96 24.72 387.24 8.32
al
Sequestratio
n
Amine 4959.24 694.30 4264.94 91.68
Capture
Plant
3/2/2013 NMD ATM 2012 42

43.  Total Cost of Capture by Amine Separation
and Mineralogical sequestration Scheme +
Compression cost of captured CO2 from
amine plant (without GLAD System
operation cost) = {(0.0832*30) +
(0.9168*(3.124 + 44.39))} = 46.06
≈ 46 US$/ton CO2
 Total Cost of Capture by Amine Separation
and Mineralogical sequestration Scheme
for sequesterable CO2 from BF exit flue
gas = (Annual cost of capture/3.2*106) =
22.07 US$/thm.
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44.  The proposed scheme has been
estimated to lead to a reduction of CO2
emission of 0.48 tCO2/THM
 Estimated cost of 22.07 US$/THM and
additional oceanic GLAD system costs.
3/2/2013 NMD ATM 2012 44

45. Reduction of carbon intensity-
Top Gas Recycle blast furnace
 With CO2 sequestration….
 Maximum CO2 emission for the
condition discussed:
0.904T CO2/THM
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46. Ore 469.5 kg + Sinter 1220.12 kg Top gas 1041.54 Nm3 (dry blast) To stoves 52.07 Nm3
Coke 199 kg (165.82 kg C) CO 47.57%
(5% of Top gas)
CO2 39.16%
H2 8.81%
N2 4.45% 989.46 Nm3
Temp. 100oC
421.74 Nm3
Shaft Efficiency VPSA
96% CO 11.16 %
CO2 87.28 %
H2 0.57 %
N2 0.97 %
DR 12.93%
565.5 Nm3
BLAST FURNACE 900oC
Heater CO 74.55 %
CO2 3.43 %
Coal 173 kg (127.22 kg C) + H2 14.95 %
1200oC
Moisture 50 gm/Nm3 N2 7.07 %
Heater
Oxygen 195.29 Nm3
(98% O2 + 2% N2)
Hot metal 1000kg
Slag 485.01 kg
3/2/2013 NMD ATM 2012 46

47. Technology options for CO2 separation and capture from
blast furnace gas from oxygen blast furnace applications
Unit: PSA Vacuum pressure swing adsorption
CO2 yield % vol 79.7
Energy consumption: gigajoules, (GJ)/tCO2 , 0.36
Unit: VPSA
CO2 yield % vol 87.2
Energy consumption: gigajoules, (GJ)/tCO2, 0.38
Unit: Amines + compression
CO2 yield % vol 100.0
Energy consumption: gigajoules, (GJ)/tCO2, 3.81
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48. Importance of Displacement
credits
 Life cycle analysis (LCA) measures the
environmental impacts over the life cycle
of a defined system
 Essentially, a „cradle to gate‟ analysis is
followed
 The basis for comparison is the
environmental impact caused to produce
one ton of cast steel, labeled as the
functional unit.
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49.  Displacement credits arise through
consideration of byproducts such as
slag and gas
 Use of slag in cement industry and use of
off gases for electricity generation are
examples of displacement credits.
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50.  Issues that reduce CO2 emissions
at the site, but increase CO2
emissions elsewhere include buying
pellets , coke, using higher scrap,
buying directly reduced iron, lime,
steam and electricity
 Scope 2 and 3 emissions
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51.  The full production chain of
energy use and CO2 emissions
may be considerably higher or
lower than the site footprint would
suggest
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52. Beyond the site foot print…
 A model based approach of LCIA of
steelmaking approach has been presented by
Birat (2010, Int. Jl. of LCA)
 Simulation of traditional processes which
guarantees the quality of data, the mass and
the energy balances (ASPEN)
 A model allows the calculation of the chemical
compositions of products and by-products
such as the steelworks gases
 Companies can assess quickly their
environmental impacts with respect to a
chosen industrial configuration using process
integration
3/2/2013 NMD ATM 2012 52

53. Additional Issues to be
considered in Abatement
 Coal and coke qualities become
important when decrease of coke rate is
contemplated
 Higher strength of coke & sufficiently
reactive coke is required
3/2/2013 NMD ATM 2012 53

54. Additional Issues to be
considered….
 The source of hydrogen:
 Procuring hydrogen externally -CO2 is
emitted at hydrogen production sites and
this needs to be sequestered
 WGSR (i.e. the one-stage reaction) for
excess BF gas, or generate from excess
COG via a two-stage reaction, namely, POX
followed by WGSR
3/2/2013 NMD ATM 2012 54

55.  Sequestration technologies are energy
intensive
 Cutting- edge technologies for energy
recovery and saving
 Development of sensible heat recovery from
steelmaking slag
 Kalina cycle /ORC for power generation
technology
 Utilization of heat pumps
3/2/2013 NMD ATM 2012 55

56. CONCLUSIONS
 Issues in Carbon Accounting
 Approach using Carbon Flux
 Importance of proper carbon balance
 CO2 from fuel gases
 Carbon abatement
3/2/2013 NMD ATM 2012 56

57. CONCLUSIONS….
 At source, possible cost optimization
 With sequestration, example case with cost
 TGR blast furnace, with sequestration
 Allocation of Emissions
 Additional issues in Abatement
pertaining to extra energy generation
and hydrogen source
 The final goal: look beyond the site foot
print…..
3/2/2013 NMD ATM 2012 57

58. Acknowledgements
 NATIONAL INSTITUTE OF OCEAN
TECHNOLOGY
 DATA SUPPORT FROM STEEL
PLANTS, NOTABLY TATA STEEL
LIMITED, DSP, AND RINL
 GRADUATE STUDENTS OF IIT
KHARAGPUR
3/2/2013 NMD ATM 2012 58

59. “Sustainability is Development that meets the
present needs without compromising
the ability of future generations to meet their needs”
3/2/2013 NMD ATM 2012 59