Co2 abatement
Transcript of Co2 abatement
Prof. P. K. Sen (IIT Kharagpur)
3/2/2013 NMD ATM 2012
CO2 ACCOUNTING AND
ABATEMENT: AN APPROACH FOR
IRON & STEEL INDUSTRY
1
• 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.
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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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Features of emission
accounting
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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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
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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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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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Typical emission profiles: energy
generation
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Fuel Gas Energy
(GJ/kNM3 )
(GJ/T )
T CO2
/kNM3
T CO2/T
coal
MWh/kNm3
MWh/T coalT CO2 /
GJ
T CO2 /
GJ
T CO2/
MWh
TCO2/
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
COAL
16.942 1.72 1.621 0.101 1.061
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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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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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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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
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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)3/2/2013 NMD ATM 2012 15
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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Typical emission profiles of fuel gases
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Fuel Gas Energy
(GJ/kNM3)
T C /kNM3 T CO2
/kNM3
T CO2 /
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
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?
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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
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Establishing a Carbon balance
(Example, Integrated Steel
Plant)
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COKE PLANT
BLAST FURNACE
Coke Oven Gas
(21.92 kg)Coal
(314.39 kg) Tar
(5.97 kg)
Coke Breeze
(60.55 kg)
Blast Furnace Gas
(408.57 kg)
Hot Metal
(44.4 kg)
Dust Loss
(5 kg)
External
Purchased Coke
(183.5 kg)
PCI
(86.91 kg)
Coke
(201.66 kg)
OVER-ALL C-BALANCE(Per ton hot metal basis)
BLAST FURNACE
Coke
(385.17 kg)
Blast Furnace Gas
(408.57 kg)
Hot Metal
(44.4 kg)
Dust Loss
(5 kg)
PCI
(86.91 kg)
BLAST FURNACE C-BALANCE(Per ton hot metal basis)
COKE PLANTCoal
(314.39 kg)
Tar
(9.52 kg)
(Per ton hot metal basis)
COKE PLANT C-BALANCE
Coke
(262.22 kg)
Coke Oven Gas
(21.92 kg)
Tar
(3.55 kg)
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?
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How do process and fuel gas
emissions compare with other
emissions?
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Process +
Fuel Gas
Generated
Energy
Energy
Chemicals
+
carbonates
External
Electricity
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
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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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
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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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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)
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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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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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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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• 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
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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
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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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Capture
Processes
CO2
feed
(tpd)
CO2 lost (tpd)
CO2
captured
(tpd)
% share
of CO2
Mineralogic
al
Sequestratio
n
411.96 24.72 387.24 8.32
Amine
Capture
Plant
4959.24 694.30 4264.94 91.68
Total CO2 of Blast Furnace exit flue gas = 223.8 tph = 5371.2 tpd
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.3/2/2013 NMD ATM 2012 43
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.
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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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BLAST FURNACE
VPSA
Ore 469.5 kg + Sinter 1220.12 kg
Coke 199 kg (165.82 kg C)
Coal 173 kg (127.22 kg C) +
Moisture 50 gm/Nm3
Top gas 1041.54 Nm3 (dry blast)
CO
CO2
H2
N2
Temp.
CO
CO2
H2
N2
CO
CO2
H2
N2
47.57%
39.16%
8.81%
4.45%
100oC
11.16 %
87.28 %
0.57 %
0.97 %
To stoves 52.07 Nm3
421.74 Nm3
989.46 Nm3
565.5 Nm3
74.55 %
3.43 %
14.95 %
7.07 %
Shaft Efficiency
96%
DR 12.93%
Hot metal 1000kg
Oxygen 195.29 Nm3
(98% O2 + 2% N2)
Heater
Slag 485.01 kg
1200oC
(5% of Top gas)
Heater900
oC
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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
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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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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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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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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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
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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
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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
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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
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CONCLUSIONS
Issues in Carbon Accounting
Approach using Carbon Flux
Importance of proper carbon balance
CO2 from fuel gases
Carbon abatement
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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…..
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Acknowledgements
NATIONAL INSTITUTE OF OCEAN
TECHNOLOGY
DATA SUPPORT FROM STEEL
PLANTS, NOTABLY TATA STEEL
LIMITED, DSP, AND RINL
GRADUATE STUDENTS OF IIT
KHARAGPUR
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