Co2 abatement

59
Prof. P. K. Sen (IIT Kharagpur) 3/2/2013 NMD ATM 2012 CO 2 ACCOUNTING AND ABATEMENT: AN APPROACH FOR IRON & STEEL INDUSTRY 1

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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Typical carbon flow diagram

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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

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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

Case Study:

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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)

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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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Abatement of emissions:

Using sequestration

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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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“Sustainability is Development that meets the

present needs without compromising

the ability of future generations to meet their needs”