The low carbon Blast Furnace

why it matters and how

Ashok Kumar
Tata Steel

Jamshedpur, 17th January, 2024

online talk at the

International Conference on Green and Sustainable Ironmaking

United Club
Jamshedpur

1
The CO2 rise
in
atmosphere
is linked to

energy
related
human made
emissions
2
plenty of ‘green steel’ headlines with two dominant themes
➔ replace coal with hydrogen; ➔ replace ironmaking with scrap
– both calling for doing away with the Blast Furnace

3
 the
low carbon Blast Furnace
why it matters
and
how
4
 Changing (rather than killing) the Blast Furnace
a better transition conversation ?
• Leverage the broader energy transition
• not confined to debates about choice of reactor choice of reduction molecules ?
• law of diminishing returns when focussed on one lever ? .. faster impact possible – steel industry woefully
behind on emissions reduction

• Hydrogen not ready to scale yet in much of the world..

• Despite impressive progress, changing electricity mix fast enough .. net zero is still far ?
• Instead a very key lever – working on 90 % of installed ironmaking capacity (BF) has gotten less attention

• BF is essentially a good idea for a steel plant - if we can solve its carbon
footprint conundrum .. minimal asset reconstruction

5
Footprint
reduction (of
steel production)
is expected to
come about
through a
bouquet of
solutions
– not one silver
bullet

IEA
Net Zero Roadmap A Global Pathway
to Keep the 1.5 °C Goal in Reach
2023 Update

6
Energy consumption by source, World

Primary energy is yet

mostly fossil fuel based
A multiple factor growth in electricity
capacity would be required by most
economies if primary energy needs,
currently met by fossil fuels (coal, natural
gas, oil), also have to move to renewables
or nuclear energy based electricity

(credit: chart from Our World in Data based on BP Statistical Review of

World Energy (2021))
Efficiency factor used to make sources comparable
own commentary

7
Even with
impressive
progress, it could
take 15-25 years
for bulk
electricity to be
‘green’

8
What is the
carbon footprint
of electricity
itself ?
while reducing fast, the
current carbon footprint
of electricity is yet too
high in most countries

making immediate
electrification of steel
industry not a useful
startegy for mitigating
climate change

9
 why
coal and hydrogen (on earth)
are not really equivalents ?
and
how they can be
10
Renewables
based
electricity is
very resource
intensive:
and it takes a long time to
get there

Bill Gates:
How to Avoid a Climate Disaster: The Solutions
We Have and the Breakthroughs We Need

How much stuff does it take: Weight of materials,

measured in metric tons, per terawatt-hour of
electricity generated. “Solar PV” refers to solar
photovoltaic panels, which convert light from the
sun into electricity. Source: U.S. Department of
Energy, Quadrennial Technology Review: An
Assessment of Energy Technologies and Research
Opportunities (2015), https://www.energy.gov.

11
 Managing emissions vs managing energy production
downstream vs upstream efforts - C and H as energy vectors

Primary energy
Solar, wind, geo

Capture EnergyConversion
(solar, wind, to geo) Storage
Concentrated energy Solar/wind/geoCapture, Conversion,
Electricity / hydrogen Storage
Battery, hydro, vessels
Coal, NG
Accumulated over geological
time scale Energy production management

Energy use
C
Energy use H

Limited tailpipe issues

Emission management water as by product
Capture Pipeline/ Storage Conversion
CO2 Shipping CCS CCU, hydrocarbons 12
Kumar, A. DBA thesis at Sumas, Switzerland, 2022
Even with
impressive
progress, it
could take 15-
25 years for
bulk electricity
to be ‘green’

13
 Large scale shift to
H2-DRI-EAF
proposition for India
(at least till mid-century)
even after assuming ambitious
growth in scrap availability

➢ does not reduce CO2

footprint based on H from 2
expected grid electricity (without CCS)

➢ demands unrealistic
proportion of renewables
electricity / H2 capacity – starving
other vital sectors of economy, e.g. replacing
biomass based cooking
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Switching ironmaking from BFs to DRI shafts:
a lot more than changing reductant molecules (from C to H) ?

DRI Blast Furnace

• Iron oxide - reduction 88-95 % • Iron oxide - reduction ~100 %

❖ Iron ore gangue – stays in, either pre-melt or handle in ✓ de-slagging of gangue → BF slag to cement
steelmaking
❖ Carburization - add C into reduction shaft or during
subsequent melting ✓ Carburization of iron ~ near saturation
❖ De-S in steelmaking
✓ De-S of iron > 85 % in BF + rest at HM DeS station
❖ Import energy – for steelworks other users
✓ Export energy in gas for steelworks heating and power gen ~ 4
GJ/thm
❖ Import energy – for melting, refining
✓ Energy rich liquid iron – meet steelmaking needs + absorb
20% scrap

15
Locked in
assets
World steel industry is
deeply invested

in highly capital intensive

assets – with lifespan of
~50 years

large part of these are

less than 15 years old –
in growing economies -
wherein
new additions
rather than replacement
is on the agenda

16
 Extent of change to existing steel plants
modifying energy flows through BF vs changing all iron and steelmaking

BF gas BF, BOF,

Air / BOF slag
Raw cleaning CO gasses
oxygen & reverts
Material and based
production manageme Extent of
handling distribution Power
& heating nt plants changes to
system plants facilities with
low carbon BF
Iron Ore solution
BF Secondary Continuous
agglomerat
Stockhouse BOF vessel Metallurgy Casting
ion plants BF reactor Extent of changes to
& charging plant plant
Sinter facilities with
system
Pellets Hydrogen DRI
solution
Cast house HM De-S,
Coke By- Liquid iron +
Coke
products handling Pre-
Ovens
plant slag treatment
granulation plant

Figure 6 : Investment in integrated steel plants is spread over large number of facilities. The red and blue boxes map out the extent
of change needed in transitioning to lower carbon footprint by following the BF decarbonization route and hydrogen based DRI-
EAF route
(conceptual – based on general features and investments in integrated steel plants )
17
Kumar, A. DBA thesis at Sumas, Switzerland, 2022
Increased
availability and use
of scrap
is already accounted for – in
determining

size of the
challenge
and as such is

not a lever for

decarbonizing
primary steel production
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 A sliding scale for assessing energy efficiency and energy footprint improvements
example of plant A improving from point 1 → 2 – normalising the scrap mix effect

improvement

Reported / claimed
Plant
1
t CO2/t steel A,
m Mix effect

Energy efficiency & R

actual
energy footprint
improvement a
Plant
A, 2
CO2 intensity,

Scrap 8 → 28 % Electricity footprint 500 g/kWh

Electricity footprint 300

Electricity footprint 60

Scrap % in mix 0 25 50 75 100

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 the
low carbon Blast Furnace
why it matters
and
how
20
 Decarbonising the Blast Furnace
Potential impact on
Key process interventions fossil carbon use

• DeMuGH
Decrease Molecule use for Generation of Heat
augment with renewables based heat – solar thermal, electrical, plasma 40-50 %
• RePuM
Recycle Partially used Molecules
recycle top gas after stripping H2O, CO2, adding heat

• SwiRM
Switch Reduction Molecules
replace fossil carbon with renewables based hydrogen / COG, and sustainable bio carbon
25 %
20 kg H2 ~ 15% + 10 % replacement by bio carbon

• CCUS 25-35 %
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 Blast Furnace process – separating reduction and energy needs

Carbon for reduction only Carbon as used in BF today

Fe2O3 + 1.5 C = 2Fe + 1.5 CO2  energy Fe2O3 + 4 C + 1.5 O2 = 2Fe + 2 CO + 2 CO2 → energy

• 151 kg C / thm + 45 kg (for HM C dissolution) = 196 kg/thm • 403 kg C / thm + 45 kg (for HM C dissolution) = 448 kg/thm
• Energy needed 8.5 GJ/thm (reactions) + 2.3 GJ/thm (heating + losses) • Energy used 8.5 GJ/thm (reactions) + 2.3 GJ/thm (heating + losses)
• Energy export to power + ironmaking zone & downstream heating 6 GJ/thm
augmented by 20 kg/thm hydrogen
Fe2O3 + 0.84 C + 0.66 H2 = 2Fe + 0.84 CO2 + 0.66 H2O  energy

• 85 kg C / thm + 45 kg (for HM C dissolution) = 130 kg/thm

22
The BF distributes more energy than it
uses for “ironmaking” per se

18 % energy available as input for

steelmaking; & cement production
33 % energy exported as BF gas
for heating and power generation
applications

47 % energy used in ironmaking

reactions and melting

2 % energy as losses

Figure 7 : An energy accounting view of

inputs and outputs from the BF
(own calculations based on first principles thermodynamic data)
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 Blast Furnace through the energy lense → an Energy Distributor

33 % Energy in
BF gas - fuel for
steel and power
plant

Hot air / oxygen

Energy IN C in COKE
18 GJ / tHM 47 % Ironmaking process Energy OUT
C + H2 in injected
fuels

18 % Energy in
metal + slag for
downstream
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Blast Furnace: rearranging Energy sources & flows

Renewable
heat & Limited export
electricity Energy in BF gas -
for fuel for steel and power
conditioning plant replaced by
and heating renewables
gas & air

C in recycled gas Energy OUT

Hot air / oxygen Ironmaking process

C in COKE
C + H2 in injected fuels
Energy in metal +
slag for downstream
25
 Recycling reduction molecules is key

Remove H2O
If the DRI shaft operated in ‘one
Remove CO2
Top eta CO ~ 44 % pass’ mode (like the BF),
gas eta H2 ~ 27 %
the consumption of natural gas
Add fresh
CO, H2 would be three times;
Heating
Fe2O3 + CO + 3 H2 → Fe + CO2 + 3 H2O
… and the CO2 footprint to just
DRI make DRI (using Natural Gas) would
shaft be higher than that of making hot
metal in the BF (using coke / coal) !

26
 Kumar, A. DBA thesis at Sumas, Switzerland, 2022

Blast Furnace through the CARBON lense (case of enhanced top gas recycle)

→ RECYCLE C in export gas to BF itself, leaving general energy demands outside BF to be met by renewable energy

205 kg C as CO in BF top gas- 200 kg C as

RECYCLED after separation of CO2 CO2 in BF top
gas (735 kg CO2)
CO
H2 CO2
N2 strip

typical Carbon OUT

BF gas
CO/ CO2
~ 1.0 e.g. Pressure

Carbon C in COKE H2 4 % Swing

N2 bal Adsorption
~250 C + H2 in injected
fuels
kg / tHM 45-50 kg as C in
metal – for use in
steelmaking
Figure 11: A vision for carbon optimized BF - through the carbon lens : recycled carbon (as CO, with added H2 and heat ) avoids ~ 200 kg/thm
of fresh carbon units consumption; while 200 kg/thm of carbon units (as CO2) get captured for CCUS. It is the sum total of BF TGR concept
27
superimposed with ‘renewables based’ heat and hydrogen; and CCUS. (own calculations based on first principles thermodynamic data)
Bypass
molecule use
for raising
temperature ?
e.g.
High temperature
heat ..

… directly through
concentrated solar
28
Storage of high temperature heat concepts… ..
addressing intermittency problem of renewable energy

29
Energy needed for “heating” does not necessarily need to come from
carbon, hydrogen or even electricity – it can simply be direct heat from
solar or geothermal sources

A lot of energy for steelmaking is merely heat – and current

developments in concentrated solar will answer to meeting significant
part of the steel requirement
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Plasma : electrical energy → heat

31
 Kumar, A. DBA thesis at Sumas, Switzerland, 2022

Heat content of materials inside BF →

Heat exchange
view of the Blast Furnace Solids and liquids
Gas
heat supply via gas
=
High temperature
heat demand: heat
heating / melting solids
+ reduction heat Heat created by
+ losses Carbon (in coke, coal) -
Medium temperature heat Oxygen reactions
 descending solids / melt

within the process

Heat created by reactions within →
the process, augmented by Largely difficult to
heated air blast from outside the replace Coke and
Low / medium
temperature
BF this heat – can be
→ reduced to an extent
ascending gas →

heat
Possible to reduce need for ‘in by plasma heating of
Heat supplied by excess heat process heat’ by preparing gas outside
in ascending gas reduction gas and heating it
→ outside the BF – deploying
The ascending gas – whether renewable energy sources
generated within or injected
from outside – has excess heat

ambient-900 oC 900-1500 oC 1500-2300 oC

Process Temperature within BF →
Figure 14: Heat and temperature view of BF process – categorized by ‘quality of heat’. It has been assessed that the highest temperature heat
32process)
within may still need to be generated in-situ – though the limit can be aspired to change over time. (own conceptualization based on first understanding of BF
 Kumar, A. DBA thesis at Sumas, Switzerland, 2022

Blast Furnace process – “externalising” energy sources

Limited gas generation within BF: balancing gas amount and temperature through hot gas injection at various levels

gas T
Current BF gas T
Top gas recycle +
energy input
 descending solids / melt

Height within BF
ascending gas →

Hot gas
injection

Hot gas
injection

100 900 1500 2300 100 900 1500 2300 3000

Gas temperature within BF oC High oxygen
flame T
Figure 15: Keeping the internal BF process intact – by replacing heat and reduction molecules from in-situ carbon use with
those injected from outside (heated & recycled top gas). (own conceptualization based on understanding of BF process and TGR concept) 33
 Role of Coke in the BF process
Regeneration of reducing gas In part
Injection of
CO2 + C  2CO taken over
conditioned
H2O+ C → CO + H2 … by coal
reducing gas
injection
gas

Coke bed enables Continued Continued

liquid – gas role for role for
counterflow coke coke

metal
slag

Generation of heat & reducing gas Taken over Replace by

by coal external heat
½O2 + C → heat + CO injection & molecules
CxHyO → xCO + yH2 … 34
Figure 5 : Continuing evolution of the BF over 200 years – and further potential for reduction in energy consumption.
chart credit IEA source 35
BFs starting to change amongst large steelmakers

36
 Innovations on existing assets & processes
impact of early start compared to delayed realization of "perfect" solutions
CO2 accumulation in the
atmosphere over the years
attributable to global steel
industry, with following
pathways:
A delayed ídeal
solution’ leads to
Business as usual – with
projected electricity footprint build up of more
improvements built in
climate stress (30Gt
Blast Furnace System –
with some recycling
emissions) by mid
innovations incorporated
century
Blast Furnace System –
with some recycling
innovations + CCS in one
third capacity incorporated

Electrolyser hydrogen
based iron production (DRI)
melted in EAF (electricity
based)

37
 Findings: Climate change and Steel industry
▪ Global warming is result of accumulation of GHG molecules in the atmosphere

▪ World is falling behind in reining in emissions of GHGs – needed for restricting global warming.
→ Global steel industry too is amongst the laggards – facing both technological and economic hurdles to
lowering CO2 emissions from primary production

▪ Steel industry declared plans / project announcements are focused largely on electrification (incl
hydrogen as energy vector). These:
➢ shift the onus for providing energy to outside of the steel industry,
➢ come largely from Europe - with limited appeal for other regions with diverse economic and geographical
conditions;
➢ demand unrealistic amounts of renewables-based electricity - many geographies do not appear to have the
luxury for allocation or potential for production - of commensurate renewables based electricity capacity
38

Kumar, A. DBA thesis at Sumas, Switzerland, 2022

 Findings: Broadening the Pathways..
1. Creating rather than ‘killing’ energy alternatives
Distinguishing between energy, energy vectors, emissions; Recognize earth’s carbon cycle, circularity, efficiency opportunity
2. Why the BF matters - and will continue to do so
Integrated metallurgical and energy efficiency, existing capacity, potential
3. Rethinking the BF
Distinguishing carbon and energy functionalities, renewable heat, carbon circularity,

4. Further process reconfiguration possibilities

Leveraging hydrogen better; synthetic hydrocarbons, synergy across industries
5. Changing the BOF process
Absorbing increased scrap arising without building new steel plants
6. Focus innovation effort
Direct solar to hydrogen, renewable heat, heat storage, gas separation technology, materials
7. Improvements in measurement framework
Sliding scale primary vs secondary steel production, cumulative emissions over time rather than specific intensity
39

Kumar, A. DBA thesis at Sumas, Switzerland, 2022

Thank you
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