Proceedings of CUChE Alumni Symposium 2022
On Circular Economy on Sustainable Basis: The Role of Chemical Engineers
CUChEAA ISBN: 978-81-954649-1-3
December 2022 P a g e | 24 Volume 2, Issue 1
Decarbonisation: Role of CO
2
Capture in the Power and Industrial Sectors
Jayanta De
Project Process Manager, Wood Plc, Shinfield Park
Reading, RG2 9FW, UK, email: jayantakumar.de@woodplc.com
Abstract
In recent decades, the problem of global warming has become a key challenge and one of the most internationally
discussed issues. In 2021, the world saw around 200 countries come together at COP26 in Glasgow to align with reaching
net zero emissions by the middle of the century. This Conference of Parties (COP) conference was built on the adoption
of the Paris agreement and other framework agreements to commit to act on limiting an average global temperature
increase above pre-industrial levels of 1.5°C (IPCC, 2014). One of the four driving actions agreed in the Glasgow Climate
Pact was ‘mitigation’ to reduce greenhouse gas emissions.
Electricity and heat production are responsible for the lion’s share (25%) of greenhouse gas emissions. Global industries
(mainly cement manufacturing, iron and steel production, and chemicals manufacturing) also contribute to 21% of
greenhouse gas emissions. The balance of the greenhouse gas emission comes from agriculture (24%), transportation
(14%), gas heating /cooling in buildings (6%), and other energy (10%) (IPCC, 2014). Therefore, the power sector and
global industries produce almost 50% of the greenhouse gas emissions, which come from the usage of fossil fuels. To
reduce emissions, these sectors will need to either capture the greenhouse gas or replace the fossil fuels with other zero-
emission alternatives such as green electricity (renewable), green hydrogen (via electrolysis of water using renewable
power), or blue hydrogen (using fossil fuel as feedstock integrated with CCS).
This paper reviews the main contributors to CO
2
emissions in the power and industrial sectors and discusses key
challenges of CO
2
capture that the industry is facing to find a cost-effective solution. Wood has developed a methodology
(SCORE) that facilitates industries’ understanding of a road map to decarbonisation. This uses Substitution, Capture,
Offsetting, and Reduction options to Evaluate how best to tackle carbon emissions. CCS plays a key role in the road to
decarbonisation.
Keywords: greenhouse gas, zero emissions, fossil fuels, green hydrogen, blue hydrogen, CCS
1.0 Introduction
World leaders committed to act on limiting an average
global temperature increase above pre-industrial levels
of 1.5°C in 2021 at COP26 in Glasgow. To make a
significant reduction in greenhouse gas emissions,
mitigations are required in major fossil fuel users in the
power and industrial sectors.
Figure 1 depicts the greenhouse gas emissions by the
different sectors. The power sector and global industries
produce almost 50% of the greenhouse gas emissions
which come from the usage of fossil fuels. To reduce the
emissions, these sectors will need to either capture the
greenhouse gas or replace the fossil fuels with other zero
emission alternatives such as green electricity
(renewable), green hydrogen (via electrolysis of water
using renewable power) or blue hydrogen (using fossil
fuel as feedstock integrated with CCS).
This paper analyses the main contributors to CO
2
emissions in the power and industrial sectors and
discusses key challenges of CO
2
capture that the industry
is facing to find a cost-effective solution.
Fossil fuel-based power plants emit large amounts of
CO
2
into the atmosphere which can be integrated with
the CO
2
capture and sequestration (CCS) process for
sustainable power production. In CCS integrated power
plants, very low-pressure flue gas is routed to a solvent
absorption process to remove CO
2
which is then
Proceedings of CUChE Alumni Symposium 2022
On Circular Economy on Sustainable Basis: The Role of Chemical Engineers
CUChEAA ISBN: 978-81-954649-1-3
December 2022 P a g e | 25 Volume 2, Issue 1
desorbed in the regenerator for sequestration. Handling
of high volume and low-pressure flue gas challenges the
more conventional high-pressure gas processing
methods and normal equipment design.
Figure 1: Global Greenhouse Emissions by Economic
Sector (IPCC, 2014) (EPA, 2022)
The global industry sector mostly uses natural gas and in
some cases products from oil refining as a source of fuel.
Combustion of hydrocarbons produces CO
2
emissions
similar to power plants, and therefore needs a similar
CCS process to decarbonise the sector. Alternatively,
hydrogen can be used as fuel to generate heat and power.
The hydrogen needs to be produced either via green or
blue routes.
The emissions produced by cement plants largely result
from fossil fuels used to generate heat as well as from
chemical processes that transform limestone to clinker in
the kiln to produce cement. CCS will play an important
role to decarbonise the cement industry along with
alternative approaches to lower emissions by reducing
the limestone content with recycled CO
2
into concrete.
In the iron and steel industry, the major contributor to
CO
2
emissions is the blast furnace and basic oxygen
furnace, which uses coking coal as a base material. This
industry is one of the most carbon-intensive sectors and
is very challenging to decarbonise. The use of CCS to
capture low-pressure CO
2
from blast furnaces will need
to be an essential feature in existing steel plants. The
steel producers are currently developing the strategies to
decarbonise the sector, such as, improving efficiency
and using biomass as an alternate reductant or fuel.
2. Overview of the CO
2
Capture and Sequestration
Technical Chain
The CO
2
Capture and Sequestration process utilises a
series of processes that can be divided into four steps:
CO
2
capture from industrial or combustion processes;
CO
2
compression and purification (e.g., dehydration);
CO
2
transportation and CO
2
injection in the reservoir. To
understand the suitability of the CCS chain in the power
and industrial sector, it is important to explore the
different parts of the system.
2.1 CO
2
Capture
CO
2
can be captured by several mechanisms. The
following three categories are more common to
implement in short to medium-term decarbonisation
goals depending upon when in the process CO
2
is
removed: post-combustion, pre-combustion, and oxy-
combustion. The following sections provide a high-level
overview of these three main categories.
2.1.1 Post-Combustion Capture
In the post-combustion capture process, CO
2
is captured
from flue gases of combusted fossil fuels and/or
biomass. These systems typically use a liquid solvent
(e.g., amine-based solvent) to capture the low
concentration CO
2
present in the flue gas (normally 3-
15% by volume) from the main constituent nitrogen
(from air). A typical amine-based CO
2
capture diagram
is shown below in Figure 2.
Post-combustion capture processes using amines are
widely applied in industrial manufacturing processes,
refineries, and gas processing industries. In the post-
combustion process, very low-pressure flue gas is routed
to Direct Contact Cooler (DCC) to remove a large
amount of heat prior to the absorption process. A Blower
is employed to provide the pressure required for the flue
gas to enter the Absorber. The amine solution is used to
remove CO
2
from the flue gas. The rich amine from the
Absorber is then heated by steam to release highly
concentrated CO
2
in the Desorber and the CO
2
-free
amine (lean amine) is routed back to the Absorber. The
concentrated CO
2
(around 97%) from the Desorber is
sent for further treatment and compression.
In recent years, novel CO
2
separation technologies such
as membranes, solid adsorbents, and cryogenics are
being developed to compete with post-combustion
capture and these may offer cost advantages in the
future.
Figure 2: Schematic of typical CO
2
Post-combustion
capture process
2.1.2 Pre-Combustion Capture
In pre-combustion capture processes, the primary fuel is
fed into a reactor with air or oxygen and steam to
produce synthesis gas (Syngas), which mainly consists
Electricity
and Heat
Production
25%
Global
Inductries(
Cement,
Steel,
Chemicals)
21%
Agriculture
and Other
Land Use
24%
Transporat
ion
14%
Building
Others
10%
Proceedings of CUChE Alumni Symposium 2022
On Circular Economy on Sustainable Basis: The Role of Chemical Engineers
CUChEAA ISBN: 978-81-954649-1-3
December 2022 P a g e | 26 Volume 2, Issue 1
of hydrogen and carbon monoxide. The carbon
monoxide is further mixed with steam in a second
reactor (“shift reactor”) to produce additional hydrogen
along with CO
2
. The resultant stream of hydrogen and
CO
2
can further be separated into individual
constituents. Hydrogen is a carbon-free energy carrier so
if the CO
2
is captured and stored, it can be utilised to
produce heat and power. This hydrogen produced in the
reformer integrated with CCS is called ‘blue hydrogen’
#
.
The CO
2
concentrations from the shift reactor are
typically 15-60% by volume on a dry basis. The primary
stage of fuel conversion step is costly and involved than
post-combustion capture; however, the relatively high
concentration of CO
2
and high pressures are more
favourable for CO
2
separation.
# Hydrogen can also be generated using electrolysis of
water utilising renewable energy sources, which is
termed ‘green hydrogen’. Both blue and green hydrogen
can be utilised to decarbonise the power and industrial
sectors.
2.1.3 Oxy-Combustion Capture
Oxyfuel combustion systems combust fuels in the
presence of oxygen instead of air to produce a flue gas
which is mainly comprised of water vapour and CO
2
rather than CO
2
, N
2
, and water. This results in flue gas
streams with high concentrations of CO
2
(>80% CO
2
by
volume) and the volume of flue gas is considerably low.
The oxygen purity required for oxyfuel combustion is
~95-99%. The water vapour is removed from the flue
gas through cooling and compression. Furthermore,
additional treatment may be required to remove
contaminants and non-condensable gases (i.e., nitrogen)
from the flue gas prior to the final CO
2
disposal.
Theoretically, oxyfuel combustion systems can capture
the CO
2
but the requirement for supplementary gas
treatment processes to remove impurities (e.g., sulphur
and nitrogen oxides) reduces the capture efficiency to
~90%. Although large-scale oxygen separation systems
are commercially available, oxyfuel combustion for CO
2
capture has not been deployed at an industrial scale to
date and is only in the demonstration stage.
2.2 CO
2
Compression and Purification
Captured CO
2
from absorption (or other processes) is a
low-pressure stream and contains water and oxygen.
These contaminants can cause corrosion in the
downstream equipment and pipelines. The low-pressure
saturated CO
2
stream is routed to dehydration to remove
the moisture and then sent to the oxygen removal unit to
meet the specification of CO
2
which is suitable for
transportation.
In all CCS schemes, the most important and energy-
intensive step is compression. It requires a large amount
of power to increase the pressure of the CO
2
to achieve
the transport and injection conditions. Captured CO
2
goes through low pressure first and then a high-pressure
compression system based on the requirement of the
injection pressure. The high-pressure compression
utilises part compression followed by pumping in the
dense phase region (supercritical). These are generally
multistage integrally geared centrifugal machines.
2.3 CO
2
Transportation
Most of the high-pressure CO
2
pipelines operate in the
dense phase and carry large volumes of CO
2
from pure
stream sources (such as power plants and hydrogen
reformers) to the ultimate destination at the injection
well. The pipelines are mainly carbon steel. The
corrosion rate of carbon steel in dry supercritical CO
2
is
low, hence it is important to remove the moisture from
CO
2
to a minimum level in the conditioning step.
2.4 CO
2
Injection
Injection of captured CO
2
is the final and very important
step of the CCS technical chain. CO
2
can be injected into
deep saline aquifers, depleted hydrocarbon reservoirs, or
deep un-minable coal seams. The injection pressure
could be in the region of 150- 200 barg based on the
characteristics of the reservoir.
Therefore, to apply the CCS process it is essential that
the following aspects are assessed to decarbonise the
industrial sector.
CO
2
Capture Process - post-combustion, pre-
combustion, oxy-combustion.
Combustion fuel - natural gas, coal, oil, biomass
etc.
Site location - distance from a potential injection
storage site, pipeline length
Cooling system - air cooling, water cooling
Means of CO
2
Transport - onshore/offshore
pipeline, ship tankers, etc.
Physical state of CO
2
for transport - vapour
phase, dense phase
Storage type - depleted oil or gas fields, saline
aquifers, EOR etc
Sink type - onshore, offshore.
In the following sections, the above processes have been
explored further to understand which are more suitable
for the power and industrial sectors.
3. Power Plants
3.1 Overview of Industry
Across the world, power plants mostly burn fossil
fuels such as coal, oil, and natural gas to produce
electricity. A steam turbine generator is generally used
for coal or oil-based power stations, which convert
mechanical energy to electrical energy. It is estimated
that more than 85 percent of electricity produced in the
world utilises steam turbines (Rackley, 2017). In the
natural gas-fired plants, a combustion turbine is
employed, which utilises the dynamic pressure of the
high-pressure fuel gas and is mixed with air in the
combustion chamber to operate the turbine.
Combined Cycle Gas Turbine (CCGT) plants (also
called cogeneration plants or CHP (combined heat and
power plants) use a gas turbine, a steam boiler, and a
steam turbine (See figure 3) to generate electricity. The
hot exhaust gas (temperature approx. >550°C) from the
gas turbine exchanges heat with water to produce steam
which in turn produces electricity in the steam turbine
generator (STG). The combined cycle improves the
Proceedings of CUChE Alumni Symposium 2022
On Circular Economy on Sustainable Basis: The Role of Chemical Engineers
CUChEAA ISBN: 978-81-954649-1-3
December 2022 P a g e | 27 Volume 2, Issue 1
overall efficiency of the plant significantly, and mostly
all modern power plants are combined cycle fired by
natural gas.
Figure 3: Simplified Schematic of Combined Cycle
Power Plant
All the fossil fuel-based power plants emit a large
amount of CO
2
, which is a great concern when tackling
global warming. The table below summarises the annual
CO
2
emissions from power plants.
Table 1: CO
2
emissions from fossil fuel-based power
plants (Metz, 2005)
Power
Plant
Fuel
Number
of large
point
sources
Average
Annual
Emissions
per source
(Mt-CO
2
)
Coal
2025
3.9
Natural
Gas
1728
0.9
Oil
1108
0.9
The source of the CO
2
is the flue gas which is emitted
through the flue gas stack. This is generally visible from
long distances in the power plant.
3.2 Characteristics of CO
2
-containing streams
The typical flue gas characteristics from fossil fuel
combustion are shown in Table 2.
The range of CO
2
content varies from 3% to 15%; coal-
fired power stations produce high concentration CO
2
(12%-15%) while the CO
2
content is low (3% to 5%) for
gas-fired plants.
Table 2: Typical fossil fuel power plant flue gas
characteristics#
#: CO is not considered in the data which may be present
due to incomplete combustion.
3.3 Decarbonisation opportunities and challenges
Post-combustion capture is widely used in natural gas-
fired and combined cycle power stations. This process
can also be deployed to other power stations which use
coal and oil as fossil fuels. However, additional units
will be required to remove impurities in the flue gas,
such as sulphur and nitrogen oxides to avoid
contamination of the CO
2
capture solvent. Furthermore,
due to the low pressure of the flue gas, a large volume of
gas needs to be handled, which calls for larger
equipment and incurs high capital costs investment
(Popa, 2011). The low CO
2
concentration in the flue gas
also demands highly reactive chemical solvents to
capture CO
2
and a large volume of solvent needs a large
amount of energy to regenerate the solvents and release
CO
2
.
On the other hand, the pre-combustion capture can offer
a process that produces high pressure and high
concentration CO
2
which reduces the size of the CO
2
capture equipment. A less reactive physical solvent can
also be utilised which has lower energy consumption for
regeneration. This process has great potential to produce
blue hydrogen that can be used as fuel in a gas turbine
based combined cycle plant. However, technological
advancement is required to use hydrogen in gas turbines.
4. Cement Plant
4.1 Overview of Industry
The cement industry is considered one of the most
prominent contributors to global CO
2
emissions, with
around 6% of total CO
2
emissions from the stationary
sources. Typically, of that 6% around 40% of the CO
2
is
linked with fossil fuel combustion in the kiln process,
about 50% is due to the decarbonation of limestone and
the remaining 10% is associated with transportation and
handling (IEAGHG, 2008).
Portland Cement, which is the most common and
referred to as the industry standard cement, is produced
via the conversion of calcium carbonate (limestone) to
calcium oxide (lime) with CO
2
at high temperatures.
Large quantities of fuel, often fossil fuels based, are used
for the highly energy intensive reactions.
Main stages of the cement process in the plant are (See
Figure 4):
Limestone and clay are quarried, crushed, and
transported to the site. The raw materials are
stored and homogenised to ensure a consistent
end product.
The limestone and clay are milled and
combined to form the raw mix. Again,
materials are stored and homogenised to ensure
a consistent end product.
The raw mix enters the top of the pre-heater
tower, flows down through a series of cyclones,
and is heated by hot flue gas flowing up. The
last stage is a pre-calciner, fired by a pulverised
Parameter
Power Plant Fuel Type
Coal
Natural Gas
Pressure
1 Atm or slightly above
Temperature
~100°C (Dependent on heat recovery
rate)
CO
2
12% - 15% vol.
3% - 5% vol.
O
2
5% vol.
15%
N
2
~81% vol.
Sox
500 - 5000 ppm
<1 ppm
NOx
100 - 1000 ppm
100 - 500 ppm
Particulates
1000 10000 mg/m
3
10 mg/m
3
Proceedings of CUChE Alumni Symposium 2022
On Circular Economy on Sustainable Basis: The Role of Chemical Engineers
CUChEAA ISBN: 978-81-954649-1-3
December 2022 P a g e | 28 Volume 2, Issue 1
coal burner (with tertiary air), which converts
CaCO
3
in the limestone to CaO, liberating CO
2
.
The raw mix enters the rotary cement kiln,
which is fired with pulverised coal. The high
temperature and long residence time convert
solids to cement clinker
The cement clinker leaves the hot end of the
rotary kiln and is cooled with air on a moving
grate cooler
The clinker is ground and blended with gypsum
to form the cement product.
On the gas side, hot flue gas from the combustion in the
rotary kiln flows into the bottom of the pre-heater tower
and pre-calciner. Additional flue gas is generated by the
pre-calciner burner and combines with the main flue gas
flow, which flows up through the cyclone stages of the
pre-heater tower and heats up the raw mix.
The flue gas flow is split between the raw mills and fuel
mills, where it is used to heat the raw materials. After as
much useful heat as possible is recovered from the flue
gas, bag filters remove the dust, before induced draft
fans pull the flue gas into the stack.
The difficulty that comes with mitigating the CO
2
emissions created during the production of cement is that
the majority of CO
2
is released by a chemical reaction, it
cannot be eliminated by changing the fuel source or
increasing efficiency.
Figure 4: Cement Plant configuration
4.2 Characteristics of CO
2
containing stream
The concentration of CO
2
in the flue gas from cement
production ranges from 15 to 30% by volume as shown
below in Table 3 (IEAGHG, 2008).
Table 3: Typical gas composition in cement industry
flue gas stream
Component
Concentration
CO
2
15-30% (v/v)
NO
2
5-10% NOx
NOx
<200-3000
mg/Nm3
SO
2
<10-3500
mg/Nm3
O
2
8-14% (v/v)
4.3 Decarbonisation opportunities and challenges
The CO
2
concentration in the flue gas from cement
production is higher than in the power plants and post-
combustion CO
2
capture could be appropriate for cement
kilns. However, as discussed earlier, the post-
combustion process requires a large quantity of heat for
amine regeneration which is not generally available at
the cement plant.
A separate plant would be required to provide heat and
power which needs a separate post-combustion capture
as well to decarbonise the sector. Blue or green
hydrogen can be potentially used to generate heat and
power, but the technology needs to be matured to use
100% hydrogen in the gas turbine for power generation.
T
he flue gas from the cement plants contains dust and
other solid impurities, which pose additional challenges
that need to be addressed prior to the use of capture
technology. O
xyfuel combustion can be deployed in the
cement kilns, but process chemistry needs to be assessed
to understand the impacts of a high CO
2
content in the
flue gas.
5 Refinery and Global Chemical Industry
5.1 Overview of Industry
The CO
2
emissions in the refinery sector positions at the
top alongside the power sector and the cement industry.
Refineries account for approximately 4% of the global
CO
2
producers, which is estimated to be ~1 billion tons
of CO
2
annually (Jiri van Straelan, 2010).
A refinery uses approx. 2% -8% of feedstock as fuel to
generate heat and power depending upon the
configuration of the plant. A relatively large refinery
producing 300,000 barrels per day, would have annual
CO
2
emissions ranging from 0.8 4.2 million tonnes
(Jiri van Straelan, 2010).
For a typical complex refinery, the key CO
2
emission
sources (Jiri van Straelan, 2010) are shown in Table 4.
Table 4: Major CO
2
emission sources for a complex
refinery
Emission
Source
Description
Furnaces
and
Boilers
Fuel is combusted to generate heat and
steam required by distillation and
processing units and emits CO
2
Utilities
A large amount of CO
2
is produced for
the production of steam and power.
Fluidised
Catalytic
Cracker
Process of upgrading heavy hydrocarbon
to profitable products.
Hydrogen
Production
Hydrogen is required for various refining
processes such as hydrocracking,
hydrodesulphurization, and
isomerization; most refineries produce
hydrogen onsite.
Along with oil refineries, the chemical industry uses
nearly 90% of hydrogen gas produced globally in the
ammonia (about 50%) and methanol plant. Due to
tighter environmental regulations on the usage of raw
fossil fuels, hydrogen demand in the refinery and
chemical sectors is continuously increasing to meet the
Proceedings of CUChE Alumni Symposium 2022
On Circular Economy on Sustainable Basis: The Role of Chemical Engineers
CUChEAA ISBN: 978-81-954649-1-3
December 2022 P a g e | 29 Volume 2, Issue 1
energy demand. Additionally, ammonia is becoming the
energy carrier to produce green energy and it is expected
that the demand for hydrogen will further increase.
Moreover, the importance of hydrogen could increase
significantly with regard to decarbonising transport fuel
(i.e., the use of vehicles with fuel cells).
Most of the hydrogen is generated from fossil fuels
such as coal and natural gas. In the refinery, other
sources like refinery off-gases, heavy refinery residues
and petcoke are also used to produce hydrogen.
Recently, electrolysis of water using renewables source
of power is becoming a promising method to generate
green hydrogen.
5.2 Characteristics of CO
2
containing stream
In the refinery, the range of CO
2
concentration in the
flue gas varies from 4% at Cogen plant / Gas Turbine to
8 10% at the Furnaces and Boilers stacks. FCC
generates around 12% CO
2
stream while gasifier can
produce with 90% + CO
2
.
Typical stream compositions in a Hydrogen plant (SMR)
are shown in Error! Reference source not found.Table 5
.
Table 5: Hydrogen Plant Flue Gas Stream composition
5.3 Decarbonisation opportunities and challenges
CO
2
emissions at the refineries and hydrogen plants can
be minimised through different routes. Most of the new
generation hydrogen production plants are highly
efficient and achieved CO
2
emissions reduction nearly
10% above their theoretical minimum. Although energy
conservation is often the most attractive route, even the
most energy efficient refinery will continue to use a
significant amount of energy and consequently produce
a large amount of CO
2
. The route to decarbonise the
refinery sector even further would be through carbon
capture and storage.
All three routes discussed in Section 2, can be applied to
the refinery.
Oxy-combustion: Pure oxygen rather than air can be
used for combustion and the burners may be oxy-fired.
The resultant flue gas with high CO
2
concentrations will
be further treated to remove contaminants prior to
storage.
Pre-combustion capture: As refineries and chemical
industries use a large quantity of fuel, the fuel can be
converted to hydrogen and CO
2
(SMR process). The
CO
2
is removed from the hydrogen and stored to
generate blue hydrogen. This process benefits from high-
pressure CO
2
capture, which is easier to handle.
However, this will not achieve 90% of the CO
2
reduction.
Further reduction of CO
2
emissions in addition to pre-
combustion capture from hydrogen production can only
be achieved by integrating CCS to capture CO
2
from
SMR flue gas.
Gasifiers with precombustion capture can supply the
utility demand of refinery, which can decarbonise the
sector significantly.
Post-combustion capture: This can be applied to most of
the furnaces, boilers, and gas turbines for power
generation. This solution can easily be retrofitted to
existing facilities, where CO
2
can be captured from flue
gas prior to emission to atmosphere.
6. Iron and Steel Plant
6.1 Overview of Industry
The iron and steel making plant has the highest energy
consumption (8-10% of annual industry energy
consumption) (Minh T Ho, 2013) and approximately 7%
of total world CO
2
emissions (IEA, 2020) is generated
by this industry. Fossil fuels are burnt during the
production of the iron and steel making which results in
producing the greenhouse gas.
The main process steps for the steel plants are (refer to
figure 5):
Coal is converted to coke in the coke oven
Iron ore and limestone are blended and heated
in the sintering plant
The sintering plant product and coke are fed to
the blast furnaces, which produce molten iron
In the Basic Oxygen Steelmaking (BOS) plant
the molten iron is transformed into steel in
presence of oxygen
Steel is continuously cast, and steel strip
products are formed using hot and cold rolling.
The coke oven plant, blast furnace (BF), and
BOS plant each produce process off-gas. The
different off-gases vary in composition and
calorific value, so they are blended and
supplemented with natural gas to be used for
process heating and power generation.
Figure 5: Steel Plant configuration
Approximately 2.6 tonnes of CO
2
per tonne of steel
(IEA, 2020) is produced in conventional integrated steel
production. However, the CO
2
emission is much less in
Stream
Concentration (mol% - Wet
Basis)
CO
2
CO
CH
4
PSA Inlet
15.0
16
4.0
5.0
3.0
3.5
PSA Tail
Gas
45
50
14.5
15.0
8.5
9.5
SMR Flue
Gas
19
20
N/A
N/A
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the mini mill configuration (0.6-0.9 tonnes of CO
2
per
tonne of steel), which is 35% of the conventional method
of steel production. Even though the emission is less in
the mini-mill configuration, the industry prefers the
conventional method due to higher quality steel and to
avoid undesired material from scrap steel.
In the steel-making process, the maximum amount of
CO
2
is produced in the blast furnace when iron ore is
converted to molten iron. The CO
2
constitutes a major
component in the off-gas from the furnace which is
generally called blast furnace gas (BFG). CO
2
is also
produced in the coke oven (heating of coal), the sinter
plant (ore preparation), and the BOS (reduction of
carbon in steel).
6.2 Characteristics of the CO
2
containing stream
There are four major sources of CO
2
emissions from the
plant as shown in Figure 5:
Coke Ovens
Sinter Plant
Blast Furnace Stoves
Power Plant
Refer to Table 6 below for a typical summary of the
composition of these four major streams.
Table 6: Composition summary for main CO
2
emission
sources
Coke
Oven
Sinter
Plant
Blast
Furnace
/Stoves
Power
Plant
Composition, mol%
Argon
0.82
0.9
0.83
0.89
0.8
Nitrogen
64.1
70.2
64.9
69.2
64.1
Water
Vapour
9.5
8
4.4
3.8
7
Oxygen
9.6
16.7
4.2
4.4
9.1
Carbon
Dioxide
16
4.2
25.7
21.7
19
Total
100
100
100
100
100
Contaminants, mg/Nm
3
NOx
986
210
42.1
30.3
48.6
SO
2
103
380
41.7
25.0
89.2
CO
5561
6250
6250
5520
8.7
Particulates
14.9
57.1
3.8
3.1
1.3
There are also other sources of CO
2
emissions from the
plant from hot rolling and the Continuous Annealing
Process Line (CAPL). However, these are not good
candidates for carbon capture as they consist of
numerous small burners, which would make capture
very difficult.
The percentages of CO
2
emissions from each area of the
plant are demonstrated graphically in Figure 6.
6.3 Decarbonisation opportunities and challenges
Based on figure 6, there are potential opportunities exist
for the CO
2
capture from the power plant using post
combustion processes which contributes 50% of the steel
plants’ total emissions. Post-combustion CO
2
capture
technologies have the advantage of being able to be
retrofitted to existing plants without major process
integration and disruption to the existing operation.
Using pre-combustion CO
2
capture technologies,
hydrogen can be used to fuel the power plant.
Figure 6: Percentage of CO
2
emissions from integrated
iron and steel plant by area
Blast furnace gas contains around 70% of the carbon
contribution to an integrated steel mill (excluding power
generation), which is consumed as fuel gas within the
steel mill (IPCC, 2002). This typically contains 20-25%
by volume of CO
2
. The pressure of this stream is
typically 2-3 bar. The concentration of the CO
2
is
considerably higher than in the typical flue gas from the
power station, which will help reducing the energy
consumption of the capture process. Off gas from an
oxygen steel furnace (typically 70% CO and 16% CO
2
)
can also be a possible candidate for CO
2
capture. New
development on the direct reduction process for iron and
steel industry will significantly reduce CO
2
emissions by
capturing CO
2
(Kelly Thambimuthu, 2002)
7. SCORE methodology and sector-wise
decarbonisation methods
Wood has developed a decarbonisation SCORE
methodology (Wood, 2022) which provides a roadmap
to setting and delivering emissions reduction targets to
the industry. This structured process will be able to
guide how the decarbonisation goal of the organisation
will be achieved and lead to a successful outcome. The
decarbonisation SCORE methodology can be directed to
single or multiple assets. The key steps are as follows.
Substitute -substitution of fuel or feedstocks or alternate
source.
Capture use of correct CO
2
capture methods, to
reduce or eliminate greenhouse emissions to the
atmosphere. Global industries, especially, Cement, Iron,
and Steel will benefit from retrofitting the CO
2
capture
in the existing plants.
Offset - achieving decarbonisation/clean air goals by
offsetting across the sector
Reduce improving energy efficiency and reducing the
Carbon footprint.
Evaluate the right solution to maximise the
decarbonisation goal.
Proceedings of CUChE Alumni Symposium 2022
On Circular Economy on Sustainable Basis: The Role of Chemical Engineers
CUChEAA ISBN: 978-81-954649-1-3
December 2022 P a g e | 31 Volume 2, Issue 1
As discussed in sections 3 to section 6, the SCORE
methodology can be applied to decarbonise the power
and industrial sectors where the CCS plays an important
role.
8. Conclusion
The CO
2
emission can be minimised utilising the CCS
technical chain in the power sector and large energy-
consuming global industry sectors which includes iron
and steel, cement, petrochemicals production, and oil
refining. CO
2
can also be captured at the hydrogen
production unit which uses fossil fuels as feedstock. This
method of hydrogen production will provide a pathway
to launch large-scale infrastructure for use of blue
hydrogen as an energy carrier.
Using post-combustion processes, CO
2
from the flue
gases produced by the combustion of fossil fuels can be
captured using the proven technology of solvent
absorption. This technology has improved significantly
in the last few decades so that it can be used in low-
pressure applications. Novel CO
2
separation
technologies, including membranes, solid adsorbents,
and cryogenics are also being developed, which can
further enhance the decarbonisation goals.
However, decarbonisation is a complex undertaking. A
technology shift is required to move away from the
conventional approach and using novel solutions is
essential to decarbonise the industry. At the same time,
capturing CO
2
at reasonable costs has always been a
challenge in the past and this needs to be considered in
the future for successful implementation. In the 1950s-
1960s, the industry has seen a bold move to transform
energy production from coal-based feedstock to oil and
gas. A similar move is required to decarbonise the power
and industrial sectors.
Wood has developed a methodology (SCORE) that
facilitates industries’ understanding of a road map to
decarbonise. This uses substitution, capture, offsetting,
and reduction options to evaluate how best to tackle
carbon emissions. CCS plays a key role in the road to
decarbonisation.
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