Seminar 2nd Semester (New)

7/31/2019 Seminar 2nd Semester (New)

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Chapter 1

Introduction

Most of the Countries today face four basic interdependent challenges namely; increasing food

prices, non-sustainable depletion of natural resources, Climate Change and Volatile Fuel Prices.

Most of the Resources are scare and have alternate uses. For example, crops such as corn,

sunflower etc. which are traditionally used as a food crop can also be used to obtain fuel as a

substitute to fossil fuels. It is this conflict between food and fuel (food vs. fuel) that makes things

complex.

Most of the non-renewable technologies are cheap but they cause large amount of Green House

Gas (GHG) emissions. Most of the Renewable technologies on the other hand produce limited

emissions but are expensive. The objective of every country is to try to achieve an optimum

energy mix so as to reduce the GHG emissions and at the same time keep fuel and electricity

prices within a competitive range. It is for this reason that high dependence on fossil fuel based

technologies is expected to continue in the near future. As a result of increased research,

renewable technologies are expected to become cheaper and they will be incorporated in the

energy mix as and when they become competitive with fossil fuel based technologies.

.

Meanwhile, scientists have been looking into other options to reduce the overall CO2 emissions

from fossil fuel utilization while keeping the cost per unit energy output lower than that of

renewable sources at present. There are a large number of options being looked into such as

improving energy efficiencies, switching to less carbon intensive technologies, nuclear energy,

Carbon Capture and Storage (CCS) etc. Among these the most promising technology in terms of

capacity of CO2 abatement is CCS. According to IPCCs Special Report on Carbon Dioxide

Capture and Storage (2005), CCS has the potential to reduce overall mitigation costs and

increase flexibility in achieving greenhouse gas emission reductions.


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The various Carbon Capture Technologies available mainly fall into either one of these

categories, namely; Pre Combustion Capture, Post Combustion Capture and Oxy-fuel

Combustion [1]. Pre Combustion Capture is applied in the case of Gasification or Partial

Oxidation. An inherent advantage associated with Pre Combustion Capture is that the gases are

usually produced at a higher pressure and the CO2 concentration in the stream is higher than that

of simple combustion [1]. As a result, the costs associated with capture are lower and the energy

penalty to implement carbon capture is also lower than Post Combustion Capture [1]. Post

Combustion Capture is employed in case of CO2 capture from flue gases of processes. Oxy-fuel

capture technology is in demonstration phase. This technology aims at using pure Oxygen in the

combustion process [2]. A portion of flue gases is recirculated to control the flame temperatures.As a result of Oxy-fuel combustion what is produced is a concentrated stream of CO2 and H2O.

Broadly, there can be three possible pathways for CO2 storage [3]:

1. Geological and Oceanic: This includes both underground terrestrial and oceanic

0sequestration.

2. Chemical: This includes fixing of CO2 in industrial chemicals such as Methanol, urea,

inorganic and organic carbonates etc. and CO2 use in Enhanced Oil Recovery (EOR).

3. Biological: This includes CO2 sequestration in both Terrestrial Biomass and Algae.

Among these Geological Sequestration appears to have the maximum capacity for CO2

sequestration. At present, Chemical and Biological sequestration are viewed as means to

accelerate the initial uptake of Geological Sequestration by generating additional revenues [4].


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Figure 1.1 Different CO2 Storage Pathways

It is also important to note here that there are certain gaps in our understanding of Geological

Sequestration. There are certain apprehensions among the scientific community regarding the

side effects of Geological Sequestration such as induced seismic activity, contamination of

underground water and possible leakages [5]. This knowledge gap is expected to fill as our

practical experience with Geological Sequestration increases. Besides, Geological Sequestration

is an expensive technology. Unless a Carbon Tax is levied there isnt any financial incentive for

companies to go for Geological Sequestration. The other two pathways, i.e. Chemical and

Biological, are expected to generate some additional revenue and alternate energy sources that

can help increase the uptake of Geological Sequestration in its initial stages [4].

Chemical Storage basically aims at reuse of the CO2 to form industrial products. Different

products have different lifetimes, for example if we use the CO2 to form urea then as and when

the urea is put to use the CO2 would be released back into the atmosphere. Hence, people have

been proposing some closed carbon loops in which the CO2 can be fixed to form a particular

chemical and then when upon usage these chemical release CO2, the CO2 can be collected and

pumped back into the loop to produce the same or an alternate chemical [6]. Another possible

utilization route for CO2 can be to produce chemicals like carbonates which can fix the CO2 for a

long period of time.

CO2 Storage Pathways

BiologicalChemicalGeological and Oceanic


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Biological Sequestration aims at sequestering CO2 by biological means such as in terrestrial

biomass (Forests, Grasslands etc.) or oceanic biomass (Algae etc.). Terrestrial biomass, mainly

due to their low rate of CO2 fixation, requires a larger area to sequester a unit weight of CO2.

Chapter 2 looks into what are the processes that have a major share in anthropological CO2

emissions. It also looks into what are the different CO2 capture technologies available.

Chapter 3 looks into the various industrial CO2 reuse options available. It also looks into their

relative capacities for CO2 Storage.

Chapter 4 looks into the relative potential of Terrestrial Biomass sequestration and Algae based

sequestration by taking a 900 tonne per day Ammonia plant as case study.Chapter 5 enlists major conclusions from this study


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Chapter 2

Major CO2 Sources and Capture technologies

2.1 Major CO2 Sources:

The major CO2 sources are Power Plants, Cement manufacturing plants and Refineries. A list of

various CO2 sources and their relative share in total CO2 emissions is listed in Table 2.1:

Table 2.1 Major CO2 emitting Processes and their share in total anthropogenic emissions as of2005(Reprinted from [1])

An important characteristic of flue gas streams which affects the capture cost is its CO2

concentration. Higher the CO2 concentration lower is the capture cost [4]. Table 2.2 enlists

various sources and their respective CO2 concentration.


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Table 2.2 CO2 concentration in the flue gases from different sources (Source: [1])

Source

CO2 Concentration (%)

(Approximate)

Power Station Flue Gas:

Coal Fired Boiler 14

Natural Gas Fired Boiler 8

Natural Gas Combined Cycle 4

Coal-Oxygen Combustion >80

Power Station Pre-Combustion capture

of CO2:

Coal Gasification Fuel Gas 40

Natural Gas Partial Oxidation Fuel Gas 24

Blast Furnace Gas:

Before Combustion 20

After Combustion 27

Cement Kiln Off-Gas 14-33

Oil Refinery and Petrochemical

Plant Fired Heaters 8

2.2 CO2 Capture Technologies

There are primarily three Carbon dioxide capture technologies:

Post Combustion Capture: This technique is employed when sequestering CO2 from

diluted flue gases from combustion processes. The flue gasses are generally at low


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pressures. The concentration of CO2 in the flue gasses generally ranges from about 4%

(volume %) for natural gas fired plants to 14% (volume %) for pulverised coal fired

plants [7]. The problem with dilute CO2 streams is that if we sequester them without first

concentrating them with CO2, the gasses would occupy large volumes and since our

storage capacity is limited, it would limit the maximum amount of CO2 that we can store.

Besides compressing dilute flue gas stream implies higher capture cost and an increase in

energy penalty. Similarly, if the gases are at lower pressures the size of the equipment

would have to be large implying an increase in costs [7].

Amine solutions (MEA, DEA etc.) are used to absorb CO2 from the flue gases. The

Amine solution is later heated with the help of steam in order to regenerate the aminesolution and get a highly concentrated CO2 stream. This regeneration process is highly

energy intensive [7]. Figure 2.1 depicts this technology when applied to a Gas turbine

combined cycle.

Figure 2.1 Gas turbine combined cycle with post-combustion capture of CO2 (Reprinted

From [7])


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Pre Combustion Capture: This technique involves partial oxidation/gasification of

fossil fuels producing a stream which is predominantly CO, N2and H2. The CO is

generally converted to CO2 in what is called a Shift Reactor. As a result the stream

becomes highly concentrated in CO2 and is generally at high pressures implying lower

equipment costs. It also allows use of Physical solvents rather than chemical solvents

implying that a mere pressure reduction and slight heating is all that is necessary to

regenerate the solvent. At present, this technology is already employed in various

ammonia manufacturing and coal, petcoke gasification plants Figure 2.2 depicts the

technology in a Coal fired IGCC plant.

Figure 2.2 Coal fired IGCC with pre-combustion capture of CO2 (Reprinted From [7])

Oxy-fuel Combustion: The dilution of the flue gas stream is primarily caused due to the

large amount of N2 that comes from air. If oxygen is used instead of air, the flue gas will

primarily consist of CO2, H20 and excess Oxygen. The flame temperature would be

higher. In order to control the flame temperature a part of the flue gases is recycled. CO2

concentration in flue gases reaches up-to 80% [4] thereby making CO2 capture


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economical. Another advantage associated with Oxy-fuel combustion is that NOx

emissions are suppressed mainly due to the absence of nitrogen. A major disadvantage

associated with Oxy-fuel combustion is that the generation of pure oxygen through an Air

Separation Unit (ASU) is an expensive process both in terms of capital costs and

operating costs [7].

Figure 2.3 Oxy-Fuel Capture based CCS (Reprinted From [2])

Tables 2.3 and 2.4 shows the energy penalties imposed as a result of Post Combustion and Pre

Combustion capture. As is evident, the energy penalties imposed in the case of Post Combustion

Capture are greater than that for Pre Combustion Capture.

Table 2.3 Post Combustion Capture penalty (Pulverized Coal Fired Power Plant)

(Reprinted from [7])

Table 2.4 Pre Combustion Capture Penalty (Coal Fired IGCC Plant)



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Chapter 3

Chemical Storage

3.1 Industrial use of CO2:

3.1.1 Differentiation between Captive and Non-Captive uses [4]

Captive uses refer to processes in which CO2 is an intermediate product in the process. For

example, use of CO2 in Methanol and Urea manufacturing. Non Captive uses refer to processeswhose demand of CO2 is to be met by an external source.

Some people find this differentiation necessary because captive uses dont provide an

opportunity to store CO2 that is being emitted by large sources such as Power Plants [4].

Figure 3.1 Annual US CO2 utilization (Captive + Non-Captive uses) in 1989



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Figure 3.2 Approximate proportion of current CO2 demand by end use (Worldwide, non-Captive

uses only)


Considering only the non-captive uses, the total demand for CO2 (reuse) amounts to 80 MMT /yr

[4]. Enhanced Oil Recovery (EOR) accounts for nearly 50 MMT/yr of the total demand. Of this

50 MMT/yr about 40 MMT/yr is met by natural CO2 reservoirs [4]. This is because the cost of

bulk CO2 in market is higher than what they have to incur by extracting CO2 from natural

reservoirs. The price of bulk CO2 is expected to decrease on introduction of carbon tax [4]. As

discussed earlier the CO2 sources may be divided in two broad categories based on the

concentration of CO2 in the stream they produce. Sources such as Natural Gas processing plants,

Fertiliser plants and IGCC plants produce a stream that is concentrated with CO 2. The bulk price

of such streams varies in the range of US$ 15-19/tonne [4]. While, on the other hand sources

such as Pulverized Coal Power Plants produce a stream that is diluted with nitrogen and is

generally at low pressures. If it is assumed that the plant supplying this stream processes it to

bring it at par with its concentrated counterpart, the cost of the stream would rise to be

US$>50/tonne [4].


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Presently, it has been estimated that about 500 MMT/yr supply of the concentrated stream exits,

while, an additional 18000 MMT/yr is supplied in the form of dilute stream [4].

3.1.2. Thermodynamic Stability of CO2:

Table 3.1 enlists the Gibbs free energy of formation of CO2 and certain other carbon containing

compounds. Such a table can help us to identify which product could be formed more easily

from CO2.

Table 3.1 Gibbs free energy of formation, G0for CO2 and other chemicals

(Reprinted from: [7])

An important inference which we can draw from the Table 3.1 is that CO2 is more stable than

most of the other carbon containing compounds. Only organic carbonates (DMC) and inorganic

carbonates (MgCO3 and CaCO3) are more stable than CO2.Hence an ideal choice for chemically

storing CO2 would be to produce organic and inorganic carbonates which are relatively more

stable than CO2. Another appealing characteristic of carbonates is that the transformation of CO2


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to carbonates is an exothermic process thereby any additional energy input by burning of fossil

fuels to propel the conversion is avoided, hence ensuring maximum CO2 sequestration.

Another important aspect of chemical storage of CO2 is that the chemicals should have

substantial shelf life, for example polymers and inorganic carbonates. Chemical such as Urea and

Methanol generally have a low shelf life. They are able to store the fixed CO 2 only for small

durations. They release the fixed CO2 as soon as they are put to use.

To produce chemicals less stable than CO2 we must ensure that the energy input that we give to

facilitate the conversion must cause lesser emissions than what we fix. Smith and Thambimuthu

[6] proposed a simple carbon free energy cycle for CO2 utilization (Figure 3.3).

Power Plant /

Other CO2 Source

Non Fossil Energy

Synthesis

Fuel Utilization

Energy

Fuel

Electricity

CO2

CO2 Chemicals

(Typically

having large

shelf life)

A CO2 based

Secondary

Energy Cycle

Energy

Figure 3.3 A CO2 based secondary energy cycle (Source: [6])


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Such a cycle can be used to produce chemicals having higher Gibbs free energy than CO2. For

maximum net sequestration of CO2 the energy input to this process needs to be from a renewable

source. This cycle essentially mimics the natural carbon cycle in the nature through which

atmospheric CO2 is fixed by the means of photosynthesis. The only limitation to this cycle is in

the case of production of chemical having low shelf life. In such a case, once the chemicals are

put to use they would release the CO2 that had been sequestered during their manufacturing,

while the CO2 sources, primarily Power Plants (as they are the largest CO2 emitters), would

continue to emit CO2. Hence, until and unless the chemicals have large shelf life (as in the case

of CO2 based polymers or carbonates) there wont be much contribution to net CO2

sequestration.

In order to avoid the limitation associated with the cycle proposed by Smith and Thambimuthu

some people [9, 10] have worked on what is called a Carbon neutral secondary energy cycle.

They have proposed the use of CO2 to produce fuels such as Methane and Methanol as per

reactions (1) and (2). In fact the recently proposed Methanol Economy is also based on similar

concept. This energy needed for this conversiom is to be supplied from renewable sources.

Figure 3.4 shows such a cycle.

CO2 + 4H2 CH4 + 2H2O Go298 = 113.6 kJ/mol (3.1)

CO2 + 3H2 CH3OH + H2O Go298 = 3.9 kJ/mol (3.2)


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Figure 3.4 A comprehensive CO2 and secondary energy utilization strategy

(Reprinted From [7])

3.1.3. CO2 reuse technologies:

Some of the reuse technologies that are important in terms of their CO2 storage potential* are

listed below:

Enhanced Oil Recovery (EOR):

Overview:

After the limit of primary production from a well is reached, EOR is used to further

increase the oil yield by 7-23 % [4]. EOR requires CO2 at high pressures to be pumped

into the oil well. At high pressures CO2 is miscible in Oil, resulting in oil swelling and

reduction in its viscosity, thereby facilitating its recovery.

* Please Note that we have discussed only non-captive uses of CO2 in this section


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Technology Status:

CO2 was first used in EOR in the early 1970s in Texas, USA. Hence, this technology can

be considered as mature.

CO2 Storage Potential:

Site specific but typical value: 0.5 t CO2/barrel of Crude [4]. A study recently noted that

at least 8 billion tonnes of CO2 could be sequestered in the US by using EOR [11].

CO2 Sources:

EOR needs concentrated CO2 stream. Current demand of CO2 for EOR in USA is 50

MMT/yr, of which 40 MMT/yr is supplied via naturally occurring CO2 reservoirs (Price:

US$ 15-19/tonne).

Benefits:

Increased Crude Oil recovery.

Barriers:

High CAPEX and OPEX costs and uncertainties over long term Oil prices are some of

the barriers to large scale CO2 propelled EOR [4].

Urea yield boosting in case of Ammonia production from SMR:Overview:

Natural Gas based Urea plants usually produce 5-10% surplus Ammonia. This excess

Ammonia can be reacted with non-captive CO2 in order to boost the yield of Urea [4].

Technology Status:

Urea manufacturing from Ammonia and CO2 is a mature technology with most of the

Urea in the world being manufactured through this technology.


0.73 t CO2/ tonne Urea. Typical Plant size: 100-400 tpd CO2 [4].

CO2 Sources:

CO2 from reformer flue gases in an SMR plant can be used as a feedstock for Urea yield

boosting [4].


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Benefits:

Mainly because of the mature state of CO2 to Urea technology, it is one of the few

technologies which can be used presently to generate revenue without much investment

required in R&D.

Barriers:

The decision to convert Ammonia to Urea depends upon the relative prices of Ammonia

and Urea. Though the fertiliser industry in India is regulated but worldwide there are

countries where the volatility in prices of Ammonia and Urea poses the biggest barrier in

implementation of this technology [4].

CO2 as a working fluid for Enhanced Geothermal Systems (EGS):

Overview:

In this technology supercritical CO2 is used as a heat transfer fluid.

Technology Status:

There are some Pilot plants are either in operation or development in Australia, USA and

Germany[4].


The storage potential is site specific. Typical Value: 24 t CO2/day/ MWe [4]

CO2 Sources:

Dry concentrated CO2 stream is needed for enhanced EGS.

Benefits:

Minimised water usage.

Barriers:

Remains to be proved at a large scale.

CO2 has lower specific heat than water, resulting in a higher flow rate

requirement for same amount of heat transferred.

Storage Capacity of CO2 varies to a large extent from site to site.

There are also uncertainties regarding long term storage of CO2.


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Polymer processing:

Overview:

Traditionally, polymers have been made from petroleum derivatives such as ethylene,

propylene etc. A new approach to polymer processing being looked into these days is to

use CO2 along with traditional feedstocks. Polycarbonates are produced by combining

CO2 with epoxides over a Zinc based catalyst system. The epoxide can be changed in

order to affect the properties of the end product. Typical polycarbonates include Poly-

Propylene Carbonate (PPC) and Poly-Ethylene Carbonate (PEC).

Technology Status:

Novomer Ltd. has been operating a Pilot batch plant at Kodak Speciality Chemicalsfacility in Rochester, NY. They are also looking into developing a continuous plant in

order to reduce production costs. The CO2 based polymers made by Novomer are being

tested and they have been found to be comparable and sometimes even superior to

traditional polymers [4].


Typical Storage potention 0.5 t CO2/ tonne product [4]

Benefits:

High CO2 storage capacity and comparable (sometimes even superior) properties with

respect to traditional petroleum based polymers are some of the advantages associated

with CO2 based Polymers.

Barriers:

Technology still at demonstration phase.

Since the Polycarbonates are aliphatic, they could degrade in as short a period

as 6 months and release the CO2 that has been fixed during their

manufacturing [4].

The cost of the final product needs to be lowered to make it competitive with

traditional polymers.


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Inorganic Carbonate Mineralisation:

Overview:

For long term CO2 storage we can store it in the form of inorganic carbonates by reacting

it with Alkali and Alkali-earth metal oxides that are normally found in naturally

occurring silicate rocks such as serpentine, forsterite, periclase and olivine. This

carbonation of oxides occurs naturally in nature but at a very slow pace. Presently,

research is focussed on accelerating this rate. Besides silicate rocks, people have also

been looking into using industrial waste streams.

Calera Corporation has developed a process in which they contact flue gases with water

and solid oxides in an absorber. Mineral Carbonates which precipitate out are separatedand dewatered. Supplementary Cementitious materials (SCM), aggregate and other

building related materials are produced by this process. They have also developed a novel

low voltage technology known as Alkalinity Based on Low Energy(ABLE) to generate

the required alkalinity [12].

Skyonic have also developed a technology which they call Skemine. Skymine

technology also removes CO2 from industrial waste streams and produces solid carbonate

and/or bicarbonates [13].

Technology Status:

Calera Corporation is operating a continuous pilot scale plant in Moss Landing,

California with a capacity of 5t/day of Supplementary Cementitious Material (SCM).

Another demonstration plant is also under construction. Calera is also constructing a pilot

plant based on its proprietary technology ABLE [4].


0.5 tonne CO2/ tonne Carbonate formed [4]

CO2 Sources:

Moderately concentrated stream of CO2 is required for this process.


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Benefits:

Utilisation of waste stream, ability of the technology to work on moderately concentrated

CO2 stream and the ability to capture other emissions such SO2 and heavy metals are

some of the advantages of Caleras Process.

Barriers:

Not every silicate reserve can be used for this process.

Environmental emissions caused by mining of Silicate materials.

Carbonation Technology is still in research phase.

CO2 as a feedstock for liquid fuel production:

Overview:

CO2 is also being looked at as a future source of liquid fuels such as Methanol and

Formic Acid. As can be seen from Table 3.1 some amount of energy would be needed to

perform this conversion. These processes generally have low efficiencies; its for this

reason that the energy input required for the process should come from a renewable

source.

Technology Status:

Carbon Recycling International (CRI), Finland is developing a commercial plant to

produce renewable methane from CO2. Another company Mantra Venture Group

(Mantra), USA is in negotiations for building first commercial plant based on producing

formic acid from CO2 [4].


1.375 t CO2/ t Methanol and 0.95 t CO2/ t Formic Acid.

CO2 Sources:

Concentrated CO2 stream is required.

Benefits:

Methanol can be used as an energy carrier.

The use of existing petroleum based infrastructure is a benefit of CO2 to liquid fuels

approach.


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Barriers:

Low efficiency and high capital costs.

Most of the technologies are costlier than their petroleum based counterparts.

CO2 as a feedstock for Di-Methyl Carbonate (DMC):

Overview:

Traditionally, DMC has been manufactured from phosgene but amidst recent safety

concerns over its use people have started looking at Carbon monoxide and Carbon

dioxide as alternative feedstocks for DMC. DMC is primarily used as a solvent and motor

fuel octane booster.


0.5 t CO2/ t DMC.

CO2 Sources:


Benefits:

Safety issues associated with phosgene can be avoided.

Life Cycle Analysis (LCA) of DMC manufacturing process via phosgene and

CO2 have shown that the phosgene route has an environment impact four

times that of CO2 pathway [7].

Barriers:

Low shelf life

CO2 use for Bauxite Residue Carbonation:

Overview:

Bauxite to Alumina conversion results in the formation of a highly alkaline (pH=13)

bauxite residue slurry (red mud). Red mud is usually a mixture of minerals and some

alkaline liquor (NaOH) from Bayer extraction process. This slurry is carbonated with the

help of CO2 thereby reducing the pH to about 10 and making its disposal easier [4].


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Technology Status:

Alcoa Ltd. has been operating a trial plant based upon this technology for the last seven

years. Its patents over the technology have ended [4].


The CO2 storage capacity of untreated Red Mud is approximately 35kg of CO 2/tonne of

Red Mud (dry). If the residue is treated with sea water its storage capacity increase to 750

kg CO2/ tonne of Red Mud [4].

CO2 Sources:


Benefits:Due to the process of carbonation the pH of the Red Mud drops from 13 to 10 which

make its disposal easier and cheaper.

Barriers:

Low Storage capacity.

3.1.3.1. Differentiation between processes based on their feedstock quality and the nature

of CO2 storage:

Figure 3.5 Segregation of various CO2 reuse technologies based on their CO2feedstock stream

(Source: [4])

Process Requiring Concentrated CO2 Stream

Enhanced Oil Recovery (EOR)

Urea Yield Boosting

Polymer Processing

Bauxite Residue Carbonation

Renewable Methanol

Formic Acid

Process Requiring Dilute CO2 Stream

Algae Cultivation

Mineral Carbonation

Terrestrial Biomass Sequestration


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Figure 3.6 An overview of various CO2 reuse technologies



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3.1.4. Current and Future potential demand of potential CO2 uses:

Table 3.2 Current and Future potential demand of potential CO2 uses (Reprinted from [4]):

Presently most of the CO2 demand is from EOR. A report recently published by Global CCS

institute has projected the potential demand from emerging uses (discussed above) in the future.

The data from the report is shown in Table 3.3. Processes such as Inorganic Mineralisation, CO2


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to liquid fuels (Methanol and Formic Acid) and Algae Cultivation are expected to contribute

significantly to the demand for CO2 in the future.

Table 3.3 Future potential CO2demand from emerging uses (Reprinted from [4]):

Considering the fact that Power Plants (dilute sources) are the major emitters of CO2 we may

have to either enrich the flue gases in CO2 or shift to IGCC in order to produce a concentrated

stream so that it may be utilised in EOR, CO2 to liquid process which are expected to have

significant demand for CO2 in the future.


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Table 4.1 CO2 storage by Terrestrial Biomass

Sample Calculations for a Ammonia plant based on Coal (Lignite) gasification:

Capacity of Ammonia Plant: 900 TPDCarbon-di-Oxide

Emissions: 600000

TPY

(Approximate) OR 1643.836 TPD

Carbon Mass to

be Sequestered: 163636.4 TPY OR 163.6364 ktC/yr

A B C D F

Total Carbon

Uptake

Increment

(kt C)

Carbon

Fraction

of Dry Matter

Annual

Biomass

Increment

(kt dm)

C=(A/B)

Annual

Growth

Rate [14]

(t dm/ha)

Area of

Biomass Stocks

(kha)

F=(C/D)

Acacia (Tropical

Plantations)163.64 0.5 327.27 15 21.818182

The area required comes out to be equivalent to ~92 times the area of IIT Bombay.

A similar set of calculations were done for Algae. The results are shown in Table 4.2.

Table 4.2 CO2 Storage potential of Algae

Typical CO2 Fixation by Algae: 1.8 tCO2/t dry algal biomass [15]

Algal Growth Rate: 98 g/m2/day [15]

Assuming, that Algae is Harvested as soon as it achieves maturity:

Area Required to sequester all CO2 from this particular Plant: 9318796 m2 OR 2302.72 acre

The area required comes out to be equivalent to ~4 times the area of IIT Bombay.


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Conclusions

During the transition from fossil to renewable energy powered world, Carbon Capture and

Storage (CCS) appears to have great potential to reduce the present level of emissions while at

the same time keeping the energy costs within a competitive range.

The different technologies available for carbon capture were looked into and Pre Combustion

capture appeared to be the most promising one.

Among the three possible pathways for CCS, Geological Sequestration appears to be the mostpromising one. But during its initial stages of deployment scientists are looking for means that

could generate some additional revenues which could in turn accelerate the uptake of Geological

Sequestration. The other two pathways, i.e. Chemical and Biological Storage, seem to do just

that.

Enhanced Oil Recovery (EOR) has the largest share in CO2 reuse at present. But, at present, it

meets about 80% of its requirement through natural CO2 reservoirs. Most of the other CO2 reuse

technologies, expected to have significant demand for CO2 in future, are in either research or

demonstration phase. Hence, in the near future EOR is expected to play a major role in storing

CO2 while generating extra revenues. There are certain other technologies like inorganic

carbonate mineralisation and CO2 conversion to liquid fuels (Methanol and Formic Acid) that are

expected to have substantial demand for CO2 in the future. Based on the specifications of the

CO2 feed stream (concentrated or diluted with N2) the different technologies were divided into

two categories. Also, based on the nature of CO2 storage (permanent or temporary) the

technologies were segregated. For temporary storage of CO2 people have proposed some closed

cycles in which the CO2 is converted into liquid fuels with the help of some renewable form of

energy. The CO2 formed during their use is again recycled to be converted into liquid fuels.


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Among the two Biological storage routes (i.e. Terrestrial Biomass and Algal Storage) available

Algal storage seems to be more promising mainly because it requires ~25 times less area than

what is required for Terrestrial Biomass sequestration. This is mainly because of the enormous

growth rates of Algae.


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References

1. IPCC, 2005:IPCC Special Report on Carbon Dioxide Capture and Storage. Prepared byWorking Group III of the Intergovernmental Panel on Climate Change [Metz, B., O.Davidson, H. C. de Coninck, M. Loos, and L. A. Meyer (eds.)]. Cambridge UniversityPress, Cambridge, United Kingdom and New York, NY, USA, 442 pp*.

2. Scottish Carbon Capture and Storage, Oxy-Fuel Combustion Capture,http://www.geos.ed.ac.uk/sccs/capture/oxyfuel.html, April 10, 2012.

3. Muhs J. et al., A Summary of Opportunities, Challenges and Research Needs-Algae Biofuels & Carbon Recycling, Utah State University, May 2009.

4. Global CCS Institute and Parsons Brinckerhoff,Accelerating the uptake of CCS:Industrial Use of Captured Carbon Dioxide, Global CCS Institute and ParsonsBrinckerhoff, March 2011.

5. Katzer J et al., The Future of Coal, Massachusetts Institute of Technology, 2007.

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8. IEA Working Party on Fossil Fuels Task force on Zero Emissions Technology Strategy,Challenges for large-scale CO2 Utilization and Sequestration, IEA WPFF, March 2002.

9. Aresta, M, Perspective of carbon dioxide utilization in the synthesis of chemicals:Coupling chemistry and biotechnology,Advances in Chemical Conversions forMitigating Carbon Dioxide, Elsevier Science B.V., 114, 65-76., 1998

10. Arakawa, H., Research and development on new synthetic routes for basic chemicals bycatalytic hydrogenation of CO,Advances in Chemical Conversions for MitigatingCarbon Dioxide, Elsevier Science B.V., 114, 19-30, 1998

11. World Resources institute, CO2-Enhanced Oil Recovery,http://www.wri.org/publication/content/8355, April 10, 2012.

12. Calera Corporation, The Science: Carbonate Formation,http://calera.com/index.php/technology/the_science , April 10, 2012.

*The Format of the reference is in accordance with the authors request.


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13. Skyonic Limited, The Skymine Process, http://skyonic.com/skymine/, April 10, 2012.

14. IPCCs Task Force on National Greenhouse Gas Inventories,Revised 1996 IPCC

Guidelines for National Greenhouse Gas Inventories, 1996

15. Sun S. and Hobbs R., Power Plant Emissions to biofuels, Arizona Public Service, DE-FC26-06NT42759, 2008.

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