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CIVE40010 - Energy and environmental engineering > Carbon Capture and Storage > Flashcards

Carbon Capture and Storage Flashcards

1
Q

What is CCS?

A
  • Power plant
  • CO2 can be captured from a process or the atmosphere and permanently stored geologically
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2
Q

What is required for CCS?

A
  • Transport to transfer it to the site
  • A suitable injecting site
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3
Q

Why do we need CCS?

A
  • Oil and gas will reach a plateau
  • Coal consumption projected to drop by 60% in 2050
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4
Q

What will remain a major source of energy globally?

A

Fossil fuels

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5
Q

What sectors are the major contributors to emissions?

A
  • Electricity and heat
  • Aviation and shipping
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6
Q

How much CO2 does the IEA say has to be sequestered?

A

120 Gt CO2 by 2050

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7
Q

How much CCs do we have?

A

About 50 MtCO2/a operational

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8
Q

How much CCS do we have in various stages of development?

A

About 310 MtCO2/a

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9
Q

What is conventional combustion?

A
  • You have a mix of hydrocarbon and air and when combusted will result in flue gas
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10
Q

What does the combustion of hydrocarbon and air generate?

A

Hydrogen and CO2

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11
Q

What is post combustion capture?

A

Uses a solvent to capture CO2 from the flue gas of power plants

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12
Q

Describe steps of post combustion capture?

A
  • Separate your flue gas
  • Will have a pure CO2 stream and clean flue gas
  • Then separate CO2 and nitrogen
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13
Q

What is pre combustion capture?

A
  • Avoids have CO2 gas in the flue gas in the first place
  • aka clean combustion
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14
Q

What does pre combustion capture convert the fuel into?

A

Hydrogen with steam and oxygen

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15
Q

What is oxy-fuel combustion?

A

Where the separation is done before the combustion
- Separate air into nitrogen and oxygen and combust fuel with pure oxygen

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16
Q

What stage is the concept stage?

A

TRL1

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17
Q

Which technology readiness levels prose the most challenges?

A

TRL3, TRL6 and TRL7

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18
Q

What category is TRL9?

A

Commercial

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19
Q

When was post-combustion first patented?

A

1930

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20
Q

How do the solvent and CO2 interact in post-combustion?

A
  • Solvent absorbs CO2 to regenerate solvent and this is heated up so CO2 boils out
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21
Q

Why type of energy is used for the solvent regeneration in post-combustion?

A

Parasitic energy

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22
Q

What is beneficial about the post-combustion technology?

A
  • Retrofittable
  • CCS can be installed after
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23
Q

What pressures is post-combustion done at?

A

1- 2 bar_a

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24
Q

Where has there been commercial deployment of post-combustion plants?

A
  • Boundary Dam, Canada
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25
Q

How much did the boundary dam in Canada cost?

A

£840 M

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26
Q

At what temperatures do amines degrade?

A

120˚C -140˚C

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27
Q

When is solvent susceptible to chemical degradation?

A

Susceptible to chemical degradation in O2, SO2, CO2, high temperatures

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28
Q

Why are degradation products bad?

A

Degradation products could present health risks, need to be monitored → cancer

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29
Q

What was the measured amine loss from the first pilot plant?

A

≈ 0.35 - 2.0 kg solvent/tCO2

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30
Q

What are the disadvantages post-combustion?

A
  • High CapEx - large gas volumes → large equipment
  • Parasitic energy ➔ reduced plant efficiency
  • Solvent losses & solvent disposal
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31
Q

What is the process of post-combustion capture?

A
  1. Adhesion of species/molecules to a solid surface
  2. Porous solids are used in a cyclic process to
    separate gas mixtures
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32
Q

What research focus is typically associated with sorbent regeneration for CO2 capture?

A

Vacuum Swing Adsorption (VSA) due to fast cycle times and greater throughput

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33
Q

Why has Temperature Swing Adsorption (TSA) not been traditionally considered for sorbent regeneration?

A

Due to longer cycle times of more than 6-12 hours

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34
Q

How does TSA compare to VSA in terms of CO2 recovery?

A

TSA offers better CO2 recovery compared to VSA

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35
Q

What does the degree of absorption of COP2 depend on?

A

Pressure concentration and temperature

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36
Q

What are the key features of rotary absorbers in commercial applications?

A
  • Laminated gas channels with adsorbent coated on laminations
  • negligible pressure drop
  • higher gas throughput
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37
Q

How does the rotary absorber function to increase efficiency?

A

By putting material on a rotary wheel and rotating the wheel about one revolution per minute

38
Q

What is the purpose of exposing the other half of the rotary wheel to steam?

A

To heat the solvent for enhanced performance

39
Q

What are the advantages of post combustion capture?

A
  • Retrofittable
  • Range of operating conditions, many potential materials available
  • Particularly well suited for low concentrations ➔ direct air capture
  • Potentially cheaper and more environmentally friendly than amine absorption
40
Q

What are the disadvantages of post combustion capture?

A
  • Challenging material selection
  • Need for cyclic processes
  • Energy requirements to generate vacuum
  • So far only used for small volumes, expensive to scale up
41
Q

How does the process of pre-combustion CO2 capture work?

A
  • Take a fuel like coal, gas or biomass
  • React with steam and oxygen
  • CO2 is separated from
    The first part of the process is identical to the conventional H2 production process
42
Q

What happens when steam and oxygen react in pre-combustion capture?

A
  • Syngas proudced
43
Q

What happens when syngas is reacted?

A

CO2 and H2 produced

44
Q

What are the CO2 capture options in pre-combustion?

A
  • Pressure swing adsorption
  • Cryogenic separation
  • Physical absorption
  • Chemical absorption
45
Q

When was pre-combustion first employed?

A

1966

46
Q

What is the basis of cryogenic separation in pre-combustion capture?

A

It’s fundamentally based on the different boiling and condensation points of species

47
Q

What are the boiling points of CO2, CO, and H2 at 7 bar_a?

A

CO2: -50 °C, CO: -170 °C, H2: -244 °C

48
Q

Why is cryogenic separation not economically feasible if CO2 content in syngas is less than 40%mol?

A

Because it requires a significant amount of energy to cool the gas stream down

49
Q

What are the advantages of pre-combustion?

A
  • Uses processes that are already commercially used
  • Lower energy penalty than post-combustion capture
  • Overall hydrogen production process can be very efficient (60 – 65%) – does not include efficiency of power plant!
50
Q

What are the disadvantages of pre-combustion?

A
  • High CapEx - high cost
  • Complex process – low flexibility
  • No commercial scale demonstration of pre-combustion capture for power generation
51
Q

What takes place in oxyfuel combustion?

A
  • O2 separated from air
  • Fuel is combusted in pure oxygen
  • Flue gas (ideally) only contains H2O and CO2
  • H2O can be condensed
  • No further separation of CO2 is required
52
Q

What is the most sensible method for air separation to produce O2 and why?

A

Cryogenic distillation, due to its maturity, very high capacity and purity, though it has high energy requirements

53
Q

Why is vacuum swing adsorption not suitable for high capacities in air separation?

A

While mature and capable of producing high purity O2, its capacity is medium, and it cannot achieve very high capacities

54
Q

What are the characteristics of membrane technology for air separation?

A

High purity, very low capacity

55
Q

Why is cryogenic air separation considered expensive?

A

Due to its high energy requirements

56
Q

Where do cement emissions come from?

A

2/3 form limestone

57
Q

How can gas turbine CCS technology be applied to cement production?

A

It can be applied to the flue gas from the furnace to capture CO2

58
Q

How is CO2 transported?

A

Pipelines and ships

59
Q

What are examples of small scale CCS?

A

trucks, rail

60
Q

Under what conditions is CO2 transported?

A

100 bar, 30˚C or liquified

61
Q

What is CO2 storage reattach based on?

A
  • Site characterization
    – Plume migration
    – Managing risks of leaking
    – Detecting leaks with certainty
62
Q

How much of properly stored CO2 will remain over 10,000 years?

A

> 98%

63
Q

Why might CCS processes emit more CO2 than they capture?

A

Due to the emissions associated with the additional energy required to operate the CCS technology

64
Q

What is the difference between Captured CO2 and Avoided CO2?

A

Captured CO2 refers to the gross amount of CO2 captured, whereas Avoided CO2 refers to the net CO2 after accounting for the emissions from CCS operations

65
Q

What factors impact the cost of CCS?

A
  • Location in the world
  • Technology
  • Labour
  • Commercial
  • Capture process
  • Transport
  • Storage
66
Q

What does the learning curve show?

A

Costs will reduce over time as more plants are built

67
Q

Whats the most expensive thing to do in the whole CCS process?

A

Most expensive thing to do is build the first commercial plant

68
Q

How does cost change with concentration of CO2?

A

It becomes more expensive to separate a more dilute stream

69
Q

How much CO2 present in air?

A

0.0004%mol

70
Q

What does net negative mean?

A

Net negative is removing more CO_2 from the atmosphere than you emit

71
Q

What is Biochar in the context of GGR technologies?

A

Biochar involves harvesting a tree, converting it into charcoal to trap CO2, and then burying the charcoal in soil or the ground

72
Q

How does Direct Air Capture (DAC) work for removing CO2?

A

DAC technology captures CO2 directly from the atmosphere by using a chemical agent, like amine, to absorb CO2, which is then removed and stored permanently

73
Q

What is Ocean Fertilization as a GGR method?

A

Ocean fertilization aims to increase algae growth in the ocean, which in turn captures and stores CO2 in biomass

74
Q

What is BECCS?

A

A feasible technology that combines bioenergy production from biomass with carbon capture and storage to reduce atmospheric CO2

75
Q

What are important considerations for BECCS deployment?

A

Social aspects and acceptance, ensuring the technology is welcomed and supported by communities

76
Q

What is the purpose of life cycle analysis in BECCS?

A

To calculate net carbon removals by accounting for all emissions associated with the process, ensuring a genuine reduction in atmospheric CO2

77
Q

Is BECCS 100% efficient in capturing and storing CO2?

A

No, it is not 100% efficient, indicating that some emissions may still be released or not all CO2 generated is captured

78
Q

How can CO2 capture be utilised?

A
  • EOR
  • Chemicals
  • Plastics
  • Food/beverage
79
Q

What are the disadvantages and advantages of DACCS?

A
  • Lower land requirement
  • Higher social acceptance
  • Energy consumer
  • Very expensive
80
Q

What are the disadvantages and advantages of BECCS?

A
  • Higher land requirement
  • Lower social expectance
  • Energy producer
  • Cheaper
81
Q

What does performance of plants depend on?

A

Where you are in the world

82
Q

What is DACCS?

A

DAC reduces the carbon dioxide concentration in the atmosphere as a whole through absorption

83
Q

What are the global CO2 emissions per year?

A

35000 MT/yr

84
Q

Why are we not seeing any CCS? From a political standpoint.

A
  • Regulations and permitting
  • No mandates for CCS
  • Carbon prices not high enough
85
Q

Why are we not seeing any CCS from an economical standpoint.

A
  • No inherent value: not doing CCS will always be cheaper
  • Product (CO2) has no value
  • Transport & storage infrastructure
86
Q

How can we make CCS a commercial reality?

A
  • Reduces capital costs for developer
  • Incentives for carbon capture
  • Mandates
  • Pick the right application
87
Q

What are the criticisms of CCS?

A
  • Unreliable / technically infeasible
  • Increases emissions
  • Prolongs use of fossil fuels
88
Q

What is greenwashing?

A

Greenwashing is when a company falsely claims its products or practices are more eco-friendly than they actually are, misleading consumers.

89
Q

What is CO2 a waste product of?

A

Industrial sewage

90
Q

What should CO2 removal possibly be based on?

A

historical emissions

91
Q

What can CCS provide?

A
  • CCS can provide value with power system resilience
  • CCS can provide emission reductions for industry

CIVE40010 - Energy and environmental engineering (21 decks)

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