Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

CPE406 Energy from Biomass and Waste > Biofuels via Thermochemical Conversion > Flashcards

Biofuels via Thermochemical Conversion Flashcards

1
Q

What is the definition of a biofuel?

A

Any fuel (solid, liquid or gaseous) that is produced from organic matter (living or once living material) in a short period of time is viewed as a biofuel. They burn cleaner than fossil fuels (less particulates, NOx, SOx) and are biodegradable unlike fossil-derived fuels.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why is it hard to capture CO2 emissions in the transportation sector and why are biofuels critical to this issue?

A

Because there are millions of separate mobile sources the only way to reduce GHG from transport is by substitution of fossil fuels by biofuels.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What category of conventional/advanced biofuels to first gen, second gen, and third gen biofuels fall into?

A

1st - conventional

2nd+3rd - advanced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are 1st gen biofuels produced from?

A

Food crops (sugar, starch or lipid) inc palm, rapeseed, soy, beets and cereals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Give 3 examples of 1st gen biofuels

A

Sugarcane ethanol, starch-based/corn ethanol, biodiesel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where are 1st gen biofuels already produced on a large scale?

A

US and Brazil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are 2nd gen biofuels produced from?

A

Non-food biomass (cellulose, hemicellulose or lignin) inc virgin wood, agricultural waste, forestry waste and energy crops (eg. miscanthus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Give 2 examples of 2nd gen biofuels

A

Cellulosic ethanol, synthetic diesel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Name 4 oxygenate biofuels and which classification they come under

A

Methanol (2), ethanol (1 or 2), butanol (1 or 2), DME (2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Name 4 hydrocarbon biofuels and which classification they come under

A

Diesel (1 or 2), gasoline (2), jet fuel (2), SNG (1 or 2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Name one non-oxygenate, non-hydrocarbon biofuel and which classification it is

A

Hydrogen (1 or 2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are 3rd gen biofuels produced from?

A

Autotrphic organism algae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Give two examples of 3rd gen biofuels

A

Biodiesel, butanol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Give 4 disadvantages of 1st gen biofuels

A
  1. Low productivity of biofuels per hectare
  2. High fertiliser requirement
  3. Food vs fuel competition
  4. Land availability issues
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Give 3 advantages of 2nd gen biofuels

A
  1. Wider range of biomass feedstocks
  2. Higher quality of biofuels products
  3. Products compatible with conventional fuels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Give 4 advantages of 3rd gen biofuels

A
  1. Very high yields (up to 9000 gallons of biofuel per acre - 10x what the best traditional feedstock has achieved)
  2. Diversity of cultivation (grown in many different ways: open ponds, closed-loop systems and photo-bio-reactors)
  3. Can be grown in places not suitable for agriculture eg. the sea
  4. Fuels produced can be very diverse
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Give 1 disadvantage of 3rd gen biofuels

A
  1. Requires large amounts of resources (water, nitrogen and phosphorous to grow)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does the Renewable Energy Directive say about transport fuels?

A

That 10% of transport fuels sold in all EU countries should be replaced by renewable fuels by 2020 and the use of biofuels must result in an overall GHG saving of 35%. Only 7% of this can come from food crops so the other 3% must come from advanced biofuels (0.5%) and renewable electricity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the Renewable Transport Fuel Obligation (RTFO) and how is it met?

A

It is the UK’s implementation of EU policies on renewable fuels and only biofuels that comply with sustainability criteria are included (35 min. GHG saving). Therefore 450,000 L/y of biofuels for transport must be sold, and this is achieved manufacturers either by supplying biofuels and earning certificates of by buying certificates from companies that supply biofuels.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the main focus of biochemical conversion of 2nd gen biofuels?

A

Ethanol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Give some disadvantages of biochemical conversion of biofuels

A
  • A limited fraction of the biomass can be converted with the known enzymatic hydrolysis we have today
  • Lignin is not convertible in any case, but can used for heat or co-product through combustion
  • Limited feedstock variability as the microorganisms must be tailored to the feedstock
  • R&D breakthroughs are needed to improve conversion and reduce costs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Give 5 examples of biofuels from 2nd gen thermochemcial conversion

A

Fischer-Tropsch (FT) fuels, DME, methanol, mixed-alcohols, green diesel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Give 4 advantages of biofuels via thermochemical conversion

A
  1. Can cope with a high degree of feedstock availability
  2. Conversion technologies are available for FT fuels, FME, methanol but R&D is required
  3. Commercial scale-impletation is lacking but there are large overlaps with commerciallt established fossil fuel conversion technologies (eg. syngas to liquid fuels) that could be easily adapted
  4. It makes use of all the cell wall componenets including lignin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the main focus of biofuels from thermochemical conversion?

A

Synthetic fuels (fuels from syngas)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Which two main routes are used to produce biofuels thermochemicalle?

A

Syngas and liquefied biomass

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is BTL?

A

Biomass-to-liquids: the term refers to processes that produce synthetic fuels through a thermochemical route

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Name the process that converts syngas to gasoline/diesel

A

Fischer-Tropsch synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Describe the 3 processes that can convert syngas to just gasoline

A
  1. methanol used as in intermediate - from syngas to methanol then methanol to gasoline
  2. same as above but methanol to gasoline occurs through mobil-olefins-to-gasoline-and-distillate (MOGD) process
  3. Syngas conversion directly to gasoline
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Name two process that convert bio-oil to gasoline

A
  1. Hydrotreating

2. Hydrocracking

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is the aim of the BioTfuel demonstration project in France?

A

Launched in 2010 to integrate all the stages of the BTL process chain and bring them to market. This has been heavily subsidised by French public funds. The biomass is torrefied, then mixed with some fossil fuel, then gasified in a 1200-1600 deg C, 30-40 bar entrained flow gasifier, then the syngas is conditioned and cleaned before converted into liquid hydrocarn fuels by the Fischer-Tropsch process. Two pilot plants have been built and industrial scale production will begin in 2020.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

How does the German BTL pilot plant operate?

A

It started operation in 2013 and processes around 500 kg/h of straw or wood in a decentralised fast pyrolysis process, which turns it into ‘biosyncrude’ which has a smaller volume and higher energy density. It is then converted to syngas in an 80 bar entrained flow gasifier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

How did the discontinued Choren process work and why was it discontinued?

A

Used two gasifiers - oxygen and steam - to produce syngas for Fischer-Tropsch conversion but fell through when building a full scale plant due to financial difficulty.

33
Q

Which three fuels can be produced by thermochemical conversion of synas?

A

Methanol, gasoline and diesel

34
Q

Give 4 uses of methanol as a commodity chemical

A
  1. as a solvent
  2. as anti-freeze in pipelines
  3. a chemical feedstock for the production of plastics
  4. used for production of gasoline
35
Q

Which catalysts are used to produce methanol?

A

Cu, Zn or Al

36
Q

Give the 3 reactions that occur over the catalyst in methanol production.

A

Drawing 48

37
Q

Give an example of a process used to produce methanol

A

ICI Low Pressure Tech - developined in 1966, 5-10 MPa, 200-300 deg C using a highly selective copper oxide catalyst

38
Q

What is gasoline?

A

A mixture of hydrocarbons having a carbon number primarily in the range C5-C11 (paraffins/alkanes, aromatics, olefins/alkenes, cycloalkanes)

39
Q

Which 3 ways can gasoline be produced?

A
  1. Fischer-Tropsch
  2. via methanol
  3. via DME (Ch3OCH3)
40
Q

Who was the MTG process developed by?

A

ExxonMobil

41
Q

Describe the MTG process.

A

Fixed beds and fluidised beds of proprietary catalysts are used. Gaseous methanol is used.
1. Dehydration of methanol over Al catalyst to produce DME
2. Dehydration over a zeolite catalyst to produce gasoline
Therefore a large amount of water is produces

42
Q

Draw a BFD for the MTG process

A

Drawing 49

43
Q

What 3 fractions is the gasoline from MTG distilled into

A

Light gasoline
Heavy gasoline
HVP gasoline

44
Q

Give a typical example of typical amounts of products obtained from 1000 kg of methanol

A

387 kg gasoline (C5-C11), 46 kg LPG (C3-C4), 7 kg fuel gas (C1-C2) and 560 kg water

45
Q

What temperature is dehydration of methanol to DME carried out at?

A

300-320 deg C

46
Q

What temperature is dehydration of DME to gasoline carried out at?

A

400-420 deg C

47
Q

What was the first MTG plant?

A

Motuni, New Zealand from 1985-97 to make 1/3 of New Zealand’s transport fuels to reduce import requirements and therefore dependence on fossil fuels. It produced unleaded gasoline but was abandoned due to a decrease in crude oil prices. The plant still makes methanol from syngas.

48
Q

What 3 improvements have ExxonMobil mate to MTG technology (2nd gen) and how have they affected the process?

A

Reduction in heat input requirements, compressor duty and heat EX surface area, reduced capital by 10-15% and the first one of these designs became operational in 2009 (but syngas comes from coal gasification).

49
Q

Why was the Topsue gasoline synthesis created and on what principle does it work??

A

To reduce investment costs and therefore production costs of synthetic gasoline.
Syngas of a H2:CO ratio of close to 1 feeds the process where the synthesis of methanol, DME and gasoline are integrated into one loop by first passing the syngas into an oxygenate synthesis (to produce methanol/DME) and then converting to gasoline in the next reactor.

50
Q

What carbon number range does diesel fall into?

A

C8-C21

51
Q

What process converts syngas into diesel?

A

Fischer-Tropsch

52
Q

Why was the Fischer-Tropsch reaction discovered?

A

To convert coal into liquid fuel in WW2 Germany as access to petroleum was sparse. Interest in the process rose again due to its importance in production of liquid fuels from biomass.

53
Q

What catalyst is usually used in the Fischer-Tropsch process?

A

Iron or cobalt

54
Q

What H2:CO ratio is needed for Fischer-Tropsch and how is it achieved?

A

2, through syngas conditioning

55
Q

Is the Fischer-Tropsch reaction endo or exothermic?

A

Highly exothermic

56
Q

Give 2 motivations for using the Fischer-Tropsch process

A
  1. Liquid fuels are easier to transport than gas fuels

2. Syngas is converted into value-added chemicals rather than using it as a fuel on its own

57
Q

What is the most well known use of FTS (Fischer-Tropsch synthesis)?

A

SASOL in South Africa

58
Q

Give the overall reaction for the Fischer-Tropsch process

A

Drawing 50

59
Q

What are the 4 main products of FTS?

A

Gasoline, jet fuel, diesel and chemical feedstock

60
Q

What 4 factors does the selectivity of FTS depend on?

A
  1. Process parameters (temperature, pressure, residence time)
  2. Catalyst (type and support)
  3. Reactor type
  4. Syngas composition
61
Q

Name 3 types of reactor used for FTS

A
  1. Fixed-bed
  2. Slurry-bed
  3. Fluidised bed
62
Q

Draw a fixed bed FTS reactor

A

Drawing 51

63
Q

Draw a slurry-bed FTS reactor

A

Drawing 52

64
Q

Give the temperatures and favoured product for LTFTS and HTFTS

A

LTFTS - 200-240 deg C, diesel

HTFTS - 300-350 deg C, gasoline

65
Q

What is the typical operating pressure of FTS?

A

20-40 bar

66
Q

Give an example HTFTS

A

Iron based catalyst, fluidised bed reactor at 340 deg C, gasoline yield 40%

67
Q

Give an example of LTFTS

A

Cobalt-based catalyst, slurry-bed reactor at 200-240 deg C, diesel yield 20%

68
Q

Why does bio-oil need to be upgraded to be used at a transportation fuel?

A

Because it has a high oxygen content (40-60%), and this is a huge challenge. It then also needs to be refined.

69
Q

Which is more developed, biofuels from syngas of bio-oil?

A

Biofuel from syngas

70
Q

What is the typical heating value of bio-oil?

A

13-18 MJ/kg

71
Q

What is the motivation for hydrotreating bio-oils?

A

The higher the hydrogen content of a petroleum product, the better the quality due to the high CV. Therefore the addition of hydrogen to the bio-oil is beneficial.

72
Q

Is hydrotreating or hydrocracking more commonly used and why?

A

Hydrotreating because it is cheaper and commercially available.

73
Q

What conditions and catalyst are used for hydrotreating?

A

Up to 500 deg C at atmospheric pressure with a NiMo or zeolite catalyst

74
Q

Describe the principle of hydrotreating

A

Non-destructive hydrogenation that improves product quality without altering the boiling range

75
Q

What operating conditions are expected from hydrocracking?

A

Over 250 deg C where hydrogenation accompanies cracking, 7-143 bar, dual function catalyst (

76
Q

Describe the catalyst used for hydrocracking

A

Dual-function catalyst, nickel core provides hydrogenation and silica-alumina or zeolite supports and provides the cracking function (alumina most widely used)

77
Q

Why are aromatic compounds from hydrocracking further refined?

A

To produce liquid hydrocarbon fuels of high octane number

78
Q

What are the 5 challenges associated with biofuel production from bio-oil?

A
  1. Improving conversion efficiencies
  2. Improving catalysts
  3. Reduce CAPEX & OPEX
  4. Find financial subsidies (required)
  5. Cost of biomass (find long-term supply contracts)

CPE406 Energy from Biomass and Waste (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions