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GASIFICATION OFSOLID FUELS
Motivation for the development of gasification
technology
Economy
Energy Security Environmental Protection
U.S.A. China
UE
”Coal reserves”� USA: 1.4 × 1011 toe � China: 5.6 × 1010 toe� India: 4.7 × 1010 toe� “Europe”: 5 × 1010 toe
”Fossil fuel reserves”� Nat. gas (world): 1.6 × 1011 toe� Oil (world): 1.5 × 1011 toe� Coal (world): 5.2 × 1011 toe� Σ: 8.3 × 1011 toe
� World growth energy consumption 02-04: 4%
Fossil fuel reserves
Gasification process
Gasification of solid fuels is the transformation of combustiblesubstance into the gaseous fuel, which is the result of the impact of the gasifying medium on the fuel, at high temperature and under atmospheric or increased pressure.
gasifyingmedium
temperature, pressure
coal gases
ash
Gasifying media
• water steam (H2O), • air (21% O2 + 79% N2),• carbon monoxide (CO2),• oxygen (O2),• hydrogen (H2).
Fuels that can be gasified
•bituminous coal,•lignite,•peat,•oil shale,•biomass,• waste.
Main stages of gasification of solid
fuels Gasification of most of solid fuels has two stages:
• degassing of the solid fuel,• gasification of the coke residue.
high temperature
Gasifying medium
gases gases
coal
coke
Relative time of gasification stages
- degassing of the solid fuel: 1
-gasification of the coke residue : 10-100
- Autothermal – the energy required for thegasification is produced inside of the reactor
due to exothermic reactions
- Allothermal - the energy required for thereaction is produced outside of the reactor.
Classification of gasification technology due to
the way of covering the energy needs of the
process
Methods of gasification
largeentrained flow
small, mediumfluidized bed
smallfixed bed
Scale of the processMethod of gasification
Environmental aspects of fuel
gasification technology
Advantages:1. Easy CO2 sequestration.2. Removal of most pollutants from the gas before the
turbine (solids, sulphur, heavy metals ,...) 3. Low emission of SO2, NO2, and dust.
Disadvantafes:1. Gasification is similar to coking of coal. .2. Hydrocarbons (benzene), hydrogen sulfide and dust
are emitted. 3. Effluents are produced.
Comparison of emissions of major
pollutants
Application of gasification
processes
1. Ppower generationin integrated gasificationcombined cycle(IGCC ) power blocks
2. Production of synthesis gas for chemicaltechnology
3. Production of artificial motor fuels (syntheticpetrol and diesel)
4. Production ofsynthetic gas (SNG)
Coal gasification
Basic processes of coal gasification
a) Lurgi, b) Winkler, c) Koppers–Totzek
Lurgireactor
coal↓↓↓↓
temperature
293 K
heating and drying 573 K
degassing zone 873 K
heating of coke 1073÷1273 K
secondary
strefa redukcji
1073 K
1273 K
combustion zone 19731773 K
slag zone 1073 K
ash cooling zone773 K
xxxxxxxxx grate xxxxxxxx
ash pan ↑ ↑ ↑ steam + oxygen
primary
Chemistry of coal gasification
Reactions ∆H, kJ/mol
A.
Primary reactions
1.2. 3.4.5.
Water gas production: C + H2 O = CO + H2Boudouard reaction : C + CO2 → 2COPartial oxidation: C + 2H2 O → CO2 + 2 H2Hydrogasification : C + 2H2 → CH4Incomplete combustion: C + 1/2O2 → CO
117.9160.075.8
-87.1-122.1
B.
Secodary reactions
6. 7.8.
Conversion of carbon monoxide with steam: CO + H2O → CO2 + H2Methanisation : CO + 3H2 → CH4 + H2O
CO2 + 4H2 → CH4 +2H2O
-40.8-205.0-163.0
C. Combustion reactions
9.10.11.
Combustion of coke: C + O2 → CO2Combustion of carbon monoxide: CO + 1/2O2 → CO2Combustion of hydrogen H2 + 1/2O2 → H2O
-397.7-282.1-240.1
Basic scheme of coal gasification
Types of gas obtained by
coal gasification process
catalytic conversion or metanisation
~ 36high-caloric
water steamand oxygen
8-20Medium-caloric
water steamand air
4-8low-caloric
Gasifyingmedium/
technology
Caloric value,MJ/m3
Type of gas
COAL AS RAW MATERIAL FOR
GASIFICATION
Bituminous coal as raw materialfor gasification
Criteria for selection of coals for gasification:
• high reactivity (vs. CO2)• content of ash and its melting temperature• coking ability• fragmentation
Bituminous coal as raw materialfor gasification
�Low reactivity�Behaviour of the mineralsubstance
� Low content of volatileparts
�Low humidity (up to 10%)�High density �High strength of coke
DisadvantagesAdvantages
Lignite as raw materialfor gasification
�Very high reactivity�Behaviour of the mineralsubstance
� High content of volatileparts
�High humidity (do 55%)�Low density �Low strenght of coke
AdvantagesDisadvantages
PYROLYSIS OF COAL
Characteristics of pyrolysis
process
Coal pyrolysis is its thermal decomposition without oxygen access.
Meaning of pyrolysis process:• stage of combustion process• stage of gasification process• independent fuel technology
coal
formationof radicals
decomposition
thermalstabilizationof radicals
polymerization and carbonization
reactions
volatile products
in the gaseousphase
reactions
secondary
temperature increase
solid product of carbonization
Thermal decomposition of
coal
Stages and products of coal
pyrolysis coal
activated coal
heating and activation
primary pyrolysis
secondarypyrolysis
intermediate products
pyrolysis products
end products targas semi-coke
semi-coketargas
tar
gase
ous
hydr
ocar
bons
an
d hy
drog
en carbon oxides
and water
Products of pyrolysis of bituminous coal
(Vdaf=32%)
Comparison of degassing of
bituminous coal and lignite
721378
55161118
1.11.20.81.1
semi-cokeprimary-tar
watergas
Bituminouscoal
1.11.81.20.9
semi-cokeprimary-tar
watergaz
Lignite
Content of hydrogen in products, %
Degassing products, %Fuel
VOLATILE PRODUCTS
OF PYROLYSIS
Composition of volatile parts of
coal
Ingredient
Lignitefrom Montana
%
Bituminous coalfrom Pittsburgh
%
6,9 MPa He1000 °C, 3–10 s
6.9 MPa He850–1070 °C, 2–10 s
COCO2H2OCH4C2H4C2 H6Ciekłe HCtarcarbonizate
9.010.612.92.50.60.2–
3.059.9
2.51.79.53.20.50.90.712.062.4
TAR
Characteristics of tar
Tar is a mixture of semi-solid and liquid products of thermal decomposition of natural organic substances.
Products derived from tar• aromatic compounds: benzene, toluene, xylenes, phenol, naphthalene, anthracene, carbazole,• oils• pitch
Yield of tar from coking process
volatile parts Vdaf, %
yeld
ofta
r, %
Products of thermal decomposition of tar aromatic hydrocarbons
acidic
components
unsaturatedcompounds
alkalinecomponents
paraffinsand
naphthenes
naphthalene
Liquid fractions from pyrolysis of tar
Effect of carbonization temperature on the secretion of
aromatic hydrocarbons from coal
anthracene
benzol
naphthalene
toluene
xylene
optimum range for the formation of aromatic hydrocarbons
Yield of liquid products, depending on the
conditions of carbonization of bituminous
coal
10
5
2335
< 50
< 50
< 5< 0.1
600
1000
600600
Low-temp. degassingHigh-temp. degassingLurgi-RuhrgasGarret
Gain of liquid products,
%daf
Grain size, mm
Temperature, C
Process
Parameters of coal gasification
process
Parameter
Gasification process (first generation)
Lurgi WinklerKoppers–
Totzek
Type of coallignite or
bituminousmainly lignite any
Grain size, mm 6–60 3–8< 0.1
(pulverized)
Gasifying mediumoxygen &
water steamoxygen &
water steamoxygen &
water steam
Gasification pressure, MPa 2.5–3 atmosph. atmosph.
Temp. of raw gas, °C do 600 800–950 1400–1600
Composition of gas, H2%vol. CO
CO2CH4
36–4018–2527–329–10
35–4630–5013–251–3
21–3255–657–120.1
Gasifier output, Mg/h 30 up to 30 30-35
LCV of gas, MJ/m3 11.2–11.7 9.2–13 10.6–11.8
Gasification efficiency, % up to 99 up to 90 90–96
Gasification technology
(second generation)
Gasifier
Gas Dry BGL
Uhde Shell/
Prenflo
Conoco- Philips
E-gas (Dow) G.E.
Texaco
GE Texaco Quench
KRW Transport
CO 54 62.7 50.3 49.6 49.6 21.1
H2 30 29.7 38.8 37.5 37.5 19.4
CO2 5 2 8.5 10.4 10.4 9.0
CH4 7.5 ~0 0.1 0.1 0.1 2.5
N2 + Ar 2.9 5.3 1.9 1.9 1.9 45.4
**E c (LHV) 47.1% 47.4% 46.7% 45.1% 39.7% 49.8%
**E H (LHV) 51.3% 49.8% 49.4% 48.3% 41.2% 51.7%
kg coal/kg O2 2.0 1.35 1.52 1.26 1.26 1.79
Nm3 syngas/Nm3 O2* 6.73 3.05 3.42 2.92 2.92 4.00
Shenhua evaluation 3.13 2.56
No of references 2 10 2 60-a a 1
LCV, MJ/m3 11.2 - 11.8
Shell’s reactor in Buggenum
Texaco process diagram
Coal, H2O
water steam
raw gas
waste gas
waste water
1 – reactor, 2 – slag reciver, 3 – gas cooler, 4 – scru bber, 5 – settling tank, 6 – heat exchangers, 7 - pump slag
gas
oxygen
coal - water slurry
Reactor (gasifier)
Impact of the gasifying medium on composition of obtained gas
29.928.813.322.24.30.90.6
450.0440.0
19.119.79.67.043.30.80.560.067.0
H2, %CO, %CO2, %H2ON2, %NH3, %H2S, %H2S exit reactor, ppmH2S equilibrium, ppm
Gasification usingoxygen
Gasification usingair
Lignite, T = 450ºC, P = 20 bar
applications of coal gasification
technologies
Applications of coal
gasification technologies
0
2
4
6
8
10
12
14
16
18
20
MW
thof
gas
Chemistry Powergeneration
Fischer–TropschSynthesis Gaseous fuels
Planed
In use
Applications of coal
gasification technologies
Planed
Present
Am
ount
of p
rodu
ced
syng
as[M
Wt]
Industrial applications of coal
gasification
� SASOL (RPA) – 24 mil. tons of coal,6 mil. tons of liquid fuels
� Dakota Gas Co. (USA) – 6 mil. tons of lignite, 1.5 mld m3 of SNG , sequestration of 1 mil. tons of CO2
� Polk Station (USA) – 250 MW net� Wabash River (USA) – 262 MW net� Puertollano (Spain) – 318 MW net� Buggenum NUON (Netherlands) – 253 MW net
Sasol’s plant in Secunda (RPA)(Lurgi reactors)
Main products:•oils,• gasoline,• SNG
Demonstration plants
(slurry reactors)
Example of application of GE-Texaco
gasification technology
Tampa Electric Polk Power Station
�Mulberry, FL�1 x GE radiant + convective syngas cooler
�250 MW; 1 x GE 7FA�1st syngas: July 1996 as DOE project
� Commercial oper: 2001�Coal/petcoke mix to optimize fuel cost
�2004 availability 95%�Lowest cost power in TECO portfolio
GE’s IGCC (Integrated GasificationCombined Cycle) process
The Chemistry of Texaco method
� CxHy + H2O + O2 → aH2 + xCO
� For example:
4 CH + 2 H2O + O2 ���� 4 H2 + 4 CO (Hydrocarbon) (Water) (Oxygen) (Hydrogen) (Carbon Monoxide)
IGCC CO2 Capture Readiness
CO2SHg
Water Gas ShiftCO+H2O -> CO2+H2
PowerPower
Oxygen,Feedstock
Process Gas OnlyHigh P, Low Vol
High Driving Force
Slag
Proven Process
AGRAGR / / SRUSRUOptional ShiftOptional ShiftGasificationGasification
Diffusion CombustorDiluent NOx
Control
H2
Proven Turbines
Proven Gasification
• 28 GE Gas Turbines operating at 50%+ H2
• Validated F-class combustion to 90% H2
• 60+ GE Licensed Gasification Units operating worldwide
• 12 with solid feedstock
• >25 GE Licensed Gasification Units operating worldwide using shift reaction to produce H 2
• >25 GE Licensed Units operating worldwide using AGR technology to completely remove CO 2 from shifted syngas
The list of reference installations in EU
RWE2016£0.8bnSCPC1000UKRWE, Tilbury
RWE2014< €1bnIGCC450GermanyRWE, Germany
Statoil2014NGCC820NorwayMongstad
Shell, Statoil2011?NGCC860NorwayTjeldbergodden
Siemens2011€1.7bnIGCC1000GermanySiemens
Nuon20111 G€IGCCmultifuel1200NetherlandsMagnum
E.ON2011?IGCC450UKKillingholme
Powerfuel2010?IGCC900UKHatfield
SSE2011?SCPC, retrofit500UKFerrybridge
BP, SSE2010$0.6bnNG to H2350UKPeterhead Miller
ProgressiveEnergy
2009$1.5bnIGCC800UKTeeside
?2009?NGCC385NorwayKårstø
Vattenfall2008??30GermanySchwarze Pumpe
Total2006?oxyfuel50FranceLacq
ParticipantsProposedstart
CapitalPower plantcapture
technology[1]
Capacity(
CountryProject
RWE2016£0.8bnSCPC1000UKRWE, Tilbury
RWE2014< €1bnIGCC450GermanyRWE, Germany
Statoil2014NGCC820NorwayMongstad
Shell, Statoil2011?NGCC860NorwayTjeldbergodden
Siemens2011€1.7bnIGCC1000GermanySiemens
Nuon20111 G€IGCCmultifuel1200NetherlandsMagnum
E.ON2011?IGCC450UKKillingholme
Powerfuel2010?IGCC900UKHatfield
SSE2011?SCPC, retrofit500UKFerrybridge
BP, SSE2010$0.6bnNG to H2350UKPeterhead Miller
ProgressiveEnergy
2009$1.5bnIGCC800UKTeeside
?2009?NGCC385NorwayKårstø
Vattenfall2008??30GermanySchwarze
Total2006?oxyfuel50FranceLacq
ParticipantsProposedstart
CapitalPower plantcapture
technology[1]
Capacity(MWe)
CountryProject
Biomass gasification
Why gasification of biomass?
Gasification of biomassis regarded as a promising way of its conversion into fuel gas that can be used in:
•gas turbines,•reciprocating internal combustion engines,•fuel cells.
Ability of biomass
to degassing
type of biomass
wheatstraw
(psze-nica)
oat straw
(owies)
barley straw
(jęcz-mień)
alder wood
(olcha)
beech wood
(buk)
pine wood
(sosna)
degree of degassing,
% mas.
85,9 83,7 85,1 85,2 86,1 85,7
Pyrolysis, thermal decomposition -degassing
Biomass pyrolysisis incomplete thermal decomposition, which products are:
• coke,• condensing liquid ingredients,• tar,• gases.
Products of
thermal
decompo-
sition
of wood
Components of pyrolysis gas
The main components of pyrolysis gas are:H2, H2O, CO, CO2, CH4 & highly-carbonized hydrocarbons.
Temperature, °°°°C
Gas components, % vol.
H2 CO CO2 HC
600 13 37 25 25
700 20 38 23 19
Effect of pyrolysis conditions on
its products
Type of pyrolysis
Heating speed, °°°°C/s
Temp., °°°°C
Time Main product
slow(carbonisation)
<< 1 400 days charcoal
conventional 102÷103 600 5-30 min.
gas, oil, coke
flash 103 – 106 deg/s 650 < 1 s bio-oil
Products of biomass pyrolisys
gas
tarbio-oil
biomass
coke
Types of biomass gasifiers
There are two main groups of reactors used for thegasification of biomass:
• fixed bed,• fluidized bed.
Usualy, low-capacity gasifiers are fixed bed reactors, and high-capacity (used in waste incinerators and power industry) are fluidized bed reactors
Types of fixed bed reactors for gasification
of biomass
cocurrent(downdraught)
countercurrent(updraught)
Fluidized bed gasifier
biomasa
ŜuŜel
popiół
gaz
biomass
ash
gas
slag
Scheme of circulating fluidized bed rector made by Foster Wheeler
Main features of biomas gasifiers
Type of gasifier
Content in gas Variability of gas
parameters
Maximum power,MW t
tar dust
Fixed bed:cocurrentcountercurrent
Fluidized bed.:bubblecirculating
v. highlow
mediumlow
lowlow
highv. high
v. highhigh
v. lowv low
1,5 10
30100
Application of biomass gasification
Gasification of wood in fluidised bed
reactor
Parameter Unit Value Gas comp.,% vol
Mass flow of wood kg/s 1,6CO − 14,7
CO2 − 13,3
CH4 − 3,7
H2 − 7,3
H2O − 16,1
N2 − 44,9
Volumetric low of air m3/s 1,8
Air excess coefficient − 0,3
Temperature of air °C 415
Temperature of gas °C 800÷900
Lower caloric value of wood MJ/kg (daf)
16,6
Lower caloric value of gas MJ/m3 4,8
Yield of gas m3/kgwood 2
Co-firing of biomass gasification gas in pulverised coal fired boiler
540°C17 MPa
Processing
fly ash
50 MW
350 MW
pulverized coal
boiler
gas flame
biomass
gasifier
ash
Synthetic gas production (SNG)
Reasons for interest in SNG
production technology
� SNG production technology was developed in the 70s
� Reasons for interest in SNG technology:
• High gas prices
• Energetic security of state
• Technology improving.
SNG production technology
GasifierH2/CO ≈3H2/CO <1
ASUWatersteam
CO ShiftConverter
CO + H2O ����H2 + CO2
Acid GasRemoval
WSATM
O2
Sulfuric acid
H2SO4
CO2
SyngasCoalTREMPTM
Air
CO2/H2S
SNG
Watersteam
Watersteam
Watersteam
Methanisation reactions
CO + 3H2 = CH4 + H2O (-∆H0298 = 206 kJ/mol)
CO2 + 4H2 = CH4 + 2H2O (-∆H0298 = 165 kJ/mol)
Notes:- Are exothermic- Ocurr in the presence of a catalyst
Composition of SNG
8450 - 8675HHV, Kcal/Nm3
2 - 3 N2 + Ar
nilCO
0.5 - 1H2
0.5 - 1CO2
94 - 96CH4
% molComponent
Bibliography
1. Hessley R.K., i inni, Coal Science, John Willey, 1986.
2. Tenger Sz., Współczesne metody chemicznej przeróbki węgla, PWN, W-wa, 1981.
3. Kowalski J., Rosinski S., Chemia i technologia węgla brunatnego, PWN, W-wa, 1957.
4. Tomeczek J., Zgazowanie węgla, Wyd. Politechnika Śląska, Gliwice, 1991.