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.