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© Woodhead Publishing Limited, 2013
427
16 Coal gasification and conversion
D. J. HARRIS and D. G. ROBERTS, CSIRO Energy
Technology, Australia
DOI : 10.1533/9781782421177.3.427
Abstract : Coal is a valuable resource used as a source of energy all over the world. Most applications burn coal for small and large scale power generation, or use coal as a reductant in metallurgical applications. There is, however, the opportunity to use coal as an energy feedstock for the production of a range of fuels and chemicals as well as high-effi ciency electricity, via gasifi cation-based technologies or direct coal-to-liquids systems.
This chapter explores the technologies, applications, barriers and research challenges associated with gasifi cation and conversion of coal for the production of high effi ciency power, transport fuels, and chemicals. It considers some of the emerging technologies which aim to reduce costs and emissions associated with coal use. These technologies also offer integrated pathways to cost-effective CO2 capture from coal-based plant.
Key words : gasifi cation, coal-to-liquids, IGCC, CCS.
16.1 Introduction
Coal has been used as an energy source for more than two thousand years.
In modern times its use has been dominated by thermal power generation
in pulverised fuel (pf)-fi red combustion boilers and as a fuel and reduc-
tant in iron and steelmaking applications. Countries abundant in coal rely
on it heavily for domestic power generation: in Australia, about 78% of the
electricity generated comes from the combustion of black and brown coals
(Commonwealth of Australia, 2012). Gasifi cation technologies provide a
fl exible foundation for high-effi ciency, low emissions systems capable of sup-
porting coal conversion to a range of energy and chemical products.
16.1.1 Conversion of coal to energy and chemical products
There is considerable interest in addressing the issues regarding emissions
from coal use, in particular those of greenhouse gases (CO 2 in particular).
From a power generation perspective, this must start with effi ciency: most
of Australia’s installed coal capacity operates with thermal effi ciencies of,
428 The coal handbook
© Woodhead Publishing Limited, 2013
at best, 35–37% with many older installations and those operating on high
moisture coals operating at effi ciencies less than this. To meet the increasing
demand for power and increasingly stringent environmental requirements,
new technologies for power generation from coal must address cost, reli-
ability, by-product management challenges, and provide a high-effi ciency
technology platform to directly reduce CO 2 emissions intensity as well as
creating a path for commercially viable carbon capture and storage (CCS)
technologies which will inevitably be required for coal to maintain a strong
role in future power generation technology portfolios.
There is also the opportunity through coal-to-liquids conversion technol-
ogies (either direct liquefaction or indirect CtL via gasifi cation routes) to
use widely available reserves of black and brown coals to partially replace
imports of oil for the production of transport fuels.
Gasifi cation is a fl exible coal utilisation technology that can address both
of these concerns. Gasifi cation of coal is a process whereby coal is con-
verted to a syngas, which is predominately a mixture of carbon monoxide
and hydrogen. As shown schematically in Fig. 16.1, syngas is a precursor to
an extensive range of energy and chemical products: it can be combusted in
a combined cycle turbine system for effi cient production of electricity, fed
into a Fischer-Tropsch plant for the production of a range of liquid fuels,
reformed to methane to provide synthetic natural gas (SNG), converted to
Liquid fuels andhydrocarbons
SNG
CoalGasification
IGCCElectricitySyngas
Energydistribution?
Fuelcells
Methanol
MTG
Gasoline
Chemicals
Ammonia
Fertilisers
H2
Fischer-Tropsch
Directliquefaction
16.1 Some typical options for coal-derived products, either from direct
liquefaction or via gasifi cation for syngas production.
Coal gasifi cation and conversion 429
© Woodhead Publishing Limited, 2013
methanol and used to produce gasoline, or used as a precursor for the pro-
duction of a range of fertilisers, explosives and other chemicals.
The chemical processes that comprise gasifi cation are considerably dif-
ferent from those which occur in more traditional coal-combustion based
pf boilers. A fundamental difference is the oxygen to carbon ratios used: pf
systems typically operate with excess air, whereas gasifi cation systems use
signifi cantly lower oxygen:carbon ratios, and this stoichiometry is carefully
controlled to ensure that optimum gasifi cation conditions are present for
the specifi c fuel–technology combination. Consequently, the coal combus-
tion reactions have a minor role in the coal gasifi cation conversion process,
and the much slower, endothermic coal gasifi cation reactions with steam
and carbon dioxide dominate the conversion process.
These fundamental differences mean that the coal properties and indices
that are used to characterise fuel suitability for use in pf applications (and
which form specifi cation criteria for marketing purposes) are not relevant
to coal assessment for gasifi cation. As the physical and chemical reaction
processes that constitute the gasifi cation process are vastly different from
those found in coal combustion, a different set of fuel performance and
coal characterisation criteria are needed. Gasifi cation reactions are several
orders of magnitude slower than the combustion reactions, making their
impact on coal behaviour and gasifi er design more signifi cant. Some gasifi -
ers also require coal mineral matter to melt and fl ow out of the gasifi er as a
slag, which places particular requirements on the viscosity behaviour of the
Installed
4 × 104
3 × 104
2 × 104
Syn
gas
prod
uctio
n (M
Wth
)(eq
)
104
0Chemicals Fuels Power
Planned
16.2 Planned and installed coal gasifi cation plants for the production
of chemicals, fuels, and electricity. (Source: Data from Gasifi cation
Technologies Council, 2012.)
430 The coal handbook
© Woodhead Publishing Limited, 2013
molten mineral matter (more details on coal properties required for specifi c
gasifi cation technologies are given in Section 16.3).
There is, however, considerable international experience in coal gasifi ca-
tion for a range of applications. Coal gasifi cation is an important part of the
global chemical industry, and plays a key role in the production of liquid
fuels. Gasifi cation for power generation is a growing industry (see Fig. 16.2)
and will be an important technology for reducing the greenhouse gas emis-
sions from coal-based power generation, as it provides a particularly suit-
able, high effi ciency platform for integrated CO 2 capture.
16.1.2 Coal gasifi cation for power generation
Integrated Gasifi cation Combined Cycle (IGCC) uses syngas from gasifi ca-
tion of coal (or mixtures of coal with biomass or other hydrocarbon mate-
rials such as petroleum coke), and integrates this with a combined-cycle
steam and gas turbine system for electricity generation. Integrating gasifi ca-
tion processes with combined cycle turbine systems for power generation is
relatively new: there are currently six commercial-scale coal-based IGCC
demonstration plants around the world.
Although none of the current dedicated IGCC plants capture and
store CO 2 , capture and storage of CO 2 produced from coal gasifi cation
for Synthetic Natural Gas (SNG) production is being demonstrated in
the US by the Dakota Gasifi cation Company. The CO 2 from this plant is
delivered by high pressure pipeline to the Weyburn CO 2 storage project
in Canada.
An IGCC plant consists of four main operating components:
1. an oxygen plant (current technologies use cryogenic air separation units
(ASU) although advanced, high effi ciency membrane based oxygen
plants are being developed and these have several promising attributes
for IGCC applications). Some plants use air rather than oxygen as the
gasifi cation medium. Air blown plants are less amenable to chemicals
production applications and to high levels of pre-combustion CO 2 cap-
ture than oxygen blown gasifi ers.
2. a gasifi cation plant – for converting solid or liquid hydrocarbon fuels
into synthesis gas (syngas)
3. a syngas gas clean-up system and
4. a combined cycle power plant.
The ASU separates the major components from air and supplies the gas-
ifi er with a stream of high pressure oxygen. The gasifi er reacts coal (or a
variety of hydrocarbon fuels) with this oxygen in a controlled manner to
produce syngas (principally CO and H 2 ). Syngas is then cleaned to remove
Coal gasifi cation and conversion 431
© Woodhead Publishing Limited, 2013
particulates and other potential pollutant species. Finally, syngas is burnt in
a high effi ciency combined cycle gas turbine plant which comprises a gas
turbine, steam turbine, generator and other supporting infrastructure. A
schematic of a typical IGCC process is shown Fig. 16.3, and the existing
coal-fi red IGCC demonstration plants are summarised in Table 16.1.
Table 16.1 Coal-fi red IGCC demonstration plants
Plant Location Output
(MWe)
Feedstock Gasifi er Operation
Tampa Electric
Polk Plant
Polk County, FL
USA
250 Bituminous
Coal and
Pet Coke
GE 1996–Present
ConocoPhillips
Wabash River
Plant
West Terre Haute,
IN USA
262 Bituminous
Coal and
Pet Coke
E-Gas ® 1995–Present
NUON/
Demkolec
Willem-
Alexander
Buggenum, The
Netherlands
253 Bituminous
Coal and
Biomass
Shell 1994–Present
ELCOGAS/
Puertollano
Puertollano,
Spain
318 Coal and
Petroleum
Coke
Prenfl o ® 1998–Present
CCP Nakoso, Japan 220 Bituminous
Coal
MHI 2007–Present
Vresova Czech Republic 350 Coal/lignite Lurgi,
Siemens
1996–Lurgi
2008–Siemens
Pulverised coaloxygen / steam
recycle char
Gasifier
Productgas
Gas cooler
Boiler
Electricity
Electricity
Gas turbine
Steam turbineBoilerfeed water
Hot gas cleaning (540–1000°C)
Fly slag,char forrecycle
S and N compoundsremoval
CombustorAirBoiler
feed waterQuenched
slag frit
Boilerfeed water
2 M
Pa
(20
ATM
)15
00–2
000°
C
16.3 Schematic representation of an IGCC power station using a high
pressure entrained-fl ow gasifi er (Harris and Patterson, 1995).
432 The coal handbook
© Woodhead Publishing Limited, 2013
IGCC power generation effi ciencies are higher than those possible with
many supercritical (SC) pf power stations, and offer considerably more
opportunities for future increases from improvements in gasifi er and turbine
design, oxygen production technologies, syngas cleaning materials, water-gas
shift processes and CO 2 separation technologies. Furthermore, the effi ciency
penalties associated with CO 2 capture from gasifi cation-based plant are
already signifi cantly less than those applying to commercial post-combustion
CO 2 capture systems which can operate on fl ue gas streams from conven-
tional combustion power stations, making them particularly well suited as a
platform for power generation applications incorporating CCS.
The fi rst commercial scale IGCC plants were implemented during the
1990s in the USA and Europe. These projects followed the coincident
development of high pressure gasifi ers in the chemical and refi nery sector,
improvements in gas turbine technology and demands for improved envi-
ronmental performance of coal utilisation.
Further developments in gas turbine and gas clean-up technology, and
now the additional requirement for CO 2 reduction, suggest that IGCC
offers a fl exible technology platform with the potential for the supply of
energy to society through production of decarbonised electricity in parallel
with synthetic liquid fuels, fertilisers and chemicals from coal.
However, the deployment of IGCC to date has been limited by its rela-
tively high capital cost, some initial experiences where the early plants had
diffi culty meeting very high utility reliability standards, and a generally poor
understanding in the current utility industry of IGCC technology and its
potential. Clearly the costs of deploying new, high effi ciency plant and of
capturing and storing CO 2 are signifi cantly greater than those associated
with the deployment of mature conventional technologies. In many coun-
tries there are still no clear commercial drivers for signifi cant investment
in new-technology large power plants with high effi ciencies and lower CO 2
emissions or for the commercial deployment of large-scale CCS projects.
Given the potential for IGCC-based systems to meet increasing electricity
demands with a signifi cant reduction in CO 2 emissions, there is considerable
research and development around the world aimed at addressing the cost and
performance barriers of gasifi cation-based power generation technologies.
16.2 Conversion of coal to liquids and chemicals (CtL)
Coal gasifi cation-based processes for conversion of coal to liquid fuels
and chemicals have been in commercial operation for considerably longer
than gasifi cation for power generation. Methods for the conversion of coal
to liquid fuels (CtL) have been available since the 1930s, but widespread
acceptance of the technologies has been hindered by the availability of
cheaper petroleum resources. Major applications of the technologies for
Coal gasifi cation and conversion 433
© Woodhead Publishing Limited, 2013
coal conversion have typically been related to political isolation, such as
in Germany during World War II and in South Africa during the extended
period of political isolation. Despite the restricted applications of the tech-
nologies, substantial research efforts have been undertaken in numerous
countries in preparation for the eventual decline in petroleum availability.
In broad terms, conversion technologies appear to be fi nancially viable if
petroleum prices remain above US$ 35/bbl for the long term, but fi nancial
and technology risk factors have tended to delay investment while there is
the potential for petroleum crude prices to drop below US$ 70/bbl.
16.2.1 Direct CtL
Direct Coal Liquefaction (DCL) commonly refers to catalytic hydrogenation
of coal in a recycled oil solvent at high pressures with a catalyst. While a range
of process confi gurations have been proposed, the most common version
involves at least two high pressure slurry reactors in a series using a dispersed
iron-based catalyst and hydrogen supplied from a parallel gasifi cation system.
Typically, the liquefaction reactors operate at temperatures of up to 450 ° C and
pressures up to 200 bar with a 3-phase slurry of coal, recycle oil and hydrogen.
A major ambition in research is to achieve signifi cant cost savings by reducing
the intensity of these conditions in order to reduce the capital cost.
DCL is distinctly different in operation from the indirect processes. As
the coal is not gasifi ed, there is limited opportunity to remove impurities
and the products are related to the original structures in the coal. There are
considerable improvements in effi ciency in oil production compared to indi-
rect processes, but there is also more sensitivity to coal properties.
16.2.2 Indirect CtL
Indirect coal-to-liquids processes rely on the conversion of coal to syngas,
in the same manner as the IGCC power stations discussed earlier. Instead
of cleaning and combusting the syngas, however, indirect CtL processes use
the syngas in catalytic conversion processes to produce specifi c hydrocarbon
fuels. Coal properties, therefore, have less of an impact on the nature of the
liquid fuels produced, and are important from a gasifi cation perspective in the
same way as they are for IGCC or production of chemicals and fertilisers.
Fischer-Tropsch synthesis technologies have been used since the 1930s and
involve the use of a catalyst to convert synthesis gas mixtures (containing high
concentrations of carbon monoxide and hydrogen) into long chain hydrocar-
bons. Depending on the catalyst and operating conditions used there are differ-
ences in the length of the chains formed and the byproducts that can result.
Typically, the Low Temperature Fischer-Tropsch (LTFT) process will pro-
duce what is termed waxy crude, basically a mixture of long chain hydrocarbons
434 The coal handbook
© Woodhead Publishing Limited, 2013
similar to paraffi n wax, as a raw product and this will then be hydrocracked to
reduce the chain lengths to suitable sizes for automotive fuels. The waxy crude
will contain some alcohols and olefi ns (unsaturated hydrocarbons), as well as
the major product of alkanes (paraffi ns), but these will be hydrogenated to
produce alkanes in the hydrocracker.
An alternative Fischer-Tropsch process, High Temperature Fischer-Tropsch
(HTFT), uses an iron-based catalyst to produce a range of hydrocarbons
directly suitable for automotive fuels. The higher temperature synthesis has
the advantage of producing a wider range of compound types, such as aromat-
ics, that improve the suitability of the product fuels for automotive use.
The methanol to gasoline (MTG) process uses a zeolite catalyst to spe-
cifi cally produce a range of hydrocarbons only in the LPG and gasoline size
ranges. The standard Exxon Mobil process consists of reforming, methanol
synthesis, methanol dehydration to dimethyl ether (DME) and gasoline syn-
thesis stages; however, Hald ø r-Topsoe have developed a lower cost version
of this that combines methanol synthesis and dehydration.
16.3 Gasification technologies
There is a variety of commercially-available gasifi cation technologies, each
being well suited to particular fuels and applications. These gasifi cation
technologies differ signifi cantly in their requirements for fuel preparation
and properties, pressures and temperatures of operation, nature and quality
of the syngas produced, effi ciencies of operation, scale of production, and
capital and operating costs. The main gasifi er technology variants are usu-
ally described in relation to the nature of the presentation of the fuel to the
gasifi cation media. The basic classifi cations are entrained fl ow, fl uidised bed,
or fi xed bed; although there are now technologies emerging, such as circulat-
ing fl uid-bed technologies, that operate near the boundaries of these sys-
tems and share features of these different types. The characteristic features of
these gasifi er technology types is described briefl y below. A detailed descrip-
tion of the leading processes and their commercial applications is provided
by Higman and van der Burgt in their comprehensive treatise on industrial
gasifi cation processes (Higman and van der Burgt, 2008). The IEA Clean
Coal Centre has also recently published excellent reviews on the commercial
technology confi gurations currently available from the leading gasifi cation
technology developers (Carpenter, 2008; Barnes, 2011; Mills, 2012).
16.3.1 Entrained fl ow gasifi ers
Entrained fl ow gasifi ers feed pulverised coal at high pressures into a gasifi er
where temperatures and pressures are high (up to, and possibly over 1800–
2000 K and 2.0–4.0 MPa) and residence times are low (up to 5 s). Due to
Coal gasifi cation and conversion 435
© Woodhead Publishing Limited, 2013
their high reaction rates, entrained fl ow gasifi ers offer high throughput and
conversion for a wide range of feedstocks, making them the most common
gasifi cation technology for large IGCC applications (Table 16.2).
The available commercial entrained fl ow gasifi cation technologies are
differentiated by particular combinations of feeding method and oxidant
type, gasifi er confi guration and construction material, and mode of syngas
quench. The impacts of these variations on fuel requirements and syngas
quality (and therefore suitability for downstream applications) means that
most technology vendors are continually exploring variants to their gasifi er
design and syngas-processing confi guration. For example, Shell now offers
a partial quench system and Siemens is developing a radiant syngas cooler
confi guration to suit specifi c applications.
Slurry-fed gasifi ers (such as the GE gasifi er) overcome issues associated
with feeding powdered solids into pressure vessels and can operate at very
high pressures; however, the increased reliability and decreased capital cost
comes at the expense of a greater oxygen demand due to the increased
thermal load. Refractory-lined gasifi ers (such as GE, Phillips 66 EGas) are
extremely fl exible in mineral matter content and properties of the feedstock,
but are more susceptible to ceramic liner erosion and corrosion than water-
wall (or membrane-lined) gasifi ers. Membrane-walled gasifi ers (such as
Shell and Siemens) require a protective slag layer to form, which is strongly
dependent on the properties of the coal used.
Two-stage gasifi ers (such as the MHI and Phillips 66 EGas gasifi ers) have
two coal injection points: one in the ‘combustion’ stage, where heat is gener-
ated to melt the mineral matter and to drive the gasifi cation reactions, and
one in the second stage, where coal and char are ‘gasifi ed’ using the heat and
gaseous products from the combustion stage. The second stage also serves
as a ‘chemical quench’, whereby the progress of the gasifi cation reactions
partially cools the syngas and stores this heat as chemical energy in the syn-
gas. They consequently have greater cold gas effi ciencies than single-stage
Table 16.2 Characteristics of the leading commercial goal gasifi cation
technologies
Technology Stages Oxidant Feed Confi guration Gasifi er wall
Shell, PRENFLO 1 O 2 Dry Up-fl ow Water-wall
GE 1 O 2 Slurry Down-fl ow Refractory
Conoco-Phillips E-Gas 2 O 2 Slurry Up-fl ow Refractory
MHI 2 Air Dry Up-fl ow Refractory
and Water-
wall
Siemens 1 O 2 Dry Down-fl ow Water-wall
Source: Harris and Roberts, 2010.
436 The coal handbook
© Woodhead Publishing Limited, 2013
gasifi ers; however, this can be offset by higher rates of unconverted carbon
(and char recycle) and the possible production of some tar species (two-
stage gasifi ers often have a char-recycling capability, which increases the
total carbon conversion but also increases the capital cost).
Most entrained fl ow gasifi ers are oxygen-blown, as the presence of signif-
icant amounts of N 2 is detrimental to the downstream chemical production
processes for which most of these gasifi ers were designed. For oxygen-blown
gasifi cation, air is separated in an air-separation unit (ASU) and high purity
O 2 (usually over 90%) is used as the oxidant, usually with steam to manage
the temperature. There are signifi cant capital and operating costs associated
with operating an air-separation unit: the ASU can comprise up to 15% of
the capital cost of an IGCC plant, and consume up to 20% of the power
generated (Lowe et al ., 2008). The greater gas volumes associated with air-
blown gasifi cation, however, are also signifi cant: gasifi ers must be larger, and
downstream syngas cooling and cleaning plant must also be larger (Higman
and van der Burgt, 2008). For IGCC applications, therefore, there is a trade-
off between capital cost and operating cost and reliability.
The need for higher effi ciencies and lower cost for gasifi cation systems,
particularly for application in the power generation sector, is driving new
initiatives in gasifi er design. Several new technology variants have emerged
in recent years and these are at various stages of development and commer-
cialisation. Some of the leading examples are indicated below.
Pratt and Whitney Rocketdyne (PWR) is developing a high intensity, com-
pact gasifi cation technology aimed at signifi cantly reducing the size and cost
of commercial scale gasifi cation systems. The technology builds on PWR’s
rocket engine experience and comprises a high pressure dense phase dry
feed system with rapid mixing via multiple fuel injectors. The gasifi cation
reactions proceed in a high velocity plug fl ow tubular reaction zone with
advanced gasifi er wall cooling system. The technology is currently undergo-
ing pilot scale testing using an 18 ton/day test facility at the Gas Technology
Institute at Des Plaines, Illinois. Performance and design targets include
90% reduction in size and up to 50% reduction in cost of the gasifi er unit
(Darby, 2010).
Several commercial scale gasifi cation technology variants are now reach-
ing demonstration scale in China and these are expected to be deployed
in future coal to chemicals and liquid fuels plants which are undergoing
strong growth in China (Minchener, 2011). The most mature of these is
the ‘Opposed Multi-burner’ (OMB) gasifi er developed by the Institute of
Clean Coal Technology (ICCT) at the East China University of Science and
Technology. This gasifi er uses a coal-water slurry feed injected through four
opposed fi red burners at the top of the down-fl ow gasifi er unit. A dry-fed
variant is also under development. The gasifi er also uses an internal water
quench system which simplifi es slag removal and gas clean-up. The Huaneng
Coal gasifi cation and conversion 437
© Woodhead Publishing Limited, 2013
Clean Energy Research Institute (HCERI), formerly the Thermal Power
Research Institute (TPRI), has developed a 2-stage up-fl ow entrained fl ow
gasifi er which is part of the Chinese GreenGen project. Phase 1 of this proj-
ect is now under way and plans include operation of a 400 MW IGCC dem-
onstration project in 2015.
16.3.2 Fixed-bed gasifi ers
Fixed-bed gasifi ers (shown schematically in Figure 16.4) operate in a man-
ner similar to blast furnaces, where lump coal is fed from the top and oxygen
(and therefore heat) is supplied from the bottom. Solids residence times are
high and coal mineral matter is removed either dry (as in the SASOL-Lurgi
gasifi ers) or as a slag (as in the slagging British Gas-Lurgi technology).
Fixed-bed gasifi ers have specifi c requirements of coal properties: struc-
tural stability of the slowly moving bed of coal and char is important, as is
the ability for gas to permeate uniformly through the coal and char bed. The
relatively low throughput per unit, somewhat low degree of fuel fl exibility
and the tendency for the syngas to contain relatively high levels of tars make
Coal
Bunker
Feeder
Coallock Quench
liquor
Crude gas togas cooling
Steam
Waste heatboiler
Boiler feedwater
Quenchcooler
Rotatinggrate Stream and
oxygen
Ash lock
Ash to sluiceway
Gas liquor
16.4 The Sasol-Lurgi dry-bottom fi xed-bed gasifi cation technology (Van
Dyk et al ., 2004).
438 The coal handbook
© Woodhead Publishing Limited, 2013
fi xed-bed gasifi ers generally better suited to applications such as chemicals,
SNG and liquid fuels production than for large-scale IGCC power genera-
tion applications.
16.3.3 Fluidised and circulating bed gasifi ers
A range of fl uid-bed processes have been used as the basis of gasifi cation
for syngas production. These gasifi ers involve the fl uidisation of a bed of
feedstock and ‘bed material’, often a mixture of coal ash and (possibly) a
calcium-based sorbent for in-bed capture of sulphur species. The coal feed
particle size (~1–3 mm) is smaller than fi xed-bed gasifi ers (10–50 mm), but
signifi cantly larger than entrained fl ow gasifi ers (< 200 μ m), and the tem-
peratures of operation are lower than entrained fl ow gasifi ers, typically 850–
900 ° C. This low temperature is required to ensure that the mineral matter in
the feed remains dry and does not become sticky, although agglomerating
fl uidised bed technologies operate at slightly higher temperatures in order
to remove the ash as large agglomerates. The lower operating temperatures
of fl uidised bed gasifi ers mean that high fuel reactivity is important, and
they may be particularly suitable for feedstocks with high levels of volatile
alkali species. Hence fl uidised beds are commonly used for biomass, lignite
and brown coal gasifi cation.
The method of fl uidising the bed varies between technologies, and gener-
ally the key variable is the velocity of fl uidising gas. Figure 16.5 demonstrates
this for three of the more common fl uidised bed approaches: stationary
Gas flowSolids flow
Stationary fluid bed
Vel
ocity
Circulating fluid bed Transport reactor
Increasing solidsdensity
Increasing expansion
Mean gas velocity
Mean solids velocity
Slipvelocity
16.5 Regimes of fl uid-bed operation (Higman and van der Burgt, 2008).
Coal gasifi cation and conversion 439
© Woodhead Publishing Limited, 2013
(and bubbling) fl uidised bed, where the bed and the gas above the bed form
two discrete phases; circulating fl uidised bed, where there is a considerable
degree of particle carryover and recirculation into the fl uidised bed; and the
transport gasifi er, which involves a high degree of entrainment and recircu-
lation of the bed material.
The deployment of large-scale fl uidised bed gasifi ers is not widespread
and most commercial units are small by power utility standards. There are
several fl uidised bed gasifi cation plants in Europe and Asia where they are
used primarily for conversion of biomass and waste material to syngas for
power generation or other applications. The 100 MW coal-fi red IGCC dem-
onstration project at Pi ñ on Pine in Nevada was based on a Kellogg Rust
Westinghouse agglomerating fl uidised bed gasifi er. At the time of its dem-
onstration, this plant was unable to be successfully operated under commer-
cial power industry reliability and availability requirements due to problems
with the reliability of the gas-cleaning plant and general integration issues
(Cargill et al ., 2001). The Transport Integrated Gasifi cation (TRIG TM ) tech-
nology is being developed by Southern Company and KBR, and several
commercial projects to demonstrate this technology are in development
(e.g. Pinkston and Salazar, 2007).
16.4 Coal properties and gasification performance
The range of gasifi er technologies discussed above leads to a spectrum of
fuel properties suitable for gasifi cation. These properties differ signifi cantly
between entrained fl ow, fi xed bed, and fl uidised bed gasifi ers. It is clear,
however, that traditional properties used to assess a coal’s suitability for use
in pf combustion applications are not suitable for assessing coals for use in
gasifi cation. Table 16.3 summarises some of the key coal properties that are
known to make particular feedstocks suitable for use in specifi c gasifi cation
technologies. Subsequent sections discuss these in more detail in the context
of specifi c gasifi er technology variants.
16.4.1 Coal properties suitable for entrained fl ow gasifi ers
The key fuel property for use in entrained fl ow gasifi cation is the ability of
the coal mineral matter to melt and fl ow out of the gasifi er as a liquid slag.
Measurements of the Ash Fusion Temperature (AFT) of ash can give some
insights into the temperature at which the mineral matter will soften and melt,
without providing important information regarding the viscosity and fl ow
behaviour of the slag. Measurements of slag viscosity are more suited to charac-
terising coal mineral matter in terms of its behaviour under entrained fl ow gas-
ifi cation conditions, and for quantifying the fl ux addition requirements, if any.
© W
oodhead P
ublis
hin
g L
imite
d, 2
013
Table 16.3 Summary of general coal requirements for use in specifi c coal gasifi cation technologies
Entrained fl ow Fluidised bed Fixed bed
Example Shell, GE, Siemens, MHI, Prenfl o High temperature Winkler, KBR
TRIG transport gasifi er
Sasol-Lurgi, British Gas-Lurgi
Coal Pulverised
For slurry feed low moisture or hydrophobic coals
preferred.
Crushed (0.5–5 mm), TRIG
fi ner. Often mixed with a
bed material to aid heat
transfer and to capture
S-species.
Lump (5–80 mm).
Optimal PSD to maintain
bed integrity.
Strong requirements of coal
caking and agglomerating
behaviour.
Reactivity High reactivity coals may be cheaper to run; most
fuels can be accommodated with appropriate
knowledge.
Lower operating temperature
means reactive coals, such
as sub-bit and lignite, are
favoured.
Can handle a range of
reactivities due to long
residence time, suited to
coals with ‘moderate’ to
‘high’ reactivity.
Ash
content
Refractory systems: less ash is better. Possible
issues with slag corrosion/erosion.
Non-refractory systems have a minimum ash
requirement to protect wall.
High AFT required to prevent
ash melting or sticking.
Agglomerating FBGs have
stringent requirements on
ash melting and softening
behaviour.
Dry-bottom gasifi ers have
similar requirements of
fl uidised bed gasifi ers.
Low ash content preferred;
dry bottom can
accommodate high ash.
Slag Slag fl ow with 25 Pa s or less at tapping
temperature. Tcv (temperature of critical
viscosity) less than operating temperature.
Ash softening and/or melting is
not desirable.
For slagging operation
requirements are similar
to that for entrained fl ow
gasifi cation; for dry-bottom
operation requirements are
similar to that for fl uidised
bed.
Source: Collot, 2002, 2006.
Coal gasifi cation and conversion 441
© Woodhead Publishing Limited, 2013
It is now generally considered that to be suitable for use in entrained
fl ow gasifi cation technologies, the acceptable range for slag viscosity of a
specifi c sample is 5–25 Pa s at a temperature of 1400–1450 ° C (Hurst et al ., 1999a; Hurst et al ., 1999b; Hurst et al ., 2000). Coals are sometimes fl uxed at
up to 10–20% by weight of ash in order to reduce the temperature required
to form a suitably viscous slag. There are, of course, economic and effi ciency
penalties associated with fl ux addition, meaning that accurate calculations
of fl ux requirements are important.
Whilst the inherent fuel fl exibility of entrained fl ow gasifi ers is high,
reactivity properties of fuels are important for ensuring proper gasifi er
design, and in optimising gasifi er performance during fuel switching or
blending activities. Reactivity is an all-encompassing term describing
the relative ease (and speed) with which a particular fuel can be con-
verted to syngas. It is used to describe a range of parameters, from fun-
damental kinetic expressions through to relative assessments of the rate
of conversion of different fuels under specifi c laboratory or gasifi cation
conditions.
The intense conditions found in entrained fl ow gasifi cation allow most
carbonaceous fuels to be gasifi ed, regardless of their reactivity. Highly reac-
tive fuels, however, require lower temperatures (and therefore reduced
oxygen consumption) with smaller gasifi ers to achieve satisfactory conver-
sion levels compared with less reactive fuels. This leads to a reduction in
capital and operating costs. Knowledge of coal reactivity under entrained
fl ow conditions is therefore important for gasifi er design, and in evaluating
the most suitable operating conditions for a specifi c coal. This requires an
understanding of two key aspects of coal reactivity for entrained fl ow gas-
ifi cation: volatile yields from devolatilisation, and the nature and reactivity
of the char produced.
Volatile yields under entrained fl ow gasifi cation conditions are often
different from the volatile matter assays returned from proximate analy-
sis (Roberts and Harris, 2003). Furthermore, this difference is dependent
on a range of competing variables, including coal type (Kochanek et al ., 2011). It is diffi cult to predict the volatile yield of a specifi c coal under a
particular combination of temperature, pressure, and heating rate, without
supporting laboratory measurements made under appropriate conditions
of temperature, pressure, and heating rate. Reactivity of the char pro-
duced from devolatilisation is known to be strongly dependent on a com-
bination of structure and intrinsic reactivity properties. By understanding
both of these aspects of char reactivity, accurate models can be developed
(Hla et al ., 2005) that relate coal properties to gasifi cation behaviour, and
ultimately how fuel variations can impact on gasifi er performance (see
later sections).
442 The coal handbook
© Woodhead Publishing Limited, 2013
16.4.2 Coal properties suitable for fi xed and fl uidised bed gasifi ers
Fixed-bed gasifi ers operate with a fi xed or slowly moving bed of lump coal
(5–50 mm), through which the oxidant (and product) gases fl ow. This places
particular requirements on the structural and porous properties of the coal,
as the bed of fuel is required to be self-supporting whilst allowing the reac-
tants and products to permeate. Reactivity requirements are, generally, sec-
ondary, as the particles have long residence times (up to an hour) usually
allowing for good conversion of a range of coals.
The implications for coal requirements in slagging fi xed-bed gasifi ers are
similar to those for entrained fl ow gasifi cation: the mineral matter must
melt and fl ow out of the gasifi er as a molten slag. In this context, require-
ments are similar to those of a blast furnace. Conversely, dry-bottom fi xed
bed gasifi ers have similar requirements of the mineral matter to con-
ventional pf combustion systems, where the ash should not melt or form
agglomerates.
Fluidised bed gasifi ers operate at intermediate temperatures, low enough
to prevent the softening and melting of the coal mineral matter, but high
enough to achieve satisfactory conversion levels. The low temperatures (rel-
ative to entrained fl ow gasifi cation) mean that fl uidised bed gasifi cation is
particularly suitable for high-reactivity coals, which can achieve good con-
version in residence times of up to a few minutes.
16.5 Tools for gasification performance assessment
It is clear from the descriptions in the previous sections that there are no
readily-determinable coal properties that can be used for routine assessment
of a fuel for use in the variety of gasifi cation technologies in use and under
development. We do know, however, that our understanding of coal perfor-
mance in combustion systems (such as pf boilers) cannot be used directly to
make an assessment of the suitability of coals for use in gasifi cation. In order
to estimate coal suitability for use in gasifi cation-based systems, we need to
have models based on sound experimental data that accurately refl ect coal
behaviour under the wide range of conditions present in the different gasifi -
cation technologies. The development and application of these models need
to be supported by a practical coal test procedure, which can assess the key
stages of the conversion of coal in a gasifi er – in particular those stages that
affect the operation of specifi c gasifi er technologies allowing the differentia-
tion of coal performance under gasifi cation conditions.
Perhaps the most defi nitive of the coal properties is the behaviour of
the mineral matter, in particular its ability to fl ow at temperatures that are
suitable for entrained fl ow and slagging fi xed bed technologies, or for its
Coal gasifi cation and conversion 443
© Woodhead Publishing Limited, 2013
tendency to agglomerate or foul surfaces in fl uidised bed or dry-bottom
fi xed-bed gasifi ers.
The ash fusion temperature (AFT) is a common analysis performed on a
coal sample as part of its routine characterisation, and can be a useful indi-
cator of the general suitability of a specifi c coal for entrained fl ow gasifi ca-
tion. The AFT, however, is unable to provide information regarding the fl ow
characteristics of the coal’s molten slag; therefore more advanced techniques
are required for coal assessment and gasifi er operation optimisation.
Facilities exist for the measurement of coal slag viscosities at entrained
fl ow gasifi cation temperatures, and accompanying models are able to opti-
mise potential coal blends or fl ux addition requirements (e.g. Patterson et al ., 1998; Hurst et al ., 1999a; Hurst et al ., 1999b; Patterson and Hurst, 2000). As
noted above, to be suitable for use in entrained fl ow gasifi cation technolo-
gies, the maximum limit for slag viscosity is about 25 Pa s (ideally under 15
Pa s) at a temperature of 1400–1450 ° C (Patterson et al ., 1998). By analysing
the composition of the mineral matter, comparing this composition to
known samples, and by making measurements of slag viscosity behaviour,
the potential suitability of a specifi c sample from a slag behaviour perspec-
tive can be assessed. Furthermore, if a coal sample has mineral matter that
does not perform satisfactorily, then blending or fl uxing strategies can be
developed (see Fig. 16.6).
Studies of mineral matter suitability are supported by laboratory and
technical scale measurements of specifi c aspects of the coal conversion pro-
cess. Of particular signifi cance are the amount and nature of the char pro-
duced from devolatilisation, and how fast this char is converted to syngas
(Fig. 16.7). Using laboratory-scale facilities (e.g. Harris et al ., 1999) reliable,
transportable data are able to be generated that refl ect important aspects of
coal conversion behaviour under gasifi cation conditions (Harris et al ., 2003;
Kajitani et al ., 2006).
A key aspect of these studies is the ability to interrogate the gasifi ca-
tion process under conditions relevant to entrained fl ow gasifi cation, using
laboratory-scale, high pressure, entrained fl ow facilities (e.g. Fig. 16.8). Such
facilities allow the temporal resolution of the coal and char gasifi cation pro-
cess over a range of temperatures, pressures, and O:C ratios. This provides
unique and important insights into the impact of coal type and operating
conditions on coal behaviour under gasifi cation conditions (e.g. Figs 16.9
and 16.10) and provide insights into the chemical and physical reaction
processes that lead to these differences (e.g. Figs 16.11 and 16.12). Along
with the slag formation and fl ow issues discussed above, this knowledge is
able to be linked with operating strategies of pilot-scale gasifi cation systems
(Roberts et al ., 2012a, 2012b).
To allow regular and reliable application of a sound fundamental under-
standing of gasifi cation science to the solving of real industrial problems,
444 The coal handbook
© Woodhead Publishing Limited, 2013
40
30
20
Vis
cosi
ty (
Pa.
s)
10
013001200 1400
100/20Ash/CaCO3
Bulk sampleCoal B
100/10 100/0
ExperimentalPredicted
Experimental
Coal ash A
Ash/CaCO3100/75 100/50 100/25
100/100
Predicted
1500Temperature (°C)
1600
40
30
20
Vis
cosi
ty (
Pa.
s)
10
013001200 1400 1500
Temperature (°C)1600
40
30
20
Vis
cosi
ty (
Pa.
s)
10
013001200 1400 1500
Temperature (°C)1600
Tcv
Experimental
S102 Coal ash
Predicted
16.6 Slag viscosity measurements at different temperatures,
demonstrating the impact of fl ux addition (Patterson and Hurst, 2000).
Coal gasifi cation and conversion 445
© Woodhead Publishing Limited, 2013
knowledge of coal pyrolysis, char formation, char reactivity, slag formation
and fl ow, and coal gasifi cation behaviour needs to be integrated in a form
that is applicable to a range of gasifi cation technologies and, eventually, gas-
ifi cation-based energy systems. The fundamental, experimental gasifi cation
research in Australia has always been undertaken in parallel with the devel-
opment of mechanistic models designed to allow more widespread applica-
tion of the outcomes.
Work by Shan et al. (Shan, 2000) and Liu et al. (Liu et al ., 2000) mod-
elled coal devolatilisation and char reactivity, respectively, under the high
pressures relevant to entrained fl ow gasifi cation technologies. Hla et al . (Hla
et al ., 2005; Hla et al ., 2006) integrated these models into an overall one-
dimensional gasifi cation model that was able to describe well gasifi cation
measurements made in research reactors such as the entrained fl ow reactor
in Fig. 16.8. Application of these gasifi cation models to the complex fl ow
systems present in industrial-scale gasifi ers (Hla et al ., 2011) allows impacts
of feedstock variation and operating parameters to be estimated (Figs 16.13
and 16.14).
By integrating these performance models with our understanding of slag
formation and fl ow behaviour, we can begin to understand the implications
of variations in feedstock quality, operating conditions, etc. on the perfor-
mance of a gasifi er and, ultimately, the performance of gasifi cation-based
systems for the production of power or other products. This requires the
integration of the fundamentally-based gasifi cation and gasifi er models
Pyrolysis
Heterogeneouschar-gas reaction
Volatile evolution
Char combustionO2
CO/CO2
CO2 and H2O
CO + H2
Char gasification
Ash and slag formation
16.7 A schematic of the coal conversion process. (Source: After Harris
and Patterson, 1995.)
446 The coal handbook
© Woodhead Publishing Limited, 2013
discussed here with process simulation tools. Whilst there exists a large
number of studies in the literature whereby process modelling approaches
are used to compare different technology combinations, those using gas-
ifi cation as an enabling technology are not able to differentiate based on
Gas analysis
Feeder, 1–5 kg/hrParticle size–180+45 μm
Preheating and mixing(O
2, N2, H2O, and CO2)
Three-section reaction zone: temperatures upto 1500°C, residence times 0.5–3.0 s
Oil-cooled isokinetic sampling probeand gas analysis system
Water quench
16.8 CSIRO’s high pressure entrained fl ow gasifi cation reactor, for
studying details of coal gasifi cation behaviour under gasifi cation
conditions (Harris et al ., 2006).
Coal gasifi cation and conversion 447
© Woodhead Publishing Limited, 2013
coal reactivity, conversion, or slag behaviour. This has fl ow-on effects for the
development of tools to support a transition to the next generation of power
and fuels production systems in Australia and around the world: gasifi cation
with effi cient, large-scale carbon capture.
16.6 Gasification as a route to efficient carbon capture
Capturing CO 2 from coal-fi red plant will impact on the capacity and effi ciency
regardless of the platform technology. The nature of gasifi cation-based pro-
cesses, however, mean that this impact is signifi cantly less than for technologies
which have not integrated the carbon capture step with the process scheme.
Carbon capture is estimated to decrease overall conversion effi ciency by
more than 6 % points and to increase capital cost by up to 40%. As with
×× ×× × ×
+
+
+
+ +
+
+++
+ +++
×× ××
×
×
50(a)
(b)
CRC297
95965
CRC252
CRC272
CRC283
CRC263
CRC240
CRC296
CRC298
CRC274
CRC310
CRC284
CRC299
CRC281
CRC252
CRC263
CRC298
CRC274
CRC299
CRC358
CRC281
40
30
Gas
ifica
tion
effic
ienc
y (%
)G
asifi
catio
n ef
ficie
ncy
(%)
20
10
0
00 50 100
O:C Stoichiometry (%)
150 200 250
20
40
60
80
+
16.9 Effects of O:C ratio on gasifi cation effi ciency at 20 bar pressure
and (a) 1100 ° C and (b) 1400 ° C for a wide range of Australian coals
(Harris et al ., 2006).
448 The coal handbook
© Woodhead Publishing Limited, 2013
the main IGCC plant, substantial improvements to the CCS process com-
ponents can be envisaged and development of these would substantially
reduce the cost and effi ciency penalties associated with CCS as part of a
gasifi cation-based system.
+
+
++
++
××××
×
××
××
×
×
×
××
×
××
100(a)
80 Char conversion CRC274
CRC310
CRC299
CRC358
CRC281
CRC252
CRC274
CRC298
CRC263
CRC358
Pet coke
Vol
atile
rel
ease
60
40
20
0
100(b)
80
60
40
20
00.0 0.5 1.0 1.5 2.0
Residence time (s)
Car
bon
conv
ersi
on (
%)
Car
bon
conv
ersi
on (
%)
2.5 3.0
16.10 Effects of temperature (a) 1100 ° C and (b) 1400 ° C and coal type on
conversion at 20 bar pressure and an O:C of ~1:1 (Harris et al ., 2006).
100
80
CRC252 CRC272 CRC2811673 K1573 K1473 K1373 K1273 K
Sub bit, high vol Bituminous Semi anthracite
60
40
20
00.0 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5
Residence time (s)Residence time (s)
Cha
r co
nver
sion
(%
)
Residence time (s)2.0 2.5 3.0
16.11 Impacts of char structure on high temperature gasifi cation
reaction rates. (Source: After Roberts et al ., 2010.)
Coal gasifi cation and conversion 449
© Woodhead Publishing Limited, 2013
Regardless of the application, syngas produced from gasifi cation requires
treatment to remove solid and gaseous impurities and to prepare the gas
stream for subsequent processes, whether they be thermal (e.g. gas tur-
bine) or chemical (e.g. Fisher-Tropsch catalytic conversion to fuels) systems.
Gasifi cation-based chemical processes have proven and well-developed
solvent-based systems to remove sulphur and other acid gases such as CO 2
from the syngas prior to conversion to the desired product. Common com-
mercial solutions are based on the Rectisol and Selexol processes, which
have been extensively proven in a range of applications.
First-generation IGCC-CCS systems (i.e. IGCC with carbon capture) use this
proven solvent technology for integrated capture of CO 2 as part of the process
scheme, with the resulting H 2 -rich gas used in H 2 turbines for power genera-
tion. A typical commercial gasifi cation-based hydrogen and CO 2 production
2
CRC252 CRC272 CRC2810
–2
–4
–6
1673 K1573 K1473 K1373 K1273 KFBR dataRegime 2Regime 1
–8
–10
–12
–140.0005 0.0006 0.0007 0.0008
1/temperature (1/K) 1/temperature (1/K) 1/temperature (1/K)
0.0009 0.0005 0.0006 0.0007 0.0008 0.0009 0.0005 0.0006 0.0007 0.0008 0.0009 0.0010
16.12 High temperature gasifi cation reaction rates, demonstrating
the transition from ‘intrinsic’ reactivity conditions to those at higher
temperatures where pore diffusion limitations are signifi cant. (Source:
After Roberts et al ., 2010.)
60CRC701CRC702CRC703CRC704
90
85
80
80
75
70
CG
E (
%)
65
50
40
30
20
Gas
com
posi
tion
(vol
%)
10
01.0 1.1 1.2 1.3 1.4 1.5 1.6 0.9 1.0 1.1 1.2
Stoichiometry (O:C ratio)
1.3 1.4 1.5 1.6Stoichiometry (O:C ratio)
16.13 Example of the use of gasifi cation models to understand the
impact of coal properties on gasifi er performance (Hla et al ., 2011).
Here, CGE = ‘cold gas effi ciency’, an indicator of the relative effi ciency
of the performance of the gasifi er in converting energy in the feed to
energy in the syngas.
450 The coal handbook
© Woodhead Publishing Limited, 2013
process is shown in the upper schematic of Fig. 16.15. Hot syngas leaving the
gasifi er unit is cooled (often using a wet quench) before it is cleaned of gas-
eous and particulate impurities. The clean syngas is then reacted with addi-
tional steam in a multi-stage shift reactor to convert CO to CO 2 and to produce
7
6
5
4
Gas
ifier
hei
ght (
m)
Gas
ifier
hei
ght (
m)
3
2
1
00.000
7
6
5
4
3
2
1
00.000 0.020 0.040 0.060 0.0800.005 0.010
Liquid slag thickness (m)Gas temp.
(°C)
Solid slag thickness (m)0.015
Benyon Seggiani Benyon Seggiani
16.14 Model simulations of gas temperature and slag thickness on the
wall of the ELCOGAS Prenfl o gasifi er (Benyon et al ., 2001).
Gasifier
Coal
CO+H2
CO + H2O = CO2 + H2
CO2+H2 H2
CO2
H2
CO2
Gascleaner
High Tshift
Membrane shifter
Coal
Mem
bran
ere
acto
r
Cur
rent
tech
nolo
gy
Low Tshift
Gas separation
16.15 Conventional and prospective syngas cleaning, processing and
gas separation technologies for CO 2 capture from large-scale hydrogen-
based energy systems.
Coal gasifi cation and conversion 451
© Woodhead Publishing Limited, 2013
additional hydrogen. This is an exothermic process and requires staged cooling
to maintain catalyst activity and appropriate conversion yields. The CO 2 /H 2 gas
mixture is then separated, often using solvents or pressure swing adsorption
processes to produce pure CO 2 and hydrogen product streams.
The need for a multi-stage process with multiple heating and cooling
cycles adds complexity and cost (both in capital and operating) and reduces
the thermal effi ciency of the process. Whilst technically mature and well-
demonstrated, there is the opportunity to decrease capital and operating
costs for more widespread application in the power industry through the
development of new gas separation systems involving high temperature
water-gas shift catalysts, membrane-based systems for separating CO 2 and
H 2 , and the integration of these multi-stage unit processes into a single ‘cat-
alytic membrane reactor’, or CMR.
Current research efforts are addressing each of the critical steps in the
technology chain illustrated in Fig. 16.15 with the aim of developing simpli-
fi ed, integrated syngas processing technologies as indicated conceptually in
the lower diagram in Fig. 16.15.
Alloy membranes offer a solution to the challenge of large-scale, cost-
effective separation of CO 2 and H 2 as part of the next generation gas
1e-7
9e-8
8e-8
7e-8
6e-8
V-Ni-Pd
V-Ti-Ni
V85Ni15
Pd75Ag25
Pd
a-Ni42Nb28Zr30
V-Ni-Al
5e-8
4e-8
Per
mea
bilit
y (m
ol m
–1 s
–1 P
a–0.
5 )
3e-8
2e-8
1e-8
0280 300 320 340
Temperature (°C)360 380 400 420
16.16 Hydrogen permeability of different alloy materials, compared
with the ‘benchmark’ of palladium. (Source: After Dolan et al ., 2011.)
452 The coal handbook
© Woodhead Publishing Limited, 2013
separation systems (Dolan et al ., 2006; Dolan et al ., 2009). By seeking alter-
native materials to expensive palladium, and addressing issues of durability,
membranes that meet the US DoE performance targets can be manufac-
tured which are infi nitely selective to hydrogen and can be operated at
temperatures suitable for gasifi cation-derived syngas processing. By alloy-
ing vanadium, titanium and nickel, crystalline membranes with permeabili-
ties orders of magnitude greater than those for palladium membranes can
be manufactured (Fig. 16.16). There is also the option of using amorphous
materials (lower dataset in Fig. 16.16) which offer slightly reduced perme-
abilities but with signifi cant savings in cost.
Combining membrane materials such as these with water-gas shift reac-
tion catalysts, it is possible to continuously (and with 100% selectivity)
remove H 2 from the process using a catalytic membrane reactor (CMR).
Such systems allow greater-than-equilibrium conversion of syngas to sepa-
rate streams of CO 2 and H 2 in a single process step. This has the potential to
replace the high and low-temperature water-gas shift process, and the sol-
vent extraction and regeneration processes, with a single reactor unit offer-
ing a considerable decrease in both capital and operating costs.
It is important to ensure that gasifi cation-based technologies such as
IGCC are considered a part of the ‘CCS’ solution to ongoing coal use in a
carbon-constrained world. Whilst they do require investment in plant which
has not traditionally been used in the power generation sector, and which
has associated with it increased costs and perceptions of risk, this chapter has
shown that, from an international perspective, there is a signifi cant amount
of operating experience with coal gasifi ers. These technologies have also
been demonstrated at a commercial scale for power generation. Ongoing
research and development activities around the world are addressing issues
regarding cost and risk in terms of gasifi er design and operation, as well as in
advanced technologies for effi cient and cost-effective carbon capture.
16.7 References Barnes, I. (2011) Next generation coal gasifi cation technology , Report Number
CCC/187 IEA Clean Coal Centre.
Benyon, P., Boyd, R. and Lowe, A. (2001) Engineering Applications of Gasifi er Data-Gasifi er Simulations , Cooperative Research Centre for Black Coal Utilisation,
Commonwealth of Australia, CRC Research Report 29.
Cargill, P., DeJonghe, G., Howsley, T., Lawson, B., Leighton, L. and Woodward, M.
(2001) Pinon Pine IGCC Project – Final Technical Report to the Department of Energy , DOE Award Number DE-FC21-92MC29309.
Carpenter, A. M. (2008) Polygeneration from Coal , Report Number 978-92-9029-
458-0 IEA Clean Coal Centre.
Collot, A. G. (2002) Matching gasifi ers to coals , IEA Coal Research Report CCC/65
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Collot, A. G. (2006). Matching gasifi cation technologies to coal properties.
International Journal of Coal Geology, 65 , 191–212.
Commonwealth of Australia (2012) Energy White Paper 2012 , Commonwealth of
Australia, Department of Resources, Energy and Tourism, ISBN 978-1-922106-
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Darby, A. (2010) In Gasifi cation Technologies Conference , Gasifi cation Technologies
Council, Washington DC.
Dolan, M. D., Dave, N. C., Ilyushechkin, A. Y., Morpeth, L. D. and McLennan, K. G.
(2006) Review: Composition and operation of hydrogen-selective amorphous
alloy membranes. Journal of Membrane Science, 285 , 30–55.
Dolan, M. D., Dave, N. C., Morpeth, L. D., Donelson, R., Kellam, M., Liang, D. and
Song, S. (2009) Ni-based amorphous alloy membranes for hydrogen separation
at 400 ° C. Journal of Membrane Science, 326 , 549–555.
Dolan, M. D., Song, G., Liang, D., Kellam, M. E., Chandra, D. and Lamb, J. (2011)
Hydrogen transport through V 85 Ni 10 M 5 alloy membranes. Journal of Membrane Science, 373 , 14–19.
Gasifi cation Technologies Council (2012) http://www.gasifi cation.org/database1/
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Harris, D. J. and Patterson, J. H. (1995) Use of Australian Bituminous Coals in IGCC
Power Generation Technologies. Australian Institute of Energy News Journal, 13 , 22–32.
Harris, D. J. and Roberts, D. G. (2010) ANLEC R&D Scoping Study: Black Coal IGCC , CSIRO Report EP103810 CSIRO Energy Technology.
Harris, D. J., Roberts, D. G. and Henderson, D. G. (2003) Gasifi cation Behaviour of Australian Coals , ACARP Project C9066, Final Report (ET/IR 630R) CRC for
Coal in Sustainable Development.
Harris, D. J., Roberts, D. G. and Henderson, D. G. (2006) Gasifi cation behaviour of
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for ACARP Project C6052 CRC for Black Coal Utilisation, August 1999.
Higman, C. and van der Burgt, M. (2008) Gasifi cation, Gulf Professional Publications,
Burlington, MA.
Hla, S. S., Harris, D. J. and Roberts, D. G. (2005) A coal conversion model for interpre-
tation and application of gasifi cation reactivity data. International Conference on Coal Science and Technology , Okinawa, Japan.
Hla, S. S., Harris, D. J. and Roberts, D. G. (2006) CFD modelling for an entrained fl ow
gasifi cation reactor using measured ‘intrinsic’ kinetic data. Fifth International Conference on CFD in the Process Industries , Melbourne, Australia.
Hla, S. S., Roberts, D. G. and Harris, D. J. (2011) Using Fundamental Data to Model
Entrained Flow Gasifi cation: Impacts of Coal Type on Gasifi er Performance.
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Hurst, H. J., Novak, F. and Patterson, J. H. (1999b) Viscosity measurements and
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Hurst, H. J., Patterson, J. H. and Quintanar, A. (2000) Viscosity measurements and
empirical predictions for some model coal gasifi er slags-II. Fuel , 79 , 1797–1799.
Kajitani, S., Suzuki, N., Ashizawa, M. and Hara, S. (2006) CO2 gasifi cation rate analy-
sis of coal char in entrained fl ow coal gasifi er. Fuel , 85 , 163–169.
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Systematic Study of the Effects of Pyrolysis Conditions on Coal Devolatilisation.
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