1. 1 Copyright © 20xx by ASME
Proceedings of ASME Turbo Expo 2010: Power for Land, Sea and Air
June14-18, 2010, Glasgow, Scotland
GT2010-22225
SYNGAS FUEL HYBRID 45 MW GTCC/ORC POWER PLANT USING MODULAR
500 TPD COAL/BIOMASS MODULAR PYROLYTIC GASIFICATION
Septimus van der Linden
BRULIN Associates, LLC
Chesterfield, Virginia, USA
Mark Wiley
Wiley Consultants, LLC
Denver, Colorado, USA
Gary Williams
Earth Fuels Corporation
Sandton,Gauteng, South Africa
Roel Swart
Ansaldo Thomassen B.V
Rheden, Netherlands
ABSTRACT
This paper presents a solution for developing economies
where power shortages require power plants in the range of
30/50 MW or larger to support industrial facilities such as
mining or industrial parks where natural gas is not available
and where diesel fuel is expensive, but where coal is readily
available.
Recent developments with Pyrolytic gasification systems by
Wiley Consulting, capable of modular 500tpd of coal or
biomass, were investigated for power starved sub-Saharan
African countries. This Gasifier does not require an oxygen
plant and produces a Syngas that can be combusted in
modified FR6B gas turbines. The Syngas needs to be
compressed and the parasitic load is accommodated with
steam injection for NOx control and power enhancement to
power the fuel gas compressor. To simplify the exhaust heat
power recovery, the Cascading Closed Loop Cycle (CCLC)
Organic Rankine Cycle (ORC) system was integrated into
this system, resulting in a nominal 45 MW coal or biomass
power plant at altitudes over 1000m achieving 40%+
efficiency.
Coal fired steam plant Rankine cycle was considered
expensive and inefficient due to the requirements of low
emissions as well as more than 70% of the fuel energy
rejected in the condensing system. Using the Gas Turbine
Brayton cycle to combust Synthesis Gas (produced by an
innovative Pyrolytic and modular gasification process that
did not need an oxygen plant) was considered a practical
alternative, especially as the Gas Turbine is air cooled. To
fully capture the value of the Syngas fuel, the Gas Turbine
exhaust energy would be recovered in an ORC which
avoided the use of water and provided excellent load
following characteristics as well as the capability to
turndown to 40% or lower loads.
The criteria established for the power plant was to build and
commission the plant in 24 months or less. This
necessitated looking at available used and refurbished
generating equipment. The modular Gasifier, already
demonstrated as a 250 tpd system, could readily be scaled to
500 tpd coal or biomass with about the same footprint and
dispatched in modules for fast installation. The availability
of a used 38 MW class GT for refurbishment and
modification to Syngas fuel combustion system allowed site
installation within one year and the provision of emergency
power using available diesel fuel.
This paper will fully describe the 45 MWe Hybrid GT/ORC
Combined Cycle power plant utilizing the innovative
Pyrolytic coal gasification process as the fuel source for an
efficient low emissions power supply.
INTRODUCTION
Northam Platinum Mine on the eastern limb of the Bushveld
Complex in South Africa required a fast track solution to
overcome power curtailments imposed by ESKOM, the
state utility, and avoid mining interruptions. Earth Fuels
Corp (EFC), the project developer and marketing partner for
Wiley gasifiers in Africa, proposed an available used and
refurbished 40 MW BBC vintage reheat steam turbine
condensing power plant. The Syngas fueled packaged
boilers selected to match the turbine inlet steam conditions
are factory assembled and fully transportable, thus reducing
installation time. This option initially appeared attractive.

2. 2 Copyright © 20xx by ASME
But it required removal of the power plant in Europe and
reassembling at the mine site, requiring extensive
foundations and installation of new water cooled condensing
system. This option was abandoned in favor of a Syngas
fired gas turbine.
Using an available used (and refurbished) 25 or 38 MW Gas
Turbine converted to combust Syngas is a more efficient
solution and provides good heat source for power recovery
with an ORC. This arrangement generates power with an
efficiency of 40%+ and, based on best current estimates for
equipment and modular plant installation, is the best cost
option using one 500 tpd Gasifier.
Against the advantage of best efficiency Gas Turbine plant
performance and ratings is weighed the disadvantage of
altitude and ambient temperature derating. In addition, the
Syngas must be compressed to a higher pressure with
associated parasitic losses. The higher ambient above ISO
ratings at 15 oC (potentially 30-40 oC) can be partially
overcome with Evaporative Inlet Air Cooling or inlet air
fogging.
Two sizes of heavy duty Gas Turbines are considered.
These are currently available in the used market. Both have
power recovery to meet the minimum 20 MWe requirement
in the range of 28 to 38 MW. The GT exhaust heat power
recovery requires a Wetted Surface Air Cooled (WSAC)
condenser minimizing water consumption. Like any
condensing plant operating in high ambient temperature,
recognition is also made of plant derating.
For the 30 MW plant, one Gasifier will not be fully loaded
thereby offering reserve fuel capacity. Use of the additional
fuel is open to further discussion. The 40 MW plant will
fully load the Gasifier and is a very good solution to the
Mine’s needs. To meet an anticipated short schedule for
power delivery and allowing for a possible longer
commissioning time with the Gasifier, it was recommended
to vigorously pursue the dual-fuel Gas Turbine option to
overcome critical power shortages. This project entails the
use of a Modular (500 tpd) Pyrolytic Coal Gasification plant
to generate clean Syngas that can be used for power
generation.
There is a critical shortage of generation capacity in South
Africa and vital industries such as mining and metals have
as much as 10% power curtailment. Generating power in
small blocks of 40-80 MW is a viable option for mines, the
industrial sector and small city power plants.
Scaling-up of the Syngas demonstration plant to 500 tpd
modular plant has been studied, costed and considered as a
readily deliverable system including gas clean-up to the
remote mine. Plant footprint is compact and multiple units
can be located at one site to produce the power plant needs.
Coal quality and caloric content will define Syngas
production rate and Btu/heating value content.
Information provided by EFC on available coals for the
project indicates a range of 23-25 MJ/kg. Using the 24
MJ/kg coal (10321 Btu/lb) the 500 metric tpd Pyrolytic
Gasifier would produce a nominal 369.25 GJ/hr (350
MBtu/hr) of synthesis gas, this is based on pre-determined
margin in the design and test results of the demonstration
unit. The Syngas will have a heating value of LHV = 16080
kJ/kg (400 Btu/scf); volume % composition: 40% CO +
40%H2 + 10% CH4 + 10% CO2
.
The ability to combust the (compressed) Syngas in the
combustion GT would be the best direct conversion of
Syngas to electric power. However, the impact of
compression costs as well as site altitude and ambient have
some negative consequences, i.e. lower power production.
The benefits of higher conversion efficiency from Syngas to
electrical power are low emissions and the elimination of
the high maintenance steam water cycle.
Modular Coal Gasification Combined Cycle Power Plant
This power plant consists of one Combustion Gas Turbine
modified to combust the delivered Syngas to the fuel gas
boost compressor. The GT performance is determined by
site altitude and ambient conditions. Steam injection to
reduce NOx emissions in the combustion process will be
incorporated with steam generated in the Gasifier.
The GT exhaust energy is recovered in a power recovery
ORC, eliminating the water/steam cycle. The propane
working fluid is condensed in WSAC(Wetted Surface Air
Cooled) condensers. Cooling of the totally enclosed water
air cooled (TEWAC) electric generator, the GT and the fuel
gas compressors will be accomplished with water/air
coolers. Power will be delivered at the generator breakers
for distribution into the electrical supply. Auxiliary power
for system start-up and parasitic loads will be back-fed from
the electrical supply. GT start-up fuel No2 diesel will be
provided by on-site storage tanks. Control room,
incorporating a Distributed Control System (DCS), will
include operation and monitoring of the power plant
systems.
The Syngas is provided by a modular 500 tpd Pyrolytic
Gasifier using specific coals to supply the fuel gas delivery
at a boosted pressure of 20/22 barg.,at the indicated site
conditions. See Table 1.
Fig. 1 – Modular 500 tpd Wiley Gasifier

3. 3 Copyright © 20xx by ASME
Expected Site Power Generation
With the Syngas delivered at a pressure of 20 barg. at the
indicated site conditions, the GT performance calculation is
give in Table 1.
Fuel: Syngas (LHV –16080 kJ/kg: Composition:
(Mole %) 40% CO + 40% H2 + 10% CH4 = 10% CO2):
RH inlet air 60%
Inlet pressure drop 102 mmH2O in let dP
Exhaust pressure drop102 mmH2O Exhaust dPst
Aux. Power consumption 10 kW
Altitude 1000m.
Ambient temp. 10 – 25 – 40 oC
Modified FR6B SynGas Performance
oC Ambient 15 25 40
kW* 37919 35337 31290
kg/s Fuel 7.22 6.877 6.3
kg/s Exh 132 126.2 116.5
oC Exh 529 536 549
*at Generator Terminals
Table 1 Modified FR6B Syngas Performance
The modified performance Table 1 includes steam injection
to reduce NOx to 89mg/Nm3 @ 15% O2. The GT6B Gas
Turbine operating at site altitude and average daily ambient
temperature of 25 oC will deliver 35 MWe with the Syngas
provided by the 500 tpd Coal Gasification Plant. The Gas
Turbine load can be varied from 100% to 40% load; the
exhaust heat flow will vary accordingly. The exhaust
energy is recovered in an ORC known as CCLC developed
by WOWGen®, the power recovery will vary with load and
ambient temperature, with the plant performance indicated
in Table 2, including fuel gas compression losses.
Load kW 25 C kW 15 C
100 44252 48100
80 36743 40300
75 34157 37645
40 23500 25732
Table 2 Gasification Combined Cycle plant
performance Full and Part load (un-cooled inlet)
The Gas Turbine exhaust provides thermal input to the
propane working fluid in a Heat Recovery Unit (HRU). The
GT exhaust gas 427,329 kg/hr at a temperature of 536 oC
will generate 15,949 kWe at the generator terminals.
Allowing for pumping and parasitic losses for the air cooled
condenser, the net output is reduced to 13,252 kWe at 25 oC
ambient. The power recovery and overall plant performance,
including part load, is shown in Table 2.
Performance at 40 oC would be similar to 25 oC with the
implementation of evaporative inlet cooling which would
also benefit the 25 oC rating as described later. The system
will load up after synchronization from minimum self
sustaining load on Syngas and ramp up to any load setting.
Excess Syngas during the load ramp or part load will be
flared till the Gasifier adjusts to the load settings. There
will be some tuning for final site conditions, keeping in
mind that daily high temperature spikes in summer will
impact power plant output.
The Coal Gasification System
Thermo Technologies, LLC, has unlimited right of use of
The Wiley Integrated Syngas Technology (TWIST), its
worldwide patent pending biomass and/or coal gasification
process. This process integrates several individual
technologies to convert almost any carbon-containing
feedstock into a Syngas (which consists of hydrogen and
carbon monoxide), capture and recycle flue gas including
CO2, clean the Syngas, and treat process water. A
commercial scale reference plant (175/250 tons per day
capacity) was initially constructed in Denver, Colorado,
under an EPC contract with Thermo Conversions, LLC and
placed in service in December 2007. This plant (See Fig.2)
was relocated to the customer’s site in Toledo, Ohio, where
it provides Syngas to a retro-fitted coal steam boiler
providing steam to the University of Toledo hospital and
other buildings. This move proved not only the modularity
but also the portability features of the plant which was
dismantled, shipped, reconstructed and in operation again in
less than 120 days. This plant has demonstrated a 60%
reduction in CO2 emissions in comparison with coal for the
same amount of generated heat.
Fig. 2 – Operational Unit in Denver, Colorado
The designed production capacity for an installed plant is
between 250 and 500 tons per day of dry carbon feedstock.
The basic chemical reaction used in this process is C + H2O
= CO + H2. This process operates in a heated, oxygen
starved environment known as Pyrolysis which drives off
moisture and volatile gases contained in the feedstock. This

4. 4 Copyright © 20xx by ASME
process produces carbon char and ash which is then
separated prior to a second stage reactor converting the
carbon molecule into a gas stage. This is accomplished with
heat, pressure and the injection of ionized water in a process
known as gasification and a water shift reaction. It is
important to note that this is not a typical gasification
process which requires the injection of Oxygen for the
reaction: C + O2 + H2O = CO + H2, nor is it combustion
which is represented by C + O2 = CO2 (Carbon Dioxide).
The TWIST process actually reduces CO2 through the
following reaction: CO2 + CO = 2CO. The hot Syngas is
water quenched and cleaned of its impurities in a proprietary
ionized water treatment system delivering a clean dry
Syngas without a liquid discharge. Ash recovered from the
system’s filter press is in a semi-solid form that can be
further processed to recover elements contained in the ash,
can be used in production of cement, used as a fertilizer or
for land fill. A portion of the ash can be recovered as a bio-
char to be used as a soil amendment which provides for
carbon dioxide capture and sequestration. Three tons of
CO2 are contained in one ton of bio-char.
Modular design promotes assembly/disassembly (25 truck
loads) Fig 3. Small footprint 500 tpd 30.5m x 30.5m x 7.6m
Fig. 3 – 500 tpd SynGasCo Gasifier Footprint
CCLC Power Recovery System
Organic Rankine Cycle (ORC). Steam turbine power plants,
refrigeration cycles and single stage turbo-expander systems
are the most common and well-known thermal energy
recovery systems in use today. Thermodynamically, one of
the most efficient ways to convert thermal energy (heat)
below 427 °C to mechanical energy is with ORC cycles.
[Ref 1]
The optimum heat transfer fluid to use in a Rankine Cycle is
primarily dependent on the temperature of the heat source –
the higher thermal energy (flow, pressure and temperature),
the more efficient the conversion from the thermal to
electrical energy. Typical heat transfer fluids used are
ammonia, Freon, water, propane, iso-pentane, iso-butane
and others. The proposed system Fig 4 uses propane since it
will vaporize and condense at low temperatures; but unlike
other fluid medium used in Organic Rankine cycles,
propane can also be used at much higher temperatures
427/500 °C. The propane used is not consumed and only
serves as the working fluid (heat transfer medium) in a
hermetically sealed closed loop to convert thermal energy to
mechanical energy. Another benefit of the propane closed
cycle is the start-up time as immediate vaporization allows
for immediate power generation in the expander.
Furthermore, closed loop systems require no or very little
manual operation or supervision; hence remote or un-
attended operation is possible (except for routine
maintenance).
Based on the available thermal energy, the optimization
between costs and efficiency can result in combining the
closed propane cycle with a backpressure vapor cycle – two
expanders and two fluid streams are used in series. This
allows the thermal energy (heat) from the discharge of the
first expander to be used to vaporize a second propane
stream that is expanded in a second turbo-expander to
increase the efficiency. Fig. 5.The integral second expander,
indicated by the dotted area is what differentiates the CCLC
system from current operating ORC systems.
The turbine exhaust directly heats the propane working fluid
in HX1 to a temperature of 400°C at a pressure of up to 50
barg., before entering EXP1 recovering 7250 kW. The
exhaust stream still contains superheat and is used to
vaporize a second propane stream that is expanded in EXP2.
The HX 2 &3 are Recuperator and Pre-heaters respectively
Fig. 4 – CCLC Process Flow Diagram
The CCLC system (WOWGen®) is a unique arrangement
of off-the-shelf components. The components consist of
commercially available turbo-expanders, heat exchangers
and pumps, available from numerous competing
manufacturers. The CCLC system components have
millions of hours of reliable and nearly maintenance free
service, primarily in refineries, petrochemical and
geothermal plants. Turbo-expanders have been used for
decades in hundreds of applications and are typically used to

5. 5 Copyright © 20xx by ASME
drive generators, pumps and compressors in the most
demanding of applications. Turbo-expander companies offer
reliable turbo-expanders in both radial inflow (centrifugal)
and axial configurations in sizes ranging from a fraction of a
HP up to 50,000 HP.
Fig 5 represents the power recovery from the GT6B at the
Northam Mines site conditions of 15 °C and 25° C from
40% to 100% gas turbine load Table 1.
Northam Mines GT6B
Performance
8000
10000
12000
14000
16000
100 80 75 40
% L oad
NetkWgenerated
kW 25C
amb
kW 15C
amb
Fig. 5 – Expected Performance kW output from
GT and Exhaust Power Recovery at site altitude
Full and Part load.
Gas Turbine Modifications
The selected existing FR6B for the project combustion
system, presently a (natural) gas fired Gas Turbine, is not
suitable for firing synthetic gaseous fuels (Syngas).
Modifications would be required.
To fire on Syngas and be able to co-fire diesel No2 as a
back-up fuel, the entire combustion system must be replaced
with a system supporting this mode of operation.
Furthermore, this combustion system should also be capable
of accepting steam injection to suppress NOx emissions,
and nitrogen buffering (and purging) to prevent back
flashing during operation while firing on liquid fuel.
Consequently, all existing on-base fuel piping and (fuel)
control systems need to be removed from the present Gas
Turbine unit and be replaced by systems to control firing on
liquid fuel and Syngas, supported by nitrogen supply for
purging and buffering.
The existing steam injection system is suitable for the
capacity required for suppressing NOx up to a limit of
approximately 42 ppm (12.000 kg/hr), and could remain
although new interconnection steam piping is required to
reconnect the Syngas fuel nozzles to the on-base steam
manifold.
A brief description of firing MS6001B gas turbine units on
Syngas is provided below.
Gas Turbine Syngas combustion systems rely on fuel
flexibility that is measured by four key characteristics:
• Capability to deal with low heating value fuel
containing varying hydrogen content.
• Operability on a wide range of fuels, including
start-ups, transfers and system upsets.
• Capability to co-fire synthesis gas distillate oil over
a wide total heat input.
• Low emissions.
The key component in meeting these requirements is the
Gas Turbine combustor.
Combustor Design Modification
The Gas Turbine combustor is the principal process device
for the entire SynGas plant. The standard Syngas
combustor for MS6001B gas turbines is derived from the
MS7001E Syngas combustor. See Fig. 6. Since hydrogen is
a typical constituent of synthesis gases, Dry low NOx
(DLN) combustors are not appropriate for synthesis gas due
to hydrogen’s high flame speed which can initiate flashback
and combustor failure. The MS 6001B combustor has
evolved from a standard combustor and allows a wider
range of fuel constituents and includes co-firing capability.
The lower specific calorific content of synthesis gas requires
that the combustor be able to process more than five times
the fuel flow relative to a natural gas combustor. Also,
combustion of 100% Syngas results in NOx emissions that
exceed regulatory requirements, so dilution of the Syngas
with nitrogen, water, CO2 or combinations is needed to
achieve the desired performance.
Fig.6 - MS 6001B dual-fuel Syngas Combustor
Owing to the can-annular design of GE turbines, a single
can may be fully tested and proven at full airflow and
pressure for many machines over the entire range of cycle
conditions before releasing it to the field. The performance
of new designs is subsequently verified in the field.
The MS6001B SynGas combustion system has been
operational successfully since 1995 at three different sites
and has demonstrated reliable operation on a large range of
Syngas compositions. Syngas machines require a start-up
fuel because of the dangers of starting on fuels containing
hydrogen. This start-up fuel allows many plants to be fully
commissioned and to begin operation on backup fuel with
introduction of Syngas capability phased-in at a later date.
The dual fuel capability has been developed into a standard
co-firing feature so users can design plants for higher power

6. 6 Copyright © 20xx by ASME
output if Syngas production is restricted or if a plant is
contemplating parallel or staged co-production for the
utilization of Syngas.
Mixed fuel operation or co-firing has become an important
operating mode to enhance economics. Co-firing was first
used at the Texaco El Dorado IGCC plant in Kansas where
the Gasifier provides about one third of the Gas Turbine
thermal input requirements. Since starting in 1996, the El
Dorado GT has performed at better than 97% power
availability. The Thomassen supplied units for Shell Pernis
and Schwarze Pumpe have natural gas and distillate fuel for
co-firing and have demonstrated high flexibility combined
with high reliability.
For a dual fuel design, the co-firing operability standard is
in the 70/30% range. This range is dictated by combustion
system control requirements at low fuel flow rates.
However, a new system now operating at Exxon Singapore
is capable of operating over the 90/10% range. Mixed fuel
operation can generally be accommodated down to < 30%
load. For a dual fuel Syngas/distillate application, the
distillate can be controlled down to 10% while the Syngas is
generally regulated over the 30%-70% range. During
operation on distillate fuel, the Syngas system is purged and
includes inert and main air purge systems for this design.
Both nitrogen buffering and air from the compressor
discharge (CPD) are used for gas piping purging during
distillate operating modes.
Co-firing (duel fuel) has a wide demonstrated operating
range, for two specific projects; co-firing was designed as
follows:
Schwarze Pumpe: Unit was capable of running full load
range on either fuel; mixed fuel operation is possible within
the range of minimum 10% distillate (90% SynGas) and
maximum 70% distillate (30% SynGas) referenced to the
unit heat consumption. No mixed fuel operation allowed
when not connected to the grid and generating some MW of
power.
Shell Pernis: Unit operation is very flexible due to more
sophisticated fuel system. Again full load range capability
on either fuel. Mixed fuel operation will be possible at
almost any ratio of natural gas and SynGas. For fuel system
stability reasons a minimum flow of 5% was set for each
fuel. [Ref2]
Control Modifications
Ansaldo Thomassen (ATH) developed a gas turbine control
system based on the Siemens® S7 series Programmable
Logic Controller (PLC). This control system has to perform
the following functions for a gas turbine application and
auxiliary systems:
• Start/stop sequencing of the Gas Turbine;
• Speed/Load/Temperature/Acceleration control;
• Protection & Limiting with Safety Integrity Level (SIL)
integration in the main controller;
• Control of auxiliary systems.
The TC-7 can easily be exchanged with a Mark I/ Mark II/
Mark IV/ Mark V. The dimensions are exactly the same
with the predecessor cabinet, so no mechanical support
change is needed. Electrical and instrumentation changes
are minimized. The cable entrance is at the bottom so no
additional marshalling boxes are needed for cable extension.
Instrumentation can be adapted to fulfill SIL requirements.
Approved flame detectors and the gas nozzle start pressure
switch are common instruments to be adapted.
The IEC61508 standard requires that a target SIL is assigned
for any new or retrofitted safety instrumented system (SIS).
The SIS consists of instrumentation or control systems that
are installed for the purpose of mitigating the hazard or
bringing the turbine to a safe state in the event of process
failure. Thomassen developed a digital turbine controller
with implemented SIL requirements.
The heart of this controller in a duplex configuration is the
twin Central Processing Unit (CPU) in one physically
separated rack. The twin CPUs are connected to each other
via a high speed fiber optics link. For the most important
functions, i.e. the servo loops, the CPU is joined with a high
speed analog input card and an analog output card.
The TC-7 software is based on the deterministic properties
of the CPU. Fast acting parts of the TC-7 software will
have a refresh rate (cycle time) of 10 msec, and slower parts
100 msec. These cycle times can be adjusted to fulfill the
requirements of the Gas Turbine and its process properties.
GT Inlet Evaporative Cooling
The Northam Mine site is located at an altitude of 1000m.
and experiences a wide range of temperatures with summer
daily peaks reaching 40 oC and nighttime temperatures
dropping to 15 oC; three winter months would experience
somewhat lower inlet conditions. The average daily
temperature of 25 oC was selected to determine the plant
performance. Inlet evaporative cooling was proposed
because experience in Spain with the FR6B under similar
conditions ranging from 20 to 40 oC showed output increase
from 2.0 MW to 4.26 MW at 40 oC with Munters
PreCooler. [Ref: 3]
The basic idea behind this Munters PreCooler technology is
the increase of the combustion air density by reduction of
the combustion air temperature through adiabatic cooling.
The PreCooler Systems are equipped with high efficiency
cooling media available in either CELdek® or the non-
flammable GLASdek®. See Fig. 7

7. 7 Copyright © 20xx by ASME
Fig. 7 – Munters PreCooler
Water is evaporated to pure cold vapor by the Munters
PreCooler. This produces a cooling effect which provides
an intake air at higher density which allows the Gas Turbine
to achieve increased power output (at least 5-6%, and up to
60% in very hot or dry climates) as well as increased
operating efficiency. By using natural principles, the
Munters PreCooler has a low investment and operational
cost which allows for very short pay-back periods of 12-24
months. For this Northam Mine project installation, a
combined housing was selected for the air intake filtration
and the air pre-cooler, thus reducing the investment cost
substantially. See Fig. 8.
Fig. 8 – The Combined Housing
Installing the pre-cooler prior to the first filter stage will
remove approximately 90% of the particles normally
removed by the first air filter stage. This increases
significantly the service life and therefore reduces
maintenance costs. This benefit is also extended to the fine
filters, especially in the dusty environment of the mining
operation at Northam.
Fuel Gas Compression
Syngas from the Gasifier is delivered cooled to 20 oC and at
a relatively low pressure of 3.4 barg. This supply must be
pressurized to maximum 22 barg. for the GT combustion
system. The fuel gas compressor is a critical component of
the GT generation system; it calls for reliable and well
proven compression equipment. In addition, for power
consumption to be kept low, the compressor must load
follow the GT fuel requirements from start-up through the
operating range from 100% load down to the specified 40%
downturn.
For the Northam application, a Kobelco screw fuel gas
compressor was selected. This screw compressor has a
unique slide valve mechanism that instantly and
automatically maintains constant delivery pressure, despite
fluctuations in suction pressure or GT load. More
importantly, this positive displacement compressor uses less
power than centrifugal compressors, resulting in substantial
power savings over the 40% to 100% operating range. The
factory packaged skid-mounted system allows for fast site
installation on slab foundations, complementing the
modular approach of the complete coal fired power plant.
Conclusions
This project demonstrated that, in areas where power is
needed in Southern Africa, the mining industry has options
for small power generation plants using readily available
and abundant coal without having to resort to expensive
liquid fuels. The availability of used and refurbished
industrial Gas Turbines, modified for Syngas operation,
together with a modular Gasifier allows for fast deliveries of
the major components of a power plant and completion
within a time frame of 18 months.
The GT plant is basically air-cooled, as is the power
recovery plant, eliminating the steam water cycle and
associated costs of water management. This factor increases
overall plant reliability and availability especially in remote
mining areas. The quality of water for the Gasifier is not
critical to the process, thus allowing use of “gray” water
from the mining operation.
In South Africa low cost coal and huge central power plants
currently ensure some of the lowest electrical rates in the
world. These will definitely increase as the large and newer
Medupi and Kusile ESKOM Power coal fired plants (4800
MW), with air cooled condensing, come on line in the next
two years at a cost of $2800/3000/kW. It was not intended
that this Hybrid Coal Fired Power Plant would compete
with larger, newer and more efficient PC plants. However,
it is still cost effective in terms of $2079/kW low operating
costs and good efficiency for onsite power generation at
current coal costs of $27-34 /metric ton.
Due to the global economic downturn, this Northam
Platinum Mine project did not proceed. But new platinum
mine development by Northam in South Africa will generate
new power demand. The modular Hybrid Coal Gasification
Combined Cycle as proposed by project developer Earth
Fuels Corporation will continue to be a good choice to meet
the power needs for a modular power plant and the phased
development anticipated for approval in the first half of
2010 for Northam Mine’s large 103 million ounce resource.

8. 8 Copyright © 20xx by ASME
References:
[1] Romero, H. Mario, van der Linden, Septimus.” Heat
Recovery Technology Improves Efficiency and Reduces
Emission.” IMEC 2008-66296
[2] Kamminga, Piet, Bjorge, Robert “IGCC Experiences and
Applications for the European Market”
[3] “The Increased Importance of Evaporative Coolers
for Gas Turbines and Combined Cycles”. VGB Power Tech
9/2000
Acknowledgements:
Wiley Consulting LLC;
Special thanks to Marcus Wiley for arranging a visit to the
University of Toledo, Ohio to examine the TWIST Gasifier
in operation and review test results.
Ansaldo Thomassen BV;
Thanks to ATH for the facilities visit in Rheden, to view the
Gas Turbine refurbishing workshops, including Combustor
,Gas Fuel skids and Controls modifications, as well as the
detailed performance calculations.
Northam Platinum Mines;
Thanks to the Technical and Operating staff at the Mines for
their support in accepting innovative solutions for power
generation to meet their growing needs.
Earth Fuels Corporation:
Thanks to Gary Williams, accompanying the Northam
Mines Power Plant engineers to inspect the Pyrolytic
Gasifier in operation at the University of Toledo, Ohio.
WOW Energies Inc;
Thanks to Kristofer Hunt providing site adjusted CCLC
performance calculations for the CCLC power recovery.