September – October 2014
Flow scaling key to
higher power output
page 14
10% more power at
high ambient temps
page 20
Flying high with new
FT4000 gas turbine
page 30
www.gasturbineworld.com
Temple I power plant has now
started commercial operation
By Junior Isles
In addition to being the first Siemens Flex-Plant in Texas,
it is the first in the USA to feature Shaping Power for
increased power production on hot days.
U
S independent power producer
Panda Power Funds recently
started up its Temple I combined cycle power plant near Austin, Texas.
The 758 MW combined cycle gas turbine (CCGT) power plant is:
o
The first Flex-Plant in Texas, addressing the need for fast start and
ramping.
o
First use of ‘Shaping Power’ in the
US, allowing 10 per cent more power
at high ambient temperature.
o
Capable of delivering 60 percent
of full load in less than 25 minutes.
Texas is one of the fastest growing
states in the US, with four of the
fastest growing cities in the country.
With a population that is expanding at
more than 1,000 people per day, demand growth is projected to outpace
growth in supply.
The target reserve margin in the
ERCOT transmission system region
serving Texas is 13.75 per cent. However, at a load growth rate of 2-3 per
cent, Panda predicts that margins will
fall to about 5 per cent by 2023.
At the same time, the state has a
considerable amount of wind power,
which calls for flexible conventional
power generation to provide support
when the wind is not blowing.
The scenario creates a perfect opportunity for investing in gas fired
20 GAS TURBINE WORLD September – October 2014
generation in the Lone Star state.
“There’s a big need for power.
With reserve margins declining and
coal challenged as a generating fuel,
we see a great opportunity to capture
a first-mover advantage in Texas,”
says Bill Pentak, Vice President of
Investor Relations and Public Affairs,
Panda Power Funds.
With ERCOT essentially being an
island, unable to import power, Pentak believes that its high efficiency
CCGT units are the “perfect solution”. Not only will they be high up
the dispatch merit order, due to their
high efficiency, they will also be able
to dispatch power at short notice and
ramp up and down.
Satisfying the market conditions
dictated the choice of technology for
Temple I. The plant, being built by a
consortium of Siemens and Bechtel,
uses Siemens’ Flex-Plant technology.
It is the first time the technology is
being deployed in Texas and only the
third time in the US.
Siemens provided the thermodynamic cycle design and power island
engineering, delivered the main plant
equipment and also has a long-term
service agreement for the main generation components.
erator and an SPPA-T3000 instrumentation and control system.
Siemens also supplied two Benson duct-fired heat recovery steam
generators (HRSGs) manufactured by
NEM USA Corp. The steam turbine
produces about a third of the power of
the facility with two-thirds from the
gas turbines.
Each gas turbine has a 13-stage axial flow compressor with can-annular
combustors and a 4-stage turbine. The
plant has a multi-shaft 2-on-1 configuration, where exhaust gas from
the turbines enters the HRSGs to generate steam that is then fed to a single
steam turbine.
The steam turbine, which has a
combined HP/IP section with a double-flow LP section, is designed to
use steam at temperatures of approximately 1050°F (565.5°C) and pressures of approximately 2400 psi (165
bar). Like each of the gas turbines,
the steam turbine, has its own generator.
This configuration has the flexibility to run the gas turbines without
powering the steam turbine (if less
power is needed), run only one gas
turbine, or run both gas turbines and
the steam turbine for full plant output.
Plant configuration
The power island includes two SGT65000F gas turbines, one SST6-5000
steam turbine, two SGen6-1000A
generators, one SGen6-2000H gen-
Highly flexible
The Temple I power station is capable of being synchronised to the grid
in 10 minutes, making it suitable for
complementing Texas’ considerable
wind power generation. Baseload is
reached in less than 60 minutes.
Jacki Engel, Product Line Manager, Siemens Energy Solutions Americas comments: “The plant is really
designed with the end user in mind.
It will allow Panda to optimize profitability and provide reliable, flexible,
clean generation for the Texas market.”
The HRSGs are an integral part
of the Flex-Plant as they allow unrestricted gas turbine ramping. They
are horizontal, three- pressure natural
circulation once-through boilers with
reheat.
Each of the HRSGs is capable of
delivering 99.5 kg/s of high-pressure
steam at 159 bar and 567°C. The boilers are also equipped with supplementary firing to help optimize plant
performance.
The Benson boiler technology essentially replaces the thick-walled
drum in the HP section of a conventional boiler. Eliminating thick-walled
components enables the boiler to
warm faster, allowing it to receive energy faster from the gas turbine.
“We talk a lot about integration and
the major components are critical, but
maximizing the value of these components through the bottoming cycle design is what sets the Flex-Plant apart,”
says Engel.
“Some of the key features of this
integration include a two-stage attemperation scheme, steam turbine piping
warm-up strategy, and an auxiliary
boiler that allows the plant to maintain high metal temperatures over a
longer shutdown period so the plant
can be started quickly. These are all
brought together and controlled by the
SPPA-T3000 control system.”
Such integration enables Temple I
to achieve 60 per cent of its 758 MW
baseload power output in less than 25
minutes.
In addition to allowing Panda to
deliver power to the grid faster, the
shorter start time helps to reduce the
plant’s emissions footprint. Temple
I is able to maintain air compliance
standards i.e. carbon monoxide (CO)
emissions less than 10 ppm and nitrogen oxide (NOx) emissions less than
2 ppm.
Engel explains: “In a conventional
[CCGT] plant, from the start of the
gas turbine, you will come up to, say,
25 per cent [of full load] and hold, so
you can bring some of your big metals up to temperature.
“But that is not the most efficient
place for a gas turbine to hold – not
only are you burning fuel but you are
also loading up on your start-up emissions. The fast start capability brings
about an 85% reduction in CO and
close to 90% on NOx.”
Another attribute that makes the
plant so flexible is the inclusion of
Shaping Power in the gas turbine. According to Siemens, Shaping Power
can boost turbine output by 10 per
cent on hot days. “You start to see
the benefits of Shaping Power above
70°F,” said Engel.
It is the first time the technology is
being used in the US.
Gas turbines suffer significant
de-rating at high ambient temperatures. Siemens’ Shaping Power technology allows the gas turbine’s inlet
guide vanes (IGVs) to be opened on
hot days. This increases mass flow
through the engine, and also contributes additional exhaust gas flow for
the bottoming cycle, resulting in overall higher plant output.
“Historically this was done only
with slow-moving duct firing in the
HRSGs, says Engel. “With Shaping
Power, the fast-moving gas turbine
is filled up first so the topping cycle
generates power more efficiently and
exhaust energy is also increased since
you have more mass flow through the
turbine.
“On top of that you still have the
ability to duct fire, as needed. The
result is a lower heat rate for a given
megawatt level, with the ability to
generate more power output.”
Station Site Manager Sean Hausman points out that “we can gain 1.52% of efficiency by sliding in to this
Figure 1. Temple I is online and ready to feed power into the ERCOT grid on demand.
www.gasturbineworld.com GAS TURBINE WORLD September – October 2014 21
power shaping mode. It leans-out the
engine a bit and sure, it shaves [off] a
few megawatts of our net capability,
but there is an overall improvement in
efficiency.
“And as demand grows we can easily transition out of this mode within
minutes into a typical combined cycle
mode and fire our duct burners.”
Steam water cycle
Cooling for the plant is provided by
cooling towers supplied by International Cooling Tower Inc. These remove heat from the cycle through water vaporization and air circulation. Hotter water from the steam turbine condenser is pumped to the top
of the cooling tower where it then
runs down the ‘fill material’ (essentially corrugated plastic). Air in turn
is pulled up through the fill material
by the large fans and cools the water. The water collects in the cooling tower basin where it is then pumped back
to the condenser to repeat the process.
These cooling towers have twelve
(12) individual cells with fans each
measuring more than 30 ft. in diameter.
A Steam and Water Analysis System (SWAS) helps control the purity of water and steam in the HRSGs
and steam turbine, which is required
to be ultra-pure. The plant operators
and chemists use the SWAS to verify
proper operation of the condensate
polisher system and chemical injection systems.
There are two main SWAS shelters at the facility with a total of 27
sample streams from both HRSGs and
the steam turbine. Some 51 analyzers measure the chemical properties
of the steam and water. For example,
they measure pH, conductivity, dissolved oxygen, sodium, and silica.
These elements prevent rust, oxidation and/or fouling, or the unwanted
material on solid surfaces.
The analyzers are extremely accurate. For example, the dissolved
oxygen analyzer can measure 1 part
of oxygen per 1 billion parts of water.
22 GAS TURBINE WORLD September – October 2014
Figure 2. The once-through HRSGs are central to the plant’s flexible performance.
The Temple Plant is permitted as a
Zero Liquid Discharge (ZLD) facility,
which means no process or wastewater is permitted to leave the site.
Most of the water for this plant
is supplied from the City of Temple
Waste Water Treatment Plant Facility.
It is reclaimed water that would otherwise be lost and discharged into the
local water streams. This water con-
Figure 3. The SPPA-T3000 control system manages the integrated operation of all
of the major equipment in the plant.
servation measure helps to conserve a
valuable natural resource.
The high water quality required to
run the plant is met by further treating
the reclaimed water through the onsite
clarifiers, purification filters and reverse osmosis units.
All process wastewater streams are
treated through the ZLD wastewater
treatment equipment. Here the wastewater is treated and separated into two
process streams.
Clean water is recycled back into
the process systems for further reuse
and the reject water is discharged to
the site evaporation pond.
Plant control
The SPPA-T3000 control system
manages the integrated operation of
all of the major equipment in the plant
to enable fast, flexible operation while
assuring all components are operating
within their individual design envelopes.
The control system monitors and
processes approximately 9000 data
points for the core power island and
approximately 2500 more for the rest
of the plant.
According to Siemens, the control
system is designed with a database
set up like the worldwide web, which
enables the hardware to be easily upgraded as technology changes without
needing to change out the whole control system.
The logic programmed into this
integrated system monitors conditions
throughout the plant and provides operators with real-time information on
equipment status.
This information from the control
system is remotely monitored at the
Siemens Power Diagnostic Center in
Orlando, where experts track trends
throughout the fleet. A dedicated engineer tracks the behaviour of this
particular plant and looks for changes
over time, which enables early warning of potential problems before they
happen.
The control room is manned 24/7.
Temple 2 will also be controlled from
24 GAS TURBINE WORLD September – October 2014
Figure 4. Steam and Water Analysis System (SWAS) helps control the purity of water.
this same control room. Should there
be a need, this plant can be started
and stopped from the Power Diagnostics Center in Orlando.
Safe construction
Bechtel was responsible for the balance-of-plant engineering, overall
plant construction, procurement, and
led the commissioning of the facility.
The plant, which was completed two
weeks ahead of schedule, was built on
a short time schedule – just two years
from ground-breaking in September
2012.
Describing the early work, Mike
Robinson, Project Manager for
Bechtel recalls that “we had about
80,000 cubic yards of excavation.
There were about 24,000 cubic yards
of concrete and over 1,000 tons of
steel that went in across the plant.
Construction, basically took place almost around the clock. We were literally making concrete pours in the
middle of the night.”
Notably, all the work including
some complex heavy lifts of the gas
turbine was performed without incident. “For the entire duration of the
project [more than 2 million manhours] there was not a single lost-time
accident… There were no injuries and
no incidents around the heavy lifts –
and there were some significant lifts.
A jack and slide system was used to
lift and position the gas turbines. The
heaviest lift performed onsite was the
steam turbine-generator weighing 375
tons.”
In addition to completing the project without incident and two weeks
ahead of guaranteed schedule, Robinson noted that the plant performance
was also better than its guarantees.
“We got through performance testing in one shot and the reliability and
availability were close to 100% during testing.”
More flexible plants
Just two weeks after the start-up of
Temple I, Panda Power also fired up
what is essentially a sister project in
Sherman, Texas.
With Temple I and Sherman up and
running, work is now firmly focused
on Temple II. This plant is expected
to start commercial operation next
summer, to add another 758 MW to
the site.
The projects are part of a growing
Panda portfolio of combined cycle
projects that demonstrate the importance of flexibility in many parts of
the US. n