Efficient CHP Plant Concepts with High Operating...
Transcript of Efficient CHP Plant Concepts with High Operating...
POWER-GEN Russia 2015 Moscow, Russia 3 - 5 March 2015
Copyright © 2015 AZG Consulting GmbH
Efficient CHP Plant Concepts with High Operating Flexibility
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Efficient CHP Plant Concepts with High Operating Flexibility
Presented at Power-Gen Russia, Moscow, March 2015
Authors: Marina Darozhka, Frank Rossig, Nicholas Bellamy,
SSS Gears Ltd./AZG Consulting GmbH
CHP is one of the world’s most efficient energy technologies with overall efficiency of
up to 80% or more. Numerous successful installations are operating throughout the
world and are proving its reliability, as well as the reduction of energy cost and
greenhouse emissions.
1. General introduction.
Combined Heat and Power (CHP) is a very general term covering various
technologies and applications. Technologies can be distinguished based on the
prime mover, which can be reciprocation engine, fuel cells, microturbine, gas turbine
or steam turbine with boiler. Gas turbine and steam turbine driven technologies are
making up to nearly 90 percent of the complete CHP generated capacity worldwide.
These two technologies will be in focus of this paper.
Fig.1 – CHP Efficiency Advantages [1]
Thinking on operation systems of Combined Heat and Power plants, it can be
distinguished between:
- Toppingcycle, where electricity is produced utilizing high temperature and pressure
steam energy, and the waste heat is used for thermal energy generation purposes;
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- Bottomingcycle, where the energy source is used in the first line to supply a high
temperature thermal energy, and the excessive or waste heat energy is used for
electricity production.
Gas turbines for CHP plants can be used in a variety of configurations, whereas the
thermal energy from the exhaust heat is a byproduct from electrical power
generation:
- Simple cycle operations with CHP, where fuel is combusted in the gas turbine
and the exhaust gases are led to the heat recovery steam generator to produce
useful thermal energy, or the exhaust gases are used directly in some process
applications;
- Combined-cycle operations, where the high pressure steam is generated from the
gas turbine exhaust within the heat recovery steam generator and used for driving a
steam turbine to generate additional electrical power. Lower pressure steam can be
extracted from the steam turbine and used directly in a process or for district heating,
or can be converted to other forms of thermal energy including hot or chilled water.
Steam turbines within the CHP plants often generate electricity as a byproduct of
heat and steam generation. Steam turbines do not directly convert fuel to electric
energy but operate on the high pressure steam generated within the steam
generators such as boilers. Steam turbine driven CHP plants can operate on a vast
variety of fuels, like natural gas, solid waste, all types of coal, wood, wood waste and
agricultural byproducts.
Depending on the desired plant performance and specification a variety of steam
turbine designs can be used. Basically it can be distinguished between following
steam turbine types:
- Backpressure steam turbines with the fixed pressure ratio, the power generation
capability of those depends on the steam flow. Should the heat production drop, the
power generation will be also reduced;
- Condensing steam turbines expand the pressurized steam down to well below
atmospheric pressure, at which point steam is exhausted to a condenser at vacuum
conditions;
- Condensing turbines with extraction options. In these turbines portion of steam
can be extracted at an intermediate or low pressure level in order to supply steam at
certain pressures and temperatures for process and district heating.
Steam turbines may have one or several pressure casings, and the design has to be
chosen based on efficiency and flexibility optimization of the power plant.
Nowadays the demand for electrical power is rarely constant and generating plants
may have to operate at reduced power for significant periods. Power plant designed
primarily for power generation can, however, be a valuable energy source for other
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consumers. Processes and heating systems can use steam available from
periodically under-loaded power plants. Also the demand for steam can be as
variable as the demand for electrical power. A Combined Heat and Power plant
should, therefore, be capable of easily accommodating daily or seasonal changes in
demand for both heat and power.
A Combined Heat and Power Plant designed to operate with maximum flexibility
could incorporate a connectable and disconnectable device between the low
pressure and high pressure turbine cylinders. At times of reduced electrical demand,
the steam exhausting from the high pressure turbine is diverted for other uses and
the low pressure turbine cylinder is disconnected. When full electrical output is
demanded, steam flow to the low pressure turbine cylinder is restored and the turbine
is automatically reconnected to drive the generator. Such a system has cost
advantages over a plant comprising two separate turbines each driving its own
generator. The key element in such system is a reliable device for disengaging and
re-engaging the low pressure turbine cylinder.
The same principle can be applicable for CHP systems with several single casing
steam turbines each driving a single generator.
2. CHP applications.
When considering diverse CHP applications, the combination of following categories
can be used:
- District heating and cooling;
- Process heat and steam supply;
- Electricity supply to buildings and districts.
Fig.2 – Typical CHP Process Steam / District Heating Schematic Drawing
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2.1 District Heating and Cooling.
Space heating of buildings is a popular use for CHP heat. Homes, offices and leisure
and shopping complexes are all consumers. District heating grids are particularly
popular in developed countries with generally low ambient temperatures especially
when building developments mix residential, retail and leisure construction close to
industrialised zones.
As well as heating applications, CHP heat may also be used for cooling applications.
In this case, the heat is used to induce flash evaporation of a working fluid to its
saturation point. The evaporation of course causes auto-refrigeration, thus cooling
the working fluid, which may then form part of a cooling grid.
District heating and cooling are generally “groundwork up” solutions, where the
building developer considers a complete building and energy supply solution, as
opposed to building only. Consequently, district heating and cooling examples are
most common in expanding areas which already have district heating available.
As the heat consumed in district heating and cooling cycles is generally at a lower
temperature and pressure than that used for process applications, larger quantities of
the plant waste heat can be used and therefore higher efficiencies are achieved.
District heating demand can fluctuate seasonally.
2.2 Process Heat and Steam.
Industry consumes large amounts of heat. This heat consumption is not only limited
to space heating requirements of offices and factories, but also industrial processes.
Industrial process applications include paper production, sugar refining, drying (e.g.
paint and processed chemicals) chemical and petrochemical engineering applications
(e.g. steam turbine driven machines) and sterilizing and cleaning equipment.
Unlike district heating, whose demand will typically fluctuate with seasonal weather
patterns, process steam requirements tend to have predictable demand. However,
agriculturally dependent industrial processes (e.g. sugar refining) can yield seasonal
demands consistent with crop cycles, especially where processing is geographically
close to the source material growth.
This shows that Combined Heat and Power plants might contribute to improving
energy efficiency in situations where the alternative production is represented by
conventional thermal power plants.
3. SSS Clutches as a device to connect and disconnect steam turbines.
Arrangements with automatic main drive synchronising self-shifting clutches to
connect and disconnect different drivers have been successfully applied worldwide
for more than 60 years. These automatic SSS Clutches have proven to be extremely
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reliable throughout the lifetime of the power plant even with daily connection and
disconnection of the driver. When installed on CHP plants, SSS Clutches disconnect
steam turbines or its cylinders from the generator train whenever the steam from the
steam generator is needed for district heating or process steam applications. When
additional electrical power generation is needed, the SSS Clutch will automatically re-
connect the steam turbine to the generator without disturbing the electrical power
generation from the main drive.
During the shut-down sequences of the turbine the SSS Clutch disengages
automatically, leaving the generator rotating being driven by the remaining driving
machine - gas turbine or steam turbine.
The SSS Clutch is a bespoke freewheel mechanism, which automatically engages
and disengages through shaft speed control only. SSS Clutches in operation range in
power from a few kW up to 320 MW and from operation speeds between 1 rpm to
16000 rpm.
When the SSS Clutch input speed attempts to rotate faster than that of the output
side, a pawl and ratchet mechanism synchronises the main clutch driving teeth into
alignment so that the helical splines will shift the main clutch driving teeth
automatically into mesh, thus engaging the clutch. When the input side slows down
relative to the output side, the main driving teeth are automatically moved out of
mesh, thus disengaging the SSS Clutch.
Fig.3 – SSS Clutch Operating Principle
Clever use of internal oil distribution and centrifugal force prevent metal to metal
contact when the clutch is overrunning. Engagement and disengagement are
cushioned by an internal dashpot action where required, and the main driving teeth
are designed with conservative loading. These steps prolong clutch life, therefore
under normal operation an SSS Clutch will outlive the life of the plant main
machinery.
A – Pawl
B – Main driving teeth
C – Helical Sliding Component
D – Helical Spline
E – Input Component
F – Output Component
G – Ratchet Teeth
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There are different designs of SSS Clutches available:
- Semi-rigid SSS Clutches:
These clutches can be used within the installations
where alignment is closely controlled. For example,
the clutches can be mounted within the steam
turbine bearing pedestal or inside a gearbox. This
type of clutches can be in-line or quill-shaft mounted.
The semi-rigid SSS Clutch design accepts small
angular and axial expansion movements of the
adjacent machine shafts to compensate for thermal
growth requirements.
For the semi-rigid SSS Clutch designs, when engaged and transmitting torque, the
clutch should be considered as a solid shaft.
- Spacer type SSS Clutches:
These clutches are suitable to be installed
between shafts subject to misalignment. These
clutches have a double set of teeth and act as a
flexible coupling. Also these clutches can
accommodate large axial expansions if
necessary.
- Encased SSS Clutch packages:
These clutches are supplied as self-
supporting units within the casings. The
package includes an input and output shaft,
each supported and located by combined
white metal journal / thrust casing bearings.
The input and output shafts support the
overhung mass of the clutch input and
output sub-assemblies respectively. Although the 4 bearing Encased SSS Clutch
design extends the train length when compared with a solution incorporated within
the turbine pedestals, standardized steam turbine designs can be used thus greatly
reducing design time and cost. Therefore, in return this concept offers reduced
engineering input and therefore total installation costs and realization time for the
customized CHP plant application.
Alternatively, Encased SSS Clutch packages can be designed self-lubricated with
ball bearings.
- SSS Clutch couplings:
This clutch design can accept radial misalignment and axial growth between each
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Fig.4– Fredrikstad Bio-El CHP Power plant Photo courtesy of Hafslund
steam turbine and the generator through
two single element flexible membranes,
one at each end. Two ball bearings are
located on the clutch input shaft, which in
turn support the clutch output assembly.
This SSS Clutch Coupling design is
therefore shaft mounted, self supporting
and includes seals to contain an integral, self-lubricating oil supply which removes
the need for any pressurized oil supply to the SSS Clutch or any additional oil tight
casing.
4. CHP Experience with disconnectable steam turbines.
Steam consumption can often vary depending on seasonal, industrial and agricultural
demands. These demand fluctuations create a challenge for CHP station designers
who must satisfy varying heat, electrical power and process steam demands. In
addition to achieving high plant efficiency, short payback periods and limited
installation costs, the solution may also require significant operational flexibility to
cope with these fluctuating demands.
The following examples describe seven CHP facilities ranging low and high powers,
where total operational flexibility and high efficiency were prime concerns for the
designer.
4.1 Bottomingcycle.
As described in Chapter 1, in so called bottoming cycle the CHP plant primary goal is
to produce the heat energy. Power generation is possible as utilization of the
excessive heat or industrial steam.
4.1.1 Waste to power: Fredrikstad Bio-El CHP Plant, Norway.
The city of Fredrikstad is situated in the south-west of Norway close to the Swedish
border and is having nearly 78000 inhabitants. The Fredrikstad CHP plant
commissioned in 2008 has a thermal generation capacity of 25 MW and is fired on
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homogenous, sorted waste, of which 80% origin from the industry and 20% is
municipality waste [2]. Each year the plant recycles energy from around 45000 to
60000 tonnes of waste-based fuel. This results in an annual supply of 110 GWh of
industrial steam to industrial customers in Øra and district heating to Fredrikstad,
together with some electricity generation.
The plant has a main goal to deliver heat to a district heating network and process
steam. Electricity generation is a byproduct. The operational strategy is influenced by
district heating demand, process steam demand and electricity prices.
The facility consists of a 25 MW steam boiler, one generator of 5,68 MW, one back
pressure turbine and one condensing turbine. The turbines are connected to the
generator as shown on the picture. The back pressure steam turbine is a Dresser
Rand B5S-5 is solidly coupled with the generator and the condensing steam turbine
is a Dresser Rand B7S-3 connected to the generator through the Size 92FT Spacer
SSS Clutch. This allows the plant to be operated with or without condensing steam
turbine.
During winter periods the plant has to produce high amount of process and district
heat, therefore the condensing turbine is stopped and the low pressure steam is led
to the heating grid. In summer this excessive heat is not required, therefore the
condensing LP turbine can be connected to the generator in order to produce
additional electricity.
The supply temperature of the district heating water varies between 120 and 90 °C
according to outdoor temperature, usually not above 115°C. The return temperature
varies between 60 and 80 °C.
The production in 2010 was 53 GWh of district heating, 49,8 GWh of steam and 14,2
GWh of electricity. Total energy recovery rate is 70,1%. This relatively low energy
recovery rate is caused by the plant operating based on the certain amount of
incoming waste and the demand for heat or electricity. During low heat demand
seasons not all the excessive heat can be utilized for electric power generation and
thus needs to be cooled, which results in the reduced total energy recovery rate [3].
For this application a size 92FT Spacer SSS Clutch of a spacer type was chosen.
This clutch can accommodate some radial misalignment and has a relatively small
installation length and light weight which has to be supported by the shafts of the
adjacent machines.
4.1.2 Natural Gas fired CHP plant Plauen, Germany.
The city of Plauen is located in central east part of Germany, in Saxony, inhabited by
approximately 68,000 people. The city is supplied with heat via 50 km of district
heating pipes to 13,400 private households. Other consumers include the City’s
hospital, administration offices, and large industrial facilities including Plauen Steel
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Steam - 60 t/h to grid - 5,7 Bar pressure to grid - 240°C to grid
Electricity - 1 MWe Backpressure turbine - 0,32 MWe Backpressure turbine - 1500 rpm generator
Technology, WeMa Vogtland (instrument machines plant) and Schneider Textile
Coloration and Finishing. The power plant was originally built in 1988 as coal fired
power plant. In 1994 the plant was upgraded to operate on natural gas (or on light oil
as a reserve). Heat generators are 4 boilers with total power of 28 MW. The complete
power plant is supplying up to 150 MWth to the grid. One of the features of the district
heat grid is that it has more than 90m of altitude differences [4].
In year 2000 the owner decided to upgrade a plant with a steam turbine which could
utilize the existing differences between the fresh steam conditions from the boilers
and the steam conditioned required for district heat to generate electricity for the own
needs of the plant.
Today two backpressure steam turbines drive one common generator at Plauen
within the Hammerstrasse plant. Both turbines are Kühnle, Kopp & Kausch (now
Siemens Frankenthal) back pressure turbines. The AFA4 steam turbine can produce
0.32 MWe, whereas the AFA6 machine can provide 1.0 MWe via a 1500 rpm
generator.
Fig.5 –CHP Plant Hammerstraase Plauen (Germany) Photo courtesy of Siemens Frankenthal
The ST tandem train can generate between 50 kW and 1300 kW of electricity,
depending on the requirements of the grid in heat. I.e. the more steam is generated
for the grid, the more electricity can be produced.
The maximal total amount of fresh steam is 60t/h, and if the grid demand is smaller,
the not required turbine can be stopped. Ca. 6 t/h are already sufficient to drive one
of the turbines and to generate 50kW or more of electricity. So, depending on
winter/summer operation mode, the plant can operate larger or smaller turbine, or
both.
Splitting the steam turbine demand either side of one generator, with an SSS Clutch
connecting or disconnecting each turbine as required, allows a wide range of CHP
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operating modes which promotes higher operational flexibility with regards to
seasonal changing district heat requirements.
One major consideration of the turbine packager was to keep the design of the steam
turbines standard. The SSS Clutch design chosen was an “off the shelf” unit, an SSS
Clutch Coupling, which can accept radial misalignment and axial growth between
each steam turbine and the generator through two single element flexible
membranes, one at each clutch end. Two ball bearings are located on the clutch
input shaft, which in turn support the clutch output assembly.
4.2 Toppingcycle.
In topping cycle, as described above, electricity is produced utilizing high temperature
and pressure energy, and the waste heat is used for thermal energy generation
purposes.
4.2.1 Vuosaari ‘B’, Finland: a multishaft CCGT plant with high operation
flexibility.
Finland is a world leader in CHP. In 2007, 65% of Finland’s thermal electricity
production, 74% of the heat needed for district heating and 29% of the Finnish
electricity supply was provided by CHP. In 2004, CHP saved Finland 8 million tonnes
of carbon dioxide emissions [1].
Vuosaari is a district of Eastern Helsinki in Finland noted for its rapid residential
growth, although also renowned for retaining large areas of unspoilt landscape with a
population of approximately 35000 people. District heating is particularly popular and
well established in Helsinki providing approximately 90% of the city’s heating needs.
Fig.6– Helsingin Energia / Siemens Finspäng, Vuosaari ‘B’ (Finland) CHP Plant Schematic Drawing
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Helsingin Energia, winner of a European Regional Energy Champion Award from the
European Parliament in November 2008, owns and operates the Vuosaari ‘B’ CHP
plant. Vuosaari ‘B’ provides up to 470 MWe of electricity and 400 MWth of district
heat from a multi-shaft combined cycle plant incorporating 2 x Siemens V94.3 gas
turbines (rated 163 MWe each) and an ABB Stal (now Siemens Finspäng) steam
turbine train (rated 172 MWe).The challenge of providing both peak district heating
demand and peak electricity demand can be fulfilled by Vuosaari ‘B’ concurrently.
This feat is possible because a hot water accumulating tower has been included. The
tower can store up to 25000 m3 of hot water just below 100°C which equates to
around 1400 MWth of energy [5].
The basic principle behind CHP with a hot water accumulator is simple and similar to
that of a domestic heating supply utilizing off-peak electricity to store heat overnight.
When peak electricity is not required, the LP steam turbine is shut down, allowing
100% of the LP steam to be used to heat water, which is stored in the hot water
accumulator.
Shutting down the LP turbine in this case is only possible because of the SSS clutch
located between the LP and IP sections of the ABB Stal steam turbine train, which
drives one common generator. Even when district heating and peak electricity
requirements coincide, the station is capable of fulfilling both demands. The heat
energy is already stored and available for supply, whereas the LP turbine can be
restarted to produce peak electricity as the SSS clutch automatically re-engages.
Consequently, the generating process of the plant is not interrupted whilst the LP is
reconnected through the clutch to the generator system.
During warmer periods, when district heating is required less, or not at all, the LP
turbine is automatically connected to the generator by the SSS Clutch to produce
maximum electricity.
In this case, an SSS Spacer Clutch type was supplied, which in addition to the
normal automated engaging and disengaging mechanism features two sets of torque
transmitting gear teeth allowing the clutch to take up radial and axial misalignment.
This capability allows the SSS Clutch to absorb the thermal growth of the LP and
HP/IP steam turbines, similar to the function of a geared, spacer type flexible
coupling.
To summarise, Vuosaari “B” provides peak and base load electrical power, district
heat requirements and offers flexible operation from a plant which has a 92%
maximum design efficiency. These features make Vuosaari ‘B’ one of the most
versatile CHP plants in the world and an excellent example of total plant flexibility.
4.2.2 MHI / KDHC Hwaseong, South Korea.
Many CHP plants exist in Scandinavia, in particular Finland. Cold winters and
existing CHP infrastructure make this area ideal for CHP expansion. However, other
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Steam - 472,1 t/h to grid - 410 MWth power heat - 4,6 Bar pressure to grid - 292°C to grid
ST Electricity - 425 MWe HP turbine power - 97,4 MWe LP turbine power - 3600 rpm generator
countries are also well versed with CHP. In fact, 60% of South Korea’s households
are supplied with heating energy by Korea District Heating Company (KDHC) through
a network of 1164 km of twin row pipes. In 2006, CHP saved South Korea 2644
tonnes of air pollutants and 1739 tonnes of greenhouse when compared with
conventional heating alternatives [6].
Hwaseong City is situated in the south west corner of the Gyeonggi-do province,
approximately 40 km south west of Seoul. Large local companies include Kia and
Hyundai cars and Samsung Semiconductor. Geographic location, shallow coastal
water levels and exposure to Siberian air streams give rise to low winter
temperatures.
Fig.7 – KDHC / MHI Hwaseong (Korea) CHP Plant, Photograph courtesy of MHI
KDHC own and operate a CHP power plant in Hwaseong City which consists of 2 x
MHI MW501F gas turbines supplying exhaust heat through an HRSG to an MHI
steam turbine train consisting of 425 MWe HP and a clutched 97,4 MWe dual flow LP
steam turbine arrangement.
As well as supplying up to 522 MWe (rated) of electricity to Korea Electric Power
Corporation, the steam section of the plant provides up to 410 MWth in hot water and
domestic heating requirements to approximately 51000 households
The clutched LP turbine allows Hwaseong power plant to choose between supplying
steam for district heating or generating extra electricity, all from one steam turbine
train.
Some may argue that the SSS Clutch may be replaced with a generic spacer
coupling which is disconnected when district heat is required. However, a clutched
LP turbine provides several advantages:
- Instantly flexible to accommodate daily changes in weather patterns;
- Possibility for instant LP turbine disconnection in case of trip/failure etc.;
- Automated and therefore:
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- No requirements to interrupt generation during disconnection or
reconnection of LP turbine;
- No risk of damage to equipment during coupling removal;
- No intensive labour required.
MHI selected a “between pedestal bearings” positioning of the SSS Clutch to provide
adequate support for the SSS Clutch which behaves like two separate overhung
masses when operating in the disengaged condition.
This particular semi rigid SSS Clutch includes a Lock-In facility to assist with dual
(HP+LP) turbines starting mode. Normally, when starting the HP and LP turbines
simultaneously, the LP turbine speed lags behind that of the HP section. This occurs
because the LP machine is much heavier and therefore slower to accelerate, so the
SSS Clutch would normally disengage. To avoid this condition, this SSS Clutch can
be locked into engagement before starting and accelerated to nominal speed without
LP turbine disconnection occurring.
Fig.8 – HP + LP Startup Graphs with and without SSS Clutch Lock-In
Once at full speed, the SSS Clutch Lock-In is deactivated to allow automatic LP
turbine disconnection and subsequent reconnection as required.
4.2.3 KauVo, Lappeenranta, Finland.
Both examples cited above in section 4.2.1 and 4.2.2 include large steam turbines
fired by the exhaust heat from gas turbines. Plants in toppingcycle fired by the heat
from combusted waste products also exist. The following example is fired entirely
with byproducts of the wood and paper industry - bark, residual peat, wood
stampings and chippings.
Electricity consumption in Finland is increasing and some existing plants are being
decommissioned. Also, neighboring Sweden produces half its electricity from nuclear
plant, some of which are more than 30 years old. If Swedish nuclear plants are
decommissioned, opportunities will arise for Finland to export electricity across the
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Steam - 295 m
3 paper mill
- 385 MW Total power: 110 MWth district heat 150 MWth process steam 125 MWe electrical power -- 16,5 + 12 + 4,5 Bar pressure to paper mill - 547°C to paper mill
Electricity - 95+30 MWe condensing turbine power - 20 MWe Backpressure turbine power - 3000 rpm generator
border into Sweden.
This potential is giving current electrical generation facilities more scope for
expanding their capabilities. KauVo is one such expansion.
Lappeenranta is a city of approximately 60000 inhabitants in South-East Finland,
about 30 kilometres away from the Russian border. The local economy is mainly
industrial including paper mills owned by UPM, city facilities and a local university
which specialises in forest and energy technology.
Kaukas is one of the many paper and sawmills owned and operated by UPM, who
are also operating CHP power plant at Kaukaan Voima or “KauVo”.
The plant rotating machinery consists of two steam turbines separated by an SSS
Clutch. One steam turbine is a condensing machine, the other a heating turbine and
both drive one common generator through one single shaft line.
The machine supplies up to 295 m3 max of steam at 547°C to the paper mill at 3
pressures: 16.5, 12 and 4.5 Bar. Total power output for the plant is 385 MW, which
can be broken down to 110 MWth district heat, 150 MWth process steam and 125
MWe generator output.
Fig.9 – UPM Lappreenranta “KauVo” (Finland) / Siemens Goerlitz CHP Plant, 3D drawing courtesy of Siemens
All the desired flexibility is available at this plant, again due to a clutched turbine,
which in this case is a double flow heating turbine. The heating turbine should run for
approximately 8000 hours per annum. As the heating turbine is connected and
disconnected through an SSS Clutch, the system can cope almost instantly with any
changes in the predicted operation hours, promoting further plant flexibility.
Of course, 8000 hours equates to almost 1 constant year running, so it is important to
define that a major factor for including an SSS Clutch at this plant was the added
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benefit of being able to service the heating turbine whilst the condensing turbine
continues running.
The condensing turbine is fitted with a switchable condensing section which allows
the choice of operation as a non condensing turbine at 95 MWe with 30 MWth
passing to the steam supply route or as a 125 MWe full condensing turbine. The
condensing turbine steam supply pressure is 112 Bar.
This plant shows another SSS Clutch design configuration for CHP plant with the
integration of a 4 bearing Encased SSS Clutch package. Because of this particular
clutch package, as described above, standardised steam turbine designs were used
which was greatly reducing design time and cost. This concept offers reduced
engineering input and therefore total installation costs and realisation time for the
customised CHP plant application.
4.2.4 Köln Nieh 3 Combined cycle gas turbine plant KA26-1 SS DH Ecoheat ™.
Köln Niehl 3 power plant is planned for commissioning in 2016 and is situated in the
city of Cologne, Germany and is going to operate by German energy supplier
RheinEnergie. The power plant should produce 453 MWe and around 265 MWth and
supply up to one million households with electricity and 50000 households with
district heat [7].
Fig.10 – Köln Niehl 3 construction site and schematic machinery arrangement, Photograph courtesy of Alstom
The power plant is being build straight next to the operating Niehl 2 power plant
within the densely packed area. One of the challenges for designers were limited
road access and space available for construction of the new power plant. This was
one of the reasons why a single shaft CCGT plant concept, where the gas turbine
and the steam turbine are driving the same generator, was chosen.
Electrical efficiency of the power plant is projected to be over 60% which will make it
one of the most efficient nowadays working power plants. Total fuel utilization rate of
the plant will be over 88% due to its district heat integration.
The power plant consists of one Alstom GT26 gas turbine, one hydrogen cooled
TOPGAS generator and a compact three casing STF30C reheat steam turbine
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connected to the shaft train via a Size 340T SSS Clutch.
During the summer periods the plant is going to operate in the condensing mode
providing full power generation to the electrical grid. During winters the plant will
operate in heating mode for maximal heat production to the district heating grid. In
this operation mode a maximal steam extraction from the three-casing ST is required.
In order to minimize ventilation losses for this operation regime, the double flow LP
section was optimized for very low steam flow and pressures. It is also possible to
operate the plant in simple cycle GT mode only.
This high operational flexibility, fast start up and high efficiency is feasible because of
the SSS Clutch connecting and disconnecting the ST during the plant start up and
changing operation modes. This semi-rigid SSS Clutch design of the size 340T is
installed within the ST bearing pedestal ensuring the shortest possible machinery
train length.
4.2.5 Concept: Single shaft CCGT power plant PGU-165 with Saturn (Russia)
GT-110.
Fig.11– Saturn PGU 165 plant arrangement, drawing courtesy of Saturn, ODK
Russian GT manufacturers haven’t practically realized the single shaft combined
cycle concepts yet. The largest gas turbine which is manufactured in Russia by
Saturn (part of ODK) is the GT-110. This gas turbine is being supplied as a simple
cycle package together with a 110 MW generator.
Russia is well known for a large district heating network and thus for vast demand of
thermal energy supply. Additionally, the average age of the electricity generating
plants in Russia is still very high and the main focus of the authorities for generation
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capacities replacement are the combined-cycle power plants fired by natural gas.
Saturn has fulfilled a large concept work to design a modern modular CCGT power
plant of a single shaft design. The new package is meant to be flexible in terms of
choice variety of steam turbines and includes the GT-110 gas turbine solidly coupled
with the new design hydrogen cooled generator ТТК-165-2УЗ-ГП (165MW) and pre-
planned Skoda 55MW MTD40SA steam turbine [8].
This new power plant can be operated in base load supplying the total electrical
power generation capacity of 165MW to the grid or can operate in heating mode with
simultaneous generation of 110 MW electrical and 35 MW thermal power. The total
machinery train length is 75 m.
Fig.12 – SSS Clutch Encased package with integrated TG device for GT turning
The challenge for designers was the rework of the existing simple cycle concept,
replacing the turning gear devices for the GT and generator which was previously
installed on the free end of generator. Changing the GT design was not possible and
therefore was not considered. Another task was ensuring the option of including any
desired standard ST of the suitable power but keeping the compact length of the
machinery train. Thus the special Size 216T Encased SSS Clutch design with three
bearings and integrated turning gear device with an electrical motor for GT and
generator turning was developed. The weight of the clutch output shaft has to be
supported by the generator bearing on the exciter side. Therefore the clutch package
and the generator together with the GT will be mounted on the same base plate.
Any standard ST of the suitable power and required operation mode can be installed
on the input side of the SSS Clutch package, connected through a suitable tooth
coupling providing additional modularization flexibility.
The calculated efficiency of the plant will be over 52% together with the high fuel
utilization ratio.
18
5 Conclusions.
All of the above examples demonstrate the broad versatility of CHP Plants. Although
they may appear complex, they all possess diverse operational flexibility giving rise to
higher efficiency rates when compared with separated electrical, heat and industrial
steam generation. In all cases studied, SSS Clutches are a key component which
assists in offering extended flexibility of the plant.
As indicated in several examples above, the CHP Plants discussed in this paper
have reduced carbon emissions when compared with separate generation.
A big challenge for new CHP development exists where the construction, electrical
generation as well as domestic heating and process steam industries need to work in
unison during town and city planning. This is especially true of areas which are not
yet familiar with CHP. The prize for a successful collusion is the opportunity to
receive government sponsorship in the form of carbon credits, tax benefits in the form
of enhanced capital allowance, popularity amongst the public from “green
advertising” and the potential to offer less expensive utility bills for residents and
industrial steam consumers.
References :
/1/ Finnish energy industries. Combined Heat and Power Production.
/2/ Renewable solid fuels replacing electricity and oil in an existing thermal energy
market, – Arild Dahlberg, Hafslund.
/3/ Analysis on Methods and the Influence of Different System Data When
Calculating Primary Energy Factors for Heat from District Heating Systems, -
Magnhild Kallhovd, 2011.
/4/ Die Summe macht’s: Nachrüsten von Dampfturbinen im Heizwerk lohnt sich. –
Energiespektrum 09/2002.
/5/ “Local Warming: Helsingin Energia Uses CHP to Heat the City” - Drew Robb,
PowerMag 2010.
/6/ KDHC website - http://www.kdhc.co.kr/eng/
/7/ “Alstom liefert und wartet eine der weltweit effizientesten Gasund
Dampfturbinenanlagen in Deutschland“, - Alstom Communication, 2012.
/8/ Концепция создания моноблока ПГУ-165 нв базе серийного газотурбинного
двигателя ГТД-110. – М.Р. Гасуль, М.Н. Леонов, Газотурбинные технологии
2012.
/8/ CHP Plant – Optimum Efficiency, Total Flexibility. – Nicholas Bellamy, Power-Gen
Europe 2009.