GAS TURBINE COGENERATION ACTIVITIES – NEW POWER
PLANTS FOR URALKALI’S FACILITIES
Alexander Gushchin ,
Siemens Russia
Ian Amos,
Product Strategy Manager, SGT-400,
Siemens Industrial Turbomachinery Ltd, UK
Guy Osborne,
Sales Manager, Siemens Industrial Turbomachinery Ltd, UK
Abstract
Siemens Industrial Turbomachinery Ltd. is supplying four SGT-400 Gas Turbine generating
packages rated at 12.9MWe each, to Uralkali JSC of Russia for installation at two potassium
mines in Berezniki City. The SGT-400 engines are the key components for two cogeneration
plants which are located in one of the main industrial centers of the Ural region. Each
cogeneration plant will comprise two generating sets in order to provide efficient and reliable
production of power and steam for use in the mines and for the manufacturing process.
Cogeneration, the combined production of electrical power and heat, has been a well
established technology for many decades. There are a number of factors which make the
installation of a cogeneration facility attractive. These include significant cost savings relative
to the separate supply of electricity and heat, and improved security of power supply.
The evaluation carried out by Uralkali JSC looked at a number of alternative options for the
prime mover, including reciprocating gas engines, and took into consideration life cycle costs,
flexibility of operation, maintenance philosophies and regulatory requirements for the control
of emissions.
Gas turbines have the ability to burn a variety of fuels and the technology in the Siemens
product range includes options for dual fuel operation, with automatic uninterrupted
changeover from gas to liquid fuel and back again, whilst under load. Control of emissions
resulting from the burning of fossil fuels is becoming increasingly important to comply with
legislation and for protection of the environment. Low Emissions combustor technology
minimises the generation of NOx and CO, whilst reduction of CO2 is inherent in cogeneration
schemes, with typical overall thermal energy efficiencies in excess of 80%.
Gas turbine cogeneration solutions are suited for a wide range of industry segments requiring
heat and power. Typical applications would be for the pulp and paper industries, and also the
ceramics, food and beverage, chemical and pharmaceuticals industries. Cogeneration plants
can also be used as an efficient means of supplying power and heat for local district heating
schemes.
The first two SGT-400 units were delivered to Uralkali JSC in January 2006 and the
remaining two are scheduled for March 2006. These are the first SGT-400 gas turbines to be
© Siemens AG 2006. All rights reserved.
supplied to the Russian Federation, although to date Siemens have supplied over 100
industrial gas turbines to existing customers in the Russian market, including Gazprom,
Surgutneftegas, Rosneft, Lukoil, Sakhalin Energy and the Caspian Pipeline Consortium.
New Power Plants for Uralkali JSC
Uralkali JSC, a leading global supplier of potassium fertilizer, is proceeding with the
construction of its power station installations at two potassium mines in Berezniki City,
located in the Ural region of the Russian Federation.
The power stations, rated at 25MW, will be constructed at Uralkali's Mining Divisions 1 and
4 and will each be equipped with two SGT-400 gas turbines. The gas turbines are fired on
natural gas and are coupled to waste heat recovery units in the turbine exhaust to raise process
steam. The power stations expand the capacity of the existing power grid and engineering
infrastructure at the Uralkali sites. At a rating of 12.9MWe each, the Siemens' SGT-400 gas
turbine closely meets Uralkali's requirements. The steam generated in the waste heat recovery
units will be used in the production of potassium chloride.
Construction at the sites started in 2005, managed by the general contractors
UralVNIIPIEnergoprom, based in the city of Yekaterinburg. The power stations will start
producing electricity in the summer of 2006, with an estimated project pay-back time of 6 or
7 years. In the second stage of the electro-generation development, it is planned to construct
additional power stations to supply electricity to Uralkali's Mining Divisions 2 and 3.
Energy costs represent 12 percent of Uralkali’s total cost of production. The new power
stations will enable Uralkali to supply 85 percent of its required electrical power and 100
percent of its thermal requirement. The savings made by generating their own electricity and
using the waste heat for the production of steam will be very significant. The innovation will
result in a major reduction in production costs and help Uralkali maintain their competitive
edge in the potassium fertilizer market.
The case for cogeneration.
Industrial power users often have a requirement for energy in the form of both electricity and
heat and have been able to choose between different technical solutions to satisfy this need.
• The emergence of large central electrical generation capacity in the developed
countries, in the middle of the last century, with a good transmission infrastructure,
led to a common practice of buying electricity from the generating companies. The
heat demand is then met by burning fossil fuel locally.
• An alternative and well established technology has been to satisfy the energy
requirements using cogeneration at the location of the demand. Cogeneration is the
combined production of electrical power and heat from a single fuel source and has
been used over many decades.
The choice of energy supply is dependant on a large number of variables but will essentially
be based on a consideration of the costs of energy and the security of supply.
© Siemens AG 2006. All rights reserved.
In ‘simple cycle’ operation, the heat contained in the exhaust gases of the gas turbine is lost to
atmosphere, and with typical industrial turbine exhaust temperatures of about 500ºC, this
limits the efficiency of the plant to about 35%. This would usually make the generation of
electrical power on its own uneconomic, assuming there was an available grid connection.
In the case of a gas turbine cogeneration system, the
exhaust heat is recovered in a heat recovery system (or
it can be used for direct drying in some applications).
In the majority of installations, the heat recovery
system will be a steam generator, raising either
saturated or superheated steam for factory process or
heating. The exhaust gases from the stack are now
much lower than for the simple cycle case (140ºC)
and overall thermal efficiencies are increased to more
than 80%, making the economics of operation much
more attractive.
Cool Exhaust
Gas
Factory
Water Returned to
CHP Plant
Steam Supply to
factory process
Fuel
~
Gas Turbine Generating Set
The ratio of heat to power will vary considerably from industry to industry and even within
the same industry segment. In many cases the required heat will exceed the amount that can
be recovered in the exhaust waste heat recovery unit. Additional steam can be raised by
adding supplementary firing to the system, burning more fuel in the turbine exhaust before the
gas enters the boiler. Typical values for unfired and fired steam raising capabilities of
industrial gas turbines are shown below, along with further detail for SGT-400.
200
Steam (12 bar, 200)
175
unfired
fired
150
e
Fi r
125
d
a
s te
m
r
i
ai s
ng
100
75
0
5
10
15
20
25
SGT-700
0
SGT-600
SGT-500
SGT-400
25
s
r
te a m
ais i
Steam values
are indicative
only. Actual
values depend
on site
configuration.
ng
SGT-800
i re d
Unf
SGT-300
50
SGT-100
Steam (tonnes/hr) [12 bar, saturated]
Steam Raising Capabilities for Gas Turbine Cogeneration Plant
30
35
40
45
50
Power (MWe)
© Siemens AG 2006. All rights reserved.
Energy Cost Savings
The main motivation for end users of this technology is to secure savings in energy costs.
If the energy costs and operating profile of the factory or utility are identified, the potential
savings can be calculated. Savings of more than 30% have been demonstrated, but local
electricity tariffs and fossil fuel prices can vary significantly, as well as any grid connection
charges. The example below shows how an estimate of the annual fuel savings can be
calculated easily. The numbers are based on a real case.
Site Requirements :
Assumptions
15,000 kWe electrical
32,041 KW thermal
Gas Turbine Power
Gas Turbine Heat Rate
Gas Turbine Exhaust Heat
Gas price
Electricity price
GT running hrs
Boiler efficiency
External supply
Power (kW)
15,000 electric import
35,601 boiler gas fuel
Hours
run
8,760
8,760
12,861 kWe
36,991 kW
18,401 kW
0.01403 €/kWh
0.046 €/kWh
8,400 hrs/yr
90%
Gas Turbine Cogeneration Solution
Cost (€)
6,044,400
4,375,476
(32,041/0.9)
Power (kW)
GT not running
15,000 electric import
32,041 thermal
GT running
2,140 electric import (15,000-12,861)
36,991 gas turbine fuel
(32,041-18,401)/0.9
15,155 boiler fuel
10,419,876
Annual Savings
Hours
run
360
360
8,400
8,400
8,400
Cost (€)
248,400
179,814
826,896
4,359,463
1,786,112
7,400,685
3,019,191
© Siemens AG 2006. All rights reserved.
Security of Supply
Many industrial processes operate continuously, and unscheduled interruptions to either
electrical supply or steam can cause a complete shutdown of the plant and an expensive loss
of production. An unreliable grid connection can be an important factor in deciding to install
a cogeneration system. Normal philosophy would be to operate the gas turbine cogeneration
plant in parallel with the grid, if available, with the turbine capable of operating in island
mode without interruption to site power in the event of a grid failure.
Cogeneration cycle variations
There are a number of variations to the standard gas turbine cogeneration cycle. These
include;
Auxiliary Firing.
When steam is required continuously for a process, auxiliary firing of the boiler will
enable steam to be produced independently of the gas turbine by having an additional
air intake at the entry to the boiler. When the gas turbine is shut down, the auxiliary
burners continue to operate in order to maintain the steam supply.
Trigeneration
Trigeneration is the simultaneous production of Power, Heat and Cooling from a
single fuel source. The steam from the waste heat recovery boiler is used for process
(or heating) and a proportion is passed through an absorption chiller. This chiller
cools a circulating chilling circuit which is used for air conditioning in the facility.
The amount of heat and cooling generated can be varied according to facility needs.
Combined Cycle with extraction for CHP
The Combined Cycle is used for Power and Heat generation. It incorporates a gas
turbine and steam turbine generating set. Process steam is extracted from the steam
turbine casing and diverted to process via a control valve. Steam flow is varied
according to the process needs. As more steam is diverted to the process, the output
of the steam turbine power generator is reduced.
Gas Turbine Direct Drying
The exhaust gases from a gas turbine are directed into a drying cell or kiln. The
purity of the hot exhaust gas is such that contamination of product is not a concern.
This method eliminates the need for gas-fired or electrically heated kilns and is a
very efficient method of generating power and simultaneously drying. Alternative
schemes using auxiliary firing and air-to-air heat exchangers for indirect drying are
also used.
More detailed description of these can be found in “A Guide to Cogeneration “, (see
references).
Gas turbine cogeneration is also used in district heating applications, with additional
efficiency gains made by using low grade waste heat for the production of hot water. An
SGT-400 installed in Germany during 2005 has demonstrated an overall thermal efficiency in
excess of 87%.
© Siemens AG 2006. All rights reserved.
Cogeneration Evaluation
Early in 2004 Uralkali commenced their evaluation of the various different technical schemes
available that would enable them to eventually make theirthe equipment selection. Initially all
options were considered, including conventional power plant using steam-raising boilers and
steam turbine driven generators, and cogeneration plants driven by both reciprocating gas
engines and gas turbines. The steam turbine design was discounted at an early stage as not
meeting the project’s full requirements due to lower overall efficiency and need for high
pressure, high quality steam. Whilst the latest gas engines are very efficient at generating
electricity, they have several drawbacks. These include only being able to produce small
amounts of steam without additional firing,using the low temperature exhaust gases through a
waste heat boiler; They are generally unable to operate using more than one type of fuel, the
unit is very heavy and is therefore more difficult to transport, and it requires a large
foundation due to the reciprocating design using a large crankshaft and pistons. It also
requires frequent changes of lubricating oil. Gas engines also have a more intensive
maintenance regime when compared to gas turbines, again due to the number of moving parts
and the wear between components within the engine.
Once the selection of the prime mover had been narrowed down to gas turbines, Uralkali
investigated several options including both domestic and Western manufacturers. Within the
size range considered there are two basic designs of gas turbine, aeroderivative and industrial.
The aeroderivative gas turbine is very closely based on units originally designed for use on
aircraft but additionally has a separate power turbine to drive the generator. The
aeroderivative unit is manufactured from materials designed to save weight and is usually
more expensive. Aeroderivatives can be more efficient than the industrial design in ‘simple
cycle’ but the low exhaust temperature gives lower steam raising capability and lower overall
thermal efficiency. Its biggest downfall when compared against the industrial design is the
more rigorous maintenance schedule resulting in reduced availability. The industrial design of
gas turbine has a life expectancy of at least two hundred thousand operating hours that
equates to twenty-five years, provided that the OEM maintenance recommendations are
followed. This is possible due to the more heavy duty design of the main casings, blades and
combustion systems and the lower stresses and temperatures within the engine core. However,
the latest generation of industrial gas turbines now have impressive efficiency figures coupled
with very low exhaust emissions when using low emissions combustions technology.
The Siemens SGT-400 offers high electrical efficiency along with good steam-raising
capability due to the high temperatures and low mass flow of the exhaust gases. The generator
package is supplied in two parts, one containing the engine core along with all its auxiliary
systems and the other comprising the AC generator and reduction gearbox. This allows
transportation by road or rail in a fully assembled and tested state. Note: the SGT-400 meets
the Russian rail authorities’ requirements for rail bridge and tunnel access.
Industrial gas turbines generally require one scheduled inspection each year that equates to
approximately eight thousand five hundred operating hours. This inspection varies annually,
depending on the total number of hours operated by the engine core, the operating
environment and the number of start cycles. In the case of the SGT-400, the core engine
requires a major overhaul after six years or forty-eight thousand operating hours. One of the
advantages over other gas turbine manufacturers is the ability, if necessary, to carry out most
maintenance work at site with the engine still installed on the package. Due to the casing
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design with horizontally split joints, even turbine blading and combustion system components
can be changed at site.
Uralkali also looked at the local service support capabilities of the various suppliers, as they
appreciated the difficulties of exporting equipment to allow maintenance procedures. Even
temporarily exporting components requires export licenses and often results in delays,
especially when trying to re-import the item that may have been overhauled or modified and
appears different to the item originally exported. Siemens now has a dedicated service office
in Moscow that employs local Customer Support Managers to answer technical queries,
arrange the supply of specialist engineers and spare parts and liaise between the end user and
the main manufacturing centres in Europe. Siemens employ Russian nationals who have been
factory trained to service our range of over one hundred units already operating locally and
are now opening a new service centre in Krasnodar that will be used to store spare parts and
specialist tooling plus be equipped to overhaul engine cores without the need to transport
them outside of Russia. All of the above service-related issues were taken into account by
Uralkali during the feasibility study.
Fuel capabilities
The Uralkali installation, like the vast majority of cogeneration applications, will use natural
gas as fuel, although industrial gas turbines have a high degree of flexibility in respect of fuel
type, and operation is possible on a range of gaseous and liquid fuels. The list of fuels which
can be used is continuing to expand due to ongoing combustor development programmes.
Increasingly, there is a wish to exploit “opportunity fuels” which are generally those fuels
considered to be “waste” products.
Gaseous Fuels
Liquid Fuels
Natural Gas
Diesel
Wellhead Gas
Kerosene
Refinery Waste
Gas
Ethanol
Sewage Gas
Naphtha
Landfill Gas
LPG
Coke Oven Gas
However many of these alternative fuels may require
additional treatment to remove constituents which
could cause damage to the turbine. For example;
• Metals and acids cause corrosion in the gas turbine
and should be removed to within acceptable limits.
• Tars and liquid slugs should be removed from gas
fuels to within acceptable limits.
• Particulates can cause erosion of gas turbine
components and should be removed to within
acceptable limits.
Coal Bed Methane
Bio Gas
Dual fuel capability, which allows automatic uninterrupted changeover from gas to liquid fuel
whilst under load and back again, is another feature providing additional security of supply.
Environmental Considerations
The trend of increasing legislation on the control of emissions from fossil fuel power plants is
forecast to continue. This will put more emphasis on thermal efficiencies and also low
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emissions combustor technologies. Gas turbine cogeneration schemes compare favourably
with other technologies;
Pollutant
Effect
Carbon Dioxide
Greenhouse gas Cycle Efficiency
Carbon
Monoxide
Sulphur Oxides
Poisonous
DLE System
Acid Rain
Fuel Treatment
Nitrogen Oxides
Hydrocarbons
Smoke
Method of Control
Ozone Depletion DLE System
Smog
Poisonous
DLE System
Greenhouse gas
Visible pollution DLE System
• CO2 emissions are minimised by
using inherently efficient power
and heat generation schemes such
as Cogeneration, with over 80%
thermal
efficiency
typically
achieved.
• Industrial gas turbines have well
proven low emissions combustion
systems to limit the production of
Nitrogen Oxides and Carbon
Monoxide at levels well below that
achieved for reciprocating units.
Siemens Industrial Gas Turbine Experience in the Russian Federation
The first two Siemens SGT-400 gas turbine generator packages for delivery to Uralkali were
despatched from the factory in England in January 2006, with the remaining two being
despatched in March 2006. These are the first SGT-400 gas turbine packages to be supplied
into the Russian Federation although to date Siemens have supplied over one hundred
industrial gas turbines to customers in the Russian market and Siemens are currently the
leading Western supplier of gas turbines in the 4MW to 15MW range into the Russian
Federation. Existing operators include the Caspian Pipeline Consortium, Gazprom, Krasnodar
Heat and Power, Lukoil, Moscow City, Rosneft, Sakhalin Energy, Surgutneftegas, Togliatti
Azot and Total. Whilst the majority of these units operate on either pipeline natural gas or
diesel fuels, several use wellhead gas taken from the oil fields of Siberia. This wellhead gas
would normally be flared to atmosphere and can contain contaminants including hydrogen
sulphide (H2S), but by burning it in a gas turbine the power is effectively produced for free, at
the same time as reducing emissions.
It is important that all chosen suppliers can work comfortably with the local design institutes
and EPC contractors as well as working to the latest GOST-R and ROSTECHNADZOR
Certification standards to allow importation and also installation, commissioning and
operation of equipment. Experience of supplying and installing equipment for operation in the
harsh environments in Russia is also critical and Siemens have units operating at winter
temperatures to below -57OC using a variety of different heating designs to ensure the
combustion and ventilation heating systems operate successfully. In the Uralkali project the
excess energy produced by the lubricating oil coolers is used to provide heat for buildings,
again increasing total the efficiency of the plant.
Siemens have identified the Russian Federation as one of the key world markets for both
power generation equipment and plants and will continue to invest heavily in the local
infrastructure and support networks to allow our customers to operate their gas turbine based
cogeneration systems to the highest levels of availability and reliability. There are enormous
opportunities for cogeneration plants in Russia, both at new industrial sites and also at
existing facilities due to expansion or replacement of old inefficient equipment.
© Siemens AG 2006. All rights reserved.
REFERENCES
A Guide to Cogeneration : The European Association for the Promotion of Cogeneration
http://www.cogen.org/Downloadables/Projects/EDUCOGEN_Cogen_Guide.pdf.
© Siemens AG 2006. All rights reserved.