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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
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.
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.
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.
0 5 10 15 20 25 30 35 40 45 500
25
50
75
100
125
150
175
200
Steam Raising Capabilities for Gas Turbine Cogeneration Plant
Steam (12 bar, 200)
Power (MWe)
Stea
m (t
onne
s/hr
) [1
2 ba
r, sa
tura
ted]
Unfired steam raisingFired steam ra
isingunfiredfired
SG
T-1
00
SG
T-3
00
SG
T-4
00
SGT
-500
SG
T-6
00
SG
T-7
00
SGT
-800
Steam values are indicative only. Actual values depend on site configuration.
~
Fuel
Cool Exhaust Gas
Factory
Water Returned to CHP Plant
Steam Supply to factory process
Gas Turbine Generating Set
~~~
Fuel
Cool Exhaust Gas
Factory
Water Returned to CHP Plant
Steam Supply to factory process
Gas Turbine Generating Set
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 : 15,000 kWe electrical 32,041 KW thermal
Assumptions Gas Turbine Power 12,861 kWe Gas Turbine Heat Rate 36,991 kW Gas Turbine Exhaust Heat 18,401 kW Gas price 0.01403 €/kWh Electricity price 0.046 €/kWh GT running hrs 8,400 hrs/yr Boiler efficiency 90%
External supply Gas Turbine Cogeneration Solution Power (kW) Hours
run Cost (€) Power (kW) Hours
run Cost (€)
15,000 electric import 35,601 boiler gas fuel
(32,041/0.9)
8,760 8,760
6,044,400 4,375,476
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 15,155 boiler fuel (32,041-18,401)/0.9
360 360 8,400 8,400 8,400
248,400 179,814
826,896
4,359,463 1,786,112
10,419,876 7,400,685 Annual Savings 3,019,191
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.
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.
However many of these alternative fuels may require additional treatment to remove constituents which could cause damage to the turbine. For example;
Bio Gas
Coal Bed Methane
Coke Oven Gas
LPGLandfill Gas
NaphthaSewage Gas
EthanolRefinery Waste Gas
KeroseneWellhead Gas
DieselNatural Gas
Liquid FuelsGaseous Fuels
Bio Gas
Coal Bed Methane
Coke Oven Gas
LPGLandfill Gas
NaphthaSewage Gas
EthanolRefinery Waste Gas
KeroseneWellhead Gas
DieselNatural Gas
Liquid FuelsGaseous Fuels
• 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.
emissions combustor technologies. Gas turbine cogeneration schemes compare favourably with other technologies;
• 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.
Pollutant Effect Method of Control
Carbon Dioxide Greenhouse gas Cycle Efficiency Carbon Monoxide
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.