Russia’s first power plant to be built on the basis of a turnkey EPC contract by a non-Russian company is nearing completion in the capital city of Moscow. The €300 million ($378 million) advanced combined-cycle cogeneration facility, officially titled Mosenergo Moscow TPP-26 Unit 8, will also be the most efficient in the country. Here in a special report, PEi describes the plant and looks at the role of Alstom, whose unique partnership with local power group Energomachinostroitelny Alliance (EM Alliance), represents the first major contribution by a foreign company to Russia’s growing demand for heat and power.

It would be no exaggeration to suggest that on the outskirts of metropolitan Moscow, Europe’s biggest city, a new chapter is being written in the development of the power industry of one of the continent’s most inscrutable and fiercely nationalistic countries. The Great Bear has broken with tradition and, for the first time, opened its market to intervention by a major global company to produce a combined heat and power (CHP) plant that could set a new benchmark for Russia’s power industry with its efficiency of 59 per cent – the highest efficiency of any combined-cycle power plant (CCPP) in Russia. Its commissioning will be a powerful spur to the development of similar projects not only in Moscow but also in other regions of Russia and the Commonwealth of Independent States (CIS) countries as a whole.

Click here to enlarge image

CHP is firmly established in Russia’s power culture. Historically, it has widely used cogeneration plants to set up regional district heating in its cities. But the new Unit 8 at TPP-26 takes existing technology to an entirely new plane. Importantly, the unique partnership means that Russian industry has the opportunity to participate from access to new technology, since much of the key equipment to be used in the construction of the new generation plant is being manufactured by local suppliers. Similarly, the execution of detailed engineering of some elements of the plant by Russian design organizations will prepare the ground for further co-operation. On Alstom’s part, the venture represents an opportunity to adapt its regular working practices to an entirely new market. Alstom is working closely with its client, partner and other stakeholders to meet the ambitious target of delivering the plant within the contractual timescale, to budget and, most importantly, to the quality expected.

The plant is being built for Mosenergo, the biggest utility provider in the Moscow region and a company devoted to developing electric power in the metropolitan region and central Russia, by a consortium comprising Alstom and local partner EM Alliance under a turnkey engineering, procurement and construction (EPC) contract. It is based on Alstom’s KA26 combined-cycle power plant in a multi-shaft, one-on-one configuration (KA26-1) and uses the company’s unique ‘Plant Integrator’ approach, drawing on its expertize as an EPC contractor and original equipment manufacturer (OEM). The plant will deliver 420 MW of electric power and up to 265 MWth of district heating, bringing the maximum overall efficiency of the plant to more than 85 per cent in terms of fuel utilization. Moreover, Alstom’s design gives the plant the flexibility to perform in various operating modes, a factor that will enable the client to reduce gas usage by some 30 per cent compared with existing plants in Russia.


A simplified flow diagram of the TPP-26 combined-cycle CHP plant
Click here to enlarge image

The TPP-26 project forms part of Mosenergo’s programme to develop Moscow’s power network to meet the fast-growing demand for power and heat in the capital’s populous metropolitan district of Vostriakovsky. It will be the eighth unit of a 1410 MW generating power plant operated by Mosenergo at the site. Alstom is responsible for all the engineering, procurement, construction and commissioning of the new unit, including the single KA26-1 multi-shaft combined-cycle unit, control systems, electrical rooms and transformer units, the steam extraction system for the district heating element of the contract and gas fuel plant (gas preparation centre, booster systems and diesel generators).

Click here to enlarge image

Alstom says its ‘Plant Integrator’ approach creates more value for the customer by optimizing investment costs, integrating operating and maintenance costs and reducing lead times to produce electricity faster while improving fuel efficiency over the plant’s life cycle, and overall plant reliability. It points to being one of the few OEMs in the market able to offer all the major power generation technologies in-house; this, it says, enables it to bring together the knowledge and expertise of the ‘architect-engineer’, or EPC contractor with those of an OEM, integrating all of the installed components into a fully optimized plant.

Alstom believes that, with this approach, it has the appropriate capabilities, the required skills and credentials to contribute significantly to power expansion and replacement capacity needs in precisely the way currently being undertaken in Moscow. Moreover, it believes its approach is highly conducive to meeting the increasing demand globally for EPC turnkey solutions, as is particularly the case in the liberalized European market. This comprehensive approach to turnkey EPC includes performance and schedule guarantees, warranties and assurances encompassing the entire scope of the plant, rather than being limited to individual components or packages. In this way, says Alstom, end-user risk is significantly reduced.

Moscow TPP-26 Unit 8 uses Alstom’s proven and mature combined-cycle technology based on the advanced class GT26 gas turbine, with more than two million operating hours operating experience. The full line-up includes a three-casing, double-flow, low-pressure steam turbine, air-cooled generators, a water-cooled condenser and a three-stage re-heat, horizontal type heat recovery steam generator (HRSG). The unit’s control system is based on Alstom’s ALSPA P320 technology.

Mosenergo – the client

The last 18 months have seen major changes at Mosenergo. In April 2007, the majority of the stock of the company was acquired by Gazprom, the Russian natural gas giant, which now holds a 53.47 per cent stake in Mosenergo. Gazprom, which itself is a major stockholder in a number of large Russian power generation companies, including OGK-2, OGK-6 and TGK-1 (Lenenergo), has thus strengthened its position in the country’s power generation sector.

Today, Mosenergo has a total installed capacity of 11.1 GW from 17 power plants, representing some 8 per cent of all thermal generation capacity in Russia. Almost all of these plants are based on cogeneration and fuelled by natural gas. District heating in Moscow is on a scale unequalled anywhere else in the world.

A steady growth in gross domestic product (GDP) in recent years, rising to an average of 8.9 per cent, has led to a situation where the Russian power market is developing rapidly, but the power sector has suffered badly over many decades from under investment. Existing power plants are ageing – typically more than 20 years old with fuel efficiencies of less than 38 per cent. Installed capacity has languished around the 215 GW level, leading to a general shortage in power generation. To put it simply, electricity supply will not meet the demand in the coming years. To counter this position, Russia plans to invest $118 billion in new plant to 2012, representing an increase of 20 GW of new gas fired capacity.

Mosenergo has a large programme of its own for the development and technical upgrading of the Moscow’s power network by 2010. It plans to commission more than 2400 MW of capacity by constructing new cogeneration units, as well as modernizing and re-engineering existing installations at a number of its power plants.

Acknowledging that the continuing development of Moscow’s grid is impossible without further reinforcement of central power supplies, Mosenergo has set itself a demanding improvement strategy. It includes, over the next ten years, eliminating current capacity deficiencies in the Moscow region and doubling the installed capacity of its power stations, based on contemporary technologies. And, significantly, ‘contemporary’ is the key. Mosenergo has stated that it wants to sweep aside the inefficiencies of the past and invest in only the latest technologies offering real economic advantages.

Alstom KA26 technology

In winning the TPP-26 project, Alstom says it was able to offer the most effective combined-cycle power plant technology in its class virtually off-the-shelf. The designer, manufacturer and supplier is providing the key equipment from a single source. Answering one of the key project drivers of the Unit 8 contract, the company says that a huge reduction in gas consumption in the first year of operation alone translates into a massive $55 million (based on 2011 expected gas prices) saving.

The solution adopted at TPP-26 comes after the recognition of the fact that utilities, independent power producers and merchant power generators face unprecedented change – deregulation and tougher competition, shifting consumption trends and more stringent emissions legislation. Alstom has developed a range of turbines – the GT24 and GT26 in particular – that rise to these challenges. They also need to ensure reliability of supply yet reduce the cost per kWh of producing electricity. Raising efficiency remains a constant challenge. And finally the flexibility to fuel gas composition needs to be addressed in times of the global transport of fuel gas.

Alstom has integrated its heavy-duty GT26 gas turbines into an optimized single-shaft or multi-shaft combined-cycle generating block – the KA26 Reference Plants. In the mid-1990s, Alstom introduced two similar sequential combustion gas turbines, the GT24 for the 60 Hz market and the GT26 for the 50 Hz market. Since their launch in 1995, these advanced class GT24/GT26 units have demonstrated this technology platform offers significant advantages to the plant operator – superior operating flexibility, low emissions, high part-load efficiency and world class levels of reliability being amongst them.


The onsite erection of the GT26 gas turbine, which offers a high power density in a compact design
Click here to enlarge image

These benefits are brought about by utilizing the concept of sequential combustion, a principle introduced as early as 1948 as a means of increasing efficiency at low turbine inlet temperature levels. Sequential combustion, the re-heat principle for gas turbines, had already been applied to earlier (at that time Brown Boveri) units, but using two side-mounted silo combustors.

In the case of TPP-26, the GT26 combustion system is based on the well-proven Alstom combustion concept using the EV (EnVironmental) burner in an annular combustor followed by the SEV (Sequential EnVironmental) burner in the second combustion stage. This dry, low NOx EV burner has a long operating history and is used across the whole range of Alstom gas turbines. By integrating the concept of a dry, low-NOx EV burner and sequential combustion into a single-shaft engine, the GT24/GT26 design is able to achieve a high power density in a compact unit with a small footprint.


A. Turbine hall, B. HRSG, C. Transformer, D. Forced draft cooling tower, E. Tank, F. Administration building/control room & warehouse
Click here to enlarge image

The sequential combustion system, or reheat cycle concept, is a key technology behind the GT26. Compressed air is heated in the first stage EV combustion chamber by adding around 50 per cent of the total fuel (at baseload). After this, the combustion gas expands through the single stage, high-pressure (HP) turbine, which reduces the pressure by approximately a factor of two. The remaining fuel is then added in the second stage SEV combustion chamber, where the combustion gas is heated a second time to the maximum turbine inlet temperature and finally expanded in the four-stage low-pressure (LP) turbine.

TPP-26 Unit 8 will burn either natural gas or, as a back-up, liquid fuel. With a rated output of 288.3 MW at an ambient temperature of 15 ºC and ISO conditions, the gas turbine will have an exhaust gas flow rate of 616 kg/s, leaving the turbine at a temperature of 616 ºC. At that point it will enter a three-pressure re-heat, horizontal type HRSG. From there the steam enters the three casing steam turbine.

Alstom says the concept gives the new generation of turbines the commercial edge. In today’s dynamic power generation market environment, operational flexibility is a major consideration for customers and crucial for commercial success. Since their start in commercial operation, the KA24/KA26 combined-cycle power plants have enjoyed industry leading operational flexibility.

Alstom says this is due to a combination of a number of key advantages offered by its advanced technology. These include: excellent start-up characteristics for hot, warm and cold starts; operational flexibility from 100 per cent down to 40 per cent combined-cycle power plant (CCPP) load and below; high part-load efficiency and low NOx emissions down to 40 per cent CCPP load and below; extremely low ‘parking load’ during off-peak periods at about 20 per cent CCPP load; and, a very good fuel flexibility capability with regard to varying natural gas compositions.

Start-up behaviour

The start-up behaviour of a power plant is determined both by the start-up time and the reliability. Alstom says the start-up time of the KA26 combined-cycle power plant, like the KA24, is short in comparison to other gas turbines of a similar size. With the optimal plant concept it has been shown that the combined-cycle baseload is reached within 50 minutes for a hot start (i.e. after about an eight hour shut-down). This short start-up time means the plant is able to supply power sooner and therefore earn money for its owner. This ability is an important advantage in a market environment with a volatile electricity price. It allows the operator to take opportunities with minimal time delay.

Secondly, Alstom’s monitoring of its KA24/KA26 fleet has demonstrated a power plant start-up reliability of more than 95 per cent. This, says Alstom, is again important because a missed start can be extremely expensive in terms of buying in the previously committed power. There may also be further benefits such as revenues from non-spinning reserve payments.

The short start-up times and high start-up reliability thus have the ability to boost revenue for customers, compared to CCPPs using other technologies. Depending on the individual plant economic model, these considerations could represent millions of euros of additional operating revenues each year.

High part-load efficiency

High part-load efficiency is important in achieving high operational flexibility. In low price periods, part-load efficiency is the crucial factor when it comes to flexibility and profitability. It gives the operator the added option to decide whether or not to continue to run the CCPP during the low price periods by reducing the power output to a minimum without sacrificing substantial efficiency. This operational mode reduces the number of starts during these low price periods, and therefore decreases the associated starting costs.

Additionally, the lifetime consumption that is related to the number of starts of the gas turbine can be controlled by freely choosing whether the gas turbine is shut-down during low price periods, or not. This offers an important advantage, which significantly increases the flexibility in outage planning.

Furthermore, the high part-load efficiency indirectly allows control of the cumulative emissions of the power plant, since a decrease in the number of starts reduces the absolute emissions produced during start-up.

Moreover, Alstom says, the company has developed an operating mode – the ‘low load operation concept’ – which is capable of maintaining all the required emission levels at loads lower than 25 per cent of the CCPP’s maximum, thus allowing the operator to ‘park’ the units during off-peak hours. This is much lower than has been seen in the CCPP market to date, and is again a feature arising from the Alstom sequential combustion technology. Also, as an alternative to any daily ‘cycling’ mode, this feature does not reduce hot gas path lifetime, and further increases plant flexibility and its ability to cope with new operating regimes.

Plant in Detail

The generation block consists of one Alstom GT26 gas turbine and one steam turbine arranged in a multi-shaft configuration, each turbine provided with its own air-cooled generator. In addition the block features one HRSG, one water-cooled condenser, two steam/water heat exchangers for district heating, and the auxiliaries required to operate the plant.


The cutaway schematic clearly shows both the generation block and the district heating system of the high-efficiency TPP-26 CHP plant
Click here to enlarge image

It is anticipated that the plant will need to accommodate daily load variations in the range between 50-100 per cent relative active load. However, daily start-up and shut-down cycles are also envisaged, as is short-term plant operation at gas turbine loads down to 30 per cent. District heat extraction will be possible between 30-100 per cent of gas turbine load. The facility will be capable of operating at baseload without any restrictions in an ambient temperature range of -42 ºC to 37 ºC. Design ambient conditions are: ambient temperature (-3.1 ºC); and ambient pressure (995 mbar); relative humidity (77 per cent).

The plant is designed to operate principally with natural gas and oil as the back-up fuel. It complies with strict near-field and far-field noise guarantees which are considerable more onerous than the industry ‘norm’ and below those stipulated in the contract for the plant’s metropolitan location. Abnormal operation modes such as equipment failure or block trip, however, are excluded from these noise guarantees. Furthermore, steam turbine bypass operation, plant start-up and shutdown, as well as peak load operation are also excluded from the near-field noise guarantees.

Major Components and Systems

 

Gas Turbine

The GT26 type gas turbine consists of one common rotor for one HP turbine stage and four LP turbine stages and 22 compressor stages. Heat input is performed by two annular combustion chambers (EV & SEV burners), applying the sequential combustion principle. The HP turbine is located downstream of the EV burners and upstream of the SEV burners for first expansion of the exhaust gas. The turbine inlet air is filtered in the air intake block.

The rotor is rigidly coupled to the generator shaft. The airflow through the gas turbine is controlled by the angular position of three variable guide vane (VGV) rows, placed in front of the first three compressor blades rows. During part-load above the 25 per cent gas turbine load, the turbine controller maintains the exhaust gas temperature at the maximum part-load temperature by opening the VGV and increasing fuel injection to both combustors.

For cooling and sealing purposes, air is drawn off the compressor at a number of stages. Two airflows are partly cooled external to the gas turbine by a ‘once through cooler’, which is connected to the water steam cycle, producing additional steam and thus power through the steam turbine. An anti-icing and air pre-warming system based on a heat exchanger is provided in order to preheat the air during icing conditions, enabling the normal operation of the gas turbine.

Steam Turbine

The Alstom STF30C steam turbine consists of one reheat type single flow HP chamber, one single flow IP (intermediate pressure) chamber and one double flow LP chamber. The turbines are rigidly coupled. HP live steam enters the HP turbine through a single valve block, consisting of one stop and one control valve, and is expanded to re-heat pressure. The cold re-heat steam is mixed with the IP steam, generated in the HRSG, and re-heated. The LP steam enters the IP turbine exhaust through a one stop and one control valve, where it is mixed with the IP steam before entering the LP turbine. The outlet steam of the LP turbine is discharged to the water-cooled condenser.

The IP steam turbine is equipped with extractions for district heating operation. Steam for the district heater DH1 is drawn off from the IP exhaust. District heater DH2 receives steam from the IP steam turbine at an intermediate stage. During pure condensing mode, a minimum amount of steam is flowing through the last stages of the IP turbine in order to prevent ventilation, and discharged into an intermediate state of the LP steam turbine.

Generators

An Alstom TOPAIR type generator is driven by one gas turbine at 19 kV rated terminal voltage, while the steam generator drives a TOPAIR at 15 kV. The generators have a two-pole, three-phase synchronous type of air-cooled design. The hot air is re-cooled in heat exchangers located in the generator housing. The heat is transferred into cooling water and rejected to atmosphere through a remote cooling system.

The gas turbine-generator is equipped with a static frequency converter for starting the generator as a synchronous motor. During start-up, the starting energy is provided – via redundant connection from the station service transformers – by the high voltage (HV) grid across the generator step-up unit transformer. Starting without a power supply from the HV grid is not possible.

Heat Recovery Steam Generator

A single, horizontal type HRSG, triple pressure re-heat unit operates in natural circulation mode for the LP, IP and HP systems. Heat discharged from the gas turbine as hot exhaust gas serves as the heat source to produce superheated HP, IP and re-heat steam and superheated LP steam.

The HP/IP feedwater pumps feed the HRSG, which the LP feedwater is extracted downstream of the second row of IP/LP economizers. The feedwater flows are pre-heated in the respective economizers and admitted via control valves into the HP, IP and LP drums. Saturated steam is generated at the HP, IP and LP evaporator.


Consruction of the single, horizontal-type HRSG
Click here to enlarge image

The HP steam is led to the multi-stage HP super-heater, the IP steam to the IP super-heater and subsequently to the re-heater. The LP steam is super-heated also. At the outlet of the HRSG, the HP and re-heat steam are attemperated with feedwater extracted from the HP economizer feedwater line and IP economizer section.

A blow down tank collects the drains of the HRSG and the drains of the steam turbine external steam system, which are located near the HRSG. After separation, steam is discharged to atmosphere and condensate is discharged to the wastewater system.

Main Steam System

The main steam system consists of the HP steam line, the cold re-heat steam line, the IP steam line and the LP steam line. The HP steam line transfers the HP steam produced in the HRSG to the HP section of the steam turbine. The HP steam is expanded in the steam turbine and released into the cold re-heat steam line. When the steam turbine is not in operation, the HP bypass guides the HP steam into the cold re-heat steam line. The cold re-heat steam line transfers the cold re-heat steam back to the HRSG, where it is re-heated and mixed with the IP steam.

Steam is taken from the cold re-heat steam line for the supply of the air removal system and the gland steam system. It also supplies the auxiliary steam header with steam and acts as a secondary supply of the high temperature cogeneration heater.

Condensing System

This is a horizontally arranged two-pass condenser, cooled directly using water from the cooling tower. Non-condensable gases on the steam side are extracted at a defined point of every tube bundle with the lowest pressure – the so-called ‘air coolers’.

District Heating System

The district heaters (DHs) consist of surface heat exchangers. District heating water enters the inlet water box of the first heater, flows through the tubes and leaves the heater via the outlet water box; then it passes through the second district heater in much the same way. Condensing heater DH2 is fed with steam turbine extraction steam, while the condensate from it drains into DH1 through an expansion device. The condensing and sub-cooling heater DH1 is fed with cascade condensate from DH2, steam turbine extraction steam and with hot feedwater from the HRSG. The hot water from the HRSG drains into the heater through its expansion device. Cooled condensate from the heater DH1 leaves the heater via the heater condensate extraction pumps, of which there are four.

Fuel Gas Supply System

Fuel gas is delivered to the plant by a pipeline. Because of the high variability in supply pressure and quality of the feed gas, it has to be treated or conditioned before it can be fed to the gas turbine fuel gas blocks. The fuel gas enters the plant via the main gas inlet valve and passes the redundant gas scrubber units. Separated condensate is collected in a skid and returned to the client systems. A redundant fuel gas compressor system increases the gas pressure according to the needs of the gas turbine. In this way, gas pressure is controlled by a dedicated system of recirculation.

Instrumentation & Control (I&C)

The I&C system permits the safe running and supervision of the whole CHP plant. Alstom’s scope of work covers the control and monitoring of the gas turbines, water and steam cycle, HRSG, steam turbine, all the auxiliaries, and steam turbine generator, including the electrical equipment.

Operation Modes

These are loosely divided into ‘Condensing Mode’ and ‘District Heating’ modes. Both are considered in the plant automation and are designed to be selectable by the plant operator through a human machine interface module.

Condensing Mode

In this operating mode the exhaust steam from the HP steam turbine is re-heated in the HRSG and directed into the IP steam turbine, passing a crossover line into the LP steam turbine, and finally condensed. In this mode, the steam extraction control and check valves are closed, hot circulated feedwater is returned to the feedwater tank, the DH water control valve is closed and the DH condensate pumps are out of operation. The load of the power plant is controlled according to the grid requirements (i.e. electric load/frequency).

District Heating Mode

In this operational mode the steam turbine is in operation and on equal or higher than minimum DH load, the steam extraction control and check valves are open, hot circulated feedwater is being fed into the DH1, the DH water control valve is open and the DH condensate pumps are in operation.

District heating network operators will determine the water flow and heater outlet temperature in accordance with the required heat load. The DH flow controller will throttle the DH water control flap according to requirements.

Alstom’s Russian Coup

As one of the few OEM manufacturers in today’s market that has all the major power generation technologies in-house, Alstom believes its foray into this little know European market marks a significant coup for the company.

As the power industry continues down the path to liberalization, competition for new and burgeoning power markets are bound to attract intense competition. Being the first to win over customers in markets such as Russia, which has traditionally kept itself to itself, is without doubt a breakthrough. Having the skills set in-house, with the ability to transfer technologies to power-hungry nations at the European Union’s back door, would seem to be a good place to start.

Division of Labour

Alstom says it knew from the outset the importance of teaming up with a strong local partner to build Unit 8, a groundbreaking venture by any standard, being the first time a major European developer has led a project of such a magnitude in Russia. Consequently, the division of responsibilities was set out at an early stage.

Alstom’s activities can be split between its two commercial units, Alstom Russia, a locally deployed resource of EPC expertize employing some 50 engineers and support staff, and Alstom (Switzerland). Their individual roles are outlined as follows:

The Alstom Russia unit acts as the consortium leader and includes Alstom’s ‘Plant Business’ department. One of the key activities of the division is what Alstom calls the ‘Russification’ of its activities – that is, assimilating the specific features required to construct power stations suited to the Russian market environment. Its duties include assigning technical supervisors for installation works. It is also responsible for the supply of the heat recovery system of the new plant – the HRSG, designed and manufactured according to Russian specifications and regulations.

Interestingly,it is showing the most dynamic development of all of Alstom Russia’s divisions, and the current goal is for further significant growth.

Alstom (Switzerland) is responsible for the conceptual engineering, including all the basic engineering of the plant, (but also encompasses the detailed engineering for the gas and steam turbine). The parent company also undertakes the assignment of technical consultants and oversees the engineering package associated with the basic engineering of the HRSG.

Crucially, Alstom (Switzerland) is responsible for the supply of all the key equipment, as laid out in the ‘Plant Integrator’ concept promoted by the company. This includes the supply of the GT26 gas turbine and steam turbine, each with a generator (including auxiliary systems), and the ALSPA control system.

For its own part, EM Alliance provides some detailed engineering works on areas not covered by Alstom. Its responsibilities also include the execution of all civil works and associated plant erection, and pre-commissioning and commission (together with Alstom).

Other areas of responsibility include such items as the procurement of the cooling tower and cooling water pumps, and the supply of electrical equipment, such as step-up transformer, auxiliary transformer and switchboards..