RECENT TREND ON GAS TURBINEPOWER PLANT

SANTOSH VERMA (P10TM 053)AJESH KT (P10TM 037)MTECH-TURBO MACHINES

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Introduction

The gas turbine has seen a drastic rise in popularity within the power generation industry.

Until the end of the 1960s gas turbines were almost used in the aviation industry.

During the 1970s and 1980s they started to find favour as standby and peak power units because of their facility for rapid start-up.

At the end of the twentieth century the gas turbine had become one of the most widely used prime movers for new power generation applications.

Later most potential combined cycle power plant has been the developed.

The combines gas and steam turbines in a single power station, can provide a cheap, high-capacity, high-efficiency power generation unit with low environmental emissions.

OVERVIEW OF INDIA’S POWER SECTOR

India's power market is the fifth largest in the world.

The current installed capacity of power plants is 140000 MW

In the past few years, there has been considerable growth in power plants based on renewable sources of energy.

The current installed capacity based on these sources is about 6,200 MW of total utility capacity.

The power sector is high on India's priority as it offers tremendous potential for investing companies based on the sheer size of the market and the returns available on investment capital.

Regional wise power Generation in India

Development of Gas turbine power plants in India

The present installed capacity of gas turbine power plants is about 9000 MW,which is 13 % of the total thermal power plant capacity.

Govt. of India has permitted installation of additional 12000 MW of liquid fuel based power plants.

The major gas turbine power plants are combined cycle plants and few smallcapacity plants are on open cycle mode. The gas turbine power plants arehaving varying unit sizes.

Gas Turbine power plant capacity in World

Existing technology based on the Thermal Power

The Thermal Power Stations in the country are mostly based on the following technologies:

Steam Power Plants

Gas Turbine Power Plants

.

Gas Turbine power plant Vs Steam Power Plants

It is simple in design as compared to steam power station since no boilers and their auxiliaries are required.

It is much smaller in size as compared to steam power station of the same capacity .

Very high power-to-weight ratio, compared to steam turbine power plant.

The initial and operating costs are much lower than that of equivalent steam power station.

The Steam Power Plants are mostly coal-based power plants and so more polluted the atmosphere.

Gas turbines run at even higher temperatures than steam turbines, the temperature may be as high as 1100 – 12600C.

The maintenance charges are quite small.

Storage of fuel requires less area and handling is easy.

THE WORLD‘S FIRST INDUSTRIAL GAS TURBINE SET – GT NEUCHÂTEL

4 MW GT for Power Generation

Working principle of Gas Turbine plants

Air is compressed(squeezed) to high pressure by a fan-like device called the compressor.

Then fuel and compressed air are mixed in a combustion chamber and ignited.

Hot gases are given off, which spin the turbine wheels.

Most of the turbine’s power runs the compressor. Part of it drives the generator.

Gas Turbine Power Plant

Gas Turbine Power Plants Components

Gas turbines have three main parts:

i)Air compressor ii) Combustion chamberiii) Turbine

Air compressor:

The air compressor and turbine are mounted at either end on a common horizontal axle(shaft), with the combustion chamber between them.

Gas turbines are not self starting. A starting motor initially drives the compressor till the first combustion of fuel takes place, later, part of the turbine’s power runs the compressor.

The air compressor sucks in air and compresses it, thereby increasing its pressure.

Combustion chamber

In the combustion chamber, the compressed air combines with fuel and the resulting mixture is burnt.

The greater the pressure of air, the better the fuel air mixture burns.

Modern gas turbines usually use liquid fuel, but they may also use gaseous fuel, natural gas or gas produced artificially by gasification of a solid fuel.

The combination of air compressor and combustion chamber is called as gas generator.

Turbine:

oThe burning gases expand rapidly and rush into the turbine, where they cause the turbine wheels to rotate.

oHot gases move through a multistage gas turbine.

oLike in steam turbine, the gas turbine also has fixed(stationary) and moving(rotor) blades.

oThe stationary blades guide the moving gases to the rotor blades and adjust its velocity.

oThe shaft of the turbine is coupled to a generator or machinery to drive it.

Modern Gas Turbine Power Plant

Combined cycle power plant costs

Capacity(MW)

Cost

($million)

Cost/kW

(US$)

Start-up

UK (Teeside) 1875 1200 640 1993

Bangladesh(Sylhet)

90 100 1110 1995

India (Jegurupadu)

235 195 830 1996/1997

Malaysia (Lumet) 1300 1000 770 1996/1997

Indonesia (Muara Tawar)

1090 733 670 1977

UK (Sutton Bridge)

790 540 680 1999

Vietnam (Phu My 3)

715 360 500 2002

USA (Possum Point)

550 370 670 2003

Algeria 723 428 590 2006

Pakistan 775 543 700 -

Gas Turbine Fuel Flexibility The increasing demand for energy and the continuing increases in

prices for standard fuels demand greater , flexibility in the use of fuels in gas turbine.

As nations look for domestic energy security, lessened environmental impact and reduced effect from variable fuel costs, they have examined alternate or non-traditional fuel sources for large

power generation.

Gas turbine based generation systems offer efficient energy conversion solutions for meeting the challenge of fuel diversity while maintaining superior environmental performance.

Traditional Gas Turbine Fuel• Natural gas is a significant fuel source for power generation and will continue to fuel a large share of power additions

Non-Traditional Gas Turbine Fuels

•Oils Process

•Process By-products Fuels

•Low Calorific Value (LCV) Fuels

•Syngas and Synfuels

Non-Traditional Gas Turbine Fuels

As continuous-flow machines with robust design and universal combustion systems, gas turbines have demonstrated distinctive capabilities to accept a wide variety of fuels.

Oils, including crudes and other refiner residuals, which are heated to acceptable levels to enable the needed viscosity for gas turbine combustion.

Off gases or by-products of industrial processes – derived from the chemical, oil and gas, or steel sectors, many of these fuels cannot be transported or stored, and their essential appeal will be to reduce fuel supply in industrial plants in the carbon-constrained environment.

Syngas and synfuels – derived directly from abundant fossil carbon (refinery residuals, coal, lignite, tar sands, and shale oil), they represent great potential for the carbon-constrained economy, provided they are subjected to carbon capture.

Bio-liquid fuels – more evenly distributed around the world, they are of prime interest due to their overall neutral carbon balance.

The graphic below uses two scenarios based on the change in the price of oil to show the share of various fuels used in gas turbine .

Integrated Gasification Combined Cycle (IGCC) is a promising technological solution for long-term power needs

The plant concept for a gas turbine operated with syngas can be an IGCC plant .

Syngas provides increased flexibility for the use of available energy sources.

Syngas can be produced from a wide variety of coal grades, but also from biomass, petroleum coke and refinery residues.

Purified synthetic gas not only increases the flexibility of the useable energy sources, it also enables use of these energy sources in gas turbines targeting electricity, heat production and CO sequestration & storage

IGCC PLANT

From both an efficiency and an environmental prospective, Integrated Gasification Combined Cycle (IGCC) is a promising technological solution for long-term power needs.

IGCC actually combines:

• Advanced conversion efficiency• Solid and liquid feed stocks from local sources• Competitive capital expenses• Most favorable pollution emissions control (NOx, SO2, mercury, PM10)• CO2 capture readiness, when combined with Carbon Capture and Storage (CCS)• Fuel flexibility• Generation of industrial feedstock gases (Syngas, H2, etc.)

A gasifier that combines coal and steam with a controlled amount of oxygen under high pressures to produce hydrogen and carbon monoxide.

Converting the carbon monoxide to additional hydrogen and carbon dioxide in the shift conversion. Further processing the gasses to remove sulfur, mercury, and carbon dioxide.  Sequestering the carbon in a depleted oil formation, enabling enhanced oil recovery, or in a deep saline formation.

Producing a mostly hydrogen fuel, emitting only 10 percent of the carbon released by an integrated gasification combined-cycle coal project without carbon capture.

The hydrogen is fed to gas turbines where electricity is generated. Exhaust heat from the gas turbines is used to create steam and drive additional turbines.

The use of these technologies in a full-scale, 600-megawatt (MW) commercial generating facility.

gasifier

The potential fuels utilized on high efficiency gas turbines are illustrated in Figure

Power plant configuration, non-integrated, partial and full air side integration

Status of Global IGCC Project

GreenGen Project:

GreenGen is a joint venture representing China’s largest electric utilities and coal companies.

GreenGen IGCC Coal Power Plant

Location: Tianjin City, Bohai Rim, ChinaCapture Method: IGCC/ Pre-combustion

The main aims of GreenGen project are to develop and demonstrate a coal-based power generation system with hydrogen production through coal gasification, power generation from a combined-cycle gas turbine and fuel cells, and efficient treatment of pollutants and CO2.

two 400-megawatt IGCC uni Volume: Stage I: 250 MW, Stage II: 650 MW

Shenhua Group, State Development & Investment Co., China Coal Group, and the Chinese government and Peabody Energy.

Pollution oriented

Shanghai Shidongkou power plant:

This is an ultra critical, coal fired power plant with a capacity of 660 MW located in northern shanghai.

Shanghai Shidongkou Second power plant

The plant is located on the outskirts of Shanghai and has an installed capacity of 1200MW and consists of 2, 660MW coal fired units

The plant is additionally equipped with carbon dioxide capture technology that separates and purifies CO2 from a flue gas stream to produce 120,000 tonnes of CO2 per year.

This is the largest such facility in china and one of the world’s largest carbon capture facility in the world. The captured CO2 is used food packing, dry ice and beverage carbonation. This project has very low capture costs.

APFBCWHAT IS APFBC? The APFBC system uses the pressurized circulating fluidized bed combustion technologies developed by DOE and industry partners.

APFBC uses a circulating pressurized fluidized bed combustor (PFBC) with a fluid bed heat exchanger to develop hot vitiated air for the gas turbine’s topping combustor and steam for the steam bottoming cycle, and a carbonizer to produce hot fuel gas for the gas turbine’s topping combustor. This provides high combined cycle energy efficiency levels on coal.

Advanced circulating pressurized fluidized bed combustion combined cycle (APFBC) technology uses gas turbine combined cycle technology in combination with coal-fired equipment. APFBC allows the gas turbine to operate free of corrosion and erosion damage.

While a conventional combined cycle uses natural gas, APFBC operates at almost the same high levels of energy efficiency, but on less costly coal. APFBC has a wide tolerance for differing coal types and can use opportunity fuels, so the owner can take advantage of lowest energy price.

APFBC Repowering Considerations

There are a number of significant differences in considering APFBC for repowering applications than exist in new site applications.

· Combustion turbine type and size affect thermal and economic performance.

· A close match to existing steam conditions is desirable, unless the choice is to abandon steam turbine.

· High-temperature piping runs should be short to minimize material costs.

· Wide fuel tolerance means opportunity fuels can be used; coal or other opportunity fuels can be bought for best economy from a range of suppliers.

· Environmental emissions are superior to requirements, and significantly lower than those of the existing unit

APFBC is capable of producing electricity at 42 to greater than 50 percent net plant efficiency (HHV). APFBC is projected to have attractive low production costs. This provides high combined cycle energy efficiency levels on coal.

Advanced circulating pressurized fluidized bed combustion combined cycle (APFBC) technology uses gas turbine combined cycle technology in combination with coal-fired equipment.

APFBC allows the gas turbine to operate free of corrosion and erosion damage.

APFBC operates at almost the same high levels of energy efficiency, but on less costly coal.

APFBC has a wide tolerance for differing coal types and can use opportunity fuels, so the owner can take advantage of lowest energy price.

According to the second law of thermodynamics, when the maximum temperature of a thermal cycle is raised, the efficiency of energy conversion is increased.

It is an ideal combination in which the gas turbine uses high temperature heat energy at 1100ºC, while the steam turbine recovers power from low temperature heat energy at 600ºC or less.

By using heat cascades in the combination of two temperature ranges, thermal efficiency can be increased more in combined cycles than in simple cycles.

Increasing cycle temperature

Mitsubishi Heavy Industries (MHI) has developed a variety of advanced technologies aimed at increasing peak temperatures.

MHI is leading a development programme sponsored by the Japanese government.

In one, the high temperature parts of a gas turbine are cooled by using the steam cycle. The gas temperature at the outlet of a combustor (first vane inlet) and the temperature on the downstream side of the outlet can be increased by adopting this system for cooling the combustor. In addition, by cooling steam at the first vane, the inlet gas temperature of the first blade can be further increased.

By using the cooling effect of steam’s large specific heat, the mixing of cooling air into the main gas flow can be reduced and the maximum cycle temperature can be increased using conventional materialsMHI is working to develop systems achieving combustion temperatures of 1700ºC and a combined cycle thermal efficiency of 62 to 65 per cent (LHV) as the next standard values. To achieve this, technological breakthroughs based on new concepts that differ from simply extending conventional technologies are required in the form of new materials, cooling technologies, aerodynamic technologies, and low NOx combustion technologies.

Peak power generation

The unit capacity of large gas turbines has grown, due to increases in combustion temperature. At present, MHI’s maximum unit capacity is 330 MW for the M701G2 turbine, while for single-shaft combined power generation it is 500 MW.Though a variety of large new power sources was planned during the era of sustained economic growth, in the present rapidly varying situation, in which economic growth has slowed and various social circumstances affect the peak demand for power, a middle range capacity thermal power station capable of being constructed in a shorter period with smaller investment than a large capacity machine is needed.

New cycles

Although an increase in combustion temperature leads to a rise in overall thermal efficiency, the completely effective use of heat energy with a maximum possible combustion temperature of 2000 to 2500ºC which can be achieved by fossil fuels involves many technological issues that must be solved.

MHI has been examining the prospect of combining existing gas turbines with other cycles, to realize further increases in thermal efficiency.

The combination of gas turbines with fuel cells uses the fuel remaining after most is chemically converted into electricity in a gas turbine combined cycle to increase overall thermal efficiency.

inCO2 closed cycle ,in which air is not used as a dilution medium for combustion, flue gas is recirculated, and NOx is not emitted as exhaust.

Conclusion

In any event, gas turbines are very effective machines for efficiently converting temperatures of 1100 to 1500ºC or higher on a large scale, and it can safely be said that, in the examination of various cycles, gas turbines will play an important role as an effective means of converting combustion energy in the future.

The cost of power generation plants is expected to increase as cycles multiply in number and increase in complexity. On the other hand, issues concerning the global environment are becoming ever more serious, and an increase in thermal efficiency will become an important challenge as fossil fuel resources are used up. If a scheme for compensating additional costs can be established through new business opportunities such as CO2 ECO Right, problems associated with increased costs due to the increased complexity of cycles can be solved and the advancement of power generation plants can be accelerated.

REFERENCEShttp://en.wikipedia.org/wiki/Power_stationhttp://www.highbeam.com/doc/1G1-53490232.htmlhttp:// www.amazon.com/Gas-Turbinehttp://www.powergenworldwide.com/index/display/

articledisplay/229711/articles/power-engineering-international/volume-13/issue-5/features/gas-turbine-technology-the-future-for-gas-turbines.html

http://www.guardian.co.uk/world/2010/feb/07/gas-power-plant-explosion-connecticut

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