CLICK HERE TO DOWNLOAD PPT ON STEAM TURBINES FOR SUPERCRITICAL POWER PLANTS
STEAM TURBINES FOR SUPERCRITICAL POWER PLANTS Presentation Transcript
1.STEAM TURBINES FOR SUPERCRITICAL POWER PLANTS
2.WHAT IS SUPER CRITICAL TECHNOLOGY
3.Super critical CYCLE
4.Unit efficiency
5.
The history of steam turbine development can be described as an evolutionary advancement toward greater power density and efficiency.
The first type of advancement is improvement in mechanical efficiency by reduction of aerodynamic and leakage losses as the steam expands through the turbine.
The second type of advancement is improvement in the thermodynamic efficiency by increasing the temperature and pressure at which heat is added to the power cycle.
The focus of this presentation is predominantly on the latter type of efforts to advance the state-of-the-art in steam turbine technology.
6. THERMODYNAMIC CYCLE OPTIMIZATION
Effect of Higher Steam Conditions on Unit Performance
As the first step in the optimization of cycle steam conditions, the potential cycle efficiency gain from elevating steam pressures and temperatures needs to be considered.
Starting with the traditional 2400 psi / 1000 F (165 bar / 538 C) single-reheat cycle, dramatic improvements in power plant performance can be achieved by raising inlet steam conditions to levels up to 4500 psi/310 bar and temperatures to levels in excess of 1112 F/600 C.
It has become industry practice to refer to such steam conditions, and
in fact any supercritical conditions where the throttle and/or reheat steam temperatures exceed 1050 F/566 C, as “ultrasupercritical”.
7.Heater Selection and Final Feedwater Temperature
In order to maximize the heat rate gain possible with ultrasupercritical steam conditions, the feedwater heater arrangement also needs to be optimized.
In general, the selection of higher steam conditions will result in additional feedwater heaters and a economically optimal higher final feedwater temperature.
In many cases the selection of a heater above the reheat point (HARP) will also be warranted. The use of a separate desuperheater ahead of the top heater for units with a HARP can result in additional gains in unit performance.
Other cycle parameters such as reheater pressure drop, heater terminal temperature differences, line pressure drops and drain cooler temperature differences have a lesser impact on turbine design, but should also be optimized as part of the overall power plant cost/performance trade-off activity.
The history of steam turbine development can be described as an evolutionary advancement toward greater power density and efficiency.
The first type of advancement is improvement in mechanical efficiency by reduction of aerodynamic and leakage losses as the steam expands through the turbine.
The second type of advancement is improvement in the thermodynamic efficiency by increasing the temperature and pressure at which heat is added to the power cycle.
The focus of this presentation is predominantly on the latter type of efforts to advance the state-of-the-art in steam turbine technology.
6. THERMODYNAMIC CYCLE OPTIMIZATION
Effect of Higher Steam Conditions on Unit Performance
As the first step in the optimization of cycle steam conditions, the potential cycle efficiency gain from elevating steam pressures and temperatures needs to be considered.
Starting with the traditional 2400 psi / 1000 F (165 bar / 538 C) single-reheat cycle, dramatic improvements in power plant performance can be achieved by raising inlet steam conditions to levels up to 4500 psi/310 bar and temperatures to levels in excess of 1112 F/600 C.
It has become industry practice to refer to such steam conditions, and
in fact any supercritical conditions where the throttle and/or reheat steam temperatures exceed 1050 F/566 C, as “ultrasupercritical”.
7.Heater Selection and Final Feedwater Temperature
In order to maximize the heat rate gain possible with ultrasupercritical steam conditions, the feedwater heater arrangement also needs to be optimized.
In general, the selection of higher steam conditions will result in additional feedwater heaters and a economically optimal higher final feedwater temperature.
In many cases the selection of a heater above the reheat point (HARP) will also be warranted. The use of a separate desuperheater ahead of the top heater for units with a HARP can result in additional gains in unit performance.
Other cycle parameters such as reheater pressure drop, heater terminal temperature differences, line pressure drops and drain cooler temperature differences have a lesser impact on turbine design, but should also be optimized as part of the overall power plant cost/performance trade-off activity.
8.
Reheater pressure optimization
The selection of the cold reheat pressure is an integral part of any power plant optimization process, but becomes more important for plants with advanced steam conditions.
Reheater Pressure Optimization for Double Reheat Units
For double reheat units, the above described optimization of various design parameters is more involved and has to include a cross-optimization process in order to properly select the first and second reheat pressures.
For double reheat units without HARP, the best performance would be achieved with the first reheat pressure of approximately 1450 psi/100 bar.
However, economic considerations associated with the boiler and piping systems would typically favor reducing this to a lower level.
9.Pulverized coal-Fired Supercritical plant - 400 MWe single unit .
Single reheating configuration
Reheater pressure optimization
The selection of the cold reheat pressure is an integral part of any power plant optimization process, but becomes more important for plants with advanced steam conditions.
Reheater Pressure Optimization for Double Reheat Units
For double reheat units, the above described optimization of various design parameters is more involved and has to include a cross-optimization process in order to properly select the first and second reheat pressures.
For double reheat units without HARP, the best performance would be achieved with the first reheat pressure of approximately 1450 psi/100 bar.
However, economic considerations associated with the boiler and piping systems would typically favor reducing this to a lower level.
9.Pulverized coal-Fired Supercritical plant - 400 MWe single unit .
Single reheating configuration
10. The turbine generator is a single machine comprised of tandem HP, IP, and LP turbines driving one 3,600 rpm hydrogen-cooled generator.
The turbine exhausts to a dual-pressure condenser operating at 1.5 and 2.0 inches Hga, low- and high-pressure shells, respectively, at the nominal 100 percent load design point.
For the four-flow LP turbines, the last-stage bucket length is 30 inches, the pitch diameter is 85.0 inches, and the annulus area per end is 55.6 square feet.
The turbine exhausts to a dual-pressure condenser operating at 1.5 and 2.0 inches Hga, low- and high-pressure shells, respectively, at the nominal 100 percent load design point.
For the four-flow LP turbines, the last-stage bucket length is 30 inches, the pitch diameter is 85.0 inches, and the annulus area per end is 55.6 square feet.
11. The feedwater train consists of seven closed feedwater heaters (four low pressure and three high pressure), and one open feedwater heater (deaerator).
Condensate is defined as fluid pumped from the condenser hotwell to the deaerator inlet.
Feedwater is defined as fluid pumped from the deaerator storage tank to the boiler inlet. Extractions for feedwater heating, deaerating, and the boiler feed pump are taken from the HP, IP, and LP turbine cylinders, and from the cold reheat piping.
The net plant output power, after plant auxiliary power requirements are deducted, is nominally 402 MWe. The overall net plant efficiency is 39.9 percent.
Condensate is defined as fluid pumped from the condenser hotwell to the deaerator inlet.
Feedwater is defined as fluid pumped from the deaerator storage tank to the boiler inlet. Extractions for feedwater heating, deaerating, and the boiler feed pump are taken from the HP, IP, and LP turbine cylinders, and from the cold reheat piping.
The net plant output power, after plant auxiliary power requirements are deducted, is nominally 402 MWe. The overall net plant efficiency is 39.9 percent.
12. Pulverized coal-Fired Ultra Supercritical plant - 400 MWe - Double reheating configuration
13. Low Pressure (LP) Turbine Section
In the LP turbine section the steam is expanded down to the condenser pressure.
The LP turbine sections in supercritical plants are not different from those in
subcritical plants.
In the LP turbine section the steam is expanded down to the condenser pressure.
The LP turbine sections in supercritical plants are not different from those in
subcritical plants.
14.
Life Cycle Costs of Supercritical Coal Fired Power Plants
Current designs of supercritical plants have installation costs that are only 2% higher
than those of subcritical plants.
Fuel costs are considerably lower due to the increased efficiency and operating costs
are at the same level as subcritical plants.
15.Additional Features in Super Critical Steam cycle
Fuel flexibility is not compromised in once-through boilers.
All the various types of firing systems (front, opposed, tangential, corner, four wall, arch firing with slag tap or dry ash removal, fluidized bed) used to fire a wide variety of fuels have already been implemented for once-through boilers.
All types of coal as well as oil and gas have been used.
The pressure in the feedwater system does not have any influence on the slagging behaviour as long as steam temperatures are kept at a similar level to that of conventional drum type boilers.
16.Specific installation cost i.e. the cost per megawatt (MW) decreases with increased plant size. For countries like India and China, unit ratings from 500MW up to 900MW are possible due to their large electrical grids.
In countries with smaller grids, unit sizes of 300MW are more appropriate and the specific installation cost will be higher than that of larger plants.
17.
Why High Performance Coal Fired Power Plants Matter?
Many regions of the world are experiencing fast growing electricity demand. Permitted emissions
from power plants have been reduced so as to meet air quality standards.
Capital scarcity and competition which are maintaining downward pressure on prices of new plant.
Meanwhile electricity generated from coal currently accounts for about 40 per cent of worldwide.
Enhanced plant reduces emissions of CO2 and all other pollutants by using less fuel per unit of
electricity generated.
While the efficiencies of older power plants in developing countries like China and India are still
around 30% lower heating value (LHV), modern subcritical cycles have attained efficiencies close to
40% (LHV. Further improvement in efficiency can be achieved by using supercritical steam
conditions.
Current supercritical coal fired power plants have efficiencies above 45% (LHV). One percent
increase in efficiency reduces by two percent, specific emissions such as CO2, NOx, SOx and
particulates .
Worldwide, more than 400 supercritical plants are in operation.
Life Cycle Costs of Supercritical Coal Fired Power Plants
Current designs of supercritical plants have installation costs that are only 2% higher
than those of subcritical plants.
Fuel costs are considerably lower due to the increased efficiency and operating costs
are at the same level as subcritical plants.
15.Additional Features in Super Critical Steam cycle
Fuel flexibility is not compromised in once-through boilers.
All the various types of firing systems (front, opposed, tangential, corner, four wall, arch firing with slag tap or dry ash removal, fluidized bed) used to fire a wide variety of fuels have already been implemented for once-through boilers.
All types of coal as well as oil and gas have been used.
The pressure in the feedwater system does not have any influence on the slagging behaviour as long as steam temperatures are kept at a similar level to that of conventional drum type boilers.
16.Specific installation cost i.e. the cost per megawatt (MW) decreases with increased plant size. For countries like India and China, unit ratings from 500MW up to 900MW are possible due to their large electrical grids.
In countries with smaller grids, unit sizes of 300MW are more appropriate and the specific installation cost will be higher than that of larger plants.
17.
Why High Performance Coal Fired Power Plants Matter?
Many regions of the world are experiencing fast growing electricity demand. Permitted emissions
from power plants have been reduced so as to meet air quality standards.
Capital scarcity and competition which are maintaining downward pressure on prices of new plant.
Meanwhile electricity generated from coal currently accounts for about 40 per cent of worldwide.
Enhanced plant reduces emissions of CO2 and all other pollutants by using less fuel per unit of
electricity generated.
While the efficiencies of older power plants in developing countries like China and India are still
around 30% lower heating value (LHV), modern subcritical cycles have attained efficiencies close to
40% (LHV. Further improvement in efficiency can be achieved by using supercritical steam
conditions.
Current supercritical coal fired power plants have efficiencies above 45% (LHV). One percent
increase in efficiency reduces by two percent, specific emissions such as CO2, NOx, SOx and
particulates .
Worldwide, more than 400 supercritical plants are in operation.
18.FUTURE ULTRA SUPERCRITICAL PLANT – UNDER DEVELOPMENT
19. 800 MW Supercritical boiler
Posts
0 comments