Steam Power Plants
Technical Report
Course Project
Thermodynamics
Steam Power Plants
By: ______________________
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Steam Power Plants
Technical Report
Contents
1.
Abstract .................................................................................................................................... 3
2.
Introduction ............................................................................................................................. 3
a.
3.
Types of Power Plants ............................................................................................................. 5
a.
Thermal ................................................................................................................................ 5
b.
Renewable ............................................................................................................................ 6
4.
5.
Steam Power cycle ............................................................................................................... 4
Types of Steam Power Plant components ............................................................................... 6
a.
Steam Turbines .................................................................................................................... 6
b.
Boiler.................................................................................................................................... 7
c.
Condenser ............................................................................................................................ 7
Conclusion ............................................................................................................................... 7
References ....................................................................................................................................... 8
List of Figures
Figure 2-1: A coal-fired thermal power plant [1] ........................................................................... 3
Figure 2-2: A Rankine Cycle of steam power plants and T-S diagram .......................................... 4
List of Tables
No table of figures entries found.
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Steam Power Plants
1.
Technical Report
Abstract
Power plants are industrial systems where energy is produced all over the world. Steam power
stations are some of the most commonly used power plants in the world where flowing steam
runs. The Rankine cycle runs a steam power plant. It transforms the heat produced by an external
source into electricity. Heat can be provided by burning fuel (coal, oil, natural gas), nuclear fuels,
biogas or green energy sources such as solar energy. The objective of this paper is to conduct a
thermal analysis of the steam power plant in order to decide the parameters needed to select each
of the components of the power plant.
2.
Introduction
Steam power plants are commonly used in the world for the production of electricity, and coal is
also used to heat these plants. While the world's current coal supplies have been adequate for
around two decades, today's technology primarily used to generate coal-fired power has had
substantial negative environmental impacts. In order to allow more effective, efficient and safe use
of coal in power generation operations, attempts are also made to increase the productivity and
performance of existing plants by adjusting and retrofitting, and to create new technology for the
use of coal.
Figure 2-1: A coal-fired thermal power plant [1]
Today, several electrical generators are working to increase the performance (or heat rate) of their
current thermal generating stations, many of which are over 25 years old. Sometimes an increase
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Technical Report
in the heat intensity of just a few percent seems attractive, since it is considered that the costs and
complexities of such steps might be more manageable than more costly alternatives.
In order to further increase the efficiency of coal-to-electricity technology, their thermodynamic
performance is typically investigated. Energy technologies are typically analysed using energy
analysis in general. A greater interpretation is obtained as a more full thermodynamics view is
taken, and uses the second thermodynamics rule in combination with energy analysis, by means
of EXERGY techniques.
Exergy analysis is perhaps the most relevant of the available analytical methods, since it is a
valuable, simple and straightforward tool for determining and developing thermal generating
stations.The perspectives obtained from the exergy review on plant efficiency are insightful (e.g.,
efficiencies are determined which measure the approach to ideality, and the causes and locations
of losses in efficiency and electricity generation potential are accurately pinpointed). The results
of the exercise study will help to increase the productivity and, potentially, the economic and
environmental performance of thermal generating stations. Improvement, architecture and
optimization measures are likely to be more reasonable and systematic if the causes of exercise are
taken into consideration.
a. Steam Power cycle
Rankine cycles characterise the operation of steam heat engines typically used in
power generation plants as seen schematically here in Fig. 2-2 Power is produced in
such steam power plants by alternating vaporising and condensing the working fluid
(in many cases water, although refrigerants such as ammonia may also be used).
A simple Rankine cycle consists of four main components (steam generator, turbine,
condenser and pump).
Figure 2-2: A Rankine Cycle of steam power plants and T-S diagram
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There are four phases in the Rankine loop, each modifying the working fluid state.
The number shown in Fig describes these states. 2-2.• Phase 1-2s First the operating
fluid is drained (ideally isentropic) from low to high pressure. Pumping requires an
input of power (for example mechanical or electrical).
• Phase 2s-3: High-pressure liquid reaches the boiler where it is heated at steady
pressure by an external heat source to become a saturated vapour. Coal, natural gas,
or nuclear power are the common heat sources for power plant systems.
• Phase 3-4s: the saturated steam spreads into the turbine to produce power output.
Ideally, this is an entropic extension. This lowers the vapour temperature and
pressure.
• Phase 4s-1: Vapor reaches a condenser where it is cooled to form a saturated liquid.
This liquid will then re-enter the pump and the cycle will repeat.
3.
Types of Power Plants
The type of primary fuel or primary energy flow that provides a power plant its primary energy
varies. The most common fuels are coal, natural gas, and uranium (nuclear power). A substantially
used primary energy flow for electricity generation is hydroelectricity (water). Other flows that
are used to generate electricity include wind, solar, geothermal and tidal.
a. Thermal
Many thermal power stations use fuel to heat up water from a tank that produces steam
(usually at a high pressure). Extremely pressurised steam then passes through the pipe
to spin the fan-like blades of the turbine (see Rankine cycle for more info). If the rotor
continues to spin, it allows giant wire coils to rotate within the engine. This induces
relative (continuos) motion between the wire coil and the magnet, which moves the
electrons and begins the movement of electricity.
Fossil fuel plants can burn their fuel to produce thermal energy to power their
external heat engines. A simple cycle gas plant does not use steam like the others: it
acts like a jet engine, where natural gas is heated and burnt, and the heat produces a
friction that rotates the turbine. Combined cycle gas plants use both heat and steam.
Forms of fossil fuel plants include coal-fired power plants and natural gas power
plants, which are the major sources of electricity in the world.
Nuclear power stations employ fission processes to produce electricity. In these
plants, the uranium nucleus is separated and produces the thermal energy required to
produce steam. It then operates much like a fossil fuel power plant where steam
rotates a turbine and produces electricity. Power plants require the use of nuclear
reactors to conduct these fission processes.
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Solar thermal power plants utilize energy from the sun's light to generate the steam
needed to rotate the turbine.
b. Renewable
Renewable energy power plants get their energy directly from their respective flows in
order to produce electricity. Such main sources of energy eventually replenish
themselves, but are confined in the amount of energy available at any specific time or
place. They are thus also intermittent and quasi.
Hydroelectric systems use energy from falling water in rivers and lakes to rotate the
generator to produce electricity. This energy source appears to be more stable
(renewable) than other renewable resources, especially when the facility is off the dam.
Wind turbines get their energy from the wind, which, when it is in contact, speeds
down and transfers kinetic energy to the turbine. Air drag allows the turbine to rotate,
and the overall performance of the turbines is calculated by the Betz limit.
Solar panels use photovoltaic cells to generate electricity. The incoming photons
from the Sun reach the atoms inside the semiconductor panel, causing the electrons to
flow. Solar energy is unreliable, although it can be much more efficient when
combined with energy storage systems.
4.
Types of Steam Power Plant components
a. Steam Turbines
According to the steam operation, the turbines are divided as follows:
i. In the impulse turbine, the steam flowing out of the fixed nozzle at a very high
velocity hits the blades on the periphery of the rotor. The blades change the direction
of the steam flow without changing the pressure. The force caused by a shift in
momentum allows the turbine shaft to spin.
ii. Reaction turbine: In the reaction turbine, the steam flows constantly in both fixed
and rotating blades as the steam moves over them. The pressure drop happens
continuously on both travelling and stationary blades.
Depending on the number of pressure stages:
iii. Single-stage turbines: these turbines are mainly used for centrifugal
compressors, blowers and other related equipment.
iv. Multistage Impulse and Reaction Turbines: they are designed in a wide range
of power capacities ranging from small to large.According to the type of steam flow
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i. Axial turbines: In such turbines, steam streams parallel to the direction of the
turbine rotor.
ii. Radial turbines: In such turbines, steam streams in a direction perpendicular to
the axis of the turbine, one or two low-pressure stages are axial.
b. Boiler
The boiler may be classified as a fire tube or a water tube boiler, depending on the
content of the tube.
Fire tube boiler: in this type of boiler, the flames and the hot gases generated by the
combustion of fuel flow through the tubes while the water flows far beyond tubes.
Water tube boiler: water streaming inside the tube (water tube) while flames and
heat gases are engulfed outside the tubes.
c. Condenser
The main purpose of the condenser is to transform the gaseous form of the exhaust
steam into a liquid form at a pressure below the atmosphere. Water is used as a
cooling method to turn steam into water.
Steam condensers shall be graded as follows:
1. Plane Condenser (mixing type condensers)
a. Condenser for parallel flow jet
b. Condenser for counter flow jet (low level)
c. Barometric or high-level jet condenser
d. Condenser for the ejector
2. Surface condenser (non mixing type condensers)
a. Downstream soil condenser
b. Condenser for central flow surface
c. Condenser with regenerative surface
d. Condenser evaporative
5.
Conclusion
Exergy and energy analyses are used to investigate and further understand the operation of steam
power plants and to locate and test potential process changes to increase plant production. Any
alternate implementations of the mechanism are then proposed. Exergy is useful for providing a
comprehensive breakdown of damages, in terms of pollution and irreversibility of waste, for the
complete plants and their materials.
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References
[1]
Sherry, A., Beck, J. S., & Cruddace, A. E. (Eds.). (2014). Modern Power Station Practice:
Mechanical Boilers, Fuel-, and Ash-Handling Plant. Elsevier.
[2]
Lawrence, F., Patricia, G. B., Kayla, L. W., & Veatch, B. (1996). Power Plant
Engineering. Publisher Springer ISBN, 412064014.
[3]
Rogers, N. R. (2014). A review of technologies employed on some recent UK power plant
projects to mitigate the impact of the cooling water intake on aquatic life. WIT Transactions on
State-of-the-art in Science and Engineering, 71.
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