module 1 lectures 1-4 fundamentals of steam power 2012 class handouts

7/28/2019 Module 1 Lectures 1-4 Fundamentals of Steam Power 2012 Class Handouts

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Nicola Kotz THERMAL MACHINES

Alumni of Tuks

Honours Professional Engineer

Fossil Fuel Refining and Power GenerationExperience

Ryno Nell FLUID MACHINES

MTV 420

THERMAL AND FLUID MACHINES


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What to expect from me

Industry based experience

Patience and understanding

Respect

What I expect from you

To work hard in my class and be prepared

To be on time

To participate in class discussions

MTV 420THERMAL AND FLUID MACHINES


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LETS GET STARTED

The STUDY GUIDE Course layout

Thermal up to Spring Day

Textbooks

Practicals

Groups

30 July 2012 and ECSA

Teaching Assistants

MTV 420THERMAL AND FLUID MACHINES


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KOMATI POWER STATION


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HOW DOES IT WORK?


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Turbine Plant

Turbine centre line

LP, IP and HP Turbine

SIZE?

Generator

Condenser

Extraction Pumps Cooling towers/Fans

Auxiliary Plant

Regenerative feedwater heat exchangers

COMPONENTS OF A POWER STATION

ARNOT POWER STATION TURBINE HALL(www.eskom.co.za)


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Boiler Plant

Boiler

Boiler drum

Pumps and Pipes

Mills and mill feeders

Grinding media

Coal Bunkers

Draft Group

Fans



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Common Plant

Water Treatment Plant and distribution

Chemistry

Coal and Ash Handling

Coal and Ash Storage

Compressed Air

Smoke Stack

Effluent Handling Fire Systems

Civil Structures

Air conditioning

Fuel Oil Plant



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Electrical

Switchgear

Transformers

Motors

Control and Instrumentation

Instrumentation

Brain of the Power Station



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SIMPLIFIED VIEW

REF: Wikipedia


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So now you know what a Steam Power Plant is

Source fuel?

Why does South Africa primarily use Steam Power forElectricity Generation?

WHY STEAM POWER?

Komati Power Station

Any significance?


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Coal

Quality Calorific value

Ash content

Abrasiveness

Hardgrove index

CRITICAL TAKE HOME POINTS

Low calorific value:= low carbon= less energy= need to burn more coal= more ash=more $$

High ash content:= more ash= bigger ash plant= bigger ash dump= more $$

Abrasiveness:= wear on your grinding media= more $$

Hardgrove index:= milling requirements

= more $$

So why dont we burn thebest coal RSA can offer?


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Coal Handling

Coal Stockyard, Stacker/Reclaimer, Feeders, ConveyorBelts, Storage Silos, Bunkers

Maximum stockpile, flexibility, belt tensioning, siloand bunker design

What are key factors that affect your design?

Quality of coal

Mill capacity

Bunker Capacity

Required MW!



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Ash Handling

Dry Ash System

Ash Dump

Dust Suppression Pneumatic Handling:

Pressure Vessels,Compressors, Airslides

Conveyor Belts, scrapers Ash conditioning

Wet Ash System

Ash Dam

Sluice water Pumps

Pipes

Valves

Blockages, wear, scale


What types of Ash do you get?

Anything special that we can do with it??


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EXAMPLE OF AN ASH DAM COMPLEX


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Environmental Considerations ZLED

ZERO LIQUID EFFLUENT DISCHARGE

Ash Dam Complex

Ground water contamination Cooling towers

Is it pollution?

Storm Water

Friend or foe?

Smoke Stack Height

Distribution of particulates (90m vs 220m)

Smoke Stack Emissions

SO3 Conditioning



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Boiler

Construction of a Boiler

Height: 120 m

Tube material Types of Mills

Mill Feeders

Grinding Media

Boiler tube leaks

Boiler Dosing and Sampling

Boiler blow through



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BOILER BLOW THROUGH


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Turbine

Demin (??!!) Water

Jacking oil

Bearing oil

Vibrations

Oil analysis

Temperature probes

Blades and vanes

Is it catastrophic if a blade

breaks?



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Electrical

What is switchgear?

DOL

Bulk supply

Starting current? Motor protections

Control And Instrumentation

Heart of a power station

Controls and Monitoring

Reduces man power requirements

Pneumatic control instruments DRY AIR



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Major Components of the Steam Power Cycle

Turbine (Centreline)

Condenser

Pump

Boiler

STEAM POWER THERMODYNAMICS!


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THE IDEAL RANKINE CYCLE


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1 (1) 2 (2): Isentropic expansion of the Turbine, throttledconditions

2 3: Outflow of heat in the Condenser, constantpressure

3 4: Isentropic pumping of condensate to Boiler,

feedwater

4 1 (1): Inflow of heat in the Boiler, constant pressure


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Determine the thermal efficiency of an ideal Rankinecycle using steam as a working fluid. The condenser

pressure is 5kPa, the boiler pressure is at 3.5MPa.Saturated vapour enters the turbine inlet.

LETS DO AN EXAMPLE


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Piping Losses Friction causes a pressure drop

Is the pressure of the water entering a boiler the same as thesteam pressure exiting the boiler?

Turbine Losses

Heat transfer to surroundings neglected

Turbine =

=

The efficiency is a known parameter of a turbine (OEM)

BUT IS THE REAL WORLD IDEAL?


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Pump Losses

Work lost due to irreversibility (energy in energy out)

Heat transfer to surroundings neglected

Pump =

=

Pump efficiency Function of the pump characteristic curve

Condenser Losses

Negligible

BUT IS THE REAL WORLD IDEAL?


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DEVIATIONS FROM THE IDEAL


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Determine the thermal efficiency of a real world steampower plant. The steam enters the turbine at 3.5MPa,

350C where it expands to 7.5kPa, 40C. It is thenpumped up to 5.2MPa before entering the boiler at

5MPa, 39

C. Steam leaves the boiler at 4MPa, 400

C.The pump efficiency is 82% and the turbine efficiency is87%. Discuss where other losses occur and why.

LETS DO ANOTHER EXAMPLE


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Bleed off steam from the HP turbine and reheat inthe Boiler before expanding in LP turbine

Advantages

Improve LP exhaust quality (moisture and turbine

blades) Increased net work = lower steam flow rate

Smaller plant components = Capital cost lower

Thermal efficiency increases/decreases dependant on

when where you bleed off the steam

=

REHEAT

NB!!


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REHEAT


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REHEAT


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A REHEAT EXAMPLE

Consider a reheat cycle. Steam exits the boiler in athrottled state of 4.5MPa, 400C. After expansion inthe turbine to 450kPa, the steam is reheated to 400Cand then expanded to 7.5kPa before entering the

condenser. Determine the efficiency of the cycle.


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Heat the feedwater return with bleed steam from theturbine via a heat exchanger

Feedwater heaters

Open: changes due to mixing

Closed: stays constant

Constant pressure mixing

Energy = money

Hypothesis: Energy required heat demin from ambient vsFWH Temperature?

Thermal Efficiency improved

Avoid thermal shock in your boiler tubes

Reduce irreversibilities

Airheaters another example of regeneration

REGENERATION

Steam ExtractionFraction??


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REGENERATION 1 CLOSED FWH

Mass flows???


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REGENERATION


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REGENERATION A REALISTIC VIEW

Ref: Pg 365; Fig 11.12; Sonntag, Borgnakke and Van Wylen , Fundamentals of Thermodynamics , 5th Edition


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A REGENERATION EXAMPLE

A power plant with 1 closed FWH has a condensertemperature of 45C, a maximum boiler pressure of5MPa and a boiler exit temperature of 900C.Extraction steam at 1MPa to the FWH condenses and is

pumped to the 5MPa feedwater line where all thewater goes to the boiler at 200C. Find the fraction ofthe extraction steam flow and the two specific pumpwork inputs.


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QUESTIONS?

module 1 lectures 1-4 fundamentals of steam power 2012 class handouts

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