Steam Power Generation Pascal Tobaly IUT de St Denis Département Génie Industriel et Maintenance (G.I.M.) Welcome students of the international course on Power Generation Groeningen The netherlands November 19th 2003

Outline A bit of history Basics  First law: Internal Energy  Second Law: Entropy  Heat Engine: Thermodynamic cycle  Fluid flow: Enthalpy  Liquid vapor Equilibrium: Water and Steam Power plants  A schematic Steam Power Plant  Simple Rankine cycle  Power calculations  Superheating  ReSuperheating  Back pressure turbine  Regenerative cycle 

A BIT OF HISTORY Hero of Alexandria: First century b.c.

A BIT OF HISTORY (Continued) Hero of Alexandria: First century b.c.

A BIT OF HISTORY (Continued) Denis PAPIN (1647- 1712)

A BIT OF HISTORY (Continued) Newcommen (1712)

A BIT OF HISTORY (Continued) Watt (1769)

First Law of Thermodynamics Energy is a constant If the internal energy (U) of a system increases, then it may have been increased by addition of heat ➔ Work ➔

from the outer world

U 2−U 1=W Q

Second law of Thermodynamics Entropy (S) of an isolated system increases It will eventually increase until equilibrium is reached If entropy decreases in a given system then entropy of the outer world must have been increased by a greater amount. This may be possible only because there are energy exchanges between the system and the outer world

Q ∫ T ≤S 2−S 1 e The equality stands for a reversible transformation

Fluid Flow and Enthalpy Fluid flowing through a machine 2 2

2 1

V V h 2−h1 − =wuq 2 2 = specific enthalpy = Velocity = Usable work per unit mass of fluid q = Heat per unit mass of fluid

1

h V wu

machine

In terms of Power: 2 2

2 1

V V ˙  Q˙ mh ˙ 2−h1 − =W 2 2

W˙

Q˙

= mechanical power = heating power

2

HEAT ENGINE THERMODYNAMIC CYCLE High temperature Heat reservoir

Th

Efficiency

W =∣ ∣ Qh

Carnot:

Tc ≤1− Th

Qh (Heat input) engine Work W Qc (heat loss) Tc

Low temperature Heat reservoir

Liquid - vapour equilibrium Manometer Thermostat Gas

Vapour pressure curve

Pressure Critical point

solid liquid

Supercritical fluid vapor Tc

Temperature

Dryness fraction mg x= mg ml

Definition: P

(m = mass) Properties

L

M

v−v l x= v g −vl

G

h−h l x= h g −h l v

vl

v

vg

v = specific volume h = specific enthalpy

Entropic Diagram Water

-

Enthalpy

-

Steam

P=

cte

Mollier Diagram

Saturated vapor T=Cte

P

=

cte

et

T

=

cte

Entropy

Data on the internet

NIST Webbook http://webbook.nist.gov/chemistry/ Many physical properties including saturation properties as a function of Temperature and superheated vapor properties. Page of this department http://www-gim.iut-stdenis.univparis13.fr/thermo/thermo.html

Steam Turbine

Steam Turbine Rotor

Rankine cycle (Wet) B

Turbine

T

A A

B

Shaft

Boiler E

D

E Pump

C

D

C

S Condenser

Energy and power calculations Turbine H

B

A

Energy

V 2C V 2B h C −h B  − =wu q 2 2

Power

W˙ =m˙ wu =mh ˙ C −h B 

C

Boiler

E

S

D

Mollier Diagram

2 B

2 E

V V − =wuq Energy h B −h E  2 2 Power

˙ m˙ q= mh Q= ˙ B−h D 

Isentropic efficiency

Is not an efficiency ratio of real work to ideal (isentropic) one (with same final pressure) H 0 - 1 isentropic 0 - 2 real

0

1

2 S

Mollier diagram

wr  s= ws

Rankine Cycle with superheat Sometimes called Hirn Cycle

Superheater B

B'

T Turbine

B' A

B

Shaft

A

Boiler

E D C'

D

E

Pump

C'

Condenser

S

Energy Rankine cycle + superheat B' H B

A C' C E S D

Hot reservoir

q c =q boilerq superheater=h B−h Dh B ' −h B=h B '−h D

The reheat cycle Double stage expansion in double stage turbines Superheat again before the second expansion Superheater

re-superheater

T

B

B'

B'

B'' A

A

B

Boiler

E

C'

C'

C'' D

C''

D

E

Pump

Condenser

S

Energy

B''

B'

Hot Reservoir

H B

E – B' + C' – B'' C' C''

A

Turbine B' - C' + B'' – C''

E S D

The regenerative cycle Extract a fraction of the vapor before complete expansion Partially heat the feeding water with that vapor B

Superheater

T

B'

C'

B'

A

A

B C'

E'

boiler E'

C'

E

Mixer (feed heater)

C'' D

Pump E

D

pump

C''

Condenser

S

Regenerative cycle (continued)

B' H B

C'

C'' A

E'

E D S

Back-pressure turbine Exhaust at high pressure Hence at high temperature

Combined Heat and Power (CHP) Or cogeneration

B' H

Heat B

C'

While

C'' A

q=h D ' −h C' q=h C '' −h D

would not be usable

E'

E D S

usable

Primary energy sources At the boiler: ●

● ● ● ●

Traditional Nuclear Oil Coal Natural gas

●

Renewable

Solar (concentration) ● Geothermal ● Biomass ● Waste enhancement ●

Radiation Concentration ●

Paraboloiidic mirors

●

Cylindro-parabolic mirors

●

Miror fields

●

Advantages –

High temperatures

–

Thermodynamic cycles

–

Rankine cycle

–

Stirling cycle

Concentration ●

Four Solaire

●

Odeillo (Pyrénées)

Centrale Thémis (Pyrénées)

Solar two (U.S.A.)

Solar Two

Centrale à tour

Concentration Cylindro-parabolic mirors

Alméria (espagne)

Installing pipe at the focus

Geothermal energy ●

●

●

High temperature ( >150°C) –

Vapour → thermodynamic cycles

–

Combined heat and power

Medium Températures ( 240°C

Rhine

49

That's all Folks