P Pl tPower PlantsA1M15ENY

Lecture No 8Lecture No. 8Jan Špetlík

spetlij@fel cvut cz - subject in e-mail ENY”spetlij@fel.cvut.cz subject in e mail „ENY

Department of Power Engineering Faculty of Eelectrical Engineering CTU Technická 2Department of Power Engineering, Faculty of Eelectrical Engineering CTU, Technická 2, 166 27 Praha 6

2p

12 MPap2TWithout reheat:

2 12 MPap =

2 530 °CT =⇓

5p-1

2 3429 kJ.kgi =-1 -1

2 6,591 kJ.K .kgs =

⇓

5 3,5 kPap =

-1 -15 6,591 kJ.K .kgs =

Knowing s to the next process:

5 ,p

-11971 kJ kgi =

⇓5 27 °CT =

Total efficiency is thus:5 1971 kJ.kgi =

Knowing T to the next process:

1 27 °CT =

y( )( )

2 5 2 1

2 1 2 1

.

.i i p p vi i p p v

η− − −

= =− − −

1 27 CT0x = (condensation)

-1111 8 kJ kgi =⇓

4

4

3429 1971 1,2.10 .0,0013429 111,8 1,2.10 .0,001

− −= =

− −1 111,8 kJ.kgi =

-1 -11 0,3906 kJ.K .kgs = 1446 43,7%

3305= =

3 2,3 MPap =With reheat: 2p 2T

3 ,p

-12959 kJ ki

-1 -13 6,591 kJ.K .kgs =

⇓3p

3 277 °CT =

13 2959 kJ.kgi =

Knowing p,T to the next process:5' 5p p=

3p

4T

4 480 °CT =

g p, p

⇓

4 2,3 MPap =

-14 3420 kJ.kgi =

-1 -14 7,308 kJ.K .kgs =

⇓

Total efficiency is thus:4 gKnowing s to the next process:

y

( )( )

2 5' 4 3 2 1

2 1 4 3 2 1

..

i i i i p p vi i i i p p v

η− + − − −

= =− + − − −

-1 -15' 7,308 kJ.K .kgs =

3 5 kP

-15' 2186 kJ.kgi =

⇓

( )3429 2186 3420 2959 123429 111,8 3420 2959 12

− + − −= =

− + − −

5' 3,5 kPap =

5' 27 °CT =5' 2186 kJ.kgi

1701 45,2%3766

= =

Steam and Feedwater Circuitdr mdrum

BOILER emergency stop valve(ESV)

steamfeedwaterheating watercooling water

TURBINE

(ESV)

bypass

reheater

gair

HP

LP

IPTG

valvesteam control

bypass

superheaters

economisers(ECO)

vacuum pump

HP

riser

IPvalve

(VP)

down-comer

deaerator

heating circuitextraction

riser

burner

coolingLP heater

dcircuit

HP heaterFwP

feedwater pump (FwP)

condensate colector tank (CCT)feedwater tank

condensercondensate

pump(CoP)

FwPriser

(FwT)

TurbinesBy working medium:- Gaseous (gaseous or liquid fuels, in. temperature 600-1400°C, out.

temperature 450-600°C)temperature 450 600 C)- Steam (superheated steam, in. temperature 400-650°C, out. temperature

28-42°C)F t t (i NPP i t t 300°C t t t- For wet steam (in NPP, in. temperature 300°C, out. temperatureas previous)

By output steam pressure:y p p- Back pressure turbines (out. pressure 0,11-0,6 MPa)- Condensing turbines (out. pressure 20-40 kPa)B t t tiBy steam extraction:- Turbine with unregulated extraction (for feedwater conditioning, gland

steam etc.)- Turbine with regulated extraction (instead of above mentioned extractions

one or more additional for heating system purposes)According to number of parts:According to number of parts:- Single part (lower power ratings)- Multi part (high p. - HP, intermediate p. - IP, low p. - LP parts)

TurbinesBy principle of operation:- Impulse (whole enthalpy drop of the stage is totally changed into kinetic

energy in the stator nozzles steam pressure is the same at input and outputenergy in the stator nozzles, steam pressure is the same at input and output of stage rotor moving blades)

- Reaction (a part of enthalpy drop of the stage is additionally changed into ki ti i th t i bl d )kinetic energy in the rotor moving blades)

Impulse turbine example Reaction turbine example

TurbinesFunctioning:Each single turbine stage is consisting of:- Stationary blades i.e. solid grid of blades (a part of stator) = a set ofStationary blades i.e. solid grid of blades (a part of stator) a set of

parallel nozzles, which are converting steam pressure energy to kinetic energy at minimum losses

- Rotary blades i.e. set of blades (a part of rotor) where steam kinetic energyRotary blades i.e. set of blades (a part of rotor), where steam kinetic energy is converted into rotation energy of turbine body

Velocity of the steam leaving the nozzle:

( )212dq di da d c= + +

Generally:

F di b i i

( )2120 di d c= +

For adiabatic expansion:

( )21 0 0 12.c c i i= + −a

R l i t tl di b ti t

i0i

0p

Real process is not exactly adiabatic, entropyis rising (edge losses, friction losses on stationary and rotary blades, flow direction i

1p

1i

idiΔ 1iΔ

change etc.)s

idi 1

TurbinesO t t fl l it 0 t i t ti f t tOutput flow velocity c0=0, put into equation of state:

( ) ( ) 11 0 1 0 1 0

22. 2. . . . . 11P

Tc i i c T T r TT

κκ

⎛ ⎞⋅= − = − = − =⎜ ⎟− ⎝ ⎠0

1

1

1

2 1

T

pp v

κκ

κ

κ−

⎝ ⎠

⎡ ⎤⎛ ⎞⋅ ⎢ ⎥⎜ ⎟1

0 00

11

pp vpκ

⎢ ⎥= ⋅ ⋅ ⋅ − ⎜ ⎟⎢ ⎥− ⎝ ⎠⎢ ⎥⎣ ⎦Saint Vénant-Wantzel equation

M i fl l it f id l i th i t 0Maximum flow velocity of ideal gas is thus into vacuum p1=0:

1max 0 0 02 2 . .

1 1c p v r Tκ κ

κ κ⋅ ⋅

= ⋅ ⋅ =− −

1

0

pp

β =Pressure ratio:

1 1κ κ− −

If we define mass flow density as:

1 2[k ]1 11 2 1m κκβ β

−⎡ ⎤⋅⎢ ⎥

-1 -2[kg.s .m ]1 0 00

. 11

c p vA v

κ κρ β βκ

= = ⋅ ⋅ ⋅ ⋅ ⋅ −⎢ ⎥− ⎣ ⎦

TurbinesMaximum mass flow density occurs at

121

-k

kp

κκ⎛ ⎞β = =⎜ ⎟

⎝ ⎠

Mass flow density is not any more growing

along with further output pressure decrease

criticalpressure

01k p⎜ ⎟κ +⎝ ⎠ along with further output pressure decrease.

Other critical parameters:2T T 2 2 T⋅ κ ⋅ κ

0 1kT T .=κ+ 0 0 01 1kc p v r T= ⋅ ⋅ = ⋅ ⋅

κ + κ+Speed of sound for ideal gas:

⎛ ⎞ 1

s

pa r T⎛ ⎞∂= = κ⋅ ⋅⎜ ⎟∂ρ⎝ ⎠

1

0 0k

k k kT Ta r T p v c

κ−κ

== κ⋅ ⋅ = κ⋅ ⋅ ⋅β =and thus

In a convergent nozzle, there is no outlet velocity riseafter exceeding critical parameters – choked flow. A part of pressure energy is converted to whirlingof pressure energy is converted to whirling => to be able to rise the velocity we must use

convergent-divergent de Laval nozzle.Ma>1 supersonic flow

De Laval nozzleMach number: Ma c

a=

Ma>1 supersonic flow

Ma<1 subsonic flow

TurbinesMa>1 Ma<1

kβ

cρcβk Plyn

0 487 ideal single-atom gas

Values βk:

.cρ

c

maxc

k kc a=

0,487 ideal single atom gas

0,528 ideal two-atom gas

0,540 ideal three-atom gas

0,53 aira

,

0,55 superheated steam

0,58 saturated steam

βIn real nozzle we must take into account friction and whirling losses, sothe output velocity is lower than adiabatic which can be expressed bythe output velocity is lower than adiabatic, which can be expressed by

factor:1cϕ =idc

ϕ

and nozzle efficiency:2 0 1i i−

η ϕ 0 1

0 idi iη = ϕ =

−

TurbinesImpulse turbine:

Bl dp

emission steam

interspaceBlades:

emission steamadmission

steam stationary bladesrotary blades

Reaction turbine:shaft

impulse turbine reaction turbine

shaft

1rc1 1r op p= 1rp

1p

one stage

0c0pkondc

0c

0p1rc

kondc

1op

1ockondp 0c kond

kondp

1oc

TurbinesIn the case of reaction turbine:

i i isentropic heat drop in rotor

Degree of reaction:

0 1

0 1

ri i isentropic heat drop in rotorRi i isentropic heat drop in stage−

= =−

Shaft torque and stage power output:Working medium leaving the nozzles of stationary blades at velocityand entering the rotary blades, where the kinetic energy is converted to the

1rc

( )1 1o r oF m. c c= −

and entering the rotary blades, where the kinetic energy is converted to the

shaft torque. Thus force arising at the perimeter of wheel with rotary blades:

and the shaft torque:( )1 1o o r oM F ,r m. c c .r= = −

stage power output:

( )1 1 1 2o o r o o oP M . m. c .u c .u= ω= −

where are corresponding perimeter velocities1 2o ou ,u

Turbine Oil and Gland Steam SystemOil:Oil:Two basic functions:- Lube oil is used for machine bearing cooling and lubrication- Regulation oil is used in turbine electro-hydraulic (EH) regulation systems –

regulation quantity is oil pressure- Primary oil – turbine speedPrimary oil turbine speed- Secondary oil – valve opening position- Oil for emergency stop valve

R l ti il t bi l t t l- Regulating oil – turbine elements controlGland steam:- Turbine cannot be ideally sealed. The air is getting into the underpressure y g g p

parts of turbine, unlike the steam is leaking from the overpressure parts- To avoid this effect every part of machine set is equipped with labyrinth seals

supplied with IP gland steam (circa ~2 MPa)supplied with IP gland steam (circa 2 MPa)- Gland steam gets into (or out from) the labyrinth steam trap to slow down the

leakage in the space between rotor and stator

Turbine Oil and Gland Steam SystemESV

steamfeedwatercooling water

control valve

admission steam

gland steamoil

HP LPIP TG

lube oil

shaftglandbearing

emission steam(to condenser)

condensateemergency DC

expander

condensatefrom CoP

g ypump (EOP)

regulationoil

main oil reg. of temperature expandergland steamcondenser

(GSC)

tank (MOT)main oil reg. of temperature

oil pumps (OP) condensateto LPH(OC)

oil cooler

Condensation and Water Conditioningemission steamsteam emission steam

cooling pump(CP)

vacuum pump (VP)steamfeedwatercooling watergland steam

make-up water (DEMI)h d i d (d i )

cool/warm cooling water channels

(CP)

closed/open cooling system

oil

hydrazine dosage (de-oxygening)Condensatepump (CoP)

LP Feedwater ConditioningOC GSC

closed/open cooling system

HP Feedwater Conditioning

LPH 4LPH 3

HPH 1HPH 2

generator cooling

LPH 4

FwT

Dear.FwP

HPH 1HPH 2boiler

LPH 1LPH 2CCT

BoilersBy fuel type:- Solid (coal, coke, biomass, waste)- Gas (NG, CNG, LPG)Gas (NG, CNG, LPG)- Liquid (LFO, HFO)By output steam pressure:- Low pressure (pressure up to1,6 MPa)- Intermediate pressure (pressure 1,6-5 MPa)- High pressure (pressure 5-13 MPa)g p (p )- Extra high pressure (pressure 13-22,5 MPa)- Supercritical (pressure over 22,5 MPa)B t tBy evaporator type:- Boilers with natural circulation- Boilers with forced circulation (La Mont) boilers with low} water content- Drumless (supercritical - Sulzer, Benson)- Shell boilers (heat transfer through corrugated iron)

Fire tube boilers (flue gases are flowing inside tubes)}} water content

boilers with highwater content- Fire tube boilers (flue gases are flowing inside tubes)} water content

BoilersBy combustion device principle:- Grate (lower power outputs)- Pulverized (dry bottom – evaporators on walls, wet bottom – evaporators onPulverized (dry bottom evaporators on walls, wet bottom evaporators on

walls + bottom)- Fluidized bed (less sensitive to fuel change, desulphurization inside the boiler)Grate boilers: Main parts:Grate boilers: Main parts:

- The walls are surrounding the combustion chamberGrate with fuel feed hopper- Grate with fuel feed hopper, barrier, slag weir and ash hoppers

- Primary air inlet from belowPrimary air inlet from below

Main grate parts:- Supporting constructionSupporting construction- Grate mover (travelling grates)Travelling grate – suitable forenergetic applicationsenergetic applications

BoilersGrate boilers:Grate boilers:

effective grate lengthlength of drying

length of burn-out

Gross grate area:Q

total grate lengtheffective grate length length of burn out

2[m ]pal nr

r

m QS a L

q⋅

= = ⋅

-1[kg s ]m fuel mass flow-1 [MJ.kg ]nQ-2 [MW.m ]rq

[kg.s ]palm fuel mass flow

fuel calorific valueaverage rated heat otput

-2of grate 0 7 1 6 MW m≈[m]a,L

[ ]rq of grate 0,7-1,6 MW.m≈grate width, length

Typical burning time for grate boilers: tens of minutes

BoilersPulverized boilers:Pulverized boilers:

The boilers are equipped with hammermills for combustion lignite or black coal in p l eri ed form Boilers ha ecoal in pulverized form. Boilers have wide power output regulation range without employing stabilization (LFO). Pulverized boilers are constructed from rating 50 t/h.Typical burning time for pulverizedTypical burning time for pulverizedboilers:1 - 3 s

BoilersFluidized bed boilers:Fluidized bed boilers:Technology is based on properties of solid/fluid mixture. Combustion air inlet is at chamber bottom and blows air into solid fuel particles. Resulting fluid mixture h l ti f ith l ti l hi h ti l d Th th ihas large reaction surface with relatively high particle speeds. Thus there isachieved very intensive burning in the bed. Solid or liquid waste can be combusted this way (crushed or milled at the same grain size). Fluid combustion is s itable for aste of high s lf r content beca se comb stion prod cts can beis suitable for waste of high sulfur content, because combustion products can be separated by adding lime or limestone directly into the waste. Not applicable for sintering waste.

Classification of fluidized beds:

- Bubbling Fluidized Bed – BFB- Circulating Fluidized Bed - CFB

CFB meets nowadays requirements on emissionsand is the best choice for lignite fired power plants of hi h ti

CFB fluid boiler

higher ratings

BoilersCFB fluid boiler:CFB fluid boiler:

separatorseparator

membrane cyclon

combustion chamber

fluidized bed dosage/offtake of bottomash / sand

Boilers – Hydraulic PartPressure losses:Pressure losses:Calculation of pressures inside boiler is necessary for final dimensioning of feedwater pump (resp. turbine). Total pressure losses consist of:

t m h dp p p p pΔ = Δ +Δ ±Δ ±Δpipe friction

local resistances (inflow, outflow, knees...) hydrostatic pressure

dynamic flow pressure

Water:Espec. for laminar flow:

( , , )

2

2tl cp . . .

dΔ = λ ρ 64

λ = Re c.d=2t

ekv

pd

ρ

friction factorRe

λ = Reν

Reynolds n.kinematicviscosity

Steam:2

pr.T

ρ = 2

1 4m .mc .A .d .

= =ρ π ρ

2

1 1 2 5

16t

m r.Tp p p . . . .ld

Δ = − − λπ ρ

Evaporator:Complex model, approximated by cubic equation:

A 3 3t

Ap .m B.m C.Q.mQ

Δ = − + A,B,C konstanty

Boilers – Hydraulic PartL l i t Hydrostatic pressure: Dynamic pressure:Local resistances:

2

2m mcp . .Δ = ζ ρ∑

Hydrostatic pressure:

hp h. .gΔ = Δ ρ

Dynamic pressure:2 2

1 1 2 2

2 2d.c .cp ρ ρ

Δ = −2

local resistances factor

Natural circulation, circulation ratio:

( )zc t m zcp p p f cΔ = Δ +Δ =Pressure losses exposed by water/steam flow in evaporator are a function of velocity

Static overpressure in evaporator is caused by hydrostatic pressure difference

For natural circulation dimensioning must be found flow velocity , corresponding to *c( )sop down comer riser sopp h. .g h. .g f c−Δ = ρ − ρ =

Static overpressure in evaporator is caused by hydrostatic pressure difference

equality between losses and overpressure( ) ( )* *

zc sopf c f c=

Ci l ti tiCirculation ratio:z

v

mCRm

=water passing into riser

steam generated in evaporator

Typical value for boilers of higher ratings is 6-8.

Boilers – Hydraulic PartSteam drum: J

ISteam drum: KL

IH

GBoiler drum is a thick-walled pressure vessel (wall thickness about 10 cm)With diameter circa 1 m located in

NE

M

F

max.

norm.cyklon cyklon

With diameter circa 1 m, located in upper part of front pass of boiler. Down-comers and risers outlets are located in underneath superheater O

P

D

C

min.

3 x 50

cyklon cyklonlocated in underneath, superheater outlets in upper parts. Boiler water level is an interface for two water states. This level must be kept at

AB R

A - odvodnění bubnu H - pojišťovací ventilyB,R - zavodňovací trubky I,K,L - parovody k PK 1 C,D - várnice pravé strany J - alkalizace

states. This level must be kept at constant value circa in the middle of drum pressure vessel. No steam must enter into down-comers and no water

E,F - várnice přední stěny M,N - várnice levé strany G - napájení bubnu O,P - várnice zadní stěnyinto superheaters!