orc and kalina analysis and experience

7/27/2019 ORC and Kalina Analysis and Experience

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ORC and KalinaAnalysis and experience

Pll Valdimarsson

professor of mechanical

engineering

Sabbatical December 2003

Lecture III

2

Energy and energy use

Energy is utilized in two forms, as heat

and as work

Work moves, but heat changes

temperature (moves the molecules

faster)

These are two totally different products

for a power station

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Convertability

Work can always be changed into heat

(by friction since ste stone age)

Conversion of heat into work is difficult

and is limited by the laws of

thermodynamics. A part of the heat

used has always to be rejected to thesurroundings

4

Heat and work again

Work is the high quality, high priced

product

Heat is second class quality, a low

priced byproduct



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5

A power plant

Source

Heat

Fuel

Rejected heat

Losses

Electricity

Sellable heat

Power

plant

6

Single flash - condensing

Production well Injection well

Separator

Turbine

Cooling tower

Pump

Condenser

Pump



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7

T-s diagram

8

ORC with regenerator

Production well

Injection well

Turbine

Condenser

Pump

Regenerator

Boiler



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9

T-s diagram

-2,0 -1,5 -1,0 -0,5 0,0 0,5 1,0-50

0

50

100

150

200

250

s [kJ/kg-K]

T[C]

2300 kPa

1000 kPa

350 kPa

90 kPa0,2 0,4 0,6 0,8

0,00

45

0,026

0,063

0,15

0,37

0,89

m3/kg

Isopentane

10

ORC with paralell single flash


Separator

Turbine Cooling tower

Condenser

Pump

Condenser

Cooling towerTurbine

Boiler



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11

ORC with serial single flash


Separator Turbine

Condenser

Cooling towerTurbine

Boiler

Throttling valve



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15

Rogner, Bad Blumau

The 250 kW air-cooled geothermal CHP plantgenerates electrical power as well as districtheating using a low temperature geothermalresource.

One standard containerized ORMAT CHPmodule, generating 250 kW electricity and2,500 kW heat.

The power plant is in commercial operationsince July 2001.

16

Mokai, New Zealand

The 60 MW Geothermal Power Plant iscomprised of: one 50 MW module operating on geothermal

steam

two 5 MW units operating on geothermal brine

The power plant uses air-cooled condensersand achieves 100% geothermal fluid

reinjection to produce electrical power withvirtually no environmental impact.



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18

Kalina

Production well

Injection well

Separator

Turbine

Condenser

Boiler

Throttling valve

Cooling tower

Regenerator

Pump

Brine hx



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Geothermal experience

Rough surroundings

Aggressive chemistry

Simple and reliable solutions

Geothermal energy - a mayor economic

factor

20



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21

Conversion of heat to electricity

The Carnot efficiency applies for infinite

heat sources

The maximum efficiency is lower than

the Carnot efficiency for a source

stream with finite heat capacity

Kalina reduces entropy generation inthe heat exchange process

22

Carnot efficiency

Hot reservoir

Cold reservoir

Work output

Heat in

Heat out

1

01T

TCarnot

=



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Maximum efficiency

for a liquid source

=

21

2

1

0

)(

ln

1*TT

T

T

THEh

x

1T

2T

0T 0T

24

What is a Kalina process?

A modified Rankine cycle, or rather:

a reversed absorption cycle

Ammonia - water working fluid

Patented by Exergy Inc and A. Kalina



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The characteristics

Heat is added in a combined boiling and

separation process

at a variable temperature

Heat is rejected in a combined

condensation and absorption process

as well at a variable temperature

260 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

60

80

100

120

140

160

180

200

220

240

Temperature[C]

Ammonia mass fraction [-]

Mixture boiling at 30 bar



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Heat addition - boiler

Source

Kalina

ORC

28

The working fluid

Ammonia has a molar mass of 17, so

steam turbines can be used

The mixture properties are more

complex, usually three independent

properties are needed for the

calculation of the fourth Therefore the cycle is more flexible, and

can be closely optimized to the source



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29

The benefit

The working fluid is almost at the

temperature of the source fluid when

leaving the boiler

The variable heat rejection temperature

makes regeneration possible

30

Kalina vs. ORC

Kalina is better when the heat source

stream has a finite heat capacity

ORC and Kalina are similar when the

source is condensing steam



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Boiling curves for Hsavk

0 200 400 600 800 1000 120020

30

40

50

60

70

80

90

100

110

120

Temperature[C]

Enthalpy [kJ/kg]

Water

KalinaORC

32



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33

34

Kalina again

Production well

Injection well

Separator

Turbine

Condenser

Boiler

Throttling valve

Cooling tower

Regenerator

Pump

Brine hx



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35

36



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37

38

0 200 400 600 800 1000 1200 1400 1600

0

50

100

150

200

Enthalpy [kJ/kg]

Temperature[C]

T - h diagram

6.5

6.5

6.5

6.5

31

31

31

31

6.5

6.5

6.5

6.5

31

31

31

31

6.5

6.5

6.5

6.5

31

31

31

31



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Comparison

Power[kW]

1. law 2. law Maxliquideff.

Volumeto

turbine[m3/s]

Kalina 2000 0,13 0,45 0,56 0,57

ORC 1589 0,10 0,36 0,45 2,06

Flash cycle 1589 0,10 0,36 0,45 22,4

Themoelectricity 720 0,05 0,16 0,20 0

40

Comparison of Kalina and ORC

Heat (10MW) is available down to 80C

Cooling water (120kg/s) is available at

20C

Heat exchangers have a pinch of 3C

Condensers have a pinch of 10C



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90 95 100 105 110 115 120 125 130 135 1400

0.05

0.1

0.15

0.2

0.25

Temperature [C]

Efficiency[-]

Carnot

LiquidKalina

ORC

42

Hsavk geothermalpower plant



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General design parameters

44

Summary

Commissioned in the summer 2000

Running at ~1500 kW net 2000 - 2001

Running at ~1700 kW net since

November 2001

Final acceptance certificate issued

Total investment cost 3,7 MEUR



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Process

diagram

G121 C

80 C

90 kg/s

1950 kW

5 C

24 C

118 C

31 bara

5,5 bara

12 C

67 C

16,3 kg/s

173 kg/s

0,81 NH3

130 kW

11,2 kg/s

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The power plant



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47

Design

Standard industrial components

Turbine-generator from KKK, Germany

Electrical components CE marked

Heat exchangers from USA

Most of the tanks made in Iceland

Installed by a local contractor

48

Equipment

Evaporator, shell and tube, 1600 m2

Separator

Turbine

Recuperators

Condenser, plate, 2 x 750 m2

Hotwell

Circulation pump



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Auxillary equipment

Ammonia storage tank

Demineralized water tank

Blow down tank

50

Thermal equilibrium

Power output

Power input

14.000 kWCooling water

1.700 kWElectricity, net

15.700 kWBrine



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51

Start-up problems

Separator

Evaporator

Axial sealing of the turbine, ammonia leakage

Condensers

Miscellaneous

Main pump

Safety valves

Magnetite

52

Separator

Difficult to measure the performance of

the separator

Mist eliminator module wrongly installed

New separator installed November 2001



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53

Evaporator

Ammonia leaking into the hot water

All tubes rolled again in November

2001, no leakages since

54

Axial sealing

One axial sealing on the low pressure

side

N2 used in the sealing

The sealing has been replaced once

Leakage caused by carry-over from

separator



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Condensers

Plate heat exchangers

Important to mix liquid and vapor

Spraying nozzles modified

Increase power output by improving

performance of the condensers

56

Miscellaneous

Safety valves, leakage

Circulation pump, seals and

guides/bushings for shaft

Improvment of spraying system in

recuperator 2

Magnetite (Fe3O4)



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57

Turbine corrosion

Ferritic material in the turbine corrodes

Austenitec material is unharmed

Corrosion is from the turbine control

valve until abt 1 metre after the turbine

Influence of rotor magnetic field?

Elimination of ferritic material in the steamside of the turbine

58

Operating experience

Maximizing the output by optimizing the

strength of the NH3 H2O solution

Prevent air entering the system

Improvement of flushing and filters

The system is stable in operation



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59

Lessons learned

The technology is proven

Standard equipment has been adjusted

The plant is running according to specs

Individual equipment still may be

improved to increase output

Engineering details will improve future

plants

60

What do we have?

New thermodynamic cycle with better

efficiency in particular when the heat source

cooled down while heat is extracted

Theoretical and technical descriptions of the

processes involved.

Mathematical models that have been tested

up against Husavik Plant

Known media and known machinery



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61

The knowledge

Real experience and know how from theHusavik plant

Mathematical models and ,,steamtables, worked out in cooperation withUniversity of Iceland.

Over 30 years of experience in electrical

generation from low and mid heatsources (Geothermal)

62

Kalina references

Canoga Park, USA, demonstration plant3 6 MW, 1991-1997

Fukuoka, Japan, incineration plant, 4,5MW, 1999

Sumitomo, Japan, waste heat recovery

from a steel plant, 3,1 MW Husavik, Iceland, geothermal plant, 2,0

MW, 2000



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Krafla 1970, 60 MWel

Svartsengi 1980, 37 MWel, 60 MWdh

Nesjavellir 1990, 90 MWel, 250 MWdh

64

Were does it fit?

Temperature above 150C and good

size stands on its own.

Cogeneration of electricity and water for

district heating.

Good cold end helps

Environmental issues and subsidizing

changes these values



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65

Budgetary unit price

Budgetary price for 500 kW unit

720.000 USD

Equals 1440 USD/kW

Turbine/generator most costly unit (30-

35%)

Presuming cooling water available

66

Opportunities

Where there may be hot water or other

fluid/gas available at temperatures

between 120 and 300C

Geothermal

Waste heat

Industrial processes

Gas and diesel engine exhaust



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67

Kalina plant benefits

Energy cost efficient

Environmental issues

Green energy

Reduced emissions

Standard off the shelf equipment

68

General marketconditions

General market price 4 eurocents/kWh

General pay-back time 4 years required

General investment 1000 USD/kW

So how can 1440 USD/kW becompetitive?



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69

German law

Green electrical power generation bonus

2002-2004 1,74 eurocents/kWh




Provided plant in operation before end of 2005

70

Competitive investment ?

Given 1,65 eurocents/kWh bonus

4 year pay-back period

Additional investment acceptable for

green energy USD 528.000/MW

Total acceptable investment cost thus

USD 1.528.000/MW or 764.000 USD for

our 500 kW unit.



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Green energy?

Is waste heat recovery=green energy?

Waste heat recovery reduces emissions

CO2 quotas pricing as high as 20-25

USD/tonCO2

Average emission 800 gCO2/kWh in

fossil fuel plants

Equals values of 1,8-2,2 eurocents/kWh

72

Summary

Given green energy bonuses or CO2

evaluation the investment in a Kalina waste

heat recovery electrical generating plant is

feasible

The investment is competitive to other

investments for industrial improvements

Pay-back time of 4 years in a green energy

technology is short



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73

Introduction

Finite source heat capacity lowers this upperbound due to the reduction of the sourcetemperature as heat is removed from thesource

This results in high cost for such lowtemperature power plants, as they have tohandle large heat flows

The Kalina cycle is a novel approach toincrease this efficiency

74

The Models

It is assumed that a fluid is available attemperatures ranging from 100 to 150C

A heat customer is assumed for the primaryoutlet water at the temperature of 80C

Primary flow of 50 kg/s is assumed

Cooling water source is assumed at 15C,

and cooling water outlet is fixed at 30C It is assumed that a cooling water pump has

to overcome a pressure loss of 1 bar on thecooling water side in the condenser



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Solution

The software Engineering Equation Solver (EES) is

used to run the models

The cost model keeps the logarithmic mean

temperature difference for each heat exchanger at

the same value as found in the cycle data for the

tenders for the Husavik power plant

Estimated cost figures for individual components

were then added together in order to obtain the finalcost value

76

Process assumptions

The OCR model is based on a system

without regeneration

Isopenthane is assumed as a working

fluid

A Kalina cycle for generation of

saturated vapour for the turbine is used



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77

ORC flow sheet

Production well

Injection well

Turbine

Condenser

Pump

Boiler

78

Kalina flow sheet

Production well

Injection well

Separator

Turbine

Condenser

Boiler

Throttling valve

Cooling tower

Regenerator

Pump

Brine hx



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79

Kalina assumptions

This cycle will be limited by the dew point of the mixture,that is when the boiling of the mixture is complete, andno liquid remains at the boiler outlet

The bubble temperature of the mixture has to be lower orequal to the primary fluid outlet temperature to ensuresafe operation

The feasible region will be in the area between the 70and 80C bubble contours

The feasible area regarding the dew temperature is

limited to a value some 2-4C lower than the maximumtemperature of the primary fluid

Bubble temperature

10

20

30

40

0.6

0.8

1

20

40

60

80

100

Pressure [bar]

Bubble temperature

Ammonia ratio [-]

Bubbletemperature[C]



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Dew temperature

10

20

30

40

0.6

0.8

150

100

150

200

Pressure [bar]

Dew temperature

Ammonia ratio [-]

Dewtemperature[C]

Bubble contours

10 15 20 25 30 35 400.65

0.7

0.75

0.8

0.85

0.9

0.95

1

Pressure [bar]

Ammoniaratio[-]

Bubble temperature contours

30

40

40

50

50

60

60

70

70

70

80

80

80

90



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Dew contours

10 15 20 25 30 35 400.65

0.7

0.75

0.8

0.85

0.9

0.95

1

Pressure [bar]

Ammoniaratio[-]

Dew temperature contours

80 90

100

100

110

110

110

120

120120

120

130

130

130130

140

140

140

140

150

150

150

160

160

160

170

170 18

0

19

84

More Kalina

Both high pressure level and ammonia content aredesign variables in the Kalina cycle

This gives flexibility in the design of the cycle, andrequires as well a certain design strategy

The plant can be designed for maximum power

or with strong demands on the investment cost

The cost is 100 for the lowest cost, and the power100 for the highest power

An x denotes an infeasible solution, the cycle will notbe able to run at these ammonia content pressurecombinations



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Cost contours

15 20 25 30 35 400.65

0.7

0.75

0.8

0.85

0.9

0.95

1

Pressure [bar]

Ammoniaratio[-]

Cost contours, 100C source

101

101

101

102102

102

102

103

103

103

10

3103

104

104

104

104

105

105

105

105

106

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106

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110

110

110

110

110

Power contours

20 25 30 35 400.65

0.7

0.75

0.8

0.85

0.9

0.95

1

Pressure [bar]

Ammoniaratio[-]

Power contours, 100C source

9090

9090

9090

9090

90

90

90

9090

90

9191

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9191

9191

919191

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9191

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9292

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9393

9393

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9797

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9797

9898

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99

9999



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Cost surface

10

20

30

40

0.6

0.8

10

200

400

600

Pressure [bar]

Cost function

Ammonia ratio [-]

Cost

Power surface

10

20

30

40

0.6

0.8

1

0

50

100

Pressure [bar]

Power function

Ammonia ratio [-]

Power



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89

Discussion

The best power and best cost points are

different

The lowest cost is at 32 bar, 92% ammonia, but

highest power is at 34 bar and 88% ammonia

This leads to the definition of two different Kalina

cycles, the best power and the best cost cycles,

with different pressure and ammonia content

15 20 25 30 35 400.65

0.7

0.75

0.8

0.85

0.9

0.95

1

Pressure [bar]

Ammoniaratio[-]


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102

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102

102

103

103

103

103103

104

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10

4

104104

105

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22 24 26 28 30 32 34 36 38 400.65

0.7

0.75

0.8

0.85

0.9

0.95

1

Pressure [bar]

Ammoniaratio[-]


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70

72

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99

18 20 22 24 26 28 30 32 34 360.65

0.7

0.75

0.8

0.85

0.9

0.95

1

Pressure [bar]

Ammoniaratio[-]


101

101

101

102

102

102

10310

3

103103

104

104

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0.7

0.75

0.8

0.85

0.9

0.95

1

Pressure [bar]

Ammoniaratio[-]


70

70

72

72

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74

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7

6

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80

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4

95

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94

Comparison

Two ORC companies made a tender inthe Husavik bid

Manufacturer A offered a high power,high cost power plant, wheremanufacturer B took a moreconservative approach

Following is a comparison with both thelow cost and high power Kalina powerplants



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Cost comparison

100 110 120 130 140 1501000

1200

1400

1600

1800

2000

2200

2400

Source inlet temperature [C]

Netcost[$/kW]

Kalina vs ORC cost comparison

ORC B

ORC A

Kalina HP

Kalina LC

Power comparison

100 110 120 130 140 1500

500

1000

1500

2000

Source inlet temperature [C]

Netpower[kW]

Kalina vs ORC power comparison

Kalina HP

Kalina LC

ORC A

ORC B



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97

Results

The maximum power generated for a

given source is greater for the Kalina

cycle

Kalina cycle is well positioned against

an ORC cycle for applications with high

utilization time, a base load application

98

Results II

A heat consumer is beneficial for the ORC

cycle as it results in less temperature change

of the primary fluid during the boiling process

The Kalina cycle has the boiling or

vaporization of the fluid happening over a

temperature range up to 100C, which is

beneficial when the primary fluid returntemperature has to be minimized



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The debate

The theoretical efficiency and cost/productionratio are better for Kalina as shown above

Other arguments like difficulties withmachinery and lesser operational security oruptime are only temporary discussion items,as always for a new technology

These arguments were exactly the samebetween conventional flash cycle and ORCwhen the latter popped up 30 years ago withbetter efficiency but little track record

100

Conclusion

The Kalina cycle is thermodynamically

superior or equal to the ORC cycle

There is no black magic behind the

Kalina cycle

The startup problems that have either

been solved, or are solvable

orc and kalina analysis and experience

Documents