Technologies for Generation and Heat Exchange

Sadiq J. Zarrouk

Senior Lecturer (Geothermal Engineering)

s.zarrouk@auckand.ac.nz

Talk Outlines

• Challenges in Conventional Steam Plants (Separators)

• New Directions in Surface Facility

(Total Flow Machines)

• Heat Exchangers in Geothermal Development.

Geothermal System

From Moon (2012)

Role of Geothermal Separator

Production Well

Separator

CondensateReinjection Well

Scrubber

2-Phase Fluid

G

BrineReinjection Well

Steam Turbine

Condenser

Cooling Tower

Hot Well Pump

NCGRemoval

Reinjection Pump

Circulation Pump

Early Separators in Wairakei

U-Bend Separator

(From Grigg, 1956)

Vertical Separators

Steam Outlet

Inlet

Water Outlet

De

D

Db

z

β

Dt

α

LT

LB

Spiral Two Phase Inlet

Tangential Two Phase Inlet

TOC BOC From Zarrouk and Purnanto (2014)

Horizontal Separator

E-12E-10E-6

L

D

Mixture fluid in Steam out

Brine out

Water

Baffles

A

A

A A

Mist EliminatorSteam out

Ball Check

Valve

Baffles

Water

Ball Check

Valve

From Zarrouk and Purnanto (2014)

Separation Quality

98.8

99

99.2

99.4

99.6

99.8

1000

0.2

0.4

0.6

0.8

1

1.2

0 10 20 30 40 50 60 70 80 90

Ou

tlet

Ste

am Q

ual

ity

( %

)

Mas

s W

etn

ess

of

Ou

tlet

Ste

am (

%)

Steam Velocity at Separator Inlet (m/sec)

WK 30 (Bangma, 1960)

WK 44 (Bangma, 1960)

Lazalde-Crabtree (1984)

From Zarrouk and Purnanto (2014)

The Location of the Separator?

• Well head, Satellite or Centralised?

Production Well

Separator

CondensateReinjection Well

Scrubber

2-Phase Fluid

G

BrineReinjection Well

Steam Turbine

Condenser

Cooling Tower

Hot Well Pump

NCGRemoval

Reinjection Pump

Circulation Pump

11

Total Flow (BiPhase) Machines

Simple Total Flow System

12

TFC System Using a Working Fluid

From Smith et al (2005)

Screw Expander

Simple System

Modular Units

1-3 MWe Units

Waste Heat Steel Mile (China)

2 X 1 MWe Units at the Yangbajain Geothermal Field in Tibet running since 2008 and 2010

Heat Exchangers

Plate Heat Exchanger

Do

wn

ho

le Pu

mp

Production well

Re-Injection well

Main Plate Heat Exchangers Secondary

Plate Heat Exchangers

Primary fluid line (Geo)

Secondary fluid line

Master Valve

Secondary water circulating pumps

Problems in Plate Type Heat Exchanger

GI Records

DHE

Steins and Zarrouk (2012)

Improving DHE Performance with airlift

Types of geothermal system 22 Steins and Zarrouk (2012)

Shell and Tube Heat Exchanger

Two Shell Passes and Four Tube Passes

24

Large size Heat Exchangers

• Large Shell and Tube heat Exchanger tubes may fail due to excessive vibration generated by the shell-side fluid flow around and between tubes. There are several mechanisms that can cause vibration, but fluid-elastic instability is the most sever mechanism, which can cause tube damage in a very short time.

Erosion corrosion of

an inner shell wall

of a heat exchanger

26

Tongonan field, Philippines, Angcoy et al. (2005)

Multi-pass Flow Arrangement

27 Steins and Zarrouk (2012)

Silt Build-up

Steins and Zarrouk (2012)

29

Silica Deposition (shark skin) in Binary Plant Heat Exchanger Tubing

From Zarrouk et al (2014)

Scanning electron microscope micrograph

30

From Zarrouk et al (2014)

High density vitreous silica scale

31 From Zarrouk et al (2014)

Impact on Generation (Shark Teeth)

0

5

10

15

20

25

30

35

0

500

1000

1500

2000

2500

3000

3500

July 2005 July 2006 July 2007 July 2008 July 2009 July 2010 July 2011

Gro

ss P

ow

er

Ou

tpu

t (M

W)

Flo

w R

ate

(to

nn

e/h

r)

Date

Flow Through Both Power Plants Total Power Generated

From Zarrouk et al (2014)

Thank you

Questions ?