SELECTING THE OPTIMISED PUMP CONFIGURATION AND DRIVE OPTION FOR THE

CONDENSATE EXTRACTION AND BOILER FEED PUMPS FOR THE NEW ESKOM SUPERCRITICAL POWER STATIONS

Willem van der WesthuizenCorporate Pump Consultant

andGugu Ngcobo

Mechanical Engineer

Eskom Group TechnologyJohannesburg,

South-Africa

2011/05/13 2

ABSTRACT• Eskom has embarked on a major Capital Expenditure program to cater for

the growing demand for power as a result of a rapidly developing South African economy.

• Future developments include electrical power generation utilizing diverse technologies such as; – Fossil– Nuclear– Pebble Bed Modular Reactors– Hydro, Open Gas Cycle – Combined Cycle – Wind and Solar Energy

• The first two new Supercritical Fossil fired Power Stations, Medupi (6 Units, each 794 MW) and Kusile (6 Units, each 798 MW) are presently in the design and construction phase.

• The condensate extraction pumps and boiler feed pumps are amongst the highest consumers of auxiliary electrical power within a power station, it is therefore of utmost importance that the correct optimized pump configurations and drive options for each of these pumps is selected.

2011/05/13 3

Background to Eskom• Eskom, South Africa’s electricity utility:

• Is one of the top 10 utilities in the world by generation capacity

• Generates approximately 95% of electricity used in South Africa

• Generates approximately 45% of electricity used in Africa

• Number of employees, 37 857

• Electricity sales, 214 850GWh

• Nominal capacity, 44 193MW

• Net maximum capacity, 40 503MW

• Power lines and cables (all voltages), 381 700km

• Carbon dioxide emissions, 221,7Mt

• Total water consumption, 323 190ML

2011/05/13 4

2011/05/13 5

2010

2011/05/13 6

2010

2011/05/13 7

Capacity Expansion –Driven By Long Term Demand Forecast

Long term forecasts - national + foreign

30000

40000

50000

60000

70000

80000

90000

2005 2010 2015 2020 2025

MW

PositionModerate Eskom position based on

4% growth electricity growth supporting 6%

economic growth

77960 MW

56710 MW

Eskom moderate position 2.3% electricity

growth basedeconomic growth of 4%

Hydro

Nuclear

Oil/Gas

Power Purchase

Coal

Transmission

Renewables (Wind, Solar)

Eskom Capacity Projects Funnel [Gross Mwe]

Research PrefeasibilityFeasibility, Business

Case Study

BuildProgramme

In Operations

Opportunity Screening

165

PBMR

100

Concentrating

Solar Tower

1200

Discard Coal

1000

CBM Botswana

1000

Monontsa PS Lesotho

4800

Coal-3

4800

Coal-4

600

Moambo

Moz-Gas600

Kafue Lower Zambia

1300

Mphanda Nkuwa Moz

1200

Mmamabul Botswana

1500

Moatize Moz

400

OCGT Conversion

750

Komati

4764

Medupi

4800

Kusile

800

Grootvlei

746

Gourikwa

1337

Ankerlig

1352

Ingula

2100

Co-Gen MTPPP

International

Projects (Imported Power)

200

Arnot upgrade Phase I

1600

Camden

300

IGCC

400

Gr’tvlei

1800-5400

Coal-5

600

Maropule Botswana

1000

Mmamantswe Botswana

CCS

Carbon Capture

xx

Wave /Ocean current Energy 30-70

Or River Nam-RSA

360

KNBE Zambi

a

360

KSB Zimbabwe

1500

Pumped

Storage-D

n x 3200

Nuclear- n

Other KnownOpportunities

2000

Benga Mozambique

35

Massingir Moz

180

Lurio Moz

4500

MultiSite IPP

1600

Batoka Gorge Zim / Zam

1400

Gokwe N Zimbabwe

1000

Lebombo Swaziland

6700

Kwanza Angola

1000

DME IPP Peaker

60

Peaker Moz

500

Wind 2

540

HFO n x 300n x 800

Coal-n

Tx

Mazambique

Back-Bone

AC/DC

Note: Power import for most of the regional projects will be lower than the stated capacitydue to host country off-take

4,533 MW12, 566 MW20,680 MW18, 800 MW+ n x 3200 MW nuc.

250

Komati

100

Sere-Wind 1

3300Nuclear

(delayed)

2100

UCG

500

CBN Moz

3500

Inga III Westcor

1500

Tubatse (delayed)

nx400

CCGT nx100

Wind_Fleet

nx150

OCGT

100

Arnot upgrade Phase II

2011/05/13 9

Two new Supercritical Power Stations• The first two new Supercritical Fossil fired Power Stations,

Medupi (6 Units, each 794 MW) and Kusile (6 Units, each 798 MW) are presently in the design and construction phase.

• Both power stations have Air Cooled Condensers• The Turbine contact was awarded to Alstom and the Boiler

contract to Hitachi.• The condensate extraction pumps and boiler feed pumps

are amongst the highest consumers of auxiliary electrical power within a power station, it is therefore of utmost importance that the correct optimized pump configurations and drive options for each of these pumps is selected.

2011/05/13 10

Matimba Power Station 6x660 MW

Kendal Power Station 6x680 MW

2011/05/13 11

Progress at Medupi Power Station

Medupi and KusilePower Station

Condensate Extraction Pump

2011/05/13 13

Condensate Extraction Pump• All existing Eskom Power Stations utilize a 2 x 100%

Condensate Extraction Pump (CEP) configuration.• The older type Power Stations that don’t have any

Main Turbine bypass systems utilizes two fixed speed CEP’s with their design point the same as the Turbine Maximum Continuous Rating (TMCR) duty point.

• The pumps are horizontally split casing designs with a double entry suction impeller.

• The slow speed and double suction impellers are specifically considered in order to satisfy the NPSH requirements of the pumps.

2011/05/13 14

2011/05/13 15

Condensate Extraction Pump• On our newer larger plants with an output of

greater than 500MW, where the condensers are larger and the pump flow greater, the condensate extraction pumps are vertical multistage with the pump element mounted in a suction can which is connected directly to the hot - well of the condensers.

• All the power stations, whose outputs are greater than 500 MW per Unit, have Main Turbine Bypass Systems.

2011/05/13 16

2011/05/13 17

350 kW

2011/05/13 18

Condensate Extraction Pumps for Medupi and Kusile P/S’s

Option 1:• 2 x 100 % Vertical Spindle CEP’s

–One variable speed–One fixed speed

Option 2:• 2 x 100 % Horizontal arrange CEP’s

–One variable speed–One fixed speed

2011/05/13 19

Condensate Extraction Pumps

Horizontal CEP preferred• Simple design• Easier maintenance• Spares holding less

2011/05/13 20

Condensate Extraction PumpsPosition of CEP• Below ACC Condensate Tank• Optimum suction or NPSH available to CEP• Enclosed in a dedicated CEP building• Traveling Crane and maintenance area

provided for in building• CEP Electrical system incorporated with

ACC sub-station

2011/05/13 21

Medupi and Kusile

Boiler Feed Pump Drive Options

2011/05/13 23

Boiler Feed Pump Drive Options

• Drive options technically acceptable

1. High Speed VSD E-Motor (with low speed gearbox)

2. Low Speed VSD E-Motor (with high speed gearbox)

3. Fixed Speed Motor & Voith Vorecon

4. Fixed Speed Motor & Voith Hydraulic Coupling

2011/05/13 24

Boiler Feed Pump Drive

Booster pumpMain pump

Filter

2011/05/13 25

1. High Speed VSD Electric Motor with Speed Reduction Gearbox

Booster pumpMain pump

Filter

Speed Reduction Gearbox

High Speed VSD

Electric Motor

N = 1500 rpmN = 6000 rpm

BFP set efficiency = 81.2 %

2011/05/13 26

Speed Increase Gearbox

2. Low Speed VSD Electric Motor with Speed Increase Gearbox

Booster pump Main pump

Filter

Low Speed VSD

Electric Motor

N = 1500 rpm N = 6000 rpm

BFP set efficiency = 79.9 %

2011/05/13 27

3. Fixed Speed Electric Motor with Voith Vorecon Planetary Geared Variable Speed Fluid Drive Coupling

Booster pump Main pump

Filter

Voith Vorecon Planetary Geared

Variable Speed Fluid Drive Coupling

Fixed Speed

Electric Motor

N = 1500 rpm N = 6000 rpm

BFP set efficiency = 77.2 %

2011/05/13 28

4. Fixed Speed Electric Motor with Voith Variable Speed Fluid Drive Coupling

Booster pumpMain pump

Filter

Voith Variable Speed

Fluid Drive CouplingFixed Speed

Electric Motor

N = 1500 rpmN = 6000 rpm

BFP set efficiency = 70.2 %

2011/05/13 29

BFP Drive BFP Set Efficiency %

*Power Consumption kW Capital Cost

%High Speed VSD E-Motor + LS Gearbox 81.2 24274.8 203

Low Speed VSD E-Motor + HS Gearbox 79.9 24685.2 161

Voith Vorecon Mechanical VSD 77.2 25520.84 133

Voith Hydraulic Coupling 70.2 28103.1 100

Efficiencies of BFP Drive Options

*Power Consumption = 2 pumps @ TMCR

2011/05/13 30

Economic Evaluation• Two models were used

– Official Generation EE model– ..\..\..\BFP Drive Options vs. Load Profile rev2.xls

– Eskom Enterprise Engineering – Steag/EvonicHybrid Model

– ..\..\BFP Economic Evaluation.xls

2011/05/13 31

Capital Costs of BFP Drive Options and EE results

BFP Drive Capital Cost in R M per unit for 3 BFP sets

Capital Cost %

EE ResultsLevelised costs

R/MWh

High Speed VSD E-Motor + LS Gearbox - 203 187.11

Low Speed VSD E-Motor + HS Gearbox

- 161 186.66

Voith Vorecon Mechanical VSD - 133 186.50

Voith Hydraulic Coupling - 100 186.73

1

2

3

4

2011/05/13 32

BFP Load vs Pump set Efficiency

40

50

60

70

80

90

50 60 70 80 90 100 110

Pump Load

Pum

p se

t Effi

cien

cy

High speed VSD % Low speed VSD % Vorecon % Voith %

2011/05/13 33

Boiler Feed Pump Power Requirement

4000

6000

8000

10000

12000

14000

16000

40 50 60 70 80 90 100 110

Pump Load

Pow

er A

bsor

bed

(kW

)

Pump shaft power Booster + Main Motor Input Power High Speed VSDMotor Input Power Low Speed VSD Motor Input Power VoreconMotor Input Power Voith

2011/05/13 34

SES Meliti P/S 350 MW – Florina Greece

2011/05/13 35

Mannheim P/S – 9 MW Vorecon BFP Drive

2011/05/13 36

Boiler Feed Pump Train LayoutABB Electric Motor

Power = 19 700 kW

Speed = 1482 rpm

Weight = 48 000 kg

VOITH VORECON RW16-145 F9

Output Power = 16 192 kW

Output Speed = 5770 rpm

Weight = 45 000 kg

Main Pump HPT 350-370-6s/29A

Pressure = 275 Bar

Flow = 354 l/s

Temperature = 183 oC

Speed = 5665 rpm

Weight = 14 000 kg

Booster Pump

Pressure = 16 Bar

Flow = 354 l/s

Temperature = 183 oC

Speed = 1482 rpm

Weight = 4 500 kg

2011/05/13 37

Closing Note!• When selecting an optimised critical pump

configuration and drive option installed in a Power Plant the following need to be considered:

Power Station Operation modeCapital cost of complete pump drive trainPump set efficiency and auxiliary power absorbedAuxiliary power costSelection of proven technology and equipment with high reliability and availability

2011/05/13 38

COMMITMENT !

“If our reference list increase

with 36 – 19 MW Vorecons

We will just have to make it work! “

– Dr. Juergen Zeschky - VOITH

Thank You