SEL ECTING THE OPTIMISED PUMP SELECTING CONFIGURATION AND DRIVE OPTION FOR THE CONDENSATE CONDE NSATE EXTRACTION AND BOILER B OILER FEED PUMPS FOR THE NEW ESKOM SUPERCRIT SUPE RCRITICAL ICAL POWER STATIONS Willem van der We Willem Westhuize sthuizen n Corporate Pump Consultant and Gugu Ngco gcobo bo Mechanical Eng Engineer ineer Esko skom m Grou Group p Technolog Technolog y J ohannesb sbu urg, South-Africa
AB A B STRA STRACT CT • 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; – – – – – –
F ossil Nuclear P eb ebb ble Bed Mo Mod dula larr React Reactor ors s Hyd Hy dro, Ope Open Ga Gas s Cycl Cycle e Comb Com bined Cy Cycl cle e Win Wi nd an and d Sola Solarr E nergy
• The The first two new Su Sup percritica call Foss Fossiil fired P ower St Sta ations, Me Med dupi (6 Un Uniits, each 794 MW) and Kusile (6 Units, each 798 MW) are presently in the design and constru construction ction phas phase. e. • Th The e condensa satte 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 configurat configur ations ions and drive drive opt options ions for each of these pumps pumps is se selected. lected.
Backgr Ba ckground ound to Eskom electricit y util ity: • Eskom, South Africa’s electricit
• Is one of the top 10 utilities in the world by generation capacity • Generat enerates es approximately approximately 95% of electricity used in Sout South h Africa • Generat enerates es approximately 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 • P ow ower er lines and cables (all (all voltages voltages), ), 381 700k 700km m • Carbon dioxide emissions, 221,7Mt • To Tottal water consu sum mption, 323 190ML
2010
2010
Capacity Expansion – Driven By Long Term Demand Forecast Long term forecasts - nation al + foreign 90000
80000
Position Moderate
Eskom position based on 4% growt h electric ity growth supporti ng 6% economic growth
77960 MW
70000 W60000 M
56710 MW
50000 Eskom moderate position 2.3% electricity growth based economic growth of 4%
40000
30000 2005
2010
2015
2020
2025
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.
Matimba Power Station 6x660 MW
Kendal Power Station 6x680 MW
Progress at Medupi Power Station
Medupi and Kusile Power Station Condensate Extraction Pump
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.
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.
350 kW
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
Condensate Extraction Pumps Horizontal CEP preferred
• Simple design • Easier maintenance • Spares holding less
Condensate Extraction Pumps Position 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
Medupi and Kusile Boiler Feed Pump Drive Options
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
Boiler Feed Pump Drive
Booster pump Main pu mp
Filter
1.
High Speed VSD Electric Motor with Speed Reduction Gearbox BFP set efficiency = 81.2 %
Booster pump N = 1500 rpm
Main p ump
Speed Reduc tio n Gearbox
N = 6000 rpm
High Speed VSD Electri c Motor
Filter
2. Low Speed VSD Electric Motor with Speed Increase Gearbox BFP set efficiency = 79.9 % Booster pump
Main p ump
N = 1500 rpm
N = 6000 rpm
Low Speed VSD Electri c Motor
Speed Increase Gearbox Filter
3. Fixed Speed Electric Motor with Voith Vorecon Planetary Geared Variable Speed Fluid Drive Coupling BFP set efficiency = 77.2 % Main pu mp
Booster pump N = 1500 rpm
N = 6000 rpm
Fixed Speed
Voith Vorecon Planetary Geared
Electri c Motor
Variable Speed Fluid Dri ve Coupli ng
Filter
4. Fixed Speed Electric Motor with Voith Variable Speed Fluid Drive Coupling BFP set efficiency = 70.2 % Booster pump Main p ump
N = 1500 rpm
N = 6000 rp m
Fixed Speed
Voith Variable Speed
Electri c Motor
Fluid Drive Coupli ng Filter
Efficiencies of BFP Drive Options
BFP Drive
BFP Set Efficiency %
*Power Consumption kW
High Speed VSD EMotor + LS Gearbox
81.2
24274.8
203
Low Speed VSD EMotor + HS Gearbox
79.9
24685.2
161
Voith Vorecon Mechanical VSD
77.2
25520.84
133
Voit h Hydraulic Coupling
70.2
28103.1
100
*Pow er Cons umptio n = 2 pump s @ TMCR
Capit al Cost %
Economic Evaluation • Two models were used – Offic ial Generation EE model – ..\..\..\BFP Drive Options vs. Load Profile rev2.xls
– Eskom Enterprise Engineering – Steag/Evonic Hybrid Model
– ..\..\BFP Economic Evaluation.xls
Capital Costs of BFP Drive Options and EE results Capit al Cost in R M per unit for 3 BFP sets
Capit al Cost %
EE Results Levelised costs R/MWh
High Speed VSD EMotor + LS Gearbox
-
203
187.11 4
Low Speed VSD EMotor + HS Gearbox
-
161
186.66 2
Voith Vorecon Mechanical VSD
-
133
1 186.50
Voit h Hydraulic Coupling
-
100
186.73 3
BFP Drive
BFP Load v s Pump set Efficiency 90
80
y c n e i c 70 i f f E t e s p 60 m u P 50
40 50
60
70
80
90
100
110
Pump Load
High speed VSD %
Low speed VSD %
Vorecon %
Voith %
Boiler Feed Pump Power Requirem ent 16000
14000
) W k ( 12000 d e b r o 10000 s b A r e w 8000 o P 6000
4000 40
50
60
70
80
90
100
110
Pump Load
Pump shaft power Booster +Main Motor Input Power Low Speed VSD Motor Input Power Voith
Motor Input P ower High Speed VSD Motor Input P ower Vorecon
SES Meliti P/S 350 MW – Florina Greece
Mannheim P/S – 9 MW Vorecon BFP Drive
Main Pump HPT 350-370-6s/29A
ABB Electric Motor
Power = 19 700 kW Boiler Feed Pump Train Layout
Pressure =275 Bar Flow = 354 l/s
Speed = 1482 rpm
Temperature =183 oC
Weight = 48 000 kg
Speed = 5665 rpm Weight = 14 000 kg
Boost er Pump
Pressure = 16 Bar VOITH VORECON RW16-145 F9
Output Power = 16 192 kW Output Speed = 5770 rpm
Flow = 354 l/s Temperature =183 oC Speed = 1482 rpm
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 mode Capital cost of complete pump drive train Pump set efficiency and auxiliary power absorbed Auxiliary power cost Selection of proven technology and equipment with high reliability and availability
COMMITMENT ! “If our reference list increase with 36 – 19 MW Vorecons We will just have to make it work! “ – Dr. Juergen Zeschky - VOITH