Kriel Power Station
All operations for normal, cold, warm or hot startup loading and dloading and normal shutdown of the power plant are conducted from the unit control room in manual, or partially or fully automatic, modes as required for each functional group. The analogue control system provides fully automatic load control of the whole unit and facilities for set point of subgroups as well as manual control of each drive. Similarly, binary control provides fully automatic runup of the major plant groups plus a facility for individual drive control. In the event of the failure of running auxiliaries standby plant is automatically switched on. If main plant groups fail, the unit automatically runs back to the highest possible safe state. Datalogging computers continuously monitor the main operating and alarm systems and provide a constant flow of information on video screens and printers.
Fuel Handling
The grinding elements consist of a stationary upper grinding ring fitted with hydraulic tension rams, and 240ºC) to repeat the cycle .a lower rotating grinding ring fitted with hydraulic tension rams, and a lower rotating grinding ring spun at 32,8 r/min by a 3,3 kV GEC electrical motor through a reduction gearbox. The 11 coal grinding balls run in tracks between the upper and lower grinding rings. They are hollow spheres made from a special wearresistant steel and have a diameter of 768 mm. The grinding elements of the 12.0E mills are constructed in the same way. However, they have only 10 grinding balls with a diameter of 930 mm, a rotation speed of 26.8 r/min and a maximum grinding capacity of 60 t/h. The pulverised coal is transported from the mill by means of primary air. r/min, and that of units 4 to 6 is 650 kW at 1 485 r/min
The exhaust steam is returned to the re heater part of the boiler, where its temperature is raised to 516ºC at a pressure of about 3,2 MPa (abs). It enters the IP cylinder via the interceptor and throttle valves at 510º and 3,16 MPa (abs). Entering at the centre of the IP cylinder, the steam flows outwards and horizontally to the shaft in both directions, through 15 fixed and 15 moving blades. The IP turbine exhausts steam now enters the two LP doubleflow cylinders at a pressure of 431 kPa (abs) and a temperature of 245ºC. The steam flows through 12 moving and 12 stationary blades on each side of the Alp rotor into the condenser. Steam exhausts from the LP cylinder at 40ºC and 7,7 kPa (abs).
Kriel Circuit Diagram
TECHNICAL DATA
Generating capacity  6 x 500 MW – 3000 MW 
Fuel  
Mining company  Amcoal 
Calorific value  
(underground coal)  23.4 MJ/kg (dry basis) 
(opencast coal)  18.220.4 MJ/kg (dry basis) 
Ash content  
(underground coal)  23.4% (dry basis) 
Sulphur content  
(underground coal)  ±1% (dry basis) 
(opencast coal)  ±1% (dry basis) 
Coal consumed at full load  ±1 400 tons/h 
Total annual consumption  ±89 million tons 
Coal staithe capacity  120 620 tons 
Staithe 1  72 000 tons 
Staithe 2  48 620 tons 
Stockpile capacity  1,7 million tons 
Boiler bunker capacity  19 900 tons per unit 
Fuel oil  Waxy 
Storage capacity  1 350 tons 
Annual consumption (total)  ±4 000 kl 
Mills  
Manufacturer  Babcock & Wilcox (SA) 
Type  Mediumspeed, verticalspindle 
Number  6 per unit 
Model  10.8E – Unit 13 12.0E – 46 
Rotational speed  10.8E – 32.8 r/min 12.0E – 26.8 r/min 
Rated output  10.8E – 47.8 tons/h 12.9E – 60 tons/h 
Feeders  
Manufacturer  Stock Equipment 
Number  6 per unit 
Minimum coal  22.5 tons/h Units 13 27.9 tons/h Units 46 
Maximum coal  50.76 tons/h Units 13 57.07 tons/h Units 46 
Through put control  Variablespeed 380V DC motors 
Induceddraught Fans  
Manufacturer  Davidson & Co Ltd 
Type  Bab 141A doubleinlet impreller 
Number  2 per boiler 
Volume flow per boiler (design)  1 030 m³/s /Units 13 10162 m³/s/Units 46 
Mass flow per boiler (design) 
Generating capacity  6 x 500 MW – 3000 MW 
Fuel  
Mining company  Amcoal 
Calorific value  
(underground coal)  23.4 MJ/kg (dry basis) 
(opencast coal)  18.220.4 MJ/kg (dry basis) 
Ash content  
(underground coal)  23.4% (dry basis) 
Sulphur content  
(underground coal)  ±1% (dry basis) 
(opencast coal)  ±1% (dry basis) 
Coal consumed at full load  ±1 400 tons/h 
Total annual consumption  ±89 million tons 
Coal staithe capacity  120 620 tons 
Staithe 1  72 000 tons 
Staithe 2  48 620 tons 
Stockpile capacity  1,7 million tons 
Boiler bunker capacity  19 900 tons per unit 
Fuel oil  Waxy 
Storage capacity  1 350 tons 
Annual consumption (total)  ±4 000 kl 
Mills  
Manufacturer  Babcock & Wilcox (SA) 
Type  Mediumspeed, verticalspindle 
Number  6 per unit 
Model  10.8E – Unit 13 12.0E – 46 
Rotational speed  10.8E – 32.8r/min 12.0E – 26.8 r/min 
Rated output  10.8E – 47.8 tons/h 12.9E – 60 tons/h 
Feeders  
Manufacturer  Stock Equipment 
Number  6 per unit 
Minimum coal throughput  22.5 tons/h Units 13 27.9 tons/h Units 46 
Maximum coal throughput  50.76 tons/h Units 13 57.07 tons/h Units 46 
Throughput control  Variablespeed 
Induceddraught Fans  
Manufacturer  Davidson & Co Ltd 
Type  Bab 141A doubleinlet impreller 
Number  2 per boiler 
Volume flow per boiler (design)  1 030 m³/s /Units 13 10162 m³/s/Units 46 
Mass flow per boiler (design)  745 kg/s Units 13 778 kg/s Units 46 
Impeller shaft coupling  Bibby 
Motor output  2 360 kW Units 13 2 500 kW Units 46 
Motor speed  596 r/min 
Air control method  CSvane 
Chimneys  
Number  2 
Height  213 m 
Diameter (base)  23.8 m 
Diameter (top) ID  13.8 m 
Foundation  93 piles of 1 220 mm diameter 
Turbines  
Manufacturer  Brown Boveri/CEM 
Type  Multicylinder impulse reaction 
Rating (generator output)  550 MVA 
Speed  3 000 r/min 
Steam flow to HP turbine  415.7 kg/s at MCR 
HP exhaust steam flow to RH  381.3 kg/s 
Work rate of HP cylinder  33.85% or 146.2 MW 
HP cylinder blading efficiency  90.9% 
Steam flow to IP turbine  394.6 kg/s at MCR 
Work rate of IP cylinder  37.64% or 192.4 MW 
IP cylinder blading efficiency  92.2% 
Steam flow to LP 1  162.5 kg/s 
Steam flow to LP 2  159.8 kg/s 
Work rate of LP 1 & 2  28.51% or 174.7 MW 
LP cylinder efficiency  86.69% 
Total work of turbine train  513.1 MW 
Total efficiency  98.15% 
Condenser  
Type  Dualpressure surface 
Cooling principle  Conduction 
Type and number of tubes  26 000 admiralty brass 
Total tube surface area  23 520 m² 
Condenser pressure  7.7 kPa (abs) 
Condenser steam pressure  40ºC 
Condenser steam flow  280.7 kg/s 
Extraction pumps  
Motor manufacturer  GEC 
Type  3.3 kV induction 
Power output  1 500 kW 
Speed  1 488 r/min 
Pump manufacturer  Sulzer 
Type  Multistage 
First stage  Single impeller 
Delivery pressure  650 kPa 
Second stage  4 impellers 
Delivery pressure  650 kPa 
Second stage  4 impellers 
Delivery pressure  3 800 kPa 
Condensate at 25ºC  
pH  8.59 
Dissolved O₂  90150 
Oil  Not detectable µg/l 
CO₂  Not detectable µg/l 
SiO₂  5 µg/max 
Fe  3 µ/l max 
Low pressure Feed Heaters  
Bled steam temperature  No 1, 68ºC No 2, 86ºC No 3, 157ºC No 4, 245ºC 
Water inlet temperature  No 1, 40ºC

Water outlet temperature  No 1, 66ºC No 2, 84ºC No 3, 112ºC No 4, 141ºC 
Steam safety valve  No 3, 686 kPa No 4, 686 kPa 
Water safety valves  No 1 4, 4 000 kPa 
Deaerator  
Steam pressure  800 kPa 
Safety valve  1 100 kPa 
Water temperature  176ºC 
Feedwater After Deaerator  
Dissolved O₂  90150 µg/1max 
Boiler Feed Pumps (electric)  
Manufacturer  Sulzer 
Number  2 per unit 
Type  Multistage 
Discharge capacity  241 kg/s 
Discharge pressure  26.8 MPa (abs) 
Motor power output  10 000 kW 
Motor speed  1 492 r/min 
Main pump speed  6 826 r/min 
Flow rate control  Regulating valve 
PA Fans  
Manufacturer  Howden SA Fan Co 
Number  6 per unit 
Fabricated from  Boiler quality steel 
Assembly  Welded to impeller shaft 
Type  Single inlet type 
Coupling  Wellman Bibby 
Motor  3.3 kV squirrel cage induction 
Motor output  465 kW Units 13 650 kW Units 46 
Motor speed  1 486 r/min Units 1 485 r/min 
Fan delivery  150250ºC 
Fan delivery  510 kPa 
PulverisedFuel  
Number  36 per unit 
Fuel oil Burners  
Number  36 per unit 
Delivery capacity  305 kg/h 
Boilers  
Manufacturer
 Steinmuller 
Type  6 
Number Maximum  440 kg/s 
Final steam  17.2 MPa 
Final steam  516ºC 
Re heater steam  3.42 MPa 
Re heater steam
 516ºC 
Height (roof to  71.3 m 
Width at burner  23.5 m 
Depth at burner  14.17 m 
Boiler expansion  300 mm 
Boiler water  168 300 kg 
Furnace volume  ±10 856 m³ 
Total heating  67 639 m² 
Boiler  
Manaufacturer  KSB 
Number  1 per boiler 
Type  Wet winding 
Rated capacity  200 kg/s 
Power  850 kW 
Speed  2 950 r/min 
Voltage  3.3 kV 
Re Heaters  
Type  7 245 m², Re 3 645 m², Re 
Heat absorption  13.64 kJ/m²/s Re 26.72 kJ/m²/s Re 
Protection  4 safety valves 
Total discharge  498 kg/s 
Super heaters  
Number  3 per boiler 
Type  Convective 
Heating surfaces  4 330 m². 3 545 m² 2 700 m² 
Heat absorption  28.3 kJ/m²/s 
Protection  4 safety valves 
Total discharge capacity  440 kg/s 
Economiser  
Type  Gilled tube 
Heating surface  37 994 m² 
Heat absorption  4.6 kJ/m²s 
Air Pre heaters  
Type  Davidson regenerative 
Number  2 per boiler 
Total heating surface  65 840 m² 
Rotation speed  ±25 r/min 
Motor power  18.5 kW 
Total heat  1.85 kJ/m²s 
Precipitators  
Manufacturer  Brandt Engineering 
Type  Electrostatic, ((with SO₂ pretreatment) 
Number  2 per boiler 
Number of passes  4 
Number of fields  3 – Units 13 4 – Units 46 
Flue gas dust concentration at inlet  12.27 g/Am³ – 14.28 g/Am³ – 
Flue gas dust concentration at outlet  41.54 mg/Am³ – 17.00 mg/Am3 – 
Overall collecting efficiency  99.65% – Units 99.88% – Units 
Forced Draught Fans  
Manufacturer  Davidson & Co Ltd 
Type  Bab 92 A 
Number  2 per boiler 
Volume flow per boiler (design)  714 m³/s – Units 745 m³/s – Units 
Mass flow per boiler (design)  667 kg/s – Units 696 kg/s – Units 
Motor speed  745 r/min 
Air control method  Vane inlet control system 
Boiler Feed Pumps (turbine driven)  
Manufacturer  Sulzer 
Type  Multistage 
Number  1 per unit 
Discharge capacity  482 kg/s 
Discharge pressure  25.8 MPs (abs) 
Turbine speed  4 500 r/min at full load 
Main pump speed  Turbine speed 
Flow rate control  Turbine speed 
High pressure Feed Heaters  
6A & 6B steam safety valve  2.5 MPa 
Water inlet temperature  178ºC 
Water outlet temperature  207ºC 
Bled steam temperature  ±431ºC 
Bled steam pressure  ±1.8 MPa 
7A & 7B steam safety valve  5.0 MPa 
Water outlet temperature  240ºC 
Steam inlet temperature  297ºC 
Steam inlet pressure  3.4 MPa 
Water safety pressure for all HP heaters  25 Mpa 
Coldwater System  
Motor manufacturer  Mitsubishi 
Type  3.3 kV squirrelcage screen protected 
Rated Power  1 491 kW 
Motor poles  18 
Pump  Vertical mixed flow, centrifugal, concrete volute 
Discharge capacity  5.65 m³s 
Speed  328 r/min 
Pump power consumption  1 400 kW 
Suction branch bore at impeller  1 150 mm 
Discharge branch bore at impeller  1 500 mm 
Impeller  Stainless steel BS 3100 
Cooling Towers  
Number  4 
Type  Concrete construction natural draught 
Height  136 m 
Diameter at base ring beam  91.38 m 
Pond diameter  100 m 
Depth of pond  1.8 m 
Capacity of tower pond  12 176 m³ 
Throat diameter  58.3 m 
Diameter at the top  63.47 m 
Air inlet area  2 317 m² 
Number of vertical piles supporting shell  36 
Height of vertical piles  1.9 m 
Quantity of air at specified barometric passing through tower when cooling 9.32m³ water/s under following conditions:  
Circulating flow rate  12.3 kg/s 
Cooling range  16,719 m³/s 
Re cooled water temperature  24ºC 
Atmospheric dry bulb temperature  15.45ºC 
Atmospheric wet bulb temperature  11.05ºC 
Relative humidity  61.4% 
Mean atmospheric pressure  84.7 kPa 
Circulating Water  
pH  8.4 
Total alkalinity  120 mg/l (max) 
Hardness  400 mg/l 
Generators  
Manufacturer  CEM/BBC 
Rated capacity  555 MVA 
Terminal voltage  18 kV (50 Hz) 
Power factor  0.9 (lagging) 
Cooling medium rotor  Hydrogen at 400 kPa 
Cooling medium stator  De mineralised water 
Total efficiency of generators  98.15% 
Water and Effluent  
Total raw water consumption  150 Ml/day 
Cooling water  90 Ml/day 
Potable water production  9 Ml/day 
De mineralised water production  8.6 Ml/day 
Main Contractors  
Boilers  L&C Steinmuller (Africa) (Pty) Ltd 
Precipitators  Brandt Engineering 
Turbines  Brown Boveri/CIE, Electro Mecanique (CEM) 
Generator transformers  ASEA Electric (SA) Ltd 
Cooling towers  Monohan & Frost 
Cooling water pumps and boiler feed pumps  Sulzer Bros (SA) Ltd 
Chimneys  Monohan & Frost 
Cabling and switchgear  Hubert Davies Construction (Pty) Ltd 
Instrumentation and control  Siemens AG c/o 
Process computers  Leeds & Northrup 
Low pressure services  Stewarts & Lloyds Ltd 
Fire control system  Mather & Platt (SA) (Pty) Ltd 
Coal and ash conveyors  Spencer (Melksham) SA (Pty) Ltd 
Water treatment plant  D H Harris Ltd 
Coal silos and civil works  CMGM Glybeton & Monasiebou 