Case study-Rihand-1

EQUIPMENTS/ SYSTEMS – INSTALLED FOR RIHAND - STAGE-II.

STEAM GENERATORS :
Two combustion engineering design BHEL steam generators are of
controlled circulation single reheat, balanced draft with fusion welded
war wall panel units having a primary steam flow 1675 tonnes/hour,
Super heater out let pressure is 179 kg/ sq-cm at a temp. of 540°C
with an inlet feed water temp of 254°C .
The reheat steam flow of 1394 TPH will be raised to an outlet temp. of
540 from inlet condition of 45.8 Kg/sqcm and 336°C .
The furnace is having overall dimension width 19.177 meter and depth
15.797 meter and height 62 meter effective and the furnace walls are
fusion welded panel are large in size to minimize erection weld at site.
Each unit is having one steam drum and connected to that down take
system are suspended. There are six down takes evenly spaced along
the drum length connected to suction manifold & 3 submerged motor
boiler water circulation pumps with two outlet each forms the
circulation system.
Super Heater, Reheater and Economizer :
The super heater consist furnace roof tubes to the rear of the unit
where it cools walls of rear pass. The steam from here enters into 3
loop pendent low temp. super-heater located above economizer., with
spray facility at the out let before entering divisional panel and finally
to super heater.
The Re-heater is one stage: located in between divisional panel and
super heater exit panel.
Furnace wall is having 88-wall blower and 32 Nos. of long retract for
plates, re-heater & convective super heater heating surfaces.
TURBO-GENERATOR:
Two turbo generators of BHEL HARIDWAR Make (KWU Design) is
tandem compounds 3 cylinder machine with single flow HPT & double
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flow IPT & LPT with 6 extractions inclusive of feed water heating and
steam to feed pump drive turbine.
Each generator is water-cooled stator & hydrogen cooled rotor rated
588 KWA at 21KV with 0.85 power factor with short circuit ratio of 0.5.
Generator is having alkaliser, end winding vibration monitor, partial
discharge monitoring etc.
Excitation is direct shaft driven.
FUEL - COAL, HFO & LDO:
The primary fuel is Bitumen coal from SLC (LT) Amlori mines of NCL.
Transportation of coal is through MGR system constructed for stage-I,
with provision of doubling of track.
The coal handling plant (CHP) for stage-II is constructed by BHEL ISG
Bangalore. With a separate railway siding to track hopper (RCC)
receives coal from hopper & convey to crusher House with transfer
points (six) through conveyor reaches the silo/bunker of mills with by
pass facility for diverting the crushed coal excess of the requirement to
coal storage area. The capacity of plant is 2200 TPH with 100% stand
by, with 16 hours spread operation.
Stacked/re-claimer facility is also provided for feeding coal from coal
yard to conveying the coal to steam generator.
HFO fuel oil storage is common for with stage-I & II constructed during
stage-I. The pump house for forwarding is separate for stage –2 and
common for both 3&4 units. BHEL (Agency – M/s Techno Fab Pvt Ltd)
has constructed the LDO unloading facility for stage-II, required for
the start-up of the boiler.
ELECTRICAL SYSTEM:
The electrical transmission from the plant is by 400 KV from
Transformer (21 KV from Gen side). Each unit is having three single
phase Transformers with an individual rating of 214MVA, 21/400 KV,
cooled with off load tap changer.
AUXILIARY ELECTRICAL SYSTEMS:
The Aux. Electrical system for each unit is served with connected Unit
Transformer of 21KV/11KV - 45MVA with 2 nos Unit Auxiliary
Transformer 11KV/3.3KV – 16MVA. In addition to this, one no station
transformer & station auxiliary transformer (start up) for each unit,
having rating 80/40/40MVA-132/11/11KV & 16MVA – 11/3.3KV, are
installed with interconnection facility. One no colony service
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transformer of rating 12.5MVA – 132/11KV is installed in 132KV switch
yard. All these transformer are supplied by BHEL – Bhopal/ Jhansi.
The LT supply arrangements are as under:
Dry type service transformer 2000KVA-3.3KV/433V – 2 nos per
unit.
Dry type station service transformer 2000KVA-3.3KV/433V – 2
nos per unit.
Oil filled fire water pump house service transformer 2000KVA –
3.3KV/433V – 2 nos.
Oil filled fire water pump house service transformer 2000KVA –
3.3KV/433V – 2 nos.
Oil filled off site service transformer 2000KVA – 3.3KV/433V – 2
nos.
Oil filled ESP service transformer 1600KVA- 3.3KV/433V – 8 nos
per unit.
The MD-BFP, ID, CW, PA, FD and CEP motors, rated above 1500KW
are fed by 11KV. The mills, ECW, ACW, compressor & make-up/ raw
water motors rated above 200 KW to 1500KW are fed by 3.3KV & up
to 200 KW by 415V systems.
The each unit emergency is fed by 1200 KW DG set with one spare
common DG set.
D.C System: (Supplied by M/s HBL Nife through BHEL) 220V – 2 Nos.
with float a boost charger to supply DC emergency pumps, scanner air
fan & some selected service for 30 minutes duration.
PLANT AUXILIARY SYSTEMS:
The regenerative feed water heating system design is conventional
one. Six stages of feed water heating comprises of 3 LP heaters,
Dearator, and two high pressure heater. The LP heater & HP
heaters is tubed with SS tube material of SA688 TP 304 specification.
3x50 percent capacity condensate extraction pumps are driven by 11
KV motor. One 50% Boiler Feed pump is motor driven for start up
purpose & other 2 x 50 % Boiler capacity are turbine driven feed
pump. The feed pump turbine exhaust is connected to main turbine
condenser.
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ASH HANDLING SYSTEM : (Supplied by M/s Burn & Standard)
Boiler bottom Ash extracted in wet form & disposed off in wet form.
The fly ash is extracted in dry form from ESP to be taken to hopper for
onward transportation to ash silo in dry form or slurred in wetting
units for ultimate disposed in wet form to ash disposal area (ASH
DYKE).
The bottom ash & fly ash slurry are led into common slurry sump for
further disposal to ash disposal areas through pumps & piping work.
WATER SUPPLY & COOLING WATER SYSTEM:
Water supply for the plant is from the Rihand reservoirs and make up
water is drawn from two locations - from stage-I CW pumping system
water for DM water requirement and potable water system & make up
water requirement for CW system is drawn from stage-I CW discharge
channel, which also serves other miscellaneous requirements of ash
handling/AC & ventilation etc.
M/s PAHARPUR supplied Re-circulating & Forced draft type cooling
towers are installed for stage – II, unlike open channel for stage-I.
3x50% capacity clarified water pumps using discharge water drawn
from clarified water storage tank, through bar screen & trash rack.
The total water requirement is 60,000 m³/hour. Five numbers of half
capacity (two for each with a common standby) concrete volute
vertical pit turbine type (30400 m³/hour) pumps of M/s KBL make with
BHEL Bhopal make vertical motors are installed in CW pump house.
Single M.S. pipe of 3600mm diameter pipe carries the water from the
fore bay to plant & back to the fore bay through cooling towers.
Aux. Cooling:
For the auxiliary cooling water system, the water is drawn from CW
inlet pipe before condenser & 3x50% capacity pump will take suction
and discharge to the CW outlet at the CW out let pipe near condenser
through 2x100% capacity & 3x50% capacity plate heat exchangers of
boiler side cooling water & turbine side cooling water cooler
respectively, removing the heat of closed water DM cooling water
system of boiler common auxiliaries & turbine, generator auxiliaries.
The vacuum pump coolers are directly cooled by CW water.
The equipment cooling water is DM water closed with NaOH, is
separate overhead tank and pumping arrangement with piping to
different coolers & back to pump suction.
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2x100% capacity pumps are used for boiler side + compressor &
3x50% capacity pumps serves turbine side equipment cooling
requirement.
COMPRESSED AIR SYSTEM: (Supplied by M/s Atlas Copco through
BHEL)
The compressor air system is common for both the plants. 5
numbers of rotary screw type compressors - 3 for service air and 2 for
instrument air serves the plant requirement with a provision for
connection to stage-I.
The plant and instrument air piping at the out let of the compressor is
having facility for interconnection and the regenerative drier 2 nos is
provided with all peripherals like tank etc.
FIRE PROTECTION SYSTEM : (Supplied by M/s Wormald through
BHEL)
A comprehensive fire detection system like (infrared quratzoid bulb,
linear heat sensing cable, photoelectric type heat sensors and
protection system like high, medium velocity water spray, Hydrant
water monitor, foam system inergene system, fire extinguisher to be
actuated through sensors/manual actuation facility protects against
fire. Other associated system like pumps, tanks, booster form part of
the fire protection system.
AIR CONDITIONING & VENTILATION SYSTEM:
(Supplied by M/s ABB through BHEL)
The system comprises of central chilled water type of 2x50 vapor
absorption machine (both working) and 2x50% screw chiller normal
standby mode for main plant control room, UPS & SWAS room, ESP-
VFD control room of unit 3 &4 air-conditioning requirement. The
subsystems associated with this are cooling water system including
cooling towers & make up water system, chilled water system with
make up provision form expansion tank, air handling units at 11
different locations with fans and air flow control devise. All the controls
and operation are PLC based with hook up with main control room PLC.
Service building air conditioning requirement is met with two screw
chillers with all the peripherals as enumerated for the main plant.
BALANCE OF PLANT - Split air condition units of different capacity
serve balance of plant control room air conditioning requirement.
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THE VENTILATION SYSTEM is separate for each unit. The B-C bay
ventilation unit located at 24 meter elevation & A row at 8.5 meter
elevation serves the TG hall, MCC, switch gear room, etc. Other offside
plant and other buildings, which are not connected with main
ventilation system, are provided with ventilation fans of adequate
numbers.
AUXILIARY HEATING:
From the stage-I, steam is drawn for supply of steam for unit start up,
for serves like fuel oil heating/steam tracing, steam coil air pre heater,
vapour absorption machine, flue gas conditioning skid etc.
WATER CONDITION & QUALITY CONTROL:
The conditioning of cycle make up water is common for both units. All
other water treatment, conditioning & monitoring is separate for each
unit.
The DM plant of 100 m³/hour is of six-bed concept, supplied by M/s
Ion Exchange.
The steam generator-turbine-condenser cycle is controlled in a fashion
normal for a drum type of boiler. These include volatile chemicals for
feed water corrosion reduction such as ammonia & hydrazine and
utilize the coordinated phosphate method of control for boiler water.
The condensate polishing re-generation (CPU) is common for
both units supplied by M/s DRIPLEX through BHEL. A powdered-resin
condensate polishing system capable of handling full load condensate
with its two filters polished with by pass facility.
CW basin is provided with shock chlorination for algae control.
The equipment cooling water system will be closed with sodium
hydroxide.
A centralized water quality monitoring system receive sample from
through out the plant as well as grab sample analysis facility ensures
the plant water regime.
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CONTROL & PLANT MONITORING:
Microprocessor controller EDN MAX DNA boiler turbine controls &
protection is DDCMIS. The coordinated system is providing control
unit generation on a feed forward basis. The controls provide for
automatic operation either the constant pressure or sliding pressure
mode. Also included in the system is automatic control of super
heater by passing the steam in HP/LP by-pass system for matching the
steam temperature with the turbine metal temperature during hot
start and initial start up etc.
The system is very extensive and includes:
Generation of operating information
Generation of historical records
Control of electrical system
Large video screens
Man machine interface
Alarm system & analysis
Digital display analogue trends & dynamic graphics
Vibration monitoring system.
All the balance of plant controls are PLC based supplied by GE-FANUC
with a battery back up of HBL-Nife.
PUBLIC ADDRESS SYSTEM: (Supplied by M/s Bytes Communication
through BHEL)
A distributed amplifier based public address system is provided for
communication within the plant through hand set stations distributed
throughout the plant to ensure proper communication.
ENVIRONMENTAL ASPECTS:
Water Pollution: Since the CW system is re-circulation type there is
no significant thermal pollution.
The CW blow down water used for coal dust suppression & extraction
system & service water system is of re-circulation type.
Ash water re-circulation system is provided with adequate treatment
facilities.
Oil water separator is provided to separate the oil and the water from
the bottom would be recycled.
All the effluent (from DM plant, CPU regeneration plant, plant
drainage, oil water separator is treated at Effluent treatment plant
(supplied by M/s DRIPLEX through BHEL) before discharging to Rihand
reservoir.
Oil & Chemicals: The fuel oil, lubricant and chemicals are controlled
by containment. Chemicals like Hydrochloric acid, sodium hydroxide,
sulphur is stored in vessels with lined concrete containment.
Air Pollution:
1. In an effort, to minimize the environment impact of NTPC Rihand
stage-II, High efficiency ESP is provided with Flue gas
conditioning system (Installed first time in INDIA by M/s
Bahmann India Ltd under technical collaboration with M/s
Wahlco USA through BHEL) with Sulphur tri oxide injection to
reduce the resistibility of ash & increase collection at the plate
and SOX reduction.
2. Chimney height is 275 meter will disperse hot flue gas to
atmosphere with stack emission monitor.
Solid water waste management :
Fly ash & bottom ash - It is disposed in a separate ash dyke
(Constructed by M/s HSCL) impoundments to be reclaimed through
tree plantation after abandonment. Also fly ash collected as dry is used
for making bricks & filling of earth in the plant, township and nearby
areas.
The mill rejects from each pulverizer is sluiced individually to the
bunker (pneumatic transportation) and periodically collected and
hauled to the allotted location. The Mill Reject System is installed by
M/s Macabber Bekay through BHEL.
NOX Control:
The tangential fuel firing system, which promote large amount of
essentially horizontal re-circulation of gases in the furnace, this
completed with slow mixing of fuel air, provides for combustion, that is
inherently low in NOX reduction. The over fire air design and two
stage air admission reduce the NOX production.