Download - 03.Economiser Drum
BOILER PRESSURE PARTS
• COMPONENTS OF BOILER THROUGH WHICH FEED WATER AND STEAM FLOW AND HEAT IS ADDED
• COMPONENT HEAT ADDITIONECONOMISER 6%DRUM NILWATERWALL 50%SUPER HEATER 30% RE HEATER 14%
BOILER PRESSURE PARTS LOCATION
ECONOMISER
• PRE HEATS THE FEED WATER ENTERING THE BOILER BY USING HEAT IN OUT GOING FLUE GASES– IMPROVES BOILER EFFICIENCY– REDUCE BOILER SIZE
ECONOMISER TYPES
PLAI N TU BE FI N N ED TU BE
TU BE DESI G N
N O N STEAM I N G STEAM I N G
H EAT ADDI TI O N
I N LI N E STAG G ER ED
AR R AN G EM EN T
ECO N O M I SER
COMPARISON OF ECONOMISER TYPES
• PLAIN TUBE– EASY ON LOAD
CLEANING
• FINNED TUBE– MORE HEAT
TRANSFER AREA IN GIVEN VOLUME
– ON LOAD CLEANING DIFFICULT
Direction of Gas Flow Direction of Gas Flow
Inline Arrangement Staggered Arrangement
COMPARISON OF ECONOMISER TYPES
• STAGGERED– HIGH HEAT
TRANSFER RATE DUE TO INCREASED TURBULANCE
– ON LOAD CLEANING DIFFICULT
• INLINE– EASY ON LOAD
CLEANING
ECONOMISER DESIGN CONSIDERATIONS
• OVERALL HEAT TRANSFER AREA OF ECONOMISER DEPENDS ON– FEED WATER INLET TEMPERATURE– SATURATION TEMP.
CORRESPONDING TO OPERATING PRESSURE
– FEED WATER FLOW RATE– GAS TEMP. REQUIRED AT THE
OUTLET OF ECONOMISER
ECONOMISER DESIGN CONSIDERATIONS
• TUBE DIAMETER, LENGTH AND SPACING ARE DECIDED TO ENSURE– UNIFORM WATER FLOW THROUGH
ALL TUBES WITH LOW RESISTANCE– ECONOMISER FITIN WITH THE
DESIGN OF PRCEDING SECTION – DRAUGHT LOSS IS MINIMUM– PROVISON FOR ON LOAD
CLEANING DEVICE
LOCATION OF ECONOMISER IN A TWO PASS BOILER
ECONOMISER COIL INSIDE BOILER
ECONOMISER TUBE FAILURE
• OVER HEATING– STARVATION– SCALING
• CORROSION– INTERNAL– EXTERNAL
• EROSION
ECONOMISER RE CIRCULATION
DRUM CONSTRUCTION
FUNCTIONS OF BOILER DRUM
• TO SEPARATE WATER AND STEAM FROM WATER STEAM MIXTURE
• MIX WATER SEPARATED WITH WATER FROM ECONOMISER AND FEED TO DOWNCOMERS
• TO FACILITATE CHEMICAL DOZING
• TO FACILITATE BLOWDOWN
DRUM CONNECTIONS
STEAM SEPARATION IN DRUM
• GRAVITY SEPARATION– ADOPTED FOR
LOW PRESSURES
– USE BAFFLES TO CHANGE DIRECTION OF FLOW TO SEPARATE WATER BY GRAVITY
• CENTRIFUGAL AND GRAVITY SEPARATION– ADOPTED FOR
HIGH PRESSURES
– USE TURBO SEPARATORS OR CYCLONE SEPARATORS TO IMPART CENTRIFUGAL FORCES
GRAVITY SEPARATION USING BAFFLES
STEAM SEPARATION USING CYCLONE SEPARATORS
AUXILIARY CONNECTIONS TO THE BOILER DRUM
• CHEMICAL DOZING NOZZLE• BLOWDOWN NOZZLE• FOR THE MEASUREMENT OF
PRESSURE AND TEMPERATURE• WATER LEVEL INDICATORS• SAFETY VALVES AND AIR
VENTS
TAPPINGS FOR VARIOUS MEASUREMENTS ON THE DRUM
• THREE PAIRS FOR REMOTE LEVEL INDICATORS
• TWO PAIRS FOR LOCAL LEVEL GAUGES• TWO PAIRS FOR CONDUCTIVITY
MEASUREMENT• TWO PAIRS FOR PRESSURE
MEASUREMENT• THREE PAIRS OF THERMAL PADS FOR
MEASURING DRUM METAL TEMPERATURE
• ONE PAIR FOR HIGH LEVEL AND LOW LEVEL TRIPS
EFFECTS OF DRUM LEVEL VARIATIONS
• LOW LEVEL– STARVAION AND ULTIMATE
FAILURE OF WATERWALL TUBES
EFFECTS OF DRUM LEVEL VARIATIONS
• HIGH LEVEL– AFFECTS STEAM SEPARATION– CARRY OVER OF WATER BY STEAM
• SUPER HEATERS THERMALLY STRESSED
• SCALING IN SUPER HEATERS– OVER HEATING OF SUPER HEATERS
• WATER HAMMERING IN STEAM PIPES• PITTING ON TURBINE BLADES
AIR VENT AND SAFETY VALVES