13. Accurate unit heat rate
• The obstacles to calculating an accurate heat rate for a coal-fired
unit using this method are:
• The difficulty in accurately assessing the quantity of coal
• The inaccuracies of the as-received coal
• Uncertainty associated with measurements made over long periods of
time.
• The use of an average heating value for a fuel whose heating value
may vary widely with different fuel suppliers.
Tuesday, 8 December 15 Fußzeilentext 13
16. Boiler losses
• Fouling of Boiler heating surfaces: Affects heat transfer
• Air ingress: Disturbs furnace draft,flue gas velocities,dilutes
combustion
• High levels of unburnts in Ash: inefficient combustion,loss
of fuel value
• Poor coal calorific value: high fuel requirement, huge waste
handling
• Improper combustion: metal temperature excursions,
secondary fires
• Boiler scales: Internal tube scales affects Heat transfer,
leads to tube fails
• Sub optimized equipment operation: Equipment operation
below design
• Poor design: inadequate margins, quality of material,
resistance paths
• Poor insulation: heat radiation loss
• High pressure drops: heavy load on draft system leading to
increased power
nology 88 (2007) 1035–1043
20. Seal leaks and erosion in APH
of the flue gas entering and leaving
ater .
culated leakage includes leakages through
flexible seals are also d
across bypass seals.
High flue gas velocity on
erosion of heating el
Comparatively less erosio
baskets. Non-uniform dis
APH from economizer is
ash from economizer
regularly, heap of ash f
heaps not only affect flue
over to APH causing eros
of gas also causes erosio
bypass seals and rear side
)9.20(
)(*100
2
22
outO
inOoutO
Leakages
udes leakages through
nd sides together and is
low.. Flue gas leakage
counted for.O2 content
s air heater totally and
rring heat to heating
ream, which result in
at outlet and increased
cipitators. Similarly air
ng heated reducing air
occurred reduces boiler
high as 15 to 20 percent.
n while setting bypass
heaps not only affect flue gas distribution but also spi
over to APH causing erosion. Non uniform distributio
of gas also causes erosion of ‘T’ bars, rotor angl
bypass seals and rear side duct plates from economize
to APH along with expansion joints.
Erosion pattern
on out board
side of APH
29. Improvements in Power Plant Efficiency
• There are a number of specific improvements in power for example:
• Cleaning tubes and boilers
• maintaining instrumentation
• restoring seals
• removing deposits on turbine blades
• condenser maintenance programs
• decreasing excess oxygen to the boiler
• Instaling variable speed drives for motors
• waste heat utilization for feed water heating
• Installing a online performance diagnostic software
Tuesday, 8 December 15 Fußzeilentext 29