ROUND THE CORNER · The measured Gas outlet temperature is to corrected for measured flows,...
Transcript of ROUND THE CORNER · The measured Gas outlet temperature is to corrected for measured flows,...
Frequently Asked Questions
FAQ
Presented by:
V.Rajagopal
GEECO, Trichy, India
The measured Gas outlet temperature is to corrected for measured flows, temperatures and leakage and then compare with guaranteed Tgo.
Whether the measured gas outlet temp. is to be compared with guaranteed Tgo?
More Gas inlet flow
Less Leakage
High Gas inlet temperature
Less Air inlet Flow
High Air inlet temperature
Less X-Ratio
Gas outlet temperature will be more with
Gas Side efficiency.
X Ratio
Air Side efficiency.
What are the parameters to be monitored for checking the efficiency of Air Preheater?
(Tgi-Tgo Unc)
Gas Side Efficiency = --------------------
(Tgi-Tai)
(Tao-Tai)
Air Side Efficiency = ---------------
(Tgi-Tai)
W
ao x C
pa (T
gi-T
go Unc
) Gas Side Efficiency
X - Ratio = --------------- = ----------------------- = -------------------------------
Wgi x C
pg (T
ao-T
ai) Air Side Efficiency
Is it Possible to replace existing APH
to Higher size (Maxtra)?
It is possible in most of the cases
What is the grid size for accurately measuring the gas and air temperatures?
Complete mixing is expected after 6 to 8 times length of hydraulic diameter.
Hydraulic Diameter,
for rectangular duct
= 2ab/(a+b)
What is the approximate length of gas outlet duct for complete mixing of gas to get uniform
temperature?
b
a
Usage of 4 Bisector air preheaters in place of 2 Trisector air preheaters?
Using 4 bi-sector air preheaters ( 2 for Py. and 2 for Sy.) is useful for better efficiency, since gas qty. to Py. can be controlled by the damper.
Total leakage will be more in 4 bisector than with
2 tri-sectors
Layout is complicated with 4 bisectors
Capital investment is more in 4 bisectors
Maintenance is easier with 2 trisector
What is the effect of increasing the height of air preheater
It will increase the heat transfer area.
Improved efficiency.
It will increase the pressure drop.
What is the effect of increasing the diameter of air preheater
It will increase the heat transfer area.
Improved efficiency.
It will decrease the pressure drop.
No
Providing sacrificing basket will reduce the performance of Air Preheater
Using lesser thickness will increase the heat transfer area.
- Will slightly decrease pressure drop
Recommended:
Sacrificing element: 0.8/0.6mm
Hot End: 0.5mm, instead of 0.6/0.8mm
Hot Intermediate: 0.5mm , instead of 0.6/0.8mm
Cold End: 0.8mm , instead of 1.2/1.0 mm
Can we use Lesser thickness for elements ?
Element manufacturing has to go with
accuracy.
Always go with reputed manufacturers.
By accepting profiles from un reputed
manufacturers, money is not gained; money
is lost by the way of loosing efficiency.
Is any method of element manufacturing acceptable?
If the element profiles are manufactured
within the tolerance, then Gas out temp. will
not vary more than ± 3°C
What is the formula for calculating leakage?
%ge Leakage = -----------------------------
%ge Leakage = -------------------------------------------------------
For, O2 out = 5.0%, O
2 in = 3.5% Leakage = 8.44%
%ge Leakage = -------------------------------------------------------------
%ge CO2 out
For, CO2 out = 13.8%, CO2 in = 15.8% Leakage = 13%
(Gas Out – Gas In)
Gas In
0.9*(%ge O2 out %ge O
2 in)*100
(21 -- %ge O2
out)
0.9*(%ge CO2 in - %ge CO2 out)*100
%ge Leak
6 8 10 12 14 16 18 22 26
Tgo, ⁰ C
147 145 143 141 139 138 136 133 130
What is the effect of Leakage on Gas outlet temperature?
The leakage is reduced by at least 2.0%.
eg: from 8.5% to 6.5%
What is the effect of Double sealing?
The distance between soot blower nozzle
tip to element surface should be 300mm
What should be the distance between soot blower nozzle tip to element surface?
Deposit of unburnt Carbon particles in Air
Preheater elements leads to fire.
Causes:
• Inadequate atomization of oil
• Improper combustion
• Ignitor leak
• Fire occurrence is more during startup with
oil firing. Frequent soot blowing is required
during startup.
Why fire occurs?
Thermocouple fire detection works reliably better
compared to IRDS. Response is slower than IRDS. Less
cost.
IRDS is highly sensitive. It detects fire even before the
start of the fire itself. That is why, it is called ‘Hot Spot
Detector’. Making the system to work continuously is
difficult. More costlier.
Fire Sensing Device: Thermocouple type or Infra Red (IRDS)?
DC Motor
AC Motor
Small Steam Turbine
Other than air motor any other drive is used as auxiliary drive?
Yes. No Problem.
Whether Electric Motor and Auxiliary Drive can run simultaneously?
Run the air motor once in a week for 30
minutes to keep fit for running during
emergency. During running ensure the flow of
lubricating oil 6 – 7 drops per min.
Keep moisture trap in air line.
Air Motor does not come up during emergency?
Yes.
Whether drive pinion can be reversed?
Support brg is designed to have the L1 life of
100,000 hrs. or 13 years of operation. That
means the chance for failure within this period
is 1%
Usage of lower size brgs. will reduce the life
of brgs.
What is the life of support brg.?
Thank You