design challenges in low flue gas...
TRANSCRIPT
INTRODUCTION
Edward Green (1799-1865)
•Inventor of fuel economisers
•Founded in Wakefield, UK, 1833
•Patented fuel economiser in 1845
•More than 180 years heritage
1515
15
30 30
15 155 510
2020
30 30
10
20 20
35
20
30
30
20
35
35 35
35
3 0
20
20
30
35
G AS F LO W Research & Development Fins placed in areas of highest heat transfer. Fin weld on sides of tube where maximum heat transfer takes place. Fin material not placed where dust can accumulate above and below the tube. Fin sizes optimised for efficient use of material.
GREENS STEEL H DESIGN
Weld
Current
Forge
Pressure
• Fins are held in the correct position by Jaws. • Current and forge pressure is applied to weld fins to tube. • Tube is precisely indexed forward for next fin weld.
GREENS STEEL H PRODUCTION
STEEL H PRODUCTION
Weld
Current
Forge
Pressure
OBJECTIVES OF GHE
• To reduce the exhaust gas temperature from 160 ~ 170 Deg C to
about 110 ~ 120 Deg C.
• While a Desulphurisation / Denitrification equipment are considered,
the GHE shall assist to reduce the inlet gas temperature thereby
reducing the water consumption.
• Similarly to reduce the inlet gas temperature for the next generation
ESP’s.
APPLICATION
The GHE used for recovering waste heat and the useful
recovered heat can be used for following
1. To produce chilled water in vapour absorption machine to be
used in air conditioning
2. To produce flash steam for Desalination
3. Increase feed water temperature at economiser inlet
4. In parallel to LP heater
1. PRODUCE CHILLED WATER IN VAM
Project: NTPC Ramagundam (1 x 500 MW)
Project Details: Waste heat recovery system is designed to
recover 500 kW of thermal heat from flue gases to produce 100
tons of refrigeration.
150°C 110°C
FAN
STACK ID FAN
HEAT
EXCHANGER ESP, CCR
Flue Gas
Hot Water
Chilled Water
95°C
85°C 7°C
Hot Water Chilled
Water
Flue Gas
FLOW DIAGRAM
PERFORMANCE DATA UNIT PROPOSED GHE
FLUE GAS TEMPERATURE
HEAT EXCHANGER INLET °C 152 HEAT EXCHANGER OUTLET °C 110
FLUE GAS FLOW RATE KG/H 40,250 NM3/HR 30,746
APPROXIMATE RADIATION LOSS % 2.0 FLUE GAS COMPOSITION V / V CARBON DIOXIDE % 12.2 WATER VAPOUR % 8 TO 11 (9.5) NITROGEN % 71.2 OXYGEN % 7.0 SOX MG/NM3 1520 NOX MG/NM3 472 SPM MG/NM3 151 FLUE GAS VELOCITY HEAT EXCHANGER, AVG M/S 8.52
GAS DRAFT LOSS (OVER HEATING SURFACE ONLY)
MM WG 35
WATER FLOW RATE TONS/HR 42.5 HOT WATER PRESSURE LOSS (FRICTION ONLY)
KG/CM2 1.0
WATER TEMPERATURE HEAT EXCHANGER INLET °C 85
HEAT EXCHANGER OUTLET °C 95
SALIENT FEATURES
• Air Conditioning using Waste heat of flue gas instead of using
Electricity or Auxiliary steam.
• Reduction in Auxiliary power of 0.4 MU/yr for Ramagundam STPS.
• Green House Gas (CFC & HCFC) free thermally driven 100 TR VAM
based AC system.
• Reduction in CO2 emission is 320 T/yr for Ramagundam Super
Thermal Power Station
• Potential of scale up to meet entire Air-Conditioning requirement
using waste heat from flue gas at power plants
STEEL H VS PLAIN TUBE
Sr.
No.
Parameters NTPC Ramagundam
STEEL H PLAIN
1 Tubes wide 13 15
2 Tubes High 28 58
3 Space required LxWxH 3 X 1.5 X 3.7 3 X 1.4 X 7.4
4 Total Tube Used (m) 800 1914
5 Heat Transfer Area m2 467 229
6 Weight (Tons) 11.3 15.1
7 Air Blasters, Nos. 4 8
8 Draft loss mmwc 65 90
STEEL H VS PLAIN TUBE
Sr.
No.
Parameters NTPC Talchar
STEEL H PLAIN
1 Tubes wide 25 30
2 Tubes High 24 60
3 Space required LxWxH 4.75 X 2.75 X 3.5
5 X 2.6 X 8.3
4 Total Tube Used (m) 2250 7200
5 Heat Transfer Area m2 1527 861
6 Weight (Tons) 29.4 43
7 Air Blasters, Nos. 4 12
8 Draft loss mmwc 65 100
2. PRODUCE FLASH STEAM FOR DESALINATION
Project: NTPC Simhadri.
Project Details: Waste heat recovery system is designed to
recover 795 kW of thermal heat from flue gases to produce 5 TPH
of net distillate at less than 5 ppm from 45000 ppm cooling tower
blow down water (using 1 TPH, 0.34 bar (a) saturated steam) using
Multi-effect Distillation System.
Main
Flue gas duct of power
plant
Flue gas from power plant @
125 0C
Flue gas to chimney @ 125 0C
Flue gas
heat
exchanger Flash
chamb
er
Multi effect
desalination
Cooling tower
blow down water
45000 ppm –
60000 ppm
Distillate
at < 5
ppm
Brine
reject
EDI Boiler make
up water
at < 0.05
ppm
< 0.5 % of total flue gas
@ 125 0C
ID fan
Flue gas back to
main duct at 100 0C
PERFORMANCE DATA UNIT PROPOSED GHE
FLUE GAS TEMPERATURE
HEAT EXCHANGER INLET °C 125 HEAT EXCHANGER OUTLET °C 100
FLUE GAS FLOW RATE KG/H 113,000 NM3/HR 86,259
APPROXIMATE RADIATION LOSS % 2.0 FLUE GAS COMPOSITION V / V CARBON DIOXIDE % 12 – 13 WATER VAPOUR % 9.5 NITROGEN % 71.2 OXYGEN % 7.0 SOX MG/NM3 1300 - 1600 NOX MG/NM3 400 – 500 SPM MG/NM3 150 FLUE GAS VELOCITY HEAT EXCHANGER, AVG M/S 9.7
GAS DRAFT LOSS (OVER HEATING SURFACE ONLY)
MM WG 40
WATER FLOW RATE TONS/HR 39 HOT WATER PRESSURE LOSS (FRICTION ONLY)
KG/CM2 1
WATER TEMPERATURE HEAT EXCHANGER INLET °C 72
HEAT EXCHANGER OUTLET °C 90
SALIENT FEATURES
• Retrieval of unused thermal energy from flue gas
• No membrane replacement in the RO desalination plant
• High product water 11 quality of < 2 ppm from Multi-effect
Distillation
• Possible to use power plant cooling tower blow down as source
water for desalination
• No chemical handling
• Possibility of 100 % availability
• Reduction in DM plant operating cost
• Electrical energy consumption of 1.5 kWh /m3 for desalination plant
STEEL H VS PLAIN TUBE
Sr.
No.
Parameters
NTPC SIMHADRI
STEEL H PLAIN
1 Tubes wide 22 24
2 Tubes High 18 54
3 Space required LxWxH 3.5 X 2.5 X 2.7 3.5 X 2.1 X 6.9
4 Total Tube Used 1089 3564
5 Heat Transfer Area m2 714 426
6 Weight (Tons) Ton 15.5 24.3
7 Air Blasters, Nos. 4 8
8 Draft loss mmwc 65 85
3. FEED WATER HEATING
Project: Reduction in backend temperature by recovering heat
before ESP at Hindalco Renukoot. (70 MW COEGN PLANT).
Project Details: It is economiser retrofit project for improving heat
recovery in existing plant. Heat duty of economiser increased from
2MW to 4.7MW. Feed water temperature in economiser increased
from 117°C to 135°C. Flue gas temperature at economiser outlet
decreased from 174°C to 140°C.
4. IN PARALLEL TO LP HEATER
The GHE is used to heat the condensate return and act in parallel to
LP Heaters, thereby reducing the steam consumption. The steam
thus saved is used to generate additional incremental power.
FREQUENTLY ASKED QUESTIONS
1. What is the lowest temperature possible at the outlet
with carbon steel?
The outlet gas temperature is determined by sulphur
content in coal, acid dew point etc.
Generally the target outlet temperature is 110 - 120
DegC. The operation temperature of heating tubes shall
be taken care with respect to acid dew point. In some
cases heating tubes shall use Corten Steel either fully or
partly.
2. Is the system installed in main duct or slip
stream?
What is the largest size in service for this
application?
Usually the system installed in main duct. Depending
upon the layout it can be installed on a bypass also. At
present the largest, LT Econmiser is in operation on a
600 MW unit, in China in main duct.
3. What is the effect on ID fan loading due to
GHE’s placed in the flue gas path?
• If LT Economiser is installed before ID fan, the flue gas
impact on ID fan is:
Flue gas temperature--------lower
Flue gas volume----------less
Draft loss of flue gas----------larger
The new operation point shall be checked on ID fan
performance curve.
• If LT Economiser is installed after ID fan, flue gas
volume will not change and draft loss will become larger.
Use of ID fan’s existing head margin to kill the additional
draft loss caused by LT Economiser is recommended.
4. For the improvements done in GHE to increase the heat
duty, how much is increase in ID fan loading / system
resistance in the flue gas path?
The increase of ID fan loading will vary on case to case
basis. It is determined by GHE parameters and ID fan
parameters. The below table provides a reference
Item Description Unit 600 MW 450 MW 300 MW
GHE Thermal Duty KW 22205 17622 9824
Increase in power for ID KW 393 156 65
Decrease in power for FGD KW 80 52 24
5. What is Heat Transfer Area / Pressure Drop (in
GHE / associated duct), space requirement,
overall size of installations?
Heat transfer area is determined by project requirement.
If the project wants to generate large quantity water and
recover more flue gas waste heat, a large heating area is
needed. Space and draft loss impact each other. If there
is a large space left to install GHE, the gas velocity
through economiser can be low, and the draft loss can
be low. On the other hand, if the space is very little, the
unit is designed very compact, and draft loss will be high.
If the space is a constraint, the allowable draft loss will
be very low and use of elliptical tube is recommended.
Case
Stu
dy 1
GREENS STEEL H CASE STUDY
CASE SUMMARY
IHI in Japan had an existing coal fired boiler that was under performing. IHI failed to meet customer guarantees. It was decided that if it was possible to
improve the economiser performance the overall boiler efficiency would be increased
The problem was there was no additional space to add extra heating surface in the chamber so Greens
supplied a Steel H Retrofit Economiser
GREENS STEEL H CASE STUDY
Section of Plain Tube Economiser
Section of Steel H Economiser
Case
Stu
dy 1
GREENS STEEL H CASE STUDY
DETAILS PLAIN TUBE STEEL H
Chamber Size 22413 wide x 5555 long x 1600 high
No. of Tubes 3232 2288
Rows 202 rows (22110mm) 202 rows (22205mm)
High 16 rows (1483mm) 11.3 rows (1100mm)
Gas Temp In oC 488.33
Gas Temp Out oC
423.23 402
Water Temp In oC
278
Water Temp Out oC
308.34 321.1
Duty KW 26672 38674
Case
Stu
dy 1
GREENS STEEL H CASE STUDY
CONCLUSION
The Steel H Unit provided a 45% increase in duty and at the
same time an effective heating surface for use in boilers with high
dust laden fuels.
RESULT
IHI placed the order for a Steel H unit with Greens
Case
Stu
dy 1
PEAT FUEL BFB BOILER WITH GREENS STEEL H ECONOMISER
GREENS STEEL H CASE STUDY Case
Stu
dy 2
Economiser
Case
Stu
dy 2
GREENS STEEL H CASE STUDY
CASE SUMMARY
ESB Ireland wanted to know how a plain steel economiser
would compare commercially and technically to a Steel H
Economiser.
The following is an extract from the presentation made by
Greens.
REQUIRED PERFORMANCE DETAILS
• 274MW Peat Fired BFB Boiler.
• Maximum gas velocity 15 m/s.
• Economiser thermal duty 30.5MW
• Chamber Size 6100mm wide x 10700mm long.
• 643 tonnes/hr gas in at 422°C out 283 °C.
• 336 tonnes/hr water in at 258°C and 174.5 bar.
Case
Stu
dy 2
GREENS STEEL H CASE STUDY
P l a i n T u b e S t e e l ‘ H ’
Tube OD, mm Tube Effective Length, mm Tube pitch, h x v, mm Rows wide Rows High Total economiser height, m
42.4
9,000
90 x 90
56
124
16.600
38.1
9,400
79 x 79
70
36
4.685
ARRANGEMENT
STEEL ‘H’
v PLAIN TUBE
GREENS STEEL H CASE STUDY Case
Stu
dy 2
P l a i n T u b e S t e e l ‘ H ’
Fin Pitch, mm Total tube used, m Total Heating Surface, m2
Number of Banks Weight Tonnes
N/A
66,525
8,324
6
446
23.5
25,508
12,042
2
240
ARRANGEMENT
STEEL ‘H’
v PLAIN TUBE
GREENS STEEL H CASE STUDY Case
Stu
dy 2
P l a i n T u b e S t e e l ‘ H ’
Economiser Cost (Assembled Banks) Tube cleaning System Cost
Rs 6,97,00,000
(241%)
Rs 28,50,000
18 off
Rs 2,89,00,000
(100%)
Rs 13,50,000
11 off
CAPITAL COSTS ESTIMATE
STEEL ‘H’
v PLAIN TUBE
GREENS STEEL H CASE STUDY Case
Stu
dy 2
P l a i n T u b e S t e e l ‘ H ’
Flue Gas Velocity, max m/s Pressure loss, gas side mm WG Feed water velocity avg, m/s Pressure loss, water side, bar
15.1
160
1.35
2.6
15.0
65
1.35
0.9
OPERATION
STEEL ‘H’
v PLAIN TUBE
GREENS STEEL H CASE STUDY Case
Stu
dy 2
P l a i n T u b e S t e e l ‘ H ’
Theoretical power required, kW (friction loss + static head) Associated fan absorbed power, assuming 80% efficiency, kW Cost of Operation
482.3
602.9
Rs 23,33,00,000
199.7
249.6
Rs 9,66,00,000
FANS OPERATIONAL COSTS
STEEL ‘H’
v
PLAIN TUBE
Cost of operation assuming 15 years
at 8600 hours and Rs 3.0 kWh
GREENS STEEL H CASE STUDY Case
Stu
dy 2
P l a i n T u b e S t e e l ‘ H ’
Theoretical power required, kW (friction loss + static head) Associated feed pump absorbed power, assuming 70% efficiency, kW Cost of Operation
47.5
67.8
Rs 2,62,00,000
15.5
22.1
Rs 85,52,000
PUMPS OPERATIONAL COSTS
STEEL ‘H’
v
PLAIN TUBE
Cost of operation assuming 15 years
at 8600 hours and Rs 3.0 kWh
GREENS STEEL H CASE STUDY Case
Stu
dy 2
P l a i n T u b e S t e e l ‘ H ’
FANS PUMPS TUBE CLEANING (STEAM) TOTAL OPERATIONAL COSTS
23,33,00,000
2,62,00,000 ?
25,95,00,000
TOTAL OPERATIONAL COSTS
STEEL ‘H’
v
PLAIN TUBE
Cost of operation assuming 15 years
at 8600 hours and Rs 3.0 kWh
TOTAL OPERATIONAL SAVING WITH STEEL H 15,43,48,000
ANNUAL OPERATIONAL SAVING WITH STEEL H 1,02,89,000
9,66,00,000
85,52,000 ?
10,51,52,000
GREENS STEEL H CASE STUDY Case
Stu
dy 2
CASE STUDY 3
• 1,000MW Coal Fired Boiler.
• 286 Coils at 110mm Horizontal pitch to match wall tubes.
• Chamber 4950mm wide with coils supported from wall.
• Maximum gas velocity 15 m/s.
• 1,960 T/h gas at 533°C in / 370 °C out.
• 2,715 T/h water in at 296 °C and 300 bar.
CASE STUDY 3
Horizontal pitch (mm) 110 110 110
Vertical pitch (mm) 115.65 79 79
Tube o/d (mm) 50.8 34 31.8
Rows wide 286 286 286
Effective length (m) 4,810 4,050 4,050
Fin pitch (mm) Bare 12.7 25
Plain Tube Spiral Fin Steel ‘H’
CASE STUDY 3
Velocity (m/s) 14.9 14.4 14.7
Rows high 69 37 37
Total tube used (m) 94,275 42,247 42,399
Heating Surface (m²) 15,046 18,323 24,580
Total Height (m) 10.4 3.7 3.7
Number of banks 4 2 2
Weight (tonnes) 1,100 400 500
Press Loss (mm WG) 72 64 43
Economiser Cost (%) 100 65 63
Supportable at ends Yes No Yes
Plain Tube Spiral Fin Steel ‘H’
Wea
r R
ate
mg
kg
-1
30° 60
°
90
°
0°
In line tube arrangements
offer lowest impact angles
and minimum erosion.
From the centre line of the
tube the erosion rate increases
to a maximum at about 30º.
Then decreases rapidly as
angle approaches 0º.
Staggered In-line
Tube protected while fins can collect heat. Minimum loss of heating surface. Stainless Steel notched and formed to suit the tube. Held in place by wrap around the tube.
Ero
sio
n P
rote
ctio
n
GREENS DESIGN EXPERTISE
Boiler electrical output 350MW
Fuel: Coal
Commissioned May1997
Inspection
carried out in
April 1998.
Photograph
taken looking
down
Through tube
in direction
of gas flow.
6 Boilers each 660MWe.
Owned by National Power Plc, UK
Fired by coal with 17.5% ash.
First Unit on line 1973.
ECONOMISER Underside of
Economiser during
Installation.
Unit #3 Boiler commissioned in 1974
Inspected 31st May 1994.
No cleaning before inspection.
All gas passages clear of fouling.
No ash accumulations.
Recorded on the 25th July
1999.
Unit #1 158,206 hours.
Unit #2 164,888 hours.
Unit #3 161,877 hours.
Unit #4 109,535 hours.
Unit #5 103,863 hours.
Unit #6 99,301 hours.
500MW Boiler after firing With Orimulsion.
• Coal • Lignite • Heavy Oil • Orimulsion • Garbage or Refuse (EFW) • Bio Fuels (Rice husks/ Bagasse/Wood Straw) • Waste Heat Recovery (Cement, Coke) • Pulverised Fuels • Bubbling Fluidised Bed • Circulating Fluidised Bed • Incineration
Fu
el &
Co
mb
ustio
n
GREENS APPLICATIONS FOR STEEL H
GREENS ECONOMISERS
Recovery of Waste Heat from boiler & process flue gas streams in the Power Generation, Refining, Chemical, Process and general industries.
Individually designed to client's requirements
Industrial Economisers Greens Industrial Economisers are designed to operate with both shell package type and water tube boilers. The economic range starts at 5 Tonne/Hour.
Wide Variety of Fuels/Combustion
Power Station Economisers Greens Economisers operate with large utility super critical power boilers, ranging from 100 MW 1100 MW.