Summer Internship 2015 in
Piramal Glass LTD
KOSAMBA, SURAT GUJRAT
Glass furnace
Efficiency
Presentation from the
“MAHENDRA KUMAR BAIRWA”
Department of Ceramic Engineering
INDIAN INSTITUTE OF TECHNOLOGY
(BANARAS HINDU UNIVERSITY)
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Training Agenda: Glass
melting
Glass Manufacturing Processes
Introduction of furnace
Assessment of furnaces
Energy efficiency opportunities
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Glass Manufacturing Processes:
3
Mixed Raw
Finishing
Operations
Melting
Furnace
Inspection
and testing
Glass
Forming
Annealing
Storage
Packing
.
Fig.- Schematic for glass manufacturing
process
4
Training Agenda: Glass
melting
Glass Manufacturing Processes
Introduction of furnace
Assessment of furnaces
Energy efficiency opportunities
5
Chimney:
remove
combustion
gases
Introduction of furnace
Burners: raise or
maintain chamber
temperature
Furnace Components
Furnace chamber:
constructed of
insulating materials
Hearth: support or
carry the steel.
Consists of
refractory materials
Charging & discharging doors
for loading & unloading stock
(The Carbon Trust)
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8
Introduction of furnace
what are the Refractories
Used in the furnace?
Refractory lining of a furnace arc
Aluminium zirconium silica
refractories used in the furnace
Refractory walls of a furnace
interior with burner blocks
In the 55TPD Furnace
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Training Agenda: Glass
melting
Glass Manufacturing Processes
Introduction of furnace
Assessment of furnaces
Energy efficiency opportunities
10
Assessment of Furnaces
Heat Losses Affecting Furnace
Performance
Heat input
FURNACE
Heat in stock
Other losses
Furnace surface/skin
Openings in furnace
Hydrogen in fuel
Moisture in fuel
Flue gas
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Heat Losses in Industrial
Heating Furnaces
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Assessment of Furnaces
Instruments to Assess Furnace
Performance
Parameters
to be measured
Location of
measurement
Instrument
required
Required
Value
Furnace soaking zone
temperature (reheating furnaces)
Soaking zone and side wall
Pt/Pt-Rh thermocouple with
indicator and recorder
1200-1300oC
Flue gas temperature
In duct near the discharge end,
and entry to recuperator
Chrome Alummel Thermocouple
with indicator
700oC max.
Flue gas temperature
After recuperator
Hg in steel thermometer
300oC (max)
Furnace hearth pressure in the
heating zone
Near charging end and side wall
over the hearth
Low pressure ring gauge
+0.1 mm of Wc
Oxygen in flue gas
In duct near the discharge end
Fuel efficiency monitor for oxygen
and temperature
5% O2
Billet temperature
Portable
Infrared pyrometer or optical
pyrometer
-
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Assessment of Furnaces
Calculating Furnace Performance
Direct Method
Thermal efficiency of furnace
= Heat in the stock / Heat in fuel consumed for heating the stock
Heat in the stock Q:
Q = m x Cp (t1 – t2)
Q = Quantity of heat of stock in kCal
m = Weight of the stock in kg
Cp= Mean specific heat of stock in kCal/kg oC
t1 = Final temperature of stock in oC
t2 = Initial temperature of the stock before it enters the
furnace in oC
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Assessment of Furnaces
Calculating Furnace Performance
Direct Method - example
Heat in the stock Q =
◦ m x Cp (t1 – t2)
◦ 6000 kg X 0.12 X (1340 – 40)
◦ 936000 kCal
Efficiency =
◦ (heat input / heat output) x 100
◦ [936000 / (368 x 10000) x 100 = 25.43%
Heat loss = 100% - 25% = 75%
m = Weight of
the stock = 6000
kg
Cp= Mean
specific heat of
stock = 0.12
kCal/kg oC
t1 = Final
temperature of
stock = 1340 oC
t2 = Initial
temperature of
the stock = 40 oC
Calorific value of
oil = 10000
kCal/kg
Fuel consumption
= 368 kg/hr
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Assessment of Furnaces
Calculating Furnace Performance
Indirect Method
Heat losses
a) Flue gas loss
= 57.29 %
b) Loss due to moisture in fuel
= 1.36 %
c) Loss due to H2 in fuel
= 9.13 %
d) Loss due to openings in furnace
= 5.56 %
e) Loss through furnace skin
= 2.64 %
Total losses
= 75.98 %
Furnace efficiency =
◦ Heat supply minus total heat loss
◦ 100% – 76% = 24%
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Training Agenda: Glass
melting
Glass Manufacturing Processes
Introduction
Assessment of furnaces
Energy efficiency opportunities
17
Energy Efficiency
Opportunities:
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Energy Efficiency
Opportunities:
1. Complete Combustion with
Minimum Excess Air
Importance of excess air
◦ Too much: reduced flame temp, furnace temp, heating rate
◦ Too little: unburnt in flue gases, scale losses
Indication of excess air: actual air / theoretical combustion air
Optimizing excess air
◦ Control air infiltration
◦ Maintain pressure of combustion air
◦ Ensure high fuel quality
◦ Monitor excess air
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Energy Efficiency Opportunities:
2. Proper Heat Distribution
When using burners
Flame should not touch or be obstructed
No intersecting flames from different burners
Burner in small furnace should face upwards but not hit
roof
More burners with less capacity (not one big burner) in
large furnaces
Burner with long flame to improve uniform heating in small
furnace
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Energy Efficiency
Opportunities:
3. Operate at Optimum Furnace
Temperature
Operating at too high temperature: heat loss, oxidation,
decarbonisation, refractory stress
Automatic controls eliminate human error
Slab Reheating furnaces
1200oC
Rolling Mill furnaces
1200oC
Bar furnace for Sheet Mill
800oC
Bogie type annealing furnaces
650oC –750oC
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Energy Efficiency
Opportunities:
4. Reduce Heat Loss from Furnace
Openings
Heat loss through openings
◦ Direct radiation through openings
◦ Combustion gases leaking through the openings
◦ Biggest loss: air infiltration into the furnace
Energy saving measures
◦ Keep opening small
◦ Seal openings
◦ Open furnace doors less frequent and shorter
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Energy Efficiency
Opportunities:
5. Correct Amount of Furnace Draft
Negative pressure in furnace: air infiltration
Maintain slight positive pressure
Not too high pressure difference: air ex-filtration
Heat loss only about 1% if furnace pressure is controlled properly!
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Energy Efficiency
Opportunities
6. Optimum Capacity Utilization
Optimum load
◦ Under loading: lower efficiency
◦ Overloading: load not heated to right temp
Optimum load arrangement
◦ Load receives maximum radiation
◦ Hot gases are efficiently circulated
◦ Stock not placed in burner path, blocking flue system, close to openings
Optimum residence time
◦ Coordination between personnel
◦ Planning at design and installation stage
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Energy Efficiency
Opportunities:
7. Waste Heat Recovery from Flue Gases
Charge/Load pre-heating
◦ Reduced fuel needed to heat them in furnace
Pre-heating of combustion air
◦ Applied to compact industrial furnaces
◦ Equipment used: recuperator, self-recuperative burner
◦ Up to 30% energy savings
Heat source for other processes
◦ Install waste heat boiler to produce steam
◦ Heating in other equipment (with care!)
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Energy Efficiency
Opportunities:
8. Minimum Furnace Skin Loss
Choosing appropriate refractories
Increasing wall thickness
Installing insulation bricks (= lower conductivity)
Planning furnace operating times
◦ 24 hrs in 3 days: 100% heat in refractories lost
◦ 8 hrs/day for 3 days: 55% heat lost
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Energy Efficiency
Opportunities:
9. Use of Ceramic Coatings
High emissivity coatings
Long life at temp up to 1350
Most important benefits
◦ Rapid efficient heat transfer
◦ Uniform heating and extended refractory life
◦ Emissivity stays constant
Energy savings: 8 – 20%
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Energy Efficiency
Opportunities:
10. Selecting the Right Refractory
Selection criteria
Type of furnace
Type of metal charge
Presence of slag
Area of application
• Structural load of
furnace
• Stress due to temp
gradient & fluctuations
Working temperatures
• Chemical compatibility
Extent of abrasion and
impact
• Heat transfer & fuel
conservation
• Costs
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Summer Internship in 2015
Piramal Glass LTD
KOSAMBA, SURAT GUJRAT

Glass furnace
Efficiency
THANK YOU
FOR YOUR ATTENTION
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