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Summer Internship 2015 in Summer Internship 2015 in Piramal Glass LTDPiramal Glass LTD

KOSAMBA, SURAT GUJRATKOSAMBA, SURAT GUJRAT

Glass furnace Glass furnace Efficiency Efficiency Presentation from the

“MAHENDRA KUMAR BAIRWA”

Department of Ceramic Engineering

INDIAN INSTITUTE OF TECHNOLOGY

(BANARAS HINDU UNIVERSITY)

VARANASI (U.P.) 221005

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Training Agenda: Glass melting

Glass Manufacturing Processes Introduction of furnaceAssessment of furnaces

Energy efficiency opportunities

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Glass Manufacturing Processes:

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Mixed Raw MeltingFurnace

GlassForming

Annealing

Packing StorageFinishingOperations

Fig.- Schematic for glass manufacturing process

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Inspection and testing

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Training Agenda: Glass meltingGlass Manufacturing Processes

Introduction of furnace

Assessment of furnaces


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Introduction of furnaceFurnace Components

(The Carbon Trust)

Furnace chamber: constructed of

insulating materials

Hearth: support or carry the steel.

Consists of refractory materials

Burners: raise or maintain chamber

temperature

Chimney: remove

combustion gases

Charging & discharging doors for loading & unloading stockCharging & discharging doors for loading & unloading stock

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Introduction of 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

what are the RefractoriesUsed in the furnace?Used in the furnace?

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Training Agenda: Glass Training Agenda: Glass meltingmelting

Glass Manufacturing ProcessesIntroduction of furnaceAssessment of furnacesEnergy efficiency opportunities

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Assessment of FurnacesHeat Losses Affecting Furnace Performance

FURNACE

Flue gas

Moisture in fuel

Openings in furnace

Furnace surface/skin

Other losses

Heat inputHeat in stock

Hydrogen in fuel

FURNACE

Flue gas

Moisture in fuel

Openings in furnace

Furnace surface/skin

Other losses

Heat inputHeat in stock

Hydrogen in fuel

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Heat Losses in Industrial Heating Furnaces

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Assessment of Furnaces

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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Instruments to Assess Furnace Performance

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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)

Calculating Furnace Performance

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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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%

Calculating Furnace Performancem = 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 oCCalorific value of oil = 10000 kCal/kgFuel consumption = 368 kg/hr

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Indirect Method

Heat lossesa) 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%

Calculating Furnace Performance

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Training Agenda: Glass melting

Glass Manufacturing Processes

Introduction

Assessment of furnaces


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Energy Efficiency Opportunities:

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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

1. Complete Combustion with Minimum Excess Air

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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

2. Proper Heat Distribution

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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

3. Operate at Optimum Furnace Temperature

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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

4. Reduce Heat Loss from Furnace Openings

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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!

5. Correct Amount of Furnace Draft

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Energy Efficiency Opportunities

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

6. Optimum Capacity Utilization

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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!)

7. Waste Heat Recovery from Flue Gases

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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

8. Minimum Furnace Skin Loss

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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%

9. Use of Ceramic Coatings

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Selection criteria

Type of furnace Type of metal charge Presence of slag Area of application Working temperatures Extent of abrasion and impact

10. Selecting the Right Refractory

• Structural load of furnace

• Stress due to temp gradient & fluctuations

• Chemical compatibility

• Heat transfer & fuel conservation

• Costs

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Summer Internship in 2015 Summer Internship in 2015 Piramal Glass LTD Piramal Glass LTDKOSAMBA, SURAT GUJRATKOSAMBA, SURAT GUJRAT

Glass furnace Glass furnace Efficiency Efficiency

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