Lecture 16 - Furnace - Type and classification Notes | EduRev

: Lecture 16 - Furnace - Type and classification Notes | EduRev

 Page 1


Lecture 16 
Furnace: Type and classification  
 
Content of lecture 
 
What is a furnace? 
 
What are the components of a furnace?    
Furnaces and their applications in high temperature industries 
 
Issues in Furnace design  
 
Key words: Matte smelter, blast furnace, heat treatment, fossil fuel 
 
What is a furnace? 
A  furnace  is  essentially  a  thermal  enclosure  and  is  employed  to  process  raw  materials  at  high 
temperatures both in solid state and liquid state. Several industries like iron and steel making, non 
ferrous  metals  production,  glass  making,  manufacturing,  ceramic  processing,  calcination  in  cement 
production etc. employ furnace. The principle objectives are 
a) To utilize heat efficiently so that losses are minimum, and 
 
b) To handle the different phases (solid, liquid or gaseous) moving at different velocities for different 
times and temperatures such that erosion and corrosion of the refractory are minimum. 
What are the components of a furnace?    
The principle components are 
i. Source of energy 
Page 2


Lecture 16 
Furnace: Type and classification  
 
Content of lecture 
 
What is a furnace? 
 
What are the components of a furnace?    
Furnaces and their applications in high temperature industries 
 
Issues in Furnace design  
 
Key words: Matte smelter, blast furnace, heat treatment, fossil fuel 
 
What is a furnace? 
A  furnace  is  essentially  a  thermal  enclosure  and  is  employed  to  process  raw  materials  at  high 
temperatures both in solid state and liquid state. Several industries like iron and steel making, non 
ferrous  metals  production,  glass  making,  manufacturing,  ceramic  processing,  calcination  in  cement 
production etc. employ furnace. The principle objectives are 
a) To utilize heat efficiently so that losses are minimum, and 
 
b) To handle the different phases (solid, liquid or gaseous) moving at different velocities for different 
times and temperatures such that erosion and corrosion of the refractory are minimum. 
What are the components of a furnace?    
The principle components are 
i. Source of energy 
a)  Fossil fuel: For fossil fuel one requires burner for efficient mixing of fuel and air. 
Arrangement of burner is important. 
b) Electric energy: Resistance heating, induction heating or arc heating. 
c) Chemical energy: Exothermic reactions 
 
ii.  Suitable refractory material: Refractory design is important. Thermal enclosure of the 
furnace is designed and constructed keeping in view the requirements. For example refractory 
facing the thermal enclosure must have high refractoriness, chemically inert etc. Whereas 
refractory facing the surrounding must have low thermal conductivity to minimize heat 
y installing a heat exchanger or internally by recirculation the POC within the 
ntation and control:    Furnaces are equipped with POC analyzer and temperature 
control.   
urnaces and their applications in high temperature industries: 
escription in order to appreciate the requirement of the design of thermal enclosure, i.e. 
furnace): 
PHYSICAL PROCESSING 
losses. 
iii.  Heat exchanger:   Heat exchanger is becoming now as part of the fossil fuel fired furnaces 
in order to recover and reuse the heat of POC. Heat of POC can be used either external to 
furnace b
furnace. 
iv.  Instrume
 
 
F
 
Furnaces  are  used  for  wide  variety  of  processing  of  raw  materials  to  finished  products  in  several 
industries.  Broadly  they  are  used  either  for  physical  processing  or  for  chemical  processing  of  raw 
materials. In the physical processing the state of the reactants remains unchanged, whereas in the 
chemical processing state of the reactants changes either to liquid of gas. In the table given below some 
applications of furnaces for physical and chemical processing are given ( the reader may go through 
detailed d
 
 
Page 3


Lecture 16 
Furnace: Type and classification  
 
Content of lecture 
 
What is a furnace? 
 
What are the components of a furnace?    
Furnaces and their applications in high temperature industries 
 
Issues in Furnace design  
 
Key words: Matte smelter, blast furnace, heat treatment, fossil fuel 
 
What is a furnace? 
A  furnace  is  essentially  a  thermal  enclosure  and  is  employed  to  process  raw  materials  at  high 
temperatures both in solid state and liquid state. Several industries like iron and steel making, non 
ferrous  metals  production,  glass  making,  manufacturing,  ceramic  processing,  calcination  in  cement 
production etc. employ furnace. The principle objectives are 
a) To utilize heat efficiently so that losses are minimum, and 
 
b) To handle the different phases (solid, liquid or gaseous) moving at different velocities for different 
times and temperatures such that erosion and corrosion of the refractory are minimum. 
What are the components of a furnace?    
The principle components are 
i. Source of energy 
a)  Fossil fuel: For fossil fuel one requires burner for efficient mixing of fuel and air. 
Arrangement of burner is important. 
b) Electric energy: Resistance heating, induction heating or arc heating. 
c) Chemical energy: Exothermic reactions 
 
ii.  Suitable refractory material: Refractory design is important. Thermal enclosure of the 
furnace is designed and constructed keeping in view the requirements. For example refractory 
facing the thermal enclosure must have high refractoriness, chemically inert etc. Whereas 
refractory facing the surrounding must have low thermal conductivity to minimize heat 
y installing a heat exchanger or internally by recirculation the POC within the 
ntation and control:    Furnaces are equipped with POC analyzer and temperature 
control.   
urnaces and their applications in high temperature industries: 
escription in order to appreciate the requirement of the design of thermal enclosure, i.e. 
furnace): 
PHYSICAL PROCESSING 
losses. 
iii.  Heat exchanger:   Heat exchanger is becoming now as part of the fossil fuel fired furnaces 
in order to recover and reuse the heat of POC. Heat of POC can be used either external to 
furnace b
furnace. 
iv.  Instrume
 
 
F
 
Furnaces  are  used  for  wide  variety  of  processing  of  raw  materials  to  finished  products  in  several 
industries.  Broadly  they  are  used  either  for  physical  processing  or  for  chemical  processing  of  raw 
materials. In the physical processing the state of the reactants remains unchanged, whereas in the 
chemical processing state of the reactants changes either to liquid of gas. In the table given below some 
applications of furnaces for physical and chemical processing are given ( the reader may go through 
detailed d
 
 
 
 
Unit process Purpose Energy source 
in 
o
C 
rnace Temperature Type of fu
Carbonization ting 
y burning fuel 
 1200 Conversion of coal to 
coke 
Indirect hea
b
˜ 1000 to Coke oven 
Calcination CO
2
 from 
aCO for cement 
Production of anhydrous 
alumina for electrolysis 
ossil fuel 
 
Fossil fuel 
  1200 
  1300 
 
otary kiln  
otary kiln 
 
Removal of 
C
3
production 
 
F
 
 
˜
 
 
 
˜
 
 
 
 
R
 
 
 
R
 
 
 
Roasting ulphide into Chemical + ˜ 900 
, etc 
To convert s
oxide partially or 
completely 
Fossil fuel 
Multiple hearth 
furnace, 
Fluid bed roaster
Heating egation 
 hot working 
  
Mostly oil and 
gas fired  
 
melting points of 
Batch type or 
continuous type 
To eliminate segr
To perform
To perform heat 
treatment
Below the
materials 
Sintering To produce compacts of 
particles 
Fossil or electric Below the 
melting point 
Sintering furnaces 
 
 
 
CHEMICAL PROCESSING 
 re 
in 
o
C 
 
 
Unit process Purpose Energy source Temperatu Type of furnace 
Electrolysis of 
molten salt 
nd 
Na 
  900 ll, To produce Al,Mg a Electric energy 700 to Hall-Heroult ce
Refining To produce steel Chemical and
electric 
 1600 LD Converter 
Electric furnace 
Melting To produce castings of 
metals and alloys 
Electric and 
fossil fuel ints of 
ve metal 
and alloy 
reverberatory furnace 
nace 
Above the 
melting po
respecti
Induction furnace, 
and melting fur
Matte smelting To produce matte Chemical and ˜1200 elter, 
fossil fuel 
Flash sm
Reverberatory 
smelter 
Page 4


Lecture 16 
Furnace: Type and classification  
 
Content of lecture 
 
What is a furnace? 
 
What are the components of a furnace?    
Furnaces and their applications in high temperature industries 
 
Issues in Furnace design  
 
Key words: Matte smelter, blast furnace, heat treatment, fossil fuel 
 
What is a furnace? 
A  furnace  is  essentially  a  thermal  enclosure  and  is  employed  to  process  raw  materials  at  high 
temperatures both in solid state and liquid state. Several industries like iron and steel making, non 
ferrous  metals  production,  glass  making,  manufacturing,  ceramic  processing,  calcination  in  cement 
production etc. employ furnace. The principle objectives are 
a) To utilize heat efficiently so that losses are minimum, and 
 
b) To handle the different phases (solid, liquid or gaseous) moving at different velocities for different 
times and temperatures such that erosion and corrosion of the refractory are minimum. 
What are the components of a furnace?    
The principle components are 
i. Source of energy 
a)  Fossil fuel: For fossil fuel one requires burner for efficient mixing of fuel and air. 
Arrangement of burner is important. 
b) Electric energy: Resistance heating, induction heating or arc heating. 
c) Chemical energy: Exothermic reactions 
 
ii.  Suitable refractory material: Refractory design is important. Thermal enclosure of the 
furnace is designed and constructed keeping in view the requirements. For example refractory 
facing the thermal enclosure must have high refractoriness, chemically inert etc. Whereas 
refractory facing the surrounding must have low thermal conductivity to minimize heat 
y installing a heat exchanger or internally by recirculation the POC within the 
ntation and control:    Furnaces are equipped with POC analyzer and temperature 
control.   
urnaces and their applications in high temperature industries: 
escription in order to appreciate the requirement of the design of thermal enclosure, i.e. 
furnace): 
PHYSICAL PROCESSING 
losses. 
iii.  Heat exchanger:   Heat exchanger is becoming now as part of the fossil fuel fired furnaces 
in order to recover and reuse the heat of POC. Heat of POC can be used either external to 
furnace b
furnace. 
iv.  Instrume
 
 
F
 
Furnaces  are  used  for  wide  variety  of  processing  of  raw  materials  to  finished  products  in  several 
industries.  Broadly  they  are  used  either  for  physical  processing  or  for  chemical  processing  of  raw 
materials. In the physical processing the state of the reactants remains unchanged, whereas in the 
chemical processing state of the reactants changes either to liquid of gas. In the table given below some 
applications of furnaces for physical and chemical processing are given ( the reader may go through 
detailed d
 
 
 
 
Unit process Purpose Energy source 
in 
o
C 
rnace Temperature Type of fu
Carbonization ting 
y burning fuel 
 1200 Conversion of coal to 
coke 
Indirect hea
b
˜ 1000 to Coke oven 
Calcination CO
2
 from 
aCO for cement 
Production of anhydrous 
alumina for electrolysis 
ossil fuel 
 
Fossil fuel 
  1200 
  1300 
 
otary kiln  
otary kiln 
 
Removal of 
C
3
production 
 
F
 
 
˜
 
 
 
˜
 
 
 
 
R
 
 
 
R
 
 
 
Roasting ulphide into Chemical + ˜ 900 
, etc 
To convert s
oxide partially or 
completely 
Fossil fuel 
Multiple hearth 
furnace, 
Fluid bed roaster
Heating egation 
 hot working 
  
Mostly oil and 
gas fired  
 
melting points of 
Batch type or 
continuous type 
To eliminate segr
To perform
To perform heat 
treatment
Below the
materials 
Sintering To produce compacts of 
particles 
Fossil or electric Below the 
melting point 
Sintering furnaces 
 
 
 
CHEMICAL PROCESSING 
 re 
in 
o
C 
 
 
Unit process Purpose Energy source Temperatu Type of furnace 
Electrolysis of 
molten salt 
nd 
Na 
  900 ll, To produce Al,Mg a Electric energy 700 to Hall-Heroult ce
Refining To produce steel Chemical and
electric 
 1600 LD Converter 
Electric furnace 
Melting To produce castings of 
metals and alloys 
Electric and 
fossil fuel ints of 
ve metal 
and alloy 
reverberatory furnace 
nace 
Above the 
melting po
respecti
Induction furnace, 
and melting fur
Matte smelting To produce matte Chemical and ˜1200 elter, 
fossil fuel 
Flash sm
Reverberatory 
smelter 
Reduction 
smelting 
  
ii) To produce lead  and  
iii) To produce Zinc    
hemical and 
fossil fuel 
00at 
the tuyere in all 
the cases 
blast furnace 
e 
and 
i) To produce hot metal C
fossil fuel 
 
Chemical and 
˜1700 to 18 Iron 
Lead blast furnac
Zn blast furnace 
Converting To produce copper from 
matte 
Chemical energy 1100 to 1200 Side blown converter 
 
 
Issues in Furnace design  
ient design of thermal enclosure is important; 
 heat losses should be as minimal as possible. 
h no movement of solid and 
 takes place) should be avoided while designing the furnace chamber 
e
 of material. Furnace should be 
ped with he temperature measurement and control devices 
material exits at the desired temperature from the soaking zone and the  products of combustion 
 
1) Source of energy in processing of raw materials is fossil fuel in most cases. Even if electric energy is 
used, it is also derived from fossil fuels. Thus energy effic
particularly
 
2)  In chemical processing, fluid flow is important. Liquid and gases are flowing at high temperature so 
erosion and corrosion of the refractory is important. In addition, fluid flow also influences the rates of 
heat and mass transfer. The dead zones (dead zones are those areas in whic
liquid
 
3) Atmospher  in the furnace is also important to avoid oxidation of the material being heated 
4) Control of furnace temperature is also an important issue. Overheating and under-heating lead to 
inefficient utilization of fuel and also overheating or under-heating
equip
 
5) Furnaces are both batch and continuous type. In the continuous type for example in heating of 
ferrous material for hot working, the furnace chamber consists of preheating, heating and soaking 
zones. The material enters through the preheating zone and exits the soaking zone for rolling. But the 
flow of products of combustion is in the reverse direction. Furnace design is recuperative type in that 
Page 5


Lecture 16 
Furnace: Type and classification  
 
Content of lecture 
 
What is a furnace? 
 
What are the components of a furnace?    
Furnaces and their applications in high temperature industries 
 
Issues in Furnace design  
 
Key words: Matte smelter, blast furnace, heat treatment, fossil fuel 
 
What is a furnace? 
A  furnace  is  essentially  a  thermal  enclosure  and  is  employed  to  process  raw  materials  at  high 
temperatures both in solid state and liquid state. Several industries like iron and steel making, non 
ferrous  metals  production,  glass  making,  manufacturing,  ceramic  processing,  calcination  in  cement 
production etc. employ furnace. The principle objectives are 
a) To utilize heat efficiently so that losses are minimum, and 
 
b) To handle the different phases (solid, liquid or gaseous) moving at different velocities for different 
times and temperatures such that erosion and corrosion of the refractory are minimum. 
What are the components of a furnace?    
The principle components are 
i. Source of energy 
a)  Fossil fuel: For fossil fuel one requires burner for efficient mixing of fuel and air. 
Arrangement of burner is important. 
b) Electric energy: Resistance heating, induction heating or arc heating. 
c) Chemical energy: Exothermic reactions 
 
ii.  Suitable refractory material: Refractory design is important. Thermal enclosure of the 
furnace is designed and constructed keeping in view the requirements. For example refractory 
facing the thermal enclosure must have high refractoriness, chemically inert etc. Whereas 
refractory facing the surrounding must have low thermal conductivity to minimize heat 
y installing a heat exchanger or internally by recirculation the POC within the 
ntation and control:    Furnaces are equipped with POC analyzer and temperature 
control.   
urnaces and their applications in high temperature industries: 
escription in order to appreciate the requirement of the design of thermal enclosure, i.e. 
furnace): 
PHYSICAL PROCESSING 
losses. 
iii.  Heat exchanger:   Heat exchanger is becoming now as part of the fossil fuel fired furnaces 
in order to recover and reuse the heat of POC. Heat of POC can be used either external to 
furnace b
furnace. 
iv.  Instrume
 
 
F
 
Furnaces  are  used  for  wide  variety  of  processing  of  raw  materials  to  finished  products  in  several 
industries.  Broadly  they  are  used  either  for  physical  processing  or  for  chemical  processing  of  raw 
materials. In the physical processing the state of the reactants remains unchanged, whereas in the 
chemical processing state of the reactants changes either to liquid of gas. In the table given below some 
applications of furnaces for physical and chemical processing are given ( the reader may go through 
detailed d
 
 
 
 
Unit process Purpose Energy source 
in 
o
C 
rnace Temperature Type of fu
Carbonization ting 
y burning fuel 
 1200 Conversion of coal to 
coke 
Indirect hea
b
˜ 1000 to Coke oven 
Calcination CO
2
 from 
aCO for cement 
Production of anhydrous 
alumina for electrolysis 
ossil fuel 
 
Fossil fuel 
  1200 
  1300 
 
otary kiln  
otary kiln 
 
Removal of 
C
3
production 
 
F
 
 
˜
 
 
 
˜
 
 
 
 
R
 
 
 
R
 
 
 
Roasting ulphide into Chemical + ˜ 900 
, etc 
To convert s
oxide partially or 
completely 
Fossil fuel 
Multiple hearth 
furnace, 
Fluid bed roaster
Heating egation 
 hot working 
  
Mostly oil and 
gas fired  
 
melting points of 
Batch type or 
continuous type 
To eliminate segr
To perform
To perform heat 
treatment
Below the
materials 
Sintering To produce compacts of 
particles 
Fossil or electric Below the 
melting point 
Sintering furnaces 
 
 
 
CHEMICAL PROCESSING 
 re 
in 
o
C 
 
 
Unit process Purpose Energy source Temperatu Type of furnace 
Electrolysis of 
molten salt 
nd 
Na 
  900 ll, To produce Al,Mg a Electric energy 700 to Hall-Heroult ce
Refining To produce steel Chemical and
electric 
 1600 LD Converter 
Electric furnace 
Melting To produce castings of 
metals and alloys 
Electric and 
fossil fuel ints of 
ve metal 
and alloy 
reverberatory furnace 
nace 
Above the 
melting po
respecti
Induction furnace, 
and melting fur
Matte smelting To produce matte Chemical and ˜1200 elter, 
fossil fuel 
Flash sm
Reverberatory 
smelter 
Reduction 
smelting 
  
ii) To produce lead  and  
iii) To produce Zinc    
hemical and 
fossil fuel 
00at 
the tuyere in all 
the cases 
blast furnace 
e 
and 
i) To produce hot metal C
fossil fuel 
 
Chemical and 
˜1700 to 18 Iron 
Lead blast furnac
Zn blast furnace 
Converting To produce copper from 
matte 
Chemical energy 1100 to 1200 Side blown converter 
 
 
Issues in Furnace design  
ient design of thermal enclosure is important; 
 heat losses should be as minimal as possible. 
h no movement of solid and 
 takes place) should be avoided while designing the furnace chamber 
e
 of material. Furnace should be 
ped with he temperature measurement and control devices 
material exits at the desired temperature from the soaking zone and the  products of combustion 
 
1) Source of energy in processing of raw materials is fossil fuel in most cases. Even if electric energy is 
used, it is also derived from fossil fuels. Thus energy effic
particularly
 
2)  In chemical processing, fluid flow is important. Liquid and gases are flowing at high temperature so 
erosion and corrosion of the refractory is important. In addition, fluid flow also influences the rates of 
heat and mass transfer. The dead zones (dead zones are those areas in whic
liquid
 
3) Atmospher  in the furnace is also important to avoid oxidation of the material being heated 
4) Control of furnace temperature is also an important issue. Overheating and under-heating lead to 
inefficient utilization of fuel and also overheating or under-heating
equip
 
5) Furnaces are both batch and continuous type. In the continuous type for example in heating of 
ferrous material for hot working, the furnace chamber consists of preheating, heating and soaking 
zones. The material enters through the preheating zone and exits the soaking zone for rolling. But the 
flow of products of combustion is in the reverse direction. Furnace design is recuperative type in that 
discharge  the  preheating  zone  at  the  lowest  possible  temperature.  Different  types  of  continuous 
furnaces are in use, like walking beam type, pusher type, roller hearth type, screw conveyor type etc. 
 
6) In the batch furnaces, the load is heated for the fixed time and then discharged from the furnace. 
There are different types of batch furnaces like box type, integral quench type, pit type and car bottom 
type 
 
6) In many cases the furnace is equipped with either external heat recovery system or internal heat 
recovery system. In the external heat recovery system a heat exchanger like recuperator is installed 
outside the furnace. Here heat exchanger must be integrated with the furnace operation. In the internal 
heat recovery the products of combustion are recirculated in the furnace itself so that flame 
temperature is somewhat lowered. The objective is to reduce the NO
x
 formation.  
 
7) The products of combustion are moving at high speeds in the furnace. The flow of products of 
combustion is important to obtain rapid heat transfer and minimum thermal gradient. 
Source: George E.Totten and M.A.H.Howes: Steel heat treatment handbook 
P.Mullinger and B. Jenkins: Industrial and process furnaces 
 
 
 
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