General Information & Operation of Furnaces used in Galvanizing Lines

Introduction

Objective of this  Program is to share information related to Furnace to improve knowledge base.

•1. General Information and Combustion system.

•2. NOF Furnace and advantages.

•3. Information about CGL, Furnace.

•4. Group Discussion on – Furnace

General Information

1. Combustion : It is defined as the chemical union of the combustible material with oxygen with the

   resultant generation of light and heat.

2. Perfect Combustion : is the complete oxidation of the fuel with the exact theoretical amount of oxygen (air) required.

3. Complete Combustion : It is complete oxidation of the fuel even some excess amount of air or O2.

4. Heat Transfer :

        – Conduction.

        – Convection.

        – Radiation.

5. Thermal Efficiency = Heat I/P

                                        Heat O/P

Example –

        Furnace using 10,00,000 Kcal of fuel to heat

Steel having in it only 1,00,000 Kcal .

The efficiency = 0.1 = 10%.

6. Thermal shock : is the stain produced in a material due to sudden changes in temperature.

7. Thermal spalling :It is result of thermal shock.It is defined as a fracture of refractory material

And occurs as the breaking off of pieces from the hot surface of the refractory.

Heat and Temperature

  • What is heat ?
  • What is  Temperature ?
  • Is Heat and Temperature Same ?.

Heat and Temperature are different terms.

# Heat is form of energy.

# Temperature is result of heat energy

Example:

Heat required to increase temperature of fuel oil

And water by 30 Deg. C is different.

                                         Fuel Oil            Water

a. Initial Temperature   20 Deg. C        20 Deg. C

b. Final Temperature    50 Deg. C        50 Deg. C

c. Difference in Temp.  30 Deg. C        30 Deg. C

d. Specific heat            0.5 Kcal/Kg      1 Kcal/Kg

Heat Required in Kcal/Kg = c X d

                                       30 X 0.5           30 X 1

 Heat Required             15 Kcal/Kg.     30 Kcal/Kg.

8. Specific heat: of any substance is the quantity

 of heat (in Kcal) required to raise a unit of weight

of volume of that substance by one deg. C.

Example :

Specific heat of water is 1.

i.e. One Kcal heat is required to raise temp. of One Kg of water by one Deg. C.

Significance of Specific Heat –

1.Helpful for calculation heat requirement.

2.Helpful for calculation of fuel consumption.

Calculation of Fuel Consumption

In a Furnace, to heat 1 t of steel /hr from 20 Deg. C

to 1000 Deg. C, how much LPG is required in Kg.?

Other Information :

          Specific heat of steel = 0.165 Kcal/Kg 0C

          C.V. of LPG = 11880 Kcal/Kg.

          Furnace efficiency = 35 %.= 0.35

Solution :

Net rise in Temp. of Steel = 1000 – 20 = 980 Deg. C

Heat required = 980 x 0.165 = 161.7 Kcal/Kg

Heat consumption = 161.7/0.35 = 462 Kcal/Kg of steel.

For 1 t of steel/hr, heat produced = 462000 Kcal/hr

LPG Required = Heat Produced / C.V. = 462000/11880

                         = 38.9 Kg/hr.

9. Rate of flame prorogation : is the speed with which a flame travels through a given

    gas – air mixture.

10. Thermal expansion : is the temporary increase in volume or linear dimensions when heated. The material returns to its original dimensions when cooled.

About LPG

LPG – Liquefied Petroleum Gas is mixture of

hydrocarbons with two principal gases

propane (C3H8) and  butane(C4H10)

Features –

     * Clean – burning fuel.

     * LPG is inherently safe.

     * It can be transported and stored in liquid form

       but will vaporize and burn as a gas when

       released under normal atmosphere.

     * Inflammability limit 2% to 10%

     * An odorant ethyl mercaptan is added to

       detect LPG leakage.

     * LPG has a liquid-to-vapor expansion ratio

       of 250.(1 Lit liquid = 250 liters of vapor)

Technical Specification of LPG

                                             Propane          Butane

Formula                               C3 H8              C4 H10

Boiling Point 0F                  – 44                  33

Specific Gravity (Gas)        1.53                 2.00

Specific Gravity (Liquid)    0.51                 0.58

Ignition Temp. in Air F       920 – 1020      900 -1000

Flame temp. Max.   F          3595                3615

Energy content (Kcal/Kg)    11900              11800

Energy content (Kcal/Nm3)   23400               30700

Note : The LPG we are using in our line have

calorific value at 15.5 Deg.C

      Gross C.V. = 11824 Kcal/Kg.

      Net C.V.     = 10894 Kcal/Kg.

FURNACES USED IN GALVANIZING LINES AND ADVANTAGES OF NOF.

1.Electrically heated Furnaces –

2.DAGAL – R.T.Heating Furnace –

3.Non – Ox Furnace (Vertical Type) –

4.Non – Ox Furnace (Horizontal) –

5.Multiple combinations:

     > NOF : Reverse U – Type (Essar Project)

     > NOF Vertical – Soaking Vertical.(CGL2)

     > NOF Horizontal – Soaking Vertical (CGL1)

     > NOF, Heating, Soaking and cooling Vertical

        (OEM – Line China)

6. Depending upon Fuel used –

   # LPG Fired Furnace. # HSD Fired Furnace (R.T.)

   # Electrically Heated R.T. 

Information about CGL1 Furnace

Specification –

  • Capacity – 30 MT / Hr.
  • Fuel – LPG
  • Furnace – NOF, RTF, S/Z, J/C
  • Horizontal Non-Ox Furnace.
  • Vertical Soaking Furnace.

Lay Out of Vulcan Furnace –

httpshttps://freshgk.com/maintenance-of-galvanizing-furnace/://frshgk.com

TECHNICAL  SPECIFICATION

1.1  OVERALL  DIMENSIONS.

Total length  from entry -seal to turn down roll  54.77 mtrs

-Length of non-ox preheating section .  15.40 mtrs

-Length of radiant tube annealing section.  10.17 mtrs 

-Length of soaking section.  6.20  mtrs 

-Length of jet cooling section.  21.80 mtrs

-Length of exit section casing.  1.55 mtrs

-Width inside non-ox preheating section.  1.80 mtrs

-Width inside radiant tube annealing section.  1.55 mtrs

-Width inside jet cooling section.  1.50 mtrs

1.2  NON OXIDIZING SECTION.

-Number of heating zones  3     nos.

-Number of burners per zones  8,8,6     nos.

-Total number of main burners  22    nos.

-Total number of pilot burners  22    nos.

-Installed heating capacity per main burner 

  2,92,000 Kcal/hr (for Zone 1 and 2 )

-Installed heating capacity per main burner 

  2,32,000   Kcal/hr (for Zone  3 )

-Heating capacity per pilot burner  8,000   Kcal/hr

-Total installed heating capacity  62,40,000   Kcal/hr

-Number of water-cooled rollers (125 dia.)  5    nos.

-Entry seal water-cooled rollers (150 dia. )  2   nos.

-Connecting sleeve non-water cooled rollers (125 dia.) 1 no.

-Number of recuperators.  1    no.

Refractory insulation thickness:

Hearthing insulation:

Total lining thickness (with mortar)  385   mm

Silliminite – MCL  32   mm,  AC-IN-150  75   mm

Cold face -S  75   mm,            Mica – 500  75   mm

Hysil – 950  120   mm 

Side Wall Insulation: 

Total lining thickness (with mortar)  385   mm

AC-IN-150  113   mm,  Cold face -S  113   mm

Mica – 500  75   mm,    Hysil Insulation  80   mm

Roof Insulation:

Total lining thickness (with mortar)  460   mm

Silliminite – MCL  230   mm, Cold face -S  113   mm

Hysil – 950  65   mm,  Mineral Wool  50   mm 

RADIANT TUBE SECTION

-Number of heating zones (NO. 4 & 5)  02    nos.

-Number of radiant tubes & burners zone 4   10     nos.

-Number of radiant tubes & burners zone 5    08     nos.

-Installed heating capacity per main burner  42,000  Kcal/hr

-Heating capacity per pilot burner    5,500  Kcal/hr

-Total installed heating capacity          8,55,000  Kcal/hr

-Number of non-water cooled rollers (125 dia.)  4    nos.

Refractory insulation thickness:

  Hearth lining thickness:

  -Total lining thickness (with mortar)  330   mm

  -Hot face insu. 65 mm, Cold face insu. 65 mm

  –Hysil – 950  120   mm, Mica – 500  75   mm

  Side Wall lining thickness: 

  -Total lining thickness (with mortar)  390   mm

  -Hot face insu. 113 mm, Mica – 500  113   mm

  –Hysil -950 Insulation  160   mm 

  Roof Insulation:

  -Total lining thickness (with mortar)  295   mm

  -Hot face insulation  65   mm

  -Hysil – 950   110   mm, Mineral Wool  120   mm

SOAKING SECTION

  -Number of heating zones (NO. 6 & 7)         02 nos.

  -Heating capacity (electrical)                    500 kW.

  -No. of non-water cooled rollers (125 dia.)  02 nos.

  -No. of non-water cooled rollers (730 dia.)  05 nos.

  Refractory insulation thickness:

  -Total insu. thickness (Side wall & roof ) 350 mm

  -Ceramic fibers (density 128 kg/m^3)        50 mm

  -Ceramic fibers (density 128 kg/m^3)      150 mm

  -Mineral Wool                                     150   mm

  Hearth lining  thickness 

  -Total lining thickness   340   mm

  -Hot face – K  30   mm,  Mica – 500   230   mm

  -Hysil -950 Insulation    80   mm

JET COOLER SECTION.

  -Total number of Jet Coolers               09  nos.

  -Number of J/C with electric heaters     06  nos.

  -Number of J/C without electric heaters 03  nos.

  -Number of electric heaters per J/C     02  nos.

  -Installed heating capacity per J/C     40  kW.

  -Re-circulation fans per Jet Cooler     01  nos.

  -Heat exchangers per Jet Cooler     02  nos.

  -No. of non-water cooled rollers (125 dia.) 09 nos.

                (One for each Jet Cooler)

EXIT SECTION  (TURN DOWN ).

  -Number of rollers (730 dia. , Non driven) 01 nos.

  Refractory Lining thickness :

  -Hearth   thickness 

   Mica – 500 – 113 mm, Hysil -950 Insu.  – 50 mm

  -Side Wall thickness

   Hot face Insulation – 113 mm, Hysil -950 – 80   mm

  -Roof thickness

   Hysil -950 – 100 mm,  Mineral Wool  50   mm

POST COMBUSTION ARRANGEMENT /FLUEDUCT:

  -Number of main burners  01   nos.

  -Number of pilot burners  01   nos.

  -Heating capacity per main burner 2,50,000 Kcal/hr

  -Heating capacity per main burner 12,000Kcal/hr

  Refractory lining thickness : 

  -Flue duct before and after  recuperator 

  Hot face Insulation  113   mm

  Mica – 500  150   mm

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