knowledge on control parameters_01

Jayanta kr. MandalAsst. Mgr

B.F. OperationSAIL-ISP

Blast Furnace ControlThe Main Objectives :

Furnace Control Myth

WHAT ?Area wise details of Control Parameters

Area wise details of Control Parameters

Importance of some Crucial Parameters

Improved Gas Solid Contact Increased Reduction Rate Less Fluidization of Fines Less Flooding Tendency Less ‘Si’ in Hot Metal Increase in Metal & Slag Drainage Rate


If Furnace is Operated at LOW STOCK LEVEL there will be

And these factors will eventually Increase the COKE RATE


RAFT

Composition of Gasses leaving this Zone

Dimension, Shape & Location

All of these Three Characteristics are controlled by BLAST & TUYERE

Parameters


Kinetic energy of Blast (K.E.) = ½ . MASS. VEL2

KE of Blast effects the Depth of the Raceway(D) Zone as follows D = 0.118 X 10-3 X KE + 0.77 This in turn effects the Active Hearth Area

Positive: Raceway Depth Increases Active Hearth area Increases Per unit time Coke Burning Rate increases Productivity Increases

Negative: Coke Degradation Increases Coke Rate Increases Permeability Index decreases


Parameters RAFT

H.B.T.

O2 in Blast

Steam

CDI

Natural Humidity


HBT By 100oC = RAFT By 840CO2 Content By 1% = RAFT By 48-500CBlast Humidity By 1% = RAFT By 40-420c

Higher the RAFT, Higher will be the THERMAL EFFICIENY Higher RAFT will enhance the Heat Exchange between Gasses and Liquids resulting in a Higher Hot Metal Temp. Higher RAFT will lead to Lower Coke Rate & Higher Productivity

Too High RAFT may upset the Furnace Movement due to Earlier Melting of Burden Increased formation of gaseous SiO & Alkalis Flooding of slag in the coke grid due to increased tuyere gas velocity


Effect of Control Parameters on H. M. Production & Coke Rate.

Change in Parameters Change in H.M. Production, %

Change in Coke Rate, %

1000C increase in H.B.T + 2.0 -3.3

0.1 atm. increase in H.T.P. +1.1 -0.5

1% decrease in Coke Ash +2.0 -2.0

1% decrease in M- 10 +2.5 -2.0

1% increase in Fe in Burden +2.0 -1.8

1% decrease in Burden Fines +1.0 -0.8

10% decrease in Not-Dry Casts +0.3 -1.0

1% decrease in Off- Rod working +0.1 -0.2

10% increase in Sinter in Burden +2.0 -4.0

1% increase in O2 Enrichment +3.0 --(no affect)


Smooth Furnace Operation requires:


Prior to Cast# Volume Of Metal & Slag in the Hearth , Causing –

Sharp Rise in Blast Pressure confirming the Raceway Distortion Excessive Blast & High Diff. Press. leading to the Wind Rate Reduction & Probability of Hanging

During the Cast# Due to Higher Casting/ Production Rate –

Burden Descent is rapid & irregular, Thermal requirement increases as Under prepared Burden rapidly enters the melting & Hearth Zone Stock Line Control becomes Poor


Casting Parameters


Taphole Parameters includes: Taphole Length(L) & Taphole Diameter(d)# Hearth Drainage & Casting Rate(C.R.) depends mostly on T/H Parameters

Casting Rate(C.R.) α ------------d3

L

Miscellaneous

RAFT = -----------------------------------------------

Where, tHB = Hot Blast Temperature, 0C

W = Oxygen in Blast,Nm3/Nm3 of dry Blast α = Blast humidity, Nm3/Nm3 of dry Blast

0.9341 tHB + 8208W – α ( 2402 – 1.2177 tHB ) + 94.76

1 + W + 2 α

Miscellaneous Kinetic energy of Blast (K.E.) = ½ . MASS. VEL2

Mass = ------------------------------

Vel = ------------------------------------- Where, VB = Blast Rate. 10-3, Nm3/hr T = ( 273 + Blast Temp), K P = ( 1 + Blast Press.), Kg/cm2

αB = Total Humidity in Blast, g/Nm3

DT = Dia. of tuyeres, mm

n = no. of Tuyeres in operation

( 1293 + αB ).VB.0.0284 1000.n

280000.Vb.T.(18000 + 22.4 αB )

3891888.n.P.DT

BFG

DCIV

FCVDSVGSV

Pug Mill

GRIV

BPCV

Hot Stove W-Seal

W-Seal

HE

Gas Holder

Difuser

Dust catcher

Scrubber

R.S Element Recycle Pump

MM

TBTGVIV TS

VGE

ISV

EV

BCV

MBV

M

Demister

ScrubberU-Seal

H-Tank

Drain-Pit

GRIV

TRT

M/C

COG

BGIV

TRT equipmentsTo ThickenerFrom Thickener

Miscellaneous Top Gas Recovery Turbine (TRT) BF gas flow rate (wet) (Operation point 1) : 400,000 Nm3/h (Operation point 2) : 450,000 Nm3/h (Max flow rate) : 512,000 Nm3/h BF top pressure : 2.5 kg/cm2 gauge (max)

BF gas pressure at TRT inlet : 2.2 kg/cm2 gauge (max) : 2 kg/cm2 gauge (normal) : 1.8 kg/cm2 gauge (min) BF gas temperature at turbine inlet : 80ºC (max) : 50ºC (normal) BF gas pressure at TRT outlet : 0.125 kg/cm2 gauge (max) : 0.08 – 0.1 kg/cm2 gauge (Normal) BF gas dust content : 5.0 mg/Nm3 maximum (Dry) BF gas relative humidity : Saturated at temperature BF gas chemical composition : CO2 - 22%; CO - 25%; H2 - 4%; N2 - 49%.

knowledge on control parameters_01

Documents