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Controlling parameters During Blow down:

1. Top temperature Control

a. Start Spray at 400 deg C uptake temperature

b. Stop Spray at 300 deg C uptake temperature

2. Control of top temperature according to individual spray control andindividual uptake temperature.

3. Water inlet pressure maximum, no valve throttling.

4. Hydrogen control limit 12%

5. Gear Box temperature 70 deg max.

6. Scrubber outlet water temperature 85 deg C max.

Wind adjustments or deviations from plan should be based upon following:

Top temperature increasing and H2%in top gas below 12%

Increase water injection to control toptemperature

Top temperature increasing and H2%

in top gas above 12%

Lower the wind rate and reduce water

injection

Top temperature decreasing Decrease water injection

Hydrogen % in top gas over 15% Decrease water injection and check for

any water leak

Trace oxygen in off gas, slipping or

blowing through

Reduce Wind

Hanging Shake the furnace and check stock level

again

Blow Down Procedure:

Charging to be stopped at 16:00 hrs and blow down is to be started

with normal wind.

Top temperature and wind reductions is to be done as per abovementioned guide lines.

Measurement of stock level is to be done hourly, with only one

stock rod and electrical personnel ready at the MCC panel to lift it

from panel if it is not lifted from control room.

Stove changeover is not allowed after 10 mtrs of stock level.

MCC01 and BLT chute (no. 1 position) is to be kept running.

Nitrogen in the injection points are to be fully opened after

reaching the burden level below that point

Tuyeres are to be watched regularly Casting is to be opened at the regular intervals with higher drill bit

size(55 and 65) in order to empty out the furnace as far as possible,

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tap hole length is to be maintained >2.5 mtr. Clay quantity is to be

reduced in the last few casts for easy opening of tap hole.

PCI is to be stopped when the CO2% becomes minimum (less than

8%) as per the thermal condition of the furnace.

Heating of stove is to be stopped in case of

o Hydrogen in top gas is more than 10%

o Wind volume less than 150,000 Nm3/hr

o Stock level is more than 10 mtrs. Screw compressor is to be stopped in case of

o Top gas Hydrogen more than 10%

o GCP outlet gas temperature more than 70 deg C.

Nitrogen in gear box is to be opened for gear box cooling.

Condition for GCP disconnection

o H2% is over 18%

o O2% is over 1.0%

o CO2% equals 0.5% of CO% (when CO2% starts rising after min

value).

GCP disconnection is to be done as per standard operating

procedure; Dust catcher bleeder is to be opened.

Purging in GCP and dust catcher is to be continued.

At the end, wind is pushed for few seconds to spread dead man

coke.

Blowing down is to be stopped in case CO and H2 is present with

oxygen otherwise blowing down is to be continued till raceway is

collapsed in all the tuyeres and O2 % is more than 5% in the top

gas.

Water spray pump is to be stopped and the manual valve is to be

closed.

Wind is to be reduced to minimum, wait for 5 minutes and

two/three peephole valve is to be opened.

Furnace isolation valve is to be closed.

Open all the peep hole flanges

Check for top fire establishment.

Stove in blast is to be isolated. The Blow down is now complete.

Furnace cooling:

Take out the blow pipes one by one and put the nitrogen lances in

the tuyeres. Plug the tuyere completely with clay so that there is no

suction from tuyere. The Nitrogen lances are to be fixed by holder

with tuyere cooler.

N2 injection in the furnace and from the coal lances is to be

continued for 4 to 5 hours. Total N2 flow should be 7000 - 8000Nm3/hr.

One bleeder is to be closed.

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Top pressure is to be monitored. It is to be in positive side (more

than 250 mm water column). For better pressurization top bleeder

is to be throttled if required. One low pressure transmitter is to be

fitted with one of the uptakes and on bottom most nitrogen point is

to be converted into low pressure transmitter.

Both the pressure readings are to be continuously monitored and

recorded.

Measurement of top gas hydrogen and oxygen is to be done by topgas analyzer and it is to be recorded.

Check for oxygen level below 4%. Start the group 10 pump and

manual valve and get ready for the top spray.

When O2% is below 4% open water from water spraying nozzles.

Initially only one spray is to be used and it is to be rotated.

The criteria for water spray is

o O2 in top gas below 4%

o Positive pressure inside the furnace

o H2 limit is below 10%

When the H2% in top gas is below 0.5% stop water spraying.

Continue the N2 injection further for 4 to 5 hours.

Other bleeder is to be opened.

Stop the N2 from the lances and open all the tuyeres. Open the top

manholes and handover the furnace for repair.

N2 in the gear box is to be stopped and cooling is to be done by

fan.

Give clearance for furnace top gunning.

Post cooling activities: All the 30 tuyeres are to be taken out one by one.

Coke raking is to be done from maximum possible tuyeres

manually.

TC removal for tuyere no 2 and 3

TC is to be removed from other places ( 5 to 6) for better

ventilation and coke raking.

Cut the shell to make an opening of 2 x 2 mtr at the tuyere on 2 and3.

Remove the refractory if any behind the shell.

Platform for JCB in cast house east and coke removal by JCB.

When the gunning of the top is complete remove the coke and

rebound material to maximum possible extent by going inside the

furnace.

All the loosely packed coke and slag is to be removed.

Hearth is to be completely capped with capping material. For that

o Placement of 4 no of chain links across the furnace (diagonallyopposite the tuyeres).

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o Insertion of one inch dia pipe with bend to provide exhaust of the

gas. ( 4 to 5 in no.s)

After the capping is complete, check the burning of the gas if any

from the bent pipes. One man is to be made responsible for burning

of the gas.

Manual bosh gunning is to be done in Bosh region after cleaning of

any scab material.

After gunning job is over, the capping material is to be removed

and digging of coke in front of tap hole is to be done. A passage of

around 1.5 mtr width and long to the furnace center is to be made.

All the dogged material is to be removed.