MODIFIED MODULAR DESIGN FOR REPLACEABLE ROOF OF SINTERING
FURNACES IN STEEL PLANTS FOR CURTAIN FLAME IGNITION
TECHNOLOGY
FIELD OF INVENTION
The invention relates to the "modified modular design for replaceable roof of
sintering furnaces in steel plants for curtain flame ignition technology" for igniting
the top layer of the sinter bed. More particularly the present invention discloses
modified roof of sintering furnaces in steel plants for curtain flame ignition
technology including an arrangement of burners and support system which is light
in weight requires lower maintenance, economize fuel gas consumption and
protect the ignition hood from overheating and damage.
BACKGROUND ART
Sintering is a process of agglomeration of iron ore fines. In this process, iron ore
concentrate or iron ore fines are thoroughly mixed with blast furnace flue dust, fine
coke breeze and lime stone, moistened and loaded on to a sintering machine
grate.. An intensive flame source ignites the fuel (coke fines) contained in the
charge layer. An exhaust fan, located beneath the agglomeration charge, effects
air suction through the layer. The burning, commencing at the top of the charge
layer, gradually proceeds downwards through the layer and ends at the grate of
the machine. Burning fuel raises the temperature in excess of 1,150°C which is
sufficient to partially fuse and sinter the charge grains..Upon completion of the
burning, the whole charge layer becomes a porous lumpy product for charging into
Blast Furnace.
In general, the sinter hoods or sintering furnaces are having dimensions of 8,000-
10,000 mm length, width in relation to sinter bed width and about 1200 to 1400mm
height. The lining is done with metal clad hanging bricks in the roof and fire
clay/insulation bricks in the side walls of the sinter hood. Mixed gas (Mixture of
blast furnace and coke oven gasses) of about 1400 - 4200 calorific value (CV) is
used for making the sinter. As the burners are horizontally fixed in the side walls,

the flame do not properly touch the charge and the efficiency of the furnace is
reduced. The fuel consumption is also high.
In order to reduce the fuel consumption and improve the ignition efficiency of
sintering furnaces, a curtain type top mounted gas fired burner system has been
invented and implemented in some of the SAIL steel plants. For incorporating this
burner system in which burners are arranged in a single row and the flame length
is only about 500mm, a modular roof had been designed.
Further in prior art, the design of modular roof has been patented vide patent no.
210295 dated 24.12.2003 under the title of the patent "Development of modular
design for replaceable roof of sintering furnaces along with separators for
incorporation of curtain type top mounted gas fired burner system for igniting the
top layer of the sinter bed".
In this patent, the modular roof was made with hollow rectangular beams of
7000mm length and 540mm width and bottom and side walls of which were cast
with 70% Al2O3 containing Low Moisture Castable (LMC). The thickness of the
casting at the bottom was 250mm and at sides it was 65mm. The length of the
casting on 7000mm beams was 4000mm and remaining 3000mm was left un-cast
on both sides (1500mm) for resting on the furnace roof beams which are welded
to the vertical columns on both sides of the furnace. 3 beams of this type were
made for placement in the furnace proper and burner system is placed in between
these castings.
The disadvantages faced in this system were:
1. The hollow rectangular beams were heavy for lifting and placement on the
cross beams of the furnace welded between two vertical columns.
2. The beams were not getting cooled by the atmosphere as the beams' metallic
parts were closed from all sides.
SUMMARY OF THE INVENTION
Therefore the principle object of the present invention is to provide a novel
arrangement of burners and support system for allowing improved ignition

efficiency of sintering furnaces leading to lower fuel consumption.
Another object of the present invention is to provide an improved modular design
for replaceable roof of sintering furnaces in steel plants for curtain flame ignition
technology including an arrangement of burners and support system which
requires lower maintenance.
A further object of the present invention is to provide a novel arrangement of
burners and support system which is easy installation in sintering furnaces with
the least modification in the same.
Accordingly, the present invention provides a modified modular design for
replaceable roof of sintering furnaces in steel plants technology for incorporation
of curtain type top vertically mounted gas fired burner system, wherein the
sintering furnace comprises sinter bed and end walls he replaceable roof
comprising a plurality of cast beams for ignition hood roof supporting said top
mounted burners and these vertically fired burners being disposed in between
said main beams such that the flames of said burners ignite the top layer of sinter
bed.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be described with reference to a preferred embodiment and
accompanying figures:
Fig 1 shows roof beams design as per the prior art;
Figure 2 shows roof beams being cast with high alumina castable in accordance
with the present invention.
DETAILED DESCRIPTION
Figure 1 shows the roof system as per the prior art. The charging side and the
discharge side are as indicated. The vertical line indicates the top of the sinter
bed. The roof comprises an arrangement of cast beams with preferably low

moisture castable which may vary depending on the space availability for
installation. Two main beams separating the top mounted burners and two end
beams serving as end walls, one in the charging side and another at the discharge
side are provided. The beams are of 7000mm length and 540mm width and end
walls are cast with 70% Al2O3 containing Low Moisture Castable (LMC). The
beams are provided with SS-310 anchors and ceramic fibre blanket. The
thickness of the casting at the bottom is 250mm and at the sides is 65mm. The
length of the casting on 7000mm beams is 4000 mm and the remaining 3000 mm
is left un-cast on both sides for resting on the furnace support beams which are
welded to the vertical columns on both sides of the furnace.
In order to rectify the above, the following modifications were done with respect to
the design of the roof beams. The ignition hood roof design is modified by making
structures made of mild steel plates with stiffeners at the top and refractory casting
at the bottom in place of disclosed prior art design of using rectangular hollow
structures whose bottom and its adjacent 2 sides were cast with 90% alumina
refractory castable. Fig.2 shows the casting in progress with high alumina castable
after welding of "Y" shaped SS-304 anchors.
The beams in the modified design have become lighter by about 40-50% in
comparison to earlier rectangular hollow beams for easy placement in the roof and
also for easy replacement beams were placed in roof and burner modules were
placed between 2 of them. In both sides of these beams, end beams were made
and placed so that the furnace becomes compact and loss of energy is minimized.
The ends of said beams are left un-cast for resting on the furnace roof beams.
The beams are placed on two support beams on either side of the furnace which
are elded to vertical columns on both sides of furnace.
Fuel saving has remained same i.e. to the tune of 30-40% as in the earlier design
using rectangular beams. The life of the roof of the sinter hood furnaces at
Durgapur Steel Plant and Bhilai Steel Plant have given 1 ½ to 2 years in
comparison to maximum one year life with earlier design using rectangular beams.
A series of burners encased in metal frames are installed in the furnace roof so
that the direct impingement of gas flame is occurred on the sinter bed instead of in

the side walls in old hanging brick roof design is included in the modified roof
design of sinter furnace ignition hood. The sinter furnace ignition hood along with
comprise a combustion system in which top surface of roof beams are cooled by
atmospheric air. The disclosed modified roof design of sinter furnace ignition hood
along with combustion system in which fuel saving remained same to the tune of
30-40% as in the earlier design of furnace roof using rectangular beams. The top
surface of roof beams are cooled by atmospheric air
The modified design has been implemented in Bhilai Steel Plant, Bhilai, Durgapur
Steel Plant, Durgapur, Rourkela Steel Plant, Rourkela and finally being
implemented in Bokaro Steel Plant, Bokaro.
Numerous modifications may be made to the present invention, which still fall
within the intended scope hereof. Thus, it should be apparent that there has been
provided in accordance with the present invention a modified modular design for
replaceable roof of sintering furnaces in steel plants for curtain flame ignition
technology that fully satisfies the objectives and advantages set forth above.
Although the invention has been described in conjunction with specific
embodiments thereof, it is evident that many alternatives, modifications and
variations will be apparent to those skilled in the art. Accordingly, it is intended to
embrace all such alternatives, modifications and variations that fall within the spirit
and broad scope of the appended claims.

We claim:
1. A modified modular design for replaceable roof of sintering furnaces in steel
plants technology along with separators for incorporation of curtain type top
mounted vertically gas fired burner system, wherein the sintering furnace
comprises sinter bed and end walls defining the charging side and the discharge
side the replaceable roof comprising:
a plurality of cast beams for ignition hood roof design separating said top mounted
burners made of mild steel plates at the top and refractory casting at the bottom
and cast with 90% alumina refractory castable; and
vertically fired burners being disposed in between said beams such that the
flames of said burners ignite the top layer of sinter bed.
2. A modified modular design for replaceable roof of sintering furnaces as
claimed in claim 1, wherein said beams have casting with low moisture castable.
3. A modified modular design for replaceable roof of sintering furnaces as
claimed in any preceding claims, wherein said beams have high alumina castable
after welding of "Y" shaped SS-304 anchors.
4. A modified modular design for replaceable roof of sintering furnaces as
claimed in any preceding claim, wherein the ends of said beams are left un-cast
for resting on the furnace roof beams.

5. A modified modular design for replaceable roof of sintering furnaces as
claimed in preceding claims, wherein said beams are placed on two support
beams on either side of the furnace which are welded to vertical columns on both
sides of furnace.
6. A modified modular design for replaceable roof of sintering furnaces as
claimed in claim 1, wherein the beams are lighter by about 40-50% for easy
placement in the roof and also for easy replacement.
7. A modified modular design for replaceable roof of sintering furnaces as
claimed in claim 1, wherein the series of burners are installed in the furnace roof

so that the direct impingement of gas flame is occurred on the sinter bed instead
of in the side walls in old hanging brick roof design.
8. A modified modular design for replaceable roof of sintering furnaces as
claimed in preceding claims, wherein the top surface of roof beams are cooled by
atmospheric air.

ABSTRACT

The present invention discloses modified roof of sintering furnaces in steel plants
for curtain flame ignition technology including an arrangement of burners and
support system which is light in weight requires lower maintenance, economize
fuel gas consumption and protect the ignition hood from overheating and damage.