Field of the invention
The present invention relates to a replaceable roof for sintering furnaces for the
incorporation of curtain type top mounted gas fired burner system. In particular the
present invention relates to a replaceable roof for sintering furnaces for top mounted
burner systems for igniting the top layer of the sinter bed.
Background of the invention
Sintering is a process of agglomerating iron-ore fines for improving properties of raw
materials in iron and steel manufacture by its fluxing, desulphurisation,' and
dearsenification. In sintering process, generally iron ore concentrate or iron ore fines
are thoroughly mixed with blast furnace flue dust, fine coke breeze and limestone. The
mixture is moistened and loaded on to a sintering furnace in a layer of 200 - 350 mm
thickness. An intensive flame source ignites the fuel contained in the charge layer. The
flame source is provided by number of burners at the side wall of the sinter hood. The
furnaces are lined in the roof with metal clad hanging bricks of generally mag-chrome
quality. Side walls are lined with fire clay/insulation bricks. Burners are installed in the
side walls for horizontal firing. An exhaust fan located beneath the agglomeration
charge effects air suction through the layer. In such conventional furnaces the burning
commences at the top of the charge layer, gradually proceeds downwards through the
and ends at the grate of the furnace. Burning fuel raises the temperature in
excess of 1400°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 hood or sintering furnaces have dimensions of 8,000-10,000 mm
length 4,000 - 5,000 mm width and about 1200 to 1400 mm height. The lining is done
with metal clad hanging bricks in the roof and fire clay/insulation bricks in the side walls.
12 of burners are provided at both the side walls of the sinter hood. Mixed gas
(mixture of Blast Furnace and Coke Oven gas) of about 1800 calorific value is used for
making the sinter.
Such conventional arrangement of burners, in particular burners which are horizontal to
the side walls of sintering furnace, does not allow proper contact with the charge. As the
burners are horizontally fixed to the side walls the flames do not properly touch the
charge and the efficiency of the furnace is not satisfactory. This leads to high fuel
consumption and substantial increase in the production cost. Furthermore every year
during the capital repairs of the furnaces total bricks are dismantled and new brick lining
is carried out. This is due to the non modular design of the support structure for the
burner system. Life of the refractory in case of the conventional horizontal mounted
burner system is around a year as the refractory gets damaged due to loosening of
refractory lining and falling of bricks from roof and cracking of side wall burner blocks.
Therefore there is a need to provide a burner system and support structure which allow
improved ignition efficiency of sintering furnaces and has longer life.
Objects of the invention
Therefore the 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 a novel 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.
The applicants have now developed a replaceable roof structure for sintering furnaces
for incorporation of top mounted gas fired burner system. Such top mounted burner
systems allow better contact of the flames with the charge and also reduces the burning

zone and height of furnace which in turn reduces the cost towards refractories for lining
the furnaces.
Summary of the invention
Accordingly, the present invention provides replaceable roof for sintering furnaces 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 comprising at least two main beams separating said top
mounted burners and at least two end beams in contact with end walls of said sintering
furnace wherein said at least two beams in contact with end walls comprises at least
one in the charging side and at least one at the discharge side, thereby decreasing the
furnace height and furnace length;
vertically fired burners being disposed in between said main beams such that the flames
of said burners ignite the top layer of sinter bed.
The invention will now be described with reference to a preferred embodiment and
accompanying figures:
Figure 1 shows a conventional furnace with horizontal burners
Figure 2 shows the replaceable roof of sinter furnace of present invention
Figure 3 shows roof beam arrangement
Figure 4 shows isometric view of end beam
Figure 5 shows isometric view of main beam
Figure 6 shows cross sectional views of main beam and end beam

Description of preferred embodiment
Figure 1 shows a conventional furnace with horizontal burners. The furnace is lined
in the roof with metal clad hanging bricks of Mag-chrome quality. Side walls are lined
with fire clay/insulation bricks. Six burners (1), as seen in the elevation view, are
provided with air supply (2) and mixed gas supply (3). The charging side (4) and the
discharge side (5) are as indicated. The distance between two columns (6) is around
3000 mm.
Figure 2 shows the roof system of the present invention. The charging side (7) and
the discharge side (8) are as indicated. (9) and (10) are the front and back wall
beams with low moisture castable casting respectively. The vertical line (11)
indicates the top of the sinter bed. Air (12) and mixed gas (13) are supplied for
making the sinter. The roof system, as shown in figure 3, comprises an arrangement
of cast beams with preferably low moisture castable which may vary from 4 to 5
depending on the space availability for installation. Two main beams (14 & 15)
separating the top mounted burners (16) and two end beams (17 & 18) 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 (19) and ceramic fibre blanket (20). The thickness of the casting at
the bottom is 250mm and at the sides is 65mm. The length of the casting on 7000
mm 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. Figure 6 shows the pattern details for casting with LMC.
The beams (21) and their casting (22) for main beams (figure 6a) and end beams
(figure 6b) are shown.
The isometric views of the beams with their castings are shown in figures 4
and 5. (41) indicates the beams and (42) the castings. The main beams are
made for placement in the furnace proper and for placing the burner
system between the castings. End beams, used for separating the burning
zone from the charging zone and cooling zone, are made by joining two "I"
beams (41) encased by a metal plate on all sides of the joined T

beams for proper support. Total height of the end T beams is 700 mm and width 160
mm. Casting with LMC of 425 mm at the bottom and 65 mm at the outer face was done
of these end beams. The design is done in such a way that casting of the mainbeams
just adjacent to the end beams sit tightly on the projected refractory casting of the end
beams.
After casting the beams are air cured for 24 hours and heated slowly with mixed gas till
600°C is attained for removal of moisture completely.
For installation of above 5 beams in a conventional furnace, the furnace was shut down
and 3 m length of the furnace at the charging end is cleared off for refractory and other
structures. Two support beams are welded between two columns on either side of the
furnace. The beams cast with LMC are then lifted and places on the supporting beams
of the furnace one by one. The burners of 250 mm width are placed after 2 beams (one
end beam and one main beam) which are connected to air and gas pipe lines. Furnace
roof height above charge ievel reduced from 1400 mm to about 500 mm. All otner
horizontal burners are closed. The length of the burning zone of the furnace comes
down to 3000 mm form 8000 to 10000 mm. The efficiency of the furnace improved as
the flames are directly impinging on the sinter bed and cooling zone is increased by
5000 mm.
As the furnace working volume is reduced considerably, energy efficiency of the furnace
improves and refractories consumption is found to be reduced by about 70%.
We Claim :
1. Replaceable roof for sintering furnaces 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 (4) and the discharge side (5) the replaceable roof
comprising :
a plurality of cast beams comprising at least two main beams (14,15)
separating said top mounted burners (16) and at least two end beams
(17, 18) in contact with end walls (9 8b 10) of said sinter furnace wherein
said at least two beams in contact with end walls comprises at least one
in the charging side (7) and at least one at the discharge side(8), thereby
decreasing the furnace height and furnace length; vertically fired burners
being disposed in between said main beams such that the flames of said
burners ignite the top layer of sinter bed.
2. Replaceable roof for sintering furnaces as claimed in claim 1, comprising
three main beams (14, 15, 21) and two end beams (17, 18, 21).
3. Replaceable roof for sintering furnaces as claimed in any preceding
claim, wherein said beams have casting (22) with low moisture castable.
4. Replaceable roof for sintering furnace as claimed in any preceding claim,
wherein said beams have High chromium-Nickel alloy steel made
anchors (19) and ceramic fibre blankets (20).
5. Replaceable roof for sintering furnaces as claimed in any preceding
claim, wherein the ends of said main beams are left un-cast for resting
on the furnace roof beams.
6. Replaceable roof for sintering furnaces as claimed in claim 5, wherein
said main beams (14,15) are placed on two support beams (9, 10) on
either side of the furnace which are welded to vertical columns on both
sides of furnace.
7. Replaceable roof for sintering furnaces as claimed in claim 5, wherein
said end beams are made by joining two "I" beams (41) encased by a
metal plate on all sides of the joined 'I' beams (41) for proper support.

A replaceable roof for sintering furnaces for the incorporation of curtain type top
mounted gas fired burner system. The replaceable roof comprises a plurality of cast
beams comprising at least two main beams separating the top mounted burners and at
least two end beams in contact with end walls of the sintering furnace wherein the at
least two beams in contact with end walls comprises at least one in the charging side
and at least one at the discharge side thereby decreasing the furnace height and
furnace length and vertically fired burners being disposed in between the main beams
such that the flames of the burners ignite the top layer of sinter bed. The system results
in improved ignition efficiency of sintering furnaces leading to lower fuel consumption.