Description:
Field of Invention
The present invention relates to the field of metallurgy. More specifically the present invention relates to the development of a movable bunker system for introducing ferro-alloys and deoxidizers during tapping at a Basic Oxygen Furnace (BOF) through a chute.

Background of Invention:
Basic Oxygen Furnace in Steel Melting Shop is generally devoid of provisions (bunkers with vibro-feeders) for addition of ferro-alloys and deoxidisers into ladles during tapping. The additions of suitable quantity of de-oxidisers / ferroalloy addition not only help in reducing oxygen content of steel but improve the ferroalloy recovery. The previous Steel Melting Shop devoid of provisions (bunkers with vibro-feeders) thus used manual addition of aluminium bar or small bags of ferro-alloys at the bottom of ladle. This process of manual addition not only limits the quantity of required addition but also risky from safety point of view and limits the quantity of additions.

Some modern converters as shown in Figure 1 have been developed which included automated bunkers (for example four to add Coke, FeSi, Silico Manganese while one bunker is spared as reserved bunker). However, these bunkers have the limitations that they are fixed and they are huge in size. Thus, in situation when multiple alloys need to be added and in low quantity for example in special or quality steels (which require tapping addition of other micro alloying elements and deoxidisers in addition to existing bunkers of Coke, FeSi, Silico Manganese), the existing automated bunkers are not useful. Thus, they are added in secondary steelmaking or next stage. Tapping addition of micro alloys at tapping stage reduce load on secondary steelmaking. Also, in case of failure of the existing automated bunker, shop is forced to either stop the steelmaking process till rectification or rely on manual addition.

Thus, there is a need to provide a flexible movable bunker which can be used to add alloys or other additives in the tapping stage.

Object of the invention
It is an object of the present invention to overcome the drawbacks of the prior art.

It is another object of the present invention to provide a movable bunker for introducing ferro-alloys and deoxidizers during tapping at a Basic Oxygen Furnace (BOF) through a chute.

It is a further object of the present invention to provide a movable bunker that reduce load on secondary steelmaking.

It is a yet another object of the present invention to provide a movable bunker which would be helpful in case of failure of the existing automated bunker such that the shop will not be forced to stop the steelmaking process till rectification.

Summary of the invention
Accordingly, the present invention provides a movable bunker for tapping addition of ferro-alloys and de-oxidisers at Basic Oxygen Furnace (BOF) through chute, said bunker comprising
i. a hollow vessel (1); said vessel (1) having atleast one material charging point (4) and atleast one material discharging point (6), being accessible from atleast one side provided with a flap (3), wherein said vessel (1) contains said ferro-alloys and de-oxidisers;
ii. plurality of hanging points (5) at the top and plurality of grooves (7) at the bottom of said bunker for moving said bunker from a loading point to a charging point; and
iii. atleast a lever (2) adapted to be connected to said flap (3) such that movement of said lever (2) correspondingly facilitates opening and closing of the flap (3), thereby releasing said ferro-alloys and de-oxidisers during tapping desirably.

Brief Description of Accompanying Drawing:
Figure 1 illustrates converters with limited automated bunkers.
Figure 2 illustrates the movable bunker.
Figure 3 illustrates the top and side views of the bunker.
Figure 4 illustrates the Scheme of Addition of Deoxidisers and Ferroalloys at BOF during Tapping
Figure 5 illustrates a preferred embodiment of the present invention.

Detailed Description of the Invention
Accordingly, the present invention provides a movable bunker for tapping addition of ferro-alloys and de-oxidisers at Basic Oxygen Furnace (BOF) through chute, said bunker comprising plurality of hanging points at the top and grooves at the bottom to move from a loading point to a charging point and atleast a lever connected to an opening flap of the bunker for releasing the loaded materials at desired time during tapping.

The novel movable bunker provides the following benefits:
i. Facilitate the addition of ferro-alloys/ de-oxidisers/ fluxes during tapping which helps in reducing oxygen content of steel which helps in increasing the recovery of ferro-alloys.
ii. Reduce the spillage of ferroalloys material due to manual addition of ferroalloys/ deoxidiser during tapping.

The portable bunker of the present invention has been designed and fabricated using mild steel plates. It has the capacity to store ferro-alloys/de-oxidizers/fluxes as low as 1.4 m3 to 2.4 m3.

The bunker is provided with a lever which is connected to the opening flap of the bunker as shown in figure 3(a). Thus, the operators can release the materials with the help of a lever provided at the bunker at the required time during tapping. The system, allows for both single and multiple additions as needed for different grades and processes.

The bunker is provided with hanging points at the top and grooves at the bottom so that it can be easily moved and positioned from loading point of material (ferro-alloys/ de-oxidisers/ fluxes) to the right position of chute with help of crane or forklift as shown in figure 3(a).

The ferro-alloys can be selected from Ferro-manganese (FeMn), Ferro-silicon (FeSi), Ferro-phosphorus (FeP), Ferro-silicomanganese (FeSiMn), Ferro Niobium (FeNb), Ferro Vanadium (FeV), Nickel (Ni), Ferro Chrome (FeCr), Ferro Molybdenum (FeMo).

The de-oxidisers can be selected from aluminium (in form of bars, shots or cubes), coke, Ferro-silicon (FeSi), Ferro-silicomanganese (FeSiMn). (It may be noted that some ferroalloys acts as deoxidisers also like FeSi and FeSiMn).

The present invention can be used in BOF, having limited number of bunkers for ferro-alloys. It can be very useful for addition of special ferro-alloys which is normally not kept in bunkers. It will facilitate addition of ferroalloys / deoxidisers during heat making of any trial heats.

Design Features:
o Portability: The bunker is provided with hanging points at the top and grooves at the bottom for lifting though any cranes and forklifts which make it possible to move to and fro between loading point of ferroalloys and addition point during tapping. This makes the movable bunker for use in multiple BOFs in the shop.
o User friendly and maintenance free: The bunker is a non-automated system which makes it possible to use by an operator without much knowledge of automation system. Also, the system is almost maintenance free.
o Flexibility of time for tapping addition: This bunker is provided with a lever which is connected to the opening flap of the bunker. Thus, the operators can release the materials with the help of a lever provided at the bunker at the required time during tapping. The system, allows for both single and multiple additions as needed for different grades and processes.
o The movable bunker is designed for the addition of ferro-alloys and de-oxidizers during the tapping process in old converters that lack dedicated bunkers for tapping addition.
o Adaptability of the designed movable bunker to modern BOFs that have a limited number of bunkers for ferro-alloys, allowing for the addition of small amounts during tapping to overcome limitations and enhance steelmaking flexibility. Also, in steel melting shops with lower special steel volumes, adding small ferroalloy quantities during tapping through bunkers is impractical.
o The movable bunker can be used as a standby for addition of ferroalloys and deoxidizers in case of non-functioning of automated ferroalloy system in existing modern BOFs. This will facilitate uninterrupted steelmaking process.
o Human Safety: Use of the present bunker will avoid safety risk due to manual addition of heavy aluminium bar or bags of ferro-alloys/ deoxidiser during tapping in liquid steel.
o Addition reliability and safe operation: Manual addition of ferroalloys increases the risk of material spillage (outside ladle) due to heat, dust and narrow space. Manual addition of aluminium bar before tapping increases risk of porous plug opening due to choking of pores.

Detailed Description of Accompanying Drawing
Figure 1 illustrates the modern converters which included automated bunkers (for example four to add Coke, FeSi, Silico Manganese while one bunker is spared as reserved bunker). Figure 2 illustrates the movable bunker for tapping addition of ferro-alloys and de-oxidisers at Basic Oxygen Furnace (BOF) through chute, in accordance with the present invention.

Figure 3(a) and Figure 3(b) show the side view of the present bunker while Figure 3 (c) shows the top view. As evident from Figure 3(a), the bunker comprises a hollow vessel (1). The vessel (1) contains the ferro-alloys and de-oxidisers that is to be added during tapping. The vessel (1) has atleast one material charging point (4) and atleast one material discharging point (6), being accessible from atleast one side provided with a flap (3). The bunker is provided with plurality of hanging points (5) at the top and plurality of grooves (7) at the bottom for moving said bunker from a loading point to a charging point. There is provided atleast a lever (2) adapted to be connected to the flap (3) such that movement of said lever (2) correspondingly facilitates opening and closing of the flap (3), thereby releasing the ferro-alloys and de-oxidisers during tapping desirably.

Figure 4 illustrates the method of Addition of Deoxidisers and Ferroalloys at BOF during Tapping using the bunker of the present invention. As evident from the figure 4, the bunker can be lifted to a desired height above the ladle from where various ferro alloys or oxidiseres can be added through the chute during tapping. The bunker is provided with hanging points (5) at the top and grooves (7) at the bottom so that it can be easily moved and positioned from loading point of material (ferro-alloys/ de-oxidisers/ fluxes) to the right position of chute with help of crane or forklift.

Figure 5 illustrates a preferred embodiment of the present invention.

Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made, none of which depart from the spirit or scope of the present when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

The present invention is now being illustrated by way of non-limiting examples.

Example 1
Tested at BOF#Q in SMS-I, the bunker demonstrated operational efficiency with silico manganese, pet coke, and aluminium, offering benefits such as reduced spillage and increased recovery of ferro-alloys.

Experiments and Results
• The experiment is conducted in 65 T BOF having no automated bunker.
• In case of low carbon steel grades (IS10748 Gr-I), pet coke (25-30kg) while three pieces of aluminium bars (~60kg) were added in ladle during tapping using the bunker of the present invention. Similarly, in case of medium carbon grades (IS 2062 E-250 BR), pet coke (45-50kg), three pieces of aluminium bars (~60kg) and silico-managnese ferroalloy (~200kg) were added in ladle during tapping using the bunker of the present invention.

• Result:
Reduction in Ferroalloy Consumption: Prior to the present invention there was no provision of adding ferro-alloys and de-oxidisers. However with the present invention the same can be used for tapping addition of ferro-alloys and de-oxidisers at Basic Oxygen Furnace (BOF) through chute which resulted in decrease of Silico Manganese Consumption for IS10748 Gr-I (Kg/t) from 7.1 kg/T to 6.5 kg/T. Similarly, silico manganese consumption for IS 2062 E-250 BR decreased from 23kg/T to 21kg/T.
, Claims:
1. A movable bunker for tapping addition of ferro-alloys and de-oxidisers at Basic Oxygen Furnace (BOF) through chute, said bunker comprising
i. a hollow vessel (1); said vessel (1) having atleast one material charging point (4) and atleast one material discharging point (6), being accessible from atleast one side provided with a flap (3), wherein said vessel (1) contains said ferro-alloys and de-oxidisers;
ii. plurality of hanging points (5) at the top and plurality of grooves (7) at the bottom of said bunker for moving said bunker from a loading point to a charging point; and
iii. atleast a lever (2) adapted to be connected to said flap (3) such that movement of said lever (2) correspondingly facilitates opening and closing of the flap (3), thereby releasing said ferro-alloys and de-oxidisers during tapping desirably.

2. The movable bunker as claimed in claim 1, wherein said vessel (1) is trapezoidal in shape.

3. The movable bunker as claimed in claim 1, wherein said bunker is made of mild steel plates.

4. The movable bunker as claimed in claim 1, wherein said bunker has the capacity to store ferro-alloys/de-oxidizers/fluxes as low as 1.4 m3 to 2.4 m3.

5. The movable bunker as claimed in claim 1, wherein said ferro-alloys are selected from Ferro-manganese (FeMn), Ferro-silicon (FeSi), Ferro-phosphorus (FeP), Ferro-silicomanganese (FeSiMn), Ferro Niobium (FeNb), Ferro Vanadium (FeV), Nickel (Ni), Ferro Chrome (FeCr), and Ferro Molybdenum (FeMo).

6. The movable bunker as claimed in claim 1, wherein said de-oxidisers is selected from aluminium in form of bars, coke, Ferro-silicon (FeSi), and Ferro-silicomanganese (FeSiMn).