Field of the Invention
The present invention relates to an improved compound for desulphurization of hot metal. More
particularly, the present invention relates to the improved method of desulphurization of hot
metal by using carbide based compound (composition) and magnesium in optimum ratio to
avoid the demerits of using magnesium alone as a desulphurizer. Moreover this invention also
relates to the improved method of desulphurization of hot metal by using carbide based
compound (composition) and magnesium in definite ratio to increase the efficiency of present
CAD compound.
Background of the invention and related prior Art
Desulphurization of pig iron in a steel mill is done in lieu of desulphurization after tapping from
the blast furnace or in lieu of desulphurization in a mobile receptacle (torpedo ladle truck)
between blast furnace and steel mill. Desulphurization in the steel mill is intended to lower the
initial sulphur contents of e.g. 0.035% to 0.045% sulphur in order to create favorable conditions
for the blasting process, after which the final sulphur contents of the finished steel are so low
that higher quality of steel, such as high-duty steel, steel for the manufacture of electric plate,
roller bearing steel and the like may be produced. Desulphurization of crude iron after the
blasting process is used to vary the percentage of several components in the iron in order to
influence casting and cooling conditions as well as material properties, and also the properties of
the finished material.
The applicable metallurgic refining and/or alloying methods for the smelting of metals and
metal alloys determine the ultimate properties of the material being worked or the material flux

in the metal smelting plant. The desired properties of the material flux, in turn, determine the
planning of the metal smelting plant.
If the metal smelting plant consists of a steel mill, the material being processed goes from the
pig iron supply (blast furnace or pig iron mixer) and from the junk yard (solid metal) to the
charging hall in front of the smelting furnaces. The liquid metal (steel) tapped from the smelting
furnaces (steel mill converters) is either transported through the charging hall into the casting
hall where it is cast into upright molds, or it is transported to strand-casting facilities bordering
on the smelting furnace hall.
In accordance with a familiar proposal (technical magazine "Steel and Iron" issue of Oct. 26th,
1972, pages 1088/1089) pig iron may be desulphurized in torpedo ladles outside the steel mill in
a treatment stand between blast furnace and steel mill. Placing such treatment stand inside the
steel mill, however, will result in shorter transport distances and consequently decreased heat
loss in the liquid metal. With a treatment stand inside the steel mill, the temperatures of the
liquid metal before and after desulphurization and/or dephosphorization and/or desilicification
may be maintained more closely
The invention of the document CN101392310 states a sulfur-fixing agent for hot metal
pretreatment magnesium injection deep desulphurization and a desulphurization method, which
pertains to the technical field of hot metal pretreatment in the steelmaking process. The sulfur-
fixing agent is added before hot metal charging or during hot metal charging in the LD for hot
metal pretreatment and the addition range is 2.0 kg/t to 4.0 kg/t iron which contains the
following components by the weight percentages: CaO: 68 percent to 90 percent; MgO: 5

percent to 12 percent, SiO2: 1 percent to 5 percent, CaF2: 8 percent to 12 percent, A1203: 0
percent to 3 percent, MnO: 0 percent to 2 percent, S: less than 0.025 percent, and P205: less
than 0.06 percent. The weight percentages of various slagging constituents in the sulfur-fixing
agent are as follows: quick lime: 80 percent to 95 percent and fluorite: 5 percent to 20 percent.
The sulfur-fixing agent has the advantages that: slag formed by adding the sulfur-fixing agent
into the molten iron after magnesium injection has very high sulfur absorption capability,
relatively small viscosity and relatively low melting point; after magnesium injection, a slag
conglomeration agent is added to cause the slag to conglomerate into blocks which are easy to
remove and resulfurization is prevented.
The other document CN101392309 states a slag conglomeration agent applied to hot metal
pretreatment magnesium injection deep desulphurization and an application method thereof,
which pertain to the technical field of hot metal pretreatment in the steelmaking process. The
slag conglomeration agent is sealed and packaged at 3kg to 7kg after magnesium injection or
scattered on the slag surface evenly in the form of particulate. The addition amount is 0.5 kg/t to
1.0kg/t iron which contains the following components by the weight percentages: MgO: 32
percent to 40 percent, Si02: 0.4 percent to 1.1 percent, S: 0.010 percent to 0.025 percent, water:
0 percent to 0.5 percent, and the rest is CaO and inevitable impurities.; The weight percentages
of various slagging constituents in the slag conglomeration agent are as follows: light-burned
dolomite: 85 percent to 100 percent, and quick lime: 0 percent to 15 percent. The slag
conglomeration agent has the advantages that: the slag conglomeration agent can be added
immediately after magnesium injection to cause slag to form into blocks which are easy to
remove, and resulfurization is prevented by adding acid slag conglomeration agent that is
generally adopted

Summary of the invention
The present invention relates to an improved method of desulphurization of hot metal. More
particularly, the present invention relates to the improved method of desulphurization of hot
metal by using desulphurizing compound having both advantages calcium carbide and
magnesium. Invention also relates to using premix of desulphurizing compound for mono
injection process. Moreover this invention also relates to the improved method of
desulphurization of hot metal by using carbide based compound and magnesium in particular
ratio to increase the efficiency of present desulphurizing compound. This invention also relates
to the method which has a plurality of advantages of reasonable simple process of mono
injection, safe and reliable operation with low cost.
Detailed description of the invention
The present invention is based on the method of desulphurization of hot metal using calcium
carbide and magnesium based composition.
The present invention will be understood and its advantages more apparent in view of the
following detailed description and accompanying drawings with two sheet according to the
present invention.
Another object of the present invention is to an improved product of desulphurization of hot
metal.
Still other object of the present invention is to provide the improved product of desulphurization
of hot metal by using calcium carbide based and magnesium in particular ratio to avoid the
demerits of using magnesium and calcium carbide alone as a desulphuriser.

Another object of the present invention is to provide the method which has a plurality of
advantages of reasonable simple process, safe and reliable operation with low cost.
Another object of the present invention is that the desulphurizer composition in the improved
product for desulphurization of hot metal is CaC2 is 40-48 %, CaO is 26-30%; CaF2 is 1-4%, Mg
is 4.7-11 %; SiO2 is 1.8-3% and Al2O3 is 1-3% in which size of the material less than lmm.
Another object of the present invention is to provide the advantages of calcium carbide and
magnesium as a desulphurizer, high quality and grade of product, process simplification, cost
reduction, etc.
Another object of the present invention is that an improved method of desulphurization of hot
metal which comprises,
a) Tapping of high sulphur contained hot metal from torpedo to transfer ladle;
b) The desulphurizing composition is injected into the hot metal through the dip lance;
c) The composition reacts with the sulphur in hot metal;
d) After the injection the lance is pulled up and the slag is easily raked from the top of the
bath.
Calcium carbide based compound (composition) is used for external desulphurization of hot
metal whose efficiency can be increased by addition of certain additives. Magnesium is the
strongest desulphuriser known but magnesium alone cannot be used as a desulphurizer because
of following reasons-
a) Excess magnesium evaporate without reaction due to its Low melting (650°C)
&Vaporizing Temp (1105° C),

b) Low injection rates, limited because of the violent magnesium reaction,
c) Not suitable at high HM temperatures and
d) High Cost and volatile market prices.
Novelty of this instant invention lies on the composition for desulphurization of hot metal by
using calcium carbide and magnesium based reagent along with certain additives as a premix
for mono injection . The invention itself, additional objects and advantages thereof, will best be
understood from the following description of certain specific embodiments, when read in
connection with the accompanying drawings, in which:
FIG. 1 illustrates the diagram of the Injection of DS compound through lance of the present
invention;
FIG. 2 illustrates the specific consumption in different heats of and present calcium carbide
based compound of the present invention;
FIG. 3 illustrates the Flow Chart of method of desulphurization of hot metal of the present
invention;
Basically three kinds of injection technique used for hot metal desulphurization for injecting
desulphurising reagents, like Mono- injection, Co-injection and Multi injection. Mostly co-
injection technique is preferred by all the integrated steel plants. In this technique two
desulphurising reagents can be injected at through a dip lance. Usually calcium carbide based
and Magnesium based desulphurisers are used in co injection process. The new innovative
product is a mixture of calcium carbide, magnesium and other additives in controlled ratio as a
single reagent for desulphurization through mono injection technique.

The following reactions which takes place during desulphurization process through the product:
CaC2 + FeS + 2FeO → CaS + 3Fe + 2CO (1)
CaO + FeS → CaS + FeO (2)
Mg(s) → Mg(g) (3)
Mg(g) + FeS → MgS + Fe (4)
For a Ladle capacity of 100T and temperature of hot metal greater than 1350°C the following
table shows test results using the compound-

Average injection time is found to be 14 min with average temperature drop of 22° C.
The composition/ product has following advantages over calcium carbide based reagents during
monoinjection-

Ad vantages:
The following are the advantages observed with the compound-
1) Present invention is a effective Compound (composition) to reduce the sulfur content of
hot metal;
2) Increases the efficiency of present calcium carbide based compound,

3) It Cost effective Desulphurizing compound;
4) Can be used as a single desulphurizing reagent in mono injection method;
5) Reduces the injection and total cycle time of desulphurizing operations.
Therefore, the foregoing is considered as illustrative only of the principles of the invention.
Further, since numerous modifications and changes will readily occur to those skilled in the art,
it is not desired to limit the invention to the exact formulation as described, and accordingly, all
suitable modifications and equivalents may be resorted to, falling within the scope of the
invention.
We claim:
1) A calcium carbide and magneisum based composition for the method of desulphurization of
hot metal which comprises of CaC2, CaO, CaF2, Mg, SiO2 and Al2O3 in a particular ratio.
2) The composition for the method of desulphurization of hot metal as claimed in claim 1
wherein major ingredients are calcium carbide, lime and magnesium.
3) The calcium carbide and magnesium based composition for the method of desulphurization
of hot metal as claimed in claim 1 wherein CaC2 is 40-48%, CaO is 26-30%, CaF2 is 1-4%,
Mg is 4.7-11 %, SiO2 is 1.8-3 % and Al2O3 is 1-3% in a particular ratio.
4) The calcium carbide and magnesium based composition for the method of desulphurization
of hot metal as claimed in claim 1 wherein mono-injection technique is used for feeding
premix.
5) The calcium carbide and magnesium based composition for the method of desulphurization
of hot metal as claimed in claim 1 wherein the weight of the composition used is 0.15 % -
0.498 % of the total hot metal charge in the ladle.

6) The carbide based composition for the method of desulphurization of hot metal as claimed in
claim 1 wherein the specific consumption of the carbide based composition is 0.062-0.067
kgs of compound added/ton of hot metal/point sulphur drop.
7) The carbide based composition for the method of desulphurization of hot metal as claimed in
claim 1 which helps in slag fluidizing and reduces the metal loss.
8) The carbide based composition for the method of desulphurization of hot metal as claimed
in claim 1 wherein the bath temperature for heating is in a range of 1350-1450°C.
9) The carbide based composition for the method of desulphurization of hot metal as claimed
in claim 1 wherein the size of the ingredients is less than 1mm.
10) The New developed compound for desulphurization of hot metal is simple and compact and
provides substantial cost savings and ease of maintenance, and increases productivity.
11)The carbide based composition for the method of desulphurization of hot metal substantially
as hereinbefore described with particular reference in accompanying drawings.

ABSTRACT

The present invention relates to an improved compound for desulphurization of hot metal. More
particularly, the present invention relates to the improved method of desulphurization of hot
metal by using carbide based compound (composition) and magnesium in optimum -ratio to
avoid the demerits of using magnesium alone as a desulphuriser. Moreover this invention also
relates to the improved method of desulphurization of hot metal by using carbide based
compound (composition) and magnesium in definite ratio to increase the efficiency of present
CAD compound.