FIELD OF INVENTION:
This invention relates to a process of Desulphurisation of Hot Metal in Ladle.
BACKGROUND OF THE INVENTION:
 The most popular reagent for hot metal desulphurisation is calcium carbide based.  The calcium carbide content in such conventional reagents varies between 40% and
60%.  These reagents are expensive due to higher content of calcium carbide.  Some less expensive reagents have been developed but the performance of such reagents
with respect to success rate, metal loss, cycle time does not match with the performance
of carbide based reagents.
OBJECTS OF THE INVENTION:
 The primary object of the present invention was to develop a cost-effective calcium
carbide based special reagent.  This reagent should match the performance level of conventional calcium carbide
based reagents where the content of calcium carbide is either 42% or 52%.
BRIEF DESCRIPTION OF THE INVENTION:
According to the invention, primary object is achieved when such a compound is prepared with calcium carbide having below mentioned composition:
CaC2: 10-30 %; Slag Conditioner: 2-8% ; Volatile Matter: 2-6% ; CaO: 56-86%, and delivers the performance with respect to success rate, metal loss, cycle time comparable to 42% or 52% calcium carbide based reagent.
Furthermore, the new reagent is cost effective when compared with the cost for 42% or 52% calcium carbide based reagent.
DETAILED DESCRIPTION OF THE INVENTION:
Generally, Sulphur is considered as harmful impurities except in few grades of steel for increasing machinability of steel. Reducing atmosphere is required for removing Sulphur hot metal. The newly developed Desulphurising reagent is found very effective in removing Sulphur from hot metal. The compositions of these reagents are as follows:

Composition of desulphurization reagents:
CaC2: 10 - 30%;
Slag Conditioner:2-8%;
Volatile Matter:2-6%;
CaO : 55-90%
The development of innovative reagent involved 3 stages:
1. Lab Trials:
In lab trials parameters like flowability and Granulometry of the trial lots were observed . The results obtained for flowability and Granulometry are shown in Figl and on comparing with the results obtained by using calcium carbide based reagent, it was observed that there is no significant difference between flowability and Granulometry obtained by using new reagent.

Figl: Flowability and Granulometry
2. Pilot Industrial Trials and Extended Trials:
Prepared small batches, of new reagents and organized trials and also modified process parameters for desulphurization and both pilot scale and extended trial were successfully conducted. Pilot scale trials successfully conducted trials in 20 heats and extended trial in 2000 heats
Basic Reaction Principle:
DS reagents have different properties and behavior at different HM temperature and chemistry. Thus, only providing good reagent cannot ensure consistent performance at all HM temperature

and chemistry. Process parameters should be robust along with DS reagents. That is quantity
of different reagents to be optimized as per hot metal Sulphur, temperature, chemistry.
Thermodynamic correlations equation no. ((1), (2) & (3)) [1] were used to estimate the efficiency of reagents [2] under different conditions. Considering this along with industrial data, equation no. (4) & (5) have been developed.
(CaC2) + [S] = (CaS) + [C] ; AG°= -352,790+ 106.65*T (1)
(CaO) + [S] = (CaS) + [O] ; AG°= 109,956 -31.045T (2)
[Mg] + [S] = (MgS); AG°= - 325,986+ 98.82*T
(3)
Reagent Quantity,
C= A * e(-a*HM5) * e(-^"is) * (HMS - Aim S) * Hot Metal Qty.* (1 + (B - ln(HMQ)) (4)
Final Reagent Quantity = C* e°<*HM temp)
(5)
These equations have been used for developing right kind of reagents and related process
parameters.
Laboratory and industrial experiments have then been carried out to validate and fine tune the
amount of reagents quantity
The efficiency of desulphurisation reagents has finally been calculated based on equation (6) [3],
(6)
The complete detail is shown in the accompanying figure 1 process flowchart.
EXAMPLES:
The complete details shown in accompanying figure 1


Average Hot metal chemistry details taken for extended trials:

C(%) Mn(%) S(%) P(%) Si(%)
4.56 0.044 0.018 0.171 0.61
Performance was recorded in terms of success rate, Desulphurisation reagent cost, pot loss and metal loss.
Pot loss is the total loss incurred which includes slag and metal
The results obtained by using the above reagent is shown in table

S.No. Parameters UOM Old Reagent New Reagent Remarks
1 Calcium Carbide content % R <0.7R >30% reduction
2 Strike Rate % A 1.7A 70% improvement
3 Reduction in Hot Metal Sulphur % 0.034 0.035 -
4 DS Reagent Cost Rs/thm X 0.89X 11% reduction
5 Pot loss (slag+ metal) Kg/thm Y 0.96Y 4% reduction
6 Metal loss Kg/thm Z 0.84Z 16% reduction
7 Injection time minutes No significant variation -
8 Hot Metal Quality - No significant variation -
8 Hot Metal temperature °C No significant variation -
10 Temperature loss °C No significant variation -

WE CLAIM:
1. A reagent for producing low sulphur steel comprising:
a) Adding this reagent and magnesium
b) Slag conditioner
c) Volatile Matter
d) Decrease in DS reagent cost by around 11%
e) Pot loss (slag and metal) decreases by over 4%
f) Raking out slag as much as possible
2. The reagent as claimed in claim 1, wherein the said desulphurising reagent is:
CaC2: 10-30%; Slag Conditioner: 2-8%; Volatile Matter: 2-6%; CaO: 56-86%;
3. The reagent as claimed in claim 1 wherein the said slag conditioner mainly comprises
of Sodium, aluminium and fluorine based compound