DESC:
FIELD OF INVENTION
The present invention relates to Desulphurization (DS) of hot metal through KR-process
In particular, it relates to the development of a reagent which will generate a fluid slag during desulphurization process in KR by breaking network of silicate layer usually forms with lime This invention also relates to the improvement in efficiency by incorporating an innovative granulometry of the powder.

BACKGROUND INFORMATION
Desulphurisation of hot metal in KR relates to removal of Sulphur from hot metal as high Sulphur initiates cracks during rolling process as –
Sulphur affects both internal and surface quality of steel
Formation of iron sulphide which promotes granular weakness and cracks in steel during solidification (lowers the melting point)
Rolling and forging becomes very difficult due to hot shortness in the presence of Sulphur
High Sulphur also contributes to brittleness of steel and its existence in sulphide phase acts as a stress raiser in steel products
KR process uses lime and conventional slag fluidizers like fluorospar
Fluorospar is environmentally hazardous material and it is being avoided in most of the countries
Currently the DS reagents which are being used result in higher slag generation
Cycle time for DS is high due to 12.7 kg/ton hot metal consumption of DS reagent and hence take more time for slag raking
American patent US 4198229 presents a method of utilizing calcium carbide for the formation of refining slag in a ladle. The main objective of the proposed method is to dephosphatize steel.
Patent US 4198229 presents a method of refining slag formation resulting from blast furnace slag, lime and dolomite being placed onto the surface of molten steel in a ladle.
Carbonate materials are used for the formation of refining slag in the patents discussed. During slag formation these materials disintegrate and require an amount of heat, which may not be possible unless a ladle furnace is available. At the same time the use of calcium carbide may lead to an increase in the carbon content in low carbon steels. In addition, the use of fluorite to reduce slag viscosity is detrimental, due to its hazardous emissions. In some examples of the slag-forming material production one can observe the use of blast furnace slag, which causes an increase in the SiO2 content in the formed slag and a reduction in its refining qualities.
The other document CN103014217 discloses a desulfurizing agent, which is characterized by consisting of the following components in percentage by weight: 25-31% of calcium oxide, 10-20% of calcium fluoride, 10-25% of calcium carbide, 4.5-15% of calcium carbide, 3-6% of alumium and 5-8% of aluminium oxide, wherein the particle diameter of the desulfurizing agent is not greater than 2mm. In addition, the invention discloses an application of the desulfurizing agent in vanadium-containing molten ion krypton (KR) desulfurization and a molten iron KR desulfurization method. The desulfurizing agent disclosed by the invention is applicable to the desulfurization of the vanadium-containing molten ion.
OBJECTIVE
The main object of this invention is to increase reagents efficiency & eliminate the risk of hazards associated with Fluorspar
Another object of this invention is to reduce metal loss in KR process
The third object of this invention is to reduce cycle time
The fourth object of this invention is to reduce temperature loss
The fifth object of this invention is to reduce DS cost in KR

BRIEF DESCRIPTION OF THE INVENTION:

According to the invention, primary object is achieved when Granulometry of reagents optimized (100% <100 micron) and use synthetic cryolite with optimum flowability which will facilitate efficient addition without creating excusive dust losses and environmental pollution. Reagent having below mention composition:
Slag Conditioner such as synthetic cryolite :6-14%, CaO: 70-90%, & LOI: 1-8%
This reagent reduces the reagents consumption by 40-60% which improved desulphurisation efficiency by over 100%, reduces nitrogen consumption by over 40%, completely eliminate the uses of environmentally hazardous fluorspar and over 40% reduction in metal loss & raking time. Furthermore, the new reagent is cost effective when compared to existing desulphurisation cost. Hence this product makes desulphurisation process more sustainable.

DETAILED DESCRIPTION OF THE INVENTION:
This innovative Desulphurising reagent is very effective in removing Sulphur from hot metal through Kanbara Reactor (KR) process without uses of Fluorspar and with 40-60% reduction in reagents consumption.
Composition of desulphurization reagents:
Slag Conditioner such as cryolite :6-14%;
CaO : 70-90%
LOI: 1-8%
The development of innovative reagent involved 3 stages:
Lab Trials:
It is well established that the reaction rate increases with the decrease in a reagents size due to increase in surface area. However, decrease in particle size should be restricted to prevent dust losses. The challenge of finding optimum reagent particles size to give better efficiency without generating dust losses has been addressed during lab trial
Lab trial has conducted in following steps:
Grind 8 lots of 5kg each samples in ball mill which is replicate of horizontal mill
Measured flow index to ensure cohesiveness to restrict excessive dust losses
Measured Granulometry through Sieve Shaker Machine
The results obtained for flowability and Granulometry are shown in Fig1 and Fig2 respectively. On comparing with the target flow index 0.30 and size 100% < 100 micron, it was observed that the flow index of material is greater than target values hence the cohesiveness of reagents is more which restrict excessive dust loses and also target Granulometry achieved which improve the efficiency of reagents by increasing rate of reaction.
Figure 1: Flowability Figure 2: Granulometry
Pilot Industrial Trials:
S.N. Parameters UOM Innovative reagent
1 Success rate % 92
2 Avg. Before Desulphurisation Sulphur % 0.067
3 Avg. After Desulphurisation Sulphur % 0.001
4 Avg. Hot Metal Temperature °C 1356
5 Avg. Temperature Loss °C 30
6 Avg. consumption of Innovative reagent Kg/thm 7.44
7 Avg. Slag Raking time Min 5
Used 20 MT new reagent and organized industrial trials for desulphurization in KR process and pilot scale trials successfully conducted in 24 heats. The results obtained by using the above reagent is shown in below table no.-1
Table No.-1

The trial results are encouraging and show definite promise to reduce consumption & completely eliminate Fluorspar as 40% reduction in consumption and 100% elimination of Fluorspar at same success rate has been achieved during pilot scale trial.

Extended Industrial trials:
Used 100 MT new reagent and organized trials for desulphurization in KR process and capture more data to compare with existing performance. The results obtained in extended trials is shown in below table no.-2
S.N. Parameters UOM Conventional Reagent New reagent
1 Success rate % 95 97
2 Avg. Before Desulphurisation Sulphur % 0.042 0.043
3 Avg. After Desulphurisation Sulphur % 0.00060 0.00026
4 Avg. Hot Metal Temperature °C 1342 1340
5 Avg. Temperature Loss °C 38 31
6 Avg. Lime/ Innovative reagent consumption Kg/thm 11.6 6.7
7 Avg. Fluorspar consumption Kg/thm 1.1 0
8 Total reagents consumption Kg/thm 12.7 6.7
9 Avg. DS efficiency % 6.0 13.7
10 Stirring time Min 13:20 13:20
11 Avg. Raking time Min 12 6
12 Avg. Pot loss (Slag+Metal) Kg/thm 34.5 17.2
13 Avg. Metal loss Kg/thm 4.22 1.76
Table No.-2

Efficiency of DS reagents (?):

? = ((Hot metal S before DS-Hot metal S After DS)*Wt.of Hot metal(Kg)*Molar mass of Reagent(gram/mol))/(Wt. of Reagent(kg)*Molar mass of S (gram/mol))

Reduces consumption of reagent by 47% which increases efficiency by 127%
100% elimination of Fluorspar
Reduce slag generation and metal loss by over 50%
Reduce racking time by over 50%

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
,CLAIMS:1) A reagent for desulphurization of hot metal in Kanbara Reactor which comprises
a) Slag Conditioner such as cryolite :6-14%; b) CaO : 70-90%, c) LOI: 1-8%.

2) The reagent for desulphurization of hot metal in Kanbara Reactor as claimed in claim 1 wherein it can be added on top of hot metal through chute .
3) The reagent for desulphurization of hot metal in Kanbara Reactor as claimed in claim 1 wherein it can be added for desulphurization varies between 1 to 10 kg/ton hot metal

4) The reagent for desulphurization of hot metal in Kanbara Reactor as claimed in claim 1 wherein it consists of slag conditioner comprising of mainly Sodium, aluminium and fluorine based compound

5) The reagent for desulphurization of hot metal in Kanbara Reactor as claimed in claim 1 which improved DS efficiency of new reagents by over 100%

6) The reagent for desulphurization of hot metal in Kanbara Reactor as claimed in claim 1 wherein DS reagents having optimum Granulometry of less than 100 microns to achieve said DS efficiency.

7) The reagent for desulphurization of hot metal in Kanbara Reactor as claimed in claim 1 which reduces the Nitrogen consumption by over 40%.

8) The reagent for desulphurization of hot metal in Kanbara Reactor as claimed in claim 1 which reduces slag generation and metal loss by over 50%.

9) The reagent for desulphurization of hot metal in Kanbara Reactor as claimed in claim 1 which reduces the temperature loss by over 15%.

10) The reagent for desulphurization of hot metal in Kanbara Reactor as claimed in claim 1 which reduces the cost of desulphurization by over 20%.