WO2021064751A2

WO2021064751A2 - Hot metal desulphurisation in kanbara reactor (kr) process

Info

Publication number: WO2021064751A2
Application number: PCT/IN2020/050845
Authority: WO
Inventors: Raj Kumar Yadav
Original assignee: Jamipol Limited
Priority date: 2019-09-30
Filing date: 2020-09-30
Publication date: 2021-04-08
Also published as: CN114729410A; WO2021064751A3; JP2022550951A; KR20220075376A

Abstract

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.

Description

FIEUD 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 Si02 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

1. The main object of this invention is to increase reagents efficiency & eliminate the risk of hazards associated with Fluorspar

2. Another object of this invention is to reduce metal loss in KR process

3. The third object of this invention is to reduce cycle time

4. The fourth object of this invention is to reduce temperature loss

5. 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:

1. 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 Figl 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

2. Pilot Industrial Trials:

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.-l Table No.-l

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.

3. 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

Table No.-2

Efficiency of DS reagents (h):

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

WE CLAIM:

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%.