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Improving efficiency of De-Sulphurizing compound

Request Number N374268
Need details
Description

We manufacture a compound/reagent (Desulphurising - DS) that is used to remove Sulphur from Liquid Iron (Hot Metal or Pig Iron). This compound is a mixture of CaC2(Calcium Carbide – dominant active ingredient) + CaO (Lime) + Slag Conditioner The maximum utilization efficiency of CaC2 is 35 to 40% only.  We are exploring solutions which will enable us to improve the efficiency of CaC2 to 50% or more.

 

 

 

 

Background

CaC(Calcium Carbide) based compound is used for desulphurisation of Hot Metal (Liquid Iron) at temperature of 1280 to 1400 ◦C. The compound comprises of a mixture of Carbide based reagent (DS) (CaC2 + CaO + slag conditioner) and Magnesium that are injected into the hot metal through a co-injection system. Both the reagents are kept separately in two different silos but are injected through same lance. The fineness of this compound is 90% below 63 microns. The injection done through ceramic Lance in Nitrogen (inert gas) pressure into the hot metal. The exit end of Lance is 500 – 600mm above the base of the ladle. The rate of injection is 24 – 32 Kg/min. Typically for every Ton of hot metal 400 – 450 Kg of CaC2 and 40 – 50 Kg Mg is required to desulphurise hot metal having sulphur concentration of around 500 ppm.  The process takes about 14 to 15 minutes for completion.

 

The basic reaction that takes place is CaC2 + S = CaS + 2C.

 

 

The concentration of S in the hot metal is typically 500ppm on an average (this varies between 400 to 600 typically. In some cases it is more than 800ppm or even higher. Use of CaC2 based reagent depends on the volume of hot metal and initial sulphur in the hot metal. As per existing practices, 35 to 40 % of CaC2 reacts with the 'S' in the hot metal and t

he remaining goes to the slag as unreacted CaC2. We want to understand ways and means to improve the efficiency of utilization of CaC2 to 50% or more.

 

We believe that following factors may increase the CaC2 utilization

 

  • Increase in retention time of CaC2 in hot metal (Liquid Iron or Pig Iron). As per existing studies this is about 1.33 s/m of metal depth. Total depth is typically 7-8 feet. Higher time for reaction will improve the efficiency
  • Improve the rate of reaction of CaC2 and Sulphur (S) i.e. CaC2 + S= CaS + 2C eg: use of catalyst
  • Changing the fineness of the powder (reagent) which is currently at 90% below 63 micron. 

 

 

Key Success Criteria

The solution should

  1. Be economically feasible i.e. there should be little or no modification in the equipment used for Desulphurisation (DS) injection
  2. Not completely change the existing manufacturing facility of producing the Compound i.e. the mixture of CaC2 + CaO + Slag Conditioners

Should not increase the amount of slag generated in the process.  Ideally it should reduce it, which will ultimately reduce the metal (Fe) loss (slag is skimmed out (removed from the surface of hot metal) after DS treatment). The slag consists of CaS + CaC2 (Unreacted) + CaSiO2 (primarily)

 

Preferred Collaboration types
  • To Be Negotiated
Items to be submitted

We are looking for a concise abstract/executive summary.  The proposal should briefly describe the technical approach and provide information on technology performance, background and description of the responding team and their related experience.
 

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Point of Contact
Oliver Worsfold
Area of Interest
  • Chemical Manufacturing
  • Manufacturing & Fabrication
  • Materials Processing
Organization
Tata Steel
Due Date
March 7, 2017
Attachments
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Comments
Dear Oliver Worsfold

Greetings

The desulphurization reagent [CaC2] mentioned in the background as - "for every Ton of hot metal 400 – 450 Kg of CaC2 and 40 – 50 Kg Mg is required to desulphurise hot metal having sulphur concentration of around 500 ppm".

We feel this is very high quantity for the desulphurization of approximate 500 ppm sulphur in the hot melt. We request clarification in this regard.

Regards
Dr. Ammanamanchi Radhakrishna
Posted on 2/2/18 3:14 AM.