FIELD OF INVENTION
The present invention relates to a process of desulphurization of hot metal by external desulphurization using desulphurization reagent. More particularly, the invention relates to a method in a desulphurization process control system to determine the deployable weight and ratio of the desulphurization reagents, type of injection including co-injection ratio, and the flow-rate and pressure of the carrier gas. The invention further provides an on-line process control system for carrying out the inventive method in a Desulphurization plant.
BACKGROUND OF THE INVENTION
Hot Metal from the blast furnaces contains many impurities which are detrimental to the final quality of Steel products. Some of these impurities viz. Phosphorous (P), silicon (Si), and Carbon ( C) are removed by oxidizing these impurities in a Basic Oxygen Steelmaking converter. The removal of these impurities takes place in highly oxidizing conditions. Apart from these impurities, the sulphur (S) in the hot metal constitutes an important impurity which needs to be reduced depending upon the type of application of the final product. 'S' in the steel product is

detrimental as it forms low melting FeS' compound and resides at the grain boundaries. Once the sem finished products (billets, blooms, slabs etc.) are soaked in the furnace and taken for rolling into final products these low melting compounds melt and develop locations prone to failures, leading to failure of the final products. In the steel industry, the removal of'S' in the steel is carried out by pretreatment of Hot Metal prior to charging the hot metal into the Basic Oxygen Converters, where due to highly oxidizing condition, the reduction of 'S' is restricted. Out of the various methods available for the pretreatment of hot metal for the reduction of 'S', the submerged dispersed particle injection is the most reliable and adopted system. This involves injection of Calcium Carbide & Magnesium-based compounds in a defined ratio with the help of nitrogen gas which acts as a carrier for these materials. The amount of these compounds injected decides the extent of removal of "S' from the hot metal and also contribute towards the cost of desulphurization.
The basic goal of desulphurization is to achieve 'S' after desulphurization equal to or just less than a desired level. This process requires the correct amount of desulphurizing compounds to be injected into the hot metal so as to optimize on the compound consumption as well as the cost of desulphurization.

The prior art in the area of desulphurization of hot metal has basically been addressed through the nature of the reagents themselves (e.g. US5358550), the physical and mechanical apparatus used in the process (e.g. US4423858), the step-wise procedure for delivering the reagents (e.g. US6015448), and the systems for determining the amounts of desulphurizing reagents required to reduce the sulphur content in hot metal to meet a desired concentration (e.g. US6607577).
Vic Vaculik, from Hamilton, CA has patented (US 6607577), a method and computer program for determining the amounts of desulphurizing reagents required to reduce the sulphur content in hot metal to meet a desired concentration. The determination of the amounts of reagents is based on a multivariate statistical model of the process.
There is however no process described in the prior art that estimates the amount of desulphurising agents encompassing all the ranges of input Hot Metal 'S; (ranging from 0.040 to 0 200%), target (ranging from 0.003 to 0.050%) and optimization of the reagent injection & carrier gas flow rates.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a method in a desulphurization process contro system to determine the deployable weight and ratio of desulphurizat on reagents, injection type including co-injection ratio, and the flow-rate and pressure of the carrier gas.
Another object of the invention is to propose a method in a desulphurization process control system which operates under the principle of mass balance and desulphurization efficiency.
A further object of the invention is 1:o propose a method in a desulphurization process control system to determine the deployable weight and ratio of desulphurization reagents, injection type including co-injection ratio, and the flow-rate and pressure of the carrier gas, in which desulphrization efficiency is determined based on basic desulf efficiency and dynamic desulf efficiency.

A still further object of the invention is to propose an on-line process control system in a Desulphurization plant which is enabled to estimate the weight of desulphurization reagents including their ratio adaptable in the method of the invention.
SUMMARY OF THE INVENTION
Accordingly, there is provided a method in a desulphurization process to determine the deployable weights and ratio of the desulphurization reagents, type of injection including co-injection ratio, flow rate and the pressure of the carrier gas. Th