S. MOHANAN ET AL.

1010

output index—Operational Quality Index (OQI)—has

been applied successfully to optimize input parameters

for efficient operation. Statistical models were developed

for OQI, as well as both grade and recovery of the con-

ducting minerals individually. The predicted values ob-

tained using the models were in very good agreement

with the observed values (R2 value of 0.91 for OQI;

similar values obtained for both grade and recovery).

Process optimization, viz. maximization of OQI has been

done by keeping the constraints of grade >96% and re-

covery >98%. The maximum value of OQI obtained un-

der the given constraints is 195.53, at the following oper-

ating conditions—Temperature: 102˚C, Feed Rate: 1.75

tph and Roll Speed: 132 rpm. Under these operating

conditions, the grade and recovery obtained are 96.6%

and 98.9% respectively. Normally, the separation effi-

ciency index, which is a % recovery from the formula, is

associated with coal washing processes; while coefficient

of separation is nothing but an index derived from reco-

very/distribution percentages of concentrates and rejects.

Though these indices are useful in predicting the process

performance, using the quality and quantity of different

fractions, these are not completely significant for process

variable optimization studies. Therefore, it was found

that the concept of OQI is simple and more reliable in

this regard.

5. Acknowledgements

Authors are thankful to Tata Steel Ltd management for

the support and permission to publish this work.

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