technical NOTES

• Note: Operating cost shall be validated with present condition.
  Form the above figures; it is clear that double string preheater system has specific
  advantages over single string preheater system as under.


• If Clinker production is needed to lower down by less than 4000 TPD, the
  double string has this flexibility to run either of the two strings. Whereas this is
  very difficult to operate the plant in case of single string pre-heater system.


• As the height of double string preheater is less, capacity of erection crane gets
  reduced and erection work will be at a faster rate.


• Height of kiln feed bucket elevator is less; hence there is direct saving of power
  in double string. Similar is the case of passenger lift and PH supported Chimney
  height and resultant capital cost.


• Civil construction time will be less as height of double string pre-heater system
  is lower than single string pre-heater system at least by 30 mtr.


• If desired the plant capacity can be increased in future by changing size of cyclone,
  which is not possible in single string preheater.

At times a double string preheater also has certain disadvantages like,

• Unequal distribution of kiln feed material to both the strings with the help of
  s ingle elevator.


• Maintenance in double string system is higher as compared to single string
  because of presence of more no of cyclones and added instrumentation.
  
  
  • Refractory tonnage and radiation losses shall be more as surface area will be
    more.
  
  
  • Note: Operating cost shall be validated with present condition.
    Conclusion
    Based on the above facts, for the plant capacity above 5000 TPD it is recommended
    to go for double string preheater system as the capital cost and the operating cost
    is lower than single string preheater.
  
  
  
  

S.N. Description Unit Single String Double String

1 Civil Cost Rs.in Lacs 1397 1220

2 Steel Cost Rs.in Lacs 688 469

3 Refractory Cost Rs.in Lacs 383 413

5 Kiln Feed elevator Cost Rs.in Lacs 226 181

6 Capital Cost Rs.in Lacs 2694 2283

7 Operating Cost per annum

(Power + Fuel)

Rs.in Lacs 16386 16178