What is function of preheater immersion pipe? What is the behaviour of material inside cyclone if immersion pipe is missing ? If we have any immersion pipe missing it will effect on decarbonation degree or not ?

The function of the vortex finder is to improve the material separation efficiency in the preheater cyclones. If the vortex finder is not there then separation efficiency and preheater performance will decline. Yes, it will affect the decarbonation degree...some decarbonated material will pass back up the preheater and recarbonate. The biggest effects will be on fuel consumption and kiln output.