What is the effect of Nitrogen on Carbon Potential in a furnace

[harsuda]

Dear All,

I have employed Methanol+Acetone system for generating carbon potential (CP) inside the furnace for carburizing. Methanol is used for generating base level CP (0.4) and Acetone for enriching (1.0). I follow is boost+diffusion cycle (50%+50%). Methanol feeding starts as 750 deg. C at a rate of 1.0 lph and at 920 deg. C Acetone is passed for raising the CP to required level during boost period and the flow is regulated by a PID controller to maintain the required CP. Methanol flow is continued till the end of the cycle. During boost the CP to be maintained is 1.0 and 0.7 during diffusion. I am able to control of boost cycle CP but not able to reduce it to 0.7 during diffusion. It reduced to only to 0.9. I tried by sending Nitrogen at 1.0 bar pressure, but for my surprise the CP shoot up to 1.7. Then I stopped the Nitrogen flow and waited for 10 minutes for the CP to come down to 0.7. Then I continued the flow of Methanol and could control the CP at 0.7 throughout the diffusion cycle..

What could be the reason for increase in CP during Nitrogen feeding? What other methods can be employed to reduce the CP during diffusion?

Any help on this regard will be highly appreciated.

 

[Yallapragada1022]

Addition of air will bring the carbon potential down. Have you checked the Oxygen probe to see if it is functioning ok? You can run the shim stock to see if the carbon potential you have been reading on the controller matches with the shim reading. Try to burn the Oxygen probe, if you have one for the furnace you have been talking about.

Hope this helps.

Rao Yallapragada