excess air in raw mill

hello,

we use a ball mill for raw material grinding with central discharge, the problem arises with the difference in volume flow of air at NTP  between the inlet and the  outlet, for eg at the inlet we have a volume flow of 33000Nm3/hr, the  out let volume flow comes around to almost double this value around 70000Nm3/h. what is the reason for this sudden difference

here are some more details

inlet air first chamber= 330C,  flow = 74000m3/hr=39000Nm3/hr

outlet = 88C, flow = 100000m3/h=  81000Nm/h
 

very less amount of air is entering through the second chamber,

opinion would be greatly appreciated 

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Re: excess air in raw mill

You have very huge amount of false air ,

the main source of it :

1-Center discharge seal.

2-Double flap of meal feed.

3-circulation system.

you have to check O2 at:

1-gas duct to mill inlet.

2-gas duct after mill (duct going to static separator)

3- After static separator.

4-After cyclones.

By this way you can indentify where the air leakage.

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Re: excess air in raw mill

The main reason seems to false air ingress between mill inlet and outlet.You may find out source of false air ingress point.Most probabily from mill outlet discharge seal.

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re Re: excess air in raw mill

in addition to the above mentioned; you have to conduct mass balance considering the volume of water vapor coming out in mill outlet stream. water vapor comes from moisture content in raw material.

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