Preheater Fan Pressure

Posted in: , on 9. Aug. 2011 - 17:25


We have single line 5 stage preheater tower. I am getting 300 to 350 mmwg pressure on with 70,800 m3/hr volume on my PH fan. With this we are able to produce 350 tons of clinker. We are also having dust loss venting out of PH system at about 18 to 22%.

We have velocity as below:

kiln inlet 32.4 m/sec

5th cyclone raiser duct 31.3 m/sec

5th cyclone opening 22.7 m/sec

4th cyclone raiser duct 28.5 m/sec

4th cyclone opening 21.1 m/sec

3rd cyclone raiser duct 26.9 m/ sec

3rd cyclone opening 19.5 m/ sec

2nd cyclone raiser duct 24.14 m/ sec

2nd cyclone opening 8.22 m/sec

1st twin cyclone raiser duct 19.16 m/sec

1st twin cyclone opening 6.5 m/sec

PH down comer duct 23.3 m/sec


1. By increasing the pressure from 350 mmwg to 750 mmwg, would my clinker production increase? (do we need high pressure at PH fan? and why?)

2. The pressure at PH fan inlet be increase by preheater resistance or the fan inlet cone adjustment will generate pressure by it self. (However,our PH fan rated capacity is 750mmwg/80,000 m3/hr. Flakt supply)

3. By increasing pressure of PH fan will velocity's will change? (any effects on system by increase or decrease in velocity)

4. Will my dust loss reduce and come to industry standard at 10 to 12%?

Please help.



Re: Preheater Fan Pressure

Posted on 9. Aug. 2011 - 04:42

Dear deepak,

Use the fan laws and general resistance formula of a duct system.

The present working point of your installation is: 325 mmWC at 70800 m3/hr

A fan rated at 750 mmWc at 80000 m3/hr should deliver more air at 325 m3/hr or should deliver more pressure than 325 mmWC at 70800 m3/hr.

Probably is the rated pressure of 750 mmWC at 0 m3/hr and 80000 m3/hr at 0 mmWC.

Then is possible that 70800 m3/hr is delivered at 325 mmWC.

The resistance factor of the installation is calculated from:

Pressure1 = Resistance Factor * Airflow1^2

Pressure2 = Resistance Factor * Airflow2^2


In your case:

Airflow2 = Airflow1*SQRT(pressure2/pressure1)

Airflow2 = 70800*SQRT(750/325) = 107550 m3/hr

Air velocities will increase by 107550/70800 = 1.52 times

Whether the cyclones will still operate (or separate dust) properly has to be checked by cyclone designer.

Basic physics

Have a nice day