Effect of Immersion / dip tube in lower stage of PH cyclone

 Can any one tell what is the effect "If we removed the immersion tubes in last stage PH cyclone?"

Way Back in early 80's when the ILC technology was taking leaps and bounds, VDZ and some machinary manufacturers have extensively studied the effect of Dip tube. (specially on heat losses through ph exit and pressure drop across PH)

The first point that should be clearly understood is, Dip tube serves no other purpose but, increase precipitation efficiency of cyclone.Romoving Dip tubes in lower cyclones will invariably increase dust recirculation in PH system. (Because efficiency of top cyclones remains constant, it doesn't increases with removal of dip tubes in lower cyclones).

One possible effect of removing dip tubes in lower cyclones will be "Increased dust recirculation" (be aware of Chlorine, you should end up in buildups). The other effects could be increased heat lossed due to high temperature in PH gas (more dust + Same gas) and dilution of heat value of fuel if you used PH gases for heating.

    2) PH ID fans rpm can be reduced due to reduction of pressure losses in last stage cyclone.

Yes, There will be certainly, some reduction in Pressure losses (which of course can't be precisely predicted)

I, strongly suggest, hire some consultants or consult machinary manufactures befor proceeding with modifications..

Hope, it answer your questions.

1)Hope dust losses remained same because first 3 stages having immersion tubes and no changes in it.

Correct.

2) PH ID fans rpm can be reduced due to reduction of pressure losses in last stage cyclone.

Not sure at all! There will be a small effect on pressure drop, but it is not much. Besides, it will be counterbalanced by the increase in gas temperature (see next point), which will decrease gas density, hence decreasing the fan capacity.

3) Hope the PH outlet temp. remains same

Definitely incorrect! By removing the diptube, you will drastically decrease the dust collection efficiency of the bottom cyclones. Hot dust wil be carried out to the next stage, thus transporting heat upwards. Consequently, temperature at all stages will increase. Typically, by removing the diptubes at the lower cyclones, you will observe an increase of preheater top temperature of about 10°C to 15°C.

This is why in my company, the policy is that these diptubes should always be present.

Best regards,

Olivier Van Cantfort

hello Mr.Olivier Van Cantfort,

With respect to your views, my perception slightly differs on point 1 and 2.

Point 1

There is a general understanding amongst cement communty, that if top cyclones set up remains unchanged (owing to changes, say dip tube is removed in bottom cyclone) dust losses remains same! This, mis-understanding may be due to de facto that the effeciency of top cyclones remains unaltered say 93% or 95%, even if any changes are made in bottom cyclone. Let me explain it...

There are several factors that contributes to change in precipitation efficiency of cyclone, like:Cyclone geometry, Diptube dimensions, inlet tubrulance cut, "Grain loading" etc.,Now for this particular setup, where diptube is removed, Cyclones effeciency in bottom cyclone changes (it, should slightly decrease)..So, Grainloading in upper stages changes...Which will effect efficiency of top cyclones.(Now, i will acknowledge the fact, that this change can't be quantified, but i will not accept de facto that dust losses remains constant/cyclone efficiency remains unaltered).

Point 2

I totally  agree with your sentence "Not sure at all! There will be a small effect on pressure drop, but it is not much".

But my understanding slightly contradict with your sentences "it will be counterbalanced by the increase in gas temperature(see next point), which will decrease gas density, hence decreasing the fan capacity."..

if, i am correct, when temperature increases density should decrease. Which inturn, should add margin in fan!

Regards