PE Powder Going Out to ATM Through Equalizing Line

NG = nitrogen gas?

Yes N2 gas since we need to eleminate O2 that causing down grade to the products and safety issues

http://www.acronymfinder.com/ATM.html

ATM = atmosphere = venting out side

Maybe a filter bag over the end of the line would catch all or most of the dust. How often you would need to clean or change the bag would depend on how large it is and the amount of dust generated.

30T/month is that 30 tons or 30 tonnes. Either way I think it is too much for a bag filter. Centrifuges on the exhaust may work but I am not familiar with them. Perhaps a mechanical engineer may want to comment on it.

I thought of one wild ass idea. How about heating the exhaust to coalesce the powdered PE to pellet size. Gravity may then be all that is required to collect the pellets in some sort of a hopper. I said wild ass because I am out of my field but I did work for Dupont at one time and dealt with pelletized PE. It responded well to heat but I cant recall how hot it had to be. You may have to weigh the energy costs with the recovery value.

You need a baghouse & possibly another cyclone, depends on the exact layout. I can't imagine how much nitrogen you are just blowing out, there should be a set up that lets you conserve most of it.

for a silo system dispensing flour to scale hoppers there is a return line to the top of the silo,

weight in excess of of the amount needed for a batch is returned to the source silo, air vented to atmosphere through the filters [baghouse]

As some of the gas from the cyclone escapes to the silo pressure builds up causing a surge in the weigh hopper as it cycles. I´m guessing here that your´re using dilute-phase conveying to move the powder and that the cyclone connects to the silo via a straight chute. Then the ciclone is either incorrectly sized or not being operated at the design pressure drop as not all the nitrogen is being separated off. Check this, if at all possible, by seeing if powder is vented with the nitrogen return to the blower. Another way is to measure the actual pressure drop in the ciclone, compare to design numbers and if possible adjust blower operation accordingly. If after doing that the problem persists try placing a rotary airlock at the cyclone discharge. Bear in mind that a good airlock doesn´t come cheap.

Thanks to all for the valid points I really appreciate Coffeebean, your comment is exactly what is going on here we are transferring PE powder by a blower in dilute phase with discharge pressure 0.7 kgf/cm2 while the cyclone design pressure is 0.14 kgf/cm2 and the silo below cyclone hopper (or chute) is 0.2 kgf/cm2 (design). The equalizing vessel design pressure is 0.1 kgf/cm2.

Fahad.S,

Further to the above. Look to the cyclone´s design pressure drop, not the design pressure (as in a pressure vessel). This is the difference between the inlet pressure (feed solids-gas stream) and the outlet pressure (vent gas). Cyclone separation efficiency is a function of delta P. Any cyclone of any geometry has a narrow band of delta P values for optimum gas-solids separation.