Design issues of roof dust collectors
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I would like to ask the experts: If I want to design a dust collector for a silo, and I know the volume of the silo, how can I determine the air flow rate required for the dust collector?
It is not designed based on the volume of the silo, but is calculated according to the air volume used for conveying ash (powder). The goal is simply to suppress dust.
Reply to 2# sinafly: How is the air volume calculated when transferring ash (powder)? Is there also an exhaust fan installed behind that silo roof dust collector?
Reply to 3# liu2: The specific air volume for gas transportation needs to be asked from the gas transportation designer. A silo top dust collector can be equipped with a fan or without one; it is generally fitted with a fan. The advantage of having a fan is that a negative pressure is created inside the silo, so even if there are some devices with poor sealing (such as vacuum pressure release valves), dust will not escape outside. In fact, with a roof-mounted dust collector, whether it is necessary to equip it with a vacuum pressure release valve is still debatable.
Reply to 4# sinafly: I use a screw conveyor for feeding coal powder into my silo, not pneumatic conveying. If there is no induced draft fan, where does the air flow come from?
Using a screw conveyor, it is possible to prevent dust from escaping with only a very low amount of air flow. I’m not sure if the exhaust fan you mentioned refers to the roof exhaust fan; if a fan isn’t desired, it can be connected via pipes to the nearest dust removal duct. Pay attention to the flow velocity of the air ducts.
Reply to 6# sinafly: It works like this – a screw conveyor transports solid materials to a silo, and a dust collector is installed on top of the silo. How should the air flow rate of this dust collector be designed? Is it necessary to install an exhaust fan behind the dust collector?
If there is no exhaust at the feed end of the screw conveyor, it is necessary to use a negative pressure fan in the silo, at least to ensure an adequate airflow. If the seal is good and air leakage is minimal, then a fan with a capacity 2 to 3 times greater than that required for transporting the powder will suffice. If there are air leakage points, it is necessary to ensure that the wind speed at those points reaches 1.5 m/s. Given the uneven wind speed at various points, the actual air volume may be even higher. You could look into books on ventilation; I haven’t worked in this field for many years, so I’m not sure if what I say is completely accurate.
Reply to 8# sinafly: Could you recommend some books on the design of roof-mounted dust collectors?
Reply to 9# liu2: As far as I remember, there don’t seem to be many books that discuss bag filters in detail; this is a quite common type of dust removal method. You might want to look for books on the design of dust removal systems, or books related to dust removal in cement plants or power stations. There might be an introduction there. As for roof dust collectors, there is plenty of information available from manufacturers on the Internet; drawings can be downloaded from the “Blue Sky CAD” forum. Roof dust collectors are quite simple to use – once you learn how to use them, it’s easy to operate them.