Re: Blowing Into Bins.
The equations for cyclone design take into account the particle size and velocity to calculate the most efficient solid-air separation. But in receiving bins; filters are used to separate the air-solids. I haven’t come across any equations for calculating the position of inlet pipe into the receiving bins. General recommendations that could be followed are.
·Inlet should preferably be in the barrel section of the bin rather then cone.
·Tangential inlet is preferred over radial.
·Extra care should be take to avoid direct impact solid-air on the filter media. As it could reduce its life.
·If particle breakage is an issue a step pipe should be use at the end of the conveying line into the bin to lower the velocity.
·Avoid any ledges inside the hopper as material might build up on them especially if it is food product. ■
Conveying Into Bin
Two factors that are key when conveying directly into a bin are 1) the bulk density of the incoming material and 2) the diameter of the bin. If these are not taken into account the constantly fluidized material will overwhelm the bin vent filters and there will be essentially no bin volume available for deaerated material.
Base the bin vent filter design on an upward can velocity of not more than 1 ft/sec, consult the filter manufacturer here (do not use pleated filter elements). The filter can diameter becomes the bin diameter. Provide sufficient vertical depth to accommodate the conveyed charge of flour and and additional 1/2 diameter of headspace for disengagement of flour from the conveying stream.
Dennis Hauch, PE ■
Blowing Of Powders Into Bins
Blowing of powders directly into bins should be avoided because of the resulting dust cloud, need for a very large size bin vent filter (dust collector), and the need for potential dust explosion prevention. Suggestions given above will be useful but a pre-solids/air separator at the inlet of the bin, such as a cyclone, can also be used to minimize these problems. Design of cyclones is common knowledge. This cyclone can be installed on the side of the bin or in its top, depending upon plant layout. Important things to remember are that the air vent from the cyclone must go into a dust collector because it will contain dust particles, and the bottom solids outlet must be sloped at an angle at which the solids will easily gravity flow into the bin.
As both options will work it will be a good idea to compare their costs.
You may like to refer to my article "Design Guide for Dust Collectors" published in the March 2005 issue of Chemical Engineering.
Regards,
Amrit T. Agarwal
Consulting Engineer
Pneumatic Conveying Consulting Services
Email: polypcc@aol.com
Ph and Fax: 304 346 5125 ■
Blowing into bins.
I have an application that requires flour to be blown into a small bin. Approximately 1.2m diameter by 2m tall. I have visited a number of sites where I have seen the input pipe into such bins entering the side of the bin in the style of a cyclone.
I can see the reason for this as i presume it allows the material to settle more evenly and reduce compaction thus aiding with discharge and also slowing down the air that requires filtration. It does however redude the capacity of the bin greatly.
Is there a formula or recommendation for the positioning of this input up the height of the bin?
I am looking to design the bins myself but would be interested to hear from anyone who would be interested in manufacturing them. ■