Click here to make tpub.com your Home Page

Page Title: Free-Fall Spill of Powder with Air Velocity Normal to the Direction of Fall
Back | Up | Next

Click here for thousands of PDF manuals

Google


Web
www.tpub.com

Home

   
Information Categories
.... Administration
Advancement
Aerographer
Automotive
Aviation
Construction
Diving
Draftsman
Engineering
Electronics
Food and Cooking
Logistics
Math
Medical
Music
Nuclear Fundamentals
Photography
Religion
   
   

 



DOE-HDBK-3010-94
4.0 Solids; Powders
Four readily available materials in powder form were allowed to free-fall spill known
distances and the material airborne was collected as a function of aerodynamic particle
diameter in a cascade impactor. Two powders were nonporous and nonreactive to water,
inorganic, crystalline materials (sand and limestone). One porous, reactive, inorganic
material (cement) and one porous, reactive, organic material (flour) were also tested. Sand
and limestone are similar to some process generated wastes (e.g., slag and crucible) and
coarse fractions of process materials (e.g., heavy metal oxides). The finer cohesive heavy
metal oxides are similar in characteristics to cement but a nonreactive with water. The solid
salts of other heavy metal compounds (e.g., fluoride, chloride, oxalate, hydride) were not
represented here.
The powder fell in the test apparatus from a funnel with an interchangeable tube through a
hole in the center of the lid of the receiving hopper. The interchangeable diameter tubes
(24-, 37- and 49-mm) adjusted the material flow rates. The total mass dropped ranged from
2 to 10 kg. Flow rates (ranging from 0.1 to 10 kg/s) were determined by the time required
to release a known mass of material. The fall distance was measured from the bottom of the
tube to the top of the pile of material. The stream of falling powder impacted a natural pile
of powder formed of the same material under the same conditions. Air was entrained in the
falling powder stream.
The dusty air generated was drawn into the second section (the aerosol collection section) of
the apparatus by a fan that was turned off after all the powder had been released. A second
fan circulates the air through the elutriation column (flow velocity designed to prevent
particles >25 m AED from being carried to the cascade impactor) and air return channel.
The mass collected per impactor stage or filter was used to determine the size specific dust
generation rate, Gi (fraction of dust particles generated with an aerodynamic diameter i).
The summation of all fraction collected was the total dust generation rate, G. (The total dust
generation rate, G, is expressed as mg airborne/mg source and is equivalent to the ARF.)
The size distribution and moisture content for the source powders were determined.
At low Fs (material flow rates), the falling stream of material stops abruptly on top the pile
and slides down the sides. At higher Fs, the individual materials exhibit different behavior:
sand: the falling stream penetrates the pile and displaces material radially.
limestone: the pile is compressed by the falling stream and forms a crater, 70-
to 150-mm in diameter. The diameter of the crater increases with fall
distance. The falling powder stream strikes the center of the crater and
bounces back in all directions.
Page 4-75


Privacy Statement - Press Release - Copyright Information. - Contact Us

Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business