Methods For Producing Hollow Glass Microspheres

Report
Methods For Producing Hollow Glass Microspheres
Fabienne C. Raszewski, Ray F. Schumacher and Erich K. Hansen
Savannah River National Laboratory, Aiken, SC 29808
This work was sponsored by Washington Savannah River Company (WSRC) for the United States Department of Energy under Contract No. DE-AC09-96SR18500.
The Savannah River National Laboratory is operated for the U.S. Department of Energy by Washington Savannah River Company.
Other Methods
Flame Forming Particles
Summary of Process
• Feed material may be glass frit, other
dry particles or solutions containing the
forming components
• Compositions are typically soda lime
silicates, sodium borosilicates, etc.
• Sol – gel processing
Quench or
Feed Material
Cooling Zone
• Fly ash
Force of
Gravity*
• Liquid droplet
• Rotating electrical arc
Heated Zone
• Argon plasma jet
Heated Zone
• Feed must contain a blowing agent
• A blowing agent is a material that
decomposes and releases gas at
elevated temperature
• Commonly sulfur-containing
compounds
Up Flow
Updraft
Quench or
Cooling Zone
Feed Material
• Particles may enter the flame by:
• Falling downward due to the force of gravity
• Feed material is introduced into a flame
at elevated temperatures (~1100-1400°C)
• *An updraft may be used to control the
residence time in the flame
• Gas released by the decomposition of
the blowing agent causes particles or
droplets to expand to hollow glass shells
• Particles have a short residence time in the
heated zone
• SRNL has developed an experimental
apparatus for forming HGMs based on
this technique
• Conducive to HGMs with smaller diameters
• Ascending upward by a gaseous stream
• Residence time in heated zone is longer
• HGMs with larger diameters are produced
For More Information...
• Sodium Silicate Particles
US Pat. 2,978,339
F. Veatch
Emerson & Cuming
• Spray Drying Sodium Silicate Solutions
US Pat. 3,669,050
C. Henderson
Emerson & Cuming
• Glass Particles
US Pat. 4,661,137
P. Garnier
Saint Gobain
US Pat. 5,256,180
P. Garnier
Saint Gobain
Down Flow
• Clay Particles
US Pat. 2,676,892
• Glass Particles
US Pat. 3,365,315
US Pat. 4,391,646
US Pat. 4,767,726
US Pat. 6,254,981
J.D. McLaughlin
Ferro Corp
W.R. Beck
P.A. Howell
H.J. Marshall
R.B. Castle
3M Co.
3M Co.
3M Co.
3M Co
Industrial Processes
• Feed is introduced at the bottom of
the furnace
• Feed is introduced at the top of
the heating chamber by a
vibratory funnel
• A hot, gaseous stream carries the
feed upward
• Residence time within the hot zone of
the furnace is a function of:
• A “fluidizing agent” may be
added to the particles to
improve dispersion
• Particle mass
• Upward velocity of the gas stream
• The particles are transported
to the flame by a carrier gas
• Residence time is critical – just
enough time to form a “tough outer
skin”
• Carrier gas further disperses
particles
• Hollow sphere must then be removed
at the point of maximum expansion and
moved through regions of progressively
diminishing temperatures
• Particles fall though the flame
front where fusion occurs
• HGMs are cooled and separated
from the gas mixture by a
cyclone
• “Outer skin” cools and solidifies
providing mechanical strength
Veatch et al.
US Pat. 2,978,339
• The cyclone separates the HGMs from
the gases
• HGMs are produced with diameters of
~10 – 350 μm
• HGMs are produced with
diameters less than 125 μm
Castle
US Pat. 6,254,981

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