Methods For Producing Hollow Glass Microspheres

1
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

• Sol gel processing
• Fly ash
• Liquid droplet
• Rotating electrical arc
• Argon plasma jet

• 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.
• Feed must contain a blowing agent
• A blowing agent is a material that decomposes
  and releases gas at elevated temperature
• Commonly sulfur-containing compounds
• Feed material is introduced into a flame at
  elevated temperatures (1100-1400C)
• Gas released by the decomposition of the blowing
  agent causes particles or droplets to expand to
  hollow glass shells

For More Information...

• Up Flow
• 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

• Particles may enter the flame by
• Falling downward due to the force of gravity
• An updraft may be used to control the residence
  time in the flame
• Particles have a short residence time in the
  heated zone
• 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

• Down Flow
• Clay Particles
• US Pat. 2,676,892 J.D. McLaughlin Ferro Corp
• Glass Particles
• US Pat. 3,365,315 W.R. Beck 3M Co.
• US Pat. 4,391,646 P.A. Howell 3M Co.
• US Pat. 4,767,726 H.J. Marshall 3M Co.
• US Pat. 6,254,981 R.B. Castle 3M Co

• SRNL has developed an experimental apparatus for
  forming HGMs based on this technique

Industrial Processes

• Feed is introduced at the bottom of the furnace
• A hot, gaseous stream carries the feed upward
• Residence time within the hot zone of the
  furnace is a function of
• Particle mass
• Upward velocity of the gas stream
• Residence time is critical just enough time to
  form a tough outer skin
• Hollow sphere must then be removed at the point
  of maximum expansion and moved through regions of
  progressively diminishing temperatures
• Outer skin cools and solidifies providing
  mechanical strength
• The cyclone separates the HGMs from the gases
• HGMs are produced with diameters of 10 350 µm

• Feed is introduced at the top of the heating
  chamber by a vibratory funnel
• A fluidizing agent may be added to the
  particles to improve dispersion
• The particles are transported to the flame by a
  carrier gas
• Carrier gas further disperses particles
• Particles fall though the flame front where
  fusion occurs
• HGMs are cooled and separated from the gas
  mixture by a cyclone
• HGMs are produced with diameters less than 125 µm

Castle US Pat. 6,254,981
Veatch et al. US Pat. 2,978,339