Apparatus for distilling phosphorus

An apparatus for distilling phosphorus to reduce its arsenic content comprising:

• (a) a feed conduit for receiving molten phosphorus connected to
• (b) a heat exchanger comprising tubular means through which liquid phosphorus can be passed continuously,
• (c) means for out of contact heating of the phosphorus passing through said tubular means of said heat exchanger,
• (d) an exit conduit from said heat exchanger connected to disengaging means for permitting phosphorus heated in said heat exchanger to be separated into phosphorus vapor and phosphorus liquid, said disengaging means being located in an upstream position from and outside of the fractional distillation zone of any subsequent fractional distillation means,
• (e) fractional distillation means containing a fractional distillation zone located in a downstream position from said disengaging means and connected thereto by conduit means for passing phosphorus vapor into the fractional distillation means, said disengaging means being positioned outside said fractional distillation zone,
• (f) an internal condenser means positioned directly above said fractional distillation means, said condenser means containing vertically disposed second tubular means open at both ends, the bottom ends of said second tubular means being connected to said fractional distillation means whereby phosphorus vapor from said fractionating means can flow into the bottom ends and up into said second tubular means, condense on the inside walls thereof, and drain downwardly therefrom towards said fractional distillation tubular means,
• (g) means for cooling said second tubular means,
• (h) means located below the bottom ends of said second tubular means of said condenser for collecting and splitting the liquid phosphorus condensate from said condenser into a reflux stream, which is directed by the collecting and splitting means into the top of the fractional distillation zone, and a product stream of low arsenic phosphorus, which is directed by the collecting and splitting means into an exit conduit therefor, and
• (i) vacuum means connected to said disengaging means, fractionating means and condensing means to maintain these means under subatmospheric pressure.