Patent GB-846603-A (GB)
Title: Improvements in or relating to a process for the production of caustic alkali solutions from alkali metal amalgams and to apparatus therefor
Inventor: GLOVER SIDNEY THOMAS
IPC: H01J13/50
Filed: 1958-01-15
Abstract: A process for the continuous production of highly concentrated caustic alkali solutions (as defined) comprises the decomposition of an alkali metal amalgam comprising water dispersed in an alkali metal amalgam in a packed tower, separately delivering the aqueous and partially denuded alkali metal amalgam phases which separate out as upper and lower layers at the top of the tower, into a packed annulus surrounding the column so as to form in the annulus a dispersion of partially denuded alkali metal amalgam in the aqueous phase, and removing the caustic alkali solution from the annulus and the regenerated mercury from the base of the annulus.  As shown in the Fig. hot alkali metal amalgam from a brine cell (not shown) is fed through pipe 6 to the bottom of a tower 5 packed with graphite rings 8 so as to flood the tower. The hot amalgam entering through pipe 6 serves to heat the dispersion rising up the tower.  Water introduced under pressure through distributer <PICT:0846603/III/1> 21 is dispersed in the amalgam and causes the decomposition thereof, the resulting aqueous phase, partially denuded amalgam and hydrogen rising up the packed tower at the top of which hydrogen escapes through pipe 24 in cover plate 3.  The aqueous phase which forms as an upper layer 26 on top of the partially denuded amalgam overflows through shutes 15 into impacked annulus 12 by which it is conveyed to the base of packed annulus 10 through holes 13 in the bottom of wall 11.  Partially denuded amalgam passes out of tower 5 through holes 16 into primary distributer 17 and thence to secondary distributer 18 which divides the amalgam into droplets which are allowed to descend annulus 10 in countercurrent to the rising stream of aqueous phase. Strong caustic soda is removed from annulus 10 by pipe 23 and regenerated mercury by pipe 22 through which it is pumped back to the brine cell.  A modification (not shown) allows the cocurrent flow of partially denuded amalgam with the aqueous phase in the packed annulus by omitting the unpacked annulus 12 and passing the partially denuded amalgam layer from the top of the packed tower through a dispersion device into the top of the packed annulus down which it flows in subdivided form as a dispersion in the aqueous phase which has been caused to flood the annulus by overflow from the top of the packed tower.  A further modification of the process wherein partially denuded amalgam passes in co-current with the aqueous phase in the packed annulus comprises the removal of the caustic alkali solution produced from the packed annulus and supplying it to the base of the packed tower in place of the water feed which is then introduced into the bottom of the packed annulus, the resulting upper layer of aqueous phase which collects at the top of the tower 5 being removed as concentrated caustic alkali solution.  Packing materials specified for use in the tower and annulus are graphite, graphite-iron or graphitenickel compacts, sintered iron graphite or silicon carbide, particularly graphite which may be in the form of 1/2 -1 inch lumps or 1/2 inch Raschig rings.