Patent GB-356116-A (GB)
IPC: B01D11/04
Filed: 1930-05-28
Abstract: A volatile impurity or other constituent is removed from a liquid by subjecting the liquid to repeated contact with a carrier fluid which is treated between each contact to remove from it the constituent absorbed from the liquid treated.  The process is particularly applicable for the removal of phenol from ammoniacal liquor by means of steam.  The apparatus shown in Fig. 1 comprises a column of trays 2, 3, separated by partitions 4 which allow of the upward flow of gas therethrough but prevent the downward flow of liquid.  The ammoniacal liquor is supplied to the uppermost tray 2 through a pipe 7 and sprays 8, passes successively to the lower trays 2 through pipes 9 and is discharged finally through a pipe 11.  Steam introduced through a pipe 5 passes upward through the column in countercurrent to the liquid in each section. Phenol separated by the steam from the ammoniacal liquid in each tray 2 is removed from the steam by a solution of caustic soda in the alternate trays 3.  The soda solution is supplied to the lowermost section 3 by a pipe 12 and sprays 8. After passing through this section it is lifted by a pump 14 to the section 3 next above, and so on, being finally discharged from the top section 3 through a pipe 16.  Modified apparatus is described in which the soda solution passes downward, the successive sections 3 being connected by pipes similar to the pipes 9.  In both these forms of apparatus the steam may be caused <PICT:0356116/III/1> <PICT:0356116/III/2> to circulate repeatedly through the column.  The trays may be filled with contact material or bubbling trays may be used.  Air or steam lifts may replace the pumps 14.  Fig. 3 shows apparatus for the distillation of ammonia from ammoniacal liquor with separation of phenol.  The liquor is supplied by a pipe 23 to a column 20.  Free ammonia with carbon dioxide and hydrogen sulphide pass off through a pipe 32 and the liquor is discharged through a pipe 24 and delivered by a pump 25 to the upper end of a phenol-removing column 1.  This column is similar to that shown in Fig. 1, but of the bell-and-tray type.  The liquor from which phenol has been removed is discharged through a pipe 26 to a vessel 21 beneath the column 20, where it is mixed by means of steam supplied through a pipe 33 with a suspension of lime supplied through a pipe 27.  The liquor passes on through a pipe 28 to a column 22 in which fixed ammonia is set free by the lime and removed by steam supplied through a pipe 30.  The steam used in this column passes upwards through the phenol-separating column 1 and is led therefrom through a pipe 31 to the lower end of the column 20.  Modified apparatus is described in which the position of the column 22 and the vessel 21 are exchanged.  In this case the steam is supplied first to the phenol-removing column and passes thence first through the column 22 and then the column 20, but fresh steam may also be supplied additionally to the column 22.  Care is taken, as by the provision of insulation or steam jackets, to secure that the sections containing ammoniacal liquor and those containing soda solution are maintained at substantially the same temperature, namely just below the boiling point of the ammoniacal liquor.  A suspension of lime may be used instead of soda solution, in which case the column 20 may be omitted. The lime will retain carbon dioxide and hydrogen sulphide as well as phenol and purer ammonia will be obtained. Calcium phenolate may be recovered from the wash liquor.  A further modified form of apparatus is described in which the phenol-removing column constitutes a separate unit and the steam used therein is circulated by means of a blower.