Patent GB-695355-A (GB)
Title: Improvements in apparatus for the treatment of gases
IPC: B01D53/08
Filed: 1949-07-25
Abstract: In a process for removing undesired substances from a gas by contact with a granular bed, e.g. the removal of light hydrocarbon vapours from fuel gases by activated carbon or the removal of hydrogen sulphide from fuel gases by iron oxide, the granular bed is constantly discharged at the bottom, the material being returned to the top of the bed, and the gas flows horizontally, or substantially horizontally, <PICT:0695355/III/1> <PICT:0695355/III/2> <PICT:0695355/III/3> <PICT:0695355/III/4> through the bed.  The invention is described in respect of the removal of hydrogen sulphide, the oxide bed being confined between partitions 9, of wood, metal or plastic, having louvre-like openings.  The gas spaces 8 so formed are provided with inlet and outlet pipes 19.  A gutter 20 carries away any condensate which may form on the shell of the tower. The rotary valves 5, 6 which may be as described in Specification 695,382 [Group XXX], are supplied with air at 40, the air being at substantially the same pressure as the gas within the purifier, which gas is thus prevented from escaping through valves.  An arch-breaker of known construction may be provided for feeding the valve 6.  The discharge oxide is delivered by a worm 32, through a small buffer storage hopper 33 to the boot 34 of a bucket elevator 35 which delivers through a buffer hopper 36 to a worm 37 feeding the rotary inlet valve 5.  Fresh oxide may be added to the system at 38 and spent oxide withdrawn at 39.  Any type of return conveyer may be used, and air for revivification of the oxide may be admitted to the conveyer casing.  Air may also be admitted to the tower, e.g. by increasing the pressure at 40, to effect partial revivification of the oxide in the tower.  A pneumatic return conveyer may be used. The moisture content of the oxide may be controlled by a spray 43, or by adding steam to the gas before it enters the purifier.  In a modification, shown in sectional plan in Fig. 4, the gas is supplied to two side spaces 8 and is withdrawn from a centre space 10 between louvred partitions 11, which, if the tower is not rectilinear in section, are directed, at their vertical edges, back towards the spaces 8 so that the gas path in proximity to the shell 1 is not longer than the path in the middle of the tower.  In another modification, circular louvred partitions define an annular gas entry space in proximity to the shell 1, and a central circular gas withdrawal space.  In all the modifications, the gas flow may be reversed.  The weight of oxide in the tower results in a greater density of oxide at the bottom than at the top, with a corresponding increase in resistance to gas flow.  To compensate for this, the uppermost openings in the partition separating the oxide from the gas inlet space are at a level different from that of the uppermost openings in the outlet partition; the gases thus follow a longer path through the oxide at the top than at the bottom.  Alternatively, the louvred partitions are arranged out of the vertical to shorten the path at the bottom, or the apertures at the top of the partitions are smaller than those at the bottom.  The tendency of the oxide to pack in the tapered lower part of the shell may be lessened by arranging a vertical plate symmetrically above the valve 6, or the lower part may have one flat vertical side.  The valve 6 may be replaced by a conveyer feeding the oxide towards one side of the base of the tower. The tapered lower part may be kept relatively empty by supporting the oxide bed on a plate having apertures through which the oxide is swept by rotating arms, or the plate and arms may be replaced by an endless conveyer which directs the oxide to a side space above a rotary valve 6.  A number of towers may be arranged in a unit, each working separately, or with the gas flowing through the towers in series and the oxide from each tower being re-elevated to the top of the same tower or conveyed to the top of an adjacent tower as desired.  In Fig. 13, three towers 1 are shown in a unit, the tops of the towers being connected by screw-conveyers 37a which are fed by an elevator 35 which receives oxide discharged from each tower.  The extent to which a tower is fed with its own oxide, or with the oxide from an adjacent tower is determined by valves 46, 47 in feed conduits 44, 45 at the top of each tower. In a modification, Fig. 15, the oxide elevators 48 deliver to the upper ends of inclined shoots 44a, 45a which lead to the feed openings of the towers and are controlled by valves 46a, 47a.