Patent GB-347170-A (GB)
Title: Improvements in gas filters for use in gas analysis
IPC: B01D46/30
Filed: 1929-12-14
Abstract: A filter employed in gas-analysis apparatus contains, as filtering medium, solid crystalline common salt or equivalent salt.  The moisture in the gases forms a saturated solution of the salt which removes solid impurities and imparts to the gases a substantially constant residual moisture content corresponding with the vapour-pressure of the salt solution.  As shown in Figs. 1 and 5, wherein the invention is employed in an apparatus as described in Specification 292,607, [Class 1 (i), Chemical processes &c.], the gases are drawn, by a pump, from a furnace flue or the like, through a filter and thence through a pipe 2, into a chamber 3 into which a pipe 4, connected to the pump, opens, the pipe 4 being throttled as at 5 to byepass any desired proportion of the gases.  The non-byepassed <PICT:0347170/III/1> <PICT:0347170/III/2> <PICT:0347170/III/3> <PICT:0347170/III/4> <PICT:0347170/III/5> portion passes through the filter-column 9, Fig. 5, of common salt, or the like, and thence through a wire gauze 13, a filter of wadding 14 and filter cloths 16 which, together with the gauze 13, are stretched over resilient rings such as 19.  The cloths 16 are enclosed within a sleeve 17.  The above features are all enclosed within a cylinder having removable end-caps 22, 23, held in place by brackets 24, 25, Fig. 1, pivotally mounted on a vertical rod (not shown) the bracket 25 having a clamping screw 28.  The vertical rod is resiliently mounted on the baseboard 26 of the apparatus and, on loosening the screw 28, moves upwards permitting the removal of the cap 23, and hence of the whole filter apparatus.  The gas passes from the filter through a pipe 15, Fig. 1, to the analysis chamber B and thence is led to the pipe 4, at a point beyond the throttle 5, through a pipe 40.  The gases may be passed through calcium chloride before entering the analysis chamber B.  The saturated salt solution formed in the filter is led off through a pipe 10 having a trap 11. The Specification as open to inspection under Sect. 91 (3) (a) describes also the remainder of the gas analysis apparatus.  This comprises a U-tube connected across a nozzle in the pipe 40 to indicate the rate of flow of the gas, the analysis chamber B, Figs. 1 and 6 (Cancelled), a manometer E, Fig. 9 (Cancelled), and a syphon pump D, Fig. 11 (Cancelled) for draining the gases through the apparatus.  Gas analysis apparatus.--The gas, entering the apparatus B, Fig. 6 (Cancelled), at 15, passes through passages 30, 31 to a chamber 33, the inner wall of which comprises a porous diaphragm 35 of carbon, unglazed clay or porous glass, and passes thence through symmetrically-disposed passages to the pipe 40 (behind the pipe 15). A perforated diaphragm 37 may be provided to protect the diaphragm 35.  The absorbent liquid, for example caustic alkali solution, is supplied from a reservoir F through a chamber 53 and passages 60, 61, 62 to a chamber 68 on the other side of the diaphragm 35, whereby absorption of carbondioxide takes place, the liquid being withdrawn through a passage 71 and a pipe G having an S-bend to serve as a trap.  Subsidiary diaphragms 69, 70 are provided in the inlet and outlet passages 63, 71 adjacent the diaphragm 35.  The passages 63, 71 are connected by lateral passages, which are normally closed by screw-cocks, with a drainage channel.  The vessel F is provided with a pipe 50 opening above the liquid and projecting into the chamber 53 to regulate the level of liquid therein.  The liquid itself is supplied through a pipe 51, Fig. 1, having a spring-pressed ball-valve, which is screw-threadedly engaged with a tube leading to the bottom of the chamber 53, the tube containing a needle which bears against the bottom of the chamber 53 and holds the valve open when the connection is made.  An overflow 59 is provided in the chamber 53.  Manometer.--The upper parts of the chambers 33, 68 are connected, by passages 79, 80, 81, and 84 respectively with coaxial tubes 82, 83 leading to the manometer E, Fig. 9 (Cancelled), the tube 83 leading to a reservoir 88, Fig. 9 (Cancelled), of suitable manometric liquid, and the tube 82 opening to the atmosphere or to a tube 92 connected with the reservoir.  A flexible scale 90, for example, of rubber, running over a roller 91, permits the direct reading of the pressure difference within the chambers 33, 68.  A pressure gauge may be provided in addition to or instead of the above manometer.  The pump employed comprises a tube 45, Fig. 11 (Cancelled), connected with the pipe 4 and projecting into a chamber 46 having a water inlet 47 and a draw-off pipe 42.  Within the tube 45 is a tube 41 having a nozzle 44 at the upper end and a fine orifice 48, regulatable by a screw-plug (not shown), communicating with the chamber 46.  The tube 41 further extends downwardly and includes a single coil 43.  Water admitted at 47 enters the tube 41, and is siphoned off when the coil 43 is filled, thus sucking in air through the nozzle 44, the operation then being repeated.  At the same time water rises in the tube 45, and, if the suction is excessive, flows into the nozzle 44, thereby cutting off further suction of air, the pump thus being self-regulating.  The above subject-matter does not appear in the Specification as accepted.