Patent GB-860850-A (GB)
Title: Vapour fraction analyzer
IPC: G01N30/20
Filed: 1957-09-10
Abstract: Apparatus for use in multi-conponent vapour analysis, comprises a separating column, a sample loop, a passage of minimum length from one end of said sample loop to said column, and valve means at both ends of said loop for enabling equal volume samples to be trapped in said loop and for enabling said samples to be passed directly through said passage to said column alternately with quantities of carrier gas, to effect in said column a separation of the multi-component vapour sample into its specific components.  A carrier gas, for example helium, is first passed at a selected rate of flow from the supply container 54 through conduit 72 through the reference thermistor cell R.  Concurrently therewith, the second carrier gas stream, entering the cell block through conduit 70, purges the sample loop 82, the linear valve being in the "ir-off" position shown in Fig. 2 and passes to the separating column 78, being finally discharged from the exit end of the column directly through the measuring cell M.  The third carrier gas stream, entering the linear valve assembly through conduit 68, is arrested when the valve piston 18 is in the "air-off" position.  Similarly, two sample vapour streams enter the system through conduit 46 and, in turn, conduits 74 and 76. The piston 18 in the "air-off" position arrests the flow of sample vapour through conduit 76.  After the analyzer is thus purged on this portion of the cycle, the air drive assembly is actuated causing the piston to move to the position shown in Fig. 3 of the drawing and the carrier gas stream previously entering through conduit 70 is arrested, and the carrier gas stream in conduit 68, previously arrested, flows through annular space 30 and inlet 78 of the separating column to elute components of vapour sample from the column.  Concurrently therewith, the sample gas stream through conduit 76, previously arrested, passes through annular space 28 to sample loop conduit 82, annular space 32 and conduit 90, thereby venting to the atmosphere.  The flow of sample <PICT:0860850/III/1> vapour previously flowing through conduit 74 is arrested.  The sole purpose in providing for the flow of sample vapour through conduit 74 when the valve is in the "air-off" position, is to keep a steady flow of sample vapour throughout this portion of the cycle to ensure a fresh supply of sample vapour on the line when p  the valve is activated to the "air-on" position.  Upon the return of the piston 18 to the "air-off" position shown in Fig. 2 after a predetermined period of time, a fixed volume of sample vapour will be trapped in the sample loop 82 and, when the carrier gas stream passes through conduit 70 and annular space 28, this trapped volume of sample vapour is forced through annular space 24 and inlet 78 of the separating column where it is held either physically or chemically depending upon the selection of the column-packing material.  On the successive "air-on" portion of the cycle, the continuous passage of carrier fluid through conduits 68 and 70 to the column packing material produces successive elution of the components of the multi-component vapour sample which components successively pass from exit 80 of the separating column as binary mixtures with the carrier gas to the measuring cell M where thermal conductivity of each binary mixture is measured.