Patent GB-865705-A (GB)
Title: Isotope concentration system
IPC: C01B5/02
Filed: 1957-04-23
Abstract: <PICT:0865705/III/1> In the concentration of an isotope by exchange between chemically different, physically separable fluid substances by countercurrent contact in a system containing a number of stages of dual temperature units, a part of both enriched substances flowing between the units of each stage, except the last, is passed to the next succeeding stage and a part of both the impoverished substances flowing from each stage, except the first, is passed to the next preceding stage.  Water is pumped from conditioner 11, where O2 and CO2 are removed and acidity is neutralised to pH not less than 7, to the top of the first stage cold tower 14.  The H2O flows through 14 countercurrent to H2S gas, and part flows through heat-exchanger 17 to first stage hot tower 18, through which it also passes countercurrent to H2S gas.  The H2O from tower 18 is passed through heat-exchanger 23, stripper 67, where H2S is removed by steam and returned to tower 18, heat-exchanger 23, pipe 24, and heat-exchanger 17 to waste.  The remainder of the H2O from cold tower 14 passes through 25 to second stage cold tower 28 and continues in the same manner through third and fourth stage cold towers 42, 56 in decreasing proportion.  In each stage, part of the H2O from these towers is transferred to the next stage cold tower, as indicated, and part passed through respective heat-exchangers 32, 46, 57, which are heated with H2O drawn from first stage hot tower 18, to hot towers 36, 48, 60, whence the H2O is returned to the next preceding stage hot tower through pipes 63, 51, 39. Part of the H2S leaving hot tower 18 is passed through dehumidifier and cooler 75, separator 97, whence condensate is pumped through heater 99 back to tower 18, and cooler 100 to tower 14, whence the gas is recycled by line 79 and humidifier tower 78 to tower 18.  Humidifier 78 is in a closed cycle with dehumidifier and cooler 75, being supplied with water through 77 and returning it, after necessary make-up from 22, through 76.  The remainder of the H2S from tower 18 is passed through 70 to second stage hot tower 36, while a decreasing proportion is passed to each succeeding hot tower 48, 60, through 71, 72, respectively.  The passage of H2S between the hot and cold towers of each of the second and later stages is the same as that in the first, being respectively through dehumidifiers 84, 85, 86, separators, which supply condensate through heaters to the hot towers, and coolers to cold towers 28, 42, 56, whence H2S is returned to the next preceding cold tower through pipes 90, 92, 94. Dehumidifiers 84, 85, 86, are supplied with H2O from the circuit of dehumidifier 75.  Heavy water is withdrawn as condensate from separator 102 of the last stage through 103.  In Fig. 2 (not shown) the first stage hot tower is divided into three parallel towers, and the gas from each stage hot tower is cooled with a countercurrent of cold H2S from the first stage cold tower, which is humidified by water spray at the same time, before return to first stage hot tower.  The H2S passes through a condenser before entering each stage cold tower.  In Fig. 3 (not shown), a further section is provided between the towers where H2O from the cold tower directly contacts the H2S from the hot tower, and a portion of the heated H2O is withdrawn to a heat-exchanger, where it heats the gas recycling from the cold tower to the hot, while it is being humidified, and is returned to the further section after further heat-exchange. Tritium is also concentrated in this process, and the cold tower may be at 15-35 DEG C., the hot tower at 70-190 DEG C. and the pressure 25-275 p.s.i.a.  To reduce corrosion a substance which increases the S= concentration should be added, e.g. inorganic and/or organic bases, sulphide salts thereof, and solutions of these bases neutralised with H2S, such as sodium hydroxide, sulphide, or hydrosulphide, calcium hydrosulphide, ammonia, tetra-methyl ammonium hydroxide, di- or tri-, methyl-, ethyl-, or propyl-amines. tetra ethyl pentamine, or piperidine.  These substances also increase the hydrosulphide anion, which catalyses the exchange.  It is stated that Li6 and Li7 may be exchanged between a solution of LiCl in ethyl alcohol and Li in mercury amalgam in the same process.  Specifications 845,501 and 865,706 are referred to.