Vacuum vapour recovery

W.N. Tuttle, Recent developments in vacuum regenerated activated carbon based hydrocarbon vapour recovery systems. Port Technology International, 1, pp. 143-146,1995. 

Fig. 8.55 The effect of a 0.14Cr addition on the recovery of ductility of Al-6Zn-3Mg alloys during storage in laboratory air at 20° C after pre-exposure to water vapour-saturated air for 5 days at 70°C. The ductility ratio is the ratio of elongation-to-fracture of specimens broken under the cited conditions and under vacuum conditions...

Close valves 1 and 2. Heat for 2-3 minutes and check for an increase in pressure. A change may indicate the presence of water vapour suggesting that the pyrolysis reaction was incomplete. Open valve 2 to check vacuum recovery. A substantial fall in the vacuum also suggests residual water. Replace sample breakseal, change pyrolysis vessel in puncturing device, and re-evacuate line. 

In cases in which, often at start-up, hard-to-condense vapours which are also potentially toxic or environmentally unacceptable have to be vented, consideration should be given to scrubbing them. If a solvent recovery imit needs vacuum-making equipment, a liquid ring vacuum pump can often also be used as a vapour scrubber in addition to its main role. 

The design of the still kettle must allow it to take full vacuum since it is possible, if the system vent is blocked or closed, for almost all the vapour within the solvent recovery system to be condensed once the heating medium is turned off. Since all air will have been displaced from the system in the early stages of a batch, a vacuum will form progressively as the vapour condenses. 

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