Charcoal yield measurements

As shown in Tables 8.6 and 8.7, the volatile matter in biomass as measured by the ASTM and TG procedures is much higher than the fixed carbon content, so to significantly increase charcoal yields, the volatiles must be carbonized as well. Closed reactors can be designed to keep the volatiles in the pyrolysis zone for longer periods and increase carbonization. The use of beehive kilns, for example, affords charcoal yields up to 35%, but the process still requires several days for completion (c/. Antal et al, 1996). The Ford Motor Company process in Badger-Stafford retorts was performed over 24-h cycles and the charcoal yields were about 27% (Table 8.8). 

After the third extraction, we measure the radon and its yield by adding several cc STP of carrier Ar to the melt water with He to 1.3-atm pressure and allow the radon to build up for 4 days. We also replace the spiral glass C02 trap with a charcoal trap to insure the collection of the carrier Ar with the radon. We then He-purge the water and collect the Rn with the carrier Ar on the charcoal at liquid air temperature. The Ar plus Rn is recovered from the charcoal at 300 °C purified over hot Ti and counted in a proportional counter. 

It might be noted that Glueckauf analyzed mathematically the operation of a system in which rare gases are successively adsorbed and desorbed on a series of charcoal traps and used such a system for separating helium and neon as the final step in the determination of their abundance in air, A similar sys tem was later used for the separation of argon, krypton and xenon in an experiment to determine the relative yields of krypton and xenon isotopes from uranium fission by volume measurements on the separated gases and later mass spectrographic analysis. In these procedures a series of many traps was required. 

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