doi: 10.3850/978-981-08-7614-2_IMPRES067

ABSTRACT

Two types of host for carbon adsorbents intended for use in compact systems are studied: expanded natural graphite (ENG) and expholiated expanded sulphuric acid treated natural graphite (ESATNG, trade name Papyex™). Composite adsorbents for activated carbon (AC) with the host matrices are developed and compared. Results show that compressed ESATNG has much higher thermal conductivities than the compressed ENG. For a density of 830 kg/m³ the thermal conductivity of compressed ESATNG is 336 W/(mK), and it is of the order of one hundred times higher compared with compact ENG having similar density. The permeabilities of compact ESATNG are much more critical than the compact ENG. For example for similar densities of 300 kg/m³, the permeability of compact ESATNG is 2.0109X10^-15 m² while the permeability of compact ENG is 1.073X10^-13 m², and the value of ESATNG is about 50 times lower than the value of ENG. Compressed composite adsorbents of AC with ENG as host were produced with a high density in the range 700-720 kg/m³. Considering that the permeability will be too low using composite AC with ESATNG as host in high densities, the density range was restricted to less than 500 kg/m³. The thermal conductivities of AC/ESATNG composite are much higher than the thermal conductivities of AC/ENG composite. The optimal thermal conductivity for compact AC with ESATNG is 17.58 W/(mK), and it is about 7 times higher than the optimal value of AC/ ENG composite.

Keywords: Activated carbon, Natural graphite, Thermal conductivity, Permeability, Composite adsorbent.

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