Permeability and thermal conductivity of host compressed natural graphite for consolidated activated carbon adsorbent

Abstract

Permeability and thermal conductivity test units were set up to study the heat and mass transfer performance of the host material, i.e. expanded natural graphite (ENG), for consolidated activated carbon (AC) adsorbent. The permeability was tested with nitrogen as the gas source, and the thermal conductivity was studied using steady-state heat source method. The results showed that the values of permeability and thermal conductivity were 10^-15 to 10^-12 m² and 1.7 to 3.2 W/(m·K), respectively, while the density compressed expanded natural graphite (CENG) varied from 100 to 500 kg/m³. The permeability decreased with the increasing density of CENG, whereas the thermal conductivity increased with the increasing density of CENG. Then the thermal conductivity and permeability of granular AC were researched. It was discovered that the thermal conductivity of samples with different grain size almost kept constant at 0.36 W/(m·K) while the density was approximately 600 kg/m³. This means that the thermal conductivity was not related to the grain size of AC. The thermal conductivity of CENG was improved by 5 to 10 times compared with that of granular AC. Such a result showed that CENG was a promising host material for AC to improve the heat transfer performance, while the mass transfer performance should be considered in different conditions for utilization of adsorbent.

Keywords

permeability / thermal conductivity / expanded nature graphite / activated carbon

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Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grant Nos. 50736004, 50806043), and the National 100 Outstanding PhD Thesis Foundation in China.

Notation
B	Shape factors of the samples
K	Permeability/m2
ma	Gas mass flowrate/(kg·s-1)
p1	Inlet pressure of air/Pa
p2	Outlet pressure of air/Pa
qv	Gas volume flowrate/(L·min-1)
Q	Heat flux/W
R	Gas constant/(J·kg-1·K-1)
S	The effective heating area of the central square plate heater/m2
T	Sample temperature/K
Greek letters
λ	Thermal conductivity/(W·m-1·K-1)
ΔT	Average temperature gradient/K
Δz	Thickness of the samples/m
μ	Gas viscosity/(Pa·s)
ρ	Density/(kg·m-3)
va	Axial velocity/(m·s)

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2014 Higher Education Press and Springer-Verlag Berlin Heidelberg