Cellular coal products and processes
According to the present invention there is provided a porous coal-based material having a density of between about 0.1 g/cm 3 and about 0.6 g/cm 3 that is produced by the controlled heating of small coal particulate in a “mold” and under a non-oxidizing atmosphere. The coal starting material preferably exhibits a free swell index of between about 3.5 and about 5.0 and most preferably between about 4.0 and about 4.5. The porous product thereby produced can be machined, adhered and otherwise fabricated to produce a wide variety of low cost, low density products, or used in its preformed shape as a filter, heat or electrical insulator etc. Such porous products, without further treatment exhibit compressive strengths of up to about 6000 psi. Further treatment by carbonization or graphitization yields products that can be used as electrical or heat conductors. Methods for the production of these coal-based cellular products are also described.
1. A green carbon foam having a density ranging from about 0.1 g/cm 3 to about 0.6 g/cm 3 and a thermally conductivity below about 1 W/m° K manufactured by the process comprising:
placing swelling coal particles in a pressure controlled reactor;
heating the coal particles to a first temperature ranging from about 300° C. to about 700° C. under a non-oxidizing atmosphere, wherein the pressure of said non-oxidizing atmosphere ranges from about that for free flowing gas up to about 500 psi; and
controlling said pressure in said reactor, wherein said pressure is maintained below about 500 psi,
wherein the steps of controlling pressure and heating said coal particles produces said green carbon foam.
2. A cellular coal product comprising:
a body having an open cell structure with pore sizes up to about 500 μm, wherein the body has a compressive strength ranging from about 2000 psi to about 6000 psi and has a thermal conductivity below about 1 W/m° K.
3. The cellular coal product of claim 2 wherein the body of carbon foam is largely isotropic having approximately equal physical properties in each direction.
4. The cellular coal product of claim 2 wherein the body of carbon foam has a density ranging from about 0.1 g/cm 3 to about 0.8 g/cm 3 .
5. The cellular coal product of claim 2 wherein the body of carbon foam is semi-crystalline, turbostratically ordered, and is largely isotropic having approximately equal physical properties in each direction.