The effects of Particle Size Distribution on Density of Nanoporous Carbon. Sean Crockett, Dr. Galen Suppes, Dr. Peter Pfeifer, Parag Shah LS-MOAMP, ALL-CRAFT, Department of Chemical Engineering and Department of Physics, University of Missouri. Materials and Method. Introduction. Results.
The effects of Particle Size Distribution on Density of Nanoporous Carbon
Sean Crockett, Dr. Galen Suppes, Dr. Peter Pfeifer, Parag Shah
LS-MOAMP, ALL-CRAFT, Department of Chemical Engineering and Department of Physics, University of Missouri
Materials and Method
Methane is one of many alternative fuels that have been explored over the past few years in an effort to reduce our dependency on fossil fuels. Currently, methane can be condensed and used as a fuel for most large vehicles. The tank which contains the condensed methane typically is a bulky cylinder large enough to accommodate 3,600 pounds per square inch to store sufficient methane in the limited space on the vehicle. In an effort to make the tank more conformable to spaces available on a vehicle, a carbon adsorbent was developed that allows the use of lower pressures and “conformable” tanks. Adsorbed natural gas, or ANG, allows the methane to be stored at a lower pressure by utilizing the equivalent of a sponge to “soak up” the gas. Afterwards, the methane is released slowly from the sponge and can be burned in a combustion engine. Through extensive research, activated carbon has been found to be a good adsorber of methane and can be made from something as simple as corn cobs. “Activated” carbon has been made nanoporous with the use of a base such as KOH.
Since carbon adsorbs methane, more carbon adsorbs more methane. Also, the more carbon that resides in a certain volume, the more methane that the volume of carbon can adsorb. Taking this into consideration, it would be beneficial to maximize the amount of methane adsorbed by maximizing the carbon briquette density. Density is the mass of something divided by the volume it occupies. Therefore, there are two ways to increase the density of the activated carbon: 1) Increasing the mass within the volume and 2) Decreasing the volume that the mass occupies. In this study we utilize both methods to increase density.
Mechanical Packing of Spherical particles
Particle packing is defined as the selection of proper sizes and proportions of particulate matter so that larger empty spaces or voids are filled with smaller particles. We estimate the carbon particles to be spheres. Particle packing allows us to fit as much carbon particles as possible into a volume by filling gaps with mechanical vibration, thus shaking the particles into place. One component packings, with only one size particle size, achieved the smallest percent of its theoretical density. Binary packings got a larger percentage, and ternary packings got the largest percentage of theoretical density. Since the layers of carbon depict a range of sizes that the particles may possess, there are a number of different sizes in one layer, thus improving packing density. As another measure to increase density, we heat and press the carbon to decrease its volume. In order to predict the theoretical maximum packing factor (Φmax ) with different particle sizes we use the Furnas Model:
Φmax= Φc + (1 - Φc) Φm + (1 - Φc) (1 – Φm) Φf
Using other equations we can also predict the weights of the three fractions (per unit volume of the mix) of layers of carbon at the theoretical maximum packing factor. This way, we can predict the impact of mixed layers of spherical particles and have a general guide to give us an idea of where we should test.
McGEARY, R. K. “Mechanical Packing of Spherical Particles." Journal of the American Ceramic Society: Vol. 44, No. 10. October 1961 <http://mulibraries.1cate.com/linker?template=slinks:redirect&issn=0002-7820&title=Journal+of+the+American+Ceramic+Society&rfr_id=&provider=blackwell&pkgName=synergy&jHome=http%3A%2F%2Fwww.blackwell-synergy.com%2Fopenurl%3Fgenre%3Djournal%26stitle%3Djace>.