Reaction of Carbon Dioxide with Carbon Blocks Heat-treated at Various Temperatures
The Reaction Rate and Oxidation Profile in the Block
1986 Volume 1986 Issue 126 Pages 96-103
Details
1986 Volume 1986 Issue 126 Pages 96-103
In order to elucidate the influence of baking temperatures of carbon blocks in the oxidation with carbon dioxide, the gasification rates and exidation profiles inside of the carbon rods were investigated. The carbon materials used in this experiment were obtained from the moldings, 50×50×85mm, made from pulverized pitch cokes and binder pitch.The moldings were baked at different temperatures, 1000°C (D-1000), 1400°C (D-1400), 1800°C (D-1800) and 2200°C (D-2200), respectively. The carbon blocks produced in these manners were machined in the shape of rod, ∅20×30mm. Each of the carbon rods had almost the same pore size distribution, centering at around 4μm in radius, The oxidation was carried out on these carbon rods at 850°-1000°C in the flow of carbon dioxide and the reacted rod samples of burn-off 3.5% and 5% were obtained.
The relative gasification rates of carbon rod samples were as follows:
D-1000, D-1400>D-1800>>D-2200 at 850°and 900°C,
D-1400>D-1000>D-1800>>D-2200 at 950°and 1000°C.
After the reaction, the rod was lathed and thin layers were cut off from the surface of the rod at every0.5mm thickness. For each of the cuts, the weight loss and size change of the rod was measured and bulk density of the thin layer was calculated.The BET surface area for each of the thin layers was determined by the gas adsorption method applied to the cut off powder.
The decreasing of bulk density, which proceeds rapidly at the surface and gradually inside of the rod, was observed on each of the samples. Particular decreasing of the bulk density at the surface was found in the case of D-1000. It seems the density gradient suggests the evidence for the concentration gradient of reactant from the surface toward the inside of the rod. In the results of BET surface area, the samples heat-treated at the lower temperatures, such as 1000°C or 1400°C, had higher surface areas than those of the other samples. And rapid decreasing for D-1000and slight decreasing for D-1400were observed from the surface toward the inside of the rods. On the other hand, no remarkable changes in the surface area were found throughout the rods of samples heat-treated at the higher temperatures.
Discussion was given on these results and an equation of gasification rate was presented.
