Date of Award
Master of Engineering (ME)
Dr. W.K. Lu
The objectives of the present study were to investigate, under laboratory conditions, the strength of coke as a function of some of the key variables in the carbonization process, including the addition of some inert carbonaceous materials, and to analyze the effects of these additions on the optical properties of a particular high fluidity coal (Devco). Three coals were selected; Devco, a Canadian coal, and Madison and Chisholm both of which are American coals. Three inert carbonaceous additives were used; Devco semicoke (carbonized at 500°C), low temperature Devco coke (carbonized at 700°C), and coke breeze.
The experimental work was divided into two parts. In the first part, a full factorial design was planned and the blends of Devco coal were carbonized according to it. The variables investigated were: heating rate, size, amount, and 'type' of the inert carbonaceous blended. The dependent variable was the microstrength index (MSI). It was found that the 'type of inert' had the largest statistical weight on the results. The content and mean particle size of the additive in the blend and their interactions with the 'type' were also very significant in the strength. An empirical equation was obtained to express MSI as a function of these variables. In the second part, the blends of the three coals were carbonized according to another statistical design to investigate the following variables: heating rate, type of coal and type of inert. The 'type of coal' was found to be the most statistically significant variable. Nevertheless, the type of inert changed drastically the mechanical properties.
In single coal experiments the blending of Devco semicoke-500°C increased the MSI (i.e., 10% addition raised the index in Madison by 28%, Chisholm by 28% and Devco by 18%). On the other hand, the blending of coke breeze caused the MSI to drop (10% addition reduced the index in Madison by 29%, Chisholm by 22% and Devco by 19%). The type of inert was characterized by its microhardness, true specific gravity, and ash and volatile matter contents. The type of coal was described by an empirical function derived from accepted industrial correlations.
A relationship has been established between microstrength index and tensile strength based on data of the present work. Several samples of cokes were analyzed under the SEM and the optical microscope. It was observed that the addition of Devco semicoke-500° and low temperature Devco coke-700°C reduced the amount of isotropic carbon present in the structure; these blends also had the higher strength.
Uribe, Marco Fidel, "The Effects of some Inert Carbonaceous Additives on the Mechanical and Optical Properties of Coke" (1980). Open Access Dissertations and Theses. Paper 204.