SILICON CARBIDE MANUFACTURING

The Acheson process which is used for the production of silicon carbide, uses petroleum coke and quartz as major raw materials to produce SiC in bulk quantities. SiC is formed by carbothermal reduction process in the heat resistance furnace (Acheson furnace). Figure 1 shows some typical photographs captured during and after the experiment. The area inside the circle in figure 1(b) shows the formation of green-colored SiC. Whereas, outside the circle partially reacted/unreacted materials were found. SiC has extreme hardness, sharpness and good thermal properties and hence it is employed as an abrasive and refractory material.

The main raw materials are SiO2 and C which are made to react at a high temperature. Saw dust and salt (sometimes) are also added, so that saw dust burns and provides pores, facilitating the escape of evolved gases (at high temperature). Firing is done for about 40 hours and after cooling, the side walls are removed. An outer layer of uncombined mixture is broken away, exposing the cylindrical mass of sharp, brilliant crystals. A schematic cross sectional view of the resistor furnace, after cooling, is given in Figure 2. The whole reaction process is very complex and the productivity is low. About 11-15% of total charge is converted into SiC while theoretically it can go up to 42%. Obviously, the process is inefficient and has high potential for improvement. We have studied this process extensively both theoretically and experimentally and have increased its efficiency substantially.

We have developed a robust 1-D and 2-D mathematical models considering conduction, convection and radiation as heat transfer modes. Finite Volume Method has been employed to solve the heat balance equations. To validate the model, an experimental facility has been developed at laboratory scale. Both model and experimental data show a good agreement with each other. A Graphical User Interface for the process has also been developed.