Abstract
To better understand the mass transfer behaviors in CaC2 production from CaO and coke, this paper studies the diffusion behaviors of CaO and graphite, with or without ash, at 1500 and 1700 °C. CaO and graphite are pressed into tablets and heated alone or in close contact. Physical and chemical changes in these tablets are analyzed by XRD and SEM+EDX. In some experiments, thin Mo wires are placed between the closely contacted CaO and graphite tablets to identify the diffusion direction. It is found that the diffusion between CaO and low-ash graphite is very limited. SiO2 in a high-ash graphite diffuses into CaO tablet and reacts with CaO to form Ca2SiO4, which then diffuses into the graphite tablet easily and leads to CaC2 formation at 1700 °C.
Highlights
At temperatures of 11500 and 1700 which lower and higher formation temperature of CaC2 from calcium oxide (CaO) and C (1540 °C), respectively, little diffusion can be found between CaO and a low-ash graphite in 2 h
Indicating again the diffusion of CaO from the CaO tablet to the ash-C tablet with the aid of SiO2
Ca2 Al2 O5 and calcium aluminosilicates in these XRD spectra indicates that Al2 O3 is not as active as SiO2 in reacting with CaO at the temperature
Summary
The current CaC2 production requires a temperature of greater than 2000 ◦ C, which is realized by electric arc heating. [11] Ji et al studied the reaction of high purity graphite and CaO and reported CaC2 formation through C diffusion to CaO [12]. The diffusion behaviors reported for the CaC2 production are not consistent in the literature, and further studies are needed, especially those using different methods. In light of the above experiments, this paper studies the diffusion behaviors of CaO and graphite at temperatures relevant to CaC2 production using two closely contacted graphite and CaO tablets, with or without fine molybdenum (Mo) wires placed in between. The role of SiO2 in graphite on the diffusion behavior is emphasized
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