Kinetic Behaviors of CaC2 Production from Coke and CaO

To replace the high-temperature and energy extensive traditional calcium carbide (CaC2) production technique, characterized by electric arc heating and large granular feeds of coke and calcium oxide (CaO), methods using fine feeds with autothermal heating were reported to be promising at lower temperatures in the literature. To understand the kinetic behaviors of the low-temperature CaC2 production, a series of experiments were carried out in a thermal gravimetric analyzer (TGA) coupled online with a mass spectrometer (MS). The results indicate that the initial temperature for the CaC2 formation decreases linearly with an increase in contact points between the coke and CaO particles. The reaction proceeds differently in two temperature ranges, from 1550 to 1700 degrees C and from 1700 to 1750 degrees C. The rate-limiting step in the low-temperature range is mass transfer of solid CaO toward solid coke with an apparent activation energy of about 456 kJ mol(-1), while that in the high-temperature range is mass transfer of liquid CaO in the form of CaC2-CaO eutectics toward solid coke with a much lower apparent activation energy of about 256 kJ mol(-1). The direction of the mass transfer and the change in mass transfer mode were further confirmed by a number of special design experiments.