Kinetic Modeling of the Reaction Rate for Quartz and Carbon Pellet
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NTRODUCTION
REACTIONS between quartz and carbon in pellets can be divided into two steps: SiC producing and SiO producing.[1] In the SiC-producing step, SiO2 and C react according to the reaction SiO2 ðsÞ þ 3C ðsÞ ¼ SiC ðsÞ þ 2CO ðgÞ DH1773Kð1500 CÞ ¼ 589:7 kJ=mol
½1
During the SiO-producing step, the main reaction is between SiO2 and SiC. The reaction rate at this step is quite slow and has a constant reaction rate at experimental temperature. It is also believed that the SiC-formation reaction (Eq. [1]) in the quartz and carbon pellet can be divided into the following two steps: SiO formation (Eq. [2]) and SiO capture (Eq. [3]). SiO2 ðsÞ þ C ðsÞ ¼ SiO ðgÞ þ CO ðgÞ DH1773Kð1500 CÞ ¼ 664:5 kJ=mol
½2
FEI LI and MERETE TANGSTAD are with the Department of Material Science and Engineering, Norwegian University of Science and Technology, N-7491 Trondheim, Norway. Contact e-mail: li.feicn@ foxmail.com Manuscript submitted March 15, 2017. Article published online January 19, 2018. METALLURGICAL AND MATERIALS TRANSACTIONS B
SiO ðgÞ þ 2C ðsÞ ¼ SiC ðsÞ þ CO ðgÞ DH1773Kð1500 CÞ ¼ 74:8 kJ=mol
½3
Weimer et al.[2] summarized the reaction rate constant k(T) and activation energy E of the reaction between quartz and coke, charcoal, and carbon black (Table I) for b-SiC manufacture. The activation energies for different carbon materials differ as a result of the different intrinsic reactivities of the various carbon materials. They could also be influenced by the differences in the other parameters, such as the particle size of quartz, type of quartz, and contact between quartz and carbon. The reaction rate constants k(T) for the same carbon at the same temperature are generally consistent with each other. In this study, kinetic modeling of pellets pelletized with different carbon materials, such as charcoal, coke, coal, and quartz, and heated to different temperatures is investigated. The simplified reaction rate expression is obtained after comprehensive study of the previous data.
II.
EXPERIMENTAL
The experimental part is thoroughly described in Reference 3, and in this article, a short summary of it VOLUME 49B, APRIL 2018—839
Table I. Reaction Rate Constant k(T) and Activation Energy E Summarized in Previous Studies for Reaction 1[2] Carbon Material
D (lm)
E (kJ/mol)
Coke breeze
—
552
Coke
0.198
299
Charcoal
70
544
Carbon black
0.187
251
Carbon black
0.385
288
Carbon black
0.017
287
Carbon black
0.03
382
Carbon black
0.218
154
T (K (oC)) 1673 1723 1773 1773 1873 1973 2073 1623 1643 1673 1703 1713 1773 1873 1973 2073 1773 1873 1973 2073 1573 1673 1773 1848 1898 1948 1973 1998 2173 2273
(1400) (1450) (1500) (1500) (1600) (1700) (1800) (1350) (1370) (1400) (1430) (1440) (1500) (1600) (1700) (1800) (1500) (1600) (1700) (1800) (1300) (1400) (1500) (1575) (1625) (1675) (1700) (1725) (1900) (2000)
k (min1) 0.66 0.84 1.50 0.55 1.86 3.72 9.60 0.03 0.06 0.09 0.23 0.24 1.02 3.48 4.56 12.6 0.47 1.68 3.72 7.80 0.06 0.34 0.90 0.72 1.20 3.72 5.34 7.80 5.52 9.00
Fig. 1—Particle size distribution of
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