Carbothermal Reduction of Quartz in Methane–Hydrogen–Argon Gas Mixture

Abstract

Synthesis of silicon carbide (SiC) by carbothermal reduction of quartz in a CH4-H2-Ar gas mixture was investigated in a laboratory fixed-bed reactor in the temperature range of 1573 K to 1823 K (1300 °C to 1550°C). The reduction process was monitored by an infrared gas analyser, and the reduction products were characterized by LECO, XRD, and SEM. A mixture of quartz-graphite powders with C/SiO2 molar ratio of 2 was pressed into pellets and used for reduction experiments. The reduction was completed within 2 hours under the conditions of temperature at or above 1773 K (1500 °C), methane content of 0.5 to 2 vol pct, and hydrogen content ≥70 vol pct. Methane partially substituted carbon as a reductant in the SiC synthesis and enhanced the reduction kinetics significantly. An increase in the methane content above 2 vol pct caused excessive carbon deposition which had a detrimental effect on the reaction rate. Hydrogen content in the gas mixture above 70 vol pct effectively suppressed the cracking of methane. Carbothermal Reduction of Quartz in MethaneHydrogen-Argon Gas Mixture XIANG LI, GUANGQING ZHANG, KAI TANG, OLEG OSTROVSKI, and RAGNAR TRONSTAD Synthesis of silicon carbide (SiC) by carbothermal reduction of quartz in a CH 4 -H 2 -Ar gas mixture was investigated in a laboratory fixed-bed reactor in the temperature range of 1573 K to 1823 K (1300°C to 1550°C). The reduction process was monitored by an infrared gas analyser, and the reduction products were characterized by LECO, XRD, and SEM. A mixture of quartz-graphite powders with C/SiO 2 molar ratio of 2 was pressed into pellets and used for reduction experiments. The reduction was completed within 2 hours under the conditions of temperature at or above 1773 K (1500°C), methane content of 0.5 to 2 vol pct, and hydrogen content ‡70 vol pct. Methane partially substituted carbon as a reductant in the SiC synthesis and enhanced the reduction kinetics significantly. An increase in the methane content above 2 vol pct caused excessive carbon deposition which had a detrimental effect on the reaction rate. Hydrogen content in the gas mixture above 70 vol pct effectively suppressed the cracking of methane.

Reduction of Quartz to Silicon Monoxide by Methane-Hydrogen Mixtures

“…The increase of the reaction rate with flow rate is an indication of the effect of the external mass transfer. However, the gas flow rate also affected the thermal cracking of methane in the gas phase [16,17]; the degree of methane cracking increased with increasing residence time which decreased with increasing gas flow rate. The actual methane concentration in the fluidized bed at the gas flow rates 0.4 and 0.6 NL/min was higher than that at 0.8 NL/min, at which the optimum methane content in the gas stream was established within the range of 5 vol pct ( Figure 5).…”

Development and investigation of the technological process of plasma carbothermal reduction of slag from secondary metallurgy of aluminum

“…To emphasize the metallurgical value of the aforementioned aluminum-bearing slags and the feasibility of methane reduction, it is necessary to mention the possibility and efficiency of direct carbothermal reduction of silicon and iron from the corresponding oxide compounds or waste [32,33]. It is important to emphasize this because silicon and iron oxides are almost always present with the target aluminum oxide in the metallurgical slags of the aluminum industry and, according to the studies [22,23,24,34], this would be considered a very positive, auxiliary factor for their joint recovery, increasing the degree of extraction of valuable aluminum and receiving special multicomponent ligatures with high added value that are in demand by the industry.…”

Reducing the Carbon Footprint: Primary Production of Aluminum and Silicon with Changing Energy Systems

“…In the carbothermic process, the final metal producing step is obtained by a reaction between the intermediate compounds SiO and SiC, but an alternative silicon forming reaction seems elusive when using only hydrogen as a reduction agent as reduction of SiO to Si by H 2 is not favored by thermodynamics. Adding methane gas to the hydrogen flow enables SiC formation, which would enable Si formation at higher temperatures, but the methane content has an upper limit of a few percent to prevent methane cracking at elevated temperatures [37]. Such a process would not eliminate CO 2 emissions but has a potential to significantly reduce the emissions.…”