Pre-reduction of WO3-Co3O4 by H2-C2H4 in a fluidized bed

In order to avoid the formation of h phase (W6Co6C or W3Co3C) that adversely affects the sintering process and its products in the preparation process of ultra -fine WC -Co powder, a technical route of prereduction of WO3-Co3O4 to WO2-Co and then deep reduction carbonization to WC -Co powder has been proposed. This study mainly investigates the influence of gas partial pressure on the pre -reduction process of WO3-Co3O4 under a mixed atmosphere of H2-C2H4-Ar at 600 degrees C and establishes the kinetic equations of pre -reduction and carbon evolution. The results indicate that increasing the partial pressure of hydrogen is conducive to the rapid and complete conversion of WO3 to WO2. High carbon content can be generated by the deposition of C2H4, and it hinders the diffusion of the reducing gas; WO3 still cannot be completely reduced to WO2 as the partial pressure of C2H4 increases to 60%. For the carbon evolution of C2H4, the carbon amount is positively related to the H2 partial pressure, but it shows the highest amount and evolution rate when the ethylene partial pressure is 20%. Based on the reduction rate curves of WO3 and carbon evolution rate curves of C2H4, the rate equations of pre -reduction and carbon evolution of WO3-Co3O4 system at 600 degrees C are established. The pre -reduction reaction belongs to the first -order reaction, and its equation is expressed as follows: r= dwWO3 dt= (9 +/- 0.15) x 10-2PH20.44P0.57 C2H4 The carbon deposition rate equation of C2H4 can be expressed as follows: r 0 = dcC dt = rf - rby7.35 x 10-2 x P0.31 C2H4 (c) 2023 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.