一步法制备碳氮化钒的工艺优化试验

围绕开发连续、高效、低成本的一步法合成碳氮化钒的技术,在总结氮化钒生产工艺过程研究的基础上,以V₂O₅为原料,焦炭为还原剂,经过破碎、混料和压制成块、烘干后进行还原氮化过程,在高纯氮气气氛下探索了高温碳热还原一步法制备碳氮化钒的最佳生产工艺条件。通过对V₂O₅的还原过程进行热力学分析计算并利用FactSage热力学软件对其进行理论研究,采用XRD、SEM等测试方法对反应温度、反应时间、氮气流量、制样压力等影响因素进行单因素试验分析,结果表明,碳化钒的氮化反应是逐级进行的,碳氮化钒的反应过程为V₂O₅→V₂O₄→V₂O₃→VC→VCN。试验中产生的CO会改变炉内气体分压,会对碳化温度和氮化温度产生影响,因此反应过程中应严格控制体系的CO和N₂分压;反应时间和氮气流量对反应产物的钒、氮、碳含量产生不同的影响,钒含量和氮含量随着反应时间的增加和氮气流量的...

Experiment on process optimization of one-step preparation of vanadium carbonitride

Focusing on the development of continuous,efficient and low-cost technology for the synthesis of vanadium carbonitride by one-step method,on the basis of summarizing the research on the production process of vanadium nitride,this paper takes vanadium pentoxide as the raw material,coke as reducing agent,after crushing,mixing and pressing into blocks,drying to reduce the nitride process. The optimum technological conditions for the preparation of vanadium carbonitride by one step carbothermal reduction at high temperature were investigated under high purity nitrogen atmosphere. The reduction process of vanadium pentoxide was thermodynamically analyzed and calculated,and the theoretical analysis was carried out by FactSage thermodynamic software. The single factor test analysis of reaction temperature,reaction time,nitrogen flow rate,pressure and other influencing factors was analyzed by XRD and SEM test methods. The results show that the nitriding reaction of vanadium carbide was carried out step by step,and the reaction process of vanadium carbonitride was V₂O₅→V₂O₄→V₂O₃→VC→VCN. The CO produced in the experiment will change the gas partial pressure in the furnace,which will affect the carbonization temperature and nitriding temperature. Therefore,the CO and N₂ partial pressure of the system should be strictly controlled in the reaction process. The reaction time and nitrogen flow rate had different effects on the contents of vanadium,nitrogen and carbon in the reaction products. The vanadium content and nitrogen content increased with the increase of reaction time and nitrogen flow rate,while the carbon content decreased with the increase of reaction time.The pressure determines the porosity of the reactants. On the basis of ensuring the quality of the block product,increasing the sample preparation pressure can increase the contact area between the particles and the specific surface area of the reaction,and the reduction effect is good. Considering comprehensively,setting the carbon distribution coefficient of 35%,sample preparation pressure of 20 MPa,carbothermal reduction at 900 ℃ and nitridation reaction at 1 480 ℃ for 180 min,the test can obtain (mass percent) 75.55%V,13.91%N,4.96%C of vanadium carbonitride products finally,in line with national standards.