Modern "three-step method": vanadium pentoxide tablet production process and vanadium production process
Vanadium pentoxide is widely used in metallurgy, chemical industry and other industries, mainly for smelting ferrovanadium.
As a strategic material, vanadium occupies a very important position in the national economy and national defense of steel, electronics, chemical industry, aerospace, atomic energy, etc. Pure metallic vanadium is generally obtained by reducing vanadium pentoxide with potassium under high pressure.
The traditional "one-step method" vanadium melting process: the ammonium polyvanadate or ammonium metavanadate obtained by hydrolysis and precipitation of vanadium is directly put into the melting furnace (reverberatory furnace) with intermittent feeding, and directly heated with natural gas, industrial gas, heavy oil and other fuels. The surface of the filter cake is melted layer by layer, and vanadium sheets of a certain thickness are made on the water-cooled disc casting machine. Due to its high energy consumption, low yield, low output and other shortcomings, it can no longer meet the current vanadium market demand, especially the national environmental protection requirements, and cannot achieve clean and green production.
The modern "three-step" vanadium pentoxide tablet production process is to decompose the drying and dehydration, calcination and deammoniation, and melting and casting of the traditional one-step production process into three different process equipments, and the material input and output are continuously operated. This method has the advantages of high vanadium yield, good quality, low energy consumption, good environmental protection effect, high degree of automation, and safe and stable equipment.
The high-temperature flue gas of the melting furnace is used as the drying heat source. After the flue gas is treated by sedimentation and mixed air, it is used as the heat source of the flash dryer to directly dry the material. The wet-based ammonium vanadate filtered by the vanadium precipitation is evenly and quantitatively sent to the rotary flash dryer through a spiral feeder. The dry hot air enters the drying chamber through the gas annular gap at the bottom of the dryer main engine to conduct mass and heat transfer with the wet material for drying. The dried powder material is collected from the top outlet of the dryer main engine through a cyclone and a bag collector and then prepared for the calcination system. The clean flue gas generated by the bag collector is discharged after passing through the induced draft fan.
The hot air produced by the combustion of the calcination hot air furnace directly calcines the dry-based powdered ammonium vanadate in the calcination furnace. After flash drying, the ammonium vanadate is transported to the calcining furnace through a screw conveyor. Under the action of the negative pressure induced wind force of the calcination, the material is rapidly fluidized and calcined in the main calcination furnace and the auxiliary furnace. The dry ammonium vanadate undergoes a decomposition reaction, and ammonia is removed to generate powdered vanadium pentoxide. The generated ammonia is recycled through the original ammonia recovery system. In order to achieve energy cascade utilization and protect the bag collector of the calcination system from high temperature damage, a heat exchanger is set at the outlet of the calcination furnace to heat the high-temperature flue gas at the outlet of the calcination furnace to a certain temperature before entering the calcination bag collector. The secondary hot air exchanged by the heat exchanger is sent to the melting furnace and the burner of the calcination hot air furnace as combustion-supporting air, which improves the secondary energy utilization of the system. After calcination, the vanadium material is collected by the cyclone and bag collector to prepare for the next melting process.