Since vanadium in stone coal mainly occurs in clay minerals, it is easily converted into a soluble state by oxidative roasting. In the late 1980s, most of the stone coal vanadium plants in China used the following process. The traditional process of extracting vanadium from stone coal The main technical index of the process is (%): the conversion rate of flat kiln roasting is less than 53, the recovery rate of water immersion is 88-93, the recovery rate of hydrolyzed thick V 2 O 5 is 92-96, the recovery rate of refining is 90-93, total smelting The recovery rate is lower than 45. The low conversion rate of sodium salt roasting is one of the main drawbacks of the conventional process. There are many factors affecting the conversion rate, such as calcination temperature, time, type of additive, ratio of ingredients, calcination atmosphere, particle size of the ingredients, and the like. The table below lists the best roasting conditions and conversion rates for some stone coal vanadium plants. It can be seen that most of the roasting additives use salt, and the use of mirabilite or salt plus Glauber's salt can also achieve better results. The advantages of the traditional process are: the process is simple, the process conditions are not harsh, the equipment is simple, the investment is small, and the infrastructure is relatively fast. However, in addition to the low recovery rate, a large amount of flue gas containing hydrogen chloride, chlorine gas and sulfur dioxide discharged from the flat kiln roasting and the waste liquid after the crude V 2 O 2 precipitation are serious sources of pollution. The low comprehensive utilization rate of the flat kiln's large-scale resources cannot be ignored. Table The best roasting conditions for vanadium extraction in some stone mines Mining area Additive type and ratio Roasting time (h) Calcination temperature (°C) Calcination conversion rate (%) Zhejiang Zhuji Mine Mine (with charcoal): NaCl = 100: 16 ~ 18 >3.2 830 °C ± 20 (fluidization roasting) 72.8~78 Hunan Yiyang Mine Mine (decarbonization): NaCl = 100: 10 1 800 71.1~74.1 Sichuan Wushan Mine Mine (decarbonization): NaCl = 100: 14 ~ 18 2 750-800 64~68 Sichuan Wuxi Mine Mine (with carbon + decarbonization): NaCl = 100: 16 ~ 20 3 to 4 750-850 56.89~62.72 Hunan Yueyang Xinkaitang Mine Mine (decarbonization): NaCl = 100: 10 1 750 or less 71.7 Fangshankou Mine, Gansu NaCl Na 2 SO 4 , NaCl + Na 2 SO 4 800～850 800～850 78.0～82 60～70
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