Brief introduction of technology and equipment of roasting molybdenum concentrate by autothermal reaction rotary kiln

Brief introduction of technology and equipment of roasting molybdenum concentrate by autothermal reaction rotary kiln
While the common internal heating rotary kiln roasting molybdenum concentrate production of molybdenum oxide is advanced technical equipment developed in the molybdenum processing industry in our country in recent years, compared with traditional roasting furnace roasting equipment, it has the advantages of low labor intensity, large output of single equipment, high roasting recovery rate, good operation environment and long service life, but also exist roasting products MoO3 content relatively low. High energy consumption, large flue gas, low concentration of SO2 in flue gas deficiencies. The coal consumed by roasting 1 ton of industrial molybdenum oxide is 275KG standard coal. According to the theoretical study, the heat released by roasting molybdenum concentrate can fully meet the needs of roasting desulfurization. However, the current production process and equipment used for roasting molybdenum concentrate need to consume heat source, which is contradictory with the heat release from roasting reaction of molybdenum concentrate. Chaoyang Heavy Machinery Equipment Development Co., Ltd. has developed a new generation of self-heating reaction sulfide ore roasting rotary kiln with more significant energy saving effect and long service life on the basis of existing domestic engineering and technical equipment. Suitable for self heating reaction roasting of molybdenum concentrate and other sulfide ores.
Technical principle of roasting molybdenum concentrate by rotary kiln of autothermal reaction
The purpose of oxidation roasting of molybdenite concentrate is to remove molybdenum and sulfur content from molybdenum disulfide and convert MoS2 into MoO3 or MoO2 at high temperature. The reaction formula is as follows:
MoS2+ 3.5O2 =MoO3 +2SO2 +995.1J
As can be seen from the above equation, the roasting of molybdenum concentrate is a significant exothermic reaction, which can be completely self-heated, and the roasting process does not require external heat consumption. The thermodynamic trend and heat balance potential of molybdenum concentrate roasting are very obvious. Zero energy consumption roasting can be realized by fully recycling the heat released by oxidation of molybdenum concentrate.
Optimal design of self - thermal reaction rotary kiln
Based on the experiment of oxidation roasting mechanism of molybdenum concentrate, we put forward the optimal design scheme of self-heating reaction rotary kiln. The internal heat exchanger is added to the design of kiln body, making it reach 1. Regulate the temperature of reaction section to avoid the phenomenon of local overheating; 2. Increase the oxygen content of roasting gas, and the recovery reaction section is rich in heat; 3. The total heat transfer resistance of kiln lining is increased to strengthen the insulation effect. The thermal test of the modified rotary kiln shows that: 1. After the transformation of rotary kiln, it can automatically carry out oxidation roasting without external heat source and realize self-heating reaction roasting, which has remarkable energy-saving effect. 2. The tail gas volume of rotary kiln is reduced by about 50%, which inhibits the dilution effect of SO2 and makes the subsequent acid production process more convenient; 3. The skin temperature of the kiln body is greatly reduced, and the external heat dissipation is reduced.
Key points of autothermal reaction rotary kiln technology
A heat exchange and air supply device is set inside the rotary kiln body, and the cold air is pumped in controlled to absorb the heat released by the reaction section, adjust the temperature of the reaction section and preheat the cold air pumped in at the same time.
The clean air preheated by the reaction section enters the kiln body through the discharge end, replenishes the discharge section temperature, accelerates the desulfurization rate of residual sulfur, and improves the quality of roasted products.
The oxygen required to change the original roasting process is provided by the combustion flue gas and replaced by the oxygen provided by the air supply device. Thus, the gas volume of roasting is greatly reduced, the content of SO2 in roasting gas is increased, and the cost of acid production and tail gas treatment is reduced.
The ash box at the charging end and heat exchanger are designed as one piece, and the heat recovered from the secondary recovery can be used to dry molybdenum concentrate and improve the heat recovery efficiency.
The novel slip ring power supply device is adopted to realize the uninterrupted, safe and stable power supply of kiln blower and regulating valve.
The thermal expansion device is set reasonably inside the kiln body, which is used to compensate the thermal expansion of the kiln body and ensure the service life of the kiln body.
The kiln body is made of high quality steel, which can meet the high temperature demand and resist all kinds of corrosion.
Kiln body through the length of the internal insulation device, reduce heat emission, improve the overall thermal efficiency, improve the workshop labor environment.
Application effect of self-heating reaction rotary kiln
Molybdenum concentrate self-heating roasting technology solves the problems of overheating in the main reaction period and heat shortage in the late desulphurization period of molybdenum concentrate roasting, as well as the problems of entering the cooling air of the high temperature rotary shell and discharging the hot air. The device is simple, the heat allocation is reasonable, the temperature regulation of each section in the kiln is flexible, no external heat source is needed, the product quality is high, and the output of the equipment is large.
The roasting of molybdenum concentrate per ton can save the energy demand of 275kg standard, which is the best energy consumption index in China at present. Based on the roasting capacity of 10 tons of molybdenum concentrate per day in φ1.8x2.8 meter rotary kiln and 300 days per year, the annual standard coal can be about 825 tons and the cost can be saved about 650,000 yuan.
As the technology for molybdenum concentrate roasting oxygen supply is more sufficient, molybdenum concentrate oxidation reaction is faster, more fully resulting in better desulfurization effect, the product sulfur content is about 0.05%, far lower than the domestic sulfur content of 0.1% standard.
The content of molybdenum trioxide in the product is about 20% higher than the current technical level index, which will be beneficial to the smelting of ferro molybdenum.
Because the technology cools the high temperature area of the main reaction of molybdenum concentrate mine, the degree of sublimation of molybdenum trioxide is reduced, and the normal production of the rotary kiln dust removal system is guaranteed.
Because the hot air after heat exchange is used instead of fuel combustion flue gas to provide oxidant for molybdenum concentrate roasting, the volume of flue gas is reduced effectively, and the concentration of SO2 and dust containing molybdenum and rhenium in flue gas are increased, which provides a powerful condition for the comprehensive utilization of flue gas.
The product temperature is reduced, the material state is loose, and there is no strong irritating sulfur smoke smell, which will greatly improve the working environment and reduce the labor intensity of workers.

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