CN101921908A - Molybdenum concentrate self-heating roasting method and its device - Google Patents

Abstract

The invention relates to the technical field of producing industrial molybdenum oxide from molybdenum sulfide concentrate, and mainly proposes a self-heating roasting method and device for molybdenum concentrate; the molybdenum concentrate is roasted to produce industrial molybdenum oxide by using a rotary kiln equipped with a kiln body heat exchange device In the roasting process, the heat released by the roasting reaction of molybdenum concentrate is used to preheat the air entering from the heat exchange device of the kiln body. The preheated air is supplied into the rotary kiln from the discharge end of the kiln head, and the roasting reaction occurs with the molybdenum concentrate. It also supplements heat for the materials in the desulfurization zone in the rear section of the rotary kiln, reduces the temperature in the high-temperature reaction zone in the middle section of the rotary kiln, and completes the roasting process of molybdenum concentrate after the furnace is started without external heat supply at all. The invention solves the problems of overheating in the main reaction stage of molybdenum concentrate roasting and heat shortage in the later stage of desulfurization, 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, and the temperature adjustment of each section in the kiln is flexible. An external heat source is required, the product quality is high, and the output of the equipment is large.

Description

Molybdenum concentrate self-heating roasting method and its device

technical field

The invention relates to the technical field of molybdenum sulfide concentrate production and industrial molybdenum oxide, and mainly provides a self-heating roasting method and device for molybdenum concentrate.

Background technique

At present, about 96% of all molybdenum sulfide concentrates used at home and abroad must first be converted into industrial molybdenum oxide through roasting, and then soluble molybdenum salts can be further extracted, and then smelted into molybdenum metal or its alloys, and most of them are used in iron and steel metallurgy. When molybdenum concentrate is roasted with insufficient oxygen, MoS ₂ reacts with oxygen to form brown MoO ₂ and release heat; when oxygen is sufficient, light yellow MoO ₃ is produced and release heat at the same time. The reaction thermochemical equation is as follows:

MoS ₂ +3O ₂ →MoO ₂ +2SO ₂ +817kJ

MoO ₂ +0.5O ₂ →MoO ₃ +111kJ

MoS ₂ +3.5O ₂ →MoO ₃ +2SO ₂ +928kJ

It can be seen that the roasting of molybdenum concentrate in air is a significant exothermic reaction process, which can be completed by self-heating. The roasting process does not need to consume heat energy and should not generate low-concentration SO ₂ flue gas. However, in the roasting process of the production of roasted molybdenum concentrate, whether it is the early simple reverberatory furnace roasting, or the widely used rotary kiln roasting, multi-hearth furnace roasting, and even the flash furnace roasting and additive additives that have not been realized in industrial applications Roasting and the like all need to adopt external heat source to provide the heat of roasting to ensure the smooth progress of the reaction. Roasting heat is generally provided by external heat sources such as coal, oil, various gas, natural gas, and electricity.

At present, some domestic small enterprises still use the reverberatory furnace process to produce molybdenum oxide. When roasting molybdenum concentrate, the feeding, discharging and stirring of furnace materials are all manual operations. The roasting heat is supplied by coal, heavy oil or gas combustion, combined with the opening and closing of the furnace door. to control the firing temperature. The advantages of the reverberatory furnace roasting process are less investment in equipment and short construction period, but during the roasting process, because the fuel flue gas and the process flue gas are discharged from the same flue, the dust composition in the exhaust flue gas is complex, and the associated rhenium is not easy to recover and SO ₂ Concentration is too low (generally only 0.44～0.6%) and difficult to handle, easy to cause serious pollution of the environment. In addition, the heat utilization rate of the reverberatory furnace is low, and it has the disadvantages of high energy consumption, poor production conditions, and high labor intensity. The energy consumption of 1 ton of industrial molybdenum oxide consumes as much as 480kg of standard coal, so this process is gradually being eliminated.

Domestic large and medium-sized enterprises mostly use multi-hearth furnaces to roast molybdenum concentrate. The multi-hearth furnace is generally composed of 8-16 layers of hearth, the molybdenum concentrate is fed from the first layer, the first layer and the second layer of hearth are heated by natural gas, preheated and the flotation oil in the molybdenum concentrate is removed ( Such as steam oil or kerosene, etc.), and then the molybdenum concentrate rotates and falls into the third layer to the fifth layer. In these three layers, the exothermic reaction of the molybdenum concentrate is oxidized, and then the oxidized molybdenum dioxide and molybdenum trioxide fall into the The third layer continues to be oxidized by external heating. At this time, molybdenum dioxide is continuously oxidized and most of it is converted into molybdenum trioxide. The last two layers are usually filled with oxygen or oxygen-enriched air to strengthen the oxidation of unoxidized molybdenum dioxide and a small amount of unoxidized molybdenum dioxide. Oxidized molybdenum disulfide. And make the desulfurization complete gradually. At present, the roasting recovery rate of industrial molybdenum oxide produced by most multi-hearth furnaces is about 98%, and the higher one can reach 99%. -50m ³ , individual 100m ³ (determined by the chemical composition, particle size and flotation oil content of the Renlu molybdenum concentrate). However, the structure of the multi-hearth furnace is more complicated, and there are many moving parts in the furnace body. And the heat release of each layer of furnace reaction is uneven. When the temperature control is not good and exceeds the sublimation temperature of MoO ₃ (795°C), it will easily cause the loss of MoO ₃ sublimation, and it will also cause the sintering of the furnace charge, resulting in the blockage of the feeding port. The furnace must be cleaned regularly, which not only increases the labor intensity, but also affects normal production. The concentration of SO ₂ in the exhaust gas during multi-hearth furnace roasting is low (about 1.5%), so it is uneconomical to make acid, and it is easy to cause SO ₂ pollution and form social nuisance.

In our country, most small and medium-sized enterprises adopt the rotary kiln roasting process. During roasting, the material moves from the kiln tail to the kiln head under the action of the rotation and inclination of the kiln body, and the molybdenite starts to oxidize accordingly. According to the chemical reaction of the molybdenum concentrate in the kiln and the thermal effect of the heating furnace, the kiln can be divided into three sections, and the position of each section varies with the feeding speed, the nature of the concentrate and the chemical composition. The preheating and drying zone is located at the tail of the kiln, the temperature is between 250 and 450°C, where the materials are preheated and dried to remove oil and water; the reaction zone is in the middle of the kiln, and the temperature is between 500 and 700°C, where the molybdenum concentrate is When the stage reaches the ignition point, the oxidation reaction is carried out by its own chemical reaction heat to generate molybdenum oxide. When the residual sulfur of the material drops below 3.5%, the desulfurization cannot be continued by the spontaneous combustion reaction. At this time, the high temperature or high temperature flue gas supplied by the external heating source makes the Residual sulfur continues to be removed, the furnace temperature in this section is 350-650°C, and the roasted materials are discharged in this section.

The heating methods of the rotary kiln include electric heating, heavy oil heating, gas heating, and coal heating. The energy consumption of industrial molybdenum oxide is as high as 275kg of standard coal. In the rotary kiln roasting process, the material is in a state of continuous turning in the furnace, the roasting is sufficient, and the sulfur content in the product is small; the SO ₂ concentration in the tail gas is higher than that of the reverberatory furnace roasting process, about 1.5%, but it is still not stable. The concentration condition of 2-4% required for state acid production is not suitable for acid production.

It can be seen that the currently widely used roasting process of molybdenum concentrate not only significantly consumes fuel or other energy sources, but also provides oxidant for the roasting reaction by replacing air with oxygen-poor flue gas generated by fuel combustion, which causes the volume expansion of roasting flue gas and forms a dilution effect , so that the volume concentration of _SO2 in the roasting flue gas is only about 1%. This concentration is obviously too low to meet the concentration requirements for acid production, and it is not easy to recycle. Direct discharge will cause waste of resources and serious pollution of the environment. . At the same time, the rare element rhenium associated with the molybdenum concentrate is almost gone with the low-concentration SO ₂ flue gas, and only a few manufacturers are recycling rhenium. At the same time, about 3% of the molybdenum concentrate is lost during the roasting process , about two-thirds of which are molybdenum-containing dust that is evacuated with a large amount of flue gas.

In actual production, generally molybdenum concentrate enters the drying preheating period first after being put into the furnace. In the usual countercurrent roasting, the required preheating temperature can be reached mainly by relying on the waste heat of the flue gas; The melting point and boiling point of molybdenum oxide are very low. Considering these conditions, try to avoid high temperature, so it is necessary to discharge heat in time - usually achieved by mixing cold air or even spraying water into the high temperature area of the furnace, and using the water jacket to transfer heat. These measures The reaction intensity is suppressed, the reaction process is prolonged, and the reaction heat loss increases; in the critical late stage of desulfurization (that is, the residual sulfur removal section in the rear section of the furnace), although the relative amount of residual sulfur decreases rapidly, the absolute desulfurization rate is getting smaller and smaller. , so in turn, it is necessary to supplement heat for the material that is about to become a product - usually using the above-mentioned waste heat or flue gas waste heat cannot meet this requirement, and it needs to rely on a dedicated combustion or electric heating device. Therefore, after entering the main reaction period, following the process of turning the molybdenum-containing material to the discharge port, the important measure of existing roasting is to first discharge heat and then replenish heat. The thermal measures adopted rely on the internal combustion of fuel to raise the temperature, relying on _air suction and spraying water to cool down, so that the weight of flue gas in multi-hearth furnaces, reverberatory furnaces and most rotary kilns continues to expand. "Dilution", forming a dilution effect, making the usual concentration treatment, comprehensive utilization and acid production very difficult and costly.

Contents of the invention

In view of the above problems, the present invention provides a molybdenum concentrate self-heating roasting method and its device, the purpose of which is to solve the problem that the existing molybdenum concentrate roasting process and equipment need an external heat source to provide heat when the molybdenum concentrate is roasted, and the main reaction Excess heat in the early stage, heat shortage in the later stage of desulfurization, and excessive roasting flue gas volume and low SO ₂ concentration in roasting flue gas.

The purpose of the present invention is achieved through the following technical solutions: a self-heating roasting method for molybdenum concentrate, using a rotary kiln with a kiln body heat exchange device to roast molybdenum concentrate to produce industrial molybdenum oxide, and the roasting process uses molybdenum concentrate to roast The heat released by the reaction preheats the air entering the kiln body heat exchange device, and the preheated air is supplied into the rotary kiln from the discharge end of the kiln head, where it reacts with the molybdenum concentrate and deresidues the rear section of the rotary kiln. The material in the sulfur zone supplements the heat, reduces the temperature of the high-temperature reaction zone in the middle section of the rotary kiln, and the roasting process of the molybdenum concentrate after the furnace is started is completed without external heat supply at all.

A method for self-heating roasting of molybdenum concentrate, the process steps are:

1) Before production, the air induction function of the flue gas recovery system keeps a certain negative pressure in the rotary kiln, and the external heat source is used to uniformly preheat the inside of the rotary kiln. The head of the rotary kiln reaches 400°C and the tail of the kiln reaches 150 When the preheating temperature is above ℃, the dried and pulverized molybdenum concentrate raw materials with a particle size of 80-200 mesh are sent into the tail of the rotary kiln, and the raw materials flow from the tail of the kiln to the head of the kiln under the action of the rotation and inclination of the rotary kiln body. Stirring movement; keep the temperature of the head of the rotary kiln above 400°C;

2) The molybdenum concentrate raw material moves to the middle section of the rotary kiln, and when the temperature reaches above 380°C, the oxidation reaction begins, and the flue gas generated by the external heat source is used to provide the oxidant required for the oxidation reaction, and at the same time, the blower installed on the kiln body passes through the rotary kiln. The heat exchange device installed in the kiln provides natural air and maintains the volume fraction of oxygen in the rotary kiln at 5-8%. The natural air is used to exchange heat for the high temperature zone of the main reaction of the material in the middle section of the rotary kiln, reducing the temperature of the high temperature zone of the main reaction. Temperature, the natural air after heat exchange enters the rotary kiln through the head of the rotary kiln to supplement the oxidant for the oxidation and roasting of molybdenum concentrate, and at the same time provide part of the heat to maintain the temperature of the rear section of the rotary kiln, that is, the desulfurization section, and promote desulfurization the progress of the reaction;

3) Control the negative pressure state in the rotary kiln, gradually increase the amount of natural air supplied by the blower to the rotary kiln, and maintain the gas flow rate in the kiln at 5-11m/s. A certain negative pressure in the rotary kiln will make the sulfur dioxide gas produced by the reaction and other smoke and dust are drawn out of the rotary kiln from the kiln tail, enter the smoke and dust recovery system, and continuously draw the air preheated by the heat exchanger into the rotary kiln;

4) Coordinate control of the rotating speed of the rotary kiln body and the speed of supplying raw materials to the rotary kiln, and maintain the thickness of the material layer in the rotary kiln at 3 to 15 cm until three temperature zones are formed in the rotary kiln, namely the material drying and preheating zone in the front section of the rotary kiln , in the middle section of the rotary kiln, in the high temperature zone of the main reaction of the material between the other two temperature zones, and in the desulfurization section of the rear section of the rotary kiln; the drying and preheating zone of the material is from the kiln tail to the high temperature zone of the main reaction of the material The temperature range of the desulfurization section is from 400 to 830°C from the kiln head to the high temperature zone of the main reaction of the material, and the high temperature zone of the main reaction of the material is from the middle to the drying preheating of the material The temperature range of the zone is 940-500°C, and the temperature range from the middle part of the material main reaction high-temperature zone to the desulfurization section is 940-830°C; stop the external heat supply, increase the amount of natural air flowing into the rotary kiln, Maintain the volume fraction of oxygen in the kiln atmosphere at 8-18%, and control the negative pressure in the rotary kiln to maintain the gas flow rate in the kiln at 10-20m/s;

5) After the molybdenum concentrate is fully oxidized and roasted in the rotary kiln for 7 to 12 hours, it is stirred and rolled out of the kiln head, and the finished product is out of the kiln;

6) The dried and pulverized molybdenum concentrate raw materials are continuously fed into the tail of the rotary kiln, oxidized and roasted in the rotary kiln, and the finished product is discharged from the kiln; After the first temperature zone, that is, the entire process after the external heating is stopped, the heat of the entire process after the furnace is started is completely provided by the heat released by the roasting reaction of molybdenum concentrate, that is, it is fully utilized The heat released by the roasting reaction of molybdenum concentrate completes the roasting process; during the whole process after the furnace is started, the natural air introduced by the heat exchange device installed in the rotary kiln maintains the volume fraction of oxygen in the kiln atmosphere at 8-18%, And control the negative pressure in the rotary kiln to maintain the gas flow rate in the kiln at 10-20m/s.

A self-heating roasting method for molybdenum concentrate, the natural air entered by the frequency conversion blower passes through the heat exchange device to exchange heat with the kiln body in the high temperature zone of the main reaction of the material, so that the kiln body in the high temperature zone of the rotary kiln can be cooled once , the air heated by the kiln body in the high-temperature area is then exchanged with the kiln body in the desulfurization section of the rotary kiln material; the air with a certain temperature enters the inner cavity of the rotary kiln; it provides the required oxygen for the roasting reaction, and at the same time provides some Heat is used to maintain the temperature of the rear section of the rotary kiln, that is, the desulfurization section, to promote the desulfurization reaction, and to perform secondary cooling on the high temperature zone of the main reaction of the material.

In the above process steps, the temperature of each section in the rotary kiln is realized by adjusting the feeding amount, the air supply volume of the frequency conversion blower and the suction force of the induced draft fan.

In the self-heating roasting method of molybdenum concentrate, before production, the external heat source for evenly preheating the inside of the rotary kiln can be a coal-fired furnace or an oil or gas burner or firewood.

A molybdenum concentrate self-heating roasting device, which includes a rotary kiln with an inclination of 1 to 5%, and is supported by a front support wheel, a rear support wheel, and a gear pair of the rotary kiln shell, and the outermost shell of the rotary kiln is Metal cylinder; the front section of the rotary kiln body is the material drying and preheating section at the kiln tail, which is composed of a single or multi-layer insulation layer on the inner layer and an outer shell, and the middle section of the rotary kiln body is the material The high temperature zone of the main reaction is the refractory material layer, the outer heat exchanger (air channel) and the shell from the inside to the outside, and the rear section of the rotary kiln body, that is, the residual sulfur removal section, is the inner heat exchanger (air channel) from the inside to the outside. ), insulation layer and shell; the front part of the rotary kiln shell is equipped with a blower, the kiln head of the rotary kiln is provided with an air outlet, and the heat exchange device for introducing natural air into the rotary kiln is exchanged by the outside Heater and inner heat exchanger, the outer heat exchanger is set in the middle section of the rotary kiln body, that is, the high temperature zone for the main reaction of materials; the inner heat exchanger is set in the rear section of the rotary kiln body, that is, the residual sulfur removal area Section; the frequency conversion blower communicates with the outer heat exchanger on the rotary kiln through the air inlet connection pipeline, and the inner heat exchanger communicates with the outer heat exchanger and the air outlet respectively, and the said device is installed at the kiln head of the rotary kiln. The air outlet at the material end communicates with the inner cavity of the rotary kiln; the outer heat exchanger is set in the middle section of the rotary kiln body, that is, the high-temperature area of the main reaction of the material, so that the outer heat exchanger is connected with the frequency conversion blower and the inner heat exchanger respectively, so that The natural air entered by the frequency conversion blower first enters the outer heat exchanger. Since the outer heat exchanger is set in the middle section of the rotary kiln body, that is, the main reaction section of the kiln body is a high-temperature zone, the natural air entering the outer heat exchanger and The kiln body in the high-temperature zone of the main reaction performs heat exchange, so that the kiln body in the high-temperature zone of the rotary kiln can be cooled once, and the air heated by the kiln body in the high-temperature zone enters the inner heat exchanger, and the kiln in the desulfurization zone of the rotary kiln material The air with a certain temperature enters the inner cavity of the rotary kiln through the inner heat exchanger from the outlet of the rotary kiln head, that is, the outlet at the discharge end; the oxygen required for the roasting reaction is provided, and part of the heat is provided to maintain The temperature in the rear section of the rotary kiln, that is, the desulfurization section, promotes the desulfurization reaction, and performs secondary cooling on the high temperature area.

In order to realize the reasonable deployment and flexible control of the temperature in the rotary kiln, the outer heat exchanger and the inner heat exchanger both adopt a sealed structure, that is, both the outer heat exchanger and the inner heat exchanger are jacketed air-cooled structures , is a plurality of parallel air circulation passages divided by a certain number of ribs set on the rotary kiln body, the multiple parallel air circulation passages of the outer heat exchanger and the inner heat exchanger, said The multiple parallel air circulation channels are distributed along the circumference of the rotary kiln body, so that the air circle enters the outer heat exchanger evenly, and the air entering the outer heat exchanger along the multiple parallel air circulation channels is in harmony with the high temperature zone of the rotary kiln. The kiln body of the rotary kiln conducts heat exchange fully and evenly, so that the kiln body in the high temperature zone of the rotary kiln can be cooled once, and the air heated by the kiln body in the high temperature zone enters the inner heat exchanger evenly around the circumference, and is connected with the kiln in the desulfurization section of the rotary kiln. The body is fully and evenly heat exchanged; the air with a certain temperature enters the inner cavity of the rotary kiln evenly through the air circulation channels distributed along the circumference of the rotary kiln body by the inner heat exchanger, providing the required oxygen for the roasting reaction and providing part of the heat at the same time. To maintain the temperature of the rear section of the rotary kiln, that is, the desulfurization section, to promote the desulfurization reaction, and to perform secondary cooling on the high temperature area.

In the above device, a slip ring power supply device is used to realize the blower power supply.

The blower described in the above device is a variable frequency blower, and the inlet pipe is equipped with a regulating valve.

The beneficial effects of the present invention are:

Because the process of the present invention makes molybdenum concentrate roasting complete by the large amount of heat released by its own oxidation reaction, roasting every ton of molybdenum concentrate can save the energy demand of about 275kg standard coal, which is the best energy consumption index in China at present, so that my country's annual Processing 140,000 to 160,000 tons of molybdenum concentrate will save the country at least 38,500 tons of standard coal.

Since the process of the present invention provides more sufficient oxygen supply for the roasting of molybdenum concentrate, the oxidation reaction of molybdenum concentrate is faster and more sufficient, resulting in better desulfurization effect of the product, and the sulfur content of the product is about 0.05%, which is far lower than the international sulfur content of 0.1% % standard; the product output is about 20% higher than the existing technological level; the content of molybdenum trioxide in the product is about 20% higher than the existing technological level, which will greatly reduce the cost of smelting ferromolybdenum.

Because the process of the invention lowers the temperature of the main reaction high temperature zone of molybdenum concentrate, the sublimation degree of molybdenum trioxide is reduced, and the loss of precious molybdenum metal is reduced.

Because the present invention adopts air instead of fuel combustion flue gas to provide oxidant for molybdenum concentrate roasting reaction, effectively less flue gas volume, thereby increased roasting flue gas SO _{Concentration} and dust concentration containing molybdenum and rhenium in the flue gas, for roasting The comprehensive utilization of flue gas provides favorable conditions.

The temperature of the output product is low, the material state is loose, and there is no strong irritating sulfur smoke smell, which will greatly improve the working environment of workers and reduce the labor intensity of workers.

Description of drawings

Fig. 1 is a schematic diagram of a process equipment system with a partial section of an embodiment of the process of the present invention.

FIG. 2 is a schematic cross-sectional view along line A-A of FIG. 1 .

Fig. 3 is a schematic cross-sectional view along B-B of Fig. 1 .

In the figure, 1. Rotary flash drying and crushing device, 2. Kiln tail sealing device, 3. Rotary kiln feeding device, 4. Rotary kiln, 5. Blower, 6. Outer heat exchanger, 7. Inner heat exchanger, 8. Kiln head seal and finished material box device, 9. Solid fuel high temperature hot blast stove, 10. Front support wheel, 11. Gear pair, 12. Reducer, 13. Adjustable speed motor, 14. Rear support wheel, 15. Smoke recovery system, 16. Bag dust collector, 17. Radiator, 18. Cyclone dust collector.

Detailed ways

The present invention is further described in conjunction with drawings and embodiments.

In Fig. 1, the rotary kiln 4 has a kiln body with a length of 30m and a diameter of 2m; its tail is high, its head is low, and its inclination angle is 1°; it is supported by a front support wheel 10 and a rear support wheel 14; it is supported by an adjustable The speed motor 13 drives the gear pair 11 connected with the middle part of the rotary kiln body to drive it to rotate through the speed reducer 12. Before production, by adjusting the draft of the induced draft fan in the flue gas recovery system, the inside of the rotary kiln is maintained at a slight negative pressure (-300 ~ -800Pa), and the inside of the rotary kiln 4 is uniformly preheated by using a solid fuel high-temperature hot blast stove 9, When the kiln head of the rotary kiln 4 reaches a preheating temperature above 400°C and the kiln tail reaches a temperature above 150°C, the molybdenum concentrate raw materials with a particle size of 80-200 meshes after being dried and crushed by the rotary flash drying and crushing device 1 are sent to Entering the tail of the rotary kiln 4, the raw materials are stirred and moved from the tail of the kiln to the head of the kiln under the action of the rotation and inclination of the rotary kiln 4, and pass through the lifting plates set in the middle and rear sections of the rotary kiln. The material spreading method is to rotate with the cylinder to lift up the material. After reaching the angle of repose of the material itself, the material is gradually and evenly sprinkled along the inclined surface of the lifting plate until it is brought to the position exceeding the highest point of the cylinder. It is basically completed, so that a uniform material curtain is formed on each section of the material, and the contact area with the hot air is increased, the thermal efficiency is improved, and the energy consumption is reduced; the solid fuel high-temperature hot blast stove 9 continues to supply heat, and the temperature at the kiln head is kept at 400 °C above. When the molybdenum concentrate raw material enters the middle section of the rotary kiln 4, when the material temperature reaches above 380°C, the oxidation reaction starts, and the flue gas produced by the solid fuel high-temperature hot blast stove 9 is used as the oxidant; the blower installed at a distance of about 12m from the kiln tail is turned on. 5. Pass the drawn natural air into the outer heat exchanger 6 installed on the rotary kiln 4, 12-23m away from the kiln tail, and 11m long, and the inner side installed on the rotary kiln 4, 23-30m away from the kiln tail, 7m long Heat exchanger 7; one end of the inner heat exchanger 7 is located at the kiln head opening and communicates with the inner cavity of the rotary kiln through the air outlet of the kiln head opening; in this embodiment, the length of the inner heat exchanger 7 is 7m, One end of the inner heat exchanger 7 communicates with the outer heat exchanger 6, and the length of the outer heat exchanger 6 is 11 m; the outer heat exchanger 6 is located on the rotary kiln body in the high temperature zone of the main reaction of the rotary kiln material , located between the inner refractory material layer and the outer shell; the inner heat exchanger 7 is located on the rotary kiln body in the desulfurization zone of the rotary kiln, at the innermost layer of the rotary kiln body, and on its outer layer The insulation material layer and the shell are arranged in sequence; the natural air entering the rotary kiln is poured into the rotary kiln 4 from the kiln head under the action of a certain negative pressure generated in the rotary kiln 4 by the air introduction of the flue gas recovery system 15, Only maintain the volume fraction of oxygen in the atmosphere in the rotary kiln 4 to be 5-8%. Control the negative pressure in the rotary kiln 4 and maintain the gas flow rate in the rotary kiln 4 at about 5-11m/s. When the molybdenum concentrate raw material in the rotary kiln 4 reaches the oxidation reaction temperature above 380°C, the raw material and the blower 5 pass through the outer heat exchanger 6 and the inner heat exchanger 7 supply the natural air in the rotary kiln 4 to start a sufficient oxidation reaction, and the flue gas recovery system 15 generates a certain negative pressure in the rotary kiln 4 to make the _SO2 gas and other smoke generated by the reaction flow out of the kiln The tail part is pulled away from the rotary kiln 4, and after the dust is collected by the cyclone dust collector 18, the heat dissipation and dust collection by the radiator 17, and the dust collection by the bag filter 16, it enters the tail gas acid production system, and the natural air supplied by the blower 5 is continuously supplied. ground into the rotary kiln 4. Coordinate control of the speed of the adjustable speed motor 13, the speed of the raw materials supplied by the rotary kiln feeding device 3 to the rotary kiln 4, the speed of the frequency conversion blower 5 and the suction force of the induced draft fan, and maintain the thickness of the material layer in the rotary kiln 4 at 3-15cm , until three temperature zones are formed in the rotary kiln 4, that is, the material drying preheating zone in the front section of the rotary kiln, the high temperature zone in the middle section of the rotary kiln, and the main reaction high temperature zone between the other two temperature zones, and the high temperature zone in the rear section of the rotary kiln. Residual sulfur removal section; the temperature of the material drying preheating zone gradually increases from the kiln tail to the main reaction high temperature zone of the material, and the temperature range is 200-500°C; the residual sulfur removal section is from the kiln head to the main material reaction zone. The temperature in the reaction high-temperature zone gradually increases, and the temperature range is 400-830°C. The temperature range from the middle part of the material main reaction high-temperature zone to the material drying preheating zone is 940-500°C. The material main reaction high-temperature zone consists of The temperature range from the central part to the desulfurization section is 940-830°C. Stop the solid fuel high-temperature hot blast stove 9 for heating, increase the air volume of the blower 5, and supply more natural air through the heat exchange device to maintain the rotary kiln 4. The volume fraction of oxygen in the interior is 8-18%, and the negative pressure in the rotary kiln 4 is controlled to maintain the gas flow rate in the rotary kiln 4 at about 10-20m/s. The molybdenum concentrate raw material is fully oxidized and roasted in the rotary kiln, and then it is stirred and moved out of the kiln head, and enters the kiln head seal and finished product material box device 8, and the finished product comes out of the kiln. The dried and crushed molybdenum concentrate raw materials are continuously fed into the tail of the rotary kiln, oxidized and roasted in the rotary kiln, and the finished product is continuously discharged from the kiln; after the furnace is started, the three temperature zones in the upper part are formed in the rotary kiln. , that is, the entire process after the external heating is stopped is carried out under the state of stopping the external heating, and the heat of the entire process after the furnace is started is completely provided by the heat released by the roasting reaction of the molybdenum concentrate, that is, the roasting of the molybdenum concentrate is completely used The heat released by the reaction completes the roasting process; during the whole process after the furnace is started, the natural air introduced by the heat exchange device installed in the rotary kiln maintains the volume fraction of oxygen in the kiln atmosphere at 8-18%, and the rotary kiln is controlled Negative pressure in the kiln maintains the gas flow rate in the kiln at 10-20m.

As shown in Figure 1, and with reference to Figures 2 and 3, the front section of the rotary kiln body, that is, the material drying and preheating section at the kiln tail, is composed of a single or multi-layer insulation layer in the inner layer and a shell in the outer layer. The middle section of the rotary kiln body, that is, the high-temperature zone for the main reaction of materials, consists of a refractory material layer, an outer heat exchanger (air channel) and a shell from the inside to the outside, and the rear section of the rotary kiln body, that is, the residual sulfur removal section, consists of Inside to outside is the inner heat exchanger (air channel), insulation layer and shell; the blower 5 is installed on the front section of the rotary kiln shell, and the blower is powered by a slip ring power supply device; the blower is a frequency conversion blower, and its inlet pipe Adjusting valves are installed on the top; the kiln head of the rotary kiln, that is, the discharge end, is provided with an air outlet. The heat exchange device for introducing natural air into the rotary kiln is composed of an outer heat exchanger 6 and an inner heat exchanger 7. The outer heat exchanger Heater 6 is set in the middle section of the rotary kiln body, that is, the high-temperature zone for the main reaction of materials; the inner heat exchanger is set in the rear section of the rotary kiln body, that is, the residual sulfur removal section; the frequency conversion blower 5 is connected to the pipeline through the air inlet It communicates with the outer heat exchanger 6 on the rotary kiln. The inner heat exchanger 7 communicates with the outer heat exchanger 6 and the air outlet respectively. The inner cavity is connected; the outer heat exchanger is set in the middle section of the rotary kiln body, that is, the high temperature area of the main reaction of the material, so that the outer heat exchanger 6 is connected with the frequency conversion blower 5 and the inner heat exchanger 7 respectively, so that the frequency conversion blower enters The natural air first enters the outer heat exchanger 6. Since the outer heat exchanger is set in the middle section of the rotary kiln body, that is, the main reaction section of the kiln body is a high-temperature zone, the natural air entering the outer heat exchanger and the main reaction high-temperature zone The kiln body in the high temperature zone is subjected to heat exchange, so that the kiln body in the high temperature zone of the rotary kiln can be cooled down once, and the air heated by the kiln body in the high temperature zone enters the inner heat exchanger to exchange heat with the kiln body in the material desulfurization section of the rotary kiln , the temperature in the desulfurization section of the rotary kiln material is raised once; the air with a certain temperature passes through the inner heat exchanger 7 and enters the inner cavity of the rotary kiln from the outlet of the rotary kiln kiln head, that is, the discharge end; provides the roasting reaction The required oxygen, at the same time, provides part of the heat to maintain the temperature of the rear section of the rotary kiln, that is, the desulfurization section, to promote the desulfurization reaction, and to perform secondary cooling on the high temperature area.

The outer heat exchanger 6 and the inner heat exchanger 7 both adopt a sealed structure, that is, the outer heat exchanger 6 and the inner heat exchanger 7 are both jacketed air-cooled structures, and are installed on the rotary kiln body. Multiple parallel air circulation passages divided by a certain number of ribs, multiple parallel air circulation passages of the outer heat exchanger and inner heat exchanger, the multiple parallel air circulation passages along the rotary kiln The circumferential distribution of the kiln body allows the air to enter the outer heat exchanger evenly around the circumference, and enables the air entering the outer heat exchanger along multiple parallel air circulation channels to fully and evenly exchange heat with the kiln body in the high temperature zone of the rotary kiln, so that The kiln body in the high-temperature zone of the rotary kiln is cooled once, and the air heated by the kiln body in the high-temperature zone enters the inner heat exchanger evenly around the circumference, and fully and evenly exchanges heat with the kiln body in the desulfurization section of the rotary kiln. The temperature of the material desulfurization section is raised once; the air with a certain temperature enters the inner cavity of the rotary kiln evenly through the air circulation channels distributed along the circumference of the rotary kiln body by the inner heat exchanger, providing the required oxygen for the roasting reaction, and at the same time Provide part of the heat to maintain the temperature of the rear section of the rotary kiln, that is, the desulfurization section, to promote the desulfurization reaction, and to perform secondary cooling of the high temperature area.

Claims (9)

1. A molybdenum concentrate self-heating roasting method is characterized in that: utilize the rotary kiln roasting molybdenum concentrate with kiln body heat exchange device to produce industrial molybdenum oxide, and the roasting process utilizes the heat preheating that molybdenum concentrate roasting reaction emits The heat enters the air from the heat exchange device of the kiln body, and the preheated air is supplied into the rotary kiln from the discharge end of the kiln head, where it reacts with the molybdenum concentrate and serves as a supplement for the material in the desulfurization zone in the rear section of the rotary kiln. The heat reduces the temperature of the reaction high-temperature zone in the middle section of the rotary kiln, and the molybdenum concentrate roasting process after the furnace is started is completed without external heat supply at all. 2. according to the self-heating type roasting method of molybdenum concentrate according to claim 1, it is characterized in that: the processing step of described self-heating type roasting method is: 1) Before production, maintain a certain negative pressure inside the rotary kiln, and use an external heat source to uniformly preheat the inside of the rotary kiln. The dried and pulverized molybdenum concentrate raw materials with a particle size of 80-200 mesh are sent to the tail of the rotary kiln. Under the action of the rotation and inclination of the rotary kiln body, the raw materials are stirred and moved from the tail of the kiln to the kiln head to keep the rotary kiln The temperature at the kiln head is above 400°C; 2) The molybdenum concentrate raw material moves to the middle section of the rotary kiln, and when the temperature reaches above 380°C, the oxidation reaction starts, and the flue gas generated by the external heat source is used to provide the oxidant required for the oxidation reaction, and at the same time, the blower (5 ) provides natural air through the heat exchange device installed in the rotary kiln, and maintains the volume fraction of oxygen in the rotary kiln at 5-8%, and uses natural air to exchange heat for the high temperature zone of the main reaction of the material in the middle section of the rotary kiln, reducing the main reaction The temperature in the high-temperature zone, the natural air after heat exchange enters the rotary kiln through the kiln head, supplements the oxidant for the oxidation and roasting of molybdenum concentrate, and at the same time provides part of the heat to maintain the temperature in the rear section of the rotary kiln, that is, the desulfurization section , to promote the desulfurization reaction; 3) Control the negative pressure state in the rotary kiln, gradually increase the amount of natural air supplied by the blower to the rotary kiln, and maintain the gas flow rate in the kiln at 5-11m/s. A certain negative pressure in the rotary kiln will make the sulfur dioxide gas produced by the reaction and other smoke and dust are drawn out of the rotary kiln from the kiln tail, enter the smoke and dust recovery system, and continuously draw the air preheated by the heat exchange device into the rotary kiln; 4) Coordinate control of the rotating speed of the rotary kiln body and the speed of supplying raw materials to the rotary kiln, and maintain the thickness of the material layer in the rotary kiln at 3 to 15 cm until three temperature zones are formed in the rotary kiln, namely the material drying and preheating zone in the front section of the rotary kiln , in the middle section of the rotary kiln, in the high temperature zone of the main reaction of the material between the other two temperature zones, and in the desulfurization section of the rear section of the rotary kiln; the drying and preheating zone of the material is from the kiln tail to the high temperature zone of the main reaction of the material The temperature range of the desulfurization section is from 400 to 830°C from the kiln head to the high temperature zone of the main reaction of the material, and the high temperature zone of the main reaction of the material is from the middle to the drying preheating of the material The temperature range of the zone is 940-500°C, and the temperature range from the middle part of the material main reaction high-temperature zone to the desulfurization section is 940-830°C; stop the external heat supply, increase the amount of natural air flowing into the rotary kiln, Maintain the volume fraction of oxygen in the kiln atmosphere at 8-18%, and control the negative pressure in the rotary kiln to maintain the gas flow rate in the kiln at 10-20m/s; 5) The molybdenum concentrate is fully oxidized and roasted in the rotary kiln, and then rolled out of the kiln mouth after being fully oxidized and roasted, and the finished product is out of the kiln; 6) The dried and pulverized molybdenum concentrate raw materials are continuously fed into the tail of the rotary kiln, oxidized and roasted in the rotary kiln, and the finished products are continuously discharged from the kiln; After the three temperature zones, that is, the entire process after the external heating is stopped, the heat of the entire process after the furnace is started is completely provided by the heat released by the roasting reaction of the molybdenum concentrate, that is, completely The heat released by the roasting reaction of molybdenum concentrate is used to complete the roasting process; during the whole process after the furnace is started, the natural air introduced by the heat exchange device installed in the rotary kiln maintains the volume fraction of oxygen in the kiln atmosphere at 8-18% , and control the negative pressure in the rotary kiln to maintain the gas flow rate in the kiln at 10-20m/s. 3. The self-heating roasting method of molybdenum concentrate according to claim 1 or 2, characterized in that: the natural air entered by the frequency conversion blower passes through the heat exchange device to first exchange heat with the kiln body in the high temperature zone of the main reaction of the material , so that the kiln body in the high-temperature zone of the rotary kiln can be cooled once, and the air heated by the kiln body in the high-temperature zone is then exchanged with the kiln body in the material desulfurization section of the rotary kiln. Carry out a lift; air with a certain temperature enters the inner cavity of the rotary kiln; provides the required oxygen for the roasting reaction, and at the same time provides part of the heat to maintain the temperature of the rear section of the rotary kiln, that is, the desulfurization section, and promote the desulfurization reaction. , and carry out secondary cooling to the high temperature zone of the main reaction of the material. 4. The self-heating roasting method of molybdenum concentrate according to claim 1 or 2, characterized in that: the temperature of each section in the rotary kiln is realized by adjusting the feeding amount, the air supply volume of the frequency conversion blower and the suction force of the induced draft fan. 5. A molybdenum concentrate self-heating type roasting device is characterized in that: it includes a slope of 1 to 5%, and is supported by a front support wheel (10), a rear support wheel (14), a gear pair ( 14) Supported rotary kiln (4), characterized in that: the rotary kiln is provided with an air heat exchange device and a blower (5) is installed on the front section of the rotary kiln shell; the air heat exchange device is exchanged by the outside Heater (6) and inner heat exchanger (7), the outer heat exchanger (6) is arranged in the middle section of the rotary kiln kiln body, that is, the high temperature zone of the main reaction of the material; the inner heat exchanger (7) is arranged in The rear section of the rotary kiln body is the residual sulfur removal section; the blower (5) communicates with the outer heat exchanger (6) on the rotary kiln through the air inlet connection pipeline, and the inner heat exchanger (7) is connected to the outer heat exchanger (7) respectively. The heat exchanger (6) is connected to the air outlet at the discharge end of the rotary kiln kiln head; the air exhaust port at the discharge end of the rotary kiln is connected to the inner cavity of the rotary kiln; the outer heat exchanger (6) It is installed in the middle section of the rotary kiln body, that is, the high-temperature area of the main reaction of the material, so that the outer heat exchanger (6) is connected with the blower (5) and the inner heat exchanger (7) respectively, so that the natural air entered by the blower first enters the outer heat exchanger. In the heater (6), it exchanges heat with the kiln body in the high-temperature zone of the main reaction, and the air heated by the kiln body in the high-temperature zone enters the inner heat exchanger (7), and then exits from the rotary kiln head through the inner heat exchanger. The air outlet at the material end enters the inner cavity of the rotary kiln. 6. The molybdenum concentrate self-heating type roasting device according to claim 5 is characterized in that: the outer heat exchanger (6) and the inner heat exchanger (7) all adopt a sealed structure, that is, the outer heat exchanger ( 6) and the inner heat exchanger (7) are both jacketed air-cooled structures, which are multiple parallel air circulation channels divided by a certain number of ribs on the shell, and the outer heat exchanger ( 6) and the inner heat exchanger (7) have multiple parallel air circulation channels, the multiple parallel air circulation channels are distributed along the circumference of the rotary kiln body, so that the air enters the outer side evenly through the circumference of the blower (5) heat exchanger (6), and make the air entering the outer heat exchanger along multiple parallel air circulation channels fully and evenly exchange heat with the kiln body in the high temperature zone of the rotary kiln, and the air heated by the kiln body in the high temperature zone is uniform Entering the inner heat exchanger (7), the air with a certain temperature enters the inner cavity of the rotary kiln evenly through the air circulation channels distributed along the circumference of the rotary kiln body of the inner heat exchanger (7). 7. The self-heating roasting device for molybdenum concentrate according to claim 5, characterized in that: the outer heat exchanger (6) located on the kiln body in the high temperature zone of the main reaction of the rotary kiln material is located in the inner refractory material layer and the outer shell; the inner heat exchanger (7) located on the kiln body of the rotary kiln desulfurization zone is located at the innermost layer of the rotary kiln body, and the outer layer is sequentially provided with an insulating material layer, a shell body. 8. The molybdenum concentrate self-heating type roasting device according to claim 5, characterized in that: the blower (5) is powered by a slip ring power supply device. 9. The molybdenum concentrate self-heating roasting device according to claim 5, characterized in that: the blower (5) is a frequency conversion blower, and the inlet pipe is equipped with a regulating valve.

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