WO2014194567A1 - 窑法磷酸工艺中还原磷矿石的回转窑及解决窑法磷酸工艺窑尾结圈的方法 - Google Patents

窑法磷酸工艺中还原磷矿石的回转窑及解决窑法磷酸工艺窑尾结圈的方法 Download PDF

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Publication number
WO2014194567A1
WO2014194567A1 PCT/CN2013/081164 CN2013081164W WO2014194567A1 WO 2014194567 A1 WO2014194567 A1 WO 2014194567A1 CN 2013081164 W CN2013081164 W CN 2013081164W WO 2014194567 A1 WO2014194567 A1 WO 2014194567A1
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WIPO (PCT)
Prior art keywords
kiln
rotary kiln
rotary
phosphoric acid
tail
Prior art date
Application number
PCT/CN2013/081164
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English (en)
French (fr)
Inventor
侯拥和
魏世发
王朋生
王佳宾
Original Assignee
四川玖长科技有限公司
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Filing date
Publication date
Application filed by 四川玖长科技有限公司 filed Critical 四川玖长科技有限公司
Priority to RU2015144715A priority Critical patent/RU2640069C2/ru
Publication of WO2014194567A1 publication Critical patent/WO2014194567A1/zh
Priority to MA38574A priority patent/MA38574A1/fr
Priority to US14/958,839 priority patent/US9982947B2/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/18—Phosphoric acid
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
    • F27B7/06—Rotary-drum furnaces, i.e. horizontal or slightly inclined adapted for treating the charge in vacuum or special atmosphere
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
    • F27B7/20—Details, accessories, or equipment peculiar to rotary-drum furnaces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
    • F27B7/20—Details, accessories, or equipment peculiar to rotary-drum furnaces
    • F27B7/26—Drives
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D99/00—Subject matter not provided for in other groups of this subclass
    • F27D99/0001—Heating elements or systems
    • F27D99/0033—Heating elements or systems using burners

Definitions

  • the present invention relates to a reaction apparatus for reducing phosphate rock, and more particularly to a rotary kiln for reducing phosphate ore. ⁇ Background technique ⁇
  • wet process phosphoric acid that is, the phosphate ore is decomposed by sulfuric acid to obtain dilute phosphoric acid and solid waste residue (referred to as phosphogypsum) mainly composed of CaS0 4 ⁇ ⁇ 3 ⁇ 40, and the dilute phosphoric acid is concentrated to obtain wet-process phosphoric acid containing about 54% of phosphoric acid.
  • the main disadvantages of this process are as follows: First, a large amount of sulfuric acid is consumed; second, the waste slag phosphogypsum cannot be effectively utilized, and the entrained sulfuric acid, phosphoric acid and soluble fluoride are all dissolved in water, and are naturally washed by rainwater, which is easy to wash. Serious pollution to the environment; Third, the product phosphoric acid has a high impurity content, generally only used to produce fertilizer; Fourth, in order to ensure the economical efficiency of the product, high-grade phosphate rock must be used.
  • the method is to finely grind phosphate rock, silica and carbonaceous reducing agent (coke powder or pulverized coal) to 50% ⁇ 85%-325 mesh, add 1% bentonite ball, and dry preheat through chain dryer.
  • the pellets in the kiln reduction to control the maximum temperature of the solids is 1400 ° C ⁇ 1500 ° C, to adjust the pellet Ca0 / Si0 2 molar ratio of 0. 26 ⁇ 0.
  • the melting point of the pellet is higher than the carbothermal reduction temperature of the phosphate ore in the pellet, and the phosphorus is reduced and volatilized from the pellet in the form of phosphorus vapor, and then oxidized into the phosphorus pentoxide in the middle space of the kiln by the air introduced therein.
  • the heat released by oxidation in turn supplies the reduction reaction, most After the kiln gas containing phosphorus pentoxide is hydrated and absorbed, phosphoric acid is obtained.
  • the above-mentioned kiln phosphoric acid process idea shows a good industrial application prospect, because the principle is to use the carbothermal reduction of phosphate rock to form a gas, transfer the phosphorus in the phosphate ore to the gas phase of the rotary kiln, and utilize the gas.
  • the principle of solid separation makes the phosphorus and the remaining solid matter in the pellets separate well.
  • the P 4 gas transferred to the gas phase of the rotary kiln can react with the oxygen in the gas phase of the rotary kiln to generate P 2 0 5 , which is released.
  • the rotary kiln maintains the carbon-thermal reduction temperature of the phosphate rock, the primary energy source is used, and the combustible material produced by the carbothermal reduction of the phosphate rock and the CO can be subjected to a combustion exothermic reaction inside the rotary kiln, and is supplemented and supplied to maintain the carbon heat of the phosphate rock in the rotary kiln.
  • the energy required to reduce the temperature which is significantly reduced compared to the traditional thermal process phosphoric acid process.
  • Rotary kiln is the equipment whose kiln body runs at a certain speed (0.5 r/mir! ⁇ 3r/min). It has the advantage of continuously mechanically turning and mixing the solid materials sent into the kiln to ensure the solid materials in the kiln. The uniformity of heat is everywhere, but in turn the solid material in the kiln is also subject to the mechanical friction of the material movement. If the material strength is less than the mechanical friction, it will be easily destroyed.
  • the basic principle of the KPA process proposed by the US 0RC company is to finely grind phosphate rock, silica and carbonaceous reducing agent (coke powder or pulverized coal) to 50% ⁇ 85%-325 mesh to make pellets.
  • the material pellets used in the process are equipped with a reducing agent carbon, and the carbon undergoes a rapid oxidation reaction with oxygen in the air at a temperature of more than 350 ° C to be converted into C0 2 , if a conventional metallurgical industrial pellet is used on the grate machine.
  • high temperature consolidation 900 °C
  • the reduced carbon in the pellets is completely oxidized, and the reducing agent is lost in the rotary kiln pellets.
  • the pellets entering the kiln will be pulverized in large quantities due to the mechanical friction that can not withstand the movement of the ball in the rotary kiln.
  • Phosphate powder, silica powder and carbonaceous reducing agent which form pellets after pulverization will be separated, and the phosphate rock powder which is pulverized cannot be reduced due to intimate contact with the carbonaceous reducing agent. More seriously, once the phosphate rock is separated from the silica powder, its melting point will be drastically reduced to below 1250 °C.
  • This powdered phosphate rock passes through the high temperature reduction zone of the rotary kiln (the temperature of the layer is about 1300 °C). , all will change from solid phase to liquid phase, and then adhere to the rotary kiln lining to form the high temperature ring of the rotary kiln, hinder the normal movement of the material in the rotary kiln, and feed most of the materials added to the rotary kiln from the rotary kiln. When the end overflows the rotary kiln, the high temperature reduction of phosphorus cannot be achieved, resulting in process failure. It can be seen that due to the inherent defects of the raw materials entering the kiln, the above-mentioned KPA technology has not been used for any industrialization, scale or commercial application.
  • the solid material zone in the lower part of the rotary kiln belongs to the reduction zone, and the upper part of the zone is the gas flow zone of the rotary kiln, which belongs to the oxidation zone, the feed ball.
  • the group is added from the end of the rotary kiln, and is discharged from the kiln head area of the rotary kiln by its own gravity and the frictional force of the rotary kiln.
  • the burner for burning the rotary kiln is installed in the rotary kiln head, and the combustion fumes generated by the kiln are
  • the tail fan is taken out, and the micro-negative pressure is maintained in the rotary kiln, and the air flow is opposite to the moving direction of the material. Since there is no mechanical isolation zone in the reduction zone (solid layer zone) of the rotary kiln and the oxidation zone (the gas flow zone above the solid layer of the rotary kiln), the ball exposed on the surface of the solid zone zone will be in the gas stream with the oxidation zone.
  • the white shell of 5 the thickness of the shell is generally 300 ⁇ m ⁇ 1000 ⁇ m, and the content of P 2 0 5 in the shell layer can be as high as 30% or more; this will cause the transfer ball to P 2 0 5 in the gas phase to not exceed 60%. , resulting in a yield of phosphate in P 205 is low,
  • the waste of mineral resources and the significant increase in the cost of phosphoric acid production have caused the above-mentioned KPA process to lose its commercial application and industrial promotion value.
  • Some researchers hope to isolate the reduction zone in the rotary kiln through the volatilized gas in the layer. Oxidation zones, but industrial tests conducted in rotary kiln with an inner diameter of 2 m have shown that the presence of P 2 0 5 -rich white shell on the pellet surface is still unavoidable.
  • phosphoric acid is produced according to the KPA process proposed by 0RC, which is still very difficult in large-scale industrial applications and practices.
  • Joseph A. Megy has proposed some improved technical methods for the KPA process (see US Pat. No. 7,910,080 B), which is to set the stop at the discharge end of the kiln head of the rotary kiln cylinder while maintaining the basic KPA process.
  • the material ring is used to increase the solid material filling rate of the rotary kiln.
  • by increasing the diameter of the rotary kiln to reduce the surface area to volume ratio of the material layer in the rotary kiln the probability of the material layer being exposed on the surface of the solid material layer is reduced.
  • the process also adds a portion of petroleum coke to the material entering the rotary kiln, in order to utilize the reducing gas generated by the volatilization of the volatiles in the petroleum coke to cover between the material layer and the oxidation zone of the rotary kiln.
  • the scoring is not enough to generate enough gas, and it is difficult to form an effective separation layer between the solid layer of the rotary kiln and the gas flow zone in the rotary kiln. If the amount is too large, a large amount of fuel will be entrained in the rotary kiln material. In the slag ball cooler of the subsequent process, the remaining fuel will meet the air of the cooling slag ball and burn rapidly. The large amount of heat released by the combustion not only increases the difficulty of cooling the high temperature slag ball of the rotary kiln, but also greatly improves the process. The production cost makes the commercialization and large-scale application of the process unrealizable.
  • the material pellets to be used are double-layer composite structure, and the inner layer is made of phosphate rock, silica (or lime, limestone, etc.) and carbonaceous reducing agent after being ground and mixed.
  • the outer layer is a layer of solid fuel containing more than 20% carbon on the inner layer pellet. The inner and outer layers of the pellet are added with a binder, and the pellet is dried and consolidated.
  • Pellet inner Ca0 / Si0 2 molar ratio may be less than 0.6 or greater than 6.5, the carbonaceous reducing agent is a reducing 1 ⁇ 3 times the theoretical amount of phosphate rock, the solid fuel pellet with an outer layer of the inner layer can amount
  • the mass of the pellet is 5% to 25%;
  • the binder added to the pellet and the outer layer may be asphalt, sodium humate, ammonium humate, water glass, sulfite pulp waste liquid, syrup, lignosulfonate 2% ⁇ 15% ( ⁇ ) ⁇
  • the pellet can be dried and consolidated at a temperature of 80 ° C to 600 ° C and a consolidation time of 3 min to 120 min.
  • the above method proposed by the method uses a high temperature resistant wrapping material containing solid carbon on the pellet, and a binder is added during the wrapping so that the outer covering can adhere well to the inner pellet.
  • the double-layer composite pellets are dried and consolidated and sent to the rotary kiln.
  • the high temperature zone of the rotary kiln 300 °C ⁇ 140 (about TC) can achieve the carbon-thermal reduction of the phosphate ore.
  • the surface of the sphere is artificially coated with a coating layer containing a solid reducing agent (carbonaceous material), which can align its inner layer pellets with the gas oxidization zone containing 0 2 and P 2 0 5 in the upper part of the rotary kiln layer. Effective physical isolation.
  • the carbon in the coating layer can undergo a limited oxidation reaction with 0 2 in the oxidation zone (due to the time when the material ball is exposed on the surface of the rotary kiln layer in the industrial large rotary kiln) Shorter, less complete reaction, so that 0 2 can not be transferred to the inner pellet, ensuring that the reducing agent carbon in the inner pellet is not oxidized by the oxygen in the rotary kiln gas flow, so that P 2 0 5 in the phosphate rock
  • the reduction process can be carried out thoroughly, realizing the process of phosphate rock P 2 0 5 High reduction rate.
  • P 2 0 5 in the upper gas oxidation zone of the rotary kiln layer is also unlikely to react with carbon in the surface layer of the composite pellet, thus preventing the formation of phosphate or partial on the composite pellet.
  • phosphate compound eliminating rich P 2 0 5 of the original white shell material ball KPA generating process, the process can be obtained to ensure a high P 2 0 5 yield.
  • the method to replace the solid fuel Or partially replace the gas or liquid fuel which can further reduce the production cost of phosphoric acid.
  • we also added an organic binder during pelletizing which allows the composite pellets to reach 200kN/ball or more after drying and dehydration (below the carbon oxidation temperature in the pellet).
  • the composite pellet can resist the mechanical friction force received in the rotary kiln without being pulverized, and overcome the defects such as the poor pellet strength existing in the original KPA process. It also overcomes the phenomenon that the carbon in the pellet is prematurely oxidized in the pre-tropical zone of the rotary kiln, so that the composite pellet does not pulverize in the kiln, thereby avoiding the high temperature of the rotary kiln caused by the powder, causing the process to fail, ensuring the process. It can be carried out smoothly under the set conditions.
  • the growing kiln tail ring will seriously hinder the movement of the ball, so that the ball added to the rotary kiln will return from the tail of the rotary kiln to the outside of the rotary kiln, which not only destroys the normal operation of the process, but also
  • the kiln cleaning does not stop, which greatly reduces the operating rate of the rotary kiln, increases the production cost of phosphoric acid, and makes the kiln phosphoric acid process difficult to commercialize.
  • the existing kiln phosphoric acid process is still in need of continuous improvement and improvement by those skilled in the art.
  • the technical problem to be solved by the invention is to overcome the serious technical defects that the prior kiln phosphoric acid process cannot be produced in a long period, and to provide a simple structure, small input, low cost, and can effectively alleviate the phenomenon of the rotary kiln kiln tail ring phenomenon.
  • the rotary kiln for reducing phosphate ore is provided, and at the same time, a method for solving the kiln method of the kiln process of the kiln process is provided by a simple operation, a small input and a good effect.
  • the gas phase contains metaphosphoric acid, which will deposit in the tail of the rotary kiln. It reacts with the dust in the rotary kiln to form a metaphosphate solid, which forms a solid ring at the end of the kiln.
  • a rotary kiln including a kiln body, a kiln head box, a kiln tail box and a driving device for driving the kiln body to rotate
  • the kiln in the kiln body a fuel burner is arranged at the head
  • a feed pipe and an outlet flue connected to the external hydration tower are arranged at the kiln tail box
  • the upper part of the kiln body is not provided with a duct
  • the outlet flue is arranged at
  • the axis of the rotary kiln is centered within the radius of the kiln body, and the direction of the flue gas conveyance in the outlet flue is substantially parallel to the axis of the rotary kiln or at an angle of less than 45°.
  • the kiln body comprises an outer cylinder shell and a kiln lining disposed on the inner side of the cylinder shell (the kiln lining is mainly composed of refractory brick or refractory castable), and the kiln body rotates along the kiln
  • the length direction of the kiln is divided into a reduction zone and a pre-tropic zone.
  • the reduction zone is close to the kiln head box, and the pre-tropic zone is close to the kiln tail box.
  • the length of the reduction zone accounts for 1/3 to 3/5 of the length of the kiln body. Body length is 2/5 ⁇ 2/3.
  • the kiln lining is mainly composed of a composite refractory brick or a composite refractory castable, and the kiln lining in the reduction belt includes a layer of clay material close to the cylinder shell (small thermal conductivity) and near the cavity of the rotary kiln.
  • High-aluminum material layer high refractoriness, relatively high thermal conductivity
  • the kiln lining in the pre-tropical zone includes a layer of clay material close to the shell of the cylinder (small thermal conductivity) and a layer of silicon carbide material close to the cavity of the rotary kiln ( Low degree of reaction with metaphosphoric acid and relatively high thermal conductivity).
  • a kiln cleaning machine is arranged outside the kiln tail box, and the kiln cleaning machine is provided with a scraper which can be gradually extended into the rotary kiln tail box and can maintain relative scraping with the inner wall of the cavity. (made of heat-resistant stainless steel).
  • the axis of the rotary kiln and the horizontal plane are at an angle of 1. 7 ° to 2. 9 °
  • the aspect ratio of the kiln body refers to the length of the rotary kiln and the inner diameter of the steel shell of the rotary kiln cylinder
  • the ratio of the rotary kiln is 6% to 25%, and the rotational speed of the rotary kiln is controlled to be 0.6 r/min to 3 r/min.
  • the thickness of the refractory material of the rotary kiln is preferably 200 mm to 280 mm.
  • the rotary kiln is mounted with a plurality of thermocouples for monitoring the temperature in the kiln along the longitudinal direction of the kiln, and the thermocouple passes through the conductive ring or the wireless transmitting and receiving device and the temperature control device outside the rotary kiln. It is connected with a temperature display; the kiln head of the rotary kiln is equipped with an industrial television for monitoring the condition of the rotary kiln.
  • an air suction pump for extracting a gas sample is installed in the kiln trunk of the rotary kiln or on the outlet flue.
  • the present invention provides an effective method for solving the kiln method of the kiln phosphoric acid process kiln, and the above-mentioned rotary kiln is used for the kiln phosphoric acid process, so that the process raw material of the kiln process phosphoric acid process is from the rotary kiln.
  • the tail box feed pipe enters the cavity of the rotary kiln, ignites the fuel burner, and heats the reduction zone temperature in the rotary kiln to 1300 °C ⁇ 145 (TC, the phosphate ore raw material in the rotary kiln is subjected to the reducing agent under high temperature conditions After the reduction, the kiln flue gas is generated, and the outlet flue gas is arranged to make the kiln flue gas at the end of the rotary kiln not shift greatly when entering the exit flue, thereby preventing the kiln flue gas from being discharged.
  • the metaphosphoric acid produces centrifugal physical sedimentation at the end of the rotary kiln, so that the metaphosphoric acid component entrained in the gas stream directly enters the subsequent hydration tower with the kiln flue gas, and is converted into orthophosphoric acid by water.
  • the pre-tropical kiln lining of the rotary kiln is made into a double-layer composite refractory brick or a composite refractory castable, and the kiln lining portion of the cylindrical shell near the rotary kiln is made of clay material.
  • the lining part near the cavity of the rotary kiln is made of silicon carbide material to form a layer of silicon carbide material, so that the reaction is deposited on the kiln of the rotary kiln pre-tropical kiln and the rotary kiln lining Reduce the force, drop it by yourself, and ease the occurrence of the kiln tail ring.
  • a clear kiln machine is arranged outside the kiln tail box, and a clear kiln machine is provided Gradually extending into the rotary kiln kiln and maintaining a scraping scraper with the inner wall of the cavity; when the rotary kiln tail ring causes the material ball of the process material to return from the kiln tail to the rotary kiln, stop first Heating the fuel supply of the rotary kiln, stopping the feeding of the ball into the rotary kiln, and emptying the ball in the rotary kiln, then gradually extending the scraper in the clearing kiln into the rotary kiln, and then using the rotation of the rotary kiln itself , the kiln tail ring cutting is scraped off.
  • the present invention sets the outlet of the flue gas exhaust pipe of the rotary kiln kiln in the same direction as the axis of the rotary kiln (for the convenience of arranging to the hydration tower pipe, it may also be appropriately offset), so that the rotary kiln is discharged from the kiln.
  • the flue gas When entering the outlet flue, the flue gas will not make a large deviation in the direction of movement, thereby preventing the centrifugal physico-deposition of the meta-phosphoric acid in the kiln flue gas at the kiln tail, so that the meta-phosphoric acid directly enters the hydration with the kiln flue gas.
  • the tower converted to orthophosphoric acid when in contact with water. Due to the decrease of the metaphosphoric acid precipitated in the rotary kiln, the formation cycle of the kiln tail ring is prolonged, and the working efficiency of the rotary kiln is improved.
  • the kiln lining of the rotary kiln tail pre-tropical zone adopts a double-layer composite structure, and a layer of clay material is used in a portion close to the rotary kiln cylinder shell, and near the inner side of the rotary kiln With the silicon carbide material layer, the metaphosphate which is deposited in the pre-tropical zone of the rotary kiln can be dropped by gravity due to the difficulty in reacting the metaphosphate with the silicon carbide material.
  • a rotary kiln is provided with a scraper made of heat-resistant stainless steel.
  • the fuel supply to the rotary kiln can be stopped. And stop feeding the ball into the rotary kiln, and at the same time, the blade can be gradually extended into the rotary kiln, and the rotation of the rotary kiln itself is used to scrape off the kiln end ring.
  • thermocouple by setting a thermocouple, it is effective to ensure that the maximum temperature of the composite pellets having a Ca0/Si0 2 molar ratio of less than 0.6 is not more than 1370 ° C; The maximum temperature of the composite pellet of Si0 2 molar ratio greater than 6.5 does not exceed 1450 ° C, in order to better control the reaction conditions and ensure the quality of the product.
  • a sampling pump is provided on the flue gas discharge pipe at the outlet of the rotary kiln kiln or the kiln tail box, and the gas sample is washed and removed to be dust, and then sent to the CO and 0 2 gas analyzer for monitoring.
  • the CO and 0 2 content of the flue gas at the outlet of the rotary kiln in order to better control the range of CO and 0 2 of the kiln flue gas (generally 0 to 5%).
  • the rotary kiln of the invention has the advantages of simple structure, small input, low cost, etc., and the rotary kiln is applied to the method of the invention, and the kiln process phosphoric acid process caused by the kiln tail ring can not be solved well.
  • the problem of commercialization makes the kiln process phosphoric acid process truly commercialized, the production cycle is greatly extended, and significant economic effects are achieved in terms of energy saving and reduction of process production costs.
  • FIG. 1 is a schematic structural view of a rotary kiln according to a specific embodiment of the present invention.
  • Figure 2 is an enlarged cross-sectional view taken along line A-A of Figure 1.
  • Figure 3 is an enlarged cross-sectional view taken along line B-B of Figure 1.
  • Figure 4 is an enlarged cross-sectional view of the portion CC of Figure 1.
  • Fig. 5 is a schematic structural view of a kiln cleaning machine according to a specific embodiment of the present invention.
  • Figure 6 is an enlarged cross-sectional view taken along line D-D of Figure 5.
  • Fig. 7 is a schematic view showing the operation of the kiln cleaning machine in the embodiment of the present invention.
  • Figure 8 is an enlarged cross-sectional view taken along line E-E of Figure 7.
  • a rotary kiln for reducing phosphate rock in a kiln process phosphoric acid process as shown in Figs. 1 to 8, the rotary kiln comprising a kiln body 3, a kiln head box 1, a kiln box 6 and a driving kiln body 3
  • the drive device 5 comprises a motor, a drive pinion 4 connected to the motor, and a drive bull gear 10 meshing with the drive pinion 4, and a support device 2 for supporting the kiln body 3.
  • a kiln head dynamic seal 19 is used between the kiln head box 1 and the kiln body 3, and a kiln tail dynamic seal 9 is used between the kiln tail box 6 and the kiln body 3.
  • a fuel burner 15 and a high temperature slag ball outlet are provided, and a feed pipe 8 and an outlet pipe connected to the external hydration tower are arranged at the kiln tail box 6 of the kiln body 3.
  • Lane 7, feed tube 8 is connected to the interior of the rotary kiln.
  • the upper part of the kiln body 3 is not provided with a duct, and the outlet flue 7 is disposed on the axis of the rotary kiln, and the flue gas conveying direction in the outlet flue 7 is substantially parallel to the axial direction of the rotary kiln.
  • the kiln body 3 of the present embodiment includes an outer cylinder shell 12 and a kiln liner 11 disposed inside the cylinder shell 12, and the kiln body 3 is divided along the length direction of the rotary kiln to include a reduction belt and a pre-tropical zone, and the reduction zone is adjacent.
  • the kiln head box 1, the pre-tropical zone is close to the kiln tail box 6,
  • the length of the reduction belt can be 1/3 ⁇ 3/5 of the length of the kiln body 3 (1/2 in this embodiment), and the length of the pre-tropical zone can account for the kiln body. 3 of the length of 2/5 to 2/3 (1/2 in this embodiment).
  • the kiln lining 11 is mainly composed of a composite refractory castable (or composite refractory brick). As shown in Fig. 3, the kiln lining 11 located in the reduction zone includes a layer of clay material 17 adjacent to the casing 12 and a high alumina near the cavity of the rotary kiln. Material layer 18 (alumina 65%); as shown in Figure 4, the kiln liner 11 in the pre-tropical zone comprises a layer of clay material 17 adjacent the barrel shell 12 and a layer of silicon carbide material 16 adjacent the inner cavity of the rotary kiln.
  • a kiln cleaning machine is arranged outside the kiln tail box 6, as shown in FIG. 5 and FIG. 6, the kiln cleaning machine is placed on the platform 21 Above, the bottom of the clearing kiln is provided with wheels 22 which can roll on the platform 21. The wheels 22 are driven by the traveling speed reducing motor 23.
  • the main body of the kiln is a frame 24, and a motor-driven rotating shaft 25 is mounted above the frame 24.
  • the rotating shaft 25 extends out of the frame 24 in a substantially horizontal direction, and a supporting truss 26 is disposed around the protruding portion.
  • the free end of the protruding portion of the rotating shaft 25 is provided with a progressively extending into the rotary kiln kiln box 6 ( The scraper is rotated to facilitate the feeding of the blade) and the scraper 20 (heat-resistant stainless steel) which is relatively scraped against the inner wall of the chamber.
  • the above-mentioned rotary kiln of the embodiment can effectively solve the problem of the kiln method of the kiln phosphoric acid process kiln, and the specific operations include: using the above-mentioned rotary kiln for the kiln process phosphoric acid process, so that the process raw material of the kiln process phosphoric acid process is from the rotary kiln
  • the feed pipe 8 at the tail enters the cavity of the rotary kiln, ignites the fuel burner 15 to heat the reduction zone in the rotary kiln to 1300 °C ⁇ 1450 °C, and the phosphate ore raw material in the rotary kiln is under high temperature conditions.
  • the kiln flue gas is generated, and the outlet of the rotary kiln kiln tail is set by placing the outlet of the rotary kiln tail exit flue 7 in the same direction as the rotary kiln axis (ie, parallel to the rotary kiln axis).
  • the flue gas enters the exit flue 7, it does not shift greatly in the direction of movement, thereby preventing the meta-phosphoric acid in the kiln flue gas from generating centrifugal physical sediment at the end of the rotary kiln, so that the meta-phosphoric acid in the kiln gas directly goes out of the kiln.
  • the flue gas enters the subsequent hydration tower and turns into orthophosphoric acid when it is exposed to water.
  • the rotary kiln is placed in the pre-tropical kiln lining 11 to form a double-layer composite refractory castable (or composite refractory brick), which is used in the kiln lining portion of the cylindrical casing 12 near the rotary kiln.
  • the clay material is made into a layer 17 of clay material, and the lining portion near the inner cavity of the rotary kiln is made of a silicon carbide material layer 16 made of silicon carbide material. Due to the difficulty in reacting the metaphosphate with the silicon carbide material, the reaction is deposited in the rotary kiln.
  • the adhesion of the metaphosphate on the pre-tropical kiln lining 11 to the rotary kiln lining 11 is reduced, and the kiln lining structure can further prevent the reaction of the metaphosphate with the kiln lining 11 to cause it to fall by itself, further alleviating The occurrence of the kiln tail ring.
  • a heat-resistant stainless steel scraper 20 is disposed in the clearing kiln supporting the kiln tail box 6 of the rotary kiln of the present embodiment, and the scraper 20 is progressively extended into the rotary kiln kiln 6 and A scraper that is relatively scraped against the inner wall of the chamber; when the bobbin of the rotary kiln causes the material ball of the process material to return from the tail of the kiln to the outside of the rotary kiln, the fuel supply to the rotary kiln is stopped first, and the rotary kiln is stopped at the same time.
  • thermocouples 13 for monitoring the temperature in the kiln are installed along the longitudinal direction of the kiln body 3.
  • the thermocouple 13 passes through the conductive ring or the wireless transmitting and receiving device and the temperature control device and the temperature display outside the rotary kiln. Connected.
  • the maximum temperature of the composite pellets greater than 6.5 is not more than The reaction temperature setting at 1450 ° C.
  • An industrial television that monitors the condition of the rotary kiln is installed in the kiln head of the rotary kiln.
  • an air suction pump 14 for taking a gas sample is attached to the outlet flue 7 of the outlet of the kiln box 6 of the rotary kiln of the present embodiment. Samples are taken by the air pump 14 to remove the dust from the gas sample, and then sent to the CO and 0 2 gas analyzer to monitor the CO content of the flue gas at the outlet of the rotary kiln, so as to better control the range of the CO content of the kiln flue gas (generally 0 ⁇ 5%).
  • the axis of the rotary kiln and the horizontal plane are at an angle ⁇ of 1. 2 ° to 2. 9 ° (2.3 ° in this embodiment), and the aspect ratio of the kiln body 3 is 10 to 25: 1 (
  • the present embodiment is 15: 1)
  • the filling rate of the rotary kiln is 7% to 25% (13% in this embodiment)
  • the rotational speed of the rotary kiln is controlled to be 0.6 rpm to 3 rpm. Lr/min).
  • the thickness of the refractory material of the rotary kiln is preferably 200 to 280 (this embodiment is 220).

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Abstract

本发明公开了一种用于窑法磷酸工艺中还原磷矿石的回转窑，包括窑体、窑头箱、窑尾箱和驱动窑体转动的驱动装置，在窑头处设有燃料烧嘴，在窑尾箱处设有进料管和一连接至外部水化塔的出口烟道，窑体的上部不设置风管，出口烟道设于以回转窑轴线为中心的窑体半径范围内，且出口烟道中的烟气输送方向与回转窑的轴线方向基本平行或呈小于45°的夹角。采用本发明的回转窑进行窑法磷酸工艺时，使原料从窑尾箱进入，点燃燃料烧嘴加热，磷矿石原料在高温条件下还原后生成出窑烟气，本发明使出窑烟气在进入出口烟道时不发生较大偏移，进而阻止窑尾处产生离心物理沉降，使窑气中的偏磷酸直接随出窑烟气进入水化塔。本发明可有效缓解回转窑窑尾结圈现象。

Description

窑法磷酸工艺中还原磷矿石的回转窑及解决窑法磷酸工艺窑尾结圈的方法
【技术领域】
本发明涉及一种用于还原磷矿石的反应设备， 尤其涉及一种用于还原磷矿石的回转窑。 【背景技术】
目前世界上工业生产磷酸的方法主要有两种。 （1 ) 湿法制磷酸： 即利用硫酸分解磷矿石 得到稀磷酸和以 CaS04 · η¾0为主体的固体废渣（简称磷石膏），将稀磷酸浓缩得到含磷酸 54% 左右的湿法磷酸。 这种工艺的主要缺点： 一是要耗用大量的硫酸； 二是废渣磷石膏无法得到 有效的利用， 其中夹带的硫酸、 磷酸和可溶性氟化物均溶于水， 自然堆放后被雨水冲刷， 容 易对环境造成严重污染； 三是产品磷酸的杂质含量较高， 一般只用于生产肥料； 四是为保证 产品的经济性， 必须使用高品位磷矿。 （2 ) 热法制磷酸： 即首先将磷矿石、 硅石、 碳质固体 还原剂置于一台矿热电炉中， 用电短路形成电弧的能量， 将炉内温度加热到 1300°C以上， 将 磷矿石中的磷以 形式还原出来， 同时碳质固体还原剂被转化为 C0， 将排出矿热炉的 和 CO为主的气体用水洗涤降温， P4被冷却成固体与气相分离， 得到产品黄磷， 含 CO的废气在烟 囱出口点火燃烧后排入大气； 将得到的 加热到 80°C左右， 使其变为液相， 将其在水化塔中 与通入的空气发生氧化燃烧反应， 得到磷酸酐 P205， 再用水吸收得到磷酸。 热法制磷酸的主 要缺点： 一是要耗费大量的电能； 二是排出矿热炉后分离了 的气体还夹带有大量的氟化物
(以 SiF^P HF存在） 和少量未沉淀的气体 P4， 这将对大气环境造成严重污染； 三是含大量 CO的气体直接燃烧排空， 能源浪费很大； 四是为了保证生产的经济性， 同样需要使用高品位 磷矿石。
为了克服电能紧张、 硫铁矿资源不足和高品位磷矿石逐年减少对磷酸生产的影响， 八十 年代初美国 Occidental Research Corporation ( 0RC) 提出采用 KPA法， 即用回转窑生产 磷酸的方法（简称窑法磷酸工艺） （参见 Frederic Ledar and Won C. Park等， New Process for Technical-Grade Phosphoric Acid, Ind. Eng. Chem. Process Des. Devl985, 24, 688-697)， 并进行了 0. 84m (内） X 9. 14m回转窑中试装置的中间试验 （参见 US4389384号美国专利文 献）。 该方法是将磷矿石、 硅石和碳质还原剂（焦粉或煤粉）细磨到 50%〜85%— 325目， 配加 1%的膨润土造球， 经链式干燥机干燥预热后送入窑头燃烧天然气的回转窑中， 球团在窑内还 原， 控制最高固体温度为 1400°C〜1500°C， 调整球团 Ca0/Si02摩尔比为 0. 26〜0. 55， 使球团 熔点高于球团中磷矿石的碳热还原温度， 磷以磷蒸气的形式从球团中还原挥发出来， 然后在 窑的中部空间被通入的空气氧化成五氧化二磷， 氧化放出来的热反过来又供给还原反应， 最 后将含有五氧化二磷的窑气水化吸收即制得磷酸。
上述的窑法磷酸工艺思路显示了一种良好的工业应用前景， 因其原理是利用磷矿的碳热 还原形成 气体， 将磷矿石中的磷转移到回转窑的气相当中， 并利用气固分离原理使磷与料 球中的其余固体物质很好的进行分离， 转移到回转窑气相中的 P4气体可与回转窑气相中的氧 发生氧化放热反应生成 P205， 放出的热则供给料球中磷矿石的碳热还原 （吸热反应）， 最后将 出回转窑的含 P205的窑气水化吸收， 可获得洁净度远高于湿法磷酸的工业磷酸。 由于回转窑 维持磷矿碳热还原温度使用的是初级能源，同时磷矿碳热还原产生的可燃物质 与 CO在回转 窑内部即可进行燃烧放热反应， 补充提供给维持回转窑磷矿碳热还原温度所需能量， 这与传 统的热法制磷酸工艺相比， 其能耗得到大幅度降低。
然而， 我们的研究表明， 上述的窑法磷酸工艺在规模化的工业应用及实践中很难实现， 其主要缺陷在于：
1、 回转窑是窑体以一定速度（0. 5r/mir！〜 3r/min )运转的设备， 其优点是可以连续对送 入窑内的固体物料进行机械翻转、 混合， 保证窑内固体物料各处受热的均匀性， 但反过来窑 内固体物料亦须承受物料运动的机械摩擦力， 如果物料强度小于受到的机械摩擦力将很容易 被破坏。 美国 0RC公司提出的 KPA工艺基本原理是将磷矿石、 硅石和碳质还原剂 （焦粉或煤 粉） 细磨到 50%〜85%— 325 目后制成球团， 这三种物质必须紧密地共聚一体， 才能在混合物 中 Ca0/Si02摩尔比为 0. 26〜0. 55 的条件下， 实现混合物料在磷矿石的碳热还原温度下不熔 化， 同时， 磷矿的碳还原才能得以顺利进行。 但工艺使用的物料球团中配入了还原剂碳， 碳 在大于 350 °C温度下会与空气中的氧发生快速的氧化反应转变成 C02， 如果采用传统冶金工业 球团在链篦机上高温固结的方法 （ 900 °C )， 则球团中的还原碳会被全部氧化， 入回转窑球 团则流失了还原剂， 磷的碳热还原反应自然也无法进行， 导致工艺失败。 如果仅通过添加膨 润土作球团粘结剂在 300 °C以下进行干燥脱水， 则球团抗压强度仅为 10KN/个球左右， 落下强 度 1次 /米； 因为膨润土的作用机理主要是利用其物质结构中的层间水来调节球团干燥过程 中的水分释放速率， 提高球团在干燥过程中的爆裂温度， 其本身对提高球团强度并无显著作 用。 将这种球团送入回转窑后、 且在回转窑温度值达到 900 °C温度前， 由于承受不住回转窑 内料球运动所受到的机械摩擦力， 入窑的球团将大量粉化， 粉化后组成球团的磷矿粉、 硅石 粉和碳质还原剂等将分离， 粉化后的磷矿粉由于不能与碳质还原剂紧密接触， 将导致磷不能 被还原。 更为严重的是， 磷矿粉一旦与硅石粉分开， 其熔点将急剧降低到 1250 °C以下， 这种 粉状磷矿通过回转窑的高温还原区 （料层温度为 1300 °C左右） 时， 将全部由固相变成液相， 进而粘附在回转窑窑衬上形成回转窑的高温结圈， 阻碍物料在回转窑内的正常运动， 使加入 回转窑的大部分物料从回转窑加料端溢出回转窑， 无法实现磷的高温还原， 导致工艺失败。 可见， 由于入窑原料存在固有缺陷， 至今未见上述的 KPA技术进行过任何工业化、 规模化或 商业化的应用。
2、对于上述配碳磷矿球团的 KPA工艺而言， 在回转窑内料层下部的固体料层区属于还原 带， 料层上部则是回转窑的气流区， 属于氧化带， 进料球团从回转窑窑尾加入， 依靠其自身 重力和回转窑旋转的摩擦力从回转窑的窑头区排出， 回转窑燃烧燃料的烧嘴安装在回转窑窑 头， 产生的燃烧烟气则由窑尾的风机引出， 回转窑内维持微负压， 气流与物料的运动方向相 反。 由于在回转窑的还原带 （固体料层区） 和氧化带 （回转窑固体料层上部的气流区） 无机 械隔离区， 因此， 暴露在固体料层区表面的料球将与氧化带气流中的 、 （¾发生对流传质； 这一方面会使料球中的还原剂碳在料球被气流传热加热到磷矿石碳还原温度前被部分氧化 掉， 致使料球在回转窑还原带由于碳质还原剂的缺乏， 而得不到充分还原； 更为严重的是， 在回转窑高温区暴露于料层表面的料球， 会与窑气中已经还原生成的 P205发生进一步的化学 反应， 生成偏磷酸钙、 磷酸钙及其他的偏磷酸盐或磷酸盐， 进而导致已被还原到气相中的磷 又重新返回料球，并在料球表面形成一层富含 P205的白壳，壳层厚度一般在 300 μ m〜1000 μ m， 壳层中 P205含量可高达 30%以上； 这样会致使料球转移到气相中的 P205不超过 60%， 造成磷矿 中 P205的收率偏低， 进而造成矿产资源的浪费及磷酸生产成本的大幅度上升， 使上述的 KPA 工艺丧失商业应用和工业推广价值。 有研究人员寄望通过料层中挥发出的气体来隔离回转窑 中的还原带与氧化带， 但在内径 2m的回转窑中进行的工业试验表明， 球团表面出现富含 P205 的白壳现象仍是不可避免的。
鉴于上述提及的技术缺陷， 按照 0RC公司所提出的 KPA工艺来生产磷酸， 这在规模化的 工业应用及实践中还存在很大困难。
Joseph A. Megy对 KPA工艺提出过一些改进的技术方法 （参见 US7910080B号美国专利文 献）， 即在维持 KPA基本工艺方法不变的前提下， 通过在回转窑筒体的窑头泄料端设置挡料圈 以提高回转窑的固体物料填充率， 与此同时， 通过增大回转窑的直径以减小回转窑内料层的 表面积-体积比， 降低料层物料暴露在固体料层表面的几率， 以缩短料球中还原剂碳被回转窑 窑气中的 氧化的时间， 减少料球到达回转窑还原带前的还原剂碳的烧损， 同时减少回转窑 高温区中料球表面磷酸盐或偏磷酸盐的生成。 另外， 该工艺还通过在入回转窑的物料中加入 部分石油焦， 以希望利用石油焦中挥发分受热挥发产生的还原性气体， 使其覆盖在料层与回 转窑气流氧化区之间， 以进一步阻止回转窑气流中 、 P205与料球反应的几率， 以保证工艺的 正常进行。 然而， 提高回转窑的填充率将使料球在回转窑内承受更大的机械摩擦力， 进而将 造成料球在回转窑内更大比例的粉化， 形成更多的小于磷矿碳热还原温度的低熔点物质， 使 回转窑高温结圈更加迅速和严重， 从而更早造成工艺的失败。 而添加少量的石油焦产生的挥 发分不足以产生足够的气体， 难以在回转窑固体料层与回转窑内气流区之间形成有效的隔离 层， 若加入量过大， 则出回转窑物料中将夹带有大量的燃料， 这会导致在后续工艺的渣球冷 却机中， 剩余燃料将与冷却渣球的空气相遇并迅速燃烧， 燃烧放出的大量热量不仅增加了出 回转窑高温渣球冷却的难度， 而且又大大提高了工艺的生产成本， 使工艺的商业化、 规模化 运用变得不可实现。
鉴于上述问题， 我们经过反复研究， 曾提出过一种克服上述问题的解决方案 （参见 CN1026403C, CN1040199C 号中国专利文献）， 即采用一种双层复合球团直接还原磷矿石生产 磷酸的工艺， 具体技术解决方案是： 先将磷矿石与配入物料制成球团， 在回转窑内， 球团中 的 P205被还原成磷蒸气并挥发， 在料层上方， 磷蒸气被引入炉内的空气氧化成 P205气体， 然 后在水化装置中被吸收制得磷酸。 该技术方案的最大特点在于： 配入的物料球团采用双层复 合结构， 其内层是由磷矿石、 硅石 （或石灰、 石灰石等） 和碳质还原剂经磨碎、 混匀后造球 而成， 其外层是在内层球团上再裹上一层含碳量大于 20%的固体燃料， 球团的内、 外层配料 时添加粘结剂， 球团采用干燥固结。 球团内层 Ca0/Si02摩尔比可以小于 0. 6或大于 6. 5， 碳 质还原剂为还原磷矿石理论量的 1〜3倍，球团外层固体燃料配量可以为内层球团质量的 5%〜 25%； 球团内、 外层添加的粘结剂可以是沥青、 腐植酸钠、 腐植酸铵、 水玻璃、 亚硫酸盐纸浆 废液、糖浆、木质素磺酸盐中的一种或多种的组合，其添加量为被添加物料重量的 0. 2%〜15% (干基）。 该球团可以采用干燥固结， 固结温度为 80 °C〜600 °C， 固结时间为 3min〜120min。
我们提出的上述方法采用在球团上裹一层含固体碳的耐高温包裹料，包裹时添加粘结剂， 以使外层包裹料能良好地附着在内层球团上。 将这种双层复合球团经干燥固结后送入回转窑 中， 在回转窑高温带 （1300 °C〜140(TC左右） 可以很好地实现磷矿石的碳热还原。 由于在料 球表面人为包覆了一层含固体还原剂 （碳质物料） 的包裹层， 该包裹层可将其内层球团与回 转窑料层上部的含 02和 P205的气流氧化区进行有效地物理隔离。 当这种复合球团在回转窑固 体料层中随回转窑的旋转运动上升到回转窑固体料层表面， 并与回转窑固体料层上部的含 02 和 P205的气流氧化区接触发生对流传质时， 包裹层中的碳便可与氧化区中的 02发生有限的氧 化反应 （因在工业大型回转窑中料球暴露在回转窑料层表面的时间较短， 反应不完全）， 使 02不能传递到内层球团， 保证了内层球团中的还原剂碳不被回转窑气流中的氧所氧化， 使磷 矿石中 P205的还原过程能进行彻底， 实现了工艺过程中磷矿 P205的高还原率。 另一方面， 回 转窑料层上部气流氧化区中的 P205也不可能与复合球团表层包裹层中的碳反应， 因而阻止了 在复合球团上形成磷酸盐或偏磷酸盐化合物， 消除了原有 KPA工艺料球上富含 P205白壳的生 成， 确保了工艺可获得较高的 P205收率。 与此同时， 该方法中以固体燃料取代或部分取代了 气体或液体燃料， 这可进一步降低磷酸的生产成本。 此外， 我们提出的上述方法中在造球时还加入了有机粘结剂， 这可使复合球团在干燥脱 水后 （低于球团中碳氧化温度）， 仍可以达到 200kN/个球以上的抗压强度和 10次 /米以上的 落下强度， 因此， 该复合球团可以抵抗在回转窑内受到的机械摩擦力而不被粉碎， 克服了原 有 KPA工艺存在的球团强度差等缺陷， 也克服了球团中碳在回转窑预热带过早氧化的现象， 使复合球团在窑内不出现粉化， 进而避免了粉料造成的回转窑高温结圈致使工艺失败， 保证 了工艺能在设定的条件下顺利进行。
然而， 在我们后续的研究过程中， 又发现了一系列新的技术问题。 由于通入回转窑的助 燃空气均含有一定量的水分（因空气湿度带入的水分）， 这些水在回转窑内会与回转窑气流中 的 P205发生反应， 生成偏磷酸 （HP03)， 生成的偏磷酸又会与窑气中的粉尘反应， 在回转窑窑 尾生成复杂的偏磷酸盐，并逐渐在回转窑尾部筒体内形成结窑物（即窑尾圈），然后不断长大; 运转一段时间后， 长大的窑尾圈将严重阻碍料球的运动， 使加入回转窑内的料球从回转窑尾 部返出回转窑外， 这不仅破坏了工艺的正常运行， 且不得不停窑清理， 严重降低了回转窑的 作业率， 提高了磷酸的生产成本， 使窑法磷酸工艺难以商业应用。
因此， 为了提高现有窑法磷酸工艺的生产效率， 降低生产成本， 保证工艺的稳定运行， 现有的窑法磷酸工艺还亟待本领域技术人员进行继续的改进和完善。
【发明内容】
本发明要解决的技术问题是克服现有窑法磷酸工艺不能够长周期生产的严重技术缺陷， 提供一种结构简单、 投入小、 成本低、 可以有效缓解回转窑窑尾结圈现象的用于窑法磷酸工 艺中还原磷矿石的回转窑， 同时相应提供一种操作简单、 投入小、 效果好的解决窑法磷酸工 艺窑尾结圈的方法。
在我们长期以来开展的窑法磷酸工艺工业应用实践中， 回转窑窑尾结圈一直是困扰本领 域技术人员的重大技术难题， 因回转窑窑尾结圈导致工艺原料料球不能加入回转窑内， 同时 还阻塞了回转窑内气流的正常运动， 实践证明， 窑尾结圈问题如果得不到解决， 轻则缩短工 艺周期， 导致工艺效率下降， 工艺成本显著增加， 重则导致窑法磷酸工艺的失败。 经过我们 长年深入细致地研究， 我们最终查明了窑法磷酸工艺形成窑尾结圈的主要原因， 即窑法磷酸 工艺中由于气流含有偏磷酸， 其会在回转窑窑体尾部沉积， 最终与回转窑窑内粉尘反应生成 偏磷酸盐固体， 进而在窑尾形成固体结圈。 为解决上述技术问题， 我们通过反复的实验， 提 出了以下技术方案： 即一种所述回转窑包括窑体、 窑头箱、 窑尾箱和驱动窑体转动的驱动装 置， 在窑体的窑头处设有燃料烧嘴， 在窑尾箱处设有进料管和一连接至外部水化塔的出口烟 道， 所述窑体的上部不设置风管， 所述出口烟道设于以回转窑轴线为中心的窑体半径范围内， 且出口烟道中的烟气输送方向与回转窑的轴线方向基本平行或呈小于 45 ° 的夹角。 上述回转窑中， 优选的， 所述窑体包括外部的筒体壳和设于筒体壳内侧的窑衬 （所述窑 衬主要由耐火砖或耐火浇注料构成）， 所述窑体沿回转窑长度方向被划分包括还原带和预热 带， 还原带靠近窑头箱， 预热带靠近窑尾箱， 还原带长度占窑体长度的 1/3〜3/5， 预热带长 度占窑体长度的 2/5〜2/3。
上述回转窑中， 优选的， 所述窑衬主要由复合耐火砖或复合耐火浇注料构成， 位于还原 带的窑衬包括靠近筒体壳的黏土材料层 （导热系数小） 和靠近回转窑内腔的高铝材料层 （耐 火度高，导热系数相对大）；位于预热带的窑衬则包括靠近筒体壳的黏土材料层（导热系数小） 和靠近回转窑内腔的碳化硅材料层 （与偏磷酸反应程度低， 导热系数相对大）。
上述回转窑中， 优选的， 所述窑尾箱外配套设有一清窑机， 清窑机中设有一可渐进式伸 入回转窑窑尾箱内并可与其腔体内壁保持相对刮蹭的刮刀 （耐热不锈钢制）。
上述回转窑中， 优选的， 所述回转窑的轴线与水平面呈 1. 7 ° 〜2. 9 ° 的夹角， 且窑体的 长径比（指回转窑长度和回转窑筒体钢壳内径的比值）为 10〜25： 1，回转窑的填充率为 7%〜 25%, 回转窑的转速控制为 0. 6 r/min〜3r/min。 回转窑耐火材料厚度优选为 200mm〜280mm。
上述回转窑中， 优选的， 所述回转窑沿窑体长度方向上安装有多个监控窑内温度的热电 偶， 所述热电偶通过导电环或无线发送接收装置与回转窑外的温度控制装置及温度显示器相 连； 所述回转窑的窑头安装有监控回转窑内炉况的工业电视。
上述回转窑中， 优选的， 所述回转窑的窑尾箱内或出口烟道上安装有抽取气样的抽气泵。 作为一个总的技术构思， 本发明提供一种解决窑法磷酸工艺窑尾结圈的有效方法， 采用 上述的回转窑进行窑法磷酸工艺， 使窑法磷酸工艺的工艺原料从所述回转窑窑尾箱进料管处 进入回转窑的腔体内， 点燃燃料烧嘴， 使回转窑内还原带温度加热到 1300 °C〜145(TC， 回转 窑中的磷矿石原料在高温条件下经还原剂还原后生成出窑烟气， 通过所述出口烟道的设置使 回转窑窑尾的出窑烟气在进入出口烟道时不在运动方向上发生较大偏移， 进而阻止出窑烟气 中的偏磷酸在回转窑窑尾处产生离心物理沉降， 使夹带在气流中的偏磷酸成分直接随出窑烟 气进入到后续的水化塔中， 遇水转变成正磷酸。
作为对上述方法的进一步改进， 将所述回转窑的预热带窑衬制作成双层式的复合耐火砖 或复合耐火浇注料， 在靠近回转窑的筒体壳的窑衬部分采用黏土材料制作成黏土材料层， 在 靠近回转窑内腔的窑衬部分则采用碳化硅材料制作成碳化硅材料层， 以使反应沉积在回转窑 预热带窑衬上的偏磷酸盐与回转窑窑衬附着力降低， 自行掉落， 缓解窑尾结圈的发生。 由于 碳化硅与偏磷酸反应较难， 显著降低了偏磷酸盐在回转窑窑尾预热带的附着力， 使即使形成 的固体偏磷酸盐在回转窑窑尾靠重力能自行脱落， 以进一步缓解窑尾结圈。
作为对上述方法的进一步改进， 在所述窑尾箱外配套设有一清窑机， 清窑机中设有一可 渐进式伸入回转窑窑尾箱内并可与其腔体内壁保持相对刮蹭的刮刀； 当回转窑窑尾结圈造成 工艺原料的料球从窑尾处往回转窑外返料时， 先停止加热回转窑的燃料供给， 同时停止向回 转窑内送入料球， 并排空回转窑内料球， 然后将清窑机中的刮刀逐渐伸入至回转窑内， 再利 用回转窑自身的旋转， 将窑尾结圈切削刮除。
与现有技术相比， 本发明的优点在于：
( 1 )本发明将回转窑窑尾烟气排出管的出口设置在与回转窑轴线的同方向上（为了布置 至水化塔管道的方便， 也可以有适当偏移）， 这样使得回转窑出窑烟气在进入出口烟道时不会 在运动方向上作较大偏移， 进而防止出窑烟气中偏磷酸在窑尾处产生离心物理沉降， 使偏磷 酸直接随出窑烟气进入水化塔， 遇水转变成正磷酸。 由于回转窑内沉降的偏磷酸减少， 延长 了窑尾圈的形成周期， 提高回转窑的作业效率。
( 2 )本发明优选的方案中， 回转窑窑尾预热带的窑衬采用双层式复合材料结构， 在靠近 回转窑筒体壳的部分采用黏土材料层， 在靠近回转窑内部一侧则采用碳化硅材料层， 由于偏 磷酸盐与碳化硅材料反应困难， 使沉积在回转窑预热带的偏磷酸盐能靠重力自行掉落。
( 3 )本发明优选的方案中， 回转窑窑尾箱外装设一由耐热不锈钢制成的刮刀， 一旦窑尾 圈形成造成料球从窑尾返料， 则可停止加热回转窑的燃料供给并停止向回转窑内送入料球， 同时可将刮刀逐渐伸入至回转窑内， 利用回转窑自身的旋转， 将窑尾结圈切削刮除掉。
( 4)本发明优选的方案中， 通过设置热电偶， 能够有效保证对内球料 Ca0/Si02摩尔比小 于 0. 6的复合球团最高温度不超过 1370°C ;对内球料 Ca0/Si02摩尔比大于 6. 5的复合球团最 高温度不超过 1450°C， 以便更好地控制反应条件， 保证产物的质量。
( 5 )本发明优选的方案中， 通过在回转窑窑尾箱或窑尾箱出口的烟气排出管上设置抽气 泵取样，对气样水洗除去粉尘后送入 CO和 02气体分析仪监测回转窑出口烟气的 CO和 02含量， 以便更好地控制出窑烟气 CO和 02的含量范围 （一般为 0〜5%)。
综上所述， 本发明的回转窑具有结构简单、 投入小、 成本低等优点， 将该回转窑应用到 本发明的方法中可以很好地解决因窑尾结圈造成的窑法磷酸工艺不能商业化的问题， 使得窑 法磷酸工艺能真正实现商业化， 生产周期得以大大延长， 在节能降耗和降低工艺生产成本等 方面都具有显著的经济效果。
【附图说明】
图 1为本发明具体实施方式中回转窑的结构示意图。
图 2为图 1中 A-A处的剖视放大图。
图 3为图 1中 B-B处的剖面放大图。
图 4为图 1中 C-C处的剖面放大图。 图 5为本发明具体实施方式中清窑机的结构示意图。
图 6为图 5中 D-D处的剖视放大图。
图 7为本发明具体实施方式中清窑机工作时的原理图。
图 8为图 7中 E-E处的剖视放大图。
图例说明：
1、 窑头箱； 2、 托轮装置； 3、 窑体； 4、 传动小齿轮； 5、 驱动装置； 6、 窑尾箱； 7、 出 口烟道； 8、 进料管； 9、 窑尾动密封； 10、 传动大齿轮； 11、 窑衬； 12、 筒体壳； 13、 热电 偶； 14、 抽气泵； 15、 燃料烧嘴； 16、 碳化硅材料层； 17、 黏土材料层； 18、 高铝材料层； 19、 窑头动密封； 20、 刮刀； 21、 平台； 22、 车轮； 23、 行走减速电机； 24、 机架； 25、 旋 转轴； 26、 支撑桁架； 27、 回转窑门框。
【具体实施方式】
以下结合说明书附图和具体优选的实施例对本发明作进一步描述， 但并不因此而限制本 发明的保护范围。
实施例：
一种如图 1〜图 8所示本发明的用于窑法磷酸工艺中还原磷矿石的回转窑， 该回转窑包 括窑体 3、 窑头箱 1、 窑尾箱 6和驱动窑体 3转动的驱动装置 5， 驱动装置 5包括电机、 与电 机相连的传动小齿轮 4以及与传动小齿轮 4咬合的传动大齿轮 10， 另设有支撑窑体 3的托轮 装置 2。 窑头箱 1与窑体 3之间采用窑头动密封 19， 窑尾箱 6与窑体 3之间采用窑尾动密封 9。
在本实施例窑体 3的窑头处设有燃料烧嘴 15和高温渣球出口，在窑体 3的窑尾箱 6处设 有进料管 8和一连接至外部水化塔的出口烟道 7， 进料管 8连通至回转窑的内腔。 窑体 3的 上部不设置风管， 出口烟道 7设于回转窑轴线上， 且出口烟道 7中的烟气输送方向与回转窑 的轴线方向基本平行。
本实施例的窑体 3包括外部的筒体壳 12和设于筒体壳 12内侧的窑衬 11， 所述窑体 3沿 回转窑长度方向被划分包括还原带和预热带， 还原带靠近窑头箱 1， 预热带靠近窑尾箱 6， 还 原带长度可占窑体 3长度的 1/3〜3/5 (本实施例中为 1/2)， 预热带长度可占窑体 3长度的 2/5〜2/3 (本实施例中为 1/2)。 窑衬 11主要由复合耐火浇注料 （或者复合耐火砖） 构成， 如图 3所示，位于还原带的窑衬 11包括靠近筒体壳 12的黏土材料层 17和靠近回转窑内腔的 高铝材料层 18 (氧化铝 65%)； 如图 4所示， 位于预热带的窑衬 11则包括靠近筒体壳 12的 黏土材料层 17和靠近回转窑内腔的碳化硅材料层 16。
本实施例中， 窑尾箱 6外配套设有一清窑机， 如图 5和图 6所示， 清窑机安放于平台 21 上， 清窑机底部设有可在平台 21上滚动的车轮 22， 车轮 22通过行走减速电机 23驱动， 清 窑机的主体为一机架 24， 机架 24上方安装有一电机驱动的旋转轴 25， 旋转轴 25沿大致水平 方向延伸出机架 24外， 伸出部外围套设一支撑桁架 26， 旋转轴 25伸出部分的自由端设有一 可渐进式伸入回转窑窑尾箱 6内 （刮刀旋转可方便进刀） 并可与其腔体内壁保持相对刮蹭的 刮刀 20 (耐热不锈钢制）。 一旦窑尾圈形成造成料球从窑尾返料， 则可停止加热回转窑的燃 料供给并停止向回转窑内送入料球， 同时可将刮刀 20逐渐伸入至回转窑内， 利用回转窑自身 的旋转， 将窑尾结圈切削刮除掉。
采用本实施例的上述回转窑即可有效解决窑法磷酸工艺窑尾结圈的问题，具体操作包括: 采用上述的回转窑进行窑法磷酸工艺， 使窑法磷酸工艺的工艺原料从回转窑窑尾处的进料管 8处进入回转窑的腔体内，点燃燃料烧嘴 15，使回转窑内还原带温度加热到 1300 °C〜1450 °C， 回转窑中的磷矿石原料在高温条件下经还原剂还原后生成出窑烟气， 通过将回转窑窑尾出口 烟道 7的出口设置在与回转窑轴线的同方向上（即平行于回转窑轴线设置）， 使回转窑窑尾的 出窑烟气在进入出口烟道 7时不在运动方向上发生较大偏移， 进而阻止出窑烟气中的偏磷酸 在回转窑窑尾处产生离心物理沉降，使窑气中偏磷酸直接随出窑烟气进入到后续的水化塔中， 遇水转变成正磷酸。更进一步的， 本实施例中将回转窑位于预热带的窑衬 11制作成双层式的 复合耐火浇注料 （或复合耐火砖）， 在靠近回转窑的筒体壳 12的窑衬部分采用黏土材料制作 成黏土材料层 17， 在靠近回转窑内腔的窑衬部分则采用碳化硅材料制作成碳化硅材料层 16， 由于偏磷酸盐与碳化硅材料反应困难，这使得反应沉积在回转窑预热带窑衬 11上的偏磷酸盐 与回转窑窑衬 11的附着力降低， 这样的窑衬结构可以进一步阻止偏磷酸盐与窑衬 11的反应 结圈， 使其自行掉落， 进一步缓解窑尾结圈的发生。 再有， 通过在本实施例回转窑的窑尾箱 6外配套的清窑机内装设一耐热不锈钢制刮刀 20，该刮刀 20为一可渐进式伸入回转窑窑尾箱 6 内并可与腔体内壁保持相对刮蹭的刮刀； 当回转窑窑尾结圈造成工艺原料的料球从窑尾处 往回转窑外返料时， 先停止加热回转窑的燃料供给， 同时停止向回转窑内送入料球， 并排空 回转窑内料球， 然后将清窑机中的刮刀 20从回转窑门框 27逐渐伸入至回转窑内， 再利用回 转窑自身的旋转， 将窑尾结圈切削刮除 （清窑机的工作原理参见图 7和图 8)。 由上可见， 本 实施例的回转窑通过多重保障措施和技术手段有效缓解了窑法磷酸工艺中回转窑窑尾结圈的 难题。
另外， 本实施例回转窑沿窑体 3的长度方向上安装有多个监控窑内温度的热电偶 13， 热 电偶 13通过导电环或无线发送接收装置与回转窑外的温度控制装置及温度显示器相连。通过 设置热电偶 13， 能够有效保证对内球料 Ca0/Si02摩尔比小于 0. 6的复合球团最高温度不超过 1370 °C的反应设定温度要求； 对内球料 Ca0/Si02摩尔比大于 6. 5的复合球团最高温度不超过 1450°C的反应设定温度要求。 在回转窑的窑头则安装有监控回转窑内炉况的工业电视。
另外， 本实施例回转窑的窑尾箱 6出口的出口烟道 7上安装有抽取气样的抽气泵 14。 通 过抽气泵 14取样，对气样水洗除去粉尘后送入 CO和 02气体分析仪监测回转窑出口烟气的 CO 和 含量， 以便更好地控制出窑烟气 CO和 的含量范围 （一般为 0〜5%)。
本实施例中回转窑的轴线与水平面呈 1. 2 ° 〜2. 9 ° 的夹角 α (本实施例为 2. 3 ° )， 且 窑体 3的长径比为 10〜25： 1 (本实施例为 15： 1 )， 回转窑的填充率为 7%〜25% (本实施例 为 13%)， 回转窑的转速控制为 0. 6 r/min〜3r/min (本实施例为 lr/min)。 回转窑耐火材料 厚度优选为 200讓〜280讓 （本实施例为 220讓）。

Claims

权 利 要 求
1、 一种用于窑法磷酸工艺中还原磷矿石的回转窑， 所述回转窑包括窑体 （3)、 窑头 箱 （1)、 窑尾箱 （6) 和驱动窑体 （3) 转动的驱动装置 （5)， 在窑体 （3) 的窑头处设有 燃料烧嘴（15)， 在窑尾箱（6)处设有进料管（8)和一连接至外部水化塔的出口烟道（7)， 其特征在于： 所述窑体 （3) 的上部不设置风管， 所述出口烟道 （7) 设于以回转窑轴线为 中心的窑体半径范围内， 且出口烟道 （7) 中的烟气输送方向与回转窑的轴线方向基本平 行或呈小于 45° 的夹角。
2、 根据权利要求 1 所述的用于窑法磷酸工艺中还原磷矿石的回转窑， 其特征在于： 所述窑体 （3) 包括外部的筒体壳 （12) 和设于筒体壳 （12) 内侧的窑衬 （11)， 所述窑体
(3) 沿回转窑长度方向被划分包括还原带和预热带， 还原带靠近窑头箱 （1)， 预热带靠 近窑尾箱 （6)， 还原带长度占窑体 （3) 长度的 1/3〜3/5， 预热带长度占窑体 （3) 长度的 2/5〜2/3。
3、 根据权利要求 2所述的用于窑法磷酸工艺中还原磷矿石的回转窑， 其特征在于： 所述窑衬 （11) 主要由复合耐火砖或复合耐火浇注料构成， 位于还原带的窑衬 （11) 包括 靠近筒体壳 （12) 的黏土材料层 （17) 和靠近回转窑内腔的高铝材料层 （18); 位于预热 带的窑衬 （11) 则包括靠近筒体壳 （12) 的黏土材料层和靠近回转窑内腔的碳化硅材料层 (16)。
4、 根据权利要求 1、 2或 3所述的用于窑法磷酸工艺中还原磷矿石的回转窑， 其特征 在于： 所述窑尾箱 （6) 外配套设有一清窑机， 清窑机中设有一可渐进式伸入回转窑窑尾 箱 （6) 内并可与其腔体内壁保持相对刮蹭的刮刀 （20)。
5、 根据权利要求 1、 2或 3所述的用于窑法磷酸工艺中还原磷矿石的回转窑， 其特征 在于： 所述回转窑的轴线与水平面呈 1.7° 〜2.9° 的夹角， 且窑体 （3) 的长径比为 10〜 25 : 1范围； 回转窑的填充率为 7%〜25%， 回转窑的转速控制为 0.6r/min〜3r/min。
6、 根据权利要求 1、 2或 3所述的用于窑法磷酸工艺中还原磷矿石的回转窑， 其特征 在于： 所述回转窑沿窑体长度方向上安装有多个监控窑内温度的热电偶 （13)， 所述热电 偶 （13) 通过导电环或无线发送接收装置与回转窑外的温度控制装置及温度显示器相连； 所述回转窑的窑头安装有监控回转窑内炉况的工业电视。
7、 根据权利要求 1、 2或 3所述的用于窑法磷酸工艺中还原磷矿石的回转窑， 其特征 在于： 所述回转窑的窑尾箱 （6) 内或出口烟道 （7) 上安装有抽取气样的抽气泵 （14)。
8、 一种解决窑法磷酸工艺窑尾结圈的方法， 其特征在于： 采用权利要求 1 所述的回 转窑进行窑法磷酸工艺， 使窑法磷酸工艺的工艺原料从所述回转窑窑尾箱的进料管处进入 回转窑的腔体内， 点燃燃料烧嘴， 使回转窑内还原带温度加热到 1300°C〜1450°C， 回转窑 中的磷矿石原料在高温条件下经还原剂还原后生成出窑烟气， 通过所述出口烟道的设置使 回转窑窑尾的出窑烟气在进入出口烟道时不在运动方向上发生较大偏移， 进而阻止出窑烟 气中的偏磷酸在回转窑窑尾处产生离心物理沉降， 使窑气中偏磷酸直接随出窑烟气进入到 后续的水化塔中， 遇水转变成正磷酸。
9、 根据权利要求 8 所述的方法， 其特征在于： 将所述回转窑位于预热带的窑衬制作 成双层式的复合耐火砖或复合耐火浇注料， 在靠近回转窑的筒体壳的窑衬部分采用黏土材 料制作成黏土材料层， 在靠近回转窑内腔的窑衬部分则采用碳化硅材料制作成碳化硅材料 层， 以使反应沉积在回转窑预热带窑衬上的偏磷酸盐与回转窑窑衬附着力降低， 自行掉落， 缓解窑尾结圈的发生。
10、 根据权利要求 8或 9所述的方法， 其特征在于： 在所述窑尾箱外配套设有一清窑 机， 清窑机中设有一可渐进式伸入回转窑窑尾箱内并可与其腔体内壁保持相对刮蹭的刮 刀； 当回转窑窑尾结圈造成工艺原料的料球从窑尾处往回转窑外返料时， 先停止加热回转 窑的燃料供给， 同时停止向回转窑内送入料球， 并排空回转窑内料球， 然后将清窑机中的 刮刀逐渐伸入至回转窑内， 再利用回转窑自身的旋转， 将窑尾结圈切削刮除。
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