WO2014194565A1 - 用于窑法磷酸工艺的复合球团原料及其成型方法 - Google Patents

用于窑法磷酸工艺的复合球团原料及其成型方法 Download PDF

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Publication number
WO2014194565A1
WO2014194565A1 PCT/CN2013/081150 CN2013081150W WO2014194565A1 WO 2014194565 A1 WO2014194565 A1 WO 2014194565A1 CN 2013081150 W CN2013081150 W CN 2013081150W WO 2014194565 A1 WO2014194565 A1 WO 2014194565A1
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Prior art keywords
binder
composite
ball
powder
temperature
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PCT/CN2013/081150
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English (en)
French (fr)
Inventor
侯拥和
王佳宾
王朋生
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四川玖长科技有限公司
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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 RU2015144553A priority Critical patent/RU2650162C2/ru
Publication of WO2014194565A1 publication Critical patent/WO2014194565A1/zh
Priority to US14/958,903 priority patent/US10435300B2/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
    • C01B25/01—Treating phosphate ores or other raw phosphate materials to obtain phosphorus or phosphorus compounds
    • 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
    • C01B25/185—Preparation neither from elemental phosphorus or phosphoric anhydride nor by reacting phosphate-containing material with an acid, e.g. by reacting phosphate-containing material with an ion-exchange resin or an acid salt used alone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
    • B01J2/003—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic followed by coating of the granules
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/002—Pretreatement
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/12—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by mechanical means
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2203/00—Other substrates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2350/00—Pretreatment of the substrate
    • B05D2350/10—Phosphatation

Definitions

  • the invention relates to a raw material in a kiln process phosphoric acid process (KPA) and a preparation method thereof, in particular to a composite pellet raw material in a kiln process phosphoric acid process and a molding method thereof.
  • KPA kiln process phosphoric acid process
  • wet process phosphoric acid that is, the phosphate rock is decomposed by sulfuric acid to obtain dilute phosphoric acid and solid waste residue (referred to as phosphogypsum) mainly composed of CaS0 4 * n3 ⁇ 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 product yellow phosphorus is obtained, and the exhaust gas containing CO is ignited and burned at the outlet of the chimney, and is discharged into the atmosphere; the obtained heating is heated to about 80 ° C, and it is changed into a liquid phase, which is generated in the hydration tower and the introduced air.
  • the oxidative combustion reaction is carried out to obtain phosphoric anhydride P 2 0 5 , which is then absorbed by water to obtain phosphoric acid.
  • thermal process phosphoric acid consumes a lot of electric energy; Second, the gas separated from P 4 after being discharged from the submerged arc furnace is also entrained with a large amount of fluoride (presented by SiF ⁇ P HF) and a small amount of unprecipitated gas P. 4 , this will cause serious pollution to the atmospheric environment; Third, the gas containing a large amount of CO is directly burned and emptied, and energy is wasted; Fourth, in order to ensure the economical efficiency of production, high-grade phosphate ore is also required.
  • 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 volatilized from the pellet in the form of phosphorus vapor, and then The central space of the kiln is oxidized into phosphorus pentoxide by the ventilating air, and the heat released by the oxidation is in turn supplied to the reduction reaction, and finally the kiln gas containing phosphorus pentoxide is hydrated and absorbed to obtain phosphoric acid.
  • 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 the solid phase to the 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 join Most of the material of the rotary kiln overflows from the rotary kiln at the feed end of the rotary kiln, and 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-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 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, the consolidation temperature is 80 ° C ⁇ 600 ° C, and the consolidation time is 3 min ⁇ 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 carbothermal reduction of 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 performed completely realized process P 2 0 5 in phosphate Reduction rate.
  • an upper kiln gas stream in the oxidation zone layers P 2 0 5 can not react with the carbon composite pellet surface layer and wrapping, thus preventing the formation of a phosphate or metaphosphate on the composite pellets
  • the salt compound eliminates the formation of P 2 0 5 white shell on the original KPA process sphere, ensuring that the process can obtain a higher P 2 O 5 yield.
  • the method is replaced by solid fuel or Partially replaced Gas or liquid fuel, which further reduces the production cost of phosphoric acid.
  • the bursting composite pellet enters the rotary kiln at the high temperature reduction zone of the rotary kiln to reduce the process.
  • the technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, and provide a composite pellet which is used as a raw material for the kiln process phosphoric acid process with a smaller fluctuation range, a more stable quality, and a higher strength, and provides a corresponding step.
  • the preparation method of the aforementioned composite pellets which is reasonable, has higher utilization rate of raw materials, is more energy-saving and environmentally friendly, and has better product performance.
  • the technical proposal provided by the present invention is a composite pellet used as a raw material of a kiln phosphoric acid process, and the composite pellet is a core-shell structure in which an outer shell covers an inner sphere, and the inner sphere is mainly composed of The inner ball material and the binder are composed, the outer casing is mainly composed of a wrapping material and a binder; the inner ball material is mainly composed of a carbonaceous reducing agent powder, a phosphate rock powder and a silica powder, and the binder in the inner ball
  • the amount of addition is 1% ⁇ 12% of the mass of the inner pellet;
  • the wrapping material is mainly composed of carbonaceous reducing agent powder and silica powder, and the amount of binder added in the outer shell is 1% ⁇ 12% of the mass of the wrapping material;
  • the inner ball and the outer shell are composited into a core-shell structure by the binder.
  • the carbonaceous reducing agent powder in the present invention is preferably any one or more of anthracite,
  • the binder may be various binder products used in the existing KPA process, but as a preferred embodiment, the binder in the present invention is a mixed solution containing sodium humate.
  • the mass concentration of sodium humate in the binder 4% ⁇ 20%, the binder is prepared by mixing, reacting and filtering the coal containing humic acid (preferably weathered coal, peat or lignite) and sodium hydroxide solution.
  • the phosphate rock powder refers to a product obtained by intermittent or continuous homogenization of compressed ore powder stored in a homogenization pool after grinding, and the homogenization value is 4 the above. More preferably, the molar ratio of Ca0/SiO 2 in the inner pellet is less than 0.6 or greater than 6.5, and the amount of the carbonaceous reducing agent powder is 1 in the theoretical amount of P 2 0 5 in the reduced phosphate rock powder. 0 ⁇ 2. 0 times. 5 ⁇ 9: 1 ⁇ The mass ratio of the mass ratio of 1. 5 ⁇ 9: 1.
  • the present invention also provides a method for molding the above composite pellet, comprising the following steps:
  • (1) Preparation of inner ball Add carbonaceous reducing agent powder, phosphate rock powder and silica powder to an intensive mixer or grinder according to the ratio, and add binder according to the added amount.
  • the mixed mixture enters the mixing bin and is sent to the pelletizing machine through the metering feeding device for pelletizing, and the binder is added in the form of drops and/or mist when the ball is formed, and the amount of the binder is added. 1% ⁇ 10% of the mass of the mixture, and the inner ball is obtained after the ball is completed;
  • step (3) Forming of composite green ball:
  • the inner ball obtained in step (1) is subjected to double-layer roll sieving treatment, and the inner ball that meets the process requirement granularity is sieved and sent to another pelletizing machine for wrapping treatment.
  • the package obtained in the step (2) is fed into the pelletizer (corresponding to the setting of the electronic ball feeding device according to the setting of the inner ball), and is in the form of drops and/or mist during the wrapping process.
  • the binder in an applied form the amount of addition is 1% to 12% of the mass of the package, and the composite green ball is obtained after the wrapping treatment is completed;
  • the method for preparing the binder comprises the following steps:
  • the coal material and the sodium hydroxide solution in the above step (1) are ball-milled at a solid-liquid ratio of 1:3 to 10, and the ball milling time is generally preferably 5 min to 120 min;
  • the coal material preferably refers to weathered coal, peat and/or lignite having a humic acid content of 20% or more.
  • the mass concentration of the prepared sodium hydroxide solution It is preferably controlled at 1% to 10%.
  • the intensive mixer in the preparation of the inner ball and the preparation step of the wrapping material comprises a tilting rotating mixing drum, and the mixing barrel is provided with a rotatable agitator, and the mixing barrel is mixed
  • the direction of rotation is opposite to the direction of rotation of the agitator, so that the mixture in the mixing tank forms a turbulent flow therein to achieve a sufficient agitation effect.
  • the ball forming machine in the preparation of the inner ball and the forming step of the composite green ball is a disc type pelletizer; the sieved in the step (3) does not meet the process requirement
  • the inner ball of the particle size is sent to the wheel mill or the grinding machine for crushing. During the crushing process, the inner ball can be selectively added according to the material humidity requirement, and then returned to the powerful mixer of the step (1). Or form a closed loop in the mill.
  • the dryer used in the drying and consolidation step is a slat dryer, and the slat dryer is divided into three drying sections of low temperature, medium temperature and high temperature along the conveying direction of the composite green ball. ;
  • the low-temperature drying section is passed through a low-temperature hot air of 100 ° C to 200 ° C to extract air from top to bottom or from bottom to top, so that low-temperature hot air passes vertically through the layer, and the composite green ball is subjected to through-flow drying;
  • the low temperature hot air is exhaust gas discharged from a high temperature hot air outlet of the high temperature drying section;
  • the medium-temperature drying section is passed through a medium-temperature hot air of 150 ° C to 250 ° C to extract air from top to bottom or blast from bottom to top, so that the medium-temperature hot air passes vertically through the layer, and the composite green ball is subjected to Dry through;
  • the high-temperature drying section is passed through a high-temperature hot air of 200 ° C to 350 ° C to extract air from top to bottom or blast from bottom to top, so that high-temperature hot air passes vertically through the layer, and the composite green ball is subjected to through-flow drying.
  • the binder prepared in the invention has not only simple composition, wide source of raw materials, low cost, but also good bonding effect of the binder, which can better ensure The shape and mechanical strength of the composite pellet further overcome the problem of powder ring formation in the rotary kiln of the subsequent process;
  • the preparation process of the composite pellets in the present invention is more reasonable and optimized, the mixing is more uniform, and the consistency of the composite pellets is more easily ensured, preventing the composite spheres.
  • the ingredients in the group fluctuate (the fluctuation range of the compounding ratio in the composite pellet can be accurately controlled within 5%);
  • the preparation method of the composite pellets of the invention makes full use of the process raw materials, and the intermediate wastes in the process are all effectively utilized comprehensively, further improving the KPA. Process economy and environmental protection;
  • the drying consolidation step is also significantly improved and improved in the preferred embodiment of the invention.
  • the dryer is divided into three drying sections to make the composite green sphere.
  • the drying process is carried out in a low-to-high section; the first drying section utilizes the low-temperature hot gas waste heat discharged from the third drying section to dry the wet composite green ball in the initial stage of the dryer, which utilizes waste heat resources, another In view of the lower airflow temperature in the first drying section, it can effectively prevent
  • the bursting damage of the wet composite ball causes the pellet to be damaged, ensuring the quality of the composite pellets that are subsequently introduced into the kiln;
  • the second drying section is passed into the medium temperature hot air without water vapor to form a higher humidity difference, which makes the ball in the guarantee
  • the pellet does not burst and accelerates the drying of the pellet; finally, the moisture of the composite pellet entering the third drying section has dropped below 4%.
  • a high temperature hot air can be introduced to ensure that
  • the pellet moisture of the dryer can be controlled at 1.0%, the pellet compressive strength reaches 250KN/ball, and the drop strength reaches 20 times/1 meter, which can fully ensure operation in the reduction rotary kiln. It is not damaged, so as to ensure the normal progress of the subsequent pellet reduction process.
  • FIG. 1 is a flow chart of a binder preparation process in a specific embodiment of the present invention.
  • FIG. 2 is a process flow diagram of a composite pellet forming process in accordance with an embodiment of the present invention.
  • FIG 3 is a schematic structural view of an intensive mixer used in a specific embodiment of the present invention.
  • Figure 4 is a cross-sectional view and the working principle diagram of A-A in Figure 3.
  • Fig. 5 is a structural schematic view of a slat dryer used in a specific embodiment of the present invention.
  • Figure 6 is a cross-sectional view and the working principle diagram of B-B in Figure 5.
  • the present embodiment provides a composite pellet of the present invention for use as a raw material for a kiln process phosphoric acid process.
  • the composite pellet is a core-shell structure in which an outer shell is coated with an inner sphere, and the inner sphere is mainly composed of an inner bulb and a binder.
  • the outer casing is mainly composed of a wrapping material and a binder;
  • the inner ball is composed of carbonaceous reducing agent powder, phosphate rock powder and silica powder, and the amount of the binder in the inner ball is 6% of the mass of the inner ball (may be 1) % ⁇ 10%);
  • the package is composed of carbonaceous reducing agent powder and silica powder.
  • the amount of binder added in the outer shell is 6% of the mass of the package (may be 1% ⁇ 10%); the inner ball and the outer shell are glued
  • the binder in the composite pellet of the present embodiment is a mixed solution containing sodium humate, and the mass concentration of the sodium humate in the binder is 8%, and the binder is composed of weathered coal (or peat) containing humic acid. , lignite) and sodium hydroxide solution are mixed, reacted and filtered to prepare.
  • the phosphate rock powder in the composite pellet of the present embodiment refers to the phosphate rock powder stored in the homogenization pool after grinding and compressed air.
  • the carbon or the mass ratio of the Ca0/Si0 2 is 0.3 (less than 0.6 or greater than 6.5), carbonaceous dosing the reducing agent powder is less than 1.5-fold in phosphate powder P 2 0 5 of theory; wrapped mass ratio of the carbonaceous reducing agent feed powder and silica powder is 2.5: 1 (1 5 ⁇ 5 : The range of 1 can be).
  • the preparation method of the binder used in this embodiment is as shown in FIG. 1, and specifically includes the following steps:
  • a method for molding the composite pellet according to the embodiment shown in FIG. 2 specifically includes the following steps.
  • the carbonaceous reducing agent powder (the coal powder of -200 mesh or more, such as coke breeze, anthracite powder or petroleum coke), the phosphate rock powder (-150 mesh or more) and the silica powder (-150 mesh or more) are as described above.
  • the ratio in the composite pellets is required to be added to an intensive mixer, and the ingredients can be weighed by an electronic scale while the binder of the present embodiment is added in the above-mentioned addition amount.
  • the intensive mixer used in this embodiment comprises a tilting rotatable mixing drum comprising a casing 4 and a rotatable agitator 3 installed in the barrel.
  • the hopper 2 and the driving device 1 are further provided with a turning plough 5 on one side of the barrel, and a discharge opening 6 at the bottom of the barrel; the working principle of the powerful mixer is: the rotation direction of the mixing barrel and the rotation direction of the agitator when mixing Conversely (see Fig.
  • the fully mixed mixture is fed into the silo, and a metering feeding device metered by the electronic scale is installed in the lower part of the silo, and the metering feeding device can be a feeding device of a disc feeder plus an electronic scale combination.
  • the electronic scale is compared with the set feed amount, and the deviation is controlled by the computer control system to automatically adjust the disc rotation speed of the disc feeder so that the feed amount is equal to the set value (you can also directly use the other with the electronic scale Metering equipment).
  • the thoroughly mixed mixture is sent to a disc pelletizer through a metering feeding device for pelletizing, and the binder of the present embodiment is added in the form of droplets and/or mist application during the pelleting.
  • the addition amount is 4% to 6% of the mass of the mixture, and the inner ball is obtained after the ball is completed.
  • the carbonaceous reducing agent powder and the silica powder are added to another intensive mixer according to the ratio of the above requirements, and the binder of the embodiment is added according to the above-mentioned composite pellet addition amount, and fully mixed to obtain a wrapping material;
  • the working principle and functional structure of the intensive mixer are the same as those of the intensive mixer used in the above step 1.
  • the intensive mixer can also be replaced by a continuous feed, continuous discharge wheel mill or a grinder.
  • the inner ball obtained after the ball exiting in step 1 is subjected to double-layer roll sieving treatment (using a double-layer roll sieving machine), and the inner ball which meets the process requirement granularity is sieved and sent to another wrapping process.
  • the parcel obtained in step 2 is simultaneously introduced into the disc pelletizer, and the binder is added in the form of drops and/or mist during the wrapping process, and the amount of the binder is added.
  • an isolation layer is formed as a reduction belt and an oxidation zone outside the inner sphere to obtain a composite green ball.
  • the unqualified inner balls that are sieved out and smaller than the set particle size are sent to the wheel mill (or grinding machine) for crushing, and the materials are crushed according to the wheel mill during the crushing process.
  • the humidity requirement can be selectively added to the inner pellets in the previous batching process, and then returned to the intensive mixer of step 1 above to form a closed loop to take full advantage of the process materials and reduce the waste and waste of intermediate waste in the process.
  • the composite green ball prepared in this embodiment has a compressive strength of about 10 N/ball, and the falling strength is about 10 times/0.5 m, and the fluctuation range of the Ca0/Si0 2 molar ratio in the composite green ball of the present embodiment can Control is within 5%.
  • the composite green ball obtained after the step 3 is sent to a scale dryer for drying and consolidation.
  • the slat dryer in this embodiment includes a drying furnace body 8.
  • the drying furnace body 8 is composed of a low temperature drying section 10, a medium temperature drying section 11 and a high temperature drying section 12, and the drying furnace body 8 is
  • the top is provided with an air inlet 13 for hot air
  • the bottom is provided with an air outlet 15, and the outer periphery is covered with a heat insulating layer 14.
  • the chamber of the drying furnace body 8 is provided with a loading trolley 7, and a plurality of loading trolleys 7 are connected front and rear to form a ring shape.
  • the charging trolley 7 is provided with a venting hole 16 which is driven by a chain, and the charging trolley 7 is rotated by the chained chain to achieve continuous conveying and drying.
  • a dust remover 9 is provided at the bottom of the drying furnace body 8 to recover the soot generated during the drying process.
  • dry hot air is passed from top to bottom in the vertical direction of the material movement to achieve the purpose of drying.
  • the specific working principle of the slat drying machine in this embodiment is as follows:
  • the moving conveying direction of the composite green ball loading trolley 7 is divided into three drying sections of low temperature, medium temperature and high temperature.
  • the composite green ball first enters the low temperature drying section 10, and the low temperature drying section 10 is introduced into the low temperature hot air of 130 ° C to 200 ° C to extract air from top to bottom (or blast from bottom to top), so that the low temperature hot air passes vertically through the composite
  • the ball layer, and the composite green ball is subjected to through-flow drying;
  • the low-temperature hot air is exhausted from the high-temperature hot air outlet of the high-temperature drying section 12, and is led to the low-temperature drying section 10 by the fan;
  • the low-temperature drying section 10 is utilized High temperature drying section 12 discharge
  • the low-temperature hot gas residual heat on the other hand, due to the low temperature of the low-temperature drying section 10, can effectively prevent the burst damage of the wet composite green ball and cause the pellet damage, and
  • the composite green ball is then dried in the medium temperature drying section 11 and the medium temperature drying section 11 is passed into the medium temperature hot air of 200 ° C to 250 ° C and is ventilated from top to bottom (or from bottom to top). Blowing), the medium-temperature hot air is vertically passed through the layer, and the composite green ball is subjected to through-flow drying; the medium-temperature drying section is fed with medium-temperature hot air without water vapor, which forms a high humidity difference, which makes Accelerate the drying of the pellets while ensuring that the pellets do not burst.
  • the composite green ball dried by the medium temperature drying section 11 is then dried in the high temperature drying section, and finally the composite pellets entering the high temperature drying section 12 have been reduced to below 4%, and the high temperature drying section 12 is introduced into the temperature range of 250 °C to 350 °C.
  • High-temperature hot air is blown from top to bottom (or blast from bottom to top), allowing high-temperature hot air to pass vertically through the layer and final drying of the composite ball.
  • the high-temperature hot air of the high-temperature drying section 12 is preferably from the waste heat utilization of the subsequent cooling stage of the rotary kiln discharge, and the hot air furnace can also be separately provided for air supply.
  • the exhaust gas discharged from the low-temperature drying section 10 and the medium-temperature drying section 11 can be collected by a fan, and discharged to the atmosphere through the flue after the dust removal device 9 reaches the environmental protection requirement.
  • the moisture content of the composite pellet obtained after drying and consolidation is 1.0%, the average compressive strength of the pellet reaches 2501 ⁇ /ball, and the falling strength reaches 20 times/1 meter, which can effectively ensure the subsequent reduction of the composite pellet.
  • the rotary kiln is not destroyed during operation, thus ensuring the smooth progress of the composite pellet reduction process.
  • the composite pellets after the dryer are screened through a vibrating screen (or not) to remove the composite pellets (less than 5 mm) damaged during the drying process, so as to reduce the amount of powder that subsequently enters the rotary kiln. , thereby further delaying the ring cycle of the material in the high temperature section of the rotary kiln.
  • the composite pellets after the vibrating screen are sent from the rotary kiln tail box to the rotary kiln through the lock damper through the lock damper for subsequent high temperature reduction treatment.

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Abstract

本发明公开了一种用作窑法磷酸工艺原料的复合球团，其为外壳包覆内球的核壳形结构，内球由内球料和粘结剂组成，外壳由包裹料和粘结剂组成；内球料主要由碳质还原剂粉、磷矿石粉和硅石粉组成，包裹料主要由碳质还原剂粉和硅石粉组成，内球与外壳通过粘结剂复合成核壳形结构。该复合球团的制备包括内球的制备、包裹料的准备、复合生球的成型以及干燥固结等步骤，具体是将得到的内球进行双层辊式筛分处理，然后送入造球机中，通入包裹料，在包裹处理过程中补加粘结剂，包裹处理完成后得到复合生球；再将复合生球送入干燥机进行干燥固结，最终成型得到复合球团。本发明制得的复合球团配比波动范围更小、质量更稳定、强度更高且性能更好。

Description

用于窑法磷酸工艺的复合球团原料及其成型方法
【技术领域】
本发明涉及一种窑法磷酸工艺 （KPA) 中的原料及其制备方法， 尤其涉及一种窑法磷酸 工艺中的复合球团原料及其成型方法。
【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* n¾0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 P4 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 P4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少回转窑内料层的 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 P2O5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， 这其中就有部分技术 问题体现在原料的预处理阶段。 首先， 加有粘结剂的内球料的混合很难均匀， 致使各料球的 Ca0/Si02摩尔比很难稳定在设定值， 偏离设定值的料球在回转窑高温还原区容易出现软熔结 圈致使工艺失败； 其次， 原料预处理阶段选用的粘结剂多为现有粘结剂的简单混合， 其粘结 效果仍不够理想， 粘结剂的粘结性能还不够稳定， 这使得制备得到复合球团的力学性能和机 械强度也不够稳定； 再则， 复合球团干燥没有可选的工业设备和合适的干燥方法， 球团干燥 过程容易出现爆裂， 致使复合球团丧失强度， 爆裂的复合球团进入回转窑在回转窑高温还原 带粉化结圈， 使工艺失败。
因此， 为了使现有的窑法磷酸工艺的生产成本和能耗进一步降低以便于进行工业化、 商 业化的推广应用， 为了能更稳定地进行长周期生产， 在原料复合球团的制备阶段还亟待本领 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技术的不足， 提供一种配比波动范围更小、 质量更 稳定、 强度更高的用作窑法磷酸工艺原料的复合球团， 并相应提供步骤更为合理、 原料利用 率更高、 更加节能环保、 产品性能更好的前述复合球团的制备方法。
为解决上述技术问题，本发明提出的技术方案为一种用作窑法磷酸工艺原料的复合球团， 所述复合球团为外壳包覆内球的核壳形结构， 所述内球主要由内球料和粘结剂组成， 所述外 壳主要由包裹料和粘结剂组成； 所述内球料主要由碳质还原剂粉、 磷矿石粉和硅石粉组成， 内球中粘结剂的添加量为内球料质量的 1%〜12%； 所述包裹料主要由碳质还原剂粉和硅石粉 组成， 外壳中粘结剂的添加量为包裹料质量的 1%〜12%； 所述内球与外壳通过所述粘结剂复 合成核壳形结构。 本发明中的碳质还原剂粉优选为无烟煤、 烟煤、 焦炭、 石油焦中的任何一 种或多种。
上述的复合球团中， 粘结剂可以为现有 KPA工艺中采用的各种粘结剂产品， 但作为优选 的方案， 本发明中所述粘结剂为含腐植酸钠的混合溶液， 所述粘结剂中腐植酸钠的质量浓度 为 4%〜20%， 所述粘结剂是由含腐植酸的煤料 （优选风化煤、 泥煤或褐煤） 与氢氧化钠溶液 经混合、 反应、 过滤后制备得到。
上述的复合球团中， 优选的， 所述磷矿石粉是指磨矿后储存于均化库中的磷矿石粉料经 压缩空气间断或连续均化后得到的产物， 且均化值在 4 以上。 更优选的， 所述内球料中， Ca0/Si02的摩尔比小于 0. 6或大于 6. 5，碳质还原剂粉的配量为还原磷矿石粉中 P205理论量的 1. 0〜2. 0倍。 更优选的， 所述包裹料中碳质还原剂粉和硅石粉的质量比为 1. 5〜9： 1。
作为一个总的技术构思， 本发明还提供一种上述复合球团的成型方法， 包括以下步骤：
( 1 ) 内球的制备： 将碳质还原剂粉、磷矿石粉和硅石粉按所述配比要求加入一强力混合 机或润磨机中， 同时按所述添加量添加粘结剂， 充分混匀后的混合料进入混合料仓并通过计 量给料设备送入造球机进行造球处理， 造球时以滴状和 /或雾状施加形式补加所述粘结剂， 补 加量为所述混合料质量的 1%〜10%， 造球完成后得到内球；
( 2 )包裹料的准备： 将碳质还原剂粉和硅石粉按所述配比要求加入一强力混合机或润磨 机中， 同时按所述添加量添加粘结剂， 充分混匀后得到包裹料送入包裹料仓；
( 3 ) 复合生球的成型： 将步骤 （1 ) 中得到的内球进行双层辊式筛分处理， 筛分出符合 工艺要求粒度的内球送入另一进行包裹处理的造球机中， 同时向该造球机中 （由电子计量给 料装置按与内球料的设定对应比例）通入步骤（2 )得到的包裹料， 在包裹处理过程中以滴状 和 /或雾状施加形式补加所述粘结剂， 补加量为所述包裹料质量的 1%〜12%， 包裹处理完成后 得到复合生球；
( 4) 干燥固结： 将步骤 （3 ) 后得到的复合生球送入干燥机进行干燥固结， 最终成型得 到复合球团。
上述复合球团的成型方法中， 优选的， 所述粘结剂的制备方法包括以下步骤：
( 1 ) 原料准备： 选用含腐植酸的煤料 （粒度一般为 -20mm) 和烧碱作为原料， 将烧碱与 水混合、 按比例配制成 NaOH溶液；
( 2 )球磨混合： 将上述步骤（1 ) 中的煤料和氢氧化钠溶液按 1 : 3〜10的固液比进行球 磨混合， 球磨时间一般优选为 5min〜120min;
( 3 ) 合成反应： 将上述步骤 （2 ) 中的混合料送入带搅拌器的反应槽， 开启搅拌器并加 热到 40°C〜95°C进行合成反应， 反应时间不小于 30min (优选 30min〜180min);
( 4) 过滤： 将上述步骤 （3 ) 后的反应产物进行过滤， 过滤后得到的滤液即为粘结剂。 上述的成型方法， 所述粘结剂的制备步骤 （1 ) 中， 煤料优选是指腐植酸含量在 20%以上 的风化煤、 泥煤和 /或褐煤。
上述的成型方法， 所述粘结剂的制备步骤（1 ) 中， 配制得到的氢氧化钠溶液的质量浓度 优选控制在 1%〜10%。
上述的成型方法， 优选的， 所述内球的制备和包裹料的准备步骤中的强力混合机包括一 倾斜旋转的混合桶， 混合桶内安装有可旋转式搅拌器， 混合时所述混合桶的旋转方向与所述 搅拌器的旋转方向相反， 使混合桶内的混合料在其中形成紊流达到充分搅拌的效果。
上述的成型方法， 优选的， 所述内球的制备和复合生球的成型步骤中的造球机均为圆盘 式造球机； 所述步骤（3 )中筛分出的不符合工艺要求粒度的内球均送入轮碾机或润磨机中碾 碎， 碾碎过程中根据物料湿度要求可选择性补入所述内球料， 然后返回到所述步骤（1 ) 的强 力混合机或润磨机中形成闭路循环。
上述的成型方法， 优选的， 所述干燥固结步骤中用到的干燥机为鳞板干燥机， 该鳞板干 燥机沿复合生球的输送方向共分为低温、 中温和高温三个干燥段；
所述低温干燥段通入 100 °C〜200 °C的低温热风由上至下进行抽风或由下至上进行鼓风， 使低温热风垂直穿过料层， 并对复合生球进行穿流干燥； 所述低温热风是源自所述高温干燥 段的高温热风出口处排出的废气；
所述中温干燥段通入 150 °C〜250 °C的中温热风由上至下进行抽风或由下至上进行鼓风， 使中温热风垂直穿过料层， 并对复合生球进行穿流干燥；
所述高温干燥段通入 200 °C〜350 °C的高温热风由上至下进行抽风或由下至上进行鼓风， 使高温热风垂直穿过料层， 并对复合生球进行穿流干燥。
与现有技术相比， 本发明的优点在于：
( 1 )与现有 KPA工艺使用的粘结剂相比， 本发明中配制的粘结剂不仅成分简单、 原料来 源广泛、 成本低， 而且粘结剂的粘结效果好， 能够更好地保证复合球团的赋形及机械强度， 进一步克服后续工艺的回转窑中粉料结圈的问题；
( 2 )与现有 KPA工艺使用的复合球团相比，本发明中复合球团的制备工艺步骤更加合理、 优化，混料更加均匀， 复合球团的一致性更容易得到保证， 防止复合球团中配料出现波动（复 合球团中配料比的波动范围能够精确控制在 5%以内）；
( 3 )与现有 KPA工艺中复合球团的制备相比， 本发明复合球团的制备方法更充分地利用 了工艺原料， 工艺过程中的中间废料全部得到了有效综合利用， 进一步提高了 KPA工艺的经 济性和环保性；
( 4 )与现有 KPA工艺中复合球团的制备相比， 本发明优选方案中对干燥固结步骤也作了 重要改进和完善， 首先将干燥机划分成三个干燥段， 使复合生球的干燥过程由低到高分段进 行； 第一干燥段利用了第三干燥段排出的低温热气余热对干燥机初始段的湿复合生球进行低 温干燥， 这一方面利用了余热资源， 另一方面因第一干燥段的气流温度较低， 能够有效防止 湿复合生球的爆裂破坏造成球团损坏， 保证后续入窑的复合球团的质量； 第二干燥段通入不 带水汽的中温热风， 形成较高的湿度差， 这使得在保证球团不爆裂的情况下加速球团的干燥; 最后进入第三干燥段的复合球团水分已降到 4%以下， 此时可通入较高温度的高温热风， 在保 证球团不爆裂的情况下加速球团的干燥固结过程；
( 5 ) 本发明中出干燥机的球团水分可控制在 1. 0%， 球团抗压强度达到 250KN/个球， 落下强度达到 20次 /1米， 可以充分保证在还原回转窑内运转时不损坏， 从而保证后续球团 还原过程的正常进行。
【附图说明】
图 1为本发明具体实施方式中粘结剂制备工艺的流程图。
图 2为本发明具体实施方式中复合球团成型工艺的工艺流程图。
图 3为本发明具体实施方式中用到的强力混合机的结构示意图。
图 4为图 3中 A-A处的剖视图及工作原理示意图。
图 5为本发明具体实施方式中用到的鳞板干燥机的结构原理图。
图 6为图 5中 B-B处的剖视图及工作原理示意图。
图例说明：
1、 驱动装置； 2、 进料斗； 3、 搅拌器； 4、 壳体； 5、 翻料犁； 6、 卸料口； 7、 装料小车； 8、 干燥炉体； 9、 除尘器； 10、 低温干燥段； 11、 中温干燥段； 12、 高温干燥段； 13、 进风 口； 14、 保温层； 15、 出风口； 16、 通气孔。
【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：
本实施例提供一种本发明的用作窑法磷酸工艺原料的复合球团， 该复合球团为外壳包覆 内球的核壳形结构， 内球主要由内球料和粘结剂组成， 外壳主要由包裹料和粘结剂组成； 内 球料由碳质还原剂粉、磷矿石粉和硅石粉组成，内球中粘结剂的添加量为内球料质量的 6% (可 以是 1%〜10%)； 包裹料由碳质还原剂粉和硅石粉组成， 外壳中粘结剂的添加量为包裹料质量 的 6% (可以是 1%〜10%)； 内球与外壳通过粘结剂复合成核壳形结构。
本实施例复合球团中的粘结剂为含腐植酸钠的混合溶液， 粘结剂中腐植酸钠的质量浓度 为 8%， 该粘结剂是由含腐植酸的风化煤 （或泥煤、 褐煤） 与氢氧化钠溶液经混合、 反应、 过 滤后制备得到。
本实施例复合球团中的磷矿石粉是指磨矿后储存于均化库中的磷矿石粉料经压缩空气间 断或连续均化后得到的产物， 且均化值在 4以上； 内球料中， Ca0/Si02的摩尔比为 0. 3 (小于 0. 6或大于 6. 5均可）， 碳质还原剂粉的配量为磷矿石粉中 P205理论量的 1. 5倍以上； 包裹料 中碳质还原剂粉和硅石粉的质量比为 2. 5： 1 ( 1. 5〜5： 1的范围均可）。
本实施例中用到的粘结剂的制备方法如图 1所示的， 具体包括以下步骤：
( 1 )原料准备： 选用含腐植酸的风化煤（或泥煤、 褐煤）和烧碱作为原料， 本实施例的 风化煤中腐植酸含量在 40%以上； 将烧碱 （93%的氢氧化钠） 与水混合、 配制得到质量浓度为 2%的氢氧化钠溶液；
( 2 )球磨混合： 将上述步骤（1 ) 中的风化煤和氢氧化钠溶液按 5: 1的液固比进行球磨 混合， 球磨时间 20min;
( 3 ) 合成反应： 将上述步骤 （2 ) 中的混合料送入带搅拌器的反应槽， 开启搅拌器加热 到 90°C进行合成反应， 反应时间为 30min;
( 4) 过滤： 将上述步骤 （3 ) 后的反应产物进行过滤， 过滤后得到的滤液即为粘结剂。 一种如图 2所示的本实施例上述复合球团的成型方法， 具体包括以下步骤。
1. 内球的制备：
将碳质还原剂粉 （本实施例选用 -200 目以上的煤粉， 例如焦粉、 无烟煤粉或石油焦）、 磷矿石粉（-150目以上）和硅石粉（-150目以上）按上述复合球团中的配比要求加入一强力 混合机中， 配料时可用电子秤称量， 同时按上述添加量添加本实施例的粘结剂。
本实施例中用到的强力混合机如图 3所示， 包括一倾斜可旋转的混合桶， 混合桶包括壳 体 4和桶内安装的可旋转式搅拌器 3， 混合桶的上方设有进料斗 2和驱动装置 1， 桶内一侧还 设有翻料犁 5， 桶底设有卸料口 6; 强力混合机的工作原理为： 混合时混合桶的旋转方向与搅 拌器的旋转方向相反 （参见图 4); 在加入上述原料后， 在倾斜、 旋转的混合桶内与逆向旋转 运动的搅拌器相对旋转运动， 使其中分散的混合料行成循环物料流进而起到强力混合作用； 通过搅拌器与混合桶的逆向旋转， 还可使被混合的物料在其中形成紊流， 从而达到充分搅拌 混匀的效果； 该强力混合机是连续进料、 连续出料， 以保证生产过程的连续性。
充分混匀后的混合料送入料仓， 在料仓下部安装有通过电子秤计量的计量给料设备， 这 种计量给料设备可以是圆盘给料机加电子秤组合的给料设备， 通过电子秤计量与设定给料量 进行比较， 出现偏差由计算机控制系统自动调整圆盘给料机的圆盘转速， 使给料量与设定值 相等 （也可以直接使用带电子秤的其他计量给料设备）。
充分混匀后的混合料通过计量给料设备送入一圆盘造球机进行造球处理， 造球时以滴状 和 /或雾状施加形式补加上述本实施例的粘结剂， 补加量为混合料质量的 4%〜6%， 造球完成 后得到内球。 2. 包裹料的准备：
将上述的碳质还原剂粉和硅石粉按配比要求加入另一强力混合机中， 同时按上述复合球 团添加量添加本实施例的粘结剂， 充分混匀后得到包裹料； 本步骤中强力混合机的工作原理 和功能结构与上述步骤 1中用到的强力混合机相同。 该强力混合机亦可用连续进料、 连续出 料的轮碾机或润磨机替代。
3. 复合生球的成型：
将步骤 1中出球盘后得到的内球进行双层辊式筛分处理（采用一台双层辊式筛分机）， 筛 分出符合工艺要求粒度的内球送入另一进行包裹处理的圆盘造球机中， 同时向该圆盘造球机 中通入步骤 2得到的包裹料， 在包裹处理过程中以滴状和 /或雾状施加形式补加上述粘结剂， 补加量为包裹料质量的 4%〜6%， 包裹处理完成后在内球外部形成有作为还原带与氧化带的隔 离层， 得到复合生球。
双层辊式筛分处理后， 筛除的大于和小于设定粒径的不合格内球均送入轮碾机 （或润磨 机） 中碾碎， 碾碎过程中根据轮碾机对物料湿度的要求可选择性补入先前配料工序中的内球 料， 然后返回到上述步骤 1的强力混合机中形成闭路循环， 以充分利用工艺原料， 减少工艺 过程中间废料的排放和浪费。
本实施例制得的复合生球的抗压强度约为 10N/个球， 落下强度约为 10次 /0. 5米， 且本 实施例复合生球中 Ca0/Si02摩尔比的波动范围能控制在 5%之内。
4. 干燥固结：
将步骤 3后得到的复合生球送入一鳞板干燥机进行干燥固结。
如图 5和图 6所示， 本实施例中的鳞板干燥机包括干燥炉体 8， 干燥炉体 8由低温干燥 段 10、 中温干燥段 11和高温干燥段 12组成， 干燥炉体 8的顶部设有热风的进风口 13， 底部 设有出风口 15， 外围包覆有保温层 14， 干燥炉体 8的腔室中设有装料小车 7， 若干装料小车 7前后连接、 形成环形， 装料小车 7上开设有通气孔 16， 其采用链传动， 通过带座链条拖动 装料小车 7循环转动， 达到连续输送干燥的目的。 干燥炉体 8的底部设有除尘器 9以回收处 理干燥过程中产生的烟尘。 在复合生球物料的输送过程中， 在物料运动的垂直方向由上往下 通入干燥热风以达到干燥的目的。
本实施例中的鳞板干燥机的具体工作原理为： 沿复合生球装料小车 7的运动输送方向共 分为低温、 中温和高温三个干燥段。 复合生球先进入低温干燥段 10， 低温干燥段 10 通入 130°C〜200°C的低温热风由上至下进行抽风（或由下至上进行鼓风）， 使低温热风垂直穿过复 合生球料层， 并对复合生球进行穿流干燥； 低温热风是源自高温干燥段 12的高温热风出口处 排出的废气， 并经风机引至低温干燥段 10; 低温干燥段 10—方面利用了高温干燥段 12排出 的低温热气余热， 另一方面因低温干燥段 10的气流温度较低， 能够有效防止湿复合生球的爆 裂破坏造成球团损坏， 保证后续入窑的复合球团的质量。经过低温干燥段 10干燥后的复合生 球再进入中温干燥段 11干燥， 中温干燥段 11通入 200 °C〜250 °C的中温热风并由上至下进行 抽风（或由下至上进行鼓风）， 使中温热风垂直穿过料层， 并对复合生球进行穿流干燥； 中温 干燥段通入的是不带水汽的中温热风， 形成较高的湿度差， 这使得在保证球团不爆裂的情况 下加速球团的干燥。经过中温干燥段 11干燥后的复合生球再进入高温干燥段干燥， 最后进入 高温干燥段 12的复合球团水分已降到 4%以下，高温干燥段 12通入 250 °C〜350 °C的高温热风 并由上至下进行抽风（或由下至上进行鼓风）， 使高温热风垂直穿过料层， 并对复合生球进行 最后的干燥。 高温干燥段 12的高温热风优选来自后续回转窑出料冷却阶段的废气余热利用， 也可另行设置热风炉送风。 低温干燥段 10和中温干燥段 11排出的废气可用风机进行收集， 经除尘器 9除尘达到环保要求后通过烟道排入大气。
经干燥固结后得到的复合球团水分控制在 1. 0%,球团平均抗压强度达到 2501^/个球， 落下强度达到 20次 /1米， 可以有效保证复合球团在后续的还原回转窑内运转时不被破坏， 从而保证复合球团还原过程的顺利进行。
本实施例中出干燥机后的复合球团通过一台振动筛 （也可不设） 筛除在干燥过程中损坏 的复合球团（小于 5mm的部分）， 以减少后续进入回转窑的粉料量， 从而进一步延缓物料在回 转窑高温段的结圈周期。 出振动筛后的复合球团通过锁风阀由下料管从回转窑窑尾箱送入回 转窑进行后续的高温还原处理。

Claims

权 利 要 求
1、 一种用作窑法磷酸工艺原料的复合球团， 所述复合球团为外壳包覆内球的核壳形 结构， 其特征在于： 所述内球主要由内球料和粘结剂组成， 所述外壳主要由包裹料和粘结 剂组成； 所述内球料主要由碳质还原剂粉、 磷矿石粉和硅石粉组成， 内球中粘结剂的添加 量为内球料质量的 1%〜12%；所述包裹料主要由碳质还原剂粉和硅石粉组成，外壳中粘结 剂的添加量为包裹料质量的 1%〜12%； 所述内球与外壳通过粘结剂复合成核壳形结构。
2、 根据权利要求 1 所述的复合球团， 其特征在于： 所述粘结剂为含腐植酸钠的混合 溶液，所述粘结剂中腐植酸钠的质量浓度为 4%〜20%，所述粘结剂是由含腐植酸的煤料与 氢氧化钠溶液经混合、 反应、 过滤后制备得到。
3、 根据权利要求 1或 2所述的复合球团， 其特征在于： 所述磷矿石粉是指磨矿后储 存于均化库中的磷矿石粉料经压缩空气间断或连续均化后得到的产物，且均化值在 4以上; 所述内球料中， CaO/Si02的摩尔比小于 0.6或大于 6.5，碳质还原剂粉的配量为还原磷矿石 粉中 P205理论量的 1.0〜2.0倍；所述包裹料中碳质还原剂粉和硅石粉的质量比为 1.5〜9： 1。
4、 一种如权利要求 1〜3中任一项所述复合球团的成型方法， 包括以下步骤：
( 1 ) 内球的制备： 将碳质还原剂粉、 磷矿石粉和硅石粉按所述配比要求加入一强力 混合机或润磨机中， 同时按所述添加量添加粘结剂， 充分混匀后的混合料通过计量给料设 备送入造球机进行造球处理， 造球时以滴状和 /或雾状施加形式补加所述粘结剂， 补加量为 所述混合料质量的 1%〜10%， 造球完成后得到内球；
(2) 包裹料的准备： 将碳质还原剂粉和硅石粉按所述配比要求加入一强力混合机或 润磨机中， 同时按所述添加量添加粘结剂， 充分混匀后得到包裹料；
(3 ) 复合生球的成型： 将步骤 （1 ) 中得到的内球进行双层辊式筛分处理， 筛分出符 合工艺要求粒度的内球送入另一进行包裹处理的造球机中， 同时向该造球机中通入步骤 (2) 得到的包裹料， 在包裹处理过程中以滴状和 /或雾状施加形式补加所述粘结剂， 补加 量为所述包裹料质量的 1%〜12%， 包裹处理完成后得到复合生球；
(4) 干燥固结： 将步骤 （3 ) 后得到的复合生球送入干燥机进行干燥固结， 最终成型 得到复合球团。
5、 根据权利要求 4所述的成型方法， 其特征在于， 所述粘结剂的制备包括以下步骤: ( 1 ) 原料准备： 选用含腐植酸的煤料和烧碱作为原料， 将烧碱与水混合、 按比例配 制成 NaOH溶液；
(2) 球磨混合： 将上述步骤 （1 ) 中的煤料和氢氧化钠溶液按 1 : 3〜10 的固液比进 行球磨混合；
(3 ) 合成反应： 将上述步骤 （2) 中的混合料搅拌加热到 40°C〜95°C进行合成反应， 反应时间不小于 30min;
(4)过滤： 将上述步骤（3 )后的反应产物进行过滤， 过滤后得到的滤液即为粘结剂。
6、 根据权利要求 5所述的成型方法， 其特征在于： 所述粘结剂的制备步骤 （1 ) 中， 所述煤料是指腐植酸含量在 20%以上的风化煤、 泥煤和 /或褐煤。
7、 根据权利要求 5所述的成型方法， 其特征在于： 所述粘结剂的制备步骤 （1 ) 中， 配制得到的氢氧化钠溶液的质量浓度控制在 1%〜10%。
8、 根据权利要求 4〜7中任一项所述的成型方法， 其特征在于： 所述内球的制备和包 裹料的准备步骤中的强力混合机包括一倾斜旋转的混合桶， 混合桶内安装有可旋转式搅拌 器， 混合时所述混合桶的旋转方向与所述搅拌器的旋转方向相反， 使混合桶内的混合料在 其中形成紊流达到充分搅拌的效果。
9、 根据权利要求 4〜7中任一项所述的成型方法， 其特征在于： 所述内球的制备和复 合生球的成型步骤中的造球机均为圆盘式造球机； 所述步骤 （3 ) 中筛分出的不符合工艺 要求粒度的内球均送入轮碾机或润磨机中碾碎， 碾碎过程中根据物料湿度要求可选择性补 入所述内球料， 然后返回到所述步骤 （1 ) 的强力混合机或润磨机中形成闭路循环。
10、 根据权利要求 4〜7 中任一项所述的成型方法， 其特征在于： 所述干燥固结步骤 中用到的干燥机为鳞板干燥机， 该鳞板干燥机沿复合生球的输送方向共分为低温、 中温和 高温三个干燥段；
所述低温干燥段通入 100°C〜200°C的低温热风由上至下进行抽风或由下至上进行鼓 风， 使低温热风垂直穿过料层， 并对复合生球进行穿流干燥； 所述低温热风是源自所述高 温干燥段的高温热风出口处排出的废气；
所述中温干燥段通入 150°C〜250°C的中温热风由上至下进行抽风或由下至上进行鼓 风， 使中温热风垂直穿过料层， 并对复合生球进行穿流干燥；
所述高温干燥段通入 200°C〜350°C的高温热风由上至下进行抽风或由下至上进行鼓 风， 使高温热风垂直穿过料层， 并对复合生球进行穿流干燥。
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