CN111733330A - Method for enriching and recovering zinc by using rotary kiln - Google Patents
Method for enriching and recovering zinc by using rotary kiln Download PDFInfo
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- CN111733330A CN111733330A CN202010423233.8A CN202010423233A CN111733330A CN 111733330 A CN111733330 A CN 111733330A CN 202010423233 A CN202010423233 A CN 202010423233A CN 111733330 A CN111733330 A CN 111733330A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
- C22B7/02—Working-up flue dust
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/14—Agglomerating; Briquetting; Binding; Granulating
- C22B1/16—Sintering; Agglomerating
- C22B1/216—Sintering; Agglomerating in rotary furnaces
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/14—Agglomerating; Briquetting; Binding; Granulating
- C22B1/24—Binding; Briquetting ; Granulating
- C22B1/2406—Binding; Briquetting ; Granulating pelletizing
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/14—Agglomerating; Briquetting; Binding; Granulating
- C22B1/24—Binding; Briquetting ; Granulating
- C22B1/242—Binding; Briquetting ; Granulating with binders
- C22B1/243—Binding; Briquetting ; Granulating with binders inorganic
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B19/00—Obtaining zinc or zinc oxide
- C22B19/20—Obtaining zinc otherwise than by distilling
- C22B19/22—Obtaining zinc otherwise than by distilling with leaching with acids
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
- C22B5/02—Dry methods smelting of sulfides or formation of mattes
- C22B5/10—Dry methods smelting of sulfides or formation of mattes by solid carbonaceous reducing agents
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
- C22B7/006—Wet processes
- C22B7/007—Wet processes by acid leaching
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention provides a method for enriching and recovering zinc by using a rotary kiln. Feeding the preheated kiln-entering raw material into the tail of a reducing rotary kiln, blowing coal powder and oxygen-enriched air into the tail of the kiln, and carrying out calcination reaction for 80-100 min; under the action of a kiln head exhaust fan, the flowing direction of flue gas generated by calcination reaction is consistent with the moving direction of the kiln entering raw materials, and the flue gas and the kiln entering raw materials move from the kiln tail to the kiln head; collecting roasted ore, grinding the ore and performing magnetic separation to obtain iron ore concentrate; collecting and purifying the smoke extracted by the exhaust fan, collecting zinc-containing dust by using a dust collecting system, mixing the zinc-containing dust with the kiln raw materials for granulation to obtain a mixed kiln material, feeding the mixed kiln material into a reducing rotary kiln, and circularly performing a calcining process and a zinc-containing dust collecting process to realize the circular enrichment of zinc; when the zinc content in the flue gas reaches more than 10 percent, directly collecting zinc-containing dust in the flue gas, and recovering zinc by using an acid leaching process. The method can effectively improve the recovery rate of iron and zinc, prevent the ring formation of the rotary kiln, and has high efficiency and energy conservation.
Description
Technical Field
The invention relates to the technical field of metallurgy and mineral processing, in particular to a method for enriching and recovering zinc by using a rotary kiln.
Background
Iron ore is an important raw material in the development process of the steel industry and plays an important role in the national economic development of China. With the rapid development of the steel industry in China, the demand for iron ore is continuously increased, in order to improve the grade and comprehensive recovery and utilization rate of the iron ore, the iron ore is generally required to be subjected to necessary calcination processing, and at present, the rotary kiln-magnetic separation process based on direct reduction of reduced coal is widely utilized. The process combines roasting, ore dressing and smelting in one process, omits the processes of ore dressing, sintering, pelletizing and other high energy consumption and high pollution processes, shortens the production period, reduces the energy consumption and reduces the environmental pollution.
Meanwhile, zinc in the steel production system is mainly derived from scrap steel and iron ore raw materials initially, and although the content of the associated zinc in the iron ore is extremely low, the zinc is accumulated in the system continuously due to the circulating enrichment characteristic of the zinc. At present, the popular treatment method of iron and steel enterprises is a rotary kiln process, and the basic principle is to utilize the characteristics of low boiling point and high temperature volatility of zinc to volatilize, enrich and recover zinc in dust through reduction.
The rotary kiln process uses solid fuel as a reducing agent and uses a rotary kiln as a reactor, so that wider raw materials can be treated. The material flow movement mode inside the rotary kiln is gas-solid reverse movement, high-temperature gas is generated by a kiln head burner, the flow direction from head to tail and the material added at the kiln tail form countercurrent contact, the high-temperature gas flow is in contact with the material to carry out heat exchange, and the added material completes the smelting process in the high-temperature environment at the kiln head. The rotary kiln process has the obvious advantages of mature process, low investment and simple operation, but is not suitable for treating low-zinc materials, the metallization rate of iron materials is low, and the ring formation phenomenon often occurs in the production process. The ring formation can continuously reduce the sectional area of the rotary kiln, cause material blocking, deteriorate roasting process parameters, cause working condition change in the kiln, reduce the service life of refractory materials, and easily cause the conditions of unstable indexes of roasted mineral aggregates and the like. According to research reports, the local high temperature of fine-grained low-melting-point substances entering a kiln and a rotary kiln is the root cause of ring formation in the kiln.
The invention patent with application number CN201610737311.5 discloses a method for treating high-zinc iron-containing dust mud by using a rotary kiln. Mixing blast furnace gas ash and converter OG mud, and pelletizing; drying and preheating the wet pellets, wherein the drying and preheating heat source is hot air generated by high-temperature flue gas of the rotary kiln through a high-temperature and low-temperature composite air heat exchanger; arranging a granulated coal spray gun, a carbon residue spray gun and a granulated ore spray gun at the kiln head of the rotary kiln, and blowing high-volatile coal, carbon residue and high-grade iron ore into the kiln; feeding the dried pellets into a rotary kiln, and directly reducing and solidifying the pellets at high temperature in the rotary kiln to obtain high-temperature metallized pellets; cooling the metalized pellets, excessive carbon residue and other materials to normal temperature, and then carrying out magnetic separation to obtain metalized pellets; and removing large particle dust from the high-temperature flue gas discharged from the rotary kiln, then cooling the high-temperature flue gas in a high-low temperature composite air heat exchanger, and then feeding the high-temperature flue gas into a bag-type dust collector to recover zinc oxide powder. However, the method has the following disadvantages: the problems that the rotary kiln has low productivity and is easy to generate ring formation, the content of crude zinc oxide in the collected zinc-containing dust is low, the dezincification rate is low and the like exist.
The invention patent with the application number of CN201310490196.2 discloses a method for producing secondary zinc oxide powder by using blast furnace dust as a raw material in a rotary kiln. Uniformly mixing blast furnace smoke dust, settled powder, returned powder and lime according to a preset mass ratio, and controlling the water content of a mixture to be 16-22% by mass ratio; pelletizing the mixture according to a conventional method to obtain a furnace-entering pellet raw material, and then performing high-temperature fuming treatment on the furnace-entering raw material in a rotary kiln to produce the secondary zinc oxide powder. The prepared pellets obviously improve the air permeability of materials in the rotary kiln and reduce the comprehensive energy consumption. However, the method has disadvantages in that: the defects of low dezincification rate, low metallization rate of the reduced material and low capacity of the rotary kiln exist.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a method for enriching and recovering zinc by using a rotary kiln, which has high zinc recovery yield and can effectively prevent ring formation.
In order to achieve the purpose, the invention provides a method for enriching and recovering zinc by using a rotary kiln, which comprises the following steps:
s1, preparation of raw materials: anthracite and coke powder with the mass ratio of 1-5: 1 are used as reducing coal, and are uniformly mixed with iron ore and metallurgical dust for pelletizing and drying treatment to obtain kiln entering raw materials with preset granularity;
s2, a calcination step: preheating the kiln raw material prepared in the step S1, feeding the preheated raw material into a kiln tail of a reducing rotary kiln, blowing coal powder and preheated oxygen-enriched air with preset oxygen concentration into the kiln tail through a blower, and performing calcination reaction for 80-100 min; the kiln raw materials rotate at the speed of 2-3 min/r along with the reducing rotary kiln, sequentially pass through a preheating section, a middle section and a high-temperature section, and gradually move to a kiln head; under the action of preset air suction pressure of an exhaust fan arranged at the kiln head, the flow direction of flue gas generated by the calcination reaction is consistent with the movement direction of the kiln entering raw materials, and the flue gas and the kiln entering raw materials all move from the kiln tail to the kiln head; collecting roasted ore, grinding the ore and performing magnetic separation to obtain iron ore concentrate;
s3, flue gas treatment: and (3) collecting and purifying the flue gas extracted by the exhaust fan: firstly, collecting zinc-containing dust by using a dust collection system; then, purifying the tail gas after passing through the dust collecting system;
s4, zinc enrichment: preparing the zinc-containing dust obtained in the step S3 into a material with the granularity of 3-5 mm, mixing the zinc-containing dust with the kiln feeding raw material to obtain a mixed kiln feeding material, feeding the preheated mixed kiln feeding material into the reducing rotary kiln, and performing the calcining process in the step S2, wherein the coarse zinc oxide particles in the zinc-containing dust are reduced into gaseous zinc again and are enriched into flue gas generated by calcining; then, the flue gas is subjected to the zinc-containing dust collection process of step S3; repeating the step S4 to realize the cyclic enrichment of zinc in the zinc-containing dust;
s5, zinc recovery: when the zinc content in the flue gas obtained in the step S4 reaches more than 10%, the zinc enrichment process in the step S4 is not performed; directly collecting zinc-containing dust in the flue gas, and then recovering the zinc in the zinc-containing dust by using an acid leaching process.
Preferably, in step S1, the particle size of the kiln raw material is 5-15 mm; the ratio of the reduced coal to the iron ore to the metallurgical dust is 15-35%: 25-40%: 25-45%.
Preferably, the reduced coal has an ash content of less than 10% and the ash has a reflow temperature of greater than 1300 ℃.
Preferably, in step S2, the reducing rotary kiln is
A reducing rotary kiln of a size wherein the high temperature section has a diameter of
Length of 35m, diameter of the preheating section
A length of 25m and a diameter of the middle section of
To
The length is 10 m.
Preferably, the filling rate of the reducing rotary kiln is 10-15%.
Preferably, in step S2, the input amount of the kiln raw materials is 250-350 t/d; the preheating temperature of the kiln raw materials is more than 200 ℃.
Preferably, in step S2, the oxygen concentration in the oxygen-enriched air is 25 to 30%; the preheating temperature of the oxygen-enriched air is more than 200 ℃.
Preferably, in step S2, the blowing pressure of the blower is 150 to 200 KPa.
Preferably, in step S2, the suction pressure of the suction fan is-45 to-50 KPa.
Preferably, in step S4, the zinc-containing material is prepared by using bentonite as a binder.
Preferably, in step S5, the pickling process parameters are set as: the concentration of sulfuric acid is 130-150 g/L, the leaching time is 25-40 min, and the liquid-solid ratio of the sulfuric acid to the zinc-containing dust is 4-6: 1, the leaching temperature is 60-80 ℃, and the stirring speed is 400-600 r/min.
Compared with the prior art, the invention has the beneficial effects that:
the method for enriching and recovering zinc by using the rotary kiln has the advantages of preventing the ring formation of the rotary kiln, improving the recovery rate of zinc and simultaneously improving the utilization rate of heat energy in the kiln, and mainly comprises the following steps:
1) compared with a conventional feeding mode, the method has the advantages that fuel coal powder and kiln entering materials are fed from the same side of the kiln tail, and the flow direction of smoke generated by reduction calcination reaction is consistent with the movement direction of iron ore kiln entering raw materials under the double actions of negative pressure formed by the kiln head and pushing pressure to the kiln head by the kiln tail formed by the air blower by utilizing the exhaust fan, and the smoke moves from the kiln tail to the kiln head; the material flow movement mode inside the rotary kiln is gas-solid equidirectional movement, the kiln tail burner burns to generate high-temperature gas which forms equidirectional flow contact with the materials added at the kiln tail, the high-temperature gas flow contacts with the materials to exchange heat, the added materials sequentially pass through the preheating section, the middle section and the high-temperature section, and the smelting process is completed in the high-temperature environment of the kiln head high-temperature section.
Compared with the conventional gas-solid reverse movement feeding mode, the scheme has the advantages that: the falling speed of furnace burden in the rotary kiln is improved, the retention time of pellets in the furnace is reduced, the bonding of the pellets in the rotary kiln is reduced, and the smelting efficiency of the rotary kiln is improved; in addition, the air flow can be effectively prevented from returning and flowing, and the furnace burden can be effectively prevented from being blown back to the raw material bin by the air flow.
2) The 'internal circulation' process of the zinc-containing dust in the rotary kiln is adopted, the zinc-containing dust is granulated to increase the particle size and then is mixed with the kiln-entering raw material, and then the mixture is sent into the rotary kiln again for calcination, so that the crude zinc oxide particles are reduced into gaseous zinc again and are enriched in flue gas generated by calcination, the cyclic enrichment of zinc is realized, the grade of zinc in the zinc-containing dust is effectively improved, and the recovery yield of zinc is greatly improved. And the zinc-containing dust is granulated, the particle size is enlarged, and then enrichment is carried out, so that ring formation of the rotary kiln can be further prevented.
3) The reducing rotary kiln is adopted, and a reducing structure is generated through transition of the middle section in the length direction of the kiln body, so that the space in the kiln is suitable for the change of gas volume, flame or high-temperature flue gas is prevented from gradually leaving the surface of a kiln raw material along the process direction, the radiation heat transfer of the high-temperature section in the kiln and the convection heat transfer of the preheating section are facilitated, the uneven temperature distribution and the local high temperature in the kiln can be effectively prevented, and the ring formation is further prevented. On one hand, the diameter is changed between the high-temperature section and the preheating section, so that the pressure of the high-temperature section can be effectively kept, the radiation heat transfer from the high-temperature section to the preheating section is reduced, and the complete combustion of fuel is facilitated. On the other hand, the diameter of the preheating section is reduced, so that the heat transfer quantity of the preheating section can be increased, and kiln gas can flow along the surface of kiln raw materials and fill the kiln chamber. The diameter of the high-temperature section at the kiln head is larger than that of the low-temperature section at the kiln tail. The speed of the relative motion line of the material in the high-temperature section and the kiln wall is higher than that in the low-temperature section, the contact time of the material and the kiln wall in the high-temperature section is relatively shortened, and the fine particles are prevented from being overheated. Meanwhile, the diameter of the low-temperature section is relatively small, and the actual filling rate is relatively high, so that the reducing atmosphere of the low-temperature section is better than that of the high-temperature section, and the reduction reaction is favorably carried out. The diameter of the high-temperature section of the reducing rotary kiln is larger, so that the fuel can be fully combusted, the diameter of the preheating section is reduced, the heat can be concentrated to keep effective energy conservation, compared with the conventional through-diameter rotary kiln, the reducing rotary kiln can save about 20 percent of energy, the heat energy utilization rate in the kiln is improved, and the yield of reduction roasting is improved.
4) Oxygen-enriched air is adopted for combustion supporting, so that the blowing-in amount of combustion-supporting gas can be reduced, the smoke gas amount is further reduced, and the grade of a smoke dust product (crude zinc oxide) is improved; meanwhile, as the oxygen concentration is increased, the combustion rate is also increased, the treatment capacity of the rotary kiln is improved, and the fuel consumption is reduced. The reducing rotary kiln structure and the oxygen-enriched air combustion-supporting technology are combined and matched with each other, so that the reduction processing capacity of the rotary kiln and the heat energy utilization rate in the rotary kiln are improved to a great extent, ring formation is effectively prevented, and the grade of zinc in zinc-containing dust is improved.
5) Among the reducing coals, anthracite is mainly used for burning to maintain the temperature of the rotary kiln, and coke powder is used as a reducing agent for reaction. The coal powder material with the ash content lower than 10% and the ash soft melting temperature higher than 1300 ℃ is used as the reducing coal, when the melting point of the coal ash is high, the melting point of a multi-component compound generated by the reaction of the coal ash and ferrous oxide in iron ore is also very high, the generation of a low-melting-point compound is reduced to a certain extent, the ring formation of a rotary kiln can be effectively prevented, and the reducing roasting efficiency in the calcining process is improved. In addition, the smaller the particle size of the raw materials entering the kiln, the larger the surface curvature, the lower the melting temperature, and the materials are easy to reflow at a lower temperature, so that the materials in the kiln are bonded. And the fine-grained kiln raw materials have high activity and are easy to react to generate low-melting-point compounds, and the compounds are melted at a higher temperature to form a ring-forming substance. The method adopts the kiln-entering raw material with the granularity of 5-15 mm, has larger granularity and uniform granularity distribution size of the raw material, effectively prevents the ring formation of the rotary kiln, and improves the reduction roasting yield in the calcining process.
Therefore, the processes are mutually cooperated, the recovery rate of zinc is obviously improved, the ring formation phenomenon of the rotary kiln is effectively prevented, and the high-efficiency enrichment and recovery of the zinc are realized.
Drawings
Fig. 1 is a schematic diagram of a method for enriching and recovering zinc by using a rotary kiln provided by the invention.
Detailed Description
The technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.
Referring to fig. 1, the present invention provides a method for enriching and recovering zinc by using a rotary kiln, comprising the following steps:
s1, preparation of raw materials: anthracite and coke powder with the mass ratio of 1-5: 1 are used as reducing coal, and are uniformly mixed with iron ore and metallurgical dust for pelletizing and drying treatment to obtain kiln entering raw materials with preset granularity;
s2, a calcination step: preheating the kiln raw material prepared in the step S1, feeding the preheated raw material into a kiln tail of a reducing rotary kiln, blowing coal powder and preheated oxygen-enriched air with preset oxygen concentration into the kiln tail through a blower, and performing calcination reaction for 80-100 min; the kiln raw materials rotate at the speed of 2-3 min/r along with the reducing rotary kiln, sequentially pass through a preheating section, a middle section and a high-temperature section, and gradually move to a kiln head; under the action of preset air suction pressure of an exhaust fan arranged at the kiln head, the flow direction of flue gas generated by the calcination reaction is consistent with the movement direction of the kiln entering raw materials, and the flue gas and the kiln entering raw materials all move from the kiln tail to the kiln head; collecting roasted ore, grinding the ore and performing magnetic separation to obtain iron ore concentrate;
s3, flue gas treatment: and (3) collecting and purifying the flue gas extracted by the exhaust fan: firstly, collecting zinc-containing dust by using a dust collection system; then, purifying the tail gas after passing through the dust collecting system;
s4, zinc enrichment: preparing the zinc-containing dust obtained in the step S3 into a material with the granularity of 3-5 mm, mixing the zinc-containing dust with the kiln feeding raw material to obtain a mixed kiln feeding material, feeding the preheated mixed kiln feeding material into the reducing rotary kiln, and performing the calcining process in the step S2, wherein the coarse zinc oxide particles in the zinc-containing dust are reduced into gaseous zinc again and are enriched into flue gas generated by calcining; then, the flue gas is subjected to the zinc-containing dust collection process of step S3; repeating the step S4 to realize the cyclic enrichment of zinc in the zinc-containing dust;
s5, zinc recovery: when the zinc content in the flue gas obtained in the step S4 reaches more than 10%, the zinc enrichment process in the step S4 is not performed; directly collecting zinc-containing dust in the flue gas, and then recovering the zinc in the zinc-containing dust by using an acid leaching process.
Further, in step S1, the particle size of the kiln raw material is 5-15 mm; the ratio of the reduced coal to the iron ore to the metallurgical dust is 15-35%: 25-40%: 25-45%.
Further, in the reduced coal, the ash content is less than 10%, and the reflow temperature of the ash is greater than 1300 ℃.
Further, in step S2, the reducing rotary kiln is
A reducing rotary kiln of a size wherein the high temperature section has a diameter of
Length of 35m, diameter of the preheating section
A length of 25m and a diameter of the middle section of
To
The length is 10 m.
Furthermore, the filling rate of the reducing rotary kiln is 10-15%.
Further, in step S2, the input amount of the kiln raw materials is 250-350 t/d; the preheating temperature of the kiln raw materials is more than 200 ℃.
Further, in step S2, the oxygen concentration in the oxygen-enriched air is 25 to 30%; the preheating temperature of the oxygen-enriched air is more than 200 ℃.
Further, in step S4, bentonite is used as a binder for preparing the zinc-containing material.
Further, in step S2, the blowing pressure of the blower is 150 to 200 KPa.
Further, in step S2, the suction pressure of the suction fan is-45 KPa to-50 KPa.
Further, in step S5, the pickling process parameters are set as: the concentration of sulfuric acid is 130-150 g/L, the leaching time is 25-40 min, and the liquid-solid ratio of the sulfuric acid to the zinc-containing dust is 4-6: 1, the leaching temperature is 60-80 ℃, and the stirring speed is 400-600 r/min.
The method for zinc enrichment and recovery by using a rotary kiln provided by the invention is further described in detail by specific examples.
Example 1
The method for enriching and recovering zinc by using a rotary kiln is characterized in that the raw material is low-grade iron ore:
s1, preparation of raw materials: anthracite and coke powder with the mass ratio of 1:1 are used as reducing coal, and are uniformly mixed with iron ore and metallurgical dust for pelletizing and drying treatment to obtain kiln entering raw materials with the average particle size distribution of 5-15 mm; wherein the proportion of the reducing coal, the iron ore and the metallurgical dust is 25%: 35%: 40 percent; in the reducing coal, the ash content is 8%, and the reflow temperature of the ash is higher than 1300 ℃.
S2, a calcination step: preheating the kiln raw material prepared in the step S1 to 200 ℃, and then feeding the raw material into the tail of a reducing rotary kiln, wherein the filling rate of the reducing rotary kiln is 10%; the input amount of the raw materials entering the kiln is 300 t/d; blowing coal dust and oxygen-enriched air with the oxygen concentration of 25 percent and the preheating temperature of 200 ℃ into the kiln tail through an air blower at the blowing pressure of 150KPa, and carrying out calcination reaction for 90 min; the kiln raw materials rotate at the speed of 2.5min/r along with the reducing rotary kiln, sequentially pass through a preheating section, a middle section and a high-temperature section, and gradually move to a kiln head; under the action of an exhaust fan arranged at the kiln head and the exhaust pressure of-45 KPa, the flowing direction of the flue gas generated by the calcination reaction is consistent with the moving direction of the kiln entering raw materials, and the flue gas moves from the kiln tail to the kiln head; collecting roasted ore, cooling, and then carrying out ore grinding and magnetic separation procedures to obtain iron ore concentrate; the tailing roasting slag is transported to a cement plant and a brick plant for producing building materials.
Wherein the reducing rotary kiln is
A reducing rotary kiln of a size wherein the high temperature section has a diameter of
Length of 35m, diameter of the preheating section
A length of 25m and a diameter of the middle section of
To
The length is 10 m.
S3, flue gas treatment: and (3) collecting and purifying the flue gas extracted by the exhaust fan: firstly, collecting zinc-containing dust by using a dust collection system; and then, purifying sulfur dioxide and heavy metals in the flue gas by adopting a circulating spraying and alkali liquor absorption combined method on the tail gas passing through the dust collecting system, wherein the circulating liquid is a slurry prepared from a certain amount of sodium hydroxide and limestone.
S4, zinc enrichment: preparing the zinc-containing dust obtained in the step S3 into a zinc-containing material with the granularity of 5mm (bentonite is adopted for preparing the zinc-containing material as a binder), mixing the zinc-containing material with the kiln feeding raw material to obtain a mixed kiln feeding material, feeding the preheated mixed kiln feeding material with the temperature of 200 ℃ into the reducing rotary kiln, and performing the calcining process in the step S2, wherein the crude zinc oxide particles in the zinc-containing dust are reduced into gaseous zinc again and are enriched into flue gas generated by calcining; then, the flue gas is subjected to the zinc-containing dust collection process of step S3; and repeating the process of the step S4 to realize the cyclic enrichment of the zinc in the zinc-containing dust.
S5, zinc recovery: when the zinc content in the flue gas obtained in the step S4 reaches more than 10%, the zinc enrichment process in the step S4 is not performed; directly collecting zinc-containing dust in the flue gas, and then recovering the zinc in the zinc-containing dust by using an acid leaching process; the acid leaching process parameters are set as follows: the concentration of sulfuric acid is 140g/L, the leaching time is 30min, and the liquid-solid ratio of the sulfuric acid to the zinc-containing dust is 5:1, the leaching temperature is 70 ℃, and the stirring speed is 450 r/min.
Comparative example 1
The difference from example 1 is that: the calcination reaction of the rotary kiln is carried out by adopting a conventional feeding mode, namely, the raw materials entering the kiln are fed from the tail of the kiln, the coal powder and the oxygen-enriched air are blown from the opposite kiln head, and other steps are the same as those in the embodiment 1 and are not repeated.
In the comparative example 1, the material flow movement mode inside the rotary kiln is gas-solid reverse movement, the kiln head burner generates high-temperature gas, the flow direction from head to tail and the material added at the kiln tail form countercurrent contact, the high-temperature gas flow contacts with the material to exchange heat, and the added material completes the smelting process in the high-temperature environment at the kiln head.
The iron recovery rate of comparative example 1 was 81% and the zinc recovery rate was 69%, which was lower than the recovery efficiency in example 1.
Comparative example 2
The difference from example 1 is that: the setting that adopts conventional air as combustion-supporting gas is different, and other steps are the same as in embodiment 1, and are not described again here.
Examples 2 to 3
The difference from example 1 is that: the oxygen concentration in the oxygen-enriched air is set differently, and other steps are the same as those in embodiment 1, and are not described again.
Compared with the conventional air (the oxygen concentration is 21%) in the comparative example 2, the combustion-supporting air blowing-in amount can be reduced, so that the smoke emission is greatly reduced, and the grade of a smoke dust product (crude zinc oxide) is improved. Meanwhile, due to the fact that the oxygen concentration is improved, the combustion rate is also improved, the processing capacity of the rotary kiln for reduction roasting can be enhanced, iron ore is fully recovered, the recovery grade and the recovery rate are improved, and fuel consumption is reduced to a great extent.
Examples 4 to 7
The difference from example 1 is that: the filling rate of the rotary kiln and the input amount of the raw materials entering the kiln are set differently, and other steps are the same as those in embodiment 1, and are not described again.
When the material retention time is not changed, the filling rate of the rotary kiln and the input amount of the raw materials entering the kiln are increased, so that the output of the rotary kiln can be improved, but the material movement is limited due to the thickening of the material layer, so that the material turning and roasting are not favorable. If the filling rate and the input amount are too small, the production capacity of the equipment is not effectively utilized, and the production cost is also increased.
Comparative example 3
The difference from example 1 is that: the calcination process is carried out by adopting a conventional drift diameter rotary kiln, and other steps are the same as those in the example 1, and are not repeated.
The diameter rotary kiln adopted in the comparative example 3 is as follows:
the drift diameter rotary kiln.
The reducing rotary kiln adopted by the invention prolongs the length of the high-temperature reduction section. Because the diameter of the high-temperature section at the kiln head is larger than that of the low-temperature section at the kiln tail, the relative motion linear speed of the materials between the high-temperature section and the kiln wall is larger than that of the low-temperature section, the contact time of the materials and the kiln wall at the high-temperature section is relatively shortened, and the fine particles are prevented from being overheated. Meanwhile, the diameter of the low-temperature section is relatively small, and the actual filling rate is relatively high, so that the reducing atmosphere of the low-temperature section is better than that of the high-temperature section, and the reduction reaction is favorably carried out. Therefore, the diameter of the high-temperature section of the reducing rotary kiln is larger, so that the fuel can be fully combusted, the diameter of the preheating section is reduced, the heat can be concentrated to keep effective energy conservation, the heat energy utilization rate in the rotary kiln is improved compared with that of a conventional drift diameter rotary kiln, and the yield of reduction roasting is improved.
In comparative example 3, the recovery rate of iron was 87%, the recovery rate of zinc was 80.1%, which was lower than that in example 1, while the energy consumption was about 20% higher than that in example 1, and the ring formation phenomenon was likely to occur even when the rotary kiln was operated for a certain period of time.
Examples 8 to 11
The difference from example 1 is that: the setting of the blowing pressure and the air draft pressure is different, and other steps are the same as those in embodiment 1, and are not described again.
The increase of the blast pressure and the negative pressure of the air draft can cause the flow velocity of the smoke gas to rise, and the raw material with the smoke dust is increased, thereby increasing the zinc content in the zinc-containing dust and obviously improving the enrichment effect. However, the increase of the flue gas flow velocity destroys the reducing atmosphere in the rotary kiln to a certain extent, so that the metallization rate of iron ore is reduced, the reaction is insufficient, and the recovery yield of zinc is affected.
Comparative example 4
The difference from example 1 is that: the conventional reduced coal material with 20% ash content was used, and the other steps were the same as in example 1, and thus the description thereof is omitted.
Examples 12 to 16
The difference from example 1 is that: the parameters of the raw material in step S1 are set differently, and other steps are the same as those in embodiment 1, and are not described herein again.
The higher the proportion of the reduced coal is, namely the higher the carbon content is, the higher the gasification speed of the carbon is, and the higher the reduction speed of CO is, so that the reduction process of the iron oxide is promoted. The invention adopts the reduced coal material with low ash content, has good reactivity, can maintain higher CO concentration in a reaction space, promotes the reduction of iron oxide, allows the adoption of lower reduction temperature, is beneficial to preventing the ring formation of a rotary kiln, and can correspondingly reduce the requirements on the ash softening temperature and the ore softening temperature of the coal for reduction. Among the reducing coals, anthracite is mainly used for burning to maintain the temperature of the rotary kiln, and coke powder is used as a reducing agent for reaction.
Examples 17 to 20
The difference from example 1 is that: the rotary kiln has different settings of rotating speed and calcining time, and other steps are the same as those in example 1, and are not described again.
Along with the extension of the calcining reduction time, the iron ore is continuously oxidized, the metallization rate is gradually increased, and after the certain degree is reached, the metallization rate increase speed of the iron ore is gradually slowed down. The calcination time affects the heat transfer of the feedstock and the progress of the chemical reaction, and also determines whether the feedstock is reoxidized, so the recovery increases and decreases as the heating time increases, because: the time is too short, the calcination is insufficient, the reduction reaction is not completed, the raw material metallization rate is low, and the recovery rate is low; the reduction product is oxidized again after the time is too long, and the recovery rate is reduced.
The rotation speed of the rotary kiln determines the circulation capacity of the raw materials in the kiln and the roasting time of the raw materials in the kiln, and influences the temperature in the rotary kiln to a certain extent. The rotating speed of the rotary kiln is increased, the rolling of the materials in the kiln can be accelerated, the materials are uniformly mixed, the temperature of the materials in the kiln is uniform, and the phenomenon that the local heating of the materials in the kiln is too high is reduced. However, increasing the rotational speed of the rotary kiln inevitably reduces the residence time of the material in the rotary kiln. The low rotating speed can directly cause the reduction of the treatment capacity, the increase of the returned materials at the tail of the kiln, the poor turnover condition of the materials in the kiln, the increase of the zinc content of the slag and the reduction of the recovery yield of the zinc.
In conclusion, the invention provides a method for enriching and recovering zinc by using a rotary kiln. Feeding the preheated kiln-entering raw material into the tail of a reducing rotary kiln, blowing coal powder and oxygen-enriched air into the tail of the kiln, and carrying out calcination reaction for 80-100 min; under the action of a kiln head exhaust fan, the flowing direction of flue gas generated by calcination reaction is consistent with the moving direction of the kiln entering raw materials, and the flue gas and the kiln entering raw materials move from the kiln tail to the kiln head; collecting roasted ore, grinding the ore and performing magnetic separation to obtain iron ore concentrate; collecting and purifying the smoke extracted by the exhaust fan, collecting zinc-containing dust by using a dust collecting system, mixing the zinc-containing dust with the kiln raw materials for granulation to obtain a mixed kiln material, feeding the mixed kiln material into a reducing rotary kiln, and circularly performing a calcining process and a zinc-containing dust collecting process to realize the circular enrichment of zinc; when the zinc content in the flue gas reaches more than 10 percent, directly collecting zinc-containing dust in the flue gas, and recovering zinc by using an acid leaching process. The method can effectively improve the recovery rate of iron and zinc, prevent the ring formation of the rotary kiln, and has high efficiency and energy conservation.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for enriching and recovering zinc by using a rotary kiln is characterized by comprising the following steps: the method comprises the following steps:
s1, preparation of raw materials: anthracite and coke powder with the mass ratio of 1-5: 1 are used as reducing coal, and are uniformly mixed with iron ore and metallurgical dust for pelletizing and drying treatment to obtain kiln entering raw materials with preset granularity;
s2, a calcination step: preheating the kiln raw material prepared in the step S1, feeding the preheated raw material into a kiln tail of a reducing rotary kiln, blowing coal powder and preheated oxygen-enriched air with preset oxygen concentration into the kiln tail through a blower, and performing calcination reaction for 80-100 min; the kiln raw materials rotate at the speed of 2-3 min/r along with the reducing rotary kiln, sequentially pass through a preheating section, a middle section and a high-temperature section, and gradually move to a kiln head; under the action of preset air suction pressure of an exhaust fan arranged at the kiln head, the flow direction of flue gas generated by the calcination reaction is consistent with the movement direction of the kiln entering raw materials, and the flue gas and the kiln entering raw materials all move from the kiln tail to the kiln head; collecting roasted ore, grinding the ore and performing magnetic separation to obtain iron ore concentrate;
s3, flue gas treatment: and (3) collecting and purifying the flue gas extracted by the exhaust fan: firstly, collecting zinc-containing dust by using a dust collection system; then, purifying the tail gas after passing through the dust collecting system;
s4, zinc enrichment: mixing the zinc-containing dust obtained in the step S3 with the kiln entering raw material to obtain a mixed kiln entering material, sending the preheated mixed kiln entering material into the reducing rotary kiln, and performing the calcining process in the step S2, wherein the coarse zinc oxide particles in the zinc-containing dust are reduced into gaseous zinc again and are enriched in flue gas generated by calcining; then, the flue gas is subjected to the zinc-containing dust collection process of step S3; repeating the step S4 to realize the cyclic enrichment of zinc in the zinc-containing dust;
s5, zinc recovery: when the zinc content in the flue gas obtained in the step S4 reaches more than 10%, the zinc enrichment process in the step S4 is not performed; directly collecting zinc-containing dust in the flue gas, and then recovering the zinc in the zinc-containing dust by using an acid leaching process.
2. The method for zinc enrichment recovery by using a rotary kiln as claimed in claim 1, characterized in that: in step S1, the particle size of the kiln raw material is 5-15 mm; the ratio of the reduced coal to the iron ore to the metallurgical dust is 15-35%: 25-40%: 25-45%.
3. The method for zinc enrichment recovery by using a rotary kiln as claimed in claim 2, characterized in that: in the reducing coal, the ash content is lower than 10%, and the reflow temperature of the ash is higher than 1300 ℃.
4. The method for zinc enrichment recovery by using a rotary kiln as claimed in claim 1, characterized in that: in step S2, the reducing rotary kiln is
A reducing rotary kiln of a size wherein the high temperature section has a diameter of
Length of 35m, diameter of the preheating section
A length of 25m and a diameter of the middle section of
To
The length is 10 m.
5. The method for zinc enrichment recovery by using a rotary kiln as claimed in claim 4, characterized in that: the filling rate of the reducing rotary kiln is 10-15%; the input amount of the kiln raw materials is 250-350 t/d; the preheating temperature of the kiln raw materials is more than 200 ℃.
6. The method for zinc enrichment recovery by using a rotary kiln as claimed in claim 1, characterized in that: in step S2, the oxygen concentration in the oxygen-enriched air is 25-30%; the preheating temperature of the oxygen-enriched air is more than 200 ℃.
7. The method for zinc enrichment recovery by using a rotary kiln as claimed in claim 1, characterized in that: in step S2, the blowing pressure of the blower is 150 to 200 KPa.
8. The method for zinc enrichment recovery by using a rotary kiln as claimed in claim 1, characterized in that: in step S2, the suction pressure of the suction fan is-45 KPa to-50 KPa.
9. The method for zinc enrichment recovery by using a rotary kiln as claimed in claim 1, characterized in that: in step S4, mixing the kiln charge, the zinc-containing dust further comprises a pretreatment step of: and preparing the zinc-containing dust into a zinc-containing material with the granularity of 3-5 mm by using bentonite as a binder.
10. The method for zinc enrichment recovery by using a rotary kiln as claimed in claim 1, characterized in that: in step S5, the pickling process parameters are set as: the concentration of sulfuric acid is 130-150 g/L, the leaching time is 25-40 min, and the liquid-solid ratio of the sulfuric acid to the zinc-containing dust is 4-6: 1, the leaching temperature is 60-80 ℃, and the stirring speed is 400-600 r/min.
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