Method for treating low-grade zinc oxide ore through rotary kiln concentrated oxygen low-carbon roasting

Abstract

The invention discloses a method for treating low-grade zinc oxide ore through concentrated oxygen low-carbon roasting in a rotary kiln, which comprises the following steps of: blending low-grade zinc-containing raw materials, adding solid fuel, and uniformly mixing the materials; carrying out wet milling on the mixed material by a ball mill to 80 meshes, then carrying out solid-liquid separation, carrying out aeration-drying on the solid-phase material to control the moisture to be 8-12%, and granulating by a pelletizer for later use; when the rotary kiln is used for roasting, oxygen-enriched air is blown into the kiln head, materials are fed into the kiln tail, high-temperature roasting is completed after the materials run in the rotary kiln for one week, roasting slag is discharged from the kiln head, smoke dust is discharged from the kiln tail, and most of zinc and lead are recycled from the smoke dust of the rotary kiln. Fuel is introduced into the ore blending and grinding process, high-quality fuel is replaced with common fuel, the technological method is improved, combustion efficiency is greatly improved, energy consumption is remarkably reduced, the comprehensive utilization rate of low-grade zinc oxide resources is increased, the technological process is short, efficient and reliable, environmental pollution is small, low-carbon production is achieved, and the method is suitable for industrial production. And the method is a reliable method for effectively treating the low-grade zinc oxide ore.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for treating low-grade zinc oxide ore by concentrated oxygen and low carbon roasting in a rotary kiln. Background Art

[0002] my country's lead-zinc deposits store a large amount of sulfide ores, oxide ores and mixed ores. Oxidized lead-zinc ores and sulfide lead-zinc ores with a grade higher than 12% have been developed and utilized on a large scale due to mature development technology, and the reserves of lead-zinc resources are facing a situation of depletion; however, the mixed ores and oxide ores with a grade lower than 10%, which account for about 1 / 3 of the total reserves, have been unable to be reasonably and effectively developed and utilized due to their extremely complex phase composition and the presence of a large amount of mud and various impurities, which poses a severe test to the effective utilization of resources and environmental protection. With the increase in my country's zinc metal consumption and the depletion of high-grade zinc ore resources, as well as the characteristics of my country's oxide zinc ore resources, such as more poor ores, fewer rich ores, difficulty in processing, complex ore structure, and unstable associated components, conventional beneficiation and smelting processes are difficult to achieve the development and utilization of such resources, but the reserves of such resources are huge, and it is necessary to study the process of economic and reasonable application of such resources as soon as possible. For example, in a mine in Yunnan, the total amount of low-grade lead-zinc oxide ore has reached nearly 40 million tons, and the total amount of lead and zinc metals is nearly 3 million tons. The amount of minerals and metals in this volume has reached the scale of a medium-sized lead-zinc mine. These low-grade lead-zinc resources with complex mineral composition are difficult to realize their economic value using traditional mineral processing or smelting processes. Therefore, the efficient recycling and utilization of complex low-grade and difficult-to-process lead-zinc mineral resources plays a positive role in my country's lead and zinc resource development, environmental protection and economic development.

[0003] Zinc oxide is a commonly used chemical additive, widely used in the manufacturing process of plastics, rubber, lubricants, paints and coatings, ointments, adhesives, foods, batteries, flame retardants, liquid crystal displays, thin film transistors, light-emitting diodes and other products. At present, there are three main processes for the preparation of zinc oxide: direct method, indirect method and wet method: the direct method uses zinc concentrate as raw material, adds reducing coal and granulates it, and then reduces it at high temperature in the furnace. The zinc vapor volatilized by high temperature roasting is directly oxidized to zinc oxide after contacting with CO2 and air in the furnace gas, thereby separating it from impurities such as lead, cadmium and sulfur. This method has the disadvantages of low zinc recovery rate, high energy consumption, coarse zinc oxide particles, and easy to be contaminated by the combustion products of reducing coal. The indirect method uses metallic zinc as raw material, melts it and introduces it into the evaporation furnace under certain oxidation conditions to oxidize the zinc vapor into zinc oxide. This method has a long production process and needs to go through the steps of melting, distillation, distribution, oxidation, cooling, collection, etc., and has high requirements for equipment. The evaporation of metallic zinc needs to be completed in a sealed device at about 1000°C. Therefore, the energy consumption is extremely high, resulting in the highest production cost of this process. The wet process uses zinc-containing materials as raw materials. First, a zinc-containing solution is prepared, and carbonate is added to convert it into a zinc compound precipitate. The zinc compound precipitate is calcined to obtain zinc oxide. The disadvantage of this process is that the particle size of zinc oxide is large, and it is difficult to adjust the particle size of zinc oxide according to demand.

[0004] Traditional rotary kiln processing of low-grade zinc oxide resources requires the addition of high-quality coke ash or anthracite containing about 70% carbon as a reducing agent and a heating agent. For example, Chinese invention patent CN107227411A discloses a method for preparing high-grade secondary zinc oxide by oxygen-enriched combustion in a rotary kiln, and discloses a method for preparing high-grade secondary zinc oxide by oxygen-enriched combustion in a rotary kiln, the steps of which are: (1) preparation of zinc-containing materials: treating zinc-containing raw materials from various sources to meet the requirements of 6-20% zinc content and 10-20% moisture content; the particles with a size of generally less than 1 cm are fed into the kiln; (2) mixing the mixture: adding fuel to the mixture of zinc-containing materials, the fuel accounting for 25-35% by mass in the mixture, and the calorific value of the mixture being 1500-2000 kcal / kg; (3) putting the mixture into a rotary kiln, blowing in oxygen-enriched air for combustion, so that zinc is enriched in the smoke in the form of zinc oxide, and iron and the like are enriched in the slag; (4) collecting the smoke to obtain a secondary zinc oxide product. The zinc-containing material can be smoke, leaching slag, water-processed slag, and can be in powder, mud or block form. The amount of fuel coke or anthracite added reaches more than 50% of the ore amount, and the process energy consumption and processing cost are too high. Therefore, low-grade minerals are accumulated and cannot be reasonably fully utilized. How to simply, efficiently and industrially recover lead and zinc from low-grade zinc oxide ores has always been a problem studied by metallurgical enterprises.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for treating low-grade zinc oxide ore by concentrated oxygen and low-carbon roasting in a rotary kiln. Fuel is creatively introduced into the ore blending and grinding process, and high-quality fuel is replaced by ordinary fuel, and air is replaced by oxygen-enriched air. Through the improvement of the process method, the combustion efficiency is greatly improved, the energy consumption is significantly reduced, and the utilization of low-grade zinc oxide resources and the direct manufacture of zinc oxide powder are promoted.

[0007] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is: A method for treating low-grade zinc oxide ore by concentrated oxygen and low-carbon roasting in a rotary kiln, comprising the following steps: (1) Low-grade zinc-containing raw materials are blended to control the zinc content to 6-10%, the solid fuel blending amount is 20-25% of the mineral mass, and the calorific value of the mixture is controlled to be 1800-2200 kcal / kg; (2) After the materials are prepared, mix them evenly; (3) The mixed material is wet-milled to 80 meshes by a ball mill, and then separated into solid and liquid by a thickener and a plate and frame filter press. The solid phase material is then ventilated and dried to control the moisture content to 8% to 12%, and pelletized by a pelletizer for later use; (4) When the temperature at the tail of the rotary kiln rises to 1100°C, the prepared materials are put into the kiln from the tail, and oxygen-enriched air is blown into the kiln head for combustion. The temperature in the kiln is controlled at 1200-1280°C; (5) After the material is roasted at high temperature in the rotary kiln, the lead and zinc in the material are reduced to metal vapor and volatilized in the reducing atmosphere of the high temperature zone. The metal vapor is discharged with the flue gas under the blowing of compressed air at the kiln head and the suction of the exhaust fan at the kiln tail. Finally, the flue gas passes through the waste heat boiler, surface cooling, and bag dust collection to obtain zinc-lead smoke dust; (6) The slag enriched with impurities such as iron, calcium oxide, and silicon dioxide is discharged from the kiln head, cooled by water quenching, and then stored; (7) The oxygen-enriched concentration exceeds 85%, the pressure is 15-30 kPa, and after air distribution, it is blown into the kiln head in the form of low-concentration oxygen-enriched gas.

[0008] Testing showed that the volatilization rate of lead and zinc was over 92%.

[0009] Furthermore, the reducing agent is one or more of coke, coal powder, anthracite, charcoal and homemade additives, and the calorific value of the mixture is controlled to be between 1800 and 2200 kcal / kg.

[0010] Furthermore, the mixed materials and the wet grinding liquid are added into a ball mill and wet-grinded to 80 mesh.

[0011] Furthermore, the solid phase material obtained after solid-liquid separation is ventilated and dried to control the moisture content at 8% to 12%.

[0012] Furthermore, oxygen-rich air is blown into the kiln head for combustion, the central temperature of the rotary kiln is controlled at 1200-1280°C, and the material stays in the kiln for 30-50 minutes.

[0013] Furthermore, lead and zinc are reduced and volatilized into the flue gas, and the obtained oxidized dust is collected in key locations such as waste heat boilers, surface coolers, and bag filters.

[0014] Furthermore, experiments have verified that zinc oxide smoke contains 40% to 60% zinc (Zn), about 10% lead (Pb), and has low levels of impurities such as iron (Fe), calcium oxide (CaO), and silicon dioxide (SiO2), and the product quality is good.

[0015] After adopting the above technical scheme, the present invention has the following beneficial effects compared with the prior art.

[0016] (1) The recovery efficiency of lead and zinc can be increased to more than 92%, energy consumption can be controlled at around 20%, the grade of zinc fume can reach 40% to 60%, and the grade of lead fume can be controlled at around 10%. This effectively utilizes low-grade zinc oxide resources, significantly reduces resource recovery costs, and realizes the active exploration of ways to develop and utilize such resources.

[0017] (2) The process is short, efficient and reliable; the energy consumption is low; the metal recovery rate is high; the production process can be realized by traditional equipment without the need for additional equipment costs; the environmental pollution is small, and it meets the requirements of energy conservation, emission reduction and clean metallurgy.

[0018] (3) The process test cost is low and most enterprises have the test conditions, making it easy to promote and apply.

[0019] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are part of this application and are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings described below are only some embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings: Figure 1 It is a process flow chart of the present invention.

[0021] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention. Example

[0023] The low-grade zinc oxide ore containing 10.25% zinc and 2% lead is mixed with 25% common solid reduction fuel, which can be one or more of coal, anthracite and coke, and the calorific value of the mixture is 2150kcal / kg. After mixing and wet grinding to 80 mesh, the thickener and plate-frame filter press are used for solid-liquid separation, and the solid phase material is then ventilated and dried to control the moisture content to 10% for standby use.

[0024] The oxygen concentration exceeds 85%, and the pressure is 20-30kpa. After the air is matched, it is blown into the furnace from the kiln head in the form of low-concentration oxygen-rich to accelerate the combustion of fuel. When the center temperature of the rotary kiln rises to 1250℃, the raw materials are added in succession from the tail of the rotary kiln through the feeding device. After the materials run in the rotary kiln for one week, lead and zinc are reduced to metal vapor at high temperature and evaporated. The metal vapor is discharged with the flue gas under the action of the blowing of compressed air at the kiln head and the suction of the exhaust fan at the kiln tail. Finally, the flue gas is cooled and settled to obtain smoke dust. After the material stays in the kiln for 50 minutes, the slag is discharged from the kiln head and stored after water quenching.

[0025] After analysis and testing of the materials, the zinc fume contained 54.33% zinc, the lead fume contained 8.98% lead, the slag contained 0.15% zinc and 0.05% lead, the zinc volatilization rate was 93.68% and the lead volatilization rate was 94.37%, meeting the expected goals and achieving relatively ideal results. Example

[0026] The low-grade zinc oxide ore containing 11.70% zinc and 2.24% lead is mixed with 25% common fuel, and the calorific value of the mixture is 1964kcal / kg. After mixing and wet grinding to 80 mesh, the thickener and plate-frame filter press are used for solid-liquid separation, and the solid phase material is then ventilated and dried to control the moisture content at 12% for standby use.

[0027] The oxygen concentration exceeds 85%, and the pressure is 20-30kpa. After the air is matched, it is blown into the furnace from the kiln head in the form of low-concentration oxygen-rich to accelerate the combustion of fuel. When the center temperature of the rotary kiln rises to 1200℃, the raw materials are added in succession from the tail of the rotary kiln through the feeding device. After the materials run in the rotary kiln for one week, lead and zinc are reduced to metal vapor at high temperature and evaporated. The metal vapor is discharged with the flue gas under the action of the blowing of compressed air at the kiln head and the suction of the exhaust fan at the kiln tail. Finally, the flue gas is cooled and settled to obtain smoke dust. After the material stays in the kiln for 45 minutes, the slag is discharged from the kiln head and stored after water quenching.

[0028] After analysis and testing of the materials, the zinc fume contained 55.91% zinc, the lead fume contained 9.32% lead, the slag contained 0.11% zinc and 0.05% lead, the zinc volatilization rate was 95.13% and the lead volatilization rate was 96.75%, meeting the expected goals and achieving relatively ideal results. Example

[0029] The low-grade zinc oxide ore containing 9.89% zinc and 2.45% lead is mixed with 20% common fuel, the fuel is one or more of coal, anthracite, and coke, and the calorific value of the mixture is 1878kcal / kg. After mixing and wet grinding to 80 mesh, the thickener and plate-frame filter press are used for solid-liquid separation, and the solid phase material is then ventilated and dried to control the moisture content to 12% for standby use.

[0030] The oxygen concentration exceeds 85%, and the pressure is 20-30kpa. After the air is matched, it is blown into the furnace from the kiln head in the form of low-concentration oxygen-rich to accelerate the combustion of fuel. When the center temperature of the rotary kiln rises to 1200℃, the raw materials are added in succession from the tail of the rotary kiln through the feeding device. After the materials run in the rotary kiln for one week, lead and zinc are reduced to metal vapor at high temperature and evaporated. The metal vapor is discharged with the flue gas under the action of the blowing of compressed air at the kiln head and the suction of the exhaust fan at the kiln tail. Finally, the flue gas is cooled and settled to obtain smoke dust. After the material stays in the kiln for 50 minutes, the slag is discharged from the kiln head and stored after water quenching.

[0031] After analysis and testing of the materials, the zinc fume contained 51.35% zinc, the lead fume contained 8.62% lead, the slag contained 0.16% zinc and 0.06% lead, the zinc volatilization rate was 93.22% and the lead volatilization rate was 94.08%, meeting the expected goals and achieving relatively ideal results.

[0032] It can be seen from the above that the method of the present invention is an effective method for extracting lead and zinc from low-grade zinc oxide resources. The recovery rates of lead and zinc are both above 92%, and the process is short and reliable, the energy consumption is low, the production cost is economically controllable, and it has wide promotion and application value.

[0033] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A method for treating low-grade zinc oxide ore by concentrated oxygen and low carbon roasting in a rotary kiln, characterized in that: The following steps are involved: (1) Low-grade zinc-containing raw materials are blended to control the zinc content to 6-10%, and mixed evenly with solid reducing fuel. The amount of solid reducing fuel added is 20-25% of the mineral mass, and the calorific value of the mixture is controlled to be 1800-2200 kcal / kg; (2) The mixed material is wet-milled to 80 mesh with a ball mill, and then separated into solid and liquid using a thickener and a plate and frame filter press. The solid phase material is dried and pelletized using a pelletizer for later use; (3) When the temperature at the tail of the rotary kiln rises to 1100°C, the prepared materials are put into the kiln tail, and oxygen-enriched air is blown into the kiln head for roasting; (4) After the material is roasted at high temperature in the rotary kiln, the flue gas passes through a waste heat boiler, surface cooling, and bag dust collection to obtain zinc-lead dust.

2. The method for treating low-grade zinc oxide ore by concentrated oxygen and low carbon roasting in a rotary kiln according to claim 1, characterized in that: In step (1), the solid reducing fuel is one or more of coke, coal powder, anthracite, and charcoal, and the calorific value of the mixture is controlled to be between 1800 and 2200 kcal / kg.

3. The method for treating low-grade zinc oxide ore by concentrated oxygen and low carbon roasting in a rotary kiln according to claim 1, characterized in that: In step (2), the mixed material and the wet grinding liquid are added into a ball mill and wet-grinded to 80 mesh.

4. The method for treating low-grade zinc oxide ore by concentrated oxygen and low carbon roasting in a rotary kiln according to claim 1, characterized in that: In step (2), the solid phase material obtained after solid-liquid separation is dried by ventilation to control the moisture content at 8% to 12%.

5. The method for treating low-grade zinc oxide ore by concentrated oxygen and low carbon roasting in a rotary kiln according to claim 1, characterized in that: In step (3), the central temperature of the rotary kiln is controlled at 1200-1280°C, and the material stays in the kiln for 30-50 minutes.

6. The method for treating low-grade zinc oxide ore by concentrated oxygen and low carbon roasting in a rotary kiln according to claim 1, characterized in that: In step (3), the oxygen enrichment concentration exceeds 85%, the pressure is 15-30 kPa, and after air distribution, it is blown into the kiln head in the form of low-concentration oxygen enrichment.

Images