A method for obtaining nickel-iron alloy by smelting laterite nickel ore

Abstract

The present invention relates to the field of materials and metallurgy technology, and specifically to a method for obtaining nickel-iron alloy by smelting laterite nickel ore, wherein the batch material of the laterite nickel ore is pressed and formed to obtain material balls, and the material balls are calcined in a vertical calcining furnace to become metallized pellets. The metallized pellets are smelted and separated to obtain nickel-iron alloy and slag; the present invention can eliminate nodules in the reduction roasting stage, and at the same time can reduce the amount of air used and reduce the exhaust gas emission temperature, thereby improving thermal efficiency. The slag is ground and sorted into slag particles and slag powder, and the slag particles are rich in metal elements. The slag particles are extracted as return ore and re-incorporated into the ingredients, thereby improving the metal recovery rate. The slag powder can be used as slag micropowder. In addition, if the slag is remelted to adjust the composition, the present invention can obtain cement or steel slag phosphate fertilizer in the nickel-iron production process, which is used to replace the slag micropowder, further avoiding resource waste.

Description

Technical Field

[0001] The present invention relates to the technical field of materials and metallurgy, and in particular to a method for obtaining nickel-iron alloy by smelting laterite nickel ore. Background Art

[0002] Currently, the world's proven nickel reserves are approximately 160 million tons. Nickel minerals primarily exist in two forms: nickel sulfide ore and nickel oxide-silicate ore (also known as laterite nickel ore). Sulfide nickel ore accounts for approximately 30% of this total, while laterite nickel ore accounts for approximately 70%. Due to the high quality of sulfide nickel ore and its mature processing technology, approximately two-thirds of the world's nickel is extracted from sulfide nickel ore, while laterite nickel deposits account for 65% of the world's nickel reserves. Due to the lack of significant breakthroughs in sulfide nickel ore exploration over the past 20 years and the annual decline in global sulfide nickel ore resources, the extraction of nickel and cobalt from laterite nickel ore has become increasingly important. Consequently, the nickel industry worldwide has shifted its focus on resource development to laterite nickel ore.

[0003] The world's laterite nickel ore is mainly distributed in tropical countries within 30 degrees north and south of the equator, and is concentrated in the tropical and subtropical regions of the Pacific Rim. Laterite nickel ore is a surface weathering crust deposit resource formed by weathering, leaching and sedimentation of nickel sulfide ore rock, and has a high water content. The main components of laterite nickel ore include nickel, iron, copper, silicon, titanium and chromium. Among them, the nickel content is generally between 1% and 2%, and the iron content is relatively high, usually accounting for 30% to 50% of the total mass. The iron element is severely oxidized to a +3 valence state, resulting in an overall reddish-brown appearance, hence the name laterite nickel ore.

[0004] Laterite nickel ore can produce intermediate products such as nickel oxide, nickel sulfide, and nickel iron. Nickel sulfide and nickel oxide can be used by nickel refineries to address the shortage of nickel sulfide raw materials. Nickel iron facilitates stainless steel manufacturing, reducing production costs. Furthermore, nickel-based cathodes such as nickel-manganese-cobalt and nickel-cobalt-aluminum occupy a major share of the electric vehicle battery market. With the vigorous development of the new energy electric vehicle industry, new energy vehicle production has increased rapidly year by year. The future development prospects and market growth potential of new energy vehicles are enormous, and the demand for nickel, cobalt, and other materials in the new energy market is increasing year by year.

[0005] Ore dressing is the process of crushing and grinding the ore based on the physical and chemical properties of the different minerals in the ore. Then, using methods such as gravity separation, flotation, magnetic separation, and electrostatic separation, the process separates useful minerals from gangue minerals, minimizes the separation of various associated useful minerals, and removes or reduces harmful impurities to obtain raw materials needed for smelting or other industrial processes. Ore dressing can enrich the useful components in the minerals, reduce fuel and transportation consumption during smelting or other processing, and economically utilize low-grade ores. For some difficult-to-select ores, mineral dressing alone may not produce satisfactory results or may even be impossible to separate. Therefore, a combined mineral separation and metallurgical process is required. This combined mineral separation and metallurgical process is a process that alternates mineral processing with metallurgical methods to treat the ore.

[0006] Currently, nickel ore is primarily smelted using either pyrometallurgical or hydrometallurgical processes, producing high-grade nickel matte or intermediate nickel cobalt hydroxide (MHP), respectively. High-grade nickel matte is a eutectic of nickel, copper, cobalt, and iron sulfides, resulting from the primary smelting of nickel concentrate in an electric furnace or converter. Pyrometallurgical smelting involves mixing laterite nickel ore with coal, removing moisture in a rotary kiln, and reducing metal oxides such as nickel and iron into elemental metal alloys. This is then further refined and blown to remove impurities, producing high-grade nickel matte. Furthermore, the primary process for producing high-nickel matte from nickel ore involves smelting the ore to produce low-nickel sulfur, which is then blown to produce high-nickel matte.

[0007] Chinese patent CN111172384B discloses a method for reducing, enriching, and recovering nickel and cobalt from nickel-cobalt polymetallic oxide ores, comprising: crushing and finely grinding the nickel-cobalt polymetallic oxide ore, and then uniformly mixing it with a carbonaceous reducing agent, a metallizing agent, and water to form green pellets; drying and preheating the green pellets, and then transferring them to a reduction device lined with a carbonaceous refractory material or a carbon-containing composite refractory material, and reducing and roasting them at 900-1250°C to obtain metallized pellets; cooling, crushing, and finely grinding the metallized pellets, and then subjecting them to magnetic separation or gravity separation to obtain a nickel-cobalt mixed concentrate and middlings; scavenging the middlings to obtain a scavenged concentrate and scavenged tailings; and returning the scavenged concentrate to pelletization.

[0008] The prior art has at least the following defects: the charge in the kiln is prone to nodules.

[0009] Kiln nodules are manifested by the charge sintering into large lumps that stick to each other or hang on the wall. In severe cases, the kiln needs to be stopped for treatment, affecting normal production. Therefore, it is urgent to provide a method for obtaining nickel-iron alloy by smelting laterite nickel ore to solve the technical problem of easy nodulation of kiln charge in the existing technology, so as to improve production efficiency and reduce production costs.

[0010] In existing technology, the direct reduction to smelting furnace smelting process for laterite nickel ore using a rotary kiln or rotary hearth furnace involves crushing, screening, and grinding the ore. A reducing agent (coal powder) and a flux (limestone) are then added and mixed. Carbon-containing pellets are then formed using a disc pelletizer or a double-roller pelletizer. These carbon-containing pellets are then fed into a kiln for direct reduction to form metallized pellets. These metallized pellets are then smelted in a smelting furnace to separate the slag and iron, yielding a nickel-iron alloy. In short, this process is similar to the ironmaking to steelmaking process. However, the roles and consumption of the reducing agents and fluxes differ in the selective reduction and selective oxidation processes. In particular, since laterite nickel ore has a low nickel content and a high slag volume, the optimal smelting process requires corresponding modifications based on the raw material differences. Summary of the Invention

[0011] In order to remedy the defects of the prior art, the present invention provides a method for obtaining nickel-iron alloy by smelting laterite nickel ore. The object of the present invention is achieved through the following technical solutions:

[0012] A method for obtaining nickel-iron alloy by smelting laterite nickel ore comprises the following steps:

[0013] Crushing the raw ore of laterite nickel ore into powder, mixing it with fine-grained coal and return ore in proportion to obtain a batch material, wherein the return ore is slag particles produced after slag sorting; using a double-roll briquetting machine to press the batch material into balls;

[0014] The complete pellets are fed into a preheating zone at the top of a vertical calcining furnace. The vertical calcining furnace is surrounded by vertical furnace walls, and the interior space of the furnace body is divided into several vertically arranged furnace chambers by inclined partitions. The furnace chambers are connected by gates. The gates are used to control the material level and / or discharge rate, so that the pellets in the preheating zone form a fixed bed.

[0015] The preheated pellets are discharged from top to bottom into the calcining zone, where they encounter hot air. The hot air originates from the waste heat of slag cooling or is generated in the combustion chamber at the bottom of the furnace body. The hot air passes through the partition from bottom to top and enters the calcining zone. Metallized pellets are obtained by selective reduction reaction. The waste gas generated during the calcining process flows upward into the preheating zone, drying the pellets entering the kiln.

[0016] The metallized pellets and flux are fed into a smelting furnace, and smelted and separated to obtain nickel-iron alloy.

[0017] In a specific embodiment, after the batch material is pressed into pellets, the formed pellets are screened, and the pellets under the screen are returned for re-pelleting;

[0018] During the calcination process, the calcination temperature is controlled within the range of 700-800℃, and the ratio of CO2 to CO partial pressure is greater than 0.5; the waste gas generated by calcination is drawn out from the top of the furnace and discharged into the atmosphere after purification;

[0019] After obtaining the nickel-iron alloy, a slag tapping operation is performed to discharge the smelting slag from the slag outlet of the smelting furnace. The slag is cooled, ground and sorted to become slag particles and slag powder; the slag particles are added to the batch material as return ore, and by adjusting the addition ratio, products with different nickel contents are produced; alternatively, the slag particles are used as ironmaking raw materials; wherein, the method of cooling the slag includes water quenching or air quenching.

[0020] In a specific possible implementation scheme, there are multiple ways to obtain the hot air, including: using a blower to extract the hot air from the slag quenching section and send it to the vertical calciner; or, selecting coal gas and / or auxiliary fuel as needed, the auxiliary fuel includes coal powder, petroleum coke, and using the combustion of fuel in the combustion chamber to provide the hot air for the calcination of the pellets and adjust the combustion atmosphere; wherein the coal gas used in the combustion chamber is recovered from the exhaust gas generated by the vertical calciner, and / or comes from the smelting furnace; by using ordinary coal to provide the coal gas as fuel for the vertical calciner, the constraints on fuel variety are alleviated.

[0021] In a specific embodiment, the metallized pellets are discharged from the discharge port of the vertical calcining furnace, cooled, ground and sorted to obtain concentrate and tailings, and the concentrate is returned to the pelletizing process; after repeated smelting, high-grade nickel-iron alloy is obtained.

[0022] In a specific feasible implementation scheme, the metallized pellets and the flux are mixed evenly and then hot-charged into the smelting furnace from the upper part. The flux includes lime blocks or fluorite. The amount of return ore added is adjusted to first smelt a nickel-iron alloy with a nickel content of 8%-10%. The alloy is then transferred to a refining furnace. After adding chromium-containing metal, the stainless steel is produced by vacuum or semi-vacuum blowing using the principle of selective oxidation. When blowing begins, oxygen decarburization is first performed at normal pressure, and vacuum blowing is used in the later stage. The physical heat of the raw materials is fully utilized, which is the sensible heat and latent heat of the material, thereby reducing the energy consumption of smelting.

[0023] In a specific embodiment, after the molten steel is produced, auxiliary raw materials are added to the slag to adjust the chemical composition of the slag, and the slag is remelted, and the inorganic material is manufactured using the slag remelting process. Depending on whether the slag has been remelted and the difference in the slag remelting process, the slag powder obtained is slag fine powder, cement, or fertilizer. The method includes adding coal and limestone to the slag in proportion, adjusting the refined slag into a reducing slag by performing an oxygen blowing operation, allowing the metal oxides therein to be reduced to elemental substances as much as possible to facilitate magnetic separation, and utilizing the remaining slag to generate cement minerals, thereby obtaining cement clinker, which is ground into cement. Alternatively, apatite is added to the slag, melted at a high temperature of 1350-1500°C, and then quenched with water to form a glassy material with a particle size of less than 2 mm, which is dried and ground into calcium magnesium phosphate fertilizer, which is a steel slag phosphate fertilizer. Application of this method can reduce manufacturing costs.

[0024] In a specific embodiment, the hexavalent chromium remaining in the slag is reduced to chromium metal, or trivalent chromium, or tetravalent chromium by remelting the slag to eliminate toxicity.

[0025] In a specific feasible embodiment, during the crushing, pulverizing and sorting process of the slag, components rich in metal elements, i.e., the slag particles, are separated from the slag through the combined operation of a pulverizer, a separator and a classifier; while improving the grade of the raw materials and the metal recovery rate, the gangue minerals in the slag are ground to obtain slag powder, which is collected by a powder collection device.

[0026] In a specific possible implementation scheme, when performing the grinding and sorting operations of the slag, the cooled slag is sent to the grinding mill for grinding, sorted by the separation device, and then the fineness of the slag powder is adjusted by the classifier. The sorting methods include air separation, magnetic separation and / or electric separation.

[0027] In a specific embodiment, the slag is subjected to magnetic separation and fed into the grinding mill, which is a material bed grinding equipment, including a vertical mill or a roller press; after the slag is crushed by the vertical mill, it is fed into the separation device, which is a cyclone separator. Under the action of gravity and centrifugal force, coarse particles and metals are separated from the material as the slag particles, and the slag particles are used as return ore or ironmaking raw materials; the fine material is carried by the air flow and transported to the powder classifier, which is a rotor type powder classifier. After air separation, the fine material The coarse powder and medium-coarse powder are returned to the vertical mill after magnetic separation and / or electric separation and crushed again; the particle size of the fine powder is adjusted by adjusting the rotation speed of the rotor of the rotor-type powder concentrator, and the fine powder that meets the requirements passes through the cage-type rotor and is discharged with the air flow. The fine powder, i.e., the slag powder, is collected by the powder collecting equipment; the powder collecting equipment includes a dust collector, which is a bag dust collector or an electric dust collector, used for product collection and environmental protection; after the exhaust gas of the grinding system is purified, it is drawn out by the induced draft fan connected to the powder collecting equipment and discharged into the atmosphere.

[0028] The present invention can achieve the following beneficial technical effects by improving the calcination process, including:

[0029] (1) Adjust the proportions and reduce the amount of flux added. The insufficient amount can be supplemented during the melting stage. The batch material is pressed into balls by the pressing method, so the initial strength is high and the broken materials are few. Moreover, the balls are of uniform size and large diameter. Under natural stacking conditions, the outside of the balls is ventilated, while the inside is often in an oxygen-deficient state. Under high temperature conditions, a reducing atmosphere is generated, the temperature is difficult to increase, and the amount of liquid phase generated is relatively limited.

[0030] (2) A vertical calcining furnace is used, wherein an inclined ventilation partition is provided inside the vertical calcining furnace; after the pellets are fully dried in the preheating zone, they fall into the calcining zone by gravity, and the pellets are calcined while moving and are not easy to stick together until sintering is completed to generate the metallized pellets.

[0031] Based on this, the present invention can overcome the influence of adverse factors during the calcination process and eliminate charge nodules.

[0032] If the relevant technology is directly used, such as the batching scheme of sintered ore smelted in a blast furnace, it is inappropriate; for ordinary technicians in this field, it is necessary to understand the above knowledge and make improvements, which is obviously difficult. This is also the reason why the relevant technology cannot achieve this beneficial effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram of an embodiment of the present invention;

[0034] Figure 2 4 is a flow chart of slag grinding according to an embodiment of the present invention.

[0035] Description of reference numerals: 1-vertical calcining furnace; 11-furnace wall; 12-partition plate; 13-gate;

[0036] 2- melting furnace; 21- blower;

[0037] 3-vertical mill; 31-cyclone separator; 32-rotor powder separator;

[0038] 4-dust collector; 41-induced draft fan. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention. It should be noted that the present invention can be implemented in a variety of different ways as defined and covered by the claims. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other.

[0040] It should be additionally pointed out that, in a specific embodiment, the several embodiments provided by the present invention constitute a complete process for smelting laterite nickel ore, which starts from batching, passes through slag and iron separation, and ends with slag grinding. In the four major stages of roasting, smelting, slag remelting and slag grinding, it is necessary to understand the principles of selective reduction, selective oxidation, re-reduction and selective crushing, respectively. The principles mentioned are all described in the text; the technical problem solved by the present invention is not just to eliminate charge nodules, which should be understandable.

[0041] Among the existing technologies, the pyrometallurgical process was developed earlier and is relatively mature, with wide industrial applications. Currently, it mainly includes the rotary kiln → submerged arc furnace nickel-iron process (RKEF process) and the blast furnace smelting process.

[0042] (1) RKEF method: RKEF method is a widely used pyrometallurgical smelting process for laterite nickel ore, which is mostly used to produce high-nickel iron. The basic process of RKEF method is pre-drying, roasting, and reduction smelting. The raw ore of laterite nickel ore is sent to a drying kiln to reduce the moisture content to about 20%. Then, the ore, flux, reducing agent, etc. are mixed in proportion and sent to a rotary kiln for reduction roasting. The hot roasted sand produced by the rotary kiln is sent to an electric furnace for reduction smelting. The crude nickel iron obtained is then smelted in a refining electric furnace to produce nickel iron. The RKEF method is mature in technology, simple and easy to control equipment, and has high production efficiency. However, its disadvantages are that it consumes a large amount of metallurgical coke and electricity, resulting in high energy consumption, high production costs, excessive slag in the smelting process, high smelting temperature, and dust pollution. The RKEF method is suitable for processing nickel oxide ores (laterite nickel ore) with a nickel content of more than 1.5%, producing nickel iron with a nickel mass fraction of 20%-30% and a nickel recovery rate of 90%-95%. It can also be used to produce nickel iron alloys containing 8%-10% nickel for stainless steel production.

[0043] (2) Blast furnace smelting process: It is suitable for producing medium-nickel iron or low-nickel iron products, and is facing elimination due to the use of small blast furnaces; the main process of blast furnace smelting process is: the laterite nickel ore is dehydrated, sintered and agglomerated, and then mixed with coke and flux, and sent to the blast furnace for smelting to produce crude nickel iron, which is then refined to obtain nickel iron; the blast furnace smelting process is suitable for processing ores with low nickel content to produce medium-nickel iron or low-nickel iron products. Although its investment is low, due to the use of a volume of less than 300m 3 The small blast furnaces are facing elimination.

[0044] Compared with the prior art, the present invention has a simple structure, a reasonable design, and is easy to implement. In the embodiments of the present invention, a variety of optional implementation methods are provided, which can be selected according to actual needs. No matter which method is adopted, the prior art is no longer used for the smelting production of laterite nickel ore, and the problems in the prior art can be solved and corresponding effects can be achieved. For example, if high-grade nickel is used to produce stainless steel, this is not the most economical option. The present invention can adjust the grade of nickel in the nickel-iron alloy product as needed to directly produce stainless steel. The following embodiments can be applied to the smelting of laterite nickel ore, and can also be applied to the smelting of stone coal vanadium ore, etc. Therefore, the application of the present invention includes but is not limited to the smelting of laterite nickel ore.

[0045] Example 1

[0046] In this embodiment, laterite nickel ore is batched and pressed into pellets, which are then dried and reduction-roasted to form metallized pellets. The metallized pellets are then smelted in a furnace to obtain nickel-iron alloy.

[0047] See Figure 1 This embodiment provides a method for obtaining nickel-iron alloy by smelting laterite nickel ore, comprising the following steps:

[0048] Step 10: crushing the raw ore of laterite nickel ore into powder with a maximum particle size not exceeding 1-2 mm, mixing it with fine-grained coal and return ore in proportion, and stirring evenly to obtain a batch material; adjusting the proportion of the return ore as needed to produce products with different nickel contents; wherein the return ore is slag particles after slag sorting, and the slag particles are often rich in metal elements and can improve the metal recovery rate; and the slag particles act as crystal seeds, can induce crystallization, lower the reaction temperature of the system, and accelerate the reduction reaction.

[0049] Step 20, using a double-roll ball press to press the batch material into balls with a diameter of preferably 40-50 mm; the formed balls are screened, and the broken balls under the screen are returned to be re-balled; because they are pressed and formed, the obtained balls have high initial strength and are not easy to break during production; the ball diameter is large and uniform, the ventilation effect is good, the calcination is uniform, and it is conducive to smelting; the raw ore has moisture, and no additional water is needed when making balls, which can save water resources.

[0050] Step 30, the complete pellets are fed into the vertical calcining furnace 1, and the pellets are preheated and calcined from top to bottom to obtain metallized pellets; the vertical calcining furnace 1 is surrounded by a vertical furnace wall 11, and the internal space of the furnace body is divided into several furnaces arranged up and down by inclined partitions 12; the furnaces are connected through gates 13; the furnace located at the top of the furnace body is a preheating zone, and the gate 13 is used to control the height of the material level and / or the unloading rate to control the pellets in the preheating zone to form a fixed bed; the partition 12 is a porous plate or a grate; wherein, the furnace located at the bottom of the furnace body is a combustion chamber, and gas and / or auxiliary fuel are selected according to needs and sprayed into the combustion chamber, and the auxiliary fuel includes coal powder, petroleum coke, etc. The fuel burns in the combustion chamber, which can provide hot air for the calcination of the pellets and adjust the combustion atmosphere.

[0051] In this embodiment, the hot air inhaled by the combustion chamber comes from the slag air quenching section and is high-temperature and oxygen-rich. It is extracted by the blower 21 and sent to the combustion chamber of the vertical calcining furnace 1. The hot air passes through the partition 12 from bottom to top and enters the calcining zone. The preheated (dried) balls are unloaded from top to bottom into the calcining zone, meet the hot air, and complete the calcination. This realizes the utilization of waste heat and energy saving.

[0052] The waste gas generated during the calcination process continues upward, entering the preheating zone, where it undergoes heat exchange with the kiln pellets, drying them. The waste gas cools down, exits the furnace roof, and is purified before being discharged into the atmosphere. The coal gas used in the combustion chamber can be recovered from this waste gas. In steel mills, beneficial components in the high-temperature waste gas are separated and recovered. Gas recovery is primarily accomplished through physical and chemical methods. Physical methods include cooling, purification, and conditioning, while chemical methods employ absorption, adsorption, and desorption techniques, which are not detailed here.

[0053] After the pellets are piled up, their outer space is loose and breathable. After the coal in the outer shell of the pellets is completely consumed, charcoal often remains inside. The interior of the pellets is in an oxygen-deficient state, and a reducing atmosphere is easily formed at high temperatures, which facilitates the completion of the pre-reduction reaction of the pellets. Specifically, the nickel oxide in the raw material is reduced to form small droplets of metallic nickel, which are embedded in the ore particles, thus forming metallized pellets. The reduction of iron is a stepwise reduction process, i.e., Fe2O3 → Fe3O4 → FeO. To increase the nickel content in laterite nickel ore, the reduction conditions should be controlled so that the Fe2O3 in the ore is reduced to FeO, but not to metallic iron, so as to separate it from the already reduced metallic nickel. This is called selective reduction, and the conditions are the appropriate temperature and atmosphere, which are adjusted as needed. In this embodiment, the temperature is controlled within the range of 700-800°C, and the furnace atmosphere is adjusted to a ratio of CO2 to CO partial pressure greater than 0.5, to avoid the formation of metallic iron while allowing the nickel oxide to be smoothly reduced to elemental nickel.

[0054] By comparing with the existing technology, we can find the following differences:

[0055] 1. The ball obtained by compression molding in the present invention has high initial strength and is not easy to break during production;

[0056] 2. The kiln structure of the present invention forces the balls to be calcined while in motion, without the chance of them sticking to each other;

[0057] 3. The present invention does not add flux to the ingredients of the pellets to prevent the large-scale generation of low-melting-point minerals; the flux is added to the system only during smelting; that is, in the pellet ingredients of related technologies, lime is added in advance; the present invention does not add lime to the pellets, that is, lime blocks and fluorite are not added during the calcination stage, but are added during the smelting stage, at which time there is no need to worry about nodules; therefore, premature reaction can be prevented and nodules can be reduced.

[0058] In summary, the material loses the conditions for nodules, so the present invention can eliminate nodules in the reduction roasting stage, achieving the purpose of the invention. In addition, the present invention uses the vertical calcining furnace 1 for pre-reduction, which has other advantages, mainly manifested in:

[0059] 1. In a traditional bed, when the gas passes through a uniform solid particle bed from bottom to top at a relatively low speed, the gas only passes through the gaps between the stationary solid particles, and the height of the solid particle bed remains basically unchanged. Such a bed is called a fixed bed. As the gas flow rate increases, the solid particle bed begins to loosen, the relative positions of the solid particles are also adjusted within a certain area, and the bed height increases slightly. As the gas flow rate increases further, it is about to enter the fluidization and pneumatic transport stage. Different from the traditional bed, the present invention adds an inclined partition 12 in the furnace, and the air flow passes through the inclined partition 12 from bottom to top. With the help of gravity, only a small amount of air flow is needed to loosen the material layer to form fluidization and complete the material transportation. Therefore, the present invention can reduce the amount of air used.

[0060] 2. Because the material is in a fixed bed in the preheating zone, the material stays in the preheating zone for a long and controllable time, the gas flow rate is adjustable, and after sufficient heat exchange, the air flow slowly escapes from the fixed bed. The exhaust gas transfers almost all of its own heat to the material before being discharged from the vertical calcining furnace 1 at a temperature close to the ambient temperature. Therefore, the present invention can reduce heat loss.

[0061] 3. Although pulverized materials heat up quickly, this speed and heat consumption are two separate things. While pulverized materials heat up faster due to the increased contact area, the heat transfer efficiency (heat consumption) is not only related to the speed but also the time required for the heat transfer. Furthermore, pulverization is a significant energy consumer. While ensuring quality, reducing energy consumption (the sum of electricity and heat consumption) is the ultimate goal of the calcination industry. Therefore, as long as the equipment's insulation is adequate, time can be traded for energy consumption. Simply adhering to the suspension process is unscientific. For example, the vertical kiln pre-water pelletizing process, in which pellets are formed by bonding powders, uses water during the pellet forming process. In competition with the new dry process (suspension process), the average heat consumption of vertical kiln calcination in advanced regions reached 850 kcal / kg of clinker, comparable to the suspension process. In other words, the suspension process does not guarantee lower heat consumption, and its use is not essential.

[0062] Therefore, we can also realize that:

[0063] (1) The present invention adopts a fixed bed in the preheating stage, which can reduce the amount of air used and lower the exhaust gas emission temperature, thereby improving the thermal efficiency.

[0064] (2) The furnace of the vertical calcining furnace 1 of the present invention adopts a multi-chamber structure. The material falls back and forth, heat is evenly exchanged, and calcined in a dynamic state. The calcination intensity can be adjusted, which is beneficial to ensuring product quality.

[0065] In step 40, the metallized pellets are discharged from the discharge port of the vertical calcining furnace 1 and fed into the smelting furnace 2. After adding a flux, they are smelted. The flux includes lime blocks or fluorite. During the smelting process, the metal and the flux often contain impurities and non-metallic substances. After adding the lime blocks, the lime can react with these impurities and non-metallic substances to form easily separable slag, which floats up. After the slag is removed, the purity of the metal can be improved. Fluorite is a fluorine-containing mineral, also known as fluorspar, which is used as a flux in steelmaking. Adding fluorspar can lower the melting point of lime, improve the fluidity of the slag, and improve the desulfurization efficiency.

[0066] In this embodiment, the metallized pellets generated after selective reduction (pre-reduction) are hot-charged into the furnace from above (1000°C), fully utilizing the physical heat of the raw materials. The vertical calcining furnace 1 is matched with the smelting furnace 2, allowing the smelting furnace to receive the metallized raw materials. The metallized pellets are further reduced and melted within the furnace, separating the slag and iron, thereby significantly improving production efficiency. The smelting furnace 2, also known as the molten gasification furnace, typically uses approximately 300 kg of briquettes per ton of molten iron produced, saving coke and coking coal resources. The smelting furnace also provides coal gas for the vertical calcining furnace 1, alleviating the constraints of raw material grade in direct reduction and enabling the use of common coal types for direct reduction.

[0067] In this embodiment, the smelting furnace is a mechanical equipment that uses the heat generated by electric arc discharge to smelt metals. It is mainly used for smelting, heating and heat treatment of steel, ferroalloys, non-ferrous metals, etc. The furnace body of the smelting furnace is cylindrical or rectangular, generally made of steel, and the furnace cover and furnace bottom are built of refractory materials in sequence; electrodes are provided inside the furnace body of the smelting furnace, and below the electrodes is a smelting pool inside the furnace body. There is a protective layer on the bottom of the pool to prevent the cooling effect of the furnace bottom.

[0068] Laterite nickel ore primarily contains a variety of oxides, including NiO, Cr2O3, Fe2O3, Al2O3, and SiO2. Within the melting point range of laterite nickel ore (1300°C-1400°C), the stability of the oxides follows the order: Al2O3 > Cr2O3 > CaO > MgO > Fe2O3 > SiO2 > FeO > NiO. Therefore, NiO is reduced first, and the reduction temperature is lower than that of FeO. By utilizing the principle of selective reduction and adopting a carbon-deficient operation, almost all of the NiO in the laterite nickel ore is preferentially reduced to metallic nickel, while a moderate amount of the high-valent Fe2O3 is reduced to metal, and the remainder is reduced to FeO and enters the slag, thereby achieving nickel enrichment.

[0069] Modern smelting technology generally utilizes the above-mentioned difference to achieve the separation of nickel and iron by adjusting the temperature and atmosphere in the furnace. For example, this embodiment utilizes this principle to mix crushed laterite nickel ore with a reducing agent (fine-grained coal) to form pellets. Under a protective atmosphere, a self-reduction product is obtained. The self-reduction product is selectively oxidized in a weakly oxidizing atmosphere to obtain an oxidation product. After the oxidation product is melted, the metal is separated from the gangue to obtain a high-grade nickel-iron alloy. In short, the production process of nickel-iron alloy is a process of reduction followed by oxidation.

[0070] The nickel content in laterite nickel ore is generally between 1% and 2%. If the raw material grade is too low, the metallized pellets can be cooled, ground, and sorted, with the concentrate returned for pelletizing and the tailings made into ore powder. Alternatively, during the smelting process, the smelting slag discharged from the slag outlet of the smelting furnace 2 can be crushed, ground, and then beneficiated. This, applied in this embodiment, is equivalent to returning ore and improves metal recovery. Typically, the slag undergoes multiple air (water) quenching, crushing, and sorting processes. Repeated smelting and continuous enrichment can improve the raw material grade, facilitate smelting, and produce high-grade nickel-iron alloy. This method produces a high-grade nickel-iron alloy product with a nickel content of 30%.

[0071] It is worth mentioning that the nickel content of stainless steel is one of the key factors affecting its performance. Different types of stainless steel contain different ranges of nickel content. Different nickel contents give stainless steel different corrosion resistance, mechanical strength and heat resistance, making it suitable for different application scenarios to meet different application needs; however, nickel-iron smelting is a high-energy consumption industry after all, and the price of high-grade nickel-iron alloy is relatively high. If high-grade nickel-iron alloy is used to produce stainless steel, it does not seem to be the best choice; therefore, according to needs, the amount of return ore added is adjusted to produce nickel-iron alloys with different nickel contents, including first smelting nickel-iron alloy with a nickel content of 8%-10%, and then transferring it to a refining furnace, adding chromium-containing metal and refining, and directly producing stainless steel, which can achieve better social and economic benefits.

[0072] Iron and nickel differ in many chemical properties. Iron is very active and readily reacts with oxygen in the air to form iron oxide. Nickel is less active than iron and, therefore, is not as easily oxidized as iron. Nickel is more stable and corrosion-resistant than iron and is not easily corroded by oxidation, sulfide, or alkaline substances. Utilizing this property, nickel is used to manufacture stainless steel, a material characterized by its rust-proof and corrosion-resistant properties, containing at least 10.5% chromium and a maximum carbon content of no more than 1.2%.

[0073] When it comes to stainless steel smelting, selective oxidation is unavoidable. Here's an example: at steelmaking temperatures, when carbon and chromium encounter oxygen simultaneously, the oxidation process must occur in a certain order. This is determined by the element's affinity for oxygen: the element with the greater affinity oxidizes first. This order of oxidation is known as selective oxidation. This affinity, in turn, is related to the oxidation transition temperature (OTT), which is the intersection of the Gibbs energy change and temperature relationship between the two elements. When the smelting temperature is above the OTT, carbon is more reactive than chromium and oxidizes first. When the smelting temperature is below the OTT, chromium is more reactive than carbon and oxidizes first. In other words, chromium oxidation is more likely to occur at lower smelting temperatures, especially before reaching the specified OTT.

[0074] When using the oxygen blowing method to produce austenitic stainless steel, after the carbon in the molten iron is oxidized, 2%-2.5% of the metallic chromium will also be oxidized and enter the slag, resulting in chromium loss. Therefore, in order to reduce the oxidation loss of chromium, the molten pool temperature must be much higher than the smelting temperature of ordinary steel grades to allow the carbon in the molten iron to oxidize first. This is usually achieved by increasing the smelting temperature to ensure that the chromium is not over-oxidized during the smelting process. Regarding the blowing of stainless steel, before the birth of the oxygen blowing method, no one could produce stainless steel at a low cost, and this is the reason. For how to remove carbon and retain chromium, you can refer to the high-carbon vacuum oxygen blowing method, which achieves carbon removal and chromium retention by adjusting the temperature and atmosphere;

[0075] For example, according to metallurgical physical and chemical calculations, when the CO partial pressure is less than the standard atmospheric pressure of 101325Pa, the oxidation conversion temperature can be reduced. The smaller the partial pressure, the lower the oxidation conversion temperature. For another example, when the carbon monoxide partial pressure Pco = 10132Pa, the chromium content W[Cr] = 18%, the carbon content W[C] = 0.05%, the oxidation conversion temperature is only 1601℃, which is achievable in production. In order to blow ultra-low carbon stainless steel, such as carbon content W[C] = 0.0 2%. When Pco = 5066 Pa, the oxidation conversion temperature is 1631°C, which is still feasible. Using vacuum or semi-vacuum blowing, chromium can be fully added in one go. However, if smelting is performed under atmospheric pressure with oxygen blowing, chromium cannot be fully added in one go; otherwise, the oxidation conversion temperature is too high for the equipment to withstand. Furthermore, the higher the carbon content, the lower the oxidation conversion temperature. Therefore, at the beginning of blowing, oxygen blowing can be used for decarburization at atmospheric pressure. However, once the carbon content (W[C]) drops to a certain level, vacuum blowing must be used. This embodiment employs the above-described refining operation. After smelting is completed, the slag and iron are separated, and the nickel-iron alloy (including stainless steel) is removed from the system as a product.

[0076] Step 50: Execute slag removal operation, which includes water quenching or air quenching. After the slag is cooled and crushed, it can be stored separately and used as needed.

[0077] During normal smelting, depending on the slag tapping period, the slag is often divided into reducing slag and oxidized slag, with different chemical and mineral compositions. The most common reducing slag is the slag produced by blast furnace ironmaking; the metallized pellets in this embodiment also constitute reducing slag. The most common oxidized slag is the steel slag produced by steelmaking; in this embodiment, the oxidized slag includes refined slag after oxygen blowing and decarbonization. The oxidized slag is formed during the refining process, particularly during oxidation refining, where oxygen is blown to remove impurities from the metal, particularly carbon and other easily oxidized impurities. This process not only helps to improve the purity of the metal, but also optimizes the refining effect by controlling the composition and properties of the slag.

[0078] Step 60, the slag is ground and sorted to obtain slag particles and slag powder;

[0079] The slag is ground and sorted into slag particles and slag powder, and the sorting includes air separation, magnetic separation, and electric separation; wherein the obtained slag particles can be used as return ore as needed and mixed with the batch material in proportion for pelletizing; or, the slag particles can be used as metallurgical raw materials, such as for ironmaking.

[0080] Under normal circumstances, the slag powder becomes slag powder; further, the slag powder is cement, or steel slag phosphate fertilizer. For example, the slag composition is adjusted by slag remelting, and the slag is used as cement clinker, which is ground into cement; or steel slag phosphate fertilizer is manufactured by remelting the slag.

[0081] Example 2

[0082] During the steelmaking process, iron and other metal raw materials are placed in a furnace and heated to melt and fuse. The molten metal is then separated into two parts: slag and molten steel. Molten steel is a liquid mixture of pure iron and other ingredients, while slag is a mixture of various non-metallic oxides and impurities. Slag comes from:

[0083] (1) Gangue in an ore, which is usually aluminosilicate;

[0084] (2) Oxides formed during the refining process of crude metals;

[0085] (3) Furnace lining materials (refractory bricks) that are eroded and washed away during the smelting process;

[0086] (4) Fluxes added during the smelting process, such as lime and fluorite added to produce slag with a certain fluidity and desulfurization and dephosphorization capabilities.

[0087] Steelmaking is the process of modifying the composition and properties of steel through heating and the addition of other elements. Slag plays a major role in the smelting process, separating impurities, concentrating useful metals, and completing oxidative refining. The composition of the slag determines its solubility. During this process, the slag must be kept at a sufficient temperature for a sufficient period of time to completely dissolve and achieve the best results in improving the composition and properties of the steel. During steel production, tapping (discharging molten steel) is never a complete process, and residual steel will inevitably remain in the slag. This is typically done by tapping the steel first, followed by removing unrefined useful metals and other substances from the slag. This practice is commonly used in blast furnaces such as electric arc furnaces and converters. In existing technology, after tapping, the slag completes its historical mission and is treated as waste, with the most common use being as a low-value cement admixture.

[0088] This invention introduces the concept of slag remelting for the first time. This involves adding auxiliary raw materials to the slag after steel tapping, remelting it, and adjusting its chemical composition. This invention utilizes slag through the slag remelting process to produce inorganic materials such as cement and fertilizer. For example, based on Example 1, this embodiment performs slag remelting before the slag tapping operation in step 50 to produce cement clinker.

[0089] In conventional cement clinker production, several rate values ​​of raw materials are mainly controlled, including lime saturation coefficient (KH), silicon rate (SM) and aluminum rate (IM). The rate values ​​can simply express the relationship between chemical composition and mineral composition, clearly indicate the performance of cement clinker and its influence on calcination, and are the basic elements of cement production quality control. Among them, KH represents the degree to which silicon dioxide in the clinker is saturated with calcium oxide to form tricalcium silicate, which is generally controlled at around 0.9; the silicon ratio is the ratio of the SiO2 content to the sum of the Al2O3 and Fe2O3 contents in the clinker, which is generally controlled at around 2.2, and the silicon ratio reflects the amount of the liquid phase; the aluminum ratio is the ratio of the Al2O3 content to the Fe2O3 content in the clinker, which is generally controlled at around 1.5, and the aluminum ratio reflects the viscosity of the liquid phase; because unlike conventional production, this embodiment uses slag to produce clinker, so the control of the silicon ratio and the aluminum ratio is not very important. This embodiment mainly focuses on the size of the lime saturation coefficient (KH). In the smelting industry, the concept of the basicity of the slag is similar to it.

[0090] During the slag making process, by adjusting the basicity of the slag, most of the sulfur can be incorporated into the slag. Therefore, the slag has a strong desulfurization effect, which not only ensures the quality of the molten steel but also reduces the emission of SO2. The basicity is an index that represents the characteristics of the slag, usually expressed as the ratio of basic oxides (such as CaO) to acidic oxides (such as SiO2). The basicity of the slag has a significant impact on the performance of the slag. As the basicity increases, the fluidity of the slag improves. Moreover, during the smelting process, with the continuous addition of lime, As the alkalinity of the slag increases, its main mineral composition also transforms from CRS (olivine) → C3RS2 (rhodonite) → C2S (dicalcium silicate) → C3S (tricalcium silicate); among them, under hydrothermal conditions, olivine can be transformed into magnesium-containing hydrated silicates (such as serpentine and talc). It is generally believed that the temperature condition for this reaction to occur must reach at least 400°C, which shows that olivine is inert and therefore will not affect the performance of cement; among them, dicalcium silicate and tricalcium silicate are the dominant source minerals of cement gelling properties.

[0091] The main mineral components of Portland cement include tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite. The combined content of tricalcium silicate and dicalcium silicate exceeds 70%, playing a dominant role in cement's gelling properties. Tricalcium silicate undergoes a rapid hydration reaction, releasing a large amount of heat, contributing significantly to cement's early strength. Dicalcium silicate, on the other hand, significantly influences cement's later strength. The combined effect of these two minerals gives cement its excellent gelling properties, making it an indispensable component of concrete and other cement-based materials. During the calcination of cement clinker, some metal oxides, such as iron oxide from ferrous raw materials and steel slag, organically combine with other minerals in the clinker to form a eutectic, which then dissolves into the clinker. This solubilization not only ensures the clinker's strength but also acts as a mineralizer, promoting the raw meal's burnability and shortening the clinker calcination time.

[0092] In the prior art, slag is typically used as a cement admixture. This embodiment incorporates auxiliary raw materials into the slag and remelts it to produce cement clinker. The slag powder of the present invention achieves high added value. That is, while conventional slag is typically added to cement as an admixture, the present invention utilizes the slag to directly generate silicate minerals, such as tricalcium silicate and dicalcium silicate, which serve as the dominant minerals in cement and are the primary source of cement's gelling properties.

[0093] Moreover, there are the following differences:

[0094] Conventional sintering techniques minimize the formation of dicalcium silicate during batching, as this dicalcium silicate has four crystal forms. Slow cooling can cause these crystal forms to transform, leading to volume expansion and internal stress, which can lead to pulverization of the sintered ore and hinder sintering. In contrast, the present invention adjusts the batching ratio after steelmaking to maximize the production of dicalcium silicate and other minerals beneficial to cement performance in the slag. C2S (dicalcium silicate) readily transforms from β-C2S to the nearly non-hydraulic γ-C2S at temperatures below 500°C, expanding by 10% and causing clinker pulverization. Rapid cooling can prevent C2S crystal form transformation when the liquid phase is high. Furthermore, for most silicate minerals, slow cooling can reduce their hydration activity due to overly complete crystal development. Therefore, during slag tapping, water or air quenching is used to rapidly cool and fragment the slag, allowing it to quickly cross the crystallization temperature range and form glass or microcrystals, avoiding excessive crystallization that leads to coarse crystals and reduced activity. Among common cement minerals, dicalcium silicate has a relatively low heat of hydration. Therefore, this embodiment is suitable for producing medium-heat silicate cement and low-heat silicate cement.

[0095] In this embodiment, coal and limestone are added to the slag in proportion, and by performing an oxygen blowing operation, the refined slag can be adjusted to a reduced slag, so that the metal oxides therein are reduced as much as possible to form a single substance, which is convenient for magnetic separation; the remaining slag generates cement minerals, thereby obtaining cement clinker, and the cement clinker is ground into cement; during the grinding process, the metal elements are separated from it through selective crushing. In other words, through the remelting of the slag, most of the slag can be made into cement clinker, and then in the production process of grinding the clinker, the useful metal components therein are recovered, and the remaining slag is made into cement. Therefore, the present invention can not only improve the quality of steel and increase production efficiency, but also make full use of mineral resources and the sensible heat of the slag to avoid waste.

[0096] Optionally, a reducing agent can be added as needed, and the smelting temperature and atmosphere can be adjusted to reversely convert the oxidized slag into reduced slag. After the reduced slag is made, the FeO therein is converted into elemental iron, which is convenient for magnetic separation. After separation, it can be used as return ore for smelting nickel-iron alloys, or as a raw material for smelting other products to overcome the loss of metal elements caused by FeO entering the slag. Moreover, the reduction operation can eliminate the interference of iron elements, and the color of the slag changes from gray-black to colorless, making it suitable for producing white cement.

[0097] In addition, certain steel slags can be used as fertilizers in existing technologies. The chemical composition of steel slag phosphate fertilizers varies depending on the quality of the pig iron, the type and amount of flux, and process conditions. When sufficient SiO2 is added, the main components are calcium silicophosphate (5CaO·P2O5·SiO2 and 7CaO·P2O5·2SiO2). When insufficient SiO2 is added, the main components are tetracalcium phosphate (Ca4P2O9). The active ingredient content of steel slag phosphate fertilizers, calculated as P2O5, is typically 16% to 20%. Domestically produced steel slag phosphate fertilizers generally have a P2O5 content of 3% to 8%. Although steel mills in Anshan, Wuhan, Chongqing, and other places produce this fertilizer, its low phosphorus content and high processing costs limit its widespread application.

[0098] In this embodiment, apatite can also be added to the slag, melted at a high temperature of 1350-1500°C, and then quenched with water to form a glassy material with a particle size of less than 2 mm. After drying and grinding, high-quality calcium magnesium phosphate fertilizer can be made. The calcium magnesium phosphate fertilizer can be called molten magnesium phosphate fertilizer, which is a kind of phosphate containing phosphate (PO4 3- ) aluminosilicate glass, the calcium magnesium phosphate fertilizer can be regarded as a kind of steel slag phosphate fertilizer, its main components include Ca3 (PO4) 2, CaSiO3, MgSiO3, it is a multi-element fertilizer, its aqueous solution is alkaline, so it can be used to improve acidic soil, or, when cultivating seedlings, as base fertilizer, slowly releases nutrients, which can be absorbed by plants and has a better effect; using the slag remelting process to produce the steel slag phosphate fertilizer can reduce manufacturing costs.

[0099] Furthermore, the main forms of chromium in the human body are trivalent chromium and hexavalent chromium. Trivalent chromium is one of the essential trace elements for the human body and helps maintain normal physiological functions. However, hexavalent chromium is a toxic substance and poses a potential threat to human health. Hexavalent chromium is a poisonous substance if swallowed / extremely toxic if inhaled. Skin contact may cause allergies and may even cause hereditary genetic defects. Inhalation may cause cancer and pose a long-term risk to the environment. However, these are the characteristics of hexavalent chromium; chromium metal, trivalent chromium, or tetravalent chromium do not have these toxicities. If the hexavalent chromium remains in the slag, the toxicity can be eliminated by remelting the slag and reducing the hexavalent chromium, achieving unexpected results.

[0100] Example 3

[0101] During the smelting process of laterite nickel ore, ferronickel is produced by roasting and electric furnace smelting, which produces a large amount of slag. Specifically, for every ton of ferronickel produced, approximately 7-10 tons of slag is generated, of which nickel slag accounts for the majority. This slag not only occupies a large amount of land but also may cause environmental pollution. Therefore, research on the comprehensive utilization of this slag is of great significance. In this embodiment, during the crushing, pulverizing, and beneficiation of the slag, the combined operation of a grinding mill, a separation device, and a powder separator can improve the raw material grade and metal recovery rate during smelting, and obtain slag powder, cement, or fertilizer.

[0102] See Figure 2 On the basis of Example 1 or Example 2, the obtained slag is fed into the grinding mill for rolling, sorted by the separating device, and then the fineness of the final product is adjusted by the powder classifier. Specifically, the slag after magnetic separation is fed into the grinding mill, and the grinding mill is a material bed grinding device, including a vertical mill 3, or a roller press; the separating device is a cyclone separator 31, and the powder classifier is a rotor-type powder classifier 32; the slag is subjected to rolling, sorting and powder selection, and the sorting means include air separation, as well as magnetic separation and / or electric separation; after sorting, coarse particles and metals are discharged and can be added to the batch as return ore as needed, or used for other metal smelting; coarse powder and medium coarse powder are returned to the grinding mill for rolling again; fine powder is collected as a finished product by a powder collection device.

[0103] In detail, the main working parts of the vertical mill 3 (vertical mill) are the grinding disc and grinding roller. The motor drives the grinding disc to rotate through the reducer, and the grinding roller rolls around its own axis on the grinding disc. The material passes through the air-locking feeding device and the discharge chute to the center of the grinding disc. Due to the action of centrifugal force, an annular material bed is formed and is clamped into the gap between the grinding roller and the grinding disc. It is squeezed and crushed, and at the same time, shear force is generated due to relative sliding, which makes the material finer. The vertical mill uses the grinding roller to squeeze the material on the grinding disc, and relies on the airflow to carry the particles that meet the fineness requirements out of the mill, and collect them in the dust collector to become finished products. Inside the vertical mill, the larger particles in the airflow fall back to the grinding disc under the action of gravity for grinding. This process needs to be repeated many times to achieve the required fineness. The roller press consists of two squeezing rollers that rotate synchronously in opposite directions, one is a fixed roller and the other is a movable roller. Both vertical mills and roller presses are material bed grinding equipment.

[0104] For a long time, the mineral processing industry has generally used tube mills as grinding equipment. These tube mills include ball mills, which contain a certain number of steel balls as grinding media in their cylinders. The main function of the steel balls in the ball mill is to impact and crush the material, while also playing a certain grinding role. The existing technology often uses ball mills, which have extremely low grinding efficiency and high energy consumption. According to research and experimental measurements by grinding workers around the world, the grinding efficiency of tube mills is only a few percent, and the rest is consumed by acoustic energy and wear energy of the grinding media and liner. The fundamental reason is that tube mills usually use the principle of single-particle crushing. In single-particle crushing, each particle is crushed by contact with the crushing equipment and is directly subjected to pressure or shear force. However, material layer crushing is different from this.

[0105] The microstructure of the incoming material determines its mechanical properties. Different mineral structures result in varying resistance to damage. The primary function of the steel balls in ball mills is to impact and crush the material. However, the impact force is indiscriminate, and thus, undesirable particles are often crushed further, leading to over-grinding. Unlike single-particle crushing, bed-type grinding equipment utilizes a bed-type crushing (also known as layer-type crushing) principle. Only a small fraction of the particles come into direct contact with the crushing device. Under pressure, the material is crushed by mutual compression. Layer-type crushing achieves high crushing efficiency, as the material is crushed during this mutual compression process, eliminating unnecessary energy waste and thus saving energy. Furthermore, under normal circumstances, even the hardest minerals are no harder than steel balls. Steel balls strike the material indiscriminately, crushing both soft and hard ores, even those that don't need to be crushed, resulting in energy waste. However, when grinding rollers crush clusters of mineral particles, the softer ores are crushed first, and the softer particles then retreat into the spaces created by the harder ores, thereby avoiding further compression. This avoids energy waste.

[0106] In this embodiment, after the slag is ground by the vertical mill 3, it is fed into the separation device, which is a cyclone separator 31. The cyclone separator 31 is also called a cyclone or a cyclone dust collector. It is a dry gas-solid separation device that uses the centrifugal force generated by the high-speed rotation of the gas-solid mixture to separate solid particles from the air flow; after the slag enters the cyclone separator 31, the coarse particles in the material are separated from the material under the action of centrifugal force; under the same grinding conditions, this part of the material cannot be ground, which is equivalent to the passive screening of the grinding machine; this shows that the coarse particles are most likely metal elements (including iron) or olivine rich in iron, etc., which are all relatively hard; and in the fine material, the content of metal elements is relatively small.

[0107] The slag contains metal elements and olivines rich in metal elements, which are hard and difficult to grind. If they are large pieces, their metal element content is higher and they will be discharged from the slag outlet of the vertical mill 3. What remains is the main body of slag-forming minerals, that is, ordinary silicate minerals. Olivine minerals belong to the orthorhombic system, and their crystals are columnar, granular, colorless or off-white, and have a glassy luster. This type of mineral has good thermal stability, and these characteristics make olivine minerals more difficult to grind during processing. In contrast, ordinary silicate minerals are relatively easy to grind during processing, mainly because their crystal structure and physical properties make processing easier.

[0108] In other words, compared to common silicate minerals, olivine minerals are more difficult to grind than common silicate minerals. Consequently, under the same grinding conditions, the coarseness of the particles can vary. After air separation, the difference in particle size can be exploited to separate slag particles from slag powder. Slag particles are rich in metal elements, while slag powder is mostly composed of silicate minerals. Therefore, separating the slag particles (i.e., the coarse particles or coarse material) and using them as return ore improves metal recovery.

[0109] Then, the airflow separates the fine material from the material through the cyclone separator 31 and conveys it to the powder classifier; in this embodiment, the powder classifier is a rotor-type powder classifier 32, and the rotor-type powder classifier 32 generates a high-speed rotating airflow through the rotor; the fine material enters the powder selection chamber of the rotor-type powder classifier 32 with the airflow, and the coarse and heavy particles in the fine material are thrown to the inner wall of the powder selection chamber by the inertial centrifugal force, and lose kinetic energy after the collision and slide down along the wall to fall into the coarse powder collection cone, and the remaining particles are carried away by the rotating rising airflow. When passing through the action area of ​​the large wind blades, under the impact of the large wind blades, another part of the coarse and heavy particles are thrown to the inner wall of the powder selection chamber and lose kinetic energy after the collision. It slides down along the wall and enters the coarse powder collecting cone; after passing through the large wind blades, the medium coarse powder and fine powder continue to rise under the carry of the rising airflow, pass through the vertical guide blades and enter the secondary powder selection area. Under the action of the strong and stable plane vortex generated by the rotating cage rotor, the medium coarse powder in the dust-laden airflow is thrown to the vertical guide blades under the action of centrifugal force, loses kinetic energy after impact and falls into the medium coarse powder collecting cone, and is discharged from the medium coarse powder pipe; by adjusting the speed of the rotor, the particle size of the fine powder can be adjusted, and the fine powder that meets the requirements is discharged with the airflow through the cage-type rotor and collected by the powder collection equipment to become a finished product; the fineness of the finished product in this embodiment is set to 400 mesh and all pass, that is, the particle size does not exceed 37 microns.

[0110] In this embodiment, the coarse and heavy particles (coarse powder) and the medium coarse powder refer to materials with intermediate particle sizes, and their particle sizes are unqualified, so they are returned to the grinding mill and crushed again; the metal particles are often wrapped by the molten glass. When crushed again, the glass shatters, and the metal particles are exposed, which is convenient for magnetic separation and electric separation.

[0111] Iron and nickel have some differences in physical properties. The density of iron is 7.87g / cm 3 , while the density of nickel is 8.90g / cm 3 Nickel has a greater density than iron; the melting point of iron is 1535°C, while nickel's is 1455°C; both iron and nickel are magnetic metals, but nickel's magnetism is lower than iron's; among silicate minerals, calcium iron olivine is a mineral containing iron and therefore has magnetic properties, but the magnetism is weak; therefore, magnetic separation can be used. Furthermore, materials are classified into three categories based on their electrical conductivity: conductors, semiconductors, and insulators. Electrostatic separation is a method of separating minerals and gangue particles in a high-voltage electric field based on the differences in electrical conductivity, so it can also be supplemented by electrostatic separation.

[0112] In this embodiment, a powder collection device is installed after the powder concentrator. The device includes a dust collector 4, which can be a bag filter or an electrostatic precipitator, for product collection and environmental protection. The fine powder, specifically slag micropowder, is obtained through the powder collection device. The system exhaust gas is purified and then discharged into the atmosphere by an induced draft fan 41 connected to the powder collection device.

[0113] In summary, the present invention achieves metal enrichment through grinding and separation.

[0114] In other words, the present invention utilizes a vertical mill 3 to pulverize slag. During the grinding process, components rich in metal elements, namely slag particles, are separated from the slag. These particles can be used as return ore for batching or as concentrate for ironmaking, enriching metal minerals (including nickel ore) and facilitating metal smelting. Simultaneously, the gangue minerals in the slag are finely ground to produce slag fine powder. Furthermore, remelting the slag can produce cement or steel slag phosphate fertilizer, which can be used to replace the slag fine powder. Therefore, the present invention achieves multiple goals at once, ultimately conserving energy.

[0115] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for obtaining nickel-iron alloy by smelting laterite nickel ore, characterized in that: The following steps are involved: Crushing the raw ore of laterite nickel ore into powder, mixing it with fine-grained coal and return ore in proportion to obtain a batch material, wherein the return ore is slag particles produced after slag sorting; using a double-roll briquetting machine to press the batch material into balls; The complete pellets are fed into a preheating zone at the top of a vertical calcining furnace (1). The vertical calcining furnace (1) is surrounded by a vertical furnace wall (11), and the interior space of the furnace body is divided into a plurality of furnace chambers arranged vertically by inclined partitions (12); the furnace chambers are connected through gates (13); the gates (13) are used to control the height of the material level and / or the discharge rate, so as to control the pellets in the preheating zone to form a fixed bed; The preheated pellets are discharged from top to bottom into the calcining zone and meet with hot air; the hot air comes from the waste heat of slag cooling, or is generated in the combustion chamber at the bottom of the furnace body, and the hot air passes through the partition (12) from bottom to top and enters the calcining zone; The metallized pellets are obtained by selective reduction reaction; that is, during the calcination process, the calcination temperature is controlled within the range of 700-800°C, and the ratio of CO2 to CO partial pressure is greater than 0.5; the exhaust gas generated during the calcination process is passed upward into the preheating zone to dry the pellets entering the kiln; The metallized pellets and flux are fed into a melting furnace (2), and smelted and separated to obtain a nickel-iron alloy; After obtaining the nickel-iron alloy, a slag tapping operation is performed to discharge the smelting slag from the slag outlet of the smelting furnace (2). The slag is cooled, ground and sorted to become slag particles and slag powder. The slag particles are added to the batch material as return ore, and products with different nickel contents are produced by adjusting the addition ratio. Alternatively, the slag particles are used as ironmaking raw materials. The cooling method of the slag includes water quenching or air quenching.

2. The method for obtaining ferronickel by smelting laterite nickel ore according to claim 1, wherein: After the batch material is pressed into pellets, the formed pellets are screened, and the pellets under the screen are returned for re-balling; The waste gas generated by calcination is drawn out from the top of the furnace and discharged into the atmosphere after purification.

3. The method for obtaining ferronickel by smelting laterite nickel ore according to claim 1, wherein: There are multiple ways to obtain the hot air, including: using a blower (21) to extract the hot air from the slag quenching section and send it to the vertical calcining furnace (1); or, selecting coal gas and / or auxiliary fuel as needed, the auxiliary fuel including coal powder and petroleum coke, and utilizing the combustion of fuel in the combustion chamber to provide the hot air for the calcination of the pellets and adjust the combustion atmosphere; wherein the coal gas used in the combustion chamber is recovered from the exhaust gas generated by the vertical calcining furnace (1), and / or comes from the smelting furnace (2).

4. The method for obtaining ferronickel by smelting laterite nickel ore according to claim 1, wherein: The metallized pellets are discharged from the discharge port of the vertical calcining furnace (1), cooled, ground and sorted to obtain concentrate and tailings, and the concentrate is returned to the pelletizing process; After repeated smelting, high-grade nickel-iron alloy is obtained.

5. The method for obtaining ferronickel by smelting laterite nickel ore according to claim 1, wherein: After the metallized pellets and the flux are evenly mixed, they are hot-charged into the smelting furnace (2) from the upper part. The flux includes lime blocks or fluorite. The amount of returned ore added is adjusted to first smelt a nickel-iron alloy with a nickel content of 8%-10%. Then, the alloy is transferred to a refining furnace. After adding chromium-containing metal, the alloy is blown by vacuum or semi-vacuum blowing using the principle of selective oxidation to produce stainless steel. When blowing begins, oxygen decarburization is first performed at normal pressure, and vacuum blowing is performed later.

6. The method for obtaining nickel-iron alloy by smelting laterite nickel ore according to claim 1, wherein: After the molten steel is produced, auxiliary raw materials are added to the slag to adjust the chemical composition of the slag, and the slag is remelted, and the inorganic material is manufactured using the slag remelting process. Depending on whether the slag has been remelted and the difference in the slag remelting process, the slag powder obtained is slag fine powder, cement, or fertilizer. The method comprises the following steps: adding coal and limestone into the slag in proportion, adjusting the refined slag into reduced slag by performing an oxygen blowing operation, reducing the metal oxides therein into simple substances as much as possible, utilizing the remaining slag to generate cement minerals, thereby obtaining cement clinker, wherein the cement clinker is ground into cement; or adding apatite into the slag, melting it at a high temperature of 1350-1500°C, and then quenching it with water to form a glassy material with a particle size of less than 2mm, which is dried and ground into calcium magnesium phosphate fertilizer.

7. The method for obtaining ferronickel by smelting laterite nickel ore according to claim 6, wherein: By remelting the slag, the hexavalent chromium remaining in the slag is reduced to generate chromium metal, or trivalent chromium, or tetravalent chromium.

8. A method for obtaining nickel-iron alloy by smelting laterite nickel ore according to any one of claims 1 to 7, characterized in that: During the crushing, pulverizing and sorting process of the slag, components rich in metal elements, namely the slag particles, are separated from the slag through the combined operation of a pulverizer, a separator and a powder concentrator; while improving the grade of the raw materials and the metal recovery rate, the gangue minerals in the slag are ground to obtain slag powder, which is collected by a powder collection device.

9. The method for obtaining ferronickel by smelting laterite nickel ore according to claim 8, characterized in that: When the slag is ground and sorted, the cooled slag is fed into the grinding mill for grinding, sorted by the separation device, and then the fineness of the slag powder is adjusted by the classifier. The sorting methods include air separation, magnetic separation and / or electric separation.

10. The method for obtaining nickel-iron alloy by smelting laterite nickel ore according to claim 9, characterized in that: The slag is subjected to magnetic separation and fed into the grinding mill, which is a material bed grinding device including a vertical mill (3) or a roller press; after being crushed by the vertical mill (3), the slag is fed into the separation device, which is a cyclone separator (31); under the action of gravity and centrifugal force, coarse particles and metals are separated from the material as the slag particles, and the slag particles are used as return ore or ironmaking raw materials; the fine material is carried by the air flow and transported to the powder separator, which is a rotor type powder separator (32); after air separation, the coarse powder and medium coarse powder in the fine material are separated by the air flow. After magnetic separation and / or electric separation, the powder returns to the vertical mill (3) and is crushed again; the particle size of the fine powder is adjusted by adjusting the rotation speed of the rotor of the rotor-type powder concentrator (32); the fine powder that meets the requirements passes through the cage-type rotor and is discharged with the air flow; the fine powder, i.e., the slag powder, is collected by the powder collection device; the powder collection device includes a dust collector (4), which is a bag dust collector or an electric dust collector, and is used for product collection and environmental protection; after the exhaust gas of the grinding system is purified, it is drawn out by the induced draft fan (41) connected to the powder collection device and discharged into the atmosphere.

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