Method for obtaining ferro-nickel alloy by smelting laterite type nickel ore

Abstract

The invention relates to the technical field of materials and metallurgy, in particular to a method for obtaining ferro-nickel alloy by smelting laterite type nickel ore, which comprises the following steps: carrying out compression molding on a batch of the laterite type nickel ore to obtain pellets, calcining the pellets in a vertical calcining furnace to obtain metallized pellets, and smelting and separating the metallized pellets to obtain ferro-nickel alloy and slag; nodules can be eliminated in the reduction roasting stage, meanwhile, the use amount of air can be reduced, the exhaust gas emission temperature is lowered, and therefore the heat efficiency is improved. The slag is ground and separated into slag particles and slag powder, the slag particles are rich in metal elements, the slag particles are extracted to serve as return mine and participate in batching again, the metal recovery rate is increased, and the slag powder can be used as superfine slag powder. Besides, if the slag is subjected to remelting and component adjustment, cement or steel slag phosphate fertilizer can be obtained in the ferronickel production process and is used for replacing the superfine slag powder, and resource waste is further avoided.

Description

Technical Field

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

[0002] At present, the world's proven nickel reserves are about 160 million tons. Nickel minerals mainly exist in two forms: nickel sulfide ore and nickel oxide-nickel silicate ore (also known as laterite nickel ore). Among them, nickel sulfide ore accounts for about 30%, and laterite nickel ore accounts for about 70%. Due to the good quality of nickel sulfide ore resources and mature technology, about two-thirds of the world's nickel is extracted from nickel sulfide ore, but nickel in laterite nickel deposits accounts for 65% of nickel reserves. Since there has been no major breakthrough in the exploration of nickel sulfide ore resources in the past 20 years, with the annual decrease of nickel sulfide ore resources in the world, the extraction of nickel and cobalt from laterite nickel ore has received more and more attention. Therefore, the nickel industry in various countries in the world has shifted the focus of 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 around the Pacific Ocean. Laterite nickel ore is a surface weathering crustal deposit resource formed by weathering, leaching and deposition of nickel sulfide ore rock mass, and has a high water content. The main components of laterite nickel ore include nickel, iron, copper, silicon, titanium and chromium, among which 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 sulphide, and nickel iron. Among them, nickel sulphide and nickel oxide can be used by nickel refineries to solve the problem of insufficient nickel sulphide raw materials; as for nickel iron, it is more convenient for stainless steel manufacturing and reduces production costs. In addition, nickel-based positive electrodes such as nickel-manganese-cobalt and nickel-cobalt-aluminum occupy a major share in the electric vehicle battery market; with the vigorous development of the new energy electric vehicle industry, the output of new energy vehicles has increased rapidly year by year. The future development prospects and market growth space of new energy vehicles are very huge, and the demand for nickel, cobalt, etc. in the new energy market has increased year by year.

[0005] Ore dressing is a process of separating useful minerals from gangue minerals by gravity separation, flotation, magnetic separation, electrostatic separation, etc., after crushing and grinding the ore according to the physical and chemical properties of different minerals in the ore, and separating various symbiotic (associated) useful minerals from each other as much as possible, removing or reducing harmful impurities, so as to obtain raw materials required for smelting or other industries; Ore dressing can enrich useful components in minerals, reduce the consumption of fuel and transportation in smelting or other processing processes, and make low-grade ores economically utilized. For some difficult-to-select ores, sometimes the single method of ore dressing often does not get satisfactory results, or even cannot be separated, so it is necessary to use a combined process of ore dressing and metallurgy for treatment; the combined process of ore dressing and metallurgy is a process of treating ore by alternating ore dressing and metallurgy.

[0006] At present, nickel ore is mainly smelted by pyrometallurgical or hydrometallurgical processes to produce high-grade nickel matte or nickel-cobalt hydroxide (MHP) intermediate products respectively; wherein, the high-grade nickel matte is a sulfide eutectic of nickel, copper, cobalt, iron and other metals formed by primary smelting of nickel concentrate by electric furnace or converter, and pyrometallurgical smelting is to mix laterite nickel ore with coal, remove water through a rotary kiln, reduce metal oxides such as nickel and iron into metal alloy elements, and further refine and remove impurities to prepare high-grade nickel matte. In addition, the main process of producing high-nickel matte from nickel ore is: nickel ore is first smelted to produce low-nickel sulfur, and then low-nickel sulfur is refined 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 ore, comprising: crushing and finely grinding the nickel-cobalt polymetallic oxide ore, and uniformly mixing it with a carbonaceous reducing agent, a metallizing aid and water to form green pellets; drying and preheating the green pellets, and then transferring them into a reduction device lined with a carbonaceous refractory material or a carbon-containing composite refractory material, and performing reduction roasting at 900-1250° C. to obtain metallized pellets; cooling, crushing, finely grinding the metallized pellets, and then performing magnetic separation or gravity separation to obtain a nickel-cobalt mixed concentrate and a middling; scavenging the middling to obtain a scavenged concentrate and a scavenged tailing; and returning the scavenged concentrate to make pellets.

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

[0009] The nodules in the kiln are manifested in that the charge is sintered into large pieces, which stick to each other or hang on the wall. In serious cases, the kiln needs to be stopped for treatment, which affects 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 nodule formation in the kiln charge in the prior art, so as to improve production efficiency and reduce production costs.

[0010] In the prior art, the main process of treating laterite nickel ore by direct reduction in a rotary kiln or rotary hearth furnace → smelting furnace smelting process is: crushing, screening, grinding the laterite nickel ore, adding reducing agent (coal powder) and flux (limestone) to mix, using a disc ball maker or a roller ball press to form carbon-containing pellets, sending the carbon-containing pellets into the kiln, directly reducing them to become metallized pellets, and sending the metallized pellets into a smelting furnace for smelting to separate slag and iron to obtain nickel-iron alloy; in short, it is similar to the ironmaking → steelmaking process. However, in the two processes of selective reduction and selective oxidation, the reducing agent and flux play different roles and their consumption is also different; especially since laterite nickel ore has a low nickel content and a large amount of slag, a reasonable smelting process should be improved accordingly according to the difference in raw materials. Summary of the invention

[0011] In order to make up for 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 by the following technical solutions: A method for obtaining nickel-iron alloy by smelting laterite nickel ore comprises the following steps: The raw ore of laterite nickel ore is crushed into powder, and mixed with fine coal and return ore in proportion to obtain a batch material, wherein the return ore is slag particles produced after slag sorting; the batch material is pressed into balls by a double-roll ball press; The complete material balls are sent into the preheating zone on the top of the vertical calcining furnace. The vertical calcining furnace is surrounded by upright furnace walls to form a furnace body. The internal space of the furnace body is divided into a plurality of furnaces arranged up and down by inclined partitions. The furnaces are connected through gates. The gates are used to control the height of the material level and / or the discharge rate, so that the material balls in the preheating zone are controlled to form a fixed bed. The preheated pellets are unloaded 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 from bottom to top into the calcining zone; metallized pellets are obtained by selective reduction reaction; the waste gas generated during the calcining process goes up into the preheating zone to dry the pellets entering the kiln; The metallized pellets and flux are sent to a smelting furnace, and nickel-iron alloy is obtained through smelting and separation.

[0012] 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-balling; 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 waste gas generated by calcination is drawn out from the top of the furnace and discharged into the atmosphere after purification; After obtaining the nickel-iron alloy, a slag discharge operation is performed to discharge the smelting slag from the slag discharge port 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 products with different nickel contents are produced by adjusting the addition ratio. Alternatively, the slag particles are used as ironmaking raw materials. The method of cooling the slag includes water quenching or air quenching.

[0013] In a specific possible implementation scheme, the hot air can be obtained in a variety of ways, including: using a blower to extract the hot air from the slag quenching section and send it to the vertical calcining furnace; 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, and / or comes from the smelting furnace; by using ordinary coal to provide the coal gas as fuel for the vertical calcining furnace, the constraints on fuel varieties are alleviated.

[0014] In a specific possible implementation method, the metallized pellets are discharged from the discharge port of the vertical calcining furnace, and are cooled, ground and sorted to obtain concentrate and tailings, and the concentrate is returned to the pelletizing process; after repeated smelting, a high-grade nickel-iron alloy is obtained.

[0015] In a specific feasible implementation scheme, after the metallized pellets and the flux are uniformly mixed, they are hot-charged into the furnace from the upper part of the smelting furnace, and the flux includes lime blocks or fluorite; the amount of returned ore added is adjusted, and the nickel-iron alloy with a nickel content of 8%-10% is first smelted, and then transferred to the refining furnace, and after adding chromium-containing metal, the selective oxidation principle is used to produce stainless steel by vacuum or semi-vacuum blowing; when the blowing starts, oxygen decarburization is first carried out at normal pressure, and vacuum blowing is used in the later stage; the physical heat of the raw materials is fully utilized, and the physical heat is the sensible heat and latent heat of the material, thereby reducing the smelting energy consumption.

[0016] In a specific possible implementation method, 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 by 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 powder, cement, or fertilizer; including adding coal and limestone to the slag in proportion, adjusting the refined slag into reduced slag by performing oxygen blowing operation, allowing the metal oxides therein to be reduced to a single substance as much as possible to facilitate magnetic separation, and using the remaining slag to generate cement minerals, thereby obtaining cement clinker, and the cement clinker is cement after being ground; or, adding apatite to 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, and drying and grinding it to make calcium magnesium phosphate fertilizer, which is a steel slag phosphate fertilizer; the application of this method can reduce manufacturing costs.

[0017] 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.

[0018] In a specific feasible implementation method, 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 grinding mill, a separation device 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 collecting device.

[0019] In a specific possible implementation scheme, when the slag is ground and sorted, 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.

[0020] In a specific possible implementation scheme, 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 returned 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 are 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 airflow, and 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.

[0021] The present invention can achieve the following beneficial technical effects, by improving the calcination process, including: (1) Adjust the proportion 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 pressing method, so the initial strength is high and the broken material is less. Moreover, the balls are of uniform size and large diameter. Under natural stacking conditions, the outside is ventilated and 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. (2) A vertical calcining furnace is used, wherein an inclined ventilation partition is provided inside the vertical calcining furnace; after the material balls are fully dried in the preheating zone, they fall into the calcining zone by gravity, and the material balls are calcined while moving, and are not easy to stick together, until sintering is completed to generate the metallized pellets.

[0022] Based on this, the present invention can overcome the influence of adverse factors during the calcination process and eliminate the nodules of the charge.

[0023] If the relevant technology is directly used, such as adopting the batching scheme of sintered ore in 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

[0024] Figure 1 is a schematic diagram of an embodiment of the present invention; Figure 2 It is a flow chart of slag grinding according to an embodiment of the present invention.

[0025] Description of reference numerals: 1-vertical calcining furnace; 11-furnace wall; 12-partition plate; 13-gate; 2- melting furnace; 21- blower; 3-vertical mill; 31-cyclone separator; 32-rotor powder separator; 4-dust collector; 41-induced draft fan. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments; based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without 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.

[0027] It should be additionally pointed out that, in a specific implementation manner, several embodiments provided by the present invention constitute a complete process for smelting laterite nickel ore, the process starting from batching, through slag and iron separation, to slag grinding and ending, 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 described in the text; the technical problem solved by the present invention is not just to eliminate charge nodules, which should be understandable.

[0028] Among the existing technologies, the pyrometallurgical process was developed earlier and is relatively mature, and is widely used in industry. At present, it mainly includes the rotary kiln → ore-arc furnace nickel-iron process (RKEF process) and the blast furnace smelting process.

[0029] (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 procedures of RKEF method are pre-drying, roasting, and reduction smelting; the raw ore of laterite nickel ore is sent to a drying kiln to reduce the moisture to about 20%, and then the ore, flux, reducing agent, etc. are mixed and batched 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, and the obtained crude nickel iron is then smelted in a refining electric furnace to produce nickel iron. The RKEF method has a mature process, simple and easy-to-control equipment, and high production efficiency, but its disadvantages are that it consumes a large amount of metallurgical coke and electricity, has 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 (latite 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.

[0030] (2) Blast furnace smelting process: suitable for producing medium-nickel iron or low-nickel iron products, 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 coke and flux are added, 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 relatively low, it uses a volume of less than 300m 3 The small blast furnaces are facing elimination.

[0031] Compared with the prior art, the present invention has a simple structure, reasonable design and convenient implementation; 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 the corresponding effects can be achieved; for example, if high-grade nickel is used to produce stainless steel, this is not the most economical choice. 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.

[0032] Example 1 In this embodiment, laterite-type nickel ore is mixed and pressed into pellets, and the pellets are dried, reduced and roasted to form metallized pellets, which are then put into a furnace for smelting to obtain nickel-iron alloy.

[0033] See also Figure 1 This embodiment provides a method for obtaining nickel-iron alloy by smelting laterite nickel ore, comprising the following steps: 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, stirring it evenly, and obtaining 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, reduce the reaction temperature of the system, and accelerate the reduction reaction.

[0034] Step 20, using a double-roll ball press to press the batch material into balls, preferably with a ball diameter of 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 consistent, the ventilation effect is good, the calcination is uniform, and it is conducive to smelting; the raw ore has its own moisture, and no additional water is needed when making balls, which can save water resources.

[0035] Step 30, the complete material balls are sent into the vertical calcining furnace 1, and the material balls 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 to form a furnace body, and the internal space of the furnace body is divided into several furnaces arranged up and down by an inclined partition 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 material balls 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 coal 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 material balls and adjust the combustion atmosphere.

[0036] In this embodiment, the hot air sucked into the combustion chamber comes from the slag quenching section, which 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 enters the calcining zone from bottom to top through the partition 12. The preheated (dried) balls are unloaded into the calcining zone from top to bottom, meet the hot air, and complete the calcination. This realizes the utilization of waste heat and energy saving.

[0037] The waste gas generated during the calcination process continues to go up and enters the preheating zone, where it exchanges heat with the kiln pellets, thereby drying the pellets; the waste gas temperature drops, is drawn out from the furnace top, and is discharged into the atmosphere after purification. The coal gas used in the combustion chamber can be recovered from the waste gas; in a steel mill, the beneficial components in the high-temperature waste gas generated are separated and recovered, and the coal gas recovery is mainly carried out by physical and chemical methods, among which the physical methods include cooling, purification, regulation, etc., and the chemical methods use absorption, adsorption, desorption and other technologies, which will not be repeated here.

[0038] After the balls are piled up, their outer space is loose and breathable. After the coal in the outer shell of the balls is exhausted, there is often carbon residue inside. The inside of the balls is in an oxygen-deficient state, and a reducing atmosphere is easily formed at high temperature, which is conducive to the completion of the pre-reduction reaction of the balls; that is, the nickel oxide in the raw material is reduced to generate fine droplets of metallic nickel, which are embedded in the ore particles, so that metalized pellets are formed; wherein, the reduction of iron is a step-by-step reduction, that is, Fe2O3→Fe3O4→FeO. In order 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 be separated from the already reduced metallic nickel. The above is selective reduction, and the conditions are suitable temperature and atmosphere, which are adjusted as needed. In this embodiment, the temperature is controlled within the range of 700-800°C, and the atmosphere in the furnace is adjusted to a ratio of CO2 to CO partial pressure greater than 0.5, which is used to avoid the generation of metallic iron, but allows the nickel oxide to be smoothly reduced to generate nickel element.

[0039] By comparing with the prior art, we can find the following differences: 1. The ball obtained by pressing and molding in the present invention has high initial strength and is not easy to break during production; 2. The kiln structure of the present invention forces the balls to be calcined while in motion, without the chance of sticking to each other; 3. In the ingredients of the pellets of the present invention, no flux is added to prevent the massive generation of low-melting-point minerals; the flux is added into the system only when the pellets are smelted; that is, in the ingredients of the pellets of the related art, lime is added in advance; the pellets of the present invention do not contain lime, that is, lime blocks and fluorite are not added in the calcination stage, but in the smelting stage, at which time there is no fear of nodules; therefore, premature reaction can be prevented and nodulation can be reduced.

[0040] In summary, the material loses the conditions for nodules, so the present invention can eliminate nodules in the reduction roasting stage and achieve 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: 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 airflow passes through the inclined partition 12 from bottom to top. With the assistance of gravity, only a small amount of airflow 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.

[0041] 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.

[0042] 3. Although the heat exchange rate of materials is fast after being ground into powder, the speed of heat exchange and the amount of heat consumption are two different things: after the materials are ground into powder, although the contact area increases, resulting in fast heat exchange, the heat exchange effect (heat consumption) is not only related to the speed of heat exchange, but also to the heat exchange time. The heat exchange effect is the result of the combined effect of the two; moreover, the grinding operation is a large power consumer. Under the premise of ensuring quality, reducing energy consumption (the sum of power consumption and heat consumption) is the ultimate goal of the calcination industry; therefore, as long as the equipment insulation is passed, time can be used to exchange energy consumption, and simply sticking to the suspension process is not scientific. For example, the ball is calcined by the vertical kiln pre-watering ball forming process. The ball is made of powder material bonding. Although water is added during the ball forming process, in the competition with the new dry method (suspension process), the average level of heat consumption of vertical kiln firing in advanced areas can reach 850kcal / kg clinker, which is not inferior to the suspension process; that is to say, the suspension process does not mean low heat consumption, and the use of the suspension process is not necessary.

[0043] Therefore, we can also understand that: (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.

[0044] (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.

[0045] In step 40, the metallized pellets are discharged from the discharge port of the vertical calcining furnace 1, sent to the smelting furnace 2, and smelted after adding a flux; the flux includes lime blocks or fluorite; in the smelting process, the metal and the flux often contain impurities and non-metallic substances. After the lime blocks are added, 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 slag, and improve the desulfurization efficiency.

[0046] In this embodiment, after selective reduction (pre-reduction), the generated metallized pellets are hot-charged into the furnace from the top (1000°C), so that the physical heat of the raw materials can be fully utilized; the vertical calcining furnace 1 is matched with the smelting furnace 2, so that the smelting furnace obtains the metallized raw materials, and the metallized pellets are further reduced and melted in the furnace to separate the slag and iron, thereby greatly improving the production efficiency. The smelting furnace 2 is also called a smelting gasification furnace. Usually, the smelting furnace uses about 300kg of briquette for every ton of molten iron produced, which can save coke and coking coal resources; at the same time, the smelting furnace can also provide coal gas as fuel for the vertical calcining furnace 1, which alleviates the restriction of direct reduction by the grade of raw materials, so that ordinary coal can also be used for direct reduction.

[0047] 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 arranged inside the furnace body of the smelting furnace, and below the electrodes is a smelting pool inside the furnace body, and there is a protective layer on the bottom of the pool to prevent the cooling effect of the furnace bottom.

[0048] Laterite nickel ore mainly contains NiO, Cr2O3, Fe2O3, Al2O3, SiO2 and other oxides. In the melting point range of laterite nickel ore (1300℃-1400℃), the stability of the oxides is in the following order: Al2O3>Cr2O3>CaO>MgO>Fe2O3>SiO2>FeO>NiO, so NiO will be reduced first, and the reduction temperature is lower than the reduction temperature of FeO. Using the principle of selective reduction, carbon-deficient operation can be adopted to reduce almost all NiO in laterite nickel ore to metallic nickel first, and the high-valent Fe2O3 is reduced to metal in an appropriate amount, and the rest is reduced to FeO and enters the slag, thereby achieving the purpose of nickel enrichment.

[0049] Modern smelting technology usually 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 the crushed laterite nickel ore with the reducing agent (fine-grained coal) to make balls, obtain a self-reduction product under a protective atmosphere, selectively oxidize the self-reduction product in a weak oxidizing atmosphere to obtain an oxidation product, and separate the metal from the gangue after melting the oxidation product to obtain a high-grade nickel-iron alloy. In short, the production process of nickel-iron alloy is a process of reduction first and oxidation later.

[0050] In laterite nickel ore, the nickel content is generally between 1% and 2%; if the grade of the raw material is too low, the metallized pellets can be cooled, ground, and sorted, the concentrate can be returned to the pellets, and the tailings can be made into ore powder; or, in the smelting process, the smelting slag can be discharged from the slag outlet of the smelting furnace 2, crushed, ground, and then beneficiated, which is applied to this embodiment, and is equivalent to returning the ore, thereby improving the metal recovery rate; usually, the slag is quenched (water quenched), crushed, and sorted many times; after repeated smelting, it is continuously enriched, and the raw material grade can be improved, so as to facilitate smelting and obtain high-grade nickel-iron alloy. This method is for producing high-grade nickel-iron alloy products, containing 30% nickel.

[0051] 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 then refining, and directly producing stainless steel, which can achieve better social and economic benefits.

[0052] Iron and nickel differ in many chemical properties. Iron is very active and easily reacts with oxygen in the air to form iron oxide. Nickel is less active than iron, so it is not as easily oxidized as iron. Nickel is more stable and has higher corrosion resistance than iron. It is not easily corroded by oxidation, sulfide and alkaline substances. Using this property, one of the uses of nickel is to manufacture stainless steel. Stainless steel is steel with rust-proof and corrosion-resistant main characteristics, and a chromium content of at least 10.5% and a carbon content of no more than 1.2%.

[0053] When it comes to the smelting of stainless steel, selective oxidation is also unavoidable. Regarding the selective oxidation, an example is given: at the steelmaking temperature, carbon and chromium meet oxygen at the same time, and the oxidation must be in order, which is determined by the affinity of the elements with oxygen. The elements with greater affinity will oxidize first. The order of oxidation is determined according to the affinity with oxygen, which is selective oxidation; the affinity is related to the oxidation conversion temperature, which refers to the temperature of the intersection of the Gibbs energy change of the oxidation reaction of the two elements and the temperature relationship line. When the smelting temperature is greater than the oxidation conversion temperature, carbon is more active than chromium and oxidizes first; when the smelting temperature is less than the oxidation conversion temperature, chromium is more active than carbon and oxidizes first. In other words, at a lower smelting temperature, the oxidation reaction of chromium is more likely to occur, especially when the specific oxidation conversion temperature is not reached.

[0054] When producing austenitic stainless steel by the oxygen blowing method, after the carbon in the molten iron is oxidized, 2%-2.5% of the metallic chromium will also be oxidized and enter the slag, causing 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; 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%, and the oxidation conversion temperature is only 1601℃, which can be achieved in production. In order to blow ultra-low carbon stainless steel, such as carbon content W[C] = 0.0 2%, when Pco = 5066Pa, the oxidation conversion temperature is 1631℃, which is still feasible; using vacuum or semi-vacuum blowing, chromium can be fully added at one time. If oxygen blowing is performed at normal pressure, chromium cannot be fully added at one time, otherwise, the oxidation conversion temperature is too high and the equipment cannot bear it; and when the carbon content is higher, the oxidation conversion temperature is lower, so at the beginning of blowing, oxygen blowing decarburization can be performed at normal pressure, but when the carbon content W[C] drops to a certain level, vacuum blowing must be used. This embodiment adopts the above refining operation. After smelting is completed, slag and iron are separated, and nickel-iron alloy (including stainless steel) is removed from the system as a product.

[0055] Step 50, performing a slag discharging operation, wherein the slag discharging operation includes water quenching or air quenching; after the slag is cooled and crushed, it can be stored separately and used as needed.

[0056] During normal smelting, the slag is often divided into reducing slag and oxidized slag according to different slag discharge periods, and their chemical compositions and mineral compositions are different; among them, the most common reducing slag is the slag produced by blast furnace ironmaking; the metallized pellets in this embodiment also belong to reducing slag. The most common oxidized slag is the steel slag produced by steelmaking; in this embodiment, the oxidized slag includes the refined slag after oxygen blowing and carbon removal; the oxidized slag is formed during the refining process, especially in the oxidation refining process, by blowing oxygen to remove impurities in the metal, especially 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.

[0057] Step 60, the slag is ground and sorted to obtain slag particles and slag powder; 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, mixed with the batch material in proportion for pelletizing; or, the slag particles can be used as metallurgical raw materials, such as for iron smelting.

[0058] 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 then ground into cement; or steel slag phosphate fertilizer is manufactured by slag remelting.

[0059] Example 2 In the steelmaking process, iron and other metal raw materials are placed in a furnace and heated to melt and fuse. The molten metal is divided 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. The sources of slag include: (1) Gangue in ore, which is usually aluminosilicate; (2) Oxides formed during the refining process of crude metals; (3) Furnace lining materials (refractory bricks) that are eroded and washed away during the smelting process; (4) Flux added during the smelting process, such as lime and fluorite added to produce slag with a certain fluidity and desulfurization and dephosphorization capabilities.

[0060] Steelmaking is a process of changing the composition and properties of steel by heating and adding other elements. Slag plays a major role in separating impurities, enriching useful metals, and completing oxidation refining during the smelting process. The composition of slag determines its solubility. In this process, the slag needs to be kept at a sufficient temperature for a certain period of time to completely dissolve it in order to achieve the best effect of improving the composition and properties of steel. During steel production, it is impossible to tap the steel (discharging molten steel) cleanly, and there must be steel remaining in the slag; usually, the steel is tapped first and then the slag is tapped, which means that in the smelting process, the steel is first taken out of the molten steel, and then the unsmelted useful metals and other substances are taken out of the slag. This operation generally occurs in the smelting process of blast furnaces such as electric arc furnaces and converters. In the prior art, after the steel is tapped, the slag immediately completes its historical mission and is treated as waste. It is generally used as a cement admixture with low added value.

[0061] The present invention proposes the concept of slag remelting for the first time, which means that after steel is tapped, auxiliary raw materials are added to the slag, and the chemical composition of the slag is adjusted by remelting. The present invention uses slag to manufacture inorganic materials such as cement and fertilizer through the slag remelting process. For example, based on Example 1, this embodiment performs slag remelting before performing the slag tapping operation in step 50 to manufacture cement clinker.

[0062] 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 value can simply express the relationship between chemical composition and mineral composition, and clearly show the performance of cement clinker and its influence on calcination. It is a basic element 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 about 0.9; the silicon rate is the ratio of the SiO2 content to the sum of the Al2O3 and Fe2O3 contents in the clinker, which is generally controlled at about 2.2, and the silicon rate reflects the amount of liquid phase; the aluminum rate is the ratio of the Al2O3 content to the Fe2O3 content in the clinker, which is generally controlled at about 1.5, and the aluminum rate reflects the viscosity of the liquid phase; because it is different from conventional production, this embodiment uses slag to produce clinker, so the control of the silicon rate and the aluminum rate 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 close to it.

[0063] In the slag making process, by adjusting the basicity of the slag, most of the sulfur can enter the slag. Therefore, the slag has a strong desulfurization effect, which not only ensures the quality of molten steel but also reduces the emission of SO2. The basicity is an index representing the characteristics of the slag, usually expressed by the ratio of basic oxides (such as CaO) to acidic oxides (such as SiO2). The basicity of the slag has a significant effect on the performance of the slag. With the increase of basicity, the fluidity of the slag improves. Moreover, in the smelting process, with the continuous addition of lime, As the alkalinity of slag increases, its main mineral composition also changes 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 will not affect the performance of cement; among them, dicalcium silicate and tricalcium silicate are the dominant source minerals of cement gelling properties.

[0064] The main mineral components of Portland cement include tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite; among them, the total content of tricalcium silicate and dicalcium silicate is more than 70%, which plays a dominant role in the cementitiousness of cement; tricalcium silicate has a fast hydration reaction speed and a large heat release, which contributes greatly to the early strength of cement; while dicalcium silicate has an important influence on the later strength of cement; the two minerals work together to make cement have excellent cementitious properties, and are an indispensable component of concrete and other cement-based materials. During the burning process of cement clinker, some metal oxides, such as iron oxide in iron raw materials and steel slag, can be organically combined with other minerals in the clinker to form a eutectic, and then solid-dissolved in the clinker. This solid-solution effect can not only ensure the strength of the clinker, but also play the role of mineralizer, promote the burnability of raw materials, and shorten the clinker burning time.

[0065] In the prior art, slag is usually used as a cement admixture. In this embodiment, auxiliary raw materials are added to the slag, and the slag is remelted to produce cement clinker. The slag powder of the present invention is used with high added value; that is, conventional slag is usually added to cement as an admixture, while the present invention uses slag to directly generate silicate minerals, such as tricalcium silicate, dicalcium silicate, etc., as the dominant minerals of cement, which are the main source of cement gelling properties.

[0066] Furthermore, there are the following differences: In the process of batching sintered ore with the conventional technology, the formation of dicalcium silicate should be avoided as much as possible, because the dicalcium silicate has four crystal forms, and when the temperature is slowly reduced, the crystal form transformation will occur, the volume of the crystal will expand, and thus internal stress will be generated, which will cause the sintered ore to be easily pulverized, which is not conducive to sintering. In contrast, the present invention adjusts the proportion after the steel is produced to generate dicalcium silicate and other minerals that are beneficial to the performance of cement in the slag as much as possible. C2S (the dicalcium silicate) is easily transformed from β-C2S to γ-C2S with almost no water hardness at a temperature below 500°C, and the volume expands by 10%, causing the clinker to be pulverized. When the amount of liquid phase is large, rapid cooling can be used to prevent the crystal form transformation of C2S. Moreover, for most silicate minerals, when slowly cooled, the hydration activity will be reduced due to the over-complete development of the crystal. Therefore, when slag is discharged, the slag can be quickly cooled and broken by water quenching or wind quenching, and the crystallization temperature range can be quickly crossed to form glass or microcrystals, so as to avoid excessive crystallization leading to coarse crystals and reduced activity. Among common cement minerals, dicalcium silicate has a relatively low heat of hydration, and this embodiment is suitable for manufacturing medium-heat silicate cement and low-heat silicate cement.

[0067] 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 reduced slag, so that the metal oxides therein are reduced as much as possible to form simple substances, which is convenient for magnetic separation; the remaining slag generates cement minerals, thereby obtaining cement clinker, and the cement clinker is cement after being ground; in the process of grinding, the metal elements are separated therefrom by selective crushing. In other words, most of the slag can be made into cement clinker through the remelting of the slag, 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 by the way. 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 slag sensible heat to avoid waste.

[0068] Optionally, reducing agents are added as needed, and the smelting temperature and atmosphere are 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.

[0069] In addition, in the prior art, some steel slag can be used as fertilizer. The chemical composition of steel slag phosphate fertilizer varies depending on the quality of pig iron, the type and amount of flux and process conditions. When sufficient SiO2 is added, its main components are calcium silicophosphate (5CaO·P2O5·SiO2 and 7CaO·P2O5·2SiO2). When insufficient SiO2 is added, it is tetracalcium phosphate (Ca4P2O9). The effective ingredient content of the steel slag phosphate fertilizer is usually 16% to 20% in terms of P2O5. The P2O5 content of steel slag phosphate fertilizer produced domestically is mostly 3% to 8%. Although it is produced in steel mills in Anshan, Wuhan, Chongqing and other places, its promotion and application are limited due to its low phosphorus content and high processing cost.

[0070] In this embodiment, apatite can also be added to the slag, which is 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-containing 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 large seedlings, as a 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.

[0071] In addition, 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 of the human body. However, hexavalent chromium is a toxic substance and poses a potential threat to human health. Hexavalent chromium is a poisonous substance when ingested / extremely toxic when inhaled. Skin contact may cause allergies and may even cause hereditary gene defects. Inhalation may cause cancer and pose a lasting danger to the environment. However, these are the characteristics of hexavalent chromium, and chromium metal, trivalent or tetravalent chromium do not have these toxicities. If the hexavalent chromium remains in the slag, the toxicity can be eliminated after the slag is remelted and the hexavalent chromium is reduced, which can achieve unexpected results.

[0072] Example 3 In the smelting process of laterite nickel ore, ferronickel is produced by roasting and electric furnace smelting, and a large amount of slag is generated in this process; specifically, for every 1t of ferronickel produced, about 7-10t of slag is generated, of which nickel slag accounts for the main part; these slags not only occupy a large amount of land, but also may cause environmental pollution. Therefore, it is of great significance to study the comprehensive utilization of these slags. In the process of crushing, powdering and ore dressing of the slag, the present embodiment can improve the raw material grade, improve the metal recovery rate, and obtain slag powder, cement, or fertilizer through the joint operation of the grinding machine, the separation device and the powder separator during smelting.

[0073] See also 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 separation 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 separation device is a cyclone separator 31, and the powder classifier is a rotor powder classifier 32; the slag is rolled, sorted and powdered, and the sorting means include air separation, and magnetic separation and / or electric separation; after sorting, coarse particles and metals are discharged, and can be used as return ore to be added to the batch material or used for other metal smelting as needed; 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.

[0074] In detail, the main working parts of the vertical mill 3 (vertical mill) are the grinding disc and the 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 material falls to the center of the grinding disc through the material discharge chute. 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 crushed by the extrusion action. At the same time, shear force is generated due to relative sliding, so that the material is ground finely; the vertical mill uses the grinding roller to squeeze the material on the grinding disc, and relies on the airflow to bring the particles that meet the fineness requirements out of the mill, and collects them into finished products through the dust collector; inside the vertical mill, the larger particles in the airflow fall back to the grinding disc for grinding under the action of gravity. This process must be carried out many times to achieve the required fineness; the roller press consists of two extrusion rollers that rotate synchronously in opposite directions, one is a fixed roller and the other is a movable roller; both the vertical mill and the roller press are material bed grinding equipment.

[0075] For a long time, in the mineral processing industry, tube mills are usually used as grinding equipment. The tube mills include ball mills. A certain number of steel balls are loaded into the cylinder of the ball mills as grinding media. The main function of the steel balls in the ball mills is to impact and crush the materials, and they also play a certain grinding role. The existing technology often uses ball mills, which have extremely low grinding efficiency and high energy consumption. According to the research and experimental measurements of grinding workers in various countries in the world, the grinding efficiency of tube mills is only a few percent, and the rest is consumed by sound energy, wear energy consumption of grinding media and liner plates, etc. The fundamental reason is that tube mills usually adopt the principle of single-particle crushing. In single-particle crushing, each particle is crushed by contacting with the crushing equipment and being directly pressed or sheared by it, while material layer crushing is different from this. In the material entering the mill, the microstructure determines the mechanical properties. Different mineral structures result in different resistance to damage. The main function of the steel ball in the ball mill is to impact and crush the material. The impact force is the same, and the parts that should not be crushed are often crushed more, so it is easy to produce over-grinding. Different from the single particle crushing, the material bed grinding equipment adopts the material bed crushing (or material layer crushing) principle. Only a small part of the particles are in direct contact with the crushing equipment. Under the action of pressure, the materials are crushed by mutual extrusion. The crushing efficiency of the material layer crushing is high. The materials are crushed in the process of mutual extrusion, and there is no unnecessary energy waste, so energy saving is saved. Moreover, under normal circumstances, even the hardest minerals will not exceed the hardness of steel balls. The steel balls hit the materials indiscriminately, regardless of soft or hard ores, all of them are crushed, and those that do not need to be crushed temporarily are also crushed, so energy waste is generated. When using grinding rollers to crush mineral particle clusters, the soft ore is always crushed first, and then the soft ore particles hide in the space supported by the hard ore to escape further extrusion, thereby avoiding energy waste.

[0076] 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 barrel 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 airflow; 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 relatively hard; while in the fine material, the content of metal elements is relatively small.

[0077] The slag contains metal elements and olivines rich in metal elements, which are hard and difficult to grind. If it is a large piece, its metal element content is higher, and it will be discharged from the slag discharge port 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 grayish 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.

[0078] That is to say, compared with the common silicate minerals, olivine minerals are difficult to grind and relatively easy to grind. Thus, under the same grinding conditions, the coarseness and fineness will be different. After air separation, the difference in particle size can be used to separate slag particles and slag powder. Among them, slag particles are rich in metal elements, and slag powder is mostly silicate minerals. Therefore, the slag particles (i.e., the coarse particles, coarse materials) are separated and used as return ore, which improves the metal recovery rate.

[0079] Then, through the cyclone separator 31, the airflow separates the fine material from the material and conveys it to the powder classifier; in the present 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 a rotor; the fine material enters the powder selection chamber of the rotor-type powder classifier 32 along 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 after the collision, they lose kinetic energy and slide down along the wall and fall into the coarse powder collection cone, and the remaining particles are carried away by the rotating rising airflow, and 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. Slide down along the wall and enter the coarse powder collecting cone; after passing through the large wind blades, the medium coarse powder and fine powder continue to rise under the carrying 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; the particle size of the fine powder can be adjusted by adjusting the speed of the rotor, and the fine powder that meets the requirements is discharged with the airflow through the cage-type rotor, and is collected by the powder collecting equipment to become a finished product; the finished product fineness of this embodiment is set to 400 meshes to pass all, that is, the particle size does not exceed 37 microns.

[0080] In this embodiment, the coarse and heavy particles (coarse powder) and the medium coarse powder refer to materials with intermediate particle sizes, whose particle sizes are unqualified, so they are returned to the grinding mill and crushed again; metal particles are often wrapped by molten glass, and when crushed again, the glass shatters, and the metal particles are exposed, which is convenient for magnetic separation and electric separation.

[0081] Iron and nickel differ in some physical properties. The density of iron is 7.87 g / cm 3 , while the density of nickel is 8.90g / cm 3 , the density of nickel is greater than that of iron; the melting point of iron is 1535℃, while the melting point of nickel is 1455℃; both iron and nickel are magnetic metals, but the magnetism of nickel is lower than that of iron; among silicate minerals, calcium iron olivine is a mineral containing iron, so it has magnetism, but the magnetism is weak; therefore, magnetic separation can be used. In addition, materials are divided into three categories according to their conductivity: conductors, semiconductors and insulators. Electrostatic separation is a method of sorting in a high-voltage electric field based on the different electrical conductivity of minerals and gangue particles, so it can also be assisted by electrostatic separation.

[0082] In this embodiment, a powder collecting device is arranged after the powder classifier, and the powder collecting 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; the fine powder is obtained through the powder collecting device, and the fine powder is slag micro powder. The system exhaust gas is purified, and then drawn out by the induced draft fan 41 connected to the powder collecting device and discharged into the atmosphere.

[0083] In summary, the present invention achieves metal enrichment through grinding and sorting.

[0084] That is to say, the present invention utilizes the vertical mill 3 to crush the slag. During the grinding process, components rich in metal elements, namely slag particles, can be separated from the slag. The slag particles can be used as return ore to participate in the batching, or as concentrate for ironmaking, to achieve the enrichment of metal minerals (including nickel ore), which is beneficial to metal smelting; at the same time, the gangue minerals in the slag are ground to obtain slag powder. Furthermore, if the slag is remelted, cement or steel slag phosphate fertilizer can be obtained to replace the slag powder. Therefore, the present invention achieves multiple goals at one stroke and ultimately achieves the effect of energy saving.

[0085] 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 principle of the present invention. These improvements and modifications should also be regarded as 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: The raw ore of laterite nickel ore is crushed into powder, and mixed with fine coal and return ore in proportion to obtain a batch material, wherein the return ore is slag particles produced after slag sorting; the batch material is pressed into balls by a double-roll ball press; The complete material balls 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) to form a furnace body. The internal space of the furnace body is divided into a plurality of furnace chambers arranged vertically by an inclined partition (12); the furnace chambers are connected via a gate (13); the gate (13) is used to control the height of the material level and / or the discharge rate, so that the material balls in the preheating zone are controlled 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; metallized pellets are obtained by selective reduction reaction; the waste gas generated during the calcining process goes up into the preheating zone to dry the pellets entering the kiln; The metallized pellets and flux are fed into a smelting furnace (2) and smelted and separated to obtain a nickel-iron alloy.

2. A method for obtaining ferronickel alloy by smelting laterite nickel ore according to claim 1, characterized in that: After the batch material is pressed into balls, the balls are screened and the broken balls are returned for re-balling; 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 waste gas generated by calcination is drawn out from the top of the furnace and discharged into the atmosphere after purification; After obtaining the nickel-iron alloy, a slag discharge operation is performed to discharge the smelting slag from the slag discharge port 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 method of cooling the slag includes water quenching or air quenching.

3. A method for obtaining ferronickel alloy by smelting laterite nickel ore according to claim 1, characterized in that: 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, using the combustion of the 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. A method for obtaining nickel-iron alloy by smelting laterite nickel ore according to claim 1, characterized in that: Discharging the metallized pellets from the discharge port of the vertical calcining furnace (1), cooling, grinding and sorting to obtain concentrate and tailings, and returning the concentrate to pelletizing; After repeated smelting, high-grade nickel-iron alloy is obtained.

5. The method for obtaining nickel-iron alloy by smelting laterite nickel ore according to claim 1, characterized in that: After the metallized pellets and the flux are uniformly mixed, they are hot-charged into the smelting furnace (2) from the upper part thereof, wherein the flux comprises lime blocks or fluorite; the amount of the returned ore added is adjusted to firstly smelt a nickel-iron alloy having a nickel content of 8% to 10%, and then the alloy is transferred to a refining furnace, and after adding a chromium-containing metal, the alloy is blown by vacuum or semi-vacuum blowing according to 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 in the later stage.

6. The method for obtaining nickel-iron alloy by smelting laterite nickel ore according to claim 1, characterized in that: 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 by the slag remelting process; depending on whether the slag is remelted and the difference in the slag remelting process, the slag powder obtained is slag 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 oxygen blowing operation, reducing the metal oxides therein into simple substances as much as possible, and utilizing the remaining slag to generate cement minerals, thereby obtaining cement clinker, which 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. A method for obtaining nickel-iron alloy by smelting laterite nickel ore according to claim 6, characterized in that: 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: In the process of crushing, powdering and sorting the slag, components rich in metal elements, i.e. the slag particles, are separated from the slag through the combined operation of a grinding mill, a separation device and a powder 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 collecting device.

9. A method for obtaining nickel-iron alloy by smelting laterite nickel ore according to claim 8, characterized in that: When the slag is ground and sorted, the cooled slag is sent to the grinding mill for rolling, sorted by the separation device, and then the fineness of the slag powder is adjusted by the powder 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 combined 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 airflow. 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 an induced draft fan (41) connected to the powder collection device and discharged into the atmosphere.

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