A process for treating laterite nickel ore leach residue

Abstract

The application discloses a laterite nickel ore leaching residue treatment process and belongs to the technical field of heat treatment and equipment. The process specifically comprises series connection of an oxidation furnace and a reduction furnace, and the reduction furnace is connected with a cooler; the oxidation furnace is used for calcining neutralization and purification residues to obtain intermediate products of calcium oxide and sulfur dioxide, and the sulfur dioxide is used for sulfuric acid production; the calcium oxide is on-line dosed with acid leaching washing residues and fine coal, and then is pressed into balls, and the reduction furnace is used for secondary calcination to obtain sintered ore, and the sintered ore is cooled, ground and sorted to obtain iron concentrate and slag powder; in the secondary calcination, coal gas is obtained and is used as fuel of the oxidation furnace; hot air is obtained from the cooling process of the sintered ore and is used as combustion-supporting air of the oxidation furnace; by application of the application, different kinds of nickel residues are subjected to cascade calcination, hexavalent chromium elements are reduced, and the toxicity of hexavalent chromium is eliminated; the load of a kiln is reduced, and the product quality is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat treatment and equipment, and particularly relates to a laterite nickel ore leaching residue treatment process. BACKGROUND

[0002] Currently, the methods for extracting nickel metal from nickel ore mainly include fire method and wet method; among them, the high-pressure acid leaching process (HPAL) is to let the laterite nickel ore react with sulfuric acid at high temperature to selectively leach nickel and cobalt, that is, nickel and cobalt metal enter the leaching solution, and at the same time, part of the impurity ions such as iron, aluminum, magnesium, chromium and manganese also enter the leaching solution, the leaching solution is used to precipitate nickel-cobalt sulfide mixture or nickel-cobalt hydroxide intermediate product by using hydrogen sulfide, magnesium oxide or sodium hydroxide, etc., the intermediate product can be sold as a product, or can be further processed into a metal product; in the production process, most of the impurities such as iron and aluminum remain in the residue, and the residue is the nickel residue.

[0003] By using the laterite nickel ore and adopting the "high-pressure acid leaching (HPAL)-hydroxide precipitation" process to produce nickel-cobalt hydroxide product, the residue mainly includes neutralization and purification residue and leaching and washing residue; the main component of the neutralization and purification residue is gypsum, and the sulfur content is relatively high; the main components of the leaching and washing residue are hematite and silicon dioxide, etc., and the sulfur content is relatively low. According to estimation, about 100 tons of nickel residue will be produced for every 1 ton of metal nickel, and it is very urgent to solve the problem of resource utilization of the nickel residue.

[0004] Currently, most of the laterite nickel ore wet process projects adopt the wet high-pressure acid leaching process to extract nickel, and a large amount of iron-containing leaching residue is produced, and the annual discharge amount reaches several hundred million tons, the iron content in the residue reaches 30% to 55%, and the residue also contains valuable elements such as chromium, cobalt and nickel, which is a valuable secondary mineral resource; for the iron extraction scheme of such leaching residue, some people have tried to use coal-based (rotary kiln) magnetic roasting, but the sulfur content in the product obtained is obviously over standard; some people have also tried to use suspension magnetic roasting, but the roasting temperature of 500-600 DEG C is not enough to decompose the sulfate in the leaching residue, and other schemes such as electric furnace method have a production cost much higher than the benefit, so there is no relatively economic and mature comprehensive utilization scheme at present.

[0005] Chinese patent CN119661109A discloses a composite mineral admixture, a preparation method thereof and concrete, which comprises taking dolomite powder, gypsum and calcium hydroxide, mixing and modifying to obtain pre-modified dolomite powder; then adding hexadecyl trimethyl ammonium chloride and octyl phenol polyoxyethylene ether to obtain modified dolomite powder; and then adding nickel residue, metakaolin, desulfurization ash and grinding aid to obtain the composite mineral admixture after grinding. The concrete prepared by using the composite mineral admixture has excellent performance in terms of compressive strength, shrinkage resistance and permeability resistance, and can significantly improve the strength and durability of the concrete.

[0006] Chinese patent CN119638294A discloses a kind of multi-solid waste base non-burning water permeable brick and its preparation method, sequentially comprising the following steps: S1: pretreatment of solid waste; S2: mixing; S3: forming. This application uses nickel slag and waste concrete as water permeable brick aggregate, replacing the skeleton function of sand and stone, which not only meets the use strength but also has sufficient water permeability effect and high wear resistance. At the same time, the cement prepared by using nickel slag and steel slag as raw materials has high activity. The non-burning water permeable brick prepared by multiple solid wastes has simple process and excellent performance, which meets the construction quality requirements and has important significance for solid waste resourceization, reduction and ecological environment protection.

[0007] In actual production process, the inventors found that at least the following defects exist in the prior art:

[0008] Due to different ore-forming conditions, part of laterite nickel ore has strong oxidizing property. In the reaction process, chromium will generate hexavalent chromium in the form of Cr2O7 2- , which enters the leaching solution during leaching process, and its content can even reach 2g / L, resulting in the risk of residual hexavalent chromium in the nickel slag. Hexavalent chromium is an ingested and inhaled extremely toxic substance. Skin contact may cause sensitivity and genetic defects. Inhalation may cause cancer and have persistent danger to the environment. However, the existing technology for comprehensive utilization of nickel slag cannot eliminate the toxicity of hexavalent chromium. SUMMARY

[0009] Therefore, the present application provides a laterite nickel ore leaching residue treatment process. According to the different types of nickel slag, the calcination atmosphere of oxidation first and reduction later is selected. The intermediate product (calcium oxide) is used as raw material for the next stage of calcination and participates in batching online to realize cascade calcination.

[0010] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0011] Specifically, the purpose of the present application is achieved by the following technical solutions: a laterite nickel ore leaching residue treatment process, comprising: calcining neutralization and purification residue by using an oxidation furnace to decompose calcium sulfate in the residue and obtain calcium oxide and flue gas containing sulfur dioxide; purifying the flue gas and recovering sulfur dioxide therein for preparing sulfuric acid;

[0012] Mixing the calcium oxide with acid leaching washing residue and fine coal to obtain a mixture; after the mixture is pressed into balls, the balls are sent into a reduction furnace for reduction roasting, so that hexavalent chromium in the balls is reduced to low-valence chromium, and sintered ore is obtained; the sintered ore is cooled, ground and sorted to obtain iron concentrate and slag powder;

[0013] In the reduction roasting process, coal gas generated is led out and used as fuel of the oxidizing furnace; and hot air obtained in the cooling process of the sintered ore is used at least partially as combustion air of the oxidizing furnace;

[0014] The oxidizing furnace and the reduction furnace are connected in series, and the reduction furnace is connected with a cooler, by using the application, different kinds of nickel slag are calcined in stages, the load of the kiln is reduced, the toxicity of hexavalent chromium is eliminated, the product quality is improved, and resources and energy are saved.

[0015] As a further scheme of the application, the oxidizing furnace comprises a plurality of preheaters and combustion chambers arranged in series, the preheater is a cyclone preheater, and the combustion chamber is a suspension combustion chamber or a decomposition furnace; the reduction furnace is a rotary kiln or a vertical shaft kiln; and the cooler is a grate cooler or a single-cylinder cooler.

[0016] As a further scheme of the application, the gas outlet of the oxidizing furnace is provided with at least one of a vacuum pump and a CO detector; according to the detection result of the CO content, part of the flue gas is extracted and returned to the oxidizing furnace, or the supply amount of the oxygen-enriched air including the hot air is increased or decreased.

[0017] As a further scheme of the application, the purification treatment comprises wet washing, electric dust removal, mist removal and drying in sequence; the preparation of sulfuric acid is specifically that: sulfuric acid products are prepared through an SO2 conversion system and an SO3 absorption system; and the sulfuric acid is used for a high-pressure acid leaching process of the laterite nickel ore.

[0018] As a further scheme of the application, dust collection ash obtained from the flue gas purification treatment is returned to the oxidizing furnace, and secondary gypsum contained in the dust collection ash is decomposed by high temperature.

[0019] As a further scheme of the application, the calcium oxide is used entirely for the batching of the mixture; or part of the calcium oxide is used for the batching of the mixture, and another part of the calcium oxide is used for preparing lime milk and applied to a two-stage nickel and cobalt precipitation in the high-pressure acid leaching process or a tailing residue neutralization process.

[0020] As a further scheme of the application, the batching specifically comprises that: the calcium oxide is collected and temporarily stored through a separation cylinder connected with the outlet of the combustion chamber, and uniformly discharged through a quantitative discharger connected with a discharge port of the separation cylinder, and then mixed with acid leaching washing residue and fine coal after metering, and then enters a mixer to be uniformly mixed.

[0021] As a further scheme of the present application: the sinter is cooled, ground and sorted to obtain iron concentrate and slag powder, specifically: after the sinter is cooled, it is ground by a grinding mill and sorted by a cyclone separator to obtain coarse material and fine material; the coarse material is obtained as coarse concentrate after magnetic separation, and the rest is returned to the grinding mill as return material for regrinding; the fine material is sorted by a rotor classifier to obtain fine concentrate and slag powder; the fine concentrate and the coarse concentrate together constitute the iron concentrate.

[0022] As a further scheme of the present application: the slag powder is collected by a dust collector connected to the rear end of the rotor classifier, and the purified gas is discharged by an induced draft fan connected to the dust collector.

[0023] As a further scheme of the present application: the particle size of the fine concentrate is controlled by the rotational speed of the separator matched with the grinding mill; and / or the fineness of the slag powder is controlled by the rotational speed of the rotor classifier.

[0024] Compared with the prior art, the present application has the following advantages:

[0025] (1) The sulfur element in the nickel slag comes from the raw materials, and gypsum (calcium sulfate) generated in the acid leaching process; the present application feeds the neutralized and purified slag into the oxidation furnace separately, and the neutralized and purified slag is calcined and decomposed at high temperature, reducing the load of the kiln; then SO2 is recovered from the system exhaust gas to produce sulfuric acid, which can be recycled for high pressure acid leaching process (HPAL), thus achieving zero emission of sulfur elements.

[0026] (2) The hexavalent chromium in the nickel slag is toxic, but the toxicity of chromium metal, trivalent chromium or tetravalent chromium is much lower than that of hexavalent chromium; the present application reduces the residual hexavalent chromium in the nickel slag to low-valence chromium through secondary calcination (reduction roasting), which can eliminate the toxicity of hexavalent chromium and achieve harmless treatment of chromium; at the same time, coal gas is obtained in the reduction roasting, which is used as fuel for the oxidation furnace; and hot air is obtained from the cooler in the cooling process of the sinter, which is high-temperature and oxygen-rich, and part of it can be used as combustion air for the oxidation furnace; thus energy can be saved.

[0027] (3) The nickel slag is obtained after batching and secondary calcination, and the sinter is obtained after crushing and grinding; the product including iron concentrate and slag powder is separated from the sinter by dry magnetic separation and air separation process; the iron concentrate is used to replace iron ore, and the slag powder is used as a new admixture for high-performance concrete, which can significantly improve the comprehensive performance of concrete and its products; the iron, silicon, calcium and other elements in the product are all from the industrial waste slag in the nickel metal refining process; therefore, the present application can save resources and realize high-value utilization of industrial waste. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a schematic diagram of an embodiment of the present application;

[0029] Figure 2 is a flow chart of a staged calcination feed of an embodiment of the present application;

[0030] Figure 3 is a flow chart of a sintered ore grinding of an embodiment of the present application.

[0031] In the figure, 1 - oxidizing furnace; 11 - separation cylinder; 12 - air lock feed valve; 13 - first preheater; 14 - second preheater; 15 - combustion chamber;

[0032] 2 - reducing furnace; 21 - double shaft mixer; 22 - pair roller balling machine;

[0033] 3 - cooler;

[0034] 4 - vertical mill; 41 - cyclone separator; 42 - rotor type powder concentrator;

[0035] 5 - dust collector; 51 - induced draft fan. DETAILED DESCRIPTION

[0036] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application. It should be noted that the present application can be implemented in various different ways limited and covered by the claims, and the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0037] In the embodiments of the present application, various optional implementation manners are provided, which can be selected according to actual needs, can solve the problems in the prior art, and achieve corresponding effects; the following several embodiments can be applied to the treatment of nickel slag, and can also be applied to fluorogypsum, manganese slag, etc., therefore, the application of the present application includes but is not limited to nickel slag.

[0038] Embodiment 1

[0039] Reference is made to Figure 1 and Figure 2The embodiment provides a laterite nickel ore leaching residue treatment process, which comprises an oxidation furnace 1 and a reduction furnace 2 connected in series, the reduction furnace 2 is connected with a cooler 3, the oxidation furnace 1 comprises a plurality of preheaters and a combustion chamber connected in series, the preheater is a cyclone preheater, the cyclone preheater is also called a cyclone separator; the combustion chamber comprises a suspension combustion chamber, the suspension combustion chamber is also commonly called a decomposition furnace, fuel is combusted in the suspension combustion chamber by inhaling coal gas and combustion air to provide heat for material decomposition; the material of the feeding system is dried and calcined and then discharged from the combustion chamber along with the airflow, collected by a separation cylinder 11 connected with the combustion chamber and then fed into the reduction furnace 2; the reduction furnace 2 is a rotary kiln or a vertical cylinder kiln; the cooler 3 is a grate cooler or a single-cylinder cooler.

[0040] In the embodiment, the oxidation furnace 1 adopts a first preheater 13, a second preheater 14 and a combustion chamber 15 connected in series, and a separation cylinder 11 of the oxidation furnace 1 is connected at the outlet of the combustion chamber 15.

[0041] Nickel slag is usually divided into neutralized and purified slag and acid leaching and washing slag, and the chemical components and properties of the two are different, the embodiment utilizes the oxidation furnace 1 to calcine the neutralized and purified slag, calcium sulfate contained in the neutralized and purified slag is decomposed by heat to obtain intermediate products calcium oxide and sulfur dioxide, and the sulfur dioxide is discharged from the oxidation furnace 1 along with flue gas;

[0042] Under the condition of suitable high temperature and carbon monoxide concentration, most of the calcium sulfate is converted into calcium oxide, but a small amount of by-product calcium sulfide is generated, and the main reaction equation can be expressed as:

[0043] The by-reaction equation can be expressed as:

[0044] CaSO4+ 4CO↑ → CaS + 4CO2↑

[0045] The embodiment adopts a high-temperature decomposition method to utilize heat energy to decompose calcium sulfate; including, reducing gas such as carbon monoxide (coal gas) is introduced into the bottom of the combustion chamber of the oxidation furnace 1, the temperature interval is controlled to be 800-1200 DEG C, calcium sulfate can be decomposed into calcium oxide and sulfur dioxide gas is released; in addition,

[0046] The generation of by-product calcium sulfide reduces the sulfur dioxide concentration in the acid-making gas and reduces the desulfurization rate; therefore, further, in the embodiment, a hot air pipeline is arranged to be connected with the combustion chamber of the oxidation furnace 1, the hot air pipeline is used to provide hot air for oxidation of calcium sulfide, an oxidation zone is formed at the rear part of the combustion chamber, and the by-product calcium sulfide is oxidized to generate calcium oxide in the oxidation atmosphere with high temperature and low oxygen concentration, so that the desulfurization rate is improved.

[0047] On this basis, in another embodiment, a vacuum pump is used to operate in a semi-vacuum; including, a vacuum pump is provided at the gas outlet of the oxidation furnace 1 to reduce the gas pressure in the furnace and increase the vacuum degree; in particular, by adjusting the gas inlet and outlet valves, the vacuum degree (negative pressure) of the oxidation furnace 1 is maintained at about -3 kPa; the principle of vacuumizing is to accelerate the decomposition of calcium sulfate by reducing the number of gas molecules in the closed container. Calcium sulfate is a relatively difficult compound to decompose, and the use of semi-vacuum operation can accelerate the precipitation of SO2 gas; the reason is that the concentration of SO2 and CO2 generated by the decomposition reaction is equivalent to the decomposition pressure, and the greater the decomposition pressure, the more unstable the substance; the decomposition pressure is also called the equilibrium partial pressure, which is similar to the saturated vapor pressure, which refers to the pressure of the vapor in equilibrium with the liquid or solid under certain temperature and closed conditions. The same substance has different saturated vapor pressures at different temperatures, and increases with the increase of temperature; therefore, increasing the temperature can accelerate the reaction rate, but if the temperature is too high, the equipment will be severely burned, which is not conducive to the safety of the equipment; the use of semi-vacuum operation can reduce the calcination temperature and save energy; for example, it is not difficult to understand that water often boils at less than 100°C in high-altitude areas because of low air pressure. Moreover,

[0048] In the above reaction, the volume of the gas increases before and after the reaction, and vacuumizing makes the kinetic conditions better, promoting the forward reaction; among them, the vacuum pump is a device or equipment that can obtain vacuum by pumping the container, including a large suction fan; in simple terms, a vacuum pump is a device that uses various methods to improve, create and maintain a vacuum in a closed space; according to the working principle of the vacuum pump, the vacuum pump can be basically divided into two types, namely gas trapping pump and gas transmission pump; this embodiment creates an environment far below atmospheric pressure, and carbon monoxide (CO) burns in an environment below atmospheric pressure, i.e. CO burns under negative pressure, so that the gas in the combustion process can be effectively discharged, thereby reducing the risk of escape of CO and SO2, protecting the environment, and improving the combustion efficiency.

[0049] In this embodiment, the flue gas is discharged into the atmosphere after purification, and the contained sulfur dioxide is used for sulfuric acid production; including, a CO detection device is provided to detect the CO content in the flue gas discharge pipeline, if the CO content is higher than the set value, it indicates that the fuel is not fully burned and the combustion efficiency is low, therefore, a circulating fan is provided to extract part of the flue gas and return it to the oxidation furnace 1, and / or, the amount of oxygen-enriched air supply is increased; adjust the atmosphere, save fuel, and protect the environment.

[0050] The flue gas is purified by wet scrubbing and electric dust collection, and the collected dust is returned to the oxidation furnace 1 to decompose the secondary gypsum contained in the collected dust at high temperature. The secondary gypsum refers to the gypsum regenerated after the high-temperature CaO condenses and adsorbs SO2 in the flue gas. By eliminating gypsum circulation and reducing skinning, the sulfur content of sintered ore can be reduced, and the product quality can be improved.

[0051] As described above, after the desulfurization gypsum reacts with coal gas at high temperature, calcium oxide and sulfur dioxide are generated. The sulfur dioxide is used to produce sulfuric acid. The method for producing sulfuric acid includes the following steps: the flue gas is purified by wet scrubbing, electric dust collection, demisting, and drying, and then passes through an SO2 conversion system and an SO3 absorption system to produce finished sulfuric acid. The sulfuric acid is used for acid leaching process, which can achieve zero emission of sulfur. The core reaction for producing sulfur trioxide from sulfur dioxide is catalytic oxidation, and the chemical equation is 2SO2+ O2→ 2SO3, which needs to be carried out under the conditions of a catalyst (such as vanadium pentoxide) and a proper temperature (400-500°C).

[0052] Industrial acid production usually uses 96-98% concentrated sulfuric acid to absorb sulfur trioxide. When the concentrated sulfuric acid is sprayed from the top of the absorption tower, most of the sulfur trioxide dissolves in the sulfuric acid to generate oleum, and then various concentrations of pure sulfuric acid can be obtained by diluting the oleum.

[0053] Then, in the present embodiment, the following operations are performed: the calcium oxide is unloaded from the oxidation furnace 1, mixed with acid leaching washing residue and fine coal particles to obtain a mixture, the fine coal particles being coal particles with a particle size of 1-3 mm; after the mixture is pressed into balls, the balls are fed into the reduction furnace 2 for roasting, which is a secondary calcination; wherein,

[0054] In the present embodiment, the calcium oxide in the mixture is derived from the calcination of neutralization and purification residue and is used directly (online), including: using the separation cylinder 11 of the oxidation furnace 1 as a storage facility to separate and store in one step; and connecting a quantitative unloading device, including a rotary airlock unloader, to the discharge port of the conical part of the separation cylinder 11 for uniform unloading of calcium oxide. On this basis, part of the intermediate product calcium oxide can also be diverted for other uses; for example, in an additional embodiment, calcium oxide can be used to make lime milk, which is then used in the two-stage nickel and cobalt precipitation and tailings neutralization process of the high-pressure acid leaching process (HPAL).

[0055] That is, the calcium oxide is collected from the outlet stream of the combustion chamber as an intermediate product, then metered into the batch ingredients, and, after being uniformly stirred, pressed into balls; for example, in the present embodiment, a lock-hopper feed valve 12 and a double-shaft stirrer 21 are connected in sequence at the discharge port of the tapered portion of the separation cylinder 11, the batch ingredients are stirred uniformly, and then a pair-roller ball press 22 is used to press the batch ingredients into balls, the balls have a diameter of 40-50 mm, and the balls are fed into the reduction furnace 2 by gravity for calcination; the present embodiment uses the system's own negative pressure to reduce dust emission and protect the environment, and to load hot material into the furnace to save heat energy;

[0056] The present embodiment uses a pair-roller ball press 22 to press the batch ingredients into balls, the balls have a diameter of 40-50 mm, and are fed into the reduction furnace 2; after being pressed, the balls have high strength and are not easy to break, the size is uniform, which is beneficial to maintaining calcination in a reducing atmosphere and facilitating worker operation. Moreover, in the present embodiment,

[0057] (1) The size of the balls is uniform and the diameter is large, in the case of natural stacking, the outside is ventilated, and the inside is often in an oxygen-deficient state, combined with the use of fine coal in the present embodiment, the fine coal is wrapped in the balls, and the internal oxygen supply is relatively insufficient, the fine coal burns slower than the coal powder, causing the fire to be weaker than the coal powder, but the burning time is long, which helps to generate indirect reduction conditions; the indirect reduction is a process in which carbon monoxide generated by coal combustion is used as a reducing agent to react with metal oxides to generate metal elements and carbon dioxide; in the field, the reaction of metal oxides with CO to generate metal elements and CO2 can be represented by

[0058] MO + CO↑= M + CO2↑, where M is a metal element and MO is an oxide of the metal, this is a reversible reaction, which is restricted by the concentration of the reaction product CO2, if the concentration of CO2 is too high, the reaction will tend to stop. However, under high temperature conditions, as long as carbon exists, CO2 will not exist because CO2 will immediately react with carbon to generate CO,

[0059] CO2↑ + C = 2CO↑, the amount of gas changes from one to two, similar to a chain reaction, the generated CO is the reducing material for metal oxides; if the coal is quickly burned out, CO cannot be continuously provided, which is not conducive to the reduction of metal oxides, after all, the reduction process needs time. That is,

[0060] If lump coal is used, after the carbon on the surface is consumed, the deposition of coal ash affects the further combustion of carbon; or the carbon is used up, causing the CO2 produced by the reduction reaction to be unable to combine with carbon, resulting in too much CO2 in the environment, CO2 saturation, which loses the reduction ability, leading to the termination of the reduction reaction, and even the reversal, and no further reduction of metal oxides, which is not desirable in the present application;

[0061] Therefore, the embodiment can release CO slowly after using fine coal, keep the CO concentration in the environment at an ideal level at all times, and help the indirect reduction of metal oxides.

[0062] (2) At high temperatures, iron, nickel and chromium are very active metals and are easily oxidized. Even if they have been reduced, the products need to be protected by an atmosphere when cooling (discharging). Even if they are rapidly cooled, if there is air leakage, some of the metals will be oxidized, reducing the metallization rate. The embodiment reduces the air contact area by pressing the mixture into balls, thereby reducing the risk (degree) of oxidation of the metals after the high-valence metal oxides have been reduced to metal elements and / or low-valence metal oxides, that is, after the reduction, the products are as much as possible to avoid being oxidized again.

[0063] In addition, in the embodiment, the reduction furnace 2 is a rotary kiln, which is a rotary heat treatment equipment. The rotary kiln is composed of a cylinder, a supporting device, a transmission device, etc. The cylinder is arranged obliquely and supported by riding wheels, and is equipped with main and auxiliary transmission mechanisms. When working, raw materials are added at one end of the cylinder, calcined, and products are discharged at the other end, while the cylinder is continuously rotated to ensure uniform heating. The rotary kiln can use various fuels such as coal powder and gas. According to the heating method, it is divided into internal heating (the material directly contacts the flame, with a maximum temperature of 1600℃) and external heating (the cylinder wall conducts heat, with a maximum temperature of 1200℃), and is suitable for different process scenarios.

[0064] In the embodiment, when the material balls are calcined, the atmosphere in the furnace is controlled to be a reducing atmosphere, that is, the greater the CO partial pressure, the better. The greater the CO partial pressure, the faster and more complete the reduction of iron oxide. If the CO partial pressure exceeds 66.67% (i.e. the CO2 / CO partial pressure ratio is less than 0.5), the reduction of ferrous oxide will be triggered. At this time, ferrous oxide will be reduced to metallic iron, which is more conducive to the magnetic separation and air separation of the calcined product sinter.

[0065] In summary, the material balls are obtained after the secondary calcination of the sinter, the sinter is cooled, ground, and separated to obtain iron concentrate and slag powder, the separation method includes air separation and magnetic separation; and coal gas is obtained from the secondary calcination of the material balls, the coal gas is drawn from the reduction furnace 2 and used as fuel for the oxidation furnace 1 online; and hot air is obtained from the cooler 3 during the cooling process of the sinter, the hot air is high-temperature oxygen-rich, and part of it is used as combustion air for the oxidation furnace 1.

[0066] As can be seen, compared with the prior art, the embodiment has the advantages of simple structure, reasonable design and easy implementation.

[0067] Embodiment 2

[0068] Referring to Figure 1 and Figure 2 , the embodiment provides a laterite nickel ore leaching residue treatment process, which comprises an oxidation furnace 1 and a reduction furnace 2 connected in series, the reduction furnace 2 is connected with a cooler 3, the oxidation furnace 1 comprises a plurality of preheaters and a combustion chamber connected in series, the preheater is a cyclone preheater, the cyclone preheater is also called a cyclone separator; the combustion chamber comprises a suspension combustion chamber, which is also commonly called a decomposition furnace, fuel is burned in the suspension combustion chamber by inhaling coal gas and combustion air to provide heat for material decomposition; the material fed by the feeding system is dried and calcined and then discharged from the combustion chamber with the airflow, collected by a separation cylinder 11 connected with the combustion chamber and then fed into the reduction furnace 2; the reduction furnace 2 is a rotary kiln or a vertical shaft kiln; the cooler 3 is a grate cooler or a single-cylinder cooler.

[0069] In the embodiment, the neutralization and purification residue is calcined by the oxidation furnace 1, calcium sulfate contained in the neutralization and purification residue is decomposed by heat to obtain intermediate products calcium oxide and sulfur dioxide, and the sulfur dioxide is discharged from the oxidation furnace 1 with the flue gas;

[0070] On the basis of the embodiment 1, in the embodiment, the neutralization and purification residue in a high-temperature powder state and with a very small particle size (usually less than 50 microns) is sprayed into the hot space of the suspension combustion chamber, is rapidly heated, the sulfate contained in the neutralization and purification residue is rapidly decomposed, and the generated sulfur-containing gas enters the flue gas;

[0071] In the production of nickel-cobalt hydroxide products by using the "high-pressure acid leaching (HPAL)-hydroxide precipitation" technology, the tailings mainly come from: a. high-pressure acid leaching residue thickener underflow, b. leaching solution iron and aluminum removal underflow, c. high-pressure acid leaching tail gas washing water, two-stage nickel-cobalt hydroxide precipitation thickener overflow liquid and other smelting plant wastewater; in the traditional process, the a, b and c three kinds of slurry are combined into the tailings neutralization process, lime milk is added for neutralization treatment, the slurry pH value is adjusted to 8.1-8.5, and the neutralized slurry is pumped to the tailings storage for storage; in the embodiment, the tailings a is defined as "leaching washing residue", and the tailings b and c are combined and defined as "neutralization and purification residue".

[0072] In the embodiment, the slurry of the neutralization and purification residue is pretreated, and the pretreatment mode comprises spray drying, and the specific scheme is that: the neutralization and purification residue slurry is concentrated by a thickener, the water content is reduced to below 55%, is pumped into a drying tower to form a mist liquid, the drying tower is located between two-stage preheaters and is connected by airflow pipelines at the head and tail; the mist liquid is fully contacted with high-temperature waste gas of the system and is dried; the dried neutralization and purification residue powder enters the next-stage preheater with the airflow, is further heated, is then settled and separated by a cyclone separator, is metered and then fed into the suspension combustion chamber;

[0073] The smaller the particle size, the larger the specific surface area, and increasing the specific surface area can accelerate the decomposition reaction; the neutralization and purification slag is very fine itself, and the prior art usually adopts pressure filtration. If pressure filtration is to be performed, agglomeration will occur between the particles, and therefore, drying, grinding and screening are required after pressure filtration. The embodiment discards pressure filtration and adopts spray drying, which can fully utilize waste heat resources, and the grinding and screening processes are omitted, thereby reducing the comprehensive cost.

[0074] In addition, if classified according to chemical properties, the neutralization and purification slag includes industrial water-containing waste slag such as desulfurization gypsum and fluorogypsum, and the initial state of each is a precipitate generated in water, and the particle size is extremely small. The smaller the particle size of the material, the larger the specific surface area, which results in that the filter cake after pressure filtration has extremely strong adhesion and is easy to adhere to equipment, which brings difficulties to accurate metering. For a long time, there has been no good solution. The embodiment utilizes pumping to solve this problem by metering the flow of the slurry. This is because: the density of the slurry represents the solid content, and after concentration, the density of the slurry is controllable; the density and flow of the slurry are both easy to accurately measure, and the result of the product of the two minus the moisture is the feeding amount of the solid, which is also accurate.

[0075] Embodiment 3

[0076] With reference to Figure 1 and Figure 2 , the embodiment provides a laterite nickel ore leaching slag treatment process, which comprises an oxidation furnace 1 and a reduction furnace 2 connected in series in front and back, the reduction furnace 2 is connected with a cooler 3, the oxidation furnace 1 comprises a plurality of preheaters and a combustion chamber connected in series, the preheater is a cyclone preheater, and the cyclone preheater is also called a cyclone separator; the combustion chamber comprises a suspension combustion chamber, and the suspension combustion chamber is usually also called a decomposition furnace, fuel is combusted in the suspension combustion chamber by inhaling coal gas and combustion air to provide heat for material decomposition; the material of the feeding system is discharged from the combustion chamber after drying and calcination with the airflow, collected by a separation cylinder 11 connected with the combustion chamber and then fed into the reduction furnace 2; the reduction furnace 2 is a rotary kiln or a vertical cylinder kiln; and the cooler 3 is a grate cooler or a single-cylinder cooler.

[0077] On the basis of the embodiment 1, the embodiment first calcines desulfurization gypsum and / or neutralization and purification slag by using the oxidation furnace 1 to obtain calcium oxide; the calcium oxide is mixed with acid leaching washing slag, fine coal and auxiliary raw materials to prepare material balls, the material balls are calcined for the second time to obtain sintered ore, and the sintered ore is cement clinker.

[0078] In this embodiment, during batching, the cement clinker rate value control range is as follows: saturation ratio KH is 0.88±0.05, silicon rate SM is 2.50±0.20, and aluminum rate IM is 1.6±0.10; the material ball enters the rotary kiln online for calcination, the calcination temperature is controlled to be 1300-1500℃, the calcination time is 20-30min, and the cement clinker is obtained after being cooled by the grate cooler.

[0079] In the related art, the calcination of nickel slag is often mixed with neutralized and purified slag and acid leaching and washing slag for calcination, which causes a large load of the kiln, and there are still many other defects, and the specific reasons are analyzed as follows: if the neutralized and purified slag and the acid leaching and washing slag are mixed together for calcination, first, calcium sulfate as a mineralizer can reduce the clinker firing temperature and promote the progress of mineralization reaction; however, if excessive calcium sulfate is mixed, the liquid phase will appear early, causing adhesion and affecting production operation; however, for the acid production process, it is inevitable to mix excessive calcium sulfate; second, calcium sulfate can react with other components in the clinker to form new mineral phases, affecting the mineral composition; that is, the change of the content of calcium sulfate will affect the formation of iron phase and calcium sulphoaluminate in the clinker, and further affect the mineral composition and performance of the clinker; for example, the change of the content of calcium sulfate will cause the change of the existing form of iron oxide (FeO, Fe2O3) in the clinker, thereby affecting the physical and chemical properties of the clinker; and because calcium sulfate reacts with other components in the clinker to form solid solution, the decomposition of calcium sulfate is difficult, the amount of sulfur dioxide escaping is also correspondingly reduced, and the production of sulfuric acid is reduced.

[0080] Therefore, in the related art, there is a technical contradiction between the production of sulfuric acid by using gypsum (calcium sulfate) and the production of sintered ore (including cement clinker); the technical contradiction includes the restriction of cement varieties caused by the influence of calcium sulfate on clinker firing; the restriction is shown in, for example, when producing cement clinker and co-producing sulfuric acid by using calcium sulfate resources of industrial waste slag, it is basically to produce sulphoaluminate special cement, and it cannot produce ordinary portland cement which has a more widely used range; if ordinary portland cement is to be produced, the amount of limestone to be added needs to be increased, but the carbon dioxide generated by the decomposition of limestone will greatly dilute the concentration of sulfur dioxide, increasing the cost and difficulty of preparing sulfuric acid from sulfur dioxide. In addition, the related art cannot realize fine operation according to the specific characteristics of the materials such as particle size and moisture.

[0081] To this end, the present application creatively adopts cascade calcination, different materials with different properties are added into the system in batches, and the intermediate product calcium oxide is directly (on-line) fed into the next link, and different calcination atmospheres are selected respectively; in the reduction roasting, the residual hexavalent chromium in the nickel slag is reduced to low-valence chromium, which not only solves the technical problem that the existing technology cannot eliminate the toxicity of hexavalent chromium in the comprehensive utilization of nickel slag, eliminates the toxicity of hexavalent chromium, realizes the harmless treatment of chromium, and achieves the purpose of the application, but also overcomes the technical contradiction of the related technology; specifically, compared with the related technology, additionally, the present application can promote the decomposition of calcium sulfate and separate out sulfur element for acid production in advance; therefore, the present application can produce sulfuric acid while reducing the solid solution amount of calcium sulfate in sintered ore, and breaking the cycle of calcium sulfate in the kiln, reducing the phenomenon of skinning, and facilitating operation; produce ordinary portland cement clinker, thereby meeting the greater market demand, and then improving the ability to absorb industrial waste slag; the cycle of calcium sulfate in the kiln refers to: in the prior art, part of the calcium sulfate is taken away with the clinker, but part of it is volatilized and decomposed in the kiln, and then returns to the decomposition furnace with hot flue gas and flying sand, forming a cycle.

[0082] In short, by applying the present embodiment, cascade calcination of different types of nickel slag is realized, which can reduce the load of the kiln, improve the product quality, and save resources and energy.

[0083] Embodiment 4

[0084] Referring to Figure 1 , Figure 2 and Figure 3 , on the basis of any one of embodiments 1-3, the present embodiment further provides a treatment method of the sintered ore, including the specific steps of crushing, grinding and sorting as follows:

[0085] In the present embodiment, the sintered ore is crushed, ground and sorted by using a pulverizer and a powder separator; the pulverizer includes a vertical mill 4; the powder separator includes a cyclone separator 41 and a rotor-type powder separator 42;

[0086] The sinter is discharged after being crushed by the vertical mill 4, and the coarse material is separated from the material discharged from the vertical mill 4 by the cyclone 41. The coarse material is combined with the slag particles discharged from the slagging port of the vertical mill 4, and is subjected to magnetic separation to obtain coarse concentrate and return material, which is re-ground. The fine material separated from the material discharged from the vertical mill 4 is carried into the rotor classifier 42 by the powder separation airflow, and is separated by the rotor classifier 42 to obtain medium coarse powder and fine powder. Under the same grinding conditions, silicate minerals and their glass bodies are easier to grind than iron ore, and thus are reduced in size relatively quickly, and thus become the fine powder first. In this embodiment, the medium coarse powder is powder concentrate, and the powder concentrate is CF / CFS mineral containing FeO, i.e., calcium iron garnet / calcium iron olivine, etc. The powder concentrate has relatively large hardness, and is relatively difficult to grind compared with silicate minerals and their glass bodies. The powder concentrate and the coarse concentrate are both rich in iron elements, and thus are collectively referred to as iron concentrate. The fine powder is slag micro-powder, and the slag micro-powder contains silicate minerals such as tricalcium silicate and dicalcium silicate, which are the source of the water hardness of cement. After being made into micro-powder, the activity is better, and thus the slag micro-powder has high added value. In this embodiment, the fineness of the slag micro-powder is set to 400 mesh, i.e., all particles have a particle size of not more than 37 microns. Correspondingly, the pore size of the 400 mesh screen is about 38 microns. The slag micro-powder is discharged from the rotor classifier 42 along with the powder separation airflow. The rotor classifier 42 is also connected to a dust collector 5, and the slag micro-powder is collected by the dust collector 5. The purified gas is discharged and exhausted by the induced draft fan 51 connected to the dust collector 5.

[0087] In this embodiment, the particle size of the powder concentrate is controlled by adjusting the rotational speed of the in-mill separator matched with the vertical mill 4, and / or the fineness of the slag micro-powder is controlled by adjusting the rotational speed of the rotor of the rotor classifier 42.

[0088] Under normal circumstances, in order to ensure the quality during tapping, there is no slag in the steel, and there is steel in the slag. After the technical scheme is applied, in addition to the coarse concentrate mainly containing elemental iron being recovered, the powder concentrate can also be collected, the loss of iron elements is prevented to the maximum extent, and resources are saved. At the same time, the slag micro-powder is obtained, and high value-added utilization is realized.

[0089] The above only describes the preferred embodiments of the present application. It should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A process for the treatment of laterite nickel ore leach residue, characterised in that, The application relates to a method for producing iron concentrate and slag powder from laterite nickel ore. The method comprises the following steps: calcium oxide is obtained by calcining and neutralizing and purifying the residue, and the calcium oxide is used for the preparation of the mixture; the mixture is pressed into balls, and the balls are sent into a reduction furnace for reduction roasting, so that hexavalent chromium in the balls is reduced into low-valence chromium, and sintered ore is obtained; the sintered ore is cooled, ground and separated to obtain iron concentrate and slag powder; in the reduction roasting process, coal gas is generated and is used as fuel of the oxidation furnace; and hot air obtained in the cooling process of the sintered ore is used as combustion air of the oxidation furnace at least partially; the oxidation furnace and the reduction furnace are connected in series, and the reduction furnace is connected with a cooler; the oxidation furnace comprises a plurality of preheaters and combustion chambers which are arranged in series, the preheaters are cyclone preheaters, and the combustion chambers are suspension combustion chambers or decomposition furnaces; the reduction furnace is a rotary kiln or a vertical shaft kiln; all of the calcium oxide is used for the preparation of the mixture; or part of the calcium oxide is used for the preparation of the mixture, and the other part of the calcium oxide is used for the preparation of lime milk and is applied to the second-stage nickel-cobalt precipitation or tail residue neutralization process in the high-pressure acid leaching process; in the production of nickel-cobalt hydroxide by the high-pressure acid leaching-hydroxide precipitation technology, tail residue a is obtained from the bottom flow of a high-pressure acid leaching residue thickener, tail residue b is obtained from the iron and aluminum removal bottom flow of leaching liquid, and tail residue c is obtained from the washing water of high-pressure acid leaching tail gas, the overflow liquid of the second-stage nickel-cobalt hydroxide precipitation thickener and other waste water of a smelting plant; the tail residue a is defined as leaching and washing residue; tail residues b and c are combined and defined as neutralization and purification residue.

2. The processing of laterite nickel ore leach residue according to claim 1, characterised in that, the cooler is a grate cooler or a single-cylinder cooler.

3. The processing of laterite nickel ore leach residue according to claim 2, characterised in that, at least one of a vacuum pump and a CO detector is arranged at the gas outlet of the oxidation furnace; according to the CO content detection result, part of the flue gas is returned to the oxidation furnace, or the supply amount of oxygen-enriched air is increased or decreased, the oxygen-enriched air comprising the hot air.

4. The processing of laterite nickel ore leach residue according to claim 3, characterised in that, the purification treatment comprises wet washing, electric dust removal, mist removal and drying in sequence; the preparation of sulfuric acid is that sulfuric acid products are prepared through an SO2 conversion system and an SO3 absorption system; and the sulfuric acid is used for the high-pressure acid leaching process of the laterite nickel ore.

5. The processing of laterite nickel ore leach residue according to claim 4, characterised in that, dust collection ash obtained from the flue gas purification treatment is returned to the oxidation furnace, and high-temperature decomposition of secondary gypsum contained in the dust collection ash is carried out.

6. The processing of laterite nickel ore leach residue according to claim 5, characterised in that, the preparation of the mixture comprises the following steps: the calcium oxide is collected and temporarily stored through a separation cylinder connected with the outlet of the combustion chamber, is uniformly discharged through a quantitative discharger connected with a discharging port of the separation cylinder, is metered with the leaching and washing residue and the fine coal, and is mixed uniformly in a stirrer.

7. The laterite nickel ore leach residue treatment process of claim 1, characterised by, the cooling, grinding and separation of the sintered ore to obtain the iron concentrate and the slag powder are as follows: the sintered ore is cooled, is ground through a grinding machine, and is separated through a cyclone separator to obtain coarse material and fine material; the coarse material is magnetically separated to obtain coarse concentrate, and the remaining coarse material is returned to the grinding machine for regrinding; the fine material is separated through a rotor-type powder separator to obtain powder concentrate and slag powder; and the powder concentrate and the coarse concentrate jointly constitute the iron concentrate.

8. The processing of laterite nickel ore leach residue according to claim 7, characterised in that, The slag powder is collected by a dust collector connected to the rear end of the rotor classifier, and the purified gas is discharged by an induced draft fan connected to the dust collector and then exhausted.

9. The processing of laterite nickel ore leach residue according to claim 8, characterised in that, The particle size of the fine concentrate is controlled by the rotational speed of a separator matched with the grinding mill, and / or the fineness of the slag powder is controlled by the rotational speed of the rotor classifier.

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