A method for preparing high-metalization-rate reduced iron blocks by using low-energy consumption of laterite nickel ore high-pressure acid leaching slag

Abstract

The application discloses a method for preparing high-metalization-rate reduced iron blocks by utilizing laterite nickel ore high-pressure acid leaching slag with low energy consumption, and belongs to the technical field of metallurgical solid waste resource utilization. The method is that the laterite nickel ore high-pressure acid leaching slag is placed in a reducing atmosphere to be low-temperature reduction roasting to obtain primary roasting sand; the primary roasting sand is placed in a non-reactive atmosphere to be high-temperature desulfurization roasting to obtain final roasting sand; and the final roasting sand is formed by hot pressing to obtain reduced iron blocks. The method adopts a process flow of "first reduction, then desulfurization, and then hot pressing", has the advantages of compact flow, low energy consumption, easy recovery of iron and sulfur elements, and the like, can efficiently convert the laterite nickel ore high-pressure acid leaching slag into high-strength, low-impurity, high-metalization-rate high-quality reduced iron blocks, and simultaneously obtains high-concentration SO2 meeting the requirements of acid production, so that the iron and sulfur resources in the laterite nickel ore high-pressure acid leaching slag are scaled and high-valued and cleaned utilized, the process conditions of the method are mild and stable in operation, and the method has a good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to a processing method of laterite nickel ore high-pressure acid leaching slag, in particular to a method for preparing high-metalization-rate reduced iron blocks by low-energy consumption using laterite nickel ore high-pressure acid leaching slag, and belongs to the technical field of metallurgical solid waste resource utilization. BACKGROUND

[0002] At present, the supply structure of nickel resources has undergone a fundamental change. With the economic mineability of sulfide nickel ore resources deteriorating and becoming increasingly exhausted, laterite nickel ore has become the main source of global nickel and its product supply. For the huge reserves of low-grade limonite type laterite nickel ore, the high-pressure acid leaching process has become the mainstream trend for processing this type of resources due to its good adaptability to ores, high comprehensive recovery rate of nickel and cobalt, and low carbon emissions. However, after efficiently and selectively leaching nickel and cobalt valuable metal elements, a large amount of residual acid leaching slag is produced. The slag has a high iron content and is a potential ironmaking raw material, but due to its physical and chemical properties such as extremely fine particle size, high sulfur content, and high silicon and aluminum impurities, its resource utilization is extremely difficult. At present, the laterite nickel ore high-pressure acid leaching slag is basically treated by stacking, which not only wastes iron resources, but also poses a significant environmental risk.

[0003] There are many research reports on the recovery of iron resources from high-pressure acid leaching residue of laterite nickel ore in the prior art. Among them, the direct reduction process is considered as a potential preferred technical path for treating high-pressure acid leaching residue because it can effectively treat refractory iron minerals with fine mineral dissemination particle size and complex composition. Since sulfur significantly deteriorates the performance of steel and is considered as a very harmful impurity, deep removal of sulfur from acid leaching residue is a basic prerequisite for its use as an ironmaking raw material. Existing processes usually follow the process of “first desulfurization, then briquetting, and then reduction”. After drying, the acid leaching residue is first desulfurized in a weak reducing or oxidizing atmosphere; then the desulfurized residue is briquetted with water to form a particle size and physical and mechanical properties that meet the requirements of the direct reduction process. During the entire process, the acid leaching residue with a water content of 30% to 40% must be completely dried before desulfurization, and water must be added again during the briquetting stage. Finally, the water is removed again during the drying and preheating stage. This repeated cycle of “first drying, then wetting, and then drying” results in a significant increase in overall energy consumption due to the repeated consumption of heat energy during water evaporation and re-heating of the material. More importantly, high-pressure acid leaching residue has the characteristics of ultra-fine particle size, high silicon, and high aluminum. During direct reduction, not only are difficult-to-reduce phases such as fayalite and SiO2-Al2O3-FeO (S-A-F) glass phases generated, but these phases also wrap the unreduced iron oxides, further hindering the diffusion of reducing gas, resulting in limited final reduction degree. As a result, the metallization rate of the product is usually difficult to break through 70%, and further high-energy consumption smelting reduction is required for deep reduction and recovery of iron. For example, Chinese patent application (application publication number: CN118326154A) discloses that after the laterite nickel ore high-pressure acid leaching residue is made into material balls and mixed with limestone, it is first calcined at 900-1000°C for 45-60 min, and then smelted at 1550-1650°C for 2-3 h to obtain molten iron and hot molten slag. In essence, this is a method of reducing the decomposition temperature of sulfates by adding reducing agents, removing part of the sulfur content in the slag by calcination, thereby reducing the sulfur entering the subsequent smelting process, and finally obtaining molten iron through deep reduction of the slag during high-temperature smelting. SUMMARY

[0004] In view of the technical problems of long process, high energy consumption and low metallization rate in the prior art of treating laterite nickel ore high-pressure acid leaching residue by adopting the traditional "desulfurization first, then briquetting, and then reduction" process, the purpose of the present application is to provide a method for preparing high metallization rate reduced iron block by utilizing laterite nickel ore high-pressure acid leaching residue with low energy consumption, which adopts the process flow of "reduction first, then desulfurization, and then hot pressing", has the advantages of compact process flow, low energy consumption, easy recovery of iron and sulfur elements, and can efficiently convert the laterite nickel ore high-pressure acid leaching residue into high-strength, low-impurity and high-metal content high-quality reduced iron block, and simultaneously obtain high-concentration SO2 to meet the requirements of acid production, so as to realize the large-scale and high-value clean utilization of iron and sulfur resources in the laterite nickel ore high-pressure acid leaching residue, and the process conditions of the method are mild and stable, and the method has good industrial application prospect.

[0005] In order to achieve the above technical purpose, the present application provides a method for preparing high metallization rate reduced iron block by utilizing laterite nickel ore high-pressure acid leaching residue with low energy consumption, which comprises the following steps:

[0006] 1) The laterite nickel ore high-pressure acid leaching residue is placed in a reducing atmosphere and subjected to low-temperature reduction roasting at a temperature of 300-550 DEG C to obtain primary calcine;

[0007] 2) The primary calcine is placed in a non-reactive atmosphere and subjected to high-temperature desulfurization roasting at a temperature of 700-1000 DEG C to obtain final calcine; the final calcine is formed into a reduced iron block by hot pressing; and the sulfur dioxide flue gas generated in the desulfurization roasting process is used for acid production.

[0008] In the process of preparing high metallization rate reduced iron block by utilizing laterite nickel ore high-pressure acid leaching residue, the key is to adopt the process path of "reduction first, then desulfurization, and then hot pressing", which can not only efficiently convert the laterite nickel ore high-pressure acid leaching residue into high-strength, low-impurity and high-metal content high-quality reduced iron block, but also obtain high-concentration SO2 to meet the requirements of acid production, so as to realize the resource utilization of iron and sulfur in the laterite nickel ore high-pressure acid leaching residue, and at the same time, the energy consumption can be greatly reduced.

[0009] In the prior art, the process path of "desulfurization first and then reduction" is generally adopted, and in the desulfurization process, high temperature can cause significant sintering densification and agglomeration of the material, destroy the porous structure, reduce the reaction activity, and further lead to the decrease of the efficiency of the subsequent reduction process and the increase of energy consumption. If the reduction efficiency is to be compensated, the reduction temperature needs to be correspondingly increased, but at the same time, this can also aggravate the generation of iron olivine and other difficult-to-reduce phases, and finally seriously restrict the metallization rate.

[0010] The process route of "reduction first, desulfurization later, and hot-pressing forming later" adopted by the present application is used to reduce the laterite nickel ore high-pressure acid leaching slag at low temperature, which can avoid the generation of reduced iron phases such as fayalite and prevent the decomposition of sulfate to produce sulfur dioxide. Based on the above route design, the characteristics of the laterite nickel ore high-pressure acid leaching slag, such as porous structure, ultra-fine iron oxide particle size, and high reduction activity, can be fully utilized, and the metallization rate of iron oxide is more than 90% at low temperature, and then the primary calcine with high metallization rate is obtained. The primary calcine can further complete efficient and concentrated desulfurization under suitable temperature and atmosphere conditions, so that the residual sulfur content is less than 0.1%, and sulfur dioxide flue gas with a volume concentration of not less than 3.5% is obtained and directly used for acid production, realizing the resource utilization of sulfur element. It should be noted that, in order to obtain high-strength and high-quality reduced iron block, the process route of "desulfurization first, and then hot-pressing forming" must be followed. If hot-pressing is performed first, the dense reduced agglomerates formed will seriously hinder the escape of product gas SO2 to the outside, resulting in deterioration of desulfurization kinetic conditions and reduction of desulfurization efficiency. At the same time, the gas produced by the decomposition of alunite and other phases contained in the reduced iron agglomerates at high temperature cannot be discharged in time, and holes and micro-cracks will be formed inside, which will seriously damage the structural integrity, resulting in insufficient product strength and failure to meet the subsequent smelting requirements.

[0011] In summary, the process route of "reduction first, desulfurization later, and hot-pressing forming later" adopted by the present application can not only obtain high-strength, low-impurity, and high-metallization-rate high-quality reduced iron block, but also obtain high-concentration SO2 that meets the requirements of acid production, realizing the resource utilization of the laterite nickel ore high-pressure acid leaching slag.

[0012] As a preferred scheme, the reducing atmosphere is a gas containing hydrogen and / or carbon monoxide. The reducing atmosphere can be carbon monoxide or hydrogen, or carbon monoxide and / or hydrogen in combination with other non-reactive gases, but the volume concentration of hydrogen and / or carbon monoxide in the reducing atmosphere is not less than 20%. The present application uses gaseous reducing agents such as hydrogen or carbon monoxide, which have strong diffusion ability and are especially suitable for the characteristics of the porous structure of the laterite nickel ore high-pressure acid leaching slag and the ultra-fine particle size of iron oxide, which is beneficial to the penetration and efficient reduction of the laterite nickel ore high-pressure acid leaching slag.

[0013] As a preferred scheme, the low-temperature reduction roasting time is 0.1-3 h. The low-temperature reduction roasting temperature of the present application is controlled at 300-550 ℃. If the reduction roasting temperature is too low, the reaction kinetics is extremely slow, and the reduction efficiency is too low. If the reduction roasting temperature is too high, not only is it easy to cause the generation of a large amount of low-temperature liquid phase and other adverse phases such as fayalite, which is not conducive to obtaining a high metallization rate product and process smoothness, but also high temperature can cause the decomposition of the sulfur-containing phase containing alunite and further reaction with the reducing agent to generate H2S and other gaseous sulfides, which not only causes the difficulty in recycling and utilization of the reduction gas, but also directly reduces the sulfur recovery rate in the subsequent desulfurization step. Controlling the reduction roasting time within the preferred range not only ensures a higher metallization rate, but also reduces energy consumption as much as possible. After low-temperature reduction roasting, the metallization rate of the obtained primary calcine is not less than 90%, and the residual sulfur content is not less than 92%, which creates a favorable prerequisite for the subsequent concentrated removal of sulfur dioxide at high temperature.

[0014] As a preferred scheme, the non-reactive atmosphere is nitrogen and / or inert gas. The inert gas is, for example, argon. The non-reactive atmosphere is N2 and / or Ar, and the use of a non-reactive atmosphere can prevent the metal iron from being oxidized again, thereby ensuring the metallization rate of the final product, and can also avoid the side reaction between the reducing gas and the sulfur-containing phase, thereby directly ensuring the purity of the high-concentration SO2 flue gas and the residual sulfur content of the final product.

[0015] As a preferred scheme, the high-temperature desulfurization roasting time is 0.1-2 h. The high-temperature desulfurization roasting temperature of the present application is preferably 700-1000 ℃. If the desulfurization roasting temperature is lower than 700 ℃, the desulfurization kinetics is slow and the efficiency is low, which is not conducive to obtaining high-concentration SO2 and clean final calcine. If the desulfurization roasting temperature is higher than 1000 ℃, it is easy to cause excessive sintering between particles or softening of the material, increase energy consumption, and affect the smooth progress of the process. Controlling the high-temperature desulfurization roasting time within the preferred range can ensure the sufficient removal of sulfur while saving energy. Under the preferred high-temperature desulfurization roasting conditions, the residual sulfur content of the final calcine is less than 0.1%, and the volume concentration of SO2 flue gas is not less than 3.5%. The low residual sulfur content can ensure that the sulfur content of the final reduced iron block meets the requirements of high-quality ironmaking raw materials, avoiding adverse effects on the subsequent smelting and steel performance. The high concentration of SO2 in the SO2 flue gas provides the necessary conditions for acid production, and can be recycled for use in the high-pressure acid leaching process, thereby reducing operating costs.

[0016] As a preferred scheme, the hot-pressing forming condition is that the atmosphere is a non-reactive atmosphere, the hot-pressing temperature is 500-700 DEG C, and the pressure is 80-160 MPa. The non-reactive atmosphere, such as at least one of N2 and Ar, can effectively protect the metalized material at high temperature during hot-pressing from oxidation. Under the preferred hot-pressing condition, the hot-pressed block has a compressive strength of not less than 5 kN per piece and a metallization rate of not less than 85%. If the hot-pressing temperature is too low, the metal particles are insufficient in plasticity and the interfacial atomic interdiffusion is slow, so that it is difficult to realize sufficient densification and metallurgical bonding; if the hot-pressing temperature is too high, the thermal load and oxidation loss of the mold are significantly increased, which puts forward high requirements on the heat resistance of the equipment and the cooling system, resulting in high operation cost. If the forming pressure is insufficient, the bonding force between the particles is weak, and the product density and strength are difficult to guarantee, and if the forming pressure is too high, the equipment requirements are high, and the economic type is reduced.

[0017] As a preferred scheme, the volume concentration of sulfur dioxide in the sulfur dioxide flue gas is not less than 3.5%.

[0018] The low-temperature reduction roasting of the application can be carried out in a fluidized bed, a rotary kiln, a tunnel kiln or other furnaces suitable for continuous high-temperature (or solid reduction) treatment, which can meet the requirements of atmosphere control, temperature uniformity and continuous operation at the temperature.

[0019] The high-temperature desulfurization roasting of the application is carried out in a suspension kiln, a rotary kiln, a tunnel kiln or other furnaces suitable for continuous high-temperature (or solid desulfurization) treatment, which can provide rapid heating, good mass transfer or controllable residence time to meet the process requirements of efficient and deep desulfurization.

[0020] Compared with the prior art, the technical scheme of the application has the beneficial technical effects:

[0021] 1. The present application is based on the basic physicochemical properties of laterite nickel ore high-pressure acid leaching slag. For the first time, the process path of "reduction first, desulfurization second, and hot pressing third" is adopted, which fundamentally overturns the process path of "desulfurization first, briquetting second, and reduction third" in the treatment process of similar materials. The present application is aimed at the characteristics of "ultra-fine, high sulfur, and high silicon-aluminum" of laterite nickel ore high-pressure acid leaching slag. First, at low temperature (300-550℃), the characteristics of submicron iron oxides, such as low initial reaction temperature and high reaction activity, are utilized to preferentially complete efficient reduction, while avoiding the generation of iron olivine and S-A-F glass phase and other unfavorable phases, obtaining intermediate products with high sulfur and high metalization rate. Further, the intermediate products are subjected to high-temperature (700-1000℃) concentrated desulfurization to realize the directional enrichment and recovery of sulfur and deep desulfurization of the product. Finally, the hot material is directly hot-pressed into a shape. This process path not only avoids the energy waste caused by repeated drying in the traditional process, but also avoids the material softening, sticking, and the resulting operation problems such as ring formation and bridging caused by traditional high-temperature direct reduction (800-1200℃) from the source. Moreover, through precise coordination of the process, the problem of deep desulfurization, efficient metallization, and product quality improvement is simultaneously overcome.

[0022] 2. The present application realizes the "pre-activation-concentrated removal" segmented control of sulfur elements in laterite nickel ore high-pressure acid leaching slag and the efficient coupling of thermal energy in the whole process. First, in the low-temperature reduction stage, iron oxides are preferentially reduced, and at the same time, the pre-removal of structural water and lattice relaxation of sulfur-containing phases such as alunite are promoted. This process realizes the chemical activation of sulfur species, creating a high-reactivity basis for subsequent deep desulfurization. In the high-temperature desulfurization stage, sulfur elements are further converted into high-concentration gaseous SO2, realizing the concentrated release and resource recovery of sulfur. In addition, the reduction, desulfurization, and hot pressing processes are seamlessly coupled, and the sensible heat of the product from the upstream process is directly used as one of the input heat sources for the downstream process, constructing a highly intensive short process, which significantly reduces the huge energy loss caused by intermediate cooling and reheating of the material, and realizes the synergistic optimization of metal recovery and process energy saving.

[0023] 3, The present application realizes high-quality direct forming of finalized sand by process synergy design. The present application makes full use of the "granulation" effect of the high-temperature desulfurization step on the primary calcined sand, promotes the surface diffusion and sintering agglomeration of the particles, realizes moderate coarsening of the particle size, and effectively improves the flowability, filling property and pressing characteristics of the particles. The coarsened hot finalized sand produced in the process is further utilized, and under the synergistic effect of 500-700 DEG C and 80-160 MPa, the particles are plastically deformed, closely rearranged and interatomic diffusion, and a firm metallurgical bonding and dense structure dominated by metal bonding is formed between the metal particles. This mechanism fundamentally overcomes the defects of weak bonding, high porosity and insufficient strength caused by the mechanical interlocking of traditional cold pressing forming, and one-step preparation of high-quality reduced iron blocks with sulfur content less than 0.1%, compressive strength ≥ 5 kN / individual, and metallization rate ≥ 85%. At the same time, the densified structure significantly reduces the specific surface area and chemical activity of the product, effectively inhibits the oxidation and moisture absorption tendency during storage and transportation, thereby improving the long-term stability and applicability of the product. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The process flow chart for preparing reduced iron blocks from laterite nickel ore high-pressure acid leaching slag of the present application. DETAILED DESCRIPTION

[0025] The following specific examples are intended to further illustrate the content of the present application, but not to limit the protection scope of the claims of the present application.

[0026] The laterite nickel ore high-pressure acid leaching slag used in the following examples and comparative examples is derived from the high-pressure acid leaching residue of a certain laterite nickel ore hydrometallurgical plant in Indonesia after countercurrent washing by high-pressure acid leaching process, and its main mineral phases are hematite, hydrated hydrogen alunite, chromite and quartz, and its main components are shown in Table 1:

[0027] .

[0028] Example 1

[0029] The calcination process is carried out in a tubular furnace connected with a glove box filled with an inert atmosphere.

[0030] Firstly, the dried, crushed and classified (passed through a 1 mm screen) laterite nickel ore high-pressure acid leaching slag is placed in the tubular furnace, and reduced at 450 DEG C under 1 L / min H2 atmosphere for 0.5 hours, and after the reaction is completed, it is transferred to the glove box to obtain primary calcined sand with a metallization rate of 94% and a residual sulfur retention rate of 95%.

[0031] Subsequently, under the protection of continuous 1 L / min nitrogen, the tube furnace was heated to 850°C by programmed temperature, the aforementioned primary calcine was put in again, and high-temperature desulfurization was carried out for 1 hour, to obtain final calcine with residual sulfur of only 0.05%, and flue gas with SO2 concentration of 4.5% was detected.

[0032] After desulfurization was completed, the material was cooled to room temperature under argon protection in the furnace, and then was transferred to a preheated hot-pressing mold in a glove box through airtight operation, and was formed at 600°C, 120 MPa and in a nitrogen atmosphere, to finally obtain dense reduced iron blocks with a compressive strength of 6.8 kN per piece and a metallization rate of 88%.

[0033] Example 2

[0034] The calcination process was carried out in a tube furnace connected with a glove box filled with inert atmosphere.

[0035] First, the dried, crushed and classified (through a 1 mm screen) laterite nickel ore high-pressure acid leaching residue was placed in a tube furnace, and was reduced at 350°C under a 1.5 L / min H2 / CO mixed gas atmosphere (H2:CO = 1:1) for 2.5 hours, and after the reaction was completed, was transferred to a glove box, to obtain primary calcine with a metallization rate of 92% and a residual sulfur retention rate of 94%.

[0036] Subsequently, under the protection of continuous 0.8 L / min nitrogen, the tube furnace was heated to 950°C by programmed temperature, the aforementioned primary calcine was put in again, and high-temperature desulfurization was carried out for 0.5 hour, to obtain final calcine with residual sulfur of only 0.04%, and flue gas with SO2 concentration of 5.8% was detected.

[0037] After desulfurization was completed, the material was cooled to room temperature under argon protection in the furnace, and then was transferred to a preheated mold in a glove box, and was hot-pressed at 550°C, 100 MPa and in a nitrogen atmosphere, to finally obtain dense reduced iron blocks with a compressive strength of 5.4 kN per piece and a metallization rate of 86%.

[0038] Example 3

[0039] The calcination process was carried out in a tube furnace connected with a glove box filled with inert atmosphere.

[0040] First, the dried, crushed and classified (through a 1 mm screen) laterite nickel ore high-pressure acid leaching residue was placed in a tube furnace, and was reduced at 500°C under a 1 L / min CO atmosphere for 1.5 hours, and after the reaction was completed, was transferred to a glove box, to obtain primary calcine with a metallization rate of 95% and a residual sulfur retention rate of 93%.

[0041] Subsequently, the tube furnace was programmed to 750℃ under the protection of continuous 1.2L / min nitrogen, and the aforementioned primary calcine was put in again and high-temperature desulfurization was carried out for 0.5 hours, obtaining final calcine with residual sulfur of only 0.07%, and detecting flue gas with SO2 concentration of 3.7%.

[0042] After desulfurization was completed, the material was cooled to room temperature under argon protection in the furnace, and then transferred to a preheated mold in a glove box, and hot-pressed into a compacted reduced iron block at 650℃, 140MPa and nitrogen atmosphere, finally obtaining a compacted reduced iron block with a compressive strength of 7.1kN per piece and a metallization rate of 89%.

[0043] Comparative Example 1

[0044] The only difference compared with Example 1 is that the process flow of “first desulfurization, then reduction” was adopted.

[0045] First, the same raw materials were directly desulfurized at 850℃ under the protection of 1L / min nitrogen for 1 hour, obtaining low-sulfur calcine.

[0046] Subsequently, the calcine was reduced at 450℃ in a H2 atmosphere of 1L / min for 0.5 hours. The final product had a metallization rate of only 69% and a residual sulfur content of 0.07%.

[0047] Although SO2 concentration of 4.1% was detected during the desulfurization stage, the final product was significantly sintered and compacted due to the oxidation of iron oxides during high-temperature desulfurization, resulting in a significant reduction in the efficiency of subsequent low-temperature reduction, and high-metallization rate products could not be obtained.

[0048] Comparative Example 2

[0049] The only difference compared with Example 1 is that the process flow of “first briquetting, then desulfurization” was adopted.

[0050] First, the raw materials were reduced at 450℃ in a H2 atmosphere of 1L / min for 0.5 hours, obtaining primary calcine with a metallization rate of 94% and a residual sulfur retention rate of 95%.

[0051] Subsequently, instead of high-temperature desulfurization, it was directly hot-pressed into a block at 600℃, 120MPa. Finally, this high-sulfur briquette was attempted to be desulfurized at 850℃ in a nitrogen atmosphere of 1L / min for 0.5 hours.

[0052] It was found that the compacted structure of the briquette seriously hindered the diffusion and release of the gas product SO2, reducing the desulfurization efficiency, and the residual sulfur content in the block was still as high as 0.7% after desulfurization. The compressive strength was also deteriorated due to the internal pores and stress generated after desulfurization.

[0053] Comparative Example 3

[0054] The only difference compared with Example 1 is that the low-temperature reduction temperature is increased to 700℃.

[0055] Under this condition, the metallization rate of the primary calcine reaches 97%, but the residual sulfur retention rate decreases significantly to 40%, and the generation of harmful gases such as H2S in the tail gas is detected, indicating that the sulfur-containing phase is simultaneously decomposed in large quantities during the reduction stage. Subsequently, during high-temperature desulfurization, due to the significant reduction of available sulfur sources, the peak concentration of SO2 is only 1.2%, the flue gas concentration is low, and the recovery value is poor. This comparative example proves that excessively high reduction temperature, although beneficial to reduction, destroys the core premise of "suppressing sulfur decomposition", resulting in inefficient enrichment and recovery of sulfur resources.

[0056] Comparative Example 4

[0057] The only difference compared with Example 1 is that the high-temperature desulfurization temperature is reduced to 600℃.

[0058] Under this condition, the alunite and other sulfur-containing phases in the primary calcine are not completely decomposed, and after 0.5 hours of desulfurization, the residual sulfur content of the final calcine is still as high as 1.8%, far from meeting the requirement of less than 0.1% for high-quality raw materials. At the same time, the SO2 concentration is only 0.6%, indicating that the desulfurization temperature is insufficient, the sulfur-containing phase cannot be effectively and rapidly decomposed, and the final deep desulfurization cannot be achieved.

Claims

1. A method for preparing high-metallization reduced iron blocks using high-pressure acid leaching residue from laterite nickel ore with low energy consumption, characterized in that: Includes the following steps: 1) The high-pressure acid leaching residue of laterite nickel ore is placed in a reducing atmosphere and subjected to low-temperature reduction roasting at 300~550℃ to obtain primary roasted sand; 2) The primary roasted sand is placed in a non-reactive atmosphere and subjected to high-temperature desulfurization roasting at 700~1000℃ to obtain the final roasted sand; the final roasted sand is hot-pressed to obtain reduced iron blocks; The sulfur dioxide flue gas generated during the desulfurization roasting process is used to produce acid.

2. The method for preparing high-metallization reduced iron blocks using high-pressure acid leaching residue of laterite nickel ore with low energy consumption, as described in claim 1, is characterized in that: The reducing atmosphere is a gas containing hydrogen and / or carbon monoxide.

3. The method for preparing high-metallization reduced iron blocks using high-pressure acid leaching residue of laterite nickel ore with low energy consumption, as described in claim 1, is characterized in that: The low-temperature reduction calcination time is 0.1~3h.

4. The method for preparing high-metallization reduced iron blocks using high-pressure acid leaching residue of laterite nickel ore with low energy consumption according to claim 1, characterized in that: The non-reactive atmosphere is nitrogen and / or an inert gas.

5. The method for preparing high-metallization reduced iron blocks using high-pressure acid leaching residue of laterite nickel ore with low energy consumption according to claim 1, characterized in that: The high-temperature desulfurization roasting time is 0.1~2h.

6. The method for preparing high-metallization reduced iron blocks using high-pressure acid leaching residue of laterite nickel ore with low energy consumption according to claim 1, characterized in that: The hot pressing conditions are as follows: the atmosphere is a non-reactive atmosphere, the hot pressing temperature is 500~700℃, and the pressure is 80~160MPa.

7. The method for preparing high-metallization reduced iron blocks using high-pressure acid leaching residue of laterite nickel ore with low energy consumption according to claim 1, characterized in that: The volume concentration of sulfur dioxide in the sulfur dioxide flue gas is not less than 3.5%.

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