A high-pressure acid leaching and low-consumption process for laterite nickel ore based on efficient utilization of slag

Abstract

The invention discloses a low-consumption process treatment method for high-pressure acid leaching of laterite nickel ore based on efficient utilization of slag, and belongs to the technical field of comprehensive utilization of metallurgy and industrial solid waste. The method is to sequentially dry, crush, classify and pelletize the high-pressure acid leaching slag of laterite nickel ore with a disc ball making machine to obtain raw ball material; the raw ball material is distributed to a belt roasting machine trolley, and sequentially passes through a blast low-temperature drying section, an exhaust low-temperature drying section, a blast high-temperature drying section, an exhaust high-temperature drying section, a roasting section, a soaking section and a cooling section to obtain a low-sulfur iron-containing material; the flue gas with a sulfur dioxide concentration of ≥1 vol% generated in the roasting section is used for contact method or wet method to prepare sulfuric acid, and is circulated to the high-pressure acid leaching process of laterite nickel ore. The method has the advantages of low cost and low energy consumption, and can realize the comprehensive and efficient recovery and utilization of iron and sulfur elements in the high-pressure acid leaching slag of laterite nickel ore, and at the same time achieve the purpose of low-consumption process treatment of high-pressure leaching of laterite nickel ore, which is conducive to industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of comprehensive utilization of metallurgy and industrial solid waste, and relates to a method for treating high-pressure leaching slag of laterite nickel ore, and specifically to a low-consumption process treatment method for high-pressure acid leaching of laterite nickel ore based on efficient utilization of slag. Background Art

[0002] With the rapid development of global industry and economy, the consumption demand of nickel market, mainly stainless steel and new energy battery materials, has gradually increased. At present, laterite nickel ore, which is rich in reserves and easy to mine, has become the main source of primary nickel product extraction, accounting for more than 70%. As a typical weathering crust deposit, according to the properties of nickel-bearing minerals, the mining part of laterite nickel ore is generally divided into three parts from top to bottom: limonite layer (Ni: 0.8 ~1.5%), clay layer (Ni: 1.5 ~1.8%), and saprolitic layer (Ni: 1.5 ~3.0%). Among them, the reserves of iron oxide type and clay silicate type laterite nickel ore suitable for wet processing are nearly twice the reserves of hydrous magnesium silicate type laterite nickel ore suitable for pyrometallurgical processing. Therefore, the wet process is crucial in the large-scale development of low-grade laterite nickel ore.

[0003] The existing laterite nickel ore hydrometallurgical processes mainly include three processes: reduction roasting-ammonia leaching (Caron), sulfuric acid atmospheric pressure leaching (AL), and sulfuric acid pressure leaching (HPAL). Among them, the HPAL process is a method of using sulfuric acid as a leaching medium to complete the efficient and selective leaching of nickel and cobalt elements under high temperature (245~270℃) and high pressure (4.1~5.6MPa) conditions. This process has become the mainstream process choice for laterite nickel ore hydrometallurgical plants due to its low carbon emissions, low energy consumption, and high comprehensive recovery rate of nickel and cobalt metals, such as Ramu in Papua New Guinea, OBI nickel-cobalt project in Indonesia, Goro in New Caledonia, and Ambabovy in Madagascar. However, this method is mainly aimed at iron oxide type and clay silicate type lower grade laterite nickel ore raw materials, which contain a large amount / part of iron oxides or hydroxides as nickel-bearing minerals, so it will eventually produce a large amount of high-sulfur iron-containing slag with added value.

[0004] At present, there are three main treatment methods for HPAL slag: tailings dam accumulation, underground filter press backfill and deep sea landfill. The tailings dam accumulation process is simple and low-cost, but the environmental and risk factors are high; underground filter press backfill is safe and environmentally friendly, but the technology is difficult and the cost is high; the deep sea landfill process has a low cost, but the offshore mining area is a necessary condition, and the impact on the marine environment is still in the controversial stage. It is not difficult to see that all three treatment methods will incur certain treatment costs, and resource utilization cannot be achieved, resulting in serious waste of iron and sulfur resources. At the same time, the technologies proposed at this stage for the resource utilization of this type of slag, whether it is wet or fire treatment, are mainly aimed at the recovery of iron elements, and the recovery and utilization of sulfur resources have not yet been considered. Therefore, the final sulfur element still mainly exists in some form in the solid waste slag, which has brought serious adverse effects on corporate governance and the ecological environment.

[0005] Therefore, the development of a method that can economically process high-pressure acid leaching residue of laterite nickel ore on a large scale is of great significance to the cost reduction, efficiency improvement and sustainable development of the laterite nickel ore industry. Summary of the invention

[0006] In view of the defects of the high-pressure acid leaching slag treatment method of laterite nickel ore in the prior art, the purpose of the present invention is to provide a low-consumption process treatment method for high-pressure acid leaching of laterite nickel ore based on efficient utilization of slag, which has the advantages of low cost and low energy consumption, can realize the comprehensive and efficient recovery and utilization of iron and sulfur elements in the high-pressure acid leaching slag of laterite nickel ore, and at the same time achieve the purpose of low-consumption process treatment of high-pressure leaching of laterite nickel ore, which is conducive to industrial production.

[0007] In order to achieve the above technical objectives, the present invention provides a high-pressure acid leaching and low-consumption process for laterite nickel ore based on efficient utilization of slag, the method comprising the following steps:

[0008] (1) drying, crushing, classifying and pelletizing the laterite nickel ore high pressure acid leaching residue in sequence, and obtaining green pellets;

[0009] (2) The green pellets are placed on a belt roasting machine trolley and sequentially passed through a blast low-temperature drying section, an exhaust low-temperature drying section, a blast high-temperature drying section, an exhaust high-temperature drying section, a roasting section, a soaking section and a cooling section to obtain a low-sulfur iron-containing material; the temperature of the blast low-temperature drying section is 150-300°C, the residence time is 4-8 minutes, and the wind speed is 1.3-1.7 m / s; the temperature of the exhaust low-temperature drying section is 170-320°C, the residence time is 6-10 minutes, and the wind speed is 1.3- 1.7m / s; the temperature of the blast high temperature drying section is 360~480℃, the residence time is 1~3min, and the wind speed is 1.3~1.7m / s; the temperature of the exhaust high temperature drying section is 380~500℃, the residence time is 2~5min, and the wind speed is 1.3~1.7m / s; the temperature of the roasting section is 1185~1285℃, the residence time is 30~80min, and the wind speed is 1.8~2.6m / s; the temperature of the soaking section is 1000~1200℃, the residence time is 2~5min, and the wind speed is 1.4~2.2m / s; the cooling is blast cooling, the residence time is 15~35min, and the wind speed is 1.4~2.2m / s; cooled to a temperature <150℃;

[0010] (3) The flue gas with a sulfur dioxide concentration of ≥1 vol% generated in the roasting stage is used to prepare sulfuric acid by a contact method or a wet method and circulated to the high-pressure acid leaching process of laterite nickel ore.

[0011] The present invention adopts a disc ball making machine and a belt roasting machine roasting process to treat the high pressure acid leaching residue of laterite nickel ore:

[0012] The present invention solves the defects of high moisture content, difficulty in removing moisture, and high risk of bursting and pulverization of raw balls obtained by disc machines by reasonably designing the drying process. Based on the characteristics of low energy consumption, uniform particle size of balls, and easy mass production, the disc ball making machine is used for ball making. However, the high-pressure leaching slag of laterite nickel ore has small particle size, many voids, large specific surface area, and strong water absorption capacity. The prepared raw balls have high moisture content, and there are defects such as difficulty in removing moisture and high risk of bursting and pulverization in the subsequent drying process. The key of the present invention is to use the hot waste gas generated by the heat treatment process itself as a medium, and remove the free water, crystal water and structural moisture in the raw balls by combining low-temperature drying and high-temperature drying, effectively avoiding the problem of pellets bursting due to excessive steam pressure in the pellets under direct high-temperature drying. At the same time, the alternation of blast drying and exhaust drying can prevent the problem of structural damage of the lower material layer due to excessive moisture condensation under unidirectional airflow drying, and realize the heat recovery of low-calorie waste gas.

[0013] The present invention achieves the purpose of low consumption and low cost by reasonably designing a high-temperature treatment process to realize the production of sulfuric acid from sulfur dioxide and recycling it as well as heat recovery. On the one hand, the belt roaster has the characteristics of uniform, stable and controllable temperature to efficiently perform pyrolysis desulfurization, complete the deep separation of iron and sulfur elements, and realize the stable removal of sulfur content in the high-pressure acid leaching residue of laterite nickel ore to below 0.2%, making it an iron-containing resource with economic utilization value, which can be sold and generate economic benefits, and at the same time, the processing cost of the high-pressure acid leaching residue of laterite nickel ore is eliminated; on the other hand, the flue gas in different positions of the belt roaster can be collected in sections to achieve the concentration management of sulfur dioxide in the flue gas, provide a suitable concentration window for the subsequent self-heating equilibrium acid production of sulfur dioxide flue gas, complete the resource recovery of sulfur elements with low investment and operating costs, and recycle the sulfuric acid product for the high-pressure acid leaching process, which can significantly reduce the operating auxiliary material cost of the high-pressure acid leaching process of laterite nickel ore.

[0014] As a preferred solution, the mass content of TFe in the high pressure acid leaching residue of laterite nickel ore is 25-65%, and the mass content of S element is 0.7-12%. The water content of the high pressure acid leaching residue of laterite nickel ore is 30-50%. The content of TFe and S element in the high pressure acid leaching residue of laterite nickel ore is measured by the dry basis mass of the high pressure acid leaching residue of laterite nickel ore.

[0015] As a preferred solution, the high-pressure acid leaching residue of laterite nickel ore, after drying, crushing and classification, meets the requirement of 10% to 15% water content by mass, and the mass proportion of particles with a particle size of less than 100 μm is greater than 85%. The water content of the high-pressure acid leaching residue of laterite nickel ore has a relatively large impact on the ball making process of the disc ball making machine. If the water content is too high, it is not only not conducive to the crushing and screening operations, but also the surface of the raw ball is prone to excessive moisture during the ball making process and bonded with other particles or small balls to form irregular large balls. If the water content is too low, it may lead to insufficient bonding between particles and the raw ball is easy to break.

[0016] As a preferred solution, the diameter of the green ball material is 8-16 mm. The particle size of the green ball material affects its subsequent drying and sintering performance. If the diameter of the green ball material is too small, the permeability of the green ball material layer will be poor, which is not conducive to heat transfer and has low processing efficiency. If the diameter of the green ball material is too large, it is difficult to remove sulfur from the slag ball under high sulfur content conditions, the roasting time is long, and the energy cost is high.

[0017] As a preferred solution, the thickness of the green ball material on the belt roasting machine trolley is 50-450mm. If the thickness of the cloth is too thin, although the roasting effect is good, the heat utilization efficiency is low and the processing capacity is limited. If the thickness of the cloth is too thick, due to the problem of air flow resistance and the lower heat conduction efficiency, the temperature distribution of the upper and lower material layers is uneven, and the sulfur content in the ball material in the lower material layer is not removed up to the standard.

[0018] The present invention removes free water, crystal water and structural water in raw material balls by combining low-temperature drying and high-temperature drying, effectively avoiding the problem of pellets bursting due to excessive steam pressure in the pellets under direct high-temperature drying. At the same time, the alternation of blast drying and exhaust drying can prevent the problem of structural damage of the lower material layer due to excessive moisture condensation under unidirectional airflow drying, and realize the heat recovery and utilization of low-calorie waste gas.

[0019] As a preferred solution, the roasting section is divided into three parts along the traveling direction of the trolley, namely front, middle and rear parts, and the proportions of the total area of ​​the sintering section occupied by the three parts are: front part 5%-50%, middle part 50%-95%, and rear part ≤25%.

[0020] In the process of treating raw ball materials with a belt roaster, the dry ball materials directly enter the high-temperature roasting section without preheating, which is conducive to the release of sulfur dioxide in the front part of the roasting section, and the sulfur dioxide concentration and sulfur element removal rate in the flue gas of the roasting section show a decreasing trend from front to back. A large number of experiments show that the proportion of the front part of the roasting section to the total area of ​​the sintering section is within the range of 5% to 50%, which can obtain a high sulfur dioxide recovery rate and a high concentration of sulfur dioxide flue gas. If the area of ​​the front part accounts for too small a proportion, although it is conducive to obtaining a high concentration of flue gas, it will cause a low sulfur recovery rate; if the area of ​​the front part accounts for too high a proportion, although the sulfur recovery rate is high, the sulfur dioxide concentration in the flue gas is too low, and the self-heating balance low-cost acid production process conditions cannot be achieved. Further preferably, the front, middle and rear parts of the roasting section account for the following proportions of the roasting section area: 10% to 30% of the front part, 65% to 85% of the middle part, and ≤15% of the rear part.

[0021] As a more preferred solution, the flue gas generated in the front part of the roasting section has a sulfur dioxide concentration of ≥1 vol% and an average temperature of 250-550°C, which is used to prepare sulfuric acid and circulated to the high-pressure acid leaching process of laterite nickel ore, greatly reducing the acid consumption cost.

[0022] As a preferred solution, the average temperature of the middle part of the flue gas in the roasting section is 300-600°C, which is used to recover heat. The middle part of the flue gas has a low sulfur dioxide concentration and a high temperature, which is used for heat exchange to prepare steam, and further used in the preheating process of the high-pressure acid leaching process of laterite nickel ore. The energy consumption cost of the high-pressure leaching process of laterite nickel ore is effectively reduced.

[0023] As a preferred solution, the flue gas generated in the rear part of the roasting stage is used for high-temperature drying by air blast.

[0024] As a preferred solution, the cooling section includes cooling section I, cooling section II and cooling section III in sequence along the direction of the trolley travel; the flue gas generated by cooling section III is used in the blast low-temperature drying section; the flue gas generated by cooling section II is used in the exhaust low-temperature drying section; the flue gas generated by cooling section I is circulated to the roasting section as a combustion-supporting airflow. By recycling the heat carried by the flue gas during the roasting process to the maximum extent, it is beneficial to further reduce the processing energy consumption cost.

[0025] As a preferred solution, the flue gas from the equalizing section is used for exhausting the high-temperature drying section.

[0026] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0027] 1. Aiming at the series of problems caused by the physical characteristics of high-pressure acid leaching residue of laterite nickel ore, such as fine particle size, high porosity and large specific surface area, such as strong water absorption capacity of the material, high water holding content of raw balls, great difficulty in subsequent drying process and high risk of explosion and pulverization, the present invention constructs a disc ball making machine combined with a belt roasting machine roasting process suitable for the characteristics of high-pressure leaching residue of laterite nickel ore, adopts a combination of low-temperature drying and high-temperature drying, uses the flue gas of cooling section II and cooling section III as the low-temperature drying medium, preferentially removes part of the free water and crystallization water in the raw balls, uses the flue gas after the roasting section and the flue gas of the equalizing section as the high-temperature drying medium, removes the remaining free water and crystallization water while completing the removal of the structural water of the material in the slag, effectively avoids the problem of pellet explosion due to excessive steam pressure in the pellets under direct high-temperature drying, and can prevent the corrosion of equipment and pipelines caused by high water and high sulfur in the flue gas before the roasting section.

[0028] 2. Aiming at the difficulties that the high sulfur content and wide range of high-pressure acid leaching residue of laterite nickel ore and the difficulty in separating sulfur and iron elements are difficult, the present invention proposes a belt roasting machine heat treatment scheme for the high-pressure acid leaching residue of laterite nickel ore. On the one hand, the belt roasting machine has the characteristics of uniform, stable and controllable temperature to achieve efficient thermal desulfurization and complete the deep separation of iron and sulfur elements. On the other hand, the flue gas in different positions of the belt roasting machine can be collected in sections to achieve the concentration of sulfur dioxide in the flue gas and the flue gas temperature management, provide a suitable temperature and concentration window for the subsequent self-thermal equilibrium acid production of sulfur dioxide flue gas, and complete the resource recovery and utilization of sulfur elements with low investment and operating costs.

[0029] 3. The present invention can stably remove the sulfur content in the high-pressure acid leaching residue of laterite nickel ore to below 0.2%, making it an iron-containing resource with economic utilization value, which can be sold and generate economic benefits. At the same time, it reduces the processing cost of the high-pressure acid leaching residue of laterite nickel ore, which is beneficial to the sustainable development of the laterite nickel ore hydrometallurgical industry.

[0030] 4. The present invention aims at the problem of large amount of sulfuric acid and high cost of auxiliary materials in the high-pressure acid leaching process of laterite nickel ore. By recovering sulfur in the high-pressure acid leaching residue of laterite nickel ore to prepare sulfuric acid, the sulfuric acid is recycled for the high-pressure acid leaching process, which can significantly reduce the cost of auxiliary materials for the operation of enterprises using the high-pressure acid leaching method of laterite nickel ore. In addition, the hot exhaust gas generated during the heat treatment of the belt roaster can be used to prepare steam through heat exchange equipment for preheating the laterite nickel ore slurry before entering the autoclave, effectively reducing the energy consumption cost of the high-pressure leaching process of laterite nickel ore. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a process flow chart of the high-pressure acid leaching and low-consumption process for laterite nickel ore based on efficient utilization of slag. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with preferred implementation examples, but is not intended to limit the protection scope of the claims of the present invention.

[0033] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0034] Example 1

[0035] (1) Raw material processing: The high-pressure acid leaching residue of laterite nickel ore with a moisture content of 36.87% was dried by a rotary dryer, crushed by a double-roll crusher and sieved with a high-frequency screen to obtain a screened raw material with a moisture content of 10.5% and a particle size of 90% below 100 μm.

[0036] (2) Ball making: The disc ball making machine is used to make balls of the material under the screen to obtain raw balls with a particle size of 12 mm and a moisture content of 25.74%;

[0037] (3) Calcination: The raw balls are spread onto the belt calcining machine trolley to form a 400 mm layer, and then subjected to blower low-temperature drying, exhaust low-temperature drying, blower high-temperature drying, exhaust high-temperature drying, calcination, heat equalization, and cooling in sequence. The system of each stage is as follows: the blast low-temperature drying temperature is 255°C, the time is 5.5 minutes, and the wind speed is 1.5 m / s; the exhaust low-temperature drying temperature is 275°C, the time is 7 minutes, and the wind speed is 1.5 m / s; the blast high-temperature drying temperature is 435°C, the time is 2 minutes, and the wind speed is 1.5 m / s; the exhaust high-temperature drying temperature is 450°C, the time is 3 minutes, and the wind speed is 1.5 m / s; the roasting temperature is 1250°C, the time is 40 minutes, and the wind speed is 2.2 m / s; the uniform heating temperature is 1050°C, the time is 3 minutes, and the wind speed is 1.8 m / s; the cooling is blast cooling, the time is 17 minutes, and the wind speed is 1.8 m / s.

[0038] (4) Acid production: The flue gas from the roasting section is divided into three parts along the direction of the trolley travel: front, middle and rear. The flue gas from the front part of the roasting section accounts for 12.5% ​​of the flue area of ​​the entire roasting section. The resulting flue gas is used to prepare sulfuric acid and circulated to the high-pressure acid leaching process.

[0039] (5) Heat recovery and reuse: Part of the flue gas in the roasting section accounts for 75% of the flue area of ​​the entire roasting section. Steam is prepared by heat exchange and used in the preheating process of the high-pressure acid leaching process of laterite nickel ore.

[0040] In this embodiment, the high-pressure acid leaching slag of laterite nickel ore contains 27.99% TFe and 7.60% S, measured on a dry basis, of which the sulfur element mainly exists in the form of sulfate. The calcined agglomerate obtained in step 3) contains 39.20% TFe and 0.031% S, which can be used for molten pool smelting to recover iron raw materials. The sulfur dioxide concentration in the acid-making flue gas of the calcination section obtained in step 4) is 3.55%, which can be used to prepare sulfuric acid in a conventional contact acid-making process and circulate to the high-pressure acid leaching process. The temperature of the heat exchange flue gas of the calcination section obtained in step 5) is 450°C, and steam is prepared by heat exchange, which is used in the preheating process of the high-pressure acid leaching process of laterite nickel ore.

[0041] Example 2

[0042] (1) Raw material processing: The high-pressure acid leaching residue of laterite nickel ore with a moisture content of 36.87% was dried by a rotary dryer, crushed by a double-roll crusher and sieved with a high-frequency screen to obtain a screened raw material with a moisture content of 10.5% and a particle size of 90% below 100 μm.

[0043] (2) Ball making: The disc ball making machine is used to make balls of the material under the screen to obtain green balls with a particle size of 12 mm and a moisture content of 25.74%;

[0044] (3) Calcination: The raw balls are spread onto the belt calcining machine trolley to form a 250 mm layer, and then subjected to blower low-temperature drying, exhaust low-temperature drying, blower high-temperature drying, exhaust high-temperature drying, preheating, calcining, uniform heat treatment, and cooling treatment. The system of each stage is as follows: the blast low-temperature drying temperature is 245°C, the time is 5 minutes, and the wind speed is 1.5 m / s; the exhaust low-temperature drying temperature is 260°C, the time is 6.5 minutes, and the wind speed is 1.5 m / s; the blast high-temperature drying temperature is 400°C, the time is 1.5 minutes, and the wind speed is 1.5 m / s; the exhaust high-temperature drying temperature is 420°C, the time is 2.5 minutes, and the wind speed is 1.5 m / s; the roasting temperature is 1230°C, the time is 40 minutes, and the wind speed is 2.2 m / s; the uniform heating temperature is 1050°C, the time is 3 minutes, and the wind speed is 1.8 m / s; the cooling is blast cooling, the time is 17 minutes, and the wind speed is 1.8 m / s.

[0045] (4) Acid production: The flue gas from the roasting section is divided into three parts along the direction of the trolley travel: front, middle and rear. The flue gas from the front part of the roasting section accounts for 18.75% of the flue area of ​​the entire roasting section. The resulting flue gas is used to prepare sulfuric acid and circulated to the high-pressure acid leaching process.

[0046] (5) Heat recovery and reuse: Part of the flue gas in the roasting section accounts for 75% of the flue area of ​​the entire roasting section. Steam is prepared by heat exchange and used in the preheating process of the high-pressure acid leaching process of laterite nickel ore.

[0047] In this embodiment, the high-pressure acid leaching slag of laterite nickel ore contains 27.99% TFe and 7.60% S, measured on a dry basis, of which the sulfur element mainly exists in the form of sulfate. The calcined agglomerate obtained in step 3) contains 39.23% TFe and 0.029% S, which can be used for molten pool smelting to recover iron raw materials. The sulfur dioxide concentration in the acid-making flue gas of the calcination section obtained in step 4) is 1.27%, which can be used to prepare sulfuric acid in a wet acid-making process and circulated to the high-pressure acid leaching process. The temperature of the heat exchange flue gas of the calcination section obtained in step 5) is 435°C, and steam is prepared by heat exchange, which is used in the preheating process of the high-pressure acid leaching process of laterite nickel ore.

[0048] Example 3

[0049] (1) Raw material processing: The high-pressure acid leaching residue of laterite nickel ore with a moisture content of 36.87% was dried by a rotary dryer, crushed by a double-roll crusher and sieved with a high-frequency screen to obtain a screened raw material with a moisture content of 10.5% and a particle size of 90% below 100 μm.

[0050] (2) Ball making: The disc ball making machine is used to make balls of the material under the screen to obtain green balls with a particle size of 12 mm and a moisture content of 25.74%;

[0051] (3) Calcination: The raw balls are spread onto the belt calcining machine trolley to form a 100 mm layer, and then subjected to blower low-temperature drying, exhaust low-temperature drying, blower high-temperature drying, exhaust high-temperature drying, preheating, calcining, uniform heat treatment, and cooling treatment. The system of each stage is as follows: the blast low-temperature drying temperature is 230℃, the time is 4min, and the wind speed is 1.5m / s; the exhaust low-temperature drying temperature is 250℃, the time is 6 min, and the wind speed is 1.5m / s; the blast high-temperature drying temperature is 395℃, the time is 1min, and the wind speed is 1.5m / s; the exhaust high-temperature drying temperature is 410℃, the time is 2min, and the wind speed is 1.5m / s; the roasting temperature is 1200℃, the time is 40min, and the wind speed is 2.2m / s; the soaking temperature is 1050℃, the time is 3min, and the wind speed is 1.8m / s; the cooling is blast cooling, the time is 17min, and the wind speed is 1.8m / s.

[0052] (4) Acid production: The flue gas from the roasting section is divided into three parts along the direction of the trolley travel: front, middle and rear. The flue gas from the front part of the roasting section accounts for 12.5% ​​of the flue area of ​​the entire roasting section. The resulting flue gas is used to prepare sulfuric acid and circulated to the high-pressure acid leaching process.

[0053] (5) Heat recovery and reuse: Part of the flue gas in the roasting section accounts for 75% of the flue area of ​​the entire roasting section. Steam is prepared by heat exchange and used in the preheating process of the high-pressure acid leaching process of laterite nickel ore.

[0054] In this embodiment, the high-pressure acid leaching slag of laterite nickel ore contains 27.99% TFe and 7.60% S, measured on a dry basis, of which the sulfur element mainly exists in the form of sulfate. The calcined agglomerate obtained in step 3) contains 39.17% TFe and 0.08% S, which can be used for molten pool smelting to recover iron raw materials. The sulfur dioxide concentration in the acid-making flue gas of the calcination section obtained in step 4) is 1.07%, which can be used to prepare sulfuric acid in a wet acid-making process and circulated to the high-pressure acid leaching process. The temperature of the heat exchange flue gas of the calcination section obtained in step 5) is 415°C, and steam is prepared by heat exchange, which is used in the preheating process of the high-pressure acid leaching process of laterite nickel ore.

[0055] Comparative Example 1

[0056] Compared with Example 1, the only difference is:

[0057] In step (4), the flue gas in front of the roasting section accounts for 60% of the flue area of ​​the entire roasting section. The obtained flue gas is used to prepare sulfuric acid and is circulated to the high-pressure acid leaching process.

[0058] The sulfur dioxide concentration in the acid-making flue gas from the roasting stage obtained in step (4) is 0.34%, and the sulfur dioxide concentration is less than 1%, which is difficult to be effectively and economically utilized.

[0059] As the sulfur dioxide concentration in the flue gas of the roasting section drops sharply along the direction of the trolley's travel, most of the sulfides with low oxidation removal temperature and sulfates with high decomposition removal temperature react violently after entering the high-temperature field, and the sulfur dioxide is released in a concentrated manner. However, a small amount of sulfur-containing phases and large-particle sulfate phases closer to the inside of the pellets take a long time to be removed due to poor removal kinetic conditions. Therefore, the further the flue gas from the roasting section is, the more sharply the sulfur dioxide concentration in the flue gas drops. The flue gas in the front part of the roasting section occupies too large an area of ​​the entire roasting section flue, and the lower the average sulfur dioxide concentration in the flue gas.

[0060] Comparative Example 2

[0061] (1) Raw material processing: The high-pressure acid leaching residue of laterite nickel ore with a moisture content of 36.87% was dried by a rotary dryer, crushed by a double-roll crusher and sieved with a high-frequency screen to obtain a screened raw material with a moisture content of 10.5% and a particle size of 90% below 100 μm.

[0062] (2) Ball making: The disc ball making machine is used to make balls of the material under the screen to obtain green balls with a particle size of 12 mm and a moisture content of 25.74%;

[0063] (3) Calcination: The raw balls are spread onto the belt calcining machine trolley to form a 250 mm layer, and then subjected to blower low-temperature drying, exhaust low-temperature drying, blower high-temperature drying, exhaust high-temperature drying, calcination, heat equalization, and cooling in sequence. The system of each stage is as follows: the blast low-temperature drying temperature is 245°C, the time is 5 minutes, and the wind speed is 1.5 m / s; the exhaust low-temperature drying temperature is 260°C, the time is 6.5 minutes, and the wind speed is 1.5 m / s; the blast high-temperature drying temperature is 400°C, the time is 1.5 minutes, and the wind speed is 1.5 m / s; the exhaust high-temperature drying temperature is 420°C, the time is 2.5 minutes, and the wind speed is 1.5 m / s; the roasting temperature is 1150°C, the time is 20 minutes, and the wind speed is 2.2 m / s; the uniform heating temperature is 1050°C, the time is 3 minutes, and the wind speed is 1.8 m / s; the cooling is blast cooling, the time is 17 minutes, and the wind speed is 1.8 m / s.

[0064] In this embodiment, the high pressure acid leaching residue of laterite nickel ore contains 27.99% TFe and 7.60% S on a dry basis, wherein the sulfur element mainly exists in the form of sulfate. The roasted agglomerate obtained in step 3) contains 35.11% TFe and 3.96% S. The sulfur content is 0.2%, cannot be used directly as raw material for iron ore agglomeration / ironmaking process.

[0065] Since the pellet roasting temperature is too low, the removal reaction rate of the sulfur-containing phase is slow and the removal takes a long time. In addition, the roasting time is too short. These two factors together lead to a high residual sulfur content in the roasted balls.

[0066] Comparative Example 3

[0067] (1) Raw material processing: The high-pressure acid leaching residue of laterite nickel ore with a moisture content of 36.87% was dried by a rotary dryer, crushed by a double-roll crusher and sieved with a high-frequency screen to obtain a screened raw material with a moisture content of 10.5% and a particle size of 90% below 100 μm.

[0068] (2) Ball making: The disc ball making machine is used to make balls of the material under the screen to obtain green balls with a particle size of 12 mm and a moisture content of 25.74%;

[0069] (3) Calcination: The raw balls are spread onto the belt calcining machine trolley to form a 500 mm layer, and then subjected to blower low-temperature drying, exhaust low-temperature drying, blower high-temperature drying, exhaust high-temperature drying, preheating, calcining, uniform heat treatment, and cooling treatment in sequence. The system of each stage is as follows: the blast low-temperature drying temperature is 230℃, the time is 4min, and the wind speed is 1.5m / s; the exhaust low-temperature drying temperature is 250℃, the time is 6 min, and the wind speed is 1.5m / s; the blast high-temperature drying temperature is 395℃, the time is 1min, and the wind speed is 1.5m / s; the exhaust high-temperature drying temperature is 410℃, the time is 2min, and the wind speed is 1.5m / s; the roasting temperature is 1200℃, the time is 40min, and the wind speed is 2.2m / s; the soaking temperature is 1050℃, the time is 3min, and the wind speed is 1.8m / s; the cooling is blast cooling, the time is 17min, and the wind speed is 1.8m / s.

[0070] In this embodiment, the high pressure acid leaching residue of laterite nickel ore contains 27.99% TFe and 7.60% S on a dry basis, wherein the sulfur element mainly exists in the form of sulfate. The roasted agglomerate obtained in step 3) contains 36.81% TFe and 2.12% S. The sulfur content is 0.2%, cannot be used directly as raw material for iron ore agglomeration / ironmaking process.

[0071] Since the belt roasting process adopts a top-down heating mode using burners and heat recovery airflow, the upper material layer often contacts more heat, has high heat transfer efficiency and high temperature, while the lower material layer contacts less heat, has low heat transfer efficiency and low temperature. When the material layer is thick, the temperature difference between the upper and lower layers will exceed the desulfurization temperature window, resulting in that even if the temperature of the upper material layer is at the upper limit of the desulfurization window, the temperature of the lower material layer is not enough to remove the sulfur content to the standard of <0.2%, which ultimately leads to the failure to meet the sulfur content removal standard in the overall roasted balls.

Claims

1. A high-pressure acid leaching and low-consumption process for laterite nickel ore based on efficient utilization of slag, characterized in that: The following steps are involved: (1) drying, crushing, classifying and pelletizing the laterite nickel ore high pressure acid leaching residue in sequence, and obtaining green pellets; (2) the green pellets are placed on a belt roasting machine trolley and sequentially passed through a blast low-temperature drying section, an exhaust low-temperature drying section, a blast high-temperature drying section, an exhaust high-temperature drying section, a roasting section, a soaking section, and a cooling section to obtain a low-sulfur iron-containing material; The temperature of the blast low-temperature drying section is 150-300°C, the residence time is 4-8 minutes, and the wind speed is 1.3-1.7 m / s; The temperature of the low-temperature drying section is 170-320°C, the residence time is 6-10 minutes, and the wind speed is 1.3-1.7 m / s; The temperature of the high-temperature blast drying section is 360-480°C, the residence time is 1-3 minutes, and the wind speed is 1.3-1.7 m / s; The temperature of the high-temperature drying section is 380-500°C, the residence time is 2-5 minutes, and the wind speed is 1.3-1.7 m / s; The temperature of the roasting section is 1185-1285°C, the residence time is 30-80 min, and the wind speed is 1.8-2.6 m / s; The temperature of the soaking section is 1000-1200°C, the residence time is 2-5 minutes, and the wind speed is 1.4-2.2 m / s; The cooling is blast cooling, with a residence time of 15-35 minutes and a wind speed of 1.4-2.2 m / s; cooling to a temperature of <150°C; (3) The flue gas with a sulfur dioxide concentration of ≥1 vol% generated in the roasting stage is used to prepare sulfuric acid by a contact method or a wet method, and is circulated to the high-pressure acid leaching process of laterite nickel ore; The roasting section is divided into three parts, namely, front part, middle part and rear part, along the traveling direction of the trolley. The proportions of the three parts to the total area of ​​the sintering section are as follows: the front part is 5% to 50%, the middle part is 50% to 95%, and the rear part is ≤ 25%; The flue gas generated in the front part of the roasting section has a sulfur dioxide concentration of ≥1 vol% and an average temperature of 250-550°C, which is used to prepare sulfuric acid and circulated to the high-pressure acid leaching process of laterite nickel ore; The average temperature of the flue gas generated in the middle part of the roasting section is 300-600°C, and the heat is recovered for the pulp preheating process of the high-pressure acid leaching process of laterite nickel ore; The flue gas generated in the rear part of the roasting section is circulated to the high-temperature air-blast drying section of the green pellets.

2. The method for high pressure acid leaching of laterite nickel ore with low consumption based on efficient utilization of slag according to claim 1, characterized in that: The mass content of TFe in the high-pressure acid leaching residue of laterite nickel ore is 25-65%, and the mass content of S element is 0.7-12%.

3. A high-pressure acid leaching and low-consumption process for laterite nickel ore based on efficient utilization of slag according to claim 1 or 2, characterized in that: After drying, crushing and grading, the laterite nickel ore high-pressure acid leaching residue meets the requirement of 10% to 15% in terms of water content, and the mass proportion of particles with a particle size of less than 100 μm is greater than 85%.

4. The method for high pressure acid leaching of laterite nickel ore with low consumption based on efficient utilization of slag according to claim 1, characterized in that: The diameter of the green ball material is 8-16 mm.

5. A high-pressure acid leaching and low-consumption process for laterite nickel ore based on efficient utilization of slag according to claim 1 or 4, characterized in that: The thickness of the green pellets on the belt roasting machine trolley is 50-450 mm.

6. The method for high pressure acid leaching of laterite nickel ore with low consumption based on efficient utilization of slag according to claim 1, characterized in that: The cooling section includes cooling section I, cooling section II and cooling section III in sequence along the traveling direction of the trolley; The flue gas generated in the cooling stage III is used in the blast low-temperature drying stage; The flue gas generated in the cooling section II is used for exhausting the low-temperature drying section; The flue gas generated in the cooling stage I is circulated to the roasting stage as combustion-supporting air flow.

7. The method for high pressure acid leaching and low consumption of laterite nickel ore based on efficient utilization of slag according to claim 1, characterized in that: The flue gas in the heat equalization section is used for exhausting the high-temperature drying section.

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