Selection and Combination of Siderite Beneficiation Processes – Maximizing Resource Value

 Siderite beneficiation is a complex system engineering, and the selection of beneficiation processes is not fixed—it needs to be determined according to the specific characteristics of the ore, including particle size distribution, chemical composition, mineral intergrowth relationship, impurity content, and other factors. As mentioned earlier, the four core beneficiation processes (flotation, gravity separation, magnetic separation, magnetization roasting-weak magnetic separation) each have their own advantages and limitations. In practical industrial production, a single beneficiation process is often difficult to meet the requirements of high concentrate grade and high recovery rate. Therefore, the combination of multiple processes has become the mainstream trend of siderite beneficiation, which can give full play to the advantages of each process and maximize the utilization value of siderite resources.

First, let’s clarify the selection criteria of a single beneficiation process. For coarse-grained siderite ores (particle size 5-50mm) with simple composition and low impurity content, gravity separation (heavy-media separation or jigging separation) is the preferred method—it has large production capacity, low cost, and can effectively discard gangue. For fine-grained disseminated siderite ores (particle size less than 1mm) with complex intergrowth with gangue, flotation is more suitable—it can achieve effective separation of fine particles and improve the concentrate grade. For siderite ores with associated strong magnetic minerals (such as magnetite), magnetic separation (weak magnetic separation + strong magnetic separation) can be adopted to recover strong magnetic minerals first and then separate siderite. For difficult-to-beneficiate siderite ores (fine particle size, high impurity content, close intergrowth), the magnetization roasting-weak magnetic separation process is the most effective choice, which can fundamentally solve the problem of low separation efficiency.

On the basis of single process selection, the combination of multiple processes can further improve the beneficiation effect. The common combined processes for siderite include: gravity separation + flotation, magnetic separation + flotation, magnetization roasting-weak magnetic separation + flotation, etc. For example, in the processing of coarse to medium-grained siderite ores with fine-grained impurities, the "gravity separation + flotation" combined process is often adopted: first, gravity separation is used to recover coarse-grained siderite concentrate, and the tailings or intermediate products of gravity separation (which contain fine-grained siderite) are sent to flotation for re-selection, so as to improve the overall iron recovery rate and concentrate grade. Another example is the "magnetization roasting-weak magnetic separation + flotation" combined process for difficult-to-beneficiate siderite: after magnetization roasting and weak magnetic separation, the obtained concentrate may still contain a small amount of fine-grained gangue, which can be further purified by flotation to obtain high-grade iron concentrate (iron grade above 65%), meeting the requirements of the steel industry.

In addition to the selection and combination of processes, the optimization of process parameters is also crucial to improving beneficiation efficiency. For example, in the flotation process, the optimization of pulp pH, reagent dosage, and flotation time can significantly improve the separation effect; in the magnetization roasting process, the control of roasting temperature, reducing agent dosage, and roasting time directly affects the transformation rate of siderite to magnetite; in the gravity separation process, the adjustment of separation medium specific gravity and water flow velocity can improve the separation accuracy.

In conclusion, the selection and combination of siderite beneficiation processes must be based on detailed ore characterization and experimental research, and the principle of "adapting to ore properties, optimizing process flow, reducing cost, and protecting the environment" must be adhered to. With the continuous development of mineral processing technology, new processes and equipment (such as high-efficiency flotation reagents, advanced magnetic separation equipment, and energy-saving roasting technology) are constantly emerging, which will further promote the efficient utilization of siderite resources and provide strong support for the sustainable development of the steel industry.

Siderite Magnetization Roasting-Weak Magnetic Separation Process – Solving the Difficulty of Beneficiation

 For siderite ores with complex compositions, fine particle size, and close intergrowth with gangue minerals, single beneficiation processes (such as flotation, gravity separation, or magnetic separation) often struggle to obtain high-grade iron concentrates. At this time, the magnetization roasting-weak magnetic separation process becomes the most effective solution. This process combines roasting and magnetic separation, transforming siderite into a strong magnetic mineral through roasting, thereby realizing efficient separation with conventional weak magnetic separation equipment. It is known as the "key technology" for difficult-to-beneficiate siderite and has been widely promoted and applied in industrial production.

The core of the magnetization roasting-weak magnetic separation process is the magnetization roasting step, whose principle is to heat siderite in a reducing atmosphere (using coal, coke, natural gas, or other reducing agents) to decompose the carbonate in the ore and transform siderite into magnetite (Fe₃O₄), a strong magnetic mineral. The chemical reaction equation is: 3FeCO₃ + C → Fe₃O₄ + 3CO₂↑ + CO↑. During the roasting process, two key changes occur: first, the carbon dioxide in siderite is decomposed and discharged, which increases the iron content of the ore (theoretical iron content of magnetite is 72.4%, which is much higher than that of siderite); second, the magnetic susceptibility of iron minerals is significantly enhanced—magnetite is a strong magnetic mineral, whose magnetic susceptibility is dozens of times higher than that of siderite, making it easy to be separated by weak magnetic separation. At the same time, the magnetic properties of gangue minerals (such as quartz, calcite) remain basically unchanged, which further improves the separation effect.

The magnetization roasting process is mainly divided into three types: shaft furnace roasting, rotary kiln roasting, and fluidized bed roasting. Among them, rotary kiln roasting is the most widely used in siderite beneficiation due to its stable roasting effect, large processing capacity, and strong adaptability to ore particle size. The rotary kiln is a long cylindrical equipment that rotates continuously; the ore and reducing agent are fed into the kiln from one end, and heated to 550-700℃ (the optimal roasting temperature for siderite) by a burner at the other end. Under the action of high temperature and reducing atmosphere, siderite is gradually transformed into magnetite. After roasting, the ore (called roasted ore) is cooled to the appropriate temperature and then sent to the next process.

The roasted ore is sent to a weak magnetic separator for separation. Due to the strong magnetic properties of magnetite, it is easily adsorbed by the magnetic field of the weak magnetic separator and separated from non-magnetic gangue to form high-grade iron concentrate. The weak magnetic separation equipment used is mainly a drum magnetic separator, which has the advantages of simple structure, high processing efficiency, and low energy consumption. Compared with strong magnetic separation, weak magnetic separation has lower equipment investment and operation cost, which greatly reduces the overall cost of the beneficiation process.

The magnetization roasting-weak magnetic separation process has the advantages of high iron concentrate grade, high recovery rate, and strong adaptability to difficult-to-beneficiate siderite ores. However, it also has certain limitations: the roasting process requires a large amount of energy and reducing agents, which increases the production cost; at the same time, the roasting process will generate flue gas, which needs to be treated to meet environmental protection standards. Therefore, in industrial design, it is necessary to comprehensively consider the ore properties, economic benefits, and environmental protection requirements to optimize the process parameters.

Siderite Magnetic Separation Process – Leveraging Magnetic Properties for Efficient Separation

 As a weak magnetic mineral, siderite has a low magnetic susceptibility, which means it cannot be effectively separated by conventional weak magnetic separation equipment (such as drum magnetic separators) used for magnetite. However, with the development of magnetic separation technology, strong magnetic separation has become a feasible and efficient method for siderite beneficiation. The core principle of siderite magnetic separation is to use the difference in magnetic susceptibility between siderite and gangue minerals: under the action of a strong magnetic field, weak magnetic siderite particles are attracted by the magnetic field and separated from non-magnetic gangue minerals, achieving the purpose of beneficiation. This process is especially suitable for siderite ores with low impurity content and relatively coarse particle size, and it can also be used as a pre-separation or re-separation process in combination with other methods.

The main equipment of the siderite strong magnetic separation process is the wet strong magnetic separator, which is divided into vertical ring strong magnetic separators, horizontal belt strong magnetic separators, and high-gradient strong magnetic separators according to their structure and working principle. Among them, the vertical ring wet strong magnetic separator is the most widely used in siderite beneficiation. It has a high magnetic field intensity (up to 1.2-2.0T), strong processing capacity, and good separation effect. The equipment works in a wet state: the ore pulp is fed into the magnetic separation chamber, and under the action of the strong magnetic field generated by the magnetic system, siderite particles are adsorbed on the surface of the magnetic medium (such as magnetic rods, magnetic plates) and moved to the concentrate discharge port with the rotation of the magnetic system, while gangue minerals that are not adsorbed are discharged as tailings along with the pulp.

To further improve the iron concentrate grade and iron recovery rate, a combined process of "weak magnetic separation first, then strong magnetic separation" is often adopted in industrial production. The specific process is as follows: first, the raw ore is crushed and ground to the required particle size, and then sent to a weak magnetic separator. Although siderite is a weak magnetic mineral, some iron-bearing minerals (such as associated magnetite) in the ore can be recovered by weak magnetic separation, forming a primary concentrate. The tailings from weak magnetic separation, which are mainly composed of siderite and gangue, are then sent to a strong magnetic separator for re-selection: the strong magnetic field adsorbs siderite particles, discards most of the gangue tailings, and the obtained concentrate is combined with the primary concentrate from weak magnetic separation to form the final iron concentrate. This combined process not only improves the recovery rate of iron but also reduces the processing load of the strong magnetic separator, saving energy and reducing costs.

The advantages of the siderite magnetic separation process are obvious: it has a simple process flow, high separation efficiency, low environmental pollution (no need for a large number of chemical reagents), and strong adaptability to ore properties. However, it also has certain limitations: the magnetic field intensity has high requirements, the equipment investment cost is relatively high, and it is not suitable for fine-grained disseminated siderite ores (the separation effect is poor when the particle size is less than 0.1mm). Therefore, the selection of magnetic separation process needs to be based on the detailed analysis of ore properties and economic benefits.

Siderite Gravity Separation Process – A Mature and Environmentally Friendly Method

Gravity separation is one of the most mature, widely used, and environmentally friendly beneficiation processes for siderite. Its core principle is based on the difference in specific gravity between siderite (specific gravity 3.8-3.9) and gangue minerals (such as quartz with specific gravity 2.65, calcite with specific gravity 2.71). Under the action of gravity, centrifugal force, or fluid power, minerals with different specific gravities are separated into different products: heavy minerals (siderite) settle or move to a specific area to form concentrate, while light minerals (gangue) are discharged as tailings. This process is suitable for processing both single siderite ores and coarse to medium-grained disseminated siderite ores, and it is especially favored in large-scale mining projects due to its simple process, low cost, and low environmental pollution.

The most commonly used gravity separation processes for siderite are heavy-media separation and jigging separation, each with its own characteristics and application scenarios. Heavy-media separation is a high-efficiency gravity separation method that uses a suspension (heavy media) with a specific gravity between siderite and gangue as the separation medium. The heavy media is usually composed of heavy minerals (such as magnetite powder, ferrosilicon powder) and water, and its specific gravity is precisely adjusted to ensure that siderite (heavier than the medium) sinks to the bottom of the separation equipment, while gangue (lighter than the medium) floats on the surface and is discharged. This process has the advantages of high separation accuracy, stable product quality, and strong adaptability to ore particle size (suitable for 5-50mm ores), making it ideal for pre-separation of coarse-grained siderite to discard a large amount of gangue in advance, reducing the processing load of subsequent processes.

Jigging separation is another classic gravity separation method, which uses the vertical alternating water flow (jigging flow) generated by the jigging machine to separate minerals. The jigging flow rises and falls periodically: when the water flow rises, ore particles are suspended, and when the water flow falls, ore particles settle. Due to the difference in specific gravity, siderite (heavier) settles faster and accumulates in the lower part of the jigging chamber to form concentrate, while gangue (lighter) settles slower and is carried by the water flow to form tailings. Jigging separation is suitable for processing medium-grained siderite (2-20mm) and has the advantages of simple equipment structure, easy operation, large production capacity, and low energy consumption. It is widely used in small and medium-sized mines due to its low investment cost.

Overall, the gravity separation process for siderite has obvious advantages: large production capacity, low cost, less reagent use (thus reducing environmental pollution), and simple operation and maintenance. However, it also has limitations: the recovery rate is relatively low, especially for fine-grained siderite (particle size less than 1mm), which is difficult to separate effectively due to the influence of water flow and particle size. Therefore, gravity separation is often used in combination with other processes (such as flotation) in industrial production to achieve better beneficiation effects.

Outstanding Technological and Economic Benefits: The Successful Practice of Xinhai’s Zimbabwe 700t/d Gold Project

 The ultimate goal of the construction of any mineral processing plant project is to achieve good technological and economic benefits, which is also the core criterion for testing the success of the project. Xinhai Mining, with its advanced mineral processing technology, scientific project management and perfect full-chain service, has made the Zimbabwe 700t/d gold mineral processing plant project achieve outstanding technological and economic benefits since its operation. The plant’s gold recovery rate, production capacity, operation efficiency and other technical indicators have reached or exceeded the design requirements, and the customer has obtained considerable economic returns. This project has become a successful practice of Xinhai in the African gold mining market, and also set a benchmark for the high-efficiency development of the local mining industry in Zimbabwe.

The outstanding technological benefits of the Zimbabwe 700t/d gold project are reflected in the high gold recovery rate, stable production capacity and efficient operation of the plant. The core of the mineral processing plant’s technological benefits is the gold recovery rate, which is directly related to the utilization rate of gold resources and the economic benefits of the project. Xinhai designed a scientific and reasonable mineral processing process for this project: one-stage grinding-two-stage closed-circuit grinding and classification-gravity concentration-cyanidation-desorption electrolysis-smelting-tailings dewatering. The key optimization of adding gravity concentration link in the grinding and classification circuit effectively avoids the loss of gold in the leaching process, and the combination of gravity concentration and cyanidation leaching makes the gold in the ore be recovered to the greatest extent.

In the actual operation of the plant, the technological advantages of this process have been fully demonstrated. The one-stage grinding-two-stage closed-circuit grinding and classification process makes the ore dissociation sufficient, the particle size of the grinding product is uniform, and provides a good foundation for the subsequent gold recovery. The gravity concentration link recovers a large number of coarse-grained native gold particles in time, and the cyanidation leaching process further recovers the fine-grained gold particles in the ore. The whole process forms a seamless connection, and the gold recovery rate of the plant has reached a high level in the same type of gold plants at home and abroad. At the same time, the advanced mineral processing equipment selected and configured by Xinhai and the precise adjustment of process parameters by the technical team ensure the stability of the gold recovery rate, and there is no large fluctuation of the recovery rate during the operation of the plant, which provides a reliable technical guarantee for the stable production of the plant.

The stable production capacity is another important embodiment of the project’s technological benefits. The design production capacity of the plant is 700t/d, and after the plant is put into operation, it quickly reached the design production capacity and maintained stable operation for a long time. This is due to the scientific process design, the reasonable configuration of equipment and the optimized plant layout of Xinhai. The smooth material transportation between the workshops, the coordinated operation of various equipment and the high efficiency of the production process make the plant’s production capacity be fully released. Even in the peak production period, the plant can still maintain stable operation without the phenomenon of production capacity reduction caused by equipment failure or process bottlenecks. The stable 700t/d production capacity ensures the continuous output of gold concentrate and finished gold of the plant, and lays a solid foundation for the customer to obtain stable economic benefits.

The efficient operation of the plant is reflected in the low unit energy consumption, low production cost and high equipment operation rate. Xinhai adopted a series of energy-saving and high-efficiency mineral processing equipment and technologies in the project, such as energy-saving ball mills, efficient classifiers and closed-circuit water circulation systems, which effectively reduced the unit energy consumption of the plant’s production process. The optimized plant layout and smooth process flow reduce the energy consumption of material transportation and the loss of production process, and further reduce the production cost of the plant. At the same time, Xinhai’s strict equipment quality control and professional equipment maintenance and management make the equipment operation rate of the plant reach a high level, the downtime of equipment failure is greatly reduced, and the overall operation efficiency of the plant is significantly improved. The high equipment operation rate and low production cost make the plant have strong market competitiveness in the gold mining industry.

On the basis of outstanding technological benefits, the Zimbabwe 700t/d gold project has also achieved remarkable economic benefits for customers, which is reflected in the short investment recovery cycle, high profit margin and good long-term development potential of the project.

The short investment recovery cycle is an important manifestation of the project’s economic benefits. Xinhai effectively shortened the construction period of the project through scientific project management and advanced construction organization mode, making the plant put into production as soon as possible and the customer obtain economic returns in advance. At the same time, the plant’s stable production capacity and high gold recovery rate ensure the continuous output of gold products, and the customer’s cash flow is stable and sufficient. The low production cost of the plant further improves the profit margin of the project, making the customer’s investment recovery cycle significantly shorter than the average level of the same type of gold projects, and realizing the early realization of investment income.

The high profit margin of the project is due to the high gold grade of the raw ore and the high gold recovery rate of the plant. The raw ore gold grade of the project is up to 6g/t, which is much higher than the average grade of the same type of gold mines, which means that the plant can produce more gold products with the same ore processing capacity. The high gold recovery rate designed and realized by Xinhai makes the gold resources in the ore be fully utilized, and the output of finished gold of the plant is further increased. The low production cost of the plant and the high market price of gold form a good profit space, making the project have a high profit margin. Since the plant was put into operation, the customer’s monthly profit has reached a considerable level, and the economic benefits are very significant.

The good long-term development potential of the project is the key to the sustainable economic benefits of the customer. Xinhai fully considered the future expansion potential of the plant in the design and construction of the project, reserved a certain expansion space for the key workshops and facilities, and provided convenient conditions for the customer to expand the production scale in the future. With the continuous exploration and development of the gold mine, the ore reserve of the mine is sufficient, which can support the long-term production of the plant. At the same time, the advanced mineral processing technology and perfect production management system of the plant provide a reliable guarantee for the long-term stable operation of the plant. The combination of sufficient ore reserves, expandable production capacity and advanced technical and management level makes the project have good long-term development potential, and the customer can obtain sustainable economic benefits in the long-term production and operation.

In addition to the direct economic benefits for customers, the Zimbabwe 700t/d gold project has also brought positive social and economic benefits to the local area, including promoting the development of the local mining industry, increasing employment opportunities and driving the development of related industries. The project has introduced advanced mineral processing technology and project management experience from Xinhai to Zimbabwe, which has promoted the technological progress and industrial upgrading of the local mining industry. The construction and operation of the plant have created a large number of local employment opportunities, including construction workers, operation and maintenance personnel, and management personnel, which has improved the local employment level and residents’ income. At the same time, the operation of the plant has also driven the development of local transportation, logistics, catering and other related industries, and made a positive contribution to the local economic development.

The outstanding technological and economic benefits of the Zimbabwe 700t/d gold project are the concentrated embodiment of Xinhai’s advanced technology, scientific management and perfect service. This project is not only a successful case of Xinhai’s EPC+M+O mode in the African market, but also a powerful proof of Xinhai’s core competitiveness in the global mineral processing industry. In the future, Xinhai will continue to uphold the concept of technological innovation and sustainable development, and provide more high-quality mineral processing solutions for global mining customers, helping more mining projects achieve outstanding technological and economic benefits, and promoting the sustainable development of the global mining industry.