System to remove agglomerates from a fluidized bed

Abstract

The present invention relates to a system for the automatic removal of agglomer- ates from fluidized beds, particularly fluidized beds of a roasting reactor compris- ing a movable discharge lance flanged to the fluidized bed roaster at a nozzle grate level with a lance tip for removing bed material during retraction. The inven- tion further also covers a relating process.

Description

[0001] System to remove agglomerates from a fluidized bed

[0002] The present invention relates to a system for the automatic removal of agglomerates from fluidized beds, particularly fluidized beds of a roasting reactor comprising a movable discharge lance flanged to the fluidized bed roaster at a nozzle grate level with a lance tip for removing bed material during retraction. The invention further also covers a relating process.

[0003] For the handling of solid material, a few reactor types are known. Being known for a particularly long time is a rotary kiln. The rotary kiln is a cylindrical vessel that rotates about its axis. It is used for thermal processing of granular materials. Since its design is simple, it is robust, can handle a wide range of materials, and is suitable for high-temperature processes. Another embodiment is a multiple hearth furnace, which consists of a series of horizontal hearths or floors stacked vertically within a cylindrical shell. The material to be treated moves downward from one hearth to the next, undergoing controlled thermal processes such as roasting, calcining, or drying.

[0004] Moreover, any type of fluidized bed reactor can be used. Such a system consists of a bed of solid particles that are suspended and fluidized by an upward flow of gas (fluidizing gas), creating a fluid-like state. The use of a fluidized bed reactor is particularly improved in processes wherein a good mixing is important. This holds particularly true for roasting processes.

[0005] Roasting is a crucial metallurgical process involving the heating of ores in the presence of oxygen to induce chemical reactions that convert sulfide ores into oxides. This process is essential for the extraction and purification of metals and is used extensively in the mining and metallurgical industries.

[0006] July 16, 2025 O 1 P 381 WO The primary purpose of roasting is to oxidize sulfide ores, making them easier to reduce in subsequent smelting processes. Roasting also helps in the removal of volatile components such as sulfur, arsenic, and carbon dioxide from the ore. By transforming sulfide ores into oxides, roasting prepares the material for efficient smelting and metal recovery.

[0007] Roasting is conducted at temperatures below the melting point of the ore to avoid melting and to ensure proper oxidation. Adequate supply of oxygen is crucial to drive the necessary oxidation reactions. There are different types of roasting processes, each tailored to specific ore types and desired outcomes.

[0008] Oxidizing roasting is the most common type, where sulfide ores are directly oxidized to oxides and sulfur dioxide. For example, zinc sulfide (ZnS) is converted to zinc oxide (ZnO) and sulfur dioxide (SO2) during roasting. Also for the extraction of copper (Cu), cobalt (Co), nickel (Ni), gold (Au) as well as ferrous (Fe) roasting is a proven and widely used process. The most common sulfating roasting involves converting metals into sulfates in the presence of oxygen and sulfur dioxide. Chlorinating roasting, on the other hand, converts metals into chlorides by heating with chlorine or a chlorine-containing compound.

[0009] One of the key advantages of roasting is its ability to efficiently remove sulfur from sulfide ores, thereby reducing the environmental impact of sulfur emissions. Roasting also improves metal recovery by converting the ore into a more reactive form that can be easily reduced in smelting processes. Additionally, modem roasting systems are equipped with emission control technologies that capture byproducts like sulfur dioxide, which can be used in other industrial processes, such as the production of sulfuric acid.

[0010] Since roasting enhances the efficiency and effectiveness of subsequent reduction and smelting operation, an optimized roasting process helps to reduce energy

[0011] July 16, 2025 O 1 P 381 WO consumption, and minimizes environmental impact. As the metallurgical industry continues to seek more efficient and environmentally friendly processing methods, the importance of roasting in metal extraction and refining is likely to grow, driving further innovations and improvements in this field.

[0012] For the reactor type used as the roaster, a fluidized bed reactor is particularly preferred. Fixed-bed, multiple hearth furnace and rotary kiln systems often suffer from inefficient heat transfer, leading to uneven roasting and higher energy consumption. Moreover, traditional roasting methods typically involve higher operational costs due to their lower efficiency and greater maintenance requirements.

[0013] Fluidized bed systems have revolutionized the roasting process, offering significant advantages over traditional methods. The fluidized bed of a fluidized bed roaster consists of a bed composed of the ore to be roasted, which are suspended in an upward flow of gas. This setup creates a fluid-like state that enhances the mixing and contact between the gas and the solid particles, leading to several key benefits:

[0014] Fluidized bed systems provide superior heat transfer compared to fixed-bed or rotary kiln systems. The constant mixing of particles ensures uniform temperature distribution throughout the bed, leading to more consistent roasting. Additionally, the increased contact between the gas and solid phases in a fluidized bed enhances reaction rates. This results in faster and more efficient roasting, reducing the time required to process the ore.

[0015] Moreover, fluidized bed systems are more ecologically sound as they are designed to facilitate the capture and treatment of emissions. The high level of control over gas flow and temperature allows for the efficient capture of sulfur dioxide and other gases, minimizing environmental impact. Furthermore, the efficient heat transfer and rapid reaction rates in fluidized bed systems lead to significant energy

[0016] July 16, 2025 O 1 P 381 WO savings, making fluidized bed roasting a cost-effective solution for the metallurgical industry.

[0017] Further, fluidized bed roasters can handle a wide variety of ore types and compositions, making them versatile and adaptable to different processing requirements. Fluidized bed roasting is particularly advantageous in the processing of sulfide ores. For instance, in the production of zinc, fluidized bed roasters are used to oxidize zinc sulfide (ZnS) to zinc oxide (ZnO) while simultaneously producing sulfur dioxide, which can be captured and used in the production of sulfuric acid. This dual benefit of metal extraction and by-product recovery exemplifies the efficiency of fluidized bed systems.

[0018] Similarly, in the production of copper, fluidized bed roasting is employed to convert copper sulfide ores into copper oxides, which are then subjected to further processing steps such as smelting and electrorefining. The uniform temperature control and efficient gas-solid interactions in fluidized bed roasters enhance the overall yield and quality of the final metal product.

[0019] In summary, the adoption of fluidized bed roasting systems has notable environmental and economic benefits. By reducing energy consumption and improving the efficiency of the roasting process, these systems lower the overall carbon footprint of metallurgical operations. Additionally, the effective capture and utilization of sulfur dioxide reduce harmful emissions and create opportunities for the production of valuable by-products. From an economic perspective, the increased throughput and lower operational costs associated with fluidized bed roasting systems translate into higher profitability for mining and metallurgical companies. The ability to process a diverse range of ores with minimal downtime further enhances the economic viability of these systems.

[0020] July 16, 2025 O 1 P 381 WO However, a major problem in the application of fluidized bed technologies is the formation of agglomerates. Agglomerates pose significant challenges in fluidized bed systems, particularly those used in industrial processes like roasting, drying, and chemical reactions. These systems rely on the fluidization of solid particles by a gas flow to achieve efficient mixing, heat transfer, and reaction kinetics, but the formation of agglomerates — clusters of particles that stick together — can disrupt these processes and lead to several operational problems.

[0021] Agglomerates interfere with the fluidization process by altering the bed's dynamics. They create uneven particle distribution and cause channeling, where gas flows preferentially through paths of least resistance, bypassing large portions of the bed. This results in poor mixing and inconsistent process conditions.

[0022] One of the key advantages of fluidized bed systems is their excellent heat transfer capabilities. Agglomerates impede this by forming larger masses that do not move as freely as individual particles. This reduces the contact surface area between particles and the fluidizing gas, leading to inefficient heat transfer and temperature gradients within the bed.

[0023] In processes like roasting or chemical reactions, agglomerates can slow down reaction rates. The reduced surface area and poor gas-solid contact hinder the reactions, leading to incomplete processing of materials. This can affect product quality and yield, requiring additional processing steps or leading to waste.

[0024] Agglomerates increase the overall resistance to gas flow through the bed, causing a higher pressure drop. This requires more energy to maintain the desired fluidization velocity, increasing operational costs. In severe cases, it can lead to equipment strain and potential failures.

[0025] July 16, 2025 O 1 P 381 WO The presence of agglomerates can cause uneven wear on the equipment. The larger, heavier clusters of particles can damage the fluidizing grid, nozzles, and internal surfaces of the reactor. This leads to more frequent maintenance and shorter equipment lifespan, impacting overall system efficiency and increasing downtime.

[0026] Agglomerates can lead to blockages in discharge lines, cyclones, and other downstream equipment. This disrupts the continuous operation of the fluidized bed system, causing process interruptions and requiring manual intervention to clear the blockages. Such interruptions can be costly and time-consuming.

[0027] In processes where precise control over particle size and distribution is critical, agglomerates can compromise product quality. The uneven particle size distribution can affect the properties of the final product, such as its reactivity, purity, and physical characteristics.

[0028] To mitigate these problems, several strategies are employed in the past like the adding of additional inert material as disclosed in EP 3 294 915 B1 . Yet, this has the disadvantage that such additives must be laboriously separated from the ore particles again downward of the process.

[0029] Another possibility to reduce agglomerate formation is tackling its causes, how it is proposed e.g. in WO 2017 / 005501 A1 , wherein the water content of the injected particles is identified as one reason for agglomerate formation, which is why the particles are previously dried to a water content of max. 2 wt.-% and are pneumatically injected. Still, this is very complex.

[0030] Summing up, an addressing the issue of agglomerates is crucial for maintaining the efficiency, reliability, and cost-effectiveness of fluidized bed systems in industrial applications. The solutions known from the prior art require further steps in

[0031] July 16, 2025 O 1 P 381 WO the preparation of the feed or in the post-processing of the extracted roasted material.

[0032] Therefore, it is the aim of the current invention to propose a solution to prevent agglomerates from accumulating in the fluidized bed without the need for further steps before or after roasting.

[0033] Tis aim is solved by a system for automatically removing agglomerates from a fluidized bed of a fluidized bed roaster with the features of claim 1 .

[0034] Such a system for automatically removing agglomerates from a fluidized bed of a fluidized bed roaster, comprising a movable discharge lance flanged to the fluidized bed roaster for removing bed material during retraction. The movable discharge lance that is securely attached to the fluidized bed roaster at the nozzle grate level. The lance is designed to retract, thereby removing bed material, including agglomerates. This configuration allows for the automatic and continuous removal of agglomerates without requiring manual intervention, thus enhancing the efficiency and operational uptime of the roaster.

[0035] The size of the fluidized bed reactor depends on the throughput requirements. Industrial reactors can have diameters ranging from 1 to 15 meters and heights from 5 to 50 meters.

[0036] The nozzle grid at the bottom of the reactor is designed to distribute the fluidizing gas uniformly across the bed. Proper design and maintenance of the nozzle grid are necessary to prevent channeling and ensure even fluidization.

[0037] A number of different reactor types have been developed in fluidized bed technology beside the classic stationary bed formed by the particles to be treated. A

[0038] July 16, 2025 O 1 P 381 WO Bubbling Fluidized Bed (BFB) reactor introduces gas at the bottom, passing through a bed of solid particles at a velocity that creates bubbles within the bed. The BFB reactor offers good mixing and heat transfer, and its relatively simple design makes it easier to operate. However, it is limited to lower gas velocities, which can restrict throughput.

[0039] The Circulating Fluidized Bed (CFB) reactor operates at higher gas velocities, allowing solid particles to be carried out of the reactor. These particles are then separated from the gas in a cyclone and returned to the bed. CFB reactors are often used in large-scale processes. They are highly efficient in heat and mass transfer and can handle large volumes and higher gas velocities. The trade-off is a more complex design and higher operational costs.

[0040] Transport or Fast Fluidized Bed reactors operate similarly to CFB reactors but at even higher gas velocities, resulting in the entire bed being in a dilute phase and particles being continuously carried out of the reactor. These reactors are used in processes requiring very high throughput and rapid reactions,

[0041] Recirculating Fluidized Bed reactors ensure uniform mixing and temperature distribution by recirculating particles within the reactor. These reactors are regularly used in processes requiring very uniform conditions. They provide uniform temperature and reaction conditions but come with a more complex design and operation.

[0042] Moreover, spouted bed reactors, vibrating fluidized bed and dual fluidized bed reactors should be named.

[0043] Each type of fluidized bed reactor has specific advantages suited to particular applications based on the desired reaction conditions, particle characteristics, and process requirements. The choice of reactor type depends on factors such as the

[0044] July 16, 2025 O 1 P 381 WO nature of the feed material, the desired reaction rates, and the efficiency of heat and mass transfer needed for the process. It is important to understand that the system according to the invention can be used in any fluidized bed reactor.

[0045] Coming back to the discharge lance, it is preferred that the lance tip is fitted with specially designed discs that are optimized for breaking and removing agglomerates. These discs ensure that even the most stubborn agglomerates are efficiently disintegrated and removed from the bed material. This feature significantly improves the reliability and effectiveness of the agglomerate removal process.

[0046] Further, the lance is preferably equipped with a water-cooling system to prevent overheating during operation. This cooling mechanism ensures that the lance can operate continuously and efficiently without the risk of thermal damage. The water-cooling feature is crucial for maintaining the longevity and performance of the lance, especially in high-temperature environments typical of fluidized bed roasters.

[0047] Additionally or alternatively, a chute is strategically positioned to catch the discharged material from the lance and guide it to a downward device for further processing or disposal. This setup ensures a controlled and efficient transfer of removed agglomerates, minimizing spillage and contamination of the surrounding area.

[0048] Fluidizing nozzles are installed in specific sections of the fluidized bed to facilitate the flow of material towards the chute. The Nozzles are preferably positioned in the wall of the reactor, particularly preferred is a position primarily opposite to the lance. In addition or alternatively, nozzles are foreseen below the lance. This arrangement creates an air cushion that also transports floating particles towards the lance opening. These nozzles help maintain the fluidization state of the bed material, ensuring that agglomerates are efficiently directed to the lance for

[0049] July 16, 2025 O 1 P 381 WO removal. This feature supports the overall effectiveness and consistency of the agglomerate removal process.

[0050] Moreover, an automatic valve is preferably integrated into the discharge line to regulate the flow of removed material. This valve ensures precise control over the discharge process, preventing blockages and maintaining a steady flow of material. The automatic operation of the valve enhances the system's reliability and efficiency.

[0051] In another preferred embodiment, the system includes a temperature measurement system that monitors the flow of material within the fluidized bed. When the system detects a temperature threshold indicative of restricted flow due to agglomerates, it automatically activates the lance to remove the obstructions. This feature provides real-time response to flow issues, ensuring continuous and efficient operation.

[0052] The system includes at least one wind box that introduces a gas flow into the fluidized bed roaster to maintain fluidization. Pressure sensors are installed in the wind box to monitor the pressure drop, which is indicative of agglomerate accumulation. When the pressure sensors detect a threshold level, the control system activates the lance to remove the agglomerates, ensuring uninterrupted operation.

[0053] It is also preferred that a control system is implemented to operate the lance at predetermined intervals, targeting the removal of coarse agglomerates. This interval-based operation minimizes the removal of good flowing bed material, ensuring that the efficiency of the fluidized bed is maintained while effectively managing agglomerate buildup.

[0054] July 16, 2025 O 1 P 381 WO The control system can activate the lance based on input from the temperature measurement system and / or the pressure management system. This dual activation mechanism ensures that the lance is deployed precisely when needed, based on real-time data, to remove coarse agglomerates effectively and maintain optimal operation of the fluidized bed roaster.

[0055] The control system is fine-tuned to operate the lance at specific intervals to prevent the excessive removal of good flowing bed material. This careful calibration ensures that the removal process targets only the problematic agglomerates, preserving the overall efficiency and material balance within the fluidized bed.

[0056] Furthermore, the invention includes a process as outlined in claim 12, which can be executed using a system for automatically removing agglomerates from a fluidized bed of a fluidized bed roaster in accordance with any of claims 1 through 11. It is implicit that all features described for the system are also potential embodiments of the claimed process.

[0057] This process involves the automatic insertion of a movable discharge lance into the fluidized bed at the nozzle grate level. The lance, equipped with a specialized tip, removes bed material, including agglomerates, during its retraction. This automated process ensures continuous and efficient removal of agglomerates, reducing the need for manual intervention.

[0058] The process specifies that the lance is moved at regular intervals to target and remove coarse agglomerates. This interval-based movement minimizes the loss of good flowing bed material, ensuring that the process effectively manages agglomerate buildup while maintaining the operational efficiency of the fluidized bed roaster.

[0059] July 16, 2025 O 1 P 381 WO The typical roasting temperature range for fluidized bed reactors varies depending on the type of ore being processed. For sulfide ores (e.g., zinc sulfide, copper sulfide), the roasting temperatures generally range between 500°C and 1.000°C. For iron ores, temperatures might be slightly lower, typically between 500°C and 700°C.

[0060] Precise control of the roasting temperature is crucial to ensure efficient reaction rates and to avoid sintering or melting of the bed particles. Temperature sensors and control systems are employed to monitor and adjust the temperature within the reactor continuously.

[0061] The superficial gas velocity, which is the velocity of the fluidizing gas passing through the bed, typically ranges from 0.1 to 1.0 m / s, in a circulating fluidized bed also 0.1 to 5 m / s. This velocity must be sufficient to keep the particles in a fluidized state but not so high as to cause excessive particle entrainment and loss.

[0062] The actual gas flow rate depends on the reactor's design and the specific material being processed. For example, in a large industrial fluidized bed roaster, gas flow rates can range from several hundred to several thousand cubic meters per hour.

[0063] The particle size of the feed material is another critical factor. Typically, particles are in the range of 0.01 to 1 mm in diameter. Uniform particle size distribution is preferred to maintain consistent fluidization and reaction rates.

[0064] The density of the particles affects the fluidization behavior. Most ores have a particle density between 2,000 and 5,000 kg / m3.

[0065] The fluidizing gas often contains oxygen, particularly for oxidative roasting processes. Oxygen concentration in the fluidizing gas can range from 5% to 35%, depending on the specific reaction requirements. Inert gases such as nitrogen

[0066] July 16, 2025 O 1 P 381 WO may be used to control the reaction atmosphere and prevent undesirable side reactions. For sulfide ores, air or enriched air is commonly used to provide the necessary oxygen for oxidation.

[0067] Further developments, advantages and possible applications of the invention can also be taken from the following description of the drawing. All features described and / or illustrated form the subject-matter of the invention per se or in any combination, independent of their inclusion in the claims or their back-reference.

[0068] Fig. 1 shows schematically a roasting reactor with a system for automatically removing of agglomerates according to the invention.

[0069] In fig. 1 , the roasting reactor is illustrated as a standard fluidized bed reactor 10. However, other types of fluidized bed reactors are also suitable for this process. In a standard fluidized bed reactor configuration, the material to be treated, in the form of particles, is introduced through conduit 11. Fluidizing gas is injected via conduit 12 through a reactor nozzle grate 13. As the fluidizing gas lifts the particles, they form a fluidized bed 14 above the reactor nozzle grate 13.

[0070] To regulate the reactor temperature, additional water can be injected through conduit 15, often using water lances that are not shown in the diagram.

[0071] Particles are withdrawn from the fluidized bed 14 via conduit 18. Meanwhile, very light particles are carried into a freeboard zone 16 above the fluidized bed 14 and then removed along with the fluidizing gas through conduit 17. The parti- cle / gas mixture from conduit 17 may optionally be directed into a cyclone 20, where the particles are separated from the gas stream. Particularly if the fluidized bed 14 is designed as a circulating fluidized bed, the gas stream exits the cyclone 20 via conduit 21 , while the particles are redirected into conduit 18 through conduit 22.

[0072] July 16, 2025 O 1 P 381 WO A critical aspect of the invention is the inclusion of a movable discharge lance 30 within the fluidized bed reactor 10. This discharge lance 30 is mounted directly to the fluidized bed at the reactor nozzle grate level 13 using a mounting device 31 . Alternatively, it can be attached at a different location, provided it remains at the same level as the nozzle grate 13.

[0073] The movable discharge lance 30 is equipped with a lance tip 32 designed for removing bed material during retraction. The mounting device 31 allows the position of the lance tip 32 to be adjusted vertically within the fluidized bed 14. This adjustability ensures that agglomerates can be withdrawn from various positions in the fluidized bed 14, depending on operational parameters, particularly temperature control.

[0074] It is preferable for the material discharged by the lance 30 to fall into a chute and then be conveyed to a calcine cooler, which is not shown in the diagram. To support the material flow within the lance 30, a specific section of the bed is fluidized with fluidizing nozzles. If the material flows freely, the flow can be regulated by an automatic valve in a downward discharge line. In cases where material flow is impeded by coarse agglomerates, the lance 30, with its lance tip 32, can be inserted into the fluidized bed 14 to facilitate material movement.

[0075] July 16, 2025 O 1 P 381 WO List of references

[0076] 10 fluidized bed reactor 11 , 12 conduit

[0077] 13 nozzle grate

[0078] 14 fluidized bed

[0079] 15 conduit

[0080] 16 freeboard zone 17, 18 conduit

[0081] 20 cyclone

[0082] 21 , 22 conduit

[0083] 30 movable discharge lance

[0084] 31 mounting device 32 lance tip

[0085] July 16, 2025 O 1 P 381 WO

Claims

Claims1. A system for automatically removing agglomerates from a fluidized bed (14) of a fluidized bed reactor (10), comprising a movable discharge lance (30) flanged to the fluidized bed reactor (10) at a nozzle grate (13) level with a lance tip (32) for removing bed material during retraction.

2. A system according to claim 1 , characterized in that the lance tip (32) is equipped with specially designed discs configured to efficiently break and remove agglomerates.

3. A system according to claim 1 or 2, characterized in that the moveable discharge lance (30) is water-cooled.

4. A system according to any of the previous claims, characterized in that a chute positioned to receive the discharged material from the moveable discharge lance (30) and directing it to a downward device.

5. A system according to any of the previous claims, characterized in that fluidizing nozzles are foreseen in a specific section of the bed to support material flow to the discs.

6. A system according to any of the previous claims, characterized in that an automatic valve is installed in the discharge line to control material flow.

7. A system according to any of the previous claims, characterized in that the system features a temperature measurement system for monitoring material flow, configured to activate the lance when a temperature threshold indicating hampered flow is detected.July 16, 2025 O 1 P 381 WO8. A system according to any of the previous claims, characterized in that the at least one wind box is foreseen through which a gas flow is passed as fluidizing gas into the fluidized bed reactor (10) and that at least one pressure sensor is foreseen in the windbox which is part of a pressure measurement system for monitoring pressure drop in the windbox, configured to activate the moveable discharge lance (30) when a pressure threshold indicating accumulation of agglomerates is detected.

9. A system according to any of the previous claims, characterized in that a control system is installed for operating the moveable discharge lance (30) at intervals to remove coarse agglomerates while minimizing the loss of good flowing bed material.

10. A system according to claim 9, characterized in that the control system activates the moveable discharge lance (30) based on temperature indications from the temperature measurement system according to claim 8 and / or that the control system activates the lance based on pressure management system according to claim 9 ensuring the removal of coarse agglomerates.11 .A system according to claim 9 or 10, characterized in that the control system is configured to operate the moveable discharge lance (30) at predetermined intervals to prevent excessive removal of good flowing bed material.

12. A process for automatically removing agglomerates from a fluidized bed in a fluidized bed roaster, wherein a movable discharge lance is inserted into the fluidized bed at a nozzle grate level and remove bed material using a lance tip.July 16, 2025 O 1 P 381 WO13. A process according to claim 11 , characterized in that the lance is moved at intervals to remove coarse agglomerates while minimizing the loss of good flowing bed material.July 16, 2025 O 1 P 381 WO

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