System and method for reducing circulating load capacity of refractory iron ore dry-method pulverizing system

Abstract

The invention discloses a system and method for reducing the circulating load capacity of a refractory iron ore dry-method pulverizing system, and belongs to the technical field of mineral processing engineering. In order to solve the problems that in the dry-method powder making process of refractory iron ore, due to circulation accumulation of refractory minerals in the system, the load is increased, and a dynamic powder concentrator is prone to swelling, a parallel auxiliary powder grinding subsystem is additionally arranged on the basis of an original system. According to the system, an electric bar valve and a branch pipe are additionally arranged on a coarse-fraction discharge pipe of a dynamic powder concentrator, sorted coarse-fraction materials (0-5 mm) difficult to grind are shunted to a second surge bin, and then are specially ground by second powder making equipment until the qualified fineness that the content of-74 microns is 50% + / -5% is achieved. After being collected by a second cyclone separator, the ground product is conveyed back to the main system by a second air cushion type conveyor; the dusty gas is recycled through the second circulating fan part, and the rest of the dusty gas is connected into the original dust removal system. When the circulation load of the main system exceeds a set threshold value (such as 80% of a design value), the shunt grinding process is started, and when the load is recovered to a normal range (such as below 50% of the design value), the original process is switched back. The circulating load of the system is effectively reduced, the hidden danger of material accumulation of equipment is avoided, and the operation stability of the system and the adaptability to complex ore are improved.

Description

Technical Field

[0001] This invention relates to a system and method for reducing the circulating load of a dry grinding system for refractory iron ore, belonging to the field of mineral processing engineering. Background Technology

[0002] my country possesses abundant resources of complex and refractory iron oxide ores, characterized by their complex mineral composition, weak magnetism, and fine particle size, making it difficult to achieve ideal separation parameters using conventional high-intensity magnetic separation processes. However, if these ores undergo reduction-magnetic roasting pretreatment to transform them into strongly magnetic materials, and then supplemented with magnetic separation and reverse flotation processes, separation efficiency can be significantly improved. In recent years, with the gradual maturation and promotion of fluidized bed magnetic roasting technology, large-scale and efficient processing of such ores has become possible. However, this technology requires the iron ore to be prepared into dry powder of a specific particle size.

[0003] Against this backdrop, a dry grinding process combining high-pressure roller mills with dynamic classifiers has emerged and gradually gained industrial application. This process typically includes a high-pressure roller mill, lifting equipment, a V-type classifier, a dynamic classifier, a cyclone separator, and a bag filter. Compared to traditional grinding processes relying on wet ball milling, dry grinding eliminates lengthy steps such as product filtration, drying, and dispersion, offering significant advantages in terms of process simplicity and significantly reduced energy consumption. More importantly, the high-pressure roller mill operates based on the principle of "laminated crushing," generating numerous microcracks within the ore. This not only helps reduce over-crushing but also creates favorable conditions for subsequent roasting and sorting processes, thus achieving energy saving, environmental protection, and stable operation of the overall process.

[0004] However, in actual production, it has been found that existing dry grinding processes exhibit significant limitations when processing refractory iron ore containing hard, sclerosing minerals such as ferruginous phyllite. Even after multiple passes through a high-pressure roller mill, these refractory minerals still fail to meet the required fineness. They continuously accumulate in the system as small particles (primarily between the dynamic classifier and the high-pressure roller mill), causing a continuous increase in the system's circulating load. When the circulating load is too high, it easily leads to saturation of the dynamic classifier's processing capacity, resulting in a severe material accumulation phenomenon commonly known as "bloating." This not only disrupts the system's airflow balance and separation efficiency but also causes production interruptions, severely restricting the long-term, stable, and smooth operation of the entire dry grinding system.

[0005] Therefore, for refractory iron ore containing difficult-to-grind minerals, developing a new technology that can effectively reduce the circulating load of dry grinding systems, prevent blockage of key equipment, and ensure continuous and stable production has become a practical engineering problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The present invention aims to solve the engineering problem of the cyclic load of refractory iron ore (especially containing refractory minerals such as sclerite and ferruginous phyllite) in the dry grinding process, which is caused by the accumulation of refractory minerals in the high-pressure roller mill and dynamic classifier, resulting in the dynamic classifier "bloating" and material accumulation, and the inability of the system to operate stably.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a system for reducing the circulating load of a dry grinding system for refractory iron ore. This system innovatively adds an auxiliary grinding subsystem in parallel with the conventional dry grinding main circuit.

[0008] The original dry grinding main circuit mainly includes, in sequence, a bucket elevator A, a V-type classifier, a dynamic classifier, a bucket elevator B, a first buffer bin, a high-pressure roller mill (whose discharge returns to the bucket elevator A to form the main grinding cycle), a dynamic classifier for collecting and processing fine powder, a first cyclone separator, a first air cushion conveyor, a bucket elevator C, a finished product bin, and a bag filter for gas purification.

[0009] The core of the auxiliary grinding subsystem lies in the diversion and specialized processing device. Specifically, a branch pipe is installed on the coarse-particle discharge chute of the dynamic classifier, and an electric bar valve is installed on this branch pipe. This branch pipe guides the material to the newly added second buffer bin. The discharge port of the second buffer bin is connected to the second grinding equipment, which is dedicated to grinding the diverted, difficult-to-grind coarse-particle material. The discharge port of the second grinding equipment is sequentially connected to the second cyclone separator and the second air cushion conveyor, wherein the discharge port of the second air cushion conveyor is connected to the bucket elevator A of the main circuit, so that qualified powder can be returned to the main system. The gas outlet of the second cyclone separator is connected to a second circulating fan, the outlet of which is divided into two paths: one path returns as circulating air to the bottom of the second grinding equipment, forming the internal air circulation of the auxiliary system; the other path is connected to the bag filter dust collector of the main circuit.

[0010] Optionally, a vibrating feeder is provided at the bottom of the second buffer silo to achieve uniform feeding. An online particle size analyzer can be installed at the discharge port of the second grinding equipment for real-time monitoring of grinding fineness. The second grinding equipment can be selected from dry grinding equipment such as Raymond mills, column mills, or vertical mills.

[0011] Secondly, this invention provides a method for reducing the cyclic load using the above-mentioned system, the core of which lies in dynamically diverting and specializing grinding according to the load status of the main system. The method includes the following steps: The system monitors the circulating load of the main dry grinding circuit. When the circulating load exceeds a first preset threshold (e.g., 80% of the system design load), the electric bar valve is opened, diverting the coarse-grained material separated by the dynamic classifier to the second buffer chamber via a branch pipe. The material in the second buffer chamber is fed into the second grinding equipment for grinding, and the grinding parameters are controlled to ensure the product fineness meets the requirements (e.g., -74μm content is 50%±5%). The ground product is collected by the second cyclone separator and then sent back to the bucket elevator A of the main circuit by the second air cushion conveyor. The separated dust-laden gas enters the second circulating fan, and after pressurization, part of it is returned to the second grinding equipment as circulating air, while the remainder is sent to the main bag filter. When the circulating load of the main system drops below the second preset threshold (e.g., 50% of the design value), the electric bar valve is closed, the diversion stops, and the system resumes its original process operation.

[0012] Compared with existing technologies, this invention provides a direct and efficient engineering solution to the problems of refractory material accumulation and increased load by setting up an independent auxiliary grinding system, and its practical application advantages are significant. 1. Eliminates the problem of high circulating load: An independent grinding channel is created for hard minerals that are repeatedly circulated in the system and are difficult to grind finely. By leading them out of the main system for specialized grinding, the root cause of the vicious cycle is completely cut off, and the total circulating load of the system can be stably controlled at a low level.

[0013] 2. Completely eliminate the risk of "bloating": Because the difficult-to-grind materials are effectively diverted, the dynamic classifier no longer experiences blockage or "bloating" caused by the continuous accumulation of fine particles. The equipment operates stably, and the system air volume and sorting efficiency can be maintained at normal levels for a long time, ensuring continuous and smooth production.

[0014] 3. Improved system operating efficiency and adaptability: Core equipment such as the high-pressure roller mill in the main system can operate under optimized loads, improving grinding efficiency. Simultaneously, this method can flexibly respond to fluctuations in refractory components in the ore, automatically (or manually) activating the diversion branch line when an increase in circulating load is detected, enhancing the entire system's adaptability to complex raw materials. Attached Figure Description

[0015] Figure 1 This is a process flow diagram for existing dry iron ore grinding.

[0016] Figure 2 This is a process flow diagram of a method for reducing the circulating load of a dry grinding system for refractory iron ore according to the present invention. Detailed Implementation

[0017] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are used to more clearly illustrate the technical solutions and operation processes of the present invention, rather than to limit its scope of protection.

[0018] This invention aims to solve the problem of excessive load caused by the accumulation of refractory minerals during circulation in dry grinding systems for refractory iron ore. It mainly addresses the issue of excessive load in existing systems (process flow such as...). Figure 1 The system will be modified (as shown) by adding a parallel auxiliary grinding subsystem. The overall process is as follows: Figure 2 As shown.

[0019] I. System Composition While maintaining the existing main circuit equipment and connection relationships, the following modifications and additions will be made: Diverter Installation: A hole is drilled and welded onto the coarse-particle discharge chute of the dynamic classifier to install an electric bar valve (e.g., a 400×600 bidirectional electric bar valve). Below this valve, a sloping branch pipe (which can be made of wear-resistant steel pipe) is connected. The outlet of this branch pipe is connected to the inlet of the newly added second buffer silo. The volume of the second buffer silo can be configured according to the system's processing capacity, for example, 50 cubic meters. A vibrating feeder (such as an electromagnetic vibrating feeder) is installed at its bottom to stably supply material to subsequent equipment.

[0020] Construction of auxiliary grinding lines: The discharge port of the second buffer chamber is connected to the inlet of the second grinding equipment via a sealed feeding device. The second grinding equipment can be selected according to the material hardness and capacity requirements, such as a Raymond mill (4R3216 type), vertical roller mill, or column mill, which are suitable for dry grinding of medium and fine-grained ores. An online particle size analyzer (such as an online particle size analyzer based on the principle of laser diffraction) is installed on its product outlet pipe to monitor the grinding fineness in real time. The grinding goal is to process the material to a qualified fineness of 50% ± 5% with a -74μm (200 mesh) content.

[0021] The air outlet of the second pulverizing unit is connected to a second cyclone separator via a pipeline. The bottom conical discharge port of this separator is connected to the inlet of a second air cushion conveyor via a slurry unloader. The outlet of the second air cushion conveyor is connected to the inlet of the bucket elevator A in the original main circuit.

[0022] The top gas outlet of the second cyclone separator is connected to a second circulating fan (such as a 9-26 type high-pressure centrifugal fan). The outlet of this fan is divided into two paths through a three-way pipe: the first path (main path) returns to the bottom air inlet of the second pulverizing equipment through a regulating valve, forming the internal circulating air of the auxiliary system. It is recommended that the proportion of circulating air volume be controlled between 60% and 80% (e.g., 70%), which is adjustable; the second path (branch path) is connected to the main air duct before the original system's bag filter dust collector through a pipe.

[0023] II. Operating Method After the system modification is completed, follow these steps: 1. Normal Operation: During system startup or under normal cyclic load, the electric bar valve remains closed. All coarse-grained materials separated by the dynamic classifier return to the bucket elevator A via the original chute and then circulate into the high-pressure roller mill. The entire system operates according to... Figure 1 The existing process is in operation.

[0024] 2. Diversion Start-up: The circulating load of the system is monitored in real time by metering instruments installed in the main circuit (usually on the belt scale at the front end of bucket elevator A). When the monitored value continuously exceeds 80% of the system's design circulating load value, and it is determined to be caused by the accumulation of refractory materials, the central control room issues a command to open the electric bar valve to a predetermined opening degree (e.g., 50%). At this time, the small particles (mainly the difficult-to-crush parts in the 0-5mm particle size range) selected by the dynamic classifier are diverted and enter the second buffer chamber through the branch pipe.

[0025] The key to the above steps is that the coarse particles (usually larger in size) selected by the V-type classifier still enter the first buffer bin through the bucket elevator B and are fed into the high-pressure roller mill, so the processing path remains unchanged.

[0026] 3. Auxiliary grinding and recycling: The material in the second buffer chamber is evenly fed into the second grinding equipment (such as a Raymond mill) via a vibrating feeder. The grinding pressure, classifier speed and other parameters of the equipment are adjusted to grind the material to the set qualified fineness (-74μm content 50%±5%).

[0027] The qualified fine powder after grinding enters the second cyclone separator with the airflow, where most of the mineral powder is collected and falls into the second air cushion conveyor, and is finally sent back to the bucket elevator A of the main system.

[0028] The dust-laden gas discharged from the second cyclone separator enters the second circulating fan. By adjusting the valves, a predetermined proportion (e.g., 70%) of the circulating gas is sent back to the bottom of the second pulverizing equipment as circulating air to maintain a reasonable internal air velocity and negative pressure; the remaining gas is introduced into the main bag filter for purification. This minimizes the additional load on the main dust collection system caused by the new system.

[0029] 4. Process Monitoring and Optimization: During the operation of the auxiliary grinding line, the output particle size of the second grinding equipment is continuously monitored using an online particle size analyzer. Operators can fine-tune parameters such as the feed rate and grinding force of the second grinding equipment in real time based on the feedback data to ensure stable grinding efficiency and product quality.

[0030] 5. Diversion Stop and Resumption: Continuously monitor the main system's circulating load. When the load value steadily decreases and stabilizes below 50% of the design value, it indicates that the accumulation problem of difficult-to-grind materials has been alleviated. At this time, the electric bar valve can be gradually closed, and all coarse-grained output from the dynamic classifier can be switched back to the original main circuit for processing. The auxiliary grinding subsystem will then be shut down and ready for operation.

[0031] Through the above specific implementation methods, without changing the core process of the original system, the present invention economically and effectively solves the problem of cyclic load caused by refractory minerals by using a flexible start-stop "bypass" processing scheme, and significantly improves the overall stability and production efficiency of the dry grinding system for refractory iron ore without changing the core process of the original system.

Claims

1. A system for reducing the circulating load of a dry grinding system for refractory iron ore, characterized in that, The application relates to a main circuit and an auxiliary grinding sub-circuit of a raw dry process powder production system. The main circuit of the raw dry process powder production system comprises: a bucket elevator A; a V-type powder classifier, the feeding port of which is connected with the discharging port of the bucket elevator A; a bucket elevator B, the feeding port of which is connected with the coarse particle level discharging port of the V-type powder classifier; a first buffer bin, the feeding port of which is connected with the discharging port of the bucket elevator B; a high-pressure roller mill, the feeding port of which is connected with the discharging port of the first buffer bin, and the discharging port is connected with the feeding port of the bucket elevator A, thereby forming a main grinding cycle; a dynamic powder classifier, the feeding port of which is in airflow communication with the fine powder outlet of the V-type powder classifier; a first cyclone separator, the air inlet of which is in airflow communication with the fine powder outlet of the dynamic powder classifier; a bag-type dust collector, the air inlet of which is in communication with the air outlet of the first cyclone separator; a first air cushion conveyor, the feeding port of which is connected with the discharging port of the first cyclone separator and the bag-type dust collector; a bucket elevator C, the feeding port of which is connected with the discharging port of the first air cushion conveyor; a finished product bin, the feeding port of which is connected with the discharging port of the bucket elevator C; The auxiliary grinding sub-circuit comprises: a branch pipe, which is installed on the coarse particle level discharging pipe of the dynamic powder classifier; an electric rod valve, which is installed on the branch pipe; a second buffer bin, the feeding port of which is connected with the branch pipe; a second powder production device, the feeding port of which is connected with the discharging port of the second buffer bin; a second cyclone separator, the air inlet of which is connected with the powder grinding product airflow discharging port of the second powder production device; a second air cushion conveyor, the feeding port of which is connected with the discharging port of the second cyclone separator, and the discharging port is connected with the feeding port of the bucket elevator A; a second circulating fan, the air inlet of which is connected with the air outlet of the second cyclone separator; the air outlet of the second circulating fan is divided into two paths through a pipeline, the first path is connected with the bottom air inlet of the second powder production device, and the second path is connected with the air inlet of the bag-type dust collector. The bottom of the second buffer bin is provided with a vibrating feeder.

2. The system of claim 1, wherein, A particle size on-line detector is installed at the powder grinding product outlet of the second powder production device.

3. The system of claim 1, wherein, The second powder production device is a dry grinding device, and is selected from one of a Raymond mill, a column mill and a vertical mill.

4. The system of claim 1, wherein, The application further discloses a method for monitoring and controlling the main circuit and the auxiliary grinding sub-circuit of the raw dry process powder production system.

5. A method of reducing the circulating load of dry grinding of a refractory iron ore using the system of any one of claims 1 to 4, characterised in that, S1: monitoring the circulating load of the main circuit of the raw dry process powder production system; S2: when the monitored circulating load exceeds a first preset threshold value, the electric rod valve is opened, and the coarse particle level material separated out from the dynamic powder classifier is branched to the second buffer bin through the branch pipe; S3: the material in the second buffer bin is fed into the second powder production device for grinding, and the generated powder grinding product enters the second cyclone separator for gas-solid separation along with airflow; S4: the separated powder grinding product is transported back to the bucket elevator A through the second air cushion conveyor, and reenters the main circuit; the separated dust-containing gas enters the second circulating fan; S5: the gas pressurized by the second circulating fan returns to the second powder production device as circulating air, and the remaining part is sent into the bag-type dust collector for purification and then discharged. The first preset threshold value is 80% of the design value of the circulating load of the main circuit of the raw dry process powder production system.

6. The method of claim 5, wherein, ​ 7. The method of claim 5, wherein, Further comprising a step S6: when it is monitored that the circulating load of the main circuit of the original dry process pulverizing device decreases to a second preset threshold, the electric bar valve is closed and the shunting is stopped.

8. The method of claim 7, wherein, The second preset threshold is 50% of the design value of the circulating load of the main circuit of the original dry process pulverizing device.

9. The method of claim 5, wherein, The particle size range of the material entering the second pulverizing device is 0-5 mm; the operating parameters of the second pulverizing device are controlled so that the content of the-74 μm particle size fraction in the ground product reaches 50%±5%.

10. The method of claim 5, wherein, In step S5, the circulating gas flow rate returned to the second pulverizing device accounts for 70% of the total air output of the second circulating fan.

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