Drying and preheating device for iron ore oxidized pellets in rotary kiln

Abstract

The utility model relates to metallurgical engineering technical field, concretely relates to a rotary kiln iron ore oxidized pellet drying preheating device, the present design improves heat utilization, reduces production energy consumption through optimizing heat source utilization and heat exchange structure, secondly, through optimizing pellet motion locus and airflow field distribution, realizing the even control of pellet moisture and temperature, providing stable pretreatment basis for subsequent roasting, at the same time, through optimizing equipment structure and operating parameter, prolonging the life of key components, reducing breakdown downtime, improving the long -term stable operation ability of device, and, through strengthening waste gas airtight collection, optimizing airflow velocity to reduce dust entrainment, and designing waste gas pretreatment structure that adapts to high humidity environment, reduce dust emission concentration, reduce the pressure of subsequent environmental protection treatment, finally, through the design adjustable airflow parameter and pellet conveying structure, adapt to different raw material characteristics and working condition fluctuation, reduce the production anomaly caused by raw material change.

Description

Technical Field

[0001] This utility model relates to the field of metallurgical engineering technology, and in particular to a rotary kiln iron ore oxide pellet drying and preheating device. Background Technology

[0002] In the production of iron ore oxide pellets, the drying and preheating process plays a crucial role as a key step connecting "pellet forming" and "high-temperature roasting in a rotary kiln." Currently, commonly used drying and preheating devices in the industry, such as chain grate machines, belt dryers and preheaters, vertical preheaters, and pre-drying sections in rotary kilns, all achieve effective drying and preheating of pellets to varying degrees. These devices, through different heat exchange methods and structural designs, can remove physical water and some crystal water from the pellets, preventing them from cracking due to violent evaporation of moisture after entering the rotary kiln. At the same time, they raise the temperature of the pellets to a suitable range, laying the foundation for subsequent oxidation roasting and solid-phase consolidation. For example, chain grate machines move the pellets on the grate plates using chains, utilizing hot flue gas for drying and preheating, making them suitable for large-scale production. Vertical preheaters, on the other hand, achieve compact drying and preheating of pellets through counter-current heat exchange.

[0003] However, existing drying and preheating equipment has significant shortcomings in terms of thermal efficiency, pellet quality stability, equipment reliability, environmental protection, and raw material adaptability, making it difficult to meet the development needs of the modern steel industry for "low energy consumption, high quality, high stability, and greening." This has become the core driving force for promoting the technological improvement of this equipment. Utility Model Content

[0004] The purpose of this utility model is to provide a rotary kiln iron ore oxide pellet drying and preheating device, which aims to solve the obvious deficiencies of existing drying and preheating devices in terms of thermal efficiency, pellet quality stability, equipment reliability, environmental protection and raw material adaptability, making it difficult to meet the development needs of the modern steel industry for "low energy consumption, high quality, high stability and greening". This has become the core technical problem driving the improvement of this device.

[0005] To achieve the above objectives, this utility model employs a rotary kiln iron ore oxide pellet drying and preheating device, comprising a chain grate machine. The feeding end of the chain grate machine is equipped with a roller feeder, which consists of multiple parallel rollers with specific textures or protrusions on their surfaces. The chain grate machine includes a forced-air drying section, a forced-air drying section, a preheating section I, a preheating section II, a heat source inlet, and a waste gas outlet. The forced-air drying section is equipped with a blower end, and the forced-air drying section is equipped with... The machine is equipped with an exhaust fan end, and an auger conveyor is installed at the discharge end of the chain grate machine. The conveying end of the auger conveyor is equipped with a dust removal structure, which is also connected to the exhaust drying section. The heat source inlet end is divided into a rotary kiln, a second-stage annular cooler, and a third-stage annular cooler. The rotary kiln is connected to the preheating section II via a pipeline, and the second-stage annular cooler is connected to the preheating section I via a pipeline. Each pipeline is equipped with a regulating valve, a flow meter, and a temperature sensor.

[0006] The hot air inlet temperature of the blower drying section is 200-300℃, the wind speed is 1.0-1.5m / s, and the green pellet residence time is 3-5min.

[0007] The hot air inlet temperature of the exhaust drying section is 300-400℃, the exhaust velocity is 1.2-1.8m / s, and the green pellet residence time is 5-8min.

[0008] The hot air inlet temperature of the preheating section I is 400-600℃, the wind speed is 1.0-1.5m / s, and the green pellet residence time is 8-10min.

[0009] The hot air inlet temperature of the preheating section II is 800-1000℃, the air velocity is 0.8-1.2m / s, and the green pellet residence time is 10-12min.

[0010] The dust removal structure is a bag filter, and the bag filter is equipped with filter bags.

[0011] This invention relates to a rotary kiln iron ore oxide pellet drying and preheating device. The design improves heat utilization and reduces production energy consumption by optimizing heat source utilization (e.g., efficient recovery of waste heat from rotary kiln roasting exhaust gas) and heat exchange structure (e.g., enhanced gas-solid countercurrent heat exchange). Secondly, by optimizing pellet movement trajectory (e.g., uniform distribution and orderly tumbling) and airflow distribution, uniform control of pellet moisture and temperature is achieved, providing a stable pretreatment foundation for subsequent roasting. Simultaneously, by optimizing equipment structure (e.g., selection of high-temperature and wear-resistant materials and sealing design) and operating parameters, the lifespan of key components is extended, downtime is reduced, and the long-term stable operation capability of the device is improved. Furthermore, by strengthening the sealed collection of exhaust gas, optimizing airflow velocity to reduce dust entrainment, and designing an exhaust gas pretreatment structure suitable for high-humidity environments, the dust emission concentration is reduced (meeting ≤30mg / m³). 3 To meet environmental standards, this technology aims to reduce the pressure of subsequent environmental treatment. Finally, by designing adjustable airflow parameters (such as wind speed and temperature gradient) and pellet conveying structures, it adapts to different raw material characteristics and operating condition fluctuations, reducing production anomalies caused by changes in raw materials. The core objective of this technical solution is to achieve high efficiency, energy saving, stable quality, reliable operation, green environmental protection, and strong adaptability in the pellet drying and preheating process through structural optimization and process improvement. This provides a better pretreatment solution for rotary kiln iron ore oxide pellet production, meeting the requirements of the modern steel industry for "low cost, high quality, and sustainability" in the raw material preparation process. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the rotary kiln iron ore oxide pellet drying and preheating device of this utility model.

[0014] 1-Roller cloth feeder, 2-Chain grate machine, 3-Blower end, 4-Blower drying section, 5-Exhaust drying section, 6-Screw conveyor, 7-Filter bag, 8-Bag dust collector, 9-Preheating section I, 10-Exhaust gas emission end, 11-Heat source inlet end, 12-Exhaust fan, 13-Preheating section II. Detailed Implementation

[0015] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0016] Please see Figure 1 This utility model provides a rotary kiln iron ore oxide pellet drying and preheating device, including a chain grate machine 2. A roller feeder 1 is installed at the feed end of the chain grate machine 2. The roller feeder 1 consists of multiple parallel rollers with specific textures or protrusions on their surfaces. The chain grate machine 2 has a forced-air drying section 4, a forced-air drying section 5, a preheating section I 9, a preheating section II 13, a heat source inlet 11, and a waste gas outlet 10. The forced-air drying section 4 is equipped with a blower end 3, and the forced-air drying section 5 is equipped with... The machine has an exhaust fan 12 end, and the discharge end of the chain grate machine 2 is equipped with an auger conveyor 6. The conveying end of the auger conveyor 6 is equipped with a dust removal structure, and the dust removal structure is also connected to the exhaust drying section 5. The heat source inlet end 11 is divided into a rotary kiln, a second-stage annular cooler, and a third-stage annular cooler. The rotary kiln is connected to the preheating section II 13 through a pipeline, and the second-stage annular cooler is connected to the preheating section I 9 through a pipeline. Each pipeline is equipped with a regulating valve, a flow meter, and a temperature sensor.

[0017] In this embodiment, the entire drying and preheating device is based on the chain grate machine 2 as the main frame. The chain grate machine 2 is divided into a blower drying section 4, an exhaust drying section 5, a preheating section I 9, and a preheating section II 13 from the feed end to the discharge end. The grate bed of the chain grate machine 2 is made of grate plates that are resistant to high temperature, wear-resistant, and have good air permeability. The grate plates are installed on the chain links through a specific connection structure. The chain links form a circulating chain. The chain is driven by the head and tail drive devices to realize the continuous operation of the grate bed.

[0018] In this embodiment, the high-temperature exhaust gas (temperature can reach 800-1000℃) discharged from the rotary kiln is introduced into the preheating section II 13 through a pipeline as the main hot air source for this section; part of the flue gas discharged from the secondary cooling of the annular cooler (temperature about 400-600℃) is introduced into the preheating section I 9 to provide it with a preheating heat source; the flue gas discharged from the tertiary cooling of the annular cooler (temperature about 200-300℃) is mixed with another part of the low-temperature flue gas discharged from the secondary cooling and then transported to the blower drying section 4 for the preliminary drying of green pellets.

[0019] In this embodiment, each hot air inlet pipe is equipped with a regulating valve, a flow meter, and a temperature sensor, which can precisely control the hot air volume and temperature entering each section according to process requirements. At the same time, a hot air return pipe is set between each section. For example, part of the hot air discharged from the preheating section II 13 can be returned to the exhaust drying section 5 through the pipe, realizing the secondary utilization of heat and improving thermal efficiency.

[0020] In this embodiment, a blower and an exhaust fan are respectively installed in the forced-air drying section 4 and the exhaust drying section 5. The blower forces the mixed hot air into the space below the grate, allowing it to penetrate upwards through the grate and remove moisture. The exhaust fan creates negative pressure above the grate in the exhaust drying section 5, accelerating the drying effect of the hot air on the green balls and extracting the hot air containing moisture. After dust removal, part of the hot air is discharged, and the rest can be recycled. An appropriate amount of combustion air is also provided in the preheating section to supplement the combustion air and ensure stable hot air temperature.

[0021] In this embodiment, a roller feeder 1 is installed above the feed end of the chain grate machine 2. The roller feeder 1 consists of multiple parallel rollers with specific textures or protrusions on their surfaces. The rotation of the rollers evenly distributes the green balls from the pelletizing process onto the grate of the chain grate machine 2, ensuring a uniform thickness of the green ball layer on the grate. Generally, the thickness of the material layer is controlled at 200-300mm. By adjusting the roller feeder 1, the thickness of the material layer on the grate of the chain grate machine 2 is controlled at 200-300mm. The stability of the material layer thickness is crucial for ensuring the uniformity and stability of drying and preheating. An excessively thick material layer may result in insufficient drying and preheating of the lower layer of green balls, while an excessively thin material layer will affect production efficiency and heat utilization efficiency. During the production process, the parameters of the feeder are adjusted in a timely manner according to the properties of the green balls (such as particle size and strength) and the equipment operating conditions to ensure the material layer.

[0022] In this embodiment, the grate bed of the chain grate machine 2 operates at a stable speed under the drive of the head and tail transmission device. The speed can be adjusted according to the drying and preheating effect of the green pellets to ensure that the green pellets have sufficient residence time in each section. At the discharge end of the chain grate machine 2 (end of the preheating section II 13), there is a shovel plate. When the preheated pellets run to the position of the shovel plate, they are shoveled off by the shovel plate and enter the rotary kiln for subsequent roasting through the conveying device such as the chute.

[0023] In this embodiment, the upper cover of the chain grate machine 2 is designed to be fully sealed to reduce the leakage of hot air and dust; gas collection pipes are connected to the exhaust gas outlets of the exhaust drying section 5 and the preheating section to collect the exhaust gas in a concentrated manner.

[0024] In this embodiment, after dust removal, part of the exhaust gas is discharged to the atmosphere by an induced draft fan, while the other part can be returned to the front section of the drying and preheating device (such as the blower drying section 4) through a circulation pipeline as supplementary hot air, thereby further improving energy utilization.

[0025] Furthermore, the hot air inlet temperature of the blower drying section 4 is 200-300℃, its wind speed is 1.0-1.5m / s, and its green pellet residence time is 3-5min.

[0026] In this embodiment, by adjusting the mixing ratio of the low-temperature flue gas from the three-stage and two-stage cooling of the annular cooler entering this section, as well as the air volume of the blower, the surface temperature of the green pellet bed is ensured to be 150-200℃, and the internal temperature of the bed is ensured to be 100-150℃. The blower speed is controlled at 1.0-1.5m / s, which ensures that the hot air effectively penetrates the green pellet bed while avoiding excessive wind speed that could blow away the green pellets or damage their surface. The green pellet residence time is about 3-5 minutes, which is adjusted appropriately according to the initial moisture content of the green pellets and the drying effect to ensure that most of the free water is removed.

[0027] Furthermore, the hot air inlet temperature of the exhaust drying section 5 is 300-400℃, its exhaust velocity is 1.2-1.8m / s, and its green pellet residence time is 5-8min.

[0028] In this embodiment, by adjusting the negative pressure of the exhaust fan, the amount of recirculated hot air, and the heat exchange with the preheating stage II 13, the surface temperature of the green pellet bed is maintained at 250-350℃, and the internal temperature of the bed is maintained at 200-300℃. The exhaust fan speed is controlled at 1.2-1.8 m / s to accelerate moisture evaporation and exhaust gas discharge, while ensuring the stability of the green pellets on the grate. The green pellet residence time is about 5-8 minutes to further reduce the moisture content of the green pellets and improve their strength.

[0029] Furthermore, the hot air inlet temperature of the preheating section 9 is 400-600℃, its wind speed is 1.0-1.5m / s, and its green ball residence time is 8-10min.

[0030] In this embodiment, by adjusting the flow rate of the secondary cooling flue gas of the annular cooler and the air volume of the combustion fan, the surface temperature of the green pellet bed is maintained at 500-600℃, and the internal temperature of the bed is maintained at 400-500℃; the air velocity is controlled at 1.0-1.5m / s to ensure that the hot air is in full contact with the green pellets and achieves uniform preheating; the residence time of the green pellets is about 8-10 minutes, allowing the green pellets to begin to undergo an oxidation reaction and reach a certain preheating temperature, further reducing the moisture content of the green pellets and improving their strength.

[0031] Furthermore, the hot air inlet temperature of the preheating section II 13 is 800-1000℃, its wind speed is 0.8-1.2m / s, and its green ball residence time is 10-12min.

[0032] In this embodiment, by adjusting the amount of exhaust gas introduced from the rotary kiln and the air volume of the combustion blower, the surface temperature of the green pellet bed is maintained at 850-950℃, and the internal temperature of the bed is maintained at 800-900℃; the air velocity is controlled at 0.8-1.2 m / s to ensure heat transfer while preventing excessive impact of high-temperature hot air on the pellets; the residence time of the green pellets is about 10-12 minutes to ensure that the green pellets are fully oxidized and preheated, and have sufficient strength to enter the rotary kiln.

[0033] Furthermore, the dust removal structure is a bag filter 8, and the bag filter 8 is provided with filter bags 7.

[0034] In this embodiment, the collected exhaust gas first enters the bag filter 8, which is equipped with filter bags 7, which can effectively filter the dust in the exhaust gas, reducing the dust emission concentration to 30 mg / m³. 3 The following is an explanation of the process. To adapt to high-humidity exhaust gas environments, the filter bags are made of special waterproof and oil-proof materials. Additionally, a pre-processor is installed before the bag filter dust collector 8 to cool and dehumidify the exhaust gas, preventing the filter bags from clogging.

[0035] Compared with existing technologies, the rotary kiln iron ore oxide pellet drying and preheating device of this utility model has the advantages of high thermal efficiency, good pellet quality, stable equipment operation, excellent environmental performance, and strong raw material adaptability. The specific beneficial effects are as follows:

[0036] 1. Improved thermal efficiency and reduced energy consumption: By optimizing heat source utilization and heat exchange structure, waste heat from rotary kiln roasting can be efficiently recovered, gas-solid countercurrent heat exchange can be enhanced, and hot air loss can be reduced. Compared with traditional equipment, whose thermal efficiency is usually below 50%, the new equipment can increase the thermal efficiency to over 70% and reduce the energy consumption per unit pellet to below 250 kcal / t, significantly reducing production energy consumption.

[0037] 2. Improved Pellet Quality: The system enables uniform drying and preheating of pellets. By optimizing pellet movement trajectory and airflow distribution, residual moisture content is controlled within 3%, and preheating temperature deviation can be reduced to ±20℃, ensuring uniform moisture and temperature in the pellets. During rotary kiln calcination, pellet compressive strength fluctuations can be controlled within 5%, improving the quality of the finished pellet product.

[0038] 3. Enhanced Equipment Stability: The use of high-temperature and wear-resistant materials and optimized sealing design extends the lifespan of critical components. For example, the lifespan of the second grate plate of the chain grate machine can be extended to 2-3 years, and the wear rate of the lining material in the pre-section of the rotary kiln is reduced by more than 30%. Simultaneously, it reduces air leakage and blockages, decreasing the number of downtimes due to malfunctions to 2-3 times per year, improving production line continuity, and lowering maintenance costs to below 10% of the total equipment investment.

[0039] 4. Improved environmental performance: Enhanced closed-loop collection of exhaust gas and optimized airflow velocity reduce dust entrainment, reducing dust emission concentration to 30mg / m³. 3 The following measures meet environmental standards. Furthermore, the design of a pre-treatment structure for exhaust gases adapted to high-humidity environments can alleviate the pressure on subsequent environmental treatment and reduce exhaust gas treatment costs.

[0040] 5. Enhanced Raw Material Adaptability: Adjustable airflow parameters and pellet conveying structure allow for adaptation to raw materials with varying particle sizes, moisture content, and composition. Raw materials with particle size fluctuations of ±3mm and moisture content between 8% and 12% can be stably processed. The "runaway rate" of small-diameter pellets can be reduced to below 1%, and large-diameter pellets can be fully preheated, ensuring production process stability and pellet quality.

[0041] This utility model also provides two embodiments, as follows:

[0042] Example 1:

[0043] Structural components:

[0044] The main body of the chain grate machine 2 adopts a standard chain grate machine 2 frame. The grate bed is composed of high-temperature resistant and wear-resistant alloy steel grate plates. The grate plates are tightly connected to the chain links through a special slot structure to ensure stable operation under high temperature and heavy load conditions. The chain grate machine 2 is divided into four sections from the feed end to the discharge end: blower drying section 4, exhaust drying section 5, preheating section I 9, and preheating section II 13. Each section is separated by heat insulation plates to reduce heat cross-flow.

[0045] Hot air circulation system: High-temperature exhaust gas (approximately 850℃) from the rotary kiln is introduced into the hot air box of preheating section II 13 through high-temperature resistant pipes. Within the hot air box, it is evenly distributed to the area below the grate bed via an air distribution device. Flue gas (approximately 500℃) from the secondary cooling stage of the annular cooler is introduced into preheating section I 9, also evenly distributed via an air distribution device. Flue gas (approximately 250℃) from the tertiary cooling stage of the annular cooler mixes with some of the low-temperature flue gas from the secondary cooling stage before entering the blower box of the forced-air drying section 4. Each hot air inlet pipe is equipped with a high-precision regulating valve, a thermal resistance temperature sensor, and a gas flow meter to precisely control the flow rate and temperature of the hot air. A hot air return pipe is installed between the exhaust drying section 5 and preheating section II 13, returning some of the high-temperature hot air (approximately 600℃) discharged from preheating section II 13 to the exhaust drying section 5, improving heat utilization.

[0046] Fabric and pellet conveying structure: A variable frequency speed-regulating roller fabric feeder 1 is installed above the feed end of the chain grate machine 2. The roller surface is specially treated with a diamond pattern to effectively prevent green pellets from sticking together and ensure uniform fabric distribution. By adjusting the roller speed and roller spacing, the fabric feeder can evenly spread the green pellets on the grate bed, controlling the material layer thickness to approximately 250mm. The grate bed of the chain grate machine 2 is driven by a high-power motor at the head through a reducer and chain. The running speed can be steplessly adjusted within the range of 0.52m / min according to the green pellet drying and preheating effect. At the discharge end of the chain grate machine 2, an adjustable-angle shovel plate is installed to accurately guide the preheated pellets into the chute connected to the rotary kiln.

[0047] Waste gas treatment and environmental protection structure: The chain grate machine 2 adopts a fully enclosed steel structure shell, with the inside of the shell lined with high-temperature resistant and heat-insulating ceramic fiber material to reduce heat loss and dust overflow. High-efficiency bag filters 8 are connected to the waste gas outlets of the exhaust drying section 5 and the preheating section. The filter bags use PTFE membrane filter media, which can effectively filter fine dust in the waste gas. To prevent bag clogging, a pre-processor, including a cooling tower and a cyclone separator, is installed before the dust collector to pre-treat the waste gas by cooling and dust removal. After treatment, part of the waste gas is discharged into the atmosphere by an induced draft fan, and the other part is returned to the blower drying section 4 as supplementary hot air through a circulation pipe.

[0048] Working principle:

[0049] Drying Process: The green pellets first enter the forced-air drying section 4. The mixed hot air (approximately 250°C) is forced upwards through the green pellet layer from below the grate by a blower. The heat in the hot air is rapidly transferred to the green pellets, causing the moisture on the surface to evaporate. The water vapor flows upwards with the hot air, and some is extracted by the exhaust fan. This stage primarily removes most of the free water from the green pellets. By precisely controlling the hot air temperature, air velocity (approximately 1.2 m / s), and green pellet residence time (approximately 4 minutes), the moisture content of the green pellets is ensured to be reduced to a certain level, while preventing the green pellets from cracking due to excessive heating. After entering the exhaust drying section 5, the green pellets utilize the residual heat from the forced-air drying and, through the negative pressure created above the grate by the exhaust fan, accelerate the diffusion and evaporation of moisture from the inside of the green pellets to the surface. A portion of the high-temperature hot air (approximately 600°C) returning from the preheating section II 13 also enters the exhaust drying section 5, further improving drying efficiency. During this stage, residual free water and some crystal water inside the green pellets are removed, further reducing the moisture content and improving the strength. The hot air temperature in the exhaust drying section 5 is approximately 350℃, the wind speed is approximately 1.5m / s, and the green pellet residence time is approximately 6 minutes.

[0050] Preheating Process: After being dried by suction, the green pellets enter preheating stage I (9). Hot air (approximately 500°C) from the secondary cooling stage of the annular cooler passes upwards through the green pellet bed from below the grate. During this stage, the green pellet temperature further increases, and the magnetite begins to oxidize, with some Fe3O4 being oxidized to Fe2O3. Simultaneously, some physical and chemical reactions within the pellets begin, such as the decomposition of carbonates. By controlling the hot air temperature, air velocity (approximately 1.2 m / s), and green pellet residence time (approximately 9 min), the green pellets reach a certain preheating temperature, preparing them for the subsequent deep preheating and oxidation reaction in preheating stage II (13). After entering preheating stage II (13), high-temperature exhaust gas (approximately 850°C) from the rotary kiln enters from below the grate as the main heat source. Under high temperature, the magnetite in the green pellets further oxidizes, the oxidation reaction becomes more intense, the internal structure of the pellets begins to change, and the strength significantly increases. By precisely controlling the hot air temperature, wind speed (approximately 1.0 m / s), and green pellet residence time (approximately 11 min), the green pellets are ensured to be fully preheated and reach the ideal state for entering the rotary kiln for calcination, at which point the pellet temperature can reach approximately 850℃.

[0051] Functions and effects:

[0052] Improved thermal efficiency: By optimizing the hot air circulation system and fully recovering the waste heat from the rotary kiln and annular cooler, the thermal efficiency has increased from less than 50% in traditional equipment to over 75%. The energy consumption per unit pellet has decreased from 320 kcal / t to approximately 220 kcal / t, significantly reducing production costs.

[0053] Improved pellet quality: Due to the uniform heating of the pellets during the drying and preheating process, the residual moisture content of the pellets can be stably controlled within 2%, and the preheating temperature deviation is controlled within ±15℃. After calcination in the rotary kiln, the compressive strength of the pellets increases to over 3500N / piece, the drum strength reaches 96%, and the abrasion index decreases to 2.5%, resulting in a significant improvement in pellet quality.

[0054] Enhanced equipment stability: The grate of the chain grate machine 2 uses a new type of alloy steel material, which improves wear resistance by more than 30% and extends the grate life from the original 3-6 months to 1-2 years. At the same time, by optimizing the sealing structure and reducing air leakage, the operational stability of the equipment has been greatly improved, reducing the number of downtimes due to failures per year from the original 5-8 times to 1-2 times, and reducing maintenance costs by more than 50%.

[0055] Improved environmental performance: The efficient waste gas treatment system keeps dust emission concentration stably controlled at 20mg / m³. 3 The following figures are far below national environmental protection standards. Furthermore, by recycling waste gas, the total amount of waste gas emissions is reduced, thus lowering environmental pollution.

[0056] Enhanced raw material adaptability: This device can adapt to green pellets of different particle sizes (6-16mm) and different moisture contents (6%-10%). It can also achieve stable drying and preheating of limonite raw materials with high crystal water by adjusting process parameters, thus significantly enhancing the adaptability of raw materials.

[0057] Example 2:

[0058] Structural components:

[0059] Vertical preheater body: The vertical preheater adopts a cylindrical steel structure shell, lined with multiple layers of high-temperature resistant and heat-insulating materials to reduce heat loss. The preheater is divided into a feeding zone, a drying zone, a preheating zone, and a discharge zone from top to bottom. In the feeding zone, a rotating feeder evenly distributes green pellets across the preheater's cross-section. The drying and preheating zones are equipped with multiple hot air ducts, each introducing hot air at different temperatures. The discharge zone uses a sealed unloading device to transport the preheated pellets to the rotary kiln.

[0060] Hot air system: The high-temperature exhaust gas (approximately 900℃) from the rotary kiln is partially cooled by a waste heat boiler, reducing its temperature to 700-800℃ before being introduced into the preheating zone of the preheater. The flue gas (approximately 450℃) from the secondary cooling stage of the annular cooler is introduced into the drying zone for drying the green pellets. The hot air flows counter-currently to the pellets within the preheater, achieving efficient heat exchange. Regulating valves, temperature sensors, and flow sensors are installed on the hot air ducts to precisely control the flow rate and temperature of the hot air.

[0061] Pellet conveying and feeding structure: Green pellets are conveyed by a belt conveyor to a rotary feeder at the top of the vertical preheater. The rotary feeder is driven by a variable frequency motor, which can adjust the feeding speed and angle according to the flow rate and properties of the green pellets to ensure uniform distribution of the green pellets within the preheater. At the bottom of the preheater, the preheated pellets are continuously and stably conveyed to the rotary kiln through a sealed discharge device. The sealed discharge device adopts a double-layer gate structure to effectively prevent hot air leakage.

[0062] Exhaust gas treatment structure: The exhaust gas discharged from the top of the vertical preheater first enters the cyclone dust collector for preliminary dust removal, removing most of the larger dust particles, and then enters the bag filter 8 for fine filtration, reducing the dust emission concentration to 30mg / m³. 3 The exhaust gas, after dust removal, is partially discharged into the atmosphere by an induced draft fan, and partially returned to the drying area through a recirculation pipeline as supplementary hot air to improve heat utilization.

[0063] Working principle:

[0064] Drying Process: Green pellets enter from the top of the vertical preheater, are initially evenly distributed in the distribution area, and then enter the drying zone. Hot air (approximately 450°C) from the secondary cooling stage of the annular cooler flows upward from the bottom of the drying zone, contacting the downward-moving green pellets in the opposite direction. The heat in the hot air is transferred to the green pellets, causing the moisture on their surface to evaporate. The moisture vapor flows upward with the hot air and is discharged from the preheater. In the drying zone, by controlling the hot air temperature, air velocity, and residence time of the green pellets, most of the moisture in the green pellets is removed, reducing the moisture content to 3%-5%.

[0065] Preheating process: After drying, the green pellets enter the preheating zone. High-temperature exhaust gas (approximately 700-800℃) from the rotary kiln flows upward from the bottom of the preheating zone, exchanging heat with the green pellets in a counter-current manner. Under high temperature, the magnetite in the green pellets begins to oxidize, and the internal structure of the pellets gradually changes, increasing their strength. By precisely controlling the hot air temperature, air velocity, and green pellet residence time, the green pellets are fully preheated to the appropriate temperature for entering the rotary kiln for roasting, typically 800-850℃.

[0066] Functions and effects:

[0067] Improved thermal efficiency: Through waste heat recovery and hot air recycling, the thermal efficiency reaches about 70%, and the energy consumption per unit pellet is reduced to about 250 kcal / t, effectively reducing energy consumption.

[0068] Stable pellet quality: Due to the relatively uniform airflow distribution within the vertical preheater, the pellets are heated evenly during the preheating process, resulting in minimal residual moisture and preheating temperature deviation, thus ensuring high pellet quality stability. After calcination in the rotary kiln, the compressive strength of the pellets can reach over 3200 N / piece, the drum strength reaches 95%, and the wear index is controlled within 2.8%.

[0069] Compact equipment with a small footprint: The vertical preheater has a compact structure and can reduce the footprint by 30% to 50% compared to the chain grate machine 2, making it suitable for production enterprises with limited space.

[0070] Environmental compliance: A complete waste gas treatment system ensures that dust emission concentrations meet environmental protection requirements, while waste gas recycling reduces the total amount of waste gas emissions, achieving environmentally friendly production.

[0071] Easy to operate: The vertical preheater has a relatively simple equipment structure, a high degree of automation, and is relatively easy to operate and maintain, which reduces labor costs and labor intensity.

[0072] As can be seen from the two examples above, the rotary kiln iron ore oxide pellet drying and preheating device can achieve a highly efficient drying and preheating process under different structural forms, effectively improving pellet quality, reducing energy consumption and environmental emissions, and has significant economic and environmental benefits.

[0073] The above-disclosed embodiments are merely preferred embodiments of the present utility model and should not be construed as limiting the scope of the present utility model. Those skilled in the art can understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present utility model are still within the scope of the utility model.

Claims

1. A rotary kiln iron ore oxide pellet drying and preheating device, characterized in that, The system includes a chain grate machine. The feeding end of the chain grate machine is equipped with a roller feeder, which consists of multiple parallel rollers with specific textures or protrusions on their surfaces. The chain grate machine has a blower drying section, a forced-air drying section, a preheating section I, a preheating section II, a heat source inlet, and a waste gas outlet. The blower drying section is equipped with a blower end, the forced-air drying section is equipped with a forced-air fan end, and the discharge end of the chain grate machine is equipped with an auger conveyor. The conveying end of the auger conveyor is equipped with a dust removal structure, which is also connected to the forced-air drying section. The heat source inlet is divided into a rotary kiln, a secondary annular cooler, and a tertiary annular cooler. The rotary kiln is connected to the preheating section II via a pipeline, and the secondary annular cooler is connected to the preheating section I via a pipeline. Each pipeline is equipped with a regulating valve, a flow meter, and a temperature sensor.

2. The rotary kiln iron ore oxide pellet drying and preheating device as described in claim 1, characterized in that, The hot air inlet temperature of the blower drying section is 200-300℃, the wind speed is 1.0-1.5m / s, and the green pellet residence time is 3-5min.

3. The rotary kiln iron ore oxide pellet drying and preheating device as described in claim 2, characterized in that, The hot air inlet temperature of the exhaust drying section is 300-400℃, the exhaust velocity is 1.2-1.8m / s, and the green pellet residence time is 5-8min.

4. The rotary kiln iron ore oxide pellet drying and preheating device as described in claim 3, characterized in that, The hot air inlet temperature of the preheating section I is 400-600℃, the wind speed is 1.0-1.5m / s, and the green pellet residence time is 8-10min.

5. The rotary kiln iron ore oxide pellet drying and preheating device as described in claim 4, characterized in that, The hot air inlet temperature of the preheating section II is 800-1000℃, the wind speed is 0.8-1.2m / s, and the green pellet residence time is 10-12min.

6. The rotary kiln iron ore oxide pellet drying and preheating device as described in claim 5, characterized in that, The dust removal structure is a bag filter, and the bag filter is equipped with filter bags.

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