A two-phase fluidized roasting method

Abstract

The application provides a kind of double-phase fluidized roasting method, the roasting furnace body of the method is straight cylinder cavity, and the sealing cavity surrounded by the pouring dome and the heat preservation structure independently arranged in the furnace top;The feeding port and the discharge port of the roasting furnace are opened on the same side of the furnace body, and the feeding port is located above the discharge port;The feeding port is equipped with a drum thrower;The bottom of the roasting furnace is provided with a plurality of dispersedly arranged heat removal devices;The flue of the roasting furnace is provided with an air supplement device;During the dense-phase oxidation desulfurization process of raw materials, the heat removal device is uniformly heat-exchanged to stabilize the bed temperature, and the high-temperature steam discharged by the heat removal device is used as the medium for maintaining the constant temperature of the sealing cavity;The air supplement device is used to supplement oxygen-rich air into the flue to form a dilute-phase secondary roasting zone.The furnace top of the application uses a heat preservation structure independent of the dome, prolonging the service life of the furnace top;The feeding port is arranged above the discharge port on the same side, which hinders the dust particles in the upward flue gas, reducing the dust content of the flue gas.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metallurgical technology, specifically a two-phase fluidized bed roasting method. Background Technology

[0002] Fluidized bed roasting technology, based on the principle of gas-solid fluidization, can efficiently complete core reactions such as oxidative desulfurization and sulfation roasting of sulfide minerals under high-temperature conditions. It is a core pre-process in the hydrometallurgical processes of non-ferrous metals such as zinc, copper, and vanadium, and is also widely used in chemical, environmental protection, and other industries. With its advantages of high heat and mass transfer efficiency, fast reaction rate, large processing capacity, and high degree of automation, this technology has become the mainstream technical route for sulfide mineral roasting.

[0003] However, the fluidized bed roasting furnace used in the existing methods has always had defects such as high dust rate, high content of insoluble sulfur in the dust, easy cracking of the furnace top, and inability to handle high moisture materials.

[0004] The high dust rate is due to the fact that the existing furnace adopts a centralized heat dissipation method. This method is prone to causing local overheating (>1000℃) and material sintering in the central area of ​​the fluidized bed due to insufficient heat exchange. Therefore, in order to prevent the bed from getting out of control, the oxygen concentration of the fluidized bed is strictly limited to ≤25% during production operation. Excessive air has to be added to maintain the oxygen required for the oxidation reaction, resulting in a significant increase in the total amount of flue gas. The measured dust concentration in the flue gas is as high as 193.61 g / Nm³.

[0005] In response, some have adopted a variable cross-section structure for the furnace body, with a larger upper section and a smaller lower section, as shown in patent applications CN102382976A, CN107966024A, CN201514115U, and CN118936071A. These solutions all reduce the flue gas velocity by increasing the cross-sectional area of ​​the upper part of the furnace body, thereby promoting the settling of coarse dust particles in the enlarged section and reducing the dust concentration. However, this settling mechanism can only physically trap dust after it is generated; it does not reduce the total amount of dust at the source and can easily induce local accumulation, agglomeration, or even collapse of the furnace charge, posing a safety hazard.

[0006] In addition, some researchers have further increased the height of the furnace body to reduce the dust concentration by extending the residence time of the flue gas in the high-temperature reaction zone. However, this has led to a significant increase in the construction cost of the furnace body, and the thermal stability of the furnace body, which is wider at the top and narrower at the bottom, has become increasingly difficult to control.

[0007] The reason for the high insoluble sulfur content in the flue gas is that the flue gas volume is large and the flow rate is fast during roasting. The effective reaction time of the flue gas in the high-temperature zone is limited, and there is a lack of secondary oxidation conditions. As a result, the insoluble sulfur content in the collected flue gas is high, the flue gas quality is poor, and it affects the metal recovery rate and by-product value of subsequent leaching processes.

[0008] The reason why the furnace top is prone to cracking is that the existing furnace top adopts an integral cast refractory material structure. Its inner layer has a working temperature of ≥950℃, while the outer layer is at ambient temperature, with a temperature difference of more than 925℃ between the inside and outside. This can easily lead to cracking and failure of the furnace top during start-up and shutdown.

[0009] Therefore, in order to avoid the problem of furnace top cracking and failure, existing technology requires strict control of the temperature change rate during furnace start-up and shutdown, which leads to excessively long start-up time and affects work efficiency.

[0010] The reason why high-moisture materials cannot be handled is that the existing technology uses a belt-type feeder to supply materials to the furnace body, and high-moisture materials are prone to sticking to the bin walls and belts, making it difficult to discharge them. Summary of the Invention

[0011] The purpose of this invention is to provide a two-phase fluidized bed roasting method with low dust rate, low insoluble sulfur content in the dust, less cracking of the furnace top, and the ability to handle high-moisture materials.

[0012] The two-phase fluidized bed roasting method provided by this invention employs a two-phase fluidized bed roasting furnace. The furnace body is a cylindrical cavity, and the furnace top includes an independently installed cast dome and a sealed cavity enclosed by an insulation structure. The feed inlet and discharge outlet of the roasting furnace are located on the same side of the furnace body, with the feed inlet positioned above the discharge outlet. A roller feeder is installed at the feed inlet. A multi-layered, dispersed heat dissipation device is installed at the bottom of the roasting furnace. A make-up air device is installed in the flue of the roasting furnace.

[0013] The method includes the following steps:

[0014] S1. When the furnace is started, fluidizing air is introduced to construct the flow field inside the furnace, and pressurized steam is introduced into the insulation structure to keep the temperature of the sealed cavity at the top of the furnace constant, thereby reducing the temperature gradient between the inside and outside of the refractory material at the top of the furnace when the furnace is started.

[0015] S2. Raw materials are thrown into the furnace through the feed inlet, and fall to form a material curtain to intercept smoke and dust and preheat with the upward flue gas in a countercurrent flow.

[0016] S3. The raw material undergoes dense phase oxidation desulfurization in the fluidized bed, while the bed temperature is stabilized by uniform heat exchange through the heat dissipation device.

[0017] S4. The qualified calcined sand is continuously discharged through the discharge port;

[0018] S5. After the flue gas enters the flue, the air supply device supplies oxygen-rich air into the flue and simultaneously regulates the flue gas flow rate and residence time to form a secondary oxidation high-temperature zone to complete the dilute phase roasting.

[0019] S6. The flue gas that has completed the secondary reaction is discharged and transported to the subsequent process.

[0020] In one embodiment of the above-mentioned roasting method, the heat insulation structure adopts a high-temperature steam tube plate, including a steel plate and multiple pipes arranged at fixed intervals on its outer side, with pressurized steam inside the pipes; the cast dome is formed of refractory material.

[0021] In one embodiment of the above-mentioned roasting method, the flue includes a lower high-temperature zone and an upper medium-temperature zone. The wall of the lower high-temperature zone is integrally formed with the insulation structure. The wall of the upper medium-temperature zone is a two-phase flow film wall structure with a pressurized steam-water mixture inside. The walls of the lower high-temperature zone and the upper medium-temperature zone are sealed and connected by a steel plate, which is connected to the air supply device.

[0022] In one embodiment of the above-mentioned roasting method, the drum throwing machine includes a drum body and multiple shovel plates arranged circumferentially, with a throwing speed ≥25m / s.

[0023] In one embodiment of the above-mentioned roasting method, the heat exhaust device is composed of heat exhaust sleeves arranged in layers and staggered along the height direction of the fluidized bed in the furnace; the heat exhaust sleeves are a double-layer structure of a coaxially fitted water inlet pipe and a steam outlet pipe, and the high-temperature steam in the steam outlet pipe is introduced into the pipe of the high-temperature steam tube sheet; the heat exhaust sleeves are inclined at 5~10° through the roasting furnace, and the length of each heat exhaust sleeve extending into the furnace is 1 / 3~1 / 2 of the diameter of the fluidized bed, and the lower layer extends into the furnace longer than the upper layer.

[0024] In one embodiment of the above-described roasting method, the high-temperature steam discharged from the heat dissipation device serves as the medium for maintaining a constant temperature in the sealed cavity.

[0025] In one embodiment of the above-mentioned roasting method, the heat exhaust sleeve installation hole in the furnace body also serves as the interface for the furnace start-up device; multiple temperature detection components are arranged in layers along the height direction of the fluidized bed on the side wall of the furnace body; and multiple inspection doors are provided in the fluidized layer area of ​​the furnace body.

[0026] In one embodiment of the above-mentioned roasting method, the raw material particle size Dv(50) in step S2 is 14.8~20μm and the moisture content is 10%~15%.

[0027] In one embodiment of the above-mentioned roasting method, compressed air with an oxygen-enriched concentration of 25-30 vol% and a pressure of 15-25 kPa is added in step S5.

[0028] In one embodiment of the above-mentioned roasting method, the flue gas velocity in step S3 is controlled at 0.4~0.6m / s; the flue gas velocity in step S5 is controlled at 15~25m / s, the total residence time of the flue gas is 25~38s, and the outlet flue gas temperature is 700~800℃.

[0029] The beneficial effects of this invention are as follows:

[0030] This roasting method reduces the dust content by 50%, lowers the furnace height by 50%, and reduces start-up and shutdown time, saving significant construction and operating costs. Simultaneously, it reduces material agglomeration, enhances the ability to handle high-moisture materials, and improves material processing capacity, greatly increasing roasting efficiency. Specific details are as follows:

[0031] 1. To address the issue of high dust concentration, this method employs a multi-layered sleeve-type heat dissipation structure to disperse heat exchange within the fluidized bed. This multi-point, small-area dispersion method penetrates deep into the fluidized bed layer, replacing the traditional heat dissipation structure. This allows for timely and uniform removal of the heat from the oxidation reaction within the furnace, achieving uniform and stable fluidized bed temperature. Consequently, the fluidized bed can react at higher oxygen concentrations, significantly reducing the amount of excess air added to maintain oxygen levels. This reduces the total volume of flue gas exiting the furnace from the source, thereby significantly lowering the dust concentration.

[0032] Furthermore, since this invention solves the problem of high dust content, the roasting furnace can adopt a straight cylindrical furnace body, avoiding the safety problem of furnace charge agglomeration; at the same time, the roasting furnace can greatly reduce the furnace height and reduce construction costs.

[0033] 2. To address the issue of high insoluble sulfur content in flue gas, this method introduces oxygen-enriched compressed air into the flue, using the flue as a dilute phase roasting zone to form a stable secondary oxidation high-temperature zone within the flue. This allows for dilute phase secondary roasting of the flue gas entrained in the flue gas, significantly reducing the insoluble sulfur content in the flue gas and breaking the traditional limitation of flue gas being used only for exhaust.

[0034] 3. To address the issue of easy cracking of the furnace top, this method introduces pressurized steam into the sealed cavity of the furnace top during the furnace start-up stage. Combined with the independent insulation structure used for the furnace top, a sealed cavity with an external temperature of 250~350℃ is formed. This can control the temperature difference between the inside and outside of the cast dome during the furnace start-up process within a small range, avoiding furnace top cracking and failure. At the same time, it shortens the start-up and shutdown time, improves the continuous operation efficiency of the roasting furnace, and reduces operating costs.

[0035] 4. To address the problem of handling high-moisture materials, this method employs a roller feeder to project the raw materials into the furnace, solving the problem of difficult material feeding. Furthermore, due to the increased projection speed of the feeder, this invention further positions the feed inlet of the roasting furnace above the discharge outlet on the same side. The raw materials falling into the furnace can form a stable physical curtain, directly hindering the dust particles entrained in the upward flue gas of the fluidized bed, thus further reducing the dust content of the flue gas exiting the furnace. At the same time, the upward high-temperature flue gas can fully preheat the raw materials entering the furnace, improving the reaction efficiency of the raw materials after entering the furnace and increasing the material processing capacity per unit area of ​​the dense phase fluidized bed. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the two-phase fluidized bed roasting furnace used in an embodiment of the method of the present invention. (High-temperature steam pipes are not shown.)

[0037] Figure 2 for Figure 1 The diagram shows the structure of the high-temperature steam tube sheet in the lower high-temperature zone of the roasting furnace.

[0038] Figure 3 for Figure 1 The diagram shows the structure of the steam-water two-phase flow film wall in the upper medium-temperature zone of the roasting furnace.

[0039] The attached figures are labeled as follows:

[0040] Furnace body - 1; Gas distribution plate - 11; Furnace top - 2; Cast dome - 21; Insulation structure - 22; Flue - 3; Lower high temperature zone - 31; Upper medium temperature zone - 32; Flue outlet - 33; Elastic support structure - 34; Sealing steel plate - 35; Air supply device - 36; Discharge port - 4; Feed port - 5; Drum discharger - 6; Wind box - 7; Heat exhaust device - 8; Water inlet pipe - 81; Steam outlet pipe - 82. Detailed Implementation

[0041] The relevant technical solutions will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention. The described embodiments are only a part of the embodiments, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] like Figure 1 As shown, the two-phase fluidized bed calcination method disclosed in this embodiment employs, as follows: Figure 1 The two-phase fluidized bed roasting furnace shown includes a furnace body 1, a furnace top 2, a flue 3, a discharge port 4, a feed port 5, a drum feeder 6, a wind box 7, and a heat dissipation device 8.

[0043] The furnace body 1 is a vertically arranged cylindrical cavity structure, which is the core body of the roasting reaction. The bottom of the furnace body 1 is fixedly and sealed to the wind box 7. The top of the furnace body is a refractory and heat-insulating furnace roof 2. The flue 3 is fixedly installed at the center of the furnace roof. The discharge port 4 and the feed port 5 are opened on the same side wall of the furnace body. The roller feeder 6 is assembled correspondingly to the feed port. The heat exhaust device 8 passes through the side wall of the furnace body and extends into the fluidized layer area inside the furnace body.

[0044] The furnace top 2 includes a cast-in-place dome 21 and an insulation structure 22.

[0045] The dome 21 is cast using heavy refractory material. The thickness of the dome is greater than or equal to 350 mm. The bulk density of the refractory material is greater than or equal to 2.8 g / cm³, the linear shrinkage rate is 0 to -0.2%, and the refractory temperature is greater than or equal to 1600℃.

[0046] likeFigure 2 As shown, the insulation structure 22 is a high-temperature steam tube sheet, comprising a steel plate and multiple pipes arranged at fixed intervals on its outer side. The pipes contain pressurized steam at a temperature above 250°C. This structure ensures that the steel plate preferentially contacts the high-temperature zone, thus protecting the pipes behind it.

[0047] The insulation structure 22 is set outside the cast dome 21 with the steel plate facing the cast dome. The insulation structure and the cast dome are set independently of each other, with a gap of 150mm to 500mm reserved between them to form a sealed cavity with a stable temperature of 250 to 350℃.

[0048] The center of the cast dome 21 is connected to the flue 3, the flue inlet extends vertically upward, and the height of the furnace body 1 is equal to the overall height of the flue 3.

[0049] The furnace top of the present invention adopts an independent cast dome and insulation structure, which form a temperature-stable sealed cavity. During the start-up and shutdown process, the temperature difference between the inside and outside of the cast dome can be controlled within a small range, avoiding the problem of internal local crushing and external cracking of refractory materials due to excessive temperature gradient in the thickness direction and inconsistent expansion. At the same time, it shortens the start-up and shutdown time and improves the efficiency of long-term continuous operation of the roasting furnace.

[0050] The flue 3 includes a lower high-temperature zone 31, an upper medium-temperature zone 32, a flue outlet 33, an elastic support structure 34, a sealing steel plate 35, and a make-up air device 36.

[0051] The lower high-temperature zone 31 is a tube sheet structure integrally formed with the insulation structure 22. The flue gas temperature inside is greater than 900℃, ensuring the consistency of thermal expansion and contraction of the cast dome 21 and the flue 3. The elastic support structure 34 is installed on the outside of the lower high-temperature zone. The elastic support structure is fixedly installed on the floor corresponding to the flue to bear the overall load of the flue and avoid excessive pressure on the furnace top 2.

[0052] The upper intermediate temperature zone 32 has an approximately inverted U-shaped structure. One side of it is connected to the lower high temperature zone 31 and sealed by a sealing steel plate 35. The other side serves as a large-space dilute phase secondary roasting unit, with a flue outlet 33 at the end. The flue gas temperature in the upper intermediate temperature zone is greater than 800℃.

[0053] like Figure 3 As shown, the upper medium-temperature zone 32 adopts a two-phase flow film wall structure, including multiple pipes arranged at fixed intervals and steel plates welded and fixed between these pipes. The pipes contain a pressurized steam-water mixture at a temperature above 250°C, with a pressure greater than 4.0 MPa. Using a two-phase flow film wall for wall heat exchange has the advantages of uniform temperature, low thermal stress, and high heat exchange efficiency. It facilitates the timely removal of heat from the secondary roasting of the dilute phase, avoids the softening and adhesion of materials to the wall surface to form nodules, reduces the flue gas flow area, and prevents disruption of the secondary roasting of the dilute phase.

[0054] A sealing steel plate 35 is installed at the connection between the lower high-temperature zone 31 and the upper medium-temperature zone 32. The thickness of the sealing steel plate is 2mm. Multiple air supply holes are opened on the sealing steel plate along the circumference of the flue.

[0055] An air supply device 36 is installed outside the air supply port to supply oxygen-enriched compressed air into the flue. Through secondary oxygen supply, sulfides in the flue dust are oxidized, the high-temperature zone is extended, and the insoluble sulfur in the flue dust is further reduced.

[0056] In this embodiment, the diameter of the air supply hole is 10~20mm, and the spacing between adjacent air supply holes is 100~500mm; the oxygen-enriched compressed air supplied to the air supply device has a pressure of 15~25kPa, an oxygen concentration of 25~30vol%, and a flow rate of 10~15m / s; the flue gas flow rate in the flue is 15~25m / s, the outlet flue gas temperature is 700~800℃, and the total residence time of the flue gas in the furnace body and flue is controlled to be 25~38s.

[0057] The flue of this invention serves as a dilute-phase secondary roasting unit. Oxygen-rich compressed air is introduced through the air supply holes of the sealed steel plate, which can form a stable secondary oxidation high-temperature zone in the flue. This allows for dilute-phase secondary roasting of the dust entrained in the flue gas, significantly reducing the content of insoluble and fusible sulfur in the dust. This breaks the functional limitation of traditional flues that are only used for exhausting smoke. In addition, with the structural design of the flue, the overall height of the furnace can be significantly reduced while ensuring the roasting effect.

[0058] The discharge port 4 is located on the side wall of the furnace body 1. The height of the discharge port on the side wall is 1500mm~2700mm, and it is used to discharge the roasted sand material that has completed dense phase roasting.

[0059] The feed inlet 5 is located on the side wall of the furnace body 1. The feed inlet and the discharge port 4 are located on the same side of the furnace body 1, and the feed inlet is located above the discharge port, so that the falling path of the raw material entering the furnace and the upward path of the flue gas in the fluidized layer form a countercurrent.

[0060] This invention arranges the feed inlet and discharge outlet on the same side, with the feed inlet located above the discharge outlet. Combined with the high-speed throwing of the roller feeder, the raw materials falling into the furnace can form a stable physical material curtain, directly hindering the dust particles entrained in the flue gas rising in the fluidized bed, significantly reducing the dust content of the flue gas exiting the furnace, and reducing the operating load and blockage risk of subsequent processes. At the same time, the rising high-temperature flue gas can fully preheat the raw materials entering the furnace in a countercurrent manner, improving the reaction efficiency of the raw materials after entering the furnace and increasing the material handling capacity per unit area of ​​the dense phase fluidized bed.

[0061] The roller feeder 6 is installed on the outside of the feed inlet 5, and two roller feeders are provided. Each roller feeder includes a roller body and scraper plates. The diameter of the roller body is 700mm, and there are 5 to 10 scraper plates, which are evenly arranged around the circumference of the roller body.

[0062] In this embodiment, the working speed of the drum feeder 6 is 700-1000 r / min, which can feed raw materials with particle size Dv(50)=14.8~20μm and moisture content of 10%~15% into the furnace body 1 through the feed inlet 5 at a throwing speed of not less than 25m / s.

[0063] A gas distribution plate 11 is provided at the bottom of the furnace body 1. The furnace body is connected to the air box 7 below through the gas distribution plate. The air box is used to introduce fluidizing air into the furnace body, so that the material in the furnace body forms a fluidized bed. The flue gas velocity in the fluidized bed is controlled at 0.4~0.6m / s.

[0064] The heat exhaust device 8 adopts a multi-layer heat exhaust structure composed of heat exhaust sleeves. The heat exhaust structure has at least 2 layers, and multiple heat exhaust sleeves in each layer are distributed along the circumference of the furnace body. At the same time, the multi-layer heat exhaust structure is arranged from bottom to top along the height direction of the fluidized bed in the furnace body, and the heat exhaust sleeves of adjacent layers are staggered.

[0065] The single heat dissipation jacket has a double-layer structure, including a coaxially fitted water inlet pipe 81 and a steam outlet pipe 82. Water flows into the water inlet pipe, absorbs heat and vaporizes, forming a steam-water mixture, which is then discharged from the outlet at the top of the steam outlet pipe. The diameter of the steam outlet pipe is Φ219mm, and the diameter of the water inlet pipe is Φ108mm.

[0066] The high-temperature steam discharged from the steam outlet pipe in the heat exhaust jacket is connected to the pipe of the high-temperature steam tube sheet of the insulation structure 22 through the pipeline. It serves as a medium to maintain a constant temperature in the sealed cavity, realizing the synchronous control of the fluidization process and heat supply. This is beneficial to the thermal stability of the furnace dome structure and the reaction temperature requirements of the dilute phase secondary roasting, thereby improving the overall thermal energy utilization efficiency of the system.

[0067] The heat exhaust sleeve is inclined downward through the side wall of the furnace body 1. The inclination angle of the heat exhaust sleeve is 5~10°. The distance between the bottom heat exhaust sleeve and the bottom of the furnace body is greater than 210mm.

[0068] The length of each heat exhaust sleeve extending into the furnace body 1 is 1 / 3 to 1 / 2 of the fluidized bed diameter, and the length of the lower heat exhaust sleeve extending into the furnace body is greater than the length of the upper heat exhaust sleeve extending into the furnace body.

[0069] The heat dissipation device of this invention adopts a multi-layered staggered sleeve-type heat dissipation structure. It replaces the traditional large-area centralized heat exchange structure by dispersing heat into the fluidized bed layer at multiple points and small areas. This can remove the heat generated by the sulfur oxidation reaction in the furnace in a timely and uniform manner, and achieve uniform and stable control of the fluidized bed temperature field. Therefore, the fluidized bed can react at a higher oxygen concentration, which significantly reduces the dust rate. In addition, it can avoid the problems of material softening and agglomeration sintering into the fluidized bed and reaction runaway caused by local overheating. At the same time, it can increase the effective volume of materials in the furnace, providing a basis for improving the processing capacity of the roasting furnace.

[0070] The furnace body 1 has openings in the furnace wall for passing through the heat exhaust sleeve. The openings in the furnace wall also serve as the installation interface for the furnace start-up device, so that the furnace start-up device and the heat exhaust device 8 can share the openings in the furnace wall, disperse the furnace start-up heating points, reduce the number of openings in the furnace body, and improve the furnace start-up heating rate and the structural stability of the furnace body.

[0071] Temperature detection components are arranged in layers from bottom to top along the height of the fluidized bed on the side wall of the furnace body 1. There are 3 to 4 layers of temperature detection components, with no less than 2 components in each layer, and a total of 5 to 30 components, which are used to monitor the reaction temperature at different heights of the fluidized bed in real time.

[0072] Inspection doors are also provided on the side wall of the furnace body 1 corresponding to the fluidized bed area. The number of inspection doors is 1 to 5, which are used by operators to inspect and maintain the fluidized bed area inside the furnace.

[0073] The furnace opening device and the heat dissipation device of this invention share the furnace wall opening, which reduces the number of openings in the furnace body, realizes decentralized furnace opening and heating, further improves the structural stability of the furnace body and shortens the furnace opening time. With the layered arrangement of temperature detection components, the reaction temperature inside the furnace can be monitored in real time, ensuring the stability and controllability of the roasting process.

[0074] The two-phase fluidized bed roasting method of the present invention is implemented using the above-mentioned roasting furnace, and the specific steps are as follows:

[0075] 1. When starting the furnace, start the wind box to introduce fluidizing air to build the flow field inside the furnace. At the same time, start the heat exchange cycle and introduce pressurized steam into the furnace top and flue to keep the furnace top sealed cavity at a constant temperature of 250~350℃, and complete the furnace body heating and operation self-check.

[0076] 2. Raw materials with particle size Dv(50) = 14.8~20μm and moisture content of 10%~15% are thrown into the furnace through the high-level feed port on the same side by a drum feeder at a speed of 700~1000r / min and a speed of ≥25m / s. The falling raw materials form a material curtain, which intercepts the smoke and dust and preheats it in the countercurrent with the rising high-temperature flue gas.

[0077] 3. The raw materials fall into the fluidized bed to form a fluidized bed layer to complete the oxidation and desulfurization reaction. The heat exchange is dispersed at multiple points through the heat dissipation device to stabilize the bed temperature and avoid the soft melting and agglomeration of low melting point materials.

[0078] 4. The qualified calcined sand is continuously discharged through the high-level discharge port on the side wall; the feed and discharge rates are matched to stabilize the bed height, ensuring that the insoluble sulfur in the calcined sand is ≤0.15wt%.

[0079] 5. When the flue gas enters the intermediate temperature zone of the flue, 25-30 vol% oxygen-enriched compressed air is introduced through the air supply device to form a secondary oxidation high-temperature zone; at this time, the flue gas velocity is 15-25 m / s, and the sulfur in the flue dust is removed through secondary oxidation roasting, controlling the insoluble sulfur in the flue dust to ≤0.3 wt%;

[0080] 6. The total residence time of flue gas in the furnace body and flue is controlled to be 25~38s. After secondary reaction, the flue gas is discharged and transported to subsequent processes for treatment.

[0081] The following sections will use multiple scenarios and comparative examples to illustrate in detail the specific application methods and technical advantages of the roasting furnace used in the method of this invention compared with traditional roasting furnaces.

[0082] In embodiments of the present invention, the formulas for calculating annual material processing volume, economic benefits, and furnace start-up costs are as follows:

[0083] Annual material processing volume = area × material processing capacity × number of operating days per year (based on 330 days);

[0084] Economic benefit = (Unit product selling price - Unit product processing cost) × Annual material processing volume × Product conversion factor; where the unit product selling price is 133.21 million yuan, the unit product processing cost is 120.91 million yuan, and the product conversion factor is 0.5;

[0085] Boiler start-up cost = Diesel fuel consumption × Diesel fuel price;

[0086] Scenario 1: Table 1 below compares the overall situation of the embodiments of the present invention and the traditional method;

[0087] Table 1. Comparison of indicators between the method of the present invention and the traditional roasting method.

[0088] Comparison results:

[0089] Traditional roasting methods employ centralized heat dissipation, which requires strict control of oxygen concentration (≤25%), necessitating the addition of large amounts of air to maintain the reaction. Measured dust concentration in flue gas reached as high as 193.61 g / Nm³.

[0090] Meanwhile, in order to reduce the dust rate, traditional furnace types are forced to adopt variable cross-sections that are larger at the top and smaller at the bottom or increase the height of the furnace body. This not only requires a large construction investment of 32 million yuan, but also easily causes safety hazards such as local accumulation and agglomeration of furnace materials.

[0091] The dust content in the flue gas of this invention is reduced to 98.5-105 g / Nm³, which is nearly 50% lower than that of traditional furnaces. Furthermore, due to the solution of the dust rate problem, the height of the furnace body of this invention is sharply reduced from the traditional 30.67m to 15.4m, a reduction of nearly 50%, and the total weight of the furnace body is reduced from 1560 tons to 935 tons, saving 7.5 million yuan in construction investment.

[0092] Secondly, the invention shortens the furnace start-up time from the conventional 8 hours to 5 hours, reduces the diesel consumption for start-up to 9 tons, and reduces the cost of a single start-up from 100,000 yuan to 62,100 yuan. This not only improves the efficiency of long-term continuous operation of the roasting furnace, but also significantly reduces operating costs.

[0093] Finally, thanks to the enhanced efficiency of countercurrent preheating, the material handling capacity per unit area of ​​the fluidized bed has been significantly increased from the traditional 7-8 t / d·m² to 12-14.5 t / d·m², an increase of about 70%-80%; the annual material handling capacity has increased from 270,000 t / a to 430,000-520,000 t / a; and with the same area of ​​109 m², the annual economic benefits have jumped from 153 million yuan to 243-294 million yuan, an increase of over 60%.

[0094] In summary, the improvements of this invention can achieve the effect of reducing costs and increasing efficiency.

[0095] Scenario 2: The impact of different working conditions on the processing of high-moisture fine materials by the method of the present invention;

[0096] Table 2 below shows the data for processing materials with different moisture contents and particle sizes using the roasting furnace employed in this invention:

[0097] Table 2. Operational data of the method of the present invention under different material parameters.

[0098] The results show that the calcining furnace used in the method of the present invention can successfully process materials with a moisture content of 10%~15% and a particle size Dv(50) = 14.8~20μm, while the insoluble sulfur content of the calcined slag is less than 0.15 wt%, the insoluble sulfur content of the calcined dust is less than 0.3 wt%, and the dust content in the flue gas is less than 105 g / Nm³. 3 .

[0099] Comparative Examples 1-4

[0100] Materials 1-4 were treated using the same method as in Example 1, except that the feeding speed was 24 m / s. The results showed that the material fell towards the discharge port in the furnace, and the high-moisture material had poor fluidization characteristics, resulting in insufficient dense-phase roasting time and insoluble sulfur content greater than 0.5 wt% in the roasted slag.

[0101] Comparative Examples 5-8

[0102] Materials 1-4 were processed using the same method as in the examples, except that raw materials with a moisture content of 16% and a particle size Dv(50) = 21 μm were used. The results showed that the high-moisture materials adhered in the silo, resulting in discontinuous and unstable feeding, which caused the roller feeder's shovel plate to spin idly or be suddenly crushed by the material, leading to motor burnout.

[0103] Comparative Examples 9-12

[0104] Materials 1-4 were treated using the same method as in the examples, except that the flow velocity in the flue was 14 m / s and the oxygen concentration of the oxygen-enriched compressed air was less than 25 vol%. The results showed that the flue gas turbulence was low, the dilute phase roasting effect was not obvious, and the insoluble sulfur in the flue dust was greater than 1%.

[0105] Comparative Examples 13-16

[0106] Materials 1-4 were treated using the same method as in the examples, except that the flow velocity in the flue was 26 m / s and the oxygen concentration of the oxygen-enriched compressed air was less than 25 vol%. The results showed that the temperature of the dilute phase roasting flue gas in the flue gas rapidly decreased to 700°C, the flue gas residence time was short, and the insoluble sulfur in the flue dust was greater than 1.2 wt%.

[0107] Comparative Examples 17-20

[0108] Materials 1-4 were treated using the same method as in the examples, except that the flow velocity in the flue was 15-25 m / s and the oxygen concentration of the oxygen-enriched compressed air was greater than 30 vol%. The results showed that the insoluble sulfur in the flue dust was 0.29 wt%, the oxygen enrichment effect was not obvious, and the production cost was increased.

[0109] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A two-phase fluidized bed calcination method, characterized in that, A two-phase fluidized bed roasting furnace is adopted. The furnace body is a straight cylindrical cavity, and the furnace top includes an independently set cast dome and a sealed cavity surrounded by an insulation structure. The feed inlet and discharge outlet of the roasting furnace are located on the same side of the furnace body, with the feed inlet above the discharge outlet; a roller feeder is installed at the feed inlet. The bottom of the roasting furnace is equipped with a multi-layered, dispersed heat dissipation device. The flue of the roasting furnace is equipped with a make-up air device; The method includes the following steps: S1. When the furnace is started, fluidizing air is introduced to construct the flow field inside the furnace, and pressurized steam is introduced into the insulation structure to keep the temperature of the sealed cavity at the top of the furnace constant, thereby reducing the temperature gradient between the inside and outside of the refractory material at the top of the furnace when the furnace is started. S2. Raw materials are thrown into the furnace through the feed inlet, and fall to form a material curtain to intercept smoke and dust and preheat with the upward flue gas in a countercurrent flow. S3. The raw material undergoes dense phase oxidation desulfurization in the fluidized bed, while the bed temperature is stabilized by uniform heat exchange through the heat dissipation device. S4. The qualified calcined sand is continuously discharged through the discharge port; S5. After the flue gas enters the flue, the air supply device supplies oxygen-rich air into the flue and simultaneously regulates the flue gas flow rate and residence time to form a secondary oxidation high-temperature zone to complete the dilute phase roasting. S6. The flue gas that has completed the secondary reaction is discharged and transported to the subsequent process.

2. The two-phase fluidized bed calcination method as described in claim 1, characterized in that: The insulation structure uses a high-temperature steam tube plate, which includes a steel plate and multiple pipes arranged at fixed intervals on its outer side, with pressurized steam inside the pipes; the cast dome is formed using refractory materials.

3. The two-phase fluidized bed calcination method as described in claim 1, characterized in that: The flue includes a lower high-temperature zone and an upper medium-temperature zone. The wall of the lower high-temperature zone is integrally formed with the insulation structure. The wall of the upper medium-temperature zone is a two-phase flow film wall structure with a pressurized steam-water mixture inside. The walls of the lower high-temperature zone and the upper medium-temperature zone are sealed together by a steel plate, which is connected to the air supply device.

4. The two-phase fluidized bed calcination method as described in claim 1, characterized in that: The roller feeder includes a roller body and multiple shovel plates arranged circumferentially, with a feeding speed ≥25m / s.

5. The two-phase fluidized bed calcination method as described in claim 2, characterized in that: The heat exhaust device is composed of heat exhaust sleeves arranged in staggered layers along the height direction of the fluidized bed inside the furnace. The heat exhaust sleeve is a double-layer structure consisting of a coaxially mounted water inlet pipe and a steam outlet pipe. The high-temperature steam in the steam outlet pipe is introduced into the pipe of the high-temperature steam tube sheet. The heat exhaust sleeve is inclined at 5~10° through the roasting furnace. The length of each heat exhaust sleeve extending into the furnace is 1 / 3 to 1 / 2 of the diameter of the fluidized bed, and the lower layer extends longer than the upper layer.

6. The two-phase fluidized bed calcination method as described in claim 5, characterized in that: The high-temperature steam discharged from the heat dissipation device serves as the medium for maintaining a constant temperature in the sealed cavity.

7. The two-phase fluidized bed calcination method as described in claim 5, characterized in that: The heat exhaust sleeve installation hole in the furnace body also serves as the interface for the furnace start-up device; multiple temperature detection components are arranged in layers along the height of the fluidized bed on the side wall of the furnace body; multiple inspection doors are set in the fluidized bed area of ​​the furnace body.

8. The two-phase fluidized bed calcination method as described in claim 1, characterized in that: In step S2, the raw material particle size Dv(50) is 14.8~20μm and the moisture content is 10%~15%.

9. The two-phase fluidized bed calcination method as described in claim 1, characterized in that: In step S5, compressed air with an oxygen concentration of 25-30 vol% and a pressure of 15-25 kPa is added.

10. The two-phase fluidized bed calcination method as described in claim 1, characterized in that: In step S3, the flue gas velocity is controlled at 0.4~0.6m / s, in step S5 the flue gas velocity is controlled at 15~25m / s, the total residence time of the flue gas is 25~38s, and the outlet flue gas temperature is 700~800℃.

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