A fluidized bed granulation drying method

Abstract

The present invention relates to the technical field of fluidized bed granulation, and specifically to a fluidized bed granulation drying method, which is carried out by a fluidized bed granulation dryer. The fluidized bed granulation dryer includes a bed, a spray gun and a spray gun driving mechanism. During the granulation drying process, the spray gun is driven to move by the spray gun driving mechanism, so as to form a continuous and periodic circulating atomized droplet receiving area in the top material layer area of ​​the fluidized bed layer. The present invention realizes periodic and intermittent liquid receiving of materials in the granulation area covered by the atomization area of ​​each spray gun by continuously and periodically moving the atomized droplet receiving area, which can effectively solve the contradiction that the drying rate of biomass materials that are difficult to dry is lower than the granulation rate, thereby preventing the formation of coarse particles or agglomerates due to excessively high material humidity in the granulation area and excessively long material viscosity.

Description

Technical Field

[0001] The invention relates to the technical field of fluidized bed granulation and drying, and in particular to a fluidized bed granulation and drying method. Background Art

[0002] Fluidized bed spray granulation and drying technology is a technology that directly sprays, granulates and dries liquid materials in a fluidized bed to obtain granular products. Its working principle is that in a fluidized bed, one or more spray guns (atomizers) atomize the liquid material into tiny droplets, and spray them onto the surface of a large number of particles in the bed of granular materials in a fluidized state to complete the granulation and drying process. The so-called granulation zone is formed in the area where the droplet atomization zone and the fluidized bed meet, and the granulation and drying processes are carried out at the same time. There are two main granulation mechanisms in the granulation zone. One is that the droplets adhere multiple particles together in a "liquid bridge" manner, thereby growing in a way that the particles continue to agglomerate; the other is that the droplets adhere to the surface of a single particle to form a local or continuous liquid film, thereby growing in a way that the particle surface is continuously coated. The high-temperature gas fluidizes the particles while also providing all or part of the heat, evaporating and taking away the water in the liquid bridge or liquid film. The liquid film or liquid bridge is continuously reduced during the drying process and eventually loses its adhesive properties. The corresponding granulation process is continuously weakened and eventually stops, while the solid components in the liquid film or liquid bridge are eventually solidified as part of the particles. The above-mentioned granulation and drying process achieved by particle agglomeration or coating is continuously carried out in the fluidized bed, and finally a particle product with a certain size and properties is obtained. The continuous fluidized bed granulation dryer commonly used in industrial production is divided into various forms such as side spraying, top spraying or bottom spraying according to the position of the spray gun.

[0003] The specific implementation form of the top-down spray fluidized bed granulation dryer can be found in the fluidized bed disclosed in CN102744010B. The bed body of the fluidized bed is composed of a shell, and the shell is provided with a wind distribution chamber area, a wind distribution mesh plate, a fluidizing chamber area, and a separation chamber area from bottom to top. The top of the bed body is provided with a nozzle and an exhaust port, etc. The spray gun is arranged on the upper part of the fluidized bed and is higher than the fluidized bed layer. After the liquid is atomized, it is sprayed from top to bottom onto the upper surface of the bed layer and penetrates a certain thickness of the bed layer, thereby forming a granulation zone in the local material layer where the spray gun atomization zone contacts the fluidized material layer and completing the granulation process. The area outside the granulation zone is the drying zone, and the material is further dried in the drying zone, and finally circulated to the granulation zone to enter the next granulation process. In order to improve the heating capacity, a built-in heat exchanger can be arranged in the drying zone. According to the different production capacity of the device and the atomization capacity of the spray gun, a single-rod or multi-rod spray gun can be set, and the multi-rod spray guns are spaced a certain distance apart to avoid excessive humidity in the granulation area and untimely drying, which may cause the particles to grow into coarse particles or even agglomerate.

[0004] For many biomass materials that are difficult to dry, especially fermentation broth in the fermentation industry, waste liquid after extraction and other materials, they contain a variety of organic and inorganic components. These materials have a slow drying rate and strong viscosity (or hot viscosity), which have an adverse effect on the granulation drying process. A notable feature of this type of material during the drying process is that the rate at which moisture migrates from the inside of the droplet or wet material to the outer surface is much lower than the rate at which moisture evaporates from the outer surface to the surrounding gas environment. Therefore, its drying process is mainly controlled by the migration process of internal moisture, and it takes a long time to complete the drying. It is a typical difficult-to-dry material. During the granulation process, due to the slow drying rate of the material, the material will remain in a strong wet and sticky state for a long time, which will cause the granulation process to continue continuously. When the granulation time is too long, a large number of particles will grow to a level beyond the process requirements. When the existing top-down spray fluidized bed granulation dryer is applied to such difficult-to-dry materials, the atomization area formed by the spray gun is fixed. When the continuous migration and renewal of the material in the granulation area are insufficient, the particles in the granulation area will be continuously sprayed with droplets, and the moisture will be continuously superimposed and increased, resulting in a large number of oversized particles or agglomerates that exceed the design range, causing the fluidization in the local area to deteriorate or even dead bed, forcing production to stop. For some hot and viscous biomass materials, such as sugars or materials containing sugar components, as the temperature rises, the viscosity of the liquid, wet materials and even the dry particles themselves will increase accordingly. During the drying process, the material temperature will inevitably increase. The superposition of the two characteristics of such difficult-to-dry materials is more likely to cause the particles to grow too fast, resulting in problems such as coarse particles or agglomerates.

[0005] To solve this problem, the existing technology adopts the following methods: reducing the spray volume of a single-rod spray gun and arranging more spray guns to meet the production capacity requirements; or taking measures such as increasing the fluidization speed and designing the flow field of the bed to strengthen the renewal of particles; or reducing the air inlet temperature and reducing the single-gun spray volume to maintain the stability of granulation by reducing production capacity. These methods bring about problems such as increased equipment investment and high production costs. Summary of the invention

[0006] The object of the present invention is to provide a fluidized bed granulation drying method, which can effectively solve the contradiction that the drying rate of difficult-to-dry biomass materials is lower than the granulation rate by continuously and periodically moving the atomized liquid droplet receiving area, so as to prevent the formation of coarse particles or agglomerates due to excessively high material humidity in the granulation area and prolonged material viscosity.

[0007] An embodiment of the present invention provides a fluidized bed granulation drying method, which is carried out using a fluidized bed granulation dryer. The fluidized bed granulation dryer includes a bed body, a spray gun and a spray gun driving mechanism. The bed body is provided with an air inlet chamber, a fluidizing chamber and a sedimentation chamber in sequence from bottom to top, and an air distribution plate is provided between the air inlet chamber and the fluidizing chamber. The fluidized granular material located in the fluidizing chamber constitutes a fluidized bed layer, and the upper interface of the fluidized bed layer is located in the fluidizing chamber. The spray gun is hinged to the top of the bed body, and the nozzle of the spray gun is located above the upper surface of the fluidized bed layer. During the granulation drying process, the spray gun is driven to move by the spray gun driving mechanism, thereby forming a continuous, periodic, cyclically moving atomized droplet receiving area in the top material layer area of ​​the fluidized bed layer.

[0008] After the liquid is atomized into fine droplets by the spray gun, it falls downward to form an approximately conical atomization zone, covering the fluidized bed layer below it. The droplets fall onto the upper surface of the fluidized bed layer and penetrate into the fluidized bed layer of a certain thickness, thereby forming a granulation zone in the material layer in contact with the droplets and the area with high humidity around it. During the granulation and drying process, the spray gun is driven to move by the spray gun driving mechanism, thereby forming a continuous and periodic circulating atomized droplet receiving zone in the corresponding granulation zone. For a specific local area of ​​the entire fluidized bed area covered by the atomized droplet receiving zone, in each movement cycle of the atomized droplet receiving zone, the local area can be divided into two stages: passing through the atomized droplet receiving zone and not passing through the atomized droplet receiving zone. When passing through the atomized droplet receiving zone, the bed material in the local area receives the droplets and starts the granulation and drying process; when the atomized droplet receiving zone leaves, the liquid receiving process of the bed in the local area is terminated. During the period of stopping the liquid receiving, the hot air continuously enters the local area, and the wet material in the local area is violently mixed with the dry material in the surrounding area, so that the drying process continues, the material humidity continues to decrease, and the granulation process is rapidly weakened. When the moisture content of the material in the local area drops to a certain level, the viscosity of the material is also weakened to the point where it is not enough for granulation. At this time, the granulation process ends, while the drying process is still in progress until the dynamic equilibrium moisture of the material is reached. Under the same operating conditions, for materials with different granulation and drying characteristics, by adjusting the size, movement cycle, trajectory, movement speed and other parameters of the granulation area covered by the atomized droplet receiving area, the entire granulation and drying process can be completed before the atomized droplet receiving area passes through the local area next time, and then enter the next cycle.

[0009] By means of the above technical scheme, the technical scheme provided by the present invention has at least the following advantages: (1) The present invention realizes periodic and intermittent liquid receiving of materials in the granulation area covered by the atomization area of ​​each spray gun by continuously and periodically moving the atomized droplet receiving area, which can effectively solve the contradiction that the drying rate of biomass materials that are difficult to dry, sticky or hot-sticky is lower than the granulation rate, so that the granulation-drying process can be carried out stably, thereby preventing the formation of coarse particles or agglomerates due to excessive humidity of the material in the granulation area and prolonged stickiness of the material. (2) The area of ​​the granulation area that can be covered by a single gun atomization is expanded, which can reach several times the coverage area of ​​the existing fixed-type distribution gun, thereby significantly reducing the number of spray guns arranged and reducing the investment cost of the spray guns and the associated pipelines and control systems. (3) Compared with the multiple fixed granulation and drying zones formed when the spray gun is fixedly arranged, the granulation and drying zone formed when the spray gun of the present invention is working can cover multiple fixed granulation and drying zones and the gap area outside the granulation and drying zone. Therefore, the mobile atomized droplet receiving zone of the present invention can cover a larger range of bed area than the atomization method of the fixed arrangement of the spray gun. For a specific material, when the fluidization wind speed and inlet air temperature of the granulation bed are constant, the granulation and drying intensity per unit area of ​​the bed is a relatively stable value. Increasing the available bed area increases the equipment capacity; when the equipment capacity remains unchanged, increasing the available bed area is equivalent to reducing the granulation and drying intensity per unit area, thereby increasing the equipment operation stability.

[0010] As a preferred embodiment of the present invention, the spray gun is installed on the top of the bed through a ball hinge; the spray gun driving mechanism includes a vertical driving device, a motor and a connecting rod, the vertical driving device is used to drive the motor to move vertically, the axis of the output shaft of the motor is in a vertical direction and passes through the center of the ball hinge, and the two ends of the connecting rod are respectively pivoted to the output shaft of the motor and the spray gun; during the granulation and drying process, the spray gun is driven by the spray gun driving mechanism to rotate and / or swing periodically, so that the atomized droplet receiving area continuously and periodically moves in a closed shape trajectory.

[0011] Furthermore, within one of the cycles, the area covered by the atomized droplet receiving zone is in the shape of a ring. Since the inner ring area within the inner boundary of the ring does not receive droplet spraying, the shape of each horizontal section of the formed granulation zone is also a corresponding ring. Since the material particles constituting the fluidized bed layer are constantly undergoing violent back mixing in the vertical and horizontal directions, the annular boundary is dynamically changing. The dry particles in the outer ring area and the inner ring area of ​​the ring pass through the annular boundary and mix with the wet and sticky particles in the granulation zone, which accelerates the migration and renewal of the particles in the granulation zone, quickly reduces the wet and sticky state of the material in the granulation zone and accelerates the drying speed, thereby alleviating the contradiction that the drying rate of the material in the granulation zone is less than the granulation speed. The annular atomized droplet receiving zone has two boundaries, the outer ring and the inner ring. Therefore, compared with the receiving surface without a central airspace, the boundary area for heat and mass exchange around the granulation zone formed by the annular atomized droplet receiving zone is larger, and the heat and mass exchange efficiency is higher, so that the granulation-drying process is more stable.

[0012] As a preferred embodiment of the present invention, during the granulation drying process, the vertical position of the motor is first adjusted by the vertical drive device to determine the angle of the spray gun relative to the vertical direction; then the spray gun is driven by the motor to rotate at a uniform angular speed so that the closed shape is circular. In this technical solution, the closed shape is circular, and within one cycle, the shape of the area covered by the atomized droplet receiving area is circular or annular.

[0013] In the circular or annular receiving area of ​​the atomized liquid droplets formed in the above manner, each point in the receiving area of ​​the atomized liquid droplets rotates around the center of the circle at the same angular velocity, the particles on the same circumference have the same receiving velocity, and the ratio of the receiving time to the non-receiving time is the same, so the receiving uniformity is the best. Compared with trajectories of other closed shapes, the circular trajectory has the best granulation-drying stability. Moreover, within one of the cycles, the shape of the area covered by the receiving area of ​​the atomized liquid droplets is circular or annular, and the symmetry of the granulation area is the best, the shape is simple, and it is easier to design the flow field of the fluidized bed to strengthen the renewal of the particles in the granulation area.

[0014] As a preferred embodiment of the present invention, during the granulation and drying process, the motor is driven by a vertical drive device to reciprocate according to a period of T / 2, and at the same time, the spray gun is driven by a motor to rotate at a uniform angular speed according to a period of T, so that the closed shape has two orthogonal axes, which are respectively a major axis and a minor axis, and the closed shape has mirror symmetry about the major axis and the minor axis.

[0015] Furthermore, the cross section of the bed is rectangular, and the long axis is perpendicular or parallel to the length direction of the bed. For a bed area of ​​a certain size, the atomized droplet receiving area formed in this way can cover a larger proportion of the bed area, thereby improving the utilization rate of the bed area and ultimately increasing the overall equipment capacity; moreover, this method has better coordination with the air inlet chamber, and can more conveniently design the flow field of the fluidized bed to enhance the renewal of particles in the granulation area.

[0016] Furthermore, a rotary joint is installed on the spray gun, and the material and the atomizing medium enter the spray gun through the rotary joint.

[0017] Furthermore, the rotary joint is coaxially and rotatably sleeved on the outside of the spray gun; a material channel and an atomizing medium channel are provided in the spray gun, and a material connecting port and an atomizing medium connecting port which are respectively connected to the material channel and the atomizing medium channel are provided on the spray gun; a material annular cavity and an atomizing medium annular cavity which are respectively connected to the material connecting port and the atomizing medium connecting port are provided in the rotary joint, and a material input port and an atomizing medium input port which are respectively connected to the material annular cavity and the atomizing medium annular cavity are provided on the rotary joint.

[0018] As a preferred embodiment of the present invention, the spray gun driving mechanism is used to drive the spray gun to swing; during the granulation and drying process, the spray gun is driven by the spray gun driving mechanism to swing back and forth periodically, so that the atomized droplet receiving area is continuously and periodically cyclically moved along a straight line trajectory. In one cycle, the shape of the area covered by the atomized droplet receiving area is an arc-angled rectangle, and the arc angles at both ends are the shapes of intersecting lines symmetrical with the swing axis formed after the atomized droplet receiving area and the upper surface of the bed intersect, and its width is equivalent to the width of the atomized droplet receiving area formed by a single-rod fixed spray gun, and its length is equivalent to extending the atomized droplet receiving area formed by a single-rod fixed spray gun along the length direction. Therefore, it not only covers multiple atomized droplet receiving areas formed by multiple fixed spray guns, but also fills the gaps between these atomized droplet receiving areas, thereby achieving a larger bed area coverage ratio. At the same time, this mobile atomized droplet receiving area also brings better granulation and drying stability.

[0019] Furthermore, the spray gun driving mechanism includes a linear driving device, a sliding pin and a slot rod, the slot rod is fixedly connected to the spray gun, a linear slot is provided on the slot rod, the sliding pin slides in cooperation with the linear slot, the linear driving device is used to drive the sliding pin to move linearly, and the moving direction of the sliding pin intersects with the extension direction of the linear slot. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the fluidized bed granulation dryer in Example 1, wherein: Figure 1 a is the main view, Figure 1 b is a top view.

[0021] Figure 2 for Figure 1 A partial enlarged view of part I in the middle.

[0022] Figure 3 It is a schematic diagram of the structure of the spray gun in Example 1.

[0023] Figure 4 This is a schematic diagram of the structure of the ball hinge in Example 1.

[0024] Figure 5 It is a schematic diagram of the structure of the fluidized bed granulation dryer in Example 2, wherein: Figure 5 a is the main view, Figure 5 b is a top view.

[0025] Figure 6 It is a schematic diagram of the structure of the fluidized bed granulation dryer in Example 3, wherein: Figure 6 a is the main view, Figure 6 b is the side view, Figure 6 c is a top view.

[0026] Figure 7 The present invention is a schematic diagram of the arrangement structure of the atomized liquid droplet receiving area of ​​an existing top-down spraying fluidized bed granulating dryer.

[0027] Figure 8 This is a schematic diagram of the layout structure of the atomized droplet receiving area of ​​the fluidized bed granulation dryer in Example 4.

[0028] Fig. 9 It is a schematic diagram of the structure of the fluidized bed granulation dryer in Example 5, wherein: Fig. 9 a is the main view, Fig. 9 b is the side view, Fig. 9 c is a top view.

[0029] Fig.10 for Fig. 9 A partial enlarged view of part II.

[0030] Fig.11 The present invention is a schematic diagram of the arrangement structure of the atomized liquid droplet receiving area of ​​another existing top-down spray fluidized bed granulating dryer.

[0031] Among them: 1-bed, 2-spray gun, 3-air inlet chamber, 4-straight section of fluidizing chamber, 5-sedimentation chamber, 6-air distribution plate, 7-ball hinge, 8-motor, 9-connecting rod, 10-rotating joint, 11-material channel, 12-atomizing medium channel, 13-material connecting port, 14-atomizing medium connecting port, 15-material ring cavity, 16-atomizing medium ring cavity, 17-material input port, 18-atomizing medium input port, 19-electric push rod, 20-ball pin, 21 -slide pin, 22-slot rod, 23-linear slide, 24-fluidizing chamber expansion section, 25-air inlet, 26-return port, 27-discharge port, 28-exhaust port, 29-upper ball bowl, 30-lower ball bowl, 31-seal, 32-linear module, 33-bolt, 34-long axis, 35-short axis, 36-atomized droplet receiving area, 37-upper surface of the fluidized bed, 38-nozzle of the spray gun, 39-fixed atomized droplet receiving area, 40-atomizing area. DETAILED DESCRIPTION

[0032] The following examples are further illustrations of the present invention.

[0033] Example 1

[0034] Cysteine ​​and cysteine ​​hydrolyzate are biomass materials that are difficult to dry and have strong thermal viscosity. The existing technology uses a small-scale intermittently operated circular fluidized bed granulation dryer for granulation and drying operations, and uses a multi-rod fixed spray gun, which is set above the fluidized material layer, to spray the material liquid downward into atomization onto the material layer for granulation operations. Since the drying speed of the material liquid is very slow, the wet particles show strong thermal viscosity, and it is easy to cause caking and bed collapse. It can only be produced at low load by using a multi-rod spray gun with a small spray volume, which consumes a lot of energy and has poor economy.

[0035] This embodiment provides a fluidized bed granulation drying method, which is performed using a fluidized bed granulation dryer. The fluidized bed granulation dryer in this embodiment is a small intermittent fluidized bed granulation dryer, which is used for granulation and drying of cystine and cysteine ​​hydrolyzate, and includes a bed 1, a spray gun 2 and a spray gun driving mechanism.

[0036] like Figure 1As shown in FIG. 2 b, the horizontal cross-section of the bed body 1 is circular. An air inlet chamber 3, a fluidizing chamber and a settling chamber 5 are sequentially arranged in the bed body 1 from bottom to top, and an air distribution plate 6 is arranged between the air inlet chamber 3 and the fluidizing chamber. In this embodiment, the fluidizing chamber includes a fluidizing chamber straight section 4 and a fluidizing chamber expansion section 24, and the fluidizing chamber expansion section 24 is located above the fluidizing chamber straight section 4. It should be pointed out that for those skilled in the art, the specific form of the fluidizing chamber is not limited to the form shown in this embodiment. For example, the fluidizing chamber can be composed only of the fluidizing chamber straight section 4, or only of the fluidizing chamber expansion section 24. In addition, the fluidizing chamber can also include a fluidizing chamber straight section 4 and a fluidizing chamber expansion section 24, and in this structure, the fluidizing chamber expansion section 24 can be located below the fluidizing chamber straight section 4. The fluidized particulate material located in the fluidizing chamber constitutes a fluidized bed layer, and the upper surface 37 of the fluidized bed layer is located in the fluidizing chamber. The bed body 1 is provided with an air inlet 25, a return port 26, a discharge port 27 and an exhaust port 28. The air inlet 25 is connected to the air inlet chamber 3, the return port 26 and the discharge port 27 are both connected to the fluidizing chamber, and the exhaust port 28 is connected to the settling chamber 5.

[0037] The spray gun 2 is used to atomize liquid materials, and the spray gun 2 is installed on the top of the bed 1 through a ball hinge 7. Specifically, Figure 4 As shown, the ball hinge in this embodiment includes a ball seat and a ball pin 20, the ball seat includes an upper ball bowl 29 and a lower ball bowl 30, the lower ball bowl 30 is fixedly mounted on the bed 1, the upper ball bowl 29 is buckled on the lower ball bowl 30 and fixedly connected by bolts 33. The ball pin 20 is accommodated in the cavity formed by the upper ball bowl 29 and the lower ball bowl 30 and forms a spherical pair with the ball seat, and the ball pin 20 is fixedly sleeved on the outside of the spray gun 2. In order to ensure sealing, a sealing member 31 is provided between the ball pin 20 and the ball seat and between the ball pin 20 and the spray gun 2.

[0038] The nozzle 38 of the lance is located above the upper surface 37 of the fluidized bed.

[0039] like Figure 2 As shown, the spray gun driving mechanism includes a vertical driving device, a motor 8 and a connecting rod 9. The vertical driving device is used to drive the motor 8 to move vertically. The vertical driving device in this embodiment is a linear module 32 in the vertical direction. The axis of the output shaft of the motor 8 is in the vertical direction and passes through the center of the ball hinge 7. The two ends of the connecting rod 9 are pivotally connected to the output shaft of the motor 8 and the spray gun 2 respectively. When the vertical driving device drives the motor 8 to move vertically, the angle of the spray gun 2 relative to the vertical direction can be adjusted, thereby adjusting the spray angle of the nozzle 38 of the spray gun. When the motor 8 rotates, the spray gun 2 can be driven to rotate through the connecting rod 9.

[0040] It should be noted that when the motor 8 moves vertically, it is necessary to ensure that the connecting rod 9 and the spray gun 2 are not collinear, that is, the angle between the axis of the spray gun 2 and the vertical direction needs to be greater than 0° to avoid a "dead point". In addition, the atomized droplets of the spray gun 2 should not be sprayed onto the inner wall of the bed 1 to avoid scarring on the inner wall of the bed 1. Therefore, the angle of the axis of the spray gun relative to the vertical direction has a maximum value, and the adjustment range of the axis angle of the spray gun during actual operation is between 0° and the maximum value.

[0041] like Figure 2 As shown, the spray gun 2 is equipped with a rotary joint 10, and the material and the atomizing medium enter the spray gun 2 through the rotary joint 10. Specifically, as Figure 3 As shown, the rotary joint 10 is coaxially and rotatably sleeved on the outside of the spray gun 2, the spray gun 2 is provided with a material channel 11 and an atomizing medium channel 12, the spray gun 2 is provided with a material communication port 13 and an atomizing medium communication port 14 respectively connected with the material channel 11 and the atomizing medium channel 12, the rotary joint 10 is provided with a material annular cavity 15 and an atomizing medium annular cavity 16 respectively connected with the material communication port 13 and the atomizing medium communication port 14, and the rotary joint 10 is provided with a material input port 17 and an atomizing medium input port 18 respectively connected with the material annular cavity 15 and the atomizing medium annular cavity 16. The material input port 17 and the atomizing medium input port 18 are connected to the material source and the atomizing medium source respectively through a hose. When the spray gun 2 rotates around the center of the ball hinge 7, the rotary joint 10 rotates relative to the spray gun 2, and the hose can prevent the rotation or swing of the spray gun 2 from being interfered.

[0042] During the granulation and drying process, according to the product particle size requirements, the size of the upper surface 37 of the fluidized bed, the spray speed of the spray gun 2, the drying rate of the liquid, and other parameters, the vertical drive device is used to adjust the position of the motor 8 in the vertical direction to determine the angle of the spray gun 2 relative to the vertical direction; then the motor 8 drives the spray gun 2 to rotate at a uniform angular speed at a set speed, thereby forming a continuous and periodic circulating atomized droplet receiving area 36 in the top material layer area of ​​the fluidized bed, and the atomized droplet receiving area 36 continuously and periodically circulates along a circular trajectory.

[0043] like Figure 1 As shown in Fig. b, within one cycle, the area covered by the atomized liquid droplet receiving area 36 is circular in shape. In this embodiment, each receiving point in the atomized liquid droplet receiving area 36 rotates around the center of the circle at the same angular velocity, the particles on the same circumference have the same receiving velocity, and the ratio of the receiving time to the non-receiving time is the same, so the receiving uniformity is the best and the granulation-drying stability is the best. In addition, the granulation area has the best symmetry, a simple shape, and good matching with the shape of the circular bed, making it easier to design the flow field of the fluidized bed to strengthen the renewal of the particles in the granulation area.

[0044] The technical principle of this embodiment is described as follows: the liquid material is atomized into fine droplets by the spray gun 2 and then falls downward to form an approximately conical atomization zone 40, covering the fluidized bed layer below it, and the droplets fall onto the upper surface of the fluidized bed layer and penetrate into the fluidized bed layer of a certain thickness, thereby forming a granulation zone in the material layer in contact with the droplets and the area with high humidity around it. During the granulation drying process, the spray gun 2 is driven to move by the spray gun driving mechanism, and the atomization zone 40 performs a corresponding cyclic motion, thereby forming a continuous, periodic and cyclically moving atomized droplet receiving zone 36 on the upper surface of the fluidized bed layer. For a specific local area of ​​the entire fluidized bed area covered by the atomized droplet receiving zone 36, in each movement cycle of the atomized droplet receiving zone 36, the local area can be divided into two stages: passing through the atomized droplet receiving zone and not passing through the atomized droplet receiving zone. When passing through the atomized droplet receiving area 36, ​​the bed material in the local area receives the droplets and starts the granulation and drying process; when the atomized droplet receiving area 36 leaves, the liquid receiving process of the bed in the local area stops. During the period of stopping the liquid receiving, the hot air continuously enters the local area, and the wet material in the local area is violently mixed with the dry material in the surrounding area, so that the drying process continues, the material humidity continues to decrease, and the granulation process is rapidly weakened. When the moisture content of the material in the local area drops to a certain level, the viscosity of the material is also weakened to the point that it is not enough for granulation. At this time, the granulation process ends while the drying process is still in progress until the dynamic equilibrium moisture content of the material is reached. Under the same inlet air temperature, fluidization velocity and flow field conditions of the fluidized material layer, for materials with different granulation and drying characteristics, by adjusting the size, movement period, trajectory, movement speed and other parameters of the granulation area covered by the atomized droplet receiving area 36, ​​the entire granulation and drying process can be completed in advance at an appropriate and controllable time interval before the atomized droplet receiving area 36 passes through the local area next time, and then enter the next cycle, thereby improving the granulation and drying efficiency. This embodiment realizes periodic and intermittent liquid reception of materials in the granulation area covered by the atomization area 40 of each spray gun by continuously and periodically moving the atomized droplet receiving area, which can effectively solve the contradiction that the drying rate of viscous materials such as biomass is lower than the granulation rate, so that the granulation-drying process is carried out stably, thereby preventing the formation of coarse particles or agglomerates due to excessively high material humidity in the granulation area and excessively long material viscosity.

[0045] Example 2

[0046] Figure 5 Embodiment 2 of the present invention is shown.

[0047] The difference from Example 1 is that, in this embodiment, within one cycle, the shape of the area covered by the atomized droplet receiving area 36 is annular. Since the inner area of ​​the annular ring does not receive droplet spraying, the shape of each horizontal cross section of the formed granulation zone is also annular corresponding thereto. Since the material particles constituting the fluidized bed layer are constantly undergoing violent back mixing in the vertical and horizontal directions, the boundary of the annular ring is dynamically changing, and the dry particles in the outer area of ​​the annular ring and the inner area of ​​the annular ring pass through the boundary of the annular ring and mix with the wet and sticky particles in the granulation zone, which accelerates the migration and renewal of the particles in the granulation zone, quickly reduces the wet and sticky state of the material in the granulation zone and accelerates the drying speed, thereby alleviating the contradiction that the drying rate of the material in the granulation zone is less than the granulation speed. The annular atomized droplet receiving area has two boundaries, an outer circle and an inner circle. Therefore, compared with the circular atomized droplet receiving area, the annular atomized droplet receiving area has a larger boundary area for heat and mass exchange around the granulation area formed by the annular atomized droplet receiving area, and the heat and mass exchange efficiency is higher, thereby making the granulation-drying process more stable.

[0048] Example 3

[0049] Figure 6 Embodiment 3 of the present invention is shown.

[0050] Molasses yeast tail liquid is the tail liquid of the waste liquid in the sugar industry after fermentation and extraction of effective ingredients. It contains a variety of organic and inorganic components and has a complex composition. It is a typical difficult-to-dry material. Its drying process is mainly controlled by the migration process of internal moisture, and the drying speed is slow. Therefore, it remains in a viscous liquid or semi-solid state for most of the drying process, and has strong viscosity and thermal viscosity. When the existing top-down spray fluidized bed granulation dryer is used for granulation and drying of molasses yeast tail liquid, because the atomization and granulation area formed by the spray gun is fixed, the particles in the granulation area are continuously sprayed with droplets to increase moisture, but the material characteristics cause the drying speed of the wet material to be much lower than the granulation speed, resulting in a large number of oversized particles or lumps in the granulation area, and the fluidization of the local area deteriorates or even dead beds, and production is forced to stop. Therefore, in actual production, only a very low single-gun spray speed can be controlled, and the inlet air temperature can be reduced to maintain the stability of the granulation-drying process.

[0051] This embodiment provides a fluidized bed granulation drying method, wherein the material used for granulation is molasses yeast tail liquid. The fluidized bed granulation drying method of this embodiment is performed using a fluidized bed granulation dryer. In this embodiment, the fluidized bed granulation dryer is a continuous fluidized bed granulation dryer, comprising a bed body 1, a spray gun 2 and a spray gun driving mechanism.

[0052] like Figure 6As shown, the horizontal cross-section of the bed body 1 is rectangular, and the bed body 1 is provided with an air inlet chamber 3, a fluidizing chamber and a sedimentation chamber 5 from bottom to top. An air distribution plate 6 is provided between the air inlet chamber 3 and the fluidizing chamber. In this embodiment, the fluidizing chamber includes a fluidizing chamber straight section 4 and a fluidizing chamber expansion section 24, and the fluidizing chamber expansion section 24 is located above the fluidizing chamber straight section 4. It should be pointed out that for those skilled in the art, the specific form of the fluidizing chamber is not limited to the form shown in this embodiment. For example, the fluidizing chamber can be composed only of the fluidizing chamber straight section 4, or only of the fluidizing chamber expansion section 24. In addition, the fluidizing chamber can also include a fluidizing chamber straight section 4 and a fluidizing chamber expansion section 24, and in this structure, the fluidizing chamber expansion section 24 can be located below the fluidizing chamber straight section 4. The fluidized particulate material located in the fluidizing chamber constitutes a fluidized bed layer, and the upper surface 37 of the fluidized bed layer is located in the fluidizing chamber. The bed body 1 is provided with an air inlet 25, a return port 26, a discharge port 27 and an exhaust port 28. The air inlet 25 is connected to the air inlet chamber 3, the return port 26 and the discharge port 27 are both connected to the fluidizing chamber, and the exhaust port 28 is connected to the settling chamber 5.

[0053] The spray guns 2 are used to atomize liquid materials. The spray guns 2 are installed on the top of the bed 1 through ball hinges. The spray guns 2 are arranged in one row and five columns.

[0054] The nozzle 38 of the lance is located above the upper surface 37 of the fluidized bed.

[0055] In this embodiment, the structures of the ball hinge, spray gun driving mechanism and rotary joint are the same as those in Embodiment 1 and will not be described in detail here.

[0056] During the granulation and drying process, according to the product particle size requirements, the size of the upper surface 37 of the fluidized bed, the spraying speed of the spray gun 2, the drying rate of the liquid, and other parameters, the motor 8 is driven by the vertical drive device to reciprocate according to a preset period T / 2. At the same time, the motor 8 drives the spray gun 2 to rotate at a uniform angular speed according to a preset period T, thereby forming a continuous and periodic circulation atomized droplet receiving area 36 in the top material layer area of ​​the fluidized bed. The atomized droplet receiving area 36 continuously and periodically circulates along a closed shape trajectory. Figure 6 As shown in c, the closed shape has two orthogonal axes, which are a major axis 34 and a minor axis 35 , respectively. The closed shape has mirror symmetry about the major axis 34 and the minor axis 35 .

[0057] A closed shape is a continuous figure without breakpoints, all line segments or curves are connected inside the figure, and there are no open ports. It can be understood by those skilled in the art that "the trajectory of a closed shape" refers to "the trajectory formed by the boundary of the closed shape".

[0058] like Figure 6 As shown in c, in this embodiment, the major axis 34 is perpendicular to the length direction of the bed body 1. For a bed area of ​​a certain size, the atomized droplet receiving area formed in this way can cover a larger proportion of the bed area. Moreover, this method has better compatibility with the air inlet chamber, so it is more convenient to design the flow field of the fluidized bed, such as forming an ascending material flow in the inner ring area of ​​the atomized droplet receiving area and forming a descending material flow outside the outer ring, so as to enhance the renewal of particles in the granulation area.

[0059] It should be noted that when the motor 8 moves vertically, it is necessary to ensure that the connecting rod 9 and the spray gun 2 are not colinear, that is, the angle between the axis of the spray gun 2 and the vertical direction needs to be greater than 0° to avoid a "dead point".

[0060] The atomized droplets of the spray gun 2 should not be sprayed onto the inner wall of the bed 1 to avoid scarring on the inner wall of the bed 1.

[0061] In one of the cycles, the area covered by the atomized droplet receiving area 36 is in the shape of an annular shape. Since the inner ring area within the inner boundary of the annular shape does not receive droplet spraying, the shape of each horizontal section of the formed granulation area is also annular corresponding thereto. Since the material particles constituting the fluidized bed layer are constantly undergoing violent back mixing in the vertical and horizontal directions, the annular boundary is dynamically changing. The dry particles in the outer ring area and the inner ring area of ​​the annular shape pass through the annular boundary and mix with the wet and sticky particles in the granulation area, which accelerates the migration and renewal of the particles in the granulation area, quickly reduces the wet and sticky state of the material in the granulation area and accelerates the drying speed, thereby alleviating the contradiction that the drying rate of the material in the granulation area is less than the granulation speed. The annular atomized droplet receiving area has two boundaries, the outer ring and the inner ring. Therefore, compared with the receiving surface without a central airspace, the boundary area for heat and mass exchange around the granulation area formed by the annular atomized droplet receiving area is larger, and the heat and mass exchange efficiency is higher, so that the granulation-drying process is more stable.

[0062] Those skilled in the art will appreciate that by adjusting equipment parameters, such as the atomization angle of the spray gun 2, the height of the upper surface 37 of the fluidized bed, etc., the shape of the area covered by the atomized droplet receiving zone 36 can be made solid.

[0063] In a top-down spray fluidized bed granulation dryer of a single-machine production scale of molasses yeast tail liquid, the straight section length of the fluidized chamber is 10m, the width is 1.6m, the upper surface of the fluidized bed is about 300mm higher than the bottom of the expanded section of the fluidized chamber, the spray gun is fixedly arranged above the bed, the nozzle is about 1000mm higher than the upper surface of the bed, and when the nozzle sprays liquid, a fixed atomized droplet receiving area 39 is formed on the upper surface 37 of the fluidized bed. The boundary diameter of the fixed atomized droplet receiving area 39 is 400mm to 500mm. It is necessary to fix two rows and ten columns of spray guns to cover part of the fluidized bed (such as Figure 7 In this embodiment, the fluidized bed granulation drying method is adopted. When the fluidized bed granulator has the same size, the same material parameters and the same fluidization parameters are adopted, it is only necessary to arrange one row of five spray guns 2. The spray gun driving mechanism drives the spray guns 2 to move continuously and periodically in a circular motion, so as to ensure the stable operation of the equipment and avoid the phenomenon of agglomeration and bed collapse.

[0064] In addition to being able to solve the contradiction that the drying rate of viscous materials is lower than the granulation speed by continuously and periodically moving the liquid receiving area of ​​the atomized droplets as in Example 1, and avoiding the problem of forming coarse particles or agglomerates, in this embodiment, the area of ​​the liquid receiving area that can be covered by a single-gun atomization is several times that of the existing fixed-type distribution guns, reducing the number of spray guns to 1 / 4, thereby reducing the investment cost of the spray guns and the associated pipelines and control systems.

[0065] In addition, relative to the granulation and drying areas corresponding to the multiple fixed atomized droplet receiving areas 39 formed when the spray gun is fixedly arranged, the granulation and drying area formed when the spray gun of the present invention is working can cover multiple fixed atomized droplet receiving areas and the gap areas outside them. Therefore, the method of moving the atomized droplet receiving area of ​​the present invention can cover a larger range of bed areas than the atomization method of the fixed arrangement of the spray gun. Specifically in this embodiment, the area of ​​the atomized droplet receiving area covered by the single-rod spray gun is more than 50% of the total area of ​​the atomized droplet receiving area of ​​the four-rod fixed spray guns. When the equipment capacity remains unchanged, increasing the available bed area is equivalent to reducing the granulation and drying intensity per unit area, thereby increasing the equipment operation stability.

[0066] Example 4

[0067] The length and width of the bed of a conventional continuous granulation dryer are relatively large, resulting in a large increase in particle growth and a wider range of particle size distribution. For the production of products that require finer and uniform particle sizes, there is a problem of low yield, which increases the load on subsequent processing equipment such as screening, crushing, and return materials. Reducing the length-to-width ratio of the bed is one way to solve the above problems, but for the upper spray and lower gun insertion form, it is limited by the area of ​​the atomized droplet receiving area covered by a single gun atomization. In order to cover the entire bed layer, it is necessary to arrange multiple rows of spray guns in the width direction of the bed. The gun distribution area is small, which brings inconvenience to system layout and spray gun maintenance.

[0068] like Figure 8 As shown, the difference from Example 3 is that the length-to-width ratio of the bed 1 in this embodiment is smaller than that of the bed 1 in Example 3, the spray guns 2 are arranged in two rows and three columns, and the major axis 34 is parallel to the length direction of the bed 1.

[0069] This embodiment arranges the spray guns by continuously and periodically moving the atomized droplet receiving area in a closed figure trajectory, thereby obtaining a smaller bed length-to-width ratio than the existing granulation bed with fixed spray guns, which can better solve this problem.

[0070] Example 5

[0071] Fig. 9 , Fig.10 Embodiment 5 of the present invention is shown.

[0072] This embodiment provides a fluidized bed granulation and drying method, wherein the material used for granulation is molasses yeast tail liquid.

[0073] The fluidized bed granulation drying method of this embodiment is carried out using a fluidized bed granulation dryer. Fig. 9 As shown, in this embodiment, the fluidized bed granulation dryer is a continuous fluidized bed dryer, including a bed body 1, a spray gun 2 and a spray gun driving mechanism.

[0074] like Fig. 9 As shown, the cross-section of the bed body 1 is rectangular, and the bed body 1 is provided with an air inlet chamber 3, a fluidizing chamber, an expansion section 24 and a sedimentation chamber 5 from bottom to top. An air distribution plate 6 is provided between the air inlet chamber 3 and the fluidizing chamber. In this embodiment, the fluidizing chamber includes a fluidizing chamber straight section 4 and a fluidizing chamber expansion section 24, and the fluidizing chamber expansion section 24 is located above the fluidizing chamber straight section 4. It should be pointed out that for those skilled in the art, the specific form of the fluidizing chamber is not limited to the form shown in this embodiment. For example, the fluidizing chamber can be composed only of the fluidizing chamber straight section 4, or only of the fluidizing chamber expansion section 24. In addition, the fluidizing chamber can also include a fluidizing chamber straight section 4 and a fluidizing chamber expansion section 24, and in this structure, the fluidizing chamber expansion section 24 can be located below the fluidizing chamber straight section 4. The fluidized particulate material located in the fluidizing chamber constitutes a fluidized bed layer, and the upper surface 37 of the fluidized bed layer is located in the fluidizing chamber. The bed body 1 is provided with an air inlet 25, a return port 26, a discharge port 27 and an exhaust port 28. The air inlet 25 is connected to the air inlet chamber 3, the return port 26 and the discharge port 27 are both connected to the fluidizing chamber, and the exhaust port 28 is connected to the settling chamber 5.

[0075] The spray gun 2 is used to atomize liquid materials. The spray gun 2 is installed on the top of the bed 1 through a ball hinge 7. Those skilled in the art can understand that the spray gun 2 can also be pivotally connected to the top of the bed 1.

[0076] The nozzle 38 of the lance is located above the upper surface 37 of the fluidized bed.

[0077] In this embodiment, the structure of the ball hinge is the same as that of Embodiment 1 and will not be described again.

[0078] The spray gun driving mechanism is used to drive the spray gun 2 to swing back and forth. Fig.10 As shown, the spray gun driving mechanism includes a linear driving device, a sliding pin 21 and a slot rod 22. The slot rod 22 is fixedly connected to the spray gun 2. A linear slide groove 23 is provided on the slot rod 22. The sliding pin 21 and the linear slide groove 23 are slidably matched. The linear driving device is used to drive the sliding pin 21 to move linearly. The linear driving device in this embodiment adopts an electric push rod 19. It can be understood by those skilled in the art that the linear driving device can also adopt a cylinder or a hydraulic cylinder. The moving direction of the sliding pin 21 intersects with the extension direction of the linear slide groove 23.

[0079] During the granulation and drying process, based on the product particle size requirements, the size of the upper surface 37 of the fluidized bed, the spray speed of the spray gun 2, the drying rate of the liquid, and other parameters, the spray gun driving mechanism drives the spray gun 2 to swing back and forth periodically according to a preset reciprocating period and swing amplitude, so that the atomized droplet receiving area 36 moves continuously and periodically along a straight line trajectory.

[0080] like Fig. 9 As shown in FIG. 3 , within one cycle, the area covered by the atomized droplet receiving zone 36 is in the shape of an arc-angled rectangle, the arc angles at both ends of which are the intersecting lines formed by the intersection of the atomizing zone 40 and the upper surface of the bed layer and are symmetrical with the swing axis. The width of the arc-angled rectangle is equivalent to the width of the receiving zone formed by the single-rod fixed spray gun, and the length of the arc-angled rectangle is equivalent to the extension of the receiving zone formed by the single-rod fixed spray gun along the length direction. The receiving zone formed by the single-rod spray gun not only covers the multiple receiving zones formed by multiple fixed spray guns (such as Fig.11 As shown in the figure), it also fills the gaps between these liquid receiving areas, achieving a larger bed area coverage ratio, thus bringing better granulation and drying stability, thereby reducing the number of spray guns and the corresponding investment, and improving the overall operating stability or equipment capacity of the equipment.

[0081] like Fig. 9 As shown in c, the straight line track in this embodiment is perpendicular to the length direction of the bed body 1. For a bed area of ​​a certain size, the atomized droplet receiving area formed in this way can cover a larger proportion of the bed area, and this method has better compatibility with the air inlet chamber, and can more conveniently design the flow field of the fluidized bed to enhance the renewal of particles in the granulation area. When the length-to-width ratio of the bed body needs to be reduced for the same purpose as described in Example 3, in this embodiment, when the spray guns are fixed, four rows and five columns of spray guns need to be arranged to roughly cover the fluidized bed (such as Fig.11 In this embodiment, only one row of five columns of spray guns 2 are needed to make the atomization area 40 cover the entire bed layer, thereby reducing the number of spray guns 2 arranged and obtaining a lower aspect ratio.

[0082] The embodiments described above are merely descriptions of preferred implementation modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A fluidized bed granulation drying method, characterized in that: The invention adopts a fluidized bed granulation dryer, which comprises a bed body (1), a spray gun (2) and a spray gun driving mechanism. The bed body (1) is provided with an air inlet chamber (3), a fluidizing chamber and a settling chamber (5) in order from bottom to top, and an air distribution plate (6) is provided between the air inlet chamber (3) and the fluidizing chamber. The fluidized granular material in the fluidizing chamber constitutes a fluidized bed layer, and the upper surface (37) of the fluidized bed layer is located in the fluidizing chamber. The spray gun (2) is hinged to the top of the bed body (1), and the nozzle (38) of the spray gun is located above the upper surface (37) of the fluidized bed layer. During the granulation drying process, the spray gun (2) is driven to move by the spray gun driving mechanism, so that a continuous, periodic and cyclically moving atomized droplet receiving area (36) is formed in the top material layer area of ​​the fluidized bed layer. The spray gun (2) is mounted on the top of the bed (1) via a ball hinge (7); the spray gun driving mechanism comprises a vertical driving device, a motor (8) and a connecting rod (9); the vertical driving device is used to drive the motor (8) to move vertically, the axis of the output shaft of the motor (8) is in a vertical direction and passes through the center of the ball hinge (7), and the two ends of the connecting rod (9) are respectively pivotally connected to the output shaft of the motor (8) and the spray gun (2); during the granulation drying process, the spray gun driving mechanism drives the spray gun (2) to rotate and / or swing periodically, so that the atomized droplet receiving area (36) continuously and periodically moves in a closed shape trajectory; a rotary joint (10) is installed on the spray gun (2), and the material and the atomized medium enter the spray gun (2) through the rotary joint (10).

2. The fluidized bed granulation drying method according to claim 1, characterized in that: In one cycle, the area covered by the atomized liquid droplet receiving area (36) is in the shape of a ring.

3. The fluidized bed granulation drying method according to claim 1 or 2, characterized in that: During the granulation and drying process, the vertical driving device is used to adjust the position of the motor (8) in the vertical direction, thereby determining the angle of the spray gun (2) relative to the vertical direction; and then the motor (8) is used to drive the spray gun (2) to rotate at a uniform angular speed, so that the closed shape is circular.

4. The fluidized bed granulation drying method according to claim 1 or 2, characterized in that: During the granulation and drying process, the vertical drive device drives the motor (8) to reciprocate at a period of T / 2, and at the same time, the motor (8) drives the spray gun (2) to rotate at a uniform angular speed at a period of T, so that the closed shape has two orthogonal axes, the two orthogonal axes are the major axis (34) and the minor axis (35), and the closed shape has mirror symmetry about the major axis (34) and the minor axis (35).

5. The fluidized bed granulation drying method according to claim 4, characterized in that: The cross section of the bed body (1) is rectangular, and the long axis is perpendicular or parallel to the length direction of the bed body (1).

6. The fluidized bed granulation and drying method according to claim 1, characterized in that: The rotary joint (10) is coaxially and rotatably sleeved on the outside of the spray gun (2); a material channel (11) and an atomizing medium channel (12) are provided in the spray gun (2); a material communication port (13) and an atomizing medium communication port (14) are provided on the spray gun (2), which are respectively connected to the material channel (11) and the atomizing medium channel (12); a material annular cavity (15) and an atomizing medium annular cavity (16) are provided in the rotary joint (10), which are respectively connected to the material communication port (13) and the atomizing medium communication port (14); a material input port (17) and an atomizing medium input port (18) are provided on the rotary joint (10), which are respectively connected to the material annular cavity (15) and the atomizing medium annular cavity (16).

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