Fluidized bed drying system and energy-saving method for salt production

Abstract

This invention discloses an energy-saving fluidized bed drying system and method for salt production. The system includes a fluidized bed body divided into multiple functionally independent temperature-controlled zones along the material flow direction; a gas-fired direct-fired main hot air generator for heating the drying zone; and an auxiliary hot air generator for heating the preheating zone. Its key feature is that it further includes: a waste heat recovery system, which, through a dedicated pipeline, returns low-temperature waste gas (approximately 55°C) from the cooling zone outlet to the preheating zone inlet after dust removal, achieving efficient recycling of low-grade waste heat; an internal circulation dust removal system, which recycles humid and hot gas from the drying zone after two stages of high-efficiency dust removal, and precisely controls the circulating air volume through a proportional regulating valve, significantly reducing the emission loss of high-calorific-value heat energy; and an intelligent collaborative control system, which dynamically coordinates and controls the heating power, air valve opening, and fan speed through a controller to achieve global energy efficiency optimization. This invention achieves tiered energy utilization and intelligent regulation, with a comprehensive energy saving rate exceeding 40%, uniform temperature field within the bed, and effectively improves drying quality, product consistency, and system operational stability.

Description

Technical Field

[0001] This invention relates to the field of industrial thermal energy technology and equipment, specifically to a fluidized bed drying system for salt production and its energy-saving control method. Background Technology

[0002] In the salt industry and similar sectors, fluidized bed drying is a core piece of equipment for ensuring production efficiency and product quality. During the drying process, the recovery of waste heat from the large volume of low-temperature exhaust gas is crucial for energy conservation and emission reduction. Traditional fluidized bed systems typically generate low-temperature exhaust gas (around 55°C or higher) in their cooling section, which carries a considerable amount of waste heat. To effectively recover this waste heat and use it for preheating the upstream materials, the exhaust gas needs to be treated with dust removal and temperature regulation to achieve cascaded utilization of the heat. Currently, the closest existing technology generally adopts an integrated heating fluidized bed drying system. This type of system typically generates hot air through an indirect heating method of "boiler steam generation—steam transmission—air heat exchange," supplying hot air at a uniform temperature to the entire bed area. However, this system has significant shortcomings in heat recovery and refined control, making it difficult to meet the requirements of continuous, efficient, and stable drying processes. Specifically: 1. Inefficient use of heat energy and high system energy consumption: The use of overall or simple zone heating modes cannot match the temperature gradient requirements of materials in the pre-drying, main drying and cooling stages, resulting in serious heat waste and high overall energy consumption. 2. Low-temperature waste heat is not recovered, resulting in significant energy waste: The system does not effectively recover the low-temperature waste gas (usually ≥55℃) generated in the cooling section, and direct emission causes a large loss of usable energy. 3. Poor temperature uniformity of the bed affects product quality: Due to the simple airflow design and unreasonable zoning, the temperature distribution inside the bed is uneven, which can easily lead to inconsistent drying of materials, resulting in local clumping or excessive moisture, thus affecting the quality of the finished product. 4. Low thermal efficiency of indirect heating mode: The multi-stage indirect heating method of "boiler-steam-heat exchange" has multiple losses such as combustion efficiency, pipeline heat loss and heat exchange efficiency, resulting in low overall system thermal efficiency. 5. Low level of automation and insufficient control precision: Relying on manual experience to adjust dampers and valves makes it difficult to achieve precise and stable control of process parameters, affecting production continuity and system stability. Summary of the Invention

[0003] In view of the above background analysis, the present invention aims to provide an energy-saving fluidized bed drying system and method for salt production, so as to solve one or more of the problems existing in the prior art. To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a fluidized bed drying system for salt production. The system includes: The fluidized bed body is divided into multiple sequentially connected temperature control zones along the material travel direction. The temperature control zones include at least a preheating zone, a drying zone, and a cooling zone. The main hot air generator is used to provide high-temperature hot air to the drying zone; The system is characterized in that it further includes: The waste heat recovery subsystem is equipped with a recovery pipeline connecting the outlet of the cooling zone and the inlet of the preheating zone, which is used to recover the waste gas generated in the cooling zone and transport it to the preheating zone. An internal circulation and dust removal subsystem is installed in the drying zone to draw out a portion of the exhaust gas from the outlet of the drying zone, and after dust removal and purification, it is sent back to the drying zone for recycling. The intelligent control subsystem is connected to the sensors installed in each temperature control zone, the main hot air generator, the waste heat recovery subsystem, and the internal circulation and dust removal subsystem. It is used to coordinate the operation of each subsystem according to process parameters in order to optimize system energy efficiency. Furthermore, the main hot air generating device is a direct-fired hot air unit. Furthermore, the plurality of temperature control zones include a first preheating zone, a second preheating zone, a first drying zone, a second drying zone, and a cooling zone, and each temperature control zone is equipped with an independent airflow adjustment mechanism. Furthermore, a dust collector is installed on the recovery pipeline of the waste heat recovery subsystem. Furthermore, the internal circulation and dust removal subsystem includes at least two stages of dust collectors arranged in series. Furthermore, the intelligent control subsystem is configured to execute the following control strategies: prioritize the use of heat delivered by the waste heat recovery subsystem, and initiate supplementary heating when it is insufficient; and adjust the circulating air ratio of the internal circulation and dust removal subsystems. Secondly, based on the same inventive concept, the present invention provides a fluidized bed drying method. The method is applied to the fluidized bed drying system described above and includes the following steps: The material is processed sequentially through the preheating zone, drying zone, and cooling zone; The exhaust gas discharged from the cooling zone is recovered and transported to the preheating zone as a heat source; After dust removal and purification, part of the exhaust gas discharged from the drying zone is reintroduced into the drying zone to participate in the circulation. The intelligent control subsystem collects system operating parameters and coordinates the heat supply, air volume distribution, and waste heat recovery ratio of each zone to optimize system energy efficiency. Thirdly, the system and method provided by the present invention can produce the following beneficial effects: 1. Remarkably effective energy saving: Through multiple energy cascade utilization measures such as "zoned cascade heating + low-temperature waste heat closed-loop recovery + high-temperature hot air internal circulation," combined with a highly efficient direct-fired gas heat source, the thermal efficiency is significantly improved at the system level. Actual measurements show that this comprehensive solution can reduce overall energy consumption by more than 40%. 2. Significantly improved drying quality and temperature uniformity: Independent temperature control zones and precise airflow adjustment ensure a highly uniform temperature distribution within the fluidized bed, with temperature control accuracy within ±2℃. This results in excellent material drying consistency, effectively solving the problems of clumping or excessive moisture, and allowing the product moisture content to be stably reduced from ≤3% to ≤0.05%. 3. High system reliability and stable operation: The customized "cage + cyclone" two-stage high-efficiency dust removal system (efficiency >99%) is applied to the circulating air path in the drying area to address the characteristics of salt dust. At the same time, dust removal is also performed before waste heat recovery, which effectively prevents salt dust from corroding and clogging the fans, heat exchangers and pipes, significantly reduces the maintenance frequency and ensures long-term continuous and stable operation of the system. 4. High level of automation and intelligence: The integrated intelligent control module realizes the leap from manual experience-based adjustment to fully automated and precise control of the entire process. The system can dynamically coordinate all actuators based on real-time process data, which not only significantly improves production stability and efficiency, but also provides a data foundation for continuous process optimization. In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following detailed description, and some advantages may become apparent from the specification or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the specification, claims, and drawings. Attached Figure Description

[0004] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings. Figure 1A A schematic diagram (front view) of the overall structure of the fluidized bed drying system provided by the present invention. Figure 1B A schematic diagram (axonometric view) of the overall structure of the fluidized bed drying system provided by the present invention. Figure 1C A schematic diagram (top view) of the overall structure of the fluidized bed drying system provided by the present invention. Figure 2 This is a schematic diagram of the fluid flow direction of the fluidized bed drying system provided by the present invention; Figure 3A A schematic diagram of the cage dust collector structure (exterior) provided by the present invention; Figure 3B A schematic diagram of the cage dust collector structure (internal) provided by the present invention. Figure 4 This is a schematic diagram of the preheating zone hot air unit structure provided by the present invention; Figure 5 This is a schematic diagram of the hot air unit structure in the drying zone provided by the present invention; Figure 6 This is a schematic diagram of the cyclone dust collector provided by the present invention. Explanation of reference numerals in the attached figures: 1. Vibrating fluidized bed; 1.1. Preheating zone; 1.2. Drying zone; 1.3. Cooling zone; 2. Preheating zone hot air unit; 2.1. Embedded preheating zone fan; 2.2. Preheating zone air outlet; 2.3. Embedded preheating zone fan; 2.4. Inspection door; 2.5. Preheating zone hot air unit casing; 2.6. Preheating zone air inlet; 2.7. Preheating zone make-up air inlet; 3. Drying zone hot air unit; 3.1. Embedded drying zone fan; 3.2. Drying zone air outlet; 3.3. Embedded preheating zone fan; 3.4. Inspection door; 3.5. Preheating zone hot air unit casing; 3.6. Drying zone air inlet; 3.7. Drying zone make-up air inlet; 4. Cyclone dust collector; 4.1 Cyclone dust collector shell; 4.2 Cyclone dust collector inlet; 4.3 Cyclone dust collector outlet; 4.4 Cyclone dust collector outlet; 5. Cage dust collector; 5.1. Cage dust collector shell; 5.2. Cage dust collector inlet; 5.3. Inspection door; 5.4. Cage dust collector outlet; 5.5. Vacuum cleaner outlet; 5.6. Dust removal mechanism; 5.7. Cage filter mechanism; 5.8. Dust collection mechanism; 6. Exhaust fan; 7. Cooling fan; 8. Exhaust fan; 9. Dust extraction fan. Detailed Implementation

[0005] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. To facilitate understanding of the embodiments of this application, further explanation and description will be provided below with reference to the accompanying drawings and specific embodiments. These embodiments do not constitute a limitation on the embodiments of this application. In the drawings, the dimensions and relative dimensions of components may be exaggerated for clarity and / or descriptive purposes. When exemplary embodiments can be implemented differently, a specific process sequence may be performed in a different order than that described. For example, two consecutively described processes may be performed substantially simultaneously or in the reverse order of their description. Furthermore, the same reference numerals denote the same components. The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms “a” and “the” are intended to include the plural forms as well. Furthermore, when the terms “comprising” and / or “including” and variations thereof are used in this specification, it indicates the presence of the stated features, integrals, steps, operations, parts, components, and / or groups thereof, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, parts, components, and / or groups thereof. It should also be noted that, as used herein, the terms “substantially,” “about,” and other similar terms are used as approximate terms rather than as terms of degree, thus explaining the inherent biases in measurements, calculated values, and / or provided values ​​that would be recognized by one of ordinary skill in the art. Example 1 A specific embodiment of the present invention discloses an energy-saving fluidized bed drying system for salt production. Through systematic hardware innovation and intelligent control strategies, it achieves efficient tiered utilization of energy, aiming to significantly reduce energy consumption, improve drying quality and system operation stability. like Figures 1A to 1C As shown, this system includes a fluidized bed 1, whose interior is divided into multiple series-connected, functionally independent temperature-controlled zones along the material flow direction. Specifically, as... Figure 1A and Figure 2As shown, the temperature control zone includes at least a preheating zone 1.1, a drying zone 1.2, and a cooling zone 1.3 connected in sequence. In a preferred embodiment, the preheating zone 1.1 and the drying zone 1.2 can be further subdivided into first and second sub-zones to form five temperature control chambers connected in series, achieving more precise temperature gradient control. Each temperature control zone is equipped with an independent air distribution device and exhaust gas outlet, and is configured with an independently controlled airflow adjustment mechanism. The preheating zone 1.1 is heated by the preheating zone hot air unit 2. See also... Figure 4 The unit includes a housing 2.5, which integrates at least one embedded preheating zone fan 2.1. The housing 2.5 is equipped with a preheating zone air inlet 2.6, a preheating zone air outlet 2.2, and a preheating zone make-up air inlet 2.7. The preheating zone air outlet 2.2 is connected to the preheating zone 1.1 via an air duct. The preheating zone air inlet 2.6 is used to introduce fresh air or recovered waste heat, and the preheating zone make-up air inlet 2.7 is used to connect to a high-temperature hot air duct from the drying zone to achieve precise heat replenishment. The housing 2.5 is equipped with an inspection door 2.4 for maintenance. The main heat source for the drying zone 1.2 is the drying zone hot air unit 3. (See also...) Figure 5 The unit includes a housing 3.5, which integrates at least one embedded drying zone fan 3.1. The housing 3.5 is equipped with a drying zone air inlet 3.6, a drying zone air outlet 3.2, and a drying zone make-up air inlet 3.7. The drying zone air outlet 3.2 is connected to the drying zone 1.2 via an air duct. The core of the drying zone hot air unit 3 is a direct-fired gas heating system, which incorporates a low-NOx burner to directly generate clean, high-temperature hot air, thereby replacing the traditional indirect heating mode of "boiler-steam-heat exchange" and improving thermal efficiency from the source. This system includes a waste heat recovery subsystem to achieve closed-loop energy utilization. For example... Figure 1A , Figure 1C and Figure 2 As shown, the system includes a dedicated insulated pipe, whose inlet end is connected to the exhaust gas outlet of the cooling zone 1.3, and whose outlet end is connected to the preheating zone air inlet 2.6 of the preheating zone hot air unit 2. A cyclone dust collector 4 is connected in series on this waste heat recovery pipe to pre-remove dust from the low-temperature exhaust gas from the cooling zone, preventing dust from entering the preheating zone. Figure 6 As shown, the cyclone dust collector 4 includes a housing 4.1, on which a cyclone dust collector inlet 4.2 and a cyclone dust collector outlet 4.4 are provided, and at the bottom a cyclone dust collector discharge outlet 4.3 is provided. The purified low-temperature waste heat (temperature approximately 55-60℃) is transported to the preheating zone for reuse under the drive of the induced draft fan 8. In the drying zone 1.2, this system also includes an internal circulation dust removal subsystem. This system draws a portion of the high-temperature, low-humidity exhaust gas from the drying zone outlet and sends it to a cage-type dust collector 5 for primary deep purification. See [link / reference] Figure 3A and Figure 3B The cage dust collector 5 includes a shell 5.1, on which are provided a cage dust collector inlet 5.2 and a cage dust collector outlet 5.4. Internally, it has a rotatable cage-shaped filter mechanism 5.7 and a fixed dust removal mechanism 5.6. Externally, it is connected to a dust collection mechanism 5.8 driven by a dust collection fan 9 to achieve continuous online dust removal. The purified gas can be further purified by a second-stage cyclone dust collector 4 (or another independent cyclone dust collection unit). The clean, high-temperature gas after two-stage dust removal (comprehensive efficiency greater than 99%) is sent back to the air inlet mixing section of the drying zone 1.2 by a circulating fan (not shown in the figure), realizing a closed-loop circulation of hot air within the zone. The circulating air volume is precisely controlled by a proportional regulating valve (usually maintained at 90%-96%) to minimize the direct emission of high-calorific-value heat energy. In addition, the system also includes an exhaust fan 6 for discharging high-humidity exhaust gas from the preheating zone, and a cooling fan 7 for supplying cooling air to the cooling zone. It should be noted that the diameter of the cyclone dust collector 4, the size of the air inlet 4.2, and the air outlet 4.4 depend on the required air volume of the system and can be designed and selected according to actual process requirements. Similarly, the power and specifications of the low-NOx burner built into the hot air unit 3 in the drying zone are determined by the total heat load required by the drying process and are configurable. The working principle and energy-saving control process of this system are as follows, combined with... Figure 2 The system flowchart shown below illustrates the following: System initialization and preheating: After startup, wet materials enter the preheating zone 1.1. The intelligent control system first maximizes the use of heat provided by the waste heat recovery subsystem. The controller compares the heat required by the preheating zone with the available waste heat in real time, and dynamically adjusts the power of the induced draft fan 8 and the heat replenishment valve of the preheating zone hot air unit 2, executing a "waste heat priority, on-demand heat replenishment" strategy. The low-temperature, high-humidity exhaust gas generated during preheating is discharged by the exhaust fan 6. Main Drying and Internal Circulation: Material enters drying zone 1.2. The hot air unit 3 in the drying zone starts, providing high-temperature hot air. Simultaneously, the internal circulation dust removal subsystem starts, purifying and recycling most of the waste gas. The intelligent controller monitors the humidity of the circulating airflow in real time. By adjusting the opening of the circulating air proportional valve and the dehumidification valve, the circulating air ratio is maintained at the optimal point while ensuring the required dehumidification amount for the drying process. This achieves a highly efficient drying mode of "primarily high-temperature, low-humidity air internal circulation, supplemented by minimizing dehumidification loss." Cooling and Waste Heat Recovery: Dry materials enter the cooling zone 1.3 and are cooled by ambient air supplied by the cooling fan 7. Simultaneously, the air is heated, becoming low-temperature waste heat. This waste heat, after initial dust removal by the cyclone dust collector 4, is drawn in by the induced draft fan 8 and enters the pipeline of the waste heat recovery subsystem, completing a full closed loop of thermal energy production. The entire process described above is integrated and coordinated by a central intelligent control system (such as a PLC). The system collects real-time signals such as temperature, pressure, and humidity through a sensor network distributed in each temperature control zone, runs advanced control algorithms, and synchronously and dynamically coordinates and controls all actuators, including the heating power of the hot air unit 3 in the drying zone, the heat replenishment of the hot air unit 2 in the preheating zone, the independent air valves in each zone, the waste heat recovery valves, the internal circulation proportional valves, and the dehumidification valves, so that the entire system always operates adaptively and stably along the path of optimal global energy efficiency. The fluidized bed drying system provided in this embodiment achieves systematic and maximized energy utilization through the organic integration of the aforementioned "zoned tiered heating, low-temperature waste heat closed-loop recovery, high-temperature hot air efficient internal circulation," and intelligent collaborative control. Practical applications show that the system's overall energy saving rate can reach over 40%, the temperature field uniformity within the bed can be controlled within ±2℃, the moisture content of the dried material can be stably reduced from ≤3% to ≤0.05%, and it possesses excellent long-term operational reliability due to its efficient dust removal design. The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above description is only a specific embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A fluidized bed drying system for salt production, characterized in that, include: The fluidized bed body (1) is divided into multiple sequentially connected temperature control zones along the material flow direction. The temperature control zones include at least a preheating zone (1.1), a drying zone (1.2), and a cooling zone (1.3). The main hot air generator (3) is used to provide high-temperature hot air to the drying zone (1.2); The waste heat recovery subsystem is provided with a recovery pipeline connecting the outlet of the cooling zone (1.3) and the inlet of the preheating zone (1.1) for recovering the waste gas generated in the cooling zone (1.3) and transporting it to the preheating zone (1.1). An internal circulation and dust removal subsystem is installed in the drying zone (1.2) to draw out a portion of the exhaust gas from the outlet of the drying zone (1.2), and after dust removal and purification, return it to the drying zone (1.2) for recycling. The intelligent control subsystem is connected to the sensors installed in each temperature control zone, the main hot air generator (3), the waste heat recovery subsystem, and the internal circulation and dust removal subsystem. It is used to coordinate the operation of each subsystem according to the process parameters in order to achieve system energy efficiency optimization.

2. The fluidized bed drying system according to claim 1, characterized in that, The main hot air generating device (3) is a direct-fired hot air unit.

3. The fluidized bed drying system according to claim 1 or 2, characterized in that, The multiple temperature control zones include a first preheating zone, a second preheating zone, a first drying zone, a second drying zone, and a cooling zone (1.3), and each temperature control zone is equipped with an independent airflow adjustment mechanism.

4. The fluidized bed drying system according to claim 1, characterized in that, The waste heat recovery subsystem is equipped with a dust collector (4) on its recovery pipeline.

5. The fluidized bed drying system according to claim 1, characterized in that, The internal circulation and dust removal subsystem includes at least two stages of dust collectors arranged in series.

6. The fluidized bed drying system according to claim 5, characterized in that, The at least two-stage dust collector includes a cage dust collector (5) as the first stage and a cyclone dust collector (4) as the second stage.

7. The fluidized bed drying system according to claim 1, characterized in that, The intelligent control subsystem is configured to execute the following control strategies: prioritize the use of heat delivered by the waste heat recovery subsystem, and initiate supplementary heating when it is insufficient; and adjust the circulating air ratio of the internal circulation and dust removal subsystems.

8. The fluidized bed drying system according to claim 7, characterized in that, The intelligent control subsystem is also configured to: execute a cold preheating procedure when the system starts up; dynamically set the process parameters of each temperature control zone according to the initial moisture content of the material; and execute an orderly shutdown procedure when the system stops to utilize the residual heat of the system.

9. A fluidized bed drying method, applied to a fluidized bed drying system as described in any one of claims 1 to 8, characterized in that, Includes the following steps: The material is processed sequentially through the preheating zone (1.1), the drying zone (1.2), and the cooling zone (1.3); The exhaust gas discharged from the cooling zone (1.3) is recovered and transported to the preheating zone (1.1) as a heat source; After dust removal and purification, part of the exhaust gas discharged from the drying zone (1.2) is reintroduced into the drying zone (1.2) to participate in the circulation. The intelligent control subsystem collects system operating parameters and coordinates the heat supply, air volume distribution, and waste heat recovery ratio of each zone to optimize system energy efficiency.

10. The fluidized bed drying method according to claim 9, characterized in that, The step of "recovering the exhaust gas discharged from the cooling zone (1.3)" includes dust removal and purification treatment of the exhaust gas; And / or, the “coordinated adjustment” step includes implementing a “waste heat priority, on-demand heat supplementation” strategy, that is, calculating the required heat power and available heat power of the preheating zone (1.1) in real time, and starting and adjusting the heat supplementation only when the waste heat is insufficient.

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