Citric acid concentration evaporation crystallization drying device

Abstract

The utility model discloses a kind of citric acid concentration evaporation crystallization drying devices, including citric acid pre-concentration tank, the inlet of citric acid pre-concentration tank is connected with the outlet of pre-concentration three-effect discharge pump, the outlet of citric acid pre-concentration tank is connected with the top feed inlet of one effect falling film evaporator by citric acid pre-concentration feed pump;Steam pipeline is connected with the inlet of steam jet pump by regulating valve, the outlet of steam jet pump is connected with the shell side inlet of one effect falling film evaporator;The lower portion of one effect falling film evaporator is communicated with one effect separator, and the bottom outlet of both is jointly connected the inlet of one effect discharge pump;The outlet of one effect discharge pump is connected with the top feed inlet of two effect falling film evaporator;The top outlet of one effect separator is connected with the suction port of steam jet pump and the shell side inlet of two effect falling film evaporator simultaneously.The device can improve product crystallization efficiency, shorten production cycle;Crystalline granularity is more uniform, high purity, and steam consumption is lower.

Description

Technical Field

[0001] This utility model relates to a citric acid production apparatus, and more particularly to a citric acid concentration, evaporation, crystallization and drying apparatus, belonging to the technical field of citric acid production equipment. Background Technology

[0002] In the industrial production process of citric acid, evaporation and crystallization is the core link between purification and finished product. Its technical level directly determines product quality, production efficiency and overall cost, and has an irreplaceable impact on the competitiveness of the entire industrial chain.

[0003] In terms of production efficiency and capacity, evaporation crystallization accounts for 30% to 40% of the entire citric acid production cycle, and its rate directly restricts the scale of output for enterprises. With the expansion of the citric acid industry and the increasing market demands for product quality, the drawbacks of this traditional crystallization process are becoming increasingly apparent. From an efficiency perspective, single-effect and double-effect crystallization largely rely on simple steam heating and evaporation, which limits heat transfer and mass diffusion rates, resulting in low crystallization efficiency and making it difficult to meet the rapidly growing market demand.

[0004] In terms of product quality, traditional processes struggle to precisely control key parameters such as temperature and supersaturation during crystallization. If supersaturation rises rapidly in the early stages of crystallization, a large number of crystal nuclei will form, resulting in fine and uneven crystal particles. In subsequent processes such as centrifugation and drying, these small crystal particles are prone to agglomeration and loss, reducing product purity.

[0005] Energy cost control is another important aspect of the value of evaporation crystallization. Currently, citric acid plants mostly use single-effect and double-effect crystallization processes in their evaporation crystallization operations. In single-effect crystallization, steam can only be used once, with a large amount of waste heat being directly emitted into the environment, resulting in a heat utilization rate of less than 30%. Although double-effect crystallization reuses steam, its heat recovery efficiency is still not ideal. With continuously rising energy costs, high steam consumption significantly compresses corporate profit margins. While single-effect and double-effect crystallization processes are characterized by simple equipment and low maintenance costs, they still have significant drawbacks: low product crystallization efficiency, long production cycles, uneven crystal particle size, and low purity; and high steam consumption.

[0006] Patent CN110960874B discloses "a citric acid evaporation, concentration, and crystallization apparatus and method". This technical solution uses live steam to heat citric acid solution and employs steam ejection technology, MVR evaporation technology, and single-effect crystallization to evaporate and crystallize citric acid. Although it saves some steam, the system operates stably, and has high thermal efficiency, it has the following drawbacks: First, MVR evaporation technology has high power consumption, which will increase production costs; second, it uses live steam as the heat source for heating, which results in relatively high steam consumption compared to waste heat evaporation.

[0007] Citric acid crystals are either monohydrate or anhydrous citric acid. During hot air drying, fine crystalline dust is generated due to airflow. This dust not only affects the production environment but also poses multiple hazards. Citric acid crystal dust is irritating; contact with skin or mucous membranes can cause allergies or corrosion, and long-term inhalation may damage the respiratory mucosa. Dust released into the atmosphere can cause localized air pollution, especially forming "acid mist" or dust deposition around the factory area, impacting the ecological environment. Citric acid dust is flammable (particles <75μm may explode upon contact with an open flame), and dust accumulation may cause short circuits or mechanical failures in equipment. Dust release can lead to cross-contamination in the workshop (such as raw material dust mixing with finished products), reducing the purity of citric acid and affecting product grade.

[0008] To control dust hazards, various dust removal methods have been tried in citric acid production. Traditional dry dust removal technologies, such as cyclone dust collectors and bag filters, separate dust through centrifugal force or filter media. However, citric acid is hygroscopic, and the drying exhaust gas collection device is prone to absorbing moisture, causing citric acid to stick to the side walls of the cyclone separator and the filter bags, resulting in material accumulation and affecting the dust removal effect.

[0009] Chinese patent CN220801971U discloses a "drying device for citric acid," comprising a feeding system, a condensation system, a stirring and drying device, an air inlet system, and a collection system. The collection system includes a discharge pipe connected to a cyclone separator and a dust collector bag. The other end of the discharge pipe is connected to an induced draft fan. The discharge ports of the cyclone separator and the dust collector bag are connected to a collection box through the collection pipe, enabling multi-stage recycling of the finished product and reducing environmental pollution caused by dust. The drawback of this technical solution is that it does not consider that citric acid is hygroscopic, causing it to adhere to the side wall of the cyclone separator and the filter bag, leading to filter bag blockage and requiring frequent shutdowns for cleaning, severely impacting production continuity. Furthermore, the acidity of citric acid slowly corrodes the filter bag, shortening its service life and resulting in extremely high maintenance costs.

[0010] In conclusion, to save steam consumption and ensure product quality, the combination of waste heat pre-concentration and live steam falling film evaporation crystallization is of great significance. To control the dust hazards of citric acid, there is an urgent need to develop a new dust removal system to achieve dust recovery and meet emission standards. Utility Model Content

[0011] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, and such simplifications or omissions should not be construed as limiting the scope of the present invention.

[0012] In view of the problems existing in the above and / or prior art, this utility model is proposed.

[0013] The purpose of this invention is to overcome the problems existing in the prior art and provide a citric acid concentration, evaporation, crystallization and drying device that can improve product crystallization efficiency, shorten the production cycle, achieve more uniform crystal particle size and higher purity, and reduce steam consumption.

[0014] To solve the above technical problems, this utility model provides a citric acid concentration, evaporation, crystallization and drying device, including a citric acid pre-concentration tank 1601. The inlet of the citric acid pre-concentration tank 1601 is connected to the outlet of the pre-concentration triple-effect discharge pump 421, and the outlet of the citric acid pre-concentration tank 1601 is connected to the top inlet of a single-effect falling film evaporator 1603 through a citric acid pre-concentration feed pump 1602. Steam pipe G05 is connected to the inlet of steam jet pump 1600 via a regulating valve, and the outlet of steam jet pump 1600 is connected to the shell-side inlet of the first-effect falling film evaporator 1603. The lower part of the first-effect falling film evaporator 1603 is connected to the first-effect separator 1604, and the bottom outlets of both are connected to the inlet of the first-effect discharge pump 1605; the outlet of the first-effect discharge pump 1605 is connected to the top inlet of the second-effect falling film evaporator 1606; the top outlet of the first-effect separator 1604 is simultaneously connected to the suction port of the steam jet pump 1600 and the shell-side inlet of the second-effect falling film evaporator 1606.

[0015] Furthermore, the lower part of the double-effect falling film evaporator 1606 is connected to the double-effect separator 1607, and the bottom outlets of both are connected to the feed inlet of the crystallizer 1610 through the double-effect discharge pump 1608. The bottom outlet of the crystallizer 1610 is connected to the circulating liquid inlet of the crystallizer 1610 via a forced circulation pump 1611 and a forced evaporator 1609. The top outlet of the double-effect separator 1607 is connected to the shell-side inlet of the forced evaporator 1609; the top outlet of the crystallizer 1610 is equipped with a crystallizer discharge density sensor DT-1610 and is connected to the citric acid crystal slurry output pipe G23 through the discharge pump 1612.

[0016] Furthermore, the top outlet of the crystallizer 1610 is also connected to the shell-side air inlet of the surface condenser 1613, and the shell-side condensate outlet of the surface condenser 1613 is connected to the condensate tank 412 through the condensate return pipe G16.

[0017] Furthermore, the outlet of the citric acid crystal slurry output pipe G23 is connected to the inlet of the feed distribution tank 1701, the outlet of the feed distribution tank 1701 is connected to the inlet of the top-rotating centrifuge 1702, the bottom outlet of the top-rotating centrifuge 1702 is provided with a discharge auger 1703, the outlet of the discharge auger 1703 is equipped with a vibrating conveyor 1704, the outlet of the vibrating conveyor 1704 is connected to the feed inlet of the vibrating fluidized bed 1705; the discharge outlet of the vibrating fluidized bed 1705 is connected to the inlet of the gyratory screen 1709, the undersize outlet of the gyratory screen 1709 is connected to the inlet of the finished product buffer silo 1710, and the outlet of the finished product buffer silo 1710 is connected to the inlet of the packaging scale 1711.

[0018] Furthermore, the outlet of the gyratory screen 1709 is connected to the inlet of the remelting tank 1718, the outlet of the pre-concentration condensate pump 424 is connected to the slurry water inlet of the remelting tank 1718 through the condensate supply pipe G15, and the bottom outlet of the remelting tank 1718 is connected to the reflux port of the citric acid pre-concentration tank 1601 through the centrifugal pump 1719.

[0019] Furthermore, the outlet of the first air filter 1712 is connected to the air inlet of the finned heat exchanger 1713, and the air outlet of the finned heat exchanger 1713 is connected to the air inlet of the drying section of the vibrating fluidized bed 1705 through the blower 1714; the outlet of the second air filter 1715 is connected to the air inlet of the rotary dehumidifier 1716, and the air outlet of the rotary dehumidifier 1716 is connected to the air inlet of the cooling section of the vibrating fluidized bed 1705 through the cooling fan 1717.

[0020] Furthermore, the exhaust port of the vibrating fluidized bed 1705 is connected to the inlet of the self-excited hydraulic dust collector 1706, the outlet of the self-excited hydraulic dust collector 1706 is connected to the lower air inlet of the two-flow air-water film dust collector 1707, and the top air outlet of the two-flow air-water film dust collector 1707 is vented to the atmosphere through the induced draft fan 1708; the compressed air inlet of the two-flow air-water film dust collector 1707 is connected to the compressed air pipe G25, and the spray water inlet of the two-flow air-water film dust collector 1707 is connected to the RO water pipe G41.

[0021] Compared with the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following: 1. Citric acid evaporation and crystallization account for 40% to 50% of the total energy consumption in citric acid production, with steam consumption being particularly prominent. The heat utilization rate of single-effect crystallization is less than 30%. This device, based on the pre-concentration of waste heat, adopts live steam falling film evaporation and crystallization, which can reduce steam consumption, enhance waste heat recovery, and increase the heat utilization rate to over 60%; the steam consumption per ton of product is reduced by 0.5 to 1.2 tons, which not only controls production costs but also meets the requirements of process stability.

[0022] 2. This device adopts a combination of falling film concentration evaporation and single-effect crystallization, which can improve crystallization efficiency and product purity, and shorten the production cycle.

[0023] 3. Evaporation and crystallization utilize the condensate generated from live steam for washing and filtration in a vacuum belt filter, thus achieving condensate recycling.

[0024] 4. The citric acid drying process employs a dual wet dust removal system. Self-excited pretreatment mitigates the risk of coarse dust blockage, while a two-stage gas flow system addresses fine dust escape and water film instability, ultimately achieving ultra-clean emissions and stable operation. This system is particularly advantageous for scenarios involving multi-particle-size, high-humidity, and easily hygroscopic dust, such as citric acid drying. It meets stringent environmental standards, increases product recovery rates, and further enhances production output. It not only reduces environmental pollution but also allows for the recycling of collected dust, increasing product recovery rates. Furthermore, the equipment boasts low operating costs, convenient maintenance, and reduced production costs, improving the company's economic efficiency and achieving a win-win situation for both environmental and economic benefits. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The drawings are provided for reference and illustration only and are not intended to limit this utility model. Wherein: Figure 1 This is a flowchart of the drying and pre-concentration evaporation crystallization unit in this utility model; Figure 2 This is a flowchart of the concentration, evaporation, and crystallization unit in this invention; Reference numerals: condensate tank 412; pre-concentrated triple-effect discharge pump 421; pre-concentrated condensate pump 424; Steam jet pump 1600; Citric acid pre-concentration tank 1601; Citric acid pre-concentration feed pump 1602; Single-effect falling film evaporator 1603; Single-effect separator 1604; Single-effect discharge pump 1605; Double-effect falling film evaporator 1606; Double-effect separator 1607; Double-effect discharge pump 1608; Forced evaporator 1609; Crystallizer 1610; Crystallizer discharge density sensor DT-1610; Forced circulation pump 1611; Citric acid crystal slurry discharge pump 1612; Surface condenser 1613; Vacuum pump 1614. Feeding and distributing trough 1701; Top-rotating centrifuge 1702; Discharge auger 1703; Vibrating conveyor 1704; Vibrating fluidized bed 1705; Self-excited hydraulic dust collector 1706; Two-stage air-water film dust collector 1707; Exhaust fan 1708; Gyratory screen 1709; Finished product buffer silo 1710; Packing scale 1711; First air filter 1712; Finned heat exchanger 1713; Blower 1714; Second air filter 1715; Rotary dehumidifier 1716; Cooling fan 1717; Remelting tank 1718; Centrifugal pump 1719; Steam pipe G05; condensate supply pipe G15; condensate return pipe G16; citric acid pre-concentrated liquid output pipe G18; circulating water supply pipe G19; circulating water return pipe G20; citric acid crystal slurry output pipe G23; compressed air pipe G25; RO water pipe G41; chilled water pipe G42. Detailed Implementation

[0026] In the following description of this utility model, the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not mean that the device must have a specific orientation.

[0027] To make the technical means, creative features, achieved objectives and effects of this utility model easier to understand, the present utility model will be further described below with reference to specific illustrations. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0029] like Figure 1 As shown, in the citric acid concentration, evaporation, crystallization and drying device of this utility model, the outlet of the pre-concentration triple-effect discharge pump 421 is connected to the inlet of the citric acid pre-concentration tank 1601 through the citric acid pre-concentration liquid output pipe G18, the outlet of the citric acid pre-concentration tank 1601 is connected to the inlet of the citric acid pre-concentration feed pump 1602, and the outlet of the citric acid pre-concentration feed pump 1602 is connected to the top feed port of the single-effect falling film evaporator 1603.

[0030] Steam pipe G05 is connected to the inlet of steam jet pump 1600 via a regulating valve. The outlet of steam jet pump 1600 is connected to the shell-side inlet of first-effect falling film evaporator 1603. The lower part of first-effect falling film evaporator 1603 is connected to first-effect separator 1604. The bottom outlets of first-effect falling film evaporator 1603 and first-effect separator 1604 are connected to the inlet of first-effect discharge pump 1605. The outlet of first-effect discharge pump 1605 is connected to the top feed port of second-effect falling film evaporator 1606.

[0031] The top outlet of the first-effect separator 1604 is connected to the suction port of the steam jet pump 1600 and the shell-side inlet of the second-effect falling film evaporator 1606. The lower part of the second-effect falling film evaporator 1606 is connected to the second-effect separator 1607. The bottom outlets of the second-effect falling film evaporator 1606 and the second-effect separator 1607 are connected to the inlet of the second-effect discharge pump 1608. The outlet of the second-effect discharge pump 1608 is connected to the feed port of the crystallizer 1610. The bottom outlet of the crystallizer 1610 is connected to the inlet of the forced circulation pump 1611. The outlet of the forced circulation pump 1611 is connected to the lower tube-side inlet of the forced evaporator 1609. The upper tube-side outlet of the forced evaporator 1609 is connected to the circulating liquid inlet of the crystallizer 1610. The top outlet of the second-effect separator 1607 is connected to the shell-side inlet of the forced evaporator 1609.

[0032] The top outlet of the crystallizer 1610 is equipped with a crystallizer discharge density sensor DT-1610 and is also connected to the inlet of the citric acid slurry discharge pump 1612. The outlet of the citric acid slurry discharge pump 1612 is connected to the feed distribution tank 1701 of the citric acid drying unit through the citric acid slurry output pipe G23.

[0033] The top outlet of the crystallizer 1610 is connected to the shell-side air inlet of the surface condenser 1613. The shell-side exhaust port of the surface condenser 1613 is vented to the atmosphere via a vacuum pump 1614. The tube side of the surface condenser 1613 is connected to circulating cooling water. The shell-side condensate outlet of the surface condenser 1613 is connected to the condensate tank 412 via a condensate return pipe G16. The tube-side inlet of the surface condenser 1613 is connected to the circulating water supply pipe G19, and the tube-side outlet of the surface condenser 1613 is connected to the circulating water return pipe G20.

[0034] The working principle of the citric acid falling film concentration evaporation and crystallization unit is as follows: To reduce steam consumption and improve product purity and crystallinity, citric acid falling film concentration evaporation and crystallization adopts multi-effect falling film evaporation + single-effect evaporation crystallization.

[0035] After pre-concentration, citric acid is pumped into the citric acid pre-concentration tank 1601 via the pre-concentration triple-effect discharge pump 421 and the citric acid pre-concentrated liquid output pipe G18. Then, it is fed into the distributor at the top of the single-effect falling film evaporator 1603 by the citric acid pre-concentration feed pump 1602. The distributor then evenly distributes the material to each heating tube, allowing it to flow downwards uniformly to form a thin film. A heating medium is introduced through the outside of the heating tubes, and heat is transferred through the tube walls to the liquid film inside the tubes, causing the water in the liquid film to rapidly heat to its boiling point and evaporate. The resulting secondary steam flows downwards in parallel with the liquid film. During this process, the liquid film is continuously concentrated, and its concentration gradually increases. The concentrated liquid and secondary steam enter the first-effect separator 1604 together to separate the secondary steam from the concentrated liquid. The generated secondary steam serves as the heat source for the second-effect falling film evaporator 1606. The first-effect concentrated liquid is then pumped into the second-effect falling film evaporator 1606 for further falling film concentration via the first-effect discharge pump 1605. The concentrated liquid and secondary steam then enter the second-effect separator 1607 together to separate the secondary steam from the concentrated liquid. The generated secondary steam serves as the heat source for the forced evaporator 1609. At this point, the concentrated liquid is concentrated to near saturation and is then pumped into the crystallizer 1610 via the second-effect discharge pump 1608 to begin evaporation and crystallization.

[0036] The nearly saturated citric acid concentrate enters the crystallizer 1610 for evaporation and crystallization. Then, it is pumped into the forced evaporator 1609 by the forced circulation pump 1611. The material is fed from the bottom and discharged from the top, ensuring full contact with the heat source outside the heating tube. It is concentrated to a saturated state. The liquid and secondary steam enter the crystallizer 1610 together. Under the vacuum created by the vacuum pump 1614, the saturated citric acid solution is further evaporated, becoming a supersaturated solution. Crystals precipitate out, and the secondary steam is separated from the citric acid solution containing crystals. The secondary steam enters the surface condenser 1613, where it is condensed into condensate by circulating water and discharged into the condensate tank 412.

[0037] The material coming out of crystallizer 1610 is detected by density sensor DT-1610. When it reaches a certain density, it is pumped to the citric acid drying section by citric acid slurry discharge pump 1612. A portion of it is pumped into forced evaporator 1609 by forced circulation pump 1611 to mix with new material and continue to evaporate and crystallize.

[0038] The heat source for falling film concentration evaporation and crystallization is live steam. To reduce steam consumption, a steam jet pump 1600 is used to recover the secondary steam from the first-effect separator 1604. A small amount of high-pressure saturated steam at 0.6 MPa is used as power to draw in and mix the low-pressure secondary steam from the first-effect separator 1604 within the steam jet pump 1600. The pressure of the mixed steam is then increased to the required process pressure through a diffuser and injected into the shell of the first-effect falling film evaporator 1603 as its heat source.

[0039] After heat exchange with the material in the first-effect falling film evaporator 1603, part of the secondary steam generated by the first-effect separator 1604 is drawn into the steam jet pump 1600, while the other part enters the shell of the second-effect falling film evaporator 1606 as a heat source for the second-effect falling film evaporator 1606. Then, the secondary steam generated by the second-effect separator 1607 is used as a heat source for the forced evaporator 1609 for evaporation and crystallization. The secondary steam generated by the crystallizer 1610 exchanges heat with the circulating water in the surface condenser 1613 and condenses into condensate water, which is discharged into the condensate tank 412 through the condensate water return pipe G16 for subsequent calcium salt purification and filter cake washing.

[0040] like Figure 2 As shown, the outlet of the citric acid slurry discharge pump 1612 is connected to the inlet of the feed distribution tank 1701 through the citric acid slurry output pipe G23. The outlet of the feed distribution tank 1701 is connected to the inlet of the top-rotating centrifuge 1702. A discharge auger 1703 is installed at the bottom outlet of the top-rotating centrifuge 1702. A vibrating conveyor 1704 is installed at the outlet of the discharge auger 1703. The outlet of the vibrating conveyor 1704 is connected to the feed inlet of the vibrating fluidized bed 1705.

[0041] The outlet of the first air filter 1712 is connected to the air inlet of the finned heat exchanger 1713, and the air outlet of the finned heat exchanger 1713 is connected to the air inlet of the drying section of the vibrating fluidized bed 1705 via a blower 1714. The steam pipe G05 is connected to the steam inlet of the finned heat exchanger 1713, and the condensate from the finned heat exchanger 1713 is discharged into the condensate tank 412 via the condensate return pipe G16.

[0042] The outlet of the second air filter 1715 is connected to the air inlet of the rotary dehumidifier 1716. The air outlet of the rotary dehumidifier 1716 is connected to the air inlet of the cooling section of the vibrating fluidized bed 1705 via the cooling fan 1717. The steam pipe G05 is connected to the steam inlet of the rotary dehumidifier 1716 via a steam regulating valve, which is interlocked with the outlet temperature of the rotary dehumidifier 1716. The chilled water pipe G42 is connected to the chilled water inlet of the rotary dehumidifier 1716.

[0043] The discharge port of the vibrating fluidized bed 1705 is connected to the inlet of the gyratory screen 1709. The oversize outlet of the gyratory screen 1709 is connected to the inlet of the remelting tank 1718. The outlet of the pre-concentration condensate pump 424 is connected to the slurry inlet of the remelting tank 1718 via the condensate supply pipe G15. The bottom outlet of the remelting tank 1718 is connected to the reflux port of the citric acid pre-concentration tank 1601 via the centrifugal pump 1719. The undersize outlet of the gyratory screen 1709 is connected to the inlet of the finished product buffer silo 1710. The outlet of the finished product buffer silo 1710 is connected to the inlet of the packing scale 1711.

[0044] The exhaust port of the vibrating fluidized bed 1705 is connected to the inlet of the self-excited hydraulic dust collector 1706, the outlet of the self-excited hydraulic dust collector 1706 is connected to the lower air inlet of the two-flow air-water film dust collector 1707, and the top air outlet of the two-flow air-water film dust collector 1707 is vented to the atmosphere through the induced draft fan 1708.

[0045] The compressed air inlet of the two-flow air-water film dust collector 1707 is connected to the compressed air pipe G25, and the spray water inlet of the two-flow air-water film dust collector 1707 is connected to the RO water pipe G41.

[0046] The citric acid crystal solution after evaporation and crystallization contains a small amount of mother liquor. It is pumped into the feed distribution tank 1701 at a certain flow rate by the citric acid crystal slurry discharge pump 1612, and then centrifuged by the upward centrifuge 1702. The separated crystals are transported to the vibrating fluidized bed 1705 for drying by the discharge auger 1703 and the vibrating conveyor 1704.

[0047] The vibrating fluidized bed is divided into two parts: drying and cooling. In the drying section, hot air generated from the exchange of heat between outside air filtered by the first air filter 1712 and the steam-introduced finned heat exchanger 1713 is blown into the drying section of the vibrating fluidized bed 1705 by a blower 1714. The hot air contacts the citric acid crystals, converting the moisture in the crystals into hot gas, which is then discharged by the dust removal system. In the cooling section, cold air filtered by the second air filter 1715 and dehumidified by a rotary dehumidifier 1716 is blown into the cooling section of the vibrating fluidized bed 1705 by a cooling fan 1717. The dried citric acid crystals move forward with the vibration of the fluidized bed and enter the cooling section of the vibrating fluidized bed 1705. After contacting the cold air, they are cooled and discharged into a gyratory screen 1709 for sieving and separation. The unqualified products after sieving enter a remelting tank 1718, where water is added to dissolve them. Then, they are pumped by a centrifugal pump 1719 to a citric acid pre-concentration tank 1601 for further evaporation, concentration, and crystallization. The screened finished product enters the finished product buffer chamber 1710, waiting to be packaged into products by the packaging scale 1711.

[0048] Because citric acid crystals easily generate dust during the drying process, many citric acid plants currently use dry dust removal methods, namely cyclone separators and bag filters, to collect dust. However, citric acid is hygroscopic, and the drying exhaust gas collection device is prone to absorbing moisture, causing citric acid to stick to the side wall of the cyclone separator and the filter bag, resulting in material accumulation and affecting the dust removal effect.

[0049] Citric acid dust is highly hygroscopic and slightly acidic, so the dust removal system needs to consider preventing clogging and corrosion. This system adopts a dual wet dust removal method, consisting of a self-excited hydraulic dust collector 1706 and a two-flow air-water film dust collector 1707.

[0050] First-stage dust removal: Dust-laden gas first enters the self-excited dust collector 1706 for preliminary purification. The self-excited hydraulic dust collector is a wet dust removal device that utilizes the full contact between water and dust-laden gas to capture dust particles and purify the gas. The working process includes the following key steps: Dust-laden gas enters through the dust collector's inlet and, guided by the flow guiding device, rushes downwards towards the water surface, creating a strong impact. At this time, some larger dust particles will directly fall into the water due to inertia and be captured. Simultaneously, the gas impact on the water surface will agitate a large amount of water splashes and mist, forming an atomized zone filled with water droplets. As the dust-laden gas continues to flow upwards through this atomized zone, the fine dust particles in the gas will fully collide and contact with the water droplets and mist. Due to the adsorption effect of water, the dust particles will be adhered to the water droplets, forming dust-laden droplets. The dust-laden gas first enters the self-excited dust collector for preliminary purification. The gas, carrying a small amount of water mist, enters the next stage.

[0051] Secondary dust removal: The 1707 water film dust collector with a two-flow air device enhances purification. This device, consisting of a dual-fluid nozzle composed of compressed air and water pipes, is installed in the middle of the dust collector, spraying water as ultrafine droplets of 0.1-10μm. Powered by 0.3-0.6MPa compressed air, the water is atomized into a mist, which mixes thoroughly with the rising dust-laden gas. Fine dust particles are adsorbed by the atomized droplets, forming "dust and droplet" aggregates. Some are further intercepted by the water film, while others are separated by the top dehydration device after rising with the airflow. Compared to traditional water film dust collectors, the additional introduction of auxiliary compressed air optimizes the flow field and water film morphology within the cylinder, enhancing the gas-liquid contact area and achieving higher dust removal efficiency.

[0052] A dual wet dust removal method is employed, combining a self-excited hydraulic dust collector and a two-flow gas-water film dust collector. The dust-laden hot gas discharged from the citric acid drying equipment first enters the self-excited hydraulic dust collector for preliminary purification, removing most of the coarse dust particles and reducing the gas temperature and acidity. The purified gas, carrying a small amount of dust and water vapor, then enters the water film dust collector containing the two-flow gas device for further purification, removing the remaining fine dust particles and acidic substances. Finally, the purified gas is treated by a dehydrator at the top of the water film dust collector (containing the two-flow gas device) before being discharged in compliance with standards.

[0053] Through the above process, the graded treatment of citric acid dust is achieved. The self-excited hydraulic dust collector first efficiently removes large dust particles, reducing the processing load of the secondary gas-water film dust collector, minimizing the impact and damage of fine dust on the water film, and improving the overall system stability and reliability. The secondary gas-water film dust collector then deeply captures the remaining fine dust, ensuring that the emitted gas meets stringent environmental standards. By addressing the "risk of coarse dust blockage" through self-excited pretreatment and resolving the issues of "fine dust escape" and "water film instability" through the secondary gas device, the triple goals of "high concentration tolerance + ultra-clean emissions + stable operation" are ultimately achieved. Its advantages are particularly significant for scenarios involving multi-particle-size, high-humidity, and easily hygroscopic dust, such as citric acid drying, as it not only meets stringent environmental standards but also increases product recovery rates, further improving product yield.

[0054] The above description is merely a preferred embodiment of the present utility model, showing and describing the basic principles, main features, and advantages of the present utility model. It is not intended to limit the scope of patent protection of the present utility model. Those skilled in the art should understand that the present utility model is not limited to the above embodiments. In addition to the above embodiments, the present utility model may have other implementations without departing from the spirit and scope of the present utility model. Various changes and improvements to the present utility model are also possible. All technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by the present utility model. The scope of protection claimed by the present utility model is defined by the appended claims and their equivalents. Technical features not described in the present utility model can be implemented by or using existing technology, and will not be elaborated here.

Claims

1. A citric acid concentration, evaporation, crystallization, and drying apparatus, comprising a citric acid pre-concentration tank (1601), characterized in that: The inlet of the citric acid pre-concentration tank (1601) is connected to the outlet of the pre-concentration triple-effect discharge pump (421), and the outlet of the citric acid pre-concentration tank (1601) is connected to the top inlet of the single-effect falling film evaporator (1603) through the citric acid pre-concentration feed pump (1602). The steam pipe (G05) is connected to the inlet of the steam jet pump (1600) via a regulating valve, and the outlet of the steam jet pump (1600) is connected to the shell-side inlet of the first-effect falling film evaporator (1603). The lower part of the first-effect falling film evaporator (1603) is connected to the first-effect separator (1604), and the bottom outlets of both are connected to the inlet of the first-effect discharge pump (1605); the outlet of the first-effect discharge pump (1605) is connected to the top inlet of the second-effect falling film evaporator (1606); the top outlet of the first-effect separator (1604) is simultaneously connected to the suction port of the steam jet pump (1600) and the shell-side inlet of the second-effect falling film evaporator (1606).

2. The citric acid concentration, evaporation, crystallization, and drying apparatus according to claim 1, characterized in that: The lower part of the double-effect falling film evaporator (1606) is connected to the double-effect separator (1607), and the bottom outlets of both are connected to the feed inlet of the crystallizer (1610) through the double-effect discharge pump (1608). The bottom outlet of the crystallizer (1610) is connected to the circulating liquid inlet of the crystallizer (1610) via a forced circulation pump (1611) and a forced evaporator (1609); The top outlet of the double-effect separator (1607) is connected to the shell-side inlet of the forced evaporator (1609); the top outlet of the crystallizer (1610) is equipped with a crystallizer discharge density sensor (DT-1610) and is connected to the citric acid crystal slurry output pipe (G23) through a discharge pump (1612).

3. The citric acid concentration, evaporation, crystallization, and drying apparatus according to claim 2, characterized in that: The top outlet of the crystallizer (1610) is also connected to the shell-side air inlet of the surface condenser (1613), and the shell-side condensate outlet of the surface condenser (1613) is connected to the condensate tank (412) through the condensate return pipe (G16).

4. The citric acid concentration, evaporation, crystallization, and drying apparatus according to claim 2, characterized in that: The outlet of the citric acid crystal slurry output pipe (G23) is connected to the inlet of the feed distribution tank (1701), the outlet of the feed distribution tank (1701) is connected to the inlet of the top-rotating centrifuge (1702), the bottom outlet of the top-rotating centrifuge (1702) is provided with a discharge auger (1703), the outlet of the discharge auger (1703) is equipped with a vibrating conveyor (1704), the outlet of the vibrating conveyor (1704) is connected to the feed inlet of the vibrating fluidized bed (1705); the discharge outlet of the vibrating fluidized bed (1705) is connected to the inlet of the gyratory screen (1709), the under-screen outlet of the gyratory screen (1709) is connected to the inlet of the finished product buffer silo (1710), and the outlet of the finished product buffer silo (1710) is connected to the inlet of the packing scale (1711).

5. The citric acid concentration, evaporation, crystallization, and drying apparatus according to claim 4, characterized in that: The sieve outlet of the swing screen (1709) is connected to the inlet of the remelting tank (1718). The outlet of the pre-concentration condensate pump (424) is connected to the slurry water inlet of the remelting tank (1718) through the condensate supply pipe (G15). The bottom outlet of the remelting tank (1718) is connected to the reflux port of the citric acid pre-concentration tank (1601) through the centrifugal pump (1719).

6. The citric acid concentration, evaporation, crystallization, and drying apparatus according to claim 4, characterized in that: The outlet of the first air filter (1712) is connected to the air inlet of the finned heat exchanger (1713), and the air outlet of the finned heat exchanger (1713) is connected to the air inlet of the drying section of the vibrating fluidized bed (1705) through the blower (1714); the outlet of the second air filter (1715) is connected to the air inlet of the rotary dehumidifier (1716), and the air outlet of the rotary dehumidifier (1716) is connected to the air inlet of the cooling section of the vibrating fluidized bed (1705) through the cooling fan (1717).

7. The citric acid concentration, evaporation, crystallization, and drying apparatus according to claim 4, characterized in that: The exhaust port of the vibrating fluidized bed (1705) is connected to the inlet of the self-excited hydraulic dust collector (1706), the outlet of the self-excited hydraulic dust collector (1706) is connected to the lower air inlet of the two-flow air-water film dust collector (1707), and the top air outlet of the two-flow air-water film dust collector (1707) is vented to the atmosphere through the induced draft fan (1708); the compressed air inlet of the two-flow air-water film dust collector (1707) is connected to the compressed air pipe (G25), and the spray water inlet of the two-flow air-water film dust collector (1707) is connected to the RO water pipe (G41).

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