Drying system for high-quality crystals

Abstract

A drying system for high-quality crystals particularly relates to the technical field of drying equipment, raw materials are wet crystals obtained through treatment of raw material wet crystal pretreatment equipment, and the wet crystals sequentially pass through wet crystal coarse crushing equipment, recrystallization growing and rounding equipment, pre-drying dispersing equipment, deep drying equipment and a packaging system. A high-quality crystal product which is free of flying dust, basically free of inhalable particles, free of obvious dust adsorption on a packaging bag, higher in hardness than existing products, low in secondary crushability, good in fluidity, high in bulk density of finished products and low in moisture absorption can be obtained, and the advantages of low comprehensive operation energy consumption, low cost and the like are achieved. The production, use and operation occupational hygiene is good, the environmental protection property is good, the safety is good, and the ignition explosiveness is low.

Description

Technical Field

[0001] This utility model relates to the field of drying equipment technology, specifically a drying system for high-quality crystals. Background Technology

[0002] There are many types of crystalline materials, and the crystals come in various shapes. Crystals with an average aspect ratio greater than 3, especially greater than 5, are considered elongated crystals. Among the known amino acids alone, there are threonine, citrulline, glutamic acid, alanine, arginine, etc. There are also products from various industries such as trehalose, hydroquinone, sucralose, and succinic acid. The market volume is large and the economic value is high. The particle size varies, and they exist in salt and non-salt forms. This utility model mainly uses threonine as a typical material for demonstration and explanation. The current total output of threonine in China is nearly 1 million tons. Other amino acids and materials may also become elongated crystals depending on the crystallization conditions.

[0003] L-Threonine is an essential amino acid. It is mainly used in medicine, chemical reagents, food fortifiers, and feed additives, with its use in feed additives showing rapid growth. It is commonly added to the feed of immature piglets and poultry, and is the second limiting amino acid in pig feed and the third limiting amino acid in poultry feed. Especially after the addition of lysine to low-protein diets, threonine becomes the first limiting amino acid in growing pigs. Adding L-Threonine to compound feed has the following advantages: ① It can adjust the amino acid balance of the feed and promote the growth of livestock; ② It can improve meat quality; ③ It can improve the nutritional value of feeds with low amino acid digestibility; ④ It can reduce the cost of feed ingredients. Threonine is an important nutritional fortifier that can fortify grains, pastries, and dairy products. Like tryptophan, it has the effect of relieving fatigue and promoting growth and development. In medicine, because threonine contains hydroxyl groups, it has a water-holding effect on human skin. When combined with oligosaccharide chains, it plays an important role in protecting cell membranes and can promote phospholipid synthesis and fatty acid oxidation in vivo. Its formulation has medicinal efficacy in promoting human development and combating fatty liver, and is a component of compound amino acid infusions. Threonine is a white orthorhombic or crystalline powder, appearing as fine needles in microscopic photographs. Major domestic manufacturers include Fufeng Biotechnology, Meihua Biotechnology, and Yipin Biotechnology, among others, with varying degrees of purity.

[0004] Based on the specifications of stainless steel wire mesh, 10μm theoretically corresponds to 1600 mesh, 20μm to approximately 635 mesh, 37μm to approximately 400 mesh, and 75μm to approximately 200 mesh. Furthermore, according to standard sieves, 100μm is approximately 150 mesh, 106μm is 140 mesh, 150μm is 100 mesh, 180μm is 80 mesh, 425μm is 40 mesh, 850μm is 20 mesh, and 1mm is 18 mesh.

[0005] According to online research, dust particles commonly come in micrometer and nanometer sizes. Haze largely refers to particulate matter with a diameter of 2.5-10 micrometers suspended in the air. Of the dust in industrial environments, 5% is ultrafine dust, with a particle size less than 5 micrometers; however, this portion is the most harmful to the human body. It can be directly inhaled into the lungs, causing pulmonary fibrosis, also known as pneumoconiosis. Dust includes three components: settling dust (particle size > 100 μm, which settles relatively quickly), suspended dust (particle size 10-100 μm, which can remain suspended in the air for a long time), and inhalable particulate matter (particle size < 10 μm). Dust pollution is one of the most significant air pollutants, and in most parts of my country, it has become the primary air pollutant. Dust refers to solid particles suspended in the air. There are many names for dust, such as ash, dust, soot, mineral dust, sand, and powder, and these terms do not have clear boundaries. The International Organization for Standardization (ISO) defines suspended solids with a particle size of less than 75 μm as dust. In daily life and work, industrial dust is a major threat to human health and a primary cause of various diseases. The higher the amount of suspended dust or particulate matter in a finished threonine product, the lower its selling price. Current users hope for as little suspended dust as possible in finished threonine products, and ideally, they want inhalable particulate matter to be completely eliminated.

[0006] Currently, workplace dust concentration limits typically do not exceed 10 mg / m³ (8-hour time-weighted average concentration, TWA) for total dust concentration and 5 mg / m³ for inhalable dust concentration (PM10). Threonine dust is irritating or sensitizing, and there is a need to further reduce exposure limits. Currently, the dust emission rate measured by testing should be as low as possible, typically below 1%-5% (depending on process requirements).

[0007] For example, threonine is commonly prepared by crystallization followed by separation using a centrifuge or filter press. The main drying processes for the finished product include airflow drying, fluidized bed drying, wet extrusion granulation, and dry roller extrusion granulation. These four processes have the following drawbacks:

[0008] The combined process of primary enhanced airflow drying (average airflow velocity of 5-7 m / s within the intensifier) ​​+ primary airflow cooling (average operating airflow velocity of 10-15 m / s) results in the following: Approximately 50% of the finished product consists of particulate matter smaller than the suspended particulate matter size, and approximately 40% consists of fine dust particles smaller than the suspended particulate matter size. The inner membrane of the packaging bags adsorbs a significant amount of dust, and upon opening the bags, inhalable particulate matter is clearly visible. Workplace dust concentration limits and inhalable dust concentration values ​​are difficult to guarantee. Secondary crushing is significant, resulting in even more dust after crushing. The installed power is 380 kW, with an average steam consumption of 3.2 tons per hour and an average production capacity of 8.2 tons per hour. The average energy consumption per ton of finished product is 38 kWh of electricity and 0.39 tons of 0.6 MPa saturated steam. The intensifier requires compressed air for sealing; the amount is not statistically analyzed. The finished product has a moisture content of 0.2-0.3% and a natural bulk density of approximately 650 kg / m³. 3 In summer, clumping often occurs;

[0009] Taking crystalline threonine as an example, the finished product obtained by using a combination of enhanced airflow drying and primary airflow cooling has a high proportion of individual crystals. The individual crystals have bright surfaces, vary in length, and have a significant aspect ratio greater than 3. About half of the crystals show multiple fractures, with an average mesh size of about 150-200 mesh. About 10% of the crystals are agglomerated small particles that are grayish-white. Measurements show that these agglomerated particles contain up to 0.7% water, exceeding the overall water content. Most of the agglomerated particles are composed of small crystals smaller than 400 mesh. Crystals larger than the dust particle size mostly exist as single crystals, and the crystal fracture surfaces are relatively sharp.

[0010] Moisture absorption analysis: At 20℃ and 60-70% relative humidity, the moisture content of the finished product was approximately 1.39% after 2 hours.

[0011] Primary airflow drying (operating airflow velocity average 10-15 m / s): Approximately 60% of the finished product consists of particulate matter smaller than the suspended particulate matter size, and approximately 50% consists of fine dust particles smaller than the suspended particulate matter size. The inner membrane of the packaging bag adsorbs a significant amount of dust, and upon opening the bag, inhalable particulate matter is clearly visible. Workplace dust concentration limits and inhalable dust concentration values ​​are difficult to guarantee. Secondary crushing performance is slightly lower. The installed power is 350 kW, with an average steam consumption of 3.3 tons per hour and an average production capacity of 6.5 tons per hour. The average energy consumption parameters per ton of finished product are 43 kWh of electricity and 0.45 tons of 0.6 MPa saturated steam. The finished product moisture content is 0.15-0.3%, and the natural bulk density is approximately 650 kg / m³. 3 ;

[0012] The finished product obtained by the primary airflow drying process showed a large number of crystals broken, including in both length and diameter directions. The fracture cross-section of individual crystals was more angular and irregular. There were no gray-white agglomerated small particles, but the proportion of airborne dust and particulate matter increased.

[0013] Moisture absorption analysis: At 20℃ and 60-70% relative humidity, the moisture content of the finished product was approximately 1.45% after 2 hours.

[0014] Continuous internal heat exchange fluidized bed drying process: In the finished product, approximately 20-30% of the particles are smaller than the airborne dust particle size, 10-20% are smaller than the fine dust particle size, and 40-60% are smaller than 100 mesh. Dust is adsorbed on the inner membrane of the packaging bag, and inhalable particulate matter is present when the packaging bag is opened. Workplace dust concentration limits and inhalable dust concentration values ​​are much better, but ensuring compliance is still challenging. The installed power is 300KW, with an average steam consumption of approximately 1.1-1.2 tons per hour and an average production capacity of 6.5 tons / hour. The energy consumption parameters per ton of finished product are an average of 36 kWh of electricity and approximately 0.18-0.2 tons of 0.6MPa saturated steam. Imported dispersers require airtight seals, but the quantity is not statistically analyzed. The finished product has a moisture content of approximately 0.27% and a natural bulk density of approximately 600 kg / m³. 3 The compacted bulk density is approximately 700 kg / m³. 3 ;

[0015] Taking crystalline threonine as an example, the finished product obtained by continuous internal heat exchange fluidized bed drying process has obvious agglomerated small particles, larger than 40 mesh, accounting for more than 30%. Normally, these need to be screened out and crushed, resulting in more dust, broken crystals, severely uneven particle size, uneven color, and yellow particles that may have deteriorated. The final average mesh size of the finished product can be about 100-120 mesh.

[0016] Moisture absorption analysis: At 20℃ and 60-70% relative humidity, the moisture content of the finished product was approximately 1.33% after 2 hours.

[0017] Wet granulation followed by fluidized bed drying: The finished product contains virtually no suspended particulate matter, with an average particle size commonly ranging from 0.2-1.2 mm. Dust adsorption on the inner membrane of the packaging bag is minimal, and upon opening the bag, there is virtually no inhalable particulate matter. Workplace dust concentration limits and inhalable dust concentration values ​​are easily met. However, the finished product has low strength and is prone to secondary breakage. Binders, such as mother liquor, need to be added during granulation; otherwise, the finished granules are easily broken during transportation, and the broken granules exhibit severe moisture absorption. The dried material contains clumps. The granules need to be screened and crushed, which can be used in the upstream granulation process, increasing energy consumption. The installed power is 280-330KW, with an average steam consumption of about 1.5 tons per hour and an average production capacity of about 4 tons per hour. The energy consumption parameters per ton of finished product are an average of 56-66 kWh of electricity and about 0.3-0.38 tons of 0.6MPa saturated steam. With energy-saving devices, this can be reduced to 0.2-0.25 tons. The granulator requires compressed air sealing, but the quantity is not statistically analyzed. The finished product has a moisture content of about 0.3-0.4% and a natural bulk density of about 500 kg / m³. 3 The compacted bulk density is approximately 600 kg / m³. 3 .

[0018] Taking crystalline threonine as an example, the finished product obtained by wet granulation and fluidized bed drying process has a large number of fractures and breaks compared with the raw wet crystals, but less breakage in the diameter direction. Some binders such as mother liquor need to be added during granulation, otherwise the strength of the finished particles is relatively low and they are easily broken during transportation. The large size of the crystals in the particles and the difficulty in further breaking them are one of the main reasons for the looseness and high moisture absorption of the finished particles. For example, in the existing technology, the XZL rotary extrusion granulator has a granulation extrusion screen diameter of 200-350mm and a processing capacity of 40-400kg / h.

[0019] Moisture absorption analysis: At 20℃ and 60-70% relative humidity, the moisture content of the finished product was approximately 1.2% after 2 hours.

[0020] Dry granulation process: The finished product contains virtually no airborne dust particles; the average particle size is adjustable, commonly 10-60 mesh. A small amount of adsorbed dust is present on the inner film of the packaging bag, and very few inhalable particles are present upon opening the bag. Secondary crushing is present, and the amount of inhalable particles increases after crushing. The finished granules are easily crumbled by hand. Energy consumption is based on the three drying processes mentioned above, requiring the addition of dry roller extrusion granulation. The installed power is 66KW, steam consumption is 0 tons per hour, and the average capacity is 0.5 tons / hour. The energy consumption per ton of finished product is an additional average of 45-55 kWh. The dry granulator requires compressed air, the amount of which is not statistically analyzed. The finished product has a moisture content of approximately 0.3-0.5% and a natural bulk density of approximately 600 kg / m³. 3 The compacted bulk density is approximately 750 kg / m³. 3 This production line has experienced multiple fire and explosion accidents (dust flash explosions) during its market use.

[0021] Taking crystalline threonine as an example, the finished product obtained by dry granulation process consists of multiple small crystals. Compared with the raw material wet crystals, the small crystals are largely broken and no longer have long strip-shaped crystals. A large number of broken pieces between 0.007-0.027 mm were observed. Because there are still many shiny crystals in the particles and their size is relatively large, the finished particles are easily broken by hand.

[0022] Moisture absorption analysis: At 20℃ and 60-70% relative humidity, the moisture content of the finished product was approximately 1.15% after 2 hours. The statistical analysis of the finished products from the four existing processing methods is as follows:

[0023]

[0024] As can be seen, existing processes have some or all of the following drawbacks: Airflow drying and fluidized bed drying methods often fail to meet workplace dust concentration limits and inhalable dust concentration values, resulting in small average particle size in the finished product; wet granulation, while easily meeting workplace dust concentration limits and inhalable dust concentration values, suffers from low bulk density, high hygroscopicity, low particle strength, and high power and steam consumption; dry granulation can barely meet workplace dust concentration limits and inhalable dust concentration values, but suffers from increased energy consumption, fragility when squeezed, easy generation of inhalable dust, low production line output, high investment, and low particle strength in the finished product; except for wet granulation, existing processes all exhibit dust adsorption on the finished product packaging bags, sometimes even noticeably, and secondary breakage is evident in all processes except fluidized bed granulation; overall operating energy consumption is relatively high; and all processes exhibit significant hygroscopicity, with hygroscopicity decreasing in the order of airflow drying, fluidized bed drying, wet granulation, and dry granulation.

[0025] It is understood that there have been three fires and explosions in dry granulation, one fire in airflow drying, none in fluidized bed drying, and none in wet granulation. The probability of complaints about finished product agglomeration, from highest to lowest, is airflow drying, wet granulation, fluidized bed drying, and dry granulation. Utility Model Content

[0026] The purpose of this invention is to provide a high-quality crystal drying system that overcomes the defects of existing drying processes. It produces a high-quality crystal product with no flying dust, virtually no inhalable particulate matter, no obvious dust adsorption on the packaging bag, a hardness exceeding that of existing products, low secondary crushing, good flowability, high finished product bulk density, and low moisture absorption. Furthermore, it features low overall operating energy consumption, good occupational health, good environmental protection, good safety, and low flammability and explosiveness during production and operation.

[0027] The technical solution to achieve the above objective is: a drying system for high-quality crystals, the raw material being wet crystals, characterized in that: it includes a coarse crushing device, a recrystallization growth and rounding device, a pre-drying and dispersing device, and a deep drying device connected in sequence; wherein, the recrystallization growth and rounding device is used for vibratory conveying of the material.

[0028] The wet crystal coarse crushing equipment is used to crush long crystals with an aspect ratio greater than 3 into short columnar crystals with an average aspect ratio less than 3, especially wet crystal raw materials with an aspect ratio greater than 5.

[0029] During the recrystallization growth and rounding process, the material undergoes vibration conveying, which causes short columnar crystals to disperse, increasing the specific surface area. The crystal surface can partially recrystallize, thereby rounding the fracture surface of the crystal and causing small crystals smaller than the dust particle size to adhere to the surface of the short columnar crystals.

[0030] The pre-drying and dispersing equipment is used to initially dry the short columnar crystals, reducing the moisture content of the short columnar crystals to less than half that of the wet crystals; the deep drying equipment is used to further dry the short columnar crystals to achieve the required moisture content of the finished product.

[0031] This invention first uses a coarse crushing device to break slender crystals with an aspect ratio greater than 3 into short columnar crystals with an average aspect ratio less than 3. This causes dust particles smaller than the particle size to adhere to the surface of the short columnar crystals, avoiding the excessively small particle size caused by directly drying wet crystals. It also avoids the low bulk density and tendency to stick to particles that result from direct drying of slender crystals, which often fail to break or break easily. Furthermore, easy breakage leads to sharp fracture surfaces, high secondary crushing efficiency, large amounts of secondary dust, inhalable particulate matter, and easy agglomeration due to moisture absorption. Simultaneously, it aims to minimize breakage along the crystal diameter.

[0032] The recrystallization growth and rounding equipment enables the further recrystallization growth of short columnar crystals and the rounding of the fracture surfaces of short columnar crystals. This ensures that the dust adhering to the surface of the short columnar crystals is firmly attached to the crystals. After the slender crystals break, due to the increase in specific surface area, the probability of recrystallization of the residual high-concentration liquid on the crystal surface increases. Through vibration and friction, the sharp parts of the fracture surface are rounded, allowing the crystal as a whole to grow one layer through recrystallization.

[0033] Pre-drying and dispersing equipment achieves initial drying of short columnar crystals, reducing the moisture content to less than half that of wet crystals. This disperses the short columnar crystals, reducing the probability of adhesion, and allows for better recrystallization and adsorption and growth of dust particles on the crystal surface. Preferably, the pre-drying and dispersing equipment uses a vibrating fluidized bed, with the vibration force controlled to disperse large crystals, break long crystals into short columnar crystals, and prevent excessive crystal breakage. Furthermore, the slow evaporation of the crystals during the constant-rate drying stage (where the process air supplied to the pre-drying and dispersing equipment is constant-rate throughout) avoids the drawbacks of low bulk density, high moisture absorption, slow deep drying, unattractive finished products, high secondary breakage, and loose large particles in the finished product caused by crystal adhesion. It also further strengthens the adhesion of dust particles to the short columnar crystals, preventing them from becoming flyaway dust due to excessively rapid drying.

[0034] Deep drying is used to further dry short columnar crystals and meet the moisture content requirements of the finished product. A continuous internal heat exchange fluidized bed is preferred. During drying, fine particles smaller than the dust particle size are blown out of the internal heat exchange fluidized bed through air classification, meeting the particle size and dust-free requirements of the finished product and providing the granulation equipment with raw materials of the same size as dust or particulate matter. Within the internal heat exchange fluidized bed, the material particles undergo further deep drying, further fracture of the remaining long crystals, re-rounding of the crystal fracture surfaces, and exhaust of particulate matter through air classification. Finally, the material is discharged from the outlet. The discharged particulate matter is not directly returned to the internal heat exchange fluidized bed, nor is it directly returned to the feed inlet or feeding device. Dry granulation, wet granulation, or recrystallization processes can be used. The resulting product can be a standalone finished product or mixed with the high-quality finished product from the internal heat exchange fluidized bed.

[0035] Furthermore, the recrystallization growth and rounding equipment is equipped with process air inlet and outlet, which facilitates the introduction of process air. Through the slow evaporation of crystals in the initial stage of constant-speed drying (the process air introduced into the recrystallization growth and rounding equipment adopts constant-speed drying throughout the process), the function of this equipment can be better realized. It can achieve the advantages of better flowability of finished products, larger particle size of finished products, lower secondary crushing, lower secondary dust, and dust reduction due to direct growth or adhesion growth of dust through recrystallization.

[0036] Furthermore, both the pre-drying and dispersing equipment and the deep drying equipment are equipped with process air inlets and outlets. The temperature of the process air input to the pre-drying and dispersing equipment is lower than that of the process air input to the deep drying equipment, and the relative humidity of the process air input to the pre-drying and dispersing equipment is higher than that of the process air input to the deep drying equipment.

[0037] This allows the material to pass through the pre-drying and dispersing equipment with sufficient time and uniformity to achieve slow evaporation. Through the pre-drying and dispersing equipment, there is a time interval from the inlet to the outlet, which allows for the slow evaporation of moisture on the crystal surface, further recrystallization, and surface rolling and spreading. This is beneficial for the regrowth of short columnar individual crystals, avoids agglomeration into loose large particles similar to those that occur in direct fluidized bed drying, and also helps to further round out the fracture surfaces of short columnar crystals.

[0038] Furthermore, the temperature of the process air introduced into the recrystallization growth and rounding equipment is lower than that of the process air introduced into the pre-drying and dispersing equipment, and the relative humidity of the process air introduced into the recrystallization growth and rounding equipment is higher than that of the process air introduced into the pre-drying and dispersing equipment, so that the material has sufficient time to pass through the recrystallization growth and rounding equipment and passes through evenly to achieve slow evaporation.

[0039] Furthermore, compared with the process air introduced into the pre-drying and dispersing equipment, the process air introduced into the recrystallization growth and rounding equipment has a lower temperature and higher humidity, a smaller air volume and a longer transit time. Under the premise of achieving the breakage of long crystals into short columnar crystals, it can achieve better rounding function and reduce the possibility of adhesion between wet crystals.

[0040] Furthermore, the drying system also includes a granulation device, which is used to granulate materials with a particle size smaller than the dust output from the dust outlet of the pre-drying and dispersing equipment and / or the deep drying equipment. The materials with a particle size smaller than the dust output from the dust outlet of the pre-drying and dispersing equipment and the deep drying equipment are granulated by the granulation device. This granulation process, compared with the wet and dry granulation methods of the prior art, yields a second type of high-quality granular product with higher strength, lower moisture absorption, and lower secondary crushing properties. This high-quality granular product and a high-quality crystalline product of this invention can be combined as a finished product or used separately as a finished product.

[0041] Furthermore, the drying system also includes a fresh air heat exchanger. The exhaust vent of the deep drying equipment is connected to the fresh air heat exchanger, and the fresh air outlet of the fresh air heat exchanger is connected to the pre-drying and dispersing equipment and / or the deep drying equipment, so as to realize the recycling of waste heat. This greatly reduces the energy consumption of the production line, reduces the dust concentration, and reduces the odor of the exhaust gas.

[0042] Furthermore, the process air outlet of the deep drying equipment is connected to the process air inlet of the pre-drying and dispersing equipment.

[0043] The exhaust air of the deep drying equipment has the characteristics of higher temperature and humidity than the ambient air, which is conducive to the realization of the functions of the pre-drying and dispersing equipment, namely "slow evaporation, further recrystallization, surface rolling and spreading, which is conducive to the secondary growth of short columnar individual crystals, avoiding agglomeration into loose large particles, and further adhesion and firm growth of dust and concentrated crystal liquid on the surface of large crystals, directly reducing the proportion of dust in the material".

[0044] When the ambient humidity can achieve the above functions, the process air introduced into the pre-drying and dispersing equipment can be part or all of the ambient air. Preferably, the ambient air first passes through the exhaust heat exchanger configured in the deep drying equipment to achieve air-to-air heat exchange. While achieving ambient air heating and energy saving, the exhaust air of the deep drying equipment is cooled, relative humidity is increased, and dust and odor are removed, thus reducing the pressure and function of subsequent environmental protection processes.

[0045] Furthermore, the process air outlet of the deep drying equipment can also be connected to the process air inlet of the recrystallization growth and rounding equipment, which is beneficial to the realization of the functions of the recrystallization growth and rounding equipment.

[0046] Furthermore, a dispersing machine is connected between the pre-drying and dispersing equipment and the deep drying equipment. The dispersing machine is used to disperse the semi-finished product output from the pre-drying and dispersing equipment before it is fed into the deep drying equipment. This is beneficial for the dispersion of particles and prevents agglomeration. Preferably, a screening device is configured at the outlet end of the pre-drying and dispersing equipment. Large particles screened by the screening device enter the coarse crusher to reduce the possibility of excessive crushing of crystals in multiple stages.

[0047] Furthermore, the discharge port of the pre-drying and dispersing equipment is connected to a screening device. The screening device is equipped with a large particle material outlet and a non-large particle material outlet. The screening device is used to screen the output material of the pre-drying and dispersing equipment into large particles and non-large particles with a particle size smaller than that of the large particles. The large particle material outlet of the screening device is connected to a crusher, and the non-large particle material outlet is connected to a deep drying equipment. The crusher is used to crush the screened large particles, and the outlet of the crusher is connected to the deep drying equipment.

[0048] Furthermore, the drying system also includes a raw material wet crystal pretreatment device. The crystals obtained by the raw material liquid through concentration-evaporation-crystallization first pass through the raw material wet crystal pretreatment device to obtain raw material wet crystals. The feed port of the raw material wet crystal pretreatment device is equipped with a process air inlet, which is used to input process air to blow away some of the water on the crystal surface, reducing the possibility of agglomeration and powder crystal formation. The output process air will be filtered by a bag filter, the exhaust gas will be discharged into the air, and the dust will be collected and transported to the granulation equipment or recrystallization.

[0049] Furthermore, the wet crystal coarse crushing equipment and / or the recrystallization growth and rounding equipment are equipped with a crystal raw material liquid inlet to facilitate the addition of crystal raw material liquid to the material. The function is to facilitate the coarse crushing of wet crystals, the further recrystallization growth of short columnar crystals, and the rounding of the fracture surfaces of short columnar crystals. The principle is to wet the surface, coat, and apply a coating.

[0050] This invention achieves high-efficiency drying in a pre-drying and dispersing device, and further deep drying, long crystal breakage, re-rounding of crystal fracture surfaces, and dust or particulate matter discharge via air separation in a deep drying device, ultimately discharging from the outlet. Preferably, the air velocity in the pre-drying and dispersing device and the deep drying device are controlled, as well as the particle size of the discharged particles and the impact force between materials in the fluidized bed, to better achieve the purpose of this invention. Attached Figure Description

[0051] Figure 1 This is a system schematic diagram of Example 1;

[0052] Figure 2 This is a system schematic diagram of Example 2. Detailed Implementation

[0053] The embodiments of the present utility model are described in conjunction with the accompanying drawings. The described content is only a partial example and composition record, not a complete example, and is not intended to limit the scope of protection of the present utility model.

[0054] This utility model's technical solution has significantly different combination features from existing technologies in the field, and it also solves a different problem in substance. It achieves high-quality crystal production, demonstrating the inventiveness of this application. The basic technical features of this utility model are inseparable and interconnected. Current utility model creations generally focus on optimizing, expanding, and improving existing technologies, making it difficult to find fundamentally different technical points. Even common technical means, if combined to achieve outstanding technical effects and solve problems not addressed by existing technologies, then the corresponding utility model is inventive. A utility model achieving unexpected technical effects means that, compared to existing technologies, its technical effects undergo a qualitative change, resulting in new performance; or a quantitative change, exceeding people's expectations. Such qualitative or quantitative changes cannot be predicted or deduced in advance by those skilled in the art. When a utility model produces unexpected technical effects, it indicates that the utility model has significant features and that its technical solution is non-obvious, possessing prominent substantive specificity, thus demonstrating inventiveness.

[0055] like Figure 1 As shown, this utility model discloses a high-quality crystal drying system. The raw material is wet crystals. The drying system includes a coarse crushing device 2, a recrystallization growth and rounding device 3, a pre-drying and dispersing device 4, and a deep drying device 5 connected in sequence. The wet crystals are processed by the wet crystal coarse crushing device 2, recrystallization growth and rounding device 3, pre-drying and dispersing device 4, and deep drying device 5 in sequence to obtain the finished product.

[0056] The wet crystals described in this embodiment are obtained by processing the crystals obtained from the raw material liquid through concentration-evaporation-crystallization using a raw material wet crystal pretreatment device 1. The raw material wet crystal pretreatment device 1 can be, but is not limited to, a filter press or a centrifuge, for solid-liquid separation of the raw material wet crystals. The feed port of the raw material wet crystal pretreatment device 1 is equipped with a process air inlet for inputting process air to blow away some of the water on the crystal surface.

[0057] The wet crystal coarse crushing device 2 is connected to the output end of the raw material wet crystal pretreatment device 1. The wet crystal coarse crushing device 2 may be, but is not limited to, a stirring type, a blade type, a paddle type, or a stirring tooth type of mixer, blender, or crusher, and is used to crush long crystals with an aspect ratio greater than 3 into short columnar crystals with an average aspect ratio less than 3.

[0058] The recrystallization growth and rounding equipment 3 may, but is not limited to, use a vibrating conveyor or a vibrating screen to vibrate and convey the input material. Under the action of vibration, the short columnar crystals are dispersed, which increases the specific surface area. The crystal surface can partially recrystallize, thereby rounding the fracture surface of the crystal and causing small crystals below the dust particle size to adhere to the surface of the short columnar crystals.

[0059] The pre-drying and dispersing equipment 4 may, but is not limited to, use a vibrating fluidized bed or a stirred fluidized bed to pre-dry the input short columnar crystals, so that the moisture content of the short columnar crystals is reduced to less than half of that of the wet crystals.

[0060] The deep drying equipment 5 may, but is not limited to, use a continuous fluidized bed, a continuous internal heat exchange fluidized bed, or a drum dryer for further deep drying of the input short columnar crystals to achieve the required moisture content of the finished product. Specifically, it may, but is not limited to, use an internal heat exchange fluidized bed dryer disclosed in application number 2018115209253.

[0061] The difference between this embodiment and Embodiment 1 is that the deep drying equipment 5 adopts... Figure 2 The continuous internal heat exchange fluidized bed shown specifically includes a fluidized bed host 52, which is equipped with multiple first heat exchangers 522. The air inlet of the fluidized bed host 52 is connected to an air inlet system 51, which includes a dehumidifier 511 and a first blower 512 connected in sequence. The input end of the dehumidifier 511 is connected to the atmosphere. The outlet of the first blower 512 is connected to the air inlet of the fluidized bed host 52 on the discharge side through a second heat exchanger 513. A dust removal device 53 is connected to the air outlet of the fluidized bed host 52, which includes a cyclone separator 531 and a bag filter 533 connected in sequence.

[0062] Furthermore, the dust removal device of the deep drying equipment 5 is provided with two sets. The air outlet of the bag dust collector 533 of the first set of dust removal devices 53 is connected to the air inlet of the fluidized bed host 52 on the feeding side through the second blower 516 and the third heat exchanger 515 in sequence. The input end of the second blower 516 is also connected to a bypass 517. The deep drying air inlet flow control valve 518 is connected in series on the bypass 517 to facilitate the input of ambient air as needed. The air outlet of the bag dust collector 533 of the second set of dust removal devices 53 is connected to the induced draft fan 54, the fresh air heat exchanger 8, and the exhaust gas treatment device 9 in sequence.

[0063] The fresh air heat exchanger 8 may, but is not limited to, adopt an energy-saving heat exchanger device suitable for the exhaust gas of drying equipment disclosed in patent number 202222178689X, or may be a plate heat exchanger device.

[0064] The exhaust gas treatment device 9 can employ environmental protection devices such as water dust removal and spray towers, or it can adopt a high-temperature and high-humidity exhaust gas treatment system disclosed in patent number 202222178866.4. This is used for further treatment of the exhaust gas to achieve environmentally friendly emissions.

[0065] Figure 1 In this embodiment, the recrystallization growth and rounding equipment 3 is a closed structure, without process air entering it. As a preferred embodiment, see [link to previous description]. Figure 2 The recrystallization growth and rounding equipment 3 can also be equipped with process air inlet and outlet for introducing process air. Preferably, the process air inlet is located at the discharge end and the process air outlet is located at the feed end, so that the blowing direction of the process air is opposite to the conveying direction.

[0066] As a further explanation of this embodiment, both the pre-drying and dispersing device 4 and the deep drying device 5 are equipped with process air inlets and outlets. The temperature of the process air input to the pre-drying and dispersing device 4 is lower than that of the deep drying device 5, and the relative humidity of the process air input to the pre-drying and dispersing device 4 is higher than that of the deep drying device 5. The temperature of the process air introduced into the recrystallization growth and rounding device 3 is lower than that of the process air introduced into the pre-drying and dispersing device 4, and the relative humidity of the process air introduced into the recrystallization growth and rounding device 3 is higher than that of the process air introduced into the pre-drying and dispersing device 4.

[0067] The process air outlets of the recrystallization growth and rounding equipment 3 and the pre-drying dispersion equipment 4 are all connected to dust removal devices 53. The dust removal devices 53 connected to the process air outlets of the recrystallization growth and rounding equipment 3 and the pre-drying dispersion equipment 4 can be configured separately or directly connected to the second set of dust removal devices 53 of the deep drying equipment 5.

[0068] The process air inlet of the recrystallization growth and rounding equipment 3 is connected to the outlet of the bag filter 533 of the first dust removal device 53, and / or the fresh air outlet of the fresh air heat exchanger 8, and / or the rounding equipment air inlet system 31. The rounding equipment air inlet system 31 may include a rounding equipment air inlet fan connected to the process air inlet of the recrystallization growth and rounding equipment 3. The air inlet of the rounding equipment air inlet system 31 is connected to the atmosphere. That is, the process air introduced into the recrystallization growth and rounding equipment 3 can be one or more of the following: ambient air, direct exhaust air from the deep drying equipment 5, and fresh air after heat exchange through the fresh air heat exchanger. In this embodiment, a mixed air of the three is introduced. Furthermore, the mixed air can be set to a mixing ratio that is adjustable. The regulating function (specifically achieved by connecting a regulating valve in series on the corresponding air supply pipeline, which is a conventional technology and will not be elaborated here) achieves low temperature and high humidity, enabling slow evaporation. This is used to further recrystallize and grow short columnar crystals and round the fracture surfaces of short columnar crystals. It also ensures that dust adhering to the surface of short columnar crystals firmly adheres to the crystals. After the slender crystals fracture, the specific surface area increases, increasing the probability of recrystallization of the residual high-concentration liquid on the crystal surface. Through vibration and friction, the sharp points of the fracture surface are rounded, allowing the crystal as a whole to grow one layer through recrystallization. At this time, the crystal cannot evaporate quickly, otherwise the fracture surface of the crystal may not be fully rounded, resulting in crystalline dust. In some cases, such as Figure 1 As shown, without introducing process air, the above effect can also be achieved simply by increasing the surface area after crystal fracture, given enough time.

[0069] As a further explanation of this embodiment, the process air inlet of the pre-drying and dispersing device 4 is used to introduce pre-drying and dispersing air. The pre-drying and dispersing air undergoes heat and mass exchange and dispersion within the pre-drying and dispersing device 4. The outlet of the pre-drying and dispersing device 4 is connected to a screening device 45. The discharge from the pre-drying and dispersing device 4 is screened by the screening device 45 to separate large particles and non-large particles (specifically, small particles or a combination of medium and small particles) to reduce the possibility of excessive, multi-stage crushing of crystals. The outlet of the screening device 45 is for large particles. The coarse crusher 42 is connected to the deep drying equipment 5. Large particles are crushed by the coarse crusher 42 and then fed into the deep drying equipment 5. The non-large particle outlet of the screening device 45 is connected to the disperser 43. The non-large particles are conveyed to the disperser 43 for further dispersion. The outlet of the disperser 43 is connected to the deep drying equipment 5. After being dispersed by the disperser 43, the material is fed into the deep drying equipment 5. Heat and mass exchange and drying are carried out in the deep drying equipment 5. Alternatively, the dried material can be cooled in the deep drying equipment 5. The discharge port of the deep drying equipment 5 is connected to the packaging system.

[0070] The process air inlet of the pre-drying and dispersing equipment 4 is connected to the outlet of the bag filter 533 of the first dust removal device 53, and / or the fresh air outlet of the fresh air heat exchanger 8, and / or the process air intake system 41 of the pre-drying and dispersing equipment. The process air intake system 41 of the dispersing equipment is a conventional technology (it may include a pre-drying air intake fan connected in series with the process air inlet of the pre-drying and dispersing equipment 4, and may also connect heaters, flow regulating valves, etc. as needed). The input end of the process air intake system 41 of the dispersing equipment is connected to the atmosphere, so that the process air introduced into the pre-drying and dispersing equipment 4 can be ambient air. One or more of the following can be used: air, direct exhaust from the deep drying equipment 5, and fresh air after heat exchange through the fresh air heat exchange equipment. Preferably, the exhaust from the deep drying equipment 5 is used. The exhaust from the deep drying equipment 5 has the characteristics of higher temperature and higher humidity than the ambient air, which is conducive to the realization of the functions of the pre-drying and dispersing equipment 4: "slow evaporation, further recrystallization, surface rolling and spreading, conducive to the secondary growth of short columnar single crystals, avoiding agglomeration into loose large particles, and further adhesion and firm growth of dust and concentrated crystal liquid on the surface of large crystals, directly reducing the proportion of dust in the material".

[0071] When the ambient humidity can achieve the above functions, the process air can also be the ambient air input into the pre-drying dispersion equipment 4 through the process air intake system 41 of the dispersion equipment, or it can be the heat exchange fresh air that is heat exchanged through the fresh air heat exchange equipment 8. While achieving ambient air temperature rise and energy saving, the exhaust air of the deep drying equipment 5 is cooled, relative humidity is increased, dust is removed, and odor is removed, thus reducing the pressure and function of subsequent environmental protection processes.

[0072] Depend on Figure 2 It can be seen that the powder output from the dust removal device 53 (i.e., cyclone separator 531, bag filter 533) can be discharged, or the outlet of the dust removal device 53 can be connected to the feed inlet of the granulation equipment 7 through the airlock 532 to granulate the powder output from the dust removal device 53. It can also be directly connected to the wet crystal coarse crushing equipment 2 to input the powder output from the dust removal device 53 (i.e., cyclone separator 531, bag filter 533) into the wet crystal coarse crushing equipment 2. The granulation equipment 7 can be, but is not limited to, a dry extrusion granulator or a wet extrusion granulator. In dry extrusion, it is usually first pressed into flakes or strips, and then crushed to obtain small particles. The output end of the granulation equipment 7 can be connected to the deep drying equipment 5 to input the output material into the deep drying equipment 5. It can also be packaged separately, or transported together with the material output from the deep drying equipment 5 to the packaging system for packaging.

[0073] The granulation equipment 7 can granulate materials with a particle size smaller than the dust or particulate matter output by the system. Compared with the wet granulation and dry granulation methods in the background technology, it can obtain a second type of high-quality granular product with greater strength, lower moisture absorption, and lower secondary crushing properties than the existing process. This high-quality granular product and a high-quality crystalline product of this utility model can be combined as a finished product or used as a separate finished product.

[0074] The packaging system includes packaging machinery 67. The packaging system can also be equipped with bucket elevator 61, multi-way valve 62, screening machine 63, conveying device 64, deep cooling device 65, and finished product silo 66 as needed. The discharge end of the granulation equipment 7 and the deep drying equipment 5 is connected to the bucket elevator 61. The bucket elevator 61 can be replaced by a pneumatic conveying device, etc. The output end of the bucket elevator 61 is connected to the multi-way valve 62. The multi-way valve 62 has one inlet and two outlets. One outlet is connected to the screening machine 63, and the other outlet can be connected to the deep drying equipment 5 as needed to transport the material to the deep drying equipment 5 for laying the bottom material or balancing the material layer of the deep drying equipment 5. In the packaging system, an anti-caking agent for the finished product can also be selectively added.

[0075] The outlet of the screening machine 63 for large particles is connected to the crushing equipment 68 via a conveying device. The outlet of the crushing equipment 68 is connected to the deep drying equipment 5 via a conveying device. The outlet of the screening machine 63 for non-large particles is connected to the deep cooling device 65. The non-large particles screened by the screening machine 63 are specifically small particles or include both medium and small particles. The deep cooling device 65 can be of various types, such as hollow blade type, drum type, spiral type, gravity cooling type, etc., like the plate heat exchanger for powdery solid materials disclosed in patent number 201110393598.1. The outlet of the deep cooling device 65 is connected to the finished product silo 66. The outlet of the finished product silo 66 is connected to the packaging machinery 67. The material in the finished product silo 66 can also be connected to the deep drying equipment 5 via a conveying device, and some material can be fed into the deep drying equipment 5 for use as a base material.

[0076] As a further improvement of this embodiment, the wet crystal coarse crushing equipment and / or the recrystallization growth and rounding equipment is provided with a crystal raw material liquid inlet, which facilitates the addition of crystal raw material liquid to the material. The mass ratio of the added crystal raw material liquid (mass concentration of 17%) to the mass of the wet raw material is 53-265:1000. Preferably, the crystal raw material liquid inlet can be sprayed in by an atomizing nozzle installed on the equipment. The specific spraying position can be reasonably selected by those skilled in the art based on common sense. It can be installed in any part of the material that facilitates spraying the crystal raw material liquid into the material. The crystal raw material liquid inlet on the wet crystal coarse crushing equipment can also be directly adopted as a liquid pipe, through which the crystal raw material liquid is added.

[0077] The following uses the drying process of threonine as an example to specifically illustrate the working process of this utility model:

[0078] 1) The threonine solution is concentrated, evaporated, and crystallized, then separated by centrifuge 1 to obtain wet crystals, such as... Figure 2 As shown, process air is introduced into the discharge port of centrifuge 1 to blow away some of the water on the crystal surface, reducing the possibility of agglomeration and powder crystal formation. The output process air can be filtered by a bag filter, the exhaust gas is discharged into the air, and the dust is collected and transported to the granulation equipment or recrystallized.

[0079] Due to differences in processes among different manufacturers, the shape, size, and water content of crystals vary. The crystals are elongated, with the initial water content of wet crystals typically between 7% and 11%, averaging about 9%. The length is about 5 to 10 times the diameter, and the average size can reach 0.14mm * 0.9mm. Sometimes the average size is only 0.075mm * 0.6mm, but those with a diameter less than 0.037mm are extremely rare and mostly adhere to the surface of large crystals, but are easily separated. Threonine crystals can grow naturally at the edge of the melting tank for several days and can also grow to 3-5mm in length, and the diameter will also increase.

[0080] 2) The wet crystals are crushed by the wet crystal coarse crushing equipment 2. Specifically, a twin-shaft paddle mixer is used. The outer diameter of the mixer shell is 400mm, the power is 30KW, and the processing capacity is about 10 tons / hour. Dry powder or slurry can be added. The speed is adjustable to adjust and control the crushing force. It is necessary to avoid the wet crystals from being crushed in the diameter direction and the crystals from sticking together due to strong mixing or strong stirring.

[0081] After being crushed by a twin-shaft paddle mixer, the length of the crystals can be maintained at 1-4 times the diameter, that is, about 3 times on average, and there is basically no further crushing in the diameter direction.

[0082] 3) After crushing, the material is fed into recrystallization growth and rounding equipment 3. Under the action of vibration, the short columnar crystals disperse, increasing the specific surface area. Partial recrystallization occurs on the crystal surface, thus rounding the fracture surface of the crystals and causing small crystals smaller than the dust particle size to adhere to the surface of the short columnar crystals. The recrystallization growth and rounding equipment uses a vibrating conveyor. The process air introduced is a mixture of ambient air heated by the fresh air heat exchanger 8 and exhaust air from the deep drying equipment 5. The introduced process air at this time has the effect of low temperature, high humidity, and is adjustable. Slow evaporation is used to achieve further recrystallization and growth of short columnar crystals and to round off the fracture surfaces of these crystals. This ensures that dust adhering to the surface of the short columnar crystals adheres firmly to them. After the slender crystals fracture, the specific surface area increases, increasing the probability of recrystallization of the residual high-concentration liquid on the crystal surface. Vibration and friction are used to round off the sharp edges of the fracture surface, allowing the crystal to grow a layer through recrystallization. During this process, the crystals cannot evaporate quickly, otherwise the fracture surfaces may not be fully rounded, resulting in the formation of crystalline dust. In some cases, without introducing process air, the increased surface area after crystal fracture, given sufficient time, can also achieve the same effect.

[0083] 4) Input pre-drying and dispersing equipment 4 for pre-drying. Pre-drying and dispersing equipment 4 adopts a vibrating fluidized bed. The vibrating fluidized bed is supplied with pre-drying and dispersing air through the process air inlet system 41 of the dispersing equipment, and heat and mass exchange and dispersion are carried out in the vibrating fluidized bed.

[0084] The semi-finished product output from the pre-drying and dispersing equipment 4 has a moisture content between 1-5%, which is much higher than the 0.2-0.5% moisture content of the finished product. Threonine crystals at this moisture content level have a certain strength and are not easily broken compared to the dried finished product. The possibility of crystals clumping together is greatly reduced. In addition, the vibrating fluidized bed has a small crushing force but a repeated turning effect. Under the action of the dispersing fluidized air, the surface water of the threonine crystals can be easily reduced. Since it is completely free surface water, the required drying power is relatively low. The exhaust air from the deep drying equipment 5 can be used directly. The temperature of this exhaust air is about 50-80℃, which is much lower than the drying process air of the deep drying equipment 5 (130-160℃). The humidity of this exhaust air is much higher than that of the ambient air, resulting in a low drying rate. The surface of the threonine crystals is not easy to crack, which is beneficial to the prevention of breakage and secondary breakage of the threonine crystals. Compared with the existing technology, theoretically, the entire steam energy consumption can be reduced by half. Even if the ambient air is used directly, it can still play a role in pre-drying and dispersing. The exhaust air can also be reheated to adjust the intensity of pre-drying and dispersing.

[0085] The process air introduced into the pre-drying and dispersing equipment 4 has a lower temperature and higher humidity than the inlet process air of the deep drying equipment 5. The material has sufficient time to pass through the pre-drying and dispersing equipment 4, ensuring uniform passage and slow evaporation. This facilitates further recrystallization and surface spreading, promoting the regrowth of short columnar individual crystals of threonine, avoiding or significantly reducing agglomerated large loose particles, and further rounding the fracture surfaces of the short columnar crystals, thus greatly reducing energy consumption. The process air inlet system 41 of the pre-drying and dispersing equipment is mixed with the exhaust air of the deep drying equipment in an adjustable ratio, achieving a low-temperature, high-humidity, and adjustable effect in the process air introduced into the pre-drying and dispersing equipment 4, thus enabling adjustable evaporation rates.

[0086] In the pre-drying and dispersing equipment 4, the shape of the crystals can be preserved as intact as possible. Due to the repeated turning and gentle crushing force, some clumps of crystals can be dispersed, and excessively long crystals will break. The length can be kept on average about 1-4 times the diameter.

[0087] 5) The material exiting the pre-drying and dispersing equipment 4 is graded. Large particles are mainly agglomerated particles, so they are crushed by compression using a coarse crusher 42 to reduce the possibility of excessive crushing of crystals in multiple stages. The coarse crusher 42 can be, but is not limited to, a high-speed granulator to disperse agglomerated particles. The mesh diameter is between 2-10mm to achieve the main function of dispersion and crushing into small particles. Non-large particles are conveyed to the disperser 43 for further dispersion.

[0088] The material output from the coarse crusher 42 and the disperser 43 enters the deep drying equipment 5. After deep drying in the deep drying equipment 5, a high-quality crystalline product that meets the moisture content requirements is obtained.

[0089] The deep drying equipment 5 adopts an energy-saving fluidized bed system disclosed in patent number 202110788952.4. Due to the impact, dispersion and mixing effects of material fluidization, in addition to the basic function of drying, it can further blunt the rhomboid edges of the fracture surface of individual threonine crystals, and break the long needle-shaped crystals that are too long and easily broken again, but retain the diameter direction of most crystals without breaking. The air separation effect of fluidized air is used to discharge the small-sized dust or particulate matter from the air outlet of the deep drying equipment 5 and collect it through the cyclone separator 531 and the bag filter 533.

[0090] 6) The material with a particle size smaller than that collected by the cyclone separator 531 and the bag filter 533 in the system is fed into the roller dry extrusion granulator for granulation. Compared with the wet granulation and dry granulation in the background technology, the gap between particles is small, it is easy to compact during granulation, the power required during granulation is small, the finished product has high strength, high bulk density, low moisture absorption and low secondary crushing. This high-quality granular product and the high-quality crystalline product obtained in step 5) can be combined as a finished product or used as a separate finished product. This second product can be fed into the internally heated fluidized bed dryer 52 and mixed with the above-mentioned crystalline product as a commodity. The newly generated dust or powder is recycled and discharged to the granulation equipment 7.

[0091] The recrystallization growth and rounding device 3 and the pre-drying device 4 of this utility model can also be connected into an integrated structure. For example, the pre-drying device 4 has the recrystallization growth and rounding device 3 in the front and the pre-drying device 4 in the rear. The material output from the recrystallization growth and rounding device 3 directly enters the pre-drying device 4. The recrystallization growth and rounding device 3 may or may not be supplied with process air, while the pre-drying device 4 requires the supply of process air.

[0092] like Figure 2 As shown, the exhaust air or ambient air from the discharge side of the deep drying equipment 5, after being heated by the fresh air heat exchanger 8, can be connected to the air inlet on the feed side of the deep drying equipment 5, the process air inlet of the pre-drying equipment 4, the process air inlet of the recrystallization growth and rounding equipment 3, and the centrifuge discharge port.

[0093] IV. Specific Application Example 1: Detection of Dry Products

[0094] The surface of the crystal can partially recrystallize, thereby rounding the fracture surface of the crystal and allowing small crystals smaller than the dust particle size to adhere to the surface of the short columnar crystal.

[0095] Moisture absorption observation: At 20℃ and 60-70% relative humidity, the moisture content of the finished product was approximately 0.89% after 2 hours.

[0096] There are virtually no dust particles smaller than the specified size, and the inner film of the packaging bag adsorbs virtually no dust. Upon opening the packaging bag, there are virtually no inhalable particulate matter. The finished product appears transparent to the naked eye, with a distinct layer of recrystallization and some nodules on the crystal surface. Most of the crystals exhibit a short columnar shape, and the edges of the fracture surface tend to be rounded and polished. Analysis shows that dust particles smaller than the specified size account for less than 10% of the raw material, and particles smaller than 100 mesh account for less than 20% of the raw material.

[0097] Energy consumption: The installed capacity is 300KW, the average steam consumption is about 0.8-1 ton per hour, the average production capacity is 6 tons / hour, and the average energy consumption parameters per ton of finished product are 40 kWh of electricity and about 0.15 tons of 0.6MPa saturated steam.

[0098] Finished product parameters: The moisture content of the finished product is about 0.25-0.3%, the natural bulk density is about 680 kg / m3, and the vibrated bulk density is about 760 kg / m3;

[0099] The moisture absorption of the second high-quality granular product obtained by step 6) of Example 1 was observed: at 20°C and 60-70% relative humidity, the moisture content of the finished product was approximately 1.02% after 2 hours.

[0100] The second type of high-quality granular product was observed as follows: there was virtually no dust particle size, the average particle size was adjustable, commonly ranging from 10 to 60 mesh, the inner film of the packaging bag contained a small amount of adsorbed dust, and there were very few inhalable particles when the packaging bag was opened; each finished granule consisted of multiple small crystals, and the small crystals were partially broken compared to the raw material. Compared with the dry granulation process used for the threonine dry powder mentioned above, there were virtually no reflective crystals in the granules, the amount of dust was less, and the hand-squeezing strength was greater.

[0101] Energy consumption: Based on the above drying process, the energy consumption of dry granulation needs to be increased. The installed power is 66KW, the steam consumption is 0 tons per hour, the average production capacity is 0.6 tons / hour, and the energy consumption per ton of finished product is increased by about 38-45 kWh.

[0102] Finished product parameters: Moisture content of finished product is approximately 0.3%, and natural bulk density is approximately 610 kg / m³. 3 The compacted bulk density is approximately 760 kg / m³. 3 .

[0103] The finished product analysis statistics are as follows, in which the crystalline finished product accounts for about 80-95% of the total finished product. The two finished products can be packaged separately or mixed. When the dry granulation particles of this utility model are not needed, they can be dissolved and recrystallized to achieve all crystalline particles. All of these are optional implementation schemes.

[0104]

[0105] The third product of this invention is a finished product made by wet granulation of small crystals with a particle size of less than 100 mesh or less than dust particle size. Observation of the finished product: The finished product is similar to the wet granulation process in the background technology, but the strength is higher when squeezed by hand, the secondary crushability is lower, and the primary bulk density is higher, with a natural bulk density of approximately 550 kg / m³. 3 The compacted bulk density is approximately 650 kg / m³. 3 The moisture absorption is lower. Moisture absorption analysis at 20℃ and 60-70% relative humidity showed that the moisture content of the finished product was about 1.1% after 2 hours, indicating that the advantages of the third product are not obvious. However, compared with dry granulation, it is safer in terms of preventing fire and explosion.

[0106] The difference between Specific Application Example 2 and Specific Application Example 1 is that the feed inlet and discharge outlet of the wet crystal coarse crushing equipment 2 are sprayed with crystal raw material liquid respectively. The mass ratio of the sprayed amount of crystal raw material liquid (mass concentration of 17%) to the mass of wet raw material is 100:1000. The granular product is larger, stronger and more beautiful in appearance than the product obtained in Example 1.

[0107] This invention utilizes novel preparation and drying processes to produce a high-quality crystalline L-threonine product that is dust-free, virtually free of inhalable particulate matter, exhibits no significant dust adsorption on packaging bags, has a higher hand-squeezing hardness than existing products, low secondary crushing resistance, good flowability, a visually transparent appearance, high bulk density, and low moisture absorption. Specific controllable indicators include: dust content below 0.5%, power consumption per ton of product below 40 kWh, saturated steam at 0.6 MPa below 0.15 tons, and a bulk density of 740-780 kg / m³ using a BT-1000 powder comprehensive characteristic tester. 3 Hygroscopic analysis at 20℃ and 60-70% relative humidity showed that the moisture content of the finished product was approximately 0.89% after 2 hours, indicating a significant decrease in hygroscopicity and thus reducing the likelihood of clumping. The reduction or even elimination of dust and inhalable particulate matter improved occupational health, environmental friendliness, and safety during production. This resulted in higher product prices, with an estimated increase of 100-500 yuan per ton. In terms of selling price alone, a 100,000-ton production line would generate an additional 10-50 million yuan in profit annually. This enhanced market competitiveness for users and improved overall socio-economic benefits and technological efficiency.

[0108] In this method, the sum of dust and inhalable particulate matter, i.e., the proportion of finished products smaller than 150 mesh, is determined by sieving. Since inhalable particulate matter is difficult to sieve, optical observation and the presence of obvious adsorption and sensory adsorption on the packaging bag are used as the basis for determination. All magnified microscopic photographs above have some magnification deviation due to instrument error. Threonine moisture content determination method: Electric thermostatic drying oven, type 101-1, 105℃, half an hour.

[0109] In summary, this utility model addresses the shortcomings of traditional finished product preparation and drying processes by providing a novel preparation and drying process to achieve a high-quality crystalline finished product. Compared with products prepared by existing methods, it offers several advantages: the finished product has a noticeable granular texture, resulting in a visually appealing appearance; the sum of dust and inhalable particulate matter is virtually nonexistent in the finished product, with no significant dust adsorption on the packaging bag; the finished product is firm to the touch, exhibits low secondary breakage, and has good flowability; the drying process consumes less energy; the bulk density of the finished product is higher than that of existing processes; and the low hygroscopicity reduces the likelihood of agglomeration. This results in: minimal dust and inhalable particulate matter, low secondary breakage, improved occupational health, environmental friendliness, and safety (i.e., good explosion-proof properties) during use and production; low drying energy consumption, reducing preparation costs; high bulk density, requiring less packaging material per ton of product and lower volumetric freight costs, thus reducing packaging and transportation costs; and low hygroscopicity, extending shelf life and increasing the hardness of the finished product, minimizing the possibility of agglomeration.

[0110] This invention relates to a high-quality crystalline product and its preparation and drying process, which is mainly applicable to slender crystals. When the crystals are not slender, this invention can also be used to achieve the effects of increasing crystal size, rounding, reducing dust content, increasing bulk density, and preventing agglomeration.

[0111] The terminology used in the above-described embodiments and layout schemes of this utility model refers to existing technology. This embodiment only describes the utility model in detail. For example, as is known to those skilled in the art, fluidized bed devices or systems also require the configuration or selection of blowers, air heaters, inlet pipes, dampers, support platforms, connecting pipes from the main unit to the cyclone separator, bag filters, connecting pipes from the cyclone separator to the bag filter, induced draft fans, connecting pipes from the bag filter to the induced draft fan, water dust collectors, induced draft fan to water dust collector pipes, control systems, instruments, and optionally, semi-finished product conveyors, screening machines, crushers, seed crystal conveyors or pneumatic conveyors, screw conveyors, airlocks or shut-off valves, acceleration pipes, finished product conveyors, finished product silos, packaging machinery, and other commonly used configurations. Cooling devices can be fluidized bed cooling, drum cooling, hollow paddle dryers, solid coolers (plate or tube type, etc.), or combinations of multiple cooling methods. For example, a plate heat exchanger for granular solid materials (ZL201110393598.1) can be used to form a complete system. This is conventional technology and will not be described in detail here. (Appendix) Figures 1 to 2 The work process shown is only a partial illustration and does not represent all aspects of the work; therefore, it will not be explained in detail for all of them.

Claims

1. A drying system for high-quality crystals, wherein the raw material is wet crystals, characterized in that: It includes a coarse crushing device, a recrystallization growth and rounding device, a pre-drying and dispersing device, and a deep drying device connected in sequence; wherein, the recrystallization growth and rounding device is used for vibratory conveying of materials; The wet crystal coarse crushing equipment adopts one of the following types of mixers, blenders, or crushers: stirring type, blade type, paddle type, or stirring tooth type. The recrystallization growth and rounding equipment uses a vibrating conveyor or vibrating screen.

2. The drying system for high-quality crystals according to claim 1, characterized in that: The wet crystal coarse crushing equipment is used to crush long crystals with an aspect ratio greater than 3 into short columnar crystals with an average aspect ratio less than 3. The pre-drying and dispersing equipment is used to initially dry the short columnar crystals, reducing the moisture content of the short columnar crystals to less than half that of the wet crystals; the deep drying equipment is used to further dry the short columnar crystals to achieve the required moisture content of the finished product.

3. The drying system for high-quality crystals according to claim 1, characterized in that: The recrystallization growth and rounding equipment is equipped with process air inlet and outlet for easy introduction of process air.

4. The drying system for high-quality crystals according to claim 1, characterized in that: The drying system also includes a granulation device, which is used to granulate materials with a particle size smaller than that of the dust discharged from the dust outlet of the pre-drying dispersion device or / and the deep drying device.

5. The drying system for high-quality crystals according to claim 1, characterized in that: The drying system also includes a fresh air heat exchanger. The exhaust vent of the deep drying equipment is connected to the fresh air heat exchanger, and the fresh air outlet of the fresh air heat exchanger is connected to the pre-drying and dispersing equipment and / or the deep drying equipment to achieve waste heat recycling.

6. The drying system for high-quality crystals according to claim 1, characterized in that: The process air outlet of the deep drying equipment is connected to the process air inlet of the pre-drying and dispersing equipment.

7. The drying system for high-quality crystals according to claim 1, characterized in that: A dispersing machine is connected between the pre-drying and dispersing equipment and the deep drying equipment. The dispersing machine is used to break up the semi-finished product output from the pre-drying and dispersing equipment and then input it into the deep drying equipment.

8. The drying system for high-quality crystals according to claim 1, characterized in that: The discharge port of the pre-drying and dispersing equipment is connected to a screening device. The screening device is equipped with a large particle material outlet and a non-large particle material outlet. The screening device is used to screen the output material of the pre-drying and dispersing equipment into large particles and non-large particles with a particle size smaller than that of the large particles. The large particle material outlet of the screening device is connected to a crusher, and the non-large particle material outlet is connected to a deep drying equipment. The crusher is used to crush the screened large particles, and the outlet of the crusher is connected to the deep drying equipment.

9. A drying system for high-quality crystals according to any one of claims 1 to 8, characterized in that: The wet crystal coarse crushing equipment and / or the recrystallization growth and rounding equipment are equipped with a crystal raw material liquid inlet, which facilitates the addition of crystal raw material liquid to the material.

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