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] The present invention relates to the technical field of drying equipment, in particular to a drying system for high-quality crystals. Background Art

[0002] There are many varieties of crystalline materials, and the crystals have various shapes. Crystals with an average aspect ratio greater than 3, especially those with an aspect ratio greater than 5, are elongated crystals. Known amino acids include threonine, citrulline, glutamic acid, alanine, and arginine. Other products from various industries include trehalose, 4-diol, sucralose, and succinic acid. They have large market volumes and high economic value. They vary in particle size and exist in both salt and non-salt forms. The present invention mainly uses threonine as a typical material for demonstration. The current total domestic production of threonine alone is nearly 1 million tons. Other amino acids and materials may also form elongated crystals as the crystallization conditions change.

[0003] L-Threonine (L-Threonine) is an essential amino acid (hereafter referred to as threonine). It is primarily used in pharmaceuticals, chemical reagents, food fortifiers, and feed additives, with its use in feed additives experiencing rapid growth. In medicine, due to the presence of hydroxyl groups in its structure, threonine acts as a water-retaining agent for human skin. When combined with oligosaccharide chains, it plays a vital role in protecting cell membranes and promoting phospholipid synthesis and fatty acid oxidation in the body. Its preparations have been shown to promote human development and combat fatty liver disease, and are a component of complex amino acid infusions. Threonine appears as a white, orthorhombic or crystalline powder, with fine needle-like crystals in microscopic images. Major domestic manufacturers include Fufeng Biotechnology, Meihua Biotechnology, and Yipin Biotechnology, with varying degrees of purity.

[0004] According to the specifications of stainless steel wire mesh, 10μm is theoretically 1600 mesh, 20μm is about 635 mesh, 37μm is about 400 mesh, and 75μm is about 200 mesh. According to the standard sieve query, 100μm is about 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 are commonly classified in micrometers and nanometers. Haze, for the most part, refers to airborne particles between 2.5 and 10 microns in size. Of the dust in industrial environments, 5% is ultrafine dust, with a particle size below 5 microns. This fraction is also the most harmful to the human body. It can be directly inhaled into the lungs, causing lung fibrosis, also known as pneumoconiosis. Suspended dust consists of three components: settling dust (particles > 100 μm that settle quickly), floating dust (particles 10-100 μm that can remain suspended in the air for extended periods), and inhalable particulate matter (particles < 10 μm). Suspended dust pollution is one of the most significant air pollutants and has become the primary air pollutant in most regions of my country. Dust refers to solid particles suspended in the air. Dust is commonly referred to by a variety of names, such as dust, dust, smoke, mineral dust, sand dust, and powder, without clear boundaries between these terms. The International Organization for Standardization defines suspended solids as particles smaller than 75 μm. In our daily lives and workplaces, industrial dust is a natural threat to human health and a major cause of numerous diseases. The greater the amount of floating dust or fines in finished threonine products, the lower the selling price. Current users are seeking to minimize floating dust levels in threonine products, and they are even more eager to eliminate the presence of inhalable particulate matter.

[0006] At present, the total dust concentration limit in the workplace usually does not exceed 10 mg / m³ (8-hour time-weighted average concentration, TWA), and the inhalable dust concentration (PM10) usually does not exceed 5 mg / m³. Threonine dust is irritating or allergenic, and there is a need to further lower the exposure limit. The dust rate currently measured through experiments should be as low as possible, usually required to be less than 1%-5% (depending on the specific process requirements).

[0007] For example, threonine is generally separated by crystallization and then centrifugation or filter press. The four mainstream preparation processes for finished product drying are airflow drying, fluidized bed drying, wet extrusion granulation (wet granulation), and dry roller extrusion (dry granulation). These four preparation processes have the following disadvantages: The combined process of first-stage enhanced airflow drying (the airflow speed in the intensifier is an average of 5-7m / s) and first-stage airflow cooling (the operating airflow speed is an average of 10-15m / s) is as follows: about 50% of the finished product contains floating dust particles below the specified size, and about 40% contains dust particles below the specified size. The inner membrane of the packaging bag absorbs a lot of dust, and when the packaging bag is opened, there are obvious inhalable particles. The dust concentration limit and inhalable dust concentration value in the workplace are difficult to guarantee; the secondary crushing is obvious, and there is more dust after crushing; the installed power is 380KW, the steam consumption is an average of 3.2 tons per hour, the average production capacity is 8.2 tons / hour, the average energy consumption per ton of finished product is 38 kWh, and 0.39 tons of 0.6MPa saturated steam. The intensifier requires compressed air sealing, the amount of which has not been counted; the moisture content of the finished product is 0.2-0.3%, and the natural bulk density of the finished product is about 650kg / m 3 , agglomeration often occurs in summer; Figure 3 Taking crystalline threonine as an example, the finished product obtained by the combined process of enhanced airflow drying + first-level airflow cooling has a large proportion of single crystals in the finished product. The surface of the single crystals is bright and the lengths are different. There are many crystals with an aspect ratio greater than 3. About half of the crystals have multiple fractures. The average mesh size is about 150-200 mesh. About 10% are agglomerated small particles, which are grayish white. It has been measured that the water content of these agglomerated particles can reach 0.7%, which exceeds the overall water content. Most of the crystals are agglomerated by small crystals smaller than 400 mesh. Most of the crystals above the dust particle size exist as single crystals, and the crystal fracture surface is relatively sharp.

[0008] Hygroscopicity analysis: At 20°C and 60-70% relative humidity, the moisture content of the finished product is approximately 1.39% after 2 hours.

[0009] First-stage airflow drying (operating airflow speed is an average of 10-15m / s): in the finished product, about 60% of the floating dust particles are smaller than the particle size, and about 50% of the dust particles are smaller than the particle size. The inner membrane of the packaging bag absorbs a lot of dust, and when the packaging bag is opened, there are obvious inhalable particles. The dust concentration limit and the inhalable dust concentration value in the workplace are more difficult to guarantee; the secondary crushing performance is slightly lower; the installed power is 350KW, the average steam consumption is 3.3 tons per hour, the average production capacity is 6.5 tons / hour, and the average energy consumption parameters per ton of finished product are 43 kWh and 0.45 tons of 0.6MPa saturated steam; the moisture content of the finished product is 0.15-0.3%, and the natural bulk density of the finished product is about 650kg / m 3 ; Figure 4 Taking crystallized threonine as an example, the finished product obtained by the first-stage airflow drying process is Figure 4 It can be seen that a large number of crystals are broken, including in length and diameter. The corners of the fractured cross-section of a single crystal are relatively obvious and irregular. There are no grayish-white agglomerated small particles, but the proportion of floating dust and powder has increased.

[0010] Hygroscopicity analysis: At 20°C and 60-70% relative humidity, the moisture content of the finished product is approximately 1.45% after 2 hours.

[0011] Continuous internal heat exchange fluidized bed drying process: dust particles below the particle size account for about 20-30% of the finished product, dust particles below the particle size account for about 10-20%, and dust particles below 100 mesh account for about 40-60%. The inner film of the packaging bag adsorbs dust, and there are inhalable particles when the packaging bag is opened. The dust concentration limit and inhalable dust concentration value in the workplace are much better, but it is still difficult to ensure; the installed power is 300KW, the average steam consumption is about 1.1-1.2 tons per hour, the average production capacity is 6.5 tons / hour, the average energy consumption parameters per ton of finished product are 36 kWh, and 0.6MPa saturated steam is about 0.18-0.2 tons. The imported disperser requires airtight sealing, and the quantity is not statistically available; the moisture content of the finished product is about 0.27%, and the natural bulk density is about 600kg / m 3 , compacted bulk density is about 700 kg / m 3 ; Figure 5 、 6 Taking crystallized threonine as an example, the finished product is obtained by continuous internal heat exchange fluidized bed drying process. Figure 5 、 6 It can be seen that there are obvious agglomerated small particles in the finished materials coming out of the fluidized bed, which are larger than 40 mesh and account for more than 30%. Normally, they need to be screened out and crushed, resulting in more overall dust, broken crystals, and seriously varying finished product particle sizes. The color is uneven, and there are yellow particles that may deteriorate. The average mesh size of the final product can be about 100-120 mesh.

[0012] Hygroscopicity analysis: At 20°C and 60-70% relative humidity, the moisture content of the finished product is approximately 1.33% after 2 hours of testing.

[0013] Wet granulation plus fluidized bed drying: There is basically no floating dust particle size in the finished product, and the average particle size can be 0.2-1.2mm. There is basically no dust adsorbed by the inner film of the packaging bag. There is basically no inhalable particulate matter when the packaging bag is opened. The dust concentration limit and the inhalable dust concentration value in the workplace are easy to meet the standards; however, the finished product has low strength and obvious secondary crushing. Some binders such as mother liquor need to be added during granulation, otherwise the finished granules are easy to break during transportation and have serious moisture absorption after crushing; the dried material has lumps The pellets need to be screened and crushed, and can optionally enter the front granulation process, resulting in increased energy consumption; the installed power is 280-330KW, the average steam consumption is about 1.5 tons per hour, the average production capacity is about 4 tons / hour, and the energy consumption parameters per ton of finished product are 56-66 kWh on average, 0.6MPa saturated steam is about 0.3-0.38 tons, and energy-saving devices can reduce it to 0.2-0.25 tons. The pelletizer requires compressed air sealing, the amount of which has not been counted; the moisture content of the finished product is about 0.3-0.4%, and the natural bulk density is about 500kg / m 3 , compacted bulk density is about 600 kg / m 3 .

[0014] Figure 7 、 8 Taking crystalline threonine as an example, the finished product is obtained by wet granulation and fluidized bed drying process. Figure 7 、 8 It can be seen that a single finished granule is composed of multiple small crystals. Compared with the wet crystals of the raw material, the small crystals show a large number of fractures and crushings, but the crushing in the diameter direction is less: some binders such as mother liquor need to be added during granulation, otherwise the finished granules will have relatively low strength and be easy to break during transportation. The large crystals in the granules are difficult to further crush, which is one of the main reasons for the looseness and high moisture absorption of the finished granules. For example, in the XZL rotary extrusion granulator in the prior art, the diameter of the granulation extrusion screen is usually 200-350mm, and the processing capacity is 40-400kg / h.

[0015] Hygroscopicity analysis: At 20°C and 60-70% relative humidity, the moisture content of the finished product is about 1.2% after 2 hours.

[0016] Dry granulation process: There is basically no dust particle size in the finished product, the average particle size can be adjusted, and the common size is 10-60 mesh. There is a small amount of adsorbed dust on the inner film of the packaging bag, and there are very few inhalable particles when the packaging bag is opened; there is secondary crushing, and the inhalable particles increase after crushing, and the finished granules are easy to break by hand; the energy consumption data of dry roller extrusion granulation needs to be added on the basis of the above three drying processes. The installed power is 66KW, the steam consumption is 0 tons per hour, the average production capacity is 0.5 tons / hour, and the energy consumption per ton of finished product increases by an average of 45-55 kWh. The dry granulator requires compressed air, the amount of which is not statistically available; the moisture content of the finished product is about 0.3-0.5%, and the natural bulk density is about 600kg / m 3, compacted bulk density is about 750 kg / m 3 ; This production line has experienced multiple fire and explosion accidents (dust flash explosion) during its use in the market.

[0017] Figure 9 、 10 Taking crystalline threonine as an example, the finished product obtained by dry granulation process is Figure 9 、 10 It can be seen that a single finished particle is composed of multiple small crystals. Compared with the wet crystals of the raw material, the small crystals are broken in large quantities and there are no long strips of crystals. A large number of broken objects with a size of 0.007-0.027 mm are observed. Because there are still many shiny crystals in the particles and the size is relatively large, the finished particles are easy to break when squeezed by hand.

[0018] Hygroscopicity analysis: At 20°C and 60-70% relative humidity, the moisture content of the finished product was approximately 1.15% after 2 hours. The analysis statistics of the finished products of the four existing process methods are as follows:

[0019] It can be seen that existing processes have some or all of the following disadvantages: the workplace dust concentration limits and respirable dust concentration values of airflow drying and fluidized bed drying methods are easily substandard, and the average particle size of the finished product is small. Although the workplace dust concentration limits and respirable dust concentration values of wet granulation are easily met, they have many disadvantages, such as low bulk density, high moisture absorption, low finished granule strength, and high power and steam consumption. The workplace dust concentration limits and respirable dust concentration values of dry granulation can barely meet the standards, but they have many disadvantages, such as secondary energy consumption, easy crushing when manually squeezed and easy secondary generation of respirable dust, low production line output, high investment, and low finished granule strength. With the exception of wet granulation, all existing processes have dust adsorption on the finished product packaging bags, even significantly, and secondary crushing is obvious except for fluidized bed granulation. The overall operating energy consumption is relatively high. All processes have significant moisture absorption, and the moisture absorption order from highest to lowest is airflow drying, fluidized bed drying, wet granulation, and dry granulation.

[0020] It is understood that there have been three fire and explosion incidents in dry granulation in China, one fire incident in air flow drying, no fire incident in fluidized bed drying, and no fire incident in wet granulation. The probability of complaints about finished product agglomeration, from highest to lowest, is air flow drying, wet granulation, fluidized bed drying, and dry granulation. Summary of the Invention

[0021] The purpose of the present invention is to provide a high-quality crystal drying system that overcomes the defects of existing drying processes and achieves a high-quality crystal product with no flying dust, basically no inhalable particulate matter, no obvious dust adsorption on the packaging bag, a hardness exceeding that of existing products, low secondary breakage, good fluidity, high finished product bulk density, and low moisture absorption. It also has low comprehensive operating energy consumption, good occupational hygiene in production and operation, good environmental protection, good safety, and low ignition and explosion hazard.

[0022] The technical solution to achieve the above-mentioned purpose is: The technical solution to achieve the above-mentioned purpose is: A high-quality crystal drying system, the raw material is wet crystals, characterized in that it includes coarse crushing equipment, recrystallization growth and rounding equipment, pre-drying and dispersing equipment, and deep drying equipment connected in sequence; wherein the recrystallization growth and rounding equipment is used to vibrate and convey the material.

[0023] 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.

[0024] The material in the process of recrystallization, growth and rounding is subjected to the vibration force of vibration conveying, and short columnar crystals are formed and dispersed to increase the specific surface area. The surface of the crystal can be partially recrystallized, thereby making the fracture surface of the crystal rounded and making small crystals below the dust particle size adhere to the surface of the short columnar crystals.

[0025] The pre-drying and dispersing equipment is used to perform preliminary drying on the short columnar crystals, reducing the moisture content of the short columnar crystals to less than half of the moisture content of the wet crystals; the deep drying equipment is used to achieve further deep drying of the short columnar crystals to meet the moisture content requirements of the finished product.

[0026] The present invention first uses a coarse crushing device to crush elongated crystals with an aspect ratio greater than 3 into short columnar crystals with an average aspect ratio less than 3. This allows dust particles smaller than the dust particle size to adhere to the surface of the short columnar crystals, thus avoiding the excessively small particle size caused by direct drying of wet crystals. This also prevents the elongated crystals from breaking or breaking only slightly after direct drying, resulting in low bulk density and increased sticking. This also overcomes the shortcomings of prior art, such as sharp angles on the fracture surface, high secondary crushability and large secondary dust, the generation of inhalable particulate matter, and the dust's tendency to absorb moisture and cause agglomeration. Furthermore, the crystals should be minimized from breaking in the diameter direction.

[0027] Through the recrystallization growth and rounding equipment, the short columnar crystals can be further recrystallized and the fracture surface of the short columnar crystals can be rounded, so that the dust adhering to the surface of the short columnar crystals can be firmly connected to the short columnar crystals. After the slender crystals are broken, the specific surface area increases, and the probability of recrystallization of the residual high-concentration liquid on the crystal surface increases. Through vibration and friction, the sharp part of the fracture surface becomes rounded, and the whole crystal grows by one layer through recrystallization.

[0028] The pre-drying and dispersing equipment is used to achieve preliminary drying of the short columnar crystals, and the moisture content is reduced to less than half of the wet crystals, so that the short columnar crystals can be dispersed with each other and the probability of adhesion can be reduced. The crystal surface can better realize the recrystallization function and the adsorption and growth function of dust particles on the surface of large crystals. Preferably, the pre-drying and dispersing equipment adopts a vibrating fluidized bed, and preferably the vibration force of the vibrating fluidized bed is controlled to a force that can disperse large crystals, break long crystals into short columnar crystals, and not cause a large number of crystals to break. Preferably, the crystals are further slowly evaporated in the constant speed drying stage (the process air introduced into the pre-drying and dispersing equipment adopts constant speed drying throughout the process), so as to avoid the disadvantages of low bulk density, high moisture absorption, slow deep drying, unsightly finished products, high secondary crushing, and loose large particles in the finished products caused by crystal adhesion. It can also achieve further growth and firmness of dust adhering to the surface of the short columnar crystals and the short columnar crystals, while preventing these adhered dust from becoming flying dust due to excessive drying.

[0029] Deep drying is used to further dry the short columnar crystals to meet the moisture content requirements of the finished product. A continuous internal heat exchange fluidized bed is preferably used. While drying, fine particles below the dust particle size are blown out of the internal heat exchange fluidized bed through air separation, meeting the particle size and dust-free indicators of the finished product, and providing the granulation equipment with a source of raw materials below the dust or floating dust particle size. The material particles are further deeply dried in the internal heat exchange fluidized bed, the remaining long crystals are further broken, the crystal fracture surfaces are re-rounded, and floating dust or fine particles are removed by air separation, and finally discharged from the discharge port. After being discharged, the floating dust or fine particles do not directly return to the internal heat exchange fluidized bed, nor do they directly return to the feed port or feed device of the internal heat exchange fluidized bed. Dry granulation, wet granulation, and recrystallization processes can be optionally used. The resulting product can be an independent finished product or mixed with high-quality finished products from the internal heat exchange fluidized bed.

[0030] Furthermore, the recrystallization growth and rounding equipment is provided with a process air inlet and outlet, which is convenient for the introduction of process air. Through the slow evaporation of the 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 whole process), the function of this equipment is better realized, and the advantages of better fluidity of the finished product, larger particle size of the finished product, low secondary crushing, low secondary dust, and dust growing directly or adhering to recrystallization to reduce the dust rate can be achieved.

[0031] Furthermore, the pre-drying and dispersing equipment and the deep drying equipment are both provided with process air inlets and outlets. The process air temperature input to the pre-drying and dispersing equipment is lower than the process air temperature input to the deep drying equipment. The relative humidity of the process air input to the pre-drying and dispersing equipment is higher than the relative humidity of the process air input to the deep drying equipment.

[0032] The material has enough time to pass through the pre-drying and dispersing equipment and passes through it evenly to achieve slow evaporation. There is a time period from the feed port to the discharge port through the pre-drying and dispersing equipment to achieve slow evaporation of moisture on the crystal surface, further recrystallization, and surface rolling and spreading, which is beneficial to the regrowth of short columnar single crystals, avoids agglomeration into loose large particles similar to those that appear in direct fluidized bed drying, and is also beneficial to further rounding of the short columnar fracture surface.

[0033] Furthermore, the temperature of the process air introduced into the recrystallization, growth and rounding equipment is lower than the temperature 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 the relative humidity 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.

[0034] Furthermore, compared with the process air introduced into the pre-drying and dispersion 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 passing time. On the premise of breaking long crystals into short columnar crystals, the rounding function is better and the possibility of adhesion between wet crystals is reduced as much as possible.

[0035] Furthermore, the drying system also includes a granulating device, which is used to granulate materials with a dust particle size below the dust particle size output from the dust outlet of the pre-drying and dispersing device and / or the deep drying device. The materials with a dust particle size below the dust particle size output from the dust outlet of the pre-drying and dispersing device and the deep drying device are granulated by the granulating device, which is used to granulate materials with a dust particle size below the system. Compared with the wet granulation and dry granulation of the background technology, a second high-quality granular product with a strength greater than the background technology, a lower moisture absorption than the background technology, and a lower secondary crushing property than the background technology can be obtained. This high-quality granular product and a high-quality crystalline product of the present invention can be combined as a finished product, or can be used as a finished product alone.

[0036] Furthermore, the drying system also includes a fresh air heat exchange device, the exhaust port of the deep drying equipment is connected to the fresh air heat exchange device, and the fresh air outlet of the fresh air heat exchange device is connected to the pre-drying and dispersion equipment and / or the deep drying equipment to realize the recycling of waste heat; greatly reducing the energy consumption of the production line, reducing the dust concentration, and reducing the odor of the exhaust gas.

[0037] Furthermore, the process air outlet of the deep drying equipment is connected to the process air inlet of the pre-drying and dispersing equipment.

[0038] The exhaust air of 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 pre-drying and dispersing equipment: "slow evaporation, further recrystallization, surface rolling and spreading, which is conducive to the secondary growth of short columnar single crystals, avoiding agglomeration into loose large particles, and further attachment and growth of floating dust and concentrated crystal liquid on the surface of large crystals, which directly reduces the proportion of dust in the material."

[0039] When the ambient humidity can achieve the above functions, the process air introduced into the pre-drying and dispersing equipment can also be part or all of the ambient air. Preferably, the ambient air first passes through the exhaust heat exchanger configured for the deep drying equipment to achieve air-to-air heat exchange. While achieving the ambient air temperature increase and energy saving, the exhaust air of the deep drying equipment is cooled, the relative humidity is increased, and the dust and odor are removed to achieve environmental protection functions, thereby reducing the pressure and functions of subsequent environmental protection processes.

[0040] 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 conducive to the realization of the functions of the above-mentioned recrystallization growth and rounding equipment.

[0041] Furthermore, a disperser is connected between the pre-drying and dispersing equipment and the deep drying equipment. The disperser is used to disperse the semi-finished products output by the pre-drying and dispersing equipment and then input them into the deep drying equipment, which is beneficial to the dispersion between particles and prevents agglomeration. Preferably, a screening device is provided at the outlet end of the pre-drying and dispersing equipment, and the large particles screened by the screening device enter the coarse crusher to reduce the possibility of excessive crushing of crystals by a large number of stages.

[0042] Furthermore, the discharge port of the pre-drying and dispersing equipment is connected to a screening device, which is provided with an outlet for large particle materials and an outlet for non-large particle materials. The screening device is used to screen the output material of the pre-drying and dispersing equipment into large particle materials and non-large particle materials with a particle size smaller than that of the large particle materials. 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 device. The crusher is used to crush the screened large particle materials, and the outlet of the crusher is connected to the deep drying equipment.

[0043] Furthermore, the drying system also includes a raw material wet crystal pretreatment device. The crystals obtained by concentration-evaporation-crystallization of the raw material liquid first pass through the raw material wet crystal pretreatment equipment to obtain the raw material wet crystals. The discharge port of the raw material wet crystal pretreatment equipment is provided with a process air inlet, which is used to input process air to blow away part of the water on the surface of the crystal, thereby reducing the possibility of agglomeration and powder crystal formation. The output process air will be filtered through a bag dust collector, the exhaust gas will be emptied, the dust will be collected, and it will be transported to the granulation equipment or re-crystallized.

[0044] Furthermore, the wet crystal coarse crushing device and / or the recrystallization growth and rounding device are fed with a crystal raw material liquid. This facilitates the coarse crushing of the wet crystals, further recrystallization growth of the short columnar crystals, and rounding of the fractured surfaces of the short columnar crystals. The principle is to wet the surface, coat, and apply a coating.

[0045] The present invention realizes high-efficiency drying in the pre-drying and dispersing equipment, and realizes further deep drying, breaking of long crystals, re-rounding of crystal fracture surfaces, discharge and air separation of floating dust or dust in the deep drying equipment, and finally discharges it from the discharge port. It is preferred to control the wind speed in the pre-drying and dispersing equipment and the deep drying equipment, control the particle size of the discharged particles, and the impact force between materials in the fluidized bed, so as to better achieve the purpose of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a system schematic diagram of Example 1; Figure 2 This is a system schematic diagram of Example 2; Figure 3 This is an enlarged picture of the finished product obtained by the combined process of enhanced airflow drying and primary airflow cooling of threonine in the background technology; Figure 4 This is an enlarged microscopic photograph of the finished product of threonine obtained by the one-stage airflow drying process in the background technology; Figure 5 This is an enlarged microscopic photograph of the finished product of threonine obtained by the continuous internal heat exchange fluidized bed drying process in the background technology; Figure 6 This is a photo of the finished product obtained by using the continuous internal heat exchange fluidized bed drying process for threonine in the background technology; Figure 7 This is an enlarged microscopic photograph of the finished product of threonine obtained by wet granulation and fluidized bed drying process in the background technology; Figure 8 This is a photo of the finished product of threonine obtained by wet granulation and fluidized bed drying process in the background technology; Figure 9 This is an enlarged microscopic photograph of the finished product of threonine obtained by the dry granulation process in the background technology; Figure 10 This is a photo of the finished product obtained by dry granulation process of threonine in the background technology; Figure 11 This is an enlarged microscopic photograph of the wet crystal material of threonine after centrifugation; Figure 12 This is another magnified microscopic photograph of the wet crystal material after the threonine wet crystals are centrifuged; Figure 13This is an enlarged microscopic photograph of the wet crystal raw material after it was crushed by a double-shaft paddle mixer; Figure 14 This is an enlarged microscopic photograph of the finished product obtained by using the drying system of the present invention for threonine wet crystal raw materials; Figure 15 This is a photo of the finished product obtained by using the drying system of the present invention for threonine wet crystal raw materials; Figure 16 This is an enlarged microscopic photograph of the finished product obtained by dry granulation of small crystals below the dust particle size or below 100 mesh collected by the drying system of the present invention; Figure 17 This is a photo of the finished product obtained by dry granulation of small crystals with a dust particle size below or below 100 meshes collected by the drying system of the present invention.

[0047] Figure 18 This is a photo of the finished product obtained from the second specific application example of the solution of the present invention. DETAILED DESCRIPTION

[0048] The embodiments of the technical solution of the present invention are described in conjunction with the accompanying drawings. The described contents are only used as partial examples and component records, not all examples, and are not intended to limit the scope of protection of the present invention.

[0049] The technical solution of the present invention has distinct and combined features that distinguish it from the prior art in this field, and the problem it solves is also different. The fact that it achieves the production of high-quality crystals demonstrates the inventive nature of this application. The basic technical features of the present invention are inseparable and interrelated. Current inventions and innovations generally optimize, expand, and improve upon existing technologies, making it difficult to identify "hugely different" technical points. Even common technical means, if combined, achieve outstanding technical effects and solve technical problems not addressed by the prior art, are considered inventive. An invention achieves an unexpected technical effect when compared to the prior art, meaning that the technical effect produces a qualitative change, resulting in new performance, or a quantitative change that exceeds expectations. This qualitative or quantitative change cannot be predicted or inferred by a person skilled in the art. When an invention produces an unexpected technical effect, it demonstrates both the distinctive nature of the invention and the non-obviousness of its technical solution, demonstrating its substantial specificity and inventiveness.

[0050] 1. Example 1

[0051] like Figure 1As shown, the present invention provides a drying system for high-quality crystals. 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 sequentially processed by the wet crystal coarse crushing device 2, the recrystallization growth and rounding device 3, the pre-drying and dispersing device 4, and the deep drying device 5 to obtain a finished product.

[0052] The wet crystals described in this embodiment are obtained by treating the raw material liquid through concentration-evaporation-crystallization to obtain crystals through raw material wet crystal pretreatment equipment 1. The raw material wet crystal pretreatment equipment 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 discharge port of the raw material wet crystal pretreatment equipment 1 is provided with a process air inlet for inputting process air to blow away part of the water on the crystal surface.

[0053] The wet crystal coarse crushing equipment 2 is connected to the output end of the raw material wet crystal pretreatment equipment 1. The wet crystal coarse crushing equipment 2 can be, but is not limited to, a stirring type, a blade type, a paddle type, or a stirring tooth type mixer, a mixer, or a 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.

[0054] The recrystallization growth and rounding equipment 3 can be, but is not limited to, a vibrating conveyor or a vibrating screen, which is used to vibrate and convey the input material. Under the action of the vibration force, short columnar crystals are formed and dispersed to increase the specific surface area, and the crystal surface can be partially recrystallized, thereby making the fracture surface of the crystal rounded, and small crystals below the dust particle size adhere to the surface of the short columnar crystals.

[0055] The pre-drying and dispersing equipment 4 can be, but is not limited to, a vibrating fluidized bed or a stirred fluidized bed, which is used to preliminarily dry the input short columnar crystals so that the moisture content of the short columnar crystals is reduced to less than half of the moisture content of the wet crystals (specifically, the wet crystals output by the raw material wet crystal pretreatment equipment 1).

[0056] The deep drying equipment 5 can be, but is not limited to, a continuous fluidized bed or a continuous internal heat exchange fluidized bed or a drum dryer, which is used to further deeply dry the input short columnar crystals to meet the moisture content requirements of the finished product. Specifically, it can be, but is not limited to, an internal heat exchange fluidized bed dryer disclosed in application number 2018115209253.

[0057] 2. Example 2

[0058] The difference between this embodiment and embodiment 1 is that the deep drying equipment 5 adopts Figure 2The continuous internal heat exchange fluidized bed shown in the figure specifically includes a fluidized bed main unit 52, and a plurality of first heat exchangers 522 are arranged in the fluidized bed main unit 52. The air inlet of the fluidized bed main unit 52 is connected to the air inlet system 51, and the air inlet system 51 includes a dehumidifier 511 and a first blower 512 connected in sequence. The input end of the dehumidifier 511 is connected to the atmosphere, and the outlet of the first blower 512 is connected to the air inlet of the fluidized bed main unit 52 on the discharge side through a second heat exchanger 513. The dust removal device 53 is connected to the air outlet of the fluidized bed main unit 52, and the dust removal device 53 includes a cyclone separator 531 and a bag dust collector 533 connected in sequence.

[0059] Furthermore, the deep drying equipment 5 is provided with two groups of dust removal devices. The air outlet of the bag dust collector 533 of the first group of dust removal devices 53 is connected to the air inlet of the fluidized bed main unit 52 on the feed 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, and a deep drying air inlet flow control valve 518 is connected in series to the bypass 517 to facilitate the input of ambient air as needed. The air outlet of the bag dust collector 533 of the second group of dust removal devices 53 is connected to the induced draft fan 54, the fresh air heat exchange equipment 8, and the exhaust gas treatment device 9 in sequence.

[0060] The fresh air heat exchange device 8 can be, but is not limited to, an energy-saving heat exchanger device suitable for the exhaust gas of the drying equipment disclosed in Patent No. 202222178689X, and can also be a plate heat exchanger device.

[0061] The tail gas treatment device 9 can adopt environmental protection devices such as water dust removal and spray tower, or a warm and high humidity tail gas treatment system disclosed in Patent No. 202222178866.4 to further treat the tail gas and achieve environmentally friendly discharge.

[0062] Figure 1 In the embodiment, the recrystallization growth and rounding device 3 is a closed structure, without the introduction of process air, as the preferred embodiment, see Figure 2 The recrystallization growth and rounding equipment 3 can also be provided with a process air inlet and outlet for introducing process air. Preferably, the process air inlet is arranged at the discharge end, and the process air inlet is arranged at the feed end, so that the blowing direction of the process air is opposite to the conveying direction.

[0063] As a further explanation of this embodiment, the pre-drying and dispersing equipment 4 and the deep drying equipment 5 are both provided with process air inlets and outlets. The process air temperature input by the pre-drying and dispersing equipment 4 is lower than the process air temperature input by the deep drying equipment 5, and the process air relative humidity input by the pre-drying and dispersing equipment 4 is higher than the process air relative humidity input by the deep drying equipment 5; the process air temperature input by the recrystallization, growth and rounding equipment 3 is lower than the process air temperature input by the pre-drying and dispersing equipment 4, and the process air relative humidity input by the recrystallization, growth and rounding equipment 3 is higher than the process air relative humidity input by the pre-drying and dispersing equipment 4.

[0064] The process air outlets of the recrystallization growth and rounding equipment 3 and the pre-drying and dispersing equipment 4 are both connected to a dust removal device 53. The dust removal devices 53 connected to the process air outlets of the recrystallization growth and rounding equipment 3 and the pre-drying and dispersing equipment 4 can be configured separately or directly connected to the second group of dust removal devices 53 of the deep drying equipment 5.

[0065] The process air inlet of the recrystallization growth and rounding equipment 3 is respectively connected to the air outlet of the bag dust collector 533 of the first group of dust removal devices 53, or / and the fresh air outlet of the fresh air heat exchange equipment 8, or / and 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 may be one or more of the ambient air, the direct exhaust air of the deep drying equipment 5, and the fresh air after heat exchange by the fresh air heat exchange equipment. In this embodiment, a mixed air between the three is introduced. Furthermore, the mixed air can be set to a mixing ratio that can be adjusted. The function of regulation (specifically, it can be achieved by connecting a regulating valve in series on the corresponding air supply pipeline, which belongs to the existing conventional technology and will not be described in detail here) is to achieve the effect of low temperature and high humidity, realize slow evaporation, and be used to realize the further recrystallization and growth of short columnar crystals and the rounding of the fracture surface of short columnar crystals, so that the dust adhering to the surface of short columnar crystals and the short columnar crystals grow firmly. After the slender crystals are broken, the specific surface area increases, and the probability of recrystallization of the residual high-concentration liquid on the surface of the crystal increases. Through vibration and friction, the sharp part of the fracture surface becomes rounded, and the whole crystal grows a layer through recrystallization. At this time, the crystal cannot evaporate quickly, otherwise it will easily cause the fracture surface of the crystal to not be fully rounded and produce crystalline dust. In some cases, such as Figure 1 As shown, the above effect can be achieved without introducing process air and relying solely on the increase in surface area after crystal fracture, given a certain amount of time.

[0066] As a further explanation of this embodiment, the process air inlet of the pre-drying and dispersing equipment 4 is used to introduce pre-drying and dispersing air, and the pre-drying and dispersing air performs heat and mass exchange and dispersion in the pre-drying and dispersing equipment 4. The discharge port of the pre-drying and dispersing equipment is connected to a screening device 45. The discharge of the pre-drying and dispersing equipment 4 is screened by the screening device 45 to separate large-particle materials and non-large-particle materials with a particle size smaller than that of large-particle materials (non-large-particle materials are specifically small-particle materials or include medium-particle materials and small-particle materials at the same time) to reduce the possibility of crystals being excessively crushed in large quantities and in multiple stages. The large-particle material outlet of the screening device 45 It is connected to the coarse crusher 42, and the outlet of the coarse crusher 42 is connected to the deep drying equipment 5. The large particle material is crushed by the coarse crusher 42 and then input into the deep drying equipment 5. The non-large particle material outlet of the screening device 45 is connected to the disperser 43, and the non-large particle material is transported to the disperser 43 for further dispersion. The outlet of the disperser 43 is connected to the deep drying equipment 5, and then input into the deep drying equipment 5 after being dispersed by the disperser 43. Heat and mass exchange and drying are carried out in the deep drying equipment 5. The dried material can also be cooled in the deep drying equipment 5. The discharge port of the deep drying equipment 5 is connected to the packaging system.

[0067] The process air inlet of the pre-drying dispersion equipment 4 is connected to the air outlet of the bag dust collector 533 of the first group of dust removal devices 53, or / and the fresh air outlet of the fresh air heat exchange device 8, or / and the process air inlet system 41 of the pre-drying dispersion equipment. The process air inlet system 41 of the dispersion equipment belongs to the existing conventional technology (it can include a pre-drying air inlet fan connected in series to the process air inlet of the pre-drying dispersion equipment 4, and can also be connected in series with a heater, a flow regulating valve, etc. as needed). The input end of the process air inlet system 41 of the dispersion equipment is connected to the atmosphere, so that the process air introduced into the pre-drying dispersion equipment 4 can be the environment The exhaust of deep drying equipment 5 has the characteristics of temperature greater than ambient wind and humidity greater than ambient wind, which is beneficial to the realization of the functions of pre-drying and dispersing equipment 4: "slow evaporation, further recrystallization, surface rolling and spreading, and secondary growth of short columnar single crystals, avoiding agglomeration into loose large particles, and further attachment and growth of floating dust and concentrated crystal liquid on the surface of large crystals, which directly reduces the proportion of dust in the material".

[0068] When the ambient humidity can achieve the above functions, the process air can also be entirely the ambient air input into the pre-drying dispersion equipment 4 through the dispersion equipment process air inlet system 41, or it can be entirely the heat exchanged fresh air through the fresh air heat exchange equipment 8. While achieving the ambient air heating and energy saving, the exhaust air of the deep drying equipment 5 can be cooled, the relative humidity can be increased, and the dust and odor can be removed to achieve the environmental protection functions, thereby reducing the pressure and functions of subsequent environmental protection processes.

[0069] Depend on Figure 2 It can be seen that the powder output by the dust removal device 53 (i.e., the cyclone separator 531 and the bag dust collector 533) can be discharged, or the outlet of the dust removal device 53 can be connected to the feed port of the granulation equipment 7 through the fan 532 to granulate the powder output by the dust removal device 53. It can also be directly connected to the wet crystal coarse crushing equipment 2 to input the powder output by the dust removal device 53 (i.e., the cyclone separator 531 and the bag dust collector 533) into the wet crystal coarse crushing equipment 2. The granulation equipment 7 can be, but is not limited to, a double-roller dry extrusion granulator or a wet extrusion granulator. During dry double-roller extrusion, it is usually first pressed into sheets 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 to the packaging system together with the material output by the deep drying equipment 5 for packaging.

[0070] The granulating device 7 can granulate the dust or floating dust particles below the particle size output by the system. Compared with the wet granulation and dry granulation methods of the prior art, a second high-quality granular product with greater strength than the existing process, lower moisture absorption than the existing process, and lower secondary crushing than the finished product produced by the existing process can be obtained. This high-quality granular product can be combined with a high-quality crystalline product of the present invention as a finished product, or can be used as a separate finished product.

[0071] The packaging system includes a packaging machine 67. The packaging system can also be equipped with a bucket elevator 61, a multi-way valve 62, a screening machine 63, a conveying device 64, a deep cooling device 65, and a finished product warehouse 66 as needed. The discharge ends of the granulating equipment 7 and the deep drying equipment 5 are connected to the bucket elevator 61. The bucket elevator 61 can be replaced by an air 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 a feed port and two discharge ports, one of which is connected to the screening machine 63, and the other discharge port can be connected to the deep drying equipment 5 as needed to transport the material to the deep drying equipment 5 for laying the base material or balancing the material layer of the deep drying equipment 5. A finished product anti-caking agent can also be selectively added to the packaging system.

[0072] The large particle material outlet of the screening machine 63 is connected to the crushing equipment 68 through a conveying device, and the discharge port of the crushing equipment 68 is connected to the deep drying equipment 5 through a conveying device. The non-large particle material outlet of the screening machine 63 is connected to the deep cooling device 65. The non-large particle material screened by the screening machine 63 is specifically small particle material or includes medium particle material and small particle material at the same time. The deep cooling device 65 has hollow blade type, drum type, spiral type, gravity cooling type, etc., such as the powder and granular solid material plate heat exchanger disclosed in patent No. 201110393598.1. The discharge port of the deep cooling device 65 is connected to the finished product warehouse 66, and the outlet of the finished product warehouse 66 is connected to the packaging machine 67. The material in the finished product warehouse 66 can also be connected to the deep drying equipment 5 through a conveying device, and part of the material is input into the deep drying equipment 5 for laying the base material.

[0073] As a further improvement of this embodiment, the wet crystal coarse crushing equipment and / or the recrystallization growth and rounding equipment are added with crystal raw material liquid, and the mass ratio of the added amount of the crystal raw material liquid (mass concentration is 17%) to the wet raw material is 53-265:1000. Preferably, the crystal raw material liquid is sprayed through an atomizing nozzle installed on the equipment. The specific injection position can be reasonably selected by those skilled in the art based on common sense. It can be installed at any position in the material that is convenient for spraying the crystal raw material liquid into the material. The crystal raw material liquid can also be directly added to the wet crystal coarse crushing equipment through the liquid pipe.

[0074] 3. Specific application example 1 of the present invention

[0075] The following describes the working process of the present invention using the drying process of threonine as an example: 1) The threonine liquid is concentrated, evaporated, crystallized, and then separated by centrifuge 1 to obtain Figure 11 、 12 The wet crystals shown, such as Figure 2 As shown, process air is introduced into the discharge port of centrifuge 1 to blow away part of the water on the surface of the crystals, reducing the possibility of agglomeration and powder crystal formation. The output process air can be filtered by a bag dust collector, the exhaust gas is emptied, and the dust is collected and transported to the granulation equipment or re-crystallized.

[0076] Due to the difference in process between different manufacturers, the shape, size and moisture content of the crystals are also different. Figure 11 、 12It can be seen that the crystals are slender in shape, and the initial moisture content of wet crystals is usually between 7% and 11%, with an average of about 9%. The length is about 5-10 times the diameter, and the average size can reach 0.14mm*0.9mm. Sometimes the average size is only 0.075mm*0.6mm, but there are very few crystals with a diameter less than 0.037mm. Most of them are attached to the surface of large crystals, but are easy to separate. Threonine crystals grow naturally at the edge of the powder dissolving tank mouth for several days, and can be observed to grow to 3-5mm in length, and the diameter direction will also become thicker.

[0077] 2) The wet crystals are crushed by the wet crystal coarse crushing equipment 2, specifically a double-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 can be adjusted to adjust and control the crushing force. It is necessary to avoid the wet crystals from being crushed in the diameter direction of the crystals and the crystals from sticking together due to strong mixing or strong stirring.

[0078] like Figure 13 As shown, after being crushed by the 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.

[0079] 3) After crushing, the particles are fed into the recrystallization, growth and rounding equipment 3. Under the action of vibration, the short columnar crystals are dispersed to increase the specific surface area. The surface of the crystals can be partially recrystallized, thereby rounding the fracture surface of the crystals and making small crystals below the dust particle size adhere to the surface of the short columnar crystals. The recrystallization, growth and rounding equipment uses a vibrating conveyor. The process air introduced is the mixed air of the ambient air after being heated by the fresh air heat exchange equipment 8 and the exhaust air of the deep drying equipment 5. The process air introduced at this time has a low temperature, high humidity and an adjustable effect. Slow evaporation is used to achieve further recrystallization and growth of short columnar crystals and rounding of the fracture surface of short columnar crystals. It also allows the dust adhering to the surface of short columnar crystals to grow firmly with the short columnar crystals. After the elongated crystals break, the specific surface area increases, and the probability of recrystallization of the residual high-concentration liquid on the crystal surface increases. Through vibration and friction, the sharp part of the fracture surface becomes rounded, and the crystal as a whole grows by one layer through recrystallization. At this time, the crystal cannot evaporate quickly, otherwise it will easily cause the fracture surface of the crystal not to be fully rounded and produce crystalline dust. In some cases, without introducing process air, relying solely on the increase in surface area after the crystal breaks, and giving it a certain amount of time, the above effect can also be achieved.

[0080] 4) Input the pre-drying dispersion device 4 for pre-drying. The pre-drying dispersion device 4 adopts a vibrating fluidized bed. The vibrating fluidized bed is fed with pre-drying dispersion air through the dispersion device process air inlet system 41, and heat and mass exchange and dispersion are carried out in the vibrating fluidized bed.

[0081] The moisture content of the semi-finished product output by the pre-drying and dispersing device 4 is between 1-5%, much higher than the 0.2-0.5% moisture content of the finished product. Threonine crystals at this moisture content possess a certain strength and are less prone to breakage than the dried finished product. The likelihood of crystals clumping is greatly reduced. Furthermore, the vibrating fluidized bed has low crushing force but provides repeated agitation. The dispersed fluidized air allows the surface moisture of the threonine crystals to be easily removed. Because the surface moisture is completely free, the required drying power is relatively low. Exhaust air from the deep drying device 5 can be directly used. This exhaust air has a temperature of approximately 50-80°C, much lower than the 130-160°C process air from the deep drying device 5. This exhaust air has a much higher humidity than ambient air, resulting in a slow drying rate. This reduces cracking on the surface of the threonine crystals and helps prevent breakage and secondary breakage. Compared to existing technologies, this can theoretically reduce overall steam energy consumption by half. Even when ambient air is used directly, it can still achieve the pre-drying and dispersing effect. This exhaust air can also be reheated to adjust the strength of the pre-drying and dispersing process.

[0082] The process air introduced into the pre-drying and dispersing device 4 has a lower temperature and higher humidity than the inlet process air of the deep drying device 5. The material has sufficient time to pass through the pre-drying and dispersing device 4 and passes through it evenly, so as to achieve slow evaporation, further recrystallization, and surface rolling and spreading. This is beneficial to the re-growth of single short columnar threonine crystals, avoids or greatly reduces the aggregation of loose large particles, and is also beneficial to the further rounding of the short columnar fracture surface, which is beneficial to greatly reduce energy consumption. The process air inlet system 41 of the pre-drying and dispersing device and the exhaust air of the deep drying device are mixed and the ratio is adjustable, so that the process air introduced into the pre-drying and dispersing device 4 has the effect of low temperature, high humidity, and adjustable evaporation rate.

[0083] In the pre-drying and dispersing device 4, the shape of the crystals can be kept as intact as possible. Due to the repeated turning and gentle crushing force, some of the clumped crystals can be dispersed, and the overly long crystals are broken. The length can be kept at an average of about 1-4 times the diameter.

[0084] 5) The outlet material of the pre-drying and dispersing device 4 is classified. Since the large particles are mainly clumping particles, a coarse crusher 42 is used for extrusion crushing to reduce the possibility of excessive crushing of the crystals in large quantities and multiple stages. The coarse crusher 42 can be, but is not limited to, a fast granulator to disperse the clumping particles. The mesh diameter is between 2-10 mm, so as to achieve the purpose of dispersion and crushing into small particles. The non-large particle materials are transported to the break-up machine 43 for further dispersion.

[0085] The materials output from the coarse crusher 42 and the disperser 43 enter the deep drying equipment 5, and after deep drying in the deep drying equipment 5, a high-quality crystalline product meeting the moisture content requirements is obtained.

[0086] 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, the fracture surface corners of single threonine crystals can be further passivated, and the long needle-shaped crystals that are too long and easy to break are broken again, but most of the crystals are retained in the diameter direction without being broken. The air separation effect of fluidized air is used to discharge the small and non-compliant floating dust or dust from the air outlet of the deep drying equipment 5 and collect them through the cyclone separator 531 and the bag dust collector 533.

[0087] 6) The powder material with a particle size below the particle size collected by the cyclone separator 531 and the bag dust collector 533 in the system is input into the roller dry extrusion granulator for granulation. Compared with the wet granulation and dry granulation in the background technology, the gaps between the particles are small, the granulation is easy to compact, the power required for granulation is small, the finished product has high strength, high bulk density, low moisture absorption and low secondary crushing, and a second high-quality granular product is produced. 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 conveyed to the internally heated fluidized bed dryer 52 and mixed with the above-mentioned crystalline product as a commercial product. The regenerated dust or fines are recycled and discharged to the granulation equipment 7.

[0088] The recrystallization, growth and rounding equipment 3 and the pre-drying equipment 4 of the present invention can also be connected into an integrated structure, like the pre-drying equipment 4, the front part is the recrystallization, growth and rounding equipment 3, and the rear part is the pre-drying equipment 4. The material output by the recrystallization, growth and rounding equipment 3 directly enters the pre-drying equipment 4. The recrystallization, growth and rounding equipment 3 may or may not be introduced into the process air, and the pre-drying equipment 4 needs to be introduced into the process air.

[0089] like Figure 2 As shown, the exhaust air or ambient air on the discharge side of the deep drying equipment 5 is heated by the fresh air heat exchange equipment 8, and then 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.

[0090] 4. Specific application example 1 Dry product testing Figure 14 This is an enlarged microscopic photograph of the high-quality crystalline product obtained in step 5). Figure 15 This is a photo of the finished product of the high-quality crystalline product obtained in step 5); it can be seen that the finished product is mainly composed of crystals and includes high-quality recrystallized products, that is, a high-quality crystalline product.

[0091] The crystal surface can be partially recrystallized, thereby making the fracture surface of the crystal rounded and allowing small crystals below the dust particle size to adhere to the surface of the short columnar crystal.

[0092] Moisture absorption observation: At 20℃ and 60-70% relative humidity, the moisture content of the finished product was measured to be approximately 0.89% after 2 hours.

[0093] At the same time by Figure 14 、 15 It can be seen that there is basically no dust below the particle size, there is basically no dust adsorbed by the inner film of the packaging bag, and there is basically no inhalable particulate matter when the packaging bag is opened; the finished product has a transparent effect to the naked eye, and there is an obvious layer of recrystallization and some nodules on the crystal surface. Most of them have a short columnar shape, and the edges of the fracture surface tend to be rounded and ground; after analysis, dust particles below the particle size account for less than 10% of the raw materials, and particles below 100 mesh account for less than 20% of the raw materials.

[0094] Energy consumption: The installed power is 300KW, the average steam consumption per hour is about 0.8-1 tons, the average production capacity is 6 tons / hour, and the average energy consumption parameters per ton of finished product are 40 kWh and about 0.15 tons of 0.6MPa saturated steam; Finished product parameters: The moisture content of the finished product is about 0.25-0.3%, the natural bulk density is about 680kg / m3, and the vibrated bulk density is about 760kg / m3; Figure 16 This is an enlarged microscopic photograph of the second high-quality particle product obtained in step 6); Figure 17 This is a photo of the finished product of the second high-quality granule product obtained in step 6).

[0095] Observation on the moisture absorption of the second high-quality granular product: at 20°C and 60-70% relative humidity, the moisture content of the finished product was measured to be approximately 1.02% after 2 hours.

[0096] Observation of the second high-quality granular product: there is basically no floating dust particle size, the average particle size is adjustable, and the common range is 10-60 mesh. There is a small amount of adsorbed dust on the inner film of the packaging bag, and there are very few inhalable particles when the packaging bag is opened. The single finished granule is composed of multiple small crystals. Compared with the raw material, the small crystals are partially broken. Compared with the dry granulation process of the above-mentioned threonine dry powder, there are basically no reflective crystals in the granules, the dust volume is less, and the hand-pinch strength is greater.

[0097] 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, and the average production capacity is 0.6 tons per hour. The energy consumption per ton of finished product increases by about 38-45 kWh. Finished product parameters: finished product moisture content is about 0.3%, natural bulk density is about 610kg / m 3 , the compacted bulk density is about 760 kg / m 3 .

[0098] The finished product analysis statistics are as follows, wherein the proportion of the crystalline finished product to the total finished product is approximately 80-95%. The two finished products can be packaged separately or mixed. When the dry granulation particles of the present invention are not needed, the powder can be dissolved and recrystallized to obtain all crystalline particles, which are all optional embodiments.

[0099]

[0100] The third product of the present invention is a finished product made by wet granulation of small crystals with a dust particle size below or below 100 mesh. The finished product is similar to the wet granulation of the background technology, but the finished product has a higher hand-pinch strength, a lower secondary crushing property, and a higher primary bulk density. The natural bulk density is about 550 kg / m 3 , compacted bulk density is about 650 kg / m 3 , the hygroscopicity is lower. The hygroscopicity analysis shows that the moisture content of the finished product is about 1.1% after 2 hours at 20℃ and 60-70% relative humidity, which shows that the advantage of the third product is not obvious, but compared with dry granulation, it is safer against fire and explosion.

[0101] V. Specific application example 2 of the present invention The difference between the specific application example 2 and the specific application example 1 is that the feed port and the discharge port of the wet crystal coarse crushing device 2 are respectively sprayed with the crystal raw material liquid, and the mass ratio of the sprayed crystal raw material liquid (mass concentration is 17%) to the wet raw material is 100:1000. Figure 18 The photos of the finished product obtained in this application example show that the granular product is larger, stronger and more beautiful in appearance than the product obtained in Example 1.

[0102] The present invention uses the above novel preparation and drying process to achieve a high-quality crystalline L-threonine product with no flying dust, substantially no inhalable particulate matter, no obvious dust adsorption on the packaging bag, a hand-kneading hardness exceeding that of existing products, low secondary breakage, good fluidity, a transparent appearance of the finished product, a high bulk density, and low moisture absorption. Specific controllable indicators include: a dust rate of less than 0.5%, power consumption per ton of product of less than 40 kWh, 0.6 MPa saturated steam of less than 0.15 tons, and a finished product bulk density of 740-780 kg / m³ using a BT-1000 powder comprehensive property tester. 3According to the moisture absorption analysis at 20℃ and 60-70% relative humidity, the moisture content of the finished product was about 0.89% after 2 hours. The moisture absorption was greatly reduced, so the possibility of the finished product agglomeration was reduced. Because the dust and inhalable particulate matter were reduced or even eliminated, the occupational hygiene, environmental protection and safety of the production operation were good. The comprehensive realization of higher product prices is expected to increase by 100-500 yuan per ton. In terms of sales price alone, the 100,000-ton production line will generate an additional profit of 10-50 million yuan per year, the user's market competitiveness will be improved, and the overall social and economic benefits and technical efficiency levels will be improved.

[0103] In this method, the sum of dust and inhalable particulate matter, i.e., the proportion of finished product with a mesh size less than 150 mesh, is determined by screening. Because inhalable particulate matter is difficult to screen, optical observation and the presence of significant adsorption on the packaging and sensory adsorption are used as the basis. All magnified microscopic photographs above may have a certain magnification deviation due to instrumental error. Threonine moisture content determination method: Electric constant temperature drying oven, model 101-1, 105°C, 30 minutes.

[0104] In summary, the present invention addresses the shortcomings of the above-mentioned traditional finished product preparation and drying processes, and hereby provides a new preparation and drying process to achieve a high-quality crystalline finished product. Compared with the finished products of existing preparation methods, it has many advantages: the finished product has a clear granular feel to the naked eye and is beautiful in appearance; the sum of dust and inhalable particulate matter is basically non-existent in the finished product, and there is no obvious dust adsorption or basically no dust on the packaging bag; the finished product is hard when squeezed by hand, has low secondary crushing, and has good fluidity; the drying operation energy consumption is low; the finished product bulk density is greater than that of the existing process; the moisture absorption is low, thereby reducing the caking of the finished product. Therefore, the following corresponding advantages are achieved: because there is basically no dust and inhalable particulate matter, the secondary crushing is low, and the use and production operation have good occupational hygiene, good environmental protection, good safety, and good anti-explosion performance; the drying operation energy consumption is low, and the preparation cost is reduced; the finished product bulk density is high, less packaging materials are used per ton of product, and the freight calculated by volume is low, thereby reducing packaging and transportation costs; the moisture absorption is low, and the shelf life is extended and the hardness of the finished product is improved, and the possibility of caking is low.

[0105] The present invention relates to a high-quality crystalline product and its preparation and drying process, which is mainly suitable for slender crystals. When the crystals are not slender, the present invention can also be used to achieve the effects of enlarging and rounding the crystals, reducing the dust rate, increasing the bulk density, and preventing agglomeration.

[0106] The terms used in the above implementation modes and arrangements of the present invention are all based on the prior art. This embodiment only describes the inventive point of the present invention in detail. For example, it is well known to those skilled in the art that the fluidization device or system also needs to be configured or equipped with a blower, an air heater, an air inlet pipe, an air damper, a support platform, a main engine to cyclone separator connecting pipe, a bag dust collector, a cyclone to bag connecting pipe, an induced draft fan, a bag to induced draft fan connecting pipe, a water dust collector, an induced draft fan to water dust collector pipe, a control system, and instruments. In addition, there are also existing commonly used configurations such as semi-finished product conveying, a screening machine, a crusher, seed crystal conveying or air conveying, a spiral conveying, a fan or air closure, an acceleration tube, a finished product conveying, a finished product warehouse, and a packaging machine. The cooling device can optionally adopt fluidized bed cooling, drum cooling, a hollow blade drying and cooling machine, a solid cooler (plate type or tube type, etc.), or a combination of multiple cooling methods. For example, the solid cooler has ZL201110393598.1 plate heat exchanger for powdered and granular solid materials to form a complete system device. This belongs to conventional technology and will not be described in detail here. Appendix Figures 1 to 2 The working process is only a partial illustration, not all working forms, so they will not be explained one by one here.

Claims

1. A drying system for high-quality crystals, the raw material being wet crystals, characterized by: It includes coarse crushing equipment, recrystallization, growth and rounding equipment, pre-drying and dispersing equipment, and deep drying equipment connected in sequence; wherein the recrystallization, growth and rounding equipment is used to vibrate and convey the material.

2. The high-quality crystal drying system 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 perform preliminary drying on the short columnar crystals, reducing the moisture content of the short columnar crystals to less than half of the moisture content of the wet crystals; the deep drying equipment is used to achieve further deep drying of the short columnar crystals to meet the moisture content requirements of the finished product.

3. The high-quality crystal drying system according to claim 1, characterized in that: The recrystallization growth and rounding equipment is provided with a process air inlet and outlet to facilitate the introduction of process air.

4. The drying system for high-quality crystals according to claim 1, characterized in that: Both the pre-drying and dispersing equipment and the deep drying equipment are provided with process air inlets and outlets. The process air temperature input to the pre-drying and dispersing equipment is lower than the process air temperature 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 the relative humidity of the process air input to the deep drying equipment.

5. The drying system for high-quality crystals according to claim 3, characterized in that: The temperature of the process air introduced into the recrystallization, growth and rounding equipment is lower than the temperature 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 the relative humidity of the process air introduced into the pre-drying and dispersing equipment.

6. The high-quality crystal drying system according to claim 1, characterized in that: The drying system also includes a granulating device, which is used to granulate materials with a dust particle size below the dust particle size output from the dust outlet of the pre-drying and dispersing device and / or the deep drying device.

7. The high-quality crystal drying system according to claim 1, characterized in that: The drying system also includes a fresh air heat exchange device, the exhaust port of the deep drying equipment is connected to the fresh air heat exchange device, and the fresh air outlet of the fresh air heat exchange device is connected to the pre-drying dispersion equipment and / or the deep drying equipment to realize the recycling of waste heat.

8. The high-quality crystal drying system 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.

9. The high-quality crystal drying system 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 disperse the semi-finished products output by the pre-drying and dispersing equipment and then input them into the deep drying equipment.

10. The high-quality crystal drying system according to claim 1, characterized in that: The discharge port of the pre-drying and dispersing equipment is connected to a screening device, which is provided 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 particle materials and non-large particle materials with a particle size smaller than the large particle materials. 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 device. The crusher is used to crush the screened large particle materials, and the outlet of the crusher is connected to the deep drying device.

11. A drying system for high-quality crystals according to any one of claims 1 to 10, characterized in that: The wet crystal coarse crushing device and / or the recrystallization growth and rounding device are added with crystal raw material liquid.

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