A spray drying tower

Abstract

The invention discloses a spray drying tower. Hot gas enters from the bottom of the drying tower and is discharged from the top. The material to be dried enters from the side of the drying tower in a spray manner and is discharged from the bottom of the drying tower in powder form after being dried. The drying tower comprises: an upper tower body, which is a conical cylinder with an outlet on the top and a diameter shrinking upward. The gas after drying is discharged from the top outlet of the upper tower body; a straight cylinder section, which is a vertical downward extension of the lower end of the upper tower body. The straight cylinder section comprises, from top to bottom, a first straight cylinder section and a second straight cylinder section with equal axial lengths. The inner wall of the first straight cylinder section is circumferentially provided with a circle of short spray guns, the inner wall of the second straight cylinder section is circumferentially provided with a circle of long spray guns, and the middle inner wall of the straight cylinder section is provided with a central spray gun. The lower tower body is in a cone shape with a diameter shrinking downward. A hot gas distributor is provided at the top cross section of the lower tower body.

Description

Technical Field

[0001] The invention relates to the field of drying equipment, in particular to a spray drying tower. Background Art

[0002] Spray drying is a drying process that puts the raw material liquid into an atomizer to separate it into droplets, and obtains the powder product by direct contact between hot air or other gases and the droplets. The method of using spray dryers is mostly used in food, pharmaceuticals, chemicals and other industries. Spray drying has a fast drying speed and only takes a few seconds to complete. It is suitable for drying heat-sensitive materials. Since the drying process is completed in an instant, the particles of the finished product can basically maintain a spherical shape similar to the droplets. The product has good dispersibility, fluidity and solubility, the production process is simplified, and the operation and control are convenient. Spray drying is usually used for solutions with a solid content of less than 60%. After drying, there is no need for crushing and screening, which reduces the production process and simplifies the production process. For the particle size, bulk density and moisture of the product, within a certain range, the operating conditions can be changed to adjust, and control and management are very convenient.

[0003] When drying materials with a drying tower, if you want to increase the output, simply increasing the tower diameter and height will not have a significant effect on increasing output, and it will also waste material costs and increase investment. Therefore, by improving the internal structure of the drying tower and determining the appropriate tower diameter and height ratio, you can not only increase the output but also save materials.

[0004] And the setting of the spray gun inside the drying tower is very important. Uneven contact between the material to be dried and the hot air, too much feed, insufficient evaporation, unstable added liquid and other reasons can easily cause wall sticking. In traditional drying towers, the spray gun is set at the top of the tower, and the material flows from top to bottom.

[0005] The distribution of hot air flow is also crucial to the quality of the product. When the dry particles are exposed to high-temperature drying gas along with the rising flow of the drying gas, the quality of the dry particles may be significantly reduced due to the temperature. For food or medicine, the dry particles are exposed to a higher temperature than necessary, causing the necessary components to volatilize or deteriorate. Or, the dry particles are melted to form coarse particles, which reduces their quality. When the function of the dry particles requires dispersibility, the dispersibility will be significantly reduced. The components of the dry particles promote oxidation reactions and produce coloration. And sometimes they will catch fire. Therefore, the time that the dry particles are in contact with hot air should be minimized. Summary of the invention

[0006] In response to the above problems, the present invention discloses a spray drying tower. After many experiments, the appropriate tower diameter and height ratio of the drying tower are determined. Through the reasonable layout of the atomizing spray gun and the improvement of the internal structure of the hot air airflow channel, the hot air and material droplets can be effectively brought into full contact, the drying efficiency is improved, the wall sticking phenomenon is reduced, and the product quality is improved.

[0007] The technical solution of the present invention is as follows:

[0008] A spray drying tower, hot gas enters from the bottom of the drying tower and is discharged from the top. The material to be dried enters the drying tower from the side in a spray manner and is discharged from the bottom of the drying tower in powder form after drying. The drying tower comprises: an upper tower body, which is a conical cylinder with an outlet on the top and a diameter that decreases upward. The gas after drying is discharged from the top outlet of the upper tower body; a straight cylinder section, which is a vertical downward extension of the lower end of the upper tower body. The straight cylinder section comprises, from top to bottom, a first straight cylinder section and a second straight cylinder section with equal axial lengths. The inner wall of the first straight cylinder section is circumferentially provided with a circle of short spray guns, the inner wall of the second straight cylinder section is circumferentially provided with a circle of long spray guns, and the middle inner wall of the straight cylinder section is provided with a central spray gun. The lower tower body is a conical cylinder with a diameter that decreases downward. A hot gas distributor is provided at the top cross section of the lower tower body.

[0009] Furthermore, a plurality of short spray guns are arranged in a ring along the inner wall of the first straight cylinder section, and the short spray guns include a short spray gun arm and a short spray gun nozzle. The short spray gun is arranged at a height greater than one-half of the axial height of the first straight cylinder section. The short spray gun arm extends horizontally toward the center of the straight cylinder section. The length of the short spray gun arm is less than one-third of the radius of the straight cylinder section. The short spray gun nozzle faces downward, and the angle between the short spray gun head and the short spray gun arm is greater than 90 degrees.

[0010] Furthermore, the central spray gun includes a central spray gun arm and a central spray gun nozzle. The central spray gun arm extends horizontally to the central axis of the straight cylinder section. The central spray gun nozzle faces downward and has an angle of 90 degrees with the central spray gun arm.

[0011] Furthermore, a plurality of long spray guns are arranged in a ring along the inner wall of the second straight cylinder section, and the long spray gun includes a long spray gun arm and a long spray gun nozzle. The setting height of the long spray gun is greater than one half of the axial height of the second straight cylinder section. The long spray gun arm extends horizontally toward the center of the straight cylinder section. The length of the long spray gun arm is greater than one half of the radius of the straight cylinder section. The long spray gun nozzle faces downward, and the angle between the long spray gun arm and the long spray gun arm is greater than 90 degrees.

[0012] Furthermore, the central spray gun head, the long spray gun head and the short spray gun head are pressure atomizers.

[0013] Furthermore, the height of the straight tube section is H, the diameter is D, and H and D satisfy the following relationship: 3.3≤H / D≤3.4.

[0014] The beneficial effects of the present invention are:

[0015] The drying tower of the present invention has a tower diameter and a tower height significantly reduced compared with a traditional drying tower while maintaining the output unchanged, thereby effectively saving costs and reducing energy consumption.

[0016] According to the changes in the tower body diameter and tower body height, the number and arrangement of spray guns are changed accordingly. At the same time, the internal structure of the air flow channel is reasonably improved so that the air flow and the sprayed droplets can have a good intersection, eliminating the short-circuit phenomenon of the air flow and achieving higher heat utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of a spray drying tower according to an embodiment of the present invention;

[0018] Figure 2 A schematic diagram of the prior art structure of a spray drying tower;

[0019] Figure 3 The present invention is a schematic diagram of the structure of a hot gas distributor of a spray drying tower.

[0020] In the figure, 1. upper tower body, 2. straight cylinder section, 3. segment spray gun, 4. central spray gun, 5. long spray gun, 6. lower tower body, 7. hot gas distributor, 21. first straight cylinder section, 22. second straight cylinder section. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1

[0023] refer to Figure 1-2A spray drying tower, hot gas is input from the air inlet at the bottom of the drying tower, passes through the hot gas distributor 7, and is uniformly output to the top of the drying tower. The material to be dried enters the drying tower from the side of the drying tower in the form of spray through the atomizer, and is output from the bottom of the drying tower in powder form after drying. The drying tower includes an upper tower body 1, which is a conical cylinder with an outlet at the top and a diameter that shrinks upward. After drying, the gas is discharged from the top outlet of the upper tower body 1. The drying tower of the present invention is a countercurrent type, that is, the movement direction of the drying medium (hot air) is opposite to the movement direction of the atomized liquid, the atomized droplets move from top to bottom, and the hot air moves from bottom to top. It is characterized in that the movement direction of the hot air in the drying tower is opposite to the movement direction of the atomized droplets, and the atomized liquid droplets are suspended in the drying tower for a long time, which is very suitable for drying liquid with high water content. The disadvantage of countercurrent drying is that the finished product after drying is still in continuous contact with the high-temperature drying medium while falling, so the dried product is easily overheated and coked. Because, at the inlet of this type of material, the drying heat medium with high humidity and low temperature contacts with the liquid droplets with high water content. At the outlet of the material, the heat medium with low humidity and high temperature contacts with the powder particles with low water content. Therefore, the drying driving force at various places in the drying tower is not much different and the distribution is relatively uniform.

[0024] The straight section 2 is a vertical downward extension of the lower end of the upper tower body. The straight section includes a first straight section 21 and a second straight section 22 of equal axial length from top to bottom. The inner wall of the first straight section is circumferentially provided with a circle of short spray guns 3, the inner wall of the second straight section is circumferentially provided with a circle of long spray guns 5, and the middle inner wall of the straight section is provided with a central spray gun 4. For a drying tower with a small evaporation amount, such as a drying tower with an evaporation amount of less than 500 kg / h, a nozzle is provided at the top of the drying tower to achieve good material atomization. However, as the evaporation amount increases, a nozzle cannot achieve a good atomization. As long as the evaporation amount is large, the droplet size increases and it is easy to become a linear flow, resulting in a situation of not being dry and sandwiched powder. Therefore, it is necessary to use multiple nozzles and reasonably distribute the nozzles. On the one hand, the atomization can be uniform, and on the other hand, the moisture content of the material droplets can be avoided to be too high, so that the material is heated evenly.

[0025] The drying tower of the present invention also includes a conical lower tower body 6 with a reduced diameter downward, and a hot gas distributor 7 is provided at the top cross section of the lower tower body. The uniform distribution of hot air flow in the drying tower is very important for the drying effect of the material. In order to make the wind speed of the drying gas uniform, the hot air flow is input from the air inlet and then output to the straight section through the hot air flow distributor. When the hot air wind speed of the straight section is uniform, the dried material particles can flow into the lower tower body along the straight section to avoid the material from generating a countercurrent due to the uneven air flow during the descent process, that is, the material moves upward for a distance, resulting in a long residence time in the drying tower, causing some dried particles to adhere to the inner wall of the drying tower and the spray device, thereby causing the material particles to deteriorate due to heat, and the dispersion and quality of the product to deteriorate. The purpose of the hot air flow distributor is to make the wind speed uniform. On the premise of maintaining this function, it can be of any shape, such as a honeycomb shape or a lattice shape. There are certain requirements for the pressure loss of the hot air flow distributor. If the pressure loss is too large, the desired gas air volume may not be obtained. In addition, if the pressure loss is too small, it is easy to make the distribution effect unclear.

[0026] Further, a plurality of short spray guns 3 are arranged in a ring along the inner wall of the first straight cylinder section, and the short spray guns include short spray gun arms and short spray gun nozzles. The height of the short spray gun is greater than one-half of the axial height of the first straight cylinder section, and the short spray gun arm extends horizontally toward the center of the straight cylinder section. The length of the short spray gun arm is less than one-third of the radius of the straight cylinder section, and the short spray gun nozzle faces downward, and the angle with the short spray gun arm is greater than 90 degrees, preferably 105 degrees, so that the material can be evenly dispersed. The short spray gun head is a pressure atomizer. Pressure spray drying is to tear the material into droplets through a high-pressure pump through a high-pressure nozzle and then exchange heat and mass with the hot air in the tower to dry the atomized material into the required powder. The arrangement of the short spray guns in the first straight cylinder section is mainly based on the production capacity of the drying tower. Since the short spray guns are located in the first straight cylinder section, the position farthest from the air inlet is reduced compared to the position near the air inlet. Therefore, the flow of the short spray gun is not easy to be too large, and the droplets after atomization are mainly distributed around the drying tower. Preferably, the number of short spray guns is 3, so that the droplets from each nozzle do not cross each other during spraying, and the droplets do not become larger.

[0027] At the middle position of the axial direction of the straight section 2, a central spray gun 4 is arranged, including a central spray gun arm and a central spray gun nozzle. The central spray gun arm extends horizontally to the central axis of the straight section, and the central spray gun nozzle faces downward, with an angle of 90 degrees with the central spray gun arm. The material is mainly sprayed downward along the center of the drying tower. The airflow atomizer uses gas to blow out the material at a fast speed. The liquid material is torn into a liquid film and then atomized into fine droplets. Since the height of the central spray gun is located at the center of the straight section, the flow rate there needs to be moderate, and the flow rate can be accelerated to achieve a better drying effect.

[0028] Furthermore, a plurality of long spray guns 5 are arranged in a ring along the inner wall of the second straight cylinder section 22. The long spray guns include long spray gun arms and long spray gun nozzles. The long spray guns are arranged at a height greater than one-half of the axial height of the second straight cylinder section. The long spray gun arms extend horizontally toward the center of the straight cylinder section. The length of the long spray gun arms is greater than one-half of the radius of the straight cylinder section. The long spray gun nozzles face downward, and the angle between the long spray gun arms and the nozzles is greater than 90 degrees. The long spray gun head is a pressure atomizer. Since the long spray gun head is relatively close to the air inlet, it is suitable for a larger flow rate, so that the material droplets fill the entire cross section of the drying tower.

[0029] In the present invention, the material to be spray-dried is not particularly limited. The material can be formed into microparticle droplets by passing through an atomizer, and the solvent or dispersant can be volatilized in the dryer to obtain dry particles. For example, synthetic chemicals such as food, medicine, detergent or fertilizer, solutions or dispersions of inorganic materials such as synthetic resins, pigments or ceramics can be used. There is no limitation on the solvent or dispersant, for example, water or solvents can be used.

[0030] Example 2

[0031] refer to Figure 3 This embodiment shows the drying tower before improvement and its main technical parameters. The drying tower before improvement has a spray gun at the top of the drying tower, and the material droplets are sprayed from top to bottom, and the hot air is blown upward from the bottom of the drying tower, which is a countercurrent drying tower. The height of the straight section of the drying tower is 25 meters, and the diameter of the straight section is 7 meters. Taking the drying of washing powder as an example, the evaporation capacity of the drying tower is 13500kg / h, the initial mass fraction of the washing powder is 63~65%, the feed temperature is 55~60℃, and the air volume is 84440 m 3 / h (under standard conditions), air inlet temperature: 380~400 ℃; exhaust air volume: 103040 m3 / h (under standard conditions); exhaust air temperature: 105~120℃; powder mass fraction: 97.2%. At this time, the hourly heat supply is about 11.4 million kcal.

[0032] Example 3

[0033] This embodiment is a drying tower of the present invention, and the main technical parameters of the drying tower. Three short spray guns are evenly distributed on the upper part of the first straight section, a central spray gun is distributed in the middle of the straight section, and three long spray guns are evenly distributed on the upper part of the second straight section. The material droplets are sprayed from top to bottom, and the hot air is upward from the bottom of the drying tower, which is a countercurrent drying tower. The height of the straight section of the drying tower is 21 meters, and the diameter of the straight section is 6 meters. Taking the drying of washing powder as an example, the evaporation amount of the drying tower is 13500kg / h, the initial mass fraction of the washing powder is 63~65%, the feed temperature is 55~60℃, the inlet air volume: 65790 m3 / h (under standard conditions), the inlet air temperature: 420~450℃; the exhaust air volume: 84590 m3 / h; the exhaust air temperature: 90~100℃; the powder mass fraction: 97.3%. At this time, the hourly heat supply is about 10.1 million kcal.

[0034] Through the technical improvement of the present invention, the tower body diameter can be reduced to 6 meters and the height can be reduced to 21 meters, and the same output can still be achieved. The material and manufacturing costs alone can save about 250,000 yuan, which significantly reduces costs and improves competitive advantages. According to the changes in the tower body diameter and tower body height, the number and layout of the spray guns are changed accordingly. At the same time, after the internal structure of the airflow channel is reasonably improved, the airflow and the droplets after spraying can have a good intersection, eliminating the short circuit phenomenon of the airflow, and the heat utilization rate is higher. The original spray tower exhaust gas temperature is between 105 and 120°C. After various technical improvements, the exhaust gas temperature drops to between 90 and 100°C. Compared with a heating device with an hourly heating capacity of 10 million kcal, 31.2 million kcal of heat can be saved every day (equivalent to 6,240 kg of raw coal per day for coal with a calorific value of 5,000 kcal). Due to the reduction in tail gas emissions after the improvement, the power consumption is also reduced by about 20%, which saves energy significantly.

[0035] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A spray drying tower, wherein hot gas enters from the bottom of the drying tower and is discharged from the top, and the material to be dried enters from the side of the drying tower in a spray manner and is discharged from the bottom of the drying tower in powder form after drying, characterized in that: The drying tower comprises: The upper tower body is a conical cylinder with an outlet at the top and a diameter that decreases upward. The gas after drying is discharged from the top outlet of the upper tower body. The straight barrel section is a vertical downward extension of the lower end of the upper tower body. The straight barrel section includes a first straight barrel section and a second straight barrel section with equal axial lengths from top to bottom. A circle of short spray guns are circumferentially arranged on the inner wall of the first straight barrel section, a circle of long spray guns are circumferentially arranged on the inner wall of the second straight barrel section, and a central spray gun is arranged on the middle inner wall of the straight barrel section; The lower tower body is in a conical shape with a diameter decreasing downward, and a hot gas distributor is provided at the top cross section of the lower tower body; A plurality of short spray guns are arranged in a ring shape along the inner wall of the first straight tube section, the short spray guns include short spray gun arms and short spray gun nozzles, the arrangement height of the short spray guns is greater than one-half of the axial height of the first straight tube section, the short spray gun arms extend toward the center of the straight tube section in the horizontal direction, the length of the short spray gun arms is less than one-third of the radius of the straight tube section, the short spray gun nozzles face downward, and the angle between the short spray gun arms and the short spray gun nozzles is greater than 90 degrees; The central spray gun includes a central spray gun arm and a central spray gun nozzle, wherein the central spray gun arm extends horizontally to the central axis of the straight tube section, and the central spray gun nozzle faces downward and has an angle of 90 degrees with the central spray gun arm; A plurality of long spray guns are arranged in a ring shape along the inner wall of the second straight tube section. The long spray guns include long spray gun arms and long spray gun nozzles. The arrangement height of the long spray guns is greater than one-half of the axial height of the second straight tube section. The long spray gun arms extend horizontally toward the center of the straight tube section. The length of the long spray gun arm is greater than half of the radius of the straight tube section, and the long spray gun nozzle faces downward, and the angle between the long spray gun arm and the long spray gun arm is greater than 90 degrees; The height of the straight tube section is H, and the diameter is D, and H and D satisfy the following relationship: 3.3≤H / D≤3.

4.

2. The spray drying tower according to claim 1, characterized in that The spray heads of the central spray gun, the long spray gun and the short spray gun are pressure atomizers.

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