CN110841316A - Spray drying tower - Google Patents

Abstract

The invention discloses a spray drying tower. Hot gas enters from the bottom of the drying tower and is output from the top. The material to be dried that enters the drying tower from the side by spraying is dried and output from the bottom of the drying tower in powder form. The drying tower comprises: : the upper tower body, which is a conical cylinder with an outlet on the top that reduces its diameter upwards. After drying, the gas is discharged from the top outlet of the upper tower body; the straight cylinder section is the 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 is circumferentially arranged on the inner wall of the first straight barrel section. For the ring-length spray gun, a central spray gun is arranged on the middle inner wall of the straight cylinder section, the lower tower body is in the shape of a cone with a downward diameter reduction, and the top cross section of the lower tower body is provided with a hot gas distributor.

Description

A spray drying tower

technical field

The invention relates to the field of drying equipment, in particular to a spray drying tower.

Background technique

Spray drying is a drying process in which the raw material liquid is put into the atomizer and separated into droplets, and the powder-shaped products are obtained by direct contact of hot air or other gas with the droplets. The method of using a spray dryer is mostly used in industries such as food, pharmaceuticals, and chemicals. The drying speed of spray drying is fast, and it 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 keep the spherical shape of droplets, and the product has good dispersibility and fluidity. and solubility, the production process is simplified, and the operation control is convenient. Spray drying is usually used for solutions with a solid content of less than 60%. After drying, there is no need for pulverization and screening, which reduces the production process and simplifies the production process. The particle size, bulk density and water content of the product can be adjusted by changing the operating conditions within a certain range, and the control and management are very convenient.

When drying materials with a drying tower, it is necessary to increase the output. The increase in the diameter and height of the tower is not obvious, and the cost of materials is also wasted and the investment is increased. Therefore, by improving the internal structure of the drying tower and determining the appropriate ratio of tower diameter and height, it can not only increase the output, but also save materials.

And the setting of the spray gun inside the drying tower is very important. The contact between the material to be dried and the hot air is uneven, the feed amount is too large, the evaporation cannot be fully evaporated, and the added liquid is unstable. In the drying tower, the spray gun is set at the top of the tower, and the material flows from top to bottom.

The distribution of the hot air flow is also crucial to the quality of the product. When the dry particles are brought into contact with the high-temperature drying gas along with the upward flow of the drying gas, the quality of the dry particles may be significantly reduced due to this temperature. In food or pharmaceutical products, necessary components are volatilized or deteriorated due to exposure of dry particles to a high temperature higher than necessary. Alternatively, the dry particles are fused to form coarse particles, thereby reducing their mass. When dispersibility is required for the function of dry particles, the dispersibility is remarkably lowered. The coloration is caused by the oxidation reaction promoted by the components of the dry particles. And sometimes it catches fire. Therefore, the time that the drying ions are in contact with the hot air should be minimized.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention discloses a spray drying tower. After many experiments, the appropriate diameter and height ratio of the drying tower are determined, and the internal structure of the hot air flow channel is improved through the reasonable layout of the atomizing spray gun. After drying, it can effectively make the hot air and the material droplets fully contact, improve the drying efficiency, reduce the sticking phenomenon, and improve the product quality.

The technical scheme of the present invention is as follows:

A spray drying tower, the hot gas enters from the bottom of the drying tower and is output from the top, and the materials to be dried that enter the drying tower from the side by spraying are dried and output from the bottom of the drying tower in powder form, the drying tower comprises: an upper tower body , which is a conical cylinder with an outlet on the top that reduces its diameter upward, and the gas is discharged from the top outlet of the upper tower body after drying; the straight cylinder section is the vertical downward extension of the lower end of the upper tower body, and the straight cylinder section From top to bottom, it includes a first straight barrel section and a second straight barrel section with equal axial lengths, a circle of short spray guns is circumferentially arranged on the inner wall of the first straight barrel section, and a circle of long spray guns is circumferentially arranged on the inner wall of the second straight barrel section, The middle inner wall of the straight cylinder section is provided with a central spray gun, the lower tower body is in the shape of a cone with a downwardly reduced diameter, and a hot gas distributor is arranged at the top cross section of the lower tower body.

Further, a plurality of short spray guns are annularly arranged along the inner wall of the first straight barrel section, the short spray guns include a short spray gun arm and a short spray gun nozzle, and the set height of the short spray guns is that the axial height of the first straight barrel section is greater than At one-half, the short spray gun arm extends toward the center of the straight barrel section along the horizontal direction, the length of the short spray gun arm is less than one third of the radius of the straight barrel section, and the short spray gun nozzle faces downward, which is the same as the length of the straight barrel section. The included angle of the short spray gun arms is greater than 90 degrees.

Further, the center spray gun includes a center spray gun arm and a center spray gun spray head, the center spray gun arm extends horizontally to the central axis of the straight barrel section, the center spray gun spray head faces downward, and the angle between the center spray gun arm and the center spray gun arm is 90 degrees.

Further, a plurality of long spray guns are annularly arranged along the inner wall of the second straight barrel section, the long spray gun includes a long spray gun arm and a long spray gun nozzle, and the long spray gun is arranged at a height such that the axial height of the second straight barrel section is greater than At one-half, the long spray gun arm extends toward the center of the straight barrel section along the horizontal direction, the length of the long spray gun arm is greater than half the radius of the straight barrel section, and the long spray gun nozzle faces downwards, which is the same as the length of the straight barrel section. The included angle of the long spray gun arms is greater than 90 degrees.

Further, the central spray gun head, the long spray gun head and the short spray gun head are pressure type atomizers.

Further, the height of the straight cylinder section is H, and the diameter is D, and H and D satisfy the following relationship: 3.3≤H/D≤3.4.

The beneficial effects of the present invention are:

Compared with the traditional drying tower, the drying tower of the present invention has obvious reduction in the diameter and height of the tower under the condition of keeping the output unchanged, which effectively saves the cost and reduces the energy consumption.

According to the changes in the diameter and height of the tower body, the number and arrangement of the spray guns are changed accordingly, and 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 air flow The short-circuit phenomenon is higher, and the heat utilization rate is higher.

Description of drawings

Fig. 1 is a kind of embodiment structural representation of a kind of spray drying tower of the present invention;

Fig. 2 is a kind of prior art structural representation of spray drying tower;

3 is a schematic structural diagram of a hot gas distributor of a spray drying tower of the present invention.

In the figure, 1. Upper tower body, 2. Straight cylinder section, 3. Section spray gun, 4. Center spray gun, 5. Long spray gun, 6. Lower tower body, 7. Hot gas distributor, 21. First straight cylinder section, 22 .Second straight barrel section.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

Referring to Figure 1-2, a spray drying tower, the hot gas is input from the air inlet at the bottom of the drying tower, passes through the hot gas distributor 7, and is evenly output to the top of the drying tower, and the material to be dried is sprayed through the atomizer. It enters the tower from the side of the drying tower, and after drying, it is output in powder form from the bottom of the drying tower. The drying tower includes an upper tower body 1, which is a conical cylinder with an outlet at the top that reduces its diameter upward. After drying, the gas flows from the top. The top outlet of the tower body 1 is discharged. The drying tower of the present invention is a counter-current type, that is, the moving direction of the drying medium (hot air) is opposite to the moving direction of the atomized material liquid, the atomized droplets move from top to bottom, and the hot air moves from bottom to top. The moving direction of the hot air in the drying tower is opposite to the moving direction of the atomized droplets. The atomized droplets of the material liquid have a long suspension time in the drying tower, which is very suitable for the drying of the material liquid with high water content. The disadvantage of countercurrent drying is that the dried product is still in continuous contact with the high-temperature drying medium while falling, so the dried product is easily overheated and coked. This is because the drying heat medium with high humidity and low temperature at the inlet of this type of material is in contact with the liquid droplets with high water content. At the material outlet end, the heat medium with low humidity and high temperature is in contact with the material powder with low water content. Therefore, the drying driving force in the drying tower is not very different, and the distribution is relatively uniform.

The straight cylinder section 2 is a vertical downward extension of the lower end of the upper tower body. The straight cylinder section includes a first straight cylinder section 21 and a second straight cylinder section 22 with equal axial lengths from top to bottom. A circle of short spray guns 3 is arranged in the direction, a circle of long spray guns 5 is arranged circumferentially on the inner wall of the second straight barrel section, and a central spray gun 4 is arranged on the middle inner wall of the straight barrel section. For drying towers with small evaporation, such as drying towers with evaporation less than 500 kg/h, setting a nozzle at the top of the drying tower can achieve good material atomization, but with the increase of evaporation, using a nozzle cannot be very effective. To achieve atomization well, as long as the amount of evaporation is large, the particle size of the droplets increases, and it is easy to become a linear flow. Therefore, it is necessary to use multiple nozzles and distribute the nozzles reasonably. On the one hand, the atomization can be uniform, and on the other hand, the high moisture content of the material droplets can be avoided, so that the material can be heated evenly.

The drying tower of the present invention further comprises a conical lower tower body 6 with a diameter shrinking downward, and a hot gas distributor 7 is arranged at the top cross section of the lower tower body. The uniform distribution of the 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, after the hot air flow is input from the air inlet, it is output to the straight section through the hot air distributor. When the speed of the hot air is uniform, the dried material particles can enter the lower tower body along the straight section to avoid the reverse flow of the material due to the uneven air flow during the descending process, that is, the material moves upward for a certain distance, resulting in the stay in the drying tower. If the time is too long, part of the dried particles will adhere to the inner wall of the drying tower and the spray device, which will cause the material particles to deteriorate due to heat, and the dispersibility and quality of the product will deteriorate. The purpose of the hot air distributor is to make the wind speed uniform. On the premise of maintaining this function, it can be of any shape, such as honeycomb shape or lattice shape. There are certain requirements for the pressure loss of the hot air distributor. If it is large, the desired gas air volume may not be obtained. In addition, when the pressure loss is too small, the distribution effect tends to be insignificant.

Further, a plurality of short spray guns 3 are annularly arranged along the inner wall of the first straight barrel section, the short spray gun includes a short spray gun arm and a short spray gun spray head, and the setting height of the short spray gun is greater than half of the axial height of the first straight barrel section. , the short spray gun arm extends horizontally to the center of the straight barrel section, the length of the short spray gun arm is less than one third of the radius of the straight barrel section, the short spray gun nozzle faces downward, and the angle between the short spray gun arm and the short spray gun arm is greater than 90° degree, preferably 105 degrees, so that the material can be dispersed evenly. The short gun head is a pressure atomizer. Pressure spray drying relies on a high-pressure pump to tear the material into droplets through a high-pressure nozzle, and then exchanges heat and mass with the hot air in the tower to dry the atomized material into the desired powder. The arrangement of the short spray guns in the first straight barrel section is mainly based on the production capacity of the drying tower. Since the short spray guns are located in the first straight barrel section and are farthest from the air inlet, the drying capacity of the hot air flow is somewhat higher than that located near the air inlet. Therefore, the flow rate of the short spray gun is not easy to be too large, and the droplets are mainly distributed around the drying tower after atomization. Preferably, the number of short spray guns is 3, and the droplets of each spray head can be sprayed as far as possible so that the droplets do not intersect, and the droplets do not become larger.

In the axial middle position of the straight barrel section 2, a central spray gun 4 is provided, including a central spray gun arm and a central spray gun spray head, the central spray gun arm extends horizontally to the central axis of the straight barrel section, and the central spray gun spray head faces downward, and The included angle of the center gun arm is 90 degrees. The material is mainly sprayed downward along the center of the drying tower. The air-flow atomizer uses gas to blow out the material at a high speed. The material liquid is torn into a liquid film and then atomized into fine droplets. Because the height of the central spray gun is located in the straight section At the center of the machine, the flow rate at this place needs to be moderate, and the flow rate can be accelerated to achieve better drying effect.

Further, a plurality of long spray guns 5 are annularly arranged along the inner wall of the second straight barrel section 22, the long spray gun includes a long spray gun arm and a long spray gun spray head, and the setting height of the long spray gun is that the axial height of the second straight barrel section is greater than half the place, The long spray gun arm extends toward the center of the straight barrel section along the horizontal direction, the length of the long spray gun arm is greater than half the radius of the straight barrel 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 . The long spray gun head is a pressure type atomizer. Since the long spray gun head is relatively close to the air inlet, it is suitable for a large flow rate, so that the material droplets fill the entire cross section of the drying tower.

In the present invention, the material to be spray-dried is not particularly limited. The material can form particle droplets through the atomizer, and the solvent or dispersant can be volatilized in the dryer to obtain dry particles. For example, synthetic chemicals such as food, pharmaceuticals, detergents or fertilizers, synthetic resins, pigments can be used. Or a solution or dispersion of inorganic materials such as ceramics. There is no limitation on the solvent or dispersant, for example, water or a solvent or the like can be used.

Example 2

Referring to Figure 3, this embodiment is the drying tower before the improvement, and the main technical parameters of the drying tower. The drying tower before the improvement, the spray gun is located at the top of the drying tower, the material droplets are sprayed from top to bottom, and the hot air is from the bottom of the drying tower. Up, it is a counter-current 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 drying washing powder as an example, the evaporation capacity of the drying tower is 13500kg/h, the initial mass fraction of washing powder is 63~65%, the feeding temperature is 55~60 ℃, and the inlet air volume: 84440m ³ /h (under the standard state) , inlet air temperature: 380-400 ℃; exhaust air volume: 103040 m3/h (under standard state); exhaust air temperature: 105-120 ℃; powder mass fraction: 97.2%. At this time, the hourly heat supply is about 11.4 million kcal.

Example 3

This embodiment is the drying tower of the present invention, and the main technical parameters of the drying tower. Three short spray guns are evenly distributed in the upper part of the first straight cylinder section, a central spray gun is distributed in the middle of the straight cylinder section, and the upper part of the second straight cylinder section is evenly distributed. There are 3 long spray guns distributed. 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 counter-current 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 drying washing powder as an example, the evaporation capacity of the drying tower is 13500kg/h, the initial mass fraction of washing powder is 63~65%, the feeding temperature is 55~60 ℃, and the inlet air volume: 65790 m3/h (under standard state) , inlet air temperature: 420-450 ℃; exhaust air volume: 84590 m3/h; exhaust air temperature: 90-100 ℃; powder mass fraction: 97.3%. At this time, the hourly heat supply is about 10.1 million kcal.

Through the technical improvement of the present invention, the diameter of the tower body can be reduced to 6 meters, and the height can be reduced to 21 meters, and the same output can still be produced. The cost of optical materials and manufacturing will be saved by about 250,000 yuan, which is a significant cost reduction and improved competitive advantage. According to the changes in the diameter and height of the tower body, the number and arrangement of the spray guns are changed accordingly, and 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 air flow The short-circuit phenomenon is higher, and the heat utilization rate is higher. The temperature of the flue gas emitted by the original spray tower was between 105 and 120 °C. After various technical improvements, the temperature of the exhausted flue gas dropped to between 90 and 100 °C. Compared with a heating device that supplies 10 million calories per hour, it can save 31.2 million calories per day (equivalent to coal with a calorific value of 5,000 calories, saving 6,240 kilograms of raw coal per day), Since the reduction in exhaust emissions after the improvement also reduces power consumption by about 20%, the energy saving is significant.

The specific embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned embodiments, and can also be made within the scope of knowledge possessed by those of ordinary skill in the art without departing from the purpose of the present invention. Various changes.

Claims (6)

1. A spray drying tower, hot gas from the bottom of the drying tower enters and is output from the top, and the material to be dried which enters the drying tower from the side in a spraying mode is dried and then is output from the bottom of the drying tower in a powder shape, wherein the drying tower comprises: the upper tower body is a conical cylinder with an outlet at the top and a diameter reduced upwards, and dried gas is discharged from the outlet at the top of the upper tower body; the lower end of the upper tower body extends vertically downwards, the straight cylinder section comprises a first straight cylinder section and a second straight cylinder section which are equal in axial length from top to bottom, a circle of short spray guns are arranged on the inner wall of the first straight cylinder section in the circumferential direction, a circle of long spray guns are arranged on the inner wall of the second straight cylinder section in the circumferential direction, and a central spray gun is arranged on the inner wall in the middle of the straight cylinder section; the lower tower body is in a conical shape with a diameter reduced downwards, and a hot gas distributor is arranged at the cross section of the top of the lower tower body.

2. The spray drying tower of claim 1, wherein a plurality of short spray guns are annularly arranged along the inner wall of the first straight barrel section, each short spray gun comprises a short spray gun arm and a short spray gun nozzle, the short spray guns are arranged at heights that the axial height of the first straight barrel section is more than one half, the short spray gun arms extend to the center of the straight barrel section along the horizontal direction, the length of each short spray gun arm is less than one third of the radius of the straight barrel section, and the short spray gun nozzles face downwards and form an included angle with the short spray gun arms of more than 90 degrees.

3. A spray drying tower according to claim 1, wherein the central lance comprises a central lance arm extending horizontally to the straight section central axis and a central lance nozzle directed downwardly at an angle of 90 degrees to the central lance arm.

4. The spray drying tower of claim 1, wherein a plurality of long spray guns are annularly arranged along the inner wall of the second straight cylinder section, each long spray gun comprises a long spray gun arm and a long spray gun nozzle, the long spray gun is arranged at a height which is more than half of the axial height of the second straight cylinder section, the long spray gun arm extends towards the center of the straight cylinder section along the horizontal direction, the length of the long spray gun arm is more than half of the radius of the straight cylinder section, and the long spray gun nozzle faces downwards and forms an included angle with the long spray gun arm which is more than 90 degrees.

5. A spray drying tower according to claim 1, wherein the central, long and short lance heads are pressure atomisers.

6. A spray drying tower according to claim 1, wherein the straight barrel section has a height H and a diameter D, H and D satisfying the following relationship: H/D is more than or equal to 3.3 and less than or equal to 3.4.

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