A spray drying tower and method for drying milk powder

Abstract

The present application proposes a spray drying tower and method for drying milk powder. The tower body of the drying tower includes: a cylindrical part and a conical part. The conical part is provided with a first chamber and a second chamber covered by the first chamber along the inner wall of the tower body. A first air inlet system is provided at the junction of the cylindrical part and the conical part, and the annular air inlet cavity surrounds the outer wall covering the cylindrical part; a second air inlet system is provided at the bottom of the conical part, and a spiral gas distributor is connected to the first chamber. After the hot air forms a cyclone through the spiral gas distributor, it moves along the first chamber to the top of the tower, and contacts with the emulsion in reverse to achieve the drying preparation of milk powder. The present invention also provides a method for drying milk powder, wherein a hot air flow is blown from the bottom of the spray drying tower to the top of the tower, and the emulsion spray is sprayed downward from the top of the tower, and the hot air flow contacts with the emulsion droplets in reverse to achieve the drying of the emulsion. The present invention solves the problem that the heat-sensitive nutrients in the milk powder are lost due to the excessively high temperature of the hot air in the emulsion, and retains and improves the heat-sensitive nutrients in the milk powder.

Description

Technical Field

[0001] The invention relates to the technical field of drying towers, in particular to a spray drying tower for drying milk powder. Background Art

[0002] In the dairy processing industry, the drying of milk powder is a crucial link, which is directly related to the final quality and nutritional value of the product. The drying process is generally achieved through a milk powder drying tower, which first receives the pre-treated (including filtration, homogenization, etc.) emulsion, and then uses a high-pressure pump or centrifugal sprayer to spray these emulsions into tiny droplets. At the same time, filtered and heated hot air is introduced into the drying tower, which quickly contacts and exchanges heat with the emulsion droplets, so that the water in the droplets evaporates in a very short time to form dry milk powder particles. After drying, the milk powder particles fall to the bottom of the tower under the action of gravity or are collected by equipment such as cyclone separators, while the exhaust gas carries the remaining water and impurities out of the tower.

[0003] However, in the prior art, due to the presence of heat-sensitive nutrients in milk powder, such as lactase, lipase, unsaturated fatty acids, whey protein, casein, etc., a hot air inlet is introduced into the top of the tower in order to ensure drying efficiency. When the milk powder at the top of the drying tower is just turned into small droplets by the spray system, it will directly contact with the hot air flow at the first time, causing the milk powder to be subjected to direct thermal shock, thereby causing thermal degradation of some heat-sensitive nutrients in the emulsion and loss of the heat-sensitive nutrients. Summary of the invention

[0004] The purpose of the present invention is to solve the problem in the prior art that the traditional drying method causes the heat-sensitive nutrients in the emulsion to be thermally degraded, thereby causing the heat-sensitive nutrients in the milk powder to be lost.

[0005] In order to achieve the above-mentioned purpose, the present application proposes a spray drying tower for drying milk powder, comprising a tower top, a tower body and a tower bottom, wherein an air outlet is arranged on the tower top; the tower body comprises: a cylindrical part and a conical part, wherein the conical part comprises: a first chamber arranged along the inner wall of the tower body and a second chamber covered by the first chamber, a tie rod is arranged between the first chamber and the second chamber, and a first air inlet system is arranged at the junction of the cylindrical part and the conical part, wherein an annular air inlet chamber surrounds the outer wall of the cylindrical part; a second air inlet system is arranged at the bottom of the conical part, wherein a spiral gas distributor is connected to the first chamber.

[0006] The spray drying tower of the present application is divided into two chambers along the tower wall by dividing the conical part of the tower body, wherein the first chamber is used to pass the high-temperature hot air whose direction is changed by the spiral gas distributor, and the second chamber is used to pass the dried milk powder. After the hot air changes direction through the spiral gas distributor to form a cyclone, it gradually moves toward the top of the tower along the side wall of the first chamber. When it moves to the position where the conical part and the cylindrical part are connected, it is superimposed with the low-temperature hot air introduced through the annular air inlet chamber to form a cyclone in the opposite direction of the flow direction of the milk powder, thereby achieving reverse contact with the milk powder. While increasing the contact area between the material and the hot air, the temperature of the high-temperature hot air gradually decreases during the process of the high-temperature hot air moving along the first chamber. When it makes initial contact with the milk powder, the heat-sensitive nutrients in the milk powder will not be lost due to the excessively high temperature of the hot air, thereby solving the problem in the prior art that the heat-sensitive nutrients in the emulsion are thermally degraded by the traditional drying method, thereby causing the heat-sensitive nutrients in the milk powder to be lost.

[0007] As an improvement of the above-mentioned annular air inlet chamber of the present application, in order to ensure that the hot air transmitted from the first chamber can be evenly superimposed on the hot air introduced into the second air inlet system, and at the same time the flow path of the hot air is from the bottom of the tower to the top of the tower, the annular air inlet chamber includes: an air inlet arranged on the bottom surface, a hot air cavity covering the outer wall surface of the cylindrical portion, and an annular air outlet arranged obliquely upward and penetrating the outer wall surface of the cylindrical portion.

[0008] Furthermore, in order to enable the dried milk powder to be effectively transported to the next process through the second chamber, the drying tower also includes: a feeding device arranged at the bottom of the cone, wherein the feeding device includes: a feeding pipe passing through the spiral gas distributor and connected to the second chamber; and a cyclone separator connected to the output end of the feeding pipe.

[0009] As an improvement of the above-mentioned feed conveying pipe of the present application, in order to enable the dried milk powder to be quickly cooled down at the bottom of the tower and prevent agglomeration, a third air inlet system for introducing cold air is provided on the feed conveying pipe.

[0010] Furthermore, in order to ensure that cold air can effectively enter the second chamber, the high-temperature milk powder entering is cooled, the time the milk powder is at high temperature is shortened, and the risk of heat-sensitive substances losing their activity is further reduced. To prevent the milk powder from agglomerating, the air inlet of the third air inlet system is arranged obliquely upward.

[0011] Furthermore, in order to further ensure that the milk powder can be transported to the interior of the drying tower, a feeding system is provided on the top of the tower, including: a spray system arranged on the inner wall surface of the tower top, a feed pipe penetrating the outer wall surface of the tower top and connected to the spray system, a storage tank connected to the other end of the feed pipe, and a booster pump arranged on the feed pipe.

[0012] A method for drying milk powder using a spray drying tower for drying milk powder: a hot air flow is blown from the bottom of the spray drying tower to the top of the tower, an emulsion is sprayed downward from the top of the tower, and the hot air flow contacts the emulsion droplets in reverse direction to achieve drying of the emulsion.

[0013] The implementation is as follows:

[0014] Spraying malt extract and emulsion into the drying tower through the second spray system and the first spray system respectively, forming a spray flow from the top to the bottom;

[0015] At the same time, hot air is introduced into the drying tower through the spiral gas distributor at the bottom of the tower and the annular air inlet cavity of the tower body. The hot air formed by the spiral gas distributor passes through the first chamber and the hot air entering the annular air inlet cavity to converge to form a hot air flow, which forms a reverse contact with the spray flow.

[0016] The emulsion spray is fully in contact with the hot air during the descent process, gradually evaporating the water, while the malt extract acts as a protective layer to reduce the thermal degradation of heat-sensitive nutrients;

[0017] The dried milk powder falls into the feeding pipe, and the cold air introduced by the third air inlet system quickly cools it down and prevents it from agglomerating. At the same time, it shortens the time the milk powder is in a high temperature state, which again ensures the activity of the nutrients in the milk powder and reduces the risk of degradation. It is then discharged from the drying tower through a cyclone separator;

[0018] The hot air from the reverse drying carries water vapor into the dust removal system through the air outlet and is finally discharged from the tower.

[0019] Furthermore, for some dairy products that allow the addition of malt extract, in order to further increase the content of active ingredients in milk powder and reduce the pyrolysis of active ingredients in the emulsion, the present invention also provides a method for drying milk powder, wherein the outer layer is coated with malt extract when the emulsion is sprayed, and the malt extract coated emulsion droplets flow downward and contact the upward hot air flow in reverse. The malt extract acts as a protective layer to reduce the pyrolysis and failure of heat-sensitive nutrients.

[0020] The beneficial effects of this application are:

[0021] 1. In the milk powder drying tower of the present application, hot air flows upward from the bottom and spray flows downward from the top, forming reverse contact, which can make the material fully contact with the hot air while increasing the residence time of the milk powder in the drying tower, improving the drying efficiency and preventing the material from sticking to the wall.

[0022] 2. The milk powder drying tower of the present application adopts a bottom blowing air intake method, so that the material is exposed to high temperature only when it reaches the bottom, and then enters the discharge pipe. Cold air is introduced into the discharge pipe to quickly cool the milk powder, shortening the high temperature state time of the milk powder, and further reducing the risk of thermal degradation of heat-sensitive nutrients. At the same time, blowing cold air into the discharge pipe is also conducive to avoiding the agglomeration of milk powder and reducing the risk of blockage of the discharge pipe.

[0023] 3. The milk powder drying tower of the present application is provided with an annular air inlet cavity at the junction of the cylindrical part and the straight part, where the hot air blows upward to form an air curtain, and the milk powder cannot enter the hot air outlet. A plurality of oblique upward blowing outlets are installed along the circumference at the straight position, so that the hot air can be evenly blown in the spray direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 This is a schematic diagram of the structure of a spray drying tower for drying milk powder in an embodiment of the present application;

[0026] Figure 2 A cross-sectional view of a spray drying tower for drying milk powder in an embodiment of the present application;

[0027] Figure 3 A cross-sectional view from another perspective of a spray drying tower for drying milk powder in an embodiment of the present application;

[0028] Description of reference numerals:

[0029] 1. Top of the tower;

[0030] 2. tower body; 21. cylindrical part; 22. conical part; 221. first chamber; 222. second chamber; 223. tensioning bar;

[0031] 3. Tower bottom;

[0032] 4. First air inlet system; 41. Annular air inlet cavity; 411. Air inlet; 412. Hot air cavity; 413. Annular air outlet;

[0033] 5. Second air inlet system; 51. Spiral gas distributor;

[0034] 6. The third air inlet system;

[0035] 7. Feeding device; 71. Feeding pipe; 72. Cyclone separator;

[0036] 8. Feeding system; 81. Spraying system; 82. Feeding pipe; 83. Storage tank; 84. Booster pump;

[0037] 9. Air outlet. DETAILED DESCRIPTION

[0038] The following will be combined with the attached Figures 1 to 3The embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0039] like Figures 1 to 3 A spray drying tower for drying milk powder of the present application is illustrated, comprising a tower top 1, a tower body 2 and a tower bottom 3, an air outlet 10 is arranged on the tower top 1, the air outlet 10 is connected to a bag dust collector or other dust removal system in the prior art, and the dust removal system is omitted in the figure; the tower body 2 comprises: a cylindrical portion 21 and a conical portion 22, wherein the conical portion 22 comprises: a first chamber 221 arranged along the inner wall of the tower body 2 and a second chamber 222 covered by the first chamber 221, a tie rod 223 is arranged between the first chamber 221 and the second chamber 222, a first air inlet system 4 is arranged at the junction of the cylindrical portion 21 and the conical portion 22, wherein an annular air inlet cavity 41 surrounds and covers the outer wall of the cylindrical portion 21; a second air inlet system 5 is arranged at the bottom of the conical portion 22, wherein a spiral gas distributor 51 is connected to the first chamber 221.

[0040] In one embodiment of the present application, the first chamber 221 of the conical portion 22 is used to allow the hot air that changes direction through the spiral gas distributor 51 to form a vortex. The cylindrical portion 21 serves as the main place for preliminary drying. It is used to superimpose the low-temperature hot air introduced into the annular air inlet chamber 41 with the hot air that forms the vortex, and to form reverse contact with the milk powder for drying. Finally, the hot air that has completed drying carries water vapor and is discharged to the outside from the air outlet 10 through the dust removal system. The tie rod 223 is used to fix the second chamber 222 on the first chamber 221.

[0041] In the prior art, due to the presence of heat-sensitive nutrients in milk powder, such as lactase, lipase, unsaturated fatty acids, whey protein, casein, etc., a hot air inlet is introduced into the top of the tower in order to ensure drying efficiency. When the milk powder at the top of the drying tower is just turned into small droplets by the spray system, it will come into direct contact with the hot air flow at the first time, causing the milk powder to be subjected to direct thermal shock, thereby causing thermal degradation of some heat-sensitive nutrients in the emulsion and loss of the heat-sensitive nutrients.

[0042] In this embodiment, the conical portion 22 of the tower body 2 is divided into two chambers along the tower wall, wherein the first chamber 221 is used to pass the high-temperature hot air whose direction is changed by the spiral gas distributor 51, and the second chamber 222 is used to pass the dried milk powder. After the hot air changes direction through the spiral gas distributor 51 to form a cyclone, it gradually moves toward the tower top 1 along the side wall of the first chamber 221. When it moves to the position where the conical portion 22 and the cylindrical portion 21 are connected, it is superimposed with the low-temperature hot air introduced through the annular air inlet chamber 41 to form a cyclone in the opposite direction of the flow direction of the milk powder, thereby achieving reverse contact with the milk powder. While improving the contact degree between the material and the hot air, the temperature of the high-temperature hot air gradually decreases during the process of the high-temperature hot air moving along the first chamber 221. When it makes initial contact with the milk powder, the heat-sensitive nutrients in the milk powder will not be lost due to the excessively high temperature of the hot air, thereby solving the problem in the prior art that the heat-sensitive nutrients in the emulsion are thermally degraded by the traditional drying method, thereby causing the heat-sensitive nutrients in the milk powder to be lost.

[0043] Continue to refer to Figure 1~Figure 3 In a further embodiment, the annular air inlet chamber 41 includes: an air inlet 411 arranged on the bottom surface, a hot air chamber 412 covering the outer wall surface of the cylindrical portion 21, and an annular air outlet 413 penetrating the outer wall surface of the cylindrical portion 21 and arranged obliquely upward. In this embodiment, after the hot air at a relatively low temperature passes into the hot air chamber 412 through the air inlet 411, it is evenly transported to the tower body 2 through the annular air outlet 413. Since the opening of the annular air outlet 413 forms an angle toward the tower top 1 with the tower wall of the tower body 2, the passing hot air forms an air curtain toward the tower top 1. When the milk powder moves to the top of the first chamber 221, the milk powder can be effectively prevented from entering the first chamber 221 due to the obstruction of the air curtain. At the same time, the hot air transmitted from the first chamber 221 can also re-transport the milk powder that is not blocked by the air curtain to the second chamber 222, effectively preventing the milk powder from entering the first chamber 221 and causing blockage of the first air inlet system. At the same time, it can also prevent the milk powder that mistakenly enters the first chamber 221 from being burnt and mixed into the finished milk powder product, thereby affecting the quality of the milk powder.

[0044] Continue to refer to Figure 1 and Figure 2In a further embodiment, the drying tower further comprises: a feeding device 7 arranged at the bottom of the conical portion 22, wherein the feeding device 7 comprises: a feeding pipe 71 passing through the spiral gas distributor 51 and communicating with the second chamber 222; and a cyclone separator 72 connected to the output end of the feeding pipe 71. Specifically, after the milk powder is reversely contacted and dried with the hot air, it falls into the second chamber 222 for secondary drying. Since the hot air input end of the first air supply system 4 is arranged at the bottom 3 of the tower, that is, the bottom of the conical portion 22, its higher heat can pass through the interlayer between the first chamber 221 and the second chamber 222 to perform secondary drying on the milk powder. At the same time, the cyclone separator 72 drives the milk powder falling into the feeding pipe 71 to be transported to the next process.

[0045] Furthermore, the feeding pipe 71 is provided with a third air inlet system 6. Specifically, the third air inlet system 6 introduces cold air. Since the bottom of the conical portion 22 is used as the input end of the hot air with a relatively high temperature, and the relatively high heat can pass through the barrier between the first chamber 221 and the second chamber 222, the bottom of the conical portion 22 has a relatively high temperature, which can easily cause the milk powder that has been preliminarily dried to burn. Therefore, the introduction of cold air through the third air inlet system 6 can reduce the bottom temperature of the conical portion 22 to prevent the milk powder from burning. At the same time, the heat inside the entire second chamber 222 is balanced, so that the temperature in the second chamber 222 remains stable, and the temperature difference in different spaces is reduced.

[0046] Furthermore, the air inlet of the third air inlet system 6 is arranged obliquely upward. In this embodiment, the air inlet arranged obliquely upward can, on the one hand, guide the cold air introduced by the third air inlet system 6 so that it can quickly enter the second chamber 222. At the same time, the cold air is arranged obliquely upward, and the flow rate of the cold air escaping into the lower end of the feeding pipe 71 will be significantly reduced, which can avoid the introduction of the third air inlet system 6 to affect the stability of the cyclone separator 72.

[0047] Continue to refer to Figure 1 and Figure 3 In a further embodiment, a feeding system 8 is provided on the tower top 1, comprising: a spray system 81 provided on the inner wall surface of the tower top 1, a feed pipe 82 penetrating the outer wall surface of the tower top 1 and connected to the spray system 81, a storage tank 83 connected to the other end of the feed pipe 82, and a booster pump 84 provided on the feed pipe 82. Specifically, the emulsion is transported from the storage tank 83 to the spray system 81 through the feed pipe 82, and the emulsion is pressurized and sprayed into the drying tower by the booster pump 84, forming a spray flow from the top to the bottom, and finally contacts with the hot air to complete the drying.

[0048] As a preferred embodiment, a method for drying milk powder using the spray drying tower for drying milk powder comprises the following steps:

[0049] The malt extract and the emulsion are sprayed into the drying tower through the second spray system 91 and the first spray system 81 respectively, forming a spray flow from the top to the bottom;

[0050] At the same time, hot air is introduced into the drying tower through the spiral gas distributor 51 at the tower bottom 3 and the annular air inlet cavity 41 of the tower body 2. The hot air formed by the spiral gas distributor 51 passes through the first chamber 221 and converges with the hot air entering from the annular air inlet cavity 41 to form a hot air flow, which is in reverse contact with the spray flow.

[0051] When the dried milk powder falls into the feeding pipe 71 through the bottom of the tower body 2, the cold air introduced into the feeding pipe 71 through the third air inlet system 6 is then discharged from the drying tower through the cyclone separator 72;

[0052] The hot air of reverse drying carries water vapor into the dust removal system through the air outlet 9 and is finally discharged from the tower body.

[0053] Specifically, the technical effects of the present invention are achieved by:

[0054] 1. Bottom blowing drying tower structure:

[0055] A drying tower with bottom air intake and top spraying is designed. The hot air flows upward from the bottom of the tower and forms reverse contact with the emulsion sprayed downward from the top, thereby enhancing the heat exchange efficiency and preventing the material from sticking to the wall.

[0056] An air curtain device for blowing hot air upward is set at the bottom conical opening to prevent milk powder from entering the hot air opening. At the same time, multiple oblique upward blowing outlets are installed along the circumference of the straight cylinder section to ensure uniform distribution of hot air and promote uniform drying of the spray.

[0057] 2. Rapid cooling and anti-agglomeration device:

[0058] A discharge pipe is set at the bottom of the drying tower, and cold air is introduced into the discharge pipe to cool the milk powder immediately after leaving the high temperature area, shorten the high temperature exposure time, and further reduce the risk of degradation of heat-sensitive nutrients. At the same time, the cold air also helps prevent milk powder from agglomerating and reduce blockage in the discharge pipe.

[0059] Among them, the specific design of the drying tower structure:

[0060] The drying tower adopts a cylindrical design with a conical collecting port at the bottom to facilitate the collection and discharge of milk powder.

[0061] The air inlet is located at the center of the tower bottom or evenly distributed around the periphery, and is connected to a hot air source through a pipeline. Optionally, the hot air source can be heated by gas, steam or electricity.

[0062] The spray device is located at the top of the tower and can be equipped with multiple nozzles as needed to achieve a more uniform spray effect.

[0063] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "upper", "lower", "inside" and "outside" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present application and simplifying the description. They do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0064] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "set", "provided with", "connected", "installed" and the like should be understood in a broad sense, for example, they can be fixedly connected, detachably connected, or integrated; they can be directly connected, or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A spray drying tower for drying milk powder, comprising a tower top (1), a tower body (2) and a tower bottom (3), characterized in that: An air outlet (9) is provided on the tower top (1), and the air outlet is connected to a dust removal system; the tower body (2) comprises: a cylindrical portion (21) and a conical portion (22), wherein the conical portion (22) comprises: a first chamber (221) arranged along the inner wall of the tower body (2) and a second chamber (222) covered by the first chamber (221); a first air inlet system (4) is provided at the junction of the cylindrical portion (21) and the conical portion (22); an annular air inlet cavity (422) provided in the first air inlet system (4) 1) surrounds the outer wall of the cylindrical portion (21); a second air inlet system (5) is arranged at the bottom of the conical portion (22); a spiral gas distributor (51) arranged in the second air inlet system (5) is connected to the first chamber (221); the annular air inlet cavity (41) comprises: an air inlet (411) arranged on the bottom surface, a hot air cavity (412) covering the outer wall surface of the cylindrical portion (21), and an annular air outlet (413) penetrating the outer wall surface of the cylindrical portion (21) and arranged obliquely upward.

2. The spray drying tower for drying milk powder according to claim 1, characterized in that: The drying tower further comprises: a material conveying device (7) arranged at the bottom of the conical portion (22), wherein the material conveying device (7) comprises: a material conveying pipe (71) passing through the spiral gas distributor (51) and communicating with the second chamber (222); and a cyclone separator (72) connected to the output end of the material conveying pipe (71).

3. The spray drying tower for drying milk powder according to claim 2, characterized in that: The material conveying pipe (71) is provided with a third air inlet system (6).

4. The spray drying tower for drying milk powder according to claim 3, characterized in that: The air inlet of the third air inlet system (6) is arranged obliquely upward.

5. The spray drying tower for drying milk powder according to claim 1, characterized in that: The tower top (1) is provided with a feed system (8), comprising: a spray system (81) provided on the inner wall surface of the tower top (1), a feed pipe (82) penetrating the outer wall surface of the tower top (1) and connected to the spray system (81), a storage tank (83) connected to the other end of the feed pipe (82), and a booster pump (84) provided on the feed pipe (82).

6. The spray drying tower for drying milk powder according to claim 1, characterized in that: A tensioning rod (223) is provided between the first chamber (221) and the second chamber (222).

7. A method for drying milk powder using the spray drying tower according to any one of claims 1 to 6, characterized in that: A hot air flow is blown from the bottom of the spray drying tower to the top of the tower, and the emulsion spray is sprayed downward from the top of the tower. The hot air flow contacts the emulsion droplets in reverse direction to achieve the drying of the emulsion.

8. The method for drying milk powder according to claim 7, characterized in that: When the emulsion is sprayed, the outer layer is coated with malt extract, and the malt extract coated emulsion droplets flow downward and contact with the upward hot air flow in reverse.

Images