Double effect drying system

Abstract

To provide a double effect drying system capable of further improving drying efficiency of an object to be dried without causing a cost increase by effectively using heat of waste steam generated in the process of drying the object to be dried to reduce energy loss.SOLUTION: The drying system comprises a front stage dryer 10A for an object to be dried to be first charged thereinto, and a post-stage dryer 10B into which the object to be dried being dried in the front stage dryer 10A is transferred to complete the drying. The object to be dried is dried by introducing high-pressure steam into the front stage dryer 10A, and waste steam generated in the process of drying the object to be dried in the front stage dryer 10A is introduced into the post-stage dryer 10B for use in the final drying of the object to be dried by the post-stage dryer 10B.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a double-effect drying system in which two dryers are connected in series to continuously dry materials to be dried. [Background technology]

[0002] Conventionally, there have been known dryers for drying various types of materials with high water content, such as food waste, sludge, industrial waste, etc. In particular, the present applicant has already proposed a dryer that can achieve ideal drying conditions by developing a unique dryer called a cyclone dryer (see, for example, Patent Documents 1 and 2).

[0003] In this type of drying device, the material to be dried is placed in a vertical cylindrical main tank and is then lifted up by the rotation of rotating lifting blades called cyclone fins attached to a vertical rotating shaft. With this configuration, when the rotating lifting blades rotate, the material to be dried is pressed into a thin film against the heat transfer surface on the inner wall of the main tank by centrifugal force, and together with the action of the material to be dried being lifted up later, the material to be dried being lifted up earlier is pushed up in order, thereby enabling the material to be dried efficiently.

[0004] As a heat source for the heat transfer surface of the main vessel, high-pressure steam is generally supplied to a jacket surrounding the outer periphery of the main vessel, and the latent heat of the steam is used to evaporate the moisture contained in the material to be dried. In order to increase the efficiency of this evaporation, for example, carrier air is introduced into the main vessel from the outside and discharged out of the main vessel together with the evaporated waste steam. In this case, the waste steam becomes a waste gas mixed with air, so it is not possible to utilize the latent heat from this waste gas. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 2840639 [Patent Document 2] Patent No. 2958869 Summary of the Invention [Problem to be solved by the invention]

[0006] In the drying equipment described above, high-pressure steam is used as the heat source for the heat transfer surface, and carrier air is introduced from outside into the main tank. The rotation of the rotating lifting blades causes the material to come into contact with the heat transfer surface in the form of a thin film, causing it to evaporate due to centrifugal and inertial forces. However, it has been discovered that it is actually possible to dry the material without introducing carrier air from outside. Furthermore, if only the moisture from the material to be dried is evaporated as steam without introducing carrier air from outside, the exhaust will be only water vapor, which will be completely normal pressure water vapor.

[0007] Although the latent heat of the atmospheric pressure steam at this point holds a sufficient amount of heat, up until now this steam has simply been treated as waste steam and not been effectively utilized. In other words, the waste steam discharged from the main tank is cooled in a cooling tower with a capacity of several hundred to several thousand kilocalories using an indirect condenser, and then discharged as condensed water, resulting in a huge loss of energy.

[0008] The present invention has been made in view of the problems inherent in the conventional technology as described above, and aims to provide a double-effect drying system that can further increase the drying efficiency of materials to be dried by effectively utilizing the heat of waste steam generated during the drying of materials to be dried, thereby reducing energy loss and preventing cost increases. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, one aspect of the present invention is to provide a method for manufacturing a semiconductor device comprising: A double-effect drying system in which two dryers are connected in series to continuously dry materials to be dried, The drying system comprises a front-stage dryer into which the material to be dried is first introduced, and a rear-stage dryer into which the material to be dried in the front-stage dryer is transferred and into which the drying is completed, This dryer is characterized by the fact that it can be set to a latent heat recovery mode in which high-pressure steam is introduced into the front-stage dryer to dry the material to be dried, and waste steam generated during the drying of the material to be dried by the front-stage dryer is introduced into the rear-stage dryer and used for the final drying of the material to be dried by the rear-stage dryer. [Effects of the Invention]

[0010] The double-effect drying system of the present invention effectively utilizes the heat of the waste steam generated during the drying of the materials to be dried, thereby reducing energy loss and further increasing the drying efficiency of the materials to be dried without incurring higher costs. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an explanatory diagram schematically illustrating the overall configuration of a double-effect drying system according to a first embodiment of the present invention. [Figure 2] FIG. 4 is an explanatory diagram schematically illustrating the overall configuration of a double-effect drying system according to a second embodiment of the present invention. [Figure 3] FIG. 10 is an explanatory diagram schematically illustrating the overall configuration of a double-effect drying system according to a third embodiment of the present invention. [Figure 4] FIG. 10 is an explanatory diagram schematically illustrating the overall configuration of a double-effect drying system according to a fourth embodiment of the present invention. [Figure 5] FIG. 2 is an explanatory diagram showing the state of the material to be dried during the drying process in the dryer. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present inventors have noticed that concentrators exist for concentrating high-water content materials. A known example of such concentrators is a double-effect concentrator. In a double-effect concentrator, high-pressure steam is introduced into a first heater, and atmospheric-pressure steam evaporated from the high-water content material is introduced into a second heater. The latent heat of this atmospheric-pressure steam is used to evaporate the high-water content material evaporated in the first heater to a certain degree in the second heater, thereby producing a high-water content material with a higher concentration. The present inventors have completed the present invention by applying the configuration of such a double-effect concentrator to a dryer.

[0013] Various embodiments representative of the present invention will be described below with reference to the drawings. As shown in Figures 1 to 4, double-effect drying systems 1A to 1D according to various embodiments are systems that continuously dry materials to be dried by connecting two dryers 10A, 10B, etc. Double-effect drying systems 1A to 1D each include a front-stage dryer 10A (10C) into which the materials to be dried are initially introduced, and a rear-stage dryer 10B (10D) into which the materials to be dried are transferred during drying by the front-stage dryer 10A (10C) and into which the drying is completed. Materials to be dried range from a wide variety of materials, such as food waste, sludge, and industrial waste, and come in a variety of forms, such as granular, powdery, liquid, and lumpy.

[0014] [First embodiment] 1 is a schematic diagram illustrating the overall configuration of a double-effect drying system 1A according to a first embodiment. The double-effect drying system 1A of the first embodiment can be set to a latent heat recovery mode in which high-pressure steam is introduced into a first-stage dryer 10A to dry the materials to be dried, and waste steam generated during the drying of the materials to be dried in the first-stage dryer 10A is introduced into a second-stage dryer 10B to be used for final drying of the materials to be dried in the second-stage dryer 10B. The present invention is not limited to the embodiments described below, and detailed descriptions of well-known matters may be omitted as appropriate.

[0015] <Outline of Double-Effect Drying System 1A> As shown in Figure 1, the former-stage dryer 10A and the latter-stage dryer 10B are arranged in series, and the former-stage dryer 10A is connected to a supply hopper 14 into which the materials to be dried are initially fed. The former-stage dryer 10A is connected to the latter-stage dryer 10B via a waste steam delivery pipe 16, which delivers waste steam from the materials to be dried, and to the latter-stage dryer 10B via a transfer pipe 15a, which transports the materials to be dried during drying. The latter-stage dryer 10B is also connected to a condenser 40 via a waste gas delivery pipe 18, which delivers waste gas from the materials to be dried. The latter-stage dryer 10B is further provided with a discharge section 17 for discharging the dried products to the outside after drying is completed, and is also connected to a condensed water separation pot 50.

[0016] <First stage dryer 10A> 1, the pre-drying machine 10A includes a main tank 11A having a vertical cylindrical shape into which the material to be dried is first introduced, and a rotary winding blade 30 attached to a rotary shaft 20 extending along a substantially vertical center line within the main tank 11A. An example of each component of the pre-drying machine 10A will be described below, but the type of the pre-drying machine 10A is not particularly limited as long as it is configured to heat and dry the material to be dried, and the machine is not limited in any way to the example configuration described below.

[0017] <<Main tank 11A>> As shown in Figure 1, main tank 11A is made of metal and has a vertical cylindrical shape. Main tank 11A is placed on the floor with multiple legs attached to its bottom side, with its centerline aligned vertically. The inner wall of main tank 11A serves as heat transfer surface 12, which transfers heat from a heating means to the material to be dried. The heating means for heat transfer surface 12 may include, for example, a jacket 13 formed to surround the outer periphery of main tank 11A, and a boiler (not shown) connected to jacket 13 and communicating with it, which introduces high-temperature, high-pressure steam into jacket 13 as a heat medium.

[0018] The jacket 13 is provided with an inlet for introducing high-pressure steam into the jacket 13 and an outlet for introducing the heat transfer medium out of the jacket 13. As another example of the heating means, hot air may be introduced into the jacket 13 instead of high-pressure steam, or the jacket 13 may be composed of a heat transfer medium contained in the jacket 13 and an electric heater disposed on the outer periphery of the jacket 13. In other words, heat from the electric heater is transferred to the heat transfer surface 12 via the heat transfer medium.

[0019] <<Rotating shaft 20>> As shown in Figure 1, a rotating shaft 20 extending along the vertical centerline of the main tank 11A is provided within the main tank 11A. The rotating shaft 20 is journaled while passing through the center of the top and bottom surfaces of the main tank 11A. The upper end of the rotating shaft 20 is connected via a power transmission system to an electric motor 21 disposed above the top surface of the main tank 11A. Meanwhile, the lower end of the rotating shaft 20 is rotatably supported by a bearing 22 disposed below the bottom surface of the main tank 11A.

[0020] The rotary shaft 20 is provided with a rotary winding blade 30. The rotary shaft 20 is driven to rotate by the power of an electric motor 21, and the rotary winding blade 30 is configured to rotate in synchronization with the rotary shaft 20. The electric motor 21 may be configured to be disposed below the bottom surface instead of above the top surface. The rotary shaft 20 may also be configured to connect multiple rotary shaft portions aligned vertically on the same axis.

[0021] <<Rotating winding blade 30>> The rotary winding blades 30 are arranged in three tiers, one above the other, relative to the rotary shaft 20. However, the specific number and arrangement of the rotary winding blades 30 are design factors that can be appropriately determined depending on the height and dimensions of the main tank 11A. Each of the three tiers of rotary winding blades 30 has multiple (e.g., three) base blades 31 arranged circumferentially around the rotary shaft 20. In this embodiment, each rotary winding blade 30 has the same configuration, but they may also have different configurations, for example, by changing the number or length of the base blades 31 for each rotary winding blade 30.

[0022] The base blades 31 that make up the rotary winding blade 30 are formed to be identical to one another and are arranged, for example, with a phase difference of approximately 120 degrees. Each base blade 31 is supported so as to extend continuously from the tip of an arm 32 whose base end is attached to the rotary shaft 20. Here, the arm 32 may be considered to be part of the configuration of the base blade 31. Each base blade 31 extends in a circumferential direction around the rotary shaft 20 in a plan view and has a flat surface 31a (see Figure 5) that can carry the material to be dried from its starting end connected to the tip of the arm 32 and move it to its terminal end while winding it up.

[0023] The flat surface 31a of each base blade 31 is formed so as to extend obliquely upward from the starting end to the terminal end in the direction opposite to the rotation direction R. That is, each base blade 31 is configured so as to place the material to be dried on the flat surface 31a, wind it up, and press it into a thin film against the heat transfer surface 12 of the main tank 11A by centrifugal force P (see FIG. 5) and inertial force. Here, the flat surface 31a extends with a constant width up to a length within a 360-degree circumferential range in a plan view, and the outer peripheral edge of the flat surface 31a is formed in an arc shape that follows the cylindrical shape of the heat transfer surface 12. Note that a clearance U that allows rotation of each base blade 31 is provided between the outer peripheral edge of the flat surface 31a and the heat transfer surface 12.

[0024] <<Included configuration>> There are various configurations for feeding the materials to be dried into the main tank 11A, but for example, a supply hopper 14 for supplying the materials to be dried is provided at the lower left side of the main tank 11A. The supply hopper 14 is formed, for example, in the shape of a tank that can store a predetermined amount of materials to be dried. A screw for stirring the materials to be dried is provided in the middle of the supply hopper 14 so as to be rotatable by power. In addition, a screw for transporting the materials to be dried toward a discharge outlet that opens at the lower right end of the supply hopper 14 is provided at the bottom so as to be rotatable by power.

[0025] The discharge outlet of the supply hopper 14 is connected via a transfer pipe 14a to an inlet opening at the lower left side of the main tank 11A. A screw is provided inside the transfer pipe 14a and is rotatable by power, working in conjunction with a screw at the bottom of the supply hopper 14 to feed the materials to be dried into the main tank 11A. A valve or shutter that can be opened and closed by power is provided at the connection between the discharge outlet of the supply hopper 14 and the upstream opening of the transfer pipe 14a. This configuration makes it possible to appropriately feed the materials to be dried stored in the supply hopper 14 into the main tank 11A of the pre-drying device 10A.

[0026] Further, a discharge part 15 is provided at the lower right side of the main tank 11A for temporarily discharging the materials to be dried that are still being dried to the outside. The discharge part 15 is formed, for example, in the shape of a case that guides the materials to be dried that are located above the bottom part inside the main tank 11A to the outside. Here, a valve or shutter that can be opened and closed by power is provided at the communication port where the discharge part 15 opens into the main tank 11A.

[0027] The lower end opening of the discharge section 15 is connected via a transfer pipe 15a to an inlet opening at the lower left side of the main tank 11B of the rear-stage dryer 10B, which will be described below. A screw is rotatably provided inside the transfer pipe 15a, and this screw transfers the materials to be dried that are still being dried into the main tank 11B of the rear-stage dryer 10B. This configuration makes it possible to appropriately transfer the materials to be dried in the main tank 11A of the front-stage dryer 10A to the main tank 11B of the rear-stage dryer 10B.

[0028] Furthermore, an exhaust port opening on the top surface of the main tank 11A communicates with an inlet opening in a jacket 13 surrounding the main tank 11B of the second-stage dryer 10B, which will be described below, via a waste steam delivery pipe 16. With this configuration, it becomes possible to introduce waste steam at atmospheric pressure, which is generated in the pre-stage dryer 10A as the materials to be dried are dried, into the jacket 13 of the second-stage dryer 10B via the waste steam delivery pipe 16. In other words, the waste steam from the materials to be dried in the pre-stage dryer 10A is not simply exhausted to the outside, but the latent heat is recovered in the second-stage dryer 10B and effectively used for the final heating of the materials to be dried.

[0029] <Later dryer 10B> 1, the latter-stage dryer 10B is basically configured in the same manner as the former-stage dryer 10A, and includes a main tank 11B having a vertical cylindrical shape into which the material to be dried is first charged, and a rotary winding blade 30 attached to a rotary shaft 20 extending along a substantially vertical center line within the main tank 11B. Note that in the latter-stage dryer 10B, parts that are the same as those in the former-stage dryer 10A are given the same reference numerals and redundant explanations will be omitted, but the former-stage dryer 10A is configured to have a larger capacity than the latter-stage dryer 10B.

[0030] That is, the main tank 11B of the latter-stage dryer 10B has the same configuration as the main tank 11A of the former-stage dryer 10A, but its height is set lower, and the rotary shaft 20 supported in the main tank 11B is set shorter than that supported in the main tank 11A. Therefore, the number of rotary winding blades 30 provided on the rotary shaft 20 of the latter-stage dryer 10B is insufficient to provide three upper and lower stages, so two upper and lower stages are provided. However, the specific number and arrangement of rotary winding blades 30 in the latter-stage dryer 10B are design factors that can be determined appropriately depending on the height and dimensions of the main tank 11B.

[0031] As described above, normal pressure waste steam generated in the pre-drying machine 10A is introduced into the jacket 13 surrounding the outer periphery of the main tank 11B as a heat source for the heat transfer surface 12. The jacket 13 is provided with an inlet to which the waste steam delivery pipe 16 from the pre-drying machine 10A is connected, and an outlet to guide the waste steam from which latent heat has been recovered out of the jacket 13. The downstream end of the transfer pipe 15a is connected to an inlet located at the bottom left side of the main tank 11B.

[0032] Further, a discharge section 17 is provided at the lower right side of the main tank 11B for discharging the dried product to the outside after the final drying of the material to be dried has been completed. Similar to the discharge section 15, the discharge section 17 is formed, for example, in the shape of a case for guiding the dried product located above the bottom inside the main tank 11B to the outside. Here, a valve or shutter that can be opened and closed by power is also provided at the communication port where the discharge section 17 opens into the main tank 11B.

[0033] <<Other included configurations>> An exhaust port opening on the top surface of the main tank 11B is connected to a condenser 40 via a waste gas delivery pipe 18. The condenser 40 is connected to a blower 42 via an air delivery pipe 41. The condenser 40 receives the waste gas sent from the main tank 11B and separates it into gas and liquid using a cooling pipe. The cooling pipe of the condenser 40 is configured so that cooling water enters from the outside and exits after cooling.

[0034] The liquid separated from the waste gas by the condenser 40 is discharged as condensed water from a drain located at the bottom of the condenser 40 to the outside. The other gas passes through an air pipe 41 and is discharged to the outside by driving a blower 42. The gas separated by the condenser 40 may be further sent to a deodorizer for deodorization. The deodorizer may be, for example, a type that exposes the waste gas itself to high temperatures to burn it, or a platinum catalyst deodorizer or the like, as appropriate.

[0035] Furthermore, an outlet opening at the bottom of the jacket 13 surrounding the main tank 11B communicates with a condensed water separation pot 50 via an outlet pipe 19. The condensed water separation pot 50 communicates with a blower 52 via an air supply pipe 51. The condensed water separation pot 50 further separates water from the remaining waste steam that has not been completely evaporated after being introduced into the jacket 13. The water separated here is discharged to the outside as condensed water via a drain. The other gas passes through the air supply pipe 51 and is discharged to the outside by driving the blower 52.

[0036] <Function of double-effect drying system 1A> Next, the operation of the double-effect drying system 1A according to the first embodiment will be described. In the double-effect drying system 1A, of the two dryers 10A and 10B, the material to be dried is first loaded into the main tank 11A of the pre-drying unit 10A from a supply hopper 14, and high-pressure steam is introduced into the jacket 13 surrounding the main tank 11A. Then, the electric motor 21 is driven to rotate the rotary shaft 20 in the direction indicated by R in FIG.

[0037] In the main tank 11A, the material to be dried is scraped off the bottom of the main tank 11A by the arm 32 as the lower rotary winding blade 30 rotates, and is scooped up to the starting end of each base blade 31. The material to be dried scooped up from the starting end of each base blade 31 continues to rise toward the end of each base blade 31, being wound up in the direction opposite to the rotation direction R of the rotary winding blade 30. At this time, as shown in Figure 5, the material to be dried on the flat surface 31a of each base blade 31 is pressed into a thin film against the heat transfer surface 12 by centrifugal force P and inertial force.

[0038] As shown in Figure 5, the material to be dried pressed against the heat transfer surface 12 in the form of a thin film has a heated surface in contact with the heat transfer surface 12 on one side and an evaporation surface in contact with the air in the space inside the main tank 11A on the other side. When the material to be dried comes into contact with the heat transfer surface 12, a certain amount of moisture evaporates on the spot due to the heat from the heat transfer surface 12. Next, the material to be dried, whose moisture content has decreased due to the evaporation of moisture when it comes into contact with the heat transfer surface 12, moves to the evaporation surface so as to replace the material to be dried with a higher moisture content. When the material to be dried has moved to the evaporation surface, it is exposed to the air, which further evaporates moisture.

[0039] As the material to be dried moves from the heat transfer surface 12 side to the evaporation surface, the material to be dried that is being rolled up by each base blade 31 continuously pushes the material to be dried that is being rolled up, and the material to be dried rises along the heat transfer surface 12. In other words, the material to be dried moves from the heat transfer surface 12 to the evaporation surface, rolls up along the heat transfer surface 12, and dries efficiently as it rises.

[0040] In particular, because the rotary winding blades 30 are arranged in multiple stages, one above the other, the materials to be dried are wound up at each stage and pressed against the heat transfer surface 12 in a thin film, and the materials to be dried that are wound up later push the earlier materials up to the next stage. Therefore, the materials to be dried can be successively lifted from the lower stage to the upper stage by the rotary winding blades 30 while being continuously dried, and the entire surface of the heat transfer surface 12 in the vertical direction of the main tank 11A can be effectively used, achieving high drying efficiency by taking advantage of the vertical type.

[0041] The waste steam at normal pressure generated during drying in the former-stage dryer 10A is introduced into the jacket 13 of the latter-stage dryer 10B through a waste steam delivery pipe 16 connecting the former-stage dryer 10A to the latter-stage dryer 10B as a heat medium for final drying of the material to be dried in the latter-stage dryer 10B. The material to be dried in the former-stage dryer 10A is discharged from the discharge part 15 of the main tank 11A and is introduced directly into the main tank 11B of the latter-stage dryer 10B through the transfer pipe 15a.

[0042] In this way, in the latter-stage dryer 10B, the heat transfer surface 12 is heated by recovering latent heat from the normal pressure waste steam, and as in the former-stage dryer 10A, the rotation of each rotary winding blade 30 causes the material to be pressed into a thin film against the heat transfer surface 12 by centrifugal force and inertial force, evaporating the water content and finally drying it. Here, the normal pressure waste steam supplied from the former-stage dryer 10A has an increased heat absorption rate due to the configuration that makes use of the advantages of the vertical type described above, and can fully absorb even low latent heat calories like normal pressure waste steam.

[0043] The drying efficiency of the two dryers 10A, 10B will be explained in more detail. In the double-effect drying system 1A as a whole, for example, if it is desired to dry a material to be dried with a hypothetical moisture content of 80% down to a moisture content of 10%, the material to be dried is first dried in the front-stage dryer 10A by heating with high-pressure steam introduced into the jacket 13 until the moisture content reaches around 50%. If the weight of the material to be dried is assumed to be 1,000 kg, the material will initially have a moisture content of 800 kg and a solid content of 200 kg, but will dry down to a moisture content of 200 kg and a solid content of 200 kg.

[0044] The material to be dried that has been semi-dried in the former-stage dryer 10A and is still being dried is then transferred to the latter-stage dryer 10B, where the semi-dried material with a moisture content of 50% is finally dried to a moisture content of 10% by recovering the latent heat of the waste steam at atmospheric pressure introduced into the jacket 13. In other words, the material that was being dried is finally dried to a moisture content of 20 kg and a solid content of 200 kg.

[0045] As described above, first, in the pre-drying machine 10A, 600 kg of water is evaporated until the moisture content of the 800 kg of material to be dried is reduced to 200 kg, and then in the subsequent post-drying machine 10B, 180 kg of water is evaporated from the semi-dried material. This eliminates the need to use approximately 20% of the high-pressure steam, and when used over a long period of time (for example, several decades), it is possible to achieve significant energy savings.

[0046] Furthermore, while it would take a long time to dry 1,000 kg down to 220 kg using only the front-stage dryer 10A, the system 1A uses the back-stage dryer 10B to dry 1,000 kg down to 400 kg, significantly shortening the drying time. Therefore, compared to a conventional dryer with only the front-stage dryer 10A, the processing capacity can be further increased.

[0047] [Second embodiment] 2 is a schematic diagram showing the overall configuration of a double-effect drying system 1B according to the second embodiment. The double-effect drying system 1B according to the second embodiment also includes a front-stage dryer 10C to which the material to be dried is first introduced, and a rear-stage dryer 10D to which the material to be dried is transferred during drying by the front-stage dryer 10C and to which the drying is completed. However, unlike the double-effect drying system 1A according to the first embodiment, the order of introduction of high-pressure steam and atmospheric waste steam into the dryers 10C and 10D is reversed.

[0048] <Outline of Double-Effect Drying System 1B> That is, in the double-effect drying system 1B of the second embodiment, high-pressure steam is introduced into the rear-stage dryer 10D to perform final drying of the materials to be dried, and a preheat utilization mode can be set in which waste steam generated during the final drying of the materials to be dried by the rear-stage dryer 10D is introduced into the front-stage dryer 10C and used to preheat drying of the materials to be dried by the front-stage dryer 10C. Note that in the double-effect drying system 1B, parts that are the same as those in the double-effect drying system 1A described above are assigned the same reference numerals, and duplicated descriptions will be omitted.

[0049] In the double-effect drying system 1B of the second embodiment, the rear-stage dryer 10D is configured to have a larger capacity than the front-stage dryer 10C. Specifically, for example, the front-stage dryer 10C has a similar configuration to the rear-stage dryer 10B of the double-effect drying system 1A, and the rear-stage dryer 10D has a similar configuration to the front-stage dryer 10A of the double-effect drying system 1A.

[0050] In the double-effect drying system 1B, high-pressure steam is introduced into the jacket 13 of the latter-stage dryer 10D, and normal-pressure waste steam generated during the final drying of the semi-dried product in the latter-stage dryer 10D is introduced into the jacket 13 of the former-stage dryer 10C through the waste steam delivery pipe 16. Furthermore, in the double-effect drying system 1B, the condenser 40 is connected via the waste gas delivery pipe 18 to the main tank 11C of the former-stage dryer 10C, rather than the main tank 11D of the latter-stage dryer 10D, and the condensed water separation pot 50 is connected via the outlet pipe 19 to the main tank 11C of the former-stage dryer 10C.

[0051] <Function of double-effect drying system 1B> The double-effect drying system 1B of the second embodiment has another advantage over the double-effect drying system 1A of the first embodiment described above. That is, in the double-effect drying system 1B, the material to be dried is first fed into the front-stage dryer 10C, and by supplying atmospheric pressure waste steam from the rear-stage dryer 10D to this front-stage dryer 10C as a heat source, the front-stage dryer 10C functions as a preheating dryer for the rear-stage dryer 10D.

[0052] For example, by evaporating the moisture content of the material to be dried to about 20% in the first-stage dryer 10C, the thermal efficiency of the final drying in the second-stage dryer 10D is improved. Thus, the double-effect drying system 1B can significantly improve the drying efficiency, particularly in the second-stage dryer 10D, and achieve excellent energy savings. These advantages also contribute to shortening the drying time for materials with high moisture content.

[0053] While the materials to be dried are being subjected to final drying in the latter-stage dryer 10D, the former-stage dryer 10C also assists in the drying of the materials to be dried. The materials to be dried, which have been dried and reduced in volume in the former-stage dryer 10C, to which normal pressure waste steam is introduced, are transferred to the latter-stage dryer 10D, to which high-pressure steam is introduced. Therefore, overall, drying can be completed in a shorter time than with conventional general dryers. This also applies to the double-effect drying system 1A, in which high-pressure steam is introduced into the former-stage dryer 10A and normal pressure waste steam is introduced into the latter-stage dryer 10B, whereby drying time can be shortened compared to normal.

[0054] [Third embodiment] 3 shows a schematic diagram of the overall configuration of a double-effect drying system 1C according to the third embodiment. The double-effect drying system 1C according to the third embodiment is basically similar in configuration to the double-effect drying system 1A according to the first embodiment, but the rear-stage dryer 10B, to which atmospheric-pressure waste steam is introduced from the front-stage dryer 10A, is configured so that the interior (inside of the main tank 11B) of the rear-stage dryer 10B, to which the material to be dried is supplied during drying, can be set to a vacuum state.

[0055] 3, in the double-effect drying system 1C, the main tank 11B of the rear-stage dryer 10B is connected to a condenser 40 via a waste gas delivery pipe 18, but the condenser 40 is connected to a vacuum pump 43 instead of a blower 42 via an air delivery pipe 41. By driving this vacuum pump 43, the inside of the main tank 11B can be maintained in a vacuum state through the condenser 40.

[0056] In this double-effect drying system 1C, the boiling point of the water contained in the material to be dried in the main tank 11B can be lowered by creating a vacuum inside the main tank 11B of the rear-stage dryer 10B, into which atmospheric-pressure waste steam is introduced. This improves the absorption of low latent heat calories from the atmospheric-pressure waste steam used as a heat source in the main tank 11B, thereby increasing drying efficiency. Note that a redundant description of the configurations and effects of the same parts of the double-effect drying system 1C as those of the double-effect drying system 1A described above will be omitted.

[0057] [Fourth embodiment] 4 shows a schematic diagram of the overall configuration of a double-effect drying system 1D according to the fourth embodiment. The double-effect drying system 1D according to the fourth embodiment is basically similar in configuration to the double-effect drying system 1B according to the second embodiment, but the front-stage dryer 10C, to which atmospheric-pressure waste steam from the rear-stage dryer 10D is introduced, is configured so that the interior (inside of the main tank 11C), to which the material to be dried is first supplied, can be set to a vacuum state.

[0058] 4, in the double-effect drying system 1D, the main tank 11C of the pre-dryer 10C is connected to a condenser 40 via a waste gas delivery pipe 18, but the condenser 40 is connected to a vacuum pump 43 instead of a blower 42 via an air delivery pipe 41. By driving this vacuum pump 43, the inside of the main tank 11C can be maintained in a vacuum state through the condenser 40.

[0059] In this double-effect drying system 1D, the boiling point of the water contained in the material to be dried in the main tank 11C can be lowered by creating a vacuum inside the main tank 11C of the pre-drying unit 10C, which introduces waste steam at atmospheric pressure. This allows for better absorption of the low latent heat calories of the waste steam at atmospheric pressure, which is used as a heat source in the main tank 11C. Note that a redundant description of the configurations and effects of the same parts of the double-effect drying system 1D as those of the double-effect drying system 1B described above will be omitted.

[0060] [Other embodiments] The double-effect drying system 1A of the first embodiment and the double-effect drying system 1C of the third embodiment described above can be set to a latent heat recovery mode in which the latent heat of waste steam is recovered in the rear-stage dryer 10B. The double-effect drying system 1B of the second embodiment and the double-effect drying system 1D of the fourth embodiment described above can be set to a preheat utilization mode in which the waste steam is used for preheating drying in the front-stage dryer 10C. A single system may be configured to be able to switch between the latent heat recovery mode and the preheat utilization mode as desired.

[0061] The latent heat recovery mode and the preheat utilization mode can be easily realized by simply rearranging the positions of the piping, such as the waste steam delivery pipe 16, and associated components in each of the double-effect drying systems 1A to 1D. This makes it possible to easily change to a mode with higher drying efficiency, for example, depending on the moisture content and type of material to be dried. In this way, in a system that is designed to be able to change between modes, configuring the front-stage dryer 10A (10C) and the rear-stage dryer 10B (10D) with the same capacity increases the reproducibility of the benefits of each mode.

[0062] Specifically, for example, when the latent heat recovery mode of double-effect drying system 1A is switched to the preheat utilization mode of double-effect drying system 1B, high-pressure steam is introduced into jacket 13 of main tank 11B and atmospheric pressure waste steam generated in latter-stage dryer 10B is introduced into jacket 13 of main tank 11A without changing supply hopper 14, former-stage dryer 10A, or latter-stage dryer 10B.

[0063] For this purpose, the waste gas delivery pipe 18 is removed from the upper surface of the main tank 11B and instead communicated with the inside of the jacket 13 of the main tank 11A via the waste steam delivery pipe 16. Moreover, instead of removing the waste steam delivery pipe 16, the upper surface of the main tank 11A is communicated with the condenser 40 via the waste gas delivery pipe 18. Furthermore, the outflow pipe 19 and the condensed water separation pot 50 that were removed from the jacket 13 of the main tank 11B are instead communicated with the jacket 13 of the main tank 11A.

[0064] In this way, switching between the modes can be easily performed by simply rearranging the positions of the piping such as the waste steam delivery pipe 16 and the associated components, without changing the installation conditions of the main components, namely the supply hopper 14, the pre-drying unit 10A, and the post-drying unit 10B. The same applies to switching between the double-effect drying system 1C of the third embodiment and the double-effect drying system 1D of the fourth embodiment.

[0065] [Configuration and effects of the present invention] Although various embodiments of the present invention have been described above, the present invention is not limited to the above-described various embodiments. The present invention derived from the above-described various embodiments will be described below.

[0066] First, the present invention provides a double-effect drying system 1A, 1C in which two dryers 10A, 10B are connected in series to continuously dry materials to be dried, The drying system is provided with a front-stage dryer 10A into which the material to be dried is first introduced, and a rear-stage dryer 10B into which the material to be dried being dried by the front-stage dryer 10A is transferred and into which the drying is completed, High-pressure steam is introduced into the front-stage dryer 10A to dry the material to be dried, and waste steam generated during the drying of the material to be dried by the front-stage dryer 10A is introduced into the rear-stage dryer 10B, where it can be used for the final drying of the material to be dried by the rear-stage dryer 10B.

[0067] The double-effect drying systems 1A and 1C make it possible to recover and effectively utilize the latent heat of waste steam, which is discarded without any utilization in conventional dryers. This reduces energy loss throughout the drying system, and further improves the drying efficiency of the materials to be dried without increasing costs.

[0068] Here, in the rear-stage dryer 10B into which the waste steam is introduced, the interior (inside the main tank 11B) into which the material to be dried is supplied may be set to a vacuum state. This makes it possible to lower the boiling point of the water contained in the material to be dried in the main tank 11B, improve absorption of the low latent heat calorie of the waste steam used as a heat source in the main tank 11B, and increase drying efficiency.

[0069] The present invention also provides a double-effect drying system 1B, 1D in which two dryers 10C, 10D are connected in series to continuously dry materials to be dried, The drying system is provided with a front-stage dryer 10C into which the material to be dried is first introduced, and a rear-stage dryer 10D into which the material to be dried being dried by the front-stage dryer 10C is transferred and into which the drying is completed, High-pressure steam is introduced into the rear-stage dryer 10D to perform final drying of the material to be dried, and waste steam generated during the final drying of the material to be dried by the rear-stage dryer 10D is introduced into the front-stage dryer 10C and can be used to preheat and dry the material to be dried by the front-stage dryer 10C.

[0070] With these double-effect drying systems 1B and 1D, it is possible to effectively use waste steam, which is discarded without any use in conventional dryers, to preheat the materials to be dried before final drying. This reduces energy loss throughout the drying system, and further improves the drying efficiency of the materials without increasing costs.

[0071] In this case, too, in the pre-drying device 10C into which the waste steam is introduced, the interior (inside the main tank 11C) into which the material to be dried is supplied may be set to a vacuum state. This makes it possible to lower the boiling point of the water contained in the material to be dried in the main tank 11C, improve the rate of heat recovery from the waste steam used for preheating in the main tank 11C, and increase the drying efficiency.

[0072] In addition, the present invention may be configured such that a single system can be switched between a latent heat recovery mode in which the latent heat of waste steam is recovered in double-effect drying systems 1A and 1C, and a preheat utilization mode in which waste steam is used for preheating drying in double-effect drying systems 1B and 1D. This allows for easy switching to a mode with higher drying efficiency depending on, for example, the moisture content and type of material to be dried.

[0073] Furthermore, in the present invention, the front-stage dryer 10A / 10C and the rear-stage dryer 10B / 10D each include a main tank having a vertical cylindrical shape for receiving the material to be dried, and a rotary lifting blade provided on a rotary shaft extending along a substantially vertical center line within the main tank, the inner wall of the main vessel forms a heat transfer surface that is heated by steam introduced into a jacket provided along the outer periphery of the main vessel; The rotary lifting blades are driven to rotate, and the material to be dried in the main tank rises while being pressed against the heat transfer surface in the form of a thin film by centrifugal force and inertial force. According to such dryers 10A to 10D, the heat absorption rate is increased by taking advantage of the so-called vertical type configuration, and even waste steam at normal pressure can be fully and effectively utilized as a heat source.

[0074] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and modifications and additions that do not depart from the gist of the present invention are also included in the present invention. For example, the specific shapes and capacities of the main tanks 11A-11D in the dryers 10A-10D, as well as the specific number and arrangement of the rotary draft blades 30, are not limited to those shown in the drawings. [Industrial Applicability]

[0075] The double-effect drying system of the present invention can be used to dry various types of materials, and can be widely used as a drying system that can efficiently dry materials with high moisture content and various forms. [Explanation of symbols]

[0076] 1A~1D...Double-effect drying system 10A,10C…front stage dryer 10B,10D…Late stage dryer 11A~11D…Main tank 12...Heat transfer surface 13...Jacket 16...Waste steam delivery pipe 20...Rotation axis 30...Rotating winding blade 31...Base blade 32...Arm 40...Condenser 50...Flocculated water separation pot

Claims

1. A double-effect drying system in which two dryers are connected in series to continuously dry materials to be dried, The drying system comprises a front-stage dryer into which the material to be dried is first introduced, and a rear-stage dryer into which the material to be dried in the front-stage dryer is transferred and into which the drying is completed, A double-effect drying system characterized in that high-pressure steam is introduced into a front-stage dryer to dry the material to be dried, and waste steam generated during the drying of the material to be dried in the front-stage dryer is introduced into a rear-stage dryer and can be used for the final drying of the material to be dried in the rear-stage dryer.

2. A double-effect drying system in which two dryers are connected in series to continuously dry materials to be dried, The drying system comprises a front-stage dryer into which the material to be dried is first introduced, and a rear-stage dryer into which the material to be dried in the front-stage dryer is transferred and into which the drying is completed, A double-effect drying system characterized in that high-pressure steam is introduced into a rear-stage dryer to perform final drying of the material to be dried, and waste steam generated during the final drying of the material to be dried in the rear-stage dryer is introduced into a front-stage dryer and can be used to preheat and dry the material to be dried in the front-stage dryer.

3. 2. The double-effect drying system according to claim 1, wherein the second-stage dryer into which the waste steam is introduced has an interior that is set to a vacuum state and into which the material to be dried is supplied.

4. 3. The double-effect drying system according to claim 2, wherein the pre-drying device into which the waste steam is introduced is set to a vacuum state inside where the material to be dried is supplied.

5. A double-effect drying system in which two dryers are connected in series to continuously dry materials to be dried, The drying system comprises a front-stage dryer into which the material to be dried is first introduced, and a rear-stage dryer into which the material to be dried in the front-stage dryer is transferred and into which the drying is completed, The system can be set to a latent heat recovery mode in which high-pressure steam is introduced into the pre-stage dryer to dry the materials to be dried, and waste steam generated during the drying of the materials to be dried by the pre-stage dryer is introduced into the post-stage dryer to be used for the final drying of the materials to be dried by the post-stage dryer, A preheating utilization mode can be set in which high-pressure steam is introduced into the rear-stage dryer to perform final drying of the material to be dried, and waste steam generated during the final drying of the material to be dried by the rear-stage dryer is introduced into the front-stage dryer to be used for preheating and drying the material to be dried by the front-stage dryer, A double-effect drying system that can be switched between a latent heat recovery mode and a preheat utilization mode.

6. The front-stage dryer and the rear-stage dryer each include a main tank having a vertical cylindrical shape and configured to receive the material to be dried, and a rotary lifting blade provided on a rotary shaft extending along a substantially vertical center line within the main tank; the inner wall of the main vessel forms a heat transfer surface that is heated by steam introduced into a jacket provided along the outer periphery of the main vessel; 6. The drying system according to claim 1, wherein the rotary lifting blades are driven to rotate, so that the material to be dried in the main tank rises while being pressed against the heat transfer surface in the form of a thin film by centrifugal force and inertial force.

Images