An energy-saving drying method and system for starch

Abstract

The present invention relates to a starch energy-saving drying method and system, and relates to the technical field of starch drying. The starch energy-saving drying method comprises the following steps: subjecting wet starch to be dried to low-temperature vacuum drying to obtain a first wet starch and secondary steam generated by the low-temperature vacuum drying; compressing the secondary steam generated by the low-temperature vacuum drying and eliminating superheat, and then using it to heat and dry the first wet starch to obtain a second wet starch; subjecting the second wet starch to high-temperature vacuum drying to obtain dried high-temperature starch and secondary steam generated by the high-temperature vacuum drying; cooling the dried high-temperature starch to obtain dried starch and hot water generated by cooling; refluxing the secondary steam generated by the high-temperature vacuum drying and the hot water generated by the cooling and using them as a compensating heat source when heating and drying the first wet starch. The starch energy-saving drying method and system provided by the present invention have lower energy consumption and better starch quality, thus overcoming the shortcomings of the existing technology.

Description

Technical Field

[0001] The present invention relates to the technical field of starch drying, and in particular to an energy-saving starch drying method and system. Background Art

[0002] Starch is an important basic raw material for food and chemical industry. Most of it is processed and extracted from starch-rich plants, such as corn starch, cassava starch, potato starch, sweet potato starch, water chestnut starch (water chestnut powder), kudzu starch (kudzu powder), etc. During the processing, the slurry is first dehydrated to obtain wet starch with a moisture content of about 35-40%, and then it is dried by hot air flow or drying in a drying room (water chestnut powder) to a finished product with a moisture content of 10-14%. The thermal efficiency of hot air flow drying and drying room drying is very low, only 30-50%. my country has a large output of various starches and many manufacturers, and the energy consumption of drying accounts for a large proportion! Therefore, it is very necessary to develop energy-saving technology for starch drying.

[0003] Traditionally, water chestnut powder and kudzu root powder are sold in granular form. Consumers believe that granular water chestnut powder and kudzu root powder are more easily distinguishable from other starches and are not counterfeit. Conventional hot air drying can only produce powdered products. Consequently, manufacturers currently rely on inefficient drying rooms or tunnel carts.

[0004] Steam multi-effect evaporation and mechanical steam recompression (MVR) technologies are widely used in the concentration and evaporation of food liquids, achieving significant energy savings. However, their application in solids drying is limited, with literature searches only mentioning their application in sludge drying. Furthermore, their use in starch drying has never been documented. Summary of the Invention

[0005] To solve the above problems, the present invention provides a starch energy-saving drying method and system.

[0006] The present invention provides a starch energy-saving drying method, which comprises the following steps:

[0007] The wet starch to be dried is subjected to low-temperature vacuum drying to obtain the first wet starch and secondary steam generated by the low-temperature vacuum drying;

[0008] compressing the secondary steam generated by the low-temperature vacuum drying to eliminate superheat, and then using it to heat and dry the first wet starch to obtain a second wet starch;

[0009] subjecting the second wet starch to high-temperature vacuum drying to obtain dried high-temperature starch and secondary steam generated by high-temperature vacuum drying;

[0010] Cooling the dried high-temperature starch to obtain dried starch and hot water generated by cooling;

[0011] The secondary steam generated by the high-temperature vacuum drying and the hot water generated by the cooling are refluxed and used as a compensating heat source during the heating and drying of the first wet starch.

[0012] Furthermore, the moisture content of the wet starch to be dried is 35-40% by weight.

[0013] Furthermore, the wet starch to be dried is subjected to low-temperature vacuum drying to 50-55° C., the low-temperature vacuum drying temperature is 50-55° C., and the vacuum degree is -0.088-0.085 MPa.

[0014] Furthermore, the secondary steam generated by the low-temperature vacuum drying is compressed and desuperheated, and then used for heating and drying the first wet starch with a saturated steam temperature of 65 to 70° C. and a vacuum degree of -0.076 to 0.07 MPa.

[0015] Furthermore, the working condition parameters of the high-temperature vacuum drying include: drying temperature of 80 to 90° C., and vacuum degree of -0.054 to 0.031 MPa.

[0016] Furthermore, the moisture content of the second wet starch is 14-16% by weight.

[0017] Furthermore, the moisture content of the dried high-temperature starch is 10-14% by weight.

[0018] In a second aspect, the present invention provides a system for implementing the energy-saving starch drying method according to any one of the first aspects, the system comprising a low-temperature vacuum dryer and a low-temperature vacuum dryer heater, a low-temperature steam compressor, a high-temperature vacuum dryer and a high-temperature vacuum dryer heater, and a normal pressure dryer connected in sequence;

[0019] The low-temperature vacuum dryer and high-temperature vacuum dryer can be selected from heat-conduction type horizontal disc vacuum dryer, vertical disc vacuum dryer, hollow blade vacuum dryer, etc.

[0020] The atmospheric pressure dryer can be a heat conduction type horizontal disc atmospheric pressure dryer, a vertical disc atmospheric pressure dryer, a hollow blade atmospheric pressure dryer, etc.

[0021] The low-temperature steam compressor can be a Roots steam compressor or a centrifugal steam compressor;

[0022] The vacuum feeder of the low-temperature vacuum dryer is connected to the first conveyor belt, the low-temperature vacuum dryer is connected to the low-temperature steam compressor and the humidifier in sequence, the humidifier is connected to the low-temperature vacuum dryer heater, the low-temperature vacuum dryer heater is connected to the first vapor-liquid separator, and the first vapor-liquid separator is connected to a pump; the low-temperature vacuum dryer is connected to the high-temperature vacuum dryer via the first vacuum discharger;

[0023] The high-temperature vacuum dryer is connected to the humidifier through a second vapor-liquid separator, a second pressure reducing valve, and a non-condensable gas pressure reducing valve; the high-temperature vacuum dryer is connected to a second conveyor belt through a second vacuum feeder, and the second conveyor belt is connected to a feed hopper of a normal pressure dryer. The normal pressure dryer is provided with a cooler, and the normal pressure dryer cooler is connected to the humidifier through a third pressure reducing valve.

[0024] Furthermore, the atmospheric pressure dryer is provided with a discharge port.

[0025] The above technical solution provided by the embodiment of the present invention has at least the following advantages compared with the prior art:

[0026] The present invention provides an energy-saving starch drying method and system. This patented solution utilizes mechanical steam recompression (MVR) technology, combined with live steam double-effect evaporation, to dry wet starch in two stages: low temperature (50-55°C) and high temperature (80-90°C). Low-temperature vacuum drying prevents gelatinization (temperatures below the gelatinization temperature) when the starch has a high moisture content. Water evaporates primarily in the low-temperature stage, resulting in a longer residence time. High-temperature vacuum drying further evaporates the bound water in the starch, increasing the drying speed. The high-temperature stage has a sterilizing effect, making it a necessary step for starch products requiring sterilization (such as water chestnut powder). The relatively short residence time in the high-temperature stage reduces starch moisture content (≤16%), minimizing starch property variation and ensuring product quality. After drying, the starch is cooled in an atmospheric pressure dryer, recycling the waste heat to obtain a granular product (such as water chestnut powder). Adding a powdering cabinet for crushing and screening can also produce a powdered starch product (such as cassava starch), achieving continuous production on an assembly line. The overall energy consumption is only 18-20% of hot air drying and 12-15% of drying room. It is a very energy-saving drying method that makes up for the shortcomings of existing technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0029] Figure 1 A schematic flow chart of the energy-saving starch drying method provided in an embodiment of the present invention.

[0030] Figure 2 A schematic diagram of a starch energy-saving drying system provided in an embodiment of the present invention.

[0031] Figure 2 In: 1-first conveyor belt, 2-vacuum feeder, 3-low-temperature vacuum dryer, 4-low-temperature steam compressor, 5-low-temperature vacuum dryer heater, 6-first vacuum discharger, 7-first vapor-liquid separator, 8-pump, 9-humidifier, 10-high-temperature vacuum dryer, 11-first pressure reducing valve, 12-high-temperature vacuum dryer heater, 13-second vacuum discharger, 14-second vapor-liquid separator, 15-non-condensable gas pressure reducing valve, 16-second pressure reducing valve, 17-second conveyor belt, 18-feed hopper, 19-normal-pressure dryer, 20-cooler, 21-discharge port, 22-third pressure reducing valve. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0033] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0034] In a first aspect, the present invention provides a starch energy-saving drying method, such as Figure 1 As shown, the energy-saving starch drying method comprises the following steps:

[0035] The wet starch to be dried is subjected to low-temperature vacuum drying to obtain the first wet starch and the secondary steam generated by preheating and drying;

[0036] compressing the secondary steam generated by the low-temperature vacuum drying to eliminate superheat, and then using it to heat and dry the first wet starch to obtain a second wet starch;

[0037] subjecting the second wet starch to high-temperature vacuum drying to obtain dried high-temperature starch and secondary steam generated by high-temperature vacuum drying;

[0038] Cooling the dried high-temperature starch to obtain dried starch and hot water generated by cooling;

[0039] The secondary steam generated by the high-temperature vacuum drying and the hot water generated by the cooling are refluxed and used as a compensating heat source during the heating and drying of the first wet starch.

[0040] The present invention provides an energy-saving starch drying method. This patented solution utilizes mechanical steam recompression (MVR) technology, combined with live steam two-effect evaporation, to dry wet starch in two stages: low temperature (50-55°C) and high temperature (80-90°C). Low-temperature vacuum drying prevents gelatinization of starch when the starch has a high moisture content (temperature below the gelatinization temperature). Water is primarily controlled to evaporate in the low-temperature stage, which has a longer residence time. High-temperature vacuum drying further evaporates the bound water in the starch, increasing the drying speed. The high-temperature stage has a sterilizing effect and is a necessary step for starch products requiring sterilization (such as water chestnut powder). The relatively short residence time in the high-temperature stage and the low starch moisture content (≤16%) reduce starch property variation and ensure product quality. After drying, the product is cooled in an atmospheric pressure dryer and the waste heat is recycled to obtain a granular product (such as water chestnut powder). Adding a powdering cabinet for crushing and screening can also produce a powdered starch product (such as cassava starch), achieving the goal of continuous production on an assembly line. The overall energy consumption is only 18-20% of hot air drying and 12-15% of drying room. It is a very energy-saving drying method that makes up for the shortcomings of existing technologies.

[0041] Compared to liquid evaporation and concentration, material drying is more complex than drying materials. Since the moisture content of dry materials is generally low compared to the dry matter, simple steam mechanical recompression (MVR) produces a small amount of steam, which is insufficient to compensate for the system's heat balance. Therefore, external raw steam must be added during operation. In many cases, the added heat energy is even greater than the mechanical compression work! Therefore, the concept of multi-effect evaporation is introduced. Raw steam is first used as the heat source for the first-effect dryer to dry the material. The resulting secondary steam is then introduced into the second-effect dryer to dry the material. The secondary steam generated by the second-effect dryer is then recompressed (MVR) by a steam compressor and reused in the second-effect dryer. At the same time, hot water generated by cooling the finished product is recovered and used to preheat the dry material, significantly reducing the amount of raw steam used.

[0042] This patented solution addresses the high moisture content of wet starch, which readily gelatinizes at high temperatures and requires sterilization (e.g., water chestnut flour). It utilizes a heat-conduction vacuum dryer (optional: horizontal disc vacuum dryer, vertical disc vacuum dryer, hollow blade vacuum dryer, etc.). This system, paired with a low-temperature steam compressor (optional: Roots or centrifugal steam compressor), creates a two-effect vacuum + mechanical steam recompression (MVR) vacuum starch drying system. This system meets most starch drying requirements while significantly saving energy, consuming only 18-20% of hot air drying and 12-15% of oven drying.

[0043] It has good social and economic benefits!

[0044] Heat conduction vacuum dryers include horizontal disc vacuum dryers, vertical disc vacuum dryers, and hollow blade vacuum dryers. Atmospheric pressure heat conduction dryers also include horizontal disc, vertical disc, and hollow blade dryers. Disc and hollow blade dryers are both heat conduction dryers, characterized by a small footprint, high output per unit volume, high thermal efficiency, and low dust generation, eliminating the need for a dust collector. They also offer uniform drying, can dry both granular (such as water chestnut powder and kudzu root powder) and powdered (using a powdering cabinet for crushing and screening), and can be produced on a continuous assembly line. They offer excellent energy savings.

[0045] The vacuum dryer, vacuum feeder and vacuum discharger can use upper and lower pneumatic butterfly valves, cooperate with the intermediate storage bin, and electrically control the upper and lower butterfly valves to open and close in turn, and intermittently feed and discharge materials to achieve the purpose of locking the vacuum and feeding and discharging materials.

[0046] Commonly used steam compressors include Roots and centrifugal steam compressors. Roots steam compressors offer reliable low-speed operation, a high compression ratio, and relatively low flow rates; centrifugal steam compressors offer high speed, high flow rates, low noise, and a low compression ratio. Electric drive compresses low-temperature, low-pressure secondary steam into high-temperature, high-pressure steam for heating. With a steam recompression temperature rise of 15°C, the energy efficiency ratio is nearly 10 times higher. In evaporation engineering applications, the steam compressor inlet temperature is generally ≥80°C, the compression ratio ≤2, and the inlet and outlet saturated steam temperature difference ≤20°C. In vacuum drying environments, when the drying temperature is selected between 50 and 55°C, the steam density is very low, the volumetric flow rate is high, and the pressure differential is low. Therefore, a steam compressor with a high flow rate and low pressure differential is required.

[0047] At 50°C, the saturated water vapor pressure is 0.012Mpa (vacuum degree - 0.088Mpa), and the density is 0.083Kg / m 3 , 12m 3 / Kg; compressed to 65℃, the saturated water vapor pressure is 0.025MPa (the vacuum degree is -0.076Mpa), and the density is 0.161Kg / m3 , 6.2m 3 / kg. Compression ratio ≈ 2.08, pressure difference ≈ 0.013Mpa.

[0048] Assuming the total efficiency of the Roots steam compressor is 60% (volume coefficient 0.8, mechanical transmission efficiency 0.95, motor efficiency 0.8), the power consumption of the drive motor is: 0.072Kw / Kg steam, which is equivalent to 72Kw / h of power consumption per ton of evaporated water.

[0049] In some specific embodiments, the moisture content of the wet starch to be dried is 35-40% by weight.

[0050] In some specific embodiments, the wet starch to be dried is subjected to low-temperature vacuum drying to 50-55° C., the preheating drying temperature is 50-55° C., and the vacuum degree is -0.088-0.085 MPa.

[0051] In some specific embodiments, the secondary steam generated by the preheating and drying is compressed and desuperheated, and then used for heating and drying the first wet starch with a saturated steam temperature of 65 to 70° C. and a vacuum degree of -0.076 to 0.07 MPa.

[0052] In some specific embodiments, the working condition parameters of the high-temperature vacuum drying include: a drying temperature of 80 to 90° C., and a vacuum degree of -0.054 to 0.031 MPa.

[0053] In some specific embodiments, the moisture content of the second wet starch is 14-16% by weight.

[0054] In some specific embodiments, the moisture content of the dried high-temperature starch is 10-14% by weight.

[0055] In a second aspect, the present invention provides a system for implementing the starch energy-saving drying method according to any one of the first aspects, such as Figure 2 As shown, the system includes a low-temperature vacuum dryer 3, a low-temperature vacuum drying heater 5, a steam compressor 4, a high-temperature vacuum dryer 10, a high-temperature vacuum drying heater 12, and a normal pressure dryer 19 connected in sequence;

[0056] The vacuum feeder 2 of the low-temperature vacuum dryer is connected to the first conveyor belt 1, the low-temperature vacuum dryer 3 is connected to the low-temperature steam compressor 4 and the humidifier 9 in sequence, the humidifier 9 is connected to the low-temperature vacuum drying heater 5, the low-temperature vacuum drying heater 5 is connected to the first vapor-liquid separator 7, and the first vapor-liquid separator 7 is connected to the pump 8; the low-temperature vacuum dryer is connected to the high-temperature vacuum dryer 10 via the first vacuum discharger 6;

[0057] The high-temperature vacuum dryer 10 is connected to the humidifier 9 through a second vapor-liquid separator 14, a second pressure reducing valve 16, and a non-condensable gas pressure reducing valve 15; the high-temperature vacuum dryer 10 is connected to a second conveyor belt 17 through a second vacuum feeder 13, and the second conveyor belt 17 is connected to a feed hopper 18 of a normal pressure dryer 19, and the normal pressure dryer 19 is connected to a cooler 20, and the normal pressure dryer 19 is connected to the humidifier 9 through a third pressure reducing valve 22.

[0058] In some specific embodiments, the atmospheric pressure dryer 19 is provided with a discharge port 21 .

[0059] In some specific embodiments, the system composition is shown in the attached Figure 2 The specific process operation flow is as follows:

[0060] ① Wet starch with a moisture content of 35-40% is delivered by the first conveyor belt 1 to the vacuum feeder 2 of the low-temperature vacuum dryer 3 and enters the machine for low-temperature vacuum drying. The front section of the low-temperature vacuum dryer 3 is the preheating section, which preheats the material to 50-55°C, the drying temperature is 50-55°C, and the vacuum degree is -0.088-0.085Mpa. The evaporated secondary steam enters the low-temperature steam compressor (Roots or centrifugal) 4. After compression, the steam is sprayed with water through the humidifier 9 to eliminate superheat. The saturated steam temperature is 65-70°C (temperature rise of 15°C), and the vacuum degree is -0.076-0.07MPa. Then, it is returned to the low-temperature vacuum drying heater (disc or hollow blade) 5 to heat the starch. The condensed water is pumped out by the first vapor-liquid separator 7 with a pump 8, and the non-condensable gas is pumped away by a vacuum pump;

[0061] 2. The wet starch is dried in a low-temperature vacuum drying heater 5 to a moisture content of 14-16%, which produces minimal dust. The drying time is 2-3 hours. The starch is then discharged through the first vacuum discharger 6 and directly into the high-temperature vacuum dryer 10 for high-temperature vacuum drying. The drying temperature is 80-90°C, the vacuum level is -0.054-0.031 MPa, and the drying time is approximately 1 hour. The heated raw steam (102-108°C) enters the high-temperature vacuum dryer heater (disc or hollow blade) 12. The secondary steam is directed through the first pressure reducing valve 11 to the humidifier 9 for cooling, where it mixes with steam from the low-temperature steam compressor 4 and then enters the low-temperature vacuum dryer heater 5 to heat the starch. The condensed water and non-condensable gases are then discharged through the second vapor-liquid separator 14. The condensed water is controlled by the second pressure reducing valve 16 and the non-condensable gas pressure reducing valve 15, respectively, before entering the humidifier 9 for cooling and mixing. After this, it enters the low-temperature dryer heater 5 for further heating.

[0062] 3. The starch is dried at high temperature to a moisture content of 10-14% (according to product standards). It is then discharged from the second vacuum dispensing device 13 and transported by the second conveyor belt 17 to the feed hopper 18 of the atmospheric pressure dryer 19, where it enters the dryer for atmospheric cooling. Cooling is performed by passing running water at ≤25°C through a cooler (disc or hollow blade) 20. The cooling water flow is regulated to maintain the outlet temperature at approximately 65°C. The cooled water is then depressurized by a third pressure reducing valve 22, then mixed with the humidifier 9 and fed to the low-temperature dryer heater 5 for supplemental heating. Once cooled to below 30°C, the starch is discharged through the discharge port 21. For starches requiring a powdered form (such as tapioca starch or corn starch), it can be crushed and sieved in a powdering cabinet before being packaged into finished products. For starches requiring a granular form (such as water chestnut powder or kudzu root powder), it can be directly packaged into bags.

[0063] By adjusting the input and output of materials, the amount of heating steam, and the drying time, the moisture content of the finished product after drying can be controlled.

[0064] During system operation, low-pressure raw steam (<0.1 MPa, below the pressure vessel boiler standard) at 102-108°C is added to the high-temperature vacuum dryer heater. Hot water recovered from the finished starch cooling process is used as a compensating heat source. Controlling the amount of both steam added ensures thermal balance throughout the system, enabling continuous production.

[0065] The compensating heat source for the low-temperature vacuum dryer primarily comes from secondary steam evaporated from the high-temperature vacuum dryer and hot water recovered from the cooling of finished starch. The high-temperature vacuum dryer also shares some of the starch drying process, effectively performing a second-effect evaporation process and reducing the power consumption of the steam compressor. The recycling of cooling hot water reduces raw steam usage, further conserving energy.

[0066] It should be noted that in the energy-saving starch drying method provided in the embodiment of the present invention, the raw materials involved, unless otherwise specified or restricted, can all be commercially available products; at the same time, the process steps and parameters involved can all be carried out in accordance with the existing starch production method preparation process or using existing equipment in a conventional operating manner.

[0067] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The experimental methods in the following examples where specific conditions are not specified are generally measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0068] Example 1

[0069] This example provides an energy-saving starch drying method and system. Taking water chestnut powder drying as an example, the process includes the following:

[0070] ① Wet starch with a moisture content of 38% is transported by a conveyor belt to the vacuum feeder of the low-temperature disc vacuum dryer and enters the machine for low-temperature vacuum drying. The front section of the low-temperature disc dryer is the preheating section, which preheats the material to 50°C, the drying temperature is 50°C, and the vacuum degree is -0.088Mpa. The evaporated secondary steam enters the low-temperature Roots steam compressor. After compression, the steam is sprayed with water through the humidifier to eliminate superheat. The saturated steam temperature is 65°C (temperature rise of 15°C) and the vacuum degree is -0.076MPa. Then, it is returned to the low-temperature vacuum drying heater (disc) to heat the starch. The condensed water is pumped out through the vapor-liquid separator with a pump, and the non-condensable gas is pumped away with a vacuum pump;

[0071] 2. The wet starch is dried in a low-temperature disc vacuum dryer to a moisture content of 14%, which produces less dust. The drying time is 2.5 hours, and then the material is discharged through the vacuum discharger and directly falls into the high-temperature disc vacuum dryer for high-temperature vacuum drying. The drying temperature is 85°C, the vacuum degree is -0.042MPa, and the drying time is about 1 hour. The heated raw steam (105°C) enters the high-temperature vacuum dryer heater (disc). The secondary steam is introduced into the humidifier through a pressure reducing valve to cool it down, mixed with the steam from the low-temperature steam compressor, and then enters the low-temperature vacuum dryer heater to heat the starch. The condensed water and non-condensable gas are controlled by the condensed water pressure reducing valve and the non-condensable gas pressure reducing valve of the vapor-liquid separator respectively, and then enter the humidifier for cooling. After mixing, they enter the low-temperature dryer heater for further heating.

[0072] 3. The starch is dried at high temperature to a moisture content of 10%, discharged from the vacuum discharger, and sent to the atmospheric pressure dryer feed hopper by a conveyor belt, and then cooled at atmospheric pressure inside the machine. The starch is cooled by flowing water at ≤25℃ passing through a cooler (disc or hollow blade). The cooling water flow is adjusted to control the outlet water temperature at around 65℃. The cooled hot water is decompressed by a pressure reducing valve and then enters a humidifier for mixing, and then enters the low-temperature dryer heater for supplementary heating. When the water chestnut powder cools to below 30℃, it can be discharged through the discharge port, kept in granular form, and directly packaged in bags. The moisture content of the finished product meets local or enterprise standards of ≤13%; the color is the same as that of products dried in a hot air drying room.

[0073] Based on a drying system with a production capacity of 1000 kg / h of finished water chestnut powder (moisture content is calculated as 10%), the energy consumption indicators are as follows:

[0074] ① Wet water chestnut powder: water content 38%, feed temperature 10℃ (winter), feed rate 1452Kg / h;

[0075] ②Water evaporation: 452Kg / h;

[0076] ③ Heating steam (105℃, 0.12MPa) gas consumption: about 100Kg / h, equivalent to 80kw / h of electricity (electric boiler);

[0077] ④ Roots steam compressor power consumption: 30Kw / h, flow rate 82.4m 3 / min, pressure difference 13Kpa;

[0078] ⑤ Low temperature disc dryer heating area: 250㎡;

[0079] ⑥ High temperature disc dryer heating area: 38㎡;

[0080] ⑦ Cooling area of atmospheric pressure dryer: 38㎡;

[0081] ⑧Auxiliary equipment: disc vacuum dryer shaft stirring, feeder, transport belt, vacuum pump, etc. about 40Kw / h;

[0082] Total power consumption: 150Kw / h.

[0083] Compare this to:

[0084] ① Hot air drying: thermal efficiency is 50%, steam consumption is 904Kg / h, and auxiliary equipment such as fans are about 70Kw / h;

[0085] ② Drying in the drying room: The thermal efficiency is 30%, the steam consumption is 1507Kg / h, and the auxiliary equipment such as the fan is about 60Kw.

[0086] It can be seen that this technical solution saves a lot of steam, and the comprehensive energy consumption is only about 12% of arch room drying and 18% of hot air drying, with a very significant energy-saving effect.

[0087] Example 2

[0088] This example provides a starch energy-saving drying method and system, taking cassava starch drying as an example, including the following processes:

[0089] The difference from Example 1 is that the dried material is cassava starch, and the drying process is different: the product is dried to a moisture content of 12%. After cooling, it is crushed and sieved in a powdering cabinet to obtain a powdered product, which is then packaged into a finished product. The finished product quality meets the national standard of moisture ≤14%; the color is the same as that of the hot air dried product.

[0090] Various embodiments of the present invention may be presented in the form of a range; it should be understood that the description in a range format is only for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention; therefore, the range description should be considered to have specifically disclosed all possible subranges and single numerical values within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is intended to include any cited numeral (fractional or integer) within the indicated range.

[0091] In the present invention, unless otherwise specified, the directional words used, such as "upper" and "lower", specifically refer to the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple, respectively.

[0092] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown herein, but is intended to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A starch energy-saving drying method, characterized in that: The energy-saving starch drying method comprises the following steps: The wet starch to be dried is subjected to low-temperature vacuum drying to obtain the first wet starch and secondary steam generated by the low-temperature vacuum drying; compressing the secondary steam generated by the low-temperature vacuum drying to eliminate superheat, and then using it to heat and dry the first wet starch to obtain a second wet starch; subjecting the second wet starch to high-temperature vacuum drying to obtain dried high-temperature starch and secondary steam generated by high-temperature vacuum drying; Cooling the dried high-temperature starch to obtain dried starch and hot water generated by cooling; The secondary steam generated by the high-temperature vacuum drying and the hot water generated by the cooling are refluxed and used as a compensating heat source during the heating and drying of the first wet starch; The moisture content of the wet starch to be dried is 35-40% by weight; The wet starch to be dried is subjected to low-temperature vacuum drying to 50-55°C, the low-temperature vacuum drying temperature is 50-55°C, and the vacuum degree is -0.088-0.085Mpa; The secondary steam generated by the low-temperature vacuum drying is compressed and desuperheated, and then used for heating and drying the first wet starch, with a saturated steam temperature of 65 to 70° C. and a vacuum degree of -0.076 to 0.07 MPa; The working condition parameters of the high-temperature vacuum drying include: drying temperature of 80 to 90°C, vacuum degree of -0.054 to 0.031 MPa; The moisture content of the second wet starch is 14-16% by weight; The moisture content of the dried high-temperature starch is 10-14% by weight; The energy-saving starch drying method is carried out using the following system, which includes a low-temperature vacuum dryer and a low-temperature vacuum dryer heater, a steam compressor, a high-temperature vacuum dryer, a high-temperature vacuum dryer heater and a normal pressure dryer connected in sequence; The vacuum feeder of the low-temperature vacuum dryer is connected to the first conveyor belt, the low-temperature vacuum dryer is connected to the low-temperature steam compressor and the humidifier in sequence, the humidifier is connected to the low-temperature vacuum dryer heater, the low-temperature vacuum dryer heater is connected to the first vapor-liquid separator, and the first vapor-liquid separator is connected to a pump; the low-temperature vacuum dryer is connected to the high-temperature vacuum dryer via the first vacuum discharger; The high-temperature vacuum dryer is connected to the humidifier through a second vapor-liquid separator, a second pressure reducing valve, and a non-condensable gas pressure reducing valve; the high-temperature vacuum dryer is connected to a second conveyor belt through a second vacuum feeder, and the second conveyor belt is connected to a feed hopper of a normal pressure dryer. The normal pressure dryer is provided with a cooler, and the normal pressure dryer cooler is connected to the humidifier through a third pressure reducing valve.

2. The energy-saving starch drying method according to claim 1, characterized in that The atmospheric pressure dryer is provided with a discharge port.

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