Abstract: In order to solve the problem of drying food, Yuanhong Vacuum Drying has integrated the resources of the vacuum drying equipment, developed a continuous vacuum vacuum low temperature corn drying tower with better performance and more efficient, and its system composition, drying process, Technical parameters and economics were introduced and analyzed.
Keywords: continuity; low temperature vacuum drying; energy saving
0 Preface
When China’s grain output created a new record of “ten generations increase†since 2004, the grain output has already reached a new level of 1.2 trillion jins, but the bumper crops are not harvested, and the food lost due to mildew is as high as tens of billions of jin. In the northeastern three provinces, Inner Mongolia and other northern regions, when autumn grain harvest has entered the cold winter, is not conducive to drying the grain; the southern double cropping rice, multiple cropping rice harvest season is the plum rain season, even the cloudy weather easily cause rice germination The "grain drying tower" became a drying equipment for agricultural cooperatives and grain warehouses.
In recent years, the use of grain hot air dryers has greatly increased the proportion of dry foods, effectively prevented the mildew of food, and ensured a high yield of grain; the dryers and drying towers used for drying materials on the market are now using high temperatures. Strong air drying, drying process for the downstream, mixed flow, countercurrent and combined hot air for grain drying, the entire drying process is atmospheric type, there is a large volume of drying equipment, thermal energy utilization is low, power consumption, waste heat Less than used, poor quality after drying, long drying time, severe crushing and cracking of the grain after drying, and increased circulation losses.
In response to this situation, people used vacuum drying technology to vacuum dry the materials in a low-pressure vacuum state to solve the problem of high hot air temperature and poor quality of the materials after drying; however, vacuum drying is currently on the market. Heat is placed in parallel with the metal pipe heat dissipation, thermal conductivity and heat dissipation is low, the exhaust efficiency is low, the vacuum degree is not good to control the temperature of water vaporization, the heat energy required for drying increases, and the residual heat is not used. Now many domestic institutes, manufacturers, and companies have been conducting continuous vacuum drying for several years or even more than ten years of research and development. So far, none of them has converted continuous vacuum drying technology into product marketing; this may prove their The vacuum cryogenic drying technique adopted is not perfect, and the selected supporting vacuum equipment is not suitable for continuous vacuum drying.
1 R&D of "Farro Vacuum Drying"
“Fenghong Vacuum Drying†consulted Xu Chenghai and Zhang Shiwei of “Vacuum and Cryogenics Laboratory†of Northeastern University; Zhao Xiangtao of Zhengzhou Scientific Research Design Institute of the National Grain Reserve Bureau and many other dozens of vacuum drying expert papers. Experts in various directions. The National Institute of Grain Reserves Zhengzhou Scientific Research and Design Institute has conducted research on domestic production of more than a dozen sets of continuous vacuum low-temperature northeastern corn drying technology equipment for manufacturing and production tests conducted from November 2003 to May 2008. The home did batch and continuous vacuum drying test cases, drawing on the different drying processes of dozens of manufacturers at home and abroad.
The biggest advantage of “Farrotech vacuum drying†is the integration of resources for vacuum drying equipment and the cohesiveness of R&D team; the integrated vacuum drying R&D resource integration platform built by “Farhon Vacuum Drying†is connected to the needs of users and the other end It is connected to hundreds of famous universities and 1 million experts and scholars across the country. The research and development team of the vacuum food low-temperature drying tower project is the human resources department of “Fenghong Vacuum Dryingâ€. Everyone adopts a mode of authorized use and commissioned development to form a Win-win community of interests.
The development of new continuous vacuum drying technology is based on the main design methods of adaptability and gradual improvement of the current design; the production capacity, stability, reliability, adaptability, drying economy, continuousness of the vacuum drying tower in the design process The influence of many factors, such as sex, gives intuitive and clear comprehensive evaluation value, and chooses the right solution for the design and matching of the vacuum drying tower. The main process parameters of the continuous vacuum low temperature corn drying tower include vacuum degree, vaporization temperature, heating temperature, drying rate, drying strength, precipitation amplitude, non-uniformity, on-line moisture measurement and control and energy consumption. In order to ensure these properties, on the one hand optimization design on the vacuum drying tower and supporting equipment, on the other hand optimize the drying process parameters, both can not be taken lightly on either side. According to the thermal stability and crushing sensitivity of grain, taking into account that the food allowable temperature does not exceed 43°C (below the gelatinization temperature of starch), the effective volume of the vacuum drying chamber should be increased during the design to ensure that the material can be pre-dried within the drying tower. Heat, continuous feed and discharge requirements and even grain requirements.
Fig. 1 Fargreen vacuum drying
"Yuanhong Vacuum Drying" overcomes the shortcomings of the existing continuous vacuum vacuum drying, developed a "continuous vacuum low temperature corn drying tower", vacuum low temperature continuous drying tower adopts the overall assembly structure, modular design, standardized production Easy to transport and install on site.
2 System composition of continuous vacuum low temperature corn drying tower
(1) The conveyor cleaning system mainly consists of a conveyor belt conveyor, a bucket elevator, a cylinder cleaning screen, a magnetic separator, an inlet and outlet device, and a slide pipe. The entire logistics process is to remove large amounts of impurities, dust, powder, dust, cotton and hemp preparations, and ferromagnetic materials in the food, and avoid drying unevenly.
(2) The control system consists of control cabinets, control instruments, measuring instruments, regulating instruments, safety alarm devices, PLC programmable controllers, touch screen displays, on-line moisture sensors, temperature sensors, and various switch circuits to effectively monitor and control Dry process operation and guarantee product quality.
(3) Vacuum drying system consists of vacuum preheating chamber, vacuum drying chamber, vacuum cooling chamber, vacuum discharge valve, vacuum exhaust device, vacuum unit, vacuum condenser, pipeline, vacuum instrument, etc. The controllability and consistency of the temperature are not affected by the temperature of the heating medium. It is only determined by the degree of vacuum. The overall requirements for the pumping capacity and the pressure stability are good. In order to reduce the vaporization temperature, the vacuum degree of the system is mainly achieved.
(4) The on-line moisture testing and grain-feeding automation technology being researched and developed, because the moisture content of the wet grain and the tidal grain is different and needs different drying time. Therefore, after the design food reaches a certain amount of drying moisture, the grain can be automatically controlled. , Reduce energy consumption and improve grain drying quality.
3 Drying process of continuous vacuum low temperature corn drying tower
The drying process of the “continuous vacuum low-temperature corn drying tower†is: First, the boiler of the heat source device shall be started, and the generated heat energy shall be connected to the vacuum heat-conducting heat-dissipation device and the vacuum heat-exchange heat-dissipation device in the vacuum grain drying tower tower through the heat pipe device. In the device, the internal temperature of the drying tower is reached to the desired temperature; the food to be dried is passed through the vacuum magnetic seal discharge valve inlet, and then transferred to the preheating chamber, the drying chamber, and the cooling chamber, and the heat energy is Wet and dry grains are exchanged for moisture and heat. The moisture in the grain particles is discharged by the vacuum exhaust fan through the vacuum exhaust system. The moisture is condensed by the vacuum condenser and then discharged by the vacuum unit. The grain is preheated, dried, slowed, and dried. Sustaining the Soviet Union, drying, slowing the Soviet Union and cooling to complete the drying process, after reaching the required moisture content, exhaust through the outlet port outside the drying tower; effectively improve the vacuum thermal conductivity cooling efficiency, save energy, shorten drying time, reduce processing costs, Low-temperature drying ensures that the plant's activity in grains is not broken.
4 Main technical parameters of continuous vacuum low temperature corn drying tower
Processing capacity (corn): 300-1000t/d;
Precipitation amplitude: 5% to 20%;
Drying unevenness: ≤ 1%;
Unit heat consumption: <3800kJ/kg·H2O;
Out of tower corn crack increase rate: ≤ 5%;
Outbreak of maize shredding increase rate: ≤ 1%;
The color and odor of corn are normal and there are no coke grains and popcorn grains.
5 Performance comparison and economic analysis of continuous vacuum low temperature corn drying tower and hot air drying tower
5.1 Performance Comparison
Table 1 Performance comparison of continuous vacuum low temperature corn drying tower and hot air drying tower
Process category
Vacuum drying
Hot air drying
Heating media
Superconducting heat dissipation
heat  wind
Heating temperature ( °C )
80-90
120—160
Gasification temperature ( °C )
38-43
55-100
Precipitation amplitude ( % )
3-18
3-18
Waste heat utilization ( % )
45-65
0
Motor energy consumption ( KW )
40-80
120—220
5.2 Economic Analysis
The grain drying towers on the market now have different specifications. The heat drying unit for corn drying towers consumes 7500-5800 kJ/kg.H2O of heat; the daily processing volume ranges from 30 to 1,000 tons, including its ancillary facilities such as: foundation treatment, The price of boilers, warehouses, and grain transportation facilities is priced between RMB 3,000 and RMB 3 million. The required electricity, coal and labor costs per ton for hot air drying of grain operations are between RMB 40-60.
"Continuous vacuum low temperature corn drying tower" drying units of food heat consumption 3500-2800kJ/kg H2O; operating costs per ton of electricity, coal, labor costs, etc. in the 25-35 yuan; daily processing volume 30- 1,000 tons, including its ancillary facilities such as: foundation treatment, boilers, warehouses, food transportation and other facilities, the price can be located in 35-380 million, dry electricity for each ton of grain operations, coal, labor, etc. The cost is 18-38 yuan.
Calculate the daily processing of 300 tons of corn:
(1) Direct benefits: Saving operating costs of 15-20 yuan per ton, 5,000 yuan per day; 150,000 yuan per month; a drying season can save 600,000 yuan in four months!
(2) Indirect benefits: good quality of low-temperature dry corn, a variety of nutrients are preserved, so not only can do feed, can also be used for processing starch, food, etc.; can sell 20-50 yuan per ton, every day is 1 Million yuan; 300,000 yuan a month; a drying season can earn 1.2 million yuan more in four months!
6 Conclusion
"The "12th Five-Year Plan" high-end equipment manufacturing industry development plan" "high-efficiency, energy saving, green, environmental protection" and "localization of large-scale drying equipment," the specific requirements of the state to increase macro-control and market regulation mechanism, fully integrated drying companies Enhance the market competitiveness of enterprises.
“Continuous Vacuum Low-Temperature Corn Drying Tower†must be applied, identified, and filed by the Provincial Agricultural Bureau, and strive to enter the “National Support and Promotion of Agricultural Machinery Catalogue†to allow consumers to enjoy the national agricultural machinery subsidy policy; strive to become a “continuous vacuum low temperature corn drying Dry tower "high-tech enterprises, for agriculture, agricultural machinery, science and technology enterprises, special funds, patent support policy support.
“Continuous Vacuum Low-temperature Corn Drying Tower†Overcomes the shortcomings of the existing continuous vacuum vacuum drying, optimizes the equipment and process flow, increases the effective volume of the vacuum drying chamber, and ensures that the materials can be stored in the drying tower. Preheating, continuous feeding and discharging and uniform grain discharge requirements. At the same time, through comparison with the hot air drying tower, it was found that the continuous vacuum low temperature corn drying tower can not only save energy, but also save a lot of labor costs, and the economy is considerable. It can save 600,000 yuan in a drying season and it is worth promoting.
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