China is the most populous country in the world, and food production security has always been a top priority for the country. As the world’s largest food producer and consumer, China has adopted a series of effective measures to ensure the sustainable development of grain production. From 2004 to 2011, grain production has increased for eight consecutive years, and the national total grain output in 2011. A total of 114.24 billion kilograms (approximately 571 million tons) was achieved, creating a new historical record for domestic grain production. Faced with the year-round bumper harvest of grain, while cherishing the hard-won good conditions for agricultural development, we are also pondering how to reduce the losses caused by the production process, such as weather changes and drying after harvesting. According to statistics from relevant authorities, due to climate impacts, the grain is too late to dry or does not reach the level of safe moisture causing mildew, germination, etc., resulting in food losses of up to 5%. If we calculate the annual output of 500 million tons of grain, the equivalent of 25 million tons of grain will be destroyed. Therefore, in this sense, it is imperative to vigorously develop grain drying mechanization.
I. The concept of grain drying mechanization Grain drying is an important step in agricultural production, and it is also a key link in agricultural production and an important part of the realization of mechanization of food production. The grain drying mechanization technology is based on machinery as the main means, adopts corresponding crafts and technical measures, artificially controls the temperature, humidity and other factors, reduces the moisture content in the grain without impairing the grain quality, and makes it reach the national safe storage standard. Drying technology.
Second, the classification and advantages of grain drying mechanization
1. According to the heating method, dryers are classified into convection, conduction, radiation, and dielectric types.
(1) The convection dryer, also called the direct dryer, uses the hot drying medium to make direct contact with the wet material, transfers the heat in a convective manner, and takes away the generated steam.
(2) Conductive dryer, also known as indirect dryer, uses conductive method to transfer heat from the heat source to the wet material through the inter-metal wall. The generated wet steam can be pumped under reduced pressure, pass a small amount of purge gas or set it separately. The condenser surface condensation and other methods are removed. Dryers of this type do not use drying media and have high thermal efficiency. The products are not contaminated, but the drying capacity is limited by the heat transfer area of ​​the metal walls. The structure is also complex and often operates under vacuum.
(3) Radiation dryers use various radiators to emit electromagnetic waves of a certain wavelength range, which are selectively absorbed by the surface of wet materials and converted into heat for drying;
(4) Dielectric dryers use high-frequency electric fields to cause thermal effects within the wet material to dry.
The advantages of the above dryer:
The use of high-performance evaporator, large heat transfer area, small heat transfer temperature, the evaporator outlet air temperature is more stable;
High-efficiency gas-water separation structure has high oil-water separation efficiency.
2, according to the movement of wet materials, dryer can be divided into fixed bed, stirring, spray and combination;
3, according to the structure, the dryer can be divided into box dryer, conveyor dryer, drum dryer, vertical dryer, mechanical stirring dryer, rotary dryer, fluidized bed dryer, airflow Dryers, vibratory dryers, spray dryers, and combined dryers, etc. Third, the development trend of foreign grain drying mechanization The research of foreign grain drying machinery started in the 1940s, the developed countries from the 1950s to the 1960s The grain drying mechanization was realized and the grain drying was automated in the 1960s and 1970s. From the 1970s to the 1980s, grain drying was progressed towards high efficiency, high quality, energy saving, cost reduction, and computer control. After 90 years, the grain drying equipment had reached serialization. ,standardization. In recent years, great progress has been made in the computer simulation of grain drying processes. The continuous development of traditional software and special software has played an extremely important role in the design of grain drying machinery and the improvement of product quality.
Japan is one of the countries with the highest degree of mechanization of grain drying worldwide. The grain drying machinery industry has a long history of development and a strong R&D strength. Japan's grain drying mechanization began in the late 1950s. Through continuous scientific and technological advancement, especially with the support of government policies, its technological level has taken a leading position in the world, and the mechanization of grain drying has reached 92%.
At present, countries or regions where rice is widely grown, such as Japan, Korea, and Taiwan, actively promote the development of rice conditioning and drying equipment. In 2009, the amount of Japanese rice drying and tempering equipment was around 25,000 units. Producers of rice tempering and drying machinery, such as Yamamoto, Satake, Shizuoka and Kaneko in Japan, Korea International, Hancheng, and Sanjiu in Taiwan, all use this type as the basic model for drying rice.
Fourth, the current situation of domestic grain drying machinery The development of China's grain drying machinery began in the early days of the liberation of imitation of Japan, the former Soviet Union and other foreign dryers. Due to the complex structure of the grain drying machinery at that time, the high consumption of steel, and the high cost of production, it was not suitable for the economic and institutional conditions in rural areas and was used only by state-owned farms, grain stores and collective enterprises. Since the 1990s. With the in-depth development of rural reforms, the level of rural economy and agricultural productivity has risen relatively quickly, and professionalization and intensive management of scale have also witnessed new development. In particular, large-scale grain warehouses and seed and grain production bases of state-owned agricultural land reclamation systems gradually equiped with complete sets of grain drying equipment, and together with warehousing, processing and other facilities, they became the main representatives of grain drying machinery in China. At the same time, grain drying machinery has been introduced in advanced countries and regions in the world. Some domestic institutions and relevant research institutes have also developed a series of grain drying equipment suitable for regional characteristics to serve the domestic grain system. The development of grain drying technology gradually makes the drying machinery mature and perfect, and it also accelerates the pace of agricultural modernization. In 2010, there were 4,741 companies with a daily processing capacity of 100 tons or less, 754 companies with 100-200 tons, 132 companies with 200-400 tons, 38 companies with 400-1,000 tons and more than 1,000 tons. There are 10 companies.
In recent years, grain dryers have been listed in the purchase subsidy catalogue of the Ministry of Agriculture and some provinces, and have been valued and promoted by competent authorities at all levels. For many rice cultivation areas, such as Zhejiang, Anhui, Jiangsu, and Jiangxi, many agricultural machinery manufacturers and agricultural machinery cooperatives, drying machinery has become a kind of “rigid demand†and is being increasingly favored by purchase subsidy policies. ". For example, in Shaoxing, Zhejiang, in 2012, based on the original 60% acquisition subsidies for grain dryers, the subsidy standard was increased to 80%-90% of the purchase amount.
V. Necessity and urgency of popularizing mechanized drying technology At present, the domestic dry machinery holdings have increased rapidly at an average annual growth rate of about 50%. However, the mechanically dried grains account for only about 1% of the country's total cereal output. The national machinery grain drying can reach about 95% of the total output. It can be seen that the development of grain drying machinery in China is far from being able to adapt to the development needs of grain production.
(1) The rapid development of mechanized harvesting breaks the coordination and balance among the original production processes, resulting in a decline in the quality of the food and a loss of agricultural production. Many years of accumulation and improvement have allowed for the formation of a coordinated and balanced set of links. Production model. In the early years of artificial harvesting, rice was usually air-dried in the field for a day or two after harvesting. On the one hand, it had a certain after-ripening effect. The main reason was that the grain moisture was reduced (usually below 18%), after threshing. Rice can be stored for a short period of time without deterioration. The grain is then batched and dried on a small field to achieve long-term storage of water (about 14.5%). In recent years, the rapid advancement of mechanized harvesting and cross-regional operations have resulted in a highly efficient and rapid mechanized harvesting method that is seriously incompatible with the original method of grain drying, resulting in the inability of large quantities of high-moisture grains to be promptly dried (no field, no afternoon or evening drying, no drying), When they are stored in their pockets or stacked together, they begin to heat over time (within hours), resulting in a large drop in the taste and quality of the rice, a long period of time and even mildew.
(b) Construction of new rural areas requires mechanized grain drying Some provinces and cities (such as Jiangsu, Zhejiang, etc.) have established a framework for the construction of a new socialist countryside. The new rural construction has made detailed provisions on facilities and environment construction, and mechanized drying can be eliminated. The hidden traffic caused by drying food on highways can also make the environment in front of houses in rural areas clean and tidy.
(III) To improve people's quality of life, and to produce truly high-quality rice, mechanized grain drying is needed to meet people’s ever-increasing quality of life. In addition to measures such as varieties, cultivation methods, and growing environments, high-quality rice needs scientific and scientific drying. Storage methods and equipment to ensure the biological activity and freshness of each grain. According to foreign experience, high-moisture cereals should be machine-dried within 3 hours of harvesting, and their moisture content should be reduced to safe storage standards within 24 hours to ensure that the grain's biological activity and quality are not affected.
(D) Mechanized drying will significantly reduce food loss, save land occupation. The adoption of dry mechanization technology will make the grain drying unrestrained by climate, site and other conditions, especially when it encounters rainy and disastrous weather during the harvest season, which can significantly reduce mildew. loss. For example, in the middle and lower reaches of the Yangtze River in China, the rice harvest season is always rainy and cool, which is not conducive to drying operations. The popularization and promotion of grain dryers can reduce the use of land for drying fields (the ratio of drying area to grain planting area in scale planting areas is 1% to 1.5%). A drying machine with 12 tons of dryers can meet the grain planting area of ​​600 acres can be replaced. 6 acres of drying field, Jiangsu Province, 30 million acres of rice area, can save 300,000 acres of land for drying sites, for the lack of land resources in Jiangsu has great practical significance.
(5) It is conducive to the realization of large-scale agricultural production, and promotes the transfer of land, the transfer of agricultural labor force and the construction of rural urbanization.
6. Development Trend of China's Grain Drying Mechanization during the 12th Five-Year Plan Period The promotion of drying mechanization has accelerated the harvesting of grain production, promoted the improvement of operational efficiency and operation quality in the grain production sector, and played a role in “grabbing agriculture, preventing disasters and promoting high yieldsâ€. effect. In view of the current status of grain drying equipment in China and the needs of the vast rural market, relevant experts pointed out that the development of grain drying equipment in China will present six major development trends.
The first is to speed up the restructuring, reorganization and transformation of grain drying machinery production enterprises, solve the problems of many production enterprises, small production scale, high product cost, and low economic efficiency, so that the concentration and specialization degree of grain drying machinery are greatly improved. , Promote domestic and foreign market development and product after-sales service system construction, truly form a powerful enterprise technology innovation base, and promote the industry's technology, quality, and after-sales service competitiveness.
The second is to design equipment that will reduce high moisture content to safety standards at one time. In this respect, there are two ways to choose from: one is the traditional single drying mode, and the other is the use of the combined drying method, that is, the drying unit with more than two drying methods to synthesize a new drying process, and the grain drying technology from various countries in the world. In terms of development, this is a trend; a high-performance grain flash dryer is designed.
The third is the ability to handle high-volume, high-moisture cereals at high temperatures.
The fourth is the application of advanced measurement and control technology to achieve the development of the drying process to an automated or semi-automated direction.
Fifth, the production capacity of grain dryers has grown toward two poles. In view of this situation, product manufacturers need to develop large-scale equipment with a processing capacity of 20 tons to 30 tons per hour, which is generally purchased and operated by village and township agricultural machinery service organizations, or a professional drying mechanism based on local business conditions. At the same time, it should also be developed in the direction of small size and multi-functionality to facilitate the purchase of farmers and geographically dispersed farmers.
The development of dryers must also pay attention to energy saving and comprehensive utilization of energy, and give full play to the energy characteristics of different regions, such as adopting various joint heating methods, transplanting heat pumps and heat pipe technology, and developing solar dryers, etc.; and developing the automatic control technology of dryers. In order to ensure the realization of optimal operating conditions; In addition, as people attach importance to environmental protection, improve the dryer's environmental protection measures to reduce the leakage of dust and exhaust gas, etc., will also be in-depth research direction.
The “12th Five-Year Plan†period is an important stage of development for the transformation of traditional agriculture from our country to modern agriculture. It is a crucial period for promoting the coordinated development of urban and rural areas and the construction of a new socialist countryside and the modernization of Chinese characteristics. Strengthening the construction of modern agricultural material technologies and equipment is an acceleration. The transformation of agricultural development methods and the acceleration of agricultural modernization are important contents and important support. In 2010, the State Council promulgated and implemented the Opinions on Promoting Sound and Rapid Development of Agricultural Mechanization and Agricultural Machinery Industry, and in 2012, the Central No. 1 Document: Driven by technological innovation to lead the support of modern agricultural construction and enhance agricultural technology promotion capabilities. The development of agricultural socialization services and the guidance of national policies will further promote the mechanized development of agricultural production. Therefore, the grain drying machinery will usher in a beautiful spring.
I. The concept of grain drying mechanization Grain drying is an important step in agricultural production, and it is also a key link in agricultural production and an important part of the realization of mechanization of food production. The grain drying mechanization technology is based on machinery as the main means, adopts corresponding crafts and technical measures, artificially controls the temperature, humidity and other factors, reduces the moisture content in the grain without impairing the grain quality, and makes it reach the national safe storage standard. Drying technology.
Second, the classification and advantages of grain drying mechanization
1. According to the heating method, dryers are classified into convection, conduction, radiation, and dielectric types.
(1) The convection dryer, also called the direct dryer, uses the hot drying medium to make direct contact with the wet material, transfers the heat in a convective manner, and takes away the generated steam.
(2) Conductive dryer, also known as indirect dryer, uses conductive method to transfer heat from the heat source to the wet material through the inter-metal wall. The generated wet steam can be pumped under reduced pressure, pass a small amount of purge gas or set it separately. The condenser surface condensation and other methods are removed. Dryers of this type do not use drying media and have high thermal efficiency. The products are not contaminated, but the drying capacity is limited by the heat transfer area of ​​the metal walls. The structure is also complex and often operates under vacuum.
(3) Radiation dryers use various radiators to emit electromagnetic waves of a certain wavelength range, which are selectively absorbed by the surface of wet materials and converted into heat for drying;
(4) Dielectric dryers use high-frequency electric fields to cause thermal effects within the wet material to dry.
The advantages of the above dryer:
The use of high-performance evaporator, large heat transfer area, small heat transfer temperature, the evaporator outlet air temperature is more stable;
High-efficiency gas-water separation structure has high oil-water separation efficiency.
2, according to the movement of wet materials, dryer can be divided into fixed bed, stirring, spray and combination;
3, according to the structure, the dryer can be divided into box dryer, conveyor dryer, drum dryer, vertical dryer, mechanical stirring dryer, rotary dryer, fluidized bed dryer, airflow Dryers, vibratory dryers, spray dryers, and combined dryers, etc. Third, the development trend of foreign grain drying mechanization The research of foreign grain drying machinery started in the 1940s, the developed countries from the 1950s to the 1960s The grain drying mechanization was realized and the grain drying was automated in the 1960s and 1970s. From the 1970s to the 1980s, grain drying was progressed towards high efficiency, high quality, energy saving, cost reduction, and computer control. After 90 years, the grain drying equipment had reached serialization. ,standardization. In recent years, great progress has been made in the computer simulation of grain drying processes. The continuous development of traditional software and special software has played an extremely important role in the design of grain drying machinery and the improvement of product quality.
Japan is one of the countries with the highest degree of mechanization of grain drying worldwide. The grain drying machinery industry has a long history of development and a strong R&D strength. Japan's grain drying mechanization began in the late 1950s. Through continuous scientific and technological advancement, especially with the support of government policies, its technological level has taken a leading position in the world, and the mechanization of grain drying has reached 92%.
At present, countries or regions where rice is widely grown, such as Japan, Korea, and Taiwan, actively promote the development of rice conditioning and drying equipment. In 2009, the amount of Japanese rice drying and tempering equipment was around 25,000 units. Producers of rice tempering and drying machinery, such as Yamamoto, Satake, Shizuoka and Kaneko in Japan, Korea International, Hancheng, and Sanjiu in Taiwan, all use this type as the basic model for drying rice.
Fourth, the current situation of domestic grain drying machinery The development of China's grain drying machinery began in the early days of the liberation of imitation of Japan, the former Soviet Union and other foreign dryers. Due to the complex structure of the grain drying machinery at that time, the high consumption of steel, and the high cost of production, it was not suitable for the economic and institutional conditions in rural areas and was used only by state-owned farms, grain stores and collective enterprises. Since the 1990s. With the in-depth development of rural reforms, the level of rural economy and agricultural productivity has risen relatively quickly, and professionalization and intensive management of scale have also witnessed new development. In particular, large-scale grain warehouses and seed and grain production bases of state-owned agricultural land reclamation systems gradually equiped with complete sets of grain drying equipment, and together with warehousing, processing and other facilities, they became the main representatives of grain drying machinery in China. At the same time, grain drying machinery has been introduced in advanced countries and regions in the world. Some domestic institutions and relevant research institutes have also developed a series of grain drying equipment suitable for regional characteristics to serve the domestic grain system. The development of grain drying technology gradually makes the drying machinery mature and perfect, and it also accelerates the pace of agricultural modernization. In 2010, there were 4,741 companies with a daily processing capacity of 100 tons or less, 754 companies with 100-200 tons, 132 companies with 200-400 tons, 38 companies with 400-1,000 tons and more than 1,000 tons. There are 10 companies.
In recent years, grain dryers have been listed in the purchase subsidy catalogue of the Ministry of Agriculture and some provinces, and have been valued and promoted by competent authorities at all levels. For many rice cultivation areas, such as Zhejiang, Anhui, Jiangsu, and Jiangxi, many agricultural machinery manufacturers and agricultural machinery cooperatives, drying machinery has become a kind of “rigid demand†and is being increasingly favored by purchase subsidy policies. ". For example, in Shaoxing, Zhejiang, in 2012, based on the original 60% acquisition subsidies for grain dryers, the subsidy standard was increased to 80%-90% of the purchase amount.
V. Necessity and urgency of popularizing mechanized drying technology At present, the domestic dry machinery holdings have increased rapidly at an average annual growth rate of about 50%. However, the mechanically dried grains account for only about 1% of the country's total cereal output. The national machinery grain drying can reach about 95% of the total output. It can be seen that the development of grain drying machinery in China is far from being able to adapt to the development needs of grain production.
(1) The rapid development of mechanized harvesting breaks the coordination and balance among the original production processes, resulting in a decline in the quality of the food and a loss of agricultural production. Many years of accumulation and improvement have allowed for the formation of a coordinated and balanced set of links. Production model. In the early years of artificial harvesting, rice was usually air-dried in the field for a day or two after harvesting. On the one hand, it had a certain after-ripening effect. The main reason was that the grain moisture was reduced (usually below 18%), after threshing. Rice can be stored for a short period of time without deterioration. The grain is then batched and dried on a small field to achieve long-term storage of water (about 14.5%). In recent years, the rapid advancement of mechanized harvesting and cross-regional operations have resulted in a highly efficient and rapid mechanized harvesting method that is seriously incompatible with the original method of grain drying, resulting in the inability of large quantities of high-moisture grains to be promptly dried (no field, no afternoon or evening drying, no drying), When they are stored in their pockets or stacked together, they begin to heat over time (within hours), resulting in a large drop in the taste and quality of the rice, a long period of time and even mildew.
(b) Construction of new rural areas requires mechanized grain drying Some provinces and cities (such as Jiangsu, Zhejiang, etc.) have established a framework for the construction of a new socialist countryside. The new rural construction has made detailed provisions on facilities and environment construction, and mechanized drying can be eliminated. The hidden traffic caused by drying food on highways can also make the environment in front of houses in rural areas clean and tidy.
(III) To improve people's quality of life, and to produce truly high-quality rice, mechanized grain drying is needed to meet people’s ever-increasing quality of life. In addition to measures such as varieties, cultivation methods, and growing environments, high-quality rice needs scientific and scientific drying. Storage methods and equipment to ensure the biological activity and freshness of each grain. According to foreign experience, high-moisture cereals should be machine-dried within 3 hours of harvesting, and their moisture content should be reduced to safe storage standards within 24 hours to ensure that the grain's biological activity and quality are not affected.
(D) Mechanized drying will significantly reduce food loss, save land occupation. The adoption of dry mechanization technology will make the grain drying unrestrained by climate, site and other conditions, especially when it encounters rainy and disastrous weather during the harvest season, which can significantly reduce mildew. loss. For example, in the middle and lower reaches of the Yangtze River in China, the rice harvest season is always rainy and cool, which is not conducive to drying operations. The popularization and promotion of grain dryers can reduce the use of land for drying fields (the ratio of drying area to grain planting area in scale planting areas is 1% to 1.5%). A drying machine with 12 tons of dryers can meet the grain planting area of ​​600 acres can be replaced. 6 acres of drying field, Jiangsu Province, 30 million acres of rice area, can save 300,000 acres of land for drying sites, for the lack of land resources in Jiangsu has great practical significance.
(5) It is conducive to the realization of large-scale agricultural production, and promotes the transfer of land, the transfer of agricultural labor force and the construction of rural urbanization.
6. Development Trend of China's Grain Drying Mechanization during the 12th Five-Year Plan Period The promotion of drying mechanization has accelerated the harvesting of grain production, promoted the improvement of operational efficiency and operation quality in the grain production sector, and played a role in “grabbing agriculture, preventing disasters and promoting high yieldsâ€. effect. In view of the current status of grain drying equipment in China and the needs of the vast rural market, relevant experts pointed out that the development of grain drying equipment in China will present six major development trends.
The first is to speed up the restructuring, reorganization and transformation of grain drying machinery production enterprises, solve the problems of many production enterprises, small production scale, high product cost, and low economic efficiency, so that the concentration and specialization degree of grain drying machinery are greatly improved. , Promote domestic and foreign market development and product after-sales service system construction, truly form a powerful enterprise technology innovation base, and promote the industry's technology, quality, and after-sales service competitiveness.
The second is to design equipment that will reduce high moisture content to safety standards at one time. In this respect, there are two ways to choose from: one is the traditional single drying mode, and the other is the use of the combined drying method, that is, the drying unit with more than two drying methods to synthesize a new drying process, and the grain drying technology from various countries in the world. In terms of development, this is a trend; a high-performance grain flash dryer is designed.
The third is the ability to handle high-volume, high-moisture cereals at high temperatures.
The fourth is the application of advanced measurement and control technology to achieve the development of the drying process to an automated or semi-automated direction.
Fifth, the production capacity of grain dryers has grown toward two poles. In view of this situation, product manufacturers need to develop large-scale equipment with a processing capacity of 20 tons to 30 tons per hour, which is generally purchased and operated by village and township agricultural machinery service organizations, or a professional drying mechanism based on local business conditions. At the same time, it should also be developed in the direction of small size and multi-functionality to facilitate the purchase of farmers and geographically dispersed farmers.
The development of dryers must also pay attention to energy saving and comprehensive utilization of energy, and give full play to the energy characteristics of different regions, such as adopting various joint heating methods, transplanting heat pumps and heat pipe technology, and developing solar dryers, etc.; and developing the automatic control technology of dryers. In order to ensure the realization of optimal operating conditions; In addition, as people attach importance to environmental protection, improve the dryer's environmental protection measures to reduce the leakage of dust and exhaust gas, etc., will also be in-depth research direction.
The “12th Five-Year Plan†period is an important stage of development for the transformation of traditional agriculture from our country to modern agriculture. It is a crucial period for promoting the coordinated development of urban and rural areas and the construction of a new socialist countryside and the modernization of Chinese characteristics. Strengthening the construction of modern agricultural material technologies and equipment is an acceleration. The transformation of agricultural development methods and the acceleration of agricultural modernization are important contents and important support. In 2010, the State Council promulgated and implemented the Opinions on Promoting Sound and Rapid Development of Agricultural Mechanization and Agricultural Machinery Industry, and in 2012, the Central No. 1 Document: Driven by technological innovation to lead the support of modern agricultural construction and enhance agricultural technology promotion capabilities. The development of agricultural socialization services and the guidance of national policies will further promote the mechanized development of agricultural production. Therefore, the grain drying machinery will usher in a beautiful spring.
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