Analysis of the Technical Key Points of Grain Drying Mechanization at Production Sites

For a long time, grain drying methods in China have mainly relied on natural sunlight, turning and drying grain on drying yards, and in some cases even occupying rural roads for threshing and drying. This is not only restricted by and significantly affected by climatic conditions, but also directly endangers rural road traffic safety to a large extent. In most grain-producing areas of China, especially in Yingtan City, Jiangxi Province, located in the middle and lower reaches of the Yangtze River, the rice harvest season often falls during rainy, humid, and cool weather, making it difficult to dry paddy in time. Each year, due to climatic reasons, the loss rate from paddy that cannot be dried in time or fails to reach safe moisture levels for storage, resulting in sprouting, mildew, and insect damage, is as high as 5%-10%. To change this passive situation of relying on the weather and to reduce losses of grain already harvested, in our city, a major paddy-producing area, there is an extreme need to promote and develop grain drying mechanization technology at production sites.
Grain drying mechanization technology at production sites can not only effectively prevent losses caused by disastrous weather such as prolonged overcast and rainy conditions, ensuring increased agricultural production and income, but also has obvious advantages compared with natural drying: First, it reduces the land used for drying yards, which is of great significance for protecting arable land. Second, it is an effective way to prevent farmers from occupying rural roads to dry grain, and can prevent and reduce rural road traffic casualties. Third, because drying machinery has a high degree of automation and is simple to operate, it liberates farmers from the heavy physical labor of traditional sun-drying. It reduces labor intensity, improves working conditions, and increases labor productivity. It provides an effective means for realizing agricultural modernization, agricultural industrialization, and intensification. Fourth, it improves the quality, storability, and processing quality of paddy. Mechanical drying of paddy takes less time, and during drying there is no sprouting or mildew; the drying temperature is suitable and drying is uniform, and during the drying process it can basically be controlled so that cracking is not produced. These advantages have been confirmed by production practices at home and abroad.
I. Technical Introduction and Technical-Economic Indicators
1. Technical Introduction
Grain drying mechanization technology at production sites is a drying technology that, at the grain production site, uses machinery as the main means and adopts corresponding processes and technical measures to artificially control factors such as temperature and humidity, reducing the moisture content of grain without damaging grain quality so that its moisture content reaches the national safe storage standard. The paddy drying process is a complex process of heat and moisture transfer, accompanied by biochemical quality changes in the grain itself. During the drying process, it is necessary not only to remove excess moisture from the grain to reach the safe storage standard, but also to ensure that grain quality does not decline and is improved as much as possible.
Grain drying mechanization technology at production sites can be widely applied to farms with a certain economic strength that practice scale management, especially to large grain-growing households using agricultural mechanization in our city. This practical technology is widely used in grain departments, rural grain processing enterprises and other agricultural by-product processing enterprises, and agricultural mechanization service stations (centers), and is welcomed and praised by the broad masses of grain-growing farmers and rice processing groups.
Drying machinery mainly includes various types of drying equipment. At present, the more commonly used type is the circulating low-temperature hot-air tower dryer. The grain drying process is usually divided into four stages: preheating, moisture vaporization, tempering (temperature regulation), and cooling.
2. Technical-Economic Indicators
(1) The use of grain dryers provides a guarantee for agriculture to resist disasters and secure a bumper harvest. In grain-producing areas, continuous rainy weather is often encountered during the harvest season, and grain mildew losses are about 5%-10%. After using dryers, a bumper harvest and increased production are ensured. Calculating paddy at 1 yuan per kg and taking the loss amount as 8%, grain loss can be reduced by 40 kg per mu, worth 40 yuan.
(2) Low-temperature grain drying is timely and safe, shortens grain drying time, and allows new rice to reach the market earlier. Each kg of rice can be priced 0.04 yuan-0.06 yuan/kg higher than the rice price in the same period, increasing income by 25 yuan/mu.
(3) A comparative measurement was made of the broken rice rate after milling dried paddy. Under the same conditions, mechanical drying has a broken rice rate 5.7% lower than manual sun-drying and a rice yield 5.9% higher, thereby increasing paddy processing benefits by 30-40 yuan/mu.
The above three items together increase income by 100 yuan/mu. After deducting drying costs of 40 yuan/mu, the net income increase is 60 yuan/mu.
II. Operating Procedures
1. Technical Specifications
The quality of grain drying is related to the moisture reduction in a single pass, grain moisture, and the grain tempering process. Because grain types and uses differ, the drying process and parameter settings also differ. For the circulating low-temperature hot-air dryer, the hot-air temperature is specifically determined as follows:
Paddy is prone to cracking during the drying process, and its husk also has a significant delaying effect on heat and moisture conduction. The cracking rate of paddy is not only related to the initial moisture content, but also closely related to the hot-air temperature during drying. Therefore, during drying, the hot-air humidity is generally preferably around 45°C.
2. Key Points of Technical Implementation
(1) If a large amount of rice straw and other debris is mixed into the paddy to be dried, it will affect the flow of paddy and cause uneven drying. Therefore, coarse screening is required before drying.
(2) After harvesting, paddy should be loaded into the dryer as soon as possible. Before a batch of the required drying amount has been loaded, it is best to first carry out ventilation circulation and temporarily not ignite the burner.
(3) When drying paddy with uneven moisture content, it is necessary to ventilate and circulate for as much time as possible, and then ignite the burner.
(4) When drying varieties prone to cracking, paddy that has already shown cracking, and paddy affected by freezing damage, the drying speed should be reduced.
3. Technical Operating Procedures
The drying of paddy differs from the drying of other grains. It is a heat-sensitive grain, and if the drying speed is too fast or the parameters are improperly selected, cracking is likely to occur. Paddy has higher hardness than wheat and corn, and its husk has a significant delaying effect on the drying process, so cracking is very likely to occur during drying and cooling. When using fixed-bed drying or other static drying equipment to dry paddy, the furnace gas temperature is generally preferably 45°C; when using fluidized-bed drying equipment to dry paddy, the furnace gas temperature should generally be less than 160°C, the grain temperature at discharge should be lower than 60°C, the original moisture of paddy should be maintained at 17%-18%, the moisture reduction inside the machine should be 1-1.3%, and the moisture reduction during static tempering and cooling should be 1%-1.2%. Under these conditions, paddy will basically not crack. Practice has proved that allowing dried paddy to be piled and left standing for about 4 hours for tempering, and then using mechanical ventilation for cooling, is not only conducive to ensuring paddy quality, but may also coordinate the vaporization speed of surface moisture with the speed at which inner moisture moves to the outer layer, thereby avoiding capillary shrinkage and hardening on its surface.
III. Precautions
(1) The power supply voltage used should be within the allowable range;
(2) When using fuel equipment, before starting the burner, first check whether the fuel tank has oil and whether the oil circuit leaks oil (mainly check the filter valve, oil pipe, burner, etc.);
(3) The fuel used must meet the equipment requirements. When the burner is working, do not refuel the fuel tank;
(4) After starting the dryer, first check whether idling operation is normal (elevator, blower, upper and lower augers, etc.);
(5) During drying work, check whether combustion is normal and whether there is any abnormal odor;
(6) When switching to drying different grain varieties, clean up the grain remaining in the facility to prevent mixing;
(7) Perform good maintenance of machinery and facilities. The machinery has many electrical components and moving parts, so regular maintenance and upkeep should be carried out. Equip necessary safety protection equipment;
(8) Regularly clean the mesh plates of the drying section of the dryer so that the small holes in the mesh plates are not blocked, so as not to affect the drying effect of the dryer;
(9) When inspecting and cleaning during drying, first cut off the power supply to avoid personal safety accidents;
(10) Dryer operators need specialized training and should be assigned specifically responsible personnel. Use the dryer according to the operating procedures;
(11) The operating scale of a grain drying site at the production site should match local actual demand. The selected model should be suitable for the grain types to be dried, and the site location should facilitate transportation, especially considering convenience for transportation on rainy days;
(12) Grain dryers are generally installed indoors, requiring good ventilation and sufficient operating space to ensure normal operation on rainy days and at night. For models whose bodies are too large to be installed indoors (such as tower dryers), locations with good ventilation and relatively dry conditions should also be selected as much as possible.
IV. Applicable Machinery
It is advisable to choose Shanghai Sanjiu dryers or Wuxi Jinzi dryers.