Cleaning and drying grain are important steps in post-harvest processing. Freshly harvested grain mass has a high moisture content of up to 25%, and sometimes even higher. In addition, the grain contains weeds, the moisture content of which can reach 45%. If the grain is stored in this state, then its moisture content will increase due to the redistribution of moisture between the grain mass and foreign impurities, which can lead to crop rot, the development of pathogenic microorganisms and molds, and in the cold season to freezing. In this regard, grain cleaning and drying should be carried out immediately after it has been collected from the fields, before moisture exchange has taken place.
During grain cleaning, at least 50% of foreign impurities are removed from the mass. When the process is completed, the grain can be sent for drying. Pre-cleaning and drying of grain allows to reduce its moisture content to the required level, when the possibility of self-heating of the grain mass during long-term storage is excluded. Correctly organized cleaning and drying of the grain mass contributes to the physiological ripening of the crop, improving its marketability.
When choosing equipment for cleaning and drying grain, it is necessary to pay attention to its performance, fuel consumption volumes, safety for personnel, and the possibility of automatic operation. In the process of drying grain, it is important to distinguish between the temperature of the drying agent, which is controlled by the operator of the dryer.
To purify grain from various impurities, various equipment is used: trieurs (it detect impurities that differ from the main crop in length), destoners, sieve separators (remove impurities that differ in width and thickness), air separators (impurities with different aerodynamic properties).
Cleaning and drying grain allows to improve the quality of the grain and its processed products, increase the shelf life of the crop and minimize the loss of grain in mass.
Primary grain cleaning and storage
Primary grain cleaning, as well as its subsequent storage, are the most important processes in the entire grain production industry. Primary cleaning of grain cannot be carried out at the wrong time and, of course, without observing a number of technological subtleties of production, since grain losses in this case can reach 20% of the yield. The whole process of primary cleaning of grain is best carried out after drying grain, and preliminary cleaning before direct storage in storage, at special grain cleaning enterprises (complexes). The complex should contain a workshop for the primary processing of grain, a receiving department, a dryer (drying department), other workshops for processing and cleaning grain and, of course, a room for long-term and temporary storage of grain. The grain cleaning process can be divided into three processing stages: the first stage is preliminary cleaning, after drying, the primary cleaning begins - the second stage and the entire period ends with secondary cleaning. After these stages, the grain is sent to storage. From the above, it can be concluded that the complex must have at least three grain cleaning workshops, the most important of which is considered to be the primary grain cleaning workshop.
Let's try to take a closer look at the processing stages. The pre-cleaning process takes place in the following order. Grain must be prepared for mandatory drying. During this period, grain is cleaned of various impurities, dust, minerals, and poisonous plants. After this stage, the grain becomes more free-flowing, and its mass remains until it is sent to the dryer. As already mentioned, pre-cleaning of grain is recommended to be carried out immediately after harvest in order to avoid grain losses. The first periodof production allows to increase the shelf life of grain.
The next stage of processing is primary grain cleaning. Primary cleaning of grain is carried out immediately after drying. The essence of this process is that the grain is brought to the basic marketable condition, and the feed grain is prepared for the following grain processing operations for compound feed. In the process of primary cleaning of grain, sieve, separating and other installations are used, in some moments triers are used. Triers help to eliminate impurities that have not been removed by the grates. One important fact is the setting of the modes of the cleaning equipment. It must be adjusted so that the process of primary processing of grain takes place in one pass of the mass.
The final stage of processing is the secondary cleaning of the grain and its sorting. This moment is necessary in order to prepare marketable and fodder (feed) grain for processing, thereby bringing the grain to seed condition.