Before the drying of the grain, its moisture was 23. Determination of loss of grain mass with a decrease in humidity and fortification. in planned tons

Drying is the main technological operation on bringing grain and seed into a stable state when they are stored. Only after all excessive moisture was removed from the grain mass (that is, free water) and the grain was brought to dry state (humidity should be lower critical), one can count on its reliable safety over a long period of time.

In the southern zone (despite the dry climate), it is necessary to dry the grain and seeds of late crops (corn, sorghum, rice, sunflower, soy), and in some years and early grain crops, especially grain, which is obtained by fields.

All methods of drying are based on the sorption properties of the grain mass, that is, when drying, conditions are created that contribute to the desorption (release) of water and water vapor from grain and seeds.

Drying grain and seeds are based on two principles:

Removal of moisture from grain without changing its aggregate state and without heat supply;

With a change in the aggregate state of moisture in the grain (by converting fluid to pairs) using heat supply.

In the first principle is based Sorption The drying method at which the wet grain is mixed with moisture-absorbing materials (sawdust, silica gel, calcium chloride, sodium sulfate) or with a sheer grain. A variety of this method is Chemical drying. It is most appropriate to apply to reduce the moisture content of bean crops (Vika, peas, soybeans, beans). Due to its morphological features (dense seed shells) and chemical composition (high protein content), these seeds are very poorly giving moisture with heat drying. It is impossible to heat them hard, as they are strongly cracking. It is for such cultures and a chemical method of drying has been developed. In our zone, it is extremely rare, but it is necessary to familiarize himself with his technology.

This method is based on the high water absorption capacity of some chemicals, in particular, sodium technical sulfate (Na2SO4) or natural lake-maritime mineral - Mirabita. These substances should have a humidity of 1-5% before their use.

Drying lead, mixing powder with seeds. With the initial moisture content of the grain mass of 20% per 1 tons of seeds, 60 kg of anhydrous powder of the above preparations are taken. With the initial humidity of seeds, 25% take 120 kg per ton, at 30% - 180 kg, respectively.

Mixing lead on the site under a canopy. The mixture of seeds with the drug must be regularly stirred, since the process of extending water from seeds is accompanied by an increase in temperature. Stirring produce 3-4 times a day. Duration of drying - 5-10 days, depending on the initial humidity of seeds. After drying, the sorbent is separated from the grain mass on any separating grain-cleaning technique. The preparation after use has a very high humidity - 40-50%. Its re-use is possible only after its drying, using dryers, or the next year after drying it in the sun.

The high cost and labor intensity of the chemical method of drying limits its application.

In the second principle are based contact, Radiation and Convective Methods of drying and heat transfer.

Contact (conductive) The method is based on direct contact (contact) of the dried material with a heated surface and obtaining heat from it due to thermal conductivity. This method requires a large fuel consumption, does not provide the required uniformity of the drying, low producers, and therefore has limited use.

RadiationThe drying method lies in the fact that the heat is supplied to the dried grain in the form of radiant energy from solar or infrared rays. Example is Air sunny Drying, when moisture evaporates only through the surface of the grain bulk under the influence of solar radiation and wind. The thinner the grain layer, the more intense it is dried. Therefore, when drying wheat grain and barley, the height of its layer should be no more than 20 cm, and for fine-seamy crops - 5-10 cm.

The area for air-sun drying grain should have an asphalt coating. Ground or concrete platforms must be isolated from grain with a film to avoid moisturizing its lower layers from the moisture of the soil. The grain on the site is better scattered with a non-smooth layer, but crests with the direction of them from the south to the north.
In this case, the surface area of \u200b\u200bgrain embankment is significantly increased and the difference in partial pressure of water vapor is created between the base and the peak of the ridge, which contributes to more intensive evaporation of moisture.

In the conditions of the Crimea in the summer, the surface of the grain embankment is heated by sunlight to 50-55 ° C, and sometimes more. In this case, the air heated in the surface rises upwards, carrying out the moisture evaporated from the grain mass. This process is particularly intense in windy weather, as water pairs are not delayed above the grain surface.

In compliance with the air-sun drying rules, the moisture content of grain in sunny windy weather in our zone can be reduced per day by 3-4%. The wetger grain, the more moisture can be removed from it. It should be borne in mind that in the process of air-sun drying, along with the movement of moisture to the surface of the grain embankment, the reverse process is also occurring - moving it into the lowest layers due to the phenomenon of thermal conductivity with the formation of condensate there, which happens noticeably even to the touch. Therefore, for a successful drying, a grain weight is periodically (after 2-3 hours), moving, stirring the lower layers with the upper, already dried. If necessary, air-sunny drying can be continued the next day. Only for the night you need to collect the grain into a bunch and hide it with a tarpaulter or film.

Air drying is widely used in the farms of the southern zone due to its simplicity, low labor intensity and cost. At the same time, not only does not require expensive fuel for heat dryers, but also there is a positive effect on the grain mass. First, in the grains, the processes of post-harvest ripening are more vigorously. Secondly, during the radiation of the grain, the Sun occurs partial or even complete sterilization of the grain mass from microorganisms, especially from the most dangerous of them - mold fungi. Thirdly, an important positive effect of this drying method is to disinfection of grain mass from ticks and insects: with a 4-5 cm mound inside height in the conditions of the Crimea, they die almost completely.

A variety of air-sun drying can be considered the transfer of the grain batch with rods and grain loaders from one riot to another. This technique allows you to quickly reduce the physiological activity of the grain mass due to its drying and cooling (if the air temperature is below the grain temperature).

ConvectiveThe drying method is a method in which heat is transmitted by a grain convection from the moving agent of drying (heated air or a mixture of stuffing gases). The drying agent along with heat transfer absorbs and removes moisture from the grain. There are dryers of various designs on this method. Teplova The drying of grain in grain dryers is the most productive and technologically effective, albeit quite expensive.

With a convective method of heat transfer, the main technological characteristic is the condition of the grain layer in the process of its drying and cooling. The grain layer may be in a fixed and in rolling states.

When drying in a fixed state, the speed of movement of the grain is zero, and the speed of movement of the drying agent is less than the critical rate of particles of the grain mass. This principle is used in the louvre, tray, rack, chamber dryers of periodic action and in installations for active ventilation. The main parameters of such dryers: The temperature of the drying agent is 35-40 ° C, that is, below the maximum permissible temperature of heating of grain and seeds, the moisture is 0.5-1.5% lost per 1 hour, heat consumption 8000-20000 kJ per 1 kg of evaporated moisture . Dryers of this type have a low efficiency and do not provide the desired uniformity of the drying.

When drying in a movable condition, the speed of the grain movement is greater than zero, and the speed of the drying agent is less than the critical velocity of the particles of the dried grain mass. This principle is based on the work of shaft, recycling, drum dryers of continuous action. The temperature of the drying agent in these dryers is high, and the consumption of heat is only 5000-6000 kJ per 1 kg of evaporated moisture. They provide quick and uniform drying of grain and seeds.

Conditions and regularities of thermal drying.

Drying grain is a complex heat-based process. A strictly defined amount of heat is consumed to evaporate from it. Consequently, to dry, it is necessary to ensure continuous and simultaneous admission to the grain mass of heat and air, which will absorb evaporated moisture and take it beyond the limits of the grain mass. Drying is possible only when water vapor pressure inside the grain or above its surface is higher than in the environment. And this happens at elevated grain temperature. If the temperature of the grain surface is equal to the temperature of the drying chamber, the drying process (moisture evaporation) stops.

Heat to grain is supposed mainly by air, so it got a name Agent Dushka. The drying agent heated in the fiber device ensures the transfer of heat grain. The air simultaneously absorbs moisture, evaporated from the surface or from the inner layers of grain, and removes it beyond the grain mass. The drying agent enters the drying chamber hot and dry and comes out of it saturated moisture and chilled. With the help of a drying agent, mass exchange occurs (water exchange) and heat exchange (energy exchange).

As an agent, drying is used not only heated or unworthy air, but also a mixture of flue gases with outer air. To obtain a predetermined temperature of the drying agent, the mixture is usually made from one part of the fuel gases with a temperature of 1000 ° C and
20-30 parts of atmospheric air. If the dryer furnace works with a violation of the mode, it is possible to darke the grain and the appearance of smoke smell.

The grain, as is known, contains a free and associated moisture, which with one or another strength is held by the protein colloids, starch and other organic substances. The higher the moisture content of the grain, the more free water in it and the less energy it is necessary for its removal. With grain moisture, above 20% water evaporates almost as easily as with a free surface. As the moisture decreases the cost of heat to remove each subsequent percentage of moisture increase. It is especially difficult to remove moisture when grain humidity from 16% to dry state. These differences in the moisture ability of grain of various humidity affect the performance of the dryers.

The process of drying grain can be represented in the form of three periods.

1. A relatively short warm-up period when the drying is slowed down due to a reduced grain temperature.

2. After the warming occurs, the period of constant, the highest possible drying velocity occurs, when the evaporation of moisture from the grain surface is not yet limited to its influx from the inner layers. The speed of the drying process is determined by the ability of the grain to moisture production at a given heating temperature and the parameters of the drying agent: its temperature, humidity, movement speed. Drying speed and grain temperature during this period are constant. The amount of water in the grain varies with constant speed. The exhausted drying agent is most saturated with moisture in this period. The higher the initial moisture content of the grain, the higher the speed of the drying.

3. A period of decreasing speed of drying, begins from the moment when the flow of moisture from the central parts of the grain is lagging behind the speed of its evaporation, and areas are formed on the surface of the grain, insufficient moisture. The drying speed determines no longer an air ability to absorb moisture, and all the decreasing speed with which the grain gives moisture, as a result of which the exhaust air leaves the dryer of the inaccurated moisture. During this period, the temperature of the grain is rapidly increasingly increased from the surface, then inside, the drying speed is also quickly reduced. In the final part of the stage, the speed of drying grain drops to zero. The grain moisture is gradually decreasing and is installed at a constant equilibrium level, the use of the ability of a drying agent to absorb moisture is significantly deteriorated, and the cost of fuel increases sharply
To remove each kilogram of water.

After drying, the grain is cooled. To do this, at the final stage of drying, grain is treated with cold air. The temperature of the grain after cooling should not exceed the ambient temperature of more than 10-15 OS.

The rate of drying grain of this culture to a certain humidity is determined mainly by the amount of drying agent and its temperature. Almost all drying devices are designed with such a calculation to skip the maximum amount of drying agent through the grain mass. Thus, it is very difficult to speed up the drying by increasing the supply of heated air in excess of the calculated rate of its consumption. Therefore, the main factor in the acceleration of drying, affordable production, is to increase the temperature of the drying agent in the areas that it is possible to apply for drying a particular batch of grain or seeds in full preservation of their quality. With raising the temperature of the drying agent and heating the grain, the drying process is accelerated. The higher the temperature of the grain, the easier the water evaporates. In addition, with an increase in the temperature of the drying agent, its ability to absorb moisture increases sharply. In full saturation of moisture 1 m3 of air, it may hold 17 g of vapor water at a temperature of 20 ° C and, accordingly, 31 g at 30 ° C, 83 g at 50 ° C, 200 g at 70 ° C and 420 g at 90 ° C. However, if exceeding the known grain heating limits, it will be corrupted - the seeds will lose their germination, the food grain will not be used to obtain flour and benign bread, the grain of the fodder destination will lose its feed dignity.

2.2.3. Types of grain dryers and drying technology.

In agriculture, shaft and drums are mainly used, which operate both autonomously and are part of the grain drying complexes of the CWC. High-performance recycling dryers are also used on bakery enterprises. The economies of the southern zone are usually poorly equipped with grain drying techniques. In the Crimea, grain dryers have only those farms that are engaged in rice.

Grain drying technology in mine grain dryers.

In agricultural production for drying grain and seeds, high-performance shaft grain dryers SZSH-8, SZSH-16 and SZSH-16A are the most widely used. The drying chamber of the dryer is, the tower, in which the height is several times the sizes of the parties of the cross section.

Mine dryers are installations of continuous action. With the steady mode of operation, the grain continuously enters the top of the mine and also continuously expires from it in the lower one. The grain is moving due to the strength of gravity and bulk grain. The drying agent moves across the stream of grain (Fig. 2.6).

Fig. 2.6. Technological scheme of shaft grain dryer

1 - mines; 2 - fan; 3 - Diffuser; 4 - Pressure chamber of the agent of drying;
І - grain;ІІ - Agent dryshka

Due to the fact that the grain layer in the mine is somewhat loosened, and the grain is rotated in different directions in different directions, its interaction with the drying agent is improved and moisture exchange is accelerated. The speed of the grain and the time of finding it in the mine is adjusted using the outlet. The duration of the grain in the mine is about 40 minutes, and in one pass, its humidity decreases by 4-6%.

In order for the drying of the grain throughout the volume of the mines, it is equipped with special boxed channels, which, as it were, separated the mound into separate layers with a thickness of 100-150 mm, corresponding to the thickness of the drying zone. Each such reservoir is suitable for a fresh drying agent and after saturation moisture is displayed outside the mine. In the simplest form, the box is a pentagonal channel made of sheet metal with an open bottom face. The box is installed in a mine in a row (in a checkerboard) throughout its height. For each box in the shaft walls, the corresponding cross section of a hole is cut through which the fresh drying agent is supplied, and in this case the box is called the supplying, or the exhaust drying agent is assigned to the disintegration. The inlet holes of the supply boxes usually go in the direction of the filling device, and the outlet holes of the discharge boxes are in the opposite. All of the supply and discharge boxes have one end is deaf. The number of submarine and discharge boxes are usually the same, and they alternate or whole rows or in each row.

The important technological dignity of the mine dryers is that they can be in broad limits to regulate the duration of the grain in the drying chamber and it is enough to securely maintain the specified temperature mode of the drying of the grain mass.

Due to the presence of boxes, the entire volume of grain in the mine is a drying zone, in which there is a continuous process of moisture evaporation, which causes a decrease in the grain temperature. Consequently, in shaft dryers, the temperature of the grain is almost always lower than the temperature of the incoming drying agent, and therefore it can be heated stronger than in the simple chamber dryers. As a result, it becomes possible to significantly intensify the drying of the grain without the deterioration of its quality. Depending on the type of grain, its humidity, the intended purpose of the drying agent temperature in mine dryers is maintained at 60-120 ° C.

It is very convenient to operate and recommended for farms a mobile mine grain dryer K4-UC2-C with a capacity of 10 t / h, mounted on the MAZ-8925 car trailer chassis. The dryer has two mines, each of which has 6 rows of boxes installed in two drying and one coolant.

Mine dryers have serious technological disadvantages. The main of them lies in a limited removal of moisture in one grain pass through a mine equal to 4-6%. Therefore, for complete drying of the grain, it is sometimes necessary to process in several receptions. Abrade of partially dried grain
Waiting for repeated passes through the dryer is the reason for the reduction of its quality.

In shaft dryers, it is difficult to dry by grain with moisture content above 25% and especially above 30%. This grain mass has a bad flowability and is inclined to hang between boxes. This increases the duration of processing, overheating and even damage to the grain, and sometimes the sunbathing of light organic impurities. To improve the passage of grain through the mine, it must be pre-cleaned from large straw impurities and plant residues. Improving the drying process also contributes to the purification of the grain mass and from small fractions of impurities, blocking inter-rigorous spaces.

Grain drying technology in drum grain dryers.

In agriculture are widely used for drying grain stationary drum dryers SZSB-8 and SZSB-8A with a capacity of 8 t / h, as well as mobile drum dryers
SZPB-2.5 with a capacity of 2.5 t / h. Good results gives the use of Sat-1.5 dryers installed on the current currents in the complex with AVM-1.5 aggregate.

The drying chamber of drum grain dryers is manufactured as a rotating cylinder (drum), which allows you to successfully dry the clogged, low-power material (Fig. 2.7). The drying drum is equipped with a lifting-blade system. The blades of the drum in the process of rotation capture the grain and raise it up. Then the grain is freely referred to after they reach the corner of the skate. The agent of drying moves along the axis of the drum and actively interacts with the grain during its crosspatch. Thanks to a good contact, the grain drying agent is possible for a shorter period than in mine dryers, remove 3-5% moisture, using more intense heating.

The residence time of grain in the drum is 15-20 minutes. The temperature of the drying agent when drying the seed grain should be 100-110 ° C, and when processing food or fodder grain 180-250 ° C.

Fig. 2.7. Drum dryer SZSB-8

1 - firebox; 2 - boot chamber;
3 drying drum; 4 - cooling column

In the drum dryer, the duration of drying is practically not regulated. The residence time of the grain in the drum and the rate of its movement along the drum is determined by the intensity of the flow agent flow and the mechanical retort of the grain layer entering the drum. This is a serious technological drawback of drum dryers. To complete the drying of the grain of high humidity, it is passed through the dryer several times or used sequentially several dryers. Since the grain in the drum is exposed to elevated temperature and mechanical effects, these dryers are not recommended for drying seeds subject to cracking (peas and other legumes, corn). For drying seed grain, it is preferable to use mine or chamber dryers.

Grain drying technology in recirculation grain dryers.

In these dryers, the grain rapidly passes the heating, buttercation and intermediate cooling cycles, after which part of the recycling grain is finally cooled and sent to the warehouse. Simultaneously with the release of the dried and cooled grain, the corresponding amount of raw grain is received in the dryer, so the total mass of recycling grain remains constant. The number of cycles, which should be dried by grain depends on the required total reduction in humidity, as well as from a decrease in humidity for one cycle.

In the recirculation dryer, the grain in the heating chamber is evenly properly comes from the bunker with a loading device and falls in the form of rain in the flow of a drying agent heated to a temperature of 250-350 OS. In this case, the grain is in contact with such a hot drying agent only for 2-3 s and therefore heats up to a temperature not higher
55-60 OS. Then heated grain enters the hopper for an increase in 10-12 minutes, where the temperature is equalized and the partial redistribution of moisture between individual grains occurs. After cooling, removing part of the dried grain and the addition of new portions of raw grain heating is repeated. Due to the good mixing of the grain mass during recycling, the grain is dry evenly, its quality is preserved, and humidity can be reduced by 10-12% or more. And that is especially important, you should not form a grain consignment party before drying, as in mine grain dryers.

Grain drying modes.

Under Drying mode It should be understood as the recommended temperature of the drying agent and the maximum permissible heating temperature of grain and seeds. It is also necessary to control the overall duration of the drying and set the number of grain skips through the dryer, or drying cycles.

Drying mode is determined:

- native and species of grain and seed, or culture;

- the initial moisture of grain and seeds;

- the target appointment and quality of grain and seeds;

- Design and type of grain dryers.

The main complexity of grain drying is to work when using the maximum permissible heating temperatures of the drying agent and heating grain, ensure maximum performance of the dryer with full preservation of product quality. Exceeding the installed heating temperatures of the drying agent and grain leads to the damage of production, the use of too soft processing mode reduces the performance of the dryers.

The temperature stability of the grain during drying is determined mainly, the temperature stability of its protein substances. The excess of the permissible heating temperature of the grain causes a protein coagulation, the loss of the life functions of seeds and their ability to germination, and in wheat grain - a sharp deterioration in the extensibility of the endosperm proteins, a decrease in the amount and quality of gluten. The seed grain must be dried with a softer temperature mode, since the germ proteins are less than a rack to heating and, moreover, the germ is directly under the shell, heats up and dries first. Therefore, the rate of production during the drying of seed grain compared with the food decreases by 2 times.

Temperature resistance of grain depends on its initial humidity. Dry grain proteins are more resistant to heating, as the humidity increases, this stability decreases. Therefore, the drying of high-voltage grains should be started with a soft temperature mode and with each subsequent passage through the dryer gradually strengthen it in accordance with the required recommendations, that is, to apply the stepped drying mode.

The heat of the heating is influenced by the original quality of the grain. Food grain of wheat with weak gluten in the drying process with a slightly higher temperature of its heating improves its quality due to improving the elasticity of gluten. The wheat grain with a strong gluten must be dried especially carefully, at a reduced heating temperature, otherwise the gluten will become crumbling, and the grain is unsuitable for bread maker.

To properly operate the dryers, it is important to distinguish the heating temperature of the grain and the temperature of the drying agent. The temperature of the drying agent is almost always above the temperature of the grain. The grain is cooled if the water evaporates from its surface. The more intense evaporation, the stronger the grain is cooled, and vice versa. If the temperature of the grain takes the temperature of the air passing through interzernal spaces, this means that its drying has ceased, and the grain took the equilibrium moisture in relation to this air. The differences between the temperature of the agent of drying and grain change over wide limits depending on the type of dryer. For example, when processing seeds on mine dryers, such a difference will be 20-30 ° C, on the drums - 40-60 ° C, on recycling dryers even higher. When processing food grains, this distinction reaches
70-100 ° C and more.

Thus, determining in preserving the quality of grain during drying, its heating temperature is. The temperature of the drying agent should be such to ensure the maintenance of a given temperature of heating or seeds in accordance with their humidity, targeted appointment and source quality. Therefore, when drying the grain, it is necessary to regularly control both the temperature of the drying agent and the heating temperature of the grain.

The thermal resistance of raw grain is low, so the heating temperature of the grain of different cultures, depending on humidity and the target, changes in small limits. Seed grain of most cultures when drying are heated to 40-45 ° C, grain of food wheat to 45-55 ° C, forage grain up to 50-60 ° C. The choice of the temperature regime of the drying of large grain crops is influenced by their specific feature - poor moisture production and a tendency to cracking.

Seeds of pea, beans and other crops have a reduced specific surface of evaporation, which causes the overhang of surface layers of seeds. When they drying them, the surface layers of seeds occur, a decrease in volume. But since the reduction in the volume is first occurring only in the peripheral layers of the seed, and the inner part remains unchanged, it causes large physical stresses in the seeds, and they are cracking, initially only their shell, and then the central part. Therefore, seeds of leguminous crops are dried with softer temperature modes than seeds of grain crops. Heating of bean crop seeds should not exceed 30-35 ° C. Accordingly, the performance of the dryers is reduced.

To prevent seed cracking, as well as for processing in the most favorable conditions, the constant drying velocity has to limit one-time moisture of moisture in most types of dryers in the range of 4-6%. In the subsequent period of quotation, waiting for a re-pass through the dryer in the grain, the redistribution and leveling of humidity between the central and peripheral parts occurs. This provides with a re-processing of grain drying at a sufficiently high velocity of moisture reports. However, the limited remote moisture in one pass through the dryer sharply complicates the organization of the drying process, forces temporarily to store underwent grain, which often leads to it. This is a serious lack of a mine and drum drying.

Table 2.1. Seed grain drying mode

Culture	Humidity of seeds to drying,%	The number of grain pass through the dryer
	Drum
The temperature of the agent drying, OS.		Limit heating temperature of seeds, OS
Wheat, Rye, barley, Oats.






Buckwheat, millet





Peas, Vika, rice corn

Note: The temperature of the drying agent has drum grain dryers is maintained at 90-130 OS; Seeds of a number of crops (grain legumes, rice, corn) with less heat resistance or prone to cracking is not recommended to be dried on drum-type settings.

Table 2.2. Food Grain Drying Mode

Culture	Humidity of grain Before drying,%
	Drum
The temperature of the agent drying, OS.		Limit heating temperature of grain, OS



Rye, barley





Peas, Rice grain


Sunflower	Regardless of humidity
	Regardless of humidity

Note: In drum dryers, the temperature of the drying agent during the drying of the food grain is installed within 180-210 ° C, fodder - to 250 ° C.

Table 2.3. Wheat Food Grain Drying Mode
in a shaft grain dryer

Grain quality	Humidity of grain Before drying,%	Skip through the dryer	Limit heating temperature of grain, OS	Limit temperature agent drying, OS.
With strong gluten (IDK up to 40 units.)


With good gluten (IDK 45-75 units.)


With weak gluten (IDK more than 80 units.)

Moisture in the grain, as in any living organism, is a medium in which all metabolic reactions are performed. With an increase in grain humidity above a certain level, the so-called conditioned humidity, free moisture appears in the grain, which leads to the activation of the life of grain. The task of drying is primarily in reducing grain moisture to conditioned.

The moisture content of the grain coming into drying depends on many factors, the TE from the so-called prehistory of grain. There are four grains of moisture content - dry, medium dryness, wet and raw, which determine the resistance of grain during storage. The intervals characterizing the state of grain in humidity for different crops have different values \u200b\u200b(Table 1.15).

The moisture content of grain depends on the conditions in which it is located.

Grain is a good sorbent, which is explained by the high wellness of the grain mass and the capillary-porous structure of the grain. The entire grain is permeated with microcapillars, the radius of which is less than 10 -5 cm, and maccapillars whose radius is more than 10 -5 cm, as a result of which the active surface of the grain through which there is a moisture exchange with the environment, hundreds of thousand times the area of \u200b\u200bthe geometric surface of the grain occurs. The micro-and maccapillars of moisture in the form of a liquid or a pair circulates from the inner parts of the grain to the surface, and vice versa.

Strongly apparent flowering shells (barley, rice, oats) make it difficult to move moisture in both one and other direction, which worsens the drying process. The fruit shells have a large number of capillaries and micropores, so they do not serve as an obstacle when removing moisture from the grain during the drying process. Seed shells adjacent to fruit are characterized by a relatively weak permeability of water vapor and worsen the drying process. The nature of removal of moisture from the grain depends on the mold forms of moisture with the material.

Moisture in the grain has various forms of communication with its solid skeleton: from the most durable, due to molecular forces, to a purely mechanical retention of moisture on the surface of the grain. All molds of the connection of moisture with grain are divided into three groups: chemical bond, physico-chemical communication, mechanical communication. There is a strict border between certain types of communication. During the drying process, the moisture grain associated with the mechanical forces is removed, and partially physico is chemically connected moisture. Since there is always moisture in the grain, then its total mass is made up of weight of dry matter and mass of water:

G \u003d G C + W, kg, (1.9)

where G c is the mass of dry matter grain, kg;

W is the mass of water in the grain, kg.

The presence of moisture in the material is characterized by humidity, which is expressed as a percentage: the mass of moisture to the total mass of grain or by the mass of the grain dry matter

In the theory of drying, the moisture of material belongs to the mass of dry matter. In the practice of graining, humidity is calculated relative to the mass of wet grain.

When drying, the grain weight varies from the initial G 1 to the final G 2 due to the evaporation of moisture, i.e.

W \u003d g 1 - g 2 (1.12)

The amount of moisture evaporated in the drying process can be determined by the formula

Its thermophysical and physical properties are important for drying grain: heat capacity, thermal conductivity, temperature, specific surface, wellness, flowability, grain spinning rate.

All processes are heat - moisture exchange between the grain and the drying agent are carried out through the surface of the grain, therefore its specific surface area is of great importance - the ratio of the surface of all grains contained in one kilogram, to the volume of this grain mass. The drying process proceeds faster with increasing the specific grain surface, therefore, the smaller the grain, the more intense it is dried.

When drying, the grain mass is blowing with air or a drying agent, which is possible due to the ribbon of the grain mass. The higher the wellness, the easier the drying agent is supplied to the grain and the more intense and is evenly dry.

It is important to know the ramp of grain mass, as it is taken into account when choosing sizes, forms, angles of inclination of various nodes of grain dryers (boxes, samotane tubes, graduation devices, louvre lattices, etc.). During the period of filling of the overseas bunkers, the grain mass occurs, while heavy grains fall into the center of the bunker, and light impurities, priest grains, large impurities, vegetative parts of the plant roll to the walls of the bunkers and shafts of the grain dryers, which leads to non-uniformity of drying and heating grain.

For some grain drying designs, the feed rate of the grain is very important - this is the air velocity at which the grain placed in the vertical pipe is under the pressure of the air flow in suspension. Vitania speed is the original parameter, for example, to select the limit speeds of the drying agent at the inlet and outlet of the boxes. The averages of the feed rate of wheat ranges from 9.0 to 11.5 m / s, barley - from 8.5 to 10.5 m / s, corn and peas - from 10 to 17 m / s. The speed of the power is always taken into account when calculating, design and operation of grain dryers. When drying the grain, the process of its dehydration and heating takes into account the fact that the grain is a living organism, it is important to know its heat resistance, and the ability to maintain seed and food properties during drying process. In the drying process, grain can reduce vitality or commodity-food qualities.

Heated grain affects the organic substances contained in it (proteins, carbohydrates, fats, enzymes, vitamins). More resistant to heat carbohydrates and fats. With a grain moisture, 14%, they withstand heating to 60-65 ° C. With a higher humidity or temperature, the process of dextrization of starch, leading to the deterioration of the color of flour and decomposition of fats, resulting in an increase in the acid number of fat occurs.

Protein substances are more sensitive to heating. Changes are associated with complex biochemical transformations of a protein grain complex, leading to denaturation of proteins, loss of the ability to absorb water. Reducing the sowing properties of seed grain, reducing the exit and deterioration in the quality of gluten, reducing the bakery of food grain, the decrease in the activity of enzymes is primarily caused by denaturation of proteins. It should be borne in mind that proteins of the embryo are more sensitive to heating than endosperm proteins. Therefore, the seed grain is usually heated to 40 ° C, while the grain of food supplement is withstanding the heating to 50 ° C.

In the process of heating, the gluten is strengthened, so the drying of grain with weak gluten leads to its strengthening and, therefore, to improved quality.

In case of incorrect maintenance of drying process in grains In addition to biochemical reactions, structural and mechanical changes may occur, seal or gap shells, cracking of the kernel, bearing, etc.

The properties of the grain as an object of drying are always taken into account in the process technology and when choosing the design of the grain drying machine.

Types and grain dryers

By the nature of the use of grain dryers are divided into stationary and mobile. Stationary mounted in separate buildings or special premises, stationary open-type grain dryers were quite widespread, in which only the furnace and some equipment are protected from atmospheric exposure. Mobile grain dryers are mounted on various chassis.

According to constructive features, mine, drum pneumatic tubes and special grain dryers (chamber, bunker, conveyor) are distinguished. Principal differences in the design of grain dryers depend on the grain drying method (convective, conductive, vacuum in the high frequency current field, radiation, infrared or combined).

All types of grain dryers are presented the following basic requirements:

ensuring the required reduction in humidity and the preservation of grain quality;
cooling grain after drying;
elimination of mechanical injury grain;
convenience of maintenance and operation;
compliance with the requirements of labor protection, fire requirements and sanitary standards;
complete mechanization of all works related to drying;
equipping devices to control and regulate the drying process;
efficiency at specific costs of heat, electricity, operational costs;
maximum versatility, providing high-quality grain drying of various cultures;
minimum mass, overall dimensions and high strength of mobile grain dryers.

In the absolute majority of modern grain dryers, the convective drying method is used, in which the heat required for drying is transmitted by the grain from the heated agent of drying. The grain may be in a state of a fixed, moving, fluidized or suspended layer. As a drying agent, a mixture of flue gases with air or pure air heated in the carrier guns is usually fuel gases.

Shaft line-acting continuing grain dryers received the greatest distribution. They are used for drying wheat, rye, barley, rice, sunflower and other food and seed crops. In the drying mine, the grain under the action of gravity moves from top to bottom and permeates the drying agent. The speed of the grain in the mine is regulated by the production capacity of the exhaust mechanism of various designs.

The walls of the mines are made from reinforced concrete or steel. The performance of mine grain dryers ranges from 1 to 50 t / h.

The scheme of the shaft grain dryer is presented in Figure 1.14. The shaft direct-flow grain dryer consists of one or two drying and cooling mines, a pressure-distribution chamber, an exhaust mechanism, over - and dry bunkers, ventilation equipment and furnaces.

The drying and cooling mine has a rectangular cross section and to the top is filled with dried grain. The top of the mine is dry - designed to dry the grain, and the lower is cooling - to cool the dried grain. The design is similar. The drying part of the mine can be divided into 2-sections - drying zones - while the drying agent with different temperatures is supplied to each zone.

Inside the mine installed box with rows in a checker order for supplying and removing the drying agent (air) (Fig. 1.15).

The grain is located between the boxes. The drying agent (air) by steps into the mine through the supply boxes from the head of the distribution chamber, passes the grain layer and goes through the discharge boxes into the atmosphere or the precipitant chamber.

The box is a channel usually a five-marmed form with an open bottom side. Sometimes the walls of the boxes make the louvund.

The discharge chamber is designed to align the flow of the drying agent (air) for the purpose of uniform distribution over the supply boxes. The chamber is separated by altitude horizontal partitions to supply the drying agent into the drying or air zone in the cooling area.

The overshyl bunker is designed for continuous supply of grain in the drying and prevents the leakage of the drying agent from the upper rows of boxes, i.e. it serves as a kind of grain shutter

The exhaust mechanism is installed under the cooling area, it is designed for a uniform grain release from the drying and cooling mines throughout its cross section, as well as to regulate the productivity of grain dryers.

Depending on the design of the exhaust mechanism, the grain from the mine can be produced or continuously, or periodically, and the mechanism itself is non-extended or to have a drive.

For the feeding agent of drying or coolant in the grain drying mine, ventilation equipment fans and ducts are used. Fans can work both on the discharge and for suction of the drying agent, they must provide its settlement costs. With any version of the fan installation, the entire ventilation network (pipes, diffusers, hatches, connections, etc.) must be carefully sealed and not allow the drying agent leaks.

All type grain dryers are designed to burn fuel and mixing combustion products with atmospheric air, resulting in a drying agent supplied to the grain drying mine. For the drying of the grain, only bright low-oral types of liquid fuel or natural gas are used with a mixture of air with filling gases. Oil, fuel oil, stone coal, other types of fuel can only be used to heat air in carriers.

Diesel fuel, solar oil or tractor kerosene are used as liquid fuel in domestic grain dryers. For burning liquid fuels, injection or needle-type nozzles are used, and gaseous gas burners.

Mine convective stationary grain dryers SZS-8, WTI-8, WTF-15, SZSH-8, SZSH-1B, DSP-12, DSP-16, DSP-24, DSP-32, DSP-32 from. The numbers show the performance of the dryer in planned tons - with a decrease in wheat humidity from 20 to 14%. In agriculture, grain dryers of the SES type and SZSH grain dryers were obtained, and in the elevator industry - chipboard. From the mobile, ZPZH-8 grain dryers, KCh and KCh-US-2A, with a capacity of 8 pl. t / h

All listed grain dryers are distinguished by sufficient simplicity design, versatility and convenient to maintain and operate. The main disadvantages of mine grain dryers, the following uneven heating and drying grain in the cross section of the mine, reduce humidity for one pass no more than 6%. The difference in the humidity of the dried batch of grain is no more than 2-4%. These shortcomings are almost completely eliminated in mine recycling grain dryers. Recycling grain drying provides for the return of a part of the dried grain in a mixture with a raw grain in an overshole bunker. In the foreshort, the processes are warm - the moisture exchange between the raw and dry grain, as a result of which the raw grain is heated and partially dried. All this ultimately leads to a significant intensification of the drying process. The mine grain dryer of any type is enough to reconstruct to the recycling method of drying, while the performance rises by 30-50%.

Industry produces special recirculation grain dryers of various types. In addition to the heating of raw grain, its preheating is also used in the expense of dried grain heat in special chambers. RD-2x25-70, A1-DSP-50, A1-UPM, A1-UP-USP and Type "Tselin" - "Cerinous-30", "Tselin-50 K", "Tselin-B0," Tselin-50, were obtained. 20 "(based on ZPZH-8 grain dryers). "Tselin-36" (based on grain dryers of DSP-24-CH), "Tselin-40" (based on grain drying chip-32-from), "virgin-50" (based on grain drying chip-24-CH).

In addition to mine grain dryers in the system of bread products and agriculture, drum drum dryers Mobile SZPB-2.5 and stationary SZSB-8 are used. The main element of drum dryers is a horizontal or slightly inclined cylindrical drum at a speed of 2-6 rpm, inside of which the grain moves along the length and is dried with an air flow. Cool dried grain in cooling columns or drums.

For drying small batches of food grain and oilseeds in agriculture, bunkers are often used in agriculture.

For drying corn in the cobs, chamber dryers of the corridor and sectional types are used.

Grain drying modes

Under the drying mode, there is a certain combination of such parameters as the temperature of the drying agent, its moisture content, the speed of movement (consumption) and extremely
permissible grain heating temperature. It is determined by thermal resistance of grain, which depends on its culture, humidity, appointment and duration of thermal impact. The drying mode, in which high quality grain is ensured, and the best technical and economic equipment has been achieved, the dryers are called optimal.

A timely and properly spent drying not only increases the resistance of grain during storage, but also improves its food and seed advantages. As a result of drying, the post-harvest ripening is accelerated, the moisture is aligned, the color, an extraordinary appearance and technological properties of grain are improved.

The drying mode depends on the method of drying and the design of the grain dryers. When drying the grain in the mine straight-flow grain dryers in our country, modes are used at which the temperature of the drying agent changes gradually, as the grain passes along the drying zones. Such stepped modes are especially favorable when drying fresh grains, as well as for cereal crops.

When drying wheat, the temperature roof is differentiated depending on the initial quality of gluten - strong, normal, weak. The drying of wheat with weak gluten at elevated temperatures leads to a compaction of gluten and, therefore, to improving its quality.

When drying the grain in mine straight-flow grain dryers, the moisture is removed in one pass should not exceed 6%, and for rice grains - 3%. If this is not enough, then applies the second grain pass through the grain dryer. In mining recycling grain dryers, a decrease in humidity for one pass can be 10%, in recycling grain dryers with additional chambers for heating grain - without limiting the lifting limit.

When organizing the process and selecting the drying mode, are guided by the approved instructions and rules.

Modes of drying grain grain of some cultures in mine
direct-flow grain dryers are shown in Table. 1.16.

As can be seen from the given data, in most cases the ascending modes of drying are used. In the first zone, the agent of drying with a smaller temperature is supplied, as the grain has high humidity and less heat resistance. In the second zone, the agent of drying is already with a higher temperature.

The grain drying regimes in recycling grain dryers (Table 1.17) is also differentiated by initial grain humidity, and for wheat - and depending on the quality of gluten.

When drying grain in mine recycling grain dryers, higher grain heating temperatures are allowed than in direct flow of mine grain dryers, as they are characterized by short-term and greater seating uniformity of the grain.

Seeds of grain crops are dried in mine grain dryers of all types, with the exception of mobile. Seed grain is not recommended to dry in drum grain dryers, but can be in recycling. Seeds of wheat, sunflower, barley and leguminous crops are ears and in chamber dryers of seed processing plants. The seed grain of all cultures is also dried in warehouses at the installations of active ventilation atmospheric or heated air.

Due to the fact that the germ proteins are more sensitive to heating than endosperm proteins, the maximum heating temperature of the seed grain in the grain dryers of all types is lower than the food. According to the current instructions, the maximum heating of wheat seeds, rye, barley, sunflower, buckwheat, millet, oats should not exceed 40 ° C, and the temperature of the drying agent - 70 ° C. When dried, leguminous crops and rice grains, the heating of the seed should not exceed 35ᵒ C, and the temperature of the drying agent is 60 ᵒc.

When drying seeds, a stepped mode is used above 19%, while reduced the seed heating temperature in the first zone by 5 ° C, and the temperature of the drying agent is 10 ° C.

Organization and control of the drying process of grain

The grain directed to the drying in the mine straight-flow grain dryers is formed in the part of cultures, quality, appointment and humidity. In humidity, oscillations are allowed to 2% with grain moisture to 19% and up to 4% with humidity over 19%. First of all, they are sent to the drying of the batch of more wet grain. Before drying in mine grain dryers, grain is cleaned of coarse and light impurities, and in recycling - only from coarse.

Before launching grain dryers, it is carefully cleaned from the sera, dust, secking grain, check the operation of all equipment. Before the start of drying includes transport and grain-cleaning equipment and fill the mine with purified grain. The drying period of drying, depending on the type of grain grain dryers, culture and humidity ranges from 30 minutes to 1 hour. After about 10-15 minutes, after turning on the fans, the exhaust device and the produced grain are returned to the dryer. After the humidity of the produced grain reaches the specified, the grain dryer includes normal operation. After the start period, the normal thermal drying mode is set. During the operation of the Mine Zernosushki and the Overweight bunker must be filled with grain all the time. Extract moisture when drying is regulated, reducing (with high humidity) or increasing (with reduced humidity) the production of dry grain from the grain dryer. The temperature of the drying agent is adjusted by the amount of fuel burned and changes in the amount of atmospheric air added.

The heating temperature of the grain is adjusted as the temperature of the drying agent and the residence time of the grain in the dryer (its performance).

For proper management and control of the process of grain dryers are equipped with special devices. To monitor the filling of the flavored hopper in it, the grain level sensors are installed. The temperature of the drying agent is measured with expansion thermometers. Resistance thermometers are installed in the supply ducts immediately in front of the drying zones. The heating temperature of the grain is controlled in the lower row of supplying the drying zone using various sensors or with the help of direct measurement of the grain sample temperature selected from under these boxes. The moisture content of the grain controls the laboratory, selecting the samples every 2 hours, or with the help of low moisture meters, installed their sensors at the exit of the grain from the dryer.

During operation, the dryer must determine the amount of dried grain. To this end, the transport lines are installed all for weighing dried or raw grain. Economical and efficient work of grain dryers depends on a number of organizational events. First of all, it is necessary to make plans for grain drying for each grain dryer, specific activities for its preparation for operation, improving the quality of dried grain, as well as measures to the highest possible reduction in the cost of drying. When drawing up a drying plan, the maximum
the receipt of grain in previous years, the maximum humidity, as well as the forecast for the current year.

All incoming raw and wet grain must be sucked within 2 months (615 hours of stationary grain drying). From this condition determine the required adjustivity of grain dryers.

All continuous grain dryers, therefore it is impossible to allow their downtime, as this leads to an unjustified high loss of working time, a decrease in their performance and overruns of fuel to the secondary warming and grain.

The physical productivity of the grain dryers depends primarily from the initial and ultimate moisture content of the grain before and after drying, as well as the culture and destination of grain. Knowing the actual productivity of the grain dryer, the initial and final humidity, the intended purpose of the grain and the culture, determine the performance in planned tons, multiplying it to the transformation coefficients.

The planned ton corresponds to the drying of the grain of wheat when the humidity is reduced from 20 to 14%. Grain Purpose - Food Objectives, Type of grain dryers - shaft line, drying mode - appropriate grain with normal gluten, initial grain temperature -5 ᵒС. Translation coefficients are shown in Tables 1.18, 1.19 and 1.20.

To ensure continuous work of the grain dryers, it is necessary to have a margin of raw grain in cumulative tanks.

In case of violation of the grain drying modes, its quality is worsening the main signs of the violation of the mode:

the appearance of roasted or burnt grains, grains with wrinkled, swollen or burst shells. The reason is an excessively high temperature of the drying agent, as a result of which moisture in the grain moves slower than evaporates from the surface, the external layers of the grains are cut and burst due to volumetric stresses;
the appearance of stale grains. The reason is the low temperature and insufficient flow rate of the drying agent; It is saturated with moisture to the ultimate state and prevents the evaporation of moisture from the grain;
reducing the amount and deterioration of gluten quality. The reason is the high temperature of the drying agent, the slow motion of the grain in the mine, stagnant zones in the mine. In this case, it is necessary to reduce the temperature of the drying agent and increase the bandwidth of the outlet;

The work of grain dryers to a large extent depends on the choice of rational type of exhaust mechanism and its operation. Apply the designs of exhaust mechanisms providing continuous or periodic movement of grain in the mine. With continuous movement of grain in the mine, sustainable grain flows are usually formed moving along the path of least resistance. If the flow of grain meets local resistance, the movement of the grain in the mine slows down.

Uneven binding of grain mass occurs due to its self-supporting. When increasing the clogs of individual grain flows in the mine increases resistance to the movement of grain. It may occur anywhere in the grain dryer, but most often at the walls of the mine.

With a continuous release of grain from the mine, the grain can be delayed on the upper edges of the boxes, above and under the semi-axis (most often), where it is pressed with horizontal pressure of the moving layer of grain to the boxes and walls of the mine.

With a periodic, t e hopping, the production of a part of the grain in the mine is created conditions for "self-cleaning", since the vaults of grain are destroyed, stagnant zones in places of accumulation of straw impurities or local essence of grain flows near the walls of the mine and between the boxes. However, the exhaust mechanism of periodic action has its drawbacks. With a fixed state of grain in a mine in the intervals between the openings of the shutter, the grain can overheat from the hot surfaces of the supply boxes. In this case, the drying process and the setting of the exhaust mechanism must be organized in such a way that when the grain is opened in the mine with a chess location of the boxes, it was moved to a distance of one, three, five rows of boxes (so that the most hot grain falls on a removal series of boxes).

The unevenness of heating and drying grain is largely eliminated by using the diagonal arrangement of the supply and discharge boxes (in one row through one).

To eliminate the uneven distribution of the distribution of the drying agent according to the boxes, rationally set the supply diffusers along the entire height of the drive-distribution chamber of the drying zone.

To reduce the sorting of the grain mass, as a result of which are created
the unfavorable conditions for the movement in the cross section of the mine, it is necessary to load 3-4 by the sophisticated bunker, and the grain weight is pre-cleaned from coarse impurities in grain cleaning machines.

Establishments for saving fuel and electricity should first be attributed to the following:

ensuring full combustion of fuel;
reduce heat loss into the environment - for this, all heat mains must be insulated;
air sent for combustion of fuel preheat;
control the temperature and relative humidity of the exhaust drying agent, it should not exceed the average grain heating temperature by more than 5 ° C with relative humidity of at least 60%;
provide uninterrupted work of the grain dryer, which will avoid unforeseen losses for repeated heating of grain dryers, fireboxes, grains;
do not allow no need for two-time and more drying grain, as it causes the extra fuel consumption for a repeated heating of grain, leads to significant labor and electricity costs;
prevent breaking grain;
use the recycling method of drying;
monitor the good condition of grain dryers and all equipment.

One of the daily processing of grain is active ventilation. Materials for active grain ventilation are highlighted in a separate section (see section 3).

In accordance with the drying instructions, the grain after the grain dryer should go out with a temperature not exceeding atmospheric air temperatures. This determines, especially in the summer period of harvesting, a relatively high grain temperature sent to the grain, reaching 30-350c. In addition, grain after drying can exit a grain dryer with moisture oscillations reaching 0.5-1.0%, as a result of uneven moisture content of raw grain, entering drying, as well as possible insufficient automation of the process of drying process: temperature and flow rate Drying agent, unevenness of the movement of grain in the cross section of the drying mines, clogs of graduation devices, etc.

Reduce the temperature of the dried grain before entering it in the grain can be used with special cooling mines (columns) installed near the grain dryers. However, more preferable is the use of the "Driveaeration" method, when the grain is produced from a grain dryer with a moisture content of 1.0-1.5% greater than the critical value for dry grain and, after tracked, slowly cooled. At the same time, cooling of the grain can be carried out both in special coolers of grain and directly in granaries: grainclades and silo elevator.

In the process of "Driveaeration", not only the leveling of grain mass in humidity and temperature, but also to dry grain is occurring. Such technology is most effective for drying strong and valuable wheat varieties, seed grains, as well as grain crops, subject to cracking during drying - rice, corn, legumes.

With slow cooling, this method allows for the evaporation of moisture from grain heat, accumulated grain mass to a greater extent than with relatively fast cooling in the cooling zone of the grain dryer. In this case, the deposit (thermostatting) of the grain before it is cooling, it serves to align moisture in the grains, the distribution of which at the end of the drying process is unevenly. In addition, when using such a technology, the grain is prevented, its quality is preserved, the performance and efficiency coefficient of grain dryers increases.

Studies were carried out on a stand setting representing a block of three insulated columns with a height of 2350 mm each, an internal diameter of 250 mm, mounted on a common frame and connected in series when purging air. In each column at a distance from the gas distribution lattice 200, 650, 1100,1550 and 2000 mm, removable mesh cassettes for grain selection and measurement of its humidity and chromel-Copel thermocouples are located to measure its temperature.

Studies conducted on the grains of rice varieties of "Bedschik" and wheat of the VEGA variety by humidity, respectively, 16.2-17.2% and 15.1-18.5%, the heating temperature of 37.1-55.0 and 43.3-53 0 ° С. The temperature of the cooling atmospheric air changed from 8 to 200 ° C, the relative humidity of the air - 50-80%, the height of the grain layer - 1.6-6.0 m, the air filtration rate in the layer - 1.7-22.8 cm / s, specific Air supply was 19-334 m3 / (h · t).

When cooling the grain in a dense layer, depending on the air filtration rate, significant differences may occur at the temperature and humidity of the upper and lower grain layer (Fig. 1). As can be seen from the graph while cooling the heated grain in a dense layer of a significant height, this difference depends on the air filtration rate. For example, for the grain of the initial humidity of 16.7% with a layer height of 4.2 m and low air filtration rate of 4.9 cm / with the top layer, it is moistened, and even after 10 hours of ventilation does not reduce its humidity below the initial value, and the discrepancy in temperatures top and bottom layer maximum.

Fig.1. Changes in temperature (a) and humidity (b) of the upper and lower layers of rice grain during cooling process: 1 - air filtration rate VF \u003d 4.9 cm / s; 2 - 8.4; 3 - 12.2; 4 - 22.8; 5 - Cooling air temperature. Height of the grain layer H0 \u003d 4.2 m, the initial temperature of the grain? H \u003d 500c, the initial moisture content of the grain of WN \u003d 16.7%; o - upper grain layer; . - Lower grain layer.

With an increase in air filtration rate up to 12.2 cm / s Cooling the upper layer occurs with the beginning of the process, and the temperature difference between the upper and lower layer decreases. In this case, a decrease in the temperature of the lower layer can reach the values \u200b\u200beven below the air temperature due to the evaporation of moisture from the grain.
With a decrease in air filtration rate, the moisture takeaway into the upper grain layer is somewhat increasing, the amount of evaporated moisture of heated grain increases at the cooling process. In this case, the humidity of the upper and lower layers of grain decreases by 0.7 and 1.3%, respectively (Fig. 2). The obtained experimental data confirm the conclusion about the need for the "drive" process of establishing the optimal value of the cooling rate of grain after drying to maximize moisture from it due to heat, which has previously seen grain. At the same time, after cooling, the grain temperature in the lower and upper layers of grain embankment was 2.7 and 1.7 below the temperature of the cooling air.

Fig.2. Changing the temperature and humidity of the layer of heated grain during the cooling process: the initial moisture content of grain is 16.9%, the temperature is 540С; 200c coolant temperature; Air filtration rate of 3.5 m / s; Actual air supply 87 m3 / (bt); Height of the grain layer 2 m.

An increase in the humidity of the upper grain layer at low air filtration rates is due to the sorption of moisture to the surface of the grain from the air, which is in this case the drying agent and having increased moisture content due to evaporation of moisture from the lower layers. For rice grain in a layer of 6 M height, the increase in humidity in the upper layer during cooling can reach 0.5-0.8%. With an increase in air filtration rate and decrease in the height of the layer, moisture sorption in the upper layer and the difference in the humidity of the upper and lower layer is significantly reduced.
The minimum air filtration rate with active ventilation of the heated grain at which it will not be moisturized in the upper layer can be called conditionally "critical vents". In general, it will depend on the initial humidity and temperature of the grain, the height of the layer, the initial temperature and the relative humidity of the cooling air.
In the range of the height of the rice grain and wheat layer from 2 to 6 m, the temperature of 40-500s, humidity of 16.2-17.0%, the air cooled temperature of 10-200C with a relative humidity of 50-80% this value can be determined by empirical dependence:
VKR \u003d 0,6 + 2.3N0, (1)
where VKR is "Critical" vents, cm / s;
H0 - Height of the grain layer, m.

The duration of cooling rice grain with equal initial humidity and temperature is somewhat less than wheat grains, at the same time greater than the value of the moisture reduction, which is explained by the more intensive evaporation of moisture from the rice grain flower films.
With the increasing air filtration rate from 5-7 to 15-20 cm / s, the cooling duration decreases on average for rice grain from 10 to 3.5 hours, and for wheat grain from 12 to 5 hours. At the same time, moisture for rice grain increases from 1.2 to 1.7%, for wheat grain - from 0.5 to 1.5% (Fig. 3a).

Fig. 3. Changing humidity (a) and duration (b) cooling of the grain layer from air filtration rate:
a - initial moisture content of grain WN \u003d 16.7%, the initial temperature of the grain? H \u003d 49.7 ° C, the temperature of the cooling air temperature T0 \u003d 17.5 ° C, the height of the grain layer H0 \u003d 4,2m;
B - the initial moisture content of wheat grain WN \u003d 15.2%, 2 - 17.0, 3 - 18.3. The initial temperature? H \u003d 46.6 ° C, the temperature of the cooling air T0 \u003d 19.5 ° C, the height of the grain layer H0 \u003d 1.6 m.

With an increase in the initial moisture content of grain, the amount of evaporated moisture increases and the cooling duration (Fig. 3b) decreases. With air filtration rate of 4.9 cm / s for a wheat grain layer with a height of 1.6 m with an increase in the initial moisture content of grain from 15.2 to 18.2%, the amount of humidity decrease increases from 0.75 to 1.25%, and at speed filtration 12.2 cm / s - from 1.45 to 2.75%. In this case, the duration of cooling at low filtration rates slightly depends on the moisture content of the grain, but with an increase in air filtration rate, the effect of grain moisture increases. With air filtration rate of 12.2 cm / s and increasing grain humidity from 15.2 to 18.0%, the cooling duration is reduced from 6.3 to 4.3 hours.
The results obtained by the amount of evaporated moisture of heated grain and the duration of the cooling are satisfactorily consistent with the data.
To calculate the duration of cooling the heated layer of grain and the value of the reduction in humidity, the regression equations were obtained:
- For wheat grain:
? \u003d 7.58 + 0.75 H0 - 0.15 WF + 0.35 (? H - T0) - 0.67VF, (2)
? W \u003d 0.33 WF - 0.24 H0 - 0.02 (? H - T0) + 0.09VF - 3.78, (3)
- for rice grain:
? \u003d 12.76 + 1.99 H0 - 1.09 WF + 0.34 (? H - T0) - 0.45VF, (4)
? W \u003d 0.42 WF - 0.26 H0 - 0.065 (? H - T0) + 0.05VF - 3.0, (5)
Multiple correlation coefficients of equations (2) and (3) are 0.93 and 0.94; equations (4) and (5) - 0.97 and 0.98.
Definition area of \u200b\u200bequations (2) and (3): 1.6? H0? 4.4M; 15.1? WH? 18.5%; 23.8? (? H - T0)? 35.8 ° C; 4.2? VF? 16.0 cm / s; 43.3? ? N.< 53,0°С; 15,1 ? t0 ?19,8°С.
The area of \u200b\u200bdefinition of equations (4) and (5): 2.0? H0? 6,0m; 16.2? WH? 17.2%; 24.7? (? n - t0)? 37.0 ° C; 4.2? VF? 16.5 cm / s; 37.1? ? N? 55.0 ° C; 8.0? T0? 20.0 ° C.
In the practice of active ventilation on elevators and bakery enterprises, the value of the air supply Q (m3 / (h-T) is the ratio of air flow per ton of the ventilated grain. Taking into account this parameter, the regression equations for wheat grain and rice are obtained when calculating the duration of ventilation and moisture reduction values:
? \u003d EJR, (6)
? W \u003d 0.337 W H + 0.16 (? H - T0) + 0.004 Q - 5,59, (7)

Multiple correlation coefficients of equations (6) and (7) are 0.92 and 0.91. The content of the definition of equations (6) and (7): 15.1? WH? 18.5%; 23.8? (? n - t0)? 35.2 ° C; nineteen ? Q? 375.
Equations (6) and (7) reflect the thermophysical processes occurring in the layer of heated grain during its cooling. Thus, the duration of cooling decreases with an increase in the initial moisture content of grain due to the evaporation of moisture, as well as with an increase in the specific air supply, due to an increase in the speed of its filtering, and reduce the temperature of the cooling air. The value of the reduction in humidity increases with an increase in the initial humidity and temperature of the grain, as well as the specific air supply due to an increase in its speed in the specified range of changes to these parameters.
The results obtained served as the basis for the development of grain cooling modes in Driveaeration technologies during its production test on various grain dryers and active ventilation systems.

conclusions.
The studies have shown that the process of "driveaeration" occurs not only the leveling of grain mass in humidity and temperature, but also to dry grain. At the same time, the effectiveness of this process significantly depends on the mode parameters. The obtained data confirm the conclusion about the need for the "Driveaeration" process of establishing the optimal value of the cooling rate of grain after drying to maximize moisture from it due to heat previously spent on the heating of the grain.

The minimum air filtration rate was established with active ventilation of the heated grain, depending on the height of the layer in the area of \u200b\u200bthe parameters under study, in which it will not be moisturized in the upper layer, which is proposed to be called conditionally "critical vents rate".

To calculate the duration of the cooling of the heated layer of wheat and rice grain grain and the magnitude of the moisture reduction, the regression equations are obtained depending on the air filtration rate, the height of the layer, the initial moisture of grain, the difference between the temperature of the heated grain and cooling air, as well as the specific air supply for practical use.

Bibliography.
1. Sorochinsky V.F. Improving the efficiency of convective drying and grain cooling based on the intensification of heat and pass processes: dis. Dokt.Tehn. Nauk. M., 2003.
2. Esakov V.T. Double-step energy-saving grain drying at APK enterprises: author. dis. ... Cand. tehn science M., 1986.
3. Aniskin V.I. Technological and technical solutions to the problem of preservation of grain in agriculture: author. dis. ... dot. tehn science M., 1985.
4. Sorochinsky V.F. The use of active ventilation in the technology of the two-stage grain drying (fourth international scientific and practical. Conf. "Modern energy-saving thermal technologies (drying and thermal technology) (SETT-2011)" (September 20-23, 2011, Moscow, Russia): a collection of works, Volume 2, Section 4 / FGOU MGO MgAU. V.P. Goryachkin. - M., 2011. - P. 26-32.

V.F. Sorochinsky

The article is published in the collection:
Actual problems of drying and thermal smelter processing of materials in various industries and agro-industrial complex: a collection of scientific articles of the first international Lykovskiy scientific readings (September 22-23, 2015) / RGAU-MSHA named K.A. Timiryazeva. - Kursk: University Book CJSC, 2015. - P. 230-235

The moisture content of grain is one of the most important indicators of its quality, which is determined immediately after the reception. Water has a strong effect on the grain itself and microorganisms on its surface. On the wet grain, microbes develop faster, the number of ticks, insects increases, other changes occur.

Influence of humidity on grain quality
Humidity is a factor showing the share of nutrients of grain and the duration of its storage. The higher the moisture content in the grain mass, the less it contains nutrients and the faster it flies. An excessive amount of moisture leads to the activation of physiological, physicochemical processes. The grain begins to swell, germinate, high molecular weight biopolymers are cleaved, enzymes are activated. Nature, ray of grain decreases, it becomes vulnerable to mechanical damage. If a wet grain remains for a long time, its storage and processing becomes impossible. In any case, the release of the grain and product quality when using wet raw materials are reduced.

Water content in grain: associated and free moisture
From the above, it is obvious that drying is needed to improve the quality of grain and facilitate its processing. This procedure is carried out, given the specific state of the grain at moisture.
First of all, the moisture content of the grain is determined separately from impurities, since the humidity of different crops differs from each other.

Moisture in the grain can be:
mechanically connected (otherwise it is called free);
physico-chemically connected;
chemically connected.

Free water is removed from the grain mass easier. If the storage of grain mass is organized correctly, there should be no drop-down moisture in it. Excessive amount of moisture can be formed with sharp temperature differences or to get into the grain mass with faulty walls, roof of the repository, i.e. As a result of violation of storage rules.
Inside the grain itself, water affects the physical, chemical, biological properties of grain, which determine its value. It is possible to single out chemically bound water, only violating the structure of proteins, fats, carbohydrates, which is included. Such water molecules no longer possess the properties of the solvent, as they are associated with hydrophilic substances. Removal of linked water leads to a change in the technological features of the grain.

Estimation of moisture content

To determine the moisture content of grain, use the following gradation:

Dry grain;
medium dryness;
moist;
raw.

These estimates have a different expression depending on the culture. For seeds of legumes, this indicator is more average, and for oilsets, on the contrary, less.
The difference in indicators is explained by the chemical composition and an anatomical structure of culture. So, oilseeds contain a large amount of fat that does not hold water. Therefore, water in sunflower, Kleschin and other cultures is held in large quantities in the hydrophilic part of the grain and activates biochemical processes.

Critical moisture of grain
In a very dry grain, the breathing intensity is extremely low. On the contrary, raw grain, if it is not cooled, has free air access, actively breathes, losing up to 0.2% dry matter per day.
The level of humidity, in which free moisture occurs in the grain, and the respiratory intensity increases sharply, is called critical. Its values \u200b\u200bare different for each specific type of culture.

Bean (peas, beans, lentils) - 16%
Rye, barley, wheat - 15 - 15.5%
Sorghum, millet, corn - 13 - 14%
Mid-powerful sunflower - 10%
High-power sunflower - 7 - 8%

For major cereal crops, humidity is usually considered acceptable. With such humidity, the grain can be stored in mound up to 30m or more.
The medium-dry grain breathes already in 2 - 3 times more intense than dry, however it has a small gas exchange, so it is stored good enough. Wet grain breathes at 5 - 8 times more active than dry, raw grain - at 20 - 30 times more intense dry.
Having humidity is below 2 - 3% of the critical crate, the grain mass lasts the germination, if a sufficient amount of oxygen is provided. If the oxygen is not enough, the grain loses the sowing properties in the first months of storage.

Methods for determining moisture
The moisture content of grain can be determined by straight and indirect methods. When the grain enters the bakery points, it is necessary to quickly determine where to direct the party: for long-term storage in the elevator silo, in the warehouse of active ventilation, in the grain dryer.

Using an electrolygomer.
Determining moisture using an electrolylagomer is an express method that allows you to analyze for a few minutes. It is based on grain electrical conductivity, which depends on the content of moisture in it. Dry grain has the properties of the dielectric, in the humid state it becomes a semiconductor.
To measure humidity, the CEM-3 device is applied. In it, grain enters the space between the electrodes, according to which the electric current is passed. After 3 - 5 minutes, the moisture of grain in percent is immediately shown on the digital scoreboard of the device. The great advantage of the method is high speed. However, according to accuracy, it is noticeably inferior to the standard method for determining humidity. Electrical conductivity indicators may change due to several factors: temperatures of grain and space between the grains, the presence of impurities, the chemical composition of the culture. The influence of these factors is taken into account in the electrolanet, where, depending on the indicators, the code and mode of operation changes.

Main standard method
Excessive grain moisture is most often eliminated by dehydration in the air-thermal cabinet. The temperature and duration of the drying in this method are fixed. After drying, the loss of grind grain is determined.
The method is often used by bread-receiving, processing enterprises. It takes place in several stages:

Preliminary measurement of humidity with the help of an electrolylagomer;
drying (with humidity more than 17%);
Preparation for the operation of the excitator, fuels, drying cabinet (Sash-3M);
actually measurement.

Determining moisture standard method, without pre-drying.
It is used for grain with a humidity of less than 17%. Preliminary humidity is measured on the electrolanet. Then, to clarify the indicators, humidity is determined using a gravimetric method.
1. The basis of calculations is taken by GOSTs, which determine the rate of humidity of cereals, flour, bran.
2. The seal of the grain (20 g) is grinding for 30 seconds. on a laboratory mill. Grinding thus crushed in this way (meal) is placed in a jar with a padded plug and mixed.
3. From sample (different places) 2 samples weighing 5 g (an error is allowed in 0.01 g) and placed in 2 pre-suspended fuels.
4. Fucks put in the drying cabinet, preheated to 140 ° C. Then the temperature is reduced to 130 ° C and left for 40 minutes. This is a standard time for all grain crops, except corn. Ground corn grain is dried for 60 minutes.
5. From the drying cabinet, the fuels are removed by forceps and put for cooling for 20 minutes. in the desiccator.
6. Both fuces weighed. The value of humidity is determined by the difference of the masses of the two bins with a grain hide to drying and after. Of the two definitions, the arithmetic average is taken. If the difference between the indicators of two bins will be more than 0.2%, then the analysis must be repeated.

Determination of humidity with preliminary drying.
Drying is necessary for grain having humidity higher than 17%.
1. On technical scales, the grain is worse in the amount of 20 g, it is placed in a 10 cm diameter unit. The grain in the unit is dried in a drying closet at a temperature of 105 ° C for 8 - 12 minutes.
2. Fucks are cooled within 5 minutes. And weighed. After weighing, the grain is crushed within 30 seconds. On the laboratory mill, dehydrated.
3. The moisture content of grain is measured according to the following formula:
W \u003d 100 - (MZ - M4) * (ML - M2)
Here ML is a mass of ground grain samples to drying, M2 is a weight of the hitch after drying, the MZ is a weight of the hovercraft of the whole grain to drying, M4 - after drying.
When using preliminary drying, the discrepancy between the samples of two bins is allowed not more than 0.2% for grain crops, not more than 0.7% for corn and legumes.
In addition to the listed methods, the moisture content of grain is determined by other methods: chemical, distillation, spectral-optical, extraction.

Drying is a mandatory grain preparation process in the post-harvest period. Sushka is subject to grain material above the critical level - the level above which the free moisture begins to manifest. Before drying grain is prepared on pre-cleaning. Drying is the most energy-intensive processing process. It accounts for 2/3 of all costs. The drying process is based on the sorption properties of the grain, on its ability to evaporate moisture, with a pressure of water vapor in the grain above the environmental pressure. The higher the difference between pressures, the higher the moisture date. The drying process can be represented as 3 periods:

1) a short warm-up period when the drying goes slowly due to the reduced temperature and poor moisture movement from the center to the periphery;
2) The period of constant drying velocity is the evaporation of moisture occurs from the free surface of the water due to the constant temperature of the grain.
3) a period of decreasing speed, begins from the moment when the flow of moisture from the internal layers is insufficient.

The drying process includes the following physical phenomena: heat transfer from heat carrier grain, evaporation of moisture from the surface of the grain, moisture movement from the center to the periphery.

With the optimal drying process, evaporation occurs from the grain surface. With too high the temperature of the coolant, the moisture does not have time to move from the center to the periphery and evaporates from the inner layers of grain, which leads to loss of quality.

Methods of drying grain mass:

All methods of drying grain and seeds are divided into two groups: without special use of heat (without heat supply to the drying object); using heat.

An example of the methods of the first group is the drying by contacting the grain mass with water-based hardware consistency (dry wood, activated carbon) or the treatment of grain mass is sufficiently dry natural air. The second method is based on the creation of conditions that ensure the increase in the moisture intensity of the steam-aircraft surrounding the grain. In this case, the air agent is air, the moisture intensity, which is significantly increased as a result of heating.

It is also used by the chemical and drying with natural air using for this installation of active ventilation of the grain. Sodium sulfate drying is proposed for bean crop seeds. Natural - Dried Ozerno-Marine Mineral Miracycite - or Sodium Technical Sulfate. Drying leads, evenly mixing the agent with seeds with twinkling or using grain trucks.

Air-sunny drying - thickness of grain mound: basic grain crops - 10-20; Sentobobobic - 10-15. It is impossible to dry the grain on concrete sites, right on the ground or with a bruck bedding to the ground. The drying passes very successfully into windy weather, as the distinguished couples of water do not delay over the surface of the embankment. Air-solar drying of seeds contributes to the ripening of freshly lubricated grain and makes it more stable when stored.

Characteristics of the main types of grain dryers used in agriculture:

b drum - in the dryers of this type, the agent of drying acts on the grain during its sleeve in the rotating drum. In the drum or in the working chamber, 6 shelves are fortified, which capture the grain during the rotation of the drum. The grain is moving evenly along the drum due to the flow of the agent of drying and the grain subjoiler. After the drum, the grain enters the cooling chamber, where the ambient temperature is cooled. The time of finding grain in the drum is 15-20 minutes, which allows you to establish harsh processing modes, for example, the seed grain is processed to 110 0 C. Such dryers are used to dry high-voltage and highly productive grains. Seed grain are trying not to dry on the data dryers in the mind of hard processing modes. It is impossible to handle leguminous crops, rice and corn, so they can crack. In my farm, a dryer is used - SUBS -8A. Dryer drawing is presented in Appendix V.

line shaft - are the most common. The working chamber is presented in the form of a vertical hopper of the mine, inside the mine there are metal boxes, which make the grain mass of a more affordable drying agent and evenly gas permeable. Grain in the dryer is moving in a self-shot. The time of finding grain in the mine is 40-60 minutes. Dryers are designed for grain processing with humidity up to 30%. If the grain mass has a humidity above 20%, it is necessary to set the amount of grain pass through the dryer, and on each previous passage, the temperature of the drying agent and heating the grain must be lower. For 1, 4-6% moisture is removed through the dryer through the dryer. Mines of dryers depending on the moisture content of grain can work on a serial or parallel pattern.

b chamber - dryers of periodic action, grain during the drying process lies in the working chamber motionless and purged with heated air from the bottom, almost not used as dryers. "+" - the possibility of processing the grain of any quality of any culture. In my household used ASS-60 + HPT-600.

Drying drawings are presented in Appendix V.

Conditions and drying modes:

To the most rational organize the drying of grains and seeds, you need to know and consider the following:

- The maximum allowable heating temperature (to which temperature should be heated with this batch of grain or seeds). Overheating leads to a deterioration or even complete loss of technological and sowing qualities. Insufficient heating reduces drying efficiency and increases it in price, it is less removed by moisture at a smaller heating temperature. The maximum permissible temperature of the grain and seed depends on the culture, nature of the use, initial humidity.
- The optimal temperature of the drying agent inserted into the chamber of the grain dryer - at a reduced temperature of the drying agent compared to the recommended grain, it does not heat up to the desired temperature or to achieve this increase the period of stay in the drying chamber, which reduces the productivity of the grain dryers. The temperature of the coolant depends on the initial moisture content of the grain, destination, such as dryer.
- Features of various types of dryers. On the drum dryers, it is impossible to dry the grains, rice, corn, it is not recommended to process seeds. At mines - you can not handle grain with a humidity of more than 30% and having cloggedness of straw impurities. For one grain pass through the drum, the shaft dryers are removed about 6% moisture. In chamber dryers, you can process the grain with any humidity and clogging, but the temperature of the coolant should not exceed the maximum heating temperature of the grain.

Control and accounting of the work of grain dryers:

The most important indicator of the technological process is the heating temperature of grain and seeds. It is systematically checked, samples are taken for this. Samples are placed in wooden boxes, the maximum thermometer is introduced through the hole in the lid in grain, the maximum thermometer is introduced, constantly moving the thermometer deep into the mound. The temperature mounted in this way should not exceed the maximum permissible heating temperature for this batch. Deviation is allowed no more than + / - 3%

The most important performance indicator is the percentage of moisture. To this end, they check the moisture content of grain and seed before, and after drying. Samples are taken after the cooling chamber at least every two hours, and during the period of the installed drying mode monthly. The data is recorded in the log of the work of the grain dryers and, if the temperature modes during drying are deviated from the recommended, take the necessary measures.

Planned unit of drying and loss in the mass of grain during drying.

The performance of the dryers depends on the initial and ultimate moisture content of grain and seeds, their intended purpose and culture, a single indicator is established - the planned ton, the slope of the drying unit, which characterizes the decrease in the humidity of the 1T food wheat by 6% (from 20 to 14%).

It is very important to take into account changes in the mass of the batch due to evaporation of moisture, since losses as a result of drying is always greater than the percentage of humidity reduction, since the initial value received for 100 changes when calculating interest changes. The percentage of humidity is calculated by weight of dry matter and moisture. The indicator of loss of mass X (%) is found according to the formula:

where a and b - the moisture content of the grain before and after drying,%

The grain mass after drying P 2 (T) is found according to the formula:

where p 1 - grain weight to drying, t

Using active ventilation heated air for drying seeds:

The increase in air temperature is only 3-6 0 with significantly increases its moisture intensity, and therefore its drying ability. The greatest effect is achieved when heating the grain to a temperature of 30-35 0 s, and sometimes to the maximum allowable heating temperature of the grain. Using active ventilation bins. Duration of drying of each batch of grain - 1-3 days. It depends on the degree of heating the air, the initial moisture content of the grain mass and the specific supply of the drying agent. Drying active ventilation creates conditions for post-harvest ripening, eliminates overheating. However, with this method, it is unevenly heated and somewhat unevenly dried along the layers of the embankment: the lower layer is heated and more dried. Drying finish when the humidity of the upper layer of the mound drops to 16-17%.

Table 4.4.1

Seed grain drying modes in the farm

Culture	Humidity,%	Mark Dryer	Number of passes	Temperature, 0s
Source	Finite		Heat carrier
Winter Rye



			OS-60 + HPT-600
			OS-60 + HPT-600

Calculate the performance of the dryers by the formula:

PC - requireing the performance of the drying equipment, t / h;

SS is a seasonal amount of grain of this culture to be dried, t;

PSM - the amount of shift (2);

COP - the coefficient of daily grain flow (1.6-1.8);

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