Specialists of CJSC «SelEnergo» from Smolevichi suggest to find in nine million tonne of the produced grain a tenth million tonne by means of electronics and efficient control of drying mode.

Know-how in grain drying

In the Republic of Belarus about 80% of all the milled grain annually require drying or final drying. Drying is the most reliable method of long-term preservation of dry grain. Storage of grain with moisture content over 14% can lead to its spontaneous heating, creates favorable conditions for growth of mold fungi and bacteria, deteriorates germinating capacity and quality of fodder grain.
      At the same time it is one of the most power-consuming processes in agricultural production. For example, grain drying requires about 30-40% of fuel consumption, 15-20% of metal usage and about 10% of labor efforts for its production in the Republic. That is approximately 1,3-1,5 times higher, than consumption of resources in the same processes in similar nature-climatic conditions of the West European countries.
     The currently used in practice technologies of grain drying do not correspond to  the present-day increasing requirements to secure full safety of grain quality under drying process and to the decrease of power inputs for drying. All-round a human factor exists by grain drying. Inobservance, and sometimes the operator’s lack of knowledge in technological process of  grain drying, lead to negative consequences: grain overdrying, and sometimes – to inflaming of grain-drying plants.
At present grain drying at almost all agricultural enterprises is carried out by primitive way, without any control over the processes, going on in a columnе of grain-drying plant. The only controllable parameter, which control is organized  not at all drying plants, is  accident-sensitively high grain temperature in heating area. Manual control of  grain-drying process is restricted only by  keeping the  preset temperature of the heat carrier. In rear instances there can be observed in grain-drying plants control of  grain temperature by means of change of its speed inside the columnе of drying plant. But that helps only to avoid heating of the grain to the accident-sensitive temperature.
      Moisture content control in the process of drying is made by operator, who takes test samples of grain from the drying plant at certain periods of time and makes measurements of its moisture content with the help of portable device, which principle of operation is based on dielcometric (capacitive) method. It should be noted, that at changing of moisture content in loose materials by capacitive method the optimal results in measurement accuracy is achieved at full elimination of influence of variable volumetric mass (grain unit): at compaction of fixed mass of the material under control, and between the electrodes of the capacitance sensor up to constant volume, i. е. at constant density.
      When measuring moisture content of grain crops (wheat, rye, triticale, barley, oats, rape and maize) it is not possible to apply directly this method with high accuracy by the reason, that grain crops at low moisture content are not compressed and resist to compaction; i. е. when the grain of one crop is delivered to a grain threshing site and it is of the same moisture content, but from various parts of the field, of different ripening degree (the structure of grain is differ), and also has different relative biological composition (proteins, oils, carbohydrates and other substances, which grain accumulates from the soil in the process of ripening), the dielectric permeability differs, that is vitally important at such measurement method. The error of measurement can be about ±2%.
      That is why even the most qualified and experienced operator not always can detect in time deviations of parameters from the preset ones by technological process, failure of mechanisms or critical heating temperature. As a result, the grain at the exit from the drying plant is either overdried (about 5% of the required moisture content), or underdried (about 3%), that causes deterioration of grain quality, excessive consumption of fuel and, in case the grain is overdried, mass losses because of excessive emission of moisture by the grain.
      Automatic process control system for grain drying, developed at CJSC «SelEnergo» (located in Smolevichi, Minsk Region), in contrast to manual actions of operator, can promptly and effectively deal with the problem and make corrections of the parameters to recover the optimal performance of drying process, and in an unforeseen situations is capable to activate the emergency stop of the grain-drying plant, while in hand mode a certain period of time is required, which will be quite enough to get the off-quality grain.
      Automatic process control system for grain drying has no direct foreign and domestic analogues. It is known Automatic process control system for grain drying (company «GSI», USA) for drying plants of column type, but it has some shortcomings:

- the system is static (there is no possibility to view practical situation of the processes, going on in the column of grain-drying plant), and as a result it cannot make correction of parameters, influencing the grain drying process;
- the system performs itself sufficiently well only in such case, if the grain-drying plant is charged with grain of identical moisture content. In case moisture content of a grain portion at charging of the drying plant is different, the control mechanism of the system goes far beyond the limits of preset parameters (dramatically changing temperature parameters of heat-carrier and speed of grain movement to one or the other side).      

The above mentioned shortcomings are eliminated at designing and developing of Automatic process control system for grain drying by CJSC «SelEnergo». The start up process of grain drying comes to the operator’s choice of type of the crop, moisture content of the discharged grain from the grain-drying plant and pushing the «Start» button on computer. It should be mentioned, that drying mode itself is not selected by operator, but it is the responsibility of PC. The system, when calculating the time of charging the grain into the drying plant and its discharge velocity from the drying plant, determines with high precision the passing speed of grain inside the drying plant. On this basis the system determines the exact location and movement along the drying plant of the grain layers with certain moisture content.
      Having analyzed the received data about location of the grain layers of certain moisture content and using the data, received from flow meters, checking moisture content, from temperature sensors and gauges of grain level in grain-drying plant, the Automatic process control system of grain drying determines the required modes of operation for heat-generator, exhaust blowers, discharging device, and also determines the route of grain traffic. The system gives preference in selection of drying parameters to that layer of grain, which moisture content is close to the preset value and selects the parameters of drying mode with consideration of technological process of the given crop and economical benefit. Alongside with this the grain overdrying in drying plant is totally excluded (Fig. 1).

If within one pass it is not possible to evacuate certain quantity of grain moisture, the system sets the drying parameters (temperature of heat carrier, velocity of grain travel along the drying plant and velocity of heat carrier) in such a way, that the maximum efficiency could be achieved without interruption of technological process for the given crop. The selection of priority layer of the grain, on which readings of moisture content the control mechanism will base, is made by means of retrieval from the prepared, «expected» layers of grain such a layer, which has the lowest moisture content.


Fig. 1. Technological process of automatic control of  grain cleaning-and-drying complex on PC display.

When a heat carrier affects the grain, moisture is evacuated with certain intensity and, in case the actual moisture content of the grain layer, previously selected as “priority”, differs from the “expected”, which is needed to be at the exit from the drying plant, the system makes corrections of the control parameters of heat generator, discharging device and exhaust blower, in order to get the grain at the exit of the drying plant at the next cycle with readings of moisture content more close to the expected. In such way after a certain period of time the system will come to the stabilized mode of operation. The moisture content of the grain, received at the exit from the drying plant, will be close to the preset parameters with the accuracy up to decimals of percent. Such accuracy in readings of moisture content of the grain is achieved by application of flow-metering devices for moisture content measurements, which measuring method is based on application of microwaves. In contrast with the above mentioned method of measuring moisture content (capacitive), only moisture quantity is measured in a certain volume, and the grain structure is not taken into account. The record-keeping archive maintained by the Automatic process control system of grain drying (Fig. 2) for the operation chronology and being recorded into special file, makes it possible to follow up the operator’s work at any point of time, to check the compliance of parameters with the preset ones in technological process, to detect at the right time the incipient deviations in operation.


Fig. 2. Diagrams of numerical values of technological parameters and the operator’s actions.

The introduced warning system into the developed Automatic process control system for grain drying helps to read the temperature increase in the working area of the drying plant prior the inflammation starts, and to control the actuating mechanisms (light- and sound alarm, early warning system, cooling system, system of emergency discharge of grain and etc.). CJSC «SelEnergo» envisaged also when developing the Automatic process control system for grain drying the possibility of virtual search of malfunctions and program failures, the ways of their fast remedy with the help of high-speed internet. It is enough for the operator just to connect with service department of CJSC «SelEnergo» and to get prompt professional advice in on-line mode.
      This Automatic process control system for grain drying maintains downsizing of fuel consumption by 10-25%, owing to the fact, that the system does not allow the grain overdrying, in average not exceeding 0,5%, that practically impossible to do in manual mode of control over the process of drying. The average value of moisture content, for which the grain is overdried in manual mode, makes up 2-2,5%. For evacuation of 1% of moisture content from grain out of 20%, it should be consumed 0,9-1 litters of diesel fuel, and for evacuation of 1% of moisture content from grain out of 13% – 1,2-1,3 litters.
      At overdrying of 1 tonne of grain for 2% it should be consumed additionally about 2,5 litters of diesel fuel. For a medium-size agricultural enterprise, if they have to dry during the season about 10 thousand tonne of grain could be possible to save about 25 thousand litters of diesel fuel. The self-cost of grain drying will be downsized 1,1-1,2 times. The system helps as well to increase operational efficiency of all the complex equipment as a whole, avoid inflammation of the grain-drying plant and eliminate the effect of human factor upon the technological process.
      For the new-mounted grain cleaning-and-drying complexes and for reconditioning of the existing ones with М-819 grain-drying plants the cost of such Automatic process control system for grain drying shall make up in general 60 mln Belarusian roubles (depending on the complex multiplicity) cost of erection, starting-up, adjustment and commissioning works, including as well the cost of equipment in the amount of 35 mln Belarusian roubles. The integration period of this system into automatic control system of all the grain cleaning-and-drying complex is about two months, depending on multiplicity of technological scheme of a particular complex. The payback period of the system makes up 1-2 years. Automatic process control system for grain drying was introduced in the year 2009 at RUE «Sovkhoz-Kombinat Zarya» in Mozyr District of Gomel Region into a grain cleaning-and-drying complex with output capacity of 40 planned tonne per hour with elevator of silo-type for 20 thousand tonne of grain.