The apparatus for drying grain

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Kazakh National Technical University, Almaty

THE APPARATUS FOR DRYING GRAIN

Isembergenov N.T, Sagyndikova A.Zh., Kanay B.

Abstract

Energy saving installation for grain drying where the loaded system provides supply of grain in the bunker is offered, and in the bunker there are drying radiators which are executed from flat metal plates. And the bunker with drying radiators is completely filled with grain. On an external surface of metal plate's radiators, two parties heating elements in the form of an electric winding, which ends, are connected to the frequency converter are located. The grain movement is carried out when opening latches of the bunker by the unloaded system in process of drying down, and the speed of the movement of grain is regulated by also unloaded system. On energy saving installation process of drying of grain happens due to contact of grain with heated flat metal plates and the less than a distance between plates, the grain drying process is more effective.

Keywords: Grain drying, energy saving installation, drying radiators, electric winding, frequency converter.

energy grain drying radiator

Introduction

As we know, drying of grain is the most energy-intensive technological process of all technological operations of postharvest storage of grain. The amount of energy spent for drying makes to 70% of the total amount of the expenses falling on bringing grain to a state, standard on humidity, [1]. Practically all grain of the increased humidity of various cereals, leguminous and oil-bearing crops is exposed to drying. Correctly carried out drying of grain ensures high safety of the reaped crop, reduces his losses and provides improvement of quality of a ready-made product. According to the agricultural sector, it is necessary to dry to 50% of the harvest, and in some cases, depending on weather conditions and climatic zones of the Republic of Kazakhstan to 70-75%.

In agricultural production, in elevators and grain-plants used for drying grain installation of various designs and different principles of action. In the design of dryers at each stage focuses on thermal energy saving of 90% of total energy consumption [3].

The power preserving installation for grain drying is offered. Figure 1 shows the apparatus for drying grain, where the loaded system 1 supplies of grain in the bunker 2. In the drying bunker 2 radiators are three, which are made of flat metal plates. And the drying bunker with radiators completely filled with grain. On the outer surface of the metal plates on both sides of a radiator c, heating elements arranged in the form of an electric coil 4, the ends of which are connected to the converter. In the bunker 2 there are drying radiators 3 which are executed from flat metal plates. And the bunker with drying radiators is completely filled with grain. On an external surface of metal plates of a radiator from two parties heating elements in the form of an electric winding 4 which ends are connected to the frequency converter are located.

The grain movement is carried out when opening latches of the bunker by the unloaded system 5 in process of drying down, and the speed of the movement of grain is regulated by also unloaded system 5. Energy-saving settings on the process of grain drying is due to contact with the heated grain flat metal plates and the smaller distance between the plates, the more efficient the process of drying the grain. Thus, there is, however, grain roasting. The temperature of the grain must not exceed 55 degrees at the request of the drying technology. Temperature on the surface of flat metal plates should not exceed 80 degrees. In setting the temperature and the heating power can be adjusted by a frequency converter.

Figure 2 shows Drying radiators with a heating element 3 in the form of flat metal plates. Electrical winding 4 bows outer surface and connected to the plate (IF) frequency converter. In the electric coil is supplied a high frequency voltage, a frequency converter connected to the grid. With the passage of high frequency current around the electrical coil magnetic field is formed on the side surfaces of the heat sink is formed of metal electro moving force (EMF), which causes eddy currents, and these currents will heat the metal side of the radiator surface on both sides. The thickness of the plates is selected from the condition that the thickness of flat metal plates to the penetration depth of the eddy current.

The distance from the surface of the plate toward its thickness d, at which the current density decreases by a factor of e, i.e. by 63.2%, conventionally called the penetration depth of the current [1]. The depth of current penetration determined by the following formula:

, m (1)

Where , f - frequency, Hz; - Magnetic permeability of the conductor material in a practical system units, H / m; ? - electrically-specific material of the wire,

Magnetic permeability can be defined as

 (2)

wherein the relative magnetic permeability value for any material, which is held in directories.

From the expression (1), equating it to the plate thickness can determine the optimal frequency of the current

(3)

With regard to increasing the thickness of the heated plate to a penetration depth d at a constant current in the coil current energy transferred to the plate increases. The power can be calculated by the formula [3]

, w (4)

where W₁I₁ - ampere - turns of the coil per unit height of the plate, which is numerically equal to the magnetic field H; h is the height of the plate, m; ? - the electrical conductivity of the material of the cylinder,

= к - empirical function,

where k = 0.75.

When increasing the ratio function increases, thus increases and the power delivered to the plate. When the same constant current in the inductor - which means increase in electrical efficiency in the power transmission plate. Efficiency factor is high enough and practically does not depend on the frequency of already current, but is determined by the relation between the specific conductivity of the material of the plate, and copper, which they inductor [5]. At high frequency provides high efficiency in energy transfer to the heated body.

Apparatus for drying grain operates as follows. On a busy system 1 is continuously fed wet grain, which is fed by gravity into the bunker 2. In this case, the wet grain weight completely passes between drying radiator 3 at a certain speed. When the frequency converter high frequency current, flowing through the electrical windings forming a magnetic field on the side of the radiator metal surfaces formed electro-moving force (EMF), which causes eddy currents, and these currents will heat the metal side of the radiator surface on both side. At the grain movement down through heated side metal surfaces of a radiator from two parties drying of damp grain weight is carried out. Speed of movement of damp grain weight and respectively the grain time spent in a temperature field is defined by opening and closing of latches of the bunker that is unloading system 8 in process of grain drying. Temperature of drying of grain is regulated by the frequency converter.

Accommodation in a bunker drying radiators in the form of flat metal plates allows direct contact with the grain and feed grain hot air through a plurality of small holes of the side surfaces of radiators can significantly reduce energy consumption and implement a uniform reliable drying of grain in general. This technology is uniform grain drying a wide temperature range, which is achieved by changing the frequency and voltage of the frequency converter 6.

The main advantage is the reduction of the drying time of heating, thereby saving energy and speeding up the process of drying the grain. Saving electricity is because the heating element is disposed within the drying chamber; heat is directly transmitted grain, which implies a reduction of costs.

Figure 1 - energy-saving setting for drying grain

Figure 2 - Heating elements for grain drying: 3 - metal plate 4-electric winding, FC - frequency converter.

Literature

1. A.E. Sluhotsky Inductors // Leningrad "Engineering", 1989.

2. T.M. Halina, V.Yu. Marsov, heating system based grain-electrode-many-composite electric heaters Polzunovsky // Bulletin №2 (Part 2). -Barnaul, 2005.-S.116-119.

3. Lykov A.V. The theory of energy transfer and the substance / A.V. Lykov, Y.A. Mikhailov. - Minsk: Publishing House of Acad. Sciences of the BSSR, 1954. - 357s.

4. Lykov A.V. Heat and mass transfer in the drying process. - Gos energy publishing, 1956. - 452s.

5. Trisvyatsky LA Grain storage. - Ed. 4th, Revised. and add. M .: Co-los, 1975.- 400c.

6. Kurushin AA, plastic AN Design of microwave devices in the environment CSTMicrowaveStudio.M.: Publishing MEI, 2010. -160 p.

7. Budnikov D.А. Intensification of grain drying active ventilation using the microwave electromagnetic field: Author. dis. Candidate of Technical Sciences Zernograd: FSEIHPE ACHGAA, 2007. 16c.

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