RU2363901C1 - Method and device of formation and drying of grain layer - Google Patents

Abstract

FIELD: agriculture.

SUBSTANCE: invention relates to postharvest handling of grain and can be used in agriculture and cereal products system. Method of formation and drying of grain layer includes formation of grain layer on sieve tapered surface in top part of the device, its drying by high-temperature drying agent, discharge of material into bottom part of device and finish drying by outside air on horizontal grid. New in the method is that bottom part of dried layer on sieve tapered surface is permanently or intermittently discharged on horizontal grid and finish drying at accumulation of grain mass, equal to M=G_n·τ_bin.+h_H F ρ, t, where M - grain mass, t; G_n - nameplate capacity of device, t/h; τ_bin. - binning cycle time, h; h_H - height of drying area, m; ρ - grain bulk density, p=0.75 t/m³, F- area of horizontal grid, m². Device for formation and drying of grain layer contains body with uniform cross-section by height, sieve tapered surface in top part of device and horizontal grid in its bottom part, supplying facilities of damp and unloading of dried grain. New in the device is that area of horizontal grid is equal

where τ_bin- binning cycle time - cooling of grain on horizontal grid, τ_c=τ_bin+τ_cool, h; τ_bin. - binning cycle time; τ_cool -cooling cycle duration; h_c - height of grain; h_c=h_H+h_bin=h_H+h_H τ_bin/ τ_cool=h_H(1+τ_bin/ τ_cool); h_bin - height of binned layer of grain, h_H - height of drying area, m.

EFFECT: invention must provide qualitative and economical drying of grain by means of rational formation of layer.

6 cl, 2 dwg

Description

The invention relates to post-harvest grain processing and can be used in agriculture, the procurement system and in other sectors of the national economy when drying heat-sensitive materials.

A known method of forming a layer of grain in ventilated bins or in bins for storing dried grain [1]. The grain is fed into the upper part of the device, then, under the action of gravity, a layer is formed in its lower part. The cross-sectional profile of the layer may be triangular in the absence of a switchgear or even if this device is present. After the formation of the layer, the grain is purged with external (heated) air. This method of forming and drying the grain layer is quite reliable, simple and widespread in agriculture. Its main drawback is the inability to use drying for modern energy-saving multi-stage drying technologies.

A known method of forming and drying a grain layer on a conical surface grate in the upper part of the device, drying it with a high-temperature coolant, periodic peripheral unloading of the dried material in the lower part of the device and drying (cooling) on the horizontal sieve surface with outside air [2]. The layer is stationary with a variable height along the generatrix.

In the known method, the formation of the layer is carried out by the corresponding arrangement of circular plates on a conical lattice, delaying the material, and in the lower part of the device by periodic unloading of grain from peripheral filling funnels.

A device for its implementation is known, comprising a housing, a cone grating, means for peripheral unloading of material from the upper part of the housing, a horizontal grating in the lower part, means for supplying wet and unloading dry and cooled material [3]. The cone lattice contains circular plates for even grain distribution.

This method and device in essence is closest to the claimed and taken as a prototype.

However, the known method does not allow the formation of a layer of constant height on the conical surface, which is necessary to reduce the unevenness of drying of the grain, and the lower layer of grain adjacent to the cone lattice limits the temperature of the drying agent by heating the grain to 50 ° C, and seeds of 45 ° C. Therefore, the temperature of the drying agent cannot be higher than 10 ... 15 ° C of the heating temperature of the material. Especially when dried high-moisture material and with a long purge cycle, and the low temperature of the drying agent reduces the effectiveness of the known method.

An object of the invention is to provide high-quality and economical drying of grain by rational formation of the layer. The problem is solved due to the fact that in the method of forming and drying a grain layer (seeds, material), including the formation of a grain layer on a sieve conical surface in the upper part of the device, its drying with a high-temperature drying agent, unloading the material in the lower part of the device and drying on a horizontal according to the invention, the lower part of the grain layer to be dried on a lattice conical surface is continuously or periodically unloaded onto a horizontal lattice and dried on it when accumulated the mass of grain equal to

M = G _n τ _ex + h _H Fρ, t,

where M is the mass of grain, t; G _n - passport productivity of the device, t / h; τ _ex - the duration of the tracking cycle, h; h _H is the height of the drying zone, m; ρ is the bulk density of the grain, ρ = 0.75 t / m ³ ; F is the surface of the horizontal lattice, m ² , in addition, the layer height on the lattice conical surface is kept constant relative to the generatrix, and the material is unloaded from the top of the device along its axis.

The task is also carried out by the fact that in the device for forming and drying a grain layer containing a body with a constant cross section in height, a conical grating surface in the upper part of the body and a horizontal grating in its lower part, means for supplying wet and unloading dried and cooled material. According to the invention, the horizontal grating area is

where τ _n - duration and cooling cycle binning grain to a horizontal grille, τ _n = τ + τ _{exc OHL,} h; h _c = h _H + h _OT = h _H + h _H τ _exc / τ _cool = h _N (1 + τ _exc / τ _cool ); h _OT is the height of the grain layer to be traced, h _H is the height of the drying zone, m, in addition, a means for removing the lower layer of material (auger) is installed on the sieve cone surface, and above it an additional grate forming a layer of equal height, the cone and additional gratings are provided drive, distributor and means for removing the lower layer of material.

Comparison of the claimed method with the prototype shows that the new method is that the lower part of the dried grain layer on the sieve cone surface is constantly or periodically unloaded on a horizontal grate and dried with the accumulation of grain mass on it equal to

M = G _n τ _ex + h _H Fρ, t,

in addition, the height of the layer on the sieve conical surface is kept constant relative to the generatrix, and the material is unloaded from the upper part of the device along its axis.

Comparison of the claimed device with the prototype shows that the new device is that the area of the horizontal lattice is

in addition, a means for removing the lower layer of material (auger) is installed on the grating conical surface, and above it there is an additional grate forming a layer of equal height, the cone and additional gratings are equipped with drives, a distributor, and means for removing the lower material layer.

Thus, the invention meets the criterion of "novelty."

This method can be implemented only with the proposed constructive solution, thus ensuring the “unity of invention”.

The invention is also “industrially applicable”, as it can be used in agriculture.

The invention meets the criterion of "inventive step", since a result can be achieved that satisfies an existing need, namely, high-quality and energy-saving grain drying.

The invention is illustrated by drawings. Figure 1 shows a diagram of a General view of the device, figure 2 - curves of drying and heating temperature of the seeds.

The device includes a means of loading grain 1, the housing of the device 2, a lattice conical surface 3, means for removing the lower layer (screw) of grain 4, the drive of this means 5, the upper, limiting and additional forming layer layer lattice 6, a grain distributor 7, rollers of the cone lattice 8, the drive of these rollers 9, a heat generator 10, an air duct 11, a fan 12, a horizontal grill in the lower part of the housing 13, discharge means 14, a fan for supplying external (heated) air 15, an air heater 16, a grain layer 17 in the upper part of the device, a layer 18 in the lower part of the device fairing screw 19, the hopper 20, the grain stream entering drying 21 also dried and cooled stream 22 grain discharged into noriyu 23 and 24, the exhaust drying agent.

The method is as follows.

A layer of constant height is formed on the upper cone lattice, as the lower layer of grain adjacent to this surface reaches a conditioned or predetermined humidity, it is removed by unloading along the axis in the lower part of the device, while adding wet grain. The grain layer in the upper part of the device is purged with a high-temperature drying agent, in the lower part after the formation of a layer of a given mass - with external (heated) air.

The operation of the device is as follows.

Means of loading (noriya) 1 grain flow 21 is fed into the loading hopper 20, on the cone grate 3 and placed on it at an angle of repose. The excess grain (over discharged) 23 after overflowing the hopper 20 is discharged into the elevator 1. After drying the grain on the cone grate 3, the drives 9 and 5 are turned on, the bottom layer of grain is unloaded by the screw 4, which enters the distributor 7 and then onto the grate 13, where a thick grain layer 18. The upper layer of grain is blown with a high-temperature drying agent prepared in a heat generator 10 and supplied by a fan 12 through the air channel 11. The lower layer is blown with external air through a fan 15, if necessary, it is heated in the heater 16. The spent high-temperature drying agent and the outside air 24 are removed through transoms in the upper part of the housing 1. The dried and cooled grain 22 by means of unloading 14 is removed from the device. The grate 3 is rotated by means of rollers 8 and drive 9. The material is unloaded from this grate according to the readings of the flow moisture meter installed after the distributor 7 (not shown in the diagram), and from the horizontal grate according to the readings of a stationary moisture meter (not shown in the diagram) located above unloading means 14, triggered at regular intervals. The normal mode of operation of the device provides for the continuous operation of the unloading means 4 and 14. The complete unloading of the device is carried out by means of 14, the grill 13 is cleaned manually.

Figure 2 shows the drying curves (1, 3) and heating (2, 4) of wheat seeds obtained in a model laboratory setup, which is a sieve cassette 0.07 m high, with a drying agent speed of 0.4 m / s and its temperature 70 ° С supplied to a layer with a height of 0.25 m. Curves 1 and 2 relate to a stationary layer, curves 3 and 4 to a layer from which a cassette with a dried lower layer of 0.07 m high was removed every ~ 20 min, at the same time adding while on top of the same cassette with wet material.

As follows from figure 2, a shorter drying time - when removing the lower dried layer, while the temperature of the seeds at the end of drying does not exceed the permissible ~ 45 ± 2 ° C.

Since the drying zone in the layer extends in the direction of the drying agent, then at the moment of reaching the top of the layer of conditioned humidity of 14%, the seeds in the lower part will be overdried. The higher the temperature of the drying agent, the higher the unevenness in humidity, which according to the initial requirements for drying for seeds should not exceed ± 1.5%, for grain ± 2%. Therefore, to prepare high-quality seeds, they are dried at a drying agent temperature not exceeding the heating temperature of the seeds by more than 10 ... 15 ° C. The higher the initial seed moisture, the lower its maximum allowable heating temperature and the temperature of the drying agent. When removing the dried layer, it is possible to both eliminate overheating and withstand the permissible unevenness of drying. Therefore, the temperature of the drying agent is increased by more than 10 ... 15 ° C relative to the temperature of the material with a corresponding increase in the drying efficiency.

In the proposed method, a layer in the upper part of the device is formed on a rotating surface, the grain enters the cavity bounded by two gratings, which ensures its uniformity in height over the entire surface of the generatrix of the cone. A screw is installed on the surface of the cone lattice, a fairing is fixed above it, unloading the screw from the pressure of the upper layers of the material. Wet material from the feed hopper 20 enters the channel formed by the upper grill and fairing, is distributed along it and fills the cavity instead of being removed by a screw.

When drying the grain on a horizontal grate with outside air, it is advisable to remove 2 ... 3% moisture, which will significantly increase the efficiency of the method. For this, it is necessary to provide for grain tracking and cooling under conditions that ensure maximum moisture removal in a fairly short time. Previously, these conditions were determined [4], in particular, for wheat grain τ _cool = 5 ... 6 h, τ _ex ≈4 h, specific supply of external air q = 80 ... 120 m ³ / h · t.

Grain drying takes place in a thick layer with the formation of a “drying zone”, through which air is saturated with moisture. In this case, the evaporation rate of moisture gradually decreases and at a height h _{H the} drying stops (the relative air humidity comes into equilibrium with the moisture content of the grain). Above the zone of height h _H there is a tracking zone, since there is no heat and mass transfer. Therefore, before blowing the grain with outside air, it is necessary to form a layer on the grate, including the zones of curing and drying.

The mass of this layer can be written as:

where M is the mass of grain, t; G _n - passport productivity of the device, t / h; τ _ex - the duration of the tracking cycle, h; h _H is the height of the drying zone, m; ρ is the bulk density of the grain, ρ = 0.75 t / m ³ ; F is the surface of the horizontal lattice, m ² ,

The first term on the right side of the equation is the mass of grain that needs to be traced, and the second is the mass of the dried grain.

With constant supply of dried and dried grain and a constant supply of external air, the “drying zone” will move upward in the direction of air flow, leaving the material dried to equilibrium humidity with external air until the dried grain completely fills the device. In the case of grain with a moisture that differs over time, the operating mode of the unloading means on the cone grate will be changed, accordingly, the passport capacity of the device will be changed for both incoming and dried material, i.e. h _H ≈const. A constant value of h _H guarantees high-quality drying, including seeds, and economic efficiency of the device.

The operation of the device is as follows.

Means of loading (noriya) 1 grain flow 21 is fed into the loading hopper 20, on the cone grate 3 and placed on it at an angle of repose. The excess grain (over discharged) 23 after overflowing the hopper 20 is discharged into the elevator 1. After drying the grain on the cone grate 3, the drives 9 and 5 are turned on, the bottom layer of grain is unloaded by the screw 4, which enters the distributor 7 and then onto the grate 13, where a thick grain layer 18. The upper layer of grain is blown with a high-temperature drying agent prepared in a heat generator 10 and supplied by a fan 12 through the air channel 11. The lower layer is blown with external air through a fan 15, if necessary, it is heated in the heater 16. The spent high-temperature drying agent and the outside air 24 are removed through transoms in the upper part of the housing 1. The dried and cooled grain 22 by means of unloading 14 is removed from the device. The grate 3 is rotated by means of rollers 8 and drive 9. The material is unloaded from this grate according to the readings of the flow moisture meter installed after the distributor 7 (not shown in the diagram), and from the horizontal grate according to the readings of a stationary moisture meter (not shown in the diagram) located above unloading means 14, triggered at regular intervals. The normal mode of operation of the device provides for the continuous operation of the unloading means 4 and 14. The complete unloading of the device is carried out by means of 14, the grill 13 is cleaned manually.

To calculate the area F, we take into account that the passport productivity G _n must provide a mass of grain M _о that meets optimal conditions, then

or

where h _c - the height of the embankment of the material on the horizontal grid, m

Equating the right sides of equations (2), (3), we obtain

Given the values of G _n from (4), one can determine the value of F and other parameters of the device.

Calculation example h _H , M, M _o and F.

To calculate the height h _H, we compose a mathematical model of moisture transfer in the grain layer. The moisture mass dM ₁ , taken out of the layer by outside air, can be represented as

where β is the mass transfer coefficient from grain to air, m / s;

dF is the area from which moisture evaporation occurs, m ² ; ρ _about - grain density, t / m ³ ; U ₀ , U - moisture content of the vapor-air film on the surface of the grain and air, respectively, kg / kg

The same flow of moisture can be represented as

where G is the mass of moisture transferred from the layer, kg / s.

Equating the right sides of expressions (5) and (6), we obtain

Considering a separate elementary channel with a diameter d _e in the embankment of a grain layer, from the inner surface of which moisture evaporation occurs, the value of dF in (7) can be represented as

where dl ₀ is the length of the channel through which air passes, m.

Due to the tortuosity of the channels, the average length h _{H is} greater than the corresponding length in the direction of the pressure gradient, i.e. layer height, and can be expressed

where T is the tortuosity coefficient, which Karman in the case of a turbulent flow regime is taken equal to T≈1.50. In the case of the laminar flow regime, which is characteristic of grain cooling conditions at V ₀ ≤0.1 m / s, where V ₀ is the air velocity in the elementary channels of the layer, m / s, T≈1.2 can be taken.

The value of G can be represented as follows

where d _e is the equivalent diameter of the elementary channel, m

ε is the porosity of the grain layer, d ^' _e is the equivalent diameter of the grain, m

The velocity V _{o is} conveniently expressed in terms of the porosity of the layer ε, the air velocity above the layer V. After integration (7) from O to h _H and simplifications, we obtain

where U ₁ , U ₂ - moisture content of air at the inlet and outlet of the elementary channel, kg / kg

The values of U ₁ and U ₂ can be determined from

where φ is the relative moisture content of the air; P, P _H - atmospheric pressure and saturated vapor pressure, respectively, kPa.

At an outdoor temperature of 15 ° C and φ = 0.7, the value of U ₁ = 0.007 kg / kg. To calculate the value of U ₀ we accept the following assumption.

After curing, the surface of the grain is moistened with the formation of a vapor-air film; the value of φ ₀ when calculating U ₀ for the indicated temperature conditions can be taken to be φ = 0.99. We will assume that φ = const during the whole process of cooling the grain, in addition, we will take the grain temperature as average between the initial θ _H = 45 ° C and the final θ _K = 20 ° C-θ = 32.5 ° C. Then we get P _H = 5.0 kPa and U ₀ = 0.034 kg / kg.

We calculate the average air temperature at the outlet of the “drying zone” (t _H = 15 ° C, t _K = 45 ° C) t _cp = 30 ° C and take the maximum permissible moisture content under vapor condensation conditions - φ = 0.8, then U ₂ = 0.021 kg / kg and the value of the natural logarithm l _n (U ₀ -U ₁ / U ₀ -U ₂ ) ≈0.7.

After substituting the values of U ₀ , U ₁ and U ₂ in (12), taking the average value β≈0.5 · 10 ^-4 m ² / h (for 32.5 ° С) [5], the air velocity V = 0.025 m / s (specific feed q≈120 m ³ / h · t), porosity of the layer ε = 0.45, d _e ≈1.6 · 10 ^-3 m, we obtain h _c = 1.35 m

Taking G _n = 10 t / h; τ _ex = 4 hours; τ _cool = 5 hours; case diameter 8.5 m; (F = 50.2 m) h _H ≈1.35 m from (1) and (2) we obtain:

M = 10 · 4 + 1.35 · 50.2 · 0.75≈91 t

h _c = 1.35 (1 + 0.8) = 2.43 m

.from (4)

.

The calculation error for F compared to the accepted diameter of 8 m does not exceed 3%, therefore, for a device with a capacity of 10 t / h, the value F≈50 m ^{2 is} optimal. In this case, the supply of fan 15 will be ~ 10 thousand m ³ / h, and the power of the air heater 16, based on the maximum heating of the air at 6 ° C - 7.5 kW.

Information sources

1. M.A. Telengator, B.C. Ukolov, V.M. Tsetsinovsky. Grain seed treatment. - "The Ear", M., 1972, 76 p.

2. Storage and processing of grain // Express information. The elevator industry abroad, issue 6, M., 1989, p.1.

3. Leaflet “Top DRY Specifications”.

4. RF patent №2305241, IPC8 F26B 17/12, 2006 (prototype).

Claims (6)

1. A method of forming and drying a grain layer, including the formation of a grain layer on a sieve conical surface in the upper part of the device, its drying with a high-temperature drying agent, unloading the material into the lower part of the device and drying with outside air on a horizontal grate, characterized in that the lower part of the dried layer grains on a lattice conical surface are constantly or periodically unloaded on a horizontal lattice and dried on it with the accumulation of grain mass equal to M = G _n · τ _ex + h _H Fρ, t,
where M is the mass of grain, t; G _n - passport productivity of the device, t / h; τ _ex - the duration of the tracking cycle, h; h _H is the height of the drying zone, m; ρ is the bulk density of the grain, ρ = 0.75 t / m ³ , F is the surface of the horizontal lattice, m ² . 2. The method of forming and drying a grain layer according to claim 1, characterized in that the layer height on the sieve conical surface is kept constant relative to the generatrix. 3. The method of forming and drying a grain layer according to claim 1, characterized in that the grain is unloaded from the upper part of the device along its axis. 4. A device for forming and drying a grain layer, comprising a housing with a constant cross section in height, a conical grating surface in the upper part of the housing and a horizontal grating in its lower part, means for supplying wet and unloading dried cooled grain, characterized in that the horizontal grating area is equal to

, m ² ,
where τ _n - cycle time binning - cooling the grains on a horizontal lattice, τ _n = τ + τ _{exc OHL,} h; τ _ex - the duration of the tracking cycle; _OHL τ - duration of the cooling cycle; h _c is the height of the embankment of grain;
h _c = h _H + h _OT = h _H + h _H τ _ex / τ _cool = h _H (1 + τ _ex / τ _cool ); h _OT is the height of the grain layer to be traced, h _H is the height of the drying zone, m 5. A device for forming and drying a grain layer according to claim 4, characterized in that a means for removing the lower grain layer (auger) is installed on the sieve cone surface, and above it there is an additional grate forming a layer of equal height. 6. A device for forming and drying a grain layer according to claim 4, characterized in that the cone and additional gratings are equipped with drives, a distributor and means for removing the lower grain layer.

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