RU2422206C1 - Method dry seeds and grains and device for its realisation - Google Patents

Abstract

FIELD: agriculture. ^ SUBSTANCE: invention relates to methods of seeds and grains drying and devices for its realisation and may be used in agriculture. The method of seeds and grains drying ensures their loading, gravitation movement in a downright manner, preliminary heating, serial ventilation with a drying agent and a cooling medium and unloading. At the same time at the outlet the cooling medium is heated with the drying agent and is sent to the preliminary heating of material. The device for seeds and grains drying comprises an over-the-drier hopper 1, shafts, an air cavity 3 between shafts, sections of preliminary heating 2, drying 4 and cooling 5, facilities of loading and unloading 6, fans 16 and a furnace 15. Besides, the device comprises a heat exchanger 11, connected to sections of preliminary heating 2 and cooling 5, besides, it is located in the air cavity 3 at the inlet into drying sections 4. ^ EFFECT: invention makes it possible to increase efficiency and safety of drying process. ^ 2 cl, 2 dwg, 1 ex

Description

The invention relates to methods and devices for drying seeds and grains mainly of high humidity and can be used in agriculture and in the procurement system.

There is a known method of drying seeds and grain, according to which the material is loaded, gravitationally moved from top to bottom, sequentially vented with a drying agent and a cooling medium, and the dried and cooled material is unloaded. A device for its implementation, consisting of a silo hopper, shafts, discharge device, fans, furnace device [1].

These method and device are widespread in agriculture, but are energy consuming.

A known method of drying seeds and grain, according to which the material is loaded, gravitationally moved downward, preheated, sequentially vented with a drying agent and a cooling medium and unloaded, and the cooling medium is recycled to the drying agent [2].

A device for its implementation, consisting of a silo hopper, a shaft with zones of preheating, drying and cooling, means of loading and unloading material, fans and furnaces [2].

This method is closest to the essence of the claimed, is low-cost and selected for the prototype. Dryers working by this method also found application in agriculture of the Russian Federation.

The method has several disadvantages. The main one is the supply of a high-temperature drying agent to the heating zone, and with a reduced temperature to the drying zone, which reduces both the efficiency and safety of the process, especially when drying seeds and grain, high humidity.

A device for drying seeds and grain containing a drying hopper, mines, an air cavity between mines with a drying and cooling sections, means for loading and unloading material, fans and a furnace [3]. This device is the closest to the essence of the claimed and selected as a prototype, however, it does not allow for energy saving.

The technical task of the invention is to increase the efficiency and safety of the drying process.

The stated technical problem is achieved by the fact that in the method of drying seeds and grain, which consists in loading the material, gravitationally moving it from top to bottom, preheating it, sequentially venting it with a drying agent and a cooling medium, and unloading, according to the invention, the cooling medium is heated at the outlet with a drying agent and sent to preheating the material.

The task is also achieved by the fact that in the device for drying seeds and grain, which contains a drying hopper, mines, an air cavity between the mines, preheating, drying and cooling sections, loading and unloading means, fans and a furnace, according to the invention, the device is equipped with a heat exchanger, connected to the preheating and cooling sections and located in the air cavity at the entrance to the drying section.

Comparison of the claimed method with the prototype shows that the new method is that at the outlet the cooling medium is heated with a drying agent and sent to the preheating of the material.

Comparison of the claimed device with the prototype shows that it is new that the device contains a heat exchanger connected to the preheating and cooling sections and located in the air cavity at the entrance to the drying section.

The invention meets the criterion of "inventive step", since a result can be achieved that satisfies an existing need, namely, increasing the efficiency and safety of the drying process.

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

The method can only be implemented in the claimed device, i.e. meets the criterion of "unity of invention."

The invention is illustrated by drawings.

Figure 1 shows a diagram of a device; figure 2 - curves of the kinetics of drying of the seeds according to the claimed method and prototype, obtained in the laboratory.

The device contains a drying hopper 1, a section for preheating the material 2, an air cavity 3 enclosed between the shafts, a drying 4, a cooling section 5, a discharging means 6, a noria of dry material 7, an unloading screw 8, a noria of wet material 9, a box 10, a heat exchanger 11 , cooling medium fan 12, casing of preheating section 13, leveling screw 14, firebox 15, fan of drying agent 16, diffuser 17, collector of cooling section 18, collector of preheating section 19.

The method is as follows.

The material is loaded, gravitationally moved from top to bottom, pre-heated with a heated cooling medium from the cooling section of the dryer, sequentially vented with a drying agent and a cooling medium, and unloaded.

The device operates as follows.

The pre-cleaned seeds and grain with noria 9 are fed into the drying hopper 1, leveled with a screw 14, under the action of gravity, the material passes through sections of preheating 2, drying 4, cooling 5 in succession and is discharged by means of 6 into the screw 8 and then into the noria of dry grain 7. Dried and the chilled material enters the final cleaning.

The drying agent is prepared in the furnace 15, the fan 16 is pumped through the diffuser 16 into the drying section 4, at the input of which a heat exchanger is placed in the diffuser 17. Outside air (cooling medium) with a fan 12 is sucked in successively through the cooling section 5, the collector 18, the heat exchanger 11, the collector 19, the material preheating section 2, the casing 13 and are thrown out. According to this scheme, the drying agent and the cooling medium enter and are removed from the material through the ducts; it is also possible to distribute them in the material through sieve surfaces in a lump dryer.

The heater 11 is made of bundles of pipes arranged in a checkerboard pattern and clamped by tube boards.

The drying agent is fed into the annulus, and the outside air after the cooling section 5 into the pipes. Thus, the heat exchanger, which is located in the air cavity at the entrance to the drying section, is connected to the preheating and cooling sections

Preheating causes an increase in productivity and a reduction in energy consumption for drying. As a technical means of preheating, for example in a workpiece system, preheating chambers located in the upper part of the dryer have become widespread. A mixture of flue gases with air is supplied to these chambers from below, the temperature of which reaches 350 ° C, and material from above. Within 10-15 s, the falling material in the form of "rain" is heated and somewhat dried, then trapped in a drying bin, cyclically dried and cooled. According to this principle, recycle dryers of the Tselinnaya type work. This method has a significant drawback - you need a two-temperature furnace or a complex system for preparing a drying agent with different temperatures.

In a number of designs of grain dryers, along with recirculation of the material, recirculation of the drying agent and the cooling medium are used, including the recycle is heated in the furnace heat exchanger. However, it is advisable to do this on a purified gas medium, otherwise it is possible the accumulation of debris in the heat exchanger with the possibility of fire. To a large extent, for this reason, in type C dryers, which was chosen as the prototype, they refused to heat the cooling medium and pre-heated with a fresh drying agent, which reduced the drying process, but pre-heated spent cooling medium with a temperature of 30 ... 40 ° C ineffective.

According to the claimed method, the spent cooling medium with a temperature of 30-40 ° C can be heated to 10-15 ° C, if the temperature of the drying agent supplied to the heat exchanger at the entrance to the drying section is 130-150 ° C, at the entrance to the box of this section the temperature of the agent drying will be reduced to 110-130 ° C on the food regime and to 80-90 ° C on the seed, which corresponds to the recommendations on the drying regimes.

The effectiveness of pre-heating the grain is shown in Fig 2. In a laboratory setup, a layer of wheat 0.15 m high was purged. The temperature of the coolant was 75 ° C, the speed was 0.4 m / s, the material was periodically mixed. In the first case (cr. 1, 3) the temperature of the material was θ ₀ = 20 ° С, in the second (cr. 2,4) they were preheated to θ ₀ = 28 ° С, the initial moisture content of the material in both cases was W = 21, 8%. Material with θ ₀ = 20 ° С to a moisture content of W≈19% practically does not heat up, then its temperature quickly reaches 45 ° С (curve 3). The temperature of the heated material to θ ₀ = 28 ° C during drying initially decreases, which indicates the evaporation of moisture from the surface of the grains, then it increases more slowly than in the first case and at the end of drying it lags by 1-2 ° C from the unheated (cr. 4 ) The above graphs indicate the effectiveness of preheating, even by a small amount.

Example. We calculate the thermal and mass balances of the dryer according to the claimed method. We take the productivity of the dryer P = 20 t / h, the supply of the drying agent (heated air) Q _t = 60 thousand m ³ / h, the cooling medium (outdoor air) Q ₁ = 25 thousand m ³ / h. The initial seed moisture ω ₁ = 21%, the final ω ₂ = 14%, the temperature of the drying agent at the inlet to the heat exchanger t ₁ = 100 ° C, at the outlet t _to = 70 ° C, the temperature of the spent cooling medium t _from = 32.5 ° C, the height of the tubular heat exchanger L≈4 m. We determine the amount of heat transferred to the cooling medium, the degree of heating and moisture removal of seeds at the outlet of this section.

We take the speed of the cooling medium in the tubes of the heat exchanger V = 10 m / s, while the heat transfer coefficient is α = 25.5 W / m ² ° C [4]. The transverse area of the heat exchanger tubes will be

We take the number of pipes n = 15, then the diameter of the pipe will be

and heat transfer surface

F = πdLn = 45.6 m ² .

The amount of heat that the drying agent can transfer to the cooling medium will be

Q _t = FαΔt = 61 kW,

where Δt is the average temperature head

The degree of heating of the cooling medium will be

where c is the heat capacity of the cooling medium, c = 1.00 kJ / kg ° C.

Since the heat capacity of wheat seeds with a moisture content of 21% is 2 times higher than the heat capacity of air, they will be heated by ~ Δθ _n = 4.2 ° C.

Taking the maximum allowable heating temperature of the seeds θ _max = 43 ° C, and the initial θ ₀ = 15 ° C, then the reduction in the cost of heat for drying due to pre-heating will be

The dehumidifying ability of the heated coolant will be

Δd = d ₂ -d ₁ = 6 g / kg of air,

where d ₁ is the moisture content of the medium at the outlet of the cooling section,

d ₂ - the same at the entrance to the cooling section, 1 g of moisture per 1 kg of air. According to the Jd diagram, we determine d ₁ and d ₂ : d ₁ ≈10, ad ₂ ≈16 g / kg.

When heated, the next amount of moisture will evaporate

which amounts to 21 to 14% of the total moisture evaporated during drying of seeds

or

those. dryer productivity will increase by ~ 10% with a reduction in drying costs of 16%.

Information sources

1. Methodological recommendations for the selection and efficient use of grain shlivnoy equipment. - M., Federal State Institution "Rosinfornagrotech" p.40-41.

2. Guidelines for the selection and effective use of grain drying equipment. - M., Federal State Institution "Rosinfornagrotech" p.28-29.

3. L.D. Komyshnik, A.P. Zhuravlev, N.G. Rever. Operation of recirculating grain dryers. - M .: Agropromizdat 1986, p. 68-69.

4. Reference thermal power enterprises of non-ferrous metallurgy. M., 1982, 332-334.

Claims (2)

1. The method of drying seeds and grain, which consists in the fact that the material is loaded, gravitationally moved from top to bottom, preheated, sequentially vented with a drying agent and a cooling medium and unloaded, characterized in that the cooling medium is heated with a drying agent at the outlet and sent for preheating material. 2. A device for drying seeds and grain, comprising a drying hopper, shafts, an air cavity between the shafts, pre-heating, drying and cooling sections, loading and unloading means, fans and a furnace, characterized in that the device is equipped with a heat exchanger connected to the pre-sections heating and cooling and located in the air cavity at the entrance to the drying section.

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