RU2476085C2 - Method for pressed fibrous materials drying - Google Patents

Abstract

FIELD: food industry.

SUBSTANCE: invention relates to food industry. According to the proposed method, during drying in a vacuum-pulse drying chamber till specified moisture content is obtained one controls the moments of occurrence of stable values of the product moisture content at the specified temperature of the material heating in the process whereof one cyclically provides for a vacuum pulse with periods of time T limited by intervals T₁=[A₁-B₁]; T₂=[A₂-B₂];…T_n=[A_n-B_n]. The moisture content is measured with a capacitive multi-pin probe sensor installed at least in one of the pressed items loaded into the vacuum drier. Additionally, one proposes a device containing a capacitive multi-pin probe sensor with low and high potentials electrodes. For control of the moisture content of the product in a saturated vapour medium the high potential electrode is encased into an electrically insulated and moisture-proof shell with a tip; the tip is the shell extension.

EFFECT: inventions group allows to reduce drying time, decrease energy consumptions, produce high quality hay, exclude hay losses caused by mould deterioration during storage and produce a fodder additive in the form of grass sap.

3 cl, 4 dwg, 1 ex

Description

The proposed drying method relates to a technology for drying pressed agricultural products in a vacuum drying chamber, in particular hay, flax, etc. in bales or rolls.

Drying is the most energy-intensive operation of the whole technology of hay harvesting. The drying methods used are characterized by large quantitative and qualitative losses, which can reach 55%. The greatest losses are observed when harvesting in bales or rolls of under-dried or unevenly dried grass due to the appearance of mold even when a preservative is added. As a rule, mold is observed in the center of bales or rolls and decreases to the periphery. Similar phenomena are observed when harvesting flax trusts. Therefore, agricultural products pressed into bales or rolls are dried. The use of special drying units for active ventilation with heating of the drying agent contribute to the production of better products [1, 2]. The coolant in these installations enters the bottom of the roll and blows it from the bottom up. The moisture content of the dried products is periodically controlled by a portable device [3].

The main disadvantage of the drying method used is the significant energy consumption, which reaches up to 4136 kJ / kg of removed moisture [4].

Reducing energy costs is achieved by the method of drying plant materials in vacuum-pulse drying chambers [5]. However, the method used to control the drying process to reduce the temperature change of plant materials does not allow timely determination of the moment of the onset of steady-state moisture readings of the product in the event of equilibrium saturated steam pressure in the vacuum drying chamber.

The objective of the invention is to increase the drying efficiency of plant materials in a vacuum-pulse drying chamber, which is achieved by timely determination of the moment of steady-state moisture readings of the product when the saturated vapor pressure in the vacuum-drying chamber occurs.

Timely determination of the moments of the onset of steady-state moisture readings of the product in the event of equilibrium saturated steam pressure in the vacuum drying chamber can be provided with at least one special humidity sensor for hay, flax cutting, etc., installed in one of the rolls loaded into the chamber.

Monitoring the established readings of product moisture, for example in hay rolls, allows timely determination of the conditional humidity of hay, shortens drying time, reduces energy costs and produces high quality hay.

In addition, when drying hay in vacuum drying chambers, it is possible to collect the moisture to be removed in the form of grass juice (extracts), preserve and use it to flavor the main animal feed.

The most suitable for monitoring steady-state readings of product moisture may be devices used to control the humidity of powdered and stem media [6, 7]. However, the design of the sensors does not allow them to be used in a high humidity saturated steam environment due to the occurrence of short circuits of low and high potential electrodes.

In the proposed method, the determination of the moment of occurrence of steady-state moisture readings of a product is carried out by a device with a capacitive probe probe, in which a high potential electrode is electrically insulated and waterproof from the external environment by a shell with a tip, which is its continuation, which makes it possible to control the humidity of hay rolls even if an environment occurs in the drying chamber saturated steam.

The proposed drying method is illustrated by drawings (Fig. 1, Fig. 2, Fig. 3 and Fig. 4), which shows a possible scheme for loading a vacuum drying chamber with hay rolls and placing a multi-pin capacitive probe probe for continuous monitoring of humidity readings, a device for humidity control of the product, the design of the electrode of the high potential of the probe probe and a graph diagram of the drying mode.

The loading diagram of Fig. 1 shows the principle of loading rolls 3 into a vacuum drying chamber 1 and installing a multi-pin capacitive sensor probe 4 with a connecting cable 5 for outputting information to a measuring device.

The control device (figure 2) contains a measuring device 6 multi-pin capacitive sensor probe 4 with a high potential electrode 7 and low potential electrodes 8. Structurally, the high potential electrode 7 (figure 3) is a metal rod 9, enclosed in a sealed electrically insulating and waterproof the shell 10 with a tip 11, which is a continuation of the shell. The proposed design of the high potential electrode 7 eliminates the possibility of a short circuit with low potential electrodes 8 in a highly humid saturated vapor medium that occurs during the drying of plant materials in a vacuum-pulse drying chamber.

Figure 4 shows a graph diagram of the drying mode of fibrous pressed materials at a given temperature of heating the material in a vacuum chamber, in which a vacuum pulse is cyclically created to stop the change in moisture content of the product with time periods T limited by the intervals T ₁ = | A ₁ -B ₁ |; T ₂ = | A ₂ -B ₂ |; ... T _n = | A _n -B _n |;

Where

A ₁ , A ₂ , ... And _n is the initial period of inclusion of the vacuum pulse;

W = W ₁ , W ₂ , ... W _n - steady-state values of the product humidity or conditioned humidity in accordance with the state standard specification of the product for its storage;

B ₁ , B ₂ , ... B _n - disabling the action of the vacuum pulse;

W = W ¹ ₁ , W ¹ ₂ , ... W ^l _n is the moisture content of the product after removing part of the free or bound moisture.

Humidity control, in particular pressed hay in rolls, is carried out in the following sequence. Agricultural products, for example, rolls of hay 3 with a humidity of 30-40%, in the required quantity, depending on the volume of the vacuum pulse drying chamber 1, are loaded onto the trolley 2, a multi-pin capacitive humidity probe 4 is installed in the center of at least one roll and the trolley is moved to the inside drying chamber space. After loading, the chamber is sealed and the electric heater is turned on. In this case, hay is heated in rolls to a medium volume temperature that does not cause its denaturation and partial removal of free moisture. In addition, heating leads to a decrease in the surface tension of water in the cells and the intercellular space of hay and to an increase in water vapor pressure to values equal to the equilibrium vapor pressure at a given temperature. When the moment of equilibrium pressure of saturated steam in the vacuum drying chamber arrives, the humidity change in the hay roll no longer occurs. At this point, a vacuum is created in the drying chamber 1, which reduces the temperature of the plant material by 10-15 ° C. Plant material is briefly kept under vacuum in the chamber and then it is isolated from vacuum. In this case, a vapor pressure below equilibrium is created in the chamber and free moisture under the influence of a deep vacuum starts to leave the capillaries and intercapillary space of the plant material, due to the expansion of the dissolved and trapped gas and partially the process of vaporization in the material. After turning off the vacuum, the plant material is again maintained already under the influence of a residual vacuum until the secondary moment of the occurrence of equilibrium vapor pressure at the created temperature, continuing its heating. With the second occurrence of the moment of equilibrium pressure of saturated steam, they again produce a vacuum-pulsed effect on the plant material, but already to remove bound moisture.

Heating of the plant material followed by high-speed evacuation with heating, holding under vacuum with heating of the plant material throughout the entire volume comprise one drying cycle. The number of cycles can be at least more than two, i.e. increased many times until hay humidity of 17% is reached.

The accumulated moisture at the bottom of the drying chamber after each vacuum-pulse exposure is removed into the receiver, providing further extraction of free and bound moisture from hay in the volume of rolls.

Hay moisture and the moments of steady-state moisture readings of the product are continuously monitored by a multi-pin capacitive sensor probe 4. Information from the humidity sensor 4 is transmitted via a connecting cable 5 to the moisture indicator 6. Upon reaching the hay humidity of 17%, the rolls are unloaded from the drying chamber and sent to the storage.

Example. Agricultural products, for example wet hay in rolls, are loaded into a vacuum-pulse drying chamber, heating and vacuum-pulse exposure are performed. The installed probe sensor controls the humidity of the hay until 17% is reached, after which the rolls are unloaded from the chamber and sent for storage. The resulting extract (juice) is collected in special containers, canned and sent for flavoring the main feed to animals.

The application of the proposed method of drying hay in rolls in a vacuum drying chamber can reduce drying time, reduce energy costs, get high-quality hay, eliminate losses of hay from mold during storage and get a feed additive in the form of grass juice. For this, existing vacuum-pulsed drying chambers can be used, which eliminates the need for expensive and bulky equipment.

Information sources

1. Kuznetsov N.N. Improving the efficiency of harvesting hay pressed into rolls by optimizing the parameters of the drying process and equipment operating modes: Abstract. dis. on sois. scientist step. Candidate Tech. sciences. - SPb .: 2007. - 18 p.

2. USSR copyright certificate No. 1690607, cl. A01F 25/08, 1989.

3. Orobinsky D.F. Harvesting flax in the conditions of the North-West region of Russia: Textbook. - Vologda-Milk: IC VGMHA, 2007. - 190 p.

4. Pyatrushevichus V.I., Lyubarsky V.M. Active ventilation of herbal feed. - L .: Agropromizdat. Leningra. Separation, 1986 .-- 96 s., Ill.

5. The method of drying plant materials. RU 2238490 C2, 10.31.2002.

6. US 4,278,935, 07/14/1981.

7. SU 1223118 A, 04/07/1986.

Claims (3)

1. A method of drying fibrous pressed materials, characterized in that during the drying process in a vacuum pulse drying chamber to a predetermined humidity, the moments of the onset of steady-state readings of the product moisture at a given material heating temperature are controlled, at which a vacuum pulse is cyclically created with time periods T limited by intervals T ₁ = [A ₁ -B ₁ ]; T ₂ = [A ₂ -B ₂ ]; ... T _n = [A _n -B _n ]; moreover, humidity is measured by a capacitive multi-pin probe sensor installed in at least one of the compressed objects loaded into a vacuum dryer. 2. The method of drying fibrous pressed materials according to claim 1, characterized in that the removed saturated steam condensate from the vacuum drying chamber is collected in special containers, canned for safety and used for feeding to animals. 3. A device for controlling the moisture content of fibrous pressed materials during the drying process according to claim 1, comprising a capacitive multi-pin sensor probe with electrodes of low and high potentials, characterized in that for controlling the humidity of the product in a saturated steam medium, the high potential electrode is enclosed in an insulating and waterproof a shell with a tip, while the tip is a continuation of the shell.

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