RU2249967C2 - Method for cooling of agricultural product after drying process - Google Patents

Abstract

FIELD: cooling of bulk agricultural products.

SUBSTANCE: method involves moving bulk product under gas-distributing grid in fluidized bed; at first stage, slightly drying product at temperature of air mixture of outside air and air heated from grain layer, with temperature of mixture being 25-30°C; at second stage, providing cooling with outside air; selecting length of cooling zones so as to provide for equal moisture content of individual grains within the range of 14±2.5% and temperature not in the excess of 20-25°C.

EFFECT: improved quality of dried material and intensified heat and mass exchange during cooling process.

1 dwg, 1 tbl

Description

The invention relates to methods for cooling bulk agricultural products, mainly grain, and can be used in drying plants with external coolers creating a fluidized grain layer.

Known methods of intensifying the process of cooling grain material by increasing the relative velocity of the gaseous and solid phases, to achieve maximum mixing activity of the solid phase / 1 /. In accordance with this, as well as by the method of supplying air to the grain layer and the location of the fan relative to the cooling zone, two groups of coolers can be distinguished: built-in and remote. Structurally, they are a fixed or vibrating tray with a trellised bottom, under which atmospheric air is pumped. Due to intensive purging, in the first case, fluidization is created, in the second case, due to vibration and purging, vibrationalization of the grain layer is achieved / 1 /.

The advantages of cooling installations of the fluidized bed and the fluidized bed should include the possibility of combining the technological process of cooling the material with the simultaneous movement of the layer in the tray with a large filling factor. The disadvantages of these methods is that when cooling with outside air, uniformity of grain drying during cooling is not achieved, as well as high specific energy consumption per unit mass of the cooled material.

There is a known method of cooling bulk materials, in which, in order to increase the degree of cooling of individual grains in the first stage, before blowing in a fluidized bed, the material is blown with exhaust air in a fluidized bed during its movement in a dense layer, and the air is fed into the fluidized bed with a temperature of 0 ... 10 ° C and relative humidity not exceeding the equilibrium grain moisture.

A significant drawback of the cooler is the uneven cooling of the grain during its movement in a dense layer and the inability to dry individual grains at the first stage of purging / 2 /.

The closest in technological essence and the achieved result is a known method of cooling agricultural bulk products, including a metal grate tray into which external air is pumped under a layer of boiling material having a temperature of heating wheat seeds to 42 ° C with an exposure of the process for less than 5 minutes (Swedish dryer cooler SF type TVN) / 3 /.

The disadvantages of this method is that during short-term (quick) cooling of the grain, seed spoilage may occur, there is no possibility of increasing the uniformity of seed drying by moisture due to the excessive intensity of the process of cooling the seeds, inefficient heat and mass transfer conditions.

The invention is aimed at improving the quality of seeds, the intensification of heat and mass transfer in the process of cooling the material and the alignment of individual grains to a moisture content of 14 ± 2.5%.

A method is proposed for cooling bulk products after drying, which involves injecting an outside air under the gas distribution lattice at an angle to the direction of movement of the bulk product to form a fluidized bed of the product above the grid, characterized in that the bulk product is fed to the gas distribution lattice, the space under which is divided into two zones, and pre-dry it in a fluidized bed above the gas distribution grid in the area of the discharge channel with a mixture of external air and air, heated from the grain layer during cooling of the product, while the temperature of the air mixture is 25-30 ° C, and subsequent cooling in the fluidized bed is carried out in the area of the suction duct at a temperature of 5-15 ° C of air that is injected under the gas distribution grid, while the length of the zone of the discharge channel accounts for 2/3 of the total length of the gas distribution grill.

With this method, the moisture moves smoothly from the center of the grain to its surface, its simultaneous evaporation and cooling of the grain.

In this way, conditions are created for uniform moisture separation at the first soft cooling stage, followed by a rigid cooling stage, which prevents the drying of grains having a low humidity and intensifies the drying of grains having a high humidity.

The drawing shows a diagram of the cooling of agricultural products after drying by the proposed method.

The circuit includes a confuser 1, a loading neck 2, an exhaust chamber 3 with a louvered partition 4 for exhaust air, an exhaust chute 5 with a shutter 6. The confuser 1 is connected by a pipe 7 to the suction box of the fan 8 through an adapter 9. Above the discharge channel 10 and the suction box 11 there is a gas distribution grill 12. The space between the exhaust chamber 3 and the confuser 1 is divided into two zones: discharge A and exhaust B. The box 11 for introducing outside air is equipped with a louvered partition 13. Vent trimmer 8 by means of the diffuser 14 is connected to the discharge channel 10.

Cooling seeds according to the proposed method is as follows. At the first stage of cooling, the seeds, with their permissible heating during the drying process, for example 30-45 ° С, and final humidity after drying, for example 15 ± 3%, enter through the feed neck 2 to the gas distribution grid 12, discharge zone A, where the height of the layer to be cooled material, the specific load on the gas distribution grid 12 and the amount of cooling air regulated by the louvered partition 4 are selected in such a way that they form a mixture of outdoor air with heated air from the grain. The air mixture prepared in this way at a temperature of 25-30 ° C permeates the grain layer in the discharge zone A, while the bed is fluidized, the individual seeds are equalized by moisture, dry up to 14 ± 2.5% and they move from zone A to zone B.

At the second stage, the cooled material in the suction zone B falls under the influence of penetrating streams of external (cold) air, a fluidized state of the layer is formed, which moves to the outlet trough 5. Through the louvered partition 13, an independent stream of external air is supplied to the layer, which creates the final cooling of the material to outdoor temperature plus 3-5 ° C.

Exhausted and heated airflows in zones A and B are directed through pipeline 7 to adapter 9 of fan 8. Dust, fine dry fractions can be removed by a sediment chamber or a cyclone attached to pipeline 8 (this device is not indicated in this diagram).

The table shows the influence of the methods of supplying flows from the discharge zone A to zone B, and then to the material to be cooled, which affects the course of the combined cooling process and final drying, as well as the quality of the resulting product.

l - длины газораспределительной решетки, что интенсифицирует процесс охлаждения, при этом семена получают высокую выравненность по влажности и, следовательно, высокую всхожесть.The table shows that the process of cooling the grain and aligning it with moisture (drying) takes place in a completely fluidized bed, provided that cooling air is supplied under the gas distribution grid in zones A and B in relation to the length

l is the length of the gas distribution grid, which intensifies the cooling process, while the seeds receive high evenness in moisture and, therefore, high germination.

Sources of information

1. Nikulin E.I. "Ways to improve the efficiency of grain cooling in shaft dryers", Proceedings of VNIIZ, issue 70, 1970.

2. Copyright certificate of the USSR 826171, 04/30/1981. p.1-3, F 26 B 1/084.

3. Perch G.S. and others. "Installations for drying grain abroad." 1963.

Table
INFLUENCE OF THE NUMBER OF EXHAUSTED AIR FLOWS COMING FROM ZONES A AND B TO THE COOLED MATERIAL ON THE CHARACTER OF THE COOLING PROCESS
The conditions of the experiment: the total mass of grain passed in 1 hour to 1000 kg; total length of the gas distribution grill - 6 meters; wheat grain with a moisture content of 26.5% was dried to a moisture content of 15 ± 5% at a temperature of 43 ° C; the exit temperature of individual batches of grain was 43 ± 7 ° C, of external air - t _n = 15 ° C. Design option, (length of zones, m) Conclusions from observations of the cooling process A = 2; B-4 The fluidization regime is not stable, lowering the temperature of the grain t _z = 15 ± 2 ° C in 20 minutes, alignment of the grains with respect to moisture was not observed, and their moisture content was 15 ± 2% A = 3; B = 3 The fluidization regime partially stabilized, lowering the temperature of the grain to t _s = 22 ± 2% in 30 minutes, the evenness of the grain in moisture content was 15 ± 1.3% A = 4; B = 2 The fluidization regime is stable, a decrease in the temperature of the grain to t _s = 19 ± 2% occurred in 40 minutes, the evenness of the grain with respect to moisture was 14 ± 1.5%

Claims (1)

A method of cooling bulk products after drying, which involves injecting an outside air under the gas distribution grill at an angle to the direction of movement of the bulk product to form a fluidized bed of the product above the grid, characterized in that the bulk product is fed to the gas distribution grill, the space under which is divided into two zones, and previously dry it in a fluidized bed above the gas distribution grill in the area of the discharge channel with a mixture of external air and air, heated about from the grain layer during cooling of the product, while the temperature of the air mixture is 25 ÷ 30 ° C, and the subsequent cooling in the fluidized bed is carried out in the area of the suction duct at a temperature of 5-15 ° C of air that is injected under the gas distribution grill, while the length of the zone of the discharge channel accounts for 2/3 of the total length of the gas distribution grill.