RU1805269C - Method for drying thermolabile loose materials in multistage fluidized bed drier - Google Patents

Abstract

Usage: agriculture, food industry, in particular drying of thermolabile materials in a fluidized bed. SUMMARY OF THE INVENTION: a method for drying thermolabile materials in many light-colored fluidized bed dryers includes loading wet material into the upper bed, feeding material through a transfer device to the lower bed, unloading the dry material while drying the material in an upward flow of heat-transfer fluid to form a fluidized bed, while feeding the material from the upper channel it is carried out to the lower one, and from the lower one, in the pneumatic transport mode, to the middle one, from which the unloading is carried out. 1 s.p. f-ly, 1 ill.

Description

The invention relates to the drying of thermolabile bulk materials and can be used in agriculture and food industry for drying grain, vegetables, fruits and other thermolabile products.

The purpose of the invention is to reduce specific energy consumption due to the rational interaction of material and heat carrier flows.

This object is achieved in that in a method for drying thermolabile bulk materials in a multi-layer PS, including loading wet material into the upper PS, drying the material with an upward flow of gaseous coolant in at least three PS, and unloading the dry material, according to the invention, from the upper PS material is fed to the lower PS, from where it is then transferred to the pneumatic airway. By port part of the coolant to the overlying intermediate PS, and the dry material is unloaded from the intermediate PS located on mediocre at the top of the SS. In order to intensify the drying process, a pneumatic conveying recirculation flow is created by a part of the material heat carrier from the lower PS to the upper PS to the wet material loading zone.

This goal is also achieved by the fact that in the device for implementing the method of drying heat-sensitive bulk materials in a multi-purpose substation containing a vertical housing, separated by at least three GRU, unloading

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a branch pipe, at least two transfer pipes installed in the housing under the lower GRU, a gaseous heat carrier inlet pipe and installed in the body above the upper GRU waste heat carrier outlet pipes and a wet material inlet, according to the invention, the inlet opening of one transfer pipe is located at least the level of the upper GRU and the outlet is above the lower GRU, the inlet of the second transfer pipe is located above the lower GRU, and the outlet is above the overlying intermediate GRU, while the discharge pipe to not disposed below the level of the intermediate GRU disposed under the upper GRU To intensify the drying process it can be introduced recirculation pipe inlet which is disposed above the HRU bottom and an outlet opening - at the upper GRU. The proposed technical solution allows to reduce the specific energy consumption due to the rational sequence of interaction of the material and coolant flows. The supply of wet material to the upper GRU (to the upper substation) provides pre-heating (warming up) of the moist material with a wet heat carrier (previously all other substation substrates have passed), which intensifies the drying process and reduces the specific energy consumption by increasing the rate of moisture supply from the inside of the material to its surface . Preheating the wet material with a wet coolant also prevents the formation of a crust (shell) on the surface of the particles of particles, which sharply reduces the evaporation of internal moisture from the particles of the material. The formation of a crust material on the surface of particles leads to a sharp increase in drying time and an increase in energy consumption, maintaining the bed in a fluidized state. The supply of material from the upper GRU to the lower GRU and the subsequent transfer of material to the overlying GRU allows drying the material in a flow with a heat carrier, which makes it possible to use a high-temperature coolant with a temperature close to the maximum allowable, providing high drying speed and high thermal efficiency (which also reduces specific energy consumption).

The use of pneumotransport recirculation of a part of the material from the lower GRU to the upper GRU to the wet material loading zone intensifies the drying process, since in addition to convective (by the heat carrier flow) heating of the material located on the upper GRU, a conductive (contact) supply of heat to the wet material from the material arriving from the lower PS is also provided. In addition, this ensures the redistribution of moisture between the particles of the material, because heated material from the lower GRU adsorbs part of the moisture of the fresh (wet) material, which increases the evaporation surface.

Use of pneumatic conveying for

particle flow from the underlying GRU to

. overlying provides selective

flow (pneumatic separation) of material particles 5 ala, i.e. in this case, only those particles which have already lost sufficient moisture are transferred. And wet particles (as heavier ones) remain on this GRU with a higher layer temperature until

0 until it dries to the degree of humidity at which they can be transferred: hay to the next, overlying step (GRU). Pneumoseparation of material particles improves the quality of the finished material (since

5 eliminates its overheating and burnout) and reduces the specific energy consumption by reducing the aerodynamic drag of PS. The drawing shows an example of a device for implementing the proposed method

0 drying of thermolabile bulk materials in a three Russian substation.

The device contains a vertical

case 1, divided by three horizontal, with GRU - gratings 2. In case-1 under

5, the lower GRU 2 has a nozzle 3 for introducing a gaseous coolant, and above the upper GRU 2 there is a nozzle 4 for outputting the spent coolant and a nozzle 5 for introducing wet material. Unloading patro0 side 6 is placed not lower than the level of the average (intermediate) GRU 2. The inlet of the first transfer pipe 7, designed to transfer material from the upper GRU 2 to the lower GRU 2, is not located

5 is below the level of the upper GRU 2, and the outlet is above the lower GRU 2. The inlet of the second transfer pipe 8, which serves to transfer material from the lower GRU 2 to the intermediate GRU 2, is located above the lower GRU 2, and the outlet is above the intermediate GRU 2. The first transfer pipe 7 is equipped with a shutter-feeder 9. The inlet of the recirculation pipe 10 is located

5 above the lower GRU 2, and the outlet is above the upper GRU 2. The inlets of the second transfer pipe 8 and the recirculation pipe 10 are located in the zone as far as possible from the location of the outlet of the first transfer pipe 7. The outlet of the second transfer pipe 8 is located in the zone as far from the zone of the discharge pipe 6. The pipe 5 for the input of wet material and the outlet of the recirculation pipe 10 are located in the zone as far as possible from the zone of the inlet of the first transfer pipe 7. The discharge pipe 6 is equipped with a shutter-feeder 11 for unloading dry material.

The dryer works as follows. As an example, the drying process of feed grain is described.

The gaseous heat carrier with a temperature of 140 ° C enters through the pipe 3 under the lower GRU 2. The upward flow of the heat carrier passes sequentially from bottom to top through all three channels (GRU 2), providing them with a fluidized bed to give the grain heat to evaporate moisture. The temperature of the coolant spent in the lower PS and entering the intermediate PS (i.e., to the intermediate GRU 2) is 85 ° С, and that entering the upper PS is 65 ° С. The temperature of the spent coolant discharged from the dryer through the pipe 4 is 50 ° C. Wet grain with a temperature of 10 ° C and a humidity of 20% is fed through nozzle 5 to the upper GRU 2 in a substation with an average temperature of 40 ° C, where part of the free moisture evaporates from the grain surface and soft heating of the grain occurs. Warming the grain with a moistened coolant prevents the formation of a solid, moisture-proof crust (shell) on the grain surface and provides (intensifies) the supply of internal moisture to the grain surface. In the upper PS, light impurities are also blown out from the grain. Grain with a moisture content of 19% heated and cleaned of light impurities through the first transfer pipe 7 is fed to the lower GRU 2 in a substation with a temperature of 60 ° С via a shutter-feeder 9, where grain is dried by a high-temperature coolant with a temperature of 140 ° С at the inlet of the substation and 85 ° C at the exit of the PS. The low grain temperature (60 ° C) in the lower PS is explained by its cooling due to intensive evaporation of surface moisture. From the lower PS, grain with a temperature of 60 ° C and a moisture content of 15.5% through the second transfer pipe 8 is transported by a pneumatic transport stream generated by a part of the coolant to an intermediate PS with a temperature of 60 ° C, where grain is dried by a medium-temperature coolant with a temperature 85 ° C at the entrance to the substation and 65 ° C at the exit of

this PS. Pneumatic conveying of grain from the lower PS to the intermediate PS allows, due to a change in the velocity of the coolant in the transfer pipe 8, to create 5 pneumatic separation (classification) of the grain, which provides overloading of predominantly light (i.e. grains dried to a given moisture), and more humid (and therefore heavier grains) remain

10 in the lower PS (where the coolant temperature is higher than in the intermediate PS) until they are dried to a given humidity, Dry grain with a temperature of 60 ° C and a humidity of 14% is unloaded from

5 PS located on the intermediate GRU 2, through the discharge pipe b using the shutter-feeder 11.

In order to intensify the drying process during the processing of highly moist grain (with a moisture content of more than 20%) and ensure its drying to the required moisture content (14%), recycle of a part of the grain is used per load. To this end, open the recirculation pipe 10 and

5, part of the grain from the PS located on the lower GRU 2 is fed by the pneumatic transport stream created by the part of the heat carrier to the upper PS. Thus, in addition to convective heating of the grain located on the upper GRU 2, a conductive (contact) supply of heat to the wet grain from the grain coming from the lower PS is also provided. In addition, it provides

5 redistribution of moisture between grains, as heated grain coming from the lower PS adsorbs some of the moisture of the fresh (wet) grain.

Regulation of the flow rate of grain transported through the second transfer pipe 8 and recirculation pipe 10 is provided by changing their flow cross-section or the height of their inlet openings above the lower GRU 2.

5 Intermediate GRU 2 can be one (as in the considered case) or there can be more of them (dryers with 2-4 intermediate GRU 2 are currently tested), which allows more complete use of heat

0 coolant and, therefore, increase thermal efficiency and reduce specific energy consumption.

The studies showed that it is possible to use a high-temperature coolant in the proposed technical solution (for example, for feed grain up to 180 ° C) while maintaining the consumer properties of the material.

Compared with the prototype in the proposed solution more than 2 times lower

there is a flow of fluidizing air, with the exception of heat losses for heating the cooling air, which allows to reduce specific energy consumption by 1.2-1.5 times (depending on the initial temperature of the drying agent).

Thus, the set of essential features of the proposed technical solution allows in comparison with the prototype to reduce specific energy consumption by 1.2-1.5 times,

Claims (1)

SUMMARY OF THE INVENTION 1. Method for drying thermolabile bulk materials in many light brown dryers of a pneumatic fluidized bed, mainly three brown, including loading wet material to the upper rus, feeding material through the transfer device to the lower rus, unloading the dry material with an upward flow of coolant with the formation of a fluidized bed, characterized in that, in order to reduce specific energy consumption, the material is fed from the upper rush to the lower , and from the bottom in the pneumatic conveyor mode - to the middle, from which the unloading is carried out. f 2, The method according to claim 1, characterized in that, in order to intensify the drying process, a pneumatic conveying recirculating current is generated from the lower bed to the upper to the feed zone of the feed material. Wet material