SU661203A1 - Method of drying pulverulent materials - Google Patents

Description

one

The invention relates to the field of dispersed materials, mainly grains, and can be used in agriculture.

There is a known method of drying dispersed materials, mainly grains, by pre-drying the wet material, heat treatment in the mode of pneumatic transport with flue gases, subsequent heat and mass exchange with separation of exhaust gases from the material and cooling the latter with outside air. Moreover, the preliminary drying is carried out by mixing the wet material with recirculating material, and cooling by external air in the falling layer of the material during its transverse blowing 1.

The disadvantage of the method is that when blowing with air saturated with moisture, the falling layer of material does not provide the necessary degree of cooling (for such materials as grain).

The purpose of the invention is to improve the quality of drying by intensifying the cooling process.

This goal is achieved in that the outside air is dried with a sorbent before being supplied to the cooling and cooling is carried out in a downward flow of the gas suspension, followed by separation of the cooled material and the exhaust air, which is then directed to the preliminary zone.

drying is counter-current with wet material, while conducting conductive heat exchange between the latter and the cooled material. In this case, the sorbent, after interaction with outside air, is directed to regeneration, which is carried out by exhaust gases separated from the material.

The described method of drying dispersed materials is carried out as follows.

Wet dispersed material, such as grain, is pre-dried and fed in a mixture with a gas stream for final drying. Then the finally dried dispersed material is directed to cooling. For this, pre-dried outside air is used.

The dried dispersed material is cooled by contact heat exchange with pre-dried outside air, which in turn is cooled by the heat exchange surface to a temperature close to the dew point temperature of the incoming outside air. The direction of movement of the air is then changed in such a way that the cooled dispersed material is separated from it and consumed, and the cooled air is directed countercurrent to pre-dry the wet dispersed material. Pre-drying of a wet particulate material, for example, grains, is carried out in the following manner. Towards the cooled air flow, a moist dispersed material is fed to the heat exchange surface. As a result of the mass exchange between the cooled air and the wet particulate material, moisture is evaporated from the latter into the air. Thus, the wet dispersed material is dried and due to the latent heat of vaporization is cooled, which leads respectively to the cooling of the heat exchange surface, so Tfiak is last in contact with the wet dispersed material. Thus, the heat from the mixture of dispersed material with air is transferred through air, divided by heat, the heat exchanging surface and the wet dispersed material to air moving along the other side of the heat exchanging surface due to the evaporation of moisture from the wet dispersed material to the air that is heated, moistened is emitted into the atmosphere. The external air is pre-dried by supplying it to an air dryer, where the sorbent is directed. Here, due to heat and mass transfer between them, the scorching is dried and directed to cool the ° fff f bWiueHH6r6 dispersed material. The sorbent, saturated with moisture, is sent to the liquid sorbent regenerator, where the spent gas stream is also directed, where water is evaporated from the sorbent due to heat exchange between them and its concentration is increased. The regenerated sorbent is then precipitated to ambient temperature and fed to the dehumidification of the outside air. And the gas flow from the regenerator of the liquid sorbent is emitted into the atmosphere. Then the cycle repeats. The drawing shows a schematic view of the TATO for the implementation of the described method for drying dispersed materials; for example grains. The installation contains a pneumatic pipe 1 with noria 2, connected by a base to the firebox. 3, and the pre-drying shaft 4 with a hopper 5. The upper part of the pneumatic tube 1 is connected to a heat and mass exchange 6 having a hollow insert 7 forming a cyclone. The lower part of the heat and mass exchanger 6 communicates with the shaft 8 to cool the material. The installation has a fan 9 for supplying air to the shaft 8 through a dryer 10 and a fan And for sucking exhaust gases from the heat and mass exchanger 6 through a regenerator 12. The dryer 10 has a irrigator 13 for spraying liquid sorbent and is connected by line 14 with pump 15 to a regenerator 12, which in turn, line 16 with an air heat exchanger 17 is connected to the sprinkler 13. Mine 8 includes a discharge device 18 and a window 19 connecting it to shaft 4. Shafts 4 and 8 have a common wall 20 serving as a heat exchange surface. The installation works as follows. From the hopper 5, the wet material is fed into the pre-drying shaft 4. After that, the dried ma: material with noria 2 is directed to the pneumatic tube 1, where the flue gases from the furnace 3 are mixed together with air having a temperature of 300--400 ° C. This mixture is directed along the pneumatic tube 1 to the upper part of the heat and mass exchanger 6, where the insert 7 forming the floor forming the cyclone is installed. In a cyclone, the grain is finally dried at 70-80 ° C in the field of centrifugal forces and sent from the bottom of the heat and mass exchanger 6 to the shaft 8 to cool the dispersed material. In it, the fan 9 through the dryer 10 air serves dried outside air. In the shaft 8, the dispersed material is cooled by contact heat exchange with dried outside air, which in turn is cooled by the inclined heat exchange surface (wall 20) to a temperature close to the dew point temperature of the incoming external dried air. At the exit of the shaft 8 as a result of the direction of the air movement, the cooled dispersed material is separated from it and sent to the discharge device 18, from where it is fed to the consumer, and cold air is directed through the window 19 in countercurrent to the pre-drying shaft 4 of the dispersed material. In it from the bunker 5 serves on the heat exchange surface (wall 20) a layer of moist dispersed material, such as grain, towards the cooled air flow. In mine 4, due to heat and mass transfer between dry cooled air and a layer of wet dispersed material, moisture is evaporated from this layer into dry cooled air. In this case, the layer of wet dispersed material is dried and cooled due to the latent heat of vaporization, which leads to cooling of the wall 20, which is in contact. With a layer of wet particulate material. Thus, heat from the gas suspension in the shaft 8 through the wall 20 from the wet dispersed material is transferred to the air moving in the mine 4 due to the evaporation of moisture from the layer of the wet dispersed material into the air volume. This air in mine 4 is the preliminary