A METHOD AND A SYSTEM FOR PNEUMATICALLY CONVEYING A GRANULAR MATERIAL OUT OF A DRYING STORE

Abstract: On the bottom surface of a store for a granular material is arranged a system of air ducts (2) connected at one end with a blower (10) and having at their opposite ends a closing valve (14). The side walls of the ducts are provided with openings (20) enabling air to be let out into the material for drying the same when the valve (14) is closed. When the valve (14) is opened the air flows right through each duct, and the openings (20) are made as ejector openings, whereby the material will be drawn into the duct and thus be conveyed out of the store.

Description: A method and a system for pneumatically conveying a granular material out of a drying store. The present invention relates to a method of pneuma¬ tically conveying a granular material away from a drying store in the general manner specified in the introductory clause of claim 1. It is well known to provide in a drying store a system of spaced, parallel air ducts arranged on the flat store bottom and connected at one end with a blower while being closed at the other ends. The duct side walls are provided with a row of openings immediately above the bottom level, and each opening is provided with an air guide flap which is arranged obliquely to the longitudinal direction of the duct in such a manner that it tends to guide the local air flow outwardly and forwardly along the duct, thus tending to cause pneumatic displacement of the material adjacent the duct or rather of the material lo- cated in the groove as constituted by the elongate space between every two neighbouring ducts. Adjacent the closed duct ends this or these grooves merge in an outlet opening in the floor or wall of the store, this or these outlet openings being closable by suitable outlet valve means. When the outlet openings are closed the material can¬ not be displaced by the action of the air as blown out of the duct wall openings, and the air, therefore, is utilized as drying air generally passing up through the material above the duct system. When the drying treatment has been finished the outlet valve means are opened, and now the air - in addition to a continued drying effect - will show a conveying effect, as it causes the material in the said groove or grooves to be moved towards the outlet openings. Gradually as the material is moved along the grooves and let out from the store the overlying material will descend correspondingly, and in this manner the entire material volume as held in the store may be discharged therefrom in a simple manner by means of the same duct system which is used for the supply of drying air, and thereafter the store is ready to receive a new charge of material to be dried. As mentioned, systems of this type are generally known, and by way of example reference can be made to UK-PS 1,195,201. Despite the simplicity with which the con¬ veyor function is obtainable in addition to the function of supplying drying air to the material in a uniformly " distributed manner, the known systems show a serious draw- back in that by the emptying of the store the conveyor blowing is likely to create a pronounced dust problem in the space above the material, especially during the last phase of the emptying of the store, and besides it is well known that there is a problem already in the fact that granular material may find its way into the air ducts through the wall openings thereof, because these openings, in order to be effective especially for the conveying of the material, should normally have a size considerably larger than the size of the single grains of the material. It is the purpose of this invention to provide a new and improved method of effecting the emptying or outlet of the stored and dried material whereby the said dust problems are unlikely to occur, and whereby the size of the duct wall openings may be kept relatively large for ensuring a high conveying capacity without giving rise to special problems as to intrusion of grains into the ducts. O P According to the invention the material is caused to be conveyed in the manner stated in the characterizing clause of claim 1, i.e. by making use of the duct itself for containing the conveyed material as introduced by ejection through the wall openings. When the outlet as constituted by the duct end itself is made closable, then the duct is still usable for alternatively supplying dry¬ ing air to the material through the ejector openings, and the novel main results of using the method according to the invention will be that the conveying is effected by way of an air and material intake through the wall open¬ ings, whereby no dust is blown out in the store, and that a possible intrusion of grains into the duct during the drying phase will be unimportant, because the intruded ma- terial will automatically be removed by the subsequent conveying phase. The invention also comprises a system for air drying and pneumatically conveying a granular material according to the above method, as specified in appended claims 2-4. In the following the invention will be described in more detail with reference to the accompanying drawing, in which:- Fig. 1 is a schematic perspective view of a system according to the invention, Fig. 2 is a more detailed view of a partial length of an air duct therein, and Fig. 3 is a side elevation of a portion of one of the ducts. The system shown in Fig. 1 comprises a number of spaced, parallel air ducts 2 placed on the bottom face 4 of a grain store, the four side walls 6 of which are shown schematically only. At one end the ducts 2 are connected with a manifold 8 through which air may be blown into the ducts from a fan 10. The opposite ends 12 of the ducts 2 are located flush with the outside of the associated side wall of the store, such that the wall seals the space between the ducts, and above the duct ends 12 is arranged a valve plate 14 which, by means of any suitable actuator means such as a cylinder 16, is movable between the illu¬ strated raised or open position, in which the " duct ends 12 are uncovered, and a lowered or closed position in which all duct ends are closed. The duct ends 12 communicate with a receiver hopper 18 arranged so as to guide grain material discharged through the duct ends 12 to some suitable receptacle or conveyor. As also shown in Figs. 2 and 3 the ducts 2 are de¬ signed as inverted ϋ- or V-profiles having in each of their opposed lowermost side portions a row of openings 20. Principally, when the valve plate 14 assumes its lowered, closed position and air is supplied to the ducts 2 from the fan 10, the air will be blown out through the openings 20 and thus be supplied as drying air to the gra¬ nular material as housed in the grain store, filled into the store e.g. through an open top thereof. When the valve plate 14 is caused to close the duct ends 12, manually or by means of an actuator system such as the cylinder 16, the air from the fan 10 is free to blow right through the ducts, and -when the air velocity in the ducts is suffi¬ ciently high, the openings 20 will hereby act as ejector openings, through which the grain material is drawn into the ducts and thereafter moved through the ducts to be discharged into the hopper 18 through the open duct ends 12. For increasing the ejector effect of the openings 20 each of these openings is provided with a guide plate 22 projecting inwardly and forwardly into the duct from the upstream edge of the respective opening 20. Each guide plate 22 is of a generally triangular shape, and it seems to be particularly advantageous that the lower edge of these guide plates is somewhat upwardly inclined, diverging from the bottom surface 4. As shown in Fig. 2 the guide OM plates 22 may be constituted by bent flap portions of a bracket member 24 used as a cross spacer element between the opposite edges of the duct 2. Additionally the bracket member may serve as a means for securing the duct to the floor by means of a screw through a hole 26 in the bracket member 24 (Fig. 2) . As illustrated in Fig. 2 the ducts may be assembled from a number of duct elements 28, which may advantageous¬ ly be provided with a bracket member 24 adjacent one end thereof and with side incisions 30 at the opposite ends, whereby the ejector openings 20 at these places are formed by the juxtaposition of the duct elements. For sealing the joints one end of the elements may be provided with a rim portion 32 overlapping the adjacent end of the next ele- ent. The ducts 2 should not necessarily extend parallelly to each other along, their entire length, especially adja¬ cent their outlet ends they may be arranged in a generally converging manner such that they all merge in a single outlet opening.

Claims: CLAIMS : 1. A method of pneumatically conveying a granular ma¬ terial from a drying store, whereby conveying air is supplied through one or more ducts extending through the material, preferably along a horizontal bottom of the store, and provided with duct wall openings through which the conveying air causes the material near the duct to be conveyed longitudinally of the duct from adjacent an air receiver end of the duct towards an outlet adjacent the other end of the duct, said wall openings additionally be- ing usable for blowing drying air into the material, cha¬ racterized in that for conveying the material the conveying air is blown all the way through the duct with a volume velocity sufficient to cause the material to enter the duct by ejection through the wall openings, whereby the material is let out through the said other end of the duct. 2. A system for air drying a granular material in a drying store and for pneumatically conveying the material out of the store by the method according to claim 1 , com- prising one or more air ducts extending through the store, preferably along a horizontal bottom surface thereof, and provided with wall openings for the outlet of drying air from the duct to the material, each duct at one end being connected with blower means, while in an area adjacent the other end there is provided an outlet, through which the material may gradually leave the store along the duct by means of conveying air supplied by means of the duct, cha¬ racterized in that the duct or ducts (2) adjacent the out¬ let (12) are provided with a closing valve (14), which in its closed position conditions the said outlet of drying air through the wall openings (20) while in its open posi¬ tion it conditions a direct through-flow of air through OMPI the duct (2) , said wall openings (20) being designed so as to be operable as ejector openings for intake of mate¬ rial into the duct by said through-flow of air, said out¬ let being constituted by said other end (12) of the duct (2) itself. 3. A system according to claim 2, characterized in that the wall openings (20) are provided with a guide flap (22) projecting inwardly and forwardly into the duct from the upstream edge of the respective opening (20) . 4. A system according to claim 3, characterized in that the lower edge of the flap (22) is inclined upward¬ ly and forwardly in the duct.

Inventors: JENSEN A
Applicants: JENSEN A
Application year: 1980
Main classification: B65G53
IPC codes: B65D88, F26B9, F26B21, F26B25