EP0033009A1

EP0033009A1 - Method and equipment for treating chopped crops

Info

Publication number: EP0033009A1
Application number: EP80108110A
Authority: EP
Inventors: Odd W. Hielm
Original assignee: Kockums Construction AB
Current assignee: Kockums Construction AB
Priority date: 1980-01-29
Filing date: 1980-12-22
Publication date: 1981-08-05
Also published as: GB2068520A; DK13481A; FI804061L; BR8100299A; AU6607781A

Abstract

In the treatment of chopped crops containing a mixture of grains or other seed, such as peas, beans, etc., and other plant components, the goods are introduced into a separating section (7) through which air flows, in a rotating drum, the temperature of the air entering a preliminary drier being regulated so that the superficial moisture of the goods is mainly removed before the goods are introduced into the separating section, as a result of which the grains can be removed without being damaged by prolonged overheating. The preliminary drier and the separating section consists of an integrated, rotating drum. Round the shell of the drum there is a discharge opening (33) or a series of discharge openings for the grains, and in the separating section there are members for feeding the grains back towards the grain discharge openings to the extent that they have passed the openings without being discharged. Alternatively a plurality of openings around the drum may be replaced by one continuous opening around the drum. Furthermore there are entrainment means for lifting up straw particles in the drum so that the separating work is facilitated. In the front end of the drum there is a discharge opening (83) for the straw particles.

Description

TECHNICAL FIELD

The invention relates to a method of treating chopped crops containing a mixture of grain and lighter parts. The invention likewise relates to an equipment for drying, threshing and separating chopped crops, comprising a rotatable drum with a primary drying section and a separating section with a discharge opening for the lighter parts of the threshed crops in the remote end of the separating section, and means for blowing drying and conveying air through the primary drying and separating sections.

BACKGROUND ART

In SE 408 122 an installation for treating chopped crops is described. The installation comprises a drying device consisting of a rotating hot-air drier of the through-flow type for continuous drying of the chopped crops and a conveyor device disposed at the discharge end of the drying device to feed the dried crops to a separating device which comprises a throwing apparatus and a separator housing. The walls and bottom of the separator housing form a plurality of funnel-shaped collecting shafts, separated from one another, in the lower portion of the housing, situated at different distances from the throwing apparatus in the direction of throwing and provided with devices for feeding the material separated into different fractions to one or more devices for further treatment and taking care of the fractions. The latter devices consist of storage silos, preparation devices for producing fodder mixtures and compressing devices for producing cakes, pellets or the like.
The object of this known installation is to be able to preserve the large amounts of valuable components included in the crops, which are wasted by conventional harvesting methods, such as the straw, for example, which today is often ploughed in or burnt and which contains both parts which are rich in protein. The parts rich in cellulose consist primarily of straw and stalk portions while the parts rich in protein consist primarily of husks, leaves and parts of grains. The latter part is often called chaff.
A disadvantage of the known methods, however, is that the drying in the drying devices must be continued as long as is necessary for the parts which are most difficult to dry. This consists primarily of the straw fraction. But in order that the straw fraction may be sufficiently dried, it is difficult to avoid damaging the valuable grains at the same time. When drying in the known installations, therefore, there is a great risk that the grains may be damaged, particularly if the crop has a high moisture content. This is a very serious disadvantage of the known installation. Another disadvantage is that the installation has a high energy consumption.
Also rotatable drying and separating drums of the kind given in the introduction are previously generally known. Such a drum is described, for example, is US 2 617 529. The outlet device in the shell of the drum consists, in this case, of an opening in the shell which is normally closed by a cover but which can be opened once for each revolution which the drum rotates, namely when the opening is in the bottom position. This construction has some decisive disadvantages and limitations. As a result of the fact that the cover is opened only once per revolution, the discharge capacity is very small. Admittedly, this could be increased by increasing the number of openings, but then, on the other hand, the construction would become very complicated to guarantee the synchronism between the opening of the cover and the bottom position of the opening. In certain cases, the most decisive disadvantage, however, is that goods which are ready to be discharged must wait up to a whole revolution before the discharge can take place. If the bulk goods consist of crops with grain which should be discharged through the outlet device in the shell of the drum, this waiting for discharge may prove fatal if the temperature in the drum is so high that the grain can be damaged by being heated too long. Another limitation in providing a flap as in US 2 617 529 is that such a construction makes it more difficult to introduce a counter stream of air through the outlet, which stream of air may be desirable to prevent husks or other light parts from accompanying the grain out through the outlet.

DISCLOSURE OF INVENTION

One object of the invention is to provide a method and an equipment for drying, threshing and separating a crop which contains components of different kinds in such a manner that none of the components is damaged but on the contrary can be taken care of to be utilized in the most suitable manner. More specifically, it is an object to be able to dry and separate chopped crops which contain valuable grains, such as chopped corn, substantially without the grains being damaged during the drying regardless of the moisture content of the crop. Thus it is also an object to be able to treat crops with a very varying moisture content so that the harvest season can be extended over a considerably longer time than is possible with conventional harvest methods.
An important object of the invention is to provide a method which is economical with energy. More specifically, the object is to utilize the various hot gases which are produced or obtained in the system in an optimum manner in view of what the different fractions require with regard to gas purity and drying effect.
Another object of the invention is to provide an installation in which different types of crop can be treated, involving a high degree of utilization for the components of the installation and a considerably reduced requirement of special machines for different kinds of crops.
Further it is an object of a developed embodiment of the invention to offer an outlet device for a rotatable drying and separating drum, which renders possible a very rapid discharge of the goods which have been conveyed forwards for discharge to the section in the drum where the outlet device is situated. The object in view is that goods which have been conveyed forwards for discharge to the region in front of the outlet device shall also be discharged immediately so as not to remain in the drum unnecessarily. For this purpose, the outlet device may appropriately be adapted to cooperate with the feed member which quickly feeds the grain or corresponding goods to the region in front of the outlet device.
Within the scope of the above-mentioned general object of said embodiment, it is also an object to form the outlet device so that grains or corresponding goods are substantially prevented from rotating with the drum for another revolution or part of a revolution as soon as the goods intended for discharge have been fed forwards to the region in front of the outlet device.
It is also an object to be able to direct a stream of air in the opposite direction to the discharge direction for grain or corresponding goods so as to blow away any remaining husks or straw components from the grain material.
These and other objects can be ahcieved in that the method and the equipment are carried out in accordance with the features in the following patent claims.

BRIEF DESCRIPTION OF DRAWING

The invention will be described below with reference to the accompanying drawings, in which

Figure 1 constitutes a basic diagram of the equipment according to the invention.
Figure 2 shows a side view of a device included in the equipment which consists of an integrated primary drier, threshing mechanism and separating mechanism for chopped cereals, according to a first preferred form of embodiment of the invention.
Figure 3 constitutes a section III-III in Figure 2.
Figure 4 constitutes a section IV-IV in Figure 3.
Figure 5 shows on a large scale a cutaway portion of the separation section.
Figure 6 shows diagrammatically the internal parts of an integrated primary drier, threshing mechanism and separating mechanism included in the installation, according to a conceivable embodiment of the invention.

In some of the Figures, the various parts are shown more or less diagrammatically, and certain parts have even been omitted so that what is important for an understanding of the invention may stand out better.

BEST MODE OF CARRYING OUT THE INVENTION

The installation illustrated diagrammatically in Figure 1 comprises three drying devices, namely a device 1 which is an integrated primary drier, threshing mechanism and separating mechanism for chopped cereals, a secondary drier 2 for straw and chaff and a grain drier 3 for the final drying of the grains which are separated in the first device 1.
The integrated device 1, which will be described in more detail later with reference to Figures 2-5, can be divided into the following main parts, namely a mixing chamber 4 for drying air, a feed pipe 5 for the crop which is chopped but otherwise untreated to a primary drier 6, a separating section 7 which together with the primary drier also forms a threshing mechanism, and an outlet device 8 for grain between the primary direr 6 and the separating section 7. The primary drier 6 and the separating section 7 have the form of a coherent rotatable drum with a horixontal axis of rotation.
A screw conveyor 9 is adapted to feed chopped crops from a container 10 into a feed pipe 5 in the device 1. A belt weighing device is designated 11, a screw conveyor is designated 12 and a lock is designated 13. There is also a member 82 to regulate the feed of the conveyor 9 of goods out of the container 10 depending on the amounts recorded by weight.
Disposed after the drying device is a so-called outlet box 14 which is connected to an opening 83 in the front end of the separating section 7. A suction fan 15 and a cyclone separator 16 are connected to the outlet box 14. A conveyor 14A connects the outlet box 14 to a feed pipe 19 to the secondary drier 2. A lock 20 is disposed between the conveyor 14A and the secondary drier 2. A mixing chamber 21 for drying air is disposed in the front end of the secondary drier 2. The actual drying section in the device 2 has the form of a rotating, horizontal drying drum 22 and can be of the known type of through-flow drier for hot air. Also disposed after the secondary drying drum 22 is an outlet box 23 with a section fan 24 which is adapted, via a heat exchanger 25 and a cyclone separator 26, to separate small amounts of chaff from the conveying air and combustion gases. Separated chaff is conveyed via a lock 27 to a chaff line BL for the production of fodder cakes or pellets. The cooled waste gases from the cyclone separator 26 are drawn off in a chimney, while air heated in the wastegas heat exchanger 25 is used in the grain drier 3. The main part of the medium-weight parts of the crop which are rich in cellulose, mainly parts of straw collects in the bottom of the separating box 23. A conveyor 28 is adapted to convey this material for further treatment in a straw line HL, where the material is conditioned, for example mixed with liquor and/or molasses for fodder purposes, after which this material is also formed into fodder cakes or pellets. Furthermore, the main part of the chaff is separated in the lower portion 29 of the separating box 23 in a stream of air generated by a fan 30 which conveys separated chaff to a cyclone separator 31, after which the chaff is conveyed to the chaff line BL.
The outlet device 8 for grain is disposed in the region of a grain discharge opening 33 running round the shell of the drum at a distance behind a contraction flange 32 between the primary drier 6 and the separating section 7 in the back portion of the separating section 7. The outlet device 8 is connected, via a lock 34, a discharge conduit 35, and a coarse cleaning machine 36, to the grain drier 3. Furthermore, an inlet pipe 37 for fresh air is connected to the outlet device via a damper 38 to regulate the flow of fresh air through the pipe 37 into the outlet device 8 and from there through openings 33 into the separating section 7. The main part of the straw and chaff which has accompanied the grain into the outlet device is separated in the coarse cleaning machine 35. This cleaned portion is conveyed to the feed pipe 19 of the secondary drier.
The combustion furnace 17 can be fired with any fuel such as oil, gas, coal, wood and/or with products which are separated in the installation described. A fan 41 is provided to blow combustion gases into the mixing chamber 21 of the secondary drier 2, while a fan for blowing colder fresh air into the mixing chamber 21 is designated 42. Inside the secondary drying drum 22 there is a temperature measuring device 43 which delivers a temperature measurement to a regulating device 44. The regulating device 44 is in turn adapted to regulate the drying process by acting on a flow regulating valve 45, 46 disposed in each connecting pipe for hot flue gas and colder fresh air respectively.
Also disposed in the primary drier 6 in the device 1 is a temperature measuring device 47, more specifically immediately in front of or possibly in the region of the contraction flange 32, that is to say before the separating section 7. A regulating device, designated 48, is adapted to be able to regulate the flows into the mixing chamber 4 of hot air and cold air respectively, depending on measurements from the measuring device 47, by acting on a pair of flow regulating valves 49 and 50 in the connections 54, 55 respectively.Telemetric transmission is used for conveying the temperature values from the measuring device 47 to the regulating device 48. The hot air is adapted to be heated by the flue gases from the combustion furnace 17 in a heat exchanger 51 and is blown into the mixing chamber 5 by a fan 52. A cold-air fan is designated 53.
The device 1 will now be explained in more detail with reference to Figures 2-5. As stated, the primary drier 6 and the separating section 7 have the form of a coherent rotatable drum with a horizontal axis of rotation. The rotating drum is designated 60 in Figures 2 - 4 and is adapted to be rotated by a motor 61 about the horizontal axis rotation. The drum 60 rests against two pairs of rollers 62 which are supported, via bearing pedestals 63 by a base 64.
The primary drier 6 is provided, at the inside of the drum 60, with lifting laminations (not shown) in the form of pieces of plate directed radially inwards.
In the region in front of the outlet device 8, the drum 60 has an opening 33, Figures 1 and 4. The opening 33 consists of a gap between the drying section 6 and the separating section 7. The gap is unbroken which means that the opening 33 extends round the whole periphery of the drum. Outside the opening 33 there is disposed an annular construction 66. This consists of two angle irons 66A and 66B which have been bent into ring form with the webs of the irons facing one another and with the arms facing away from one another as seen in Figure 4. Disposed between the irons 66A and 66B are a plurality of guide-rail-shaped intermediate members 18, a pair of which are designated by 18A and 18B in Figures 3 and 4. Each intermediate member 18 extends from the outside of the drum 60 to the tip of the right angle of the angle iron. At the same time, each intermediate member 18 extends uniformly backwards in relation to the direction of rotation of the drum 1. The direction of rotation is designated by arrow A, Figure 3. The intermediate members are also somewhat convex as a result of which the construction 66 has an appearance reminiscent of an impeller or a water-wheel. The annular construction 66 thus formed is welded to the outside of the drum 60 over the opening 33 and so connects the drying section 6 and the separating section 7.
Disposed outside the ring 66 is an outlet cover, generally designated by 67. The purpose of the cover 67 is to shield the opening 33 from the environment and to connect the opening 33 to the discharge pipe 35. The outlet cover 67 comprises a discharge box 68 disposed outside the ring 66 within the sector of a circle which corresponds to the fourth quadrant of the circle with respect to the direction of rotation of the drum 60, Figure 3. The box 68 also covers a small portion of the end of the fourth quadrant of the circle. The box 68 is formed of front and back plates 68A, 68B and a pair of side plates, and the back and front paltes 68A, 68B converge to match the shape of the discharge conduit 35. Extending round the main portion of the ring 66 there is also a sheet-metal strip 70. The covering strip 70 is disposed at a very short distance from the ring 66 so that there is a narrow gap 70A between the covering strip 70 and the two arms 66C and 66D of the ring 66. The covering strip 70 is connected, by its longitudinal edges, to the outer ends of the web on a pair of angle irons 71A and 71B respectively. The angle irons 71A, 71B extend round the first and second quadrants of the circle, Figure 3, as well as the main portion of the third quadrant and their ends are also connected to a pair of portions 71C and 71D of the front and back walls 68A and 68B respectively of the outlet cover 68. The irons 71A and 71B together with extensions 71C and 71D are also connected to one another by a plurality of bolts 71E. The outlet cover 67 thus formed is mounted on the base 64 in a manner not described in the Figures. The discharge box 67 is thus mounted fixed in space while the drum 60 together with the ring 66 is adapted to be able to rotate inside the discharge box 67. In order to seal the cover against the environment, a pair of rubber seals 71F are disposed between the angle irons 71A and 66A and between the angle irons 71B and 66B respectively.
The separating section 7 is cylindrical and is clad internally with spiral threads 80 consisting of sheet-metal strips, twisted in spiral shape and directed radially inwards and welded to the inside of the drum 60, Figure 5. The threads extend along the whole cylindrical separating section 7, that is to say from the discharge opening 83 to the discharge opening 33. Disposed at a certain distance from each spiral thread 80, calculated with respect to the opening 33 is a helical row of carriers 81 consisting of pins directed radially. The pins 81 are welded to the inside of the drum 60 and are so tightly placed in the individual rows that pieces of straw which are lying crosswise cannot pass or can only do so with difficulty, while grains can pass through easily. Each row thus forms a sort of helical "rake" which can entrain long objects such as pieces of straw but to a considerably lesser extent can entrain objects consisting of finer particles such as grains, when the drum 60 rotates.
The mode of operation of the equipment described will now be explained in more detail. The chopped crops are discharged from the silo 10 by means of the screw conveyor 9 and weighed on the belt weighing device 11. The discharge from the silo 10 is controlled by means of the regulating equipment 82 so that a relatively even flow of crops is obtained. The crops are fed via the lock 13 and pipe 5 into the primary drier 6 where they meet the hot air flowing through from the mixing chamber 4. In the primary drier 6, the crops are tubled round by the said paddles when the drum 60 is rotated. The paddles lift up the chopped crops in a manner known per se and then let them fall down again into the hot air flowing through which afterwards advances the material forwards towards the constriction 32. The temperature of the air flowing through is measured by the temperature measuring device 47. The temperature of the air flowing through is regulated by means of the device 48 by adjusting the valves 49 and 50 in the pipes 54, 55 for hot air and cold air respectively. The total flow of air is maintained constant, however. Thus the temperature in the primary drier 6 is regulated so that the superficial moisture in the goods is removed to such an extent that the grains can be threshed out while the material advances forwards in the primary drier 6.
When the crops reach the constriction 32 in the region of the contraction flange, the grains are thus mainly threshed out. In the constriction, the material receives an increase in speed as a result of the fact that the air speed increases. In the course of this, the air flowing through entrains the lighter parts to a greater extent than the heavier grains, as a result of which a first separating effect is achieved. The threshing then continues in the separating section 7 to the extent that this has not already been completed in the primary drier 6. The material, particularly the straw parts, are lifted up by the pins 81 which form a helical row 76 in front of each spiral thread 80. As a result of the fact that the pins 81 in the individual rows 76 are relatively close together, the entrainment means (the pins 81) entrain primarily the straw while the grains, on the other hand, can pass to a considerable extent between the pins 81. As a result of this, a second separating effect is achieved. The material which is fed up along the walls of the drum 60 by means of the pins 81 has therefore been further impoverished with regard to grains and when the entraining material falls down into the stream of air in the separating section 7, this material is thrown to a greater extent than remaining heavier grains in the direction of the discharge openings 83. By this means, a third separating effect is achieved.
As a result of the rotation of the drum, the grain also tends to accompany the drum up the walls in the direction of rotation to a certain extent. At the same time, however, they fall down by their own weight - a fourth separating effect - and are forced by the spiral conveyors 81 towards the outlet opening 33. The grains therefore accumulate in the part of the drum which corresponds to the fourth quadrant of the circle when the drum is considered in the axial direction and the drum rotates in counter-clockwise direction, Figure 3. Thus the grains, which are generally disignated by X in Figure 3, reach the discharge opening 33 in the region in front of the discharge box 68. In this region, the intermediate members 18, such as the intermediate member 18C, are at first substantially horizontal to be adjusted more in the vertical direction at the end of the discharge box 68, that is to say when the intermediate members approach the front wall 68A. This means that before each intermediate member 18, such as the intermediate member 18D, leaves the discharge box 68 in counter-clockwise direction, the intermediate member 18D in question together with the next following intermediate member 18E form a substantially vertical channel 77A between them. The next following channel 77B is less pronouncedly vertical while the following channel 77C is not so at all. Air flows in the direction of the arrows B through all the channels 77A, 77B and 77C, which are constantly displaced to make room for new intermediate members 18 and new intervening channels. Through the first channel 77C, where the flow of grains is comparatively little in view of fact that the intermediate members 18C and 18D are more or less horizontal, the flow of air thus has an almost pure separating effect in that the air blows away any remaining husks and other lighter particles which have accompanied the grains to the discharge opening 33. The stream of air likewise has a separating effect in the following openings 77B and 77A, but the primary function of these openings is to discharge the grains X which also takes place very effectively because there the openings 77A and 77B are disposed nearly vertically.
The total effect is therefore that the predominant proportion of the lighter components, that is to say straw and chaff, is blown out through the discharge openings 83 in the far end of the separating section 7, while the grains are discharged into the outlet box 68 through the openings 33 in counter-current to the air which is continuously blown in through the conduit 37. Thus the grains may describe a reciprocating movement which in certain cases can even be repeated a number of times so that the duration of stay for some of the grains in the separating section 7 cannot be ignored. As a result of the fact that colder air is continuously blown in from the pipe 37 via the outlet box 68 and the discharge openings 33, however, the temperature in the separating section 7 is kept at such a low level that damage to the grains can be avoided completely.
The straw and other components of the crop which passed through the discharge opening 83 into the outlet box 14 are conveyed to the secondary drier 22 by means of the screw conveyor 18 and the pipe 19. Hot air from the air mixer 21 flows through the secondary drier 22. In the same manner as in the primary drier 1, the temperature in the secondary drier is regulated by adapting the flows of hot and cold gases by means of the valves 45 and 46. The combustion gases from the combustion furnace 17 are used as hot air. Before that, however, the combustion gases are used in the neat exchanger 51 to heat the air for the primary drier 1. Warm air from the cyclone separator 16 and/or 26 is used as secondary air for the combustion furnace. Thus the gas system of the installation is integrated to a great extent which affords a very high degree of energy utilixation. With regard to the method of operation of other parts of the installation described with reference to Figures 1 - 5, no special explanation is needed.
With reference to Figure 6, a rotatable drum is designated by the numeral 160. The drum 160 corresponds to the drum 60 in Figure 2. A primary drier and a separating section are designated 106 and 107 respectively. The former, as in the previous form of embodiment, is provided with lifting laminations 165 in the form of pieces of plate directed radially inwards and possibly scoop-shaped. According to this form of embodiment, the separating section 107 consists of four sections 107a, b, c and d. Disposed between the primary drier 106 and the first section 107a is a first contraction flange (orifice plate) 132a. Disposed between the first and second section 107a and 107b respectively, is a first line of discharge openings 133a, which are evenly distributed along the periphery of the drum 160. Disposed between the second and the third sections 107b and 107c respectively, is a second orifice plate 132b, and disposed between the third section 107c and the last section 107d is a second line of discharge openings 133b like the openings 133a. Outside the discharge openings 133a and 133b is an outlet device provided for each line of openings or alternatively a common outlet device (not shown in the Figure). The discharge openings 133a and 133b, respectively, may also be displaced by a gap embracing the shell of the rotating drum in a manner corresponding to the foregoing embodiment.
All the sections in the separating section 107 contain helically wound entrainment means of the same type as the element 80 in Figure 5. In Figure 6 the corresponding element is designated 180a, b, c and d with reference to the sections 107a, b, c and d. The elements 180a, b, c and d are only shown diagrammatically. The direction of the thread of the helical elements 180a and 180c in the sections 107a and 107c respectively is such that with normal rotations of the drum 160 they tend to drive material forwards in the direction of the arrows towards the discharge openings 133a and 133b respectively. In the sections 107b and 107d, the helical elements 180b and 180d are threaded with the opposite hand so that with normal rotation of the drum, they drive material backwards, see arrows, towards the openings 133a and 133b. In the last two sections 107c and 107d, pins 181c and 181d respectively are also disposed in rows 176c and 176d respectively, at a distance from the helical elements 180c and 180d respectively calculated with respect to the second line of discharge openings 133b. The object of the developed form of embodiment according to Figure 6 is to make more effective the separation of grain and straw components. With regard to the working principle, reference should be made to the basic principles which were described with reference to the previous form of embodiment.

Claims

1. A method of treating chopped crops containing on the one hand grains or other seed, such as peas, beans etc., and on the other hand other plant components, characterized in that the goods are introduced into a separating section (7), through which air flows, in a rotating drum (60), and that the temperature of the air entering the separating section is regulated so that the grains or the like can be separated without the grains being damaged by prolonged overheating.

2. A method as claimed in claim 1, characterized in that the goods are subjected to a certain amount of drying and threshing before being introduced into said separating section, by being conveyed through a primary drier (6) in a rotating drying drum, which preferably constitutes a drum (60) which is integrated with the separating drum and through which hot air is blown in the direction of conveying of the goods through the drum, and that the goods are then treated at a considerably lower air temperature in the separating section than in the primary drier, during which latter treatment the threshing is completed to the extent to which it is not already completed, while at the samt time the grains are separated from the lighter components of the goods and that the grains and the lighter components are then finally dried in separate driers (2 and 3 respectively)..

3. A method as claimed in claim 2, characterized in that the lighter components are divided into a medium light fraction represented by plant components of the type of straw, stem or stalk components and a very light fraction represented by plant components of the type of husks, flower and leaf components, and that said division is preferably carried out mainly after the final drying of the lighter components.

4. A method as claimed in claim 1, characterized in that the goods in the separating section are lifted up by entrainment means on the inside of the drum, which preferably lift up longer portions of the goods which then fall down again, while the goods are ventilated and exposed to threshing work, while at the same time the lighter components are blown by the air flowing through towards a discharge opening (83) in the far end of the drum to a greater extent than the heavier grains, which instead are conveyed by oblique, preferably helical members (80) towards one or a number of grain discharge openings (33)ein the shell of the drum at least substantially encircling said drum, and that air is continuously introduced into the separating section through said discharge openings, the separation of the lighter goods from the grain material which is discharged being made more effective.

5. A method as claimed in claim 1, characterized in that the air temperature is measured before entry into the separating section and that the temperature of the air entering the primary drier is regulated by regulating the mixing proportion between hot air and colder air with a constant flow of air into the primary drier, the hot air preferably being obtained by heating in a heat exchanger with combustion gases from the combustion furnace (17), and that the combustion gases are then appropriately used in a secondary drier (2) to dry further the lighter products separated from the grains in the separating section, the hot combustion gases preferably being mixed with colder air before it is introduced into the secondary drier in a mixing proportion which is regulated depending on the temperature in the secondary drier.

6. A method as claimed in claim 2, characterized in that the main part of the lightest goods, the chaff fraction, is separated from the rest of the lighter components in discharge casings (14, 23) with a forced stream of air, so-called aspirator, connected to the remote discharge end of the secondary drier.

7. A method as claimed in one of the preceding claims, characterized in that the grains or corresponding particles in the separating section are discharged through at least two discharge openings or lines of discharge openings disposed spaced apart in the axial direction and at least substantially encircling the drum, and that the grains or the like which are to be discharged through said openings are fed forwards and backwards from both directions towards the discharge openings.

8. An equipment for treating chopped crops, comprising a rotatable drum (60) with a separating section (7) with a discharge opening (83) for the lighter components of the threshed crop in the far end of the separating section, and means (52, 53) for blowing air through the separating section, characterized in that the separating section (7) is provided on the one hand with entrainment means (81) fixed to the inside of the drum and adapted to lift up the crop when the drum is rotated and to release the goods down again afterwards into the stream of air which is passing through the drum, and on the other hand with oblique conveying members(80) preferably helical members, fixed to the inside of the drum and adapted, on rotation of the drum, to convey goods towards a grain discharge opening encircling the drum or a plurality of grain discharge openings (33) distributed round the drum in the separating section.

9. An equipment as claimed in claim 8, characterized in that the entrainment means (81) comprise elements with a short extent in the axial direction, preferably radially directed pins, which may appropriately be disposed in rows, preferably helical rows, which form rake-like entrainment members with the capacity to entrain primarily elongated products, such as straw components, while the grains can pass between the elements in said rows.

10. An equipment as claimed in one of the claims 8-9, characterized in that the discharge openings for the grains are at least two openings encircling the drum or are disposed in at least two lines round the shell of the drum and that said oblique conveying members are adapted to feed the grains or corresponding heavier products towards the discharge openings from both directions.

11. An equipment as claimed in one of the claims 8-10, characterized by a construction (66) extending round the periphery of the drum, a stationary cover (70) which extends round the drum outside said outlet opening (12), and wherein said cover is adapted substantially to close the opening/s over the major portion of the periphery so that the passage out of goods and the passage in/out of air through the opening/s is substantially prevented when it/they are within said region of the cover, but within the remaining sector goods and air can pass through the portion of the opening or openings present there.

12. A device as claimed in Claim 11, characterized d in that said sector substantially only comprises the fourth quadrant of the circle in an imaginary section through the drum at right angles to the axis of rotation of the drum and with the drum rotating in counter-clockwise direction.

13. A device as claimed in one of the Claims 8-12, characterized in that said opening (33) consists of a gap which extends round substantially the whole periphery of the drum beL- ween two sections of the drum, and that the two sections are connected together by a plurality of intermediate members (18) in and/or outside the gap, which intermediate members have a small extent in section parallel to the shell of the drum.

14. A device as claimed in Claim 13, characterized in that said intermediate members have the form of rails, like the rails in an impeller, directed outwards and backwards in relation to the direction of rotation.

15. A deivce as claimed in one of the Claims 13 and 14, characterized in that the channels between said rails are adapted to be flowed through by air in a direction towards the goods which are discharged through the same channels.