EP4553433A1

EP4553433A1 - Improved grain dryer

Info

Publication number: EP4553433A1
Application number: EP24208601.5A
Authority: EP
Inventors: Marcelo Norberto Valfiorani
Original assignee: Ingeniera Mega SA
Current assignee: Ingeniera Mega SA
Priority date: 2023-11-09
Filing date: 2024-10-24
Publication date: 2025-05-14
Also published as: AR131020A1

Abstract

Improved grain dryer that allows to carry out the drying process in ideal conditions of temperature - humidity, thus obtaining a better quality of grain, achieving a significant reduction in energy consumption, and more particularly avoiding any type of condensation of moisture from the air supplied in the drying process that can generate harmful muds both for the operation of the equipment of the invention and for the environment.

Description

Field of the invention

The present invention relates to the field of agroindustry, and more particularly relates to an improved grain dryer which, unlike conventional dryers, allows the grain drying process to be carried out under ideal conditions of humidity and temperature, improving the quality of the grains and notably reducing energy consumption, being even more particularly that it avoids condensation of the moisture present in the air supplied and consequently avoids the formation of muds which are very harmful to the equipment and the environment.
Although in the present description reference is made to an improved grain dryer of the type consisting of a column structure from the upper end of which the volume of grain to be dried is loaded, it should be made clear that the invention can be adapted and used in different types and arrangements of grain dryers either independently or in conjunction with related means, devices or arrangements.

Description of prior art

A great variety of grain dryers are known in the field of prior art, which can be classified according to the structural particularities they present for the grain displacement path and for the grain drying air circulation. Currently, among the existing dryers, it is possible to mention the column dryers, consisting of a large prismatic body inside which vertical walls made of perforated plates are defined, dividing the columns inside which the grain descends and is loaded through an upper mouth until it leaves the machine through a lower discharge mouth. The perforated walls define channels or columns within which the grain circulates, and between these columns are defined spaces for the passage of drying air that is previously heated by means of burner systems or heaters in general.
In this way, the hot air circulates through the spaces provided for this purpose, between the grain drying columns and it must enter the columns by passing through the holes in the perforated plates that form the walls of the columns, to then pass through the mass of grain and drag with it the moisture contained therein. The grain that is against one of the faces of the corresponding column tends to remain "stuck" to that face as it descends, so that in these dryers there is a shunt in the whole column that causes the grain from one side to move to the other, which results in an undoubtedly unfavorable condition during the drying process, since the grain is overheated in relation to the other grain that is next to the opposite face.
To solve these problems, dividing floors are installed that reverse the direction of air circulation, but the grain next to the perforated plate on one or the other side of the column is still much hotter than the grain in the center of the column. Consequently, the drying quality is very poor, causing a very high rate of "cracking" of the grain. In addition, these dryers have floors in the interior thereof to produce air deviations, which is a serious inconvenience since it favors the accumulation of "lights" which generates areas of very high probability of fire outbreaks, very frequent in column dryers of this type. Also, the air backpressure required in these dryers is very high, since the air must pass through the perforations in the sheets, which means that they require a high consumption of electrical energy for the operation thereof.
Although these machines have been widely used and allow large spaces for the entry of drying air between the columns containing the grain, in addition to the disadvantages mentioned above, it should be noted that they require high costs for the manufacture of multi-perforated sheets, inside the columns they form very compact masses where the circulation of the drying air is hindered, and the surface contact of the drying air with the grain is not as efficient as expected, nor do they have the desired performance.
There are other drying machines called cascade dryers, provided with a plurality of trays in a succession of levels that allow the grain entering from an upper part of the machine to fall in a cascade manner through each of the trays, while the drying air is injected and sucked to pass through the trays and come into contact with the grain. These machines only provide a central lung through which the air enters and, after passing through the trays and the grain, exits towards the periphery of the machine, so that the thermal evaporation capacity brought by the hot air cannot be used efficiently, since it must also pass through an almost compact mass that descends only through a peripheral sector of the machine. In other words, the mass of grain loaded into the machine is not sectioned into low density portions in order to obtain a more uniform contact between the mass of hot air and the mass of wet grain.
In the particular case of conventional grain dryers whose columns include a plurality of baffles arranged alternately on both side walls. These baffles have a length such that their ends converge at a central vertical imaginary line extending along the column. In this way, the flow of grains down the column continuously describes a zigzag path determined by the succession of baffles it encounters along its path. In other words, the hot air entering through each of the inlet openings of the column comes into contact with the grain, passing through the volume of the grain as it descends, and exits the column through the outlet openings.
One of the most important deficiencies in this drying process is the "interference" effect that occurs between the baffles and the volume of grain being dried. Consequently, the entire volume of grain descends continuously following an alternating zigzag path and is permanently subjected to hot air flows. In other words, the grain is subjected to the circulation of hot air over the entire length of the column, practically in the same way as in column dryers with perforated plate walls. The grain resulting from this process shows multiple surface cracks, which is a sign of low quality, precisely because it has been subjected to constant heating, without the appropriate times for the progressive and controlled evaporation of the moisture contained.
As a result of the above, the Argentinean Patent Act No. AR047849B1 of INGENIERÍA MEGA S.A. describes a grain dryer with high thermal performance and stabilized heating of the grains during the drying process, being this dryer of the type formed by a structure of columns from whose upper end the volume of grain to be dried is loaded and which then follows a downward trajectory essentially in zigzag to be subjected to streams of hot air circulating from a succession of air inlets, defined on a first side wall of the column, towards a succession of supply air outlets, defined on a second side wall, being arranged inside the column, in correspondence with each of said air inlets and outlets, respective baffles inclined downwards to orient the drying air current and determine the trajectory of the grain descending along the column, where between each pair of baffles corresponding to the respective pairs of air inlets and outlets of each column there are wall sections, at least partially facing each other, which in combination with the extension of said baffles define zones of grain accumulation and stabilization of the grain temperature, wherein the baffles of the first wall extend up to an imaginary transverse line coinciding with a longitudinally intermediate zone of the corresponding opposite section of the second wall, the ends where each of the baffles of the first and second wall of the column terminate being transversely spaced from each other, defining in the column a continuous central longitudinal zone free of interferences for the descent of the grain.
In contrast to the previous conventional dryers, in this case the volume of grain descending along the column is crossed by hot air flows spaced far apart. In other words, as the volume of grain descends along the column, it is subjected to a sequence of hot air flows that circulate exclusively between one of the air inlets and one of the air outlets, thus forming hot air currents between which temperature stabilization zones are defined where part of the volume of grain does not receive direct drying air, the temperature thereof remains practically constant, the elimination of the contained moisture is more gradual until the grain is subjected to another stream of drying air in accordance with the next pair of inlets and outlets that it encounters immediately following during its descent and so on.
As a result of this progressive heating process with temperature stabilization zones, the grain reaches a final drying with an appropriate residual moisture content and considerably less cracking than that of grains dried with conventional dryers, which is indisputable evidence of the high quality of the grain thus processed. This is possible due to the special location and extension of the baffles and the dimensional relationship of the parts operatively linked to them, so that the side walls of each column have straight sections that together define a succession of temperature stabilization zones or "tempering" of the volume of grain that accumulates during its passage over the baffles.
In other words, as the volume of grain descends along the length of each column, several special features combine during the drying process: the zigzag path of the grain volume is less abrupt than in conventional dryers; the length of the baffles determine inside the columns a central longitudinal zone free of interference for the descent of the grain; the straight sections defined on each wall of the columns between each air inlet and each air outlet allow the accumulation of a certain quantity of grains in the corresponding "tempering" zones; and the circulation of hot air occurs exclusively between each of the inlets and the respective air outlet located lower than the corresponding inlet.
Consequently, grain drying takes place through successive stages of heating and temperature stabilization, or "tempering", where the grain loses its moisture content in a regulated and homogeneous manner. The result, as already mentioned, is a grain of optimum quality in terms of the necessary final residual moisture and a considerably low cracking index.
Although the grain dryer of the Argentine Patent Act No. AR047849B1 of INGENIERÍA MEGA S.A. has proved to work correctly in practice, the high energy consumption is a factor that has not yet been solved in any of the existing conventional grain dryers. As a result of the above, the same holder developed a grain dryer according to Patent AR110492B1 , whose reference is attached hereto. Said grain dryer comprises a main vertical structure consisting of a central body through which the grain to be dried passes, an upstream chamber for hot air intake and a downstream chamber for air exhaust. The main body has in its upper part an inlet from which the wet grains are loaded, under which there is a loading hopper that communicates with the central body.
The central body is divided into several "M" modules such as M1, M2, M3, M4, M5, M6, M7, and M8. Thus, the wet grain enters through the upper inlet and descends along the central body where it is dried during its heating by the hot air that passes through the grain mass, to finally exit through a discharge hopper located at the lower end of the dryer. The air enters the chamber and is heated by means of burners. Inside the chamber there are one or more partitions that direct the air in the desired manner.
Patent AR110492B1 has the particularity that the chamber has a second vertical partition which extends beyond the height of the partition, remaining in linear adjacency with the corresponding part between modules M7 and M8. Likewise, it presents a horizontal partition transversally to the vertical partition between modules M6 and M7. The arrangement of the vertical and horizontal partitions defines two totally isolated sectors inside the chamber, being comprised by a sector A in communication with a sector B and by at least one sector G totally separated from these two.
In this way, the air that enters through the lower part of the grain dryer passes through the burners arranged in a sector Q1 and moves from sector A to sector B, which is in communication only with modules M7 and M8 through which the grain to be dried constantly descends. Simultaneously, the other part of the air that enters through the lower part of the dryer, passes through another set of burners 22 of a sector Q2, and moves towards sector G which is in communication with modules M2, M3, M4, M5, and M6. Sector G has a lower horizontal partition between module M1 and M2, so that module M1 is isolated from the rest and functions as a module or grain cooling chamber inside the dryer since it does not have any burner. In the module M1, the grains are precooled as they fall into the discharge hopper.
On the other hand, the chamber has a vertical partition that extends from the top of the dryer downwards, being in linear adjacency with the corresponding part between the module M6 and M7 and in turn, in linearity with the horizontal partition of the upstream chamber. Wherein said partition is provided at its lower end with at least one pivoting damper that operatively isolates the air flow corresponding to modules M7 and M8 from the rest. Likewise, the chamber has a fan between modules M7 and M8, thus defining an upper sector C adjacent to module M8 and a lower sector D contiguous to module M7. Sector D is in communication with a sector F arranged adjacent to modules M1 to M6, which in turn is in communication with a pair of air extraction fans. Sectors B, C and D, together with modules M7 - M8 form a grain preheating chamber when the pivoting damper between sectors C and D is closed. This reduces energy consumption.
Although Patent AR110492B1 has proven to work in practice, drawbacks have been observed due to the temperature difference between the outgoing air (with its relative humidity level) from the drying-cooling stages and the temperature at which the dust collection cyclones or secondary minor cyclones arranged on the outside of the dryer are located, particularly in areas with colder or more humid climates. As mentioned above, the outgoing air coming from the drying-cooling modules M1-M8 is expelled through the extraction fans to the outside of the dryer. In the external part of the dryer and in operative communication with the fan chambers, where the extraction fans are located, there are the respective cyclones, secondary minor cyclones and the particle discharge pipes thereof. As the cyclones and the particle discharge pipes thereof are outdoors or at ambient temperature, their temperature is much lower than the temperature of the air supplied from the drying modules and passing through the extraction fans. This temperature difference, together with the humidity level present in the air, generates condensation. Also, as is well known, this air is loaded with particles of different particle sizes and types of dust. The combination of the condensation of the humidity in the air and the existence of dust particles in it, generates muds that fall and accumulate in the internal part of the cyclone or secondary minor cyclone as well as in the ducts or pipes of particle discharge, bringing a great inconvenience since the operation of the cyclones is affected and the dust is expelled directly to the environment.
That is, the dust collection cyclones are located outside the fan chamber, so they are in contact with the ambient air. The same happens with the secondary minor cyclones and all the piping that conducts the light materials to the light materials delivery point. The air together with the light materials (dust, soil, particulates, impurities, etc.) leaves the plant loaded with humidity due to what has been removed from the grain and with a certain temperature. This air is practically saturated (almost 100% relative humidity) and when it comes into contact with the cold surfaces (especially in places with low temperature climates) of the elements described above (cyclones, secondary minor cyclones, pipes), it condenses forming muds that eventually obstruct the air and impurities conduction passages, annulling the dust separation system. This causes the machines to expel a considerable amount of light particulates that travel through the air hundreds of meters away, which is harmful to the inhabitants.
Likewise, the generation of sludge causes the propellers of the air extraction turbines to become unbalanced. This phenomenon of sludge formation and unusability of the separators is a serious current problem in areas of low temperatures, in winter periods, in regions of high relative humidity such as ports or areas near rivers or the sea, especially in places of very low temperatures during the harvest season, generating pollution in the environment.
Thus, in view of the above, it would be convenient to have a new arrangement, device or drying machine that avoids condensation and consequently the formation of harmful muds for the operation of the equipment, reducing energy consumption without affecting the quality of the grain, and optimizing the operation times of the drying process.

BRIEF DESCRIPTION OF THE INVENTION

It is therefore an object of the present invention to provide a new improved grain dryer which allows to reduce notably the energy consumption so as to provide a much faster process and with a better grain quality.
It is further another object of the present invention to provide an improved grain dryer that avoids condensation of moisture present in the air supplied outgoing from the drying modules and passing through the dust collection equipment, particles, impurities and the like thanks to the fact that the dust collection equipment is at the same temperature as the air supplied.
It is still another object of the present invention to provide an improved grain dryer having an upstream chamber of hot air inlet provided with a vertical partition of non-linear path which allows to define two sectors of variable section.
It is yet another object of the present invention to provide an improved grain dryer having a downstream air outlet chamber provided with a plurality of air/dust extraction chambers which nucleate the extraction fans and dust collection cyclones with their respective discharge pipes so as to avoid temperature differences and consequently condensation and mud formation.
It is another object of the present invention to provide an improved grain dryer of the type comprising a vertical main structure constituted by a central body through which descends a mass of grains to be dried, an upstream chamber of hot air inlet which preheats and/or dries the mass of grains as it falls through the central body, and a downstream outlet chamber of the air supplied previously passing through the mass of grains descending along the central body, being that the main body presents in its upper part an inlet from where the wet grains are loaded and a discharge hopper arranged at the lower end of the dryer, where said upstream chamber of hot air inlet comprises at least one vertical partition defining at least two sectors of variable section; and said downstream air outlet chamber comprises a plurality of air/dust extraction chambers arranged at different heights, each of which receives and directs the air supplied to the outside.

BRIEF DESCRIPTION OF THE DRAWINGS

For greater clarity and understanding of the object of the present invention, the same has been illustrated in several figures, in which the invention has been represented in one of the preferred embodiments, all by way of example, wherein:

Figure 1 shows a partial cutaway view of a grain dryer according to the prior art; and.
Figure 2 shows a cutaway view of an improved grain dryer in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures it can be seen that the invention consists of an improved grain dryer that allows to carry out the drying process in ideal temperature-humidity conditions, thus obtaining a better grain quality, achieving a significant reduction in energy consumption, and more particularly avoiding any type of condensation of humidity from the air supplied in the drying process that may generate muds detrimental to the operation of the equipment of the invention.
First of all, reference will be made to Figure 1 related to Patent Document AR110492B1 of INGENIERÍA MEGA S.A., in order to provide a better understanding of the subject matter of the present invention. It is emphasized that Figure 1 of the prior art is related to Figure 5 of said Patent AR110492B1 , the same reference numbers being used. Wherein the grain dryer of AR110492B1 comprises in general form a main vertical structure constituted by a central body 2 through which passes the grain to be dried, a upstream hot air inlet chamber 3 and a downstream supply air outlet chamber 4. The main body 2 has in its upper part an inlet 5 from which the wet grains are loaded, under which there is a loading hopper 6 that communicates with the central body 2.
The central body 2 is divided into several modules "M" such as M1, M2, M3, M4, M5, M6, M7, and M8. Thus, the wet grain enters through the upper inlet 5 and descends along the central body 2 inside which it is dried during its fall by the hot air passing through the mass of grain, to finally exit through a discharge hopper 7 arranged at the lower end of the dryer. The air enters chamber 3 and is heated by means of burners 22. Inside chamber 3 there are one or more partitions 23 which direct the air in the desired manner.
Patent AR1 10492B1 has the particularity that the chamber 3 presents a second vertical partition 102 which extends beyond the height of the partition 23, being in linear adjacency with the corresponding part between modules M7 and M8. Likewise, it presents a horizontal partition 103 transversely to the vertical partition 102 between module M6 and M7. The arrangement of the vertical partition 102 and horizontal partition 103 defines within the chamber 3, two totally isolated sectors, being comprised by a sector A in communication with a sector B and by at least one sector G totally separated from these two.
In this way, the air entering from the lower part of the grain dryer passes through the burners 22 arranged in a sector Q1 and moves from sector A to sector B which is in communication only with the modules M7 and M8 through which constantly descends the grain to be dried. Simultaneously, the other part of the air that enters through the lower part of the dryer passes through another set of burners 22 of a sector Q2, and moves towards sector G which is in communication with modules M2, M3, M4, M5, and M6. Sector G has a lower horizontal partition 104 between module M1 and M2, so that module M1 is isolated from the rest and functions as a module or grain cooling chamber inside the dryer since it has no burner. In module M1 the grains are cooled before falling into the discharge hopper 7.
On the other hand, the chamber 4 presents a vertical partition 105 extending from the upper part of the dryer downwards, being in linear adjacency with the corresponding part between the module M6 and M7 and in turn, in linearity with the horizontal partition 103 of the upstream chamber 3. Wherein said partition 105 is provided at its lower end with at least one pivoting damper 106 which operatively isolates the air flow corresponding to the modules M7 and M8 from the rest. Likewise, the chamber 4 is provided with a fan 107 between the modules M7 and M8, thus defining an upper sector C adjacent to the module M8 and a lower sector D contiguous to the module M7. Sector D is in communication with a sector F arranged adjacent to modules M1 to M6, which in turn is in communication with a pair of air extraction fans 108.
In relation to the operation, the same is sufficiently described in Patent AR110492B1 and for such reasons will not go into descriptive details about the same. Although Patent AR110492B1 has proven to work in practice, there is a major drawback mentioned in the section of the prior art related to the difference in temperature between the outgoing air from the drying - cooling stages and the temperature at which the cyclones, secondary minor cyclones and discharge pipes for light or particulate matter arranged externally to the dryer are located and subjected to room temperature, which generates the formation of sludge that is harmful to the operation of the equipment and, consequently, by not correctly fulfilling its purpose, the dust, impurity or particle is expelled directly into the environment, which is harmful to the health of the inhabitants. It is understood that the problem is sufficiently described in the prior art section and for these reasons no further descriptive details will be entered into regarding it.
As a result of the foregoing, the inventor of the present application has developed an improved grain dryer that allows drying the grain without the risk of condensation of the air supplied that damages the operation of the equipment and the environment. It is emphasized that the same reference numbers of Patent AR110492B1 will be used to describe those parts that are the same, while for those novel parts pertaining to the invention, reference numbers starting from 200 will be used.
Thus, according to Figure 2, the improved grain dryer of the present invention is indicated by general reference 201 and comprises a vertical main structure constituted by a central body 2 through which descends a mass of grains to be dried, an upstream chamber of hot air inlet 3 which preheats and/or dries the mass of grains as it falls through the central body 2, and a downstream supply air outlet chamber 4 passing previously through the mass of grains descending along the central body 2, being that the central body 2 presents in its upper part an inlet 5 - loading hopper 6 from where the wet grains are loaded and a discharge hopper 7 arranged at the lower end of the dryer.
The present invention has as a novel feature that the upstream hot air inlet chamber 3 comprises at least one vertical partition 202 which projects a large part of the height of the central body 2. The vertical partition 202 presents a deviation 203 of its path which allows defining at least two sectors of variable section on each side of the vertical partition 202. Wherein one of the sectors of variable section of the upstream chamber 3 comprises a sector A in communication with a sector B, also of variable section, being that said sector A presents in its lower part a set of burners 22 which can be operated by various types of fuels Y located in different positions without any inconvenience, while said sector B is in communication with the modules of said central body 2 and presents at least one temperature sensor of sector B 204.
Based on the foregoing, said sector A comprises a lower section A 205 and an upper section A 206, said lower section A 205 being larger than said upper section A 206. Whereas, said sector B comprises a lower section B 207 and an upper section B 208, said lower section B 207 being smaller than said upper section B 208. Thus, said upper section B 208 of sector B is contiguous and in communication with the upper section A 206 of sector A. It is emphasized that said lower section A 205 presents a lower partition A 209 that delimits the space for circulation of the incoming air through an air inlet 210 arranged in the lower part of said sector A. The lower partition A 209 defines a larger section in the vicinity of the air inlet 210 that is reduced to delimit perimetrically the burners 22, thus allowing to better direct the incoming air towards the burners 22.
By using only one set of burners or burner chamber, energy consumption is significantly reduced. This reduction in the number of burners is achieved in part thanks to the design of sectors A and B, which now have variable sections that allow maintaining the speed of the heated air and that its entry into the modules is as homogeneous as possible, unlike Patent AR110492B1 whose sectors have constant sections and that at least sectors A and G required respective sets of burners.
As can be seen in Figure 2, the sector B of variable section is positionally coincident with at least said modules M1 to M7 of the central body 2. The lower section B 207 of the sector B is specially designed to present a smaller section than the upper section B 208 so as to maintain the velocity of the air heated by means of the burners 22 and that its distribution be as homogeneous as possible. The temperature sensor B 204 will detect the temperature at which the heated air enters the modules. Although only one temperature sensor B 204 has been described, this does not imply that the invention is limited thereto since a plurality of temperature sensors may be arranged at different heights of the sector B so as to control that the temperature does not undergo large variations that may affect the grain drying process.
In this way, the air enters through the air inlet 210, is heated by passing through the burners 22 and circulates from sector A towards sector B. As there is a reduction in section in the lower part of sector B, the velocity of the heated air is maintained and allows it to enter all the modules M1 to M8 homogeneously. The heated air enters these modules M1 to M8 and passes through the mass of descending grains that are wet, drying them and continuing its circulation as supplied air towards sector C defined by the downstream supply air outlet chamber 4.
Likewise, the downstream supply air outlet chamber 4 no longer has large baffles or vertical or horizontal partitions as in AR110492B1 . The present invention provides in said downstream supply air outlet chamber 4, a plurality of air/dust extraction chambers 211 arranged at different heights, each of which receives and directs the supplied air towards the outside.
As mentioned above, said downstream supply air outlet chamber 4 defines a sector C adjacent to the modules M1 - M8 and features at least one temperature sensor 212 that controls the temperature at which the supplied air exits, while each of said air/dust extraction chambers 211 comprises at least one chamber temperature sensor 213 and an air extraction turbine - dust extractor (primary cyclone) - secondary relief cyclone - particulate discharge pipe 214 arrangement. Also, at the top of said air extraction turbine - dust extractor arrangement (primary cyclone) - secondary relief cyclone - particulate discharge pipe 214 and temperature sensor 213, a baffle 215 is provided which helps to direct the air supplied to the outside. This joint arrangement (within the downstream air outlet chamber 4) of the extraction turbines in conjunction with the dust extractors (e.g. cyclones, secondary minor cyclones) and their respective particle discharge pipes, allows the temperature of all the components to be equal to that of the air supplied from the drying modules M1 to M8, so that since there are no temperature differences, there is no possibility of condensation and consequently the formation of sludge affecting the operation of the equipment of the invention.
It is emphasized that the chamber temperature sensor 213 detects the internal temperature of the air/dust extraction chamber 211, more particularly of the air supplied circulating inside it, in order to compare it with the temperature measured through the temperature sensor 212 of sector C. Likewise, by having a plurality of air/dust extraction chambers 211 at different heights, the extraction of air supplied to the outside is notably optimized.
On the other hand, a PLC programmable logic controller is provided which is connected to the temperature sensors of sectors B, C and the air/dust extraction chambers in order to keep track of the temperatures and compare them in the case of the temperature of sector C and the interior of the air/dust extraction chambers. Although temperature sensors have been described, humidity sensors can also be provided without any inconvenience.
In this way, the invention presents a novel air distribution and outlet to the outside where the air extractors are placed in vertical position and distributed in different heights generating a better air circulation in the volume of the drying machine which is manifested in an improvement in the drying quality and in the yields, as well as in the thermal efficiency of the equipment. Likewise, the location of the extractor propellers and the light material separators (cyclone and secondary minor cyclone) inside the same module or chamber, avoids temperature differences with respect to the air supplied, thus avoiding condensation and consequently the formation of harmful muds. That is to say, by means of the invention, the temperature of the air supplied from the drying module is equalized with the temperature at which the extractors and separators are located, thus avoiding condensation and consequently the generation of mud.
On the other hand, the invention presents a variable section division between the burner chamber and the homogenizing chamber (hot air inlet to the drying module) by means of the vertical partition 202. This difference in section of the homogenizing chamber allows maintaining a constant air velocity producing a good mixture of hot air coming from the burner. At the same time, this change of section favors the correct distribution of temperature and hot air flow to each drying module.
Thus, by means of the invention it is demonstrated that not only an important reduction in energy consumption is obtained, but also a better quality of final grain is obtained with a residual relative humidity almost null and a much faster drying process that avoids the condensation of the humidity present in the air supplied out of the drying modules, thus avoiding the generation of mud that is highly harmful both for the equipment and for the environment. In this way, the improved grain dryer of the present invention is constituted and constructed.

Claims

Improved grain dryer of the type comprising a vertical main structure consisting of a central body through which a mass of grains to be dried descends, an upstream hot air inlet chamber that preheats and/or dries the mass of grains as it falls through the central body, and a downstream supply air outlet chamber previously passing through the mass of grains descending along the central body, being that the central body presents in its upper part an inlet from where the wet grains are loaded and a discharge hopper arranged at the lower end of the dryer, being the dryer characterized in that:
said upstream hot air inlet chamber comprises at least one vertical partition defining at least two sectors of variable section;

said downstream supply air outlet chamber comprises a plurality of air/dust extraction chambers arranged at different heights, each of which receives and directs the supplied air to the outside through a baffle arranged only at the outlet of each of said air/dust extraction chambers.
Grain dryer according to claim 1, characterized in that one of the sectors of variable section of the upstream chamber comprises a sector A in communication with a sector B, also of variable section, being that said sector A presents in its lower part a set of burners, while said sector B is in communication with said central body and presents at least one temperature sensor of sector B.
Grain dryer according to claims 1 or 2, characterized in that said sector A comprises a lower section A and an upper section A, the lower section A being larger than the upper section A.
Grain dryer according to any one of the preceding claims, characterized in that said sector B comprises a lower section B and an upper section B, the lower section B being smaller than the upper section B.
Grain dryer according to any one of the preceding claims, characterized in that said upper section B of sector B is contiguous and in communication with the upper section A of sector A.
Grain dryer according to claim 1, characterized in that said central body comprises a plurality of contiguous modules, being at least one of them in positional coincidence with said sector B.
Grain dryer according to claim 1, characterized in that said downstream supply air outlet chamber defines a sector C featuring at least one temperature sensor, while each of said air/dust extraction chambers comprises at least one air extraction turbine arrangement - dust extractor (primary cyclone) - secondary relief cyclone - particle discharge pipe to the outside.
Grain dryer according to claim 1, characterized in that each of said air/dust extraction chambers has a sensor.