US2259210A - Apparatus for drying materials - Google Patents

Description

Oct. 14, 1941. MODAVE APPARATUS FOR DRYING MATERIALS Filed Sept. 22, 1938 7 Sheets-Sheet l 85 \NVENTOR ANDRE MODAVE "1 W M'WATTYS.

(Pct. 14, .1941. u A. MODAVE 2,259,210

APPARATUS FOR DRYING MATERIALS Filed Sept. 22, 1938 7 Sheets-Sheet 2 55 @1 ANDRE MODAVE INVENTOK 26 Oct. 14, 1941. A. MODAVE APPARATUS FOR DRYING MATERIALS Filed Sept. 22, 1958 '7 Sheets-Sheet 3 INVENTOR ANDRE MonA'v Oct. 14, 1941. D V 2,259,210

APPARATUS FOR DRYING MATERIALS Filed Sept. 22, 1938 7 Sheets-Sheet 4 \NVEN TOR ANDRE MODAVE Oct. 14, 1941. A. MODAVE APPARATUS FOR DRYING MATERIALS Filed Sept. 22, 1938 7 Sheets-Sheet 5 \NVE'NTOR ANDRE MOD/WE ATTYS.

Oct. 14, 1941. A. MODAVE APPARATUS FOR DRYING MATERIALS Filed Sept. 22, 1938 7 Sheets-Sheet 6 INVENTOE ANDRE NODAVE ATTVS'.

Oct. 14, 1941. A. MODAVE APPARQTUS FOR DRYING MATERIALS Filed Sept. 22, 1938 7 Sheets-Sheet 7 INVENTOR W ANDRE MOOAVE (1M1 FMW' Patented Oct. 14, 1941 APPARATUS FOR DRYINGNWATERIALS- Andr Modave, Etterbeek-Brussels, Belgium Application September 22,

1938, Serial No. 231,261

In Belgium September 25, 1937 2 Claims. (Cl. 34-166) This invention relates to an apparatus for drying, by means of a current or flow of hot gas, a material which progresses during its drying.

The object of this invention is to adapt the drying of the material, in every point of its travel, to the kind 'of treatment desired.

In the apparatus of the invention, the saturation point of the drying gasis raised in the course of its travel by introducing in the current, gas containing less vapors than the latter at the spot where the introduction takes place. The gas thus introduced in the current is preferably hot gas which has not yet'absorbed vapors evolved from the material to be dried.

The raise of the saturation point can substantially be facilitated by drawing off in addition, gas which contains vapors in the course of the travel of the drying gas.

By drying according to the present invention any condensation of liquid can be prevented inside of the apparatus and upon the material to be dried, without excessively heating said material in any point of its travel and without causing said material to be carried away on account of a too high speed of the drying current. Furthermore, it reduces the duration of the drying because it accelerates the evaporation oi the liquid to be driven oil.

This invention relates further to apparatus for heating by means of a current or flow of gas, of a material which progresses during its heating.

When a material is heated in an apparatus by means of a current of hot gas, the temperature of the heated current of gas generally decreases progressively from the entrance to the exit of the 35 apparatus.

Now, it is sometimes desirable in practice to vary sharply the temperature of the heating gas in some regions of its travel and particularly to raise the temperature of said gas.

Heretofore, when a heating of this kind was needed, the material to be treated was made to pass successively in diiferent apparatuses, heated independently from one another, each of them at the required conditions of temperature. The material was consequently not shifted continuously during its heating and was exposed to a substantial cooling during its transfer from one apparatus to another. I

The present invention aims to remove these disadvantages.

According to the invention the temperature of the heating gas is varied during its travel, by introducing in the current of heating gas, gases of a temperature difiering from that of the heating 53 gas at the point where the introduction is effected.

The drying apparatus according to the invention comprises in the circuit of the drying gas at least one means for removing gas containing vapor and at least one means for introducing gas containing less vapor than that into which the latter gas is introduced.

The invention relate furthermore to a material drying apparatus in which the material to be dried progresses, during its drying under the action of a current of hot gas.

The apparatus according to the invention comprises, several fixed containers located one above another, in a tight casing in which the hot gas circulates, and communicating two by two so that the material introduced in the uppermost container may fall from one to the next, said containers being provided with material shifting means so that said material progresses in each container in the opposite direction to that adopted for one or the other of the adjacent containers.

This apparatus has the advantage that its construction is simple, comparatively cheap and not cumbersome.

The apparatus can furthermore, with advantage, be provided with gas inlet devices and gas outlet devices in various places of the casing and of said containers, which permit either the temperature of the drying current to be .varied or the temperature to be varied and the saturation point of said current to be raised.

This invention relates finally to a drying apparatus in which the material progresses by the action of screws during its drying.

In the drying apparatus of this kind, the material is generally moved by a screw secured to a rotating drum containing the material.

In the apparatus according to the invention, the material progresses in a fixed container which contains it, under the action of two adjacent screws having their axes parallel and rotating one towards the other upwards.

This apparatus causes a division and a breaking up of the lumps of the moving material by crushing said material which tends to clog up in lumps on account of its drying. In orderto increase this breaking up action, the screws have preferably different pitches. In case these screws are located inside of superimposed containers in which the material circulates successively, while reversing each time its direction, the screws are driven in a very simple way and without great resistance, as follows: the screws contained in two fixed containers located immediately one above the other and rotating in opposite directions are secured to toothed wheels mounted in the same plane and driven by a driving chain passing around them, the toothed wheels of the screws which are placed one above the other and which rotate in the same direction being located in different planes.

Other features and details of the invention will appear in the following description of the accompanying drawings which represent diagrammatically and only by way of example an embodiment of this invention.

Figure 1 is a diagrammatical vertical and lon itudinal section of an apparatus according to the invention.

Figure 2 is a vertical and longitudinal section of a modification, taken along line II-II of Fig-' ure 3.

Figure 3 shows in plan said apparatus without the screw driving mechanism.

Figures 4 and 5 are vertical sections taken along lines IV-IV and V--V respectively of Figure 3, up to the heating furnace level exclusively.

Figure 6 shows at a greater scale the part of section IV-IV at the level of container 4.

Figure 7 is a diagrammatic plan of two adjacent screws causing the progress of the material in one container.

Figure 8 is a lateral view of a modification of one of the screws which convey material.

Figure 9 is a front view of driving mechanism for the conveying screws of the apparatus according to Figures 2 to 5.

Figure 10 is a perspective view of a plant of several juxtaposed drying apparatus.

In these various figures, similar reference characters refer to identical elements.

Referring to Figure 1, a drying apparatus is shown comprising four fixed superimposed containers indicated by 2, 3, 4 and 5. These containers communicate with one another through ducts 6, 1 and 8. The material to be dried is introduced at one end of the uppermost container 2 by means of a hopper 9 and progresses towards the opposite end, where duct 6 opens, due to the rotation of screws, only one of which is shown in In. The material is conveyed in the opposite direction in the container 3 immediately below compartment 2, by means of the rotation of screws such as II the thread of which is directed in the opposite way of the thread of screws such as I. In the containers 4 and 5 are mounted screws such as l2 and I3 similar respectively to screws l and H.

The various containers 2 to 4 are mounted in a tight casing divided in as many compartments as there are containers. The containers of the apparatus shown are indicated by l4, l5, l6 and I1. A partition I8' separates the compartments 4 and I5, a partition l9 separates the compartments i and I5 and a partition 26 separates the compartments l6 and I1 while a partition 2| acts as the bottom of the lower compartment l1.

The compartments l4 and I5 communicate with one another through lateral ducts such as 22 which connect two of the adjacent ends of these compartments while compartments l5 and 6 communicate with one another by means of ducts such as 23 located at the other end. Ducts such as 24 connect the compartments l6 and I1 under the same conditions as the compartments I 4 and I5 communicate with one another through ducts 22.

The end of the lowermost compartment l1 opposed to that where the ducts 24 open is connected by means of a flue 25 to a furnace 26, while the end of the uppermost compartment l4 opposed to the end where the ducts 22 open is connected by a short pipe 21 with the interior of the uppermost container 2.

The lowermost container 5 is provided with a means for the outlet of the gases contained therein into a main 28 with which a fan 29 is connected which draws the gases from said main. This drawing off means comprises for example a duct 30 in which a means controlling the flow of gas which should pass through it, is mounted. This controlling means is shown as a throttle 3|. The other containers 4, 3 and 2 and the compartments l1, l6, l5 and M are. also provided with a drawing ofl means constituted by a duct indicated respectively by 32', 33, 34, 35, 36, 31 and 38. Each of these ducts contains a fiow controlling means shown as a throttle and referred to respectively by 39, 46, 4|, 42, 43, 44 and 45.

The furnace 26 communicates also with a main 46 by means of a flue 41. The main 46 can be connected with each of the containers 2, 3, 4 and 5 and with each of the compartments l4, l5, l6 and I1 by means of gas introducing means constituted by a duct indicated respectively by 48, 49, 50, 5|, 52, 53, 54 and 55. In each of these ducts, there is a controlling means which controls the gas allowed to pass and which is shown as a throttle and indicated respectively by 56, 51, 58, 59, 66, 6|, 62 and 63.

In each of the ducts 48 to 55, between the respective throttle and the main 46, opens a nozzle shown respectively as 64, 65, 66, 61, 68, 69, 18 and 1|. Each of these nozzles opens, on the other hand, in the atmosphere, which provides a cold gas supply as compared with the furnace 26.

In each of the nozzles 64 to 1|, an organ has been provided, which controls the flow which may pass and which is shown in the form of a throttle indicated respectively by 12, 13, 14, 15,

16,11, 18 and 19.

The flueg 25 and 41 are further provided with air inlets 30 and 6| and with fiow regulating means 82 and 83. In addition, fiues 25 and 41 are provided with hot gas flow regulating means indicated by H 4.

The material introduced in the apparatus through the hopper 9 passes in succession in the container 2, the duct 6, the container 3, the duct 1, the container 4, the duct 8 and the container 5 before being discharged by means of a gutter 84. In practice, charging through hopper 9 and discharging through gutter 84 are carried out so as to prevent any entrance of air in the apparatus.

Drying is carried out by the heating of the material by the gases which circulate first at the outside of the containers 2 to 5, following a circuit hereinafter called primary circuit and afterwards in the inside of said containers following a circuit hereinafter called secondary circuit."

The hot gases of furnace 26 are introduced in the apparatus through flue 25, after having, if desired, their temperature lowered to the desired degree by introduction of air at 60. From the lowermost compartment l1 in which they are introduced, they pass through the ducts 24, the compartment I6, the ducts 23, the compartment l5, the ducts 22 and the compartment l4. During their entire displacement, they travel at counter-current to the material which moves in the containers they come in contact with from the outside.

' oi the throttle 83,

From the upper compartment II, the gases enter the uppermost container 2 through the duct 21 and thence they travel parallel with the material to be dried and in the same direction until glsiey are drawn out through duct 38 in the main The relative speed of gases and material is thus equal to the difierence of their absolute speeds, which tends to prevent the dried matter from being carried away. This advantage is most noticeable in the ducts 6, 1 and 8 where the speed of the falling material is substantially greater than the speed of progression in the containers under the action 01' the screws.

During their travel in contact with the material, the drying gases become loaded with vapor. In proportion as they absorb vapor they approach their saturation point. In order to avoid condensations, they can be maintained below that point, by the introduction of hot gas, proceeding from the furnace 26, and which consequently is not yet loaded with vapor. An introduction of that kind has been shown diagrammatically in the duct 58 by the opening of the throttle 58. The temperature of the additional gas thus introduced in the secondary circuit at the end of the container 4 depends not only upon the temperature of the gas coming out of the furnace 26 but also upon the extent of opening which allows the air to enter the flue 47. The temperature of the gas introduced into container 4 can, if desired, be exactly controlled by opening more or less the throttle 1'! inside of the nozzle 69 which opens into duct 58.

It should be noted that the raise of the saturation point of the drying gas which comes into contact with the material must not necessarily be accompanied by a raise of temperature. In case the material is dried at a relatively low temprature, the introduction of atmospheric air. even when colder than the gas circulating in the apparatus, could have as a result a raise of the saturation point in spite of the lowering of the temperature of the mixture. The nozzle 14 which introduces the atmospheric air should in such case open in duct 50 down stream of the throttle 58.

The raise of the saturation point of the drying gas is facilitated by the removal of vapor loaded gas, which takes place through the duct 48, due to the opening of the throttle 33. The withdrawal thus made has as a result the lowering of the speed of the gas down stream and prevents thus the dry material from being carried away by the introduction of new quantities 01' hot gas.

Due to the different ducts connected between the containers 2 to 5 and main 46 on one hand and main 28 on the other hand, the drying gas can easily be maintained in a state such that no condensation takes place in the apparatus. Thereby not only the apparatus is better preserved, but a quicker and more extensive drying is attained. According to this invention, the slimes of coal washing plants containing up to 50% water can easily be thoroughly dried.

The apparatus shown in Figure 1 allows also the reheating of the drying gas while it strikes along the outside of the containers containing the material to be dried. Such a reheating can for example be carried out, by opening the throttle 88, which allows the entry in compartment H of hot gas, the temperature 01' which can be controlled by the opening of the throttle I6.

The reheating of the gas in the primary circuit is necessary not only to maintain the gas at the desired temperature up to the end or the primary circuit without superheating at the beginning at said circuit but also to cause a sharp rise in some places of the circuit.

When treating products there may be indeed an interest in heating first moderately and afterwards more intensively. This may be the case when the heating gives rise to a chemical reaction or to a series of chemical reactions.

Assume two bodies in presence which should react during their passage through the apparatus, the reaction starting only when primed by raising the bodies to some given temperature. If the reaction evolves heat, it may be necessary to moderate the heating down stream of the spot where the reaction has started. If then another reaction should take place (for example after addition of other bodies) and if that new reaction takes place only at a temperature higher than'that reached during the first reaction, it becomes necessary to heat more intensively down stream of the place where the first reaction came to its end. The apparatus shown in Figure 1 allows perfectly a heating of that kind to be carried out even when the main purpose is not to dry the material.

Some gas inlet ducts and gas outlet ducts may theoretically be considered as superseding other ones because they open in places of the heating circuit between which there is practically no change of state of the gas. Thesame applies to all the ducts opening in the containers, such as 2 to 5 or in the compartments such as H to II, near the duct connecting two adjacent containers or two adjacent compartments with one another.

It may however be considered that in practice the use of two ducts near a connection between two containers or two compartments may allow control of the inlet or the outlet of gas more accurately than it would be possible with one single duct. If such an accuracy is not needed the throttle of only one of both ducts is of course opened.

In Figure 1, the various compartments are shown as if they were identical and consequently interchangeable. In practice, the lowermost compartment could of course be made without any duct such as 32 serving to connect it with main 28. If said compartment is provided with a duct 32, its throttle 39 is of course kept closed to prevent the direct passage into the main 28 of the heating gases coming from the furnace 26.

As a principle, the apparatus shown in Figures 2 to 5 is identical to the apparatus diagrammatically shown in Figure 1.

There are two mains 46 for the additional heating gases, one on each side of the same end of the compartments and containers. There are also two mains 28 for conveying the gases to the fan 29. These two mains are located at the other end of the compartments and containers. The ducts 22, 23 and 24 which connect two adjacent compartments are also distributed on either sides of the compartments so that the gases split into two symmetrical currents rei'erring to the middle vertical and longitudinal plane of the apparatus.

Each of the containers 2 to 5 comprises a closed trough, such as trough la (Figure 6) suspended by means of angle irons and bolts 86 on a plate which serves as a cover for said con- 7 serves at the same time as the bottom tainer and rests on the flanges of angles 01 mounted upon the interior side of the lateral walls 88 of the casing in which the container 4 is placed. The cover plate of the trough 41;

the compartment I5.

The progression of the material in each trough is brought about by the rotation of two adjacent screws having parallel axes and turning, one towards the other upwards.

The screws mounted in container 4 are indicated by I2 and I2. They turn respectively in reverse directions, as shown by the arrows X and X in order to lift the material between them while conveying it forward. Owing to this movement of the screws, the matter displaced by the screw I2 is crushed against the matter displaced by the screw I2. This crushing has a great advantage every time the material tends to clog during its drying as is the case in drying clay containing slimes.

In order to increase this crushing and consequently the breaking-up of the lumps, the screw I2 is given a slightly different pitch from that of screw I2.

Figure '7 shows as an example a screw I2 having a slightly greater pitch than screw I2.

Th screws I0 and I0 in the container 2, the screws II and II in the container 3 and the screws I3 and I3 in the container 5 are similar to screws I2 and I2 in the container 4 and work under the same conditions.

Experience proves that the breaking-up of the material is more eilicient when screws l0 to I3 and I0 to I3 are made discontinuous. Each screw comprises then, as shown in Figure 8, a plurality of blades 89 inclined in respect to the axis of the shaft 90 on which they are secured. In practice these blades need not to have helical surfaces but they can be made of simple plane sheets inclined in respect to the axis of the shaft 90.

The ends of th shafts of both screws mounted in the same container pass through plates such as 9I (Figures 2 and 6) which close openings 92 left in walls 93, located at the ends of the containers 2 to 5 and of the compartments I4 to II. These openings 92 are great enough to allow the passage of the two screws in front of which they are managed.

The plates 9I carry bearings for the trunnions of the screw shafts. These bearings can, if necessary, easily be cooled by water circulation.

To rotate the various screws I0 to I3 and I0 to I3 in the proper direction, a particularly simple and efficient mechanism has been provided.

The shafts of the screws such as I0 and II', which turn respectively in opposite direction in two adjacent containers, carry toothed wheels 94 and 95 (Figures 2 and 9) located in the same plane. The other screws I2 and I3 rotating under the same conditions carry also upon their shaft each a toothed wheel indicated respectively by 96 and 91 and located in the same plane as toothed wheels 94 and 95.

The shafts of screws I0, II, I2 and I3 carry each a toothed wheel indicated respectively by 98, 99, I00 and IOI. The latter wheels are all located in the same plane different of that containing the wheels 94 to 91. They are for exampl further away from the casing than said wheels 94 to 91.

A chain I02 meshes with the wheels 94 to IM and idling wheels I03, I04, I05 and I06. The

wheels I03 and I06 are lower than the wheels 91 and IN pertaining to the lowermost container, while the wheels I04 and I05 are higher than th wheels 94 and 98 pertaining to the uppermost container. The wheels I04 and I06 are located in the same plane as the wheels 94 to 91, while the wheels I05 and I03 are located in the sam plane as the wheels 99 to IN.

The chain I02 passes from one plane to the other either running upwards from the lower idler I03 to the upper idler I04, or running upwards from the lower idler I09 to the upper idler The lower idler wheels I06 and I03 are keyed to shafts indicated respectively by I01 and I03. These shafts carry in the same plane toothed wheels indicated respectively by I09 and H0 with which mesh a chain III driven from a motor II2 by means of a speed reducer.

When several apparatus such as that just described are needed to handle a given amount of material, they can be juxtaposed with advantage as shown in Figure 10.

In such case, the chains such as I02 of the various apparatus are driven from a common motor II2 by means of a chain III meshing with the toothed wheels I09 and H0 of each apparatus.

The space between two adjacent apparatus is closed in all directions by sheet iron such as II3 which can b insulated against heat at the same time as the outer sides of the apparatus. The sides of these apparatus which are located in front of each other need not be heat-insulated as the heat radiated by any one side serves to heat the side in front of the latter.

'In case each apparatus comprises an uneven number of superimposed containers, two chains are used to drive the toothed wheels keyed upon the shafts of the conveying screws, each of these chains moving exclusively in the plane of the wheels it drives.

Th invention is of course not exclusively limited to the embodiment shown and described and many modifications can be made to the form, the arrangement and the construction of some of the elements entering in this embodiment without to exceed the scope of the appended claims.

What I claim is:-

1. Drying apparatus comprising fixed superimposed containers containing the material to be dried, adjacent screws in each of said containers having their axes parallel and rotating one towards the other upwards, the pitch of said screws being inclined in such a direction that the material progresses in each container in the direction opposite to that adopted for any one of the adjacent containers, toothed wheels secured to said screws, the toothed wheels corresponding to screws placed immediately one above the other and rotating in a direction opposite to one another being located in a same plane while the toothed wheels corresponding to screws which are placed immediately one above the other and which rotate in the same direction are located in different planes, a driving chain meshing with the toothed wheels, communicating ducts between the containers, so arranged that the material in one container may drop from it to the next, a tight casing in which th containers are disposed, and means for circulating hot gas in said casing.

2. Drying apparatus comprising an even number of fixed superimposed containers containing the material to be dried, adjacent screws in each of said containers having their axes parallel and rotating one towards the other upwards. the pitch of said screws being inclined in such a direction that the material progresses in each container in the direction opposite to that adopted for any one of the adjacent containers, toothed wheels secured to said screws, the toothed wheels corresponding to screws placed immediately one above the other and rotating in a direction opposite to one another being located in a same plane while the toothed wheels correspondlng to screws which are placed immediately one above the other and which rotate in the same direction are located in different planes, two idling toothed wheels one of which

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