US2214981A

US2214981A - Apparatus for drying wet granular materials

Info

Publication number: US2214981A
Application number: US238046A
Authority: US
Inventors: Vissac Gustave Andre
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-10-31
Filing date: 1938-10-31
Publication date: 1940-09-17
Anticipated expiration: 1957-09-17

Description

Sept. 17, 1940. G. A. VISSAC 2,214,981

APPARATUS FORDRYING WET GRANULAR MATERIALS Filed 001;. 31, 1938 3 Sheets-Shee t 1 l NV E N TO R Gusfave Andre V/SSUC.

TTORNEY S p 17, 1940- e. A. VISSAC 2,214,981

APPARATUS FOR DRYING WET GRANULAR MATERIALS Filed 001:. 31, 1958 3 Sheets-Sheet 2 Sept. 17, 1940. G. A. vlssAc APPARATUS FOR DRYING wm' GRANULARMATERIALS 3 Sheets-Sheet 3 Filed Oct. 51, 1938 INVENTOR Gus fa V2 )4 nar V/ssac" ATTORNEY Patented Sept. 17, 1940 UNITED STATES PATENT OFFICE APPARATUS FOR DRYING WET GRANULAR MATERIALS 7 Claims.

This invention relates to improvements in apparatus for drying wet granular materials.

Different methods and apparatus for effecting the drying of wet granular materials have been suggested and used heretofore. However, the

methods and apparatus previously employed have had serious disadvantages, the chief of which is the great waste of heat in drying the materials. This waste of heat makes the drying of materials unduly costly. Another disadvantage of the known devices is that there is not sufficient control of the temperature of the hot gases used to dry the granular materials, which results in many cases in damage to the materials treated, particularly in the case of coal, which cracks and oxidizes when subjected to hot gases above a certain temperature.

It is an object of the present invention to provide a novel apparatus for drying wet granular 2 materials, including coal, so as to avoid apparent disadvantages in previously used apparatus and to provide in a simple manner means for the drying of material quickly and efficiently.

A further object of the invention is to provide 25 an apparatus which may be operated with the use of a large volume of air, at the lowest possible temperature, wherein the air is caused readily to penetrate the bed of material being dried without affecting the movement of the material 30 to any extent.

A further object of the invention is to provide an apparatus wherein heated gases may be employed for penetrating the bed of material to absorb the moisture.

A still further object is the provision of an,

apparatus including novel and simple flexible joints between the moving and stationary parts thereof.

A still further object is the provision of an apparatus including means for utilizing heat normally lost to preheat the materials to be dried.

Yet another object is the provision of an apparatus of the character described which is completely automatic in its operation.

The present invention consists essentially of one or more shaking screens for receiving and agitating the material to be dried, a hood disposed above each screen for projecting a heating and drying medium on to the material, at least 50 one hopper below each screen underlying the hood thereof, an air chamber below the hopper or hoppers communicating therewith, means connected with the air chamber for inducing pulsating air current to draw the heating and drying 55 medium through the agitated bed of material as it moves along the screen, means for circulating water through the air chamber to remove heat from the heating and drying medium as it travels therethrough, means for spraying the heated water on to the materials before they are treated, 5 and means for automatically controlling the temperature and quantity of the heating and drying medium projected on to the materials on the screen or screens, as more fully described in the following specification and illustrated in the accompanying drawings in which Figure 1 is a side view, partly in section, of the apparatus for drying the materials,

Figure 2 is a sectional view taken on the line 2-2 of Figure 1,

Figure 3 is a plan view taken on the line 33 of Figure 1, with certain parts broken away,

Figure 4 is an enlarged detail view, partly in section, of a flexible coupling,

Figure 5 is an enlarged sectional detail of one end of the air chambers of the apparatus,

Figure 6 is an enlarged sectional detail of one end of a screen, and

Figure 7 is a diagrammatic side elevation of the complete apparatus.

Referring more particularly to the drawings, i0 and II indicate two inclined compensating shaker screens supported by suitable oscillatable hangers l2 and 13 respectively, on each side thereof, suspended from beams l4 secured to vertical supports IS. The screens are preferably covered with wire mesh, perforated plates or wedge wire screen surfaces of, proper mesh and are connected to a crank shaft it through connecting rods ll disposed at an 180 angle, so that when the crank shaft I6 is operated through any suitable source of power, the screens are subjected to opposed and continuous oscillation.

The wet granular material is delivered from a chute on to screen III which is divided into two sections 2| and 22 extending longitudinally thereof. The material, after passing over screen to, is transferred to screen II and this latter screen is likewise divided into two sections 23 and 24 extending longitudinally thereof. A pair of hoppers 25 are suspended from the screen l0 underlying approximately one half said screen and another pair of hoppers 26 are suspended from the screen and underlie approximately the other half thereof. One set of hoppers 25 and 26 are disposed beneath the section 2| of the screen ill while the other set of said hoppers are disposed beneath the section 22 of the screen. Each of said hoppers is provided with a short discharge pipe 21 at the outlet opening in the bottom thereof. Similarly, a pair of hoppers 28' are suspended from the screen ll underlying substantially one half said screen and another pair of hoppers 30 are suspended from the screen and underlie substantially the other half thereof, with one set of

hoppers

28 and 30 disposed beneath the sec- ,tion 23 of said screen and the other set of hoppers disposed beneath the section 24 of the screen. Each of the hoppers 28 and 36 is provided with a short discharge pipe 3| at the outlet opening in the bottom thereof. The hoppers under the screens I8 and II are arranged in the same manner. 4

In Figure 1, only one of each of the

hoppers

25, 26, 28 and 38 is shown, the first two in elevation and the other two in section. Figure 2 shows the position of the pair of hoppers 26 in relation to the screen 10, the remaining pairs of hoppers being similarly disposed with regard to their respective screens.

A hood 32 is mounted on and overlies substantially the whole of the screen I0 and a hood 33 is mounted on and overlies the screen i l in a similar manner. The

hoods

82 and 33 are provided with inlet openings 34 and 35, respectively, in the tops thereof. An inverted V-shaped baffle plate 36 extends transversely of the hood 33 beneath the inlet opening 35 thereof and above the screen I l while'a similar bailie plate 31, see Figure 2, extends transversely of the hood 32 beneath the inlet opening 34 thereof and above the screen l0. counterbalanced flaps 40 are mounted at each end of both of the hoods 32 and 33. Each flap 48 is pivotally suspended from its hood and is provided with a weighted counterbalancing arm 4i and at its lower or trailing edge with a strip 42 formed of canvas or other suitable material, see Fig. 6. The trailing edges of these flaps rest upon the granular materials as they pass thereunder and said materials, now dried, are discharged from the screen II on to a discharge chute 43. v

A pair of

tapered air chambers

44 and 45 are situated side by side beneath the

hoppers

25, 26, 28 and 38, which chambers communicate at their forward ends respectively with sections 48 and 41 of a pulsator 48. Blades 58 and 5i, disposed at an angle of 90 with respect to each other, are mounted in the sections 46 and 41 respectively, of the pulsator 48, said blades being rotated by a suitable source of power (not shown), which source of power preferably having a variable speed drive. A passage 52, see Fig. '7, connects both sections of the pulsator 48 with gas circulating means, such as an exhaust fan 53, having an exhaust pipe 54, said fan being operated by a suitable source of power (not shown), which source may be the same as that operating the pulsator 48.

The air chamber 44 has a plurality of inlet openings 55 formed in the top thereof, one for each hopper, disposed beneath the screens l0 and H, and a sleeve 56 extending upwardly'from each of said openings. The sleeves 56 are larger than the

discharge pipes

21 and 3| of the

hoppers

25, 26, 28 and 36, so that the pipes fit into the sleeves without touching the sides thereof. From the description so far, it will be seen that the hoppers oscillate with the screen while the air chamber is stationary so that it is necessary to provide a flexible coupling therebetween.

Figure 4 is an enlarged detail of the coupling between the discharge pipe 21 of the hopper 26 and the adjacent sleeve 56 of the'air chamber 44.'

All these couplings are the same so one only need be fully described. Referring particularly to Figure 4, the upper end of the sleeve 56 is sloped so that it lies at a tangent to an imaginary circle drawn with its centre coinciding with the upper pivoting point of the hanger i2 (Fig. 1) immediately thereabove. A flange 51 is formed around and extends outwardly from the upper end of the sleeve 56, which flange lies in the same plane'as said sloped upper end. A sliding plate 58 is slidably mounted on a bearing plate 88 which, in turn, is secured to the flange 51. Asa result of this construction, the sliding plate 58 lies-at a tangent to an imaginary circle with its centre coinciding with the upper pivoting point of the hanger l2 above mentioned. This sliding plate is free to slide on the bearing plate 88 between the latter and rollers 8| held thereabove by supports 62 which are mounted on the edge of the flange 51 and extend upwardly past the bearing plate 60. An opening 63 is formed in the sliding plate 58 centrally thereof, said opening being slightly .larger than the discharge pipe of the hopper 28 which projects therethrough. When the hopper oscillates with the screen l8, both a vertical and a lateral motion is imparted thereto so that the 'discharge thereof moves through-an arc, the centre of which is the upper pivot point of the hanger I2 I referred to above.

In Fig. 4, the hopper is shown in full lines in one extreme position and in dot and dash lines in they other extreme position. The sliding plate serves as a flexible coupling to prevent gases from passing from the sleeve 56 to the atmosphere outside the device or air from entering the device. The sliding plate 58 moves laterally with the hopper while it permits said hopper to move in a vertical direction. This coupling is very effective and eificient without the disadvantages of the known types of flexible couplings. The constant flexing of the ordinary metal couplings causes the metal to crystallize while couplings of canvas or rubber rapidly tear or deteriorate.

The air chamber 45 is also provided with a plurality of-inlet openings 64 and upwardly extending sleeves 65, each of which is provided with a flexible coupling as described, between it and the discharge pipes of the hoppers extending thereinto.

Each of the inlet openings 34 and 35 of the hoods 32 and 33 is surrounded by a sleeve 61 extending upwardly from said opening, the upper end of which is sloped at the same angle as the upper ends of the sleeves 56' and 65 of the

air chambers

44 and 45. Pipes 68 extend downwardly into the sleeves 61 from a main pipe 18, said pipes 68 being smaller than the sleeves so that they do not touch the sides thereof. Flexible couplings similar to those described are provided between the sleeves 61 and the pipes 68. These couplings function in the same manner as the previous couplings, the only difference being that the sleeves on which the plates 58 are mounted oscillate while the pipes 88 are stationary. It will be seen that a vertical and lateral motion is im-' parted to the sleeves bythe hoods 32 and 38 which oscillate with the screens l0 and -l I.

The main pipe 10 is connected to a flue 1| of a v 18, respectively, by means of which the hot gases from the furnace may be directed through either the pipe 10 or the flue as des red A c d i pipe 16 is connected to the main pipe I between the flue II and the first pipe 88.

A damper 11 mounted in the pipe I0 between the flue II and the cold air pipe I8, is operatively connected by a rod I8 to a modulating motor 80 which is governed by a temperature controller 8| mounted in the passage 52. Another damper 82 mounted in the pipe I8, is operatively connected by a rod 83 to a modulating motor 84 which is governed by a temperature controller 85 mounted in the pipe 10 between the cold air pipe 18 and the first pipe 88 leading to the hood 32.

Pipes 88 and 81 extend downwardly from the

air chambers

44 and 45, respectively, adjacent the discharge ends thereof, and said pipes may, if desired, be provided with pulsators 88 and 90 operated by a common shaft 9| which is operatively connected to the pulsator 48 or to its source of power, in any suitable manner. The blades of these pulsators are set at right angles to each other. The pipes 88 and 81 extend below the surface of the water in a reservoir 92, the level of which water is maintained constant by weirs 93. Drain pipes 94 extend downwardly from the pulsator 48 below the surface of the water in the reservoir 92. The water flows from said reservoir over the weir 93 into a sump 95. Another drain pipe 96 extends downwardly from the exhaust fan 53 below the surface of the water in the sump 95. A pump 91 is adapted to pump water from the sump along either or both pipes 98 and I00, the flow of water being controlled by valves I0| and I02. The pipe 98 extendsover a chute I03 and terminates in a spray device I04 so that the granular materials are sprayed with water as they pass along said chute I03 to the chute 20. The pipe I00 extends along to the ends of the

air chambers

44 and 45 lying at the discharge end of the apparatus, where it is divided into pipes I05 and I06, one extending into each air chamber as a jet. If desired, each pipe I05 and I08 may be divided into upper and lower sections, see Fig. 7, so that water may be supplied to the air chambers and the tops and bottoms thereof. Valves I01 and I08 may be mounted in each pipe I05 and I08. If necessary, a water supply pipe IIO having a control valve III, may be connected to the system at any desired point, such as to the pipe I00, as shown.

The wet granular material to be treated, say, for example, coal, passes through the chute I03 where it is preheated by warm water from the spray I04, on to the chute 20 whence it is delivered to the shaker screen I0. The inclined shaker screens I0 and I I are subjected to opposed and continuous oscillation, during which time the coal passes over 'the screen I0 and on to the screen II, whence it is discharged into the discharge chute 43. During its travel over these screens, the coal is constantly subjected to substantially alternate vertical and horizontal movement. The horizontal movement causes the coal to move to-' wards the discharge ends of the screens and, at the same time, the vertical movement continually loosens up said coal.

When the damper I4 is closed and the dampers I5 and I1 are ,open, hot gases are drawn from the furnace 12 through the flue II, along the main pipe I0 and down through the pipes 88 into the hoods 32 and 33 in which they are dispersed laterally by the baffle plates 31 and 38. These gases pass through the bed of coal on the screens. The hot gases serve further to warm the coal and the condensed moisture thereof is shaken oil and eliminated so that by the time the coal reaches the discharge end of the screen II, it is thoroughly dried. The gases and moisture are drawn through the pairs of

hoppers

25, 28, 28 and 30 into the

air chambers

44 and 45 where most of the moisture is condensed and deposited while the cooled gases are drawn through the sections 48 and 41 of the pulsator 48 and along the passage 52 by the exhaust fan 53, whence they are discharged through the exhaust pipe 54.

As previously described, the screen I0 is divided longitudinally into two sections 2| and 22 while the screen II is also divided into two longitudinal sections 23 and. 24. The sections 2| and 23 of these screens communicate through the

hoppers

25, 26, 28 and 30 therebeneathwith the air chamber 44 and the sections 22 and 24 communicate through the

hoppers

25, 28, 28 and 30 thereoeneath with the air chamber 45. blades 50 and 5| of the pulsator 48 are arranged at right angles to each other so that the

air chambers

44 and 45 and, consequently, the hoppers connected thereto alternately communicate with the gas circulating means or exhaust fan 53.

With this arrangement, direct connection is alternately established and disestablished between the fan and the hoppers beneath each side of the screens so that the hot gases are drawn through the bed of coal on one side only of the screens I0 and II at any one particular time. By alternately interrupting the flow of gases through the bed of coal on each side of the screens in this manner, the coal is alternately loosened up on each side of the screens by the oscillation thereof. A steady flow of gases through the coal would tend to counteract the loosening effect of the screen movement, thus allowing the coal to pack. This loosening of the coal is further aided by the fact that when the pulsator closes one of the air chambers, a back surge is created in that chamber so that the gases are forced upwardly through the coal. This not only assists in loosening the coal but the gases are recirculated through the coal more completely to dry it.

Most of the moisture removed from the coal is condensed in the

air chambers

44 and 45 whence it passes through the pipes 88 and 81 into the reservoir 92 and over the weirs 93 into the sump 95. If desired, the pipes 88 and 81 may be provided with pulsators 88 and 90, the purpose of which will hereinafter appear. Any moisture condensed in the pulsator 48 passes through the drain pipes 94 into the reservoir 92 and over the weir 93 into the sump 95, while any moisture condensed in the fan 53 is directed to the sump through the drain pipe 98. It might be added here that a large percentage of the heat remaining in the gases after they have passed through the coal, is absorbed by the water in the air chambers. The warmed water is pumped from the sump 95 by the pump 9! through the pipe 98 to the spray I04 where it is brought into contact with the coal passing along the chute I03. From this it will be seen that, after having passed through the coal, the greater part of the heat from the gases normally lost, is conveyed to the coal being supplied to the apparatus, to preheat it. This is very advantageous because it is much easier to dry heated materials than cold materials and yet no extra original heat energy is necessary for this purpose.

At the same time, water may be pumped from the sump through the pipe I00 and the pipes I05 and I08 back to the

air chambers

44 and 45. This water may be pumped steadily through the air chambers, in which case, being considerably The cooler than the gases therein, it condenses the moisture removed from the coal, washes the fines passing through the screens out of the air chambers, and absorbs the greater part oi. the heat from the gases to be used to preheat the coal supplied to the apparatus, as described .above. However, if the pulsators 08 and 90 in the pipes 86 and 81 are employed, their blades are set at right angles to each other and they are set so that thepipe 86 of the air chamber 44 is closed .when the blade 50 of the pulsator 48 closes the blade SI of the pulsator 48 closes the discharge end of said air chamber. In this way, the water alternately and intermittently rises in the air" chambers 44 and 4! when the discharge ends thereof are closed. This increases the above described back surges of the gases at predetermined intervals, to provide for a thorough recirculation of the gases through the bed of coal alternately on each side thereof. This also increases the loosening efiect of the back surges of the gases on the coal.

As previously described, the sliding plates 58 permit the hoods and hoppers to oscillate in relation respectively to the air chambers and the pipes 68 and at the same time provide an efiective seal to prevent the hot gases from escaping therefrom. The counterbalanced flaps M at each end of the shaker screens permit the coal to move along the screens and yet they prevent the hot gases from escaping and air from entering at the ends of the hoods.

As a rule the gases from a furnace are too hot for use in. drying coal since the latter starts to crack and oxidize at about 400 F. so that with bituminous coal it is not safe to use gases at temperatures above 600 F. or 700 F. The tem perature controller 85 may be set at, say 600 F., with the result that any variations will act on the motor 84 to open or close the damper 02 in the cold air pipe I6 to maintain the gases supplied to the coal beds ata desired temperature.

The exhaust fan 53 operates at a constant speed and under normal conditions may, for example, induce 40,000 cu. ft. of hot gases at 600 F. into the apparatus, which gases, after accomplishing their necessary work in the dryer, may come out at, say 120 F. In this case the temperature controller 8i may be set at 120 F. Should the coal contain less moisture, a smaller amount of heat will be absorbed in the dryer for the evaporation of this moisture so that the temperature ofthe gases passing through the passage 52 will rise. In this case, the temperature controller 8| will act on the motor 80 to cause-the damper II in the pipe 10 to be partly closed. As a result of this, the control 83 will cause the damper 82 to close correspondingly. This means an increased resistance in the fan circuit, hence a drop in volume, for example, to 35,000 cu. ft. oi. hot gases at 600 F. circulating through the dryer, which is sufficient to dry the coal. Similarly, a change of resistance from the bed of coal on the screens, due to different coarseness or voltrue, will act in the same way automatically to control the volume and temperature or the gases supplied to the beds.

This apparatus may be made completely automatic in operation by the use of any of the well known types of automatic stoker with the furnace I2.

It is apparent upon consideration of the foregoing that the apparatus provides tor preheating the coal to be treated by means of heat normally wasted and for efllciently drying said coal.- In addition the apparatus is particularly efllcient through the novel means for retaining the hot gases therein and through the automatic control of the temperature and volume of gases supplied to the coal beds. I

However, it will be realized that while coal has been used as a general illustration of the material treated, theapparatus is generally applicable to the drying of a wide variety of materials.

Various modifications may be made in this invention without departing from the spirit thereof or the scope of the claims, and therefore the exact forms shown are to be taken as illustrative only and not in a limiting sense, and it is desired that only such limitationsshall be placed thereon as are disclosed in the prior art or areset torth in the accompanying claims.

I What I claim as my invention is:

1. Apparatus for drying wet granular material, comprising a shaking screen for receiving and agitating the material, a hopper disposed below an area overlying the hopper, means for introducing hot gases to the hood, gas circulating means, an air chamber connected between the hopper and the gas circulating means, pulsating means for establishing and disestablishing direct connection between the gas circulating means and the hopper, said circulating means being adapted intermittently to draw the gases through the material on the screen, and means for creating a flow of water through the air chamber to remove heat from the gases passing therethrough, and means for bringing at least some of the heated water into contact with the material being treated to preheat said material.

2. Apparatus for drying wet granular material, comprising a shaking screen for receiving and agitating the material, a hopper disposed below said screen, a hood disposed above the screen in said screen, a hood disposed above the screen in 25 an area overlying the hopper, means for intro-Q adapted intermittently to draw the gases through the material. on the screen, means for creating a flow of water through the air chamber, and means for intermittently interrupting said flow of water through the air chamber to create a back pressure through the material on the screen at predetermined intervals.

3. Apparatus for drying wet granular material, comprising a shaking screen for receiving and agitating the material, a hopper disposed below said screen, a hood disposed above the screenin an area overlying the hopper, means for introducing hot gases to the hood, gas circulating means, an air chamber connected between the hopper and the gas circulating means, pulsating means for establishing and disestablishing direct connection between the gas circulating means and the hopper, said circulating means being adapted intermittently to draw the gases through the material on the screen, means for creating a flow of water through the air chamber to remove. heat from the gases passingtherethrough, pulsating means for intermittently interrupting said flow oi. water through the air chamber to create a back pressure through the material on the screen at predetermined intervals, and means for bringing at leastsome oi the heated water into contact with the material being treated to preheat said material.

5 4. Apparatus for drying wet granular materialcomprising a shaking screen for receiving and agitating the material, "a plurality oi hoppers disposed beiow the screen underlying each side thereof, a hood disposed above the screen in an .10 area overlying the hoppers, gas circulating means, .a pair of air chambers, each chamber being connected to the hoppers underlying one side 01 the screen and to the gas circulating means, pulsating means for establishing and dis-- 15 establishing direct connection alternately between the gas circulating means and the hoppers under each side 0! the screen, means for introducing hot gases to the hood whereby said gases are directed alternately through the material on 20 each side of the screen, and means for creating a back pressure alternately in the air chambers.

5. An apparatus as claimed in claim 4 including means for creating a flow of water through each air chamber, and pulsating means for al- 25 ternateiy interrupting the flow 0! water through the air chambers, said pulsating means interrupting the flow of water in each chamber when the connection between the chamber and the gas circulating means is disestablished whereby a back pressure is created through the material on the side of the screen overlying the air chamber.

8. Apparatus for drying wet granular material comprising a plurality of shaking screens for receiving and agitating the material, a plurality of hoppers disposedbelow the screens underlying each side thereof, a hood disposed above each screen in an area overlying the hoppers therebeneath, gas circulating means, a pair of tapered air chambers, each chamber being connected to the hoppers underlying one side of the screens and to the gas circulating means, pulsating 8 means for establishing and disestablishing direct connection alternately between the gas circulating means and the hoppers under each side of the screens, counterbalanced flaps at the ends of each screen adapted to permit the material to 10 move thereunder, means for introducing hot gases to the hoods whereby said gases are directed alternately through the material on each side of the screens while said material advances therealong, and means for creating a back pressure in each air chamber when the connection between the chamber and the gas circulating means is disestablished.

'7. Apparatus for drying wet granular material, comprising a shaking screen for receiving and agitating the material, at least one hopper arranged below the screen, at least one hood disposed above the screen in' an area overlying the hopper, means for introducing hot gases to the hood for absorbing moisture from the material, gas circulating means, an air chamber connected between the hopper and the gas circulating means, means for establishing and disestabiishing direct connection between the gas circulating means and the hopper, said circulating. means being adapted'intermittently to draw the gases through the material on the screen, and means for circulating water through the chamber .to assist in condensing the moisture from the gases as they pass therethrough.

GUSTAVE ANDRE VIBSAC.