US3596890A

US3596890A - Drying apparatus

Info

Publication number: US3596890A
Application number: US799788A
Authority: US
Inventors: Alastair G M Small
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-02-19
Filing date: 1969-02-17
Publication date: 1971-08-03
Anticipated expiration: 1988-08-03
Also published as: NL6902522A; ES363780A1

Abstract

The drying apparatus of the invention incorporates two drying sections including cylindrical chambers through which the material to be dried is passed sequentially. Each drying section incorporates air nozzles arranged to discharge air tangentially inwards with respect to the axis of the associated chamber. The chamber of the second drying section in the series has heat radiating surfaces disposed in heat-exchanging relationship with the flues of a furnace the combustion air inlet of which is connected into the second drying section. Air is led to the air nozzles in proximity to the furnace flues so as to absorb heat on its way to the nozzles. Means is provided for removing dried material from the secondary drying section.

Description

O United States Patet [1113 99 [72} lnventor Alastair G. M. Small, d 3,396,680 8/1968 Hubbard I 10/8 late of Kent, England (by Monica Mary 3,396,681 8/1968 Hubbard 110/8 Small cam-ix) Primary Examiner-John J. Camby {2H Appl' 799788 Attorney-Larson Taylor & Hinds [22] Fiied Feb. 17, 1969 Patented Aug. 3, 1971 [32] Priority Feb. 19, 1968 [33] Great Britain [31] 7980/68 ABSTRACT: The drying apparatus of the invention incor- [54] DRYING APPARATUS porates two drying sections including cylindrical chambers 11 CW9 Drawing as. through which the material to be dried IS passed sequentially. Each drying section incorporates air nozzles arranged to [52] US. Cl. 263/21 A, discharge tahgemiahy inwards with respect to the i f 11o/8 R the associated chamber. The chamber of the second drying [51] lnt.C1. F2711 15/00 Section in he series has heat radiating Surfaces disposed in Field 01 Search 263/21 A, heabcxchahgihg relationship with the fl f a furnace the 21 36; /8 combustion air inlet of which is connected into the second d in section. Air is led to the air nozzles in proxirnit to the [56] References CM flii' naie flues so as to absorb heat on its way to the r iozzles. UNITED STATES PATENTS Means is provided for removing dried material from the 3,286,666 1 l/ 1966 Ohlsson t. 1 10/8 X secondary drying section.

Patented Aug. 3, 1971 5 Sheets-Sheet 1 Patented Aug. 3, 1971 3,596,890

5 Sheets-Shoat. z

Patented Aug 3, I971 3,596,899

5 Sheets-Sheet 5 FIGS Patented Aug. 3, 1971 5 Sheets-Sheet 4.

5 Sheets-Sheet 5 Patented Aug. 3, 1971 DRYING APPARATUS This invention relates to improvements in drying apparatus.

More specifically, the invention relates to improved apparatus for drying material which can be readily broken up into small pieces. The apparatus is particularly suitable for drying substances having a high moisture content and an offensive odor, e.g., chicken manure.

One type of known drying apparatus in this filed includes drum, batch and tray. dryers in which the material to be dried is moved around the, outside or inside of a heated drum or heated platform with the material being in contact with a hot surface all the time. The material is simultaneously subjected to a current of warm dry air which absorbs the moisture and mechanical means are used to turn over the load so that it is exposed to the drying medium as uniformly as possible.

The above-described type of drying apparatus is more suited to materials having a comparatively low moisture content and no smell problems. The problem of smell is of considerable importance because, as well as being unpleasant, the discharge of foul smelling vapors into the atmosphere is detrimental to health. Other difficulties experienced with known drying apparatus include the clogging of small apertures by the manure, difficulties of control, and uneven drying and damage to the material being dried by the high contact and air temperatures.

Another type of drying apparatus used in this field is the flash and attrition drying apparatus which operates most effectively with materials having an average. moisture content of 40 percent, i.e., about half the moisture content of chicken manure. ln this type of apparatus the material to be dried is pounded to pieces by hammers and is then ground and exposed to hot air. In order to keep the initial moisture content down to a workable value it is sometimes necessary to recirculate some dried material into the feed. The disadvantages of this type of apparatus are that the air temperature is very high, the apparatus will only handle material of a limited moisture content and the odor problem remains. Such drying apparatus is designed mainly for municipal sewage disposal and is not suitable for the drying of chicken manure or other material of high moisture content.

An object of the present invention is to provide drying apparatus which obviates or mitigates the aforesaid disadvantages.

A further object of the invention is to provide drying apparatus which is particularly suitable for drying foul smelling material of high moisture content such as chicken manure and which is also suitable for the drying of municipal sewage in the wet state.

Drying apparatus according to theinvention incorporates a primary drying section includinga cylindrical chamber, means for introducing material to be dried into one end of the chamber the other end of which is open, and a primary air-introducing system including air nozzles disposed around the axis of the chamber and orientated to discharge in directions inward towards the axis of the chamber and tangential with respect to the axis of the chamber, a secondary drying section connected in series with the first drying section and arranged to receive the material when it leaves the open end of the first drying section, said secondary drying section including a second cylindrical chamber presenting a heat-radiating surface and a secondary airintroducing system including air nozzles disposed around the axis of the chamber and orientated to discharge in directions inward towards the axis of the chamber and tangential with respect to the axis of the chamber, a furnace having a combustion air inlet connected to the secondary drying section and flues disposed in heat-exchanging relationship with the heat-radiating surfaces, with the primary air introducing system and with the secondary air-introducing system, means for removing dried material from the secondary drying section, and means for causing a pressure drop from the secondary drying section to the flues.

The means for causing a pressure drop from the secondary drying section to the flues may be an ejector in the flues arranged to operate by a fluid under pressure such as compressed air or steam or it may be an ejector fan, the apparatus being then arranged to operate under induced draught. Alternatively said means may be forced draught fan means arranged to introduce the primary and/or the secondary air at a pressure above atmospheric pressure, the apparatus being then arranged to operate under forced draught.

in one form of primary drying section particularly for use with material of high (e.g., 85 percent) moisture content the wall of the chamber may be formed with the air-introducing nozzles, and a convergent collecting cone coaxial with the chamber is spaced from the chambers at the open end, said cone terminating at the small end in a choke chamber constituting a discharge opening leading to the secondary drying section and being surrounded by an annular chamber for reception of moisture centrifuged out of the material on its passage along the cylindrical chamber and across the gap between the chamber and the cone.

In an alternative construction of primary drying section particularly for use with material of a lower (e.g. 60 percent) moisture content, means may be provided within the chamber for directing material to be dried into an annular stream, the air introducing nozzles surrounding the chamber at the open end being orientated to discharge in directions inwardly towards the axis of the chamber and tangential with respect to the axis.

The primary drying section and the secondary drying section may be detachably attached to one another.

The cylindrical chamber constituting the secondary drying section may include three shells disposed coaxially one within the other so that two annular chambers surround a central chamber, the inner of the two annular chambers being connected to the furnace so that it constitutes part of the flues and the inner shell which defines the central chamber constitutes a heat radiating surface, the outer of the two annular chambers being formed with entry ports for secondary air, the air nozzles of the secondary drying section connecting the outer annular chamber to the central chamber through the inner annular chamber.

The tangential orientations of the nozzles of the primary drying section and of the secondary drying section may be opposite in sense, i.e. air introduced through the nozzles of the two sections may be caused to rotate in opposite directions about the common axis of the two chambers.

The primary drying section particularly for use with material of a lower moisture content may be formed with extra airintroducing nozzles surrounding the open end of the chamber, said nozzles being so orientated that their axes have longitudinal and circumferential components with respect to the axis of the chamber.

The primary air introducing system may include a duct leading to the nozzles and disposed in contact with the inner annular chamber of the secondary drying section so that the duct is in heat exchanging relation with the inner annular chamber.

Embodiments of the invention will now be described, simply by way of example, with reference to the accompanying drawings, in which:

FIG. 11 is a sectional elevation of a primary drying section adapted for connection to a secondary drying section, this primary drying section being particularly intended for treating material of a moisture content as high as 85 percent.

FIG. 2 is a plan view ofthe primary drying section;

FIG. 3 is a sectional plan on the line 33 of FIG. 1;

F16. d depicts an alternative construction for the discharge end of the primary drying section illustrated in FIG. ll;

FIG. is a sectional elevation, on reduced scale, of a complete drying apparatus arranged for operation by induced draught;

FIG. ti is a sectional plan on the line 6-6 of FIG. 5; FIG. 7 is a sectional plan on the line 7-7 of FIG. 5;

F IG. 8 is a sectional elevation of another form of primary drying section particularly intended for treating material of a lower moisture content, e.g. up to about 65 percent and FIG. 9 is a section through the line 9-9 in FIG. 8.

Referring to FIGS. 1 to 3 of the drawings, the manure is fed through a space A in a top flanged elbow or bend. Distribution holes B in a perforated plate 2' constitute a coarse filter which serves to trap feathers and the like and also to discharge manure into the cylindrical chamber C, near its periphery, in the form of small particles or rods. In the chamber C the manure meets a rapidly rotating vortex of air caused by air entering the chamber C tangentially through nozzles C1 in the wall of the chamber C and the manure is rapidly accelerated rotationally so that it forms a thin layer around the inside wall of the chamber C. At first, the water and manure rotate together, but the higher density of the water causes separation of the free water which hugs the wall more closely than the lower density drier manure. At the same time, the whole mass, now in layers, moves downwards under the influence of gravity and the downward component of the air velocity, (which cannot move up against the incoming manure and must therefore move down).

When the layers of water and manure reach the lower end of the chamber C, they tend to fly off tangentially outwards in two separate cones of wide but different angles and it is here that final separation of the free water and the manure takes place. The water passes out into an annular chamber D and thence by way of an outlet 12' to a drainage system which may be subsurface irrigation. A trap, (shown), prevents any outward or inward flow of air between the chambers C and D or between chamber D and the part-dried material E in a convergent collecting cone 7'. The forces acting therefore are the tangential outward force caused by the rotation, the force exerted by the flow of air from the chamber C to the collecting cone 7', and the possibly small but quite perceptible surface tension between the water and the wide coned face which is machined on the outlet of the lower end of the chamber C. The collecting cone 7 is also machined and can be fixed with its upper inlet spaced at a distance from the outlet to the chamber C found best for ensuring that manure but not water is collected by the cone 7', the adjustment being made by varying the thickness of the washers 10'. A choke chamber F is formed on the collecting cone 7' to vary the pressure, if need be, between the outlet of the chamber C and the inlet of the cone 7'. The optimum diameter of the choke chamber F and the angle of slope of the cone 7 is determined by experiment. The lower outlet of the chamber F leads into the secondary drying section.

Further parts of the primary drying section are described below. Means for introducing material to the chamber C is secured to the top of the chamber C by means of bolts 1 which pass through a perforated plate 2' and an upper flange 3'. 4 denotes an air casing surrounding the chamber C constituted by a slotted sleeve 5, and air inlet 6' being in communication with the space between the casing 4' and the sleeve 5 for supply of air to the chamber C. 8' denotes a fixed sleeve supporting the collecting cone 7'. A middle flange 9' separates the air casing 4 from a water casing 11' which is provided with the aforementioned water outlet 12'. The sleeve 5 is provided with tangential slots constituting the nozzles Cl, (see FIG. 3), by means of which rotary motion is imparted to the air passing into the chamber C from the air casing 4'.

Referring now to FIGS. 5 to 7 a fan (not shown) draws cold air from the atmosphere, raises the pressure of this air, conveys it under pressure to an inlet 31, (see FIG. 7), of a duct H forming part of the primary air introducing system, and forces the air up through a pipe 2 into the primary drying section 3 containing the chamber C in the manner already described. The air passing to the primary drying section 3 is warmed to a moderate temperature in the duct H, said temperature being sufficient to start warming the manure but not enough to produce any substantial evaporation of the free water, which must remain in the liquid state for the proper functioning of the centrifugal drying.

The partly dried manure passes downwards from the primary drying section 3, through the outlet F into the chamber G of the secondary drying section.

The bound moisture of the manure which cannot be removed centrifugally is removed in the chamber G. Said chamber G consists of an inner shell 7 an intermediate shell 8 and an outer shell 9, the shell 7 and the shell 8 forming between them an inner annular chamber through which hot flue gases i from a furnace M pass on their way to a flue outlet 5, heating both

shells

7 and 8 in their passage except for a short distance at the bottom. Baffles may be used to ensure uniform circulation of these hot gases in said annular chamber. Cold air J is admitted to the outer annular chamber between the

shells

8 and 9 through air inlet holes 12 disposed all around the lower end of the outer annular chamber. The air J enters the holes 12 because of the action of induced draught and passes up through the entire length of the outer annular chamber duct to the top, absorbing heat in its passage from the hot shell 8. At the top it passes through hot air nozzles 6 into the chamber G. The heated air J which rotates in the opposite direction from the material and air entering from the primary drying section because of the orientation of the nozzles 6, mixes with the manure particles and warm air coming from the primary drying section 3.

A portion of the air J is admitted about half way up the chamber G through upwardly directed nozzles 6, to retard the fall of the manure and thus prolong the action of the radiant heat on the descending manure.

The air J which has become foul in its passage through the chamber G is led from the lower portion of the chamber G through an inlet 32 into a chamber K to where it is warmed to prevent any possibility of condensation. The foul air I passes out from the chamber K through holes 15 into a space L located along the top and front of the furnace M and then to the oil burner of the furnace, (in the quantity required for efficient combustion). The surplus foul air not required for combustion passes through holes 27 in the firebrick quarl 21 into the furnace M where it is heated to a high temperature and decomposed before passing harmlessly upwards with the flue gases. This surplus foul air performs a second essential function in that it lowers the flue gas temperature to a point where, while there is still plenty of heat for air warming, there is no risk of serious overheating of the inner shell 7 which is not, like the intermediate shell 8, cooled by a circulation of air.

The inner shell 7, though not permitted to become overheated, is hot enough to provide a high and uniform transfer of radiant heat from the shell wall'to the manure tumbling down the center of the chamber. By calculation it is arranged that the amount of radiant heat absorbed is enough to evaporate the bound moisture down to a final moisture content of about 15 percent. This is effected without heating the air surrounding the manure particles, (which air is almost transparent to radiant heat,) so that the manure itself is not overheated.

The alternative to the use of radiant heat, which alternative appears to be a feature of the previously known dryers, is to introduce much more air at the same temperature or else to heat the same amount of air to a much higher temperature in order to provide the very high latent heat of evaporation required to absorb the moisture. The introduction of increased quantities of air will, of course, create more serious air disposal problems. The use of radiant heat provides the latent heat required and the total mount of air introduced is sufficient to absorb all the moisture which must be absorbed for the final desires moisture content at the low drying chamber temperature of 200-250 F. with an ample margin for adequate drying under the most difficult conditions likely to be met.

The induced draught fan, (not shown), is arranged to maintain a degree of vacuum comparable with that used for pneumatic conveying or the collection of dust, chips and the like from machines, at the entry to a dry material outlet duct 10 located at the bottom of the chamber G. Conveniently foul air from the chamber G is directed to the inlet side of the induced draught fan, the outlet of which delivers the foul air at some slight pressure to the foul air inlet 33 and eventually to the furnace M as hereinbefore described. Except for the final passage from the fan to the inlet 32 and the furnace, the whole of the above path contains foul air at beiow atmospheric pressure as also will the fan itself at the point where a leak could occur. It follows that the chances of any escape of offensive vapors are small as leakage would be inward.

The oil burner has been specially designed on the lines of the usual pressure jet type but with a special adjustable inlet 24 for a sufficiency of foul air to burn the oil efficiently. This air inlet 24 may be fitted with vanes to rotate the air stream in the opposite direction to the spray of atomized oil and thus provides turbulence sufficient to give the best mixing and combustion. ignition and controls are conventional or as required and the usual photoelectric flame failure safety device is provided.

The furnace M is completely enclosed and under a slight pressure so that only a very short flue is required. The back firebrick 19 is spaced to allow the gases 1 access to the annular first duct or flue space of the heat exchanger. The side firebricks 240 are solid and packed behind the slag wool or insulation and the hearth 28 is insulated as shown in MG. 5. The circulation of foul air prevents overheating of the combustion chamber lid 117 and also helps to keep the front reasonably cool. The necessary explosion door 22 and frame is welded to the front of the combustion chamber and to the fixed front lb so that escape of foul air from the space L through the explosion door is not possible.

The outsides of the casings of the warm and hot air ducts are preferably lagged.

The manure inlet fitting and coarse filter or perforated plate 2' of the primary drying section 3 are readily removable as shown. Even greater accessibility may be provided by using a swept tee, (with one outlet looking up and blanked off), with removable blank flange. The whole primary section is held to the top of the chamber G of the secondary drying section by studs and nuts and the whole top of the chamber G is readily removable, (see bolted top t), to give access to the chamber G and to the annular chambers surrounding the chamber G. The bolted top and lid of the furnace M can be removed for clean ing and repairs to the refractories, and the bolted front 23 can be removed for access to the oil burner.

The alternative construction shown in FIG. t makes more use of the layering of the water and manure in the chamber C but might possibly be more liable to choking.

Referring to FIGS. ti and 9 which are of an alternative form of primary drying section the chamber C contains a coned diffuser 33 which has the effect of directing material to be dried into an annular stream issuing along the periphery of the base of the coned diffuser 33. At the open end of the chamber C there are provided vanes 34 which are disposed tangentially with respect to the axis of the chamber C, the spaces between the vanes constituting air introducing nozzles. The primary drying section is removably connected to the secondary drying section by way of a cover plate 35 coned at 36 to a wide angle. 37 denotes extra air introducing nozzles in the cover plate 35 so orientated that their axes have longitudinal and circumferential components with respect to the common axis of the chambers C and G. The cover plate 335 is formed with a flange 38 which engaged under the top cover plate of the chamber G, bolts 40 penetrating a flange ill fastened to the primary drying section being effective to force the flange 38 against the top cover plate 39 of the chamber G.

In operation of this form of primary drying section the material issuing in an annular stream past the nozzles formed by the vortex produced by the entering air. A primary drying action is performed in the vortex and the partially dried material moves downwardly into the chamber G where it is further dried as already described. it has been found that this simple form of primary drying section is extremely effective with material of a moisture content not exceeding about 65 percent. This form of primary drying section is very easily removed from the secondary drying section for servicing when required.

The apparatus is designed for continuous operation and could be set up with a complete set of screw conveyors drawing the manure direct from its source, forcing it into the apparatus, and finally extracting the dried material from the cyclone and conveying it into a bulk storage bin.

What I claim is:

ll. Drying apparatus incorporating a primary drying section including a cylindrical chamber, means for introducing material to be dried into one end of the chamber the other end of which is open, and a primary air-introducing system including air nozzles disposed around the axis of the chamber and orientated to discharge in directions inward towards the axis of the chamber and tangential with respect to the axis of the chamber, a secondary drying section connected in series with the first drying section and arranged to receive the material when it leaves the open end of the first drying section, said secondary drying section including a second cylindrical chamber presenting a heat-radiating surface and a secondary air-introducing system including air nozzles disposed around the axis of the chamber and oriented to discharge in directions inward towards the axis of the chamber and tangential with respect to the axis of the chamber, a furnace having a combustion air inlet connected to the secondary drying section and fines disposed in heat-exchanging relationship with the heat-radiating surfaces, with the primary air introducing system and with the secondary air introducing system, means for removing dried material from the secondary drying section, and means for causing a pressure drop from the secondary drying section to the flues.

2.. Apparatus as claimed in claim 1 in which the means for causing a pressure drop from the secondary drying section to the flues is an ejector in the flues arranged to operate by a fluid under pressure.

3. Apparatus as claimed in claim 1 :in which the means for causing a pressure drop from the secondary drying section to the flues is an ejector fan.

4. Apparatus as claimed in claim l in which the means for causing a pressure drop from the secondary drying section to the flues is forced draught fan means arranged to introduce the primary and/or the secondary air at a pressure above atmospheric pressure.

5. Apparatus as claimed in claim it in which the wall of the cylindrical chamber of the primary drying section is formed with the air-introducing nozzles, and a convergent collecting cone coaxial with and spaced from the chamber is provided at the open end, said cone terminating at the small end in a choke chamber constituting a discharge opening leading to the secondary drying section and being surrounded by an annular chamber for reception of moisture centrifuged out of the material on its passage along the cylindrical chamber and across the gap between the chamber and the cone.

6. Apparatus as claimed in claim ii in which means is provided within the cylindrical chamber of the primary drying section for directing material to be dried into an annular stream and the air introducing nozzles surrounding the chamber at the open end are orientated to discharge in directions inwardly towards the axis of the chamber and tangential with respect to the axis.

7'. Apparatus as claimed in claim ii in which the primary drying section and the secondary drying section are detachably attached to one another.

ti. Apparatus as claimed in claim 1 in which the cylindrical chamber constituting the secondary drying section includes three shells disposed coaxially one within the other so that two annular chambers surround a central chamber, the inner of the two annular chambers being connected to the furnace so that it constitutes part of the fiues and the inner shell which defines the central chamber constitutes a heat radiating surface, the outer of the two annular chambers being formed with entry ports for secondary air, the air nozzles of the secondary drying section connecting the outer annular chamber to the central chamber through the inner annular chamber.

dinal and circumferential components with respect to the axis of the chamber.

11. Apparatus as claimed in claim 1 in which the primary air introducing system includes a duct leading to the nozzles and disposed in contact with the inner annular chamber so that the duct is in heat exchanging relation with the inner annular chamber.

Claims

1. Drying apparatus incorporating a primary drying section including a cylindrical chamber, means for introducing material to be dried into one end of the chamber the other end of which is open, and a primary air-introducing system including air nozzles disposed around the axis of the chamber and orientated to discharge in directions inward towards the axis of the chamber and tangential with respect to the axis of the chamber, a secondary drying section connected in series with the first drying section and arranged to receive the material when it leaves the open end of the first drying section, said secondary drying section including a second cylindrical chamber presenting a heat-radiating surface and a secondary air-introducing system including air nozzles disposed around the axis of the chamber and oriented to discharge in directions inward towards the axis of the chamber and tangential with respect to the axis of the chamber, a furnace having a combustion air inlet connected to the secondary drying section and flues disposed in heat-exchanging relationsHip with the heat-radiating surfaces, with the primary air introducing system and with the secondary air introducing system, means for removing dried material from the secondary drying section, and means for causing a pressure drop from the secondary drying section to the flues.

2. Apparatus as claimed in claim 1 in which the means for causing a pressure drop from the secondary drying section to the flues is an ejector in the flues arranged to operate by a fluid under pressure.

3. Apparatus as claimed in claim 1 in which the means for causing a pressure drop from the secondary drying section to the flues is an ejector fan.

4. Apparatus as claimed in claim 1 in which the means for causing a pressure drop from the secondary drying section to the flues is forced draught fan means arranged to introduce the primary and/or the secondary air at a pressure above atmospheric pressure.

5. Apparatus as claimed in claim 1 in which the wall of the cylindrical chamber of the primary drying section is formed with the air-introducing nozzles, and a convergent collecting cone coaxial with and spaced from the chamber is provided at the open end, said cone terminating at the small end in a choke chamber constituting a discharge opening leading to the secondary drying section and being surrounded by an annular chamber for reception of moisture centrifuged out of the material on its passage along the cylindrical chamber and across the gap between the chamber and the cone.

6. Apparatus as claimed in claim 1 in which means is provided within the cylindrical chamber of the primary drying section for directing material to be dried into an annular stream and the air introducing nozzles surrounding the chamber at the open end are orientated to discharge in directions inwardly towards the axis of the chamber and tangential with respect to the axis.

7. Apparatus as claimed in claim 1 in which the primary drying section and the secondary drying section are detachably attached to one another.

8. Apparatus as claimed in claim 1 in which the cylindrical chamber constituting the secondary drying section includes three shells disposed coaxially one within the other so that two annular chambers surround a central chamber, the inner of the two annular chambers being connected to the furnace so that it constitutes part of the flues and the inner shell which defines the central chamber constitutes a heat radiating surface, the outer of the two annular chambers being formed with entry ports for secondary air, the air nozzles of the secondary drying section connecting the outer annular chamber to the central chamber through the inner annular chamber.

9. Apparatus as claimed in claim 1 in which the tangential orientations of the nozzles of the primary drying section and of the secondary drying section are opposite in sense i.e. air introduced through the nozzles of the two section is caused to rotate in opposite directions about the common axis of the two chambers.

10. Apparatus as claimed in claim 6 incorporating extra air introducing nozzles surrounding the open end of the chamber, said nozzles being so orientated that their axes have longitudinal and circumferential components with respect to the axis of the chamber.