US2559989A

US2559989A - Spray drier

Info

Publication number: US2559989A
Application number: US648774A
Authority: US
Inventors: Nyrop Johan Ernst
Original assignee: Individual
Current assignee: Individual
Priority date: 1941-10-09
Filing date: 1946-02-19
Publication date: 1951-07-10
Anticipated expiration: 1968-07-10
Also published as: CH245661A; FR920502A; NL62483C

Description

J. E. NYROP SPRAY DRIER July 10, 1951 3 Sheets-Sheet 1 Filed Feb. 19, 1946 .i r p v 1 I12 21 l7i701 Filed Feb. 19, 1946 3 Sheets-Sheet 3 y 0, 1951 J. E. NYROP 2,559,989

SPRAY DRIER In U 61?, T01

E 0 23/ ,w/cflpmm M0594 Patented July 10, 1951 SPRAY DRIER Johan Ernst Nyrop, Copenhagen, Denmark Application February 19, 1946, Serial No. 648,774 In Denmark October 9, 1941 Section 1, Public Law 690, August 8, 1948 Patent expires October 9, 1961 12 Claims. (Cl. 159-4) This invention relates to the drying of liquid matters, such as solutions, suspensions or slurries or more or less flowable colloidal systems, such as blood or fractions thereof, protein solutions, milk, condensed milk, soap at varying water contents and temperatures and many others. The term drying is used not only for the process of converting a substance into its solid, dry form, but comprises also the conversion of a liquid into a state, in which it contains less water, than it did before drying, or into a state where water is bound by crystallization. Thus the word drying," in the sense in which it is used in the following specification and in the claims, includes also condensing or concentrating or crystallizing the liquid in question.

More particularly the invention relates to dry- I ing a liquid material by atomization and distribution into a current of a gaseous drying medium, such as atmospheric air, passing through a closed drying chamber, the material to be dried and the drying medium being supplied in the upper part of the chamber and the drying medium being withdrawn from the lower part of the chamber carrying all or more or less of the dried particles of the atomized material with it. The invention comprises also the apparatus to be used for carrying out such a drying process in accordance with the present method.

Several constructions of drying apparatus working in the manner generally stated above are known. In most of them the drying medium' does not move directly from the place in the upper part of the chamber, where it is supplied thereto, to the outlet in the lower part of the chamber, through which it is withdrawn, but is also caused to revolve round the axis of the chamber, which for that purpose is generally circular or nearly so in shape. The actual movement of the drying medium in this case is therefore along a helix-line from the upper part of the chamber to the outlet near the bottom.

In some constructions of drying apparatus of the general kind stated above the drying medium is introduced at or through the outer wall of the chamber, whereby it cannot be prevented, however, that this wall takes a comparatively high temperature. As for economical reasons it is desirable to use as high drying temperature as possible, the wall will very often be so hot that material contacting therewith and adhering in its still moist condition thereto will be more or less damaged or burnt. In order to avoid this drawback, it is preferable to introduce the drying medium through a channel opening in the cen-' tral part of the chamber. In this case the walls of the chamber can be kept comparatively cool,

so that no burning of the material impelling thereon can take place. Also inthis case it is possible to impart to the drying medium introduced into the chamber a revolving movement as described above. With the latter kind of drying apparatus an excellent product is obtained even with delicate raw materials. It is a well known fact, however, that the apparatus requires much space for the production of a given quantity of dried material per unit of time.

One object of the present invention is to provide a method and an apparatus, in which less space is required for efiecting a given amount of drying, than in the known apparatus of the general kind mentioned above with or without a revolving movement of the drying medium.

Another object of the present inventioin is to provide a method and an apparatus, in which the tendency of the atomized material to adhere to certain of the surfaces surrounding the drying space, for instance the ceiling of the drying chamber or the parts di posed in the central part of the chamber, which tendency has been experienced in the case, when the drying medium is introduced from the central part of the drying chamber, can be avoided or diminished.

In a drying chamber, in which the drying medium is introduced centrally in the upper part of the chamber just below the means used for atomization and distribution of the material to be dried, there will be a tendency of the drying medium during its general movement towards the lower part of the chamber and irrespectively whether it is caused to rotate about the axis of the chamber or not to form a turbulence about a horizontal annular axis in the sense, that the drying medium is moving downwardly adjacent to the outer wall of the chamber and then moves inwardly in the lower part of the chamber and upwardly in the central part of the chamber.

This turbulence obviously occurs simultaneously with the general movement of the drying medium towards the lowerpart of the chamber and means, that in a horizontal section somewhat below the atomizer and the means of supplying the drying medium to the chamber the particles of the drying medium will move much more rapidly downwards adjacent to the outer wall of the chamber than justified by the amount of drying medium entering at the upper part of the chamber and withdrawn from the lower part of the chamber per unit of timeand the sectional area of the chamber. In contradistinction thereto, in the central part of the chamber the particles of drying medium are moving upwardly or at least they do not move downwardly at the velocity justified by the amount of drying 3 medium entering and withdrawn per unit of time and the sectional area of the chamber. In most cases this turbulence set up by the drying medium being supplied centrally to the chamber is so marked, that the particles of drying'medium are actually moving upwards in the central part of the chamber.

The said turbulence is not influenced by the drying medium being caused to rotate about the vertical axis of the chamber, but it is emphasizedifthereisusedonlyone atomizerdisposed in the middle of the chamber, which ior many other reasons is a very duirable arrangement.

' I have found that by counteracting the said turbulence a marked increase in the output of a given drying apparatus can be achieved.

As a mult of the, said turbulence the atomized material will be tansported downwardly at a comparatively great velocity in the outer parts of the chamber. The material that has thus been transported downwardly at a comparatively great velocity will partially be carried backwards and upwards by the central part of the turbulence, but much of it will not be thus returned to the turbulence but will immediately be carried further to the outlet. As a result of this too rapid travelling of a considerable part of the material comparatively little material can be supplied per unit of time in order to achieve the desired drying effect. Moreover the part of the material carried upwards at the center of the chamber will have a tendency to contact with the walls of the supply-channel for the drying medium or of the distributing means placed at the top thereof. It can hardly be prevented that the said walls of the supply channel are comparatively hot and the material adhering thereto may be damaged. Although the hot surfaces which may thus get into contact with the atomized material aresmallerthaninthecasewhenthedrying medimn is supplied from the outer wall and the quantity of material adhering thereto is also smaller, this is a drawback which it should be desirable to avoid.

With these general statements of the objects andpurposesofmyinvenflonlwillnowproceed to describe the embodiment thereof as far as the method and the apparatus concerns and the manner, in which my invention is carried out, and it will be understood, that while I have described, what may be considered preferable embodiments of my invention I do not limit myself -to the described condition or proportions herein setforthastheymaybevariedbythose skilled ,intheartinaccordancewiththeparticular purposes, for which they are intended and the conditions, under which they are to be utilized.

According to the present invention in order to remove the drawbacks mentioned above I introduce into the chamber at least one current of drying medium in a direction differing from the travelling direction of the current oi drying medium moving through the drying chamber at the place where the additional current is introduced. Bythismeansitispossibletodisturbthesaid undesirable turbulence or to counteract or even 4 to reverse it 'so that a turbulence moving in the opposite direction is produced. In an embodiment of the'method I introduce into the drying chamber a current of drying medium moving upwards along the wall of the chamber. The dryingmediumusedtoupsetthesecurrents accord ing to the embodiment of the method is withdrawn from the chamber itself, the withdrawal being carried out at atleastone point cit-be chamber diilering from that in V which it isinh-oduced again and in a direction din'ering from the direction in which the drying medium moves in the chamber or in which it would move when no additional current were impelling thereon. By thus using drying medium withdrawn from the chamber to upset the current or currents counteracting the said undesired turbulence the advantage is obtained that such drying medium will have a lower temperature than the fresh drying medium supplied centrally into the chamber and thus cannot damage the material to be dried and in case it is to,be introduced through the outer wall cannot heat the same to any undesirable temperature and cause damage to the material getting in contact with it.

In the drawing Fig. 1 is an embodiment of the drying apparatus in vertical section through the axis of the drying chamber,

Fig. 2 is another embodiment, shown in the same manner, and v V Fig. 3 shows diagrammatically the plant, in which the drying apparatus, shown in Fig. 2, works.

In Fig. 1 I is a rotating atomizerv suspended from the ceiling of a cylindrical or polygonal container, the drying chamber 2. I prefer the said rotating kind of atomizing apparatus, which permits of producing very uniform particles and spreading them evenly over the area of the drying chamber, but it is to be understood that other kinds of atomizers disposed in the upper part of the drying chamber 2 suspended from the ceiling or projecting from the upper part of the side wall can be used in sufficient number to distribute the atomized material over substantially the whole of the sectional area of the drying chamber. Just below the atomizer there is disposed centrally in the chamber a distributing member 3 for supplying the drying medium, for

7 instance hot air, steam, combustion products or the like. The distributing member in the preferred embodiment shown is placed at the opening of a duct or channel 4, introduced in the chamber through the lower part of its wall and standing vertically in the middle of the chamber. Through this channel or duct the drying medium is supplied. The lower part of the chamber 2 in the embodiment shown is formed as a cone or pyramid 9, having at its point an opening with a closure 8, through which dried material, that has settled to the bottom, can be removed. As a matter of fact, with most materials to be dried, the dry particles will be carried away with the drying medium leaving the chamber, and the conical shape of the bottom of the chamber therefore in such cases is not important.

Adjacent to the bottom of the chamber is the opening i of a duct or channel 5, through which the drying medium is withdrawn, carrying with it all or some of the dried material.

A channel It, the end of which forms a. collar surrounding the lower part of the vertical part of the duct I said collar being open at its upper end, penetrates the lower part of the wall of the chamber. Another channel I penetrates the side wall of the chamber at a point lower than that, in which the material is atomized and distributed. in the embodiment shown the channel I penetrates the wall in horizontal direction radiallytothe chamber.

The apparatus shown in Fig. 1 operates in the following manner. Leaving first out of consideration the channels it and I, by introducing the material to be dried through the atomizer and the drying medium through the channel 4 and distributor 3 and withdrawing the drying medium carrying dry material with it through the duct 5 the undesirable turbulence shown by the dotted arrows 21 will make its appearance. By now withdrawing drying medium through the channel I5 and returning it through the channel 1 this turbulence will be counteracted and a turbulence essentially as shown by the fully drawn arrows '25 will result. It will be seen that the direction, in which the drying medium is withdrawn by means of the collar and channel I5 is downwardly in the middle of the chamber, which is a direction that differs essentially from the direction, in which the drying medium would move at this point had there been no withdrawal through the duct l5 or no addition through the channel I. ,In fact it is opposite thereto. Similarly the direction,-in..which the current arrives through the channel I differs radically from the direction, in which the drying medium would move at this point if there had been no supply through said channel or withdrawal through the channel and collar Hi. In fact the undesirable turbulence in this manner may be at least partially reversed i. e. the lower part of it is reversed.

Even if the currents do not take the regular form shown in the drawing, it is evident that the undesirable turbulence is radically disturbed and it has been found that this makes possible a great increase in the output of a given chamber at the same time diminishing the quantities of matemanner: When the liquid to be dried is supplied through the atomizer I and the drying medium is supplied through the channel 4 and distributor 3 and withdrawn through the channel 5 the formation of a turbulence like the one shown by rial adhering to the walls of the duct 4 and distributing means 3. An obvious variation in this embodiment of the invention is to make the duct 1 end in an annular chamber surrounding the drying chamber and having several openings, through which the drying medium can be supplied. Another obvious variation is placing a shield or guiding surface in the interior of the chamber in front of the opening of the channel I guiding the current supplied through the same in an upward direction so as to counteract still more directly the undesirable turbulence.

In Fig. 2 another embodiment is shown. In order to make the same easily comparable with the embodiment shown in Fig. 1 so that the principle underlying the invention will appear as clearly as possible the shape of the chamber, the kind and arrangement of the atomizer and the arrangement of the supplying channel 4 and the withdrawal channel 5 for the drying medium are similar to Fig. 1. In the point of the cone forming the bottom of the chamber there is a supplying tube 28 to permit a current of drying medium to be introduced at this place. Surrounding the top of the channel 4 there is an annular chamber l4, which has an annular opening at its lowermost end so as to permit a current of drying medium to be sent therethrough downwards along the wall of the vertical part of the channel 4. In the side wall ofthe drying chamber 2 there is the opening of a channel 1 similar to the channel I of Fig. 1. Finally under the ceiling of the drying chamber 2 there is an annular chamber I3 surrounding the housing of the atomizer I and carrying on its outer wall openings I: permitting a current to be sent in outward direction closely beneath the ceiling. Both the chamber l4 and the chamber l3 are connected in a man-- ner not shown in the drawing to a supply of drying medium.

In the lower part of the cone there is placed a conical guiding surface [0 with its point downthe dotted arrows 21 will take place. In order to counteract the same, drying medium withdrawn through the channel I is supplied through the tube 28, and the chambers l4 and I3. The current arriving through the tube 28 is guided by the conical guiding surface l0, so that it runs upwards along the walls of the drying chamber thereby counteracting the downwardly going current in the outer part of the chamber. On the other hand the down-going current from theorifice of the chamber I4- counteracts the upwardly going current in the interior of the chamber.

'The withdrawal 'ofdrying medium through the border of the guiding surface ll whereby the" light and dry particles will be carried at preference with the drying medium withdrawn through the said channel whereas the heavier still moist particles will continue their way against the bottom of the cone until they are caught by the. current arriving through the tube 28 and carried again up-into the higher parts of the chamber to be further dried. The current arriving through the openings I3 serves to keep the ceiling clear of adhering'material and counteracts the local turbulence or whirl in this part of the chamber and shown in Fig. 1 by arrows 25.

Obvious variations in this embodiment of the invention may for instance consist in that a shield is provided in the chamber in front of the opening of the channel 1, said shield being so placed that the air withdrawn through said channel is introduced therein from below. As mentioned in connection with Fig. 1 the opening of the channel I may be replaced by several openings round the circumference of the chamber. Another variation is that drying medium is withdrawn through the tube 28 of the cone and introduced through the channel I. As described in connec tion with Fig. 1 the introduction of drying me'-" dium through the channel I will actively disturb the undesirable turbulence, but in this case, when drying medium is withdrawn from the point of i the cone, the guiding surface I. must be omitted to prevent the formation of a distinct current opposite to the arrows shown, along the walls of thechamber, in the downwarddirection.

Fig. 3 shows the embodiment of Fig. 2 as a part of a drying plant. 24 is a channel, through which fresh air is taken in and carried to a propelling device It, blowing the air through heating means II and through the channel 4 to the distributor 3" by which it is supplied to the drying chamber. The outlet channel 5 from the drying chamber leads to a centrifugal separator 20, in which the main part of the dried product is removed from the air and then the air is carried to a straining device, washing separator or any other device 2| adapted to absorb or remove the residue of substance still carried with the air from the separator 20. Finally the air goes through an outlet channel 23 to the atmosphere. From the outlet channel 23 a branch channel 22 returns to the inlet channel 24. Through the branch 22 a predetermined part of the air controlled by valves 2! or the like can be returned to the system and mixed with the air taken in through the channel H.

The channel 'I and tube 28 are connected by a tube IT, in which a propelling device It is inserted. The channels l3 and 14 are connected with the channel 8 or with the pressure side of the propelling device 16 by tubes not shown in the figure.

In the plant shown the purpose of the invention has been attained by circulation of a rather considerable amount of drying medium per unit of time, but the purpose can be equally well attained by the introduction by means of suitable nozzles of comparatively small quantities of drying medium at comparatively high Pressure and velocity in a manner otherwise similar to that shown and described, so that the supply is carried out in such direction and in such points that the described undesirable turbulence is counteracted, disturbed or reversed.

I claim:

1. In an apparatus for drying a mass or liquefled material, the combination of a closed chamber provided at its lower portion with a discharge duct; a pipe passed through the top of said chamber and disposed co-axially of said chamber; an atomizer on the end of said pipe and disposed in the upper portion of said chamber; a, second pipe passed through the wall of said chamber and having its terminal portion in said chamber disposed co-axially with said first pipe; a nozzle on the end of said terminal portion and disposed closely adjacent said atomizer; a discharge conduit passed through the wall ofsaid chamber and having an annular intake portion dispose about the lower end of said terminal portion; and a supply conduit passed through the wall of said chamber, connected with said discharge conduit and having per part of the chamber, said introducing pipe comprising a channel a part or which stands vertically in the middle of the chamber and carries at its top a distributor for thegasecus drying me dium a discharge pipe in the side or said chamber for the withdrawal of the drying medium together with the dried material carried thereby from the lower part or the chamber, at least one pipe in its discharge end in said chamber disposed normal to said terminal portion and intermediate said nozzle and said annular intake'portion.

2. In an apparatus for drying a mass of liquefled material, the combination of a closed chamber provided at its lower portion with a discharge duct; a pipe passed through the top oi said chamber and disposed co-axially oi said chamber; an atomizer on the end of said pipe and disposed in the upper portion of said chamber; a second pipe passed through the wall of said chamber and having its terminal portion in said chamber disposed co-axially with said first pipe; a nozzle on the end of said terminal portion and disposed closely adjacent said atomizer; a supply pipe passed through the, bottom of said chamber; a discharge pipe passed through the wall of said chamber, disposed normal to the common axis 01' said first pipe and said terminal portion, connected with said supply pipe and having its intake end in said chamber disposed below said nozzle.

3. Drying apparatus comprising a substantially closed chamber, a supply pipe in the. top of said chamber for introducing the material to be dried in the atomized state in the upper part thereof, a pipe in the side of said chamber for introducing a gaseous drying medium centrally in the uptially closed chamber, a supply pipe in the top the side of the chamber for an additional current of said medium and said material, and an outlet duct disposed peripherally at the lower part of said channel and having an aperture at the upper side thereof through which a current of said medium and said material is caused to enter in a downward direction along the wall of said.

channel.

4. Drying apparatus comprising a substantially closed circular chamber having an inverted conical bottom, a supply pipe in the top of said chainber for introducing the material to be dried in the atomized state in the upper part thereof, a pipe mounted in the side of said chamber for introducing a gaseous drying medium centrally in the upper part of the chamber and with a circulatory movement during its passage through the chamber, a discharge pipe in the side of said chamber for withdrawal of the drying medium together with the dried material carried thereby from the lower part of the chamber, and an inlet pipe in the center of said conical bottom for introducing a diffused current of said medium and said material for movement upwardly along the walls of the chamber.

5. Drying apparatus comprising a substantially closed circular chamber having a conical bottom, a supply 'pipe in the top of said chamber for introducing the material to be dried into the upper part thereof in the atomized state, a pipe mounted in the side of said chamber for introducing a gaseous medium centrally in the upper part of the chamber, a discharge pipe mounted in the side of said chamber for withdrawing the drying medium and the dried material carried thereby from the lower part of the chamber, an inlet pipe in the center of said conical bottom for introducing a drying medium and withdrawal 01 it from the lowv or part of the chamber are continued.

6. Drying apparatus. comprising a substantially closed cylindrical chamber, a supply pipe in the top of said chamber for introducing the material to be dried into the upper part thereof in the atomized state, a pipe mounted in the side of said chamber for introducing a main current of a gaseous dryin medium centrally in the upper part of the chamber, below the atomized material, a discharge pipe mounted in the side of said chamber for withdrawing the drying medium and the dried material carried thereby from the lower part of the chamber, a supply pipe in the top of said chamber for introducing an additional current of said medium and said material adjacent to the center of the ceiling of the chamber and for movement along the ceiling radially of the vertical axis of the chamber.

7. Drying apparatus comprising a substanof said chamber for introducing the material to be dried into the upper part thereof in the atomized state, a pipe in the side of said chamber for introducing a current of a gaseous drying medium centrally in the upper part of the chamber, a diffusion member for distributing said current evenly radially of the introducing pipe, said pipe for introducing said medium being disposed centrally in the chamber below said pipe for introducing the material, and said diffusion member, and having a vertical channel centrally of the chamber for leading said current to the difiusion member, said difl'usion member being mounted upon the top of said channel, an outlet duct disposed peripherally of said channel for producing an additional current of said medium and said material for movement downwardly along the wall of said channel, and a discharge port for withdrawal Of said medium and the dried material carried thereby from the lower part of the chamber.

8. In an apparatus for drying a mass of liquefled material, the combination of a closed chamber; a pipe communicating with said chamber and having an atomizing head in said chamber for introducing said mass in atomized condition into the upper portion of said chamber; a pipe extending into said chamber for introducing into the upper portion of said chamber, at a point below said atomized mass, a radially diilused current of a gaseous drying medium which would normally tend to create turbulence of said material and said medium in said chamber; inlet and discharge ports in said chamber; and current-inducing pipes connected to said ports; and a discharg from said chambe 9. Drying apparatus comprising a substantially closed chamber, a. supply pipe in the top of said chamber for introducing the material to be dried in the atomized state in the upper part thereof, a pipe in the side of said chamber for introducing a gaseous drying medium centrally in the upper part of the chamber, said introducing pipe comprising a channel a part of which stands vertically in the middle of the chamber and carries at its top a distributor for the gaseous drying medium, a discharge pipe in the side of the chamber for the withdrawal of the dryin medium together with the dried material carried thereby from the lower part of the chamber. at least one pipe in the side of said chamber for an additional current of said medium; and an outlet duct disposed peripherally at the lower part of said channel and having an aperture at the upper side thereof through which a current of said medium and said material is caused to enter in a downward direction along the wall of said channel.

10. Drying apparatus comprising a substantially closed circular chamber having an inverted conical bottom, supply pipe in the top of said chamber for introducing the material to be dried in the atomized state in the upper part thereof. a pipe mounted in the side of said chamber for introducing a gaseous drying medium centrally in the upper part of circulatory movement during its passage through the chamber, a discharge pipe mounted in the side of said chamber for withdrawal of the drying medium together with the dried material carried thereby from the lower part of the chamber, and an inlet pipe in the center of said conical bottom for introducing a, difl'used current of pipe for evacuating said mass the chamber and with a v said medium for movement upwardly along the walls of the chamber.

11. Drying apparatus comprising a substantially closed circular chamber having a cor bottom, a supply pipe in the top of said Chi. her for introducing the material to be dried into the upper part thereof in the atomized state, a pipe mounted in the side of said chamber for introducing a gaseous medium centrally in the upper part of the chamber, a discharge pipe mounted in the side of said chamber for withdrawing the drying medium and the dried material carried thereby from the lower part of the chamber, an inlet pipe in the center of said conical bottom for introducing a diliused current of said medium for movement upwardly along the walls of the chamber, and an outlet pipe for withdrawing said medium and said material from another part of the chamber in a direction differing from that in which the main current of drying medium will move when the current introduced in the center of the bottom, and the withdrawn current are discontinued, while the central introduction of the drying medium and withdrawal of it from the lower part of the chamber are continued.

12. Drying apparatus comprising a substantially closed cylindrical chamber, a supply pipe in the top of said chamber for introducing the material to be dried into the upper part thereof in the atomized state, a pipe mounted in the side of said chamber for introducing a main current of a gaseous drying medium centrally in the upper part of the chamber, below the atomized material, a discharge pipe mounted in the side of said chamber for withdrawing the drying medium and the dried material arried thereby from the lower part of the chamber, a supply pipe in the top of said chamber for introducing an additional current of said medium adjacent to the center of the ceiling of the chamber and for the movement along the ceiling radially of the vertical axis of the chamber.

JOHAN ERNST NYROP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,213,887 Krause June 30, 1917 1,374,555 Dick Apr. 12, 1921 1,490,208 Fleisher Apr. 15, 1924 1,491,026 Brindle Apr. 22, 1924 1,594,064 MacLachlan July 27, 1926 1,734,677 Kreisinger Nov. 5, 1929 1,754,941 Frohring et al Apr. 15, 1930 1,756,772 Weisberg et a1. Apr. 29, 1930 1,829,477 Douthitt Oct. 27, 1931 1,914,895 Peebles June 20, 1933 2,010,101 MacLachlan et a1. Aug. 6, 1935 2,277,827 Heath et a1 Mar. 31, 1942 2,280,073 Hall Apr. 21, 1942 2,333,333 Peebles Nov. 2, 1943 ,415,527 Peebles Feb. 11, 1947 2,473,035 Meade et a1. June 14, 1949 FOREIGN PATENTS Number Country Date 76,782 Austria June 10, 1919 478,925 Great Britain Jan. 27, 1938 530,613 Great Britain Dec. 16, 1940 552,475 Great Britain Apr. 9, 1943