Spray-drying apparatus and method of use

Abstract

Provided is a spray drying apparatus comprising a spray nozzle comprising a spray nozzle tip at the distal end of the spray nozzle, a liquid conduit for guiding a liquid to be spray-dried out through the spray nozzle tip, an atomizing component for producing a spray of droplets from the liquid exiting the spray nozzle; a drying gas conduit comprising an outlet for directing a drying gas to dry the spray of droplets; and a drying gas deflector positioned so as to deflect a flow of the drying gas away from the spray nozzle tip.

Claims

1. A spray drying apparatus comprising: (i) a spray nozzle having a proximal end and a distal end, said spray nozzle comprising: a spray nozzle tip at said distal end of said spray nozzle, said tip having a liquid exit aperture; a liquid conduit for guiding a liquid to be spray-dried out through said spray nozzle; an atomizing component for producing a spray of droplets from said liquid exiting said spray nozzle; (ii) a drying gas conduit comprising an outlet for directing a drying gas to dry said spray of droplets wherein the drying gas from the drying gas conduit flows substantially parallel to the longitudinal axis of spray nozzle and past spray-drying nozzle tip; and: (iii) a drying gas deflector having an inner volume and positioned so as to deflect a flow of the drying gas away from the spray nozzle tip, wherein the spray nozzle tip does not protrude beyond the distal end of the drying gas deflector, and wherein the liquid exit aperture is within the inner volume of the deflector.

2. A method of spray drying a liquid comprising: providing a spray drying apparatus according to claim 1; spraying a liquid as a spray of droplets from a spray nozzle tip; directing a flow of drying gas at said spray of droplets; and deflecting a flow of the drying gas away from the spray nozzle tip using said drying gas deflector.

3. The spray drying apparatus according to claim 1, wherein said atomizing component comprises an atomizing gas conduit for guiding a flow of atomizing gas out through an atomizing gas outlet to contact liquid exiting said spray nozzle tip.

4. The spray drying apparatus according to claim 1, wherein deflecting the flow of drying gas away from the spray nozzle tip prevents the drying gas exiting the drying gas outlet from heating a space within up to 3 mm of the spray nozzle tip in any direction.

5. The spray drying apparatus according to claim 1, wherein the drying gas deflector comprises an open base at a distal end.

6. The spray drying apparatus according to claim 1, wherein the drying gas deflector is mounted on the spray nozzle at a position proximal to the distal end of the spray nozzle.

7. The spray drying apparatus according to claim 1, wherein the drying gas deflector comprises a hollow, truncated cone portion having an open base in the shape of a circle; and a side section tapering to a proximal end, wherein the proximal end comprises an aperture having a circumference configured for positioning around an outer circumference, at least partially, of a position proximal to the distal end of the spray nozzle.

8. The spray drying apparatus according to claim 7, wherein the drying gas deflector further comprises a hollow cylindrical portion comprising a distal end and a proximal end, said distal end extending from the proximal end of the truncated cone portion in a direction opposite to that of the base of the truncated cone portion.

9. The spray drying apparatus according to claim 8, said hollow cylindrical portion having an inner diameter configured for positioning at least partially around an outer circumference of the spray nozzle.

10. The spray drying apparatus according to claim 8, wherein the truncated cone portion and the hollow cylindrical portion are formed as a monolithic structure.

11. The spray drying apparatus according to claim 1, wherein the drying gas deflector is mounted directly on the spray nozzle or the nozzle tip.

12. The spray drying apparatus according to claim 1, wherein the drying gas deflector is mounted directly on the atomizing component.

13. The spray drying apparatus according to claim 1, wherein the drying gas deflector is formed from a thermally insulating material.

14. The spray drying apparatus according to claim 1, wherein the inner dimensions of the drying gas deflector are such so as not to interfere with propagation of the spray.

15. The spray drying apparatus according to claim 1, wherein the liquid comprises a heat-sensitive substance.

16. The spray drying apparatus according to claim 1, wherein the heat-sensitive substance comprises fibrinogen.

17. The spray drying apparatus according to claim 1, wherein a temperature of the drying gas is at least 100 C.

18. The spray drying apparatus according to claim 7, wherein a ratio of the circumference of the open base of said distal end of said hollow, truncated cone portion to a length of the side section of said hollow, truncated cone portion is in the range of from about 1:100 to about 100:1.

19. The method according to claim 2, wherein the drying gas deflector comprises a hollow, truncated cone portion having an open base in the shape of a circle; and a side section tapering to a proximal end, wherein the proximal end comprises an aperture having a circumference configured for positioning around an outer circumference, at least partially, of a position proximal to the distal end of the spray nozzle.

20. The method according to claim 19, wherein the drying gas deflector further comprises a hollow cylindrical portion comprising a distal end and a proximal end, said distal end extending from the proximal end of the truncated cone portion in a direction opposite to that of the base of the truncated cone portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Some embodiments of the invention are described herein with reference to the accompanying figures. The description, together with the figures, makes apparent to a person having ordinary skill in the art how some embodiments of the invention may be practiced. The figures are for the purpose of illustrative discussion and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the invention. For the sake of clarity, some objects depicted in the figures are not to scale.

(2) In the Figures:

(3) FIG. 1 (Prior Art) is a schematic representation of a prior art spray-drying apparatus;

(4) FIG. 2 (Prior Art) is a schematic representation of a portion of the spray-drying apparatus of FIG. 1, showing a prior art spray-drying nozzle;

(5) FIG. 3 is a schematic representation of an embodiment of a drying gas deflector in accordance with the principles of the present invention, shown in cross-section;

(6) FIGS. 4A to 4D are schematic representations of a perspective view, proximal end view, a side view and a distal end view, respectively, of the drying gas deflector of FIG. 3;

(7) FIG. 5 is a schematic representation of the drying gas deflector of FIG. 3, and a spray nozzle on which the drying gas deflector is to be mounted;

(8) FIG. 6 is a schematic representation of the drying gas deflector of FIG. 3, mounted on a spray nozzle; and

(9) FIG. 7 is a schematic representation of a spray drying apparatus comprising a drying gas deflector fixed indirectly on the spray nozzle.

DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

(10) The invention, in some embodiments thereof, relates to a spray-drying apparatus comprising a drying gas deflector and a method of use thereof

(11) The principles, uses and implementations of the teachings herein may be better understood with reference to the accompanying description. Upon perusal of the description, one skilled in the art is able to implement the invention without undue effort or experimentation.

(12) Before explaining at least one embodiment in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description. The invention is capable of other embodiments or of being practiced or carried out in various ways.

(13) The phraseology and terminology employed herein are for descriptive purpose and should not be regarded as limiting.

(14) FIG. 3 is a schematic representation of an exemplary embodiment of a drying gas deflector 40 in accordance with the principles of the present invention, comprising a hollow, truncated-conical portion 42 having a distal end constituting distal end of drying gas deflector 44 comprising an open base with a circle-shaped periphery, and side section 46, inwardly tapering to a proximal end 48, proximal end 48 having smaller dimensions than distal end 44, proximal end 48 comprising an aperture 49 having a circumference configured for positioning at least partially around an outer circumference of a portion of spray nozzle 14 proximal to distal end 20 on which drying gas deflector is to be mounted. Side section 46 of drying gas deflector 40 has a length 50 and a thickness 52. Distal end 44 of drying gas deflector 40, comprising the open base of truncated cone portion 42 has an outer diameter 54.

(15) Drying gas deflector 40 further comprises a hollow cylindrical portion 56, comprising a distal end 57 and a proximal end 59, distal end 57 extending from the proximal end 48 of truncated conical portion 42, in a direction opposite to that of distal end of drying gas deflector 40. Hollow cylindrical portion 56 has an inner diameter 58 having a circular aperture 49 with an inner diameter so as to be positioned concentrically around a portion of spray nozzle 14 on which drying gas deflector is to be mounted, an outer diameter 60, a length 62 and a wall thickness 64.

(16) In the exemplary embodiment shown in FIG. 3, outer diameter 54 of distal end 44 of drying gas deflector 40, comprising the open base of truncated cone portion 42 of drying gas deflector 40 is 10 mm, side section 46 has length 50 of 2.9 mm and thickness 52 of 1 mm and side section 46 is configured to provide an opening angle 66 of about 118 between opposing sections 46a and 46b (shown in FIG. 3 in a side section view), that is to say, 59 from a longitudinal axis 67 of a spray nozzle on which the gas deflector is mounted. Hollow, cylindrical portion 56 has an inner diameter 58 of about 3 mm and an outer diameter 60 of about 5 mm, a length 62 of about 2.5 mm, and a wall thickness 64 of about 1 mm.

(17) FIGS. 4A to 4D are schematic representations of a perspective view towards distal end 44 (FIG. 4A), a view facing the proximal end 59 (FIG. 4B), a side view (FIG. 4C) and a view towards distal end 44 (FIG. 4D), respectively, of the exemplary drying gas deflector 40 of FIG. 3.

(18) FIG. 5 is a schematic representation of the exemplary drying gas deflector 40 described above and a spray nozzle 14 on which drying gas deflector 40 is to be mounted by sliding over a distal portion surrounding spray-drying nozzle tip 22. As shown in FIG. 5, proximal end 59 of hollow cylindrical portion 56 of drying gas deflector 40 is configured to be positioned concentrically around atomizing component 25 located at the distal end of spray nozzle 14.

(19) In the embodiment depicted in FIG. 5, proximal end 59 of hollow cylindrical portion 56 of drying gas deflector 40 is configured to fit securely directly around an outer portion of the distal end of spray nozzle 14 such that mounting of drying gas deflector 40 on spray nozzle 14 comprises pushing drying gas deflector onto the distal end of spray nozzle 14. Optionally, spray nozzle 14 and hollow cylindrical portion 56 of drying gas deflector 40 may be provided with mutually mateable components, such as matching threads, such that mounting of drying gas deflector 40 on spray nozzle 14 comprises rotating drying gas deflector 40 onto spray nozzle 14.

(20) As shown in FIG. 5, prior to mounting of drying gas deflector 40, on distal end of spray nozzle 14, drying gas from drying gas conduit 16 (see FIG. 1, not depicted in FIG. 5) flows substantially parallel to the longitudinal axis of spray nozzle 14 and past spray-drying nozzle tip 22, in a direction indicated by arrows 68, such that nozzle tip 22 is heated by the drying gas.

(21) FIG. 6 is a schematic representation of drying gas deflector 40 mounted on distal end of spray nozzle 14. Spray-drying nozzle tip 22 is positioned within the hollow defined by truncated conical portion 42 of drying gas deflector 40, and does not protrude beyond distal end 44 thereof. Drying gas from drying gas conduit 16 initially flows substantially parallel to the longitudinal axis of spray nozzle 14. Upon encountering an external surface of side section 46 of truncated cone portion 42, the flow of the drying gas is deflected outwards, and away from nozzle tip 22, in a direction indicated by arrows 70. Drying gas deflector 40 acts as a thermal insulator, preventing substantial heating of nozzle tip 22 and/or of the inner volume defined by the side section 46 of truncated-conical portion 42 of the drying gas deflector by the hot drying gas.

(22) In some embodiments, spray drying with a drying gas deflector 40 reduces the temperature by about 25% to 90%. In some embodiments the temperature at nozzle tip 22 is reduced by about 40% to 50%. In some embodiments the temperature within the inner volume is reduced by about 25% to 30%. In such embodiments, the reduction percentage is compared to the temperature of the hot drying gas measured in the same location without the use of a deflector during the spray drying process.

(23) FIG. 7 is a schematic representation of spray drying apparatus 10 comprising drying gas deflector 40 fixed indirectly on the spray nozzle, for example by connecting the deflector to the drying chamber inner walls, drying chamber proximal end or any other part of the spray dryer unit which will allow the deflector to function as described.

EXAMPLES

(24) Materials and Methods

(25) Three different drying gas deflectors 40, each according to an embodiment of the teachings herein, were provided. Specifically, drying gas deflectors 40a, 40b, and 40c having a distal end 44 with an outer diameter 54 of 6 mm, 8 mm and 10 mm, respectively, were provided. Length 50 was also changed in order to allow for diameter 54 to be either 6 mm, 8 mm or 10 mm. All other dimensions were as described above with regard to FIG. 3.

(26) Spray Drying apparatus 10 (4M8 trix, Procept Belgium) including a circulating cool water mechanism (as shown in FIG. 2) for spray nozzle 14 was used according to the manufacturer's instructions, with the following settings during a spray drying process:

(27) inlet gas flow: 0.3 m.sup.3/min;

(28) inlet air temperature: 140 C.;

(29) entering circulating cool water a temperature: 5 C.; and

(30) nozzle atomizing air flow: 11 l/m.

(31) Spray nozzle tip included a 1.2 mm diameter orifice.

Example 1: The Effect of a Drying Gas Deflector Mounted on a Spray Nozzle on Temperature During Spray-Drying

(32) For each experiment, one of the three drying gas deflectors 40a, 40b, 40c was mounted on spray nozzle 14 substantially as depicted in FIG. 6, drying gas was passed into drying gas conduit 16 at a temperature of 140 C., with no liquid passing through liquid conduit 24, and the temperature at different locations A, B, C and D relative to spray nozzle tip 22 was measured for each of gas deflectors 40a, 40b and 40c. As a control, the temperature at each of positions A, B, C and D was measured in the absence of a drying gas deflector.

(33) Positions A, B and C represent positions along the longitudinal axis of the spray nozzle: at nozzle tip 22 (A), at 1 mm below nozzle tip 22 (B), and 5 cm below nozzle tip 22 (C). Position D represents a position 5 cm below nozzle tip 22 that is about 5 cm off-axis and which is close to the edge of a spray of liquid produced during operation of spray drying apparatus 10. Positions A and B are within the inner volume defined by the side section 46 of truncated-conical portion 42 of drying gas deflector 40a, 40b or 40c, while positions C and D are outside the volume. Position D is outside the longitudinal axis of spray nozzle 14. Positions C and D represent points at which drying of the spray formed from the liquid upon exiting nozzle tip 22 occurs.

(34) Temperature measurements were performed using a thermocouple unit including a data logger TM-747D (MRC, Israel) and an air thermocouple wire (type T, MRC, Israel) as follows:

(35) A guide wire (used to position the thermocouple wire in place) was inserted through the liquid conduit 24, such that the sensor was positioned at locations A, B, C or D. The thermal sensor was covered with a silicone tube, except for the distal end of the sensor which remained exposed and was configured to measure temperature.

(36) Table 1 show the temperature in C. at the different locations, measured with or without a drying gas deflector 40 mounted on spray nozzle 14. The reduction in temperature with use of a deflector with respect to the temperature in the absence of a deflector is given in parentheses.

(37) TABLE-US-00001 TABLE 1 With drying gas deflector Without Deflector Deflector Deflector Thermal sensor drying diameter diameter diameter location gas deflector 10 mm - 40c 8 mm - 40b 6 mm - 40a A 62 35 (44%) 31 (50%) 35 (44%) B 56 40 (29%) 42 (25%) 40 (29%) C 110 50 (55%) 45 (59%) 50 (55%) D 110 103 (6%) 100 (9%) 104 (5%)

(38) The results show that when a drying gas deflector 40a, 40b or 40c according to the teachings herein was mounted on the atomizing component 25 of the spray nozzle 14, the temperature at spray nozzle tip 22 (position A) was reduced from 62 C. to between 31 C. and 35 C. (44-50% reduction in temperature), at which temperatures substantial protein denaturation does not occur during the short heating time used in the spray-drying process. At a distance of 1 mm from spray nozzle tip 22 (position B), a lesser temperature reduction of from 56 C. to between 40 C. and 42 C. was seen (25-29% reduction). At a distance of 5 cm from spray nozzle tip 22 (position C), a temperature reduction of from 110 C. to between 45 C. and 50 C. was seen (55-59% reduction), while at position D, at which presumably no deflection of drying gas occurs, no substantial reduction in temperature was seen (5-9% reduction) in the presence of a drying gas deflector 40a, 40b or 40c, such that drying of the spray will not be affected by an undesirable reduction in temperature at this location.

Example 2: The Effect of a Drying Gas Deflector Mounted on a Spray Nozzle During Spray-Drying on the Spraying Pattern of a Proteinaceous Solution

(39) 40 ml fibrinogen-containing solution, BAC2 (EVICEL Fibrin Sealant diluted with an equal volume of double distilled water (DDW)), having a fibrinogen concentration of 30 mg/ml and a total protein concentration of 50 mg/ml, was spray dried as described above, with a drying gas deflector 40c mounted on spray nozzle 14.

(40) The fibrinogen-containing solution was fed into the liquid conduit 24 at a rate of 400 ml/hour, and the effect on the spray pattern (the shape of the spray) was visually inspected.

(41) As a control, the spray pattern was observed in the absence of a drying gas deflector 40.

(42) After spray-drying of 30 ml of the fibrinogen-containing solution under the conditions described, in the absence of drying gas deflector 40c, aggregation of particles was observed at the edge of nozzle tip 22. As a result, after a time, the spray pattern was observed to deviate from a symmetrical conical shape, and droplets were accumulated on the inner surface of drying column 12. Also, it was observed that the size of the droplets produced increased over time, such that large droplets were produced instead of the fine droplets observed at the beginning of the spray-drying process.

(43) At the conclusion of the spray-drying, spray nozzle tip 22 was inspected at the orifice of spray nozzle tip 22. It was observed that the orifice of spray nozzle tip 22 was filled with solid material.

(44) Subsequently, drying gas deflector 40c, having a distal end 44 with an outer diameter 54 of 10 mm was mounted on spray nozzle 14, and the fibrinogen-containing solution was spray dried as described above. With drying gas deflector 40c mounted on spray nozzle 14, 40 ml fibrinogen-containing solution was spray-dried as described above. A uniform conical spray pattern was observed, with no deviation of the spray stream from the original direction, and the size of the droplets remained unchanged and fine during the entire process, with no observed accumulation of liquid or solids on the walls of drying column 12. At the conclusion of the spray-drying, spray nozzle tip 22 was inspected and it was observed that the orifice of spray nozzle tip 22 was clean and clear of any solid material.

(45) Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the scope of the appended claims.

(46) Citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the invention.