Field of the Invention:

The present invention relates to spray dryer apparatus for producing spray dried powders. In particular, the present invention relates to a spray dryer apparatus replaceably receiving a high pressure nozzle atomizer and a rotary centrifugal atomizer.

Background of the Invention:

Spray drying has existed as a basic material processing operation since the late l800s. Spray drying typically involves injecting a wet material in the form of droplets into a chamber and bringing the droplets in contact with drying gas, thereby producing a spray dried powders that is discharged from the drying chamber. Injection of the wet material into the drying chamber may be done using a centrifugal atomizer (or alternatively referred to as rotary centrifugal atomizer), a high pressure nozzle atomizer, or the like. The drying gas may have temperature of the order of 35-200° C and is introduced using a gas disperser.

It is well known that rotary centrifugal atomizers produce smaller particle sizes with higher bulk densities whereas high pressure nozzle atomizers are known to produce bigger particle sizes with lower bulk densities. Also, it is well known that rotary centrifugal atomizers can be used only to inject certain types of wet materials into the drying chamber and likewise, it is well known that high pressure nozzle atomizers can be used only to inject only certain types of wet material into the drying chamber.

It is also well known, that if the spray dryer is provided with a rotary centrifugal atomizer, the drying chamber is constructed as per a first set of criteria and generally, the Height vs. Diameter ratio of the drying chamber is 1:0.8. On the other hand, if the spray dryer is provided with a high pressure nozzle atomizer, the drying chamber is constructed as per a second set of criteria and generally, the Height vs. Diameter ratio of the drying chamber is 3.5:1.

It is furthermore well known, that if the spray dryer is provided with a rotary centrifugal atomizer, the drying gas has to be introduced in a downward spiralling gas flow path. As the rotary centrifugal atomizer in itself may not be best suited for introducing the drying gas in the downward spiralling gas flow path, it is a common practice to use specially designed gas disperser. On the other hand, it is well known that if the spray dryer is provided with a high pressure nozzle atomizer, the drying gas has to be introduced in a downward symmetric gas flow path. As the high pressure nozzle atomizer in itself may not be best suited for introducing the drying gas in the downward symmetric gas flow path it is a common practice to use specially designed gas disperser.

Thus, it can be said that spray dryers are designed to operate with a single type of atomizer. Because of the above, factors such as construction of the drying chamber, construction of the gas disperser, etc., are chosen as per the particular type of atomizer thus used. In particular, it can be said that, no one provides in a spray dryer a combination of gas disperser which is specifically designed for introducing the drying gas along the downward spiralling gas flow path and a high pressure nozzle atomizer. Likewise, no one provides in a spray dryer a combination of gas disperser which is specifically designed for introducing the drying gas along the downward symmetric gas flow path and a rotary centrifugal atomizer.

Even in terms of construction of the atomizers, a high pressure nozzle atomizer is not constructed to work in conjunction with a gas disperser which is specifically designed for introducing the drying air along the downward spiralling gas flow path. Likewise, a rotary centrifugal atomizer is not constructed to work in conjunction with a gas disperser which is specifically designed for introducing the drying gas along the downward symmetric gas flow path.

Also, the atomizers (both the rotary centrifugal atomizers as well as high pressure nozzle atomizers) are adopted for fixed mounting with respect to the drying chamber. Thus, the spray dryer is not provided with an attachment mechanism that can replaceably receive a high pressure nozzle atomizer and a rotary centrifugal atomizer in the same gas disperser system.

Thus, if the intent is to produce spray dried products from two wet materials, with the first wet material requiring a rotary centrifugal atomizer for injection into the drying chamber and the second wet material requiring a high pressure nozzle atomizer for injection into the drying chamber, it is a common practice to provide two separate spray dryers. Likewise, if the intent is to produce from a wet material smaller particle sizes with higher bulk densities as well as bigger particle sizes with lower bulk densities, it is a common practice to provide two separate spray dryers. The obvious disadvantage of providing two separate spray dryers include increased capital cost, increased need of space for installing two separate dryers, increased operating cost, etc.

Thus, there has been a long-unmet need to provide spray dryer apparatus that will be able to use both kind of atomizer i.e. high pressure nozzle atomizer and a rotary centrifugal atomizer.

Summary of the Invention:

This summary is provided to introduce a selection of concepts in a simplified format that is further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention nor is it intended for determining the scope of the invention.

Accordingly, the present invention provides a spray dryer comprising a drying chamber defining a top end and an opposing bottom end. The device further comprises a gas disperser fitted on the top end of the drying chamber for introducing drying gas there-into. The gas disperser is constructed so as to receive a rotary centrifugal atomizer. The gas disperser is furthermore constructed to allow removal of the rotary centrifugal atomizer and receive in its place the high pressure nozzle atomizer and vice-versa.

In an embodiment of the invention, the gas disperser comprises a top wall, a bottom wall, and at least one lateral wall extending between the top and the bottom walls. The top wall, bottom wall, and the at least one lateral wall together define an internal space. The gas disperser comprises at least one air inlet extending from the lateral wall along an outward direction. The gas disperser further comprises an aperture on the top wall, and an aperture on the bottom wall. The apertures on the top and bottom walls of the gas disperser being adapted to receive a rotary centrifugal atomizer. The apertures on the top and bottom walls of the gas disperser being further adapted to allow removal of the rotary centrifugal atomizer and receive a high pressure nozzle atomizer as replacement of the rotary centrifugal atomizer and vice-versa.

In an embodiment of the invention, a Height vs. Diameter ratio of the drying chamber is 1:1 to 1.4:1. In an embodiment of the invention, the gas disperser disposed on the top end of the drying chamber is constructed so as to introduce the drying gas so as to follow a downward spiralling gas flow path.

In an embodiment of the invention, the high pressure nozzle atomizer comprises a top plate, a bottom plate, plurality of supporting structures disposed between the top plate and the bottom plate, plurality of high pressure nozzles extending from the top plate to the bottom plate, a casing extending from the bottom plate to an intermediate position between the bottom and the top plates so as to surround the plurality of high pressure nozzles and, plurality of vanes placed within the casing so as to extend along the length of the casing.

In an embodiment of the invention, the vanes extend along at least 60% of a height of the casing. In another embodiment of the invention, the vanes extend along at least 70% of a height of the casing. In another embodiment of the invention, the vanes extend along at least 80% of a height of the casing. In another embodiment of the invention, the vanes extend along at least 90% of a height of the casing. In another embodiment of the invention, the vanes extend along at least 95% of a height of the casing. In another embodiment of the invention, the vanes extend along at least 99% of a height of the casing. In another embodiment of the invention, the vanes extend throughout of a height of the casing.

To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

Brief Description of the drawings:

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

Figure 1 demonstrates a block diagram of a spray dryer in accordance with an embodiment of the invention; Figure 2 demonstrates a sectional view of the gas disperser fitted with the high pressure nozzle atomizer in accordance with an embodiment of the invention;

Figure 3 demonstrates a bottom view of the high pressure nozzle atomizer in accordance with an embodiment of the invention; and

Figure 4 demonstrates a sectional view of the gas disperser fitted with the rotary centrifugal atomizer in accordance with an embodiment of the invention.

Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present invention. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

DETAILED DESCRIPTION OF FIGURES

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.

Reference throughout this specification to“an aspect”,“another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises... a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

Referring to Figure 1, there is provided a block diagram of a spray dryer (100) in accordance with an embodiment of the invention. The spray dryer (100) comprises a drying chamber (102) defining a top end (104) and an opposing bottom end (106). The device further comprises a gas disperser (108) disposed on the top end (104) of the drying chamber (102) for introducing drying gas there-into. The gas disperser (108) is constructed so as to receive a rotary centrifugal atomizer (110). The gas atomizer (108) is furthermore constructed to allow removal of the rotary centrifugal atomizer (110) and receive in its place the high pressure nozzle atomizer (112).

For example, when the user wishes to produce spray dried particles having smaller particle sizes with higher bulk densities, the rotary centrifugal atomizer (110) may be fitted in the gas disperser (108). On the other hand, when the user wishes to produce spray dried particles having bigger particle sizes with lower bulk densities, the rotary centrifugal atomizer (122) fitted in the gas disperser (108) may be removed and in its place, the high pressure nozzle atomizer (112) may be fitted.

By way of another example, when the user wishes to produce spray dried particles from wet materials that can be injected only via a rotary centrifugal atomizer, the rotary centrifugal atomizer (110) may be fitted in the gas disperser (108). On the other hand, when the user wishes to produce spray dried particles from wet materials that can be injected only via a high pressure nozzle atomizer, the rotary centrifugal atomizer (110) fitted in the gas disperser (108) may be removed and in its place, the high pressure nozzle atomizer (112) may be fitted.

In an embodiment of the invention, an outlet (114) is located at about the bottom end (106) of the drying chamber (102). The outlet (114) is adapted to withdraw spray dried powders thus formed in the drying chamber (102).

In an embodiment of the invention, the drying chamber (102) is provided with at least one gas withdrawing means (116) proximate to the top end (104) for withdrawing exhaust gas there-from. In an embodiment of the invention, the gas withdrawal means (116) is operably coupled to a solid-gas separator (118) for separating solids present in the exhaust gas. Generally, the solids as separated from the exhaust gas in the solid-gas separator (118) may be in the form of fines. The fines thus separated may be transported and re-introduced into the drying chamber (102) via the rotary centrifugal atomizer (110) or the high pressure nozzle atomizer (112) as may be fitted in the gas disperser (108). In some cases, the solids as separated from the exhaust gas in the solid-gas separator (118) may be treated as spray dried powders and in such case, the solid thus extracted need not be re-introduced into the drying chamber (102).

In an embodiment of the invention, the gas disperser (108) is operably coupled to a means for supplying the drying gas. In an embodiment of the invention, the means for supplying the drying gas may include a pump (120). In another embodiment of the invention, the means for supplying the drying gas may include a combination of air heating system (122) and a blower (120).

In an embodiment of the invention, each of the rotary centrifugal atomizer (110) and the high pressure nozzle atomizer (112) is adapted to introduce a wet material into the drying chamber (102). Thus, there may be provided a wet material feeder (124) which is operationally coupled to the rotary centrifugal atomizer (110) or the high pressure nozzle atomizer (112), as the case may be.

In an embodiment of the invention, there may be provided an additional drying means (126) for drying the spray dried powders withdrawn from the drying chamber (102). In an embodiment of the invention, the additional drying means (126) may be a hot-air based dryer. In an embodiment of the invention, the additional drying means (126) receive hot air from a hot air producing device (128). The additional drying means (126) may be provided with at least one gas venting means (130) for venting used gas there-from. In an embodiment of the invention, the gas venting means (130) is operably coupled to the solid-gas separator (118) for separating solids present in the used gas.

In an embodiment of the invention, a Height vs. Diameter ratio of the drying chamber (102) is 1:1. In a preferred embodiment of the invention, a Height vs. Diameter ratio of the drying chamber is 1.1:1. In a further preferred embodiment of the invention, a Height vs. Diameter ratio of the drying chamber is 1.2:1. In a furthermore preferred embodiment of the invention, a Height vs. Diameter ratio of the drying chamber is 1.4:1.

Now referring to Figure 2, there is illustrated a sectional view of the gas disperser (108) fitted with the high pressure nozzle atomizer (112). The gas disperser (108) comprises a top wall (202), a bottom wall (204), and at least one lateral wall (206) extending between the top and the bottom walls. The top wall, the bottom wall, and the at least one lateral wall together define an internal space (208). The gas disperser (108) defines at least one air inlet (210) extending from the lateral wall (206) along an outward direction. Via the at least one air inlet (210) the drying gas is introduced.

The gas disperser (108) furthermore defines an aperture (212) in the top wall (202), and an aperture (214) in the bottom wall (204). The apertures (212 and 214) are adapted to receive the high pressure nozzle atomizer (112). The apertures (212 and 214) are further adapted to allow removal of the high pressure nozzle atomizer (112) and receive the rotary centrifugal atomizer (110) as replacement for the high pressure nozzle atomizer (112) (as shown in Figure 4). Since the gas disperser (108) is located on the top end (104) of the drying chamber (102) (and is supposed to introduce the drying gas into the drying chamber), and comprises at least one air inlet (210) extending from the lateral wall (206) along an outward direction, it would be understood that the gas disperser is constructed so as to introduce the drying gas in a downward spiralling gas flow path within the drying chamber (102). Also, it would be understood that in the internal space (208), the drying gas follows a spiralling gas flow path.

As the high pressure nozzle atomizer (112) requires the drying gas to be introduced in a downward symmetric gas flow path (as opposed to downward spiralling gas flow path), it can be observed that the high pressure nozzle atomizer (112) has been substantially modified.

In an embodiment of the invention, the high pressure nozzle atomizer (112) comprises a top plate (216), a bottom plate (218), plurality of high pressure nozzles (220) extending from the top plate (216) to the bottom plate (218), a casing (222) extending from the bottom plate (218) to an intermediate position between the bottom and the top plates so as to surround the plurality of high pressure nozzles (220) and, plurality of vanes (224) placed within the casing (222) so as to extend along the length of the casing (222). The vanes (224) are spaced apart from each other and define a downward gas flow path.

In an embodiment of the invention, there may be provided at least one supporting structure (226) disposed between the top plate (216) and the bottom plate (218).

In an embodiment of the invention, the vanes (224) extend along at least 60% of a height of the casing (222). In another embodiment of the invention, the vanes (224) extend along at least 70% of a height of the casing (222). In another embodiment of the invention, the vanes (224) extend along at least 80% of a height of the casing (222). In another embodiment of the invention, the vanes (224) extend along at least 90% of a height of the casing (222). In another embodiment of the invention, the vanes (224) extend along at least 95% of a height of the casing (222). In another embodiment of the invention, the vanes (224) extend along at least 99% of a height of the casing (222). In another embodiment of the invention, the vanes (224) extend throughout of a height of the casing (222).

Referring to Figure 3, there is illustrated a bottom view of the high pressure nozzle atomizer (112). It can be seen from Figure 3 that the bottom plate is provided with a first set of apertures (302) through which the high pressure nozzles (220) protrude and second set of apertures (304) through which the drying gas exists. The second set of apertures (304) are located so as to be in proximity of the first set of apertures (302). Although in this view the vanes (224) are not visible, each of the second set of aperture (304) is formed in a space between two adjacently located vanes (224).

While, because of the construction of the gas disperser (108) the drying gas entering the internal space (208) has a tendency to follow a spiralling gas flow path, since the path provided for the drying gas to exit is only via the high pressure nozzle atomizer (more specifically via the second set of apertures (304)), the drying gas is forced to enter into the casing (222). Once the drying gas enters into the casing (222), the drying gas has to enter in the spaces provided between the vanes (224) and therefore, is forced to follow the downward gas flow path and exit via the second set of apertures (304). Thus, drying gas entering into the drying chamber instead of following a downward spiralling gas flow path, follows a downward symmetric gas flow path.

Now referring to Figure 4, there is illustrated a sectional view of the gas disperser (108) fitted with the rotary centrifugal atomizer (110). Since, the gas disperser (108) as shown in Figure 4 is identical to that shown in Figure 2, the construction of the gas disperser is not being as provided in relation to Figure 2 is not being reproduced.

As stated above, the gas disperser (108) is constructed so as to introduce the drying gas in a downward spiralling gas flow path within the drying chamber (102). Thus, in an embodiment of the invention, construction of the rotary centrifugal atomizer (110) may be as per any of the standard constructions.

In an embodiment of the invention, the rotary centrifugal atomizer (110) may include a wet material dispensing part (402) arranged to dispense the wet material; and at least one wheel or disk element (404) arranged downstream of the wet material dispensing part (402). Although not visible in Figure 4, the rotary centrifugal atomizer may further comprise a motor arranged to impart rotating motion to the wheel or disk (404) thereby cause atomizing of the wet material thus dispensed. In an embodiment of the invention, the rotary centrifugal atomizer may further include at least one inlet for introducing fines as received from the solid-gas separator. While certain present preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereto. Clearly, the invention may be otherwise variously embodied, and practiced within the scope of the following claims.