CN108291772B

CN108291772B - Spray drying system comprising an improved connection assembly and method of cleaning a system

Info

Publication number: CN108291772B
Application number: CN201580084868.7A
Authority: CN
Inventors: 莫滕·格雷格森
Original assignee: GEA Process Engineering AS
Current assignee: GEA Process Engineering AS
Priority date: 2015-11-03
Filing date: 2015-11-03
Publication date: 2020-06-09
Anticipated expiration: 2035-11-03
Also published as: NZ742309A; CN108291772A; PL3371536T3; WO2017076411A1; AU2015413693A1; EP3371536A1; EP3371536B1; DK3371536T3; AU2015413693B2

Abstract

The invention relates to a spray drying system comprising: a spray dryer having a drying chamber and a process air/gas supply; at least one powder recovery unit; a transfer line for the powder material from the powder recovery unit; a connection assembly connecting the delivery line to a clean-in-place CIP device, the clean-in-place device including a CIP line configured to carry a CIP liquid. The connection assembly comprises a sanitary valve comprising a first inlet to the delivery line, and a valve member movable between an open position in which a portion of the valve member seals the delivery line, and a closed position in which the valve member moves to provide communication between the CIP line and the delivery line, thereby allowing CIP liquid to enter or exit the sanitary valve connecting the CIP line and to enter or exit the delivery line via said first inlet. The invention also relates to a method for cleaning a spray drying system.

Description

Spray drying system comprising an improved connection assembly and method of cleaning a system

Technical Field

The present invention relates to a spray drying system comprising: a spray dryer having a drying chamber and a process air/gas supply; at least one powder recovery unit; a transfer line for powdered material, such as fines, from the powder recovery unit; and means for connecting the powder recovery unit or the transfer line to a cleaning-in-place (CIP) apparatus comprising a CIP line configured to carry a CIP liquid. Furthermore, the invention relates to a method for cleaning a spray drying system.

Background

In the field of spray drying, there are often high requirements on the hygienic conditions of the system. In order to meet today's stringent requirements, drying equipment, including spray drying systems, must meet the highest design criteria to avoid product degradation and contamination during operation of the equipment. Therefore, contamination from the outside to the inside of the system should be minimized, just as the system must be thoroughly cleaned on a regular basis.

The cleaning requirements of dry and powder handling equipment, so-called dry zones, can be met by dry or wet methods or a combination of both. Dry methods involve manual cleaning of the surface in contact with the product, or air or gas cleaning by allowing a high velocity gas stream to pass over the surface in question. Wet methods involve manually hose flushing the surface or are performed more efficiently by using automated clean-in-place systems (CIP systems).

For example, the nature of dairy products, pharmaceuticals and food products means that the possibility of product deposits forming on the surfaces of process equipment is always realistic. The fat, sugar and protein content of the product is hygroscopic and viscous under the temperature and humidity conditions present during processing. In general, it is often desirable and advantageous for drying equipment to be equipped with automatic CIP in order to reduce the downtime of the equipment. The risk of deposit formation increases with the operating time of the plant. Industrial CIP systems can clean individual items or entire process equipment, involving integration of cleaning nozzles into equipment components with their associated plumbing and instrumentation.

Typically, the operation of the CIP is controlled by a program that controls the pump and valve functions and gives the cleaning sequence the best opportunity for efficient cleaning of all parts of the equipment. Modern CIP devices are flexible and can select different washing programs, as the program software includes the flexibility to change and adapt the washing program according to experience and need when processing new products, or applying new operating conditions. Further, separate programs have been developed for specific products that may differ in cleaning efficiency, cleaning time, or the type and amount of chemicals used.

In practice, the CIP apparatus may for example use a three-tank system of a four-tank CIP kitchen (the fourth tank is used to clean the bag filter). This ensures a minimum idle time when changing from one cleaning solution to another. CIP kitchens are designed to reuse and circulate rinse water and cleaning liquid, and to heat the liquid directly or indirectly during the cleaning process. That is, caustic and acid concentrations were measured during the cycle and replenishment was automatically performed to achieve the optimum concentration.

The CIP supply line is equipped with a remotely operated valve and a CIP supply pump. The return line is equipped with conductivity probes and remotely operated valves for passing caustic, acid and water to each tank or drain.

The complex nature of the cleaning scheme is particularly evident in spray drying systems comprising transfer lines for conveying the powdered material from a powder recovery unit, such as cyclones and bag filters, downstream of the drying chamber to an upstream unit, such as the drying chamber itself, or to a unit, such as a VIBRO-FLUIDIZER^TMOr a fluid bed or the like, for treating the material discharged from the drying chamber. Typically, such transfer lines are configured to transport the powdered material in the form of fines (the smallest part of the powder product), a so-called fines return system, during normal operation. In order to clean the powder recovery unit itself, the transfer device connecting the powder recovery unit to the transfer line and the transfer line, the pipework to the relevant part is not connected with the product line, but is connected to the CIP device to allow the CIP liquid to flush the transfer device, the powder recovery unit itself and the adjacent pipework. In such systems, it is of course of critical importance that the powder flow delivery line is thoroughly dried with air/gas to ensure that the powder flow in the delivery line is not compromised by any residual moisture.

Cleaning solutions for spray drying systems comprising such return flow delivery lines are often time consuming, since it has hitherto been achieved to manually disconnect parts of the spray drying system from the production lines and connect these parts to the cleaning system. Further, during the transition from the operating mode to the CIP mode, i.e. when connecting and disconnecting the various parts of the system, there is a risk of contamination because the cleaned parts will be exposed to the outside ambient air and environment during the period between disconnection from the cleaning system and until being connected again to the production line. CIP devices also typically include flexible hoses to simplify the transition from operating mode to CIP mode and vice versa; however, such flexible hoses are associated with the risk that the bag leaves a certain amount of liquid in the non-drainable pocket. Finally, great care must be taken to ensure that the coupling connecting the CIP line with the conveying line section by means of the transfer device and/or the powder recovery unit and any accessory equipment is sealed so that no CIP liquid leakage can occur.

Disclosure of Invention

Therefore, on this background, it is an object of the present invention to provide a spray drying system which reduces the risk of contamination before, during and after a CIP process and which makes the CIP process more time-saving and simpler.

Furthermore, it is an object of the present invention to facilitate the overall operating conditions of the spray drying system by designing a more efficient CIP process.

In a first aspect of the invention, these and other objects are achieved by a spray drying system of the type mentioned in the introduction, which is furthermore characterized in that said connecting means comprise a connecting assembly comprising at least one sanitary valve comprising a first inlet to the delivery line or the powder recovery unit, and a valve member movable between an open position and a closed position, wherein in the closed position a part of the valve member seals the delivery line, and when in the open position the valve member moves to provide communication between the CIP line and the delivery line or the powder recovery unit, thereby allowing CIP liquid to enter or exit the sanitary valve connecting the CIP line and to enter or exit the delivery line or the powder recovery unit via said first inlet.

The provision of the sanitary valve makes it possible to establish a connection between the CIP line and the delivery line at any time also in the operating mode of the system. Thus, the CIP process can be performed without disconnecting any part from the spray drying system. Thus, no contaminants can enter from the ambient environment during the period in the process of switching from CIP mode to normal operation. Another advantage provided by the sanitary valve is that it reduces the manual labor required by operators in conventional systems that require manual disconnection and reconnection of parts of the spray drying system whenever a CIP process is required. Thus, the spray drying system can be in normal operation for a higher percentage of time, resulting in a higher capacity of the spray dryer. The spray drying system is safer because no contaminants can enter the transfer line, just as there are no couplings to disconnect and reconnect that could lead to risk of CIP liquid leakage. The system may be remotely operated or automated so that the operator need only switch between CIP and normal operation. This will further reduce the down time of the process line.

Furthermore, unused transfer lines can be purged during production to avoid bacterial growth in the line.

There was previously a prejudice in the art for having the valve between the CIP system and the spray drying system, as failure to fully separate could imply a risk of contamination of the spray drying product. One reason is that existing valves are designed for powders or liquids or gases, but are not suitable for all three elements.

The term "sanitary" in the art means that such sanitary valves are designed to meet the strict requirements of various authorities depending on the regulatory authorities. Thus, the term "hygiene" means that the equipment should comply with relevant regulations, in particular AAA (usa) and/or EHEDG (european union) guidelines. Typically, the sanitary requirements mean that the relevant parts of the valve are designed and made of polished stainless steel or a suitable polymer to ensure efficient cleaning and disinfection, and the risk of material and/or cleaning fluid residues is very limited.

In the preferred embodiment, the sanitary valve is a sanitary plug valve, wherein said one part of the valve member is constituted by a plug end for sealing the delivery line in the closed position and for achieving the open position by a retracting movement. The use of a common plug valve has been established in the art and such a valve is very reliable in operation. However, the present invention uses a sanitary stopcock suitable for powders, liquids and gases.

Alternatively, other valves may be used instead of the stopcock valve as long as hygienic requirements can be met. Examples of suitable valves include ball valves, bow valves, butterfly valves, knife valves, and gate valves.

In an embodiment of the invention, the inner surface of the plug end of the valve member that engages the transfer line has the same shape as the transfer line. In a further development of this embodiment, the transfer line has a cylindrical shape and, thus, the plug end of the valve member has a curvature corresponding to the inner diameter of the cylindrical transfer line. This has the following advantages: when the valve is in its closed position, the plug end will form a substantially continuous surface with the interior of the transfer line. Thus, there will be less chance of jamming corners, edges, etc. of the conveyed material. This is particularly important when the material has some moisture absorption and stickiness, in which case the product quality may be reduced, contamination may occur, and subsequent cleaning becomes more cumbersome.

In another embodiment, a seal is provided on the plug end of the valve member such that when the valve is in its closed position, an air/gas tight seal is formed between the valve and the delivery line. This seal ensures that during normal operation, when the valve is in its closed position, contaminants cannot enter the system from the external environment or the CIP line.

In a further embodiment of the invention, a gap is formed between the side surface of the plug end of the valve member and the delivery line, wherein the gap is formed at a position between the delivery line and the CIP line when the valve is in its closed position. In this way, higher tolerances can be used in the manufacture of the plug end of the valve member and any edge of the plug end can be prevented from entering the delivery line when the valve is in the closed position.

In another embodiment of the invention, the sanitary plug valve comprises both a seal forming an air/gas tight seal between the plug end of the valve member and the delivery line when the valve is in the closed position and a gap between the plug end of the valve and the delivery line such that ingress of contaminants from the external environment or CIP system through the sanitary plug valve is prevented, but at the same time any edge of the plug end can be avoided from entering the delivery line when the valve is in the closed position.

In another embodiment, the gap continues through at least a portion of the plug end such that a channel is formed. Thus, when the valve is in its closed position, clean purge air/gas can be blown through the gap so that material in the transfer line cannot enter the gap. This is achieved by blowing purified air/gas through the channels and gaps at a higher pressure than the pressure in the transfer line. This has the advantage that the risk of hygroscopic material adhering to the plug end of the valve member or powder material entering the gap between the plug end and the transfer line is low.

In a further aspect of the invention, a method for cleaning a spray drying system of the above-described type is provided. Wherein the sanitary plug valve is in a closed position when the system is in normal operation, the method comprising the steps of:

it is determined that the cleaning process is to be initiated,

moving the sanitary valve from the closed position to the open position,

supplying CIP liquid to the sanitary valve in the open position through the CIP line,

after cleaning of the system is complete, the CIP liquid is drained from the system,

air/gas is blown through the sanitary valve to dry the system,

the valve is moved to the closed position,

normal operation is restarted.

This method ensures that the spray drying system does not have to be disassembled during the changeover from production to CIP, during CIP, or back to normal operation. This reduces the risk of contaminants entering the spray drying system, as parts thereof are not exposed to a dirty external environment.

In a further embodiment of the invention, the method comprises blowing purified air/gas through the sanitary plug valve when the valve is in its closed position to prevent material in the transfer line from entering the plug valve.

In another embodiment of the invention the air/gas for drying the system after cleaning is supplied from a spray dryer process air/gas supply. During normal operation, this air/gas will be used in the spray dryer system or in the post-drying unit(s). This reduces the cost of using a CIP system that already includes a heater and pump system in the spray drying system.

In a further embodiment of the invention, the method is automated upon start-up and completion according to the above-described embodiment of the invention. Based on the response or regulatory requirements from the sensors in the system, CIP procedures may be initiated or scheduled.

Drawings

The invention will be described in more detail below by way of non-limiting examples of preferred embodiments and with reference to the accompanying schematic drawings in which:

FIG. 1 shows a schematic diagram of a prior art spray drying system;

fig. 2 shows a functional flow diagram indicating the flow of a prior art spray drying system in an operational mode and a CIP mode, respectively;

figure 3a shows a schematic flow diagram of a prior art spray drying system when in a normal operating mode;

FIG. 3b shows a schematic flow diagram of a prior art spray drying system when in CIP mode;

fig. 4 shows a schematic flow diagram of an embodiment of a spray drying system according to the present invention;

figure 5a shows a schematic flow diagram of another prior art spray drying system when in the normal operating mode;

FIG. 5b shows a schematic flow diagram of another prior art spray drying system when in CIP mode;

fig. 6 shows a schematic flow diagram of another embodiment of a spray drying system according to the present invention;

fig. 7 shows a schematic overview of another embodiment of a spray drying system according to the present invention;

FIG. 8 shows a cross-section of a sanitary plug valve in its closed position according to an embodiment of the present invention;

FIG. 9 shows an enlarged portion of a detail of the sanitary plug valve shown in FIG. 8;

FIG. 10 is a view corresponding to FIG. 8 with the sanitary plug valve in its open position;

FIG. 11 is a partial view of a sanitary plug valve according to a further embodiment of the spray drying system of the present invention; and is

Fig. 12 to 14 show views of still further embodiments of the invention corresponding to fig. 8 to 10.

Detailed Description

Fig. 1 shows a schematic view of the main components of a spray drying system 1. In a manner known per se, the spray drying system 1 comprises a spray dryer with a drying chamber 2 and a process air/gas supply 3, typically comprising an air/gas disperser. It should be noted that the term "gas" will be used with the term "air" as "air/gas" and should be interpreted to cover any gas suitable as a process gas in such a spray drying system. The drying chamber 2 also incorporates atomising means such as nozzles and/or atomising wheels.

At the lower end of the drying chamber 2, an outlet 5 for the dried material is provided. In the shown spray drying system 1, a post-treatment unit in the form of a vibrating or static fluidized bed 6 is provided. At one end, the vibrating or static fluidized bed 6 receives the dried material from the outlet 5 of the drying chamber 2 for further processing of the material, which is then collected at the outlet at the other end of the vibrating or static fluidized bed. Further downstream equipment, not relevant to the present invention, may also be present.

Furthermore, the spray drying system 1 comprises at least one powder recovery unit 4 to which the spent process air/gas with entrained particles in the process air/gas is conducted via a vent line 7. The powder recovery unit 4 may take the form of a cyclone or a bag filter, or any combination thereof.

A transfer line 11 is provided for transporting the powdery material recovered in the powder recovery unit 4 to upstream equipment, such as the drying chamber 2 itself, located at an arbitrary location, or to the vibrating or static fluidized bed 6, also located at an arbitrary location. Typically, the recovered material is in the form of a fine powder, which is a powdered material of satisfactory composition but of a size and/or configuration that requires further processing to meet quality requirements. The introduction location of the fines back into the upstream unit typically depends on the size and/or configuration of the material and the prevailing operating conditions in the drying chamber 2 and the vibrating fluidizer 6. There is also a diverter valve 9 in the system to ensure proper distribution of the returned fines.

At the lower end of each powder recovery unit 4, a transfer device 70 is provided for transferring powder from the powder recovery unit 4 to the transfer line 11. In prior art systems, such transfer devices are typically made of a rotary valve (i.e. a blow through rotary valve or a down flow rotary valve with a feed shoe) to allow air/gas to blow through to ensure transport of fines in the transfer line.

When the prior art spray drying system 1 performs a CIP process according to a specified CIP protocol, the system needs to be switched from the normal operation mode to the CIP mode. In order to allow the system to operate in both normal operation mode and CIP mode, there are means for connecting the powder recovery unit 4 and the transfer line 11. As indicated in fig. 2, switching between these two modes involves decoupling the

couplings

81, 82, 83, 84 forming part of the prior art connection arrangement from the delivery lines 11 to the various sections of the CIP arrangement 8 (shown in the figures as

CIP lines

85, 86, 87). The transition from one mode to another is performed manually by disconnecting parts of the spray drying system from the normal operation mode and connecting the CIP device. Once the CIP process is completed, reverse disconnection and connection must also be performed manually.

Hereinafter, a spray drying system according to the present invention will be described. Elements having the same, similar or corresponding function as in the prior art system will be indicated with the same reference numerals as in the description of the prior art spray drying system.

Referring now in particular to the detailed description of fig. 8 to 10, the connection assembly 10 of the spray drying system 1 according to the present invention will be described. It is noted that only those parts of the spray drying system comprising the CIP arrangement according to the present invention which differ from the prior art spray drying system 1 comprising the CIP arrangement 8 shown in fig. 2 will be described in detail.

The connection assembly 10 comprises a sanitary valve of a suitable type. In the present preferred embodiment described below, the sanitary valve is a sanitary plug valve 20 comprising a first inlet 12 to the delivery line 11, and a valve member 21 movable between an open position and a closed position, wherein in the closed position a plug end 22 of the valve member 21 seals the delivery line 11, and when in the open position the valve member 21 is retracted to provide communication between the CIP line 15 and the delivery line 11. During CIP, and as will be described in more detail below, CIP liquid from CIP supply 16 is allowed to enter sanitary plug valve 20 through CIP line 15 and into transfer line 11 via said first inlet 12, and exits through CIP line 15 to CIP drain 17.

The parts of sanitary plug valve 20 relevant to the present invention will be described in more detail below. It should be understood that other elements of sanitary plug valve 20 are well known, such as those commercially available from GEA Tuchenhagen

A type C valve.

It should also be understood that sanitary valve 20 may be formed and/or used as a two-way or three-way valve or even a more-way valve having two or more operative states, including an unactuated state and one or more actuated states. It is within the ability of those skilled in the art to adapt the sanitary valve to provide the desired number and configuration of ports and passageways.

In a preferred embodiment, the inner surface 23 of the valve member plug end 22 that engages the transfer line 11 has the same shape as the inner surface 14 of the transfer line 11. In particular, the inner surface 23 is formed as a part-cylindrical surface adapted to the cylindrical shape of the transfer line 11.

In order to ensure that the powder flow in the delivery line 11 is always kept separate from the CIP line 15, a seal 24 is provided between the valve member 21 and the delivery line 11, i.e. in the embodiment shown between the side surface 26 of the valve member plug end 22 and the wall 18 surrounding the delivery line 11.

The transfer line 11 itself and the surrounding wall 18 may in principle take any suitable form other than the illustrated cylindrical transfer line 11 and rectangular wall 18. Fig. 11 shows an alternative in which a drop tube 41 of a powder recovery unit (not shown) is connected to the connection assembly 10. However, also in this embodiment, the inner surface of the valve member plug end 22 is formed in accordance with the inner surface 44 of the drop tube 41.

In the embodiment shown, the dimensions of sanitary plug valve 20 are selected such that when valve member 21 is in its closed position, a gap 25 is formed between a side surface 26 of valve member plug end 22 and wall 18 surrounding transfer line 11. A second inlet 13 is formed at the end of the gap 25 facing the transfer line 11.

In a particular embodiment, the gap 25 extends from the seal 24 all the way to the second inlet 13 into the transfer line 11.

In the preferred embodiment of fig. 8-10, a flush valve 30 is connected to the transfer line 11. The flush valve is provided with an inlet 31 for process air/gas for introducing air/gas into the transfer line 11. In the preferred embodiment, the flush valve 30 is located very close to the transfer line 11. Alternatively, fig. 12-14 show different entry locations for the process air/gas.

Furthermore, in the embodiment shown, when the position of the valve member 21 is as shown in fig. 8, i.e. also in the closed state of the sanitary plug valve 20, the flushing valve 30 is in fluid connection with the delivery line 11 through the gap 25, air/gas can be introduced into the delivery line 11 through the second inlet 13.

The operation of the spray drying system 1 according to the present invention will now be described with particular reference to the schematic flow diagrams and system overview of fig. 4, 6 and 7, in comparison with corresponding prior art systems shown in fig. 3a-3b and 5a-5b, respectively. It should be noted that the following description is made with particular reference to the present preferred embodiment of sanitary valve 20 connected to assembly 10. The operation of a system with other types of sanitary valves is performed in a manner corresponding to the particular type of sanitary valve.

Referring first to fig. 6, it should be noted that sanitary valves 20 are provided at several locations of the spray drying system 1. Although it will be immediately clear to those skilled in the art from reading the drawings including any symbols, only four of these sanitary valves are labeled with the reference numeral 20 for the purpose of description hereinafter (left to right in FIG. 6):

in the first position, the sanitary valve 20 is a two-way valve which is closed in the unactuated state and which, when actuated into its open position, connects the powder recovery unit 4 with the CIP line 15.

In the second position, the sanitary valve 20 is a three-way valve which provides in the unactuated state an unobstructed transport of powder in the transport line 11 and which, when actuated, is able to provide a connection between the transport line 11 and the CIP line 15, as described above.

In the third position, the sanitary valve 20 has a configuration corresponding to the sanitary valve 20 in the second position, but is located downstream of all powder recovery units 4 of the spray drying system 1 of the embodiment shown in fig. 6.

Finally, in the fourth position, the sanitary valve 20 is a three-way valve but has another flow path arrangement.

As is clear from fig. 6, further sanitary valves may also be present in the spray drying system.

The initiation of the CIP procedure will be determined according to a predetermined schedule or programmed to start automatically. Until this point, normal operation continues and the sanitary valve 20 is in the closed position.

After the CIP process is initiated, sanitary valve 20 is moved from the closed position to the open position. As a result of the movement of the valve member 21, communication between the CIP line 15 and the delivery line 11 is provided. Reference is made to the above description with respect to fig. 6, which corresponds to the sanitary valve described with respect to the second position.

CIP liquid is supplied from CIP supply 16 through CIP line 15 to sanitary plug valve 20, which is now in the open position. CIP liquid from CIP supply 16 is allowed to enter sanitary valve 20 and flow into transfer line 11 via first inlet 12.

During CIP, CIP liquid is also supplied to the powder recovery unit 4 through another line (not shown). Typically, a cyclone, bag filter or other powder recovery unit is supplied with CIP liquid at the top.

After the CIP process is completed, CIP liquid is drained from the system. The drainage of the conveying line 11 takes place through the first inlet 12 of the sanitary plug valve 20, as CIP liquid is allowed to leave the conveying line 11 through the CIP line 15 and further to the CIP drainage device 17.

CIP liquid from the powder recovery unit 4 is drained through the transfer device 70 and further through the sanitary valve 20 in the second position and the sanitary valve 20 in the first position mentioned above.

After the CIP liquid is drained, air/gas is blown through the respective sanitary valve 20 to dry the system. The air/gas may have any suitable composition and temperature, but is typically heated air/gas.

Once the relevant part is sufficiently dry, the sanitary valve will move to the closed position and, as a final step, normal operation is restarted.

In the above described embodiment of the spray drying system, an additional step of blowing purified air/gas through the sanitary valve during normal operation may also be performed in order to prevent material of the transfer line from entering the sanitary valve.

Preferably, the air/gas for drying the system after cleaning is supplied from the process air/gas supply of the spray dryer. In any case, since this air/gas will be used to dry the cyclone(s) or other powder recovery unit(s), a total energy savings is achieved as no separate air/gas heating unit is required to dry the system.

The process of the method of the invention can be performed automatically from the first step to the last step.

The person skilled in the art realizes that it by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

Claims

1. A spray drying system (1) comprising

A spray dryer having a drying chamber (2) and a process air/gas supply (3),

at least one powder recovery unit (4),

a transfer line (11) for the powder material coming from the powder recovery unit (4), and

a connection device for connecting the delivery line (11) to a clean-in-place device (8) comprising a clean-in-place line (15) configured to carry a clean-in-place liquid,

it is characterized in that the preparation method is characterized in that,

said connection device comprises a connection assembly (10) comprising at least one sanitary valve (20) comprising a first inlet (12) to the delivery line (11), and a valve member (21) movable between an open position and a closed position, wherein in the closed position a portion (22) of the valve member (21) seals the delivery line (11), and when in the open position the valve member (21) moves to provide communication between the clean in place line (15) and the delivery line (11), thereby allowing clean in place liquid to enter or exit the sanitary valve (20) connected to the clean in place line (15) and to enter or exit the delivery line (11) via said first inlet (12).

2. A spray drying system according to claim 1, wherein the sanitary valve is a sanitary plug valve (20) in which said one part of the valve member is constituted by a plug end (22) for sealing the delivery line (11) in the closed position and for achieving the open position by a retracting movement.

3. A spray drying system according to claim 2, wherein the inner surface (23) of the valve member plug end (22) engaging the delivery line (11) has the same shape as the inner surface (14) of the delivery line (11).

4. A spray drying system according to claim 2 or 3, wherein a seal (24) is provided between the valve member (21) and the delivery line (11).

5. A spray drying system according to claim 4, wherein a gap (25) is formed between a side surface (26) of the valve member plug end (22) and a wall (18) surrounding the transfer line (11) when the valve member (21) is in its closed position, and wherein a second inlet (13) to the transfer line is provided at the end of the gap (25).

6. A spray drying system according to claim 5, wherein said gap (25) extends between the seal (24) and the second inlet (13) to the delivery line (11).

7. A spray drying system according to any one of the preceding claims 1 to 3, wherein a flush valve (30) is connected to the delivery line (11).

8. A spray drying system according to claim 5, wherein a flush valve (30) is in fluid connection with the delivery line (11) via said gap (25) for introducing purge air/gas through the second inlet (13).

9. The spray drying system of claim 1, wherein the powder material is a fine powder.

10. A spray drying system according to claim 3, wherein the inner surface (23) of the valve member plug end (22) is in the form of a cylindrical surface.

11. A spray drying system according to claim 4, wherein a seal (24) is provided between a side surface (26) of the valve member plug end (22) and a wall (18) surrounding the delivery line (11).

12. A method for cleaning a spray drying system according to any of claims 1 to 11, wherein the sanitary valve is in a closed position when the system is in normal operation, the method comprising the steps of:

it is determined that a clean-in-place process is to be initiated,

moving the sanitary valve from the closed position to the open position,

clean-in-place liquid is supplied through the clean-in-place line to the sanitary valve in the open position,

after the cleaning-in-place process of the system is completed, the cleaning-in-place liquid is drained from the system,

air/gas is blown through the sanitary valve to dry the system,

the sanitary valve is moved to the closed position,

normal operation is restarted.

13. A method for cleaning a spray drying system according to claim 12, wherein during normal operation, purge air/gas is blown through the sanitary valve to prevent material in the delivery line from entering the stopcock.

14. Method for cleaning a spray drying system according to claim 12 or 13, wherein the air/gas for drying the system after cleaning is supplied by the process air/gas supply of the spray dryer.

15. A method for cleaning a spray drying system according to claim 12 or 13, wherein the process from the first step to the last step is performed automatically.