Mixing system for processing sensitive substances

Abstract

 The present invention relates to a mixing system for processing of at least two substances and to a respective method of mixing at least two substances. Said mixing system comprises:
- a first vessel (12) to receive a first substance (1),
- a second vessel (14) to receive a second substance (2) to be mixed with the first substance (1),
- wherein the first vessel (12) is connectable with the second vessel (14) in a substance transferring way by means of a feeding pipe (18) to feed the first substance (1) to the second vessel (14),
- wherein the second vessel (14) is connectable with the first vessel (12) in a substance transferring way by means of a recirculation pipe (20) to feed the second substance (2) and/or a mixture of first and second substances (1, 2) to the first vessel (14),
- at least one pump (22) connected to at least one of the feeding pipe (18) or recirculation pipe (20),
- at least one mixing arrangement (16) located in at least one of first and second vessels (12, 14), and
- wherein the first and second vessels, the feeding and recirculation pipes are flushable with inert gas.

Description

[0001] The present invention relates to the field of batch systems and in particular to a mixing system for processing, preparing and mixing of at least two substances. In particular, the present invention relates to processing or mixing of substances that may or tend to deteriorate when exposed to inappropriate external conditions, such like oxygen, electromagnetic radiation and/or humidity.

[0002] Preparation and processing of sensitive substances, e.g. in the field of food production, production of cosmetics or production of biotechnological and pharmaceutical products requires well-defined processing, e.g. mixing of such substances in a protected process environment. Especially with substances that are sensitive to oxidation, their processing or mixing should take place in an environment being substantially free of oxygen or other deteriorating factors.

[0003] It is in general possible to hermetically seal a batch system for processing oxygen-sensitive substances. However, at least for feeding of the substances to such a batch or mixing system and also for conducting in-process controls ingress, entry and/or extraction of substances into and from the processing system must be provided during the process routine.

[0004] It is generally known to conduct a processing of at least two substances in an inert gas atmosphere. Hence, after feeding one or more substances to be processed to a respective vessel, the vessel is substantially hermetically sealed and flushed with an inert gas, such like nitrogen, argon, carbon dioxide or krypton to expel oxygen containing air from the vessel.

[0005] Document US 2005/0084536 A1 for instance describes a method and a device for the preparation and purification of microparticles. Said device comprises one of a plurality of processing units, wherein a processing unit comprises a processing loop including: a loop inlet, a processing vessel with an agitator, a pump, and a tangential flow filtration unit having an inlet and a retentate outlet arranged in the loop. Said processing loop may be aseptically sealed from the air surrounding the device.

[0006] Said processing vessel comprises an additional inlet through which it receives raw materials from a storage vessel via a pump. The storage vessel providing raw materials is located outside the processing loop. It is thus conceivable, that oxygen or other deteriorating substances may enter the processing vessel together with the raw material.

[0007] It is an object of the present invention to provide an improved mixing system for mixing, processing and/or for preparing at least two substances in a protected environment. The mixing system should further provide a thorough and good intermixing of the substances while keeping the influence of deteriorating factors at a minimum level. Moreover, the mixing system should be universally applicable to the mixing of solid as well as liquid substances.

[0008] It is a further object of the invention to provide a method of mixing, processing and/or for preparing at least two substances in a protected environment or in a protected atmosphere.

Summary of the Invention

[0009] In a first aspect, the invention relates to a mixing system for processing at least two substances. The system comprises a first vessel to receive a first substance and comprises a second vessel to receive a second substance to be mixed or to be processed with the first substance.

[0010] The first vessel is connectable with the second vessel in a substance transferring way by means of a feeding pipe to feed or to transfer the first substance from the first vessel into the second vessel. This way, substances initially and separately provided in the first vessel and in the second vessel, respectively, can be mutually mixed by transferring the first substance from the first vessel into the second vessel, in which the second substance can be already provided.

[0011] Furthermore, also the second vessel is connectable with the first vessel in a substance transferring way by means of a recirculation pipe to feed the second substance and/or a mixture of first and second substances from the second vessel to the first vessel. In order to transfer the at least first and/or the second substances from the first vessel into the second vessel and/or from the second vessel into the first vessel at least one pump is connected or coupled to at least one of the feeding pipe or the recirculation pipe.

[0012] Moreover, at least one mixing arrangement is provided in at least one of first and second vessels. The mixing arrangement typically comprises an agitator such as a stirrer driven by an appropriate drive to stir a mixture of first and second substances. By having at least one pump and by having a feeding pipe as well as a recirculation pipe a mixing of first and second substances does not only take place in one of first and second vessels. By way of the recirculation pipe the second substance and/or a mixture of first and second substances already located in the second vessel can be fed back to the first vessel to improve the degree of mixing of the at least two substances.

[0013] By means of the feeding pipe and the recirculation pipe a closed loop can be established by way of which the roles of the first vessel as a feeding vessel and the second vessel as a mixing vessel may be interchanged or swapped. Hence, by way of the recirculation pipe the first vessel may no longer serve as a feeding vessel only. Since the second substance located in the second vessel and also a mixture of first and second substances accumulating in the second vessel may be fed back to the first vessel an intermixing of first and second substances may also take place in the first vessel.

[0014] In effect, by means of the closed loop arrangement, provided by the feeding pipe and the recirculation pipe, both vessels may even equally serve as a feeding vessel and as a mixing vessel, respectively.

[0015] By feeding back the mixture of first and second substance to the first vessel, a complete emptying or draining of the content of the first vessel into the second vessel can be achieved. Hence, the first vessel, which may be initially filled with a first substance, e.g. in solid form can be effectively flushed by the mixture of first and second substances provided via the recirculation pipe. In this way, the entirety of the first substance initially provided in the first vessel can be supplied and transferred to the second vessel and into the respective mixture of first and second substances.

[0016] In the following, but without limiting the general concept of the above mentioned concept of interchangeability of the functions of first and second vessels, the first vessel may be denoted as a supply or feeding vessel whereas the second vessel may be denoted and may primarily serve as a mixing vessel. However, since first and second vessels may be equally interconnected by the feeding pipe in one direction and by the recirculation pipe in the opposite direction of flow, the roles of first and second vessels may also swap and interchange accordingly.

[0017] Moreover, the mixing system is not only operable for mechanically mixing of at least two substances. It may be generally adapted for processing and for mixing of solid substances, e.g. provided in granular form. It may equally be adapted for mixing of solid and liquid substances as well as for mixing of first and second liquid substances. Preferably, at least one substance is a liquid. More preferred, at least the second substance is a liquid.

[0018] According to a further embodiment, the first vessel and/or the second vessel is or are hermetically sealable against the environment. First and/or second vessels may therefore comprise a closable lid allowing to directly supply first and second substances to respective vessels and to subsequently seal said vessels against the environment. First and second vessels may either be sealed separately or together against environmental influences. Since the feeding pipe and the recirculation pipe are exclusively connected with the first and with the second vessel, interchanging of first and second substances between first and second vessels via the feeding pipe and/or via the recirculation pipe is free of any environmental influence once first and second vessels have been appropriately sealed.

[0019] By sealing first and second vessels against the environment, the mixing process taking place in the first vessel, in the second vessel and/or in the feeding- or circulation pipe can be effectively conducted absent of environmental influences.

[0020] According to a further preferred embodiment, the first vessel and/or the second vessel is flushable with an inert gas. The type of inert gas may be appropriately selected according to the sensitivity of first and second substances. For oxygen-sensitive substances, the inert gas should be free of oxygen. For instance nitrogen, argon, carbon dioxide or krypton and/or mixtures thereof may be used as an inert gas.

[0021] By flushing the first vessel as well as the second vessel with an inert gas, an oxygen concentration inside the first and/or the second vessel of only a few parts per million (ppm) or even of ≤ 1 ppm is generally attainable.

[0022] According to another preferred aspect, the first vessel and the second vessel are separately flushable with the respective inert gas. This way, first and second substances can be separately provided in first and second vessels independent from another. The first and second substances may be separately supplied to respective first and second vessels either simultaneously or sequentially.

[0023] Accordingly, first and second vessels can be simultaneously or sequentially flushed with the inert gas. By providing a separate flushing of first and second vessels with an inert gas, first and second vessels can be even flushed with different inert gases, respectively.

[0024] Preferably, flushing of first and second vessel takes place before a mixing process starts. By enabling a separate flushing of first and second vessels with an inert gas it is also possible to supply the second substance to the second vessel, to seal the second vessel and to flush the second vessel before the first vessel is filled with the first substance and before the first vessel is hermetically sealed and flushed with an inert gas accordingly.

[0025] The possibility to flush the first and/or the second vessel with an inert gas allows to conduct a large variety of different mixing processes and mixing procedures with one and the same mixing system.

[0026] According to a further embodiment, also the feeding pipe and/or the recirculation pipe is or are flushable with an inert gas. Flushing of the feeding pipe and/or of the recirculation pipe may take place separate from a flushing of first and/or second vessels. However, flushing of the feeding pipe and/or the recirculation pipe may also take place simultaneously with the flushing of first and second vessels.

[0027] In particular, the feeding pipe and/or recirculation pipe may be connected to at least one of first and/or second vessels in a substance transferring way during a flushing procedure of first and/or second vessels, accordingly. This way, flushing of the feeding pipe and/or of the recirculation pipe may take place automatically with flushing of first and/or second vessels, respectively. Hence, a flushing of the feeding pipe and/or of the recirculation pipe may occur as a side effect or as a by-product of the flushing of first and/or second vessels.

[0028] In a further preferred embodiment, the first and/or the second vessel comprises at least one inlet valve to receive an inert gas and further comprises at least one outlet valve to allow gas escaping from the first and/or the second vessel. By means of inlet and outlet valves, the first and/or the second vessel may be separately and independently flushed with the inert gas. Inert gas entering the respective vessel via the inlet valve serves to expel air or other reactant gases, such like oxygen, from the respective vessel, so that after completion of a flushing procedure the vessel is only filled with at least one of first or second substances and with a corresponding inert gas or a respective inert gas mixture.

[0029] According to another embodiment, the first vessel is arranged above the second vessel and comprises a tapered bottom portion extending into the feeding pipe. By arranging one vessel on top of the other vessel transfer of e.g. the first substance into the feeding pipe and further into the second vessel may be at least supported or even entirely governed under the effect of gravity. Moreover, since the first vessel comprises a tapered or funnel-like bottom portion, the majority of the first substance initially provided in the first vessel may easily enter the feeding pipe without leaving any residues. In this embodiment the pump is preferably arranged in or coupled to the recirculation pipe in order to provide a transfer of the mixture of substances against the effect of gravity from the second vessel into the first vessel.

[0030] Even though the arrangement of first and second vessels at different height is beneficial for gravity-supported substance transfer it is not generally required to arrange one vessel on top of the other or to arrange first and second vessels at different height levels. In general, first and second vessels may also be arranged side by side. In such a configuration use of at least two pumps, one of which coupled to the feeding pipe and the other of which coupled to the recirculation pipe are required in order to establish a closed loop circulation between first and second vessels.

[0031] According to a further embodiment, the mixing arrangement is arranged in the second vessel and comprises a stirrer. By way of the stirrer, substances located in the second vessel can be mechanically mixed or blended. When mixing a liquid substance with a solid substance, provided e.g. in granular form, it is beneficial, when the stirrer is provided in said vessel, which initially contains the liquid substance. Depending on the type of substances to be mixed the mixing arrangement may not only comprise a stirrer but may additionally or alternatively comprise a shredder member, a chopper member or rotating discs particularly adapted to mix granular or powdery substances.

[0032] This way, the mixing system may be also operable to mix first and second substances, both in solid form, e.g. in granular or powdery constitution.

[0033] According to a further embodiment, the pump is coupled with the recirculation pipe. It is then of particular benefit, when the flow through the feeding pipe is governed and controlled by gravity.

[0034] Moreover, by having the pump directly arranged in the recirculation pipe, the degree of backfeeding of substances contained in the second to the first vessel can be precisely controlled. By appropriately controlling the power and flow rate of the pump, a substance feedback or substance recirculation to the first vessel can be precisely controlled. In particular, the feedback loop may be operated occasionally and/or temporally offset to a mixing procedure taking place in the second vessel. Additionally, by regulating the pump, the rate the substances are fed back to the first vessel can be precisely controlled in order to optimize and to control the overall mixing process of the mixing system.

[0035] According to a further embodiment, the recirculation pipe extends into a bottom portion of the second vessel. Alternatively, the recirculation pipe is connectable with a pipe extension assembled in the second vessel and extending into a bottom portion thereof. These embodiments are particularly useful when the first vessel is arranged on top or above the second vessel. By means of the recirculation pipe extending into a bottom portion of the second vessel or by means of the pipe extension, the second substance and/or a mixture of first and second substances present at least in a bottom portion of the second vessel can be easily supplied to and fed to the recirculation pipe.

[0036] In further embodiments it is even conceivable, that the bottom portion of the second vessel comprises a tapered geometry directly extending into the recirculation pipe. However, with the mixing arrangement preferably arranged at or near a bottom portion of the second vessel a rather flat and even shape bottom portion of the second vessel may be preferred.

[0037] The recirculation pipe may thus extend through the bottom portion of the second vessel but may alternatively extend into the second vessel from above. Hence, the second vessel may be readily equipped with a pipe extension extending from an upper wall portion of the second vessel down into a bottom portion of the vessel's interior. The pipe extension may even extend through a lid or through opening at an upper portion of the second vessel, where it is connectable with the recirculation pipe. Hence, the housing of the second vessel may comprise a standardized connector allowing to connect the recirculation pipe with a pipe extension extending into a bottom portion of the second vessel.

[0038] In an arrangement, wherein the first vessel is arranged on top of or above the second vessel it may be of further benefit, when also the recirculation pipe or the respective pipe extension enters the second vessel via an upper wall portion thereof. This way, overall length of the recirculation pipe and/or of the pipe extension can be kept to a minimum to provide a thorough mixing and to keep eventual losses of the prepared or mixed substances due to the volume of the interconnecting pipes on a minimum.

[0039] Accordingly an outlet of the recirculation pipe extending into the first vessel may penetrate an upper side wall portion or an upper wall portion of the first vessel so that the mixture or the second substance provided by the recirculation pipe enters the first vessel from the top. This way, any substance fed back via the recirculation pipe to the first vessel will have to propagate through the first vessel from the top to the bottom before respective substances re-enter the second vessel via the feeding pipe.

[0040] In still another embodiment, the second substance is only feedable to the second vessel via the first vessel and via the feeding pipe interconnecting first and second vessels. In this embodiment, the first vessel serves as a supply vessel particularly adapted to receive first and second substances from an external supply. By feeding the second substance to the second vessel exclusively via the first vessel the second vessel itself can be kept substantially sealed against the environment.

[0041] Hence, the second vessel does not have to be actively sealed against the environment nor does it require a sealable lid.

[0042] Consequently and according to another embodiment, the first vessel comprises a hermetically closeable lid to receive the first and/or the second substance. This way, the second substance can be supplied to the first vessel. By appropriately opening a substance transferring connection between the first vessel and the second vessel, the second substance can be transferred completely from the first vessel into the second vessel via the feeding pipe.

[0043] Thereafter, the feeding pipe may be closed so that the first substance can be deposited in the first vessel.

[0044] In a further preferred embodiment, at least the second vessel comprises a sampling outlet at its bottom portion, by way of which a sampling of the mixture contained in the second vessel can be conducted, for determining at least one process parameter, e.g. a pH-value. Preferably, the sampling outlet is arranged below a minimum filling level of the second vessel so that extraction of a sample of the mixture does not come along with ingress of oxygen or air into the mixing system.

[0045] According to another aspect the invention also relates to a method of mixing at least two substances by means of a mixing system as already described above. The method of mixing or of processing the at least two substances comprises the steps of:

• feeding of a second substance to the second vessel,
• flushing the second vessel with inert gas and close it hermetically,
• feeding of a first substance to the first vessel,
• flushing the first vessel with inert gas and close it hermetically,
• executing a mixing process by:
  i) feeding the first substance to the second vessel via the feeding pipe extending between the first vessel and the second vessel,

  ii) activating amixing arrangement such as an agitator located in at least one of the first or second vessel, and

  iii) back feeding of the second substance or of a mixture of first and second substances to the first vessel via the recirculation pipe.

[0046] Activating of the agitator and back feeding of the second substance or of the mixture of first and second substances may either take place simultaneously or consecutively in an inert atmosphere. Typically, a mixing of first and second substances already takes place by activating the agitator and by feeding the first substance from the first vessel to the second vessel.

[0047] Either during a transfer of the first substance into the second vessel or after completely transferring the first substance from the first vessel into the second vessel the back feeding of the substances from the second vessel back to the first vessel may take place.

[0048] In another scenario, the back feeding of the second substance may also take place before the substance transferring passage provided by the feeding pipe is at least partially opened. In this way, the second substance initially provided in the second vessel may be at least partially or even almost entirely supplied to the first vessel, where a first mixing may take place accordingly.

[0049] In another preferred embodiment, the first vessel and/or the second vessel is or are hermetically sealed against the environment and the first and the second vessels are at least partially filled with the first and with the second substances, respectively. When first and second vessels flushed with inert gas and have been filled with respective substances, the vessels are flushed with an inert gas again before the mixing process starts.

[0050] Flushing of first and second vessels with the inert gas may take place simultaneously or consecutively. Especially when feeding the second vessel via the first vessel and via the interconnecting feeding pipe it is of particular benefit, when the second vessel is flushed with the inert gas before or after it has been at least partially filled with the second substance before the first vessel is accordingly filled with the first substance.

[0051] Thereafter, also the first vessel can be flushed with the inert gas before a substance transferring passage between first and second vessels is opened for mixing of the at least two substances. The first vessel and the second vessel may be equipped with inlet and/or outlet valves for inserting or releasing inert gas from the mixing system.

[0052] According to a further preferred embodiment, the first substance is provided as a solid substance, e.g. in granular or powdery form and wherein the second substance is provided as a liquid substance, e.g. to dissolve the first substance and/or to disperse with the first substance.

[0053] In general, the mixing system and the mixing method is applicable to a wide variety of mixing processes in the fields of food preparation as well as in chemical, cosmetic and pharmaceutical industry. Hence, first and second substances may comprise medicaments, such like injectable and/or parenteral medicaments, components of medicaments such as active pharmaceutical ingredients or further excipients or respective pre-products.

[0054] Examples of oxygen-sensitive substances are pharmaceutically active ingredients such as epinephrine, articain, acetylsalicylic acid, certain amino acids such as methionin, cysteine or tryptophan, Amphotericin B, peptides such as teriparatide, lixisenatide, peptide hormones such as thyroid hormone. Examples of substances that may or tend to deteriorate when exposed to electromagnetic radiation are vitamins or pharmaceutically active ingredients such as nifedipin, molsidomin or furosemid.

[0055] It will be further apparent to those skilled in the pertinent art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Further, it is to be noted, that any reference signs used in the appended claims are not to be construed as limiting the scope of the present invention.

Brief Description of the Drawings

[0056] In the following, a preferred embodiment of the invention is described by making reference to the drawings, in which:

Figure 1 schematically illustrates a mixing system according to the present invention and

Figure 2 is illustrative of a flowchart of a method of mixing.

Detailed Description

[0057] In Figure 1 the mixing system 10 is schematically illustrated. The mixing system 10 comprises a first vessel 12 serving as a supply or feeding vessel and comprises a second vessel 14 configured as a mixing vessel. The two vessels 12, 14 are interconnected by means of a feeding pipe 18 extending from a tapered bottom portion 13 of the first vessel 12 through an upper portion of the second vessel 14 and into the second vessel 14.

[0058] Additionally, the two vessels 12, 14 are mutually interconnected via a recirculation pipe 20 extending from an upper portion of the second vessel 14 to an upper portion of the first vessel 12. Inside the second vessel 14, the feeding pipe 18 as well as the recirculation pipe 20 may be extended by means of first and second extension pipes 34, 36, respectively.

[0059] By means of extension pipe 36 the recirculation pipe 20 effectively extents into a bottom portion of the second vessel 14. The first and second extension pipes 34, 36 may be readily installed and assembly in the second vessel 14. Via respective connectors 38, 40 located in the upper portion or in an upper wall of the second vessel 14, the feeding pipe 18 as well as the recirculation pipe 20 may be operably connected with first and second pipe extensions 34, 36, respectively.

[0060] Since the first vessel 12 is arranged on top or above the second vessel 14, a transfer of substances provided in the first vessel 12 into the second vessel 14 may be conducted only under the effect of gravity. The substance flow through the feeding pipe 18 is controllable by a regulating valve 32. By means of said valve 32 the substance transferring interconnection between the first vessel 12 and the second vessel 14 may also be completely interrupted or blocked.

[0061] The recirculation pipe 20 is coupled with a pump 22 by means of which substances contained in the second vessel 14 can be fed back to the first vessel 12. Additionally, the second vessel 14 is equipped with a mixing arrangement 16 comprising a stirrer located at a bottom portion of the second vessel 14.

[0062] In an initial configuration, wherein a first substance 1 is located in the first vessel 12 and wherein a second substance 2 is located in the second vessel 14 opening of the regulating valve 32 provides an ingress of the first substance 1 to the second vessel 14. By activating the mixing arrangement 16, first and second substances will then be actively mixed in the second vessel 14.

[0063] Simultaneously with the opening of the regulating valve 32 and/or with the activation of the mixing arrangement 16 the pump 22 may be switched on to feed back the mixture of first and second substances 1, 2 to the first vessel 12. This way, any residues of the first substance 1 remaining e.g. at the inner side walls of the first vessel 12 may be washed or flushed away and may rinse through the feeding pipe 18 into the second vessel 14.

[0064] Starting of the pump 22 may take place already during or even before opening the regulating valve 32. Moreover, starting and regulating the pump 22 may be conducted according to a pre-defined mixing schedule, so that a highly homogeneous mixture of at least first and second substances 1, 2 can be attained. By means of first and second vessels 12, 14 the feeding pipe 18, the recirculation pipe 20 and by means of the at least one pump 22 a closed loop for interchanging first and second substances 1, 2 and mixtures thereof between first and second vessels 12, 14 can be established. Since the recirculation pipe 20 is fed by the mixture of first and second substances 1, 2, in the course, especially at the end of a mixing procedure the two vessels 12, 14 will be equally supplied with a mixture of first and second substances 1, 2 exhibiting a precise and constant mixing ratio.

[0065] Hence, by means of the closed loop between first vessel 12 and second vessel 14 a highly homogeneous and precise mixing of first and second substances 1, 2 at a constant mixing ratio can be obtained.

[0066] The entire mixing system 10 is further adapted to be completely hermetically sealed against the environment. As illustrated in Figure 1 only the first vessel 12 is provided with a sealable lid 24 which can be opened for supplying first and second substances 1, 2 to the first vessel 12, respectively. Here, the second vessel 14 is void of an own lid. The second substance 2 to be initially provided in the second vessel 14 may be fed to said vessel 14 via the first vessel 12 and the feeding pipe 18.

[0067] For filling of the second vessel 14 the regulating valve 32 is opened and the second substance 2 is supplied to the first vessel 12 as it is also indicated in step 100 of the flowchart of Figure 2. Preferably, the second substance 2 is provided as a liquid substance. Accordingly, it may rinse and drain into the second vessel 14. Once the entirety of the second substance 2 is disposed in the second vessel 14, the second vessel 14 can be operably detached and decoupled from the first vessel, e.g. by closing the regulating valve 32. Then, according to step 102 of Figure 2, an inlet valve 42 and an outlet valve 44, both provided on the top or at an upper portion of the second vessel 14 may be opened to flush the second vessel 14 with an inert gas.

[0068] This way, reactant gases, such like oxygen or other gaseous substances can be effectively expelled from the second vessel 14. Once the interior of the second vessel 14 has been flushed with an inert gas, respective inlet and outlet valves 42, 44 can be closed.

[0069] Thereafter, in step 104, the first substance, e.g. in form of a powder or a solid granular material can be supplied to the first vessel 12 via the opened lid 24. Thereafter, the lid 24 can be closed and hermetically sealed. Then, in the proceeding step 106 also the first vessel 12 can be flushed with an inert gas, e.g. by opening the inlet valve 26 and the outlet valve 28. A suitable inert gas may then enter the first vessel 12 via the inlet valve 26 in order to expel a reactant or reactive gas, such like oxygen from the interior of the first vessel 12. Additionally, also an inlet valve 30 located in the feeding pipe 18 can be opened to flush the feeding pipe 18 accordingly.

[0070] Inert gas entering the feeding pipe 18 via the inlet valve 30 may stream through the e.g. powdery or granular substance 1 and may escape from the first vessel 12 via the outlet valve 28. After flushing the first vessel 12 and/or the feeding pipe 18 in step 106 the regulate valve 32 can be at least partially opened in a subsequent step 108 to allow the second substance 2 to enter the second vessel 14. At the same time or even before opening of the valve 32 the mixing arrangement 16 may be started in step 110. Simultaneously or also with a temporal offset a recirculation of the substances 1, 2 accumulating at the bottom of the second vessel 14 may be started in step 112 by activating and regulating the pump 22.

[0071] So the present mixing system 10 not only provides mixing of at lest two substances 1, 2 in a mixing vessel 14 but also provides a closed loop exchange of the mixture between the second vessel 14 and the first vessel 12, in particular for flushing any residues of the first substance 1 remaining on inside wall portions of the first vessel 12 into the second vessel 14.

[0072] As indicated in Figure 1, the outlet 25 of the recirculation pipe 20 is bended downwardly and extends through the top or through a side wall of the first vessel 12. This way, the mixture of first and second substances 1, 2 fed back through the recirculation pipe 20 enters the first vessel 12 from the top.

[0073] After a thorough mixing of the at least first and second substances 1, 2 has been achieved, the pump 22 is switched off for that the mixture completely accumulates at the bottom of the second vessel 14. Then, the mixture may be withdrawn from the second vessel 14 by means of an outlet pipe 48 extending into the bottom portion of the second vessel 14. The outlet pipe 48 as well as the first and second extension pipes 34, 36 may all be provided with and may terminate with a standardized connector 46 allowing to establish a substance transferring connection with other substance feeding systems, like pipes or similar substance feeding devices.

[0074] The second vessel 14 further comprises a sampling outlet 50 at its bottom portion by way of which samples of the mixture can be extracted during the mixing process. The sampling outlet 50 may comprise a tappet or a similar extraction device which allows extracting a small amount of the mixture for inspection purpose. Additionally, the second vessel 14 may comprise an inspection window 52 of translucent material by way of which the interior of the second vessel 14 can be visually inspected. Preferably, the inspection window 52 may be equipped with a blind or with a curtain for preventing electromagnetic radiation to enter the second vessel 14.

[0075] Additionally, when the first and second vessels 12, 14 as well as the feeding pipe 18 and the recirculation pipe 20 are made of non-transparent material, the mixing system is not only hermetically sealed against the environment but also serves to protect the substances 1, 2 disposed therein against electromagnetic radiation.

[0076] Flushing of the feeding pipe 18, in particular of a portion of the feeding pipe 18 located downstream of the regulating device 32 may also be attained with the lid 24 of the first vessel closed and by only opening the outlet valve 28 of the first vessel 12, when the regulating valve 32 is open. Then, the inert gas may enter the second vessel 14 via the inlet valve 42. It may propagate through the first extension pipe 34 and through the feeding pipe 18 into the first vessel 12 and may then escape from the first vessel 12 through the outlet valve 28. Closing of the regulating valve 32 may then hermetically seal the downstream portion of the feeding pipe 18 and the second vessel 14 from the first vessel 12.

[0077] Even though not explicitly shown in Figure 1 it is conceivable that also the recirculation pipe 20 can be provided with at least one valve in order to allow for a separate flushing of the recirculation pipe 20. It is particularly conceivable, that a regulating valve is located at the outlet 25 of the recirculation pipe 20 so that the recirculation pipe 20 can be flushed with inert gas together with the second vessel 14.

[0078] Once first and second vessels 12, 14 have been filled with respective substances 1, 2 and are flushed with a respective inert gas, the non-illustrated valve at the outlet 25 of the recirculation pipe 20 can be opened.

List of Reference Numerals

[0079] 

1

first substance

2

second substance

10

mixing system

12

first vessel

13

bottom portion

14

second vessel

16

mixing arrangement

18

feeding pipe

20

recirculation pipe

22

pump

24

lid

25

outlet

26

valve

28

valve

30

valve

32

valve

34

first extension pipe

36

second extension pipe

38

connector

40

connector

42

valve

44

valve

46

connector

48

outlet pipe

50

sampling outlet

52

inspection window

Claims

1. A mixing system for processing of at least two substances, the system comprising:

- a first vessel (12) to receive a first substance (1),

- a second vessel (14) to receive a second substance (2) to be mixed with the first substance (1),

- wherein the first vessel (12) is connectable with the second vessel (14) in a substance transferring way by means of a feeding pipe (18) to feed the first substance (1) to the second vessel (14),

- wherein the second vessel (14) is connectable with the first vessel (12) in a substance transferring way by means of a recirculation pipe (20) to feed the second substance (2) and/or a mixture of first and second substances (1, 2) to the first vessel (14),

- at least one pump (22) connected to at least one of the feeding pipe (18) or recirculation pipe (20), and

- at least one mixing arrangement (16) located in at least one of first and second vessels (12, 14).

2. The mixing system according to claim 1, wherein the first vessel (12) and/or the second vessel (14) is hermetically sealable against the environment.

3. The mixing system according to claim 1 or 2, wherein the first vessel (12) and/or the second vessel (14) is flushable with an inert gas.

4. The mixing system according to claim 3, wherein the first vessel (12) and the second vessel (14) are separately flushable with an inert gas.

5. The mixing system according to any one of the preceding claims, wherein the feeding pipe (18) and/or the recirculation pipe (20) is or are flushable with an inert gas.

6. The mixing system according to any one of the preceding claims 3 to 5, wherein the first and/or the second vessel (12, 14) comprises at least one inlet valve (26, 42) to receive the inert gas and further comprises at least one outlet valve (28, 44) to allow gas escaping from the respective vessel (12, 14).

7. The mixing system according to any one of the preceding claims, wherein the first vessel (12) is arranged above the second vessel (14) and comprises a tapered bottom portion (13) extending into the feeding pipe (18).

8. The mixing system according to any one of the preceding claims, wherein the mixing arrangement (16) is arranged in the second vessel (14) and comprises a stirrer.

9. The mixing system according to any one of the preceding claims, wherein the pump (22) is coupled with the recirculation pipe (20).

10. The mixing system according to any one of the preceding claims, wherein the recirculation pipe (20) extends into a bottom portion of the second vessel (14) or wherein the recirculation pipe (20) is connectable with a pipe extension (36) assembled in the second vessel (14) and extending into a bottom portion thereof.

11. The mixing system according to any one of the preceding claims, wherein the second substance (2) is only feedable to the second vessel (14) via the first vessel (12) and via the feeding pipe (18) interconnecting first and second vessels (12, 14).

12. The mixing system according to any one of the preceding claims, wherein the first vessel (12) comprises a hermetically closable lid (24) to receive the first and/or the second substance (1, 2).

13. A method of mixing at least two substances by means of a mixing system (10) according to any one of the preceding claims, the method comprises the steps of:

- feeding of a second substance (2) to the second vessel (14),

- flushing the second vessel with inert gas and close it hermetically,

- feeding of a first substance (1) to the first vessel (12),

- flushing the first vessel with inert gas and close it hermetically

- executing a mixing process by:

i) feeding the first substance (1) to the second vessel (14) via the feeding pipe (18) extending between the first vessel (12) and the second vessel (14),

ii) activating a mixing arrangement (16) located in at least one of first or second vessel (12, 14), and

iii) back feeding of the second substance (2) or of a mixture of first and second substances (1, 2) to the first vessel (12) via the recirculation pipe (20).

14. The method according to claim 13, wherein the first vessel (12) and/or the second vessel (14) is hermetically sealed against the environment and wherein the first and the second vessel (12, 14) at least partially filled with the first and with the second substances (1, 2), respectively, are flushed with an inert gas before the mixing process starts.

15. The method according to claim 13 or 14, wherein the first substance (1) is provided as a solid substance and wherein the second substance (2) is provided as a liquid substance.

Drawing