Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D83/00—Containers or packages with special means for dispensing contents
  • B65D83/0005—Containers or packages provided with a piston or with a movable bottom or partition having approximately the same section as the container
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling

Definitions

• biological materials e.g. proteins
• metal surfaces e.g. stainless steel surfaces
• a monolayer of high molecular weight compounds or biological materials, e.g. proteins can be extremely difficult to completely remove without costly, energy demanding and time-consuming cleaning processes, which further may cause environmental problems.
• US 7,090,753 Bl discloses an electrolytic cell which can produce charged water having excellent performance of improving surface cleaning or treatment.
• KR 1082761 A discloses a method for grinding the inner walls of a drug tank in order to maintain the degree of purity of stored drugs by minimizing the gush of metal components from the inner walls of the drug tank.
• the inner wall is i.a. grinded by an electrolytic solution, and subsequently an oxide membrane is formed by reacting the surface with 20% nitric acid solution. It is stated that the use of high purity detergents can be reduced and that the cleaning time can be shortened.
• the present invention provides an electrolytic process for removing impurities, e.g. contaminants and residues, in particular impurities consisting of biological materials, from the inner surface of a metallic container (5), said process comprising the step of
• C ⁇ P clean in place
• Figure 1 illustrates a process reactor (reaction vessel) (5) having a wall (1) used as the anode, and having arranged therein a ratable tubular member (2) for facilitating flow of the electrolyte solution (3) provided via a pump (not shown).
• the tubular member is also used as the cathode (as shown) or can have a cathode arranged therein (alternative embodiment).
• the contact area (4) is moved across a substantial part of the inner surface.
• Figure 2 illustrates a process reactor (reaction vessel) (5) having a wall (1) used as the anode, and having arranged therein a ratable member (2) for facilitating flow of the electrolyte solution (3) provided via a pump (not shown).
• the tubular member is moved close to the inner wall and has a slit which allows the electrolyte solution to exit the tubular member.
• the tubular member is also used as the cathode (as shown) or can have a cathode arranged therein (alternative embodiment).
• the elongated contact area (4) is moved across a substantial part of the inner surface.
• FIGs 4 and 5 illustrate the arrangement of a ratable spraying device within a process reactor.
• the spraying device second electrode; cathode in Figure 4 and anode in Figure 5
• the inner wall of the container first electrode; anode in Figure 4 and cathode in Figure 5
• the spraying device provides several streams (3') collectively representing the electrolyte solution (3)
• the "contact area” (4) is a collection of a number of individual contact areas (4').
• the process of the invention is particularly relevant for industrial scale equipment; hence the container preferably has a volume of at least 10 L, such as at least 100 L, or even at least 1,000 L.
• the invention resides in the finding that electrolytic cleaning of the inner surface of a metallic surface of a container can be obtained by application of a high current density by means of an electrical circuit comprising (a) the wall of the container as a first electrode (1), (b) a second electrode (2), and (c) an electrolyte solution (3) forming electrical connection between said first electrode and said second electrode, wherein the connection between the first electrode and the electrolyte solution defines a contact area (4).
• Means are included which facilitate that the contact area can be moved across at least a substantial part of the metallic inner surface of the container, while a predetermined current density is simultaneously applied at said contact area (4), i.e. the electrolytic process is effectuated over a substantial part of the inner surface.
• the current density is in the range 1-60 A/dm 2 , e.g. in the range of 1-30 A/dm 2 , such as 3-20 A/dm 2 .
• the contact area at any time of the process only represents a fraction of the total area to be treated.
• the ratio between (i) the total area of the part of the inner surface which the contact area is moved across and (ii) the contact area is at least 10: 1, such as at least 20: 1, or even at least 50: 1.
• contact area in question may be the sum of a number of individual contact areas, e.g. as illustrated in Figures 4 and 5.
• the rational behind the invention is that the high cathodic current density applied to the metallic surface, e.g. a stainless steel surface, will result in the formation of hydrogen bubbles at the inner surface of the container, and that any material which adheres to the surface thereby will be removed under the influence of the formed hydrogen and hydroxyl ions. Furthermore, the electrochemical interaction with the immobilized organic impurities at the surface will be destroyed thereby leaving the surface cleaned upon molecular or nano- scale. This is illustrated in Example 2.
• the process according to the invention cleans the inner surface using only electricity and an electrolyte solution.
• the electrolyte solution needs in principle only to contain very dilute amounts of non-toxic chemicals, such as alkali-metal hydroxides, such as NaOH and KOH, or a neutral salt, such as Na 2 SO 4 or K 2 SO 4 , in purified water.
• the electrolyte solution is preferably a solution of one or more components selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium sulphate and potassium sulphate.
• the electrolyte solution is preferably essentially free of detergents.
• the equipment used for facilitating the movement of the contact area across the inner surface may include motors, e.g. stepper motors, as well as robots. Further, the movement may - although not particularly preferred - be effected manually.
• the electrical circuit comprises the first electrode, the second electrode and the electrolyte solution.
• the first electrode is the cathode and the second electrode is the anode.
• hydrogen gas is formed at the inner surface of the container.
• the first electrode is the anode and the second electrode is the cathode.
• oxygen gas is formed at the inner surface of the container.
• That constellation makes it also possible - in a special embodiment - to passivate the stainless steel surface as a post treatment after the electrolytic CIP-cleaning, where the first electrode is used as a cathode.
• the first electrode act as the anode and that makes it possible to form a passivating layer consisting of oxides, i.e a treatment very similarly to the passivation in nitric acid.
• the Pourbaix-diagram in figure 6 indicates the possible area for passivation.
• the anodic current density which is necessary to render the process effective is typically at least 1 A/dm 2 corresponding to a potential (SHE) between +400 mV and +1500 mV.
• the current density is typically in the range 1-60 A/dm 2 , e.g. in the range of 1-30 A/dm 2 .
• the electrolyte solution is fed to the gap between the first electrode and the second electrode by means of a tubular member having a slit.
• This embodiment corresponds to the one illustrated in Figure 2.
• the residence time of the electrolyte solution may be increased by arranging a porous structure in the before-mentioned gap.
• the electrolytic process is carried out within a jet beam between the area to be cleaned (the first electrode; a cathode) and a cleaning nozzle.
• An anode is inserted into the tank in appropriate distance allowing a non-interrupted and coherent beam of electrolyte to connect to the anode and cathode (tank wall).
• the beam is moved to cover the whole area of the tank.
• the flow of the electrolyte solution is preferably predominantly laminar.
• the process according to invention comprising the step of:
• an electrical circuit comprising (a) the wall of the container as the anode (1), (b) a cathode (2), and (c) an electrolyte solution (3) of one or more components selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium sulphate and potassium sulphate, optionally further comprising a complexing agent, said electrolyte solution forming electrical connection between said anode and said cathode, the connection between the first electrode and the electrolyte solution defining a contact area (4); and
• the cleanness of the surfaces treated according to the process according to the present invention can be verified via XPS (X-ray photon Spectroscopy), e.g. as described in the Examples section.
• the process according to the invention can suitably be used for cleaning process reactors being contaminated with a variety of organic constituent, e.g. proteins, milk, etc., and the use is therefore not restricted to the drug industry.
• organic constituent e.g. proteins, milk, etc.
• XPS is a versatile technique for analyzing the top ⁇ 10 nm of a surface, providing information on the elements present at the surface and the chemical state they are in.
• Table 1 shows the XPS measurement of a pristine surface of stainless steel type 316.
• the surface is seen to consist of oxides of mainly chromium and less amounts of iron oxide.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Cleaning By Liquid Or Steam (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

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• 2008
  • 2008-03-13 WO PCT/EP2008/052971 patent/WO2008110587A1/en active Application Filing
  • 2008-03-13 EP EP08717715A patent/EP2126160A1/de not_active Withdrawn
• 2011
  • 2011-05-17 US US13/109,518 patent/US20120018298A1/en not_active Abandoned
• 2013
  • 2013-02-27 US US13/778,940 patent/US20130299520A1/en not_active Abandoned
• 2014
  • 2014-03-24 US US14/223,177 patent/US20140203044A1/en not_active Abandoned

Non-Patent Citations (1)

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